JP6020868B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to determination of a deterioration state of a developer.

  Conventionally, in a developer containing toner and a magnetic carrier, a toner concentration sensor that detects the toner concentration of the developer based on the magnetic permeability of the developer is known. A technique for detecting the deterioration of the developer based on the slope of the voltage waveform output from the toner density sensor is also known (for example, Patent Document 1).

  In addition, a technique for detecting the deterioration state of the developer during the image forming process by using the relationship between the output value of the toner density sensor and the deterioration state of the developer acquired in advance is also known. (For example, patent document 2).

JP 2006030952 A JP 2008-281788 A

  As described above, in the technique of Patent Document 1, in order to detect the deterioration state of the developer, it is necessary to calculate the slope of the voltage waveform output from the toner density sensor. As a result, the technique of Patent Document 1 has a problem that the deterioration state of the developer cannot be accurately grasped.

  Further, in the technique of Patent Document 2, when the developing condition when recording a toner image on a recording material is different from the developing condition when the developer deterioration state is acquired in advance, the developer deterioration state cannot be detected correctly. Problems arise.

  Accordingly, an object of the present invention is to provide an image forming apparatus that can determine a deterioration state of a developer by a simple technique.

  In order to solve the above problems, the invention of claim 1 is provided to store a developer containing toner and a carrier in a housing, and to provide a developing unit that supplies the toner to an image carrier and to face the housing. A detection unit that detects a density-related value of the toner at the facing position; and a determination unit that determines a deterioration state of the developer based on the density-related value detected by the detection unit; The developing unit includes an agitation unit that agitates the developer stored in the housing, and the detection unit detects a pulse signal sequentially detected according to an oscillation frequency of the developer at the opposed position. Detecting as a concentration-related value, the determination unit obtains a plurality of count values by counting the pulse signal that changes according to the stirring operation of the stirring unit for each reference time. In addition, the deterioration state of the developer is determined by comparing each of the plurality of count values. If it is determined that the developer has deteriorated, the toner is not supplied even if new toner is supplied to the housing. Based on the determination whether the density falls within the allowable range and the determination that the toner can be replenished because the density of the toner falls within the allowable range due to a decrease in the toner due to future printing, It is determined whether new toner is supplied to the developing unit or whether the toner is discharged from the developing unit.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the stirring unit includes a rotation shaft and a stirring blade extending spirally along the extending direction of the rotation shaft, and the determination is made. The unit selects a proximity count value to be counted from the plurality of count values in a state where the stirring blade is rotated to the vicinity of a proximity position close to the detection unit, and selects each proximity count value selected. By comparing, the deterioration state of the developer is judged.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the inner wall of the housing is inclined at the facing position.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the determination unit is based on a maximum count value among the plurality of count values for one cycle. The deterioration status of the developer is determined.

  The invention according to claim 5 is the image forming apparatus according to any one of claims 1 to 4, further comprising a replenishing unit that replenishes toner to the developing unit, wherein the determination unit includes a new toner in the housing. Even if the toner is replenished, it is determined that the toner concentration is within the allowable range, or that the toner concentration is within the allowable range due to the decrease in the toner due to future printing, so that the toner can be replenished. In this case, the toner is supplied to the supply unit.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the image forming apparatus further includes a replenishing unit that replenishes the developing unit with toner, and the determination unit includes a new toner in the housing. Even if the toner is replenished, the toner concentration is out of the permissible range, and even if there is a decrease in the toner due to future printing, the toner concentration is out of the permissible range. If it is determined that there is no toner, the toner is discharged from the developing unit and the toner is supplied to the developing unit.

  In the first to sixth aspects of the invention, the deterioration state of the developer is determined by comparing the count values obtained based on the detection result of the detection unit. Thereby, it is possible to suppress erroneous recognition of the deterioration state of the developer, and it is possible to replenish the toner at an appropriate timing. For this reason, it is possible to prevent the fluidity of the developer from being lowered due to the deterioration of the developer (particularly the toner) and to prevent the formation of a toner image recorded on the recording material.

  In particular, according to the second aspect of the present invention, it is possible to determine the deterioration state of the developer by comparing the proximity count values detected in the state of being rotated to the vicinity of the proximity position. Therefore, it is possible to more easily determine the deterioration state of the developer.

  In particular, according to the invention of claim 3, the inner wall of the housing at the opposed position is inclined. Thereby, it is possible to prevent the developer from accumulating at the facing position. Therefore, it is possible to better judge the deterioration state of the developer.

  In particular, according to the fifth aspect of the present invention, the toner can be replenished to the replenishing portion based on the deterioration state of the developer and the toner density in the housing. For example, when it is determined that the developer has deteriorated and the toner density is determined to be within the allowable range even when toner replenishment is performed, the determination unit does not discharge the toner from the development unit, Toner can be replenished to the developing unit.

Thereby, the ratio of the old toner in the housing can be reduced. For this reason, it is possible to prevent the occurrence of defective formation of a toner image recorded on the recording material due to the deterioration of the developer.

  In particular, according to the sixth aspect of the present invention, the toner can be discharged from the developing portion and the toner can be replenished to the developing portion based on the deterioration state of the developer and the toner concentration in the housing. For example, when it is determined that the developer is deteriorated and it is determined that the toner cannot be replenished based on the toner concentration in the housing, the determination unit discharges the toner from the development unit, Toner can be replenished to the developing unit.

  As a result, the ratio of the old toner is reduced while the toner density in the housing is within the allowable range or is approaching the allowable range. For this reason, it is possible to prevent the occurrence of defective formation of a toner image recorded on the recording material due to the deterioration of the developer.

1 is a front view illustrating an example of a configuration of an image forming apparatus according to an embodiment of the present invention. It is a front view which shows an example of a structure of the image development part vicinity. It is a figure which shows an example of a structure of a detection part. It is a front view which shows an example of a structure of the stirring part vicinity. It is a front view which shows an example of a structure of the stirring part vicinity. 2 is a block diagram illustrating an example of a functional configuration of an image forming apparatus. FIG. It is a graph of the experimental result which shows the relationship between the count value of the pulse signal output from a detection part, and time. It is a graph of the experimental result which shows the relationship between the count value of the pulse signal output from a detection part, and time. 6 is a flowchart illustrating an example of a toner replenishment procedure.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<1. Configuration of image forming apparatus>
FIG. 1 is a front view showing an example of the overall configuration of an image forming apparatus 1 according to an embodiment of the present invention. Here, the image forming apparatus 1 is used as, for example, a complex machine that includes a copying function, a printing function, a facsimile function, and the like, and prints a monochrome image or a color image by an electrophotographic method. As shown in FIG. 1, the image forming apparatus 1 mainly includes a printer unit 10, a paper feed unit 30, a fixing unit 40, a paper discharge unit 50, a display unit, an operation unit, a control unit 90, It has.

  In addition, in FIG. 1 and the subsequent drawings, an XYZ orthogonal coordinate system in which the Z-axis direction is a vertical direction and the XY plane is a horizontal plane is appropriately attached as necessary to clarify the directional relationship. Yes. Further, the arrows attached to the paper feed path R1, the paper discharge path R2, and the transport path Ra in FIG. 1 indicate the “transport direction of the recording material P” (hereinafter also simply referred to as “transport direction”).

  The printer unit 10 prints a monochrome image or a color image on the recording material P supplied via the paper feed path R1 and the transport path Ra. As shown in FIG. 1, the printer unit 10 mainly includes an image forming unit 11 (11Y, 11M, 11C, 11K), a print head unit 15, and an intermediate transfer belt 21.

A plurality (four in the present embodiment) of image forming units 11 correspond to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). As shown in FIG. 1, each image forming unit 11 (11Y, 11M, 11C, 11K) mainly includes a photosensitive drum 1.
3 (13Y, 13M, 13C, 13K), developing unit 60 (60Y, 60M, 60C, 60K), replenishing unit 70 (70Y, 70M, 70C, 70K), and primary transfer roller 18 (18Y, 18M, 18C). , 18K).

  Here, a so-called tandem system is employed as the printer unit 10 of the present embodiment, and each image forming unit 11 (11Y, 11M, 11C, 11K) has, for example, yellow, magenta, They are arranged along the intermediate transfer belt 21 in the order of cyan and black.

  In the present embodiment, the image forming units 11Y, 11M, 11C, and 11K have the same type of hardware configuration. Therefore, in the following, the image forming unit 11Y and the photosensitive drum 13Y, the primary transfer roller 18Y, the developing unit 60Y, and the replenishing unit 70Y, which are components of the image forming unit 11Y, will be described in detail.

  For convenience of illustration, the reference numerals of the photosensitive drums 13M, 13C, and 13K, the primary transfer rollers 18M, 18C, and 18K, the developing units 60M, 60C, and 60K, and the replenishing units 70M, 70C, and 70K are illustrated in FIG. It is omitted in each figure.

  Further, in the following description, the image forming units 11Y to 11K, the photosensitive drums 13Y to 13K, the developing units 60Y to 60K, and the replenishing units 70Y to 70K are collectively referred to as the image forming unit 11, the photosensitive drum 13, and the developing unit, respectively. Also referred to as part 60 and supply part 70.

  The photosensitive drum 13Y (image carrier) has a cylindrical shape or a columnar shape, and is disposed on the opposite side of the primary transfer roller 18 with the intermediate transfer belt 21 interposed therebetween. A photoconductive film is provided on the outer peripheral surface of the photosensitive drum 13Y. The charging unit (not shown) applies a charge to the outer peripheral surface of the photosensitive drum 13Y. The print head unit 15 is a so-called exposure unit, and irradiates the photosensitive drum 13 (13Y, 13M, 13C, 13K) with laser light.

  Therefore, light is emitted from the print head unit 15 to the outer peripheral surface of the photosensitive drum 13Y, and the charge on the irradiated portion is removed, whereby an electrostatic latent image corresponding to yellow is formed on the outer peripheral surface of the photosensitive drum 13Y. It is formed. Similarly, electrostatic latent images corresponding to magenta, cyan, and black are formed on the outer peripheral surfaces of the photosensitive drums 13M, 13C, and 13K, respectively.

  The developing unit 60Y supplies yellow (Y) toner transferred to the intermediate transfer belt 21. Thereby, a toner image is formed based on the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 13Y. As shown in FIG. 1, the developing unit 60 </ b> Y is provided below the intermediate transfer belt 21. The detailed configuration of the developing unit 60Y will be described later.

  The replenishing unit 70Y stores yellow (Y) toner and replenishes the corresponding developing unit 60Y with yellow (Y) toner. For example, when the electrostatic latent image on the photosensitive drum 13 is developed and the toner of the developing unit 60Y is consumed, the supply process of the supply unit 70Y is executed.

  As shown in FIG. 1, the primary transfer roller 18Y is disposed on the opposite side of the photosensitive drum 13Y with the intermediate transfer belt 21 interposed therebetween. The primary transfer roller 18Y is given a charge having a polarity opposite to that of the outer peripheral surface of the photosensitive drum 13Y. As a result, the intermediate transfer belt 21 is sandwiched between the photosensitive drum 13Y and the primary transfer roller 18Y while the photosensitive drum 13Y and the primary transfer roller 18Y rotate, whereby a yellow toner image is transferred to the intermediate transfer belt 21. Is done.

  The intermediate transfer belt 21 is an endless belt. The intermediate transfer belt 21 transfers the four color toner images primarily transferred by the image forming units 11 (11Y, 11M, 11C, and 11K) to the recording material P. As shown in FIG. 1, the intermediate transfer belt 21 is wound around a driving roller 22 and a metal driven roller 23. Further, the secondary transfer roller 25 is disposed on the opposite side of the drive roller 22 with the transport path Ra interposed therebetween.

  Then, the four-color toner images formed on the intermediate transfer belt 21 are recorded by adjusting the feed timing of the intermediate transfer belt 21 and the conveyance timing of the recording material P conveyed along the conveyance path Ra. Secondary transfer is performed on the material P.

  The paper feeding unit 30 supplies the recording material P to the printer unit 10 one by one. As shown in FIG. 1, the paper feed unit 30 is provided below the printer unit 10, and mainly includes a paper feed cassette 31, paper feed rollers 32 and 36, a registration roller 34, a manual feed tray 35, Is included.

  The paper feed cassette 31 is a storage unit that can store a plurality of recording materials P. The paper feed roller 32 feeds a plurality of recording materials P accommodated in the paper feed cassette 31 in order from the uppermost layer and supplies the fed recording materials P to the paper feed path R1.

  The manual feed tray 35 is a placement portion for the recording material P provided to be openable and closable with respect to the main body 1a. The paper feed roller 36 sequentially feeds a plurality of recording materials P placed on the manual feed tray 35 from the uppermost layer and supplies the fed recording materials P to the paper feed path R1.

  The registration roller 34 controls the timing at which the recording material P is sent out to the transport path Ra. As shown in FIG. 1, the registration roller 34 is provided downstream of the paper feed rollers 32 and 36 in the transport direction.

  The fixing unit 40 fixes the toner image transferred onto the recording material P. As shown in FIG. 1, the fixing unit 40 is disposed on the downstream side of the secondary transfer roller 25 in the path along the transport path Ra.

  The paper discharge unit 50 is provided on the downstream side of the fixing unit 40 in the transport direction, and discharges the recording material P on which the toner image is fixed to the outside of the apparatus. That is, the recording material P supplied to the paper discharge unit 50 via the transport path Ra is guided to the paper discharge path R2. As shown in FIG. 1, the paper discharge unit 50 mainly includes a paper discharge roller pair 51 provided on the paper discharge path R <b> 2 and a paper discharge tray 52.

The scanner unit 55 reads an image from an original by an automatic document feeder (ADF) method or a flat bed method. As shown in FIG. 1, the scanner unit 55 is disposed above the paper discharge unit 50.

  The display unit is configured by, for example, a liquid crystal display, and has a function as a “touch panel” that can specify a position on the screen by touching the screen with a finger or a dedicated pen. Therefore, a user of the image forming apparatus 1 (hereinafter simply referred to as “user”) gives an instruction using the “touch panel” function of the display unit based on the content displayed on the display unit, thereby The forming apparatus 1 can execute a predetermined process (for example, a process for forming an image on the recording material P supplied from the paper feeding unit 30). Thus, the display unit can be used as an input unit that receives an input operation from the user.

The operation unit is an input unit configured by a plurality of keypads. For example, the operation unit 8
When the print start button 86 included in 5 is pressed, an image forming process is performed on the recording material P. In this way, the operation unit accepts an input operation from the user, similarly to the display unit.

  The control unit 90 realizes operation control of each element of the image forming apparatus 1 and data calculation. For example, the control unit 90 receives an image signal from an external terminal (not shown) and converts the image signal into digitized image data for YK colors, and the printer unit 10 and the sheet feeding unit 30. By controlling the operation, printing processing on the recording material P can be executed. The detailed configuration of the control unit 90 will be described later.

<2. Configuration near the development unit>
FIG. 2 is a front view illustrating an example of the configuration of the developing unit 60. FIG. 3 is a diagram illustrating an example of the configuration of the detection unit 67. Each of FIG. 4 and FIG. 5 is a front view showing an example of the configuration in the vicinity of the stirring unit 63.

  The developing unit 60 stores developer DP including toner and carrier in the housing 60 a and supplies the toner to the photosensitive drum 13. Thereby, the electrostatic latent image formed on the photosensitive drum 13 is developed with toner. As shown in FIG. 2, the developing unit 60 mainly includes a developing roller 61, a supply unit 62, and a stirring unit 63. As shown in FIG. 2, the developing roller 61, the supply unit 62, and the stirring unit 63 are arranged in the housing 60a.

  Here, the developer DP of the present embodiment is a so-called two-component developer, and is a mixture of toner and carrier. The toner contained in the developer is formed of a non-magnetic material, and the carrier is formed of a magnetic material.

  The developing roller 61 is a rotating body having a cylindrical or columnar shape, and rotates around a rotating shaft 61a. A magnet is arranged inside the developing roller 61. Thus, the magnetic carrier is attracted to the outer peripheral surface of the developing roller 61. Therefore, the toner contained in the developer DP is supplied to the photoconductive drum 13 and moved from the developing roller 61 to the photoconductive drum 13, whereby the supply unit 62 supplies the developer DP stored in the housing 60a. While stirring, the toner is supplied to the developing roller 61. As shown in FIG. 2, the supply unit 62 is provided to face the developing roller 61 and rotates around the rotation shaft 62 a. The supply blade 62b extends spirally along the extending direction (Y-axis direction) of the rotation shaft 62a.

  The agitator 63 agitates the developer DP stored in the housing 60a. Similar to the supply unit 62, the stirring unit 63 includes a rotating shaft 63a and a stirring blade 63b. The stirring blade 63b extends spirally along the extending direction of the rotating shaft 63a, like the supply blade 62b.

  When the supply unit 62 and the agitation unit 63 are rotated, the developer DP in the housing 60a is agitated, and the toner and the carrier are mixed. Therefore, the toner and carrier in the housing 60a are frictionally charged and adsorb to each other.

  As shown in FIG. 2, the detection unit 67 (TCR (Toner Carrier Ratio) sensor) is provided to face the housing 60 a. The detector 67 detects the toner density-related value at the facing position FP.

  As shown in FIG. 3, the detection unit 67 mainly includes an antenna unit 67a and a circuit unit 67b. The antenna portion 67a includes one coil, and the circuit portion 67b includes two capacitors.

  As described above, the detection unit 67 is an LC tuned oscillation circuit including one coil and two capacitors, and the oscillation frequency is determined by the inductances of these coils and capacitors. Therefore, the detection unit 67 detects a pulse signal sequentially detected according to the oscillation frequency of the developer DP as a density-related value at the facing position FP.

  Here, when the stirring unit 63 is rotated, the tip of the stirring blade 63b (the end on the far side as viewed from the rotation shaft 63a) reaches the proximity position NP and approaches the detection unit 67. The nearby developer DP is removed by the stirring blade 63b (see FIGS. 4 and 5). The amount of the developer DP in the vicinity of the gap between the inner wall 60b of the housing 60a and the stirring blade 63b is compared with the amount of the developer DP when the tip of the stirring blade 63b is disposed at a position other than the proximity position NP. Less.

  Thereby, when the tip of the stirring blade 63b is disposed at the proximity position NP, the amount of the developer DP (particularly the carrier) stored in the facing position FP of the housing 60a becomes a minimum value. Therefore, the corresponding oscillation frequency has a maximum value, and the cycle of the pulse signal detected by the detection unit 67 has a minimum value.

  On the other hand, when the stirring unit 63 is further rotated and the tip of the stirring blade 63b is separated from the proximity position NP, the amount of developer DP (particularly, carrier) at the facing position FP of the housing 60a increases. Thereby, a corresponding oscillation frequency becomes small compared with the oscillation frequency when the stirring blade 63b is arrange | positioned in the proximity position NP. Therefore, the period of the pulse signal detected when the tip of the stirring blade 63b is separated from the proximity position NP is compared with the period of the pulse signal detected when the stirring blade 63b is disposed at the proximity position NP. Become bigger.

<3. Functional configuration of image forming apparatus>
FIG. 6 is a block diagram illustrating an example of a functional configuration of the image forming apparatus 1. As shown in FIG. 6, the control unit 90 mainly includes a ROM (Read Only Memory) 91, a RAM (Random Access Memory) 92, and a CPU (Central Processing Unit) 93.

  The ROM 91 is a so-called nonvolatile storage unit, and stores, for example, a program 91a. The RAM 92 is a so-called volatile storage unit, and stores, for example, data used in the calculation of the CPU 93. As the ROM 91 and the RAM 92, a flash memory that is a readable / writable nonvolatile memory may be used.

  The CPU 93 executes control of each element of the image forming apparatus 1 and various data calculation processes according to the program 91a of the ROM 91. In addition, the calculation function corresponding to the block (determination unit) 95 is realized by the CPU 93 for the block given the reference numeral 95 in the CPU 93 (see FIG. 6).

  The determination unit 95 determines the deterioration state of the developer DP based on the pulse signal (density-related value) detected by the detection unit 67. Hereinafter, a method for determining the deterioration state of the developer DP according to the present embodiment will be described.

  Here, a sufficient amount of external additive adheres to the outer periphery of the new toner immediately after replenishment. On the other hand, the external additive has fallen off from a part of the outer periphery of the toner that has deteriorated. Then, due to the difference in the adhesion state of the external additive, the fluidity of the new toner becomes higher than the fluidity of the toner that has deteriorated.

  Therefore, when the tip of the stirring blade 63b is disposed at the proximity position NP, the amount of the developer DP in the vicinity of the gap between the inner wall 60b of the housing 60a and the stirring blade 63b becomes maximum when the toner is new (FIG. 4). (See FIG. 5).

  Further, as described above, when the tip of the stirring blade 63b is disposed at the proximity position NP, the amount of the developer DP (particularly the carrier) stored in the facing position FP of the housing 60a becomes a minimum value. Therefore, the corresponding oscillation frequency has a maximum value, and the cycle of the pulse signal detected by the detection unit 67 has a minimum value.

Therefore, the period of the pulse signal detected by the detection unit 67 has the following characteristics (1) and (2). That is,
(1) When the tip of the stirring blade 63b is disposed at the proximity position NP, the cycle of the pulse signal detected by the detection unit 67 is a minimum value regardless of the progress of deterioration of the developer DP. Also,
(2) When the tip of the stirring blade 63b is disposed at the proximity position NP, the amount of the developer DP in the vicinity of the gap between the inner wall 60b of the housing 60a and the tip of the stirring blade 63b is the amount of toner contained in the developer DP. Decreases as the deterioration of For this reason, the period of the pulse signal detected by the detection unit 67 decreases as the toner deteriorates.

  FIG. 7 is a graph of experimental results showing the relationship between the count value of the pulse signal output from the detection unit 67 and the time when the toner is new (corresponding to FIG. 4). FIG. 8 is a graph of experimental results showing the relationship between the count value of the pulse signal output from the detection unit 67 and the time when toner deterioration progresses (corresponding to FIG. 5).

  Here, the vertical axis in FIGS. 7 and 8 indicates a count value obtained by counting the pulse signal of the detection unit 67 that changes in accordance with the stirring operation of the stirring unit 63 every reference time (for example, 100 ms). Moreover, the horizontal axis in FIGS. 7 and 8 indicates, for example, the time corresponding to each count value (for example, the time when the count processing of each count value is started). The reference time is set in advance according to the frequency of the detected pulse signal.

  As shown in FIGS. 7 and 8, the maximum value (see FIG. 7) of the count value in the case of the new toner is compared with the maximum value (see FIG. 8) of the count value in the case of the toner having deteriorated. It is getting smaller.

  On the other hand, as in the above characteristics (1) and (2), the minimum value of the period of the pulse signal decreases as the toner deteriorates. When the tip of the stirring blade 63b is disposed at the proximity position NP, the maximum value of the new toner count value (corresponding to FIG. 7) is the maximum value of the count value in the case of the toner having deteriorated (FIG. 8). Is smaller than

  Thus, the experimental results of FIGS. 7 and 8 agree with the above-described characteristics (1) and (2). Therefore, the determination unit 95 can determine the deterioration status of the developer DP by executing the following procedure.

  That is, in this procedure, a plurality of count values are obtained by counting pulse signals that change according to the stirring operation of the stirring unit 63 at each reference time. A count value (hereinafter also referred to as “proximity count value”) counted in a state where the stirring blade 63b is rotated to the vicinity of the proximity position NP is selected from a plurality of count values, and each selected By comparing the proximity count values, the deterioration state of the developer DP is determined.

  For example, when a maximum count value is set as a proximity count value among a plurality of count values for one cycle PD (see FIGS. 4 and 5), the determination unit No. 95 determines that the developer DP has deteriorated. Therefore, the determination unit 95 can determine the deterioration state of the developer DP by a simple comparison process.

  Further, the inner wall 60b of the housing 60a at the facing position FP is inclined with respect to the vertical direction (Z-axis direction), as shown in FIGS. As a result, the developer DP can be prevented from accumulating at the facing position FP. Therefore, it is possible to better judge the deterioration state of the developer DP.

<4. Image formation procedure>
FIG. 9 is a flowchart illustrating an example of a toner replenishment procedure. Here, with reference to FIG. 9, a toner replenishing method according to the deterioration state of the developer DP will be described.

  First, in the proximity position NP where the tip of the stirring blade 63b and the detection unit 67 are close to each other, the determination unit 95 determines whether or not the detected proximity count value is equal to or less than a threshold value (S101). . When it is determined that the proximity count value at the proximity position NP is equal to or less than the threshold value, it is determined that the developer DP has not deteriorated, and this procedure ends without executing toner replenishment.

  On the other hand, when it is determined that the proximity count value at the proximity position NP is larger than the threshold value, it is determined that the developer DP has deteriorated, and steps S102 to S105 are executed. Thereby, new toner is replenished to the housing 60a, and the deterioration state of the toner in the housing 60a is relatively improved.

  That is, in step S102, when it is determined that the toner density is within the allowable range even if new toner is supplied into the housing 60a, the process proceeds to step S105, and the toner is supplied from the supply unit 70 to the developing unit 60. On the other hand, if it is determined in step S102 that the toner density in the housing 60a is outside the allowable range due to the replenishment of new toner, the process proceeds to step S103.

  In step S103, since it is determined that the toner can be replenished because the toner density falls within the allowable range due to a decrease in toner due to future printing, the process proceeds to step S105, and the replenishing unit 70 changes to the developing unit 60. Toner is replenished.

  On the other hand, if it is determined in step S103 that the toner concentration in the housing 60a is out of the allowable range due to the replenishment of new toner even if the toner reduction due to future printing is taken into consideration, the toner from the developing unit 60 is removed. Discharged. Then, the process returns to step S102, and the processes of steps S102 to S105 are repeatedly executed until the toner can be supplied.

  In step S105, when toner is supplied to the developing unit 60, it is determined again whether or not the proximity count value at the proximity position NP is equal to or less than the threshold value (S106). When it is determined that the proximity count value at the proximity position NP is equal to or less than the threshold value, it is determined that the deterioration of the developer DP has been eliminated, and this procedure is terminated. On the other hand, when it is determined that the proximity count value at the proximity position NP is larger than the threshold value, it is determined that the deterioration of the developer DP has not been eliminated, and steps S102 to S105 are further executed.

As described above, when it is determined that the developer DP is deteriorated, the determination unit 95 further determines whether or not to discharge and replenish toner based on the toner concentration in the housing 60a. That is, when the developer DP is deteriorated and the toner density is determined to be within the allowable range even if the toner supply is executed in steps S102 and S103, the determination unit 95 removes the toner from the developing unit 60. The toner can be supplied to the developing unit 60 without being discharged.

  Thereby, the ratio of the old toner in the housing 60a is reduced. Therefore, it is possible to prevent the formation of a toner image recorded on the recording material P due to the deterioration of the developer DP.

  When it is determined that the developer DP has deteriorated and toner cannot be replenished in steps S102 and S103, the determination unit 95 discharges the toner from the development unit 60 and then causes the development unit 60 to discharge the toner. Supply toner.

  As a result, the toner concentration in the housing 60a is within the allowable range or is brought close to the allowable range, and the ratio of the old toner is reduced. Therefore, it is possible to prevent the occurrence of a defective formation of the toner image recorded on the recording material P due to the deterioration of the developer DP.

<5. Advantages of Image Forming Apparatus of Present Embodiment>
As described above, in the image forming apparatus 1 according to the present embodiment, the count value for each reference time varies periodically as the period of the pulse signal changes according to the stirring operation (see FIGS. 7 and 8). . Further, when the developer DP is stirred for a long time in the housing 60a, for example, the problem that the external additive is peeled off from the toner, the problem that the peeled external additive is buried in the carrier, and the stress in the toner itself are caused. There arises a problem that the developer is deteriorated by working.

  As described above, in the image forming apparatus 1 of the present embodiment, the deterioration state of the developer DP is not compared with the toner density but by comparing the count value obtained based on the detection result of the detection unit 67. To be judged. That is, the deterioration state of the developer DP is determined by a count value that can be obtained more simply than the toner concentration.

  Thereby, it is possible to suppress erroneous recognition of the deterioration state of the developer DP, and it is possible to replenish toner at an appropriate timing. For this reason, it is possible to prevent the fluidity of the developer DP from being lowered due to the deterioration of the developer DP (particularly, toner), and to prevent the formation of a toner image recorded on the recording material. Can be prevented.

<6. Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made.

  In the present embodiment, the calculation function of the determination unit 95 has been described as being realized by software by the CPU 93, but is not limited thereto. For example, these functions may be realized by hardware such as an electronic circuit.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Printer part 30 Paper feed part 40 Fixing part 50 Paper discharge part 55 Scanner part 60 (60Y, 60M, 60C, 60K) Developing part 60a Housing 63 Stirring part 63a Rotating shaft 63b Stirring blade 67 Detection part 70 (70Y) , 70M, 70C, 70K) Supply unit 90 Control unit 93 CPU
95 Judgment part FP Opposing position NP Proximity position P Recording material PD One cycle

Claims (6)

A developing unit for storing a developer containing toner and a carrier in a housing and supplying the toner to an image carrier;
A detection unit that is provided facing the housing and detects a density-related value of the toner at the facing position;
A determination unit that determines a deterioration state of the developer based on the density-related value detected by the detection unit;
The developing unit includes a stirring unit that stirs the developer stored in the housing,
The detection unit detects a pulse signal sequentially detected according to the oscillation frequency of the developer as the density-related value at the facing position;
The determination unit obtains a plurality of count values by counting the pulse signals that change according to the stirring operation of the stirring unit for each reference time, and compares each of the plurality of count values. , Determine the deterioration status of the developer,
When it is determined that the developer has deteriorated, it is determined whether or not the toner concentration falls within an allowable range even when new toner is supplied to the housing, and the toner is reduced due to a decrease in the toner due to future printing. Based on the determination that the toner can be replenished because the density is within an allowable range, it is determined whether the developing unit is replenished with new toner or the toner is discharged from the developing unit.
Image forming apparatus. The stirring unit includes a rotating shaft and a stirring blade extending spirally along the extending direction of the rotating shaft,
The determination unit selects, from the plurality of count values, a proximity count value that is counted in a state in which the stirring blade is rotated to the vicinity of a proximity position close to the detection unit, and each selected proximity meter Judging the deterioration status of the developer by comparing numerical values,
The image forming apparatus according to claim 1. The inner wall of the housing at the facing position is inclined,
The image forming apparatus according to claim 2. The determination unit determines a deterioration state of the developer based on a maximum count value among the plurality of count values for one cycle;
The image forming apparatus according to claim 1. A replenishing unit for replenishing toner to the developing unit;
The determination unit determines that the toner concentration falls within the allowable range even when new toner is supplied to the housing, or the toner concentration falls within the allowable range due to a decrease in the toner due to future printing. When it is determined that the toner can be replenished, the toner is replenished by the replenishing unit.
The image forming apparatus according to claim 1. A replenishing unit for replenishing toner to the developing unit;
The determination unit determines that the toner concentration is out of the allowable range even when new toner is supplied to the housing, and the toner concentration is out of the allowable range even if the toner decreases due to future printing. When it is determined that the toner cannot be replenished, the toner is discharged from the developing unit and the toner is replenished to the developing unit.
The image forming apparatus according to claim 1.

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