Patent Grant
10845729
The present invention relates to an image forming apparatus that utilizes an electrophotographic system, such as a printer, a copying machine, a facsimile or a multifunction printer.
Image forming apparatuses that utilize an electrophotographic system include a developing unit that uses a two-component developer including nonmagnetic toner (hereinafter simply referred to as toner) and magnetic carrier (hereinafter simply referred to as carrier) to develop an electrostatic latent image formed on a photosensitive drum into a toner image. For developing units, replenishment control where developer for replenishment, i.e., replenishing developer, is replenished from a replenishment unit based on toner density of developer (that is, ratio of toner with respect to a total amount of developer) in a developing unit is performed to supply toner that is consumed by image development and also to supply and replace carrier. In order to detect the toner density of developer, a permeability sensor, also referred to as an inductance sensor, is provided in the developing unit, as described in Japanese Patent Application Laid-Open Publication No. 2003-295598.
In the permeability sensor described above, magnetic permeability, which changes depending on toner density in the developer, is detected and an electric detection signal is output. However, it is known that the detection signal of the permeability sensor also varies depending on bulk density of developer. That is, even in the cases where the toner density of developer is constant, if the amount of developer in the developing unit increases and the bulk density of developer increases, the detection signal of the permeability sensor also increases, and in that case, estimated value of toner density based on the detection signal will become lower than the actual toner density. In contrast, if the amount of developer in the developing unit decreases and the bulk density of developer drops, the detection signal of the permeability sensor becomes low, and in that case, estimated value of toner density based on the detection signal will be higher than the actual toner density. As described, the detection signal of the permeability sensor varies depending on the amount of developer in the developing unit, and as a result, erroneous detection of toner density may occur. Then, various controls including replenishment control that are performed based on the detection signal acquired by the permeability sensor may not be performed properly.
According to one aspect of the present invention, an image forming apparatus includes: an image bearing member configured to bear an electrostatic latent image formed thereon; and a developing unit configured to develop the electrostatic latent image formed on the image bearing member. The developing unit includes: a container configured to contain developer including nonmagnetic toner and magnetic carrier, a first amount of the developer being sealed in the container in an initial state where the developing unit is not yet used; a developer bearing member configured to bear the developer for applying the toner to the image bearing member; and a discharge portion configured to discharge the developer from the container in a case where the developer contained in the container exceeds a predetermined amount greater than the first amount. The image forming apparatus further includes: a replenishment unit configured to replenish the container with the developer; a permeability sensor configured to output a detection signal correlated with a magnetic permeability of the developer within the container; and a controller configured to control replenishment operation of the replenishment unit depending on the detection signal output from the permeability sensor with reference to a reference signal, and configured to send a control signal to the permeability sensor for adjusting an input-output relationship between the magnetic permeability of the developer in the container and the detection signal output from the permeability sensor. The controller is configured to use, in a state where a second amount of the developer which is greater than the first amount of the developer is contained in the container, a value of the control signal different from a value of the control signal that is used in a state where the first amount of the developer is contained in the container.
According to another aspect of the present invention, an image forming apparatus includes: an image bearing member configured to bear an electrostatic latent image formed thereon; and a developing unit configured to develop the electrostatic latent image formed on the image bearing member. The developing unit includes: a container configured to contain developer including nonmagnetic toner and magnetic carrier, a first amount of the developer being sealed in the container in an initial state where the developing unit is not yet used; a developer bearing member configured to bear the developer for applying the toner to the image bearing member; and a discharge portion configured to discharge the developer from the container in a state where the developer contained in the container exceeds a predetermined amount greater than the first amount. The image forming apparatus further includes: a replenishment unit configured to replenish the container with the developer; a permeability sensor configured to output a detection signal correlated with a magnetic permeability of the developer within the container; and a controller configured to control replenishment operation of the replenishment unit depending on the detection signal output from the permeability sensor with reference to a reference signal. The controller is configured to use, in a state where the first amount of the developer is contained in the container, a value of the reference signal different from a value of the reference signal that is used in a state where a second amount of the developer which is greater than the first amount of the developer is contained in the container.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Exemplary embodiments of the invention will be described below with reference to the attached drawings
A first embodiment will be described. At first, a general configuration of an image forming apparatus according to the present embodiment will be described with reference to
Image Forming Apparatus
An image forming apparatus 100 according to the present embodiment is a tandem-type full-color image forming apparatus adopting an electrophotographic system. The image forming apparatus 100 includes image forming portions PY, PM, PC and PK which respectively form images of yellow, magenta, cyan and black. The image forming apparatus 100 is capable of forming a full-color image on a recording media based on image signals transmitted from a document reader (not shown) connected to an apparatus body 100A or an external device such as a personal computer connected in a communicable manner to the apparatus body 100A. Sheet materials such as paper sheets, plastic films and cloth are examples of the recording media.
The four image forming portions PY through PK in the image forming apparatus 100 have similar configurations, except for the difference in color of developed images. The image forming portion PK for forming black image is described below as an example, and the descriptions of other image forming portions PY, PM and PC will be omitted.
A photosensitive drum 1 serving as an image bearing member is rotatably provided on the image forming portion PK, as illustrated in
An intermediate transfer device 5 is arranged above the respective image forming portions. The intermediate transfer device 5 is configured such that an endless intermediate transfer belt 51 is stretched across a plurality of rollers and moves in the direction of the arrow. The intermediate transfer belt 51 can move bearing a toner image primarily transferred thereto as described later. A secondary transfer outer roller 54 is arranged at a position opposed to a secondary transfer inner roller 53 on which the intermediate transfer belt 51 is stretched, and having the intermediate transfer belt 51 intervened, as illustrated in
A cassette 9 storing recording media is arranged at a lower portion of the image forming apparatus 100. The recording media fed from the cassette 9 is conveyed via a conveyance roller 91 to a registration roller 92. Skewing of the recording media is corrected by having a leading edge of the recording media abut against the registration roller 92 in a stopped state and forming a loop. Thereafter, the registration roller 92 is rotated in synchronization with the toner image on the intermediate transfer belt 51, and the recording media is conveyed to the secondary transfer portion T2.
A process for forming a full color image by the image forming apparatus 100 described above will be described. At first, the surface of the photosensitive drum 1 rotated at a matched timing with the start of the image forming operation is charged uniformly by the charging unit 2. Next, the photosensitive drum 1 is scanned and exposed by a laser beam, corresponding to an image signal, emitted from the exposing unit 3. Thereby, an electrostatic latent image corresponding to the image signal is formed on the photosensitive drum 1 serving as an image bearing member. The electrostatic latent image on the photosensitive drum 1 is developed into a toner image by applying two-component developer (more specifically, by toner) stored in the developing unit 4. In the present embodiment, the developing unit 4 is a replaceable unit attached to the apparatus body 100A. In the new developing unit 4 (i.e., in an initial state where the developing unit is not yet used), a two-component developer of a predetermined amount (initial amount) of developer, is sealed in advance. In the present embodiment, the amount of developer enclosed in advance in the developing unit 4 is approximately 120 g, for example.
The toner image formed on the photosensitive drum 1 is primarily transferred to the intermediate transfer belt 51 at a primary transfer portion T1 formed between the photosensitive drum 1 and the primary transfer roller 52 with the intermediate transfer belt 51 intervened. In this state, primary transfer bias is applied to the primary transfer roller 52. Toner remaining on the photosensitive drum 1 after primary transfer is removed by the cleaning unit 7.
This kind of operation is performed sequentially in the respective image forming portions PY through PK of yellow, magenta, cyan and black, and the toner images of four colors are superposed on the intermediate transfer belt 51. Meanwhile, the recording media stored in the cassette 9 is conveyed to the secondary transfer portion T2 at a matched timing with the formation of toner image. Then, by applying secondary transfer bias to the secondary transfer outer roller 54, the four-color toner image on the intermediate transfer belt 51 is collectively secondarily transferred to the recording media. Toner remaining on the intermediate transfer belt 51 after image has been transferred at the secondary transfer portion T2 is removed by an intermediate transfer belt cleaner 55.
The recording media on which the toner image has been secondarily transferred is conveyed to a fixing unit 6. The fixing unit 6 includes a fixing roller 61 and a pressure roller 62, and the fixing roller 61 together with the pressure roller 62 form a fixing nip portion. It is noted that the fixing roller 61 may be replaced with a film or a belt, and the pressure roller 62 may be replaced with a belt. The recording media is heated and pressed when passing through the fixing nip portion. Thereby, toner on the recording media is melted and mixed, and then fixed on the recording media as a full-color image. Thereafter, the recording media is discharged by a sheet discharge roller 10 onto a discharge tray 11. Thereby, the sequence of image forming processes is completed.
Developing Unit
Next, the developing unit 4 will be described with reference to
The container 41 has an opening portion as a developing area opposed to the photosensitive drum 1, and a developing sleeve 44 is rotatably disposed in the opening portion to be partially exposed. A magnet roll 43 having a plurality of magnetic poles along a circumferential direction and not rotatable is disposed inside the developing sleeve 44. The developing sleeve 44 is formed of a nonmagnetic material, which rotates in the direction of the arrow in
A developing chamber 41a serving as a first chamber and an agitating chamber 41b serving as a second chamber which can store developer are formed in the container 41. The developing chamber 41a together with the agitating chamber 41b constitutes a circulation path through which developer is circulated. The interior of the container 41 is separated by a partition 41c into the developing chamber 41a and the agitating chamber 41b, such that the developing chamber 41a and the agitating chamber 41b are communicated at both ends in the longitudinal direction of the container 41, that is, on right and left sides in
A developing screw 46 and an agitating screw 47 are respectively provided in the developing chamber 41a and the agitating chamber 41b. In further detail, the developing screw 46 is provided in the developing chamber 41a and the agitating screw 47 is provided in the agitating chamber 41b. The developing screw 46 and the agitating screw 47 are screws having a helical blade or fin disposed around the rotation shaft, and the screws are capable of agitating and conveying developer. In the present embodiment, the developer in the developing chamber 41a is agitated and moved toward the left side of
The developer in the developing chamber 41a can be applied to the developing sleeve 44 while being conveyed by the developing screw 46. A predetermined quantity of developer supplied to the developing sleeve 44 is borne on the developing sleeve 44 by magnetic field that is generated by the magnet roll 43 and forms a developer accumulation. By rotation of the developing sleeve 44, the developer attached on the developing sleeve 44 passes the developer accumulation where the layer thickness thereof is regulated by a blade 42, and thereafter, conveyed to the developing area opposed to the photosensitive drum 1. In the developing area, the developer on the developing sleeve 44 rises up and forms a magnetic brush. Then, the magnetic brush is made to contact the photosensitive drum 1 and apply toner of the developer to the photosensitive drum 1, by which the electrostatic latent image formed on the photosensitive drum 1 is developed as toner image. Further, in order to enhance the developing efficiency, that is, application rate of toner to the electrostatic latent image, normally, a developing bias having superposed DC voltage and AC voltage is applied to the developing sleeve 44. The developer on the developing sleeve 44 after having applied toner to the photosensitive drum 1 is returned to the developing chamber 41a by further rotation of the developing sleeve 44. Toner is consumed by such developing process, and developer having lower toner density is transferred from the developing chamber 41a to the agitating chamber 41b. Toner density of developer in a new developing unit 4 in which the initial amount of developer is contained is, for example, 8%.
ACR Control
In the case of the developing unit 4 where image is developed using a two-component developer, in addition to consumption of toner accompanying the development of toner images, carrier deterioration occurs where charging performance to toner is deteriorated. When carrier deterioration proceeds, image defects such as density fluctuation and/or fogging caused by toner scattering tend to occur. Therefore, along with the replenishment of toner, ACR (Auto Carrier Refresh) control is carried out where carrier is replaced and refreshed. During ACR control as replenishment control, replenishing developer in which toner and carrier are mixed at a weight ratio of 9:1, for example, is replenished from a replenishment unit 8.
As illustrated in
Meanwhile, a replenishing portion 49 that receives replenishing developer from the replenishment unit 8 is provided on an upstream side in the conveyance direction of the agitating screw 47 in the agitating chamber 41b. Each replenishment unit 8 (refer to
In response to a detection signal (more specifically, toner density of developer based on the detection signal) of a permeability sensor 45 described later, the control unit 110 (refer to
In the agitating chamber 41b, the replenishing developer replenished to the agitating chamber 41b is agitated while being conveyed by the agitating screw 47 together with the developer transferred from the developing chamber 41a. Excessive developer that has become excessive by replenishment of the replenishing developer is discharged to the exterior of the container 41 through the discharge portion 48. With this operation, deteriorated carrier is discharged, depending on the amount of developer in the developing unit 4. As described, by having replenishing developer replenished from the replenishment unit 8, toner consumed by development is replenished and carrier is replaced.
The above-described ACR control is executed by the control unit 110 described later. The control unit 110 can compute an appropriate amount of replenishment of toner by computing an amount of toner consumption for each sheet of recording media based on density and area of image being formed, and the toner density of developer detected using the permeability sensor 45.
Permeability Sensor
In the present embodiment, the permeability sensor 45 is used to detect the toner density of developer stored in the container 41. The use of the permeability sensor 45 enables to perform ACR control at any time even while forming images, so that effective operation of the image forming apparatus 100 may be realized.
As illustrated in
The permeability sensor 45 according to the present embodiment uses inductance of coil to generate a detection signal correlated with permeability of developer as a variable to be measured. In the permeability sensor 45, the probe head 45a with a cylindrical shape is formed on a plate-like base plate portion 45b and is arranged to protrude from the base plate portion 45b. Coils not shown (including a driving coil, a detecting coil and a reference coil) that generate magnetic field when energized are arranged in the probe head 45a. Meanwhile, although not shown, electronic components other than coils, such as a capacitor, a semiconductor integrated circuit (IC), a resistance and so on, are arranged on the base plate portion 45b, and these electronic components are electrically connected to the coils on the probe head 45a.
That is, the permeability sensor 45 of the present embodiment is a sensor that adopts the principle of a differential transformer using electromagnetic induction. The differential transformer is formed by providing a driving coil, a reference coil and a detecting coil in one core. When a high-frequency (such as 500 kHz) AC voltage is input as control signal (Vin), the permeability sensor 45 emits differential output of detection signal (Vout), which can be denoted as “Vout=V2−V3”. Here, peak voltage value of the reference coil is represented by “V2” and peak voltage value of the detecting coil is represented by “V3”. For example, according to the toner density of developer sealed in the non-used, initial state (which is 8%, for example), it is assumed that the peak voltage values of the detecting coil and the reference coil are “V30” and “V20” respectively in a state where a predetermined control signal is applied. In that case, (by adjusting a ratio of number of turns of the detecting coil and the reference coil, for example) a circuit configuration of V30=V20 can be realized in a state where the toner density is set to the initial value. In this case, defining voltage variation of the detecting coil at an arbitrary toner density as “ΔV3”, a peak voltage value of “Vout=V2−V3=V20−(V30+ΔV3)=−ΔV3” will be output from the permeability sensor 45 in a differential manner as the detection signal.
In the above description, “control signal” of the permeability sensor refers to an arbitrary signal capable of adjusting the level of the detection signal with respect to the permeability of developer near the probe head 45a, i.e., an input-output relationship between the magnetic permeability of developer and the detection signal. In the present embodiment, it is assumed that drive voltage itself for exciting the driving coil is the control signal, and the amplitude thereof is represented by Vin. Instead of the above-described configuration, it is also possible to fix the drive voltage of the driving coil and amplify the output of the differential transformer (ΔV3) to obtain detection signal (Vout) so that the signal designating the amplification ratio is used as control signal. In that case, a configuration can be adopted where a signal line connected to the control unit is provided to the permeability sensor 45 independently of a power line through which power for activating the driving coil is supplied, and where DC voltage as control signal is entered to the signal line.
According to the present embodiment, adjustment is performed in advance so that the peak value of detection signal of the permeability sensor 45 is “2.5 V” in a case where the toner density of the initial amount of developer is 8%, which is referred to as a reference signal. Also, adjustment is performed such that the detection signal varies approximately linearly with respect to the toner density in a case where the toner density is 4% or higher and 12% or lower (more preferably, within a range of 6% or higher and 9% or lower). Conversion of toner density based on the detection signal of the permeability sensor 45 can be performed, for example, by the control unit 110 (refer to
By the way, according to the permeability sensor 45 described above, the detection signal, more specifically, the peak voltage value, can be varied even if the toner density is the same, depending on the level of control signal (Vin) entered to activate the permeability sensor 45. As the control signal, voltage that supplies current having a predetermined waveform is applied from a power supply 450 to the permeability sensor 45 (refer to
According further to the permeability sensor 45 described above, even if the control signal and the toner density of developer are not varied, the detection signal may be changed if a bulk density of developer is varied. The bulk density of developer varies according to the amount of developer in the developing unit 4.
Control Unit
As illustrated in
The control unit 110 according to the present embodiment includes a CPU (Central Processing Unit) 111 and a storage device 112. The storage device 112 includes a ROM (Read Only Memory) 113 and a RAM (Random Access Memory) 114. The ROM 113 stores various programs such as an image forming job and data. The CPU 111 can operate the image forming apparatus 100 by executing the various programs stored in the ROM 113. Further, the RAM 114 stores operation data and input data. The CPU 111 can refer to the data stored in the RAM 114 based on the various programs.
An image forming job is a sequence of operations from the start of forming an image based on an image signal for forming image on a recording media to the completion of the image forming operation. In other words, it is a sequence of operations that starts when a preliminary operation, so-called pre-rotation, that is required for image formation is started, continues during the image forming process and ends when the preliminary operation, so-called post-rotation, that is required to end the image forming process is completed. More specifically, it refers to a period that starts when pre-rotation is started as preparation operation prior to image forming after a printing signal is received, i.e., after an image forming job is entered, and ends after post-rotation as operation performed after image forming is completed, wherein this period includes the image forming period and the interval between sheets.
The developing motor 40, the replenishing motor 82 and the permeability sensor 45 described above are controlled by the control unit 110. In the present embodiment, the control unit 110 controls the drive of the replenishing motor 82 based on the detection signal of the permeability sensor 45, and replenishing developer is replenished by the replenishment unit 8 (refer to
Further, a new/used detector 50 for detecting whether the developing unit 4 (refer to
According to the present embodiment, the amount of developer sealed in a new developing unit 4, i.e., first amount, is approximately 120 g. On the other hand, in a case where the amount of developer becomes equal to or greater than 150 g, i.e., predetermined amount, as a result of replenishment of the replenishing developer by the execution of replenishment control, developer will be discharged from the discharge portion 48. In other words, the initial amount of developer filled in advance in the new developing unit 4 is set to 120 g, which is smaller than 150 g where discharge of developer is started. One reason for adopting such configuration is to prevent developer from being discharged meaninglessly when executing an initializing operation of idly rotating the developing screw 46 and the agitating screw 47 immediately after attaching a new developing unit 4 to the apparatus body 100A so that developer is thoroughly supplied in the container 41. For example, in a new developing unit 4, the communication ports 41f and 41g are sealed by a sealing sticker serving as an example of a sealing member, and developer is enclosed only in the agitating chamber 41b. Further, in the new developing unit 4, the opening portion of a discharge portion 48 is also sealed by a sealing member such as a shutter. When the new developing unit 4 is attached to the apparatus body 100A, the sealing realized by the sealing sticker is released either manually or automatically, and a portion of developer enclosed in the agitating chamber 41b enters the developing chamber 41a. However, developer is not thoroughly supplied across the container 41 in this state, so the developing screw 46 and the agitating screw 47 are rotated idly. In this state, if the initial amount of developer is greater than 120 g, a portion of the developer may go over the return screw 48A and be discharged from the discharge portion 48. If developer is discharged during the initializing operation, non-used developer will be discharged and wasted. Therefore, in order to prevent developer from being discharged wastefully during the initializing operation, the initial amount of developer is set at a relatively low amount to prevent discharge of developer during initializing operation.
According to the present embodiment, developer is discharged from the discharge portion 48 approximately at a point of time when the amount of developer in the developing unit 4 reaches 150 g. But during continuous image formation of solid images, for example, the amount of developer being discharged is small compared to the amount of replenishment of developer being replenished. In that case, the amount of developer in the developing unit 4 may exceed 150 g and reach a maximum of 180 g. This is because the increasing rate of carrier during continuous image formation of solid images is approximately equivalent to the discharging rate of developer when the amount of developer is 180 g. Therefore, the maximum amount of developer in the developing unit 4 is approximately 180 g in the case of the present embodiment.
As described above, in the case of the developing unit 4 adopting the ACR system, the amount of developer in the developing unit 4 may vary by the consumption of toner by image development or replenishment of developer. When the amount of developer is varied, the weight of the developer causes a change in the bulk density of developer, and the detection signal of the permeability sensor 45 may be changed (refer to
This situation is described in further detail with reference to
In consideration of the above problem, the present embodiment enables to obtain substantially the same detection signal (Vout) in cases where the toner density is the same, regardless of fluctuations of the amount of developer. This function is achieved by adjusting the control signal (Vin) entered to the permeability sensor 45, based on the amount of developer in the developing unit 4. In other words, a value of the control signal used in the initial state where a first amount of the developer is contained in the container is different from a value of the control signal used in a state where a second amount of the developer is contained in the container. The second amount is greater than the first amount, and is equal to the predetermined amount where discharge of developer starts, for example. In the present embodiment, the first amount of developer (e.g., 120 g) in the initial state is 80% to the predetermined amount (e.g., 150 g) where discharge of developer is started, but the configuration described later is also effective in a case where the amount of fluctuation is greater, that is, if the first amount is less than 80% of the predetermined amount.
Adjustment Processing
An adjustment processing of the first embodiment will be described according to
As illustrated in
The “initial amount of developer” refers to the amount of developer enclosed in advance in a new developing unit 4. The “amount of replenishing developer having been replenished by the replenishment unit 8” is calculated based on period of rotation of the replenishing screw 81.
The “amount of toner having been consumed by image development” can be computed based on an average image ratio (more specifically, a video count value) of images developed by the developing unit 4. For example, the amount of toner consumed to form an image on one recording media can be computed based on the video count value. During execution of image formation, the video count value can be used to convert into numerical form the amount of toner consumed to form an image on one sheet of recording media S by prescribing the maximum amount of toner used to form an image on the whole area of an A4-size sheet as “1000”. Then, the video count value of “1000” can be converted as the amount of toner consumption of approximately 50 mg, for example.
The “amount of developer having been discharged through the discharge portion 48” can be computed based on a table or the like prescribing the relationship between the amount of developer and the discharge rate of developer, as illustrated in
Now, a specific example of the amount of developer in the developing unit 4 will be described. Here, it is assumed that the amount of developer in the developing unit 4 at a certain timing is 175 g. Then, it is assumed that image forming job is executed, and during image formation, the developing unit 4 performs image forming operation for ten seconds and the replenishing screw 81 is rotated for five seconds. For sake of simplified description, it is assumed that the amount of replenishment of replenishing developer when the replenishing screw 81 is rotated for five seconds is 5 g. As illustrated in
The “information regarding amount of developer in developing unit” is not restricted to the information obtained from the above-described set of information of the initial amount of developer, the amount of replenishing developer having been replenished, the amount of developer having been discharged, and the amount of toner having been consumed by image development. For example, the “information regarding amount of developer in developing unit” may be a result of detection obtained by a weight detection sensor provided in addition to detect weight of the developing unit 4.
Returning to
Vin_adj=Vin −Vin_off Expression 1
As illustrated in
The control unit 110 sends the control signal after adjustment (Vin_adj) to the permeability sensor 45, acquires the detection signal (Vout) acquired in response from the permeability sensor 45 (S4), and compares the same with the reference signal (Vtgt, for example, of 2.5 V) (S5). If the difference between the detection signal and the reference signal is 0 or smaller (S5: No), the control unit 110 ends the present processing without executing the replenishment control by the replenishment unit 8. On the other hand, if the difference between detection signal and reference signal is greater than 0 (S5: Yes), the control unit 110 executes replenishment control of the replenishing developer by the replenishment unit 8 (S6 and S7). Specifically, the control unit 110 determines a replenishment period based on the difference between detection signal and reference signal (S6) and rotates the replenishing screw 81 during the determined replenishment period to replenish the replenishing developer (S7).
It is noted that even if the image forming job is completed, information regarding the amount of replenishing developer having been replenished, the amount of developer having been discharged and the amount of toner having been consumed will not be reset, and the amounts are accumulated and stored in the storage device including the ROM 113. The information is utilized to determine the amount of developer in the subsequent adjustment processing.
As described, according to the present embodiment, the influence of the change in the detection signal of the permeability sensor 45 accompanying the fluctuation of the amount of developer in the developing unit 4 can be attenuated by adjusting the control signal according to the amount of developer in the developing unit 4. That is, although the detection signal of the permeability sensor 45 varies depending on changes in toner density of developer, and also varies depending on fluctuation of the amount of developer in the developing unit 4, effects of the fluctuation of the amount of developer can be reduced. Thereby, even if the detection signal of the permeability sensor 45 has shifted because of the fluctuation of the amount (more specifically because of the fluctuation of the bulk density) of developer in the developing unit 4, advantageously, replenishment control can be executed appropriately based on the detection signal acquired by the permeability sensor 45.
Next, an adjustment processing of a second embodiment will be described according to
As illustrated in
Vtgt_adj=Vtgt+Vtgt_off Expression 2
As illustrated in
The present embodiment differs from the first embodiment in that the control unit 110 enters the control signal without adjustment (Vin) to the permeability sensor 45 and acquires the detection signal (Vout) obtained from the permeability sensor 45 (S4). Thereafter, the control unit 110 compares the acquired detection signal with the reference signal after adjustment (Vtgt_adj) (S13). If the difference between the detection signal and the reference signal after adjustment is 0 or smaller (S13: No), the control unit 110 ends the present processing without executing the replenishment control by the replenishment unit 8. Meanwhile, if the difference between the detection signal and the reference signal after adjustment is greater than 0 (S13: Yes), the control unit 110 executes replenishment control of the replenishing developer by the replenishment unit 8 (S6 and S7).
As described, according to the second embodiment, the influence of the change in the detection signal of the permeability sensor 45 accompanying the fluctuation of the amount of developer in the developing unit 4 can be reduced by adjusting the reference signal, i.e., reference value, according to the fluctuation of the amount of developer in the developing unit 4. In other words, a value of the reference signal used in the initial state where the first amount of the developer is contained in the container is different from a value of the reference signal used in a state where the second amount of the developer is contained in the container. The second amount is greater than the first amount, and is equal to the predetermined amount where discharge of developer starts, for example. Thereby, even if the detection signal of the permeability sensor 45 varies according to the fluctuation of the amount (more specifically the bulk density) of developer in the developing unit 4, advantageously, replenishment control can be executed appropriately based on the detection signal acquired by the permeability sensor 45.
In the case of the developing unit 4 of the embodiment described above, a configuration is adopted where developer is not discharged through the discharge portion 48 from the start of initializing operation until the amount of developer in the developing unit 4 increases from 120 g to 150 g. That is, in a period from the initial state where the initial amount of developer is enclosed to when the amount of developer increases to a predetermined amount and discharge of developer through the discharge portion 48 is started, the amount of discharge of developer is 0. Therefore, before discharge of developer through the discharge portion 48 is started (i.e., before the amount of developer having been replenished by the replenishment unit 8 reaches a third amount), the above-described adjustment processing can be executed based on the initial amount of developer, information regarding the amount of replenishing developer having been replenished by the replenishment unit 8, and information regarding the amount of toner having been consumed by image development, without considering the amount of discharged developer.
An adjustment processing of a third embodiment will be described according to
The control unit 110 acquires an amount of replenishing developer having been replenished (S21). As described above, replenishing developer containing toner and carrier mixed at a weight ratio of 9:1 is replenished from the replenishment unit 8. Therefore, the amount of developer increases from 120 g to 150 g by the forming of images performed after the initializing operation approximately at a point of time when a total of 300 g of replenishing developer has been replenished, which corresponds to 270 g of amount of toner consumption. That is, the third amount of developer is 300 g in the present embodiment. If the amount of replenishment after the initialization operation is 0 or greater and smaller than 300 g (S22: Yes), the control unit 110 determines the control signal offset value based on the amount of developer in the developing unit 4 (S2). However, according to the present embodiment, the control signal offset value is determined based on a table defining the relationship between the amount of replenishing developer having been replenished and the control signal offset value stored in advance in the ROM 113 or the like.
When the amount of replenishing developer having been replenished is 150 g, as illustrated in
Meanwhile, if the amount of replenishment after initializing operation is 300 g or greater (S22: No), the control unit 110 ends the adjustment processing. In that case, the amount of developer becomes 150 g or greater and the discharge of developer from the discharge portion 48 is started, so that the above-described adjustment processing according to the first embodiment should be executed.
After determining the control signal offset value, the control unit 110 determines the control signal after adjustment “Vin_adj” based on expression 1 described above (S3). Then, the control unit 110 enters the control signal after adjustment (Vin_adj) to the permeability sensor 45, acquires the detection signal (Vout) obtained from the permeability sensor 45 (S4), and compares the same with the reference signal (Vtgt, for example, 2.5 V) (S5). If the difference between the detection signal and the reference signal is 0 or below (S5: No), the control unit 110 ends the present processing without executing replenishment control by the replenishment unit 8. On the other hand, if the difference between the detection signal and the reference signal is greater than 0 (S5: Yes), the control unit 110 executes replenishment control of replenishing developer by the replenishment unit 8 (S6 and S7).
As described, according to the present embodiment, by adjusting the control signal (or by changing the reference signal), the influence of the change of detection signals of the permeability sensor 45 accompanying the fluctuation of the amount of developer in the developing unit 4 can be reduced. Thereby, even if the detection signal of the permeability sensor 45 is changed according to the fluctuation of the amount of developer (more specifically, the bulk density of developer) in the developing unit 4, replenishment control can be executed appropriately according to the detection signal acquired from the permeability sensor 45.
According to the first to third embodiments described above, the influence of the change of detection signal of the permeability sensor 45 accompanying the fluctuation of the amount of developer in the developing unit 4 can be reduced by adjusting the control signal or changing the reference signal, by which adjustment control can be executed appropriately, but the present technique is not restricted to these examples. For example, the detection signal of the permeability sensor 45 can be adjusted to correspond to the fluctuation of the amount of developer in the developing unit 4. The adjustment processing of a fourth embodiment of such case will be described according to
As illustrated in
As illustrated in
The present embodiment differs from the first embodiment in that the control signal before adjustment (Mn) is sent from the control unit 110 to the permeability sensor 45 and the detection signal (Vout) acquired in response from the permeability sensor 45 (S4) is obtained. Then, defining the detection signal before adjustment as “Vout” and the detection signal offset value determined based on the amount of developer as “Vout_off”, the control unit 110 adjusts the detection signal (Vout) obtained from the permeability sensor 45 based on the following expression 3 (S32).
Vout_adj=Vout−Vout_off Expression 3
The control unit 110 compares the detection signal after adjustment (Vout_adj) and the reference signal (Vtgt) (S33). If the difference between the detection signal after adjustment and the reference signal is 0 or smaller (S33: No), the control unit 110 ends the present processing without executing replenishment control by the replenishment unit 8. On the other hand, if the difference between the detection signal after adjustment and the reference signal is greater than 0 (S33: Yes), the control unit 110 executes replenishment control of replenishing developer by the replenishment unit 8 (S6 and S7).
As described, according to the present embodiment, the influence of the change of detection signal is reduced by adjusting the detection signal of the permeability sensor 45 that is influenced by the fluctuation of the amount of developer in the developing unit 4. Thereby, even if the detection signal of the permeability sensor 45 is changed according to the fluctuation of the amount of developer (more specifically the bulk density of developer) in the developing unit 4, replenishment control can be executed appropriately based on the detection signal acquired by the permeability sensor 45.
According to the embodiments described above, it is stated that the discharge of developer is started when the amount of developer in the developing unit reaches 150 g or greater, but there may be a case where a small amount of developer discharge, such as 30 mg/min or smaller, occurs due to developer leak even when the amount of developer in the developing unit is smaller than 150 g. Such minute developer leak should not be considered as amount of discharge.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2018-020398, filed on Feb. 7, 2018, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-020398 | Feb 2018 | JP | national |
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| Number | Date | Country | |
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| 20190243280 A1 | Aug 2019 | US |
