Image forming apparatus

Abstract

To improve accuracy of detecting concentration of toner in developer by preventing a toner concentration sensor having a wide detection range from erroneously detecting a conductive material other than the developer in the detection range.SOLUTION: An image forming apparatus 100 performs control of correcting an output value from an inductance sensor 47 with a correction value to calculate toner concentration and supplying developer to a developer container 44 on the basis of the calculated toner concentration, and updates the correction value when drum cartridges 10Y, 10M, 10C, 10Bk are replaced.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus, such as a copying machine or a laser beam printer, that utilizes a dry electrophotographic method. [Background technology]

[0002] Conventionally, a developing device includes a developing sleeve as a rotatable developer carrier that carries a two-component developer containing a non-magnetic toner and a magnetic carrier. In a developing method using a two-component developer, in order to obtain reproducibility of the image density of an output image, it is necessary to stably maintain the weight ratio of the non-magnetic toner in the two-component developer (hereinafter, referred to as "toner concentration") within a narrow range. Conventionally, in such a developing method, in order to maintain the toner concentration of the two-component developer circulating in the developing container within a predetermined range, a sensor for detecting the toner concentration is provided on the wall surface of the developing container, and the amount of developer replenished is adjusted according to the detection result by the sensor.

[0003] A known sensor for detecting the toner concentration of the developer in the developer container is an inductance sensor whose inductance changes according to the ratio of magnetic material in the developer. Such an inductance sensor detects the toner concentration in the developer based on an output value that changes according to the amount of magnetic material present within the detection range.

[0004] Conventional inductance sensors have a configuration in which a coil is wound around an iron core and has a detection part that protrudes from a board, or a configuration in which a coil is pattern-printed directly on a board (for example, Patent Document 1). Inductance sensors in which a coil is pattern-printed directly on a board (hereinafter, referred to as "pattern coil sensors") do not have an iron core in the detection part, and can be produced relatively inexpensively. Since such pattern coil sensors do not have an iron core, magnetic field concentration is less likely to occur, and they have the characteristic of having a wider detection range than sensors with iron cores. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-012078 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in an image forming apparatus equipped with a conventional pattern coil sensor, the detection range of the pattern coil sensor is wide, and therefore there is a problem that conductive objects other than developer, such as metal plates, within the detection range of the pattern coil sensor are erroneously detected.

[0007] An object of the present invention is to provide an image forming apparatus that can improve the detection accuracy of the toner concentration in a developer by preventing the toner concentration sensor, which has a wide detection range, from erroneously detecting conductive objects other than a developer within its detection range. [Means for solving the problem]

[0008] The image forming apparatus according to the present invention is an image forming apparatus that forms an image on a recording medium, and includes an image carrier, a cleaning member that removes toner on the image carrier, an exchangeable cartridge that is detachably mounted in a main body of the image forming apparatus, and a developing device that develops an electrostatic latent image formed on the image carrier to form a toner image on the image carrier, the developing device including a developing container that contains a developer containing non-magnetic toner and a magnetic carrier, a developer carrier that supplies the developer contained in the developing container to the electrostatic latent image on the image carrier, and a detection surface that faces the developing container, The toner concentration sensor detects the toner concentration of the developer based on the magnetic permeability in the developer measured through the detection surface, and has a detection sensitivity of 10% or more when the detection surface is at a position 1 mm away from the magnetic body, assuming that the detection sensitivity is 100% when the detection surface is in contact with the magnetic body; and a control means for calculating the toner concentration by correcting the output value of the toner concentration sensor with a correction value, controlling the replenishment of the developer to the developing container based on the calculated toner concentration, and updating the correction value when the cartridge is replaced. Effect of the Invention

[0009] According to the present invention, it is possible to improve the detection accuracy of the toner concentration in the developer by preventing the toner concentration sensor with a wide detection range from erroneously detecting conductive objects other than the developer within the detection range. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of an image forming apparatus according to a first embodiment of the present invention. [Diagram 2] 1 is a schematic side cross-sectional view of a developing device included in an image forming apparatus according to a first embodiment of the present invention. [Diagram 3] 1 is a schematic cross-sectional plan view of a developing device provided in an image forming apparatus according to a first embodiment of the present invention. [Figure 4] 2 is a schematic diagram of an inductance sensor included in the image forming apparatus according to the first embodiment of the present invention. FIG. [Diagram 5] 5 is a diagram showing the relationship between the output sensitivity of the inductance sensor included in the image forming apparatus according to the first embodiment of the present invention and the distance from the detection surface. FIG. [Figure 6] 2 is a block diagram showing a configuration of a developing device included in the image forming apparatus according to the first embodiment of the present invention. FIG. [Figure 7] 4 is a flowchart showing the operation of the image forming apparatus according to the first embodiment of the present invention. [Figure 8] 4 is a flowchart showing an initialization control process executed by the image forming apparatus according to the first embodiment of the present invention. FIG. [Figure 9] 1 is a schematic diagram of a portion of an image forming apparatus according to a first embodiment of the present invention. [Figure 10] 4 is a flowchart showing a drum unit replacement process executed by the image forming apparatus according to the first embodiment of the present invention. FIG. [Figure 11] FIG. 11 is a flowchart showing a drum unit replacement process executed by an image forming apparatus according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0012] (Embodiment 1) <Configuration of Image Forming Apparatus> The configuration of an image forming apparatus 100 according to the first embodiment of the present invention will be described in detail with reference to FIG.

[0013] The image forming apparatus 100 employs a so-called tandem system and forms an image on a recording medium. Specifically, the image forming apparatus 100 includes exposure devices 3Y, 3M, 3C, and 3Bk, developing devices 4Y, 4M, 4C, and 4Bk, a fixing device 7, and drum cartridges 10Y, 10M, 10C, and 10Bk. The image forming apparatus 100 also includes primary transfer rollers 61Y, 61M, 61C, and 61Bk, an intermediate transfer belt 62, a secondary transfer roller 63, and a secondary outer transfer roller 64.

[0014] The exposure devices 3Y, 3M, 3C, and 3Bk expose the surfaces of the charged photosensitive drums 1Y, 1M, 1C, and 1Bk of the drum cartridges 10Y, 10M, 10C, and 10Bk with a laser, thereby forming electrostatic latent images on the photosensitive drums 1Y, 1M, 1C, and 1Bk.

[0015] The developing devices 4Y, 4M, 4C, and 4Bk form toner images on the photosensitive drums 1Y, 1M, 1C, and 1Bk of the drum cartridges 10Y, 10M, 10C, and 10Bk by applying a developer to the electrostatic latent images formed on the photosensitive drums 1Y, 1M, 1C, and 1Bk of the drum cartridges 10Y, 10M, 10C, and 10Bk. The configurations of the developing devices 4Y, 4M, 4C, and 4Bk will be described in detail later.

[0016] Here, a two-component developer, which is a mixture of a magnetic carrier and a non-magnetic toner, is used as the developer. The developing devices 4Y, 4M, 4C, and 4Bk are supplied with non-magnetic toner. The developing devices 4Y, 4M, 4C, and 4Bk may be configured to be supplied with magnetic carrier together with the non-magnetic toner.

[0017] The fixing device 7 heats and pressurizes the recording medium conveyed from the secondary transfer unit 65 described below, thereby fixing the toner image transferred to the recording medium in the secondary transfer unit 65 to the recording medium. The fixing device 7 conveys the recording medium with the fixed toner image toward a discharge roller (not shown).

[0018] The drum cartridges 10Y, 10M, 10C, and 10Bk are replaceable and detachably mounted in the main body of the image forming apparatus 100, and form toner images of four colors: yellow, magenta, cyan, and black. The drum cartridges 10Y, 10M, 10C, and 10Bk each include photosensitive drums 1Y, 1M, 1C, and 1Bk, chargers 2Y, 2M, 2C, and 2Bk, and cleaners 8Y, 8M, 8C, and 8Bk.

[0019] A toner image is formed on the photosensitive drums 1Y, 1M, 1C, and 1Bk as image carriers by rotating them at a predetermined speed.

[0020] The chargers 2Y, 2M, 2C, and 2Bk uniformly charge the photosensitive drums 1Y, 1M, 1C, and 1Bk.

[0021] Cleaners 8Y, 8M, 8C, and 8Bk as cleaning members remove residual toner remaining on the photosensitive drums 1Y, 1M, 1C, and 1Bk after transfer to the intermediate transfer belt 62 by the primary transfer rollers 61Y, 61M, 61C, and 61Bk from the photosensitive drums 1Y, 1M, 1C, and 1Bk.

[0022] The primary transfer rollers 61Y, 61M, 61C, and 61Bk transfer the toner images formed on the photosensitive drums 1Y, 1M, 1C, and 1Bk onto the intermediate transfer belt 62.

[0023] A plurality of color toner images are transferred onto the intermediate transfer belt 62 in a superimposed manner by primary transfer rollers 61Y, 61M, 61C, and 61Bk.

[0024] The secondary transfer roller 63 and the outer secondary transfer roller 64 come into contact with each other to form a secondary transfer section 65. The secondary transfer section 65 transfers a four-color toner image onto a recording medium conveyed from a paper feed cassette (not shown), and conveys the recording medium onto which the four-color toner image has been transferred to the fixing device 7.

[0025] <Configuration of the developing device> The configuration of the developing devices 4Y, 4M, 4C, and 4Bk according to the first embodiment of the present invention will be described in detail with reference to Figures 2, 3, and 6. In Figure 3, the arrow indicates the direction in which the developer is transported. Since the developing devices 4Y, 4M, 4C, and 4Bk each have the same configuration, the developing devices 4Y, 4M, 4C, and 4Bk will be collectively referred to as the developing device 4.

[0026] The developing device 4 includes a developing sleeve 41, a magnetic field generating section 42, a restricting member 43, a developing container 44, a first screw 45a, a second screw 45b, a first connecting section 46a, and a second connecting section 46b. The developing device 4 also includes an inductance sensor 47, a CPU 51, a ROM 52, a RAM 53, a toner supply motor 54, a developing drive motor 55, and a display section 101.

[0027] The developing sleeve 41 as a developer carrier is non-magnetic, contains a magnetic field generating unit 42, and rotates around the outer periphery of the magnetic field generating unit 42. The developing sleeve 41 supplies the developer contained in a developing container 44 to the electrostatic latent images in the development areas of the photosensitive drums 1Y, 1M, 1C, and 1Bk.

[0028] The magnetic field generating section 42 generates a magnetic field to cause the surface of the developing sleeve 41 to carry the developer.

[0029] The regulating member 43 regulates the height of the magnetic brush formed on the developing sleeve 41 .

[0030] The developing container 44 contains a developer, and includes a developing chamber 44a, an agitating chamber 44b, and a partition wall 44c.

[0031] The developing chamber 44a is provided with a first screw 45a that is rotatable. The developing chamber 44a supplies the developer to the developing sleeve 41.

[0032] A second screw 45b is rotatably provided in the mixing chamber 44b. The mixing chamber 44b and the developing chamber 44a form a circulation path for the developer.

[0033] The partition wall 44c extends vertically from the bottom wall of the developing container 44, and divides the developing container 44 into a developing chamber 44a and an agitating chamber 44b.

[0034] The developer contained in the developing container 44 is a two-component developer made of a mixture of negatively charged non-magnetic toner and magnetic carrier. The non-magnetic toner is made of a resin such as polyester or styrene that contains coloring agents and wax components, and is powdered by pulverization or polymerization. The magnetic carrier is made of a core made of resin particles kneaded with ferrite particles and magnetic powder, and has a resin coating on the surface.

[0035] The first screw 45a is rotated by the driving of the developing drive motor 55, and conveys the developer in the developing chamber 44a while stirring it.

[0036] The second screw 45b is rotated by the driving of the development drive motor 55, and transports the developer supplied to the mixing chamber 44b from a toner bottle (not shown) and the developer in the mixing chamber 44b while stirring them, thereby making the toner concentration uniform.

[0037] The first screw 45a and the second screw 45b transport the developer in opposite directions along the axial direction of the developing sleeve 41. The first screw 45a and the second screw 45b circulate the developer in the developing container 44 via the first connecting portion 46a and the second connecting portion 46b.

[0038] The first communication portion 46a is formed at the left end of the partition wall 44c between the developing chamber 44a and the stirring chamber 44b in FIG. 3, and communicates the developing chamber 44a with the stirring chamber 44b. The first communication portion 46a is an area through which the developer is transferred from the developing chamber 44a to the stirring chamber 44b.

[0039] The second communication portion 46b is formed at the right end of the partition wall 44c between the developing chamber 44a and the stirring chamber 44b in FIG. 3, and communicates the developing chamber 44a with the stirring chamber 44b. The second communication portion 46b is an area that transfers the developer from the stirring chamber 44b to the developing chamber 44a.

[0040] The inductance sensor 47, which serves as a toner concentration sensor, is provided slightly above the bottom surface of the stirring chamber 44b. The inductance sensor 47 has a detection surface S that faces and abuts against the stirring chamber 44b. The inductance sensor 47 is a magnetic permeability sensor that detects the toner concentration of the developer based on the magnetic permeability of the developer measured through the detection surface S. Specifically, the inductance sensor 47 utilizes the inductance of a coil to output a pulse signal corresponding to the magnetic permeability of the developer in the stirring chamber 44b as a detection signal to the CPU 51.

[0041] The contact position of the inductance sensor 47 with respect to the stirring chamber 44b is not limited to a position slightly above the bottom surface of the stirring chamber 44b, but may be the bottom surface of the stirring chamber 44b. The configuration of the inductance sensor 47 will be described in detail later.

[0042] The CPU 51 as a control means reads out and executes a control program stored in the ROM 52 to control the image forming operation while using the RAM 53. The CPU 51 controls the driving of the toner supply motor 54 based on a detection signal input from the inductance sensor 47 and a table stored in the ROM 52.

[0043] The ROM 52 stores a control program and a table in which the output pulse count value corresponds to the toner concentration.

[0044] The RAM 53 is a system work memory for the CPU 51 to operate.

[0045] The toner supply motor 54 operates under the control of the CPU 51 to supply developer from a toner bottle (not shown) to the mixing chamber 44b. The mixing chamber 44b may be supplied with only non-magnetic toner of the developer, not limited to the case where developer is supplied.

[0046] The developing drive motor 55 is driven under the control of the CPU 51 to rotate the first screw 45a and the second screw 45b.

[0047] The display unit 101 displays predetermined information under the control of the CPU 51 .

[0048] In the developing device 4 having the above-described configuration, the developer in the developing chamber 44a, in which the non-magnetic toner has been consumed by the developing process and the toner concentration has decreased, moves into the mixing chamber 44b through the first connecting portion 46a by the conveying forces of the first screw 45a and the second screw 45b.

[0049] <Inductance sensor configuration> The configuration of the inductance sensor 47 of the developing device 4 according to the first embodiment of the present invention will be described in detail with reference to FIG.

[0050] The inductance sensor 47 includes a coil 47a, a coil driving section 47b, an output section 47c, a connector 47d, and a substrate 47e.

[0051] The coil 47a is a wiring pattern formed on a substrate 47e.

[0052] The coil driving unit 47b electrically drives the coil 47a based on a control signal input from the connector 47d. The coil driving unit 47b is configured with a circuit having a capacitor, and configures an LC resonant circuit with the coil 47a that resonates due to the inductance of the coil 47a. The LC resonant circuit configured by the coil 47a and the coil driving unit 47b oscillates with a resonance period corresponding to the magnetic permeability of the developer.

[0053] The output unit 47c is a pulse generating circuit having a comparator that converts an analog signal waveform generated when an LC resonant circuit formed by the coil 47a and the coil driving unit 47b oscillates into a digital signal, and outputs a binarized pulse signal, which is a digital signal, to the connector 47d.

[0054] The connector 47d is connected to the CPU 51. The connector 47d outputs a control signal input from the CPU 51 to the coil driving unit 47b, and outputs to the CPU 51 a pulse signal input from the output unit 47c.

[0055] The substrate 47e has the coil 47a, the coil driving section 47b, and the output section 47c formed thereon, and also has a connector 47d mounted thereon.

[0056] The resonance period of the resonance circuit formed by the coil 47a and the coil driving unit 47b varies depending on the density of the magnetic material present in the vicinity of the coil 47a. Specifically, when the toner concentration of the developer in the vicinity of the coil 47a is low, the ratio of magnetic carriers contained in the developer per unit volume becomes large, the apparent magnetic permeability of the developer becomes high, and the resonance period becomes long. On the other hand, when the toner concentration of the developer is high, the ratio of magnetic carriers contained in the developer per unit volume becomes small, the apparent magnetic permeability of the developer becomes low, and the resonance period becomes short.

[0057] Using the above-mentioned characteristics, the CPU 51 measures the time required to count a predetermined number of pulses of the pulse signal output from the output portion 47c, thereby detecting the toner concentration of the developer in the vicinity of the coil 47a.

[0058] For example, when the toner concentration near the coil 47a is 10[%], the resonance period of the resonance circuit formed by the coil 47a and the coil driving unit 47b is 1000[kHz]. In this case, when the number of pulses to be counted is set to 5000 pulses, the time required to count 5000 pulses is 5000[μsec]. In addition, when the clock used to measure the time required for counting is set to 20[MHz], 5000[μsec] measured with the 20[MHz] clock is measured as 100000[cnt]. In this case, the output pulse count value is 100000[cnt].

[0059] Furthermore, when the toner concentration near the coil 47a is 8[%], the resonance period of the resonance circuit formed by the coil 47a and the coil driving unit 47b becomes longer than that when the toner concentration is 10[%], and becomes 990[kHz]. In this case, when the number of pulses to be counted is set to 5000 pulses, the time required to count 5000 pulses is about 5050[μsec]. Furthermore, when the clock used to measure the time required for counting is set to 20[MHz], 5050[μsec] measured with the 20[MHz] clock is measured as 101000[cnt]. In this case, the output pulse count value becomes 101000[cnt].

[0060] <Distance characteristics of inductance sensors> The distance characteristic of the inductance sensor 47 of the developing device 4 according to the first embodiment of the present invention will be described in detail with reference to FIG.

[0061] 5 shows the output sensitivity as a ratio of the output at each position when the distance between the magnetic plate and the detection surface S is changed to the output of the inductance sensor 47 at the position where the detection surface S of the inductance sensor 47 contacts the magnetic plate, which is a magnetic body. The magnetic plate used was made of ferrite (relative magnetic permeability is about 200) with a diameter of 13 [mm] and a thickness of 1.5 [mm]. In addition, FIG. 5 also shows the output sensitivity of an inductance sensor configured with an iron core provided at the center of the detection coil, as a comparison with the inductance sensor 47 of this embodiment, which is a pattern coil sensor.

[0062] 5, the inductance sensor 47 has a certain degree of output sensitivity up to a distance of about 4 to 5 mm, although the output sensitivity attenuates as the distance from the magnetic plate increases. On the other hand, an inductance sensor using an iron core has an iron core at the center of the coil, so the magnetic field used to detect the magnetic plate is concentrated around the coil. For this reason, the output sensitivity of an inductance sensor using an iron core is approximately 0 at a distance of 1 mm from the magnetic plate.

[0063] When the detection sensitivity of the inductance sensor 47 is 100% in a state where the sensor is in contact with the magnetic plate (a state where the output sensitivity is 1), it is preferable that the sensor has a detection sensitivity of 10% or more (output sensitivity of 0.1 or more) at a position where the detection surface S is 1 mm away from the magnetic plate. As shown in FIG. 5, the output sensitivity of the inductance sensor 47 is 0.3 at a position where the detection surface S is 1 mm away from the magnetic plate, and the detection sensitivity at this time is 30%. Therefore, the detection sensitivity of the inductance sensor 47 at this time is 10% or more.

[0064] On the other hand, an inductance sensor with an iron core provided at the center of a detector coil has an output sensitivity of approximately 0 at a position 1 mm away from the magnetic plate. Therefore, the detection sensitivity of the inductance sensor with an iron core provided at the center of a detector coil in this case is 0%.

[0065] <Operation of the image forming device> The operation of image forming apparatus 100 according to the first embodiment of the present invention will be described in detail with reference to FIG.

[0066] The operation shown in FIG. 7 is started by the CPU 51 reading out and executing a control program stored in the ROM 52.

[0067] First, the CPU 51 starts the developing operation, and starts stirring the developer in the developing device 4 by driving the first screw 45a and the second screw 45b of the developing device 4 (S1).

[0068] Next, the CPU 51 reads out a detection value from the detection signal input from the inductance sensor 47, and calculates an average value of the read out detection values ​​for one period of the second screw 45b as an output pulse count value as an output value. Then, the CPU 51 detects the toner concentration associated with the calculated output pulse count value in a table stored in the ROM 52 (S2).

[0069] Next, the CPU 51 determines the amount of toner to be replenished based on the determined toner concentration (S3). Specifically, the CPU 51 calculates the toner concentration of the developer by correcting the output value of the inductance sensor 47 using the correction value stored in the RAM 53, and determines the amount of toner to be replenished to the developing container 44 based on the calculated toner concentration.

[0070] Next, the CPU 51 outputs a signal to the toner supply motor 54 to instruct the toner supply motor 54 to supply developer, thereby driving the toner supply motor 54 to supply the determined amount of developer from a toner bottle (not shown) to the mixing chamber 44b (S4).

[0071] Next, the CPU 51 performs image formation (S5).

[0072] Next, the CPU 51 determines whether or not the paper is being passed continuously (S6).

[0073] If continuous paper passing is determined (S6: Yes), the CPU 51 returns to the operation of step S1.

[0074] On the other hand, if continuous paper passing is not being performed (S6: No), the CPU 51 stops the operation of the image forming apparatus 100.

[0075] <Initialization control process> In recent years, in order to meet the demand for higher image quality and higher speed, the image forming apparatus 100 is required to detect the toner concentration with higher accuracy. Furthermore, when the inductance sensor 47 is shipped from the factory, the output voltage varies even for the same toner concentration due to individual variations, variations in installation into the developing container 44, variations in the applied control voltage, etc. For this reason, the output voltage of the inductance sensor 47 is initialized by executing an initialization control process described below when the developing device 4 is installed in the device body at the time of initial installation of the image forming apparatus 100 shipped from the factory.

[0076] Specifically, at the time of initial installation, the toner concentration of the developer in the developing device 4 is the same as at the time of shipment from the factory, so the output pulse count value counted based on the co-moving frequency detected by the inductance sensor 47 at the time of initialization is set to Sig_ini.

[0077] The toner concentration during image formation is calculated by dividing the difference between the output pulse count value Cnt_ini, counted based on the resonance frequency detected by the inductance sensor 47, and Sig_ini by the toner concentration sensitivity [% / V]. Here, the toner concentration sensitivity is the rate at which the output value changes in response to a certain change in toner concentration. For example, if the output value changes by 0.25 V when the toner concentration changes by 1%, the toner concentration sensitivity is 0.25 [% / V].

[0078] This allows the inductance sensor 47 to detect the toner concentration with high accuracy regardless of variations in output voltage.

[0079] Next, the initialization control process executed by the image forming apparatus 100 according to the first embodiment of the present invention will be described in detail with reference to FIG.

[0080] 8 is started by starting the initial initialization when the image forming apparatus 100 is initially installed after being shipped from the factory. The developer in the developing container 44 is guaranteed to have the same toner concentration as at the time of initial shipment (10% TD in this embodiment) since no replenishment toner is mixed therein.

[0081] First, the CPU 51 outputs a drive signal to the development drive motor 55 to start idling (idling) the first screw 45a and the second screw 45b of the development device 4, thereby starting the stirring of the developer in the development container 44 (S11). Then, the CPU 51 drives the first screw 45a and the second screw 45b to rotate idling for a predetermined time. This idling is performed by rotating the first screw 45a and the second screw 45b for a predetermined time in a state where an electrostatic latent image is not formed on the photosensitive drum 1. By performing the idling in this manner, the developer in the development container 44 can be stirred, the toner charge amount can be stabilized, and the accuracy of the subsequent processing can be improved.

[0082] Next, the CPU 51 applies an AC electric field to the inductance sensor 47, and obtains a detection signal corresponding to the magnetic permeability of the developer from the inductance sensor 47 (S12).

[0083] Next, the CPU 51 obtains the output pulse count value Sig_ini based on the detection signal obtained by the inductance sensor 47, and records the obtained output pulse count value Sig_ini in the RAM 53 (S13). The output pulse count value Sig_ini recorded in the RAM 53 is used as an initial correction value when calculating the toner concentration based on the detection signal obtained by the inductance sensor 47 thereafter.

[0084] Next, the CPU 51 stops outputting the drive signal to the development drive motor 55 to stop the idling drive of the first screw 45a and the second screw 45b of the development device 4, thereby stopping the stirring of the developer in the development container 44 (S14).

[0085] Then, the CPU 51 ends the initialization control process and transitions to a state where normal image formation is possible.

[0086] At this time, CPU 51 controls display unit 101 to display the fact that the initialization control process has been completed. An operator such as a serviceman can recognize that the initialization control process has been completed by looking at the display on display unit 101. Note that the fact that the initialization control process has been completed may not only be displayed on display unit 101, but may also be displayed on an external terminal such as a personal computer (not shown) connected to image forming apparatus 100.

[0087] <Influence of adjacent drum cartridges> The influence of the adjacent drum cartridges 10Y, 10M, 10C, and 10Bk in the image forming apparatus 100 according to the first embodiment of the present invention will be described in detail with reference to FIG.

[0088] Since the drum cartridges 10Y, 10M, 10C, and 10Bk each have the same configuration, the drum cartridges 10Y, 10M, 10C, and 10Bk will be collectively described as the drum cartridge 10. Since the photosensitive drums 1Y, 1M, 1C, and 1Bk each have the same configuration, the photosensitive drums 1Y, 1M, 1C, and 1Bk will be collectively described as the photosensitive drum 1. Furthermore, since the cleaners 8Y, 8M, 8C, and 8Bk each have the same configuration, the cleaners 8Y, 8M, 8C, and 8Bk will be collectively described as the cleaner 8.

[0089] Here, the cleaner 8 includes a cleaning blade support member 8a that supports the cleaning blade 8b, and the cleaning blade 8b that comes into contact with the photosensitive drum 1 to remove residual toner remaining on the photosensitive drum 1. The cleaning blade support member 8a is conductive, and the cleaning blade 8b is made of resin or rubber such as urethane rubber. The cleaning blade support member 8a is bent toward the downstream side in the rotation direction of the intermediate transfer belt 62 (the right side in FIG. 9) so that it can be attached inside the drum cartridge 10.

[0090] In a tandem type image forming apparatus 100, adjacent developing devices 4 and drum cartridges 10 are arranged with as little space between them as possible in order to reduce the size of the main body of the apparatus. As a result, the inductance sensor 47 of one adjacent developing device 4 and the cleaning blade support member 8a in the other adjacent drum cartridge 10 are in close proximity to each other as shown in FIG.

[0091] The inductance sensor 47 generates a magnetic field from both sides of the coil 47a in response to energization, and therefore generates a magnetic field not only inside the developing container 44 but also on the cleaning blade supporting member 8a side. Therefore, the inductance sensor 47 is more susceptible to the magnetic influence of the cleaning blade supporting member 8a as the gap between the adjacent developing device 4 and drum cartridge 10 becomes narrower.

[0092] When a new drum cartridge 10 is installed in the image forming apparatus 100 due to replacement of the drum cartridge 10 or the like, the magnetic influence of the cleaning blade support member 8a on the inductance sensor 47 changes. For example, the magnetic influence of the cleaning blade support member 8a on the inductance sensor 47 changes depending on the mounting orientation of the cleaning blade support member 8a in the drum cartridge 10. In addition, the magnetic influence of the cleaning blade support member 8a on the inductance sensor 47 changes depending on the change in the relative position between the drum cartridge 10 and the inductance sensor 47.

[0093] In this case, the output value of the inductance sensor 47 changes, so that the toner concentration in the developing container 44 may be erroneously detected.

[0094] In response to this, the CPU 51 can accurately calculate the toner concentration by executing the drum unit replacement process shown in FIG.

[0095] <Drum unit replacement process> The drum unit replacement process executed by image forming apparatus 100 according to the first embodiment of the present invention will be described in detail with reference to Fig. 10. In Fig. 10, drum cartridge 10 will be referred to as Dr cartridge.

[0096] First, during normal image formation, the CPU 51 obtains a detection signal corresponding to the magnetic permeability of the developer from the inductance sensor 47 (S21).

[0097] Next, the CPU 51 obtains an output pulse count value Cnt_A based on the detection signal obtained from the inductance sensor 47, and stores the obtained output pulse count value Cnt_A in the RAM 53 (S22). At this time, the CPU 51 updates the output pulse count value Cnt_A stored in the RAM 53 every time the output pulse count value Cnt_A is obtained.

[0098] Next, the CPU 51 determines whether the drum cartridge 10 has been replaced (S23).

[0099] If the drum cartridge 10 has not been replaced (step S23: NO), the CPU 51 returns the process to step S21.

[0100] On the other hand, if the drum cartridge 10 has been replaced (step S23: YES), the CPU 51 outputs a drive signal to the developing drive motor 55 to drive the developing device 4 for a predetermined time (S24).

[0101] Next, the CPU 51 acquires a detection signal corresponding to the magnetic permeability of the developer from the inductance sensor 47, and obtains an output pulse count value Cnt_B based on the acquired detection signal (S25).

[0102] Next, the CPU 51 reads out the output pulse count value Cnt_A before the replacement of the drum cartridge 10 from the RAM 53, and compares the read out output pulse count value Cnt_A with the output pulse count value Cnt_B. Then, the CPU 51 determines whether the difference ΔCnt between Cnt_A and Cnt_B is equal to or greater than a predetermined value (S26).

[0103] If the difference ΔCnt is less than the predetermined value (step S26: NO), the CPU 51 ends the drum unit replacement process.

[0104] On the other hand, if the difference ΔCnt is equal to or greater than the predetermined value (step S26: YES), the CPU 51 calculates Sig_Cnt'=Sig_Cnt+ΔCnt, updates the correction value Sig_Cnt stored in the RAM 53 (S27), and then ends the drum unit replacement process. By updating the correction value Sig_Cnt, it is possible to reduce the effect of the difference ΔCnt on the output pulse count value counted next time and thereafter.

[0105] Here, Sig_Cnt is an output pulse count value as a correction value, and the initial value is the same value as Sig_ini (Sig_Cnt=Sig_ini). Sig_Cnt is updated sequentially by the process of step S27. Sig_Cnt′ is the updated Sig_Cnt.

[0106] In this way, in the image forming apparatus 100 using the inductance sensor 47 with a wide detection range, even if the position of the cleaning blade support member 8a fluctuates due to replacement of the drum cartridge 10, etc., the inductance sensor 47 can perform detection with high accuracy.

[0107] In this embodiment, the output value of inductance sensor 47 is corrected with a correction value to calculate the toner concentration, and the developer is replenished to developer container 44 based on the calculated toner concentration, and the correction value is updated when replacing drum cartridge 10. This prevents erroneous detection of metal objects other than developer within the detection range of inductance sensor 47, which has a wide detection range, and improves the detection accuracy of the toner concentration in developer.

[0108] (Embodiment 2) The configuration of the image forming apparatus according to the second embodiment of the present invention is the same as that of the image forming apparatus 100, and therefore the description thereof will be omitted. Also, the operation of the image forming apparatus according to this embodiment is the same as that shown in Fig. 7, and therefore the description thereof will be omitted. Furthermore, the initialization control process executed by the image forming apparatus according to this embodiment is the same as that shown in Fig. 8, and therefore the description thereof will be omitted.

[0109] <Drum unit replacement process> The drum unit replacement process executed by the image forming apparatus according to the second embodiment of the present invention will be described in detail with reference to Fig. 11. In Fig. 11, the drum cartridge 10 will be referred to as Dr cartridge.

[0110] In the drum unit replacement process shown in Fig. 10, only one output pulse count value before replacement of the drum cartridge 10 is stored. In contrast, in this embodiment, multiple output pulse count values ​​of the inductance sensor 47 during image formation are recorded, and the average value (Cnt_Mean) of the multiple recorded output pulse count values ​​and the standard deviation (Cnt_SD) of the average value are calculated. Then, if the difference (ΔCNT) between the output pulse count value after replacement of the drum cartridge 10 and the average value (Cnt_Mean) is equal to or greater than the standard deviation (Cnt_SD), the correction value (Sig_Cnt) is updated.

[0111] First, during normal image formation, the CPU 51 obtains a detection signal corresponding to the magnetic permeability of the developer from the inductance sensor 47 for each passing of paper (S31).

[0112] Next, the CPU 51 obtains the output pulse count value Cnt_0 based on the detection signal obtained from the inductance sensor 47, and stores a plurality of the obtained output pulse count values ​​Cnt_0 in the RAM 53 (S32). At this time, the CPU 51 overwrites and updates the output pulse count value that was stored earliest among the plurality of output pulse count values ​​Cnt_0 stored in the RAM 53. Here, the number of output pulse count values ​​Cnt_0 stored in the RAM 53 is exemplified as 10.

[0113] Next, the CPU 51 determines whether or not the drum cartridge 10 has been replaced (S33).

[0114] If the drum cartridge 10 has not been replaced (step S33: NO), the CPU 51 returns the process to step S31.

[0115] On the other hand, if the drum cartridge 10 has been replaced (step S33: YES), the CPU 51 outputs a drive signal to the developing drive motor 55 to drive the developing device 4 for a predetermined time (S34).

[0116] Next, the CPU 51 acquires a detection signal corresponding to the magnetic permeability of the developer from the inductance sensor 47, and obtains an output pulse count value Cnt_A based on the acquired detection signal (S35).

[0117] Next, the CPU 51 reads out the multiple output pulse count values ​​Cnt_0 before replacement of the drum cartridge 10, which are stored in the RAM 53. Then, the CPU 51 calculates the average value (Cnt_Mean) of the multiple read output pulse count values ​​Cnt_0 and the standard deviation (Cnt_SD) of the average value (Cnt_Mean) (S36).

[0118] Next, the CPU 51 determines whether the difference ΔCNT between the output pulse count value Cnt_A after replacement of the drum cartridge 10 and the average value Cnt_Mean is equal to or larger than the standard deviation (Cnt_SD) (S37).

[0119] If the difference ΔCNT is less than the standard deviation (Cnt_SD) (step S37: NO), the CPU 51 ends the drum unit replacement process without updating the correction value Sig_Cnt since the variation in the toner concentration of the developer in the developing container 44 is within the allowable range.

[0120] On the other hand, if the difference ΔCNT is equal to or greater than the standard deviation (Cnt_SD) (step S37: YES), the CPU 51 calculates Sig_Cnt'=Sig_Cnt+ΔCNT and updates the correction value Sig_Cnt stored in the RAM 53 (S38). Then, the CPU 51 ends the drum unit replacement process.

[0121] In this way, even if there are areas in the developing container 44 where the toner concentration is locally high due to a toner supply operation or the like being performed immediately before replacing the drum cartridge 10, the detection accuracy by the inductance sensor 47 can be improved.

[0122] In this embodiment, the correction value Sig_Cnt may be updated when the difference ΔCNT between the output pulse count value Cnt_A after replacing the drum cartridge 10 and the average value Cnt_Mean is equal to or greater than a predetermined value. In this case, the amount of calculation can be reduced compared to when the standard deviation (Cnt_SD) is calculated, and therefore the processing speed of the drum unit replacement process can be increased.

[0123] The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit and scope of the present invention.

[0124] Specifically, in the above-described first and second embodiments, it is possible to reduce not only the magnetic influence caused by the cleaning blade support member 8a but also the magnetic influence caused by a conductive object arranged in the vicinity of the inductance sensor 47 inside the drum cartridge 10. An example of a conductive object other than the cleaning blade support member 8a that has a magnetic influence on the inductance sensor 47 is a transport member that transports the developer collected by the cleaners 8Y, 8M, 8C, and 8Bk.

[0125] In the above-described first and second embodiments, the inductance sensor 47 is magnetically influenced by the cleaning blade support member 8a, but the present invention is not limited to this. The inductance sensor 47 is also magnetically influenced by the supporting metal plate 48 disposed below the developing device 4. The magnetic influence of the supporting metal plate 48 on the inductance sensor 47 changes when the relative position between the developing device 4 and the supporting metal plate 48 changes. In this case, for example, the CPU 51 updates the correction value Sig_Cnt when the relative position between the developing device 4 and the supporting metal plate 48 changes due to replacement of the developing device 4 or the like, and when the difference between the output pulse count values ​​before and after the change in the relative position is equal to or greater than a predetermined value.

[0126] The disclosure of this embodiment includes the following configuration.

[0127] (Configuration 1) An image forming apparatus for forming an image on a recording medium, the image forming apparatus comprising: an image carrier; a cleaning member for removing toner from the image carrier; an exchangeable cartridge that is detachably mounted in an apparatus body of the image forming apparatus; and a developing device that develops an electrostatic latent image formed on the image carrier to form a toner image on the image carrier, the developing device comprising a developing container that contains a developer containing a non-magnetic toner and a magnetic carrier; a developer carrier that supplies the developer contained in the developing container to the electrostatic latent image on the image carrier; and a detection surface that faces the developing container, and a measuring device that measures the amount of toner through the detection surface. an image forming apparatus comprising: a toner concentration sensor that detects a toner concentration of the developer based on a magnetic permeability in the developer determined by the magnetic permeability sensor, and has a detection sensitivity of 10% or more when the detection surface is 1 mm away from the magnetic body, assuming that the detection sensitivity is 100% when the detection surface is in contact with the magnetic body; and a control means that calculates the toner concentration by correcting an output value of the toner concentration sensor with a correction value, controls the replenishment of the developer to the developing container based on the calculated toner concentration, and updates the correction value when the cartridge is replaced.

[0128] (Configuration 2) The image forming apparatus according to configuration 1, characterized in that the control means updates the correction value when a difference between the output value before replacement of the cartridge and the output value after replacement of the cartridge is equal to or greater than a predetermined value.

[0129] (Configuration 3) The image forming apparatus according to configuration 1, characterized in that the control means updates the correction value when a difference between the average value of the output value before replacement of the cartridge and the output value after replacement of the cartridge is equal to or greater than a predetermined value.

[0130] (Configuration 4) The image forming apparatus according to configuration 1, characterized in that the control means updates the correction value when a difference between an average value of the output value before replacement of the cartridge and the output value after replacement of the cartridge is equal to or greater than a standard deviation of the average value.

[0131] (Configuration 5) 5. The image forming apparatus according to claim 1, wherein the control unit sets the output value at the time when the developing device is installed in the apparatus main body as the initial correction value.

[0132] (Configuration 6) 6. The image forming apparatus according to claim 1, wherein the control unit calculates the toner concentration based on a difference between the output value and the correction value during image formation. [Explanation of symbols]

[0133] 1 Photosensitive drum 1Y Photosensitive drum 1M Photosensitive drum 1C Photosensitive drum 1Bk Photosensitive drum 4. Developing device 4Y developing device 4M developing device 4C developing device 8. Cleaner 8a cleaning blade support member 8b Cleaning blade 8Y Cleaner 8M Cleaner 8C Cleaner 8Bk Cleaner 10 Drum Cartridge 10Y drum cartridge 10M drum cartridge 10C Drum Cartridge 10Bk drum cartridge 41 Developing sleeve 44 Developer container 44a Developing Room 44b Mixing chamber 44c Bulkhead 45a First screw 45b Second screw 47 Inductance Sensor 47a Coil 47b Coil driver 47c Output section 47d Connector 47e Board 48 Support metal plate 51 CPU 54 Toner supply motor 55 Development drive motor 100 Image forming device 101 Display section

Claims

1. An image forming apparatus, a replaceable cartridge that includes an image carrier and a cleaning member that removes toner from the image carrier, and that is detachably mounted in the image forming apparatus; a developer carrying a developer containing toner and a carrier for developing an electrostatic latent image formed on the image carrier; a developer container containing the developer; a transport screw for transporting the developer contained in the developer container; and an inductance sensor having a detection unit for detecting magnetic permeability of the developer contained in the developer container, wherein the inductance sensor has an output sensitivity that satisfies B / A≧0.1, where A is an output value when the detection unit detects the magnetic permeability of a predetermined magnetic body in a state where the inductance sensor is not attached to the developer container and a predetermined magnetic body is placed at a position where it contacts the detection unit, and B is an output value when the detection unit detects the magnetic permeability of the predetermined magnetic body in a state where the inductance sensor is not attached to the developer container and the predetermined magnetic body is placed at a position 1 mm away from the detection unit in a vertical direction passing through the detection unit; a driving unit that is driven to replenish the developer to the developing container; a control unit that controls the drive unit based on an output value of the inductance sensor before the cartridge is replaced with a new one for the image forming apparatus, an output value of the inductance sensor after the cartridge is replaced with a new one for the image forming apparatus, and the magnetic permeability of the developer detected by the detection unit; An image forming apparatus comprising:

2. The control unit When a difference between an output value of the inductance sensor before replacing the cartridge in the image forming apparatus and an output value of the inductance sensor after replacing the cartridge in the image forming apparatus is equal to or greater than a predetermined value, controlling the driving unit based on an output value of the inductance sensor before replacing the cartridge with respect to the image forming apparatus, an output value of the inductance sensor after replacing the cartridge with respect to the image forming apparatus, and the magnetic permeability of the developer detected by the detection unit; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. The control unit When a difference between an average value of the output value of the inductance sensor before replacing the cartridge in the image forming apparatus and an output value of the inductance sensor after replacing the cartridge in the image forming apparatus is equal to or greater than a predetermined value, controlling the driving unit based on an output value of the inductance sensor before replacing the cartridge with respect to the image forming apparatus, an output value of the inductance sensor after replacing the cartridge with respect to the image forming apparatus, and the magnetic permeability of the developer detected by the detection unit; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

4. The control unit When a difference between an average value of the output value of the inductance sensor before replacing the cartridge in the image forming apparatus and an output value of the inductance sensor after replacing the cartridge in the image forming apparatus is equal to or greater than a standard deviation of the average value, controlling the driving unit based on an output value of the inductance sensor before replacing the cartridge with respect to the image forming apparatus, an output value of the inductance sensor after replacing the cartridge with respect to the image forming apparatus, and the magnetic permeability of the developer detected by the detection unit; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

5. The inductance sensor further has an output unit that outputs a pulse signal corresponding to the magnetic permeability detected by the detection unit.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

6. The inductance sensor further comprises a substrate; The detection unit is an area on the substrate where a coil is formed by a pattern.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

Images