JP4273892B2 - Toner concentration detection apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a technique for detecting toner density in a developing device in an image forming apparatus.

  2. Description of the Related Art A two-component development method in which development is performed using a two-component developer containing toner and carrier (magnetic powder) has become widespread. As a method widely used in electrophotographic apparatuses incorporating a developing device adopting a two-component developing method, by a developer conveying means such as an auger provided with a spirally provided blade around a rotationally driven rotating shaft A toner concentration sensor is arranged in the vicinity of the path through which the developer is transported, and the toner density is detected by causing the sensor to measure the magnetic permeability of the developer in the sensor facing portion, and the developing device is replenished. There is a method of adjusting the amount of toner (hereinafter referred to as replenished toner amount) based on the detected toner density.

  In this method, the toner density of the developer at the sensor facing portion is detected based on the change in the magnetic permeability of the developer (that is, the output signal waveform of the toner density sensor). Not only changes depending on the amount and density of the developer. The timing at which the amount and density of the developer at the sensor facing portion change greatly includes immediately after the start of driving of the developer conveying means. Immediately after the start of driving of the developer conveying means, the amount and density of the developer at the sensor facing portion are determined based on the internal state of the developing device while the developer conveying means is stopped or the development that may occur at the initial operation of the developer conveying means. It can vary greatly depending on the presence and scale of the drug collapse. The internal state of the developing device that may affect the amount and density of the developer at the toner density sensor facing portion includes, for example, the positional relationship between the stopped auger blades and the sensor facing portion, and the developer conveyance The internal environment (for example, humidity) of the developing device when the developer is left without being conveyed and the developer is left without being conveyed is exemplified.

  Immediately after the start of driving of the developer conveying means, the amount and density of the developer at the sensor facing portion are not stabilized due to the above-mentioned circumstances, and this causes the output signal of the toner density sensor to change greatly, and the accurate toner density is set. It cannot be detected. Under such circumstances, if the replenishment toner amount is adjusted based on the output signal of the toner density sensor, an inappropriate adjustment is performed. In order to avoid this problem, the use of the output signal of the toner density sensor for adjustment of the replenishment toner amount is started not after the start of driving of the developer conveying means but when a predetermined delay time has elapsed from this point. Can be considered. The effectiveness of this method is described below.

  FIG. 11 is a diagram illustrating an example of a change in the output signal (voltage signal) of the toner density sensor accompanying the start of driving of the developer conveying unit. In this figure, the horizontal axis indicates the elapsed time from a certain point in time, the vertical axis indicates the voltage value of the output signal of the toner density sensor, and the plotted circular points indicate the actual value of the output voltage of the toner density sensor. When the developer conveying means starts to be driven at a time point of 4800 ms, the actual measurement value periodically fluctuates in a short time unit, but rapidly decreases and stabilizes in the vicinity of 6200 ms in a long time unit.

  Periodic fluctuations in short time units are fluctuations depending on the principle that the developer is conveyed. For example, in the case of an auger, the developer is pushed and conveyed by a spiral blade that is rotationally driven, so the amount of developer at the sensor facing portion is periodically changed according to the positional relationship between the blade and the sensor facing portion. fluctuate. The influence of such periodic fluctuations is eliminated by specifying a predetermined number of higher-order measured values from a plurality of measured values obtained within a period of one cycle or more, and obtaining the average value of the specified measured values. The The square points plotted in the figure show the average values thus obtained.

  When these average values are connected by a straight line or a curve, it can be seen that the output signal of the toner density sensor is stabilized after a time of about 1.4 s has elapsed since the start of driving of the developer conveying means. Therefore, the above average value is not calculated (that is, the toner concentration is not detected) until 1.4 s has elapsed from the start of driving of the developer conveying means, and is output from the toner concentration sensor after the lapse of 1.4 s. The average value may be calculated using a signal. In the figure, the output signal of the toner density sensor is not completely stable after 1.4 s, but the degree of instability does not adversely affect the adjustment of the replenishment toner amount. The above can be said to be sufficiently stable even after 1.4 seconds.

By the way, if the driving time of the developer conveying means is unnecessarily long, useless stress is applied to the developer, and the developer deteriorates wastefully. For this reason, the developer conveying means is driven for a time required for development. As shown in Table 1, the time required for development depends on parameters such as the sheet conveyance speed of the image forming apparatus, the sheet size, the number of output sheets, and the sheet thickness. Note that the paper thickness is related to the time required for development because the paper transport speed is reduced when thick paper is used. It can be said that it depends only on the size and the number of output sheets. Looking at the specific examples in Table 1, for example, the paper transport speed for plain paper is 220 mm / s, and the pre-paper drive time from the start of driving of the developer transport means until the top of the paper arrives at a predetermined position is 0. 150 s, the sheet conveyance path when the sheet trailing drive time from when the trailing edge of the sheet passes a predetermined position until the end of driving of the developer conveying unit is 0.094 s, and a plurality of sheets are continuously output Drive time when only one postcard-sized plain paper having a length of 139.7 mm in the paper transport direction is output in an image forming apparatus having a paper length margin of 30 mm, which is a distance secured between the papers in FIG. Is {(139.7 + 30) * 1} /220+0.150+0.094≈1.015 s, and two continuous A4-size plain paper sheets with a length of 210 mm in the paper transport direction are output continuously. Total drive time of the case that is {(210 + 30) * 2} /220+0.150+0.094≒2.426s. Thus, the time required for development varies depending on the above parameters.

  In the image forming apparatus shown in Table 1, when the thickness of the paper to be used changes, the driving speed of the developer conveying means (for example, the rotational speed of the auger) also changes. This is because the driving speed of the developer transport means (for example, the rotational speed of the auger) is decreased in accordance with the decrease in the paper transport speed when using thick paper. On the contrary, as long as the thickness of the sheet does not change, the output stabilization time from the start of driving of the developer conveying means to the stabilization of the output signal of the toner density sensor is constant. For example, the output stabilization time for plain paper is 1.400 s. In addition, the image forming apparatus detects the toner density using an output signal for three cycles from the toner density sensor. That is, an operation for obtaining an output signal for three cycles (hereinafter referred to as a toner concentration measurement set) is performed in order to detect the toner concentration once. The measurement one set time, which is the time required for one toner density measurement set, is 0.441 s when the paper is plain paper. That is, when the paper is plain paper, the driving time required for stable measurement necessary for detecting an accurate toner density is 1.400 s + 0.441 s = 1.841 s.

  The total drive time when two sheets of A4-size plain paper are continuously output is 2.426 s, which is longer than the drive time required for stable measurement (1.841 s) when the paper is plain paper. Therefore, the drive margin time obtained by subtracting the latter from the former becomes a positive value (0.585 s). That is, one or more toner density measurement sets can be performed while the developer conveying means is being driven. On the other hand, the total drive time when only one postcard-sized plain paper is output is 1.015 s, which is shorter than the drive time required for stable measurement when the paper is plain paper. 0.826 s). That is, it is not possible to carry out one toner density measurement set while the developer conveying means is being driven.

  In view of the circumstances described above, Patent Literature 1 describes two techniques. The first technique is a technique for controlling the delay time from the start of driving of the developer conveying means to the start of using the output signal from the toner density sensor for detecting the toner density in accordance with the developer deterioration time. The second technique is a technique for determining whether or not the amount or density of the developer is stable based on an output signal from the toner density sensor, and extending the driving time of the developer conveying means according to the determination result. It is.

  In the first technique, the delay time becomes longer when the developer deteriorates. However, as shown in Table 1, when the driving time of the developer conveying means is short, the toner density can be detected within the driving time. There is a risk of disappearing. In the second technique, it is necessary to compare the toner density detection result with the previous detection result in order to determine whether the amount and density of the developer are stable. For this comparison, a plurality of detections are required. However, when the driving time of the developer conveying means is short, such detection itself becomes difficult.

Japanese Patent Laid-Open No. 2004-228688 considers that the output value of the toner density sensor becomes unstable immediately after the start of driving of the developer conveying means, and the output value is a parameter such as the delay time, the paper size, and the number of output sheets. A technique for correcting the toner density and using it for detecting the toner density is described. In this technique, when the driving time of the developer conveying unit is shorter than the delay time, there is a possibility that the output value of the toner density sensor cannot be obtained within the driving time. Of course, if the delay time is extremely shortened and the output value of the toner density sensor is obtained immediately after the developer conveying means is driven, this problem can be avoided, but a sufficient delay time cannot be secured. The output value obtained is very unstable. Even if such an unstable output value is corrected using the above parameters, it cannot be corrected completely. In addition, it is conceivable to predict the behavior of the output value of the toner density sensor immediately after the start of driving of the developer conveying means, and to increase the accuracy of the correction, but the behavior of the output value of the toner density sensor immediately after the start of driving is It varies greatly depending on the time during which the developer conveying means has been stopped, the toner concentration, the stop position of the developer conveying means (positional relationship between the blade and the toner concentration sensor at the time of stopping), the environment such as temperature and humidity. Therefore, the prediction is difficult.
JP-A-10-307434 JP 7-20712 A

  An object of the present invention is to provide a technique capable of detecting the toner concentration more accurately and stably and suppressing the stress applied to the developer.

The present invention is provided with a toner concentration sensor for measuring the magnetic permeability inside the developing device, and for accurately detecting the toner concentration from the start of driving of the conveying means for conveying the developer including toner and carrier inside the developing device. In the toner concentration detection device that detects the toner concentration in the developing device using a value measured by the toner concentration sensor within a period from when the secured delay time has elapsed until the end of driving, the driving of the conveying unit A determination unit for determining whether or not the detection of the toner density can be completed before the driving of the driving conveyance unit is completed, and a case where the completion determination unit determines that the detection is not possible In addition, the present invention provides a toner density detecting device having an extending means for extending the driving time of the conveying means during driving.
According to this toner concentration detection device, when the detection of the toner density cannot be completed before the driving of the driving conveyance unit is completed, the driving time of the driving conveyance unit is extended.

The present invention also includes a toner concentration sensor for measuring the magnetic permeability inside the developing device, and accurately detects the toner concentration from the start of driving of the conveying means for conveying the developer including toner and carrier inside the developing device. In the toner concentration detection device for detecting the toner concentration in the developing device using a value measured by the toner concentration sensor within a period from when a delay time ensured for elapse of time to the end of driving, the conveying means During the driving of the toner, the completion determination means for determining whether or not the detection of the toner density can be completed before the driving of the driving means being driven is completed, and the completion determination means determines that the detection is impossible. The toner density detecting device having the shortening means for shortening the delay time when the transport means is driven next time is provided.
According to this toner density detection device, when the detection of the toner density cannot be completed by the end of the driving of the driving conveyance means, the delay time at the next driving of the conveyance means is shortened. The

The present invention also includes a toner concentration sensor for measuring the magnetic permeability inside the developing device, and accurately detects the toner concentration from the start of driving of the conveying means for conveying the developer including toner and carrier inside the developing device. In the toner concentration detection device for detecting the toner concentration in the developing device using a value measured by the toner concentration sensor within a period from when a delay time ensured for elapse of time to the end of driving, the conveying means During the driving of the toner, the completion determination means for determining whether or not the detection of the toner density can be completed before the driving of the driving means being driven is completed, and the completion determination means determines that the detection is impossible. Only when the detection of the toner density can be completed by shortening the delay time until the driving of the driving conveyance unit is completed. When it is determined that it is possible by the shortening determination means and the shortening determination means, the delay time at the next driving of the transport means is shortened, and when it is not determined by the shortening determination means that it is possible Provides a toner density detecting device having time control means for extending the driving time of the conveying means during driving.
According to this toner concentration detection device, when the detection of the toner density cannot be completed by the time the driving of the driving conveyance unit is completed, the detection of the toner concentration is performed by the conveying unit being driven. It is determined whether or not the driving can be completed by the reduction of the delay time. If possible, the delay time at the next driving of the transport means is shortened. On the contrary, when it is not possible, the driving time of the conveying means during driving is extended.

The present invention also includes a toner concentration sensor for measuring the magnetic permeability inside the developing device, and accurately detects the toner concentration from the start of driving of the conveying means for conveying the developer including toner and carrier inside the developing device. In the toner concentration detection device for detecting the toner concentration in the developing device using a value measured by the toner concentration sensor within a period from when a delay time ensured for elapse of time to the end of driving, the conveying means During the driving of the toner, the completion determination means for determining whether or not the detection of the toner density can be completed before the driving of the driving means being driven is completed, and the completion determination means determines that the detection is impossible. Only if the detection of the toner density can be completed by extending the driving time until the driving of the driving conveyance unit is completed. If it is determined by the extension determining means and the extension determining means that the driving time of the driving means being driven is extended, and if it is not determined by the extension determining means, the transfer is There is provided a toner density detecting device having time control means for shortening the delay time when the means is driven next time.
According to this toner concentration detection device, when the detection of the toner density cannot be completed by the time the driving of the driving conveyance unit is completed, the detection of the toner concentration is performed by the conveying unit being driven. It is determined whether or not the driving can be completed by extending the driving time. If possible, the drive time of the conveying means being driven is extended. Conversely, if it is not possible, the delay time at the next drive of the transport means is shortened.

The present invention also provides an image forming apparatus that includes any one of the above-described toner concentration detection devices and that forms an image using the toner concentration detected by the toner concentration detection device.
According to this image forming apparatus, image formation is performed using the toner density detected by the toner density detecting apparatus described above.

  According to the present invention, it is possible to stably detect an accurate or substantially accurate toner density before the driving of the conveying unit is completed, and in comparison with an aspect in which the driving time of the conveying unit is uniformly set long, Stress applied to the developer can be suppressed. Further, in the image forming apparatus, it is possible to form an image using an accurate toner density that is stably detected, and to set the productivity of image formation to a uniformly long driving time of the conveying unit. It can be made higher in comparison. Further, as is clear from these facts, the present invention is suitable for use in an image forming apparatus (for example, a high speed machine) in which image forming productivity is important.

  A toner concentration detection apparatus and an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. However, in order to facilitate understanding of the present invention, a general image forming apparatus having a general toner concentration detecting device will be described first. In addition, the same code | symbol is attached | subjected to the common part in each figure used for description.

[Configuration of General Image Forming Apparatus]
FIG. 1 is a diagram schematically illustrating a configuration of a general image forming apparatus. This image forming apparatus is an image forming apparatus having a tandem configuration using an intermediate transfer belt, and includes four processing systems corresponding to respective colors of Y (yellow), M (magenta), C (cyan), and K (black). . In the following description, the alphabet which shows the system of the said processing system is used for the code | symbol of the components which comprise a processing system. In the following description, unless otherwise specified, it is assumed that components constituting the image forming apparatus are supported by a housing (not shown) of the image forming apparatus.

  The image forming apparatus includes an intermediate transfer belt 20 on which a toner image is primarily transferred. The intermediate transfer belt 20 is stretched around a drive roll (not shown) that rotates in one direction, a driven roll 22, and a tension roll 23 that applies tension to the intermediate transfer belt 20, and is driven from upstream to downstream by the drive roll. The Further, a belt cleaning device (not shown) for cleaning the intermediate transfer belt 20 is provided upstream of the position where the toner image is primarily transferred.

  Further, the image forming apparatus presses the units 10Y, 10M, 10C, and 10K that form toner images of the respective colors and the intermediate transfer belt 20 that are arranged in order from upstream to downstream, and the units 10Y, 10M, 10C, and 10K. Thus, the primary transfer rolls 5Y, 5M, 5C, and 5K that superimpose the toner images for four colors formed on the units 10Y, 10M, 10C, and 10K and primarily transfer them to the intermediate transfer belt 20, and the toners for the four colors. A secondary transfer roll 15 that presses the sheet P conveyed by a conveyance roll (not shown) to the intermediate transfer belt 20 on which the images are primarily transferred and the sheet P on which the toner image is secondarily transferred by the secondary transfer roll 15. And a fixing device (not shown) for fixing the toner image on the paper P by overheating and pressurizing.

  When the unit 10Y is supplied with a photosensitive drum 1Y on which a toner image is formed, a charger 2Y for charging the photosensitive drum 1Y, and an image signal of a color (Y) corresponding to the unit 10Y, the unit 10Y uses the image signal. The exposure light 3 modulated in this manner is irradiated onto the photosensitive drum 1Y at a timing corresponding to the color, and the exposure unit 3 for forming an electrostatic latent image and the photosensitive drum 1Y on which the electrostatic latent image is formed are connected to the unit 10Y. A developing device 4Y of a two-component development system that forms a toner image by attaching a corresponding color (Y) toner, a toner concentration sensor 8Y that measures the toner concentration in the developing device 4Y using magnetic permeability, and formation A cleaning device (not shown) that cleans the photosensitive drum 1Y and removes residual toner after the transferred toner image is primarily transferred to the intermediate transfer belt 20 is provided. The longitudinal direction of the developing device 4Y coincides with the depth direction in the drawing.

  A toner box 7Y is connected to the developing device 4Y through a pipe having an auger built therein, and toner of color (Y) corresponding to the unit 10Y is supplied from the toner box 7Y to the developing device 4Y through the pipe. . The amount of toner supplied to the developing device 4Y is adjusted by the rotation time of the dispense motor 9Y.

  Each of the units 10M, 10C, and 10K has the same configuration as that of the unit 10Y, and includes the components that do not constitute other units except for the exposure unit 3. Further, like the toner box 7Y is connected to the unit 10Y, the other units are also connected to toner boxes containing other colors of toner.

  The exposure unit 3 is a component common to the units 10Y, 10M, 10C, and 10K, but its function varies from unit to unit. For example, when functioning as a component of the unit 10M, when the image signal of the color (M) corresponding to the unit 10M is supplied, the exposure light modulated using the image signal is processed at a timing corresponding to the color. Irradiate the drum 1M.

  Further, the image forming apparatus inputs an image reading unit (not shown) that reads a document image to be copied and outputs an image signal, and an image signal output from the image reading unit, and performs screen processing or the like on the image signal. An image processing unit (not shown) that performs image processing and outputs an image signal after image processing, and a controller 32 are provided. An output signal from the temperature / humidity sensor 6 that measures the temperature and humidity in the image forming apparatus is input to the controller 32.

  FIG. 2 is a block diagram showing the configuration of the controller 32. As shown in this figure, the function of the controller 32 is performed when the CPU 321 reads a program stored in the ROM 322 and executes the RAM 323 as a work area. For example, when an image signal is supplied from the image reading unit, the CPU 321 inputs this signal via the image input unit 324, performs color conversion on the input image signal, and generates an image signal for each color of YMCK. An image signal is supplied to the exposure unit 3 via the image output unit 325. In addition, when an image signal is supplied from an external device (for example, a personal computer) of the image forming apparatus, the CPU 321 inputs this signal via the image input unit 326, performs color conversion on the input image signal, and performs each color of YMCK. And the generated image signal is supplied to the exposure unit 3 via the image output unit 325.

  Further, the CPU 321 uses the image signal supplied to the exposure unit 3 to calculate the image density by counting the number of pixels of the image for each color, and uses it for toner density control. Further, the image forming apparatus includes a UI (user interface) 36 for the user to perform various settings. The CPU 321 inputs a signal indicating the operation content of the UI 36 via the A / D converter 327 and inputs the signal. An image mode represented by the signal, which is determined from the density, paper size, number of output sheets, paper thickness, and the like is used for toner density control. Further, the image forming apparatus inputs a signal from the temperature / humidity sensor 6 via the A / D converter 327 and uses the input signal for toner density control.

[Internal and peripheral configurations of toner density detection devices 50Y, 50M, 50C, and 50K]
FIG. 3 is a diagram illustrating an internal configuration and a peripheral configuration of the toner concentration detection device 50Y. In the developing device 4Y, the front direction in the drawing corresponds to the vertically upward direction, and the left-right direction in the drawing corresponds to the longitudinal direction. The toner concentration detection device 50Y includes a developing device 4Y, a toner concentration sensor 8Y, and a controller 32. The developing device 4Y is one of general developing devices that employ a developing system that discharges excess developer, and includes a wall 51Y and a partition plate 52Y that rises from the bottom of the wall 51Y. The partition plate 52Y divides the space formed by the wall 51Y into a substantially cylindrical reverse stirring and conveying space 53Y and a forward stirring and conveying space 54Y extending in the longitudinal direction of the developing device 4Y.

  Each agitating / conveying space is provided with blades spirally provided around a rotation axis extending in the longitudinal direction of the developing device 4Y, and the surrounding developer DY is agitated by being driven to rotate around the rotation axis. In addition, augers 55Y and 56Y are provided for transporting. In addition, a gap is provided between both ends of the partition plate 52Y in the longitudinal direction and the wall 51Y, and the agitation transport spaces are connected to each other via these gaps. That is, the developer DY fed from the toner box 7Y through the pipe is conveyed in the direction away from the discharge port 57Y (hereinafter referred to as the reverse direction v2) while being stirred by the auger 55Y in the reverse direction agitating and conveying space 53Y. The developer DY thus transported is transported in a forward stir transport space 54Y by the auger 56Y in a direction approaching the discharge port 57Y (hereinafter referred to as the forward direction v1).

  In addition, a regulating member 58Y that blocks the developer DY is provided in front of the discharge port 57Y in the forward direction v1. The regulating member 58Y is provided so as to rise from the bottom wall 51Y that forms the forward stirring and conveying space 54Y. In other words, the excessive developer DY (overflowed developer) conveyed by the auger 56Y beyond the upper end of the regulating member 58Y flows into the internal space of the collection unit 59Y.

  In the forward direction v1, there is the above-described gap connecting the two agitation transport spaces in front of the regulating member 58Y. The bottom of the gap is lower than the upper end of the regulating member 58Y. That is, of the developer DY transported in the forward direction v1 by the auger 56Y in the forward stirring transport space 54Y, the developer DY blocked by the regulating member 58Y flows into the reverse stirring transport space 53Y. It has become. Therefore, a large amount of the developer DY is circulated and conveyed while being stirred in the developing device 4Y. The developing device 4Y has a developing roll (not shown) that attracts the developer DY circulated and conveyed in the developing device 4Y with a magnetic attractive force. The developing roll is arranged so that the toner in the developer DY adhering to itself is attracted to the photosensitive drum 1Y by electrostatic attraction.

  The toner concentration sensor 8Y is located in the forward agitating / conveying space 54Y at a position outside the forward agitating / conveying space 54Y of the developing device 4Y, near the discharge port 57Y, and upstream of the regulating member 58Y in the forward direction v1. It is arranged toward the portion close to the position, and its output terminal is connected to the controller 32. The CPU 321 of the controller 32 inputs signals from the toner density sensors 8Y, 8M, 8C and 8K via the A / D converter 327, and detects the toner density using these signals. Further, the CPU 321 determines the toner density in the developing devices 4Y, 4M, 4C, and 4K on the UI 36 based on the detected toner density, the calculated pixel density, the signal from the UI 36, and the signal from the temperature / humidity sensor 6. A drive signal for matching with the target toner density corresponding to the image mode determined by the signal from is supplied to the dispense motors 9Y, 9M, 9C and 9K via the D / A converter 328.

  On the other hand, the developing motor 38Y is a motor that rotationally drives each part of the developing device 4Y including the augers 55Y and 56Y, and rotates the rotating shaft at a constant speed only while the supplied drive signal MY is on. A developing motor 38M is provided for the developing device 4M, a developing motor 38C is provided for the developing device 4C, and a developing motor 38K is provided for the developing device 4K. These motors are also controlled by the CPU 321. The

  FIG. 4 is a flowchart showing the flow of toner density measurement processing performed by the CPU 321. As shown in this figure, when the drive signal MY supplied to the developing motor 38Y is turned on, the CPU 321 starts a timer (step S1), and after a predetermined delay time t1 (eg, 1.4 s) has elapsed, Implementation of the density measurement set is started (steps S2 and S3). However, if the drive signal MY is turned off before the delay time t1 has elapsed, the toner density measurement set is not performed. In addition, when the delay time t1 elapses, the CPU 321 performs a toner density measurement set every time a predetermined interval time t2 elapses (steps S3 and S4).

  In the toner density measurement set for Y color, the CPU 321 inputs a signal output from the toner density sensor 8Y at predetermined time intervals. In addition, when the number of signal inputs in the toner density measurement set in progress reaches a predetermined number, the CPU 321 specifies a predetermined number of measurement values in descending order from the measurement values represented by the input signals. The average value of the measured values is calculated, and the toner density measurement set is completed. The average value thus calculated is the detected toner density. Note that when the drive signal MY is turned off during the toner density measurement set, the above average value is not calculated. Further, in the toner density measurement set, the CPU 321 inputs the signal output from the toner density sensor 8Y, and the number of times the signal is input, the time when the augers 55Y and 56Y are rotated three times completes the toner density measurement set. It is prescribed as follows.

  The internal configuration and peripheral configuration of the toner concentration detection device 50Y are as described above, and the other toner concentration detection devices 50M, 50C and 50K have the same configuration as the toner concentration detection device 50Y. However, the controller 32 is a component common to the toner concentration detection devices 50Y, 50M, 50C, and 50K, but the function thereof is different for each toner concentration detection device. For example, when functioning as a component of the toner concentration detection device 50M, the above-described toner concentration measurement processing is performed for M colors in order to make the toner concentration of the color (M) corresponding to the toner concentration detection device 50M appropriate. The toner density is detected, and the rotation of the dispense motor 9M is controlled using the detection result.

[Operation of general image forming apparatus]
Next, the operation of this embodiment will be described. However, in the following description, it is assumed that the image mode has already been set using the UI 36 and the document image has been read by an image reading unit (not shown).

  An image signal corresponding to the document image is supplied to the controller 32 after image processing. The CPU 321 of the controller 32 performs color conversion on the supplied image signal to generate an image signal of each color of YMCK, supplies the generated image signal to the exposure unit 3, and outputs an image pixel for each of the generated image signals. Count the number to calculate the image density. The exposure unit 3 irradiates the photosensitive drum 1Y charged by the charger 2Y with exposure light modulated using the supplied Y-color image signal. The exposure unit 3 performs the same processing as described above for each color of MCK. As a result, electrostatic latent images are formed on the rotating photosensitive drums 1Y, 1M, 1C, and 1K at a timing corresponding to each color.

  On the other hand, the CPU 321 of the controller 32 turns on the drive signals MY, MM, MC and MK supplied to the developing motors 38Y, 38M, 38C and 38K. As a result, the developing motors 38Y, 38M, 38C, and 38K start driving. In addition, the CPU 321 performs toner density measurement for each color.

  FIG. 5 is a diagram showing a state of toner density measurement related to Y color by the CPU 321. As shown in this figure, the CPU 321 performs the toner density measurement set after a delay time t1 has elapsed since the drive signal MY supplied to the developing motor 38Y is turned on. Further, the CPU 321 performs the toner density measurement set every time the interval time t2 elapses from the time when the delay time t1 elapses. In each toner density measurement set, the CPU 321 calculates an average value. This average value is a detection result of the toner density in the developing device 4Y.

  The CPU 321 that has detected the toner density, based on the detected toner density, the calculated image density, the image mode set using the UI 36, and the output signal of the temperature / humidity sensor 6, dispense motors 9Y, 9M, The rotation times of 9C and 9K are obtained, and a drive signal for rotating the dispense motors 9Y, 9M, 9C and 9K for the obtained rotation time is supplied to the dispense motors 9Y, 9M, 9C and 9K.

  The dispense motors 9 </ b> Y, 9 </ b> M, 9 </ b> C, and 9 </ b> K to which the drive signal is supplied from the controller 32 rotate for the rotation time obtained by the controller 32. Thereby, an amount of toner corresponding to the rotation time of the dispense motors 9Y, 9M, 9C, and 9K is supplied from the toner boxes 7Y, 7M, 7C, and 7K to the developing devices 4Y, 4M, 4C, and 4K through the pipes. Is done.

  In the developing device 4Y, the developer DY including the toner and the carrier replenished through the pipe from the toner box 7Y is circulated and conveyed while being stirred. In this circulation and conveyance process, only the excess developer DY conveyed beyond the regulating member 58Y flows into the internal space of the collection unit 59Y. Further, in this circulation conveyance process, a part of the developer DY being circulated adheres to the rotating developing roll by the magnetic attraction force. The toner contained in the developer DY adhered to the developing roll is attracted and adhered to the photosensitive drum 1Y on which the electrostatic latent image is formed by electrostatic attraction force. The same thing occurs in the other developing devices 4M, 4C and 4K, and toner images of the respective colors are formed on the photosensitive drums 1Y, 1M, 1C and 1K.

  The toner images formed on the photoconductive drums 1Y, 1M, 1C, and 1K are primarily transferred onto the same portion of the intermediate transfer belt 20 and then transferred to the paper P and fixed. Incidentally, after the toner image is primarily transferred to the intermediate transfer belt 20 from the photosensitive drums 1Y, 1M, 1C, and 1K, residual toner is removed, and the toner is removed from the developing rolls of the developing devices 4Y, 4M, 4C, and 4K. After the toner adheres to the photosensitive drums 1Y, 1M, 1C, and 1K, the adhered carrier is removed.

[Problems of general image forming apparatus]
From the time when the drive signal MY is kept on, that is, the drive time of the augers 55Y and 56Y is the time required for one toner density measurement set (the time for which the augers 55Y and 56Y are rotated three times) and the delay time t1. If it is too short, the CPU 321 of the controller 32 cannot detect the toner density in the developing device 4Y. If such image formation occurs continuously many times, image formation with an inappropriate toner density is performed. Such an inconvenience occurs similarly for other colors.

  An embodiment of the present invention that can solve these disadvantages will be described below. However, the difference between the toner density detecting device and the image forming apparatus according to the embodiment of the present invention from the general toner density detecting device and the image forming apparatus described above is the contents of the program executed by the CPU 321 of the controller 32, that is, the ROM 322. Only the stored contents. Therefore, in the following description, the reference numerals attached to the hardware constituting a general image forming apparatus are used as they are. Note that the processing performed by the CPU 321 in the embodiments described below is performed in parallel with the toner density measurement processing shown in FIG. In order to avoid complicated explanation, only the process related to the Y color will be described below. Further, it is assumed that the number of consecutive times described later is set to zero when the image forming apparatus is shipped.

[First Embodiment]
FIG. 6 is a flowchart showing the flow of drive time control processing performed by the toner concentration detection apparatus according to the first embodiment of the present invention. As shown in this figure, when the drive signal MY is turned on, the CPU 321 constituting the toner density detection apparatus waits until the drive signal MY is turned off (step SA1: NO). When it is time to turn off the drive signal MY (step SA1: YES), the CPU 321 determines whether the average value has not been calculated once since the drive signal MY was turned on immediately before (exact toner). It is determined whether or not the density cannot be detected (step SA2). The driving time of the augers 55Y and 56Y is determined according to the image mode, and depending on the image mode, the driving time of the augers 55Y and 56Y becomes extremely short, so the result of this determination may be affirmative.

  If this determination result is negative, an accurate toner density has been detected, so the CPU 321 sets the number of consecutive times to zero (step SA3), turns off the drive signal MY (step SA4), and controls drive time. The process ends. As a result, the image forming apparatus according to the present embodiment operates in the same manner as a general image forming apparatus. On the contrary, if the determination result is affirmative, the CPU 321 adds 1 to the number of consecutive times (step SA5), compares the number of consecutive times with a predetermined number of times threshold, and determines whether the former is equal to or greater than the latter. Is determined (step SA6). The number threshold is stored in the ROM 322, for example.

  This threshold value is a value obtained by adding 1 to the upper limit of the number of times of image formation performed continuously without detecting the toner density. If the continuous frequency is less than the threshold value, the toner density is detected. Therefore, it is possible to form an image without doing so. Therefore, if the determination result is negative, the CPU 321 turns off the drive signal MY (step SA4) and ends the drive time control process. As a result, the image forming apparatus according to the present embodiment operates in the same manner as a general image forming apparatus. Conversely, if the determination result is affirmative, the CPU 321 acquires an extension time to be added to the drive time (step SA7).

This extended time is a preset time, and is stored in the ROM 322, for example. In this embodiment, as shown in Table 2, the extended time is the driving time of 1.841 s required for measuring the accurate toner density in the image mode (development processing) in which the driving time of the augers 55Y and 56Y is the shortest. Is a time of 0.826 s or longer (for example, 1.500 s) obtained by subtracting a driving time of 1.015 s determined according to the image mode.

  The CPU 321 that has acquired the extension time adds the extension time to the drive time determined from the image mode, temporarily extends the drive time of the augers 55Y and 56Y, sets the number of continuous times to zero (step SA8), and performs drive time control processing. Exit. Note that the CPU 321 keeps the drive signal MY on until the extended drive time elapses. Accordingly, the augers 55Y and 56Y are driven for a time obtained by adding the extension time to the drive time corresponding to the image mode. For example, even in the image mode where the drive time of the augers 55Y and 56Y is the shortest, the augers 55Y and 56Y are driven by 1.015 + 1.500 = 2.515s. Therefore, the CPU 321 finishes at least one toner density measurement set while the augers 55Y and 56Y are being driven.

  Thus, according to the present embodiment, even if the driving time corresponding to the image mode is shorter than the delay time t1 and the measurement one set time, at least once while the augers 55Y and 56Y are driven. An accurate toner density in the developing device 4Y can be detected. Therefore, the toner density can be detected stably. In addition, according to the present embodiment, the driving time is extended only when the driving time corresponding to the image mode is shorter than the delay time t1 and the measurement one set time. It is possible to avoid the situation where stress is applied. Furthermore, according to the present embodiment, even if the driving time corresponding to the image mode is shorter than the delay time t1 and the measurement one set time, the driving time is not extended if the continuous number is less than the number threshold. Therefore, the stress applied to the developer can be further reduced.

[Second Embodiment]
FIG. 7 is a flowchart showing the flow of a drive time control process performed by the toner concentration detection apparatus according to the second embodiment of the present invention. The flow shown in this figure is different from the flow shown in FIG. 6 only in that step SB1 is provided instead of step SA2.
In the present embodiment, when it is time to turn off the drive signal MY (step SA1: YES), the CPU 321 is a drive that has a predetermined actual drive time that is an elapsed time since the drive signal MY was turned on immediately before. It is determined whether it is less than the time threshold (step SB1). The driving time threshold value is stored in the ROM 322, for example, and is a value indicating the time obtained by adding the delay time t1 to the measurement one set time. Therefore, the result of the determination is whether or not the accurate toner density cannot be detected. This substantially matches the result of the determination (determination in the first embodiment).

If the determination result is negative, the CPU 321 performs processing after step SA3, and if affirmative, performs processing after step SA5. As a result, the driving time of the augers 55Y and 56Y is temporarily extended by the acquired extension time only when the continuous number is equal to or greater than the number threshold.
Therefore, according to this embodiment, the same effect as that obtained by the first embodiment can be obtained.

[Third Embodiment]
FIG. 8 is a flowchart showing the flow of the drive time control process performed by the toner concentration detection apparatus according to the third embodiment of the present invention. The flow shown in this figure is different from the flow shown in FIG. 6 only in that step SC1 is provided instead of step SA2.
In the present embodiment, when it is time to turn off the drive signal MY (step SA1: YES), the CPU 321 determines a drive time threshold that is determined according to the image mode such as the number of pages, size, paper type, and the like. It is determined whether it is less than (step SC1). The drive time threshold value is stored in the ROM 322, for example, and is a value indicating the time obtained by adding the delay time t1 to the measurement 1 set time. The drive time is from the time when the drive signal MY is turned on immediately before to the present time. Since it substantially coincides with the elapsed time, the result of the determination substantially coincides with the result of the determination whether the accurate toner density cannot be detected (determination in the second embodiment).

If the determination result is negative, the CPU 321 performs processing after step SA3, and if affirmative, performs processing after step SA5. As a result, the driving time of the augers 55Y and 56Y is temporarily extended by the acquired extension time only when the continuous number is equal to or greater than the number threshold.
Therefore, according to the present embodiment, it is possible to obtain the same effect as that obtained by the first embodiment and the second embodiment.

[Fourth Embodiment]
By the way, in each of the above-described embodiments, there is a possibility that the time until the image forming apparatus stops after the end of image formation becomes long, and the productivity of image formation may decrease. Prior to the description of the fourth embodiment of the present invention, this problem will be described.
FIG. 9 is a diagram illustrating the end timing of each process at the end and after the end of image formation in a general image forming apparatus. As shown in this figure, (1) First, when the rear end of the last image to be formed is exposed, the exposure process is completed. (2) Immediately after the trailing edge of the exposure passes the developing position, the driving of each part of the developing device is completed. On the other hand, the charging of the transfer is turned off immediately after the trailing edge of the exposure passes the transfer position. Note that the timing when driving of each part of the developing device ends is immediately after the rear end of the exposure passes the developing position, in order to prevent the deterioration of the developer due to wasteful conveyance. (3) Next, when the transfer charging off region passes, the charging is turned off. The reason for this timing is that the on-region of transfer charging is charged once and then erased. Such erasing experience is necessary to erase the charging history of the photosensitive drum due to transfer charging. (4) Next, when the charging off region passes the developing position, the developing bias is turned off. This timing is used to avoid a situation where unnecessary toner or carrier adheres to the photosensitive drum. (5) Next, when the charge off region passes erase, the drive motor for the photosensitive drum is stopped and the erase lamp is turned off. In other words, the erase is turned off after the erase is experienced in the ON region of the transfer charge.

  As is apparent from this figure, the driving of each part of the developing device is completed at time A immediately after the rear end of exposure of the last image to be formed passes through the developing device. Continue operation. Therefore, within the range in which the timing (5) is not delayed, delaying the timing for ending the driving of each part of the developing device does not affect the productivity of image formation in the image forming apparatus. I understand that. The extent to which the driving end of each part of the developing device can be delayed is up to the point B when the developing bias is turned off. If each part of the developing device continues to be driven after the point of time B, in order to prevent toner fogging due to this driving, it is necessary to extend the on time of charging of the photosensitive drum and the on time of the developing bias. This is because the timing is delayed.

  On the other hand, in each of the above-described embodiments, the driving time of the augers 55Y and 56Y is extended by the extension time in a specific case. The extension time is a fixed value set in advance, but the upper limit is not set. Therefore, depending on the extended time to be set, there is a possibility that the developing device continues to be driven even after the time point B and the productivity of image formation is lowered.

  The toner density detection device and the image forming apparatus according to the present embodiment solve such problems. In the drive time control process in the present embodiment, the CPU 321 ends the image formation using the driven augers 55Y and 56Y even if the drive time of the driven augers 55Y and 56Y is extended. The longest extension time is acquired within a range in which it is not necessary to extend the time until the next image formation can be started. Specifically, when extending the drive time, the CPU 321 acquires an extended time such that the end time of the extended drive time coincides with the development bias OFF time of the developing device 4Y. Of course, it is also possible to acquire an extended time such that the driving of the augers 55Y and 56Y ends slightly before the development bias off time. Further, the development bias OFF time substantially coincides with the time when the time at which the portion at the charging position of the photosensitive drum 1Y moves to the development position has elapsed from the charging OFF time of the photosensitive drum 1Y. As a reference, the CPU 321 may acquire the extended time. That is, the end time of the driving time of the augers 55Y and 56Y being driven by the CPU 321 is synchronized with the time when the image forming apparatus next turns off the developing bias or the time when the charging of the photosensitive drum 1Y is next turned off. As such, the extension time may be acquired.

  According to the present embodiment, the time from the time point (2) to the time point (5) is longer than the difference time between the total time of the delay time t1 and the measurement one set time and the shortest driving time. In this case, the same effect as that obtained by the first embodiment can be obtained. Furthermore, according to the present embodiment, the end time of the extended drive time does not pass the off time of the developing bias of the developing device 4Y, so that the image forming productivity in the image forming device is not lowered.

[Fifth Embodiment]
The toner concentration detection apparatus according to the fifth embodiment of the present invention is configured to control the delay time, not the drive time, and is suitable for use in a general image forming apparatus having the characteristics shown in Table 3. . As shown in Table 3, the image forming apparatus according to the present embodiment is a high-speed machine having a sheet conveyance speed of 440 mm / s, and the initial value of the delay time (output stabilization time) is set to 1.000 s. Yes. In this image forming apparatus, the output signal of the toner density sensor is almost stable when 0.500 s has elapsed from the start of driving of the auger in the developing device, and completely stabilized when 1.000 s has elapsed.

  FIG. 10 is a flowchart showing the flow of a delay time control process performed by the toner concentration detection apparatus according to the fifth embodiment of the present invention. The flow shown in this figure is different from the flow shown in FIG. 6 in that step SD1 is replaced with step SA2, step SD2 is replaced with step SA3, step SD3 is replaced with step SA6, and step SD4 is replaced with step SA7. Is only a point having step SD5 instead of step SA8.

  In the present embodiment, when it is time to turn off the drive signal MY (step SA1: YES), the CPU 321 determines whether or not an accurate toner density cannot be detected (step SD1). This determination process is the same as the determination process in step SA1, SB1 or SC1. If the determination result in step SD1 is negative, the accurate toner density is detected using the delay time of 1.000 s, so the CPU 321 resets the delay time while setting the number of consecutive times to zero. The initial value (1.000 s) is restored (step SD2). Next, the CPU 321 performs processing after step SA4.

  Conversely, if the determination result in step SD1 is affirmative, the CPU 321 adds 1 to the number of consecutive times (step SA5), compares the number of consecutive times with a predetermined number of times threshold, and the former is greater than or equal to the latter. It is determined whether or not there is (step SD3). However, this number threshold is different from the number threshold in step SA6, and is the upper limit itself of the number of times of image formation performed continuously without detecting the toner density. This is because even if it is found that the delay time should be reduced at the timing when the drive signal MY is turned off, the reduction of the delay time is effective at the next image formation.

  If the determination result is negative, the CPU 321 turns off the drive signal MY (step SA4) and ends the drive time control process. As a result, the image forming apparatus according to the present embodiment operates in the same manner as a general image forming apparatus. Conversely, if the determination result is affirmative, the CPU 321 acquires a shortened time to be subtracted from the delay time (step SD4).

  This shortening time is a preset time, and is stored in the ROM 322, for example. In this embodiment, as shown in Table 3, the shortening time is the driving time necessary for measuring the accurate toner density in the image mode in which the driving time of the augers 55Y and 56Y is the shortest among the frequently used image modes. The time is 0.431 s or more (0.500 s) obtained by subtracting the driving time 0.789 s determined according to the image mode from 1.220 s.

  The CPU 321 that has acquired the shortening time subtracts the shortening time from the delay time to obtain a new delay time (0.500 s), sets the number of consecutive times to zero (step SD5), and ends the delay time control process. However, if the new delay time is much shorter than the time from when the developing device auger starts to drive until the output signal of the toner density sensor is almost stabilized, do not subtract the shortened time any longer. The delay time is used as a new delay time.

  Thereafter, the CPU 321 performs toner density measurement processing based on the newly obtained delay time. Therefore, the next toner density measurement set is performed 0.500 s after the augers 55Y and 56Y start driving. Therefore, if the next image mode is not a mode in which one postcard-sized plain paper is output, the accurate toner density is detected, the delay time and the continuous count are reset, and the initial values are restored (steps SA1, SD1,. SD2, SA4). When the next image mode is a mode in which one postcard-sized plain paper is output, the toner density is not detected, 1 is added to the continuous count, and the delay time (0.500 s) is maintained as it is ( Steps SA1, SD1, SA5, SD3, SD4, SD5).

According to the present embodiment, when applied to an image forming apparatus in which the initial value of the delay time is set to be long, the same effect as that obtained by the first embodiment is obtained for a frequently used image mode. Obtainable. Further, since the driving time of the auger of the developing device is not extended, it is suitable for use in an image forming apparatus (especially a high-speed machine) in which image forming productivity is important. When the initial value of the delay time is set to be sufficiently long, the same effect as that obtained by the first embodiment can be obtained for all image modes. For example, the initial value of the delay time is 1.000 s, although the output signal of the toner density sensor is substantially stabilized at the time when 0.400 s has elapsed from the start of driving the auger of the developing device. In this case, as shown in Table 4, the shortening time can be set to 0.600 s instead of 0.500 s. 0.600 s is the difference between the sum of the measurement set time (0.220 s) and the delay time (1.000 s) (1.220 s) and the shortest drive time of the developing device auger (0.630 s) Since the time is equal to or longer than the time (0.590 s), if the delay time is shortened by 0.600 s, an accurate toner density can be detected for all image modes. Therefore, if the new delay time in step SD5 is much shorter than the time from when the auger of the developing device starts driving until the output signal of the toner density sensor is substantially stabilized, the reduction time is further subtracted. Therefore, the process of using the delay time as it is as a new delay time becomes unnecessary.

[Sixth Embodiment]
In the toner concentration detection apparatus and the image forming apparatus according to the sixth embodiment of the present invention, the CPU 321 basically performs a delay time control process shown in FIG. However, the CPU 321 determines whether or not it can be dealt with by reducing the delay time when the number of consecutive times becomes equal to or greater than the number threshold, and only when it is determined that it can be dealt with, acquires the reduced time or calculates a new delay time. . Note that “whether or not it can be dealt with by shortening the delay time” means whether or not the detection of the toner density can be completed within the driving time by shortening the delay time. If the CPU 321 determines that it is impossible to deal with, the CPU 321 obtains the extension time or temporarily extends the drive time. According to the present embodiment, for example, when only one postcard-sized plain paper shown in Table 3 is output, a solution by extending the driving time can be achieved.

[Seventh Embodiment]
In the toner concentration detection apparatus and the image forming apparatus according to the seventh embodiment of the present invention, the CPU 321 basically performs a delay time control process shown in FIG. However, the CPU 321 determines whether or not it can be dealt with by extending the drive time when the number of consecutive times becomes equal to or greater than the number threshold, and only when it is judged that dealt with is not possible, obtains a shortened time or calculates a new delay time. Do. Note that “whether it can be dealt with by extending the driving time” means whether it is possible to complete the detection of the toner density within the driving time by extending the driving time. If the CPU 321 determines that it can handle, the CPU 321 obtains the extension time or temporarily extends the drive time. According to the present embodiment, for example, when the drive time is extended and the productivity of image formation is reduced, a solution by reducing the delay time can be achieved.

[Deformation]
The present invention can be implemented in any form obtained by modifying the above-described embodiment within a range determined by the invention-specifying matters described in the claims. Various modifications are shown below.

  For example, in the third embodiment, whether or not the driving time determined according to the image mode is less than the driving time threshold is determined not only immediately before the driving of the augers 55Y and 56Y but from immediately after the driving is started to immediately before the driving is ended. You may make it perform at the time of.

  For example, in the embodiment in which the driving time of the augers 55Y and 56Y is extended, the extended time of the driving time may be dynamically determined. As a method of dynamically determining the extension time, for example, from the time obtained by adding the delay time t1 to the measurement one set time required for one toner density measurement set, the drive signal MY is turned on immediately before. There is a method in which the extension time is dynamically calculated by subtracting the actual drive time that is the elapsed time or the drive time determined according to the image mode. Of course, the extended time may have a slight margin. According to such an aspect, the stress applied to the developer can be further reduced.

  Further, for example, in an aspect in which the driving times of the augers 55Y and 56Y are dynamically extended, the end time of the extended driving time passes the charging off time of the photosensitive drum 1Y or the developing bias of the developing device 4Y. In such a case, an extension time may be adopted such that the end time coincides with the charging off time of the photosensitive drum 1Y or the developing bias off time of the developing device 4Y.

  Further, for example, in the fifth embodiment, the delay time may be shortened sequentially over multiple stages instead of shortening the delay time by one stage. According to this aspect, as the necessity of detecting the toner concentration increases, the degree of sacrificing the accuracy of toner concentration detection increases. In this embodiment, when the toner density is detected, the delay time may be returned to the immediately preceding delay time instead of returning to the initial value.

  For example, instead of extending the driving time or reducing the delay time only when the number of continuous times reaches a certain number, the driving time is always extended or the delay time is shortened when the toner density cannot be detected. May be performed.

  A plurality of hardware may cooperate to perform the above-described control processing. For example, a part of the drive time control process may be executed by the first hardware, and the other part may be executed by the second hardware.

  Further, for example, the present invention may be applied to an image forming apparatus having a multiple cycle configuration instead of a tandem configuration.

  Further, for example, the present invention may be applied to an image forming apparatus using another intermediate transfer body instead of the intermediate transfer belt 20.

  Further, the present invention is applied to an image forming apparatus that directly transfers a toner image to a storage medium transported by a storage medium transport unit such as a transport belt or a transport roll instead of an intermediate transfer system. Also good.

  Further, the present invention may be applied to an image forming apparatus that does not have the temperature / humidity sensor 6. In this case, the controller 32 controls the rotation of the dispense motors 9Y, 9M, 9C, and 9K based only on the image density, the signal from the UI 36, and the signals from the toner density sensors 8Y, 8M, 8C, and 8K.

  Further, for example, the present invention can be applied to a developing device that transports a developer only in one direction or an image forming apparatus that includes a developing device that transports the developer using a transporting unit different from the auger.

1 is a diagram schematically illustrating a configuration of a general image forming apparatus. FIG. 2 is a block diagram showing a configuration of a controller 32 configuring the image forming apparatus. 2 is a diagram illustrating an internal configuration and a peripheral configuration of a toner concentration detection device 50Y constituting the image forming apparatus. 4 is a flowchart showing a flow of toner density measurement processing performed by a CPU 321 constituting the controller 32. FIG. 6 is a diagram showing a state of toner density measurement by the CPU 321. 4 is a flowchart showing a flow of drive time control processing performed by the toner concentration detection apparatus according to the first embodiment of the present invention. 6 is a flowchart illustrating a flow of a drive time control process performed by a toner concentration detection device according to a second embodiment of the present invention. 10 is a flowchart illustrating a flow of a drive time control process performed by a toner concentration detection device according to a third embodiment of the present invention. FIG. 6 is a diagram illustrating the end timing of each process at the end and after the end of image formation in a general image forming apparatus. 10 is a flowchart illustrating a flow of a delay time control process performed by a toner concentration detection device according to a fifth embodiment of the present invention. FIG. 6 is a diagram illustrating an example of a change in an output signal (voltage signal) of a toner concentration sensor accompanying the start of driving of a developer conveying unit.

Explanation of symbols

32... Controller, 321... CPU (completion determining means, extending means, shortening means, shortening determining means, extension determining means, time control means), 4Y, 4M, 4C, 4K... Developing device, 50Y, 50M, 50C, 50K. Toner density detection device, 55Y, 56Y ... auger (conveying means), 8Y, 8M, 8C, 8K ... toner density sensor, DY ... developer.

Claims (16)

A delay provided to accurately detect the toner concentration from the start of driving of a conveying means that includes a toner concentration sensor for measuring the magnetic permeability inside the developing device and conveys the developer including toner and carrier inside the developing device. In a toner concentration detection device for detecting a toner concentration in the developing device using a value measured by the toner concentration sensor within a period from the time elapsed until the end of driving,
A completion determining unit that determines whether or not the detection of the toner density can be completed before the driving of the driving conveying unit is completed during the driving of the conveying unit;
A toner concentration detection apparatus comprising: an extension unit that extends a drive time of the driving conveyance unit only when it is determined by the completion determination unit to be impossible. The extension means determines the drive time of the driving means being driven only when the completion determination means determines that the extension is not possible, and the time required for the toner density sensor to measure the value used for detecting the toner density. The toner density detection device according to claim 1, wherein the toner density detection device is extended by a time equal to or longer than a time obtained by subtracting the shortest drive time of the transport unit from the sum of the delay time and the delay time. The extending means has the developing device only when the driving time of the driving conveying means is extended and the driving time of the driving conveying means is extended only when the completion determining means determines that it is impossible. The image forming apparatus is extended by the longest time that is not required to extend the time from the end of image formation using the driving conveying means until the next image formation can be started. Item 2. The toner concentration detection device according to Item 1. When the driving means of the conveying means that is being driven is extended, the extension means determines whether the end time of the driving time is the time when the image forming apparatus having the developing device next turns off the developing bias or the photosensitive member The toner concentration detection device according to claim 3, wherein the driving time is extended so as to synchronize with a time when charging is turned off next. The extension means counts the number of times that the completion determination means has determined that it is impossible, and when the completion determination means determines that the extension is impossible and when the number of times reaches a predetermined number 2. The toner concentration detection apparatus according to claim 1, wherein the driving time of the driving means during driving is extended. A delay provided to accurately detect the toner concentration from the start of driving of a conveying means that includes a toner concentration sensor for measuring the magnetic permeability inside the developing device and conveys the developer including toner and carrier inside the developing device. In a toner concentration detection device for detecting a toner concentration in the developing device using a value measured by the toner concentration sensor within a period from the time elapsed until the end of driving,
A completion determining unit that determines whether or not the detection of the toner density can be completed before the driving of the driving conveying unit is completed during the driving of the conveying unit;
A toner density detecting device comprising: a shortening unit that shortens the delay time when the transport unit is driven next time only when it is determined by the completion determining unit to be impossible. The shortening means shortens the delay time at the next driving of the conveying means by the longest time that can detect the toner density almost accurately only when the completion judging means determines that the toner density is impossible. The toner concentration detection apparatus according to claim 6, wherein The shortening means measures the delay time when the transport means is next driven only when the completion determining means determines that it is impossible, and measures the value used by the toner density sensor to detect the toner density. The toner density detection apparatus according to claim 6, wherein the toner density detection device is shortened by a time equal to or longer than a difference time between a sum of the time required for the time and the delay time and a shortest drive time of the transport unit. The shortening means counts the number of times that the completion determining means determines that it is impossible continuously, and when the completion determining means determines that it is impossible and when the number of times reaches a predetermined number 7. The toner concentration detection apparatus according to claim 6, wherein the delay time in the next driving of the transport unit is shortened. A delay provided to accurately detect the toner concentration from the start of driving of a conveying means that includes a toner concentration sensor for measuring the magnetic permeability inside the developing device and conveys the developer including toner and carrier inside the developing device. In a toner concentration detection device for detecting a toner concentration in the developing device using a value measured by the toner concentration sensor within a period from the time elapsed until the end of driving,
A completion determining unit that determines whether or not the detection of the toner density can be completed before the driving of the driving conveying unit is completed during the driving of the conveying unit;
Whether or not the detection of the toner density can be completed by the shortening of the delay time only when the completion of the detection of the toner density by the completion of the driving of the conveying unit is completed only when it is determined by the completion determining unit. A shortening judging means for judging;
When it is determined by the shortening determination means that the above-mentioned shortening is possible, the delay time at the next drive of the transport means is shortened, and when it is not determined by the shortening determination means that the transport is being performed. A toner concentration detecting device having time control means for extending the drive time of the means. A delay provided to accurately detect the toner concentration from the start of driving of a conveying means that includes a toner concentration sensor for measuring the magnetic permeability inside the developing device and conveys the developer including toner and carrier inside the developing device. In a toner concentration detection device for detecting a toner concentration in the developing device using a value measured by the toner concentration sensor within a period from the time elapsed until the end of driving,
A completion determining unit that determines whether or not the detection of the toner density can be completed before the driving of the driving conveying unit is completed during the driving of the conveying unit;
Whether or not the detection of the toner density can be completed by the extension of the driving time only when the completion of the detection of the toner concentration is completed by the end of the driving of the driving means. An extension determination means for determining;
When it is determined by the extension determining means that the driving means is driven, the driving time of the driving means is extended. When the extension determining means is not determined to be possible, the transport means is driven next time. A toner concentration detection device comprising: a time control means for shortening the delay time. The completion determination unit determines whether the toner concentration is being detected by determining whether or not the toner concentration is detected after the start of driving immediately before the end of driving while the transport unit is being driven. The toner density detection device according to claim 1, wherein it is determined whether or not the driving can be completed before the driving of the conveying unit is completed. The completion determining unit determines whether or not the elapsed time from the start of the driving is longer than the time necessary for detecting the toner density immediately before the end of driving while the transport unit is being driven. Accordingly, it is determined whether or not the detection of the toner density can be completed before the driving of the driving conveyance unit is completed. Toner concentration detection device. The completion determination unit determines whether the time from the start to the end of the driving is longer than the time necessary for detecting the toner concentration during the driving of the transport unit. 12. The toner density detection device according to claim 1, wherein it is determined whether or not the detection of the toner can be completed before the driving of the driving conveyance unit is completed. The completion determining unit detects the toner density during the driving of the conveying unit, the time from the start to the end of the driving determined according to the mode of the image being formed by the image forming apparatus having the developing device. Determining whether or not it is possible to complete the detection of the toner density before the driving of the driving means being driven is completed. The toner concentration detection device according to claim 1.   An image forming apparatus comprising the toner concentration detection device according to claim 1, claim 10, or claim 11, wherein image formation is performed using the toner concentration detected by the toner concentration detection device.

Images