JP2008180779A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device in an image forming apparatus such as a copying machine, a facsimile machine, a printer and a printing machine, which can detect different levels of toner by one sensor and with which toner replenishment can be effectively performed. <P>SOLUTION: One photoelectric sensor 55 is provided to detect the quantity of toner in the developing device 10. The level of toner is detected from the detection signal of the sensor. The upper and lower threshold values are set so that replenishment of toner starts and stops. In addition, the threshold value equivalent to the level at which the replenishment stops is varied with time from the start of the replenishment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, and a printing machine.

  An image forming apparatus such as a copying machine forms an electrostatic latent image on a photosensitive member, and the electrostatic latent image is visualized by a developing device using toner as a developer. Since the above toner is consumed by use, it is necessary to replenish it at an appropriate stage. Conventionally, it is common to replenish the toner by replacing the toner cartridge provided in the developing device with a new one. It was the target.

  However, in the method of replenishing toner with a toner cartridge, if the amount of toner to be accommodated is increased, the toner cartridge becomes larger, so that the necessary space is increased accordingly, and the developing device and the image forming apparatus must be increased in size. There was a problem. On the other hand, if the toner cartridge is made smaller, the amount of toner to be stored becomes smaller, which causes a problem that it must be frequently replaced. As a solution to these problems, one described in Patent Document 1 below has been proposed.

In the above-mentioned Patent Document 1, a developing device provided in an image forming apparatus is provided with a toner filling portion that can be filled with toner from the outside. The filling portion is filled with toner. A valve structure for maintaining the closed state except when the filling injection member is inserted, and a sensor for detecting the remaining amount of toner and the full state are provided. More specifically, a full detection sensor S1 is provided on the upper side and a remaining amount detection sensor S2 is provided on the lower side with respect to the axial center position of the conveying screw that conveys toner in a predetermined direction. When it is detected that S2 has reached a predetermined amount of toner, toner supply is started, and when the sensor S1 detects fullness, supply is stopped.
JP 2003-223045 A

  However, as in the invention described in Patent Document 1, in the configuration in which sensors are provided in two upper and lower portions and the replenishment start level and the full level are detected by separate sensors, the upper and lower sensors are separated by a predetermined interval. Therefore, it is necessary to provide a space for that purpose, and is not suitable for application to a small-sized developing device with a small space.

  For example, in a developing device that uses a one-component toner, the developing device itself is small. Therefore, in a configuration in which the upper limit level and the lower limit level are detected by two upper and lower sensors, there is a limit to disposing both the sensors above and below. The detection position of the lower limit level is lowered, and the remaining amount of toner when the remaining amount is detected becomes very small. When the remaining amount of toner before the start of replenishment is reduced, when the toner is replenished, the replenished toner goes directly onto the developing roller, causing a problem that streaky irregularities appear in the image. In addition, when the ratio of new toner replenished in the vicinity of the developing roller becomes high, the toner remaining in the developing device becomes poorly charged, and so-called fogging occurs in which the toner falls in the non-image area. there were.

  Further, in the configuration in which the upper and lower limits are detected by two upper and lower sensors, it is necessary to reduce the interval between the two sensors in order to keep the ratio of the toner to be replenished within a predetermined range and prevent the above-described unevenness and fogging problems. However, in a developing device reduced in size, such as a one-component developing device, there is a problem that the upper and lower sensors cannot be provided close to each other because the space is small. Moreover, the provision of two sensors has a problem that the cost increases accordingly.

  On the other hand, when toner is replenished, the amount of light passing through the developing device changes with the replenishment time due to new toner entering by the replenishment operation and the apparent specific gravity of the toner changing due to stirring. However, since it affects the level at which fullness is detected, it has been difficult to achieve a stable and small amount of toner supply.

  Therefore, the present invention is suitable to detect two different toner amount levels only by providing one sensor even in a small developing device such as a one-component developing device. Provided is an image forming apparatus that can perform a replenishment of toner and that can control the amount of replenishment of toner to a small amount and does not cause a charging failure or streak unevenness at the time of replenishment. The purpose is that.

  In order to solve the above problems, the present invention employs the following configuration.

In other words, the first aspect of the present invention includes a hopper portion into which toner for development is placed,
A stirring member that stirs the toner inside the hopper,
A toner replenishing device for replenishing toner into the hopper,
One sensor for detecting the amount of toner inside the hopper,
A control device that receives a detection signal from the sensor and outputs a supply command and a supply stop command to the toner supply device based on the detection signal;
The control device detects that the toner is full based on the detection signal of the sensor at the time of toner replenishment, and sets a threshold value for stopping the replenishment, and the threshold value starts at least toner replenishment The predetermined period after that changes with the toner replenishment time,
The control device is an image forming device that stops toner supply when it is detected that the toner amount has reached an upper limit level.

According to the second aspect of the present invention, a threshold value for detecting that the toner amount is a lower limit level that needs to be replenished is set in the control device,
The control device is the image forming apparatus according to the first aspect of the present invention, wherein replenishment of toner is started when it is detected that the toner amount is small based on the threshold value.

  According to a third aspect of the present invention, the threshold value for stopping toner replenishment is set more easily to detect the presence of toner than the threshold value for starting toner replenishment. This is an image forming apparatus.

  According to a fourth aspect of the present invention, after the replenishment time has elapsed, the threshold value for stopping toner replenishment is set to detect the toner present state more easily than the threshold value for starting toner replenishment. The image forming apparatus according to the second or third aspect of the present invention.

  The image forming apparatus according to the present invention detects the amount of toner with one sensor, but among the threshold values for processing the detection signal, the upper threshold value for stopping the replenishment operation is changed according to the replenishment time. Thus, the full state can be detected stably, and the amount of replenishment can be reduced.

  Hereinafter, embodiments of the present invention will be specifically described. FIG. 1 is a schematic diagram showing a configuration of an image forming apparatus 1. A photoconductor 3 including a rotating drum is provided inside a machine frame 2. Is to be supplied. Around the photosensitive member 3, a charging member 5, a cleaning member 6, a sliding contact member 7 and the like for charging the photosensitive member 3 are provided.

  A developing device 10 is provided so as to face the outer peripheral surface of the photoreceptor 3. The developing device 10 shown in the figure is a rotary developing device that alternately supplies four color toners to the photosensitive member 3 by rotation, and is divided into four sections (developing devices) 10a, 10b, 10c, and 10d. Each section is a different color developer. The developing device 10 is supplied with toner from the toner replenishing device 15 when the remaining amount of toner reaches a predetermined amount. Reference numeral 16 denotes a supply pipe provided in the toner supply device 15. The toner supply device 15 is provided with a toner transport device (not shown).

  An intermediate transfer unit 20 is provided so as to be in contact with the photoreceptor 3 formed of the rotating drum. The intermediate transfer unit 20 includes a transfer belt 21 that circulates in the direction of the arrow, and a transfer portion 22 is provided at one end thereof. A fixing unit 25 is provided on the downstream side of the intermediate transfer unit 20. In FIG. 1, 26 is a paper cassette, and 28 is a discharge roller.

  In this image forming apparatus 1, a photosensitive member 3 composed of a rotating drum is charged by a charging member 5, and an image is written on the outer peripheral surface of the photosensitive member 3 by a laser scanning unit to form a latent image. The latent image is developed by the developing device 10 to become a visible image with toner, and is transferred to the intermediate transfer belt 21. The rotary developing device 10 supplies toner of the necessary color (held separately in each of the four developing devices) to the photoreceptor 3 while rotating at a predetermined timing.

  The visible image transferred to the intermediate transfer belt 21 is transferred to a sheet fed from the sheet cassette 26 at a predetermined timing by the transfer unit 22 and then fixed by heat and pressure applied by the fixing unit 25. The The sheet on which the image is formed in this manner is discharged to the outside by the discharge roller 28.

  On the other hand, since the toner for developing the image is consumed by use, it is replenished by the replenishing device 15 when the remaining amount in the developing device 10 reaches a predetermined amount. This replenishment amount is preferably reduced to some extent so as not to cause the streaky unevenness and fog. Specifically, for example, it is preferable to use about 5 g of new toner with respect to 40 g of old toner. FIG. 2 is an enlarged view of one section 10a of the developing device 10. In this developing device 10a, a hopper portion 30 for supplying toner and the toner in the hopper portion 30 are supplied to the developing roller 31 side. A stirring member 40, a supply roller 32 that supplies toner supplied from the hopper 30 to the developing roller 31, and a regulating member 34 that regulates and charges the toner of the developing roller 31 are provided. Reference numeral 35 denotes a seal member that seals a portion where the developed toner returns to the developing device and prevents toner spillage.

  As shown in FIG. 3, the stirring member 40 is provided in the hopper portion 30. The stirring member 40 includes a stirring member shaft 41 and stirs toner while rotating. The stirring member shaft 41 is provided with a stirring blade 42 with a window 42a. By stirring by the stirring member 40, a part of the powdery toner rises and affects the amount of light passing through the sensor 55. For this reason, the amount of toner can be detected by one sensor based on the density of transmitted light. On the upper side of the stirring member 40, a cleaning rotary disk 45 is provided, and the rotary disk 45 is provided with a pair of left and right rod-like members 46 and 46 protruding from both diametrical positions. Light guide cleaning members 47 and 47 made of a thin film are attached to the pair of rod-like members 46 and 46. When toner supply control to the developing device is started, the rotating disk 45 rotates in a predetermined direction, and the cleaning member 47 cleans the surface of the light guide described later.

  A pair of light guide members 50 are provided at the level at which the rotary disk 45 for cleaning is provided, that is, slightly above the agitation shaft member 41, at both left and right positions in the hopper 30. FIG. 4 shows these arrangements. The light guide member 50 is made of a transparent acrylic resin, and includes a light emitting side light guide member 51 and a light receiving side light guide member 52, and a photoelectric sensor 55 is formed outside the side surface of the developing device 10. A light emitting element 56 and a light receiving element 57 are provided. The light emitted from the light emitting element 56 passes through the light emitting side light guide member 51 to reach the tip, bends at right angles from the inclined tip and crosses the hopper 30, and then receives the light receiving side light guide member. The light enters the light receiving element 57 through 52.

  As the toner replenishment control is started, newly replenished toner enters between the light guide cleaning member 47, the light emitting side light guide member 51, and the light receiving side light guide member 52. The surface of the guide member 50 is frictionally cleaned, and the old toner adhering to the surface of the light guide member 50 is removed.

  The light emitting element 56 and the light receiving element 57 are connected to the control device 60. The control device 60 converts an analog signal representing the amount of light received from the light receiving element 57 as a voltage into a digital signal. Since the toner is powder, when it is agitated, the light passage from the light-emitting side light guide member 50 to the light-receiving side light guide member 51 is interrupted, and the operation of light passing immediately after passing through the cleaning member 47 is repeated. Gives the amount of light and shade change. For this reason, the voltage representing the amount of light received by the light receiving element 57 changes in an analog manner in a wave shape. If the amount of toner is large, light does not easily pass through, so the voltage of the light receiving element 57 becomes low. Conversely, when the amount of toner is small, light is easily transmitted, and thus the voltage of the light receiving element 57 becomes high. Therefore, an appropriate threshold value for controlling the toner amount is set in the memory of the control device 60 in correspondence with the voltage value and converted into a digital signal. As the threshold value, basically, two values are set corresponding to level 1 indicating the upper limit (full state) of toner supply and level 2 indicating the lower limit to start toner supply. deep. That is, when the actual toner level is high, the threshold value is low, and when the actual toner level is low, the threshold value is high. However, as will be described later, when considering the friction cleaning function of the light guide cleaning members 47, 47, the relationship between the toner level and the threshold value may be reversed (see FIG. 6).

  The position of the sensor 55, the toner replenishment start level, and the full level at which replenishment should be stopped may be set to the most preferable values according to the model and the like. The threshold value may be set to such a value that these levels are actually detected.

  FIG. 5 is a flowchart showing control for replenishing toner based on the detection of the sensor 55. The toner replenishment control will be described with reference to FIG. In this embodiment, the sensor 55 is not always driven. When the toner consumption amount reaches the second predetermined amount (ST4) during printing (development) (ST1), the sensor 55 is driven. , Detecting the remaining amount of toner. First, the printing rate by printing is integrated (ST2), and based on this, the toner consumption is calculated (ST3). It is determined whether or not the calculated toner consumption has reached a predetermined value (level 2) (ST4). If No, the process returns to the start, and if Yes, toner replenishment control is started.

  In the toner replenishment control, it is determined whether or not the remaining amount of toner detected by the sensor 55 is sufficient for printing (whether it is greater than level 2) (ST31), and the remaining amount of toner is sufficient for printing. If it is determined that the amount is sufficient, a printing operation is performed. Whether or not the remaining amount of toner is sufficient can be determined by comparing the voltage of the light receiving sensor 57 with the threshold value for starting replenishment (corresponding to level 1). When the calculated consumption amount reaches a predetermined amount, but the remaining amount of toner by the sensor is determined to be equal to or higher than level 2, predetermined additional consumption is performed and toner supply control is started again.

  If the remaining amount of toner is at the level at which replenishment should be started (level 2), the rotary of the developing device is rotated, and the replenishment target developer (for example, 10a) is moved to the replenishment position (ST32). Next, the supply pipe 16 is inserted into the developing device 10a (ST33). In this state, the screw, container and the like provided in the supply pipe 16 are driven to start toner supply (ST35).

  When a predetermined time has elapsed from the start of replenishment, it is determined whether or not the toner amount has become full (level 1) (ST36). If not, replenishment is continued. If it is detected that the toner is full, the toner supply is stopped (ST37), the calculated consumption is reset (ST38), and the replenishment target developer is stopped (ST39). The supply pipe 16 is extracted from the developing device (ST40). This completes the toner supply control.

  Whether the amount of toner in the developing device is an amount to start toner supply (level 2) or a full state to stop supply (level 1) depends on the voltage of the light receiving element 57 constituting the sensor 55. Detected by the threshold value set in the control device 60 for digitization. In this embodiment, two types of threshold values for level 1 and level 2 are set, and each level is detected, but the threshold value for detecting level 1 representing the amount for which supply should be stopped is set. It is preferable that the threshold value for detecting level 2 is set so that the presence of toner can be detected more easily. That is, the former value (threshold value for detecting level 1) is set larger than the latter value (threshold value for detecting level 2). This is because the light guide cleaning members 47 and 47 correspond to a change in the light amount caused by cleaning the surface of the light guide member 50 when the toner is replenished. That is, since old toner adheres to the surface of the light guide member 50, the light transmission amount is reduced. However, the light guide cleaning members 47 and 47 clean the surface to gradually increase the light transmission amount. This is because even if the toner level is the same, the output voltage of the light receiving element is higher than immediately after the start of replenishment. FIG. 6 shows the relationship between the threshold values corresponding to level 1 and level 2. Note that the voltage value for detecting toner fullness is stabilized after a certain time (20 seconds in the embodiment) has elapsed. The change in the threshold value during the period until stabilization will be described later.

  By doing so, the amount of toner replenishment can be reduced, and even when additional replenishment is performed, it is possible to suppress the occurrence of charging defects and streak unevenness in the developing device and obtain a good image. That is, if this is not done, the amount of light received by the light receiving element 57 is increased only by polishing the surfaces of the light guide cleaning members 47 and 47 even though the toner level is not lowered. This is because the applied voltage becomes high and the toner level is erroneously determined to be “low”.

  In the above description, the relationship between the threshold values corresponding to level 1 and level 2 after the voltage value for detecting toner full is stabilized (20 seconds after the start of replenishment shown in FIG. 6) has been mainly described.

  Next, the change in the threshold value corresponding to level 1 in the period from the start of replenishment to the elapse of a predetermined time T (20 seconds in the illustrated example) will be mainly described. An example of the “replenishment time after a predetermined time” according to the present invention corresponds to the time after the time when the solid line and the dotted line in FIG. 6 cross each other.

  FIG. 6 shows these two thresholds, and the upper limit threshold H1 for detecting fullness (level at which replenishment is stopped) is set so as to change with the replenishment time, as shown by the solid line in the figure. That is, for a predetermined time T (20 seconds in the illustrated example) from the start of replenishment, the threshold value (V) rises linearly from 0 to 1.5 and thereafter remains constant. Further, the level requiring replenishment (referred to as “empty detection level”) is maintained constant (0.5 V in the illustrated example) as indicated by the broken line in the figure.

  The amount of light received by the light receiving element 57 tends to gradually change (usually increases) with the start of the replenishment operation due to the effect that the surface of the light guide member is cleaned by the cleaning member 47, etc. Accordingly, if the threshold value for detecting the upper limit is set so as to change with time from the start of replenishment, it is possible to detect stably even if the amount of received light changes.

  As a specific example, for example, when the signal of the light emitting element 26 is set so that a maximum signal of 3.2 V can be obtained when light passes through the developing device, the threshold value level is constant (1.0 V). When supply control is performed, the supply amount changes in the range of 5 to 10 g, and it is difficult to control the supply amount at 5 g or less. However, as shown in FIG. 6, by controlling the threshold, the replenishment amount can be lowered to a range of 2 to 4 g, and at the same time, replenishment errors can be reduced.

  After the replenishment time has elapsed (approximately 7 seconds in FIG. 6), the upper threshold value after the start of toner replenishment is greater than the lower threshold value for determining the start of toner replenishment. It is preferable to set the presence easily. If the relationship between the threshold values is as described above, it is possible to prevent excessive supply of new toner even when additional replenishment is performed, and to suppress the occurrence of charging defects and streak unevenness in the developing device. It is easy to obtain an image.

  This developing device can detect two different toner levels using one (one set) sensor. Even in a small-sized developing device with little space, this sensor can store two levels of toner. It is possible to effectively perform toner replenishment control so as to detect the amount and prevent printing defects and image defects. In the above description, the rotary type developing device has been described as an example, but the same applies to a non-rotary type developing device. Further, the developing device using a one-component toner as the toner has been described as an example, but it goes without saying that the present invention can be similarly applied to a two-component developing device.

  The image forming apparatus of the present invention can be employed as a copying machine, a printer, a facsimile, or the like.

Sectional drawing which represents typically the structure of the image forming apparatus which is one embodiment of this invention Enlarged sectional view of the developing device in the image forming apparatus of the present embodiment Enlarged perspective view of the main part of the developing device in the present embodiment Plan view of the developing device in the present embodiment Flowchart diagram illustrating toner supply control in the present embodiment The figure explaining the example of a setting of the threshold value in this Embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Machine frame 3 Photoconductor 5 Charging member 10 Developing apparatus 15 Replenishment apparatus 20 Intermediate transfer unit 55 Sensor 56 Light emitting element 57 Light receiving element 60 Control apparatus

Claims (4)

A hopper that holds toner for development;
A stirring member that stirs the toner inside the hopper,
A toner replenishing device for replenishing toner into the hopper,
One sensor for detecting the amount of toner inside the hopper,
A control device that receives a detection signal from the sensor and outputs a supply command and a supply stop command to the toner supply device based on the detection signal;
The control device detects that the toner is full based on the detection signal of the sensor at the time of toner replenishment, and sets a threshold value for stopping the replenishment, and the threshold value starts at least toner replenishment The predetermined period after that changes with the toner replenishment time,
The control device is an image forming apparatus that stops toner supply when it is detected that the toner amount has reached an upper limit level. The control device is set with a threshold value for detecting that the toner amount is at a level that requires replenishment,
The image forming apparatus according to claim 1, wherein the control device starts toner supply when it is detected that the toner amount is small based on the threshold value.   The image forming apparatus according to claim 1, wherein the threshold value for stopping toner replenishment is set to detect a toner present state more easily than the threshold value for starting toner replenishment.   The threshold value for stopping toner supply after the replenishment time has elapsed is set to detect the state of toner more easily than the threshold value for starting toner supply. The image forming apparatus described.

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