JP2018128559A - Toner concentration detection device and developing device using the same, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner density detection device that is a non-contact type and can accurately detect toner concentration and a developing device using the same, and an image forming apparatus.SOLUTION: A toner concentration detection device detects the concentration of toner in a developer that is conveyed through an internal space formed by a wall surface as a conveyance path with a sensor provided on the outside of the wall surface; the internal space of a first area facing a detection area of the sensor across the wall surface in the conveyance path is smaller than those of second areas adjacent to the first area in the conveyance path.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a toner concentration detection device, a developing device using the same, and an image forming device, and is suitable for controlling the toner concentration of a two-component developer composed of a carrier and toner to an appropriate value.

  In the image forming apparatus, in order to perform stable electrostatic latent image formation by supplying appropriate toner from the developing device to the photosensitive drum, it is necessary to maintain the toner concentration in the developer at an appropriate value. For this purpose, it is necessary to detect the toner density with high accuracy and to supply an appropriate amount of developer according to the detection result. As a detection method, a system configuration has been proposed in which a carrier in a developer is a detection target and the concentration is detected from a change in inductance of a coil of an LC resonance circuit. In this case, the ratio of the toner to the carrier is detected as the toner concentration.

  Patent Document 1 proposes a sensor (contact sensor) in which a winding coil formed by winding a conductive wire around a bobbin-shaped member is covered with a resin case, and the detection unit is fitted into the wall surface of the developer. ing. However, in such a configuration of fitting on the wall surface of the developing device, the developing device and the sensor must be in close contact with each other by sticking a double-sided tape around the fitting portion in order to ensure installation reliability. In this case, if the double-sided tape is peeled off, a cost for repair is required. Further, when the fitting to the developing device wall surface is insufficient, the developer may leak out.

  Therefore, Patent Document 2 proposes a toner concentration detection sensor (non-contact sensor) that uses a spiral pattern drawn on a printed circuit board as a coil of an LC resonance circuit. This sensor is affixed without making a hole for fitting in the developing device wall surface, and is not in contact with the developer in the developing device.

JP-A-1-50080 Japanese Utility Model Publication No. 6-76961

  At present, there is a tendency to reduce the amount of carrier in the developing device from the viewpoint of cost reduction, but in the case of a conventional toner concentration sensor that is fitted on the wall surface of the developing device, the coil does not move even when the amount of developer is small. Enclosed protrusions narrow the developer transport path. Thus, by increasing the volume of the developer in the vicinity of the detection area of the sensor, accurate toner detection can be performed without air being present in the detection area.

  However, in the case of a non-contact type toner density sensor, it does not affect the developer transport state in the developing device, so that the developer is pushed up like the above-mentioned type of sensor that fits on the developing device wall surface. There is no. Therefore, when the volume of the developer is low, air enters the detection region of the sensor. Since air is equivalent to toner for the sensor, the sensor detects higher than the toner density of the actual developer.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a non-contact type toner density detecting device capable of correctly detecting a toner density, a developing device using the same, and an image forming apparatus.

  In order to achieve the above object, a toner concentration detection device according to the present invention is a sensor provided outside the wall surface for measuring the toner concentration in the developer conveyed using an internal space formed by the wall surface as a conveyance path. The first area facing the detection area of the sensor via the wall surface in the conveyance path is a second adjacent to the first area in the conveyance path. The internal space is narrower than the area of (5).

  A developing device and an image forming apparatus according to the present invention include the toner density detecting device.

  According to the present invention, it is possible to provide a non-contact type toner density detecting device capable of correctly detecting the toner density, a developing device using the same, and an image forming apparatus.

1 is a schematic configuration diagram of an image forming apparatus using a toner concentration detecting device and a developing device according to an embodiment of the present invention. 1 is a configuration diagram illustrating a relationship between a toner concentration detection sensor and a developing device according to an embodiment of the present invention. The timing chart which shows the specification of the period counter 305 regarding the toner concentration detection apparatus which concerns on embodiment of this invention. FIG. 3 is a perspective view showing a positional relationship between a toner concentration detection device according to an embodiment of the present invention and a wall surface of the developing device 14. (A) is sectional drawing seen from the rotation axis direction of the developer conveyance screw in the vicinity of the detection range of the toner density | concentration detection sensor 300 which concerns on embodiment of this invention, (b) is sectional drawing in the prior art example as a comparative example. (A) is a diagram showing the behavior of the developer inside the developing device facing the toner density sensor 300 according to the embodiment of the present invention, and (b) is the behavior of the developer inside the developing device in the conventional example as a comparative example. Illustration (A) is a diagram showing a first region facing the detection region of the toner density sensor and a second region adjacent to the first region as a developer conveyance path inside the developing device in the embodiment of the present invention. (B) is a figure which shows the 1st area | region facing the detection area | region of the toner density sensor in a modification, and the 2nd area | region adjacent to a 1st area | region.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

<< First Embodiment >>
(Image forming device)
As shown in FIG. 1, an image forming apparatus 100 using a toner density detecting device and a developing device of the present embodiment optically reads an original image with an image reading unit 1R, and outputs an image signal for each color component to an image output unit. Send to 1P. In the image reading unit 1R, when a document is placed on the document table and the copy button is pressed by the user, light is emitted from the light source, and light reflected by the document is received by the image sensor 90 via the reflecting mirror. Reflected light from the document received by the image sensor 90 is divided into reflected light for each color component of yellow, magenta, cyan, and black by a color filter, and converted into an image signal for forming a toner image of each color component. The

  The image signals of the respective color components are input to exposure devices 13a, 13b, 13c, and 13d corresponding to the color components of image forming units 10a, 10b, 10c, and 10d, which will be described later. In the image output unit 1P, four image forming units 10a, 10b, 10c, and 10d are arranged in a line. The image forming unit 10a forms a black toner image, the image forming unit 10b forms a cyan toner image, the image forming unit 10c forms a magenta toner image, and the image forming unit 10d forms a yellow toner image. To do.

  The image forming unit 10a includes a charger 12a, an exposure device 13a, a developing device 14, a primary transfer roller 35a, and a drum cleaner 15a around a photosensitive drum 11a that carries a black toner image. Here, the charger 12a charges the photosensitive drum 11a. The exposure device 13a receives the image signal corresponding to the black color component described above, and forms an electrostatic latent image corresponding to the black color component on the photosensitive drum 11a. To do.

  The developing device 14 visualizes the electrostatic latent image formed on the photosensitive drum 11a as a toner image using a developer having toner. As the developer in this embodiment, a two-component developer having a toner and a carrier is used.

  The primary transfer roller 35a transfers a black color component toner image carried on the photosensitive drum 11a to an intermediate transfer belt 30 described later. The drum cleaner 15a removes toner remaining on the photosensitive drum 11a. Since the image forming units 10b, 10c, and 10d have the same configuration as the image forming unit 10a, the description thereof is omitted here. The above-described intermediate transfer belt 30 is an image carrier on which a toner image is carried, and the toner image of each color component formed by the image forming units 10a, 10b, 10c, and 10d is carried on the intermediate transfer belt 30 in an overlapping manner. As a result, a full-color toner image is formed.

  The intermediate transfer belt 30 is wound around a drive roller 32 that rotates the intermediate transfer belt 30, a driven roller 33, and a secondary transfer counter roller 34 described below. 1 is rotated in the direction of arrow B. A portion where the primary transfer roller 35a presses the photosensitive drum 11a via the intermediate transfer belt 30 is defined as a primary transfer nip portion Ta.

  Around the intermediate transfer belt 30, a secondary transfer roller 36 for transferring the toner image on the intermediate transfer belt 30 onto a recording material P such as paper is disposed. A portion where the secondary transfer roller 36 presses the secondary transfer counter roller 34 via the intermediate transfer belt 30 is defined as a secondary transfer nip portion Te. Further, a belt cleaner 50 for removing toner remaining without being transferred from the intermediate transfer belt 30 to the recording material P is provided as shown in FIG.

(Developing device, toner concentration detection device, toner concentration control device)
Next, the developing devices 14a, 14b, 14c, and 14d as developing devices provided in the above-described image forming apparatus will be described in detail. Here, each of the developing devices 14a, 14b, 14c, and 14d can be equipped with a toner concentration detecting device formed mainly with a toner concentration detecting sensor. Then, the toner density is controlled by the toner density control device using the detection result of each toner density detection device.

  FIG. 2 is a configuration diagram showing the relationship between the toner density control device and one of the developing devices 14a, 14b, 14c, and 14d (denoted as the developing device 14 in the drawing for the sake of simplicity). The developer replenishing mechanism shown in FIG. 2 develops from a toner bottle (not shown) that is replaceably attached to the apparatus main body to the developing device 14 via a hopper 200 as a storage container for temporarily storing the developer. It is configured to replenish the agent. For convenience, the hopper 200 is shown as viewed from the side, and the developing device 14 is shown as viewed from above. The developing device 14 contains a two-component developer having a toner and a carrier.

  The developing device 14 carries a stirring screw 144 as developer conveying means composed of two sets and a stirred developer so that the developer is cyclically conveyed while stirring in the arrow direction in FIG. A developing sleeve 143 as a developer carrying member is a main member. In the present embodiment, the two agitating screws 144 that rotate around the rotation shaft are rotationally driven by a drive motor 145 via gears, and this drive motor 145 is driven by a developer replenishment control unit 400 described later. The configuration is controlled. The developing sleeve 143 is rotationally driven by a driving motor 146, and the driving motor 146 is configured to be driven and controlled by a motor control unit (not shown).

  In such a developing device 14, the developer is transported by the stirring screw 144 using the inner space formed by the wall surface 14 s (FIG. 5, FIG. 7) as the inner wall of the housing, and is transferred to the developing sleeve 143. A developer is carried. Then, the toner concentration in the developer conveyed using the internal space formed by the wall surface 14s as a conveyance path is detected via the wall surface 14s by a toner concentration detection sensor (hereinafter referred to as sensor) 300 provided outside the wall surface 14s. ing.

  More specifically, the sensor 300 is installed in a housing in the apparatus so that the coil 301 serving as a detection member is close to the side surface of the developing device 14. Here, when the developer in the developing device 14 is stirred by the stirring screw 144, the toner is electrostatically adsorbed to a carrier as a magnetic material. The carrier to which the toner is attached is carried on the developing sleeve 143 by a magnetic force from a magnet (not shown), and only the toner is consumed by developing the electrostatic latent image as a toner image.

  The sensor 300 includes constituent elements surrounded by a broken line shown in FIG. The coil 301 and the capacitor 302 form a parallel resonance circuit. One end of the capacitor 302 is connected to the plus terminal of the operational amplifier 303 and further connected to a resistor 304 that positively feeds back the output of the operational amplifier 303. The other end of the capacitor 302 is connected to the negative terminal of the operational amplifier 303.

  A reference voltage vref is applied to the negative terminal of the operational amplifier 303. The reference voltage vref is ½ level of the power supply vcc of the operational amplifier. A self-oscillation circuit is formed by the configuration of these 301 to 304. When there is no magnetic substance around the circuit, the resonance period T of this self-excited oscillation circuit is expressed by the following equation, where L is the inductance of each coil of the coil 301 and C is the capacitance of the capacitor 302.

  The carrier in the developer is a magnetic substance, and when the relative permeability as the developer is μs, the inductance when the coil detects the developer is changed from L to μsL. The resonance period T of the oscillation circuit at this time is expressed by the following equation.

  The developer accumulated in the developing device 14 develops because when the toner in the developer is consumed by developing the electrostatic latent image with the toner, the amount of carrier, which is a magnetic material, relatively increases. The relative magnetic permeability as the agent is increased, and the resonance period T is increased. On the other hand, when the amount of toner in the developer is increased by replenishing a developer with a high toner ratio, which is approximately 90% toner from the hopper 200, the amount of carrier as a magnetic material is relatively reduced. The relative permeability as a developer is lowered, and the resonance period T is shortened.

  The period counter 305 counts the resonance period, which changes in accordance with the carrier ratio in the developer, in this way with the clock transmitted from the oscillator 306. The sensor 300 is configured by the members 301 to 306 described above. In the present embodiment, the sensor 300 is constructed by mounting other components on a substrate on which a winding forming the coil 301 is printed.

  The count chart of the period counter 305 is shown in the time chart of FIG. The period counter 305 counts the time corresponding to 2048 cycles of the resonance signal. In this way, by counting a certain number of periods, a minute change in the oscillation period can be clearly expressed without using a remarkably fast clock as a count clock. As for the count value of the count cycle 1 on the chart, the count data 1 is stored in the cycle count value register when the count is completed.

  After the count period 1, the count of the count period 2 is performed again after an interval of 4096 cycles, and the value of the period count value register is updated to the count data 2. For example, when the resonance frequency transitions around 1 MHz, the count data is updated around 6.144 ms. If the clock used for counting is 6 MHz, the count data is a value around 12288.

  The developer replenishment control unit 400 as a developer replenishment control unit reads count data stored in the cycle count value register of the cycle counter 305 via serial communication. If the read count data is larger than the developer replenishment determination level, it is determined that the toner is consumed and the carrier concentration in the developer is high (the toner concentration is lower than a predetermined value). Then, the screw 206 is rotated via the motor 207 to supply a developer having a high toner concentration from the hopper 200.

  FIG. 4 is a perspective view showing an arrangement image of the sensor 300 on the side surface of the developing device 14. A coil 301 is formed on the side of the printed circuit board 600 that contacts the wall surface 14s of the developing device 14 (the back surface of the printed circuit board 600) via a capacitor 302 and a via. In FIG. 4, the X direction is the developer transport direction, the Y direction is perpendicular to the X direction and directly facing the sensor 300, and the Z direction is perpendicular to the X and Y directions.

  Other members constituting the sensor 300 are integrated in the IC 500 except that the oscillator 306 is mounted alone. Serial communication signals to the power source, the ground, and the developer replenishment control unit are supplied via the connector 501.

  FIG. 5 is a cross-sectional view orthogonal to the longitudinal direction of the developing device 14 in the vicinity of the detection range of the sensor 300 (the X direction, which is the developer transport direction). FIG. 5A shows a configuration in this embodiment in which a protrusion (convex shape) 700 is provided on the inner wall 14a of the developing device 14 at a position (inside the wall surface 14s) facing the coil pattern of the coil 301 in the sensor 300. is there. FIG. 4B shows a cross-sectional view of a configuration of a comparative example having no protrusions with respect to FIG.

  FIG. 6 is a diagram illustrating the behavior of the developer inside the developing device 14 as viewed from the direction facing the sensor 300 (the Y direction in FIG. 4). FIG. 6A shows a configuration in which a protrusion 700 is provided on the inner wall 14a of the developing device 14 of the present embodiment. FIG. 6B shows a configuration in a comparative example having no protrusion.

  In the case of FIGS. 5A and 6A, the flow path (conveyance path) of the developer conveyed from the upstream by the protrusion 700 of the inner wall 14a of the developing device 14 formed within the detection range of the sensor 300. ) Is narrowed in the vicinity thereof (FIG. 7A). That is, when the developer is transported using the internal space formed by the s wall surface 14s of the developing device 14 as a transport path, a region that faces the detection region of the sensor 300 via the wall surface 14s in the transport path (the first shown in FIG. 7). In the region 1 L1), the internal space is narrowed.

  The first area L1 has a narrower inner space than the second area L2 adjacent in the conveyance path. More preferably, the internal space of the first region L1 is narrower than all other regions in the transport path. In FIG. 7, the protruding portion 700 is arranged away from the sensor 300 as shown in FIG. 7B in addition to the case close to the sensor 300 as shown in FIG. May be.

  In this embodiment, even when the amount of the developer in the developing device 14 is small, the developer is pushed up to the detection range of the sensor 300, so that the air layer is hardly detected. Therefore, proper toner density detection is performed.

  On the other hand, in the case of FIG. 5B and FIG. 6B, since there is no protrusion 700, the developer is pushed up to the detection range of the sensor 300 when the amount of the developer in the developing device 14 is small. The sensor 300 sees the air layer as toner. For this reason, the detected toner density becomes larger than the actual value. In this case, even if the actual toner density is low and the toner needs to be replenished from the hopper 200, the toner is not replenished, and an image having an appropriate density cannot be formed.

  According to the present embodiment shown in FIG. 5A and FIG. 6A, the shape of the inner wall 14a of the developing device 14 is merely changed to a protruding shape, so that an increase in cost due to additional parts does not occur. Then, the toner density can be detected properly, and the reliability of image formation can be maintained.

(Modification)
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

(Modification 1)
In the above-described embodiment, the position where the protrusion 700 faces the sensor 300 via the inner wall 14a (the direction perpendicular to the sensor 300 as shown in FIGS. 7A and 7B is the 0 degree direction with respect to the sensor 300. However, the present invention is not limited to this. You may provide in the direction (for example, 90 degree direction) different from a 0 degree direction and a 180 degree direction with respect to the sensor 300 in the cross section orthogonal to a conveyance path.

(Modification 2)
In the embodiment described above, on the assumption that the diameter of the outer peripheral portion of the wall surface of the developing device 14 is constant along the conveyance path, the first area facing the sensor 300 in the conveyance path is more than the second area. Although the internal space is narrowed (FIG. 7), the present invention is not limited to this. In the area | region corresponding to a 1st area | region, the diameter of the outer peripheral part of a wall surface is narrower than the area | region corresponding to a 2nd area | region, and a 1st area | region is rather than the 2nd area | region adjacent to a 1st area | region. A configuration in which the internal space is narrowed may be used.

(Modification 3)
In the above-described embodiment, at least one of the photosensitive drum 1 and the developing device 14 may be provided as a cartridge that can be attached to and detached from the apparatus main body of the image forming apparatus, or both may be fixed inside the apparatus main body of the image forming apparatus. The structure provided may be sufficient.

14 s ··· Wall surface, 300 ·· Toner density detection sensor, 700 ··· Projection, L 1 ··· First region, L 2 ··· Second region

Claims (12)

A toner concentration detection device that detects a toner concentration in a developer conveyed through an internal space formed by a wall surface via a conveyance path by a sensor provided outside the wall surface,
The internal space of the first region facing the detection region of the sensor via the wall surface in the transport path is narrower than the second region adjacent to the first region in the transport path. A toner concentration detecting device.   2. The toner density detection device according to claim 1, wherein the inner space of the first area is narrower than all the areas different from the first area in the conveyance path.   3. The toner concentration detection apparatus according to claim 1, wherein the wall surface in the first region is provided with a protruding portion on an inner side so as to narrow the internal space.   4. The toner concentration detection apparatus according to claim 3, wherein the protrusion is provided in one of a region near the sensor or a region far from the sensor as the wall surface facing the detection region of the sensor. 5.   5. The toner concentration detection apparatus according to claim 1, wherein a diameter of an outer peripheral portion of the wall surface is constant along the conveyance path.   2. The toner concentration detection device according to claim 1, wherein a diameter of an outer peripheral portion of the wall surface is narrower in a region corresponding to the first region than in a region corresponding to the second region. .   7. The toner concentration detection apparatus according to claim 1, wherein the developer is a two-component developer having the toner and a carrier.   The toner concentration according to claim 7, wherein the sensor includes a self-excited oscillation circuit including a coil and a capacitor, and detects a ratio of the toner to the carrier based on a resonance period of the self-excited oscillation circuit. Detection device. A toner concentration detection device according to any one of claims 1 to 8,
A developer transport means provided in the internal space and transporting along the transport path while rotating the developer;
A developer carrying member carrying the developer conveyed by the developer conveying means;
A developing device comprising:   The developing device according to claim 9, wherein the developer conveying unit includes a stirring screw that rotates around a rotation shaft.   11. The developing device according to claim 9, further comprising a control unit that replenishes the developer when the toner concentration detected by the toner concentration detecting device is lower than a predetermined value. An image carrier;
A developing device according to any one of claims 9 to 11,
And at least one is provided as a cartridge that can be attached to and detached from the apparatus main body of the image forming apparatus, or both are fixedly provided inside the apparatus main body,
An image forming apparatus further comprising an exposure device for forming an electrostatic latent image on the image carrier.