JP2015087691A - Fluidity detecting device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and accurately recognize fluidity of a developer in an image forming apparatus.SOLUTION: A representative configuration of a fluidity detecting device and an image forming apparatus relating to the present invention includes four surfaces (wall surface 81, pressurizing member 82, first wall surface 2a, second wall surface 2b) consisting of two pairs of facing surfaces, a screw 3a for applying a pressure to a developer in a space S blocked by four surfaces, and at least two first pressure sensors 83a and a second pressure sensor 83b which are provided along the direction parallel to the four surfaces in the space S, on the first wall surface 2a, being one of the four surfaces, and detect a pressure of the developer. The fluidity of the developer is detected from a ratio between output values of at least two first pressure sensor 83a and second pressure sensor 83b.

Description

  The present invention relates to a fluidity detection device that detects the fluidity of a developer and an image forming apparatus using the fluidity detection device.

  As a developing device of a conventional image forming apparatus, there is one that uses a two-component developer using toner and a carrier. The two-component developer is triboelectrically charged by being stirred, and the toner is charged to a target charge polarity and charge amount. Depending on the state of use of the image forming apparatus, the developer itself may deteriorate, the fluidity of the developer may decrease, the developer coating state may become unstable, and image defects such as density unevenness may occur.

  Therefore, Patent Document 1 proposes a method of detecting the toner deterioration state by grasping the retention of the developer due to the decrease in fluidity from the bulk and wall pressure. Then, the flowability of the developer is controlled within a predetermined range by performing a toner discharging operation or the like based on the deterioration state of the toner.

  Patent Document 2 proposes a method of grasping the fluidity of the developer by actively driving the pressure detection means with respect to the developer.

JP2008-076428 JP 2006-106590 A

  However, the developer is a powder, and it is very difficult to accurately detect the fluidity of the powder. In order to grasp the bulk density of the developer, it is necessary to evaluate the bulk density from the volume change while keeping the weight of the developer constant. For this reason, a mechanism for keeping the amount of developer constant in weight in the developing device is required. Moreover, since the change in the bulk density itself is very small, it is disadvantageous in terms of detection accuracy.

  Further, the pressure of the powder is easily affected by the developer filling amount and the conveyance amount. For example, when fluidity is detected by the load on the developer and the pressure applied to the inner wall of the developer container with respect to the developer, when the powder is stirred at a constant speed, the load on the screw changes with the fluidity. There is no monotonous increase or decrease. For this reason, it is difficult to accurately detect fluidity.

  SUMMARY An advantage of some aspects of the invention is to easily and accurately grasp the fluidity of a developer in an image forming apparatus.

  In order to solve the above problems, a representative configuration of the fluidity detection device and the image forming apparatus according to the present invention includes four surfaces formed by two pairs of opposing surfaces, and a space closed by the four surfaces. Pressurizing means for applying pressure to the developer, and at least two of the four surfaces that are provided along a direction parallel to the four surfaces of the space to detect the pressure of the developer Detecting means, and detecting the fluidity of the developer from the ratio of the output values of each of the at least two detecting means.

  According to the present invention, the fluidity of the developer can be easily and accurately grasped in the image forming apparatus.

1 is a configuration diagram of an image forming apparatus according to a first embodiment. 1 is a configuration diagram of a developing device according to a first embodiment. FIG. 3 is a diagram illustrating the inside of the developing device according to the first embodiment. It is a block diagram of the fluidity | liquidity detection apparatus in the non-pressurized state which concerns on 1st Embodiment. It is a block diagram of the fluidity | liquidity detection apparatus in the pressurization state which concerns on 1st Embodiment. It is sectional drawing of the developing container which concerns on 1st Embodiment. It is a figure which shows the fluidity | liquidity detection apparatus periphery which concerns on 1st Embodiment. 6 is a control flow of a developer according to the first embodiment. It is a block diagram of the fluidity | liquidity detection apparatus which concerns on 2nd Embodiment. 5 is a configuration diagram of a pressure sensor of Comparative Example 1. FIG. 6 is a configuration diagram of a pressure sensor of Comparative Example 2. FIG. It is a block diagram of the pressure sensor of the comparative example 3. It is a figure which shows an experimental result.

[First Embodiment]
A fluidity detection device and an image forming apparatus according to a first embodiment of the invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an image forming apparatus according to the present embodiment.

  As shown in FIG. 1, an image forming apparatus 100 according to the present embodiment has photosensitive drums (image carriers) 4 (4Y, 4M, 4C, and 4K) juxtaposed. An electrostatic latent image is formed on the photosensitive drums 4Y to 4K by exposing the surfaces of the photosensitive drums 4 to 4K charged by the primary charger 21 (21Y to 21K) with a laser 22 (22Y to 22K). The

  The electrostatic latent image is developed as a toner image of each color of yellow, magenta, cyan, and black by the developing device 1 (1Y to 1K). The toner images of the respective colors are primarily transferred onto the intermediate transfer belt 24 by the primary transfer roller 23 (23Y to 23K). Transfer residual toner remaining on the photosensitive drums 4Y to 4K after the primary transfer is removed by a cleaner 26 (26Y to 26K).

  The toner image primarily transferred to the intermediate transfer belt 24 is secondarily transferred to the sheet 27 by the secondary transfer roller 23z. The sheet 27 on which the toner image is secondarily transferred is heated and pressed by the fixing device 25 to fix the toner image, and is discharged outside the apparatus. Transfer residual toner remaining on the intermediate transfer belt 24 after the secondary transfer is removed by the intermediate transfer belt cleaner 26z.

(Developing device 1)
FIG. 2 is a configuration diagram of the developing device of the present embodiment. As shown in FIG. 2, the developing device 1 includes a developing container 2, screws 3 a and 3 b, a developing sleeve 5, a magnet roll 6, and a magnetic blade 7. The developing container 2 includes a two-component developer using toner and carrier.

  The developer stored in the developing container 2 is stirred by screws 3 a and 3 b disposed in the developing container 2 and circulates in the developing container 2. As a result, frictional charging of the toner is promoted, and the toner density is made uniform throughout the developer. The charged toner is fixedly disposed in the developing sleeve 5, electrostatically adsorbed to the developing sleeve 5 by the magnet roll 6, and regulated to a certain amount by the magnetic blade 7. The developer that has moved to the development site by the rotation of the developing sleeve 5 generates magnetic spikes, and the toner moves to the photosensitive drum 4 in accordance with the electrostatic latent image to perform development.

(Fluidity detection device 8)
FIG. 3 shows the inside of the developing device. As shown in FIG. 3, the fluidity detection device 8 is disposed between the two screws 3a and 3b. The fluidity detecting device 8 is disposed at a place where the developer is transported from the screw 3a far from the developing sleeve 5 to the screw 3b. Thus, the developer flow sent from the screw 3a to the screw 3b is used to supply the developer to the detection portion.

  4 and 5 are configuration diagrams of the fluidity detection device 8 according to the present embodiment. As shown in FIGS. 4 and 5, the fluidity detection device 8 includes a wall surface 81, a pressure member (pressure means) 82, a first pressure sensor 83 a (detection means), and a second pressure sensor 83 b (detection means). )have. The developing container 2 has a first wall surface 2a and a second wall surface 2b. The wall surface 81, the pressure member 82, the first wall surface 2a, and the second wall surface 2b constitute four surfaces consisting of two pairs of opposed surfaces.

  The first wall surface 2a is orthogonal to the second wall surface 2b. The wall surface 81 is provided in parallel with the second wall surface 2b. The pressure member 82 is sandwiched between the wall surface 81 and the second wall surface 2b. The pressing member 82 is movable in a direction orthogonal to the first wall surface 2a. Specifically, the pressure member 82 can reciprocate between a position A in FIG. 4 and a position B in FIG. The pressure member 82 is a moving surface that constitutes one of the four surfaces.

  The pressure sensors 83a and 83b are provided on the first wall surface 2a. As shown in FIG. 6, the pressure sensor 83 a (one detection means) is provided at a position facing the pressure member 82. The pressure sensor 83b (the other detection means) is provided at a position that does not face the pressure member 82.

  The sensor surface of the pressure sensor 83a is orthogonal to the moving direction of the pressure member 82. Since the pressure applied to the powder (developer) is easily attenuated, highly accurate detection can be performed by matching the applied pressure direction with the detection direction.

  The pressure sensors 83a and 83b need to detect 1 to 200 g per square centimeter. In the present embodiment, pressure sensors using a polymer thick film are used as the pressure sensors 83a and 83b. By using a strain gauge such as a diaphragm, it can be detected with high accuracy.

  In the present embodiment, there are two detection means (pressure sensors 83a and 83b), but the present invention is not limited to this. There may be at least two, and the detection accuracy may be increased by three or four.

  As shown in FIGS. 4 and 5, a space S surrounded by a total of four surfaces of the first wall surface 2 a, the second wall surface 2 b, the wall surface 81, and the pressure member 82 is formed. The space S is filled with a developer, and the developer in the space can move in a uniaxial direction (developer transport direction) parallel to the four surfaces. That is, as shown in FIG. 7, the developer in the space S can move in a direction perpendicular to the longitudinal direction of the screw 3a by the conveying force of the screw 3a. The axis through which the developer (powder) can move is reduced, and the pressure member 82 is moved in a direction approaching the first wall surface 2a to apply pressure to the developer in the space S.

  Then, how the pressure applied to the developer is dispersed is detected by the pressure sensors 83a and 83b, and the fluidity of the developer is detected. In this way, an evaluation value that accurately reflects the fluidity of the developer is obtained by evaluating the rate of attenuation of the pressure using two or more pressure sensors 83a and 83b having different distances from the pressure member 82. It is done.

  Furthermore, an evaluation proportional to the fluidity is performed by evaluating a ratio R (R = P2 / P1) between the pressure P1 detected by the first pressure sensor 83a and the pressure P2 detected by the second pressure sensor 83b in the pressurized state. A value is obtained. The output of the pressure sensor shows a higher value as the force applied to the pressure sensor is larger. Therefore, the higher the developer fluidity and the more uniformly the force applied to the pressure member 82, the closer the pressure P2 detected by the second pressure sensor 83b approaches the pressure P1 detected by the first pressure sensor 83a. The ratio R takes a large value. The maximum value of the ratio R is when the pressures P1 and P2 of the pressure sensors 83a and 83b show the same value (that is, P1 = P2), and R = 1.

  The fluidity of the developer detected as described above is a very effective characteristic for grasping the deterioration state of the toner. When the toner is repeatedly stirred, the toner is exposed to a mechanical stress with the carrier every time the toner is triboelectrically charged, and the characteristics necessary for the toner such as chargeability and developability of the toner are deteriorated. There is a relationship between chargeability, developability, and developer fluidity. Along with the decrease in fluidity, the chance of frictional charging decreases, the uniformity decreases, and the chargeability decreases. Further, the developability as shown by the development efficiency at the time of development is greatly reduced.

(Control unit 300)
Therefore, in this embodiment, the fluidity of the developer is detected by the fluidity detection device 8 described above in order to maintain the toner characteristics over a long period of time. When the fluidity of the developer is lowered, the control unit 300 (see FIG. 1) controls the replacement of the toner in the developer as an operation for restoring the developer performance.

  FIG. 8 is a diagram illustrating the control of the developer according to the present embodiment. As shown in FIG. 8, the control unit 300 first sets a target lower limit value RL (RL = 0.4 in the present embodiment). Then, the pressing member 82 is moved from the position A in FIG. 4 to the position B in FIG. 5 in a direction approaching the first wall surface 2a (S2), pressure is applied to the developer, and the pressure P1 is applied by the pressure sensors 83a and 83b. , P2 is detected (S3). The controller 300 calculates the ratio R between the pressures P1 and P2 (S4), and determines whether R is equal to or greater than the lower limit value RL (S5). If R is greater than or equal to the lower limit value RL in S5, the process returns to S2. If R falls below the lower limit value RL in S5, an operation of replacing the toner in the developer is executed (S6), and the process returns to S2.

  In this way, by accurately grasping the fluidity of the developer and appropriately controlling it, the fluidity of the developer and further the deterioration state can be kept within a certain range, and the quality of the output image can be kept stable. Can do.

[Second Embodiment]
Next, a fluidity detection apparatus and an image forming apparatus according to a second embodiment of the present invention will be described with reference to the drawings. The same parts as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted.

  FIG. 9 is a configuration diagram of the fluidity detection device according to the present embodiment. As shown in FIG. 9, the fluidity detection device 18 of the present embodiment is different from the fluidity detection device 8 of the first embodiment in that the pressure member 82 is not provided, but the wall surface 81 is provided instead of the wall surface 81. Instead of the sensors 83a and 83b, pressure sensors 85a and 85b are provided.

  The wall surface 84 is formed of two L-shaped surfaces, a surface facing the first wall surface 2a and a surface facing the second wall surface 2b. Also in this embodiment, the developer has a space S surrounded by the four surfaces of the wall surface 84, the first wall surface 2a, and the second wall surface 2b. As in the first embodiment, the space S is filled with the developer, and the developer in the space S is movable in a uniaxial direction parallel to the four surfaces. That is, as shown in FIG. 7, the developer in the space S is moved in a direction perpendicular to the longitudinal direction of the screw 3a (from the front of FIG. 9) by the conveying force of the screw (pressurizing means, developer conveying member) 3a. It is possible to move.

  The pressure sensors 85a and 85b are provided on the second wall surface 2b along the developer transport direction. When pressure is applied to the developer in the space S by the conveying force of the screw 3a, the pressure sensors 85a and 85b detect the pressures P1 and P2 of the developer in the space S. The pressure dispersion can be detected by the pressure P1 detected by the pressure sensor 85a close to the screw 3a and the pressure P2 detected by the pressure sensor 85b far from the screw 3a. By comparing the pressures P1 and P2, the developer Fluidity is detected. Also, an evaluation value proportional to the fluidity can be obtained by evaluating the ratio R (R = P2 / P1) of the pressures P1 and P2.

(Experiment)
For the fluidity detection devices 8 and 18 of the first and second embodiments and Comparative Examples 1 to 3 below, an experiment for comparing the fluidity of the developer was performed.

[Comparative Example 1]
As shown in FIG. 10, the comparative example 1 is provided with a paddle 31 and a pressure sensor 32 in place of the fluidity detecting device 8 of the first embodiment. The paddle 31 is provided on the rotating shaft 3a1 of the screw 3a. The pressure sensor 32 is disposed on the paddle surface 31 a that presses the developer of the paddle 31. The pressure sensor 32 detects the fluidity of the developer. The paddle 31 conveys and stirs the developer as the screw 3a rotates. Since the pressure applied to the paddle surface 31a when stirring is changed depending on the fluidity of the developer, the fluidity is detected by this pressure.

[Comparative Example 2]
As shown in FIG. 11, in Comparative Example 2, in the fluidity detection device 8 of the first embodiment, one pressure sensor 86 is provided instead of the pressure sensors 83a and 83b. The pressure sensor 86 is provided at a position facing the moving direction of the pressure member 82, and detects the developer pressure to detect the developer fluidity.

[Comparative Example 3]
As shown in FIG. 12, Comparative Example 3 is provided with a wall surface 87 in place of the wall surface 81 in the fluidity detection device 8 of the first embodiment. The wall surface 87 is obtained by omitting a surface provided in parallel with the second wall surface 2 b of the wall surface 81. Thereby, the developer in the space S can be moved in a direction orthogonal to the second wall surface 2b. That is, as compared with the first embodiment, the degree of freedom of the developer in the space S increases from one axis to two axes.

(experimental method)
In each embodiment and each comparative example, an experiment was conducted to determine how accurately the evaluation value of fluidity can be detected using a plurality of developers (the following conditions 1 to 4). The evaluation value of the fluidity is the ratio R = P2 / P1 in the first and second embodiments and the comparative example 3. In Comparative Examples 1 and 2, since there is one sensor, the output value itself of the pressure sensors 32 and 86 is used as the fluidity evaluation value instead of the ratio R. The toner was prepared by mixing a binder resin, a colorant pigment, and a wax, followed by kneading, pulverization, and classification steps, and a pulverized toner having an average particle diameter (D4) of 5 microns was used. Titanium oxide was used as the external additive.

Developer condition 1: 200 g of developer mixed with 8% by weight of toner with no external additives added to the carrier,
Developer condition 2: As an external additive, a toner is prepared by externally adding 1.0% by weight to a titanium oxide toner, and 200 g of a developer in which the toner is mixed at 8% by weight with respect to a carrier.
Developer condition 3: As an external additive, a toner was prepared by externally adding 1.0% by weight to a titanium oxide toner, and 250 g of a developer in which the toner was mixed at 8% by weight with respect to a carrier.
Developer Condition 4: As an external additive, 200 g of a developer prepared by externally adding 2.0% by weight of titanium oxide to the toner and mixing the toner with 8% by weight of the carrier.

  FIG. 13 is a diagram showing experimental results. The developer measured values in FIG. 13 indicate measurement results ffc obtained by measuring the developers under conditions 1 to 4 using a fluidity measuring device. The measurement result ffc is an index obtained by a powder shear test using a powder rheometer FT4 (manufactured by Sysmex), and was used for evaluating the fluidity of a developer composed of two components. In this fluidity measuring apparatus, a circular shear is rotated while changing the main stress of the shear test, a stress shear diagram is created from the rotational torque, and a measurement result ffc is obtained. The larger the value of ffc, the easier it is to flow and the higher the fluidity. As measurement conditions, a shearing element having a diameter of 24 mm was used, and the maximum principal stress was measured at 9 kPa.

  The correlation shown in FIG. 13 is obtained by calculating the correlation coefficient between the evaluation value of each developer and each measurement result ffc. The correlation coefficient is a generally defined evaluation value that indicates a correlation between data strings composed of two sets of numerical values (x and y). For example, in the first embodiment, it is calculated from (x, y) = (0.05, 8), (0.25, 12), (0.25, 12), (0.55, 15). The correlation is 0.97. The closer the correlation coefficient is to 1 (-1 for inverse correlation), the more linear the relationship is, and the results of the same tendency as the fluidity measured by the fluidity measuring device are obtained, and the fluidity is correctly detected. It represents.

  As shown in FIG. 13, the measurement result ffc tends to be high under developer conditions 1 to 4.

  In the first embodiment, for developer conditions 1 to 4, the fluidity evaluation value (ratio R) increases in the same manner as the measurement result ffc, so that fluidity can be accurately detected. Also, the same value is returned for developer conditions 2 and 3 having different developer amounts. The correlation coefficient = 0.97, which indicates that the first embodiment can accurately detect the fluidity.

  In the second embodiment, as in the first embodiment, the fluidity evaluation value (ratio R) and the measurement result ffc show a good correlation. However, as shown in developer conditions 2 and 3, the developer It can be seen that the accuracy is slightly reduced when the amount changes. The pressure applied to each pressure sensor 85a, 85b is created by the screw 3a, and the pressure direction created by the screw 3a and the pressure sensors 85a, 85b are parallel to each other, and the sensitivity for detecting pressure dispersion is reduced. It is expected that. However, for developer conditions 1, 2 (3), and 4, the evaluation value (ratio R) of the developer condition with high fluidity is the evaluation value of the fluidity (ratio R) of the developer condition with low fluidity. ), Which is a good result.

  In Comparative Example 1, developer conditions 1, 3, and 4 and the evaluation value of fluidity are small. However, the fluidity evaluation value of developer condition 2 is significantly smaller than the fluidity evaluation value of developer conditions 3 and 4. Similarly, in Comparative Example 2, the evaluation value of fluidity is lowered with developer conditions 1, 2, and 4. However, the evaluation value of fluidity is greatly increased under developer conditions 2 and 3, and the order is changed. End up. Similarly, in Comparative Example 3, the evaluation values of the fluidity are significantly increased with the developer conditions 1, 2, and 4, but the evaluation value of the fluidity is decreased under the developer conditions 2 and 3, and the order is changed. End up.

  In Comparative Example 3, two pressure sensors 83a and 83b are used. However, since the degree of freedom of the developer is increased as compared with the first embodiment, the pressure received by the pressure sensors 83a and 83b is low. , The accuracy is degraded. That is, in Comparative Example 3, the developer has a spatial degree of freedom of two or more axes, and it is difficult to apply pressure to the developer.

  Therefore, when trying to determine the fluidity from the evaluation values of the fluidity of Comparative Examples 1 to 3, since the correspondence with the fluidity cannot be obtained around R = 0.2, accurate developer detection cannot be determined. . Further, developer conditions 2 and 3 have the same developer properties, but differ in the amount of developer charged in the developer. Also in this case, the evaluation values of the fluidity of Comparative Examples 1 to 3 are different values, and an accurate developer state cannot be detected.

  As described above, according to the first and second embodiments, the fluidity of the developer can be easily and accurately grasped in the image forming apparatus. In order to correctly evaluate the fluidity of the developer, as shown in the first and second embodiments, it is effective to cover at least two faces in total and cover a total of four faces and press some of the faces. Pressure can be applied to the developer. Further, by capturing the applied pressure with two or more pressure sensors having different distances from the pressure source and obtaining the ratio R, the degree of pressure dispersion can be evaluated and the fluidity can be correctly evaluated.

A, B ... Positions P1, P2 ... Pressure R ... Ratio RL ... Lower limit S ... Space ffc ... Measurement result 1 ... Developing device 2a ... First wall surface 2b ... Second wall surface 3a, 3b ... Screw (developer conveying member) )
3a1 ... rotating shaft 4 ... photosensitive drum 5 ... developing sleeve 6 ... magnet roll 7 ... magnetic blades 8 and 18 ... fluidity detecting device 31 ... paddle 31a ... paddle surfaces 81 and 84 ... wall surface 82 ... pressure member (pressurizing means, Moving surface)
83a ... 1st pressure sensor (detection means)
83b 2nd pressure sensor (detection means)
85a, 85b ... Pressure sensor (detection means)
DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus 300 ... Control part

Claims (7)

Four surfaces consisting of two pairs of opposing surfaces;
Pressurizing means for applying pressure to the developer in the space blocked by the four surfaces;
One of the four surfaces, provided along a direction parallel to the four surfaces of the space, and having at least two detection means for detecting the pressure of the developer,
A fluidity detecting apparatus, wherein the fluidity of a developer is detected from a ratio of output values of each of the at least two detecting means.
The fluidity detecting device according to claim 1, wherein the pressurizing unit is a moving surface that constitutes one of the four surfaces.
The one of the two detection means is provided at a position facing the moving surface, and the other detection means is provided at a position not facing the moving surface. 3. The fluidity detecting device according to 2.
The fluidity detecting device according to claim 3, wherein a sensor surface of the detecting unit provided at a position facing the moving surface is orthogonal to a moving direction of the moving surface.
The fluidity detecting device according to claim 1, wherein the pressurizing unit is a developer conveying member that conveys the developer in a direction parallel to the four surfaces of the space.
A developing device for developing the electrostatic latent image formed on the image carrier using a developer;
The fluidity detecting device according to any one of claims 1 to 5, wherein the fluidity of the developer in the developing device is detected.
An image forming apparatus comprising: a control unit that performs control to replace the developer in the developing device when the fluidity of the developer detected by the fluidity detecting device is lowered.
The developing device includes two developer conveying members that convey the developer,
The image forming apparatus according to claim 6, wherein the fluidity detecting device is disposed at a place where the developer is conveyed from one developer conveying member to the other developer conveying member.

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