JP2015108761A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress permeability fluctuations caused by the density variation of a developer, even when an external factor occurs.SOLUTION: An image forming apparatus 1 includes a stirring and conveying member 23 and a toner concentration detection sensor 28. The stirring and conveying member 23 includes a shaft member 24, a spiral member 25 extending in a spiral direction around the shaft member 24 and conveying the developer in an axial direction A, a first plate-like member 26 extending in the axial direction A and connecting the spiral member 25 on the upstream side in the conveyance direction G of the developer and the spiral member 25 on the downstream side in the conveyance direction G, and a second plate-like member 27 extending from the spiral member 25 on the upstream side in the conveyance direction G to the downstream side in the conveyance direction G along the axial direction A and forming a space L between the second plate-like member 27 and the spiral member on the downstream side. In the spiral member 25, a part facing the detection surface 29 of the toner concentration detection sensor 28 is notched. The first plate-like member 26 and the second plate-like member 27 are arranged so as to face the detection surface 29.

Description

  The present invention relates to an image forming apparatus.

  Conventionally, the toner concentration of the two-component developer circulating in the developing device in the image forming apparatus is calculated by detecting the magnetic permeability of the two-component developer including toner and carrier. This magnetic permeability detection result fluctuates not only due to the toner concentration but also due to fluctuations in the bulk density of the developer (the amount of air contained in the developer) or fluidity changes. For example, when an environmental change such as temperature and humidity occurs or when the process speed is switched, a change in the bulk density of the developer or a change in fluidity occurs, so that the detection result of the magnetic permeability changes.

  In this case, a technique is known in which the toner density fluctuation is suppressed by stabilizing the state of the developer in the detection region of the toner density detection sensor. For example, in the technique described in Patent Document 1, only one agitation blade is provided in one area including a portion facing the detection area of the toner concentration detection sensor of the agitating and conveying member that agitates and conveys the developer. A diffusion blade and a stirring blade are provided in the region. In the technique described in Patent Document 2, the stirring and conveying member is not provided within the detection range of the toner concentration detection sensor.

JP 2006-91704 A JP 2009-8780 A

  However, the techniques described in Patent Documents 1 and 2 are not sufficiently effective in changing the state of the developer when an external factor (switching of process speed, environmental fluctuation, etc.) occurs. For example, in the technique described in Patent Document 1, since the portion facing the toner concentration detection sensor is configured only by the stirring blade, when the process speed is changed or the environment changes, the developer is discharged from both sides of the stirring blade. By spilling, the amount of the developer held by the stirring blade is greatly different. Further, during one rotation of the stirring blade, the density distribution of the developer at the portion desired by the toner density detection sensor also changes. Therefore, when an external factor occurs, the state fluctuation of the developer cannot be suppressed, and the magnetic permeability fluctuation due to the density change of the developer occurs.

  In the technique disclosed in Patent Document 2, since the agitating and conveying member is not provided in the detection range of the toner concentration detection sensor, the fluidity of the developer deteriorates in a high temperature and high humidity environment, and the developer adheres to the sensor detection surface. As a result, an error occurs in the detection result itself. Therefore, the techniques described in Patent Documents 1 and 2 have room for improvement in terms of suppressing magnetic permeability fluctuations due to changes in developer density when external factors occur.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of suppressing fluctuations in magnetic permeability due to changes in developer density even when external factors occur.

  In order to solve the above problems, an image forming apparatus according to the present invention includes a stirring and conveying member and a toner concentration detection sensor. The agitating and conveying member conveys the two-component developer containing the nonmagnetic toner and the magnetic carrier while stirring. The toner concentration detection sensor detects the magnetic permeability according to the mixing ratio of the non-magnetic toner and the magnetic carrier contained in the developer conveyed by the stirring and conveying member in order to detect the toner concentration of the developer. The stirring and conveying member includes a shaft member, a spiral member, a first plate member, and a second plate member. The spiral member extends in a spiral direction around the shaft member and conveys the developer in the axial direction of the shaft member. The first plate-like member extends in the axial direction of the shaft member, and connects the upstream spiral member in the developer transport direction and the downstream spiral member in the developer transport direction. The second plate-like member extends from the spiral member on the upstream side in the developer transport direction to the downstream side in the developer transport direction along the axial direction of the shaft member, and on the downstream side in the developer transport direction. A space is formed between the spiral member. A portion of the spiral member facing the detection surface of the toner concentration detection sensor is cut away, and the first plate member and the second plate member are arranged to face the detection surface of the toner concentration detection sensor. ing.

  According to the image forming apparatus of the present invention, the spiral member is cut away at a portion facing the detection surface of the toner concentration detection sensor, and the first plate member and the second plate member are configured to detect the toner concentration. Since the sensor is disposed so as to face the detection surface of the sensor, the developer is not conveyed in the direction along the axial direction of the shaft member by the spiral member in the region facing the detection surface of the toner concentration detection sensor. The developer is transported in the rotation direction of the stirring transport member. The first plate-like member extends in the axial direction of the shaft member and connects the upstream spiral member in the developer transport direction and the downstream spiral member in the developer transport direction. The developer is held by the first plate-like member and stirred in the rotation direction. The second plate-like member extends from the spiral member on the upstream side in the developer transport direction to the downstream side in the developer transport direction along the axial direction of the shaft member, and on the downstream side in the developer transport direction. Since a space is formed between the spiral member and the developer, the developer is held by the second plate member and stirred in the rotation direction, and the developer is removed from the second plate member through the space. One plate wraps around. Thereby, even when an external factor is generated, the flow of the developer in the portion facing the detection surface of the toner density detection sensor can be stabilized. As described above, even when an external factor is generated, it is possible to suppress fluctuations in magnetic permeability due to changes in developer density. Here, switching of the process speed, which is one of external factors, is performed due to, for example, an increase in heat caused by excessive use of the image forming apparatus, a difference in paper type or office environment, and the like.

  Further, the first plate-like member extends in the axial direction of the shaft member between one pitch of the spiral member, and is located on the upstream side in the developer transport direction and on the downstream side in the developer transport direction. The second plate-shaped member is connected to the spiral member between two pitches of the spiral member in the developer transport direction along the axial direction of the shaft member from the upstream spiral member in the developer transport direction. It is desirable that a space is formed between the first spiral member and the second spiral member extending downstream and downstream in the developer transport direction. Thereby, conveyance of the developer by the 1st plate-like member and the 2nd plate-like member can be performed more suitably.

  Further, it is desirable that the first plate-like member is arranged so that the center position of the first plate-like member and the center position of the detection surface overlap in the direction along the axial direction of the shaft member. When the first plate-like member is arranged in this way, the accuracy of the detection result by the toner concentration detection sensor can be improved.

  Further, the distal end of the second plate-like member on the downstream side in the developer transport direction is closer to the outer peripheral side on the opposite side of the shaft member in the developer transport direction than the base end side on the shaft member side. It is desirable to extend downstream. When the tip of the second plate-like member has such a shape, the developer can be suitably circulated from the second plate-like member to the first plate-like member, and the magnetic permeability variation due to the density change of the developer. Can be further suppressed.

  According to the present invention, even when an external factor is generated, it is possible to suppress the magnetic permeability fluctuation due to the density change of the developer.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a vertical sectional view showing the developing unit of FIG. 1. FIG. 2 is a side view illustrating a configuration of a stirring and conveying member around a toner concentration detection sensor of the developing unit in FIG. 1. FIG. 4 is a side view showing in detail a configuration of a stirring and conveying member in the vicinity of the toner concentration detection sensor of FIG. 3. FIG. 4 is a side view showing in detail a configuration of a stirring and conveying member in the vicinity of the toner concentration detection sensor of FIG. 3. It is a graph which shows the sensitivity fluctuation rate at the time of the process speed fluctuation | variation by the shape of the front-end | tip of a 2nd plate-shaped member. 6 is a side view illustrating a configuration of a stirring and conveying member in the image forming apparatus of Comparative Example 1. FIG. 6 is a graph illustrating an output waveform of a toner concentration detection sensor measured for each condition in Example 1. 6 is a graph showing a control voltage necessary for controlling toner density with a constant sensor output in Example 1. 6 is a graph showing an output waveform of a toner concentration detection sensor measured for each condition in Comparative Example 1. 6 is a graph showing a control voltage necessary for controlling toner density with a constant sensor output in Comparative Example 1;

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  First, a schematic configuration of the image forming apparatus according to the present embodiment will be described with reference to FIG. As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment is an apparatus capable of forming a color image using, for example, magenta, yellow, cyan, and black. The image forming apparatus 1 includes a recording medium conveyance unit 10 that conveys a sheet P, a developing unit (developing apparatus) 20 that develops an electrostatic latent image, a transfer unit 30 that secondarily transfers a toner image onto the sheet P, and a peripheral unit. A photosensitive drum 40 that is an electrostatic latent image carrier on which an image is formed on the surface, and a fixing unit 50 that fixes the toner image onto the paper P are configured.

  The recording medium conveyance unit 10 accommodates a sheet P as a recording medium on which an image is finally formed, and conveys the sheet P onto the recording medium conveyance path. The sheets P are stacked and stored in a cassette. The recording medium transport unit 10 causes the paper P to reach the secondary transfer region R at the timing when the toner image transferred to the paper P reaches the secondary transfer region R.

  Four developing units 20 are provided for each color. The developing unit 20 develops the electrostatic latent image formed on the photosensitive drum 40 with the toner supplied from the toner tank 5 provided to face each developing unit 20, and generates a toner image. Each toner tank 5 is filled with magenta, yellow, cyan and black toners, respectively. Details of the configuration of the developing unit 20 will be described later.

  The transfer unit 30 conveys the toner image formed by the developing unit 20 to the secondary transfer region R where the toner image is secondarily transferred to the paper P. The transfer unit 30 includes a transfer belt 31, suspension rollers 31a, 31b, 31c, and 31d that suspend the transfer belt 31, a primary transfer roller 32 that sandwiches the transfer belt 31 together with the photosensitive drum 40, and a transfer belt together with the suspension roller 31d. And a secondary transfer roller 33 that sandwiches 31.

  The transfer belt 31 is an endless belt that is circulated and moved by suspension rollers 31a, 31b, 31c, and 31d. The primary transfer roller 32 is provided so as to press the photosensitive drum 40 from the inner peripheral side of the transfer belt 31. The secondary transfer roller 33 is provided so as to press the suspension roller 31 d from the outer peripheral side of the transfer belt 31.

  Four photosensitive drums 40 are provided for each color. Each photoconductor drum 40 is provided along the moving direction of the transfer belt 31. A developing unit 20, a charging roller 41, an exposure unit 42, and a cleaning unit 43 are provided on the periphery of the photosensitive drum 40.

  The charging roller 41 uniformly charges the surface of the photosensitive drum 40 to a predetermined potential. The exposure unit 42 exposes the surface of the photosensitive drum 40 charged by the charging roller 41 according to the image formed on the paper P. As a result, the potential of the portion exposed by the exposure unit 42 on the surface of the photosensitive drum 40 changes, and an electrostatic latent image is formed.

  The cleaning unit 43 collects the toner remaining on the photosensitive drum 40 after the toner image formed on the photosensitive drum 40 is primarily transferred to the transfer belt 31. Waste toner obtained by the cleaning unit 43 is transferred to a waste toner collecting device by a screw or the like.

  Next, the configuration of the developing unit 20 will be described in more detail with reference to FIGS. FIG. 2 is a vertical sectional view showing the configuration of the agitating and conveying member around the toner concentration detection sensor of the developing unit 20 of FIG. As shown in FIGS. 2 and 3, the developing unit 20 includes a developing roller 21, a conveying member 22, a stirring and conveying member 23, and a toner concentration detection sensor 28. 3 and the subsequent drawings, the illustration of the photosensitive drum 40 is omitted.

  The developer used in the developing unit 20 is a two-component developer including, for example, a nonmagnetic toner and a magnetic carrier. The developing roller 21 adjusts the toner and the carrier so as to have a desired mixing ratio, and further carries the developer with an optimum charge amount by mixing and stirring to uniformly disperse the toner. The developing roller 21 rotates and conveys the developer to a region facing the photosensitive drum 40. As a result, the nonmagnetic toner in the developer carried on the developing roller 21 moves to the electrostatic latent image formed on the peripheral surface of the photosensitive drum 40, and the electrostatic latent image is developed.

  The conveying member 22 is rotatably arranged in the developing unit 20 and conveys the developer in a conveying direction H substantially parallel to the rotation axis of the developing roller 21 by a rotating operation. The conveying member 22 carries a predetermined amount of developer on the circumferential surface of the developing roller 21 that rotates in the forward direction with the conveying member 22. The conveying member 22 includes a shaft member 22a and a spiral member 22b formed on the peripheral surface of the shaft member 22a. The spiral member 22b has a spiral blade shape, and rotates the developer clockwise when viewed in the transport direction H, thereby transporting the developer from the upstream side to the downstream side in the transport direction H.

  The agitating / conveying member 23 is disposed in the developing unit 20 at a position farther from the developing roller 21 than the conveying member 22 so as to be able to rotate so as to face the conveying member 22 over substantially the entire length thereof. ing. The conveying member 22 and the agitating / conveying member 23 are disposed in a space separated by the housing of the developing unit 20, and these spaces communicate with each other on the upstream side in the developer conveying direction H. The stirring and conveying member 23 includes a shaft member 24, and a spiral member 25, a first plate member 26, and a second plate member 27 formed on the peripheral surface of the shaft member 24. The agitating and conveying member 23 agitates the developer by a rotating operation and conveys the developer in a conveying direction G substantially parallel to the axial direction A of the shaft member 24. The transport direction G is a direction facing the transport direction H.

  The spiral member 25 extends in the spiral direction around the shaft member 24 of the agitation transport member 23, and transports the developer in the axial direction A of the shaft member 24. The spiral member 25 has a spiral blade shape, and includes a first transport unit 25 a that transports the developer in the transport direction G, and a second transport unit 25 b that transports the developer in the direction opposite to the transport direction G. The first transport unit 25 a rotates counterclockwise when viewed in the transport direction G, and transports the developer from the upstream side to the downstream side in the transport direction G. The second transport unit 25 b is formed at the end 24 b of the shaft member 24 on the downstream side in the transport direction G, and transports the developer in the direction opposite to the transport direction G. As a result, the developer is pushed up at the end 24 b without clogging, and the developer is transported from the agitation transport member 23 to the transport member 22.

  The first plate member 26 has a conveyance force in the rotation direction B of the agitation conveyance member 23. The first plate member 26 is a substantially rectangular stirring paddle, and is erected on the shaft member 24. The first plate-like member 26 extends along the axial direction A of the shaft member 24 in one pitch S <b> 1 of the spiral member 25. The length in the longitudinal direction of the first plate-like member 26 (the length in the axial direction A of the shaft member 24) is substantially equal to the length of one pitch S1 of the spiral member 25. The first plate-like member 26 connects the spiral member 25 on the upstream side in the developer transport direction G and the spiral member 25 on the downstream side in the developer transport direction G in one pitch S1. The length of the first plate member 26 in the short direction (the length rising from the shaft member 24) is substantially equal to the length of the spiral member 25 rising from the shaft member 24. The first plate-like member 26 holds the developer and stirs it in the rotation direction B without substantially conveying the developer in the axial direction A.

  The second plate-shaped member 27 has a conveying force in the rotation direction B of the stirring and conveying member 23. The second plate member 27 is a substantially rectangular stirring paddle, and is erected on the shaft member 24. The second plate-like member 27 extends along the axial direction A of the shaft member 24 in, for example, S2 between two pitches of the spiral member 25. The length of the second plate member 27 in the longitudinal direction (the length of the shaft member 24 in the axial direction A) is shorter than the length of the two pitches S2 of the spiral member 25. The second plate-shaped member 27 extends from the upstream spiral member 25 in the developer transport direction G to the downstream side in the developer transport direction G in the two pitches S2, and the downstream spiral member A space L is formed between the two. The length of the second plate member 27 in the short direction (the length rising from the shaft member 24) is substantially equal to the length of the spiral member 25 rising from the shaft member 24. Therefore, the length of the second plate member 27 in the short direction is substantially equal to the length of the first plate member 26 in the short direction. The second plate-shaped member 27 holds the developer in the rotational direction B without substantially conveying the developer in the axial direction A, and stirs it in the rotation direction B. The developer is caused to flow from the two plate-like members 27 to the first plate-like member 26 (see FIG. 5).

  The toner concentration detection sensor 28 detects the toner concentration of the developer conveyed by the agitating and conveying member 23 in order to detect the toner concentration of the developer. The toner concentration detection sensor 28 detects the magnetic permeability according to the mixing ratio of the nonmagnetic toner and the magnetic carrier contained in the developer. The toner concentration detection sensor 28 has a detection surface 29 that faces the developer conveyed by the agitation conveyance member 23. The first plate-like member 26 and the second plate-like member 27 rotate in a direction (rotation direction B) for scooping up the detection surface 29. The toner concentration detection sensor 28 is disposed, for example, at an angle of approximately 45 ° with respect to the horizontal plane so that the detection surface 29 faces the first plate-like member 26 and the second plate-like member 27.

  The toner density detection result is confirmed by the output voltage from the toner density detection sensor 28. This output voltage has a periodic waveform shape as the stirring and conveying member 23 rotates even if the toner concentration is constant. This is because the developer is periodically and densely formed by the agitating and conveying member 23. When the developer is large and the magnetic permeability is high, the developer is in a dense state, and the output from the toner concentration detection sensor 28 is high. When the developer is low and the magnetic permeability is low, the developer is in a rough state, and the output from the toner concentration detection sensor 28 is low.

  Next, with reference to FIGS. 4 and 5, the details of the configuration of the agitation transport member 23 around the toner concentration detection sensor 28 will be described. 4 and 5 are side views showing in detail the configuration of the stirring and conveying member 23 around the toner concentration detection sensor 28 of FIG. As shown in FIGS. 4 and 5, the spiral member 25 is cut out at a portion facing the detection surface 29 of the toner concentration detection sensor 28. For example, the spiral member 25 is cut out by S1 for one pitch connected by the first plate member 26. That is, no member having a conveying force in the axial direction A of the shaft member 24 such as the spiral member 25 is disposed in a region facing the detection surface 29 of the toner concentration detection sensor 28.

  The first plate member 26 and the second plate member 27 are erected on the shaft member 24 at positions that are separated from each other by approximately 180 ° in the circumferential direction of the shaft member 24. The first plate member 26 and the second plate member 27 are disposed so as to face the detection surface 29 of the toner concentration detection sensor 28. That is, the first plate-like member 26 and the second plate-like member 27 are arranged at overlapping positions in the axial direction A of the shaft member 24. Further, the first plate member 26 has a center position 26 c of the first plate member 26 and a center position 29 c of the detection surface 29 of the toner concentration detection sensor 28 in the axial direction A of the shaft member 24 of the stirring and conveying member 23. They are arranged so as to overlap.

  The leading end 27d of the second plate-like member 27 on the downstream side in the developer transport direction G has an oblique shape. The distal end 27d of the second plate member 27 extends on the outer peripheral side 27f on the opposite side of the shaft member 24 to the downstream side in the developer conveying direction G, rather than on the base end side 27e on the shaft member 24 side. ing.

  Here, the effect by having the shape in the front-end | tip 27d of the 2nd plate-shaped member 27 as mentioned above is demonstrated using FIG. FIG. 6 is a graph showing the sensitivity fluctuation rate when the process speed fluctuates depending on the shape of the tip 27d of the second plate member 27. The horizontal axis in FIG. 6 shows the shape of the tip 27d. For example, the term “perpendicular to the end face” refers to a case where the downstream side in the developer transport direction G at the front end 27d is substantially the same on the base end side 27e and the outer peripheral side 27f, that is, a case where it extends perpendicularly to the shaft member 24. Is shown. On the right side of the end surface perpendicular to the right end, when the distal end 27d extends to the downstream side in the developer conveying direction G on the outer peripheral side 27f longer than the base end side 27e, that is, the developer is conveyed relative to the shaft member 24. The case where it inclines in the downstream of the direction G is shown. On the left side of the end surface perpendicularly, when the distal end 27d extends to the downstream side in the developer conveying direction G on the base end side 27e longer than the outer peripheral side 27f, that is, the developer is conveyed with respect to the shaft member 24. The case where it inclines in the upstream of the direction G is shown. The vertical axis in FIG. 6 shows the sensitivity fluctuation rate when the process speed fluctuates. The sensitivity fluctuation rate at the time of process speed fluctuation is the fluctuation rate of the control voltage necessary for controlling the toner density with a constant voltage output from the toner density detection sensor 28 when the process speed condition changes.

  As shown in FIG. 6, at the front end 27d of the second plate-like member 27, the process speed increases when the downstream side in the developer transport direction G is longer on the outer peripheral side 27f than on the base end side 27e. Sensitivity fluctuation rate at the time of fluctuation is low. That is, since the tip 27d of the second plate member 27 has such a shape, the first plate 27d from the tip 27d of the second plate member 27 through the space L in the direction indicated by the arrow F. Since the developer can be suitably wound around the member 26 (see FIG. 5), it is possible to further suppress the magnetic permeability variation due to the change in the developer density due to the process speed variation.

  As described above, according to the image forming apparatus 1 according to the present embodiment, the spiral member 25 is notched at the portion facing the detection surface 29 of the toner density detection sensor 28, and the first plate-like member 26 and the second plate member 26. Since the plate-like member 27 is disposed so as to face the detection surface 29 of the toner concentration detection sensor 28, the spiral member 25 causes the shaft member 24 in the region facing the detection surface 29 of the toner concentration detection sensor 28. The developer is transported in the rotational direction B of the agitation transport member 23 without being transported in the direction along the axial direction A. The first plate-like member 26 extends in the axial direction A of the shaft member 24 and has an upstream spiral member 25 in the developer transport direction G and a downstream spiral member 25 in the developer transport direction G. Therefore, the developer is held by the first plate member 26 and stirred in the rotation direction B. The second plate-like member 27 extends from the spiral member 25 on the upstream side in the developer conveying direction G along the axial direction A of the shaft member 24 to the downstream side in the developer conveying direction G. Since the space L is formed with the spiral member 25 on the downstream side in the transport direction G, the developer is held by the second plate-like member 27 and stirred in the rotation direction B. The second plate-shaped member 27 goes around the first plate-shaped member 26 through the space L. As a result, even when an external factor occurs, the developer flow in the portion facing the detection surface 29 of the toner concentration detection sensor 28 can be stabilized. As described above, even when an external factor is generated, it is possible to suppress fluctuations in magnetic permeability due to changes in developer density.

  The first plate member 26 extends in the axial direction A of the shaft member 24 in one pitch S1 of the spiral member 25 and transports the developer with the spiral member 25 on the upstream side in the developer transport direction G. The second plate member 27 is connected to the spiral member 25 on the downstream side in the direction G, and the shaft member extends from the spiral member 25 on the upstream side in the developer conveying direction G in the interval S2 between the two pitches of the spiral member 25. A space L is formed between the spiral member 25 extending downstream in the developer transport direction G along the axial direction A of the developer 24. Therefore, the developer can be transported more suitably by the first plate member 26 and the second plate member 27.

  The first plate member 26 is arranged so that the center position 26 c of the first plate member 26 and the center position 29 c of the detection surface 29 overlap in the direction along the axial direction A of the shaft member 24. By arranging the first plate-like member 26 in this way, the accuracy of the detection result by the toner concentration detection sensor 28 is improved.

  Further, the distal end 27d of the second plate-like member 27 on the downstream side in the developer conveying direction G is on the outer peripheral side 27f on the opposite side of the shaft member 24 rather than on the base end side 27e on the shaft member 24 side. , And extends downstream in the developer transport direction G. Since the tip 27d of the second plate-like member 27 has such a shape, the developer can be suitably circulated from the second plate-like member 27 to the first plate-like member 26, and the density of the developer can be improved. It is possible to further suppress the permeability fluctuation due to the change.

  The length of the first plate-like member 26 in the short direction and the length of the second plate-like member 27 in the short-side direction are substantially equal, so the first plate-like member 26 and the second plate-like member 27 The balance of the amount of developer held between them can be maintained, which is preferable.

[Example]
Hereinafter, in order to explain the above effects, examples implemented by the present inventor will be described. In addition, this invention is not limited to a following example.

Example 1
In Example 1, when the image forming apparatus 1 using the developing unit 20 having the stirring and conveying member 23 according to the above-described embodiment is operated, the process speed condition and the environmental condition are changed to change the toner density detection sensor 28. The output waveform was measured. The process speed conditions were changed such that 153 mm / sec was a low process speed and 305 mm / sec was a high process speed. Environmental (temperature and humidity) conditions were changed to 10 ° C. and 10% as low temperature and low humidity, and 30 ° C. and 85% as high temperature and high humidity. The toner concentration detection sensor 28 is a variable control voltage type.

(Comparative Example 1)
FIG. 7 is a side view illustrating the configuration of the stirring and conveying member in the image forming apparatus of Comparative Example 1. In Comparative Example 1, when operating the image forming apparatus using the developing unit 100 having the agitating / conveying member 101 as shown in FIG. 7, the process speed condition and the environmental condition are changed to change the toner density detection sensor 28. The output waveform was measured. Process speed conditions and environmental conditions were the same as in Example 1. A stirring / conveying member 101 shown in FIG. 7 includes a shaft member 102, and a spiral member 103 and a plate-like member 104 formed on the peripheral surface of the shaft member 102. The spiral member 103 has a spiral blade shape, and is continuously arranged without being cut out even at a position facing the detection region of the toner concentration detection sensor 28. The plate-like member 104 is a substantially rectangular stirring paddle, and only one plate member 104 is arranged at a position facing the detection region of the toner concentration detection sensor 28 of the spiral member 103.

(result)
The measurement results in Example 1 are shown in FIGS. FIG. 8 is a graph showing an output waveform of the toner concentration detection sensor 28 measured for each condition in the first embodiment. The horizontal axis in FIG. 8 indicates time, and the vertical axis in FIG. 8 indicates voltage. 8A is a low process speed and low temperature and low humidity condition, FIG. 8B is a low process speed and high temperature and high humidity condition, and FIG. 8C is a high process speed and low temperature and low humidity condition. 8 (d) shows the case of high process speed and high temperature and high humidity.

  Comparing FIG. 8A and FIG. 8C, in the first embodiment, the waveform shape is substantially the same between the low process speed and the high process speed, and the waveform output The height hardly changed. Even when FIG. 8B and FIG. 8D were compared, the same result was obtained. That is, even if the process speed conditions fluctuated, it was possible to suppress magnetic permeability fluctuations due to changes in developer density.

  Comparing (a) in FIG. 8 and (b) in FIG. 8, the waveform shape is substantially the same in the case of low temperature and low humidity and in the case of high temperature and high humidity, and the output height of the waveform almost fluctuates. There wasn't. Even when FIG. 8C and FIG. 8D were compared, the same result was obtained. In other words, even if the environmental conditions fluctuated, the magnetic permeability fluctuation due to the density change of the developer could be suppressed.

  FIG. 9 is a graph showing a control voltage necessary for controlling the toner density with a constant sensor output in the first embodiment. The horizontal axis in FIG. 9 indicates the toner density, and the vertical axis in FIG. 9 indicates the control voltage. The line a in FIG. 9 corresponds to the case of FIG. 8A, the line b in FIG. 9 corresponds to the case in FIG. 8B, and the line c in FIG. 9), the line d in FIG. 9 corresponds to the case of (d) in FIG.

  As shown in FIG. 9, in Example 1, the slopes of the lines a to d were substantially constant. Specifically, the degree of change in inclination due to process speed fluctuation (change rate between the inclination value of line d and the inclination value of line b) was 0.3%. In addition, the degree of change in inclination due to changes in environmental conditions (change rate between the inclination value of line c and the inclination value of line d) was 13%. That is, the degree of change in the control voltage with respect to the toner density can be regarded as substantially constant regardless of variations in process speed and environmental conditions, and substantially the same control voltage can be used regardless of external factors. confirmed.

  On the other hand, the measurement results in Comparative Example 1 are shown in FIGS. FIG. 10 is a graph showing the output waveform of the toner concentration detection sensor 28 measured for each condition in Comparative Example 1. The horizontal axis in FIG. 10 indicates time, and the vertical axis in FIG. 10 indicates voltage. 10A is a low process speed and low temperature and low humidity condition, FIG. 10B is a low process speed and high temperature and high humidity condition, and FIG. 8C is a high process speed and low temperature and low humidity condition. 10 (d) shows the case of high process speed and high temperature and high humidity.

  Comparing FIG. 10 (a) and FIG. 10 (c), in Comparative Example 1, the waveform shape and the waveform output height fluctuate greatly between the low process speed and the high process speed. did. In particular, at low process speeds, the output value does not drop significantly after the maximum peak, whereas at high process speeds, the output value drops significantly after the maximum peak and takes the smallest value. . This is because, at a high process speed, the developer conveying force is high, and therefore the gap on the downstream side in the rotational direction of the plate-like member 104 becomes large, thereby increasing the difference in density of the developer in the rotational direction. by. Moreover, it was the same even if FIG.10 (b) and FIG.10 (d) were compared. That is, the variation in magnetic permeability due to the change in the density of the developer increased due to the variation in the process speed condition.

  Comparing FIG. 10 (a) and FIG. 8 (b), the waveform shape and output height fluctuated greatly between the case of low temperature and low humidity and the case of high temperature and high humidity. Even when FIG. 8C and FIG. 8D were compared, the same result was obtained. This is due to a change in the fluidity of the developer in the entire detection region of the toner density detection sensor due to a change in environmental conditions. That is, the variation in magnetic permeability due to the change in the density of the developer increased due to the variation in environmental conditions.

  FIG. 11 is a graph showing a control voltage necessary for controlling the toner density with a constant sensor output in Comparative Example 1. The horizontal axis in FIG. 11 indicates the toner density, and the vertical axis in FIG. 11 indicates the control voltage. The line a in FIG. 11 corresponds to the case of FIG. 10A, the line b in FIG. 11 corresponds to the case in FIG. 10B, and the line c in FIG. The line d in FIG. 11 corresponds to the case of (d) in FIG.

  As shown in FIG. 11, in Comparative Example 1, the slopes of the lines a to d varied greatly. Specifically, the degree of change in inclination due to process speed fluctuation (change rate between the inclination value of line a and the inclination value of line c) was 97%. In addition, the degree of change in slope due to changes in environmental conditions (the rate of change between the slope value of line c and the slope value of line d) was 90%. That is, it has been confirmed that the degree of change in the control voltage with respect to the toner density varies greatly due to variations in process speed and environmental conditions.

  As described above, according to Example 1 and Comparative Example 1, in the image forming apparatus 1 using the developing unit 20 having the stirring and conveying member 23 according to the above-described embodiment of the present invention, even if the process speed and the environment vary, the developer It was confirmed that fluctuations in magnetic permeability due to changes in the density can be suppressed. That is, according to the image forming apparatus 1, it was confirmed that the magnetic permeability fluctuation due to the density change of the developer can be suppressed even when an external factor is generated.

  The preferred embodiments of the present embodiment have been described above. However, the present invention is not limited to the above-described embodiments. The present invention is not limited to the gist described in each claim and can be modified or applied to others. It may be what you did.

  For example, in the above embodiment, the length in the short direction of the first plate member 26 and the length in the short direction of the second plate member 27 are substantially equal to each other, but are not limited thereto, and are different from each other. It may be a length. Moreover, although the shape of the 1st plate-shaped member 26 and the 2nd plate-shaped member 27 was made into the substantially rectangular shape, it is not restricted to this, A various shape can be taken in the range with the said effect.

  Although one first plate member 26 is disposed, the present invention is not limited to this, and a plurality of the first plate members 26 may be disposed, for example. The same applies to the second plate member 27. Moreover, although the 1st plate-shaped member 26 and the 2nd plate-shaped member 27 were standingly arranged in the shaft member 24 in the circumferential direction of the shaft member 24 in the position mutually separated substantially 180 degrees, it is not restricted to this. For example, the position where the first plate-like member 26 and the second plate-like member 27 are erected on the shaft member 24 may be a position separated from each other by an angle other than approximately 180 ° in the circumferential direction of the shaft member 24. Good.

  The 1st plate-shaped member 26 is not restricted to what connects the helical member 25 in S1 between 1 pitch, You may connect the helical member 25 in the range wider than S1 between 1 pitch. Moreover, the 2nd plate-shaped member 27 is not restricted to what forms the space L in S2 between 2 pitches, The space L may be formed in the range wider than S2 between 2 pitches.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 23 ... Agitation conveyance member, 24 ... Shaft member, 25 ... Spiral member, 26 ... First plate member, 26c ... Center position, 27 ... Second plate member, 27d ... Tip, 27e ... Base end side, 27f ... outer peripheral side, 28 ... toner density detection sensor, 29 ... detection surface, 29c ... center position, A ... axial direction, G ... conveying direction, L ... space, S1 ... 1 pitch, S2 ... 2 pitch while.

Claims (4)

An agitating and conveying member for conveying the two-component developer containing the non-magnetic toner and the magnetic carrier while stirring;
In order to detect the toner concentration of the developer, a toner concentration detection that detects a magnetic permeability according to a mixing ratio of the non-magnetic toner and the magnetic carrier contained in the developer conveyed by the stirring and conveying member. A sensor,
An image forming apparatus comprising:
The stirring and conveying member is
A shaft member;
A spiral member extending in a spiral direction around the shaft member and transporting the developer in the axial direction of the shaft member;
A first plate member extending in the axial direction of the shaft member and connecting the spiral member on the upstream side in the transport direction of the developer and the spiral member on the downstream side in the transport direction of the developer;
The spiral member on the downstream side in the developer transport direction extends from the spiral member on the upstream side in the developer transport direction along the axial direction of the shaft member to the downstream side in the developer transport direction. A second plate member in which a space is formed between the member and
Have
The spiral member is cut away at a portion facing the detection surface of the toner concentration detection sensor,
The image forming apparatus, wherein the first plate-like member and the second plate-like member are arranged to face a detection surface of the toner concentration detection sensor. The first plate-like member extends in the axial direction of the shaft member between one pitch of the helical member, and the transport direction of the spiral member and the developer on the upstream side in the transport direction of the developer Connecting the spiral member on the downstream side of
The second plate-like member is downstream in the developer transport direction along the axial direction of the shaft member from the spiral member upstream in the developer transport direction between two pitches of the spiral member. And a space is formed between the spiral member and the downstream side of the developer in the transport direction.
The image forming apparatus according to claim 1. The first plate-like member is arranged so that a center position of the first plate-like member and a center position of the detection surface overlap in a direction along the axial direction of the shaft member.
The image forming apparatus according to claim 1. The distal end of the second plate-like member on the downstream side in the developer transport direction is closer to the outer peripheral side, which is the opposite side of the shaft member, than to the base end side, which is the shaft member side. Extending downstream in the transport direction,
The image forming apparatus according to claim 1.