JP2017116666A - Development device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress increase of internal pressure in a case of a development device, and suppress discharge of a developer.SOLUTION: A development device 20 comprises: a discharge path D for discharging air in a case 24 toward an opening part 24b side; and a guide plate 27 for guiding air which is discharged from a discharge port of the discharge path D. The discharge path D faces a non-carrying portion X2 on an end part of a developing roller 21. The discharge path D is formed of a groove 24c which is provided on an inside surface of a case upper wall 24a. The guide plate 27 guides air which is discharged from the discharge port of the discharge path D to a space between the case upper wall 24a and the developing roller 21, and on a carrying portion X1 side on the developing roller 21.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a developing device.

  An image forming apparatus provided with a developing device is required to increase the printing speed. For this reason, also in the developing device, the rotational speeds of the developer carrier, the agitation transport member, and the like are increased. When the developer carrying member or the like is rotated at a high speed, the amount of air taken into the developing device also increases. In order to suppress an increase in internal pressure in the case of the developing device, the developing device is provided with a discharge path for discharging the air in the case to the outside. However, when the discharge path is provided, the developer may be discharged from the discharge path along the air flow. For this reason, for example, Patent Document 1 describes that a filter is provided in order to prevent the developer from being discharged from the discharge path.

Japanese Patent Application Laid-Open No. 2003-215917

  When the discharge of the developer is suppressed by using a filter as in the apparatus described in Patent Document 1, the filter needs to be replaced because the filter is clogged. Therefore, in this technical field, there is a demand for a developing device that can suppress the discharge of the developer while suppressing an increase in internal pressure in the case of the developing device.

  The developing device of the present invention includes a developer container, an agitating / conveying member, a developer carrier, a layer regulating member, a case, a discharge path, and a first guide member. The developer storage unit stores a developer including toner and a carrier. The agitating and conveying member conveys the developer accommodated in the developer accommodating portion while agitating. The developer carrying member carries the developer stirred by the stirring and conveying member and rotates so that the carried developer is carried to the photosensitive member. The layer regulating member is located below the rotation axis of the developer carrying member and regulates the layer thickness of the developer carried by the developer carrying member. The case forms a developer accommodating portion, and accommodates the stirring and conveying member, the developer carrying member, and the layer regulating member. The case has an opening at a portion where the developer carrying member faces the photoreceptor. The discharge path discharges air in the case toward the opening side. The first guide member guides the air discharged from the discharge port of the discharge path. The discharge path is located downstream of the developing region in which the developer carrying member supplies the toner to the photosensitive member in the developer transport direction. The discharge path faces the non-carrying portion of the developer at the end of the developer carrying member. The discharge path is formed by a groove provided on the inner side surface of the case upper wall that covers the upper portion of the developer carrier in the case. The first guide member guides the air discharged from the discharge port between the case upper wall and the developer carrier and to the developer carrying part side of the developer carrier.

  The air in the case is discharged out of the case by the discharge path formed by the groove on the case upper wall. Thereby, the internal pressure rise in a case can be suppressed. Further, the air discharged through the discharge path is guided to the side of the developer carrying member by the first guide member. As a result, the discharged air is drawn into the case together with the air flow toward the inside of the case that is caused by the developer carried on the carrying portion being transported into the case. That is, even if the developer discharged in the air discharged through the discharge path is contained, the developer included in the discharged air is returned to the case again. As described above, the developing device can suppress the discharge of the developer while suppressing the increase of the internal pressure in the case.

  The position where the discharge path is provided may be a position where the developer carried at the carrying portion enters the discharge path. In this case, as the developer carrying member rotates, the rising of the developer carried on the carrying site passes through the discharge path. The air passing through the discharge path is discharged while passing through the spikes of the developer moving in the discharge path. Therefore, even if developer is contained in the air discharged through the discharge path, the developer in the air is adsorbed by the spikes of the developer carried on the carrying part. For this reason, discharge of the developer can be further suppressed.

  The developing device further includes a second guide member. The second guide member guides the discharge direction of the air so that the air passing through the discharge path is discharged toward the support portion side of the developer carrier. The developer carrier includes a magnet arranged so that a magnetic component in a tangential direction has a peak toward an end of the upper wall of the case on the opening side. The discharge port may be located between the half-value position of the magnetic component in the tangential direction having a peak toward the end portion on the opening side in the case upper wall and the end portion on the opening side in the case upper wall. . In this case, the air passing through the discharge path is discharged toward the rising edge of the developer. A large amount of air can be taken into the spike at the rising position of the spike of the developer. For this reason, the air and developer discharged from the discharge path can be efficiently taken into the ear and returned to the case.

  A part of the wall portion forming the discharge path may be constituted by a developer carried on a carrying portion of the developer carrying body. In this case, the developer contained in the discharged air is adsorbed by the developer constituting the wall portion of the discharge path when passing through the discharge path. Thereby, discharge of the developer can be further suppressed.

  Let A be the distance between the upper surface of the developer carrier and the upper wall of the case. Let B be the height of the ear of the highest developer among the ears of the developer carried on the carrying part of the developer carrying member. A and B may satisfy the relationship of A <B. In this case, the tip of the tip of the developer carried on the carrying part contacts the case upper wall. Then, the tip of the rising edge of the developer in contact with the upper wall of the case enters the discharge path. As a result, the developer contained in the air discharged through the discharge path is adsorbed by the tip of the tip of the developer that has entered the discharge path. For this reason, discharge of the developer can be further suppressed.

  The end portion on the opening side of the case upper wall may protrude toward the photoreceptor side with respect to the first guide member. In this case, the gap between the photoconductor and the case upper wall can be reduced. Accordingly, the amount of air flowing through the gap between the photosensitive member and the case upper wall is reduced, and the amount of air taken into the case in the developer carrying member can be increased. That is, the air discharged through the discharge path can be efficiently returned into the case.

  The first guide member may be attached to the opening and may cover the end of the developer carrier. In this case, the first guide member can guide the air discharged from the case and prevent the developer from scattering from the opening by covering the opening.

  A part of the wall portion forming the discharge path may be configured by a seal member disposed between the non-carrying portion of the developer carrying member and the case upper wall. In this case, the discharge path can be easily formed by the seal member disposed between the non-carrying portion of the developer carrying member and the case upper wall.

  According to the present invention, it is possible to suppress developer discharge while suppressing an increase in internal pressure in the case of the developing device.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment. FIG. 6 is a cross-sectional view around a discharge path of the developing device. FIG. 6 is a top view showing the periphery of a portion where a discharge path of the developing device is provided. FIG. 5 is a view of a portion where a discharge path of the developing device is provided as viewed from the opening side. It is sectional drawing which shows the discharge route circumference. It is a comparison result which shows the wind speed of the air discharged | emitted from a developer discharge port. It is sectional drawing of the surroundings of the discharge path of the developing device in the 1st modification. FIG. 10 is a top view illustrating the periphery of a portion where a discharge path of a developing device according to a first modification is provided. It is sectional drawing around the developing roller of the developing device in the 2nd modification. It is a top view which shows the circumference | surroundings of the site | part in which the discharge path of the developing device in a 2nd modification was provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

(Overall configuration of image forming apparatus)
First, a schematic configuration of the image forming apparatus according to the present embodiment will be described. The image forming apparatus 1 is an apparatus that forms a color image using magenta, yellow, cyan, and black colors. As shown in FIG. 1, the image forming apparatus 1 includes a recording medium transport unit 10 that transports a sheet P, a developing device 20 that develops an electrostatic latent image, and a transfer unit 30 that performs secondary transfer of a toner image onto the sheet P. A photosensitive drum (photosensitive member) 40 that is an electrostatic latent image carrier on which an image is formed on the peripheral surface, and a fixing unit 50 that fixes the toner image onto the paper P.

  The recording medium transport unit 10 transports the paper P as a recording medium on which an image is formed on the transport path R1. The paper P is stacked and accommodated in the cassette K, picked up by a paper feed roller, and conveyed. The recording medium transport unit 10 causes the paper P to reach the secondary transfer region R2 via the transport path R1 at the timing when the toner image transferred onto the paper P reaches the secondary transfer region R2.

  Four developing devices 20 are provided for each color. Each developing device 20 includes a developing roller (developer carrying member) 21 that carries the toner on the photosensitive drum 40. In the developing device 20, the toner and the carrier are adjusted so as to have a desired mixing ratio, and further, the developer is mixed and stirred to uniformly disperse the toner to adjust the developer to which the optimum charge amount is given. The developer is carried on the developing roller 21. Then, the developer is conveyed to a region facing the photosensitive drum 40 by the rotation of the developing roller 21. When the developer is conveyed, the toner of the developer carried on the developing roller 21 moves to the electrostatic latent image formed on the peripheral surface of the photosensitive drum 40. Thereby, the electrostatic latent image is developed.

  The transfer unit 30 conveys the toner image formed by the developing device 20 to the secondary transfer region R2 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 circulates and moves 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. On the circumference of the photosensitive drum 40, a developing device 20, a charging roller 41, an exposure unit 42, and a cleaning unit 43 are provided.

  The charging roller 41 is a charging unit that uniformly charges the surface of the photosensitive drum 40 to a predetermined potential. The charging roller 41 moves following the rotation of the photosensitive drum 40. The exposure unit 42 exposes the surface of the photosensitive drum 40 charged by the charging roller 41 according to an 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 four developing devices 20 develop the electrostatic latent image formed on the photosensitive drum 40 with toner supplied from a toner tank N provided opposite to each developing device 20, and generate toner images. . Each toner tank N is filled with magenta, yellow, cyan and black toners. 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.

  The fixing unit 50 attaches and fixes the toner image secondarily transferred from the transfer belt 31 to the paper P on the paper P. The fixing unit 50 includes a heating roller 52 that heats the paper P, and a pressure roller 54 that presses the heating roller 52. The heating roller 52 and the pressure roller 54 are formed in a cylindrical shape. The heating roller 52 includes a heat source such as a halogen lamp inside. A fixing nip portion that is a contact area is provided between the heating roller 52 and the pressure roller 54. By passing the paper P through the fixing nip portion, the toner image is melted and fixed on the paper P. After the toner image is secondarily transferred to the paper P, the toner remaining on the transfer belt 31 is collected by a belt cleaning device.

  Further, the image forming apparatus 1 is provided with discharge rollers 62 and 64 for discharging the paper P on which the toner image is fixed by the fixing unit 50 to the outside of the apparatus.

  Subsequently, a printing process by the image forming apparatus 1 will be described. When an image signal of an image to be recorded is input to the image forming apparatus 1, the image formation control unit of the image forming apparatus 1 rotates the paper feed roller to pick up and convey the paper P stacked on the cassette K. . Based on the received image signal, the charging roller 41 uniformly charges the surface of the photosensitive drum 40 to a predetermined potential (charging process). Thereafter, the exposure unit 42 irradiates the surface of the photosensitive drum 40 with laser light to form an electrostatic latent image (exposure process).

  In the developing device 20, the electrostatic latent image is developed to form a toner image (developing process). The toner image thus formed is primarily transferred from the photosensitive drum 40 to the transfer belt 31 in a region where the photosensitive drum 40 and the transfer belt 31 face each other (transfer process). On the transfer belt 31, toner images formed on the four photosensitive drums 40 are sequentially stacked to form one stacked toner image. The laminated toner image is secondarily transferred onto the paper P conveyed from the recording medium conveyance unit 10 in the secondary transfer region R2 where the suspension roller 31d and the secondary transfer roller 33 face each other.

  The sheet P on which the laminated toner image is secondarily transferred is conveyed to the fixing unit 50. By passing the paper P between the heating roller 52 and the pressure roller 54 while applying heat and pressure, the laminated toner image is melted and fixed on the paper P (fixing step). Thereafter, the paper P is discharged to the outside of the image forming apparatus 1 by the discharge rollers 62 and 64.

(Configuration around the developing device)
Next, the configuration around the developing device 20 will be described. As shown in FIGS. 2 to 5, the developing device 20 includes a developing roller 21, a first stirring and conveying member 22, a second stirring and conveying member 23 (see FIG. 1), a case 24, a layer regulating member 25, a sealing member 26, And a guide plate (first guide member) 27. The developing roller 21, the first agitating / conveying member 22, the second agitating / conveying member 23, the layer regulating member 25, and the seal member 26 are provided in a developer accommodating chamber (developer accommodating portion) H formed by the case 24. ing.

  The developing roller 21 supplies toner to the electrostatic latent image formed on the peripheral surface of the photosensitive drum 40. The developing roller 21 carries the developer stirred by the first stirring / transporting member 22 and the second stirring / transporting member 23. The developing roller 21 rotates so that the carried developer is conveyed to the photosensitive drum 40. Specifically, the developing roller 21 includes, for example, a developing sleeve 21a and a magnet 21b disposed inside the developing sleeve 21a. The developing sleeve 21a is a cylindrical member made of a nonmagnetic metal. In the developing roller 21, only the developing sleeve 21 a rotates about the rotation axis L. A magnet 21 b disposed in the developing sleeve 21 a is fixed to the case 24.

  The magnet 21b has a plurality of magnetic poles. In the magnet 21b, for example, different magnetic poles are alternately arranged in a region facing the photosensitive drum 40. The magnet 21b conveys the developer on the developing sleeve 21a by a magnetic force. On the developing sleeve 21a, a spike of developer is formed by magnetic force. In the development region S, the developing roller 21 brings the developer spike into contact with or close to the electrostatic latent image on the photosensitive drum 40. The development area S is an area where the toner carried by the development sleeve 21 a is supplied to the photosensitive drum 40. That is, the developing area S is an area where the developing roller 21 and the photosensitive drum 40 are closest to each other. As a result, the 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.

  A supporting portion X1 and a non-supporting portion X2 are formed on the outer peripheral surface of the developing sleeve 21a. The non-supporting portion X2 is located at each end of the developing sleeve 21a. The supporting part X1 is provided between the two non-supporting parts X2. The carrying portion X1 is formed by providing a plurality of grooves on the outer peripheral surface of the developing sleeve 21a along the extending direction of the developing sleeve 21a. The carrying part X1 is a part that carries the developer by the magnetic force of the magnet 21b. The unsupported portion X2 is a portion where the developer is not supported.

  Further, a layer regulating member 25 is provided on the upstream side in the rotation direction of the developing sleeve 21a with respect to the developing region S where the developing sleeve 21a and the photosensitive drum 40 face each other. The layer regulating member 25 is located below the rotation axis L of the developing sleeve 21a. The layer regulating member 25 is a member that equalizes the layer thickness of the developer adhered on the peripheral surface of the carrying portion X1 in the developing sleeve 21a to a uniform thickness layer (regulates the layer thickness).

  The first agitation and conveyance member 22 and the second agitation and conveyance member 23 agitate the magnetic carrier and the non-magnetic toner constituting the developer in the developer storage chamber H to rub the carrier and the toner. Charge. The first stirring and conveying member 22 and the second stirring and conveying member 23 convey the developer in the developer storage chamber H while stirring the developer.

  The case 24 accommodates the developing roller 21, the first stirring / transporting member 22, the second stirring / transporting member 23, the layer regulating member 25, and the seal member 26. The case 24 forms a developer storage chamber H that stores a developer including toner and a carrier. The case 24 has an opening 24 b at a position where the developing roller 21 faces the photosensitive drum 40. The toner in the developer storage chamber H is supplied to the photosensitive drum 40 through the opening 24b.

  The upper part of the developing roller 21 is covered with a case upper wall 24 a of the case 24. When the developing roller 21 rotates, air is taken into the case 24 from the space between the developing roller 21 and the case upper wall 24a with the movement of the spikes of the developer formed on the carrying portion X1. The flow of air taken into the case 24 is indicated by an arrow Y1 in FIGS. In order to discharge the air in the case 24, the developing device 20 is provided with a discharge path D. The discharge path D extends from the case 24 toward the opening 24 b of the case 24. The air in the case 24 is discharged from the case 24 toward the opening 24b through the discharge path D. This discharged air flow is indicated by an arrow Y2 in FIGS.

  The discharge path D is located on the downstream side in the developer conveying direction from the developing region S where the developing roller 21 supplies toner to the photosensitive drum 40. The discharge path D faces the non-carrying portion X2 of the developing roller 21. The discharge path D is formed by a groove 24c provided on the inner side surface (lower side surface) of the case upper wall 24a. The groove 24c is provided from the inside of the case 24 to the end of the case upper wall 24a on the opening 24b side. By providing the groove 24c in the case upper wall 24a to form the discharge path D, a large cross-sectional area of the discharge path D can be secured, and the air in the case 24 can be discharged efficiently.

  A seal member 26 is disposed in the groove 24c. As the seal member 26, for example, PTFE felt may be used. The seal member 26 is arranged between the non-carrying part X2 of the developing roller 21 and the case upper wall 24a, and closes the gap between the non-carrying part X2 and the case upper wall 24a. A part of the wall portion forming the discharge path D is constituted by a side surface of the seal member 26.

  As shown in FIG. 5, the distance between the upper surface of the developing roller 21 and the case upper wall 24a is A. Among the spikes F of the developer carried on the carrying part X1 of the developing roller 21, the height of the highest spike F is B. The height of the developer spike F here is the height of the developer spike F at the portion facing the lower surface of the case upper wall 24a. Further, the height of the developer spike F here may be the height at the position where the magnetic force component in the normal direction of the magnetic pole of the magnet 21b has a peak. The magnetic pole is a magnetic pole that is located downstream of the developing region S in the developer transport direction and is located in a region where the developing roller 21 faces the case upper wall 24a.

The distance A between the upper surface of the developing roller 21 and the case upper wall 24a and the height B of the developer spike F satisfy the following formula (1).
A <B (1)
The developing roller 21 is disposed in the case 24 so as to satisfy the relationship of A <B. As a result, the gap between the upper surface of the developing roller 21 and the case upper wall 24a is filled with the spike F of the developer. In FIG. 5, only a part of the developer spike F between the upper surface of the developing roller 21 and the case upper wall 24a is shown.

  A part of the wall part forming the discharge path D is constituted by the developer carried on the carrying part X1 of the developing roller 21, specifically, a part of the wall part constituting the discharge path D is It is constituted by a spike F of developer that fills the gap between the upper surface of the developing roller 21 and the case upper wall 24a.

  As shown in FIG. 5, the discharge path D is formed at a position facing the non-carrying part X2, and a position where the tip of the rising edge F of the developer carried on the carrying part X1 enters. The magnet 21b may be provided in the carrying part X1 of the developing sleeve 21a, or a part thereof may enter the non-carrying part X2 as shown in FIG. When a part of the magnet 21b enters the non-supporting part X2, the discharge path D may be provided in a part facing the magnet 21b (the state shown in FIG. 5), and the discharge path D faces the magnet 21b. It may be provided in a portion that is not (a portion outside the magnet 21b). Regardless of the length of the magnet 21b and whether or not the discharge path D is opposed to the developing sleeve 21a, the discharge path D is located at a position where the tip end of the developer spike F carried on the carrying portion X1 enters. It only has to be formed.

  The guide plate 27 is attached to the opening 24 b of the case 24 so as to cover a part of the opening 24 b of the case 24. The guide plate 27 covers a part of the end portion of the developing roller 21 on the side where the discharge path D is provided. The guide plate 27 faces the discharge port of the discharge path D. The discharge port of the discharge path D is an end portion on the opening 24b side of the case 24 in the discharge path D.

  The guide plate 27 guides the air discharged from the discharge port of the discharge path D. Specifically, the guide plate 27 guides the air discharged from the discharge port of the discharge path D between the lower surface of the case upper wall 24a and the outer peripheral surface of the developing roller 21 as indicated by an arrow Y2 ( (See FIG. 4). Further, the guide plate 27 guides the air discharged from the discharge port of the discharge path D to the carrying portion X1 side of the developing roller 21 as indicated by an arrow Y2 (see FIGS. 3 and 4).

(the flow of air)
Next, the flow of air taken into the case 24 and the air discharged from the case 24 will be described. When the developing roller 21 rotates, air is taken into the case 24 from between the developing roller 21 and the case upper wall 24a as indicated by an arrow Y1. The air taken into the case 24 is discharged from the discharge path D as the pressure in the case 24 increases. More specifically, as shown by an arrow Y2, the air passing through the discharge path D travels from the case 24 toward the opening 24b, and is then guided by the guide plate 27 toward the carrying portion X1. The air guided to the carrying portion X1 side is again taken into the case 24 as indicated by the arrow Y1 as the developing roller 21 rotates.

(Comparison result)
Next, the comparison result of the internal pressure in the case 24 when the discharge path D is provided and when the discharge path D is not provided will be described. The developing device 20 includes a developer discharge port for discharging an old developer. The developer discharge port is provided, for example, near the end of the first stirring / conveying member 22 in the case 24. As a comparison result of the internal pressure in the case 24, the wind speed of the air discharged from the developer discharge port was compared. That is, when the wind speed of the air discharged from the developer discharge port is fast, the internal pressure in the case 24 is higher than when the wind speed is slow.

  As shown in FIG. 6, when the discharge path D is provided in the developing device 20, the wind speed of the air discharged from the developer discharge port is slower than when the discharge path D is not provided. . That is, when the discharge path D is provided, the internal pressure in the case 24 is low. As a result, when the discharge path D is provided, the amount of developer discharged from the developer discharge port is smaller than when the discharge path D is not provided.

  The present embodiment is configured as described above, and the air in the case 24 is discharged out of the case 24 by the discharge path D formed by the groove 24c of the case upper wall 24a. Thereby, the internal pressure rise in case 24 can be controlled. Further, the air discharged through the discharge path D is guided to the carrying portion X1 side of the developing roller 21 by the guide plate 27. As a result, the discharged air is drawn into the case 24 together with the air flow toward the case 24 that is generated when the developer carried on the carrying portion X <b> 1 is conveyed toward the case 24. That is, even if the developer discharged in the air discharged through the discharge path D is contained, the developer included in the discharged air is returned to the case 24 again. As described above, the developing device 20 can suppress the discharge of the developer while suppressing the increase in the internal pressure in the case 24.

  The discharge path D is provided at a position where the spikes F of the developer carried on the carrying part X1 enter the discharge path D. In this case, with the rotation of the developing roller 21, the spike F of the developer carried on the carrying portion X <b> 1 passes through the discharge path D. The air passing through the discharge path D is discharged while passing through the developer heads F moving in the discharge path D. Therefore, even if developer is contained in the air discharged through the discharge path D, the developer in the air is adsorbed by the spikes F of the developer carried at the carrying portion X1. For this reason, discharge of the developer can be further suppressed.

  A part of the wall portion forming the discharge path D is constituted by a developer carried on the carrying portion X1 of the developing roller 21. In this case, the developer contained in the discharged air is adsorbed by the spikes F of the developer constituting the wall portion of the discharge path D when passing through the discharge path D. Thereby, discharge of the developer can be further suppressed.

  The distance A between the upper surface of the developing roller 21 and the case upper wall 24a and the height B of the rising edge F of the developer carried on the carrying portion X1 satisfy the relationship of A <B. In this case, the tip of the developer spike F carried on the carrying part X1 contacts the inner side surface of the case upper wall 24a. Then, the tip of the developer spike F in contact with the case upper wall 24a is bent and enters the discharge path D. As a result, the developer contained in the discharged air is adsorbed by the tips of the developer spikes F that have entered the discharge path D. For this reason, discharge of the developer can be further suppressed.

  The guide plate 27 is attached to the opening 24 b of the case 24. The guide plate 27 covers the end of the developing roller 21. In this case, the guide plate 27 can guide the air discharged from the case 24 and can prevent the developer from scattering from the opening 24b by covering the opening 24b.

  A part of the wall portion forming the discharge path D is constituted by a seal member 26 disposed between the non-carrying portion X2 of the developing roller 21 and the case upper wall 24a. In this case, the discharge path D can be easily formed by the seal member 26.

(First modification)
Next, a first modification will be described. The developing device according to this modification is obtained by changing the configuration of the seal member 26 of the developing device 20 in the embodiment. As illustrated in FIGS. 7 and 8, the developing device 20 </ b> A according to the first modification includes a seal member 126 instead of the seal member 26 of the developing device 20 in the embodiment. About another structure, it is the same as that of the developing device 20 which concerns on embodiment, and attaches | subjects the same code | symbol and abbreviate | omits description.

  The seal member 126 is disposed in the groove 24c. The seal member 126 is disposed between the non-carrying part X2 of the developing roller 21 and the case upper wall 24a, and closes the gap between the non-carrying part X2 and the case upper wall 24a. A part of the wall portion forming the discharge path D is constituted by a side surface of the seal member 126.

  The seal member 126 includes a guide portion (second guide member) 126a that protrudes toward the carrying portion X1 side. The guide portion 126a guides the air discharge direction so that the air passing through the discharge path D is discharged toward the carrying portion X1 side of the developing roller 21. As a result, the air passing through the discharge path D collides with the guiding portion 126a, changes its direction, and is discharged toward the carrying portion X1.

  Further, the magnet 21b includes a magnet arranged so that a magnetic component in a tangential direction has a peak toward an end of the case upper wall 24a on the opening 24b side. In FIG. 7, the magnetic force component in the tangential direction formed around the developing roller 21 is indicated by a broken line. The half-value position of the magnetic component in the tangential direction having a peak toward the end on the opening 24b side of the case upper wall 24a is defined as a half-value position T. The discharge port of the discharge path D is located between the half-value position T and the end of the case upper wall 24a on the opening 24b side. A guiding portion 126a is provided so that the discharge port is located at this portion. The discharge port of the discharge path D is an end portion on the photosensitive drum 40 side in the discharge path D.

  In this case, the air passing through the discharge path D is discharged toward the rising position of the rising of the developer on the carrying portion X1. A large amount of air can be taken into the spike at the rising position of the spike of the developer. For this reason, the air and developer discharged from the discharge path D can be efficiently taken into the ear and returned to the case 24.

  The guide portion 126a may be provided integrally with the seal member 126 or may be a separate body.

(Second modification)
Next, a second modification will be described. The developing device according to this modification is obtained by changing the configuration around the case upper wall 24a of the developing device 20 in the embodiment. As shown in FIGS. 9 and 10, the case upper wall 24a of the developing device 20B according to the second modification has an extension 24x. About another structure, it is the same as that of the developing device 20 which concerns on embodiment, and attaches | subjects the same code | symbol and abbreviate | omits description.

  The extension 24x protrudes from the end of the case upper wall 24a on the opening 24b side toward the photosensitive drum 40 rather than the guide plate 27. The extension 24x may be provided only in a portion where the guide plate 27 is not provided as shown in FIG. Alternatively, the extension 24x may be provided over the entire developing roller 21 at the end of the case upper wall 24a on the opening 24b side. In this case, the upper end part of the guide plate 27 may be fixed to the lower surface of the extension part 24x, for example.

  Since the case upper wall 24a has the extension portion 24x, the end portion on the opening 24b side of the case upper wall 24a protrudes toward the photosensitive drum 40 from the guide plate 27. As a result, the developing device 20B can reduce the gap between the photosensitive drum 40 and the case upper wall 24a. Accordingly, the amount of air flowing toward the upper side (downstream in the rotation direction of the photosensitive drum 40) through the gap between the photosensitive drum 40 and the case upper wall 24a is reduced, and the amount of air taken into the case 24 by the developing roller 21 is reduced. Can be increased. That is, the air discharged through the discharge path D can be efficiently returned into the case 24.

  The extension 24x may be integrated with the case upper wall 24a or may be a separate body. The configuration of the extension 24x of the second modification can also be applied to the developing device 20A in the first modification.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. For example, it is not essential to have the configuration in which the tip of the developer spike F supported on the supporting portion X1 enters the discharge path D. That is, the discharge path D may be provided at a position away from the carrying site X1 (a position where the tip of the developer spike F does not enter the discharge path D). It is not essential that a part of the wall portion forming the discharge path D is constituted by the developer carried on the carrying part X1. It is not essential that the distance A between the upper surface of the developing roller 21 and the case upper wall 24a and the height B of the developer spike F satisfy the formula (1).

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 20 ... Developing apparatus, 21 ... Developing roller (developer carrier), 22 ... First stirring / conveying member (stirring / conveying member), 23 ... Second stirring / conveying member (stirring / conveying member), 24 ... Case, 24a ... Case upper wall, 24b ... Opening, 24c ... Groove, 25 ... Layer regulating member, 26, 126 ... Seal member, 27 ... Induction plate (first induction member), 40 ... Photosensitive drum (photosensitive member) , 126a ... guide part (second guide part), D ... discharge path, H ... developer storage chamber (developer storage part), L ... rotation shaft (rotation axis of developer carrier), S ... development region, T ... half-value position, X1 ... supporting part, X2 ... non-supporting part.

Claims (8)

A developer containing portion for containing a developer containing toner and a carrier;
An agitating and conveying member for conveying the developer contained in the developer containing portion while stirring;
A developer carrying member that carries the developer stirred by the stirring and conveying member and rotates so that the carried developer is conveyed to a photoreceptor;
A layer regulating member that is positioned below the rotation axis of the developer carrying member and regulates the layer thickness of the developer carried by the developer carrying member;
A case that forms the developer accommodating portion, accommodates the agitating / conveying member, the developer carrying member, and the layer regulating member, and has an opening at a portion where the developer carrying member faces the photoconductor; ,
A discharge path for discharging the air in the case toward the opening,
A first guide member for guiding the air discharged from the discharge port of the discharge path;
With
The discharge path is located downstream of the developing region in which the developer carrying member supplies the toner to the photoreceptor in the transport direction of the developer, and the development at the end of the developer carrying member. Facing the non-carrying part of the agent,
Further, the discharge path is formed by a groove provided on the inner surface of the case upper wall that covers the upper portion of the developer carrying member of the case,
The first guiding member guides the air discharged from the discharge port between the upper wall of the case and the developer carrier and to the developer carrying part side of the developer carrier. apparatus.   The developing device according to claim 1, wherein the position where the discharge path is provided is a position where the developer carried by the carrying portion enters the discharge path. A second guide member for guiding the air discharge direction so that the air passing through the discharge path is discharged toward the carrying portion of the developer carrying body;
The developer carrier includes a magnet arranged so that a magnetic component in a tangential direction has a peak toward an end of the case upper wall on the opening side,
The discharge port is located between the half-value position of the magnetic component in the tangential direction having a peak toward the end on the opening side of the case upper wall and the end on the opening side of the case upper wall. The developing device according to claim 1, wherein the developing device is located.   4. The developing device according to claim 1, wherein a part of the wall portion forming the discharge path is configured by the developer carried on the carrying portion of the developer carrying body. 5. . The distance between the upper surface of the developer carrier and the upper wall of the case is A,
When the height of the top of the developer among the ears of the developer carried on the carrying part of the developer carrier is B,
The developing device according to claim 1, wherein A and B satisfy a relationship of A <B.   6. The developing device according to claim 1, wherein an end portion on the opening portion side of the case upper wall protrudes toward the photoconductor side with respect to the first guide member.   The developing device according to claim 1, wherein the first guide member is attached to the opening and covers an end portion of the developer carrier.   A part of the wall portion forming the discharge path is configured by a seal member disposed between the non-carrying portion of the developer carrying member and the case upper wall. The developing device according to claim 1.

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