Developing device and image forming apparatus

Abstract

To optimize the amount of excess developer to be discharged without changing the size of a developing device.SOLUTION: A developing device 14 comprises: a housing 30 that stores developer; a supply port that supplies the developer to the housing 30; a spiral blade 51b that stirs the developer while conveying the developer in a predetermined conveyance direction (B direction) in the housing 30; a discharge port that discharges the developer conveyed by the spiral blade 51b; and a regulation member 60 that is provided between the spiral blade 51b and the discharge port and regulates the conveyance of the developer to the discharge port. The regulation member 60 has chipped parts 60a passing through in the conveyance direction (B direction).SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a developing device and an image forming apparatus.

Background Art

[0002] An electrophotographic image forming apparatus includes a developing device that develops a latent image formed on a photoreceptor using toner. In the case of a developing device that uses a two-component developer containing toner and carrier, a developing housing that houses the developer, a developing roller that supplies toner to the photoreceptor, and a stirring member that conveys the developer to the developing roller while stirring the developer are provided. In this configuration, while toner is consumed by development, the carrier remains in the developing housing. Therefore, as the developing operation is repeated, the carrier deteriorates, and the triboelectrification ability with respect to the toner decreases. Therefore, a configuration is known in which a predetermined amount of carrier is continuously replaced by replenishing the developer and discharging excess developer. For example, Patent Documents 1 and 2 disclose a configuration in which a regulating member that blocks the developer conveyed by the stirring member is provided, and the developer that has overcome the regulating member is discharged from the discharge port.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, the developing device needs to be designed according to the processing speed required for the image forming apparatus. For example, when comparing a high-speed machine with a low-speed machine, the higher the speed of the machine, the greater the supply amount of the developer per unit time, and the greater the discharge amount of the surplus developer per unit time. When adopting the configurations disclosed in Patent Documents 1 and 2, in order to vary the discharge amount of the surplus developer, it is necessary to vary the specifications of the stirring member (such as the number of turns of the blades, the pitch, the diameter, etc.), but inevitably the size of the housing also needs to be varied, so there is a problem that the high-speed machine becomes larger. Further, changing the size of the housing causes a problem of increased cost.

[0005] In view of the above circumstances, an object of the present invention is to optimize the discharge amount of the surplus developer without changing the size of the developing device.

Means for Solving the Problems

[0006] To solve the above problems, a developing device according to the present invention includes a housing that houses a developer, a supply port that supplies the developer to the housing, a spiral blade that stirs the developer while transporting it in a predetermined transport direction within the housing, a discharge port that discharges the developer transported by the spiral blade, and a regulating member that is provided between the spiral blade and the discharge port and regulates the transport of the developer to the discharge port, and the regulating member has a missing portion that penetrates in the transport direction.

[0007] The missing portion may be circumferentially spaced from the end portion on the downstream side in the transport direction of the spiral blade.

[0008] The missing portion may be a slit formed along the radial direction.

[0009] An image forming apparatus according to the present invention further includes a photosensitive drum on which a latent image is formed, and the developing device according to any one of claims 1 to 3 that supplies a developer to the photosensitive drum.

Advantages of the Invention

[0010] According to the present invention, it is possible to optimize the discharge amount of surplus developer without changing the size of the developing device.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0012] Hereinafter, a developing device 14 and an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to the drawings.

[0013] First, the overall configuration of the image forming apparatus 100 will be described. FIG. 1 is a front view schematically showing the internal configuration of the image forming apparatus 100. Hereinafter, the side closer to the paper surface in FIG. 1 is defined as the front side (front) of the image forming apparatus 100, and the left and right directions will be described with reference to the direction when viewing the image forming apparatus 100 from the front. In each figure, U, Lo, L, R, Fr, and Rr indicate up, down, left, right, front, and rear, respectively.

[0014] The image forming apparatus 100 includes a printer 1, a scanner 110, and an original document conveying device 120. The scanner 110 is provided above the printer 1, and the original document conveying device 120 is provided above the scanner 110. The original document conveying device 120 conveys the original document via the reading position of the scanner 110. The scanner 110 is a flatbed type image scanner that reads the original document and generates image data. The printer 1 forms an image based on the image data on the sheet S.

[0015] The printer 1 includes a rectangular parallelepiped main body housing 3. Inside the lower part of the main body housing 3, a paper feed cassette 4 for accommodating the sheet S and a paper feed roller 5 for feeding the sheet S rightward from the paper feed cassette 4 are provided. Above the paper feed cassette 4, an image forming device 6 for forming a toner image by an electrophotographic method is provided, and above the upper right of the image forming device 6, a fixing device 7 for fixing the toner image on the sheet S is provided. Above the fixing device 7, a discharge roller 8 for discharging the sheet S on which the toner image is fixed and a discharge tray 9 on which the discharged sheets S are stacked are provided.

[0016] Inside the main body housing 3, a conveyance path 10 is provided that extends from the paper feed roller 5 through the image forming device 6, the fixing device 7 to the discharge roller 8. The conveyance path 10 is formed using plate-like members that face each other with a gap for the sheet S to pass through. Conveyance rollers 17 for sandwiching and conveying the sheet S are provided at a plurality of locations in the conveyance path 10. A registration roller 18 is provided upstream of the image forming device 6 in the conveyance direction Y. To the right of the fixing device 7, a reverse conveyance path 10R is provided that branches from the conveyance path 10 downstream of the fixing device 7 in the conveyance direction Y and merges into the conveyance path 10 upstream of the registration roller 18 in the conveyance direction Y.

[0017] The image forming apparatus 6 includes a photosensitive drum 11 whose potential changes upon irradiation with light, a charging device 12 that charges the photosensitive drum 11, an exposure device 13 that emits laser light according to image data, a developing device 14 that supplies toner to the photosensitive drum 11, an intermediate transfer unit 15 that transfers the toner image from the photosensitive drum 11 to a sheet S, and a cleaning device 16 that removes the toner remaining on the photosensitive drum 11. The intermediate transfer unit 15 includes an endless intermediate transfer belt 15B wound around a driving roller 15D and a driven roller 15N, a primary transfer roller 151 that faces the inner peripheral surface of the intermediate transfer belt 15B at a position corresponding to the photosensitive drum 11 and generates a primary transfer bias, and a secondary transfer roller 152 that faces the outer peripheral surface of the intermediate transfer belt 15B at a position corresponding to the driving roller 15D and generates a secondary transfer bias. A toner container 20 that supplies toner to the developing device 14 is connected to the developing device 14.

[0018] The image forming apparatus 6 includes four sets of the photosensitive drum 11, the charging device 12, the exposure device 13, the developing device 14, the primary transfer roller 151, the cleaning device 16, and the toner container 20, and forms a color image by overlapping four-color toner images on the intermediate transfer belt 15B. Note that the present invention may be applied to an image forming apparatus 100 that forms a color image with three or fewer or five or more colors of toner.

[0019] The control unit 2 includes an arithmetic unit and a storage unit. The arithmetic unit is, for example, a CPU (Central Processing Unit). The storage unit includes storage media such as a ROM (Read Only Memory), a RAM (Random Access Memory), and an EEPROM (Electrically Erasable Programmable Read Only Memory). The arithmetic unit performs various processes by reading and executing a control program stored in the storage unit. Note that the control unit 2 may be realized only by an integrated circuit without using software.

[0020] On the front side of the scanner 110, an operation display unit (not shown) is provided. The operation display unit includes a display panel, a touch panel provided over the display surface of the display panel, and a keypad adjacent to the display panel. The control unit 2 causes the display panel to display a screen representing the operation menu, status, etc. of the printer 1 and the scanner 110, and controls each part of the printer 1 and the scanner 110 according to the operations detected by the touch panel and the keypad.

[0021] The basic image forming operation of the printer 1 is as follows. When a single-sided printing job is input to the printer 1 from the operation display unit or an external computer, etc., the paper feed roller 5 feeds the sheet S from the paper feed cassette 4 to the conveyance path 10, the registration roller 18 whose rotation has been stopped corrects the skew of the sheet S, and the registration roller 18 feeds the sheet S to the image forming device 6 at a predetermined timing. In the image forming device 6, the charging device 12 charges the photosensitive drum 11 to a predetermined potential, the exposure device 13 writes a latent image on the photosensitive drum 11, the developing device 14 forms a toner image by developing the latent image using the toner supplied from the toner container 20, the primary transfer roller 151 transfers the toner image to the intermediate transfer belt 15B, and the secondary transfer roller 152 transfers the toner image to the sheet S. Subsequently, the fixing device 7 sandwiches and conveys the sheet S and melts the toner image to fix the toner image on the sheet S, and the discharge roller 8 discharges the sheet S to the discharge tray 9. The cleaning device 16 removes the toner remaining on the photosensitive drum 11. In the case of double-sided printing, the sheet S with the toner image fixed on the first side is fed into the conveyance path 10 via the reverse conveyance path 10R, and the toner image is transferred to the second side.

[0022] [Developing Device] Next, the developing device 14 will be described. FIG. 2 is a front view schematically showing the internal configuration of the developing device 14. FIG. 3 is a cross-sectional view showing the internal configurations of the first conveyance path 40 and the second conveyance path 41. FIG. 4 is an enlarged cross-sectional view of the rear portions of the first conveyance path 40 and the second conveyance path 41.

[0023] The four developing devices 14 have the same configuration. The developing device 14 (see FIGS. 2 and 3) includes a housing 30, a stirring member 31, a developing roller 53, and a driving device 33. The housing 30 houses a developer containing toner and a carrier therein. The stirring member 31 stirs the developer in the housing 30 while conveying it. The developing roller 53 conveys the developer in the housing 30 from the stirring member 31 toward the photosensitive drum 11. The driving device 33 rotates the stirring member 31 and the developing roller 53.

[0024] [Housing] The housing 30 is made of, for example, a resin material. The housing 30 is formed with its longitudinal direction being the front-rear direction. An opening 30a (see FIG. 2) is formed on the upper right side surface of the housing 30. A partition wall 30b (see FIGS. 2 to 4) is provided along the longitudinal direction of the housing 30 at the bottom inside the housing 30. The partition wall 30b divides the internal space of the housing 30 into a first conveyance path 40 and a second conveyance path 41. The first conveyance path 40 and the second conveyance path 41 are provided parallel to each other.

[0025] A communication portion 42 (see FIG. 3) that communicates the first conveyance path 40 and the second conveyance path 41 is formed at the front end portion of the partition wall 30b. A communication portion 43 that communicates the first conveyance path 40 and the second conveyance path 41 is formed at the rear end portion of the partition wall 30b.

[0026] The housing 30 is formed with a supply port 30c (see FIGS. 3 and 4) for supplying toner from the toner container 20 to the first conveyance path 40. The supply port 30c is provided near the communication portion 43.

[0027] A discharge case 46 (see FIGS. 3 and 4) is provided behind the second conveyance path 41. A discharge port 47 is formed on the lower surface of the discharge case 46. A recovery bottle 35 for storing the discharged developer is connected to the discharge port 47.

[0028] [Stirring member] The stirring member 31 (see FIGS. 2 and 3) is composed of a first stirring member 50 arranged along the first conveyance path 40 and a second stirring member 51 arranged along the second conveyance path 41.

[0029] The first stirring member 50 and the second stirring member 51 (see FIGS. 3 and 4) are each formed by providing spiral blades 50b and 51b on the circumferential surfaces of the rotary shaft portions 50a and 51a. The first stirring member 50 and the second stirring member 51 are each supported by the housing 30 via the rotary shaft portions 50a and 51a, and rotate in the counterclockwise direction in FIG. 2. The spiral blade 50b and the spiral blade 51b are formed with the same pitch and in opposite winding directions. The first stirring member 50 conveys the developer in the A direction (see FIGS. 3 and 4), and the second stirring member 51 conveys the developer in the B direction.

[0030] The second stirring member 51 (see FIGS. 3 and 4) includes a reverse spiral blade 51c behind the spiral blade 51b, and a discharge blade 51d behind the reverse spiral blade 51c. The reverse spiral blade 51c is arranged at the rear end portion in the second conveyance path. The reverse spiral blade 51c is formed in a spiral shape with a winding direction opposite to that of the spiral blade 51b. The discharge blade 51d is arranged in the discharge case 46 and is formed in a spiral shape with the same winding direction as the spiral blade 51b.

[0031] [Developing roller] The developing roller 53 (see FIG. 2) is arranged above the second stirring member 51. The developing roller 53 has a fixed shaft portion 53a, a magnetic pole member 53b, and a developing sleeve 53c. The fixed shaft portion 53a is supported by the housing 30 and is non-rotatable. The developing sleeve 53c is formed in a cylindrical shape from a non-magnetic material and covers the magnetic pole member 53b. The developing sleeve 53c has a gap with the magnetic pole member 53b, is supported by the fixed shaft portion 53a, and rotates in the counterclockwise direction in FIG. 2.

[0032] The developing roller 53 is exposed from the opening 30a of the housing 30 and faces the photosensitive drum 11. The developing roller 53 is electrically connected to a developing bias power source (not shown). The developing bias power source applies a developing bias, which is a superposition of a DC voltage and an AC voltage, to the developing roller 53.

[0033] A layer thickness regulating blade 56 is provided at the opening 30a of the housing 30. Assuming that the region where the developing roller 53 and the second stirring member 51 are closest is the proximity region C, and the region where the developing roller 53 and the photosensitive drum 11 are closest is the proximity region D, the tip of the layer thickness regulating blade 56 faces the developing sleeve 53c on the downstream side of the proximity region C and on the upstream side of the proximity region D in the rotation direction of the developing roller 53. The layer thickness regulating blade 56 has a gap with the outer peripheral surface of the developing sleeve 53c. The layer thickness regulating blade 56 regulates the layer thickness of the magnetic brush formed on the outer peripheral surface of the developing sleeve 53c.

[0034] The drive device 33 (see FIG. 3) is an electric motor that transmits a driving force to the first stirring member 50, the second stirring member 51, and the developing roller 53 via a gear train 58. When the drive device 33 is rotationally driven, the first stirring member 50, the second stirring member 51, and the developing roller 53 rotate.

[0035] [Regulating member] FIG. 5 is a perspective view showing the rear parts of the first conveyance path 40 and the second conveyance path 41. FIG. 6 is a perspective view showing a cross-section of the rear parts of the first conveyance path 40 and the second conveyance path 41.

[0036] The regulating member 60 is provided between the spiral blades 51b and the reverse spiral blades 51c of the second stirring member 51. The regulating member 60 regulates the conveyance of the developer to the discharge port 47. The regulating member 60 is a disc-shaped member. The regulating member 60 is provided on the rotating shaft portion 51a of the second stirring member 51. The center of the rotating shaft portion 51a and the center of the regulating member 60 coincide. The regulating member 60 rotates together with the rotating shaft portion 51a and the spiral blades 51b.

[0037] The regulating member 60 has a missing portion 60a that penetrates in the conveying direction (direction B in FIG. 4). The missing portion 60a is a slit formed along the radial direction. The missing portion 60a is provided at a position circumferentially spaced apart from the end portion 51e on the downstream side in the conveying direction (direction B) of the spiral blade 51b.

[0038] Next, the operation of conveying and stirring the developer by the developing device 14 will be described. The developer supplied from the toner container 20 to the housing 30 through the supply port 30c (see FIGS. 3 and 4) is conveyed in the A direction through the first conveying path 40 by the first stirring member 50, moves to the second conveying path 41 through the communication portion 42, and is conveyed in the B direction by the second stirring member 51. The developer conveyed in the B direction is blocked by the regulating member 60 and mainly moves in three flows.

[0039] That is, the developer moves separately into a flow to the communication portion 43, a flow over the regulating member 60, and a flow through the missing portion 60a. Among these, the developer flowing into the communication portion 43 flows into the first conveying path 40, and stirring and conveying are continued.

[0040] On the other hand, the developer that has overcome the regulating member 60 is mainly divided into two flows. A part of the developer that has overcome the regulating member 60 is pushed back by the reverse spiral blade 51c and flows into the first conveying path 40 through the communication portion 43. The other developer overcomes the reverse spiral blade 51c and is conveyed in the B direction by the discharge blade 51d, and is discharged from the discharge port 47 as surplus developer.

[0041] On the other hand, the developer that has passed through the missing portion 60a is pushed back by the reverse spiral blade 51c and flows into the first conveying path 40 through the communication portion 43. That is, the discharge amount of the surplus developer changes depending on the amount of the developer passing through the missing portion 60a.

[0042] For example, to increase the discharge amount of the surplus developer, the amount of the developer passing through the missing portion 60a may be decreased. For example, by reducing the number of the missing portions 60a or making the missing portion 60a smaller, the amount of the developer passing through the missing portion 60a is decreased.

[0043] Also, the amount of developer passing through the defective portion 60a varies depending on the circumferential position of the defective portion 60a. If the defective portion 60a is adjacent to the end portion 51e on the downstream side in the conveyance direction (B direction) of the spiral blade 51b, the developer directly flows from the end portion 51e into the defective portion 60a, and the amount of developer passing through the defective portion 60a increases. Conversely, when the defective portion 60a is circumferentially spaced apart from the end portion 51e, the developer is temporarily blocked by the restricting member 60. While being blocked, a part of the developer gets over the restricting member 60, so that the amount of developer passing through the defective portion 60a decreases. The longer the distance between the defective portion 60a and the end portion 51e, the longer the time for blocking the developer, and thus the more the amount of developer getting over the restricting member 60 and the less the amount of developer passing through the defective portion 60a.

[0044] For example, when designing two models of image forming apparatuses 100 with different processing speeds, the high-speed model consumes more toner per unit time than the low-speed model, so the amount of carrier remaining in the housing 30 also increases. Therefore, the high-speed model needs to increase the discharge amount of surplus developer per unit time. According to the present embodiment, the discharge amount of surplus developer varies depending on the number, size, position, etc. of the defective portions 60a. Thus, according to the present embodiment, the discharge amount of surplus developer can be optimized without changing the size of the developing device 14.

[0045] According to the developing device 14 according to the present embodiment described above, there are provided a housing 30 for accommodating a developer, a supply port 30c for supplying the developer to the housing 30, a spiral blade 51b that agitates while conveying the developer in a predetermined conveyance direction (B direction) in the housing 30, a discharge port 47 for discharging the developer conveyed by the spiral blade 51b, and a restricting member 60 provided between the spiral blade 51b and the discharge port 47 for restricting the conveyance of the developer to the discharge port 47. The restricting member 60 has a defective portion 60a penetrating in the conveyance direction (B direction). According to this configuration, since the discharge amount of surplus developer varies depending on the number and size of the defective portions 60a, the discharge amount of surplus developer can be optimized without changing the size of the developing device 14.

[0046] Further, according to the developing device 14 according to the present embodiment, the missing portion 60a is separated in the circumferential direction from the end portion 51e on the downstream side in the conveyance direction (B direction) of the spiral blade 51b. According to this configuration, since the discharge amount of the surplus developer changes depending on the distance between the missing portion 60a and the end portion 51e on the downstream side in the conveyance direction (B direction) of the spiral blade 51b, the discharge amount of the surplus developer can be optimized without changing the size of the developing device 14.

[0047] Further, according to the developing device 14 according to the present embodiment, the missing portion 60a is a slit formed along the radial direction. According to this configuration, since the missing portion 60a is formed by opposing two semicircular plates and attaching them to the rotary shaft portion 51a, the missing portion 60a can be formed with a simple configuration.

[0048] Further, according to the image forming apparatus 100 according to the present embodiment, the image forming apparatus 100 includes a photosensitive drum 11 on which a latent image is formed, and a developing device 14 that supplies a developer to the photosensitive drum 11. According to this configuration, an image can be formed with accurate density.

[0049] The above embodiment may be modified as follows.

[0050] In the above embodiment, an example in which the regulating member 60 is provided between the spiral blade 51b and the reverse spiral blade 51c has been shown, but the reverse spiral blade 51c may have the function of the regulating member 60. For example, a missing portion 60a may be provided in the foremost portion (the spiral blade 51b side) of the reverse spiral blade 51c. Also with this configuration, the discharge amount of the surplus developer can be optimized without changing the size of the developing device 14. In addition, the number of components can be suppressed.

[0051] In the above embodiment, an example in which the missing portion 60a of the regulating member 60 is a slit formed along the radial direction has been shown, but the missing portion 60a may have other shapes. For example, the missing portion 60a may be a hole, and the shape of the hole may be circular, polygonal, or the like.

Explanation of reference numerals

[0052] 11 Photoconductor drum 30 Housing 30c Supply port 47 Discharge port 51b Screw blade 51e End portion on the downstream side of the conveying direction of the screw blade 60 Regulation member 60a Defective portion 100 Image forming apparatus G Gap

Claims

1. A housing for accommodating a developer, A replenishing port for replenishing the developer into the housing, A spiral blade for stirring the developer while conveying it in a predetermined conveying direction within the housing, A discharge port for discharging the developer conveyed by the spiral blade, A regulating member provided between the spiral blade and the discharge port for regulating the conveyance of the developer to the discharge port, and comprising: The regulating member has a missing portion penetrating in the conveying direction, and the developing device is characterized in that.

2. The developing device according to claim 1, wherein the missing portion is circumferentially spaced apart from an end portion on the downstream side in the conveying direction of the spiral blade.

3. The developing device according to claim 2, wherein the missing portion is a slit formed along the radial direction.

4. A photosensitive drum on which a latent image is formed, An image forming apparatus, comprising the developing device according to any one of claims 1 to 3 for supplying a developer to the photosensitive drum.

Images