Developing device and image forming apparatus

Abstract

To improve upper conveyance properties of upper conveying means to convey powder to first stirring and conveying means regardless of the rotation speed of second stirring and conveying means, compared to a case where the upper conveying means is fixed to a rotation shaft of the second stirring and conveying means.SOLUTION: A powder conveying device comprises: a developer holding body that holds developer; stirring and supplying means that stirs the developer and supplies it to the developer holding body; stirring and conveying means that is arranged vertically below the stirring and supplying means, and stirs and conveys the developer; upper conveying means that is arranged on the downstream side in a conveyance direction of the stirring and conveying means, and conveys the developer conveyed from the stirring and conveying means to the stirring and supplying means above it; and speed increasing means that increases the speed of rotation of a rotation shaft of any one of the stirring and conveying means, the stirring and supplying means, and the developer holding body, and transmits the driving force to the upper conveying means.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] This invention is Developing device and an image forming apparatus. [Background technology]

[0002] Conventionally, technologies relating to developing devices have already been proposed, for example, as disclosed in Patent Documents 1 to 3.

[0003] Patent Document 1 discloses a configuration in which a first communication port imparts a transport force to the developer from the first developer transport path toward the second developer transport path, and the communication port transport member is a separate member from the first developer transport member and the second developer transport member, and the communication port transport member control means controls the drive speed of the communication port transport member based on the detection results of a toner concentration sensor.

[0004] In Patent Document 2, the developer transfer means is provided with a plurality of pressing members that move from below to above, thereby pressing and pushing up the developer from below, and is configured so that when the pressing members press the developer, the developer can pass from the surface side above the pressing members to the surface side below them.

[0005] In Patent Document 3, the communicating portion has an inverted cone shape tapering downward in the direction of gravity, and inside it, a transfer conveying member is provided, separate from the developer stirring and conveying member, for conveying the developer toward the developer stirring and conveying member, and the transfer conveying member is configured so that, in the communicating portion, the transfer conveying capacity, which corresponds to the amount of developer that can be conveyed per unit time toward the developer stirring and conveying member, is higher than the stirring and conveying capacity, which corresponds to the amount of developer that can be conveyed per unit time in the conveying direction by the developer stirring and conveying member. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-98286 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-68616 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-78034 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of this invention is to improve the upward transport ability of powder to the first agitating and transporting means by the upward transporting means regardless of the rotation speed of the second agitating and transporting means, compared to when the upward transporting means is fixed to the rotation shaft of the second agitating and transporting means. [Means for solving the problem]

[0009] Claim 1 The invention described in the above includes a developer carrier for holding a developer, a stirring and supplying means for stirring the developer and supplying the developer to the developer holder; a stirring and conveying means disposed vertically below the stirring and supplying means for stirring and conveying the developer; an upper conveying means disposed downstream of the agitating and conveying means in a conveying direction, and configured to convey the developer conveyed from the agitating and conveying means to the agitating and supplying means above; a speed increasing means for increasing the rotation speed of any one of the rotation shafts of the stirring and conveying means, the stirring and supplying means, and the developer carrier, and transmitting the rotation speed to the upper conveying means; Equipped with 、 The speed increasing means increases the rotation speed of the rotating shaft of the mixing and conveying means, and includes a first transmission means that increases the driving force of the rotating shaft of the mixing and conveying means and transmits it to the intermediate shaft, and a second transmission means that transmits the driving force of the intermediate shaft to the upper conveying means. It is a developing device.

[0012] Claim 2 The invention described in the above is characterized in that the first and second transmission means are made up of a combination of pulleys and belts. Claim 1 2. The developing device according to claim 1.

[0013] Claim 3 The invention described in a developer carrier that holds a developer; a stirring and supplying means for stirring the developer and supplying the developer to the developer holder; a stirring and conveying means disposed vertically below the stirring and supplying means for stirring and conveying the developer; an upper conveying means disposed downstream of the agitating and conveying means in a conveying direction, and configured to convey the developer conveyed from the agitating and conveying means to the agitating and supplying means above; a speed increasing means for increasing the rotation speed of any one of the rotation shafts of the stirring and conveying means, the stirring and supplying means, and the developer carrier, and transmitting the rotation speed to the upper conveying means; a reverse direction conveying means disposed obliquely below the developer holder along a vertical direction and configured to convey the developer in a direction opposite to that of the agitating and conveying means, The speed increasing means is a developing device that temporarily transmits the driving force of the agitating and transporting means to the rotation shaft of the reverse direction transporting means, increases the rotation speed of the rotation shaft of the reverse direction transporting means, and then transmits the increased rotation speed to the upward transporting means.

[0014] Claim 4 The invention described in the above relates to a method for conveying a conveyance member, and the conveyance member has a plurality of flat plate members arranged along the circumferential direction on the outer periphery of the shaft member, the flat plate members being oriented radially outward. Claim 1 2. The developing device according to claim 1.

[0015] Claim 5 In the invention described in the above, the upward conveying means is driven at a rotation speed 1.5 to 3.0 times that of the rotation shaft of the agitating and conveying means. Claim 4 2. The developing device according to claim 1.

[0016] Claim 6 The invention described in the above includes an image carrier that holds a latent image, a developing means for developing the latent image on the image carrier; Equipped with As the developing means Claims 1 to 5 10. An image forming apparatus using the developing device according to any one of claims 1 to 9. [Effects of the Invention]

[0018] Claim 1 According to the invention described above, the upward transport ability of the upward transport means to the stirring and supply means can be improved regardless of the rotation speed of the stirring and transport means, compared to when the upward transport means is fixed to the rotation shaft of the stirring and transport means.

[0019] Claim 1 According to the invention described in the above, the speed increasing means can reduce the area occupied by the speed increasing means compared to when the speed of rotation of something other than the rotation shaft of the stirring and transporting means is increased.

[0020] Claim 1According to the invention described above, the speed increasing means can have a simpler configuration than when it does not have a first transmission means that increases the driving force of the rotating shaft of the mixing and conveying means and transmits it to the intermediate shaft, and a second transmission means that transmits the driving force of the intermediate shaft to the upper conveying means.

[0021] Claim 2 According to the invention described in the above, the first and second transmission means can align the rotation directions in adjacent regions, compared to when the first and second transmission means are made up of a combination of gears.

[0022] Claim 3 According to the invention described in the above, the speed increasing means does not require the provision of a new intermediate shaft, compared to when the driving force of the stirring and conveying means is first transmitted to the rotating shaft of the reverse direction conveying means, and the rotation of the rotating shaft of the reverse direction conveying means is not increased and transmitted to the upper conveying means.

[0023] Claim 4 According to the invention described above, the upward conveying means can improve the upward conveying ability of the developer compared to a case where the upward conveying means does not have multiple flat plate members facing radially outward along the circumferential direction on the outer periphery of the shaft member.

[0024] Claim 5 According to the invention described above, the upward conveying means can ensure the upward conveyance of the developer and can prevent the developer from scattering, compared to when it is driven at a rotation speed less than 1.5 times or more than 3.0 times the rotation speed of the rotation shaft of the stirring and conveying means.

[0025] Claim 6 According to the invention described in Claims 1 to 5 In comparison with a case where the developing device according to any one of the above items (1) to (3) is not used, the upward transporting performance of the developer by the upward transporting means to the agitating and supplying means can be improved regardless of the rotation speed of the agitating and transporting means. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus to which a developing device according to a first embodiment of the present invention is applied; [Figure 2] 1 is a cross-sectional view showing the configuration of an image forming device of an image forming apparatus according to a first embodiment of the present invention; [Figure 3] 1 is a vertical cross-sectional view showing a developing device according to a first embodiment of the present invention; [Figure 4] 4 is a cross-sectional view taken along line IV-IV in FIG. 3, showing the developing device according to the first embodiment of the present invention. [Figure 5] 1 is a cross-sectional view showing the configuration of a main part of a developing device according to a first embodiment of the present invention. [Figure 6] FIG. 2 is a perspective view showing the configuration of a paddle member. [Figure 7] 4 is a graph showing the operation of the developing device. [Figure 8] 1 is a perspective view showing the configuration of a main part of a developing device according to a first embodiment of the present invention; [Figure 9] 1 is a perspective view showing the configuration of a main part of a developing device according to a first embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0028] [Embodiment 1] 1 shows an image forming apparatus to which the powder conveying device and developing device according to embodiment 1 are applied. In the figure, the width direction along the horizontal direction of the image forming apparatus is designated as the X direction, the depth direction along the horizontal direction of the image forming apparatus is designated as the Y direction, and the height direction along the vertical direction of the image forming apparatus is designated as the Z direction.

[0029] <Overall configuration of image forming apparatus> The image forming apparatus 1 according to the first embodiment is configured as, for example, a color printer. The size of the device body 1a along the X direction of this image forming apparatus 1 is equivalent to that of a conventional full-color printer, and in addition to full-color images consisting of four colors, yellow (Y), magenta (M), cyan (C), and black (K), it is also possible to simultaneously form images of metallic colors such as gold (G) and silver (S), single colors such as red (R), green (G), and blue (B), corporate colors such as Mizuho Financial Group's Cosmic Blue and Horizon Red, and specific colors (hereinafter referred to as "spot colors") consisting of various hues such as transparency and white.

[0030] This image forming apparatus 1 includes a plurality of image creating devices 10 that form toner images developed with toner constituting a developer 4; an intermediate transfer device 20 that holds each toner image formed by the image creating devices 10 and transports it to a secondary transfer position where it is finally secondarily transferred onto a recording sheet 5 (an example of a recording medium); a paper feeder 50 that stores and transports the required recording sheet 5 to be supplied to the secondary transfer position of the intermediate transfer device 20; and a fixing device 40 that fixes the toner image on the recording sheet 5 that has been secondarily transferred by the intermediate transfer device 20. The plurality of image creating devices 10 and the intermediate transfer device 20 constitute an image forming section 2 that forms an image on the recording sheet 5. The device body 1a of the image forming apparatus 1 is formed by supporting structural members, an exterior cover, etc. The two-dot chain line in the figure indicates the main transport path along which the recording sheet 5 is transported within the device body 1a.

[0031] The imaging device 10 is composed of four imaging devices 10Y, 10M, 10C, and 10K, each dedicated to forming a toner image of four colors—yellow (Y), magenta (M), cyan (C), and black (K)—and an imaging device 10S, which forms a toner image of a special color (S). These five imaging devices 10 (S, Y, M, C, and K) are arranged in a line along the X direction in the internal space of the device main body 1a. In the illustrated embodiment, the special color imaging device 10S is arranged most upstream in the direction of movement of the intermediate transfer belt 21 of the intermediate transfer device 20, and the yellow (Y), magenta (M), cyan (C), and black (K) imaging devices 10 (Y, M, C, and K) are arranged sequentially along the direction of movement of the intermediate transfer belt. However, the placement of the special color image forming device 10S is not limited to this, and it may be placed at the most downstream side along the direction of movement of the intermediate transfer belt, or it may be placed between the yellow (Y), magenta (M), cyan (C) and black (K) image forming devices 10 (Y, M, C, K).

[0032] Each of the image forming devices 10 (S, Y, M, C, K) has the same configuration except for the color of the image to be formed. Each of the image forming devices 10 (S, Y, M, C, K) has a rotating photosensitive drum 11 as an example of an image carrier (image forming means). Around the photosensitive drum 11, the following devices as examples of image forming means are mainly arranged. The main devices are a charging device 12 that charges the peripheral surface (image bearing surface) of the photosensitive drum 11, on which an image can be formed, to a required potential; an exposure device 13 that irradiates the charged peripheral surface of the photosensitive drum 11 with light based on image information (signal) to form an electrostatic latent image (for each color) with a potential difference; developing devices 14 (S, Y, M, C, K) as an example of a developing means that develops the electrostatic latent image with toner of developer 4 of the corresponding color (S, Y, M, C, K) to form a toner image; primary transfer devices 15 (S, Y, M, C, K) that transfer each toner image to an intermediate transfer device 20; and drum cleaning devices 16 (S, Y, M, C, K) that remove and clean any toner and other deposits that remain on the image bearing surface of the photosensitive drum 11 after the primary transfer.

[0033] The photoreceptor drum 11 has an image bearing surface formed on the circumferential surface of a grounded cylindrical or columnar substrate, which has a photoconductive layer (photosensitive layer) made of a photosensitive material. The photoreceptor drum 11 is supported so that it rotates in the direction indicated by arrow A by power transmitted from a drive device (not shown).

[0034] The charging device 12 is composed of a contact-type charging roll 121 that is placed in contact with the photosensitive drum 11. A cleaning roll 122 that cleans the circumferential surface of the charging roll 121 is placed on the back side of the charging roll 121. A charging voltage is supplied to the charging device 12. If the developing device 14 performs reversal development, the charging voltage supplied is a voltage or current of the same polarity as the charging polarity of the toner supplied from the developing device 14. Note that the charging device 12 may also be a non-contact charging device such as a scorotron that is placed in a non-contact state on the surface of the photosensitive drum 11.

[0035] The exposure device 13 is an LED print head that forms an electrostatic latent image by irradiating the photosensitive drum 11 with light corresponding to image information using LEDs (Light Emitting Diodes) as a plurality of light-emitting elements arranged along the axial direction of the photosensitive drum 11. Note that the exposure device 13 may also be one that deflects and scans laser light configured according to the image information along the axial direction of the photosensitive drum 11.

[0036] 2, each of the developing devices 14 (S, Y, M, C, K) is configured by arranging, inside a housing 140 formed with an opening and a chamber for storing developer 4, a developing roll 141 as an example of a developer holder that holds the developer 4 and transports it to a development area facing the photosensitive drum 11, a supply auger 142 as an example of agitation and supply means that agitates the developer 4 and transports it so that it passes through the developing roll 141, an admix auger 143 as an example of agitation and transport means that agitates the developer 4 and transports it to the supply auger 142, a counter auger 144 that transports the developer 4 peeled from the developing roll 141 in a direction opposite to the transport direction of the admix auger 143, and a layer thickness regulating member 145 that regulates the amount (layer thickness) of the developer held on the developing roll 141. In this developing device 14, a development voltage is supplied between the developing roll 141 and the photosensitive drum 11 from a power supply device (not shown). The developing roll 141, supply auger 142, and admix auger 143 rotate in the required direction by power transmitted from a drive device described later. Furthermore, two-component developers containing non-magnetic toner and magnetic carrier are used as the five color developers 4 (S, Y, M, C, and K). The configuration of the developing device 14 will be described in detail later.

[0037] The developing devices 14 (S, Y, M, C, K), particularly the spot color developing device 14S, are configured to be detachable from the device main body 1a of the image forming device 1. The developing devices 14 (S, Y, M, C, K) can be replaced by a user with a new developing device 14 (Y, M, C, K) or a developing device 14S of another spot color.

[0038] The primary transfer device 15 (S, Y, M, C, K) is a contact-type transfer device equipped with a primary transfer roll that rotates in contact with the periphery of the photosensitive drum 11 via the intermediate transfer belt 21 and is supplied with a primary transfer voltage. As the primary transfer voltage, a DC voltage showing a polarity opposite to the charge polarity of the toner is supplied from a power supply device (not shown).

[0039] The drum cleaning device 16 is composed of a container-shaped main body 160 with a portion open, a cleaning plate 161 that is arranged so as to come into contact with the peripheral surface of the photosensitive drum 11 after primary transfer with a required pressure to remove and clean any adhering matter such as residual toner, and a delivery member 162 such as a screw auger that collects the adhering matter such as toner removed by the cleaning plate 161 and transports it to a recovery system (not shown). The cleaning plate 161 is a plate-shaped member (for example, a blade) made of a material such as rubber.

[0040] 1, the intermediate transfer device 20 is disposed below each of the image forming devices 10 (S, Y, M, C, K) in the Z direction. The intermediate transfer device 20 is mainly composed of an intermediate transfer belt 21 that rotates in the direction indicated by arrow B while passing through a primary transfer position between the photosensitive drum 11 and the primary transfer device 15 (primary transfer roll), a plurality of belt support rolls 22-25 that rotatably support the intermediate transfer belt 21 while maintaining a desired state from its inner surface, a secondary transfer device 30 as an example of secondary transfer means that is disposed on the outer peripheral surface (image bearing surface) of the intermediate transfer belt 21 supported by the belt support roll 25 and performs a second transfer of the toner image on the intermediate transfer belt 21 to the recording paper 5, and a belt cleaning device 26 that removes and cleans toner, paper dust, and other deposits that remain on the outer peripheral surface of the intermediate transfer belt 21 after passing through the secondary transfer device 30.

[0041] An endless belt made of a material in which a resistance adjuster such as carbon black is dispersed in a synthetic resin such as polyimide resin or polyamide resin is used as the intermediate transfer belt 21. The belt support roll 22 is configured as a drive roll that is rotated by a drive unit (not shown) and also serves as an opposing roll for the belt cleaning device 26, the belt support roll 23 is configured as a surface finishing roll that forms the image forming surface of the intermediate transfer belt 21, the belt support roll 24 is configured as a tension applying roll that applies tension to the intermediate transfer belt 21, and the belt support roll 25 is configured as an opposing roll that faces the secondary transfer device 30.

[0042] 1, the secondary transfer device 30 is a contact-type transfer device that includes a secondary transfer roll 31 that rotates in contact with the circumferential surface of the intermediate transfer belt 21 and is supplied with a secondary transfer voltage at a secondary transfer position, which is the outer circumferential surface of the intermediate transfer belt 21 supported by the belt support roll 25 of the intermediate transfer device 20. A DC voltage having the same polarity as or opposite to the charge polarity of the toner is supplied as the secondary transfer voltage from a power supply device (not shown) to the secondary transfer roll 31 or the belt support roll 25 of the intermediate transfer device 20.

[0043] The fixing device 40 is configured so that, inside a housing (not shown) in which an inlet and an outlet for the recording paper 5 are formed, a heating belt 41 that rotates in the direction indicated by the arrow and is heated by a heating means so that the surface temperature is maintained at a predetermined temperature, and a pressure roll 42 that rotates in contact with the heating belt 41 at a predetermined pressure and is driven to rotate substantially along the axial direction of the heating belt 41, are arranged. In this fixing device 40, the contact area where the heating belt 41 and the pressure roll 42 come into contact is a fixing processing section that performs the required fixing process (heating and pressurizing).

[0044] The paper feeder 50 is disposed so as to be located below the intermediate transfer device 20 in the Z direction. This paper feeder 50 is mainly composed of one (or more) paper containers 51 that store stacks of recording paper 5 of desired sizes, types, etc., and feeders 52, 53 that feed the recording paper 5 one sheet at a time from the paper container 51. The paper container 51 is attached so that it can be pulled out, for example, from the front side of the device main body 1a (the side that the user faces when operating it).

[0045] Examples of the recording paper 5 include plain paper used in electrophotographic copiers, printers, etc., thin paper such as tracing paper, and overhead projector sheets. To further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper 5 is as smooth as possible, and for example, coated paper in which the surface of plain paper is coated with a resin or the like, or so-called thick paper with a relatively large basis weight such as art paper for printing, can also be suitably used.

[0046] The image forming apparatus 1 according to the first embodiment is configured to be capable of forming images on recording paper 5, including plain paper having a basis weight of 106 gsm or less, first thick paper having a basis weight of more than 106 gsm but not more than 200 gsm, and second thick paper having a basis weight of more than 200 gsm. The image forming apparatus 1 has at least a first process speed for forming an image on plain paper, a second process speed for forming an image on the first thick paper, and a third process speed for forming an image on the second thick paper. The first process speed is set to the fastest, the second process speed is set to the next fastest, and the third process speed is set to the slowest. The control device 200 determines the type of recording paper 5 and switches the process speed among the first, second, and third process speeds. The drive speeds of the photosensitive drum 11, the developing device 14, and the fixing device 40 are switched depending on the process speed.

[0047] Between the paper feed device 50 and the secondary transfer device 30, there is provided a paper feed transport path 56 which is composed of one or more paper transport roll pairs 54, 55 and a transport guide (not shown) that transport the recording paper 5 fed from the paper feed device 50 to the secondary transfer position. The paper transport roll pair 55, which is located immediately before the secondary transfer position in the paper feed transport path 56, is configured as, for example, a roll (registration roll) that adjusts the transport timing of the recording paper 5. Between the secondary transfer device 30 and the fixing device 40, there is provided a transport belt 57 for transporting the recording paper 5 fed from the secondary transfer device 30 after the secondary transfer to the fixing device 40. Further, downstream of the fixing device 40, there is provided a curl correction device 58 that corrects curls in the recording paper 5 that has been fixed by the fixing device 40. Near a paper discharge port formed in the device main body 1a of the image forming apparatus 1, there is provided a discharge transport path 60 which includes a paper discharge roll pair 59 for discharging the fixed recording paper 5 fed by the curl correction device 58 to a paper discharge section (not shown) provided on one side of the device main body 1a.

[0048] On the upstream side of the discharge conveyance path 60 in the conveyance direction of the recording paper 5, there is provided a branch conveyance path 62 equipped with a paper conveyance roll pair 61 that branches the conveyance direction of the recording paper 5 sent out by the curl correction device 58 diagonally downward. Below the branch conveyance path 62, there is arranged a reversing conveyance path 64 equipped with a reversing roll pair 63 that reverses the front and back of the recording paper 5. Above the reversing conveyance path 64, there are formed branching paths into a discharge conveyance path 66 equipped with a paper discharge roll pair 65 for discharging the recording paper 5 that has been reversed by the reversing conveyance path 64 to a paper discharge section (not shown), and a duplex conveyance path 68 equipped with a duplex conveyance roll pair 67 for forming an image on the back side of the recording paper 5 that has been reversed by the reversing conveyance path 64.

[0049] 1, reference numeral 200 indicates a control device that comprehensively controls the operation of the image forming apparatus 1. The control device 200 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), or a bus connecting the CPU, ROM, etc., a communication interface, etc. (not shown).

[0050] In this embodiment 1, the photosensitive drum 11, developing device 14, etc. are configured as individual units and are configured to be detachable from the device main body 1a of the image forming apparatus 1. The photosensitive drum 11, together with the charging device 12, drum cleaning device 16, etc., configures a photosensitive unit. The developing device 14 configures a developing unit by itself. When these photosensitive units and developing units are installed in the device main body 1a of the image forming apparatus 1, they are connected to a driving device (not shown) provided in the device main body 1a, and are driven by the transmission of driving force.

[0051] <Operation of image forming device> The basic image forming operation of the image forming apparatus 1 will be described below.

[0052] Here, we will explain the operation in the special color + full color mode, which uses the five image creating devices 10 (S, Y, M, C, K) to form a full color image composed of a combination of four color (Y, M, C, K) toner images, and a special color (S) image.

[0053] When the image forming apparatus 1 receives image information and command information requesting a full-color image forming operation (printing) from a personal computer (not shown) or an image reading device, etc., via a communication unit (not shown), the control device 200 starts the five image forming devices 10 (S, Y, M, C, K), the intermediate transfer device 20, the secondary transfer device 30, the fixing device 40, etc.

[0054] 1, in each imaging device 10 (S, Y, M, C, K), first, each photosensitive drum 11 rotates in the direction indicated by arrow A, and each charging device 12 charges the surface of each photosensitive drum 11 to a required polarity (negative polarity in the first embodiment) and potential. Next, exposure device 13 irradiates the surface of the charged photosensitive drum 11 with light emitted based on image information obtained by converting image information input to image forming device 1 into each color component (S, Y, M, C, K), and forms electrostatic latent images of each color component composed of a required potential difference on the surface.

[0055] Next, each image forming device 10 (S, Y, M, C, K) supplies toner of the corresponding color (S, Y, M, C, K) charged to the required polarity (negative polarity) from the developing roll 141 to electrostatically adhere to the electrostatic latent image of each color component formed on the photosensitive drum 11, thereby developing it. Through this development, the electrostatic latent image of each color component formed on each photosensitive drum 11 is visualized as a toner image of five colors (S, Y, M, C, K) developed with the toner of the corresponding color.

[0056] Next, when the toner images of each color formed on the photosensitive drum 11 of each image creating device 10 (S, Y, M, C, K) are transported to the primary transfer position, the primary transfer device 15 (S, Y, M, C, K) performs primary transfer of the toner images of each color in a state where they are superimposed in order onto the intermediate transfer belt 21 rotating in the direction indicated by arrow B of the intermediate transfer device 20.

[0057] Furthermore, in each imaging device 10 (S, Y, M, C, K) where the primary transfer has been completed, the drum cleaning device 16 scrapes off any adhering matter to clean the surface of the photosensitive drum 11. This makes each imaging device 10 (S, Y, M, C, K) ready for the next image formation operation.

[0058] Next, the intermediate transfer device 20 holds the primarily transferred toner image and transports it to the secondary transfer position by the rotation of the intermediate transfer belt 21. Meanwhile, the paper feeder 50 sends out the required recording paper 5 to a paper feed path 56 in accordance with the image creation operation. In the paper feed path 56, a pair of paper transport rolls 55, which act as registration rolls, feeds and supplies the recording paper 5 to the secondary transfer position in accordance with the transfer timing.

[0059] At the secondary transfer position, the secondary transfer device 30 performs secondary transfer of the toner images on the intermediate transfer belt 21 all at once onto the recording paper 5. After the secondary transfer is completed in the intermediate transfer device 20, the belt cleaning device 26 removes and cleans the surface of the intermediate transfer belt 21 to remove any toner or other adhering matter remaining thereon after the secondary transfer.

[0060] Next, the recording paper 5 onto which the toner image has been secondarily transferred is peeled off from the intermediate transfer belt 21 and then transported to the fixing device 40 via a transport belt 57. In the fixing device 40, the recording paper 5 after the second transfer is introduced into the contact area between the rotating heating belt 41 and pressure roll 42 and passed through, thereby performing the necessary fixing process (heating and pressurizing) to fix the unfixed toner image onto the recording paper 5. Finally, the recording paper 5 after fixing is straightened by a curl straightening device 58, and is then discharged by a paper discharge roll pair 59 to a paper discharge section (not shown) installed, for example, on one side of the device main body 1a.

[0061] Furthermore, when an image is formed on both sides of the recording paper 5, the recording paper 5 with an image formed on one side is not discharged to a paper discharge section (not shown), but is transported again to the secondary transfer device 30 via a reversing transport path 64 that reverses the recording paper 5 and a double-sided transport path 68, and a toner image is transferred to the back side of the recording paper 5. The recording paper 5 with the toner image transferred to the back side is transported by a transport belt 57 to the fixing device 40, where it is subjected to a fixing process (heating and pressure), and then discharged by a paper discharge roll pair 59 to a paper discharge section (not shown) installed on the side of the image forming apparatus 1.

[0062] By the above operation, the recording paper 5 is outputted, on one or both sides of which an image in a special color is formed in addition to a full-color image formed by combining five color toner images.

[0063] <Configuration of the developing device> 3 and 4 are a cross-sectional view of the developing device functioning as a powder conveying device according to the first embodiment, and a cross-sectional view taken along line IV-IV in FIG.

[0064] As shown in FIGS. 3 and 4 , the developing device 14 includes a housing 140 in the shape of an elongated box with a generally rectangular cross section, which houses a chamber for storing developer 4 (an example of powder). The housing 140 of the developing device 14 has an opening 140a on the side facing the photosensitive drum 11. A developing roll 141 (an example of a developer carrier (receiving means)) is disposed in the opening 140a of the housing 140 so as to be rotatable counterclockwise in the drawing, with a portion of the opening 140a exposed to the outside. The developing roll 141 includes a magnet roll 141a having a plurality of magnetic poles of predetermined polarities magnetized and fixedly disposed at required positions along the circumferential direction, and a cylindrical developing sleeve 141b disposed around the magnet roll 141a so as to be rotatable counterclockwise in the drawing. A layer thickness regulating member 145, which regulates the layer thickness of the developer 4 held on the surface of the developing roll 141 and transported, is disposed above the developing roll 141, with a required gap between them.

[0065] Furthermore, a supply auger 142 is rotatably provided inside the housing 140 of the developing device 14 as an example of an agitation supply means (first agitation and transport means) that agitates the developer 4 and transports it so that it passes through the developing roll 141 on the back side of the developing roll 141. As shown in FIG. 4, the supply auger 142 is composed of a rotation shaft 142a and a spiral transport blade 142b that is integrally formed on the outer periphery of the rotation shaft 142a. A coupling 142c is provided at one end along the axial direction of the rotation shaft 142a of the supply auger 142 to which a driving force is transmitted from a driving device (not shown) on the device main body 1a when the developing unit is attached to the device main body 1a of the image forming apparatus 1. In addition, at the other end along the axial direction of the rotation shaft 142a of the supply auger 142, there are provided a recovery auger 142d which recovers a portion of the developer 4 transported by the supply auger 142 by transporting it in the opposite direction to the transport direction of the transport blade 142b, and a discharge auger 142e which transports the recovered developer 4 transported by the recovery auger 142d in the opposite direction to the recovery auger 142d and drops it downward by gravity to discharge it.

[0066] Furthermore, inside the housing 140 of the developing device 14, an admix auger 143 as an example of a stirring and conveying means (second stirring and conveying means) that stirs and conveys the developer 4 is rotatably provided below the supply auger 142 in the vertical direction. The admix auger 143 is composed of a rotary shaft 143a and a spiral conveying blade 143b integrally formed on the outer periphery of the rotary shaft 143a. A supply auger 143c is provided at one end of the rotary shaft 143a in the axial direction of the admix auger 143, which conveys toner and the like supplied from a supply port 140b opened at one end of the housing 140 into the inside of the housing 140. A paddle member 70 as an example of an upward conveying means is provided at the other end of the rotary shaft 143a in the axial direction of the admix auger 143, which conveys the developer 4 conveyed by the admix auger 143 to the supply auger 142 located vertically above.

[0067] A partition wall 146 having an upwardly curved end on the developing roll 141 side is arranged horizontally between the supply auger 142 and the admix auger 143. At both longitudinal ends of the partition wall 146, first and second communication passages 148 and 149 for transferring the developer 4 between the supply auger 142 and the admix auger 143 are opened, as shown in FIG.

[0068] The developer 4 transported to the supply auger 142 is supplied to the developing roll 141 while being transported in the axial direction by the supply auger 142. The developer 4 transported to one end in the axial direction by the supply auger 142 is transported to the admix auger 143 via a second communication passage 149.

[0069] The developer 4 that has been transported to the surface of the developing roll 141 and contributed to development is peeled off from the surface of the developing roll 141 by a peeling magnetic pole (not shown) of the magnet roll 141a. As shown in FIG. 3, a counter auger 144 is provided below the developing roll 141 as an example of a reverse direction transport means that transports the developer 4 in a direction opposite to the transport direction of the admix auger 143. The counter auger 144 is composed of a rotary shaft 144a and a spiral transport blade 144b that is integrally formed on the outer periphery of the rotary shaft 144a. The outer diameter of the counter auger 144 is set smaller than that of the admix auger 143. The developer 4 that has been peeled off from the surface of the developing roll 141 moves to the admix auger 143 while being transported by the counter auger 144 in a direction opposite to the transport direction of the admix auger 143.

[0070] As shown in FIGS. 5 and 6 , the paddle member 70 is rotatably attached coaxially to the downstream end of the admix auger 143 via a shaft member 71. The paddle member 70 has a plurality of flat plate members 72 (two in the illustrated example) facing radially outward at the axial end of the shaft member 71 facing the admix auger 143, with the flat plate members 72 forming a required angle (180 degrees in the illustrated example) with respect to each other along the circumferential direction. The shaft member 71 of the paddle member 70 has a cylindrical portion 75 with a large outer diameter at one axial end. Inside the cylindrical portion 75, a bearing member 76 for rotatably supporting the extension portion 143a' of the rotation shaft 143a of the admix auger 143, which has a small outer diameter, and an oil seal member 77 for preventing the intrusion of the developer 4 are disposed. A reversing auger 73 is disposed in the axial center of the paddle member 70, which transports the developer 4 transported by the admix auger 143 in the reverse axial direction. Furthermore, a loosening auger 74 that loosens the developer 4 and discharges it to the outside from a lower discharge port 140c is integrally formed on the paddle member 70 near the axial end of the reversing auger 73. The other axial end of the shaft member 71 of the paddle member 70 is rotatably supported by the housing 140 of the developing device 14 via a bearing member 78 and an oil seal member 79.

[0071] In the conventional developing device, the paddle member 70 is integrally provided on the rotation shaft 143a of the admix auger 143. Therefore, in the image forming apparatus 1 to which the developing device 14 is applied, when the process speed changes depending on the type of recording paper 5, the developing roll 141, the supply auger 142, the admix auger 143, etc. of the developing device 14 are rotated at the process speed.

[0072] When the recording paper 5 is the second thick paper having the largest basis weight, the image forming apparatus 1 sets the process speed to the slowest speed. Then, the developing device 14 rotates the developing roll 141, supply auger 142, admix auger 143, etc. at the slowest speeds. Therefore, the developing device 14 has a technical problem in that when the developer 4 is transported to the end in the axial direction by the admix auger 143 and then transported by the paddle member 70 to the supply auger 142 located above in the vertical direction, as shown in FIG. 7 , the centrifugal force of the paddle member 70 is insufficient, and in extreme cases, the developer 4 cannot be transported to the supply auger 142.

[0073] Therefore, the developing device according to this embodiment 1 is configured to include a speed increasing means for increasing the rotation speed of the rotation shaft of any one of the stirring and conveying means, the stirring and supplying means, and the developer carrier, and transmitting the rotation speed to the upper conveying means.

[0074] In the developing device according to the first embodiment, the speed increasing means is configured to increase the rotation speed of the rotation shaft of the stirring and transporting means.

[0075] 8 and 9, in the developing device 14 according to the first embodiment, a first pulley 81, which serves as an example of a speed increasing means, is fixedly attached to the axial tip of the shaft member 71 of the paddle member 70. A first belt 83 is stretched between the first pulley 81 and a second pulley 82, which is fixed to a rotation shaft 144a of the counter auger 144. The first pulley 81 and the second pulley 82 have the same outer diameter, and rotate the counter auger 144 at the same speed as the admix auger 143. The first and second pulleys 81 and 82 and the first belt 83 constitute a first transmission means.

[0076] A third pulley 84, which is an example of a speed-increasing means, is fixedly attached to a rotating shaft 144a, which is an example of an intermediate shaft of the counter auger 144. A second belt 86 is stretched between the third pulley 84 and a fourth pulley 85, which is fixed to the shaft member 71 of the paddle member 70. The fourth pulley 85 has an outer diameter smaller than that of the third pulley 84. The rotational drive force of the rotating shaft 144a of the counter auger 144 is accelerated and transmitted to the paddle member 70, thereby driving the paddle member 70 to rotate. The rotational speed of the paddle member 70 is set to be 1.5 to 3.0 times that of the rotating shaft 143a of the admix auger 143. In this first embodiment, the paddle member 70 is set to be driven to rotate at a rotational speed 2.0 times that of the rotating shaft 143a of the admix auger 143. If the rotation speed of the admix auger 143 is 400 rpm, the rotation speed of the paddle member 70 is 2.0 times that, or 800 rpm. The third and fourth pulleys 84, 85 and the second belt 86 constitute a second transmission means.

[0077] <Operation of the developing device> In the image forming apparatus 1 to which the developing device according to this embodiment 1 is applied, it is possible to improve the upward transport performance of the developer by the upper transport means to the stirring and supply means regardless of the rotation speed of the stirring and conveying means, compared to when the upper transport means is fixed to the rotation shaft of the stirring and conveying means, as follows.

[0078] That is, in the image forming apparatus 1 according to this embodiment 1, when the control device 200 determines that the recording paper 5 is the second type of thick paper, the process speed is switched to the slowest third process speed, and the photosensitive drum 11, the developing device 14, or the fixing device 40, etc., are driven.

[0079] Then, in the developing device 14, as shown in FIG. 3, the developing roll 141, the supply auger 142, the admix auger 143, etc. are rotated at the slowest driving speed.

[0080] 5, in the developing device 14 according to the first embodiment, the paddle member 70 is rotatably mounted coaxially on the rotation shaft 143a of the admix auger 143. The rotational drive force of the admix auger 143 is transmitted to the rotation shaft 144a of the counter auger 144 via the first pulley 81 and the first belt 83 attached to the rotation shaft 143a, and the counter auger 144 is rotated in the same direction as the admix auger 143.

[0081] In addition, the rotational driving force of the counter auger 144 is transmitted to a fourth pulley 85 attached to the end of the shaft member 71 of the paddle member 70 via a third pulley 84 attached to its rotation shaft 144a and a second belt 86, and the paddle member 70 is driven to rotate at a rotational speed 2.0 times the rotational speed of the admix auger 143.

[0082] Therefore, even when the process speed in image forming apparatus 1 is set to the speed corresponding to the second thick paper, which is the slowest, the rotation speed of admix auger 143 in developing device 14 is increased, and paddle member 70 is rotationally driven at 2.0 times the speed. Therefore, in developing device 14, as shown in Fig. 7, paddle member 70 is rotationally driven at a speed 2.0 times the rotation speed of admix auger 143, and developer 4 is reliably transported via first communicating passage 148 to supply auger 142 located vertically above by centrifugal force exerted by flat plate member 72 of paddle member 70.

[0083] In this way, in the developing device 14 according to this embodiment 1, it is possible to improve the upward transport of developer 4 by the paddle member 70 to the supply auger 142 regardless of the rotation speed of the admix auger 143, compared to when the paddle member 70 is fixed to the rotation shaft 143a of the admix auger 143.

[0084] In the above embodiment, the image forming apparatus is described as an image forming apparatus that forms a full-color image, but it goes without saying that the image forming apparatus may also be a monochrome image forming apparatus.

[0085] In addition, in the above embodiment, the rotational driving force of the admix auger is first transmitted to the counter auger, and then transmitted from the counter auger to the paddle member at an increased speed. However, the rotational driving force of the developing roll or supply auger may be configured to be transmitted directly to the paddle member at an increased speed.

[0086] In addition, in the above embodiment, a case has been described in which a speed-up means consisting of a pulley and a belt is used to first transmit the rotational driving force of the admix auger to the counter auger, and then transmit the force from the counter auger to the paddle member at an increased speed, but this is not limited to this, and a speed-up means consisting of a combination of multiple gears may also be used. [Explanation of symbols]

[0087] 1...Image forming device 1a...Device body 14...Developing device 142...Supply Auger 143...Admix Auger 70...Paddle member 81...First pulley 82...Second pulley 83...First Belt 84...Third pulley 85...4th pulley 86...Second Belt

Claims

1. a developer carrier that holds a developer; a stirring and supplying means for stirring the developer and supplying the developer to the developer holder; a stirring and conveying means disposed vertically below the stirring and supplying means for stirring and conveying the developer; an upper conveying means disposed downstream of the agitating and conveying means in a conveying direction, and configured to convey the developer conveyed from the agitating and conveying means to the agitating and supplying means above; a speed increasing means for increasing the rotation speed of any one of the rotation shafts of the stirring and conveying means, the stirring and supplying means, and the developer carrier, and transmitting the rotation speed to the upper conveying means; Equipped with The speed increasing means increases the rotation speed of the rotating shaft of the stirring and conveying means, and the developing device has a first transmission means that increases the driving force of the rotating shaft of the stirring and conveying means and transmits it to the intermediate shaft, and a second transmission means that transmits the driving force of the intermediate shaft to the upper conveying means.

2. 2. The developing device according to claim 1, wherein said first and second transmission means are formed by a combination of a pulley and a belt.

3. A developer holder for holding a developer; a stirring and supplying means for stirring the developer and supplying the developer to the developer holder; a stirring and conveying means disposed vertically below the stirring and supplying means for stirring and conveying the developer; an upper conveying means disposed downstream of the agitating and conveying means in a conveying direction, and configured to convey the developer conveyed from the agitating and conveying means to the agitating and supplying means above; a speed increasing means for increasing the rotation speed of any one of the rotation shafts of the stirring and conveying means, the stirring and supplying means, and the developer carrier, and transmitting the rotation speed to the upper conveying means; a reverse direction conveying means disposed obliquely below the developer holder along a vertical direction and configured to convey the developer in a direction opposite to that of the agitating and conveying means, The speed increasing means temporarily transmits the driving force of the agitating and conveying means to the rotation shaft of the reverse direction conveying means, increases the rotation speed of the rotation shaft of the reverse direction conveying means, and then transmits the increased rotation speed to the upward conveying means.

4. 2. The developing device according to claim 1, wherein said upward conveying means comprises a plurality of flat plate members arranged along a circumferential direction on an outer periphery of a shaft member, said flat plate members facing radially outward.

5. 5. The developing device according to claim 4, wherein said upward transport means is driven at a rotational speed 1.5 to 3.0 times that of the rotational shaft of said stirring and transport means.

6. an image carrier that holds a latent image; a developing means for developing the latent image on the image carrier; Equipped with An image forming apparatus using the developing device according to any one of claims 1 to 5 as the developing means.

Images