An image forming apparatus

Abstract: An image forming apparatus includes first and second frames (1, 2) separable from each other, wherein the first and second frames constitutes a main assembly of the image forming apparatus; a process cartridge (4) detachably mountable to the main assembly, wherein the process cartridge contains an image bearing member (10) and at least one image forming device actable on the image bearing member; a developing unit (5) detachably mountable to the main assembly separately from the cartridge, the developing unit forming a developed image on the image bearing member; wherein the main assembly is seperable in a first mode in which the cartridge (4) and the developing unit are in either of the first frame or the second frame and in a second mode in which the cartridge (4) and the developing unit are in different ones of the first and second frames.

Description: The present invention relates to an image forming apparatus such as a copying machine or printer, more particularly to an image forming apparatus usable with a process cartridge detachably mountable thereto and a developing unit which is separate from the process cartridge and which is detachably mountable thereto. In order to make maintenance operation easier, an image forming apparatus has been put into practice in which an image bearing member and at least one of image forming means actable thereon is unified in the form of a cartridge, which is detachably mountable to a main assembly of the image forming apparatus. In addition an image forming apparatus has been proposed in which the process cartridge and a developing unit are separately detachably mountable to the main assembly of the image forming apparatus. With this structure, when the service life of the image bearing member or another image forming means in the process cartridge is different from the consumption of the developer in the developing unit are different, the structure is economical since only one of the process cartridge or the developing unit that requires exchange, can be changed. Particularly in the case of a color image forming apparatus using plural color developers, the consumption speed of the different color developers, are not necessarily the same. In this case, the developer quickly consumed is accommodated in a developing unit which is separate from the process cartridge, and the other developer or developers are accommodated in the process cartridge. Then, only the developer quickly consumed can be replenished without exchanging the other part, and therefore, it is economical. However, the number of parts detachably mountable to the main assembly increases, so that the operativity is worsened. For example, even when only the developing unit is to be exchanged, the developing unit can not be taken out without taking out the cartridge. In another example, when the jammed sheet is to be cleared, the developing unit as well as the cartridge, has to be taken out. This invention relates more particularly to an image forming apparatus, as described in patent specification US-A-5041872, comprising a main assembly having first and second frames which can be opened up with respect to each other; a process cartridge detachably mounted in the main assembly and including an image bearing member; and a developing unit detachably mounted in the main assembly for supplying developer to the image bearing member; wherein the main assembly is operable in a first mode in which the process cartridge and developing unit are both in the first frame and in a second mode in which the process cartridge and developing unit are in different ones of the first and second frames. The present invention is characterised in that the main assembly is operable in a third mode in which the process cartridge and developing unit are both in the second frame. Accordingly, the operativity of the process cartridge and developing unit is further improved. Specific embodiments of the present invention as defined by the appended claims will now be described by way of example with reference to the accompanying drawings, in which:- Figure 1 is a sectional view of an image forming apparatus according to a first embodiment of the present invention, where it is opened in a first mode. Figure 2 is a sectional view of the image forming apparatus which is opened in a second mode. Figure 3 is a sectional view of the image forming apparatus which is opened in a third mode. Figure 4 is a front view illustrating engagement between a shaft and an engaging member in a holding mechanism. Figure 5 is a front view illustrating engagement between a shaft and an engaging member in a holding mechanism. Figure 6 is a sectional view of an image forming apparatus according to a second embodiment of the present invention. Figure 7 is a front sectional view of an image forming apparatus according to the second embodiment of the present invention. Figure 8 is a sectional view of an image forming apparatus according to a third embodiment of the present invention. Figure 9 is a sectional view of an image forming apparatus according to a fourth embodiment of the present invention. Figure 10 is a sectional view of an image forming apparatus according to the fourth embodiment of the present invention, which is opened in a first mode. Figure 11 is a side view of the image forming apparatus which is opened in a second mode. Figure 12 is a sectional view of the image forming apparatus which is opened in a third mode. Figure 13 shows an operation panel of an image forming apparatus according to an embodiment of the present invention. Figure 14 is a block diagram of a control system of an image forming apparatus according to an embodiment of the present invention. Figure 15 is a flow chart showing a relation between a sensor and a display of an image forming apparatus according to an embodiment of the present invention. In the embodiments,the image forming apparatus comprises a detachably mountable process cartridge having a plurality of developing means and a detachably mountable developing unit. However, the process cartridge may be different if it contains an image bearing member and at least one image forming means actable on the image bearing member. Referring to Figures 1, 2, 3, 4 and 5, an image forming apparatus according to a first embodiment of the present invention will be described. A main assembly 1 of a multi-color image forming apparatus according to this embodiment of the present invention, comprises a lower frame (first casing) 1 and an upper frame (second casing) 2 which is rotatable relative to the lower frame about a shaft 3. The main assembly 1 accommodates a process cartridge 4 and a sub-cartridge (developing unit) 5, which are separately detachably mountable thereto. The sub-cartridge 5 is positioned relative to an image bearing member 10 in the main cartridge 4. The main cartridge 4 contains an image bearing member 10, three color developing devices 15 (15A, 15B and 15C) (image forming means) positioned relative to the image bearing member 10, a cleaner 16 (image forming means), a charger 50 (image forming means) or the like. The sub-cartridge 5 contains one color developing device 5A positioned relative to the image bearing member 10 of the main cartridge 4. In addition, the main assembly 1 contains a sheet feeding unit 6, an image transfer drum 7, an image fixing unit 8 and the like. The upper frame 2 is provided with a scanner unit 9. The description will be made as to an image forming process. The image bearing member in the form of a photosensitive drum 10 is uniformly charged by the charger 50. Then, light is projected from a scanner unit 9 onto the photosensitive member 10 in the main cartridge 4 in accordance with the color of the developer of the developing device 15A, so that an electrostatic latent image for the color is formed. The latent image on the photosensitive member is passed through a position where a developer carrying member (developing sleeve) 15a of the developing device 15A is opposed to the image bearing member. At this time, the developer (toner) carried on an outer periphery of the sleeve 15a is transferred onto the image bearing member 10 to develop the latent image into a visualized image. In the case of an overlaid development and simultaneous transfer system, the latent image formation and the image development are repeated on the image bearing member in accordance with the selected developing device 15B, 15C and 5A. In this manner, plural developed images are formed on the image bearing member 10 and they are simultaneously transferred onto a transfer material. The transfer material is subjected to an image fixing operation, and is discharged. In the case of overlaid transfer system, the first color developed image is transferred onto a transfer material or an intermediate transfer member, and the latent image formation, development and transfer operation is repeated for the required colors. The transfer material is then subjected to an image fixing operation, and is discharged. When the images are transferred onto an intermediate transfer member, the images are sequentially transferred from the intermediate transfer member onto the transfer material. Then, the transfer material is subjected to an image fixing operation and is discharged. At the time of the development for each color, a developing bias is applied between the developer carrying member of the developing device and the image bearing member, the developer carrying member is rotated, and/or the distance between the developer carrying member and the image bearing member is reduced to a developable gap therebetween. By doing so, the developing action occurs. The image transfer of the developed image from the image bearing member onto the transfer material or onto the image transfer member, is effected by electric force provided by the various voltage for moving the developer (developed image) of the image bearing member onto the transfer material and physical force due to the contact of the transfer member and the developer. In this embodiment, an overlaid transfer system is used. The transfer sheet supplied from the sheet feeding unit 6 is retained on an outer periphery of the transfer drum 7, and the developed images of the colors are sequentially transferred from the image bearing member 10 onto the sheet. The sheet having received the transfer of the developed image is fed to an image fixing unit 8 after being separated from the transfer drum 7. Then, it is subjected to the image fixing operation and is discharged to the outside of the main assembly. In Figure 1, a reference numeral 6 designates a sheet feeding unit for accommodating a transfer material or recording sheet S; 40, a pick-up roller for singling out the recording sheet S from the sheet feeding unit; 41, a registration roller; 42, a discharging roller; 43, a sheet discharging tray; 44, a guide; and 40, a transfer discharger. In this embodiment, the main cartridge 4 is provided with two engaging members 11, and the sub-cartridge 5 is similarly provided with two engaging members 13. The upper frame 2 is provided with two shafts 12 and 14 extending in a direction perpendicular to the sheet of the drawing, which are rotatable. The shafts 12 and 14 are adapted to be engaged with the engaging members 11 and 13, respectively of the main cartridge 4 and the sub-cartridge 5. The engaging member 11 (13), as shown in detail in Figures 4 and 5, is provided with an engaging hole 11a (13a) and a groove 11b (13b) cut-away portion in the engaging hole 11a (13a). When the shaft 12 (14) engageable with the engaging hole 11a (13a) is in the phase shown in Figure 4, the shaft 12 (14) penetrates through the groove 11b (13b) of the engaging member 11 (13) and is released from the engaging member 11 (13). When the shaft 12 (14) is in the phase shown in Figure 5 by 90 degrees rotation from the state shown in Figure 4, the shaft 12 (14) is unable to penetrate through the groove 11b (13b) of the engaging member 11, and therefore, the shaft 12 (14) and the engaging member 11 (13), are in engagement. When the apparatus is opened by opening the upper frame 2 with the shafts 12 and 14 are in the phase shown in Figure 4, the shafts 12 and 14 are allowed to be released from the engaging members 11 and 13, respectively. Therefore, as shown in Figure 1, the main cartridge 4 and the sub-cartridge 5 both remain in the main assembly 1 (first mode). Then, the main cartridge 4 can be taken out of the main assembly 1 and may be exchanged with a fresh one. When the upper frame 2 is opened while one 12 of the shafts is in the phase shown in Figure 5, and the other shaft 14 is in the phase of Figure 4, then the shaft 12 is engaged with the engaging member 11, and therefore, the shaft 14 is released from the engaging member 13. Therefore, as shown in Figure 2, the main cartridge 4 is raised together with the upper frame 2, and only the sub-cartridge 5 remains in the main assembly 1 (second mode). Accordingly, with this mode, only the sub-cartridge 5 can be taken out of the main assembly 1 and can be exchanged with a fresh one. It should be noted that there is no need of taking the main cartridge 4 out of the main assembly 1. This improves the operativity. Furthermore, when the upper frame 2 is opened with the shafts 12 and 14 being in the phases shown in Figure 5, the shafts 12 and 14 are engaged with the engaging members 11 and 13. Therefore, both of the main cartridge 4 and the sub-cartridge 5 are raised together with the upper frame 2, as shown in Figure 3. In other words, the apparatus can be opened with the cartridge 4 and the developing unit 5 placed in the frame which is different from the frame in the first mode (third mode). In this mode, a jammed sheet in the sheet feeding unit 6 or the transfer drum 7 can be easily removed, and the transfer drum 7 can be easily cleaned or serviced with good operativity. The first, second and third modes, may be selected by a selector 55 shown in Figure 13. As will be understood from the foregoing, the apparatus of this invention is openable in a first mode in which the process cartridge and the developing unit are both in one of the first and second frames, and in a second mode in which the process cartridge and the developing unit are in the different frames. By doing so, the maintenance operation such as jam clearance or cartridge or developing unit exchange, can be carried out without difficulty, despite the fact that plural elements are detachably mountable to the main assembly. It is further preferable that a display means is provided to notify the operator of which mode is to be selected. As for such display means, a display 52 may be provided on the operation panel 51, as shown in Figure 13. The display sequence will be described in conjunction with a block diagram of Figure 14 and a flow chart of Figure 15. When a sensor (first detecting means) for detecting a remaining amount of the toner in the process cartridge detect toner empty (step 2), or when a residual toner sensor for detecting full of residual toner (third detecting means 54), detects a cleaner full (step 1), a display promoting the operator to exchange the cartridge 4 is displayed on the display 52 (step 5). Also displayed on the display 52 is the mode which the operator should select. Then, the operator depresses the switches 55 and 56 on the operation panel 51 to open the apparatus in the first mode, by which the second frame 2 is opened. When a sensor for detecting the remaining amount of the toner in the developing unit 5 (second detecting means 57) detects toner empty (step 3), the display 52 promotes exchange of the developing unit 5 (step 6). Furthermore, the display 52 also displays that the second mode is to be selected by the operator. Then, the operator depresses the switches 58 and 56 to select the second mode on the operation panel 51, by which the second frame 2 is opened. When a sheet jam is detected by a jam sensor 59 disposed along a sheet passage (step 4), the display 52 promotes the operator to open the apparatus in the third mode (step 7). Then, the operator depresses the switches 60 and 56 on the operation panel 51 to open the apparatus in the third mode, so that the second frame is opened in the third mode. In the foregoing example, the first, second and third modes are selected by selector switches 55, 58 and 60. It is further preferable that the first, second and third modes are automatically selected by a controller 61 in accordance with detection signals from the sensors 53, 54, 57 and 59. If a plurality of developing units are used, the opening modes are changed, accordingly. The block diagram of Figure 14 will be described in detail. A controller 61 for controlling the entirety of the image forming apparatus comprises a CPU in the form of a microprocessor or the like, a ROM for storing control program or various data, and a RAM which is used as a work area of the CPU and which temporarily stores various data. The controller 61 receives signals from a sheet jam sensor 59 and a remaining toner detecting mechanism 53 for detecting the remaining amount of the toner in the process cartridge. The detecting mechanism may include an antenna line to detect the change of the electrostatic capacity between itself and the developing sleeve. Furthermore, it receives image signals from a host device 62 in the form of a computer or a word processor or the like. In response to such signals, the controller 61 controls, the image exposure operation, charging operation, developing operation, image transfer operation, image fixing operation (process operations), conveyance of the recording material (registration roller, discharging roller or the like) and a driving source. Referring to Figures 6 and 7, a second embodiment of the present invention will be described. Figure 6 is a side sectional view of a multi-color image forming apparatus according to this embodiment. Figure 7 is a front sectional view of the same. The same reference numerals as in Figures 1 - 3, are assigned to the elements having the corresponding functions, and the detailed description thereof are omitted for simplicity. In this embodiment, the main cartridge 4 and the sub-cartridge 5 are provided with two projections 21 and 22, respectively. The upper frame 2 is provided with hooks 17 and 18 rotatable about respective shafts 19 and 20. End portions 17a and 18a of the hooks 17 and 18 are selectively engageable with the projections 21 and 22. They are provided with arms 17b and 18b which are crossed at the center of the shafts 19 and 20. To the crossing portions of the arms 17b and 18b, two members 23 and 24 guided in perpendicular directions, are contacted. The upper frame 2 is provided with a rotatable shaft 25 extending in a direction of the sheet of the drawing of Figure 6 (horizontal direction in Figure 7). In the middle portion of the length of the shaft 25, two cams 26 and 27 are fixed, and the two cams are contactable to the members 23 and 24. A knob 28 is fixedly mounted to an end of the shaft 25. Each of the cams 26 and 27 has a large radius portion and a small radius portion. The cams 26 and 27 are rotatable by the knob 28. When the large radius portions of the cams 26 and 27 are contacted to the members 23 and 24, the members 23 and 24 are lowered to lower the crossing portions of the arms 17b and 18b of the hooks 17 and 18, so that the hook members 17 and 18 are opened to release the engagement between end portions 17a and 18a of the hooks 17 and 18 with the projections 21 and 22. When small radius portions of the cams 26 and 27 are contacted to the members 23 and 24, the hooks 17 and 18 are closed, and the end portions 17a and 18 of the hooks 17 and 18 are engaged with the projections 21 and 22. The selection of the large or small radius portions of the cams 26 and 27 are determined by the position of the knob 28. When the upper frame 2 is opened with the large radius portions of the cams 26 and 27 contacted to the members 23 and 24, the engagements between the hooks 17 and 18 and the projections 21 and 22, are released, by which both of the main cartridge 4 and the sub-cartridge 5 remain in the main assembly 1. In this state, the main cartridge 4 is taken out of the main assembly 1 and can be exchanged with a fresh one. When a small radius portion of one 26 of the cams is contacted to the member 23 by rotating the knob 28, and a large radius portion of the other cam 27 is contacted to the member 24, one of the hooks 17 is engaged with the projection 21, and the other hook 18 is released from the engagement with the projection 22. When the upper frame 2 is opened in this state, the main cartridge 4 is raised with the upper frame 2, while the sub-cartridge 5 remains in the main assembly 1. The sub-cartridge 5 may be taken out of the main assembly 1, and may be exchanged with a fresh one. When the small radius portions of the cams 26 and 27 are contacted to the members 23 and 24 by rotation of the knob 28, the hooks 17 and 18 are engaged with the projections 21 and 22. When the upper frame 2 is opened, the main cartridge 4 and the sub-cartridge 5 are both raised together with the upper frame 2. Therefore, the jammed sheet in the sheet feeding unit 6 or the transfer drum 7, may be removed, or the transfer drum may be cleaned or serviced, with high operativity. Referring to Figure 8, a third embodiment of the present invention will be described. Figure 8 is a sectional view of a multi-color image forming apparatus according to this embodiment. In this embodiment, too, similarly to the first and second embodiments, the main cartridge 4 and/or the sub-cartridge 5, is raised together with the upper frame 2 by a selection and holding mechanism. In this embodiment, when the main cartridge 4 and the sub-cartridge 5 are raised together with the upper frame 2 as shown in the Figure for the purpose of jam clearance, a part 29 of the sheet feeding mechanism is raised together. At this time, the sub-cartridge 5 is fixed on a member 30 supporting the part 29 of the sheet feeding mechanism, so that it is raised by the upper frame 2 together with the member 30. In the first and second embodiments, the engaging member 13 (Figure 1) and the projection 22 (Figure 6) are provided in the sub-cartridge 5 itself, but it is provided on the member 30 in this embodiment. Since the part 29 of the sheet feeding mechanism is raised together with the sub-cartridge 5 by the upper frame 2 in this embodiment, the jam clearance operation is made further easier. Referring to Figures 9, 10, 11 and 12, a fourth embodiment will be described. Figure 10 is a side sectional view of a multi-color image forming apparatus according to this embodiment. Figures 10 - 12 are side sectional views of the image forming apparatus in various modes. In this embodiment, the upper frame 2 is provided with a frame 31 for holding the main cartridge 4 and a frame 32 for holding the sub-cartridge 5, and they are rotatable about a shaft 3. The upper frame 2 is provided with fixing members 33 and 34 for fixing the frames 31 and 32 to the upper frame 2, and the fixing members 33 and 34 are rotatable about shafts 35 and 36. The fixing members 33 and 34 are urged in the direction indicated by unshown springs. Adjacent the fixing members 33 and 34 of the upper frame 2, there are slide levers 37 and 38 slidable in the vertical direction. When the slide levers 37 and 38 are slid upwardly, end portions of the fixing members 33 and 34 are urged by the slide levers 37 and 38 to rotate in the counterclockwise direction about the shafts 35 and 36, by which the engagement between the fixing members 33 and 34 and the frames 31 and 32, are released. When the slide levers 37 and 34 are slid upwardly, the engagement between the fixing members 33 and 34 and the frames 31 and 32, are released. Then, if the upper frame 2 is opened, the frames 31 and 32, as shown in Figure 10, the main cartridge 4 and the sub-cartridge 5 remain in the main assembly 1. Therefore, the main cartridge 4 is taken out of the main apparatus 1, and may be exchanged with a fresh one. When only one of the slide levers 38 is slid upwardly, the engagement between the fixing member 33 and the frame 31 is released, and the engagement between the fixing member 34 and the frame 32 is released. When the upper frame 2 is opened, the frame 31 and the main cartridge 4 mounted thereon are raised together with the upper frame 2, as shown in Figure 11. The sub-cartridge 5 supported on the frame 32 remains in the main assembly 1. Then, the sub-cartridge 5 may be taken out of the main assembly 1, and can be exchanged with a new one. When the upper frame 2 is opened without sliding the slide lever 37 or 38, the frames 31 and 32 and the main cartridge 4 and the sub-cartridge 5 supported thereon, are raised together with the upper frame 2, as shown in Figure 12. With this state, the jammed sheet in the sheet feeding unit 6 or the transfer drum 7 can be removed without difficulty, and in addition, the cleaning and servicing operations to the transfer drum 7 can be carried out with good operativity. As described in the foregoing, according to the present invention, the apparatus is operable in a first mode in which the cartridge and the developing unit are located in the same frame (first or second), and in a second mode in which the cartridge and the developing unit are located separately in the first or second frames. Therefore, the jam clearance operation, the maintenance operation, exchanging operation of the cartridge or the developing unit, can be carried out without difficulty.

Claims: An image forming apparatus, comprising: a main assembly having first and second frames (1, 2) which can be opened up with respect to each other; a process cartridge (4) detachably mounted in the main assembly and including an image bearing member (10); and a developing unit (5) detachably mounted in the main assembly for supplying developer to the image bearing member; wherein the main assembly is operable in a first mode in which the process cartridge and developing unit are both in the first frame and in a second mode in which the process cartridge and developing unit are in different ones of the first and second frames; characterised in that: the main assembly is operable in a third mode in which the process cartridge and developing unit are both in the second frame. An apparatus according to claim 1, wherein the process cartridge further includes charging means (50) for charging the image bearing member. An apparatus as claimed in claim 1 or 2, wherein the process cartridge further includes developing means (15) for forming a developed image on the image bearing member. An apparatus according to claim 3, wherein the developing means includes a plurality of developing sections (15A, 15a; 15B, 15b; 15C, 15c). An apparatus according to claim 4, wherein the plural developing sections contain, in use, different color developers. An apparatus according to claim 5, wherein the different color developers have yellow, magenta, and cyan colors. An apparatus according to any of claims 3 to 6, further comprising first detecting means (53) for detecting a remaining amount of developer in the process cartridge and second detecting means (57) for detecting a remaining amount of developer in the developing unit. An apparatus according to claim 7, further comprising display means (52) for displaying necessity for exchange of the cartridge or the developing unit in accordance with an output of the first or -second detecting means. An apparatus as claimed in any preceding claim, wherein the process cartridge further includes cleaning means (16) for removing residual matter from the image bearing member. An apparatus according to claim 9, further comprising third detecting means (54) for detecting an amount of the matter collected by said cleaning means. An apparatus according to claim 10 when claim 9 is dependent on claim 7, further comprising display means (52) for displaying necessity for exchange of the cartridge or the developing unit in accordance with outputs of the first, second and third detecting means. An apparatus according to claim 10 or 11, further comprising control means (61) for automatically selecting the first, second or third mode in accordance with outputs of said first, second and third detecting means. An apparatus according to any preceding claim, further comprising means for manually selecting said first, second or third mode. An apparatus according to any preceding claim, wherein said developing unit contains a black developer. An apparatus according to any preceding claim, wherein a second developing unit is detachably mounted in said main assembly.

Inventors: INOMATA MITSUGU, INOMATA, MITSUGU, INOMATA, MITSUGU, C/O CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1992
Main classification: G03G15
IPC codes: G03G15, G03G21