IMAGE FORMING APPARATUS

Abstract: An image forming apparatus comprises a main body (100) and a processing unit (111, 113) detachably mounted in the main body. The processing unit includes at least one of an image bearing member (111) and developing device (113). The number of image forming repetitions of the processing unit are counted by a counter (36) in the main body (100). When the counted number of the processing unit reaches a reference value (5) representing the effective life of the pro­ cessing unit, an alarm device (6) actuates to notify the user that the effective life of the processing unit has been reached.

Description: The present invention relates generally to an image forming apparatus and more particularly to an apparatus in which at least one of a photosensitive body and a developing device is made a replaceable processing unit so that the unit can be detachably used in a main apparatus. It is general practice in the field of the electrostatic copying apparatus to set effective lives for the photosensitive body and developing device in order to ensure production of good copies. Further, in order to facilitate maintenance a system has been adopted for recent copying machines in which the photosensitive body and developing device are replaceable processing units. When the units have reached the ends of their effective lives, an expert serviceman on a periodic round can replace them. In a conventional copying apparatus, the frequency of regular service calls is determined on the basis of the frequency of utilization by the standard user. Therefore, the users who make very frequent use of a copying apparatus have no choice but to carry out maintenance themselves, since their business operations would be slowed if they waited for a regular call by an expert serviceman. Since the general user has little related technical knowledge or experience, in most cases this maintenance is difficult to carry out. Similarly, the general procedure for deciding when to replace a photosensitive body is to periodically check a total counter on the apparatus main body and replace the photosensitive body when the number of copies has reached a counted value corresponding to the photosensitive body's effective life. However, since the photosensitive body replacement period is very much longer than that of the developing device, people in a busy office are liable to forget to check this properly. Further, the deterioration of images is not easily noticed, since it progresses only a little each day. As a result, there is tendency to continue using the photosensitive body well beyond its effective life. Because of this, there is a strong demand for measures to make user maintenance of this type of equipment easier. Recently, a twin color copying apparatus which can copy selectively with a black color toner and a red color toner has been developed. Either the black developing device containing carrier particles and black color toner or the red developing device containing carrier particles and red color toner is selectively set into the apparatus main body corresponding the desired color copy. Therefore, it is difficult to accurately count the number of image formations for each color developing device by reference to the counter provided on the apparatus main body. As a result, the effective life of above carrier particles in each color developing device may come to an end unexpectedly so that the user will not have sufficient time to prepare a new developing device. In such case, the main apparatus must remain unused until the new device is readied. This means a loss of time. DE-A-34 47 504 discloses a copier apparatus in which a separate count of copying operations is maintained for each toner colour, so that the operator can tell when each colour is likely to need replenishing. It is an object of the invention to provide an image forming apparatus in which a replaceable processing unit is provided with an identity indicating means and when it is mounted in the apparatus main body a count means is set so as to count the repetitions of the identified processing unit or the number of image formations carried out by the identified unit. More specifically, it is an object of the invention to make it possible to accurately indicate the end of the effective life of each such replaceable processing unit and to keep the apparatus always in the best condition for use. Accordingly the present invention provides an image forming apparatus comprising: a main body; at least two types of processing units in said main body to be used for image forming operations; said processing units including a first unit having a first prescribed effective life and a second unit having a second prescribed effective life different from that of said first unit, both units being detachably mounted in said main body, and each of said processing units including an identity indicating means for representing the identity of the respective processing unit; detecting means for detecting the identity of each of said processing units and producing an identity code corresponding to each of said processing units; storage means associated with each of said processing units for separately storing the number of image forming operations completed by each of said processing units; first memory means for storing values representative of the number of image forming repetitions corresponding to the different effective lives of the processing units; second memory means for storing the identity code of each of said processing units, produced by said detecting means; and means for comparing the number of image forming operations completed by each processing unit stored in said storage means with the corresponding values stored in said first memory means. Preferably the comparing means includes means for generating a coincidence signal when the number of image forming repetitions of a processing unit in the apparatus equals the corresponding stored value in the first memory means. The apparatus also includes alarm means operatively connected to the comparing means and responsive to the coincidence signal for indicating when the processing unit in the apparatus has reached the number of image forming repetitions corresponding to the effective life of the processing unit. Fig. 1 is a schematic sectional view of the main part of a laser printer to which the present invention is related; Fig. 2 is a schematic plan view showing a photosensitive drum and a developing device; Fig. 3 is a block diagram of the electric circuit for operation control; Fig. 4 is a block diagram of the electric circuit according to the present invention; Fig. 5 is a schematic electric circuit of the identity indicator and the detector shown in Fig. 4; Fig. 6 is a schematic diagram of the memory shown in Figure 4; Fig. 7 is a flowchart showing the flow of operation when the present invention is applied to the developing device; and Fig. 8 is a flowchart showing the flow of operation when the present invention is applied to the photosensitive drum. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a schematic sectional view of a laser printer according to the present invention. Reference numeral 100 denotes a printer main body. An optical system 101 is provided in main body 100. Optical system 101 includes a polygon mirror 102, a lens group 103 and a set of reflecting mirrors 104 and 105. Polygon mirror 102 is rotatable about the X axis by a suitable means, and light from a laser light source (not shown), which is provided in a position that is vertical with respect to a paper plane, is directed by polygon mirror 102 onto lens group 103. A photosensitive drum unit 111, constructed as a cartridge, is replaceably mounted in main body 100. A main charger 112, a cartridge unit type developing device 113, a transfer charger 111, a separation charger 115 and a cleaning blade 116 are arranged around a photosensitive drum 111a rotatable in the direction of the arrow. Developing device unit 113 comprises known structural elements Such as a casing 113a, a magnetic roller 113b, a developing agent separation blade 113c and a stirring auger 113d. In casing 113a, a two-component developing agent comprising a mixture of carrier particles and toner powder is contained. Developing device unit 113 is constructed as a cartridge and is replaceably mounted in main body 100. In Fig. 2, a guide frame 113e is slidably supported on a pair of slide rails 101a and 101b provided in main body 100. Developing device unit 113 is detachably mounted on guide frame 113e. A handle 113g is provided at the front end of guide frame 113e so that guide frame 113e may be slidably pulled out from main body 100. An identity indicator 1 is provided on developing device unit 113 so as to be connected to a detector 2 provided in main body 100. A handle 113f is attached to developing device unit 113. Developing device unit 113 can be detached from guide frame 113e by carrying handle 113f. Photosensitive drum unit 111 is detachably mounted on guide frame 113e. An identity indicator 11 is mounted on photosensitive drum unit 111 so as to be connected to a detector 12 mounted in main body 100. A handle 111b is attached to photosensitive drum unit 111. Photosensitive drum unit 111 can be detached from guide frame 113e by carrying handle 111b. An exchangeable cassette type paper supply section 121 consists of a paper supply cassette 122, a paper supply roller 123, an intermediate transporting roller 124, a first guide plate 125, a pair of aligning rollers 126 and a second guide plate 127. Paper supply roller 123 defines an approximate semicircle, as shown in the drawing, and when it rotates one turn, a leading edge portion of a sheet of cut paper (not shown) stacked in paper supply cassette 122 is supplied to the right as seen in the drawing, the length of this leading edge portion corresponding to the effective circumferential length of roller 123. The sheet of paper is then led via first guide plate 125, intermediate transporting roller 124, aligning rollers 126 and second guide plate 127 to photosensitive drum 111a. Numeral 131 denotes a transport belt for leading the sheet of paper to a thermal fixing roller 132 in a subsequent stage following toner transfer onto the paper and numeral 133 denotes an intermediate roller by which, following fixing, the sheet of paper is led via a third guide plate 134 and exit rollers 135 to a receiving tray 136. Numeral 141 denotes a paper detecting switch for detecting the passage of copies that are delivered. Paper detecting switch 141 comprises an actuator 142 which projects into a cut-out portion 134a formed at the upper end of third guide plate 134. A sheet of paper being delivered pushes down actuator 142 as it passes this location, and the number of sheets delivered is counted based on electrical signals corresponding to the number of times actuator 142 actuates. A light source 143 and a photodetector 144 constitute a paper delivery detection means that detects whether the sheet of paper is present or not via a detection hole 136a formed near the lower edge of receiving tray 136. Numeral 150 denotes a control circuit device that effects control of the printer. As shown in Fig. 3, control circuit device 150 comprises a data control section 152 and a print control section 153. A host system 151 as typified by a computer or word processor, is connected to data control section 152 of control circuit device 150. Code data from host system 151 is converted into dot-image data and stored in a page memory (not shown) in data control section 152. This stored dot-image data is output to print control section 153. In print control section 153, a laser beam is modulated in accordance with the input dot-image data from data control section 152 and is directed onto photosensitive drum 111 via optical system 101. This permits subsequent production of a copy by the electrophotographic system. Fig. 4 shows a block diagram of the electric circuit. Identity indicator 1 is provided on developing device unit 113 as shown in Fig. 2. As shown in Fig. 5, identity indicator 1 comprises a diode circuit 1a consisting of 4 diodes D4, D8, D13 and D20 of a possible 20 diodes D1-D20, selectively connected in parallel with each other, and a connector CN1 consisting 20 terminals connected to detector 2. That is, identity indicator 1 generates a 20-bits of code representing an identity of specific developing device unit 113, by selectively connecting several diodes among 20 diodes D1-D20, for example. The code generated from identity indicator 1, as shown in Fig. 5, which represents the identity of developing device unit 113 is "00010001000010000001", for example. Since all that is needed is to make a distinction between one unit and other units, the identity representing code may be just a manufacturing serial number of the developing device unit, for example. Detector 2 is provided in main body 100 as shown in Fig. 2, and connects to identiy indicator 1 when developing device unit 113 is mounted in main body 100. As shown in Fig. 5, detector 2 comprises a switching circuit 2a consisting of a group of switching elements SW1-SW20 sequentially actuated, a connector CN2 consisting of 20 terminals connected to connector CN1 of identity indicator 1, an electric source B and an output terminal OT being connected to a nonvolatile memory device 3. Nonvolatile memory device 3 comprises an identity code store portion 3A and a counter portion 3B. That is, as shown in Fig. 6, identity code store portion 3A consists of plural memory area 3A1-3An for storing codes detected by detector 2. Further, counter portion 3B consists of plural shift register 3B1-3Bn for counting print signals output from a printer operation control circuit 8. Each shift register 3B1-3Bn corresponds to memory area 3A1-3An respectively. A comparator 4 receives counted print signals from counter portion 3B of nonvolatile memory device 3 for comparing the counted print signals with a reference value output from a reference value memory 5. In reference value memory 5, a valve "5,000", for example, is stored. The value "5,000" represents an effective life of developing device unit 113. Comparator 4 outputs a coincidence signal when the value of counted print signals from counter portion 3B and the reference value from memory 5 are the same. An alarm device 6 receives the coincidence signal from comparator 4, and comprises a display or buzzer, etc. for warning that the effective life of developing device unit 113 has reached its end. When the effective life of the developing device unit reaches the end, since the surface of carrier particles become to smooth after long term use, the carrier particles cannot give enough triboelectric charge to the toner powder. Therefore, the developing operation is poorly performed. A printer operation halt means 7 receives the coincidence signal from comparator 4 for supplying a printer operation halt signal to a printer operation control circuit 8 when the coincidence signal is received from comparator 4. Printer operation control circuit a outputs print signals and stops the printing operation. Identity indicator 11 is provided on photosensitive drum unit 111, as shown in Fig. 2. The structure and circuit arrangement of identity indicator 11 is similar to identity indicator 1 provided on developing device unit 113, as shown in Fig. 5. Only the connection of the diodes to the terminals of connector CN1 are different from the arrangement shown in Fig. 5. Identity indicator 11 generates a 20-bit code representing the identity of specific photosensitive drum unit 111, by selectively connecting several diodes among 20 diodes D1-D20. As in the case of the developing device unit described above, all that is needed is to make a distinction between one unit and other units. The identity representing code may be just a manufacturing serial number of the photosensitive drum unit. Detector 12 is provided in main body 100 as shown in Fig. 2, and connects to identity indicator 11 when photosensitive drum unit 111 is mounted in main body 100. Detector 12 defines the same structure and circuit arrangement as described above for the developing device unit. Detector 12 is connected to non-volatile memory device 3, as described above with relation to the developing device unit. A comparator 13 receives counted print signals from counter portion 3B of nonvolatIle memory device 3 for comparing the counted print signals with a reference value output from a reference value memory 14. In reference value memory 14, a value "10,000", for example, as a reference value is stored. The value "10,000" represents the effective life of photosensitive drum unit 111 in which photosensitive drum 111a is formed of an organic photoconductive material, for example. Comparator 13 outputs a coincidence signal when the value of counted print signals from counter portion 3B and the reference value from memory 14 are the same. An alarm device 15 receives the coincidence signal from comparator 13, and comprises a display or buzzer, etc. for indicating that the effective life of photosensitive drum unit 111 has reached its end. When the effective life of the photosensitive drum unit reaches the end, since the photoconductive material of the photosensitive drum wears out, a poor electrostatic latent image forming operation is performed. A printer operation halt means 7 receives the coincidence signal from comparator 13 for supplying a printer operation halt signal to a printer operation control circuit 8, when the coincidence signal is received from comparator 13. Printer operation control circuit 8 outputs print signals and stops the printing operation, as described above with relation to the developing device unit. In a factory, when a main body including a developing device unit and a photosensitive drum unit, and a replaceable developing device unit and replaceable photosensitive drum unit are manufactured, the effective life of the developing device unit and the photosensitive drum unit, respectively, are pre-set in the main body. Also, the developing device unit and the photosensitive drum unit are pre-set with the identity code thereof, respectively. That is, a limited number printing repetitions that represents the effective life of each of the developing device unit and the photosensitive drum unit is stored in a reference value memory provided in the main body. An identity code for distinguishing between one unit and other units, is set in an identity indicator of each of the developing device unit and photosensitive drum unit. The operation of an image forming apparatus thus arranged will be described. When an unused developing device unit 113 is mounted in main body 100, as shown in Fig. 2, identity indicator 1 of unit 113 is connected to detector 2 of main body 100. As shown in Fig. 5, detector 2 detects the identity code, e.g., "00010001000010000001" from identity indicator 1. That is, switching elements SW1-SW20 of switching circuit 2a sequentially actuate to generate code signals through electric source B and diodes D4, D8, D13 and D20. The code signals are output from output terminal OT of circuit 2a and input to nonvolatile memory device 3. In device 3, the identity code "00010001000010000001" corresponding to the code signal input is stored in memory area 3A1 of identity code store portion 3A as shown in Fig. 6, and shift register 3B1 corresponding to memory area 3A1 of memory device 3 is set as a counter. Printer operation control circuit 8 outputs one print signal to shift register 3B1 every time main body 100 performs one printing operation. Shift register 3B1 counts the printing signals output from printer operation control circuit 8, and the counted value is input from shift register 3B1 to comparator 4. Comparator 4 compares the value output from shift register 3B1 and reference value in memory 5. In reference value memory 5, the value "5,000" as a reference value representing an effective life of developing device unit 113 has been previously stored, as described above. When the two values output from shift register 3B1 and reference value memory 5 coincide, a coincidence signal is output to alarm device 6 and printer operation halt means 7. As a result, printer operation halt means 7 outputs a printer operation halt signal to control circuit 8, and control circuit 8 stops the printing operation of main body 100. At the same time, alarm device 6 is actuated to notify the user that the printer is inoperative. This alarm actuation indicates that developing device unit 113 is to be replaced immediately, and it is then necessary to replace the developing device unit with a new device unit. Counted value "5,000" is stored in shift register 3B1 of memory device 3. Thus, if the developing device unit with which replacement is effected is an old one, the apparatus immediately goes into a state in which replacement is demanded. When a first developing device unit that is still usable is replaced by a second developin device unit, the used number of times of the first developing device unit is stored in the nonvolatile memory device provided in the main body. That is, as shown in Fig. 6, the number of image forming repetitions of the first developing device unit is stored in shift register 3B1 corresponding to memory area 3A1 containing the identity code of the first developing device unit. In like manner, the number of image forming repetitions of the second developing device unit is stored in shift register 3B2 corresponding to memory area 3A2 containing the identity code of the second developing device unit. The number of image forming repetitions of each developing device unit has an identity code which is stored in non-volatile memory device 3. Thus, after a black developing device unit containing black developing agent is replaced by a red developing device unit containing red developing agent, used and replaced by the black unit again, the black unit effective life can be still accurately monitored. Although the operation of the developing device unit has been described in the above embodiment, the description about the operation of the photosensitive drum unit is omitted since the operations of the photosensitive drum unit and the developing device unit are almost same. In developing device unit 113, the reference value stored in reference value memory 5 is "5,000", for example. However, in photosensitive drum unit 111, the reference value stored in reference value memory 14 is "10,000", for example. In the present invention, a developing device or photosensitive drum is constructed as a replaceable unit, and an identity indicator is provided on this replaceable unit. When the unit is mounted in a printer main body, an identity code signal generated from the identity indicator is automatically set in the printer main body as an identifying signal by which the unit is distinguished from other units. As described above, the image forming apparatus according to present invention accurately indicates the end of the effective life of a replaceable processing unit end keeps the apparatus always in the best condition for use. While the present invention has been particularly shown and described in connection with a laser printer, it is to be understood that the application of the processing unit of the invention is not limited to a laser printer only. As another application of the processing unit of the present invention, mention may be made of, for example, copying apparatus or facsimile apparatus.

Claims: 1. An image forming apparatus comprising: a main body (100); at least two types of processing units in said main body (100) to be used for image forming operations; said processing units including a first unit (113) having a first prescribed effective life and a second unit (111) having a second prescribed effective life different from that of said first unit (113), both units (113, 111) being detachably mounted in said main body (100), and each of said processing units (113, 111) including an identity indicating means (1, 11) for representing the identity of the respective processing unit (113, 111); detecting means (2, 12) for detecting the identity of each of said processing units (113, 111) and producing an identity code corresponding to each of said processing units (113, 111); and storage means (3B) associated with each of said pocessing units (113, 111) for separtely storing the number of image forming operations completed by each of said processing units (113, 111); characterised by first memory means (5, 14) for storing values representative of the number of image forming repetitions corresponding to the different effective lives of the processing units; second memory means (3A) for storing the identity code of each of said processing units, produced by said detecting means (2, 12); and means (4, 13) for comparing the number of image forming operations completed by each processing unit stored in said storage means (3B) with the corresponding values stored in said first memory means (5, 14). 2. Apparatus according to claim 1 wherein said first unit of processing unit comprises a developing device (113) and said second unit of processing comprises a photosensitive unit (111). 3. Apparatus according to claim 2 wherein said comparing means (4, 13) includes means for generating a coincidence signal when the first or second values representative of the different prescribed effective lives of each of said processing units (113, 111) in the apparatus equals the corresponding number stored in said storage means (3B) for each processing unit. 4. Apparatus according to claim 3 further comprising alarm means (6, 15) operatively connected to said comparing means (4, 13) and responsive to the coincidence signal for indicating when each of said processing units (113, 111) in the apparatus has reached the corresponding value of image forming operations corresponding to each of the first and second prescribed effective lives. 5. Apparatus according to any preceding claim further comprising at least one mounting unit including a guide frame (113e) mounted to said main body (100) for slidable movement between a first position in which said guide frame (113e) is in said main body (100) and a second position in which said guide frame (113e) is outside of said main body (100), said two types of processing units (113, 111) being detachably mounted to said guide frame (113e). 6. Apparatus according to any preceding claim wherein said identity indicating means (1, 11) includes a first electrical connector (CN1) comprising a plurality of conductors, and said detecting means (2, 12) includes a second electrical connector (CN2) comprising a plurality of conductors, said first and second connectors (CN1, CN2) being connected to each other when said processing units (113, 111) are mounted in said main body (100), said detecting means (2, 12) also including means for sequentially actuating conductors of said second electrical connector (CN2). 7. Apparatus according to claim 6 wherein said identity indicating means (1, 11) includes a diode circuit connected to said first electrical connector (CN1), said diode circuit including a plurality of parallel connected diodes (D1-Dn). 8. Apparatus according to claim 6 or claim 7 wherein said actuating means of said detecting means (2, 12) includes a switching circuit connected to said second electrical connector (CN2), said switching circuit operating to sequentially actuate conductors of said second electrical connector (CN2) and said diode circuit when said first and second electrical connectors (CN1, CN2) are connected to each other. 9. Apparatus according to any preceding claim wherein said second memory means includes a nonvolatile memory device (3). 10. Apparatus according to claim 9, wherein said nonvolatile memory device (3) comprises an identity code storage portion (3A) including a plurality of memory areas (3A1-3An) for storing identity codes produced by said detecting means (2, 12). 11. Apparatus according to any preceding claim wherein said storage means (3B) includes a plurality of shift registers (3B1-3Bn). 12. Apparatus according to claim 11 wherein each of said shift registers (3B1-3Bn) corresponds to a respective memory area for separately storing the number of image forming operations of one of said processing units (113, 111). 13. Apparatus according to claim 3 further comprising control means (7) responsive to the coincidence signal for preventing further operation of said processing units (113, 111) in the apparatus. 14. Apparatus according to any preceding claim wherein said identity indicating means comprises a manufacturing serial number for uniquely identifying each of said processing units.

Inventors: TANIMOTO, YASUFUMI PATENT DIVISION
Applicants: KABUSHIKI KAISHA TOSHIBA
Application year: 1986
Main classification: G03G15
IPC codes: G03G21, G03G15