Image forming apparatus with automatic toner exhausting mechanism

Abstract: An image forming apparatus provides a mechanism for exhausting waste toner or developing powder and is constructed to have a sensor (27) for sensing an amount of waste toner in a recovery vessel (4) when the developing powder is sensed to be degraded and a determining unit for determining if the carried developing powder is overflown from the recovery vessel (4) based on the sensed result. If it is determined that it is not overflown, the developing powder is recovered in the recovery vessel (4). Further, the unit for continuing the formation of an image is also provided. If the recovery vessel (4) may provide a spared space for the waste toner after the developing powder is recovered in the recovery vessel (4), the formation of the image is continued.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus of an electrophotographic type such as a copying machine or a laser printer, and more particularly to an improvement of a mechanism for automatically exhausting waste developing powder to a recovery vessel. 2. Background of the Invention The inventors of the present invention know this type of image forming apparatus which is constructed to remove the toner left on a photosensitive body by using a cleaning device and recover the waste toner into a recovery vessel. If the developing powder stored in the developing bath has two kinds of components mingled, the carrier component is degraded earlier. It is, therefore, necessary to exhaust the degraded developing powder and exchange the waste developing powder with new powder. The inventors of the present application know three related arts about the technique for recovering the waste toner and water developing powder. Two of these related arts are: Japanese Patent Lying Open No. 60-153066 (Related Art 1) Japanese Utility Model Lying Open No. 63-180864 (Related Art 2) For the related art 1, a leased recovery vessel is mounted to the exhaust port of a developing bath. After checking for the recovery vessel, the exchange of the developing powder is started. Since the related art 1 needs the leased recovery vessel, however, the leased recovery vessel entails idle operations such as transportation and storage of the vessel. For the related art 2, the residual toner on a photosensitive body is removed by a cleaning device and is recovered in a recovery vessel. The waste developing powder in the developing bath is also recovered into the same recovery vessel. The related art 2, however, does not have means for indicating how much of waste toner is now recovered in the recovery vessel. Though the recovery vessel is full of the waste toner, the situation may appear where the exchange of the degraded developing powder with the new powder is started. In this case, the waste developing powder is not allowed to be stored in the recovery vessel, that is, the waste is overflown from the recovery vessel. For the related art 3 (in house state of the art), in a case that the waste developing powder is not overflown, the waste is allowed to be recovered. Even if it is determined that the waste is overflown, no measures are suggested. Document JP-A-1 91 162 discloses a developer recovering device for an electrophotographic image forming apparatus which provides a recovery container where a developer which is discharged from a developing container is recovered and stored. The electrophotographic image forming apparatus comprises a developing bath, a cleaning unit, a recovery vessel for recovering toner from said cleaning unit and degraded developer from said developing bath, means for carrying the developer from the bath into said recovery vessel, means for sensing a developer degrading time, and means for sensing the amount of waste toner in said recovery vessel. SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic image forming apparatus having an automatic waste developer exhausting mechanism which is capable of smoothly recovering and exchanging developing powder according to the amount of the current recovered toner and providing a proper message from a machine side to a maintenance officer or a user in doing the service maintenance of the image forming apparatus itself. The object is achieved by an electrophotographic image forming apparatus according to the preamble part of claim 1, characterized in that said electrophotographic image forming apparatus further comprises a determining means for determining whether the amount of wasted toner reaches a predetermined amount in which said recovery vessel needs to be exchanged or not based on the sensed result of said second means and a value stored by means for storing an amount of the developing powder in said developing bath; a controlling means for controlling said carrying means so as to cause said carrying means to carry the developing powder into said recovery vessel when the result of said determining means indicates that said recovery vessel needs to be exchanged; and a continuing means for continuing the image formation by delaying exchanging of said recovery vessel when the determined result of said determining means does not indicate that said recovery vessel needs to be exchanged. The mechanism according to a first aspect of the invention is constructed to exchange the developing powder when the recovery vessel is full of the waste without exhausting the waste developing powder if the waste in the recovery vessel is smaller than the reference amount at the time of exchanging the developing powder. This construction makes it possible to reduce the overall troublesome operation. Hence, the copying operation is allowed to be continued until the waste toner in the recovery vessel reaches the reference amount even if the developing powder enters into the exchange time. The mechanism according to a second aspect of the invention is allowed to set such a number of copies as keeping the exchange period to a proper value. This results in preventing the quality of copies from being lowered. The mechanism according to a third aspect of the invention is constructed to carry the degraded developing powder to the recovery vessel. In general, the number of copies is on the order of several thousands to several ten thousands. It means that the exchange of the developing powder is not carried out several times during the life of the machine itself. When the toner reaches the first level, therefore, the life data of the developing powder is checked. If the life of the developing powder is left, the toner is allowed to be carried to the second level and the copying operation is enabled. This results in reducing the exchange frequency of the recovery vessel. Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a construction of an image forming apparatus; Fig. 2 is a function block diagram showing an image forming apparatus; Fig. 3 is a view showing a recovery vessel included in the image forming apparatus; Fig. 4 is a view showing an operation panel provided in the image forming apparatus; Fig. 5 is a flowchart showing an operation of the image forming apparatus; Fig. 6 is a function block diagram showing an image forming apparatus according to a first embodiment of the present invention; Fig. 7 is a view showing amounts of toner and developing powder in a recovery vessel included in the image forming apparatus shown in Fig.6; Fig.8 is a function block diagram showing an image forming apparatus according to a second embodiment of the present invention; Fig. 9 is a flowchart showing the controlling operation of the image forming apparatus shown in Fig. 8; Fig. 10 is a function block diagram showing an image forming apparatus according to a third embodiment of the present invention; Fig. 11 is a view showing a relation between waste toner and developing powder in a recovery vessel included in the image forming apparatus; and Fig. 12 is a flowchart showing the controlling operation of the image forming apparatus. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 is a view showing an image forming apparatus Fig. 2 is a function block diagram showing said image forming apparatus. Fig. 3 is a view showing a recovery vessel included in the image forming apparatus shown in Fig. 2. Fig. 4 shows a keyboard and a display unit on an operation panel. Fig. 5 is a flowchart showing the recovering operation executed in the image forming apparatus. As shown in Fig. 1, a numeral 1 denotes a photosensitive body. A numeral 2 denotes a developing bath for developing an electrostatic latent image formed on the photosensitive body 1. A numeral 3 denotes a cleaning unit for cleaning the residual toner left on the photosensitive body 1. A numeral 4 denotes a recovery vessel for recovering the waste toner from the cleaning unit 3 and the degraded developing powder in the developing bath 3. The photosensitive body 1 is formed like a drum. The developing bath 2, a transfer unit 5 and the cleaning unit 3 are located around the photosensitive body 1. The developing bath 2 provides a developing roller 6 and stirring rollers 7, 7a fitted therein. On the top of the developing bath 2 are provided a toner feeding bath 8 and a developing powder feeding bath 9. In response to a signal sent from a toner density sensor 10, the toner is fed from the toner feeding bath 8. In response to a developing powder exchange signal, the developing powder is fed from the developing powder feeding bath 9. On the bottom of the developing bath 2 is provided a shutter 11 for exhausting or discharging the developing powder. Under the shutter 11, a bed plate 12 of the developing bath is located. The bed plate 12 serves as a carrying screw wall. The bed plate 12 provides the carrying screw 13 for exhausting the waste developing powder in itself. A waste developing powder carrying means (see Fig. 1) is composed of the screw 13 and a recovery pipe 20 connecting the developing bath 2 to the recovery vessel 4. In the recovery vessel 4, the waste toner is carried from the cleaning unit 3 by means of another screw. When the developing powder needs to be exchanged, the waste developing powder is exhausted into the recovery vessel 4 by means of the screw 13. To exhaust the degraded developing powder in the developing bath, the shutter 11 is pulled to the side of a user through the effect of a rack ad a pinion. The shutter 11 has the right and the left ends formed like a hook and is fitted to the developing bath along the longer side of the developing bath 2. By pulling the shutter 11, the developing powder is dropped from an opening of the developing bath 2 into the space above the screw 13 and the bed plate 12. The rollers 6, 7, 7a and the screw 13 are driven so that the developing powder in the developing bath 2 may be guided into the recovery vessel 4. After recovering the developing powder, the shutter 11 is returned to an original state. Then, the new developing powder is fed from the feeding bath 9 and the exchange of the developing powder is terminated. As shown in Fig. 2, the foregoing recovery mechanism is constructed to have a unit 19 for carrying waste developing powder, a unit 21 for sensing a degrading time of developing powder, a unit 22 for sensing a waste toner amount in the recovery vessel 4 when the developing powder is sensed to be degraded, a unit 23 for storing an amount of waste developing powder, a unit 24 for determining whether or not the carried developing powder is overflown from the recovery vessel 4, based on the sensed result of the waste toner amount sensing unit 22 and the set value of the storing unit 23, and a unit 25 for outputting a recovery indication signal to the waste developing powder carrying unit 19 if the determining unit 24 determines that the carried developing powder is not overflown. As shown in Fig. 4, the image forming apparatus (herein, a copying machine) provides the keyboard 38 and the display unit 29 on the operation panel for inputting a recovery indicating signal to the developing powder carrying unit 19 in accordance with the determined result of the unit 24. Further, the control unit 25 is provided in the image forming apparatus. Turning to Fig. 2, the sensing unit 21 for sensing the degrading time of the developing powder is composed of a counter for counting a number of copies and outputting a signal when the counted value reaches a predetermined value. The unit 22 for sensing the waste toner amount is composed of a weight sensor 26 located under the recovery vessel 4 and an optical sensor 27 located on the side of the recovery vessel 4 as shown in Fig. 3. The unit 24 for determining whether or not the waste developing powder is recovered and the unit 25 for controlling the carrying are composed of a CPU, a program ROM and a data RAM loaded in a one-chip microcomputer. In the foregoing arrangement, as referring to Figs. 2 and 5, when the number of copies reaches a predetermined one, the sensing unit 21 determines that the developing powder is degraded. Then, the operation of exchanging the developing powder is started. When exhausting the developing powder, through the effect of the weight sensor or the optical sensor of the waste toner amount sensing unit 22, the waste toner amount in the recovery vessel 4 is sensed. Next, the determining unit 24 determines whether or not the addition of the sensed waste toner amount in the recovery vessel 4 and the amount of the pre-stored developing powder in the developing bath 2 exceeds the left volume of the recovery vessel 4. If it is determined that the carried developing powder is not overflown from the recovery vessel 4, the control unit 25 serves to drive the screw 13 and the shutter 11 of the carrying unit 19. If it is overflown, the waste developing powder is not allowed to be exhausted. For driving the screw 13 and the shutter 11, the key 38 on the operation panel is allowed to be operated. If the determining unit 24 determines that the waste developing powder is overflown, the key 38 is disallowed to be operated for inhibiting the driving of the elements of the carrying unit through the effect of the carrying control unit 25. At a time, the display unit 29 on the operation panel indicates a message "Exchange a recovery bottle". When a maintenance officer replaces the recovery bottle with an empty one or a bottle with a smaller amount of the waste toner amount, the amount sensing unit 22 and the recovery determining unit 24 determine whether or not the waste developing powder is overflown from the recovery bottle. If not, the key 38 on the operation panel is allowed to be operated. The waste toner amount sensing unit 22 is not limited to the weight sensor 26 and the optical sensor 27. Any means may be used if it enables to make sure of the amount of the waste toner. In turn, the description will be directed to the first embodiment of the present invention as referring to Figs.6 and 7, in which Fig. 6 is a function block diagram showing an image forming apparatus according to this embodiment and Fig. 7 shows an amount of toner and developing powder in a recovery vessel. In the image forming apparatus according to this embodiment, as shown in Fig. 6, a waste developer exhausting mechanism is provided to have a unit 19 for carrying waste developing powder, a unit 21 for sensing a degrading time of developing powder, a unit for sensing a waste toner amount in the recovery vessel 4 when the degrading time of the developing powder is sensed, a unit 24 for determining whether or not the exhausted amount of the developing powder reaches the amount of the vessel exchanging time, a unit 28 for delaying the recovery of the waste developing powder and continuing the formation of the image if the determined result indicates the vessel should not be exchanged, and a unit 25 for outputting a recovery signal to the carrying unit 19. To control those units, a microcomputer is used. The other components and relation among them of this embodiment are the same as those of the foregoing recovery mechanism. In the above construction, assume that the waste toner amount in the recovery vessel 4 is at the A level (see Fig. 7) at the exchanging time of the developing powder. If the necessary amount of the developing powder to be exhausted to the recovery vessel 4 is C - B, the spared space of (B - A) is left in the recovery vessel 4. To reduce the overall troublesome operation, it is better to exchange the recovery vessel when it is filled rather than to exchange it when the spared space is left. According to this embodiment, therefore, at the exchanging time of the developing powder, the copying operation is allowed to be continued until the waste toner level in the recovery vessel 4 reaches B. To sense the level B, any kind of sensors such as a weight sensor and an optical sensor may be used. When the waste toner level reaches B, the waste developing powder is exchanged. This results in reducing the troublesome operation of the user or the maintenance officer. In turn, the description will be directed to a second embodiment of the present invention as referring to Figs. 8 and 9, in which Fig. 8 is a functional block diagram showing an image forming apparatus according to the second embodiment and Fig. 9 iS a flowchart showing the control of the image forming apparatus. In the image forming apparatus according to this embodiment, as shown in Fig. 8, a waste developer exhausting mechanism is provided to have a unit 21 for sensing when the developing powder is degraded, a unit 22 for sensing an amount of waste toner in the recovery vessel 4 when the sensing unit 21 senses the developing powder is degraded, a unit 23 for storing a predetermined amount of waste developing powder, a unit 24 for determining whether or not the carried developing powder is overflown from the recovery vessel 4 according to the sensed result of the sensing unit 22 and the set value of the storing unit 23, a unit 31 for counting a number of copies based on a degrading signal from the sensing unit 21, and a unit 28 for continuing the formation of an image only if the counted result of the counting unit 31 is equal to the set value or less and the recovery vessel 4 leaves a spared volume after the waste developing powder is recovered. The other components and relation among them of this embodiment are the same as those of the first embodiment. Then, the flow of the copying operation will be described as referring to Fig. 9. A copying operation is started. Assuming that the ** copies are set as around a time when the developing powder is degraded, a counter in the machine itself is started when the number of processed copies reach **. To set the time when the developing powder is degraded, it is possible to use not only the number of copies but the number of revolutions counted since the rollers are started. Then, the number of allowable quality-kept copies counted from the ** is set as x to the counter. If the counter indicates x or less and the recovery vessel 4 leaves the spared space after the developing powder is recovered into the vessel 4 at this time, the copying operation is OK. If no spared space is left, the copying operation is not allowed. Then, the developing powder is exchanged. If the recovery vessel 4 leaves the spared space, when the counter reaches a value of x, the copying operation is stopped. At a time, the exchange of the developing powder is started. By setting the counter so that the exchange time of the developing time does not exceed a certain limit, it is possible to keep the proper quality of copies. In turn, the description will be directed to a third embodiment of the present invention as referring to Figs. 10, 11, and 12, in which Fig. 10 is a functional block diagram showing an image forming apparatus according to the third embodiment, Fig. 11 is a view showing a relation between an amount of waste toner and an amount of developing powder in a recovery vessel, and Fig. 12 is a flowchart showing the control of the image forming apparatus. As shown in Fig. 10, the recovery mechanism included in this embodiment is provided to have a unit 22 for sensing an amount of waste toner, a first level determining unit 35 for determining whether or not the sensed result of the sensing unit 22 reaches a reference amount of the waste toner, a second level determining unit 36 for determining whether or not the sensed result of the sensing unit 22 reaches the amount in which the vessel needs to be exchanged, a unit 28 for continuing the formation of an image if the determined result of the first level determining unit 35 reaches the reference volume of the waste toner but the sensed result of the sensing unit 21 is not allowed to reach the degrading time, a unit 25 for outputting a recovery signal to the waste developing powder carrying unit 19 when the sensing unit 21 senses the developing powder is degraded, and a display unit 37 for prompting the recovery vessel 4 to be exchanged when the determined result of the second level determining unit 36 reaches the amount in which the vessel needs to be exchanged. The first level means an amount in which maximum storage of the waste toner is allowed. The second level means an amount between the amount of the first level and the full amount of the recovery vessel. The other components and relations among them are the same as those of the first embodiment. In the foregoing arrangement, when the developing powder needs to be exchanged, it is carried into the recovery vessel 4. In general, however, the exchange of the developing powder corresponds to about several thousands to several ten thousands copies. When the toner reaches the first level, therefore, the life data of the developing powder is checked. If the life of the developing powder is still left, the toner is allowed to be carried into the second level. Then, the copying operation is allowed. The life data of the developing powder may be the number of copies (counter values), the image density, the rotating time of the rollers in the developing bath, and so forth. By setting the first recovery level for the maximum storage of the waste toner and the second recovery level for the storage of the degraded developing powder on the waste toner storage, therefore, it is possible to make the most use of the recovery vessel 4 and reduce the exchanging frequency of the recovery vessel 4.

Claims: An electrophotographic image forming apparatus comprising: a developing bath (2) for developing an electrostatic latent image on a photosensitive body (1) with a developing powder comprising toner; a cleaning unit (3) for cleaning residual toner on said photosensitive body; a recovery vessel (4) for recovering waste toner from said cleaning unit and degraded developing powder from said developing bath; a carrying means (19) for carrying the developing powder from said developing bath into said recovery vessel; a first means (21) for sensing a degrading time of the developing powder; and a second means (22) for sensing an amount of waste toner in said recovery vessel when said first means senses the degrading time of the developing powder, characterized in that said electrophotographic image forming apparatus further comprises a determining means (24) for determining whether the amount of wasted toner reaches a predetermined amount in which said recovery vessel needs to be exchanged or not based on the sensed result of said second means and a value stored by means (23) for storing an amount of the developing powder in said developing bath; a controlling means (25) for controlling said carrying means so as to cause said carrying means to carry the developing powder into said recovery vessel when the result of said determining means indicates that said recovery vessel needs to be exchanged; and a continuing means (28) for continuing the image formation by delaying exchanging of said recovery vessel when the determined result of said determining means does not indicate that said recovery vessel needs to be exchanged. An electrophotographic image forming apparatus according to claim 1, wherein said first means (21) comprises a counter. An electrophotographic image forming apparatus according to claim 1, wherein said second means (22) comprises a weight sensor or an optical sensor. An electrophotographic image forming apparatus according to claim 1, wherein said determining means (24) and said controlling means (25) are respectively composed of a one-chip microcomputer having a CPU, a program ROM and a data RAM. An electrophotographic image forming apparatus according to claim 1, characterized in that said electrophotographic image forming apparatus further comprises a counting means (31) for counting a number of copies based on the sensed result of said first means, that said determining means (24) determines whether or not the developing powder would be overflown from said recovery vessel (4) on carrying of the developing powder by said carrying means (19) based on the sensed result of said second means (22) and a value stored by means (23) for storing an amount of the developing powder in said developing bath (2), and that said continuing means (28) continues the image formation when the counted result of said counting means does not reach a predetermined number and the sensed result of said second means does not reach a predetermined amount. An electrophotographic image forming apparatus according to claim 1, characterized in that said electrophotographic image forming apparatus further comprises a first level determining means (35) for determining whether or not the amount of wasted toner sensed by said second means (22) reaches a reference amount of the waste toner; a second level determining means (36) for determining whether or not the amount of wasted toner sensed by said second means reaches a predetermined amount in which said recovery vessel (4) needs to be exchanged; and a displaying means (37) for displaying the exchanging of said recovery vessel when the determined result of said second level determining means indicates that the amount of waste toner reaches the predetermined amount; that said continuing means (28) continues the image formation when the sensed result of said first means does not indicate the degrading time even if the determined result of said first level determining means indicates that the amount of waste toner reaches the reference amount, and that said controlling means (25) controls said carrying means (19) so as to cause said carrying means to carry the degraded developing powder into said recovery vessel when said first means senses the degrading time of the developing powder.

Inventors: AIMOTO TOYOKA, OHKAWA YASUNOBU, AIMOTO, TOYOKA, OHKAWA, YASUNOBU
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1992
Main classification: G03G15
IPC codes: G03G21, G03G15