Image processing equipment

Abstract: The present invention relates to an image processing equipment in which the impression current given to the corona discharger for charging in the pre-fatigue process can be controlled according to the surface speed of the photosensitive body so that a higher potential than the necessity can not be formed on the surface of the photosensitive body when carrying out the pre-fatigue process prior to image forming actions.

Description: This invention relates to a method and an apparatus for executing a pre-fatigue process in an electrostatic image processing equipment such as, for instance, a copying machine. Description of the Prior Art Conventionally, since it needs a certain period of time to eliminate traps in a photosensitive body and stabilize the photosensitive body in an electric charging process especially for an organic photosensitive body and an arsenic-selenium photosensitive body of photosensitive bodies used in an image processing equipment in a copying machine or a laser beam printer, there are some cases where it is impossible to eliminate changes of the copying density in the first several copies from start of image processing even though the conditions of each process are optimized. For this reason, such a trial that an electric charging and static eliminating process can be repeated one to five cycles before starting an actual image processing when the switch for starting the image processing is turned on and the image processing action can be started has been made. For instance, the JP-A-60-241080 disclosed such an image processing equipment. The processing for repeating the electric charging and static eliminating process prior to such an actual image processing process as shown above is called "Pre-copying process" or "Pre-fatigue process", and it is an excellent technique in the point of attempting to stabilize the charging capacity at the point when an actual image processing starts. As such a pre-fatigue process is conducted prior to starting the image processing action, it is general that the pre-fatigue process is carried out on starting the main motor to drive a drum, etc. in order to shorten the time of the first copy. Actually however, a time lag occurs without fail until a rotary body reaches the constant revolution speed thereof when starting the main motor. For this reason, as the surface speed of a photosensitive body is slower in the period of the time lag than that on usual image processing, the charging efficiency (corona discharge efficiency) by a charger is made higher, and thus an electric charge of higher potential than the usual charging potential is formed on the surface of a photosensitive body until the time lag is over. As an extraordinarily high potential portion is formed on the surface of a photosensitive body as shown above, the high potential portion can not be sufficiently lowered to such a level as not to be developed even though an exposure process is subsequently executed, thereby causing toner to be adhered to be like a band when the high potential portion passes through the developing portion. Such a toner image is just like so-called black solid and a great deal of toner is adhered. Therefore, when the high potential portion passes through a cleaning device, a cleaning blade thereof may be damaged, and a cleaning trouble may occur. This is because a toner image of black solid as shown above exceeds the allowance capacity of scraping by the cleaning blade. Besides, as a great deal of toner is discharged from the developing device as shown above, there is another problem that the toner consumption is large, too. Furthermore, as in the pre-fatigue process a series of image processing processes are carried out without transferring a transcribing paper, toner may be directly adhered to the transcribing charger, and there causes another problem that the transcribing charger is much stained. Still furthermore, since a high potential which remarkably exceeds the optimal voltage is formed on the surface of the photosensitive body as shown above, the insulation of the photosensitive body is destroyed, thereby resulting in defective imaging and pin holes. JP-A-63-19 11 67 discloses the compensation of fatigue in a copying process. In this document the degree of fatigue in a copying device is determined for controlling the electrostatic charge current of an electrostatic charge electrode. The control is performed in response to the speed of the photosensitive drum. However, this control is performed during a copying procedure to compensate for a fatigue of the photosensitive body. US-A-4 621 920 describes a preconditioning method for a rotating photosensitive recording drum of a copying machine, comprising the consecutive steps of erasing uniformly a full copying portion of said photosensitive drum by energizing an erase lamp; charging uniformly a full copying portion of said photosensitive drum, and energizing a prefatigue lamp to expose uniformly a full copying portion of said photosensitive drum to infrared and visible rays, all said steps being performed prior to recording of an image on said photosensitive drum and erasing and charging said drum for said recording. As to the regulation of the prefatigue lamp, this document merely discloses to start energizing this lamp when a portion of the drum which has been charged by a charge corotron is immediately below the prefatigue lamp, and to terminate the energization of the prefatigue lamp when the drum has completed one revolution. US-A-4 797 707 likewise discloses a prefatigue treatment. In conformity with the teaching of this document the prerotation for subjecting a photosensitive member to the fatigue treatment in advance is regulated in accordance with both the rest time after the completion of a previously executed copying operation and the current temperature of the photosensitive member. SUMMARY OF THE INVENTION It is an object of the invention to solve various problems described in the above and incidental to introduction of the pre-fatigue process by that any higher potential than the necessity may not be formed on the surface of the photosensitive body in the pre-fatigue process. In order to achieve the above object, the invention provides a method as defined in claim 1 and an image processing equipment as defined in claim 4. In a preferred embodiment, the pre-fatigue process is started after the peripheral speed of the photosensitive body has reached a constant value and the potential given to the surface of the photosensitive body by a charger is made equivalent to that on usual copying processing and is such a potential as can be sufficiently eliminated in a subsequent static eliminating process. Therefore, such problems as toner may be consumed more than the necessity, defective cleaning may occur, the cleaning blade may be damaged or furthermore the transcribing charger is stained, can be prevented. In addition, the photosensitive body can be freed from any breakage of insulation thereof because only a voltage within the permissible range thereof is given thereto. In another preferred embodiment, the impression current upon the corona discharger is changed in conformity with the changes of the measured surface speed of the photosensitive body. Various means are considered as means for changing the impression current according to the changes of the peripheral speed of the photosensitive body. For instance, there are means for impressing the corona current according to the speed by detecting the surface speed of the photosensitive body or a motor to drive it. Also in the case that the corona current is changed according to the peripheral speed of the photosensitive body as described in the above, the potential given upon the surface of the photosensitive body is made equivalent to that on usual copying processing and can be sufficiently eliminated in the static eliminating process of usual light energy, which is installed up to the subsequent developing portion. Therefore, such problems as toner may be consumed more than the necessity, defective cleaning may occur, the cleaning blade may be damaged or furthermore the transcribing charger is stained, can be prevented. In addition, the photosensitive body can be freed from any breakage of insulation thereof because only a voltage within the permissible range thereof is given thereto. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram for explaining the control details of the image processing equipment according to the first embodiment of the invention, Fig. 2 is a flow chart showing the procedure of the same control details, Fig. 3 is a block diagram for explaining the control details of the image processing equipment according to the second embodiment of the invention, Fig. 4 is a flow chart showing the procedure of the same control details, and Fig. 5 is a graph showing one example of the memory details. Protection is sought only for the embodiments covered by the claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS While only certain embodiments of the present invention will be described, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the present invention as claimed. The image processing equipment according to the first embodiment of the invention has almost no change in the hardware thereof from a conventional general copying machine described for instance in the JP-A-60-241080 as shown in Fig. 1. Namely, as shown in Fig. 1, a copy button 2 is connected to the input section of a micro computer 1 which can control the whole system of a copying machine, together with many of switches installed at the operation section. 3 is a timer which is actuated by a clock for determining the cycle of control of the above micro computer 1. The timer 3 is set and reset by commands which come from the micro computer 1. A charger 5, a static eliminator lamp 6 and a main motor 7 are connected to the output side of the micro computer 1 through driver circuits 4a, 4b and 4c, respectively. A pulse plate and a pulse generator 8 including an optical sensor which converts the revolution amount of the pulse plate to electric pulse signals and transmits the electric pulse signals to the micro computer 1 are connected to the main motor 7. Such a pulse generator 8 may be of any type which can detect the revolution synchronized with the main motor 7. For instance, it can be composed of a pulse plate and a photo sensor for detecting the revolution thereof, which is directly installed at the main motor 7 or at the drive system from the main motor 7 to the photosensitive body. And a rotary encoder can be used, too. Consecutively, with reference to a flow chart shown in Fig. 2, the ensuing description explains the processing procedure of the image processing equipment. When the copy button is pressed down (step S1) under such a condition that any image processing action is not carried out, the main motor 7 begins driving, thereby causing the photosensitive body drum to begin to rotate (Step S2). At this time, the photosensitive body drum gradually begins to rotate with, for instance, a time lag of 0.1 to 0.2 seconds. Simultaneously, the micro computer 1 resets the timer 3 (Step S3). Also at the same time, the counter 9 which utilizes a register in the micro computer 1 is cleared (Step S4). Consecutively, in the step S5, the micro computer 1 waits for input from the pulse generator 8. As a pulse is inputted from the pulse generator 8, the value of the counter 9 is increased by only 1 (Step S6), and it is then judged (in the step S7) whether or not the value of the counter 9 reaches an appointed set value C o . The above steps S5 through S7 are repeated until the value of the counter 9 reaches the set value C o . At the moment when the value of the counter 9 reaches the set value C o , it is judged in the step S8 whether or not the period of time T, measured by the timer 3, from having reset the timer in the step S3 to that the value of the counter 9 has reached the set value C o comes near the range of the tolerance D for the appointed cycle time T o . If the period of time T is not sufficiently near the range of the tolerance D thereof, the processing returns to the step S4 by way of reset processing of the timer 3 in the step S9. Thus, the time T that the value of the counter 9 reaches C o from zero (0) is decreased by speed acceleration of the main motor 7. At the moment when the time T sufficiently comes near the appointed cycle time T o , i.e., at the moment when the surface peripheral speed of the photosensitive body drum is constant, the processing goes to the step S10, wherein the pre-fatigue process is executed. As the pre-fatigue process is completed, the processing goes to usual copying actions (Step S11). After that, copying actions known to the public are carried out by the set quantity, and then the processing is terminated. In the above embodiment, it is judged by comparing the period of time with the appointed cycle time T o whenever the counter counts the appointed pulses (C o ) whether or not the warming-up of the photosensitive body drum is completed since the pulse width is sufficiently fine. However, in the case that the pulse cycle is rough, it may be good that it is judged by measuring the interval between mutual pulses by means of a timer whether or not the time of interval is constant. The composition of the hardware of an image processing equipment according to a second embodiment of the invention is shown in Fig. 3. As shown in this figure, the point in which the composition of the hardware of the second embodiment is different from that of the hardware of the first embodiment shown in Fig. 1 is only that a memory M is connected to the micro computer 1. The memory M memorizes the measurement time t i by the timer 3 and the voltage value V i of the charger outputted corresponding thereto as pair. The memorizing details of the memory M is set as per machine. Fig. 5 shows one example of the memorizing details of such a memory M. Also, in the embodiment it is supposed that the photosensitive body drum is almost completely warmed up in t o seconds since start of the revolution of the photosensitive body drum. Consecutively, with reference to the flow chart shown in Fig. 4, the ensuing description explains the processing procedure of the image processing equipment. Also, in the ensuing description, S1, S2, .... indicates the number of the processing procedures (Step). When the copy button is pressed down (step S1) under such a condition that any image processing action is not carried out, the main motor 7 begins driving, thereby causing the photosensitive body drum to begin to rotate (Step S2). At this time, the photosensitive body drum gradually begins to rotate with, for instance, a time lag of 0.1 to 0.2 seconds. Simultaneously, the micro computer 1 resets the timer 3 (Step S3). In the step S4, it is waited that the time t of detection by the timer 3 firstly becomes t₁. As the time t of detection becomes t₁, the voltage value V₁ corresponding to t₁ shown in Fig. 5 is searched for in the memory M and is impressed to the charger 5. As voltage impression to the charger 5 is completed, it is consecutively judged (in the step S5) whether or not the time t of detection reaches to (the warming-up time of the main motor 7). If not, the processing returns to the step S4, and the routines S4 and S5 are repeated. Then, the voltage V i is impressed on t i seconds. As the detection time t reaches t o , the original target voltage V o of the pre-fatigue process is impressed to the charger 5 (in the step S6), thereby causing the pre-fatigue processing to be maintained up to the required period of time t e of the pre-fatigue process (in the step S7). V o is the voltage of the charger suited to usual copying actions or a slightly lower voltage than the voltage of the charger, and such a voltage as can not be developed by irradiation of a subsequent eliminator lamp 6 is selected. Furthermore, as the pre-fatigue process is completed, usual copying actions (Step S8) is started. Consecutively, usual copying actions known to the public are carried out by the set quantity, thereby causing the processing to be terminated. In the pre-fatigue process in the second embodiment, the main charger 5 is used in charging, and an eliminator lamp 6 is used to eliminate electric charge. However, a halogen lamp for forming an image can be used instead of the eliminator lamp 6. In this case, the light of a halogen lamp which is reflected to a white sheet attached to the rear side of the document table is irradiated to the surface of the photosensitive body drum. Furthermore, a transcribing unit is used for charging and a static eliminator lamp is used for eliminating electric charge. But an eliminator lamp 6 can be used instead. Also, though in the embodiment the memorizing details of the memory M is composed of "pair of the time of detection and the impression voltage corresponding thereto", it can be composed as "pair of the revolution speed of the main motor or the photosensitive body drum and the impression voltage corresponding thereto". In this case, the revolution speed of the main motor or the photosensitive body drum can be detected by pulse signals coming from the pulse generator 8, and the impression voltage corresponding thereto is searched for in the memory M.

Claims: Method for executing a pre-fatigue process in an image processing equipment, including an electric charging and static eliminating process on a photosensitive body prior to image processing actions, characterized in that the surface speed of the photosensitive body is measured and the impression current applied to a corona charger (5) for charging the photosensitive body in the pre-fatigue process is controlled in response to the measured surface speed of the photosensitive body. Method according to claim 1, wherein the pre-fatigue process is started after the measured surface speed of the photosensitive body has reached a constant value, and a constant impression current is applied to the corona charger (5) during the pre-fatigue process. Method according to claim 1, wherein the impression current applied to the corona charger (5) during the pre-fatigue process is changed in conformity with changes of the measured surface speed of the photosensitive body. An image processing equipment having means (1, 3 to 8, M) for executing a pre-fatigue process and including a motor (7) for driving a photosensitive body, a corona charger (5) for electrically charging the photosensitive body, means (6) for eliminating static charges from the photosensitive body, and a microcomputer (1) for controlling said motor (7), said corona charger (5) and said static charge eliminating means (6), characterized in that means (8) for measuring the surface speed of the photosensitive body are provided, and said microcomputer (1) is programmed such as to control the impression current applied to said corona charger (5) in response to signals which represent said surface speed and which are applied to said microcomputer (1) from said surface speed measuring means (8). An image processing equipment according to claim 4, wherein said microcomputer (1) is programmed such as to start the pre-fatigue process after it has judged in response to signals from said surface speed measuring means (8) that the surface speed has reached a constant value. An image processing equipment according to claim 4, wherein said microcomputer (1) is programmed such as to change the impression current applied to the corona charger (5) during the pre-fatigue process in conformity with changes of the measured surface speed as evidenced by the signals applied to said microcomputer (1) by said surface speed measuring means (8).

Inventors: TANAKA NARIAKI, YOSIDA TAKESHI, TANAKA, NARIAKI, YOSIDA, TAKESHI
Applicants: MITA INDUSTRIAL CO LTD, MITA INDUSTRIAL CO. LTD.
Application year: 1990
Main classification: G03G21
IPC codes: G03G21