Process cartridge and electrophotographic image forming apparatus

Abstract: The present invention provides a process cartridge comprising an electrophotographic photosensitive member, a developing means for developing a latent image formed on the electrophotographic photosensitive member, a developer remained amount detecting member for detecting a remained amount of developer in the developing means, and a nonvolatile memory means for memorizing information corresponding to at least the print number of sheets and the developer remained amount in such a manner that such information can be read out and re-written by an image forming apparatus. The present invention also provides an electrophotographic image forming apparatus to which such a process cartridge can detachably mounted.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a page printer and the like, and more particularly it relates to an electrophotographic image forming apparatus having an improved process cartridge portion. Related Background Art In conventional electrophotographic image forming apparatuses using electrophotographic image forming process, a process cartridge in which an electrophotographic photosensitive member and process means acting on the electrophotographic photosensitive member are integrally assembled as a cartridge unit which can detachably mounted to a main body of an image forming apparatus has been used. By using such a process cartridge, since the user himself can perform the maintenance of the apparatus without any expert, the operability is greatly improved. Thus, the process cartridge has widely been used in electrophotographic image forming apparatuses. In the electrophotographic image forming apparatus using the process cartridge, since the user himself must exchange the process cartridges, it is required to provide a means for informing the user of the exchanging time for the process cartridge. To this end, in the past, a remained amount of toner in the process cartridge was detected in the following manners to inform the user of the exchanging time for the process cartridge. (1) A conductive antenna is disposed in the vicinity of a developing sleeve, and a remained amount of toner is judged on the basis of electrostatic capacity between the antenna and the sleeve (i.e., dielectric constant of toner is utilized). (2) A laser light emitting element and a light receiving element are provided, and a remained amount of toner is judged on the basis of the fact that the light emitted from the light emitting element is not received by the light receiving element if there is any toner between these elements (i.e., light shielding ability of toner is utilized). (3) A remained amount of toner is judged on the basis of a weight of a toner container (i.e., weight of toner is utilized). (4) The number of copies from the initiation of copy is stored by using a re-writable memory means. Or, (5) A total light emitting time of a laser is stored by using a re-writable memory means. SUMMARY OF THE INVENTION A first concern of the present invention is to provide a process cartridge and an electrophotographic image forming apparatus to which such a process cartridge can be mounted, which can further improve the above-mentioned conventional techniques and which can always detect a remained amount of toner correctly to inform the user of the present printable number of sheets. A second concern of the present invention is to provide a process cartridge and an electrophotographic image forming apparatus to which such a process cartridge can be mounted, which can always detect a remained amount of toner correctly regardless of a kind of a process cartridge to be used. A third concern of the present invention is to provide a process cartridge and an electrophotographic image forming apparatus to which such a process cartridge can be mounted, which can always detect a remained amount of toner more correctly to inform the user of usable days of toner. A fourth concern of the present invention is to provide an electrophotographic image forming apparatus which can always detect a remained amount of toner more correctly by using a plurality of detection means for detecting the remained amount of toner. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view of an image forming apparatus according to a first embodiment of the present invention; Figs. 2 and 3 are flow charts for calculating the present printable number of sheets of the image forming apparatus according to the present invention; Fig. 4 is a sectional view showing a process cartridge; Fig. 5 is a graph showing a relation between a toner amount and electrostatic capacity; Figs. 6 and 7 are flow charts for calculating the number of printable days of the image forming apparatus according to the present invention; Fig. 8 is a view showing an arrangement for counting a laser light emitting time of an image forming apparatus according to another embodiment of the present invention; Fig. 9 is a graph showing a relation between a toner amount and electrostatic capacity, and weight and the electrostatic capacity. DETAILED DESCRIPTION First of all, an entire construction of an electrophotographic image forming apparatus will be explained with reference to Fig. 1. The image forming apparatus includes an electrophotographic photosensitive drum (latent image bearing member) 3, a charge device 2 for uniformly charging the photosensitive drum 3, an exposure device 7 for forming an electrostatic latent image on the photosensitive drum 3 by using laser light, and a developing device 5 for visualizing the electrostatic latent image formed on the photosensitive drum 3 as a visualized image, which developing device has a developing sleeve (developer bearing member) 5a, a developer regulating member 5b and a hopper 5d for storing toner (developer) 5c. The image forming apparatus further includes a transfer device 4 for transferring the visualized image formed on the photosensitive drum 3 onto a transfer sheet 8, a fixing device 9 for fixing the visualized image transferred to the transfer sheet 8 onto the transfer sheet, and a cleaning device 6 for removing the toner 5c remaining on the photosensitive drum 3 (not transferred to the transfer sheet 8), which cleaning device has a cleaning blade 6a urged against the photosensitive drum 3 and a waste toner container 6b. The photosensitive drum 3, charge device (charge roller) 2, developing device 5 and cleaning device 6 are integrally assembled as a cartridge unit (process cartridge CRG) which can easily be replaced by a new one, for example, when the toner stored in the hopper 5d is used up. In the illustrated example, a non-volatile memory 15 is provided on the process cartridge so that read/write of the memory 15 can be effected from the side of the main body of the electrophotographic image forming apparatus outside of the process cartridge. The information of the process cartridge itself regardless of the electrophotographic image forming apparatus is stored in the memory, but, the read/write is permitted only when the process cartridge is mounted on the main body of the electrophotographic image forming apparatus and the memory 15 of the process cartridge is connected to a connector 16 of the main body of the electrophotographic image forming apparatus. The illustrated example is characterized in that both a means for detecting a remained amount of toner and the non-volatile memory are provided on the cartridge CRG. Prior to detailed explanation of the illustrated example, (1) method and means for detecting the remained amount of toner and (2) non-volatile memory and its role will be explained. [(1) Method and Means for Detecting Remained Amount of Toner] (1-1) Means for Detecting Remained Amount of Toner As the means for detecting the remained amount of toner, any conventional arrangement can be used so long as information regarding the remained amount of toner can fundamentally be detected. More specifically, an arrangement of capacity detecting type, an arrangement using a magnetic sensor, an arrangement for detecting a weight of toner or an arrangement of light permeable type can be used. In the illustrated example, the means for detecting the remained amount of toner is constituted by an antenna electrode (remained amount detecting member) for detecting electrostatic capacity and a remained amount detecting circuit for the remained amount on the basis of the detected electrostatic capacity. (1-2) Method for Detecting Remained Amount of Toner Next, a method for detecting the remained amount of toner using the antenna for detecting the electrostatic capacity will be described with reference to Fig. 4. In Fig. 4 which is a sectional view the cartridge which is detachably mountable to the main body of the electrophotographic image forming apparatus, an antenna electrode 1 is horizontally disposed within the developing device 5, and is connected to a remained toner amount detecting circuit 17 of the main body of the electrophotographic image forming apparatus when the cartridge is mounted to the electrophotographic image forming apparatus. In the remained toner amount detecting circuit 17, the remained amount of toner is detected by reading capacitance between the antenna electrode and the developer (toner) bearing member. That is to say, the detected capacitance between the antenna 1 and the developing sleeve 5a is varied with an amount of toner therebetween. (1-3) Position of Antenna Electrode In Fig. 5 which is a graph showing a relation between the amount of toner in the developing device and the detected electrostatic capacity, the electrostatic capacity does not substantially change until the toner is decreased to a certain amount and thereafter is changed greatly. The greater a distance between the antenna electrode and the developing sleeve, the greater is the noise. If the antenna is disposed in the vicinity of the developing sleeve the electrostatic capacity does not change until immediately before the toner is used up. Thus, the proper position of the antenna electrode must be selected. [(2) Non-volatile Memory and its Role] (2-1) Non-volatile Memory As the non-volatile memory, any memory can be used so long as signal information can be stored in a re-writable manner. For example, a RAM, an electrical re-writable memory means such as a ROM, or a magnetic memory means such as a magnetic memory medium, a magnetic bubble memory or photo-magnetic memory can be used. In the illustrated example, NV-RAM (NonVolatile Random Access Memory) is used. (2-2) Role of Non-volatile Memory In the illustrated example, each cartridge is provided with the NV-RAM. With this arrangement, for example, even when several cartridges CRG are used in association with a single electrophotographic image forming apparatus (i.e., when a color image is formed) or even when a single cartridge CRG is used in association with a plurality of electrophotographic image forming apparatuses, the remained amount of toner in each cartridge can be detected without any problem. In the illustrated example, the following three information data are stored in the memory. (i) Predetermined number of printed sheets upon past electrostatic capacity detection and its electrostatic capacity; (ii) Present number of printed sheets; and (iii) Present printable number of sheets. Now, the above three data will be explained. [Predetermined number of printed sheets upon past electrostatic capacity detection and its electrostatic capacity] In the illustrated example, the electrostatic capacity is measured every predetermined number of sheets. The predetermined number is selected to multiple of hundred (100) in an initial condition remaining a relatively large amount of toner (since there is substantially no change in electrostatic capacity) and to multiple of ten (10) from when the remained amount of toner is decreased below a predetermined value (value "A" in Fig. 5) to start the change in electrostatic capacity. The electrostatic capacity is measured every said predetermined number of sheets, and, among the measured values, only two sets of latest data are preserved in the following manner. When the predetermined number is reached, a CPU reads in two sets of past data from the NV-RAM and performs calculation (which will be described later) by using these two sets of data and the present data (three sets of data in total). Thereafter, the latest data is memorized in address a of the NV-RAM and previous data (data latest but one) is memorized in address b of the NV-RAM (information memorized in the address b before the data is read in is lost). [Present number of printed sheets] After the printing is finished, the CPU reads in the "present number of printed sheets" stored in the NV-RAM, and a value obtained by adding one to the read-in data is memorized in the NV-RAM so that the number of printed sheets regarding the cartridge itself is always memorized. [Present printable number of sheets] The display value of the electrophotographic image forming apparatus is associated with the present printable number of sheets. Initial condition (Up to the value A in Fig. 5): The present printable number of sheets when the toner is decreased to the value A in Fig. 5 is calculated on the basis of the remained amount of toner when the change in electrostatic capacity is started (value A in Fig. 5) and the general average print ratio, and the calculated value is memorized (in the illustrated embodiment, this value is referred to as "X" hereinafter). This value is not re-written until the remained amount of toner reaches the value A in Fig. 5. From when the change in electrostatic capacity is started (After the value A in Fig. 5): (1) In a case where the present printable number of sheets was calculated (calculation is effected every ten printed sheets) The calculated present printable number of sheets is re-written and memorized (calculating method will be described later). (2) In a case where the present printable number of sheets is not calculated. Immediately after the printing is finished, the CPU reads in the present printable number of sheets from the NV-RAM, and a value obtained by subtracting one from the present printable number is re-written and memorized in the NV-RAM. In the illustrated example, in order to increase the process speed by decreasing the access number between the cartridge and the main body of the image forming apparatus, a value of comparative printable number of sheets is stored in a memory of the CPU of the electrophotographic image forming apparatus (it is not necessary that a memory of this CPU is a non-volatile memory). The re-writing of this value will be described later. On the basis of the above explanation, the operation of the illustrated embodiment will now be described with reference to a flow chart shown in Fig. 2. Flow 1 (flow for preparation for printing): Step S0: the cartridge is mounted to the main body of the image forming apparatus or the power source is turned ON. Steps S1 and S2: the present number of sheets and the present printable number of sheets stored in the NV-RAM of the cartridge are read in. If the present number of sheets is zero (0), the program goes to a step S3; otherwise, the program goes to a step S5. Steps S3 and S4: the present number of sheets and the electrostatic capacity are memorized in the NV-RAM and the comparative print number of sheets is memorized in the memory of the CPU, and the fact that the number of sheets more than X can be printed is displayed. Step S5: the print number of sheets memorized in the address a of the NV-RAM (number memorized at the latest) is read in and this value is memorized in the CPU as the comparative print number of sheets. Step S6: if the present printable number of sheets is X, the program goes to the step S4; otherwise, the program goes to a step S7. Step S7: the present printable number of sheets is displayed. Flow 2 (flow during the printing): A step S8: the printing is effected. Steps S9 and S10: the present number of sheets is read in from the NV-RAM, and a difference between a value obtained by adding one to the read number and the comparative print number of sheets is calculated. Step S11: if the difference is 100, the program goes to a flow 3 (steps S13 to S17); otherwise, the program goes to a step S12. Flow 3 (flow ascertaining whether the electrostatic capacity decreased to a predetermined amount) Step S13: values regarding the electrostatic capacity memorized in the addresses a, b of the NV-RAM are read in and the present electrostatic capacity is calculated. Step S14: the present electrostatic capacity is assumed on the basis of the present electrostatic capacity and past electrostatic capacity memorized in the addresses a, b. Steps S15, S16 and S17: if the assumed value is greater than a constant value, it is judged that sufficient toner exists, and the present number of sheets and the electrostatic capacity are memorized in the NV-RAM (the latest data is memorized in the address a and the data latest but one is memorized in the address b) and the comparative print number of sheets is memorized in the CPU, and a waiting condition is maintained for the print in the step S8. If the assumed value is smaller than the constant value, the program goes to a step S18. Step S18: the initiation of reduction of toner is warned to the user, and the present number of sheets and the electrostatic capacity are memorized in the NV-RAM (the latest data is memorized in the address a and the data latest but one is memorized in the address b) and the comparative print number of sheets is memorized in the CPU, and a waiting condition is maintained for the print in the step S8. Flow 4 (during the normal printing after the toner is decreased from the constant value) Step S8b: the printing is effected. Steps S9b and S10b: the present number of sheets is read in from the NV-RAM, and a difference between a value obtained by adding one to the read number and the comparative print number of sheets stored in the CPU is calculated. Step S11b: if the difference is 10, the program goes to a flow 5 (steps S21-S26); otherwise, the present number of sheets is memorized, one is subtracted from the present printable number of sheets, and the program goes to a step S19. Step S19: if the present printable number of sheets is zero (0), the program goes to a step S25; otherwise, the present printable number of sheets is memorized, the display is effected and the program goes to the print waiting condition in step S8b. Flow 5 (flow for calculating the present printable number of sheets) Steps S21 and S22: an average print ratio and the present printable number of sheets are calculated in manners which will be described later. Step S23: if the present printable number of sheets is zero (0), the program goes to a step S25; otherwise, the program goes to a step S24. Steps S24 and S26: the present printable number of sheets is displayed, and the present print number of sheets, electrostatic capacity and present printable number of sheets are memorized in the NV-RAM and the comparative printable number of sheets is memorized in the CPU, and then the program goes to the print waiting condition in step S8b. Step S25: the exchange acceleration is alarmed to the user. Next, the method for assuming the electrostatic capacity, method for converting the assumed value into the toner amount, method for seeking the past average toner use ratio and method for seeking the present printable number of sheets will be explained. [Method for assuming electrostatic capacity and method for converting assumed value into toner amount] Now, the method for converting the electrostatic capacity into the toner amount will be described. (1) The maker previously seeks an ideal relation between the toner amount and the electrostatic capacity, and such a relation is previously inputted in the ROM of the image forming apparatus (when the relation can be closely resembled to a certain function, such a function is memorized, and, when the relation cannot be closely resembled to a certain function, discrete data are memorized in the ROM of the image forming apparatus). (2) When the electrostatic capacity is detected, a relation between the detected electrostatic capacity value and two past electrostatic values at predetermined number (of sheets) (three values in total) is resembled to a straight line by using the method of least squares, thereby assuming the present electrostatic capacity. By using this method, a possible inadvertent error can be reduced. (3) The assumed value of the electrostatic capacity obtained in the above item (2) is applied to the above-mentioned ideal relation between the toner amount and the electrostatic capacity, thereby seeking the present toner amount corresponding to the assumed value.. [Method for seeking past average toner use ratio and method for seeking present printable number of sheets] (1) On the basis of the present toner amount sought by the above method, the toner amount used up to now is calculated by using the following equation: (toner amount used up to now) = (initial toner amount) - (present toner amount) (2) On the basis of the present print number of sheets and the toner amount used up to now, the past average toner use ratio is calculated by using the following equation: (past average toner use ratio) = (toner amount used up to now)/(present print number of sheets) (3) On the basis of the present toner amount and the past average toner use ratio, the present printable number of sheets is calculated by using the following equation: (present printable number of sheets) = (present toner amount)/(past average toner use ratio). [Measuring interval] Although the measuring interval between the measurements of the electrostatic capacity is not defined clearly, the smaller the measuring interval the more correct detection of the remained amount of toner. However, if the measuring interval is too small, since a large number of errors are picked up, there is a danger of obtaining a value different from the actual value. Thus, selection of an appropriate measuring interval is required. [Detecting method] In the illustrated example, a relation between three latest data regarding the print number of sheets and the electrostatic capacity is resembled to a straight line by using the method of least squares, thereby assuming the present electrostatic capacity value. On the basis of the values, the fact that the reduction of the toner amount from the constant value is started can be detected. However, the detection can be effected by judging whether the present electrostatic capacity exceeds the constant value. In this case, there is a merit that contents to be memorized in the memory can be reduced but is demerit that the result is apt to be influenced upon the error. The fact that the reduction of the toner amount from the constant value is started can be detected in the following methods: (1) The detection is effected by using the difference between the latest past electrostatic capacity and the present electrostatic capacity. (2) The detection is effected by using a ratio between the number of sheets and the change in electrostatic capacity (the number of data to be used and memorized can be selected freely). (3) Plural sets of the past predetermined number and electrostatic capacity are reserved, and the data is fitted to a relation between the remained amount of toner and the electrostatic capacity obtained by the method of least squares, and the detection is effected by using the relation with reduction of error (this method is effective when the memory has the adequate capacity). As mentioned above, by providing the memory on each cartridge and by using the above-mentioned toner remained amount detecting mechanism, it is possible to detect the correct remained amount of toner and to display the present printable number of sheets for the user. The electrophotographic image forming apparatus is not limited to the laser printer of inverse developing type shown in the illustrated embodiment, but may be embodied as general electrophotographic image forming apparatuses such as word processors, facsimiles or copying machine of normal developing type. Next, a second example will be explained. The second example is characterized in that, as well as (1) the past predetermined print number of sheets and electrostatic capacity, (2) the present print number of sheets and (3) the present printable number of sheets, (4) "date" is also memorized or stored in the memory means (such as NV-RAM) of the cartridge (data at initiation of use is memorized and is unchanged), so that the number of usable days of the cartridge can be calculated and displayed. That is to say, the second example is the same as the first example from the view point of appearance, but is different from the first example in the points that the information stored in the non-volatile memory is increased by one and calculation and display contents effected in the electrophotographic image forming apparatus slightly differ from those in the first embodiment. Now, the "date" and a method for seeking the "number of usable day" of the cartridge (different from the first example) will be explained. [Date data] The date data is transferred between the computer and the NV-RAM when the first sheet is printed after the cartridge is mounted to the image forming apparatus or after the power source is turned ON. In the illustrated example, the date information inputted in the computer is used as the date data, but, the information included in the electrophotographic image forming apparatus may be used, or the data information may be included in the cartridge itself or the date data may be inputted by the user himself. [Number of usable days of cartridge] A method for seeking the number of usable days of the cartridge will be described with reference to a flow chart shown in Figs. 6 and 7. (The flow chart shown in Figs. 6 and 7 has flows similar to those in the first example Only the difference from the first example will be explained.) Step S30: date when the printing is firstly effected is memorized in the memory of the cartridge (date is not re-written later). Steps S31 and S32: until the toner is decreased to the predetermined amount to start the change in the electrostatic capacity (up to the point A in Fig. 5), the number of usable days is calculated on the basis of the usable number of sheets (= (insurance number of sheets) - (present print number of sheets)) and the number of used days of the cartridge (function of present date and initial date). Step S33: in order to prevent an error, the number of usable days is not displayed until the 100 or more sheets are printed. Step S34: the calculation of the number of usable days after the change in electrostatic capacity is started is effected in the following manner: (1) The number of used days of the cartridge is sought, and, on the basis of the sought number and the present print number of sheets, the average print number of sheets per day is calculated by the following equation: (average print number of sheets per day) = (present print number of sheets)/(number of used days) (2) On the basis of the present printable number of sheets obtained in the same manner as the first embodiment and the average print number of sheets per day calculated in the above item (1), the number of usable days of the cartridge is calculated by the following equation: (number of usable days of cartridge) = (present printable number of sheets) ÷ (average print number of sheets per day). Incidentally, this calculation is fundamentally performed once a day (If the power source is turned ON twice or more a day or if the cartridge is mounted/dismounted twice or more a day, the calculation is performed by twice or more). When this method is used at the initial condition of the cartridge, since the great error may be caused, the display is not effected until 100 or more sheets are printed. By using the above-mentioned method, the number of usable days of the cartridge depending upon the frequency of use and/or usage condition of the user can be calculated. Further, since the average use ratio of toner per day and the print number of sheets per each month were memorized (the print number of sheets per each month is calculated on the basis of the print number of sheets and the number of used days), when the cartridge is collected for re-cycle, market survey can be performed on the basis of the information data of the collected cartridges. Thus, the replacement dates of the cartridge can be judged, thereby improving the usability. At the same time, the usage tendency of the cartridge in the market can be judged more correctly. In the illustrated example, although not fully explained due to the limitation of the capacity of the memory, calendar information (days of the week and holidays) may be set so that the number of usable days can be calculated more correctly by memorizing the past print numbers of sheets for each weekday and holiday. Next, an embodiment of the present invention will be explained. As mentioned in connection with the first example, regarding the detection of toner remained amount using the antenna, in the initial use condition of the cartridge, although the remained amount of toner cannot be detected, when the toner is reduced below the predetermined amount, the remained amount of toner can be detected correctly. On the other hand, regarding a total laser emitting time detecting method which will be described later, although the remained amount of toner can generally be detected correctly in the initial use condition of the cartridge, the error is accumulated as the print number of sheet is increased. In consideration of the above, the embodiment of the present invention is characterized in that the printable number of sheets can be determined more correctly from the initiation of usage of the cartridge by combining the above two detection results with weighting. Now, the total laser emitting time detecting method used in the embodiment and a construction of the embodiment will be explained. [Total laser emitting time detecting method] The total laser emitting time detecting method in this embodiment will be explained with Fig. 8. In Fig. 8, a modulator 20 serves to modulate an image signal inputted from a computer into laser input voltage and to turn ON/OFF a laser 23 in correspondence to the image signal. The laser 23 is connected to the modulator 20 and adapted to emit laser light in response to the modulated signal. A counter 21 connected to the modulator 20 serves to measure time information corresponding to output time from the modulator 20 to the laser 23, i.e., exposure time of a laser beam 24 emitted from the laser 23 onto the photosensitive drum 3. That is to say, a clock pulse generating means 22 such as a crystal oscillator is connected to the counter 21, and the counter 21 and the clock pulse generating means 22 constitute an adding means for counting the number of clock pulses during the duration of the laser emitting signal. The remained amount of toner is detected by assuming that the counted values is in proportion to the amount of used toner. [Construction] In this embodiment, as well as (1) the past predetermined print number of sheets and electrostatic capacity, (2) the present print number of sheets and (3) the present printable number of sheets, (4) "total laser emitting time count number" and (5) "weight" (from 0 to 1) are also memorized, and there is provided a sequence for effecting the total laser emitting time detection and a sequence for detecting the present remained amount of toner by changing the weighting. The other construction of the embodiment is the same as the first example. Now, the different points (from the first example) will be described. [Present printable number of sheets] The present printable number of sheets initially memorized in the memory is re-written whenever the sheet is printed, and the re-written value is displayed on the main body of the image forming apparatus. [Total laser emitting time count number] The total laser emitting time count number is added to the previous value read out from the NV-RAM whenever the sheet is printed, and the resultant value is re-written in the NV-RAM. [Weight] The weighting means that, among the results of the total laser emitting time detection and the antenna toner remained amount detection, the total laser emitting time detection result is weighted by the numeral value; namely, when 1 is weighted, only the total laser emitting time detection result is used, when 0.5 is weighted, both the total laser emitting time detection result and the antenna toner remained amount detection result are used by half, and, when 0 is weighted, the total laser emitting time detection result is not used. More specifically, the printable number of sheets are assumed by using the following equation: (assumed value of printable number of sheets) = aX1 + (1-a)X2 where, a is weight, X1 is the printable number of sheets by obtained by the total laser emitting time detection and X2 is the printable number of sheets by obtained by the antenna toner remained amount detection. Fig. 9 is a graph showing a relation between the remained amount of toner and the electrostatic capacity and a relation between the weight and the electrostatic capacity. In the illustrated embodiment, the relation between the electrostatic capacity and the weight is selected to become a straight line f in Fig. 9. In Fig. 9, a point C is a point dividing a line segment EB to 9:1 (i.e., line segment EC : line segment BC = 9 : 1), and a point D is a point bisecting the line segment BE. Now, the toner remained amount detecting method will be fully explained by using Fig. 9. (1) Electrostatic capacity between B and C Only the value sought by the total laser emitting time detection is used. (2) Electrostatic capacity between C and D On the basis of the weighting a sought by the electrostatic capacity and the values X1, X2 sought from the antenna toner remained amount detection and total laser emitting time detection equations, the remained amount of toner is assumed by using the equation, i.e., (assumed value of printable number of sheets) = aX1 + (1-a)X2 (3) Electrostatic capacity between D and E Only the value sought by the antenna toner remained amount detection is used. Although the above-mentioned weight is used to prevent the abrupt change in the value of the printable number of sheets when the total laser emitting time detection is switched to the antenna toner remained amount detection, it is not necessary that the function of the weighting shows the linear relation as shown in Fig. 9, but an appropriate function such as higher order function or two-value function may be used. On the basis of the above-mentioned explanation, the flow of the embodiment will be described. The above-mentioned weight is determined by inputting the electrostatic capacity assumed by using the antenna toner remained amount detection into the function of the weight stored in the image forming apparatus. After the weighting is determined, in accordance with the determined value, the following two remained amount detections are effected, and the printable number of sheets is calculated by using the assumed value of the toner remained amount calculated by the respective detections and the weighting and the above-mentioned equation. [Antenna toner amount detection means] When the weighting = 1: Since the value of the antenna toner remained amount detection is not used, the calculation is not effected. When the weighting ≠ 1: The printable number of sheet is calculated in the manner described in connection with the first embodiment. [Total laser emitting time detection means] When 0 < weighting ≤ 1: The present printable number of sheets is calculated in the following manner whenever the sheet is printed. (1) On the basis of the toner amount used up to now sought by the total laser emitting time and the present print number of sheets, the past average use ratio of toner is calculated by using the following equation: (past average use ratio of toner) = (toner amount used up to now) ÷ (present print number of sheets) (2) On the basis of the present toner amount and the past average use ratio of toner, the present printable number of sheets is calculated by using the following equation: (present printable number of sheets) = (present toner amount)/(past average use ratio of toner). When the weighting = 0: The detection is not effected. As mentioned above, by the remained amount of toner is detected by the combination of the total laser emitting time detection and the antenna toner remained amount detection, it is possible to seek the present printable number of sheets from the initial condition of the cartridge. In the illustrated embodiment, while an example that only the total laser emitting time detection is used as an auxiliary means until the electrostatic capacity can be detected was explained, another means such as a sheet number detecting means may be used or two or more kinds of toner remained amount detecting means may be used. Incidentally, the process cartridge in the aforementioned examples and embodiment may incorporate therein an electrophotographic photosensitive member, and a charge means, a developing means or a cleaning means as a cartridge unit which can detachably mounted to the main body of the image forming apparatus, or may incorporate therein an electrophotographic photosensitive member, and at least one of a charge means, a developing means and a cleaning means as a cartridge unit which can detachably mounted to the main body of the image forming apparatus, or may incorporate therein an electrophotographic photosensitive member and at least a developing means as a cartridge unit which can detachably mounted to the main body of the image forming apparatus. Alternatively, the cartridge may be a developer cartridge including only a toner hopper and a developer drum, or may be a replacement toner hopper only. The electrophotographic image forming apparatus is of type using electrophotographic process and capable of forming an image on a recording medium and may include an electrophotographic copying machine, an electrophotographic printer (laser printer, LED printer and the like) and an electrophotographic facsimile. As mentioned above, according to the present invention, since the non-volatile memory means for memorizing the information regarding the print number of sheets and the remained amount of toner is provided on the process cartridge and such information can be read out and re-written by the image forming apparatus, the correct present remained amount of toner of each cartridge can be detected and the image forming apparatus to which such a process cartridge can be mounted can be provided. Further, since the image forming apparatus includes the means for counting the print number of sheets, means for storing the information regarding the relation between the toner remained amount and the electrostatic capacity, means for determining the present remained amount of toner on the basis of the relation between the toner remained amount and the electrostatic capacity stored in the memory means and the detected value of the toner remained amount detecting member, means for calculating the difference between the initial toner amount and the present toner amount and the average toner reduction ratio up to now (based on the present toner amount), and means for calculating the printable number of sheets on the basis of the present toner amount and the average toner reduction ratio, the user can easily know the present printable number of sheets. Further, since the image forming apparatus includes the means for calculating the number of usable days on the basis of the present printable number of sheets and the past average print number of sheets, the user can know the number of usable days in the future. In addition to the antenna as the detection member for detecting the toner remained amount, the second toner remained amount detecting means is also provided so that, when the value of the electrostatic capacity measured by the antenna is constant, the toner remained amount is detected only by using the value sought by the second toner remained amount detecting means, and, from when the value of the electrostatic capacity measured by the antenna is changed, the toner remained amount is detected only by using the value sought by the antenna. With this arrangement, the toner remained amount in the initial condition of the cartridge (which is hard to be detected by the antenna) can be detected by the second toner remained amount detecting means, and, from when the value of the electrostatic capacity is changed, the toner remained amount can be detected by the antenna with high accuracy. By weighting the values obtained by the antenna and the second means, the detection value can smoothly be translated from one of two means to the other.

Claims: An image forming apparatus for use with a detachable cartridge (CRG) having a hopper (5d) for containing a developer and a memory means (15) adapted to store information corresponding to a light emitting time period of a light emitting means (7) detected by a light emitting time detecting means (21) and to an amount of developer in said hopper (5d) detected by a developer amount detecting means (1), said image forming apparatus comprising: an image bearer member (3); said light emitting means (7) for illuminating said image bearer member with light in accordance with image information; said developer amount detecting means (1) for detecting information corresponding to an amount of developer in said hopper; developing means (5) for developing a latent image formed on said image bearer member; said light emitting time detecting means (21) for detecting information corresponding to a light emitting time period of said light emitting means (7); and process means (18) adapted to retrieve the information stored in the memory means (15) and to obtain information corresponding to a developer remaining amount in said hopper in accordance with the information detected by said developer amount detecting means (1) and the information detected by said light emitting time detecting means (21). An image forming apparatus according to claim 1, wherein said process means is adapted to obtain a developer remaining amount on the basis of the information detected by said light emitting time detecting means until the information according to the amount of developer detected by said developer amount detecting means reaches a predetermined value, and said process means is adapted to obtain a developer remaining amount on the basis of the information detected by said developer amount detecting means and the information detected by said light emitting time detecting means after the information according to the amount of developer detected by said developer amount detecting means reaches the predetermined value. An image forming apparatus according to claim 2, wherein said process means (18) is adapted to obtain a developer remaining amount on the basis of information obtained by weighting the information detected by said developer amount detecting means (1) and information obtained by weighting the information detected by said light emitting time detecting means (21) after the information according to the amount of developer detected by said developer amount detecting means reaches the predetermined value. An image forming apparatus according to any one of claims 1 to 3, wherein said process means (18) is adapted to calculate the number of printable sheets on the basis of the obtained developer remaining amount. An image forming apparatus according to any one of claims 1 to 4, wherein said developing means has a developer supply member (5a) for feeding developer to said image bearer member (3), and wherein the information detected by said developer amount detecting means (1) is a value corresponding to capacitance between said developer supply member and said developer amount detecting means. An image forming apparatus according to any one of claims 1 to 5, wherein said light emitting means is adapted to emit a laser light to said image bearer member to form a latent image, and wherein the information detected by said light emitting time detecting means (21) is time information corresponding to a time period for emitting the laser light. A cartridge (CRG) detachably mountable to an image forming apparatus including an image bearer member (3), a light emitting means (7) for illuminating said image bearer member with light in accordance with image information, a developer amount detecting means (1) for detecting information according to an amount of developer in a developer hopper, a light emitting time detecting means (21) for detecting a light emitting time period of said light emitting means, and a developing means (5) for developing a latent image on said image bearer member formed by exposing said image bearer member to the light emitted by said light emitting means in accordance with the image information, said cartridge comprising: said developer hopper (5d) for containing a developer; and a memory means (15) having a first memory address adapted to store information corresponding to a light emitting time period of said light emitting means (7) and a second memory address adapted to store information corresponding to an amount of developer in said hopper (5d) detected by said developer amount detecting means (1). A cartridge (CRG) according to claim 7, wherein said light emitting means (7) emits a laser light to said image bearer member to form a latent image, and wherein the information corresponding to the light emitting time period of said light emitting means (7) is time information corresponding to a time period for emitting the laser light. A cartridge according to claim 7 or claim 8, wherein said developing means has a developer supply member (5a) for feeding developer to said image bearer member, and wherein the information corresponding to the amount of developer in said hopper (5d) detected by said developer amount detecting means (1) is a value corresponding to capacitance between said developer supply member and said developer amount detecting means. A cartridge according to any one of claims 7 to 9, further comprising said developing means (5). A cartridge according to claim 10, further comprising said image bearer member (3). A memory device to be mounted on a process cartridge, a developer cartridge, or a replacement toner hopper usable with a main body of an image forming apparatus, the image forming apparatus including an image bearer member (3), a developing means (5) for developing a latent image on said image bearer member formed by exposing said image bearer member to light emitted by a light emitting means (7) in accordance with image information, a developer amount detecting means (1) for detecting an amount of developer in said developing means, and a light emitting time detecting means (21) for detecting a. light emitting time period of said light emitting means, said memory device comprising: a first memory address adapted to store information corresponding to the light emitting time period of said light emitting means (7) detected by said light emitting time detecting means (21); and a second memory address adapted to store information corresponding to the amount of developer detected by said developer amount detecting means (1). A memory device according to claim 12, wherein said light emitting means (7) is adapted to emit a laser light to said image bearer member (3) to form a latent image, and wherein the information corresponding to the light emitting time period of said light emitting means is time information corresponding to a time period for emitting the laser light. A memory device according to claim 12 or claim 13, wherein said developing means has a developer supply member (5a) for feeding developer to said image bearer member (3), and wherein the information corresponding to the amount of developer in said developing means detected by said developer amount detecting means (1) is a value corresponding to capacitance between said developer supply member and said developer amount detecting means.

Inventors: MATSUMOTO HIDEKI, OKANO KEIJI, YAMAGUCHI SEIJI, MATSUMOTO, HIDEKI, OKANO, KEIJI, YAMAGUCHI, SEIJI
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1997
Main classification: G03G21
IPC codes: G03G21, G03G15