JP2005128150A - Service life detecting device for image carrier and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a service life detecting device for an image carrier for carrying out detection of service life at high precision without being influenced by operation environment and aging of a drum, and to provide an image forming apparatus using the device. <P>SOLUTION: The service life detecting device for the image carrier in the image forming apparatus is constituted so that the wear value W of a photoreceptor drum (the image carrier) 114 is calculated by using W=K×Pt+α×Dt (wherein Pt is electrification application time, Dt is drum rotation time, K is a coefficient determined according to a discharge current value and α is an appropriate constant value). The service life of the image carrier is determined on the basis of the integrated value S of the wear value W. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image carrier lifetime detection device used in electrophotographic technology, and an image forming apparatus using the lifetime detection device.

  In an image forming apparatus using an electrophotographic technology, the surface of an image carrier is uniformly charged to a predetermined potential, and then a laser beam is irradiated to create a potential difference between an irradiated portion and a non-irradiated portion. It is well known that there is a step of developing by attaching a).

  In the above process, a drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) is generally used as an image carrier.

  Conventionally, corona charging, which is a non-contact charging method, has generally been used as a charging means for charging a photosensitive drum. However, in recent years, a contact charging method that is advantageous in terms of low-pressure process, low ozone generation, low cost, etc. Is becoming mainstream. In the contact charging method, for example, a roller-shaped charging member (hereinafter referred to as a charging roller) is brought into contact with the surface of the photosensitive drum, and a voltage is applied to the charging roller to charge the photosensitive drum.

  When the image forming apparatus repeats printing, the photosensitive drum is worn. This is because, in addition to the above-described charging roller, the cleaning device for removing the residual toner on the photosensitive drum and the recording paper on which the image is transferred are repeatedly contacted.

  On the other hand, the photosensitive drum is greatly related to the image quality in the electrophotographic image forming apparatus. Therefore, it is extremely important to accurately detect the life of the photosensitive drum.

As a photosensitive drum life detection device,
(1). A drum rotation detector is provided to measure the number of rotations of the photosensitive drum and notify the life when the accumulated number of rotations reaches a predetermined number of rotations.
(2). Counts the number of prints and notifies the life when the total number of prints reaches a predetermined number.
(3). Measures the film thickness of the photosensitive material on the surface of the photosensitive drum, and reports the life when the film pressure is below a predetermined value (film pressure measures the amount of current flowing by applying an AC bias to the photosensitive drum. To calculate.)
These have been widely used conventionally (for example, refer to Patent Document 1).

  However, in the case of (1), since the relationship between the time during which the charging voltage is actually applied to the photosensitive drum and the rotational speed of the photosensitive drum is not constant, the life detection accuracy is not good. In (2), the charging time per sheet varies depending on the paper size, and the charging time per sheet varies depending on how many sheets are printed in one job. There wasn't. In addition, the items listed in (3) are greatly affected by environmental conditions and manufacturing variations (variations between lots) of charging rollers and photosensitive drums, and it is difficult to accurately detect the life.

  As a device that solves the problems of these life detection devices and detects the life more accurately, a device that calculates the drum wear value W from both the charging application time and the drum rotation time and detects the life by the integrated value is proposed. Has been.

  In this apparatus, the drum consumption value W is calculated by the following equation.

W = Pt + α × Dt (Formula 1)
Here, Pt is a charging application time, Dt is a drum rotation time, and α is an appropriate constant.
The value obtained by integrating the drum consumption value W calculated by Equation 1 is recorded in the nonvolatile memory as the integrated consumption value S, and the life of the photosensitive drum is reached when the integrated consumption value S exceeds a predetermined value. Notify that you have reached.

  Further, a method for calculating the drum consumption value W by the following equation 2 instead of the equation 1 has been proposed.

W = M × Pt + α × Dt (Formula 2)
Here, M is a coefficient corresponding to a current value flowing into the charging roller from the high voltage generation circuit (hereinafter referred to as a total charging current value). A plurality of candidate values are predetermined for M, and are selected from the candidate values according to the total charging current value.

  In general, in a process on a photosensitive drum, a required voltage in a region where a latent image is not formed (hereinafter referred to as a non-image region) is lower than a required voltage in a region where a latent image is formed (hereinafter referred to as an image region). For the purpose of extending the life of the drum, there are cases where control is performed to keep the discharge current in the non-image area low. In some cases, control is performed to change the discharge current according to variations in the pressure roller, such as differences between manufacturers.

  Even in such a case, the lifetime can be detected with higher accuracy by calculating the drum consumption value W by Equation 2.

  Further, in selecting the coefficient M, parameters other than the total charging current such as the charging frequency can be included in the conditions.

For example, when printing on paper such as thick paper, there is a case where control is performed such that the process speed is lowered and the charging frequency is lowered accordingly. Since it is known that there is a difference in the consumption of the photosensitive drum depending on the charging frequency even if the discharge current value is the same, in such a case, by adding the charging frequency to the selection condition of the coefficient M, a more precise lifetime can be obtained. It can be detected.
JP-A-1-66669

  However, in the method of calculating the drum consumption value W by the above-described equation 2, the coefficient M is determined based on the total charging current value, and therefore the accuracy is deteriorated due to the use environment and the influence of the change with time of the drum. was there.

  Hereinafter, this problem will be described with reference to FIG.

  In the figure, 1201 is a high voltage generating circuit, 1202 is a capacitive load generated between the charging roller and the photosensitive drum, and 1203 is a discharge path between the charging roller and the photosensitive drum.

  The charging total current value It is the sum of the actual discharge current Is and the capacitive load current Ic. The discharge current Is has an influence on the deterioration of the photosensitive drum. When the discharge current Is increases, the deterioration of the photosensitive drum is accelerated and the life is shortened. However, there is a difference between the total charging current value It and the deterioration of the photosensitive drum. There is no direct relationship (see JP-A-9-190144).

  On the other hand, the relationship between the total charge current value It and the discharge current value Is is not always constant, and varies depending on the film thickness of the photosensitive layer and dielectric layer of the photosensitive drum, and the environmental conditions of the charging member and air.

  For example, in a high-temperature and high-humidity environment, discharge is more likely to occur than in a low-temperature and low-humidity environment, so that the ratio of the discharge current value Is to the charging total current value It is increased.

  Further, since the film pressure of the photosensitive drum becomes thinner as the use is repeated, the capacitive load increases in the photosensitive drum having a long usage time, and as a result, the ratio of the discharge current value Is to the total charging current value It decreases. .

  As described above, the conventional method has a problem that the accuracy is deteriorated due to the use environment and the influence of change over time.

  The present invention has been made under such circumstances, and is a life detection device for an image carrier capable of performing life detection with higher accuracy without being affected by the use environment or changes in the drum over time. Another object of the present invention is to provide an image forming apparatus using this apparatus.

  In order to solve the above-mentioned problems, in the present invention, the image carrier lifetime detecting device is configured as described in the following (1) to (5), and the image forming device is configured as described in the following (6) to (9). Constitute.

(1) A device for detecting the lifetime of an image carrier in an image forming apparatus,
First computing means for computing a wear value W of the image carrier;
Second calculation means for calculating the cumulative consumption value S by integrating the consumption values W calculated by the first calculation means;
Storage means for storing the cumulative consumption value S calculated by the second calculation means;
Determination means for determining the life of the image carrier based on the accumulated consumption value S stored in the storage means;
With
The first calculation means calculates the wear value W by a function using K as a coefficient, and the coefficient K is calculated from a plurality of candidate values of the coefficient K stored in the storage means in advance. An apparatus for detecting a lifetime of an image carrier, wherein a discharge current value discharged to the image carrier is selected as at least one condition.

(2) In the image carrier life detecting device according to (1),
The storage means stores in advance a prescribed lifetime value Z of the image carrier, and the determining means compares the cumulative consumption value S with the prescribed lifetime value Z to determine the lifetime of the image carrier. A device for detecting the life of an image carrier to be determined.

(3) In the image carrier life detecting device according to (1) or (2),
The coefficient K is a life detection device for an image carrier selected from a plurality of candidate values of the coefficient K according to a plurality of conditions including the discharge current value and the charging frequency.

(4) In the image carrier life detecting device according to any one of (1) to (3),
The first calculating means is a life detecting device for an image carrier that calculates the consumption value W by a function of the coefficient K and a time Pt during which a voltage is applied to the image carrier.

(5) In the image carrier life detecting device according to (4),
The first calculating means calculates the wear value W,
W = K × Pt + α × Dt
Where K is a coefficient selected from the plurality of candidate values, Pt is a time during which a voltage is applied to the image carrier, α is an appropriate coefficient, and Dt is a time during which the image carrier is driven. Image carrier life detection device that calculates based on.

  (6) An image forming apparatus for detecting the lifetime of the image carrier using the image carrier lifetime detector according to any one of (1) to (5).

(7) In the image forming apparatus according to (6),
An image forming apparatus in which a process cartridge including at least the image carrier and the storage unit is configured to be detachable from an apparatus main body.

(8) In the image forming apparatus according to (6) or (7),
An image forming apparatus comprising warning means for warning the user of the life of the image carrier.

(9) In the image forming apparatus according to (8),
The storage means stores in advance at least one life warning value Y having a value smaller than the specified life value Z, and compares the accumulated wear value S with the life warning value Y to compare the accumulated wear value. An image forming apparatus that warns a user by the warning means when S is larger.

  According to the present invention, there is provided an image carrier life detection device capable of performing life detection with higher accuracy without being affected by a use environment, a drum change with time, and the like, and an image forming apparatus using the device. can do.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  An “image forming apparatus” that is Embodiment 1 will be described.

  In FIG. 1, reference numeral 101 denotes an electrophotographic laser beam printer which is an image forming apparatus of this embodiment.

  102 is a deck, 103 is a deck sheet presence sensor, 104 is a sheet size detection sensor that detects the size of a recording sheet, 105 is a pickup roller, 106 is a deck feeding roller, 107 is a retard roller, and 108 is a feeding roller. 109, feeding roller pair, 110 a registration roller pair, 111 a pre-registration sensor, 112 a laser scanner unit, 113 a process cartridge, 114 a photosensitive drum, 115 a charging roller, 116 a developer, 117 Is a transfer roller, 118 is a static elimination needle, 119 is a conveyance guide, 120 is a fixing roller, 121 is a first halogen heater, 122 is a pressure roller, 123 is a second halogen heater, 124 is a fixing discharge sensor, and 125 is a double-sided roller. Flapper, 126 is a paper discharge sensor, 127 is a pair of paper discharge rollers, and 128 is a reverse low Pair, 129 is a reversal sensor, 130 is a D-cut roller, 131 is a duplex sensor, 132 is a duplex transport roller pair, 133 is a laser unit, 134 is a polygon mirror, 135 is a scanner motor, 136 is an imaging lens group, and 137 is a return. Mirror 138, main motor 139 high voltage power supply, 140 printer controller, 141 display panel, 142 external device, 143 MPU, 144 interface, 145 storage device, P recording sheet.

  The laser beam printer 101 has a deck 102 for storing the recording sheet P, a deck sheet presence sensor 103 for detecting the presence of the recording sheet P in the deck 102, and a sheet for detecting the size of the recording sheet P in the deck 102. The recording sheet P is paired with a size detection sensor 104, a pickup roller 105 that feeds the recording sheet P from the deck 102, a deck feeding roller 106 that transports the recording sheet P fed by the pickup roller 105, and the deck feeding roller 106. A retard roller 107 for preventing double feeding of P is provided.

  A feed sensor 108 that detects a feeding / conveying state is provided downstream of the deck feeding roller 106 in the sheet conveying direction (hereinafter simply referred to as “downstream”), and a feeding conveyance for conveying the recording sheet P further downstream. A roller 109, a registration roller pair 110 that conveys the recording sheet P in synchronization with the image forming operation, and a pre-registration sensor 111 that detects the conveyance state of the recording sheet P to the registration roller pair 110 are provided.

  Downstream of the registration roller pair 110, a process cartridge 113 constituting an image forming unit that forms a toner image on the photosensitive drum 114 based on laser light from a laser scanner unit 112, which will be described later, is attached to the apparatus main body. It is detachably attached.

  The process cartridge 113 is provided with a rotatable photosensitive drum 114, a charging roller 115 and a developing device 116 around the photosensitive drum 114, and a cleaning device (not shown). The latent image is uniformly charged and selectively exposed from the laser scanner unit 112 to form a latent image. The latent image is developed with toner by the developing device 116 to be visualized.

  Further, the process cartridge 113 is provided with a nonvolatile storage element 145, and a printer control unit 140 described later can write information into the storage element 145 in addition to reading information from the storage element 145.

  Then, by applying a transfer bias voltage to the transfer roller 117, the toner image is transferred to the conveyed recording sheet P to form an image.

  Disposed downstream of the transfer roller 117 are a static elimination needle 118 and a conveyance guide 119 for removing charges on the recording paper P and promoting separation from the photosensitive drum 114.

  Further downstream of the conveyance guide 119, in order to thermally fix the toner image transferred onto the recording paper P, a fixing roller 120 provided with a first halogen heater 121 for heating inside, and also for heating inside the same. The pressure roller 122 provided with the second halogen heater 123, the fixing paper discharge sensor 124 for detecting the conveyance state from the fixing unit, and the recording paper P conveyed from the fixing unit to the paper discharge unit or the double-side reversing unit A double-sided flapper 125 for switching between the paper discharge unit and the paper discharge sensor 126 that detects the paper conveyance state of the paper discharge unit and a paper discharge roller pair 127 that discharges the recording paper are disposed downstream of the paper discharge unit. It is arranged.

  On the other hand, in order to print on both sides of the recording paper P, the recording paper P after one-side printing is reversed, and the recording paper P is fed to the double-side reversing part side for feeding again to the image forming part by forward and reverse. The recording paper P is transported from a pair of reversing rollers 128 for switching back, a reversing sensor 129 for detecting a paper transporting state to the reversing rollers 128, and a lateral registration portion (not shown) for aligning the lateral position of the recording paper P. A D-cut roller 130 for detecting the recording paper P in the double-side reversing unit, and a double-sided conveying roller pair 132 for conveying the recording paper P from the double-side reversing unit to the paper feeding unit. Yes.

  The laser scanner unit 112 scans the photosensitive drum 114 with a laser unit 133 that emits a laser beam modulated based on an image signal transmitted from an external device 142, which will be described later, and the laser beam from the laser unit 133. A polygon mirror 134, a scanner motor 135, an imaging lens group 136, and a folding mirror 137. The main motor 138 supplies power to each part.

  In addition to the charging roller 115, the high-voltage power supply 139 has a high-voltage circuit that supplies a desired voltage to the developing device 116, the transfer roller 117, and the charge removal needle 118.

  A circuit for supplying power to the charging roller 115 in the high-voltage power supply 139 (hereinafter referred to as a charging high-voltage circuit) is a structure largely related to the present invention, and will be described later with reference to FIG.

  The printer control unit 140 controls the laser printer 101, and includes an MPU (microcomputer) 143 having a RAM, a ROM, a timer, a digital input / output port (all not shown), and various input / output control circuits. (Not shown).

  The display panel 141 displays the status of the laser beam printer 101 and conveys information to the user.

  The printer control unit 140 is connected to an external device 142 such as a personal computer via an interface 144.

  FIG. 2 shows a charging high voltage circuit.

  In the figure, 201 is an MPU in the printer control unit 140, 202 is RAM, 203 is ROM, 204 is a timer, 205 is an I / O port, 206 is a D / A port, 207 is an A / D port, 208 to 242 Is a resistor, 243 to 254 are capacitors, 255 to 259 are diodes, 260 to 264 are transistors, 265 to 269 are operational amplifiers, 270 is a Zener diode, 271 is a high voltage transformer, 272 is a filter circuit, 273 is a high voltage transformer drive circuit, 274 Is a DC high voltage generating circuit, and 275 is an output terminal.

  The charging output circuit generates a charging high voltage in which the AC high voltage is superimposed on the DC high voltage, and outputs it from the output terminal 275. The output terminal 275 is connected to the charging roller 115 in contact with the photosensitive drum 114. When a clock pulse (PRICLK) is output from the I / O port 205 of the MPU 201, the transistor 263 performs a switching operation via a resistor 229 for pull-up and a base resistor 228, and a resistor 227 for pull-up and a diode The signal is amplified to a clock pulse having an amplitude corresponding to the output of the operational amplifier 267 connected via H.259. When this amplitude is large, the drive voltage amplitude of a sine wave input to the high voltage transformer 271 described later also increases, and as a result, the high voltage AC voltage level also increases. The amplified clock pulse is input to a filter circuit 272 including resistors 216 to 226, capacitors 244 to 249, and operational amplifiers 265 and 266 via a capacitor 249. The filter circuit 272 outputs a sine wave centered on + 12V. Is output.

  This output is amplified by a push-pull high-voltage transformer drive circuit 273 and input to the primary winding of the high-voltage transformer 271 via the capacitor 254, and a sine AC high voltage is generated on the secondary winding side. One side of the secondary side of the high voltage transformer 271 is connected to the DC high voltage generation circuit 274 via the resistor 238, and a high voltage bias in which AC high voltage is superimposed on the DC high voltage is output from the output terminal 275 via the output protection resistor 208. Is output and supplied to the charging roller 115.

  Next, the current detection unit of the AC high voltage circuit will be described. The AC current generated by driving the AC high-voltage generating circuit passes through the capacitor 251, and the half wave in the arrow A direction flows through the diode 255 and the half wave in the arrow B direction flows through the diode 256. The half wave in the direction of arrow A that has passed through the diode 255 is input to an integrating circuit composed of an operational amplifier 268, a resistor 233, and a capacitor 252, and is converted into a DC voltage. The output terminal voltage V1 of the operational amplifier 268 has the following characteristics.

V1 = − (Rs × Imean) + Vt (Formula 3)
Here, Imean is the average value of the half wave of the alternating current, Rs is the resistance value of the resistor 233, and Vt is the voltage input to the positive input of the operational amplifier 268. The output of the operational amplifier 268 is connected to the positive input of the operational amplifier 267 and compared with the level of the current control signal PRICNT connected to the negative input. The current control signal PRICNT is a signal for setting an alternating current level. Here, when the output voltage V1 of the operational amplifier 268 is larger than the current control signal PRICNT, the output of the operational amplifier 267 becomes large. As described above, when the output of the operational amplifier 267 increases, the amplitude of the clock pulse input to the filter circuit 272 increases and the high-voltage AC voltage increases. With this configuration, the level of the high-voltage AC voltage is controlled so that the AC current has a value corresponding to the current control signal PRICNT. That is, constant current control according to the current control signal PRICNT is performed.

  Next, the voltage detection unit of the charging output circuit will be described. The voltage detection circuit detects a peak voltage of the charging AC voltage. The charged output is divided by the capacitor 243, the resistor 210, and the resistor 211, and only the AC component is converted to a low voltage level and input to the positive input of the operational amplifier 269. Here, the capacitance value of the capacitor 243 is set so that the impedance value is sufficiently smaller than the total impedance of the resistor 210 and the resistor 211. Further, the operational amplifier 269 is driven by both positive and negative power supplies, and can be input with positive / negative bipolar voltage at the input terminal and can output positive / negative bipolar voltage at the output terminal. . The converted AC voltage further passes through a voltage follower circuit constituted by an operational amplifier 269, and is converted into a DC voltage corresponding to the peak value of the charged AC voltage by a peak hold circuit constituted by a diode 258, a capacitor 253, and a resistor 242. Then, it is input to the analog input terminal 207 of the MPU 143 (detection signal name: PRIVS).

  The level of the detection signal: PRIVS can be expressed by the following equation where the peak value of the charging AC voltage is Vp and the forward voltage value of the diode 258 is Vf.

PRIVS = λ × Vp−Vf (Formula 4)
Here, λ is a value determined by the resistors 210 and 211 and the capacitor 243 and can be approximated by the following equation.

  In the above formula, R210 represents the resistance value of the resistor 210, and R211 represents the resistance value of the resistor 211 (hereinafter, expressed in a similar manner).

  The frequency of the charging alternating current (hereinafter referred to as charging frequency) depends on the frequency of the clock pulse (PRICLK). In this embodiment, the charging frequency during normal printing is 2000 Hz, but in the low-speed mode described later, the charging frequency is lowered to 1600 Hz.

  Next, FIG. 3 shows a sequence during the printing operation of the image forming apparatus in the present embodiment. When the main power supply of the laser beam printer 101 is turned on, a pre-multi-rotation process is performed in which a series of processes such as driving the fixing device and raising the fixing device to a predetermined temperature is performed, and then a standby state is entered. Next, when a print start command is received from an external device 142 such as an external personal computer, a pre-rotation process, which is a predetermined print preparation stage, is executed, and then a printing operation is performed on the recording sheet P through a series of electrophotographic processes. Enter the printing process. Here, in the mode in which a plurality of printing operations are executed, a predetermined process is executed in the inter-sheet process until the printing operation for the next recording sheet is performed, and then the second and subsequent printing processes are performed. Move. When the printing process for the last recording paper is completed, the printer returns to the standby state after the post-rotation process.

  The image forming apparatus according to the present embodiment is in a low-speed mode in which the printing process speed is increased to 0.8 times the normal speed when printing on cardboard or the like for the purpose of securing fixing properties.

  Next, a charging high voltage control method performed during the printing operation in the image forming apparatus according to the present exemplary embodiment will be described. In this embodiment, the discharge current Is is estimated from the total charging current value and the charging voltage value in the pre-rotation process and the printing process, and the charging high voltage control is performed so that the discharge current Is becomes a desired value. This method is called a “discharge current control method” and is known in Japanese Patent Laid-Open No. 2001-201921.

  FIG. 4A shows the characteristics of the charging total current value and the charging AC voltage peak value when a charging AC high voltage is applied to the charging roller 115. FIG. 4 (b) shows the characteristics of the voltage detection signal PRIVS and the current control signal PRICNT corresponding to FIG. 4 (a). The total charging current is an alternating current. In the figure, Vh is a voltage at which the discharge phenomenon starts. LINE-A is a characteristic line in a non-discharge generation region where no discharge occurs, and LINE-B is a characteristic line in a discharge generation region where discharge occurs. The difference between the two lines is the discharge current Is. A1, A2, B1, and B2 indicate points to be detected.

  In the charging control in this embodiment, the characteristic equations of LINE-A and LINE-B are calculated from the voltage detection signal PRIVS and the current control signal PRICNT at the points A1, A2, B1, and B2, and further from the two characteristic equations. A charging current value at which the level of the discharge current Is becomes a predetermined value is calculated, and a charging AC high voltage level at the time of printing is determined.

  FIG. 5 shows a flow chart of a series of charging control for determining the charging AC high voltage level. First, the charging DC circuit is driven in step 502 (denoted as S502 in the figure, the same applies hereinafter), a predetermined DC bias is applied to the charging roller 115, and then the characteristics of LINE-A are calculated in steps 503 to 508.

(1) Calculation of LINE-A LINE-A is a line in a non-discharge generation region. The characteristics of this line are calculated by sampling points A1 and A2 in the non-discharge generation region in FIG. 4B. First, after setting the level of the charging current control signal PRICNT to Vc1 (step 503), the AC voltage is applied to the charging roller 115 by switching the charging AC ON signal PRION to the LOW level. (Step 504) Then, the voltage detection signal PRIVS at that time is detected and sampling of the point A1 is performed (step 505). PRIVS at this time is set to Vt1. Subsequently, after the level of the charging current control signal PRICNT is switched to Vc2 (step 506), the voltage detection signal PRIVS is detected and sampling at point A2 is performed (step 507). PRIVS at this time is set to Vt2. In step 508, the LINE-A characteristic formula: y = fa (x) is calculated from the points A1 and A2 in the non-discharge generation region detected by the above method. The characteristic equation is obtained by approximating the following equation using A and B as constants.

y = fa (x) = A × x + B (Formula 6)
(2) Calculation of LINE-B Subsequently, in steps 509 to 513, LINE-B is calculated. LINE-B is a line in the discharge generation region. The characteristics of this line are calculated by sampling points B1 and B2 in the discharge generation region in FIG. First, the level of the charging current control signal PRICNT is switched to Vc3 (step 509), the voltage detection signal PRIVS at that time is detected, and sampling at point B1 is performed. The PRIVS level at this time is set to Vt3 (step 510). Subsequently, after the level of the charging current control signal PRICNT is switched to Vc4 (step 511), the voltage detection signal PRIVS is detected and sampling at point B2 is performed. PRIVS at this time is set to Vt4 (step 512). In step 513, the LINE-B characteristic formula: y = fb (x) is calculated from the two points B1, B2 and B2 in the discharge generation region detected by the above method. The characteristic equation is obtained by approximating the following equation using C and D as constants.

y = fb (x) = C × x + D (Expression 7)
(3) Calculation of Charging Current Control Value Subsequently, at step 514, the level of the charging current control signal PRICNT at which the discharge current level becomes a predetermined value: Vc (cnt) is calculated.

  The discharge current corresponds to the difference between LINE-B and LINE-A. In FIG. 4A, when the target control value of the discharge current is Is, the target discharge current level can be obtained by controlling the charging current value to Ic (cnt). Therefore, the level Vc (cnt) of the charging current control signal PRICNT can be calculated by using the two characteristic formulas calculated by the above method, y = fa (x) and y = fb (x). When the level width of the charging current control value PRICNT corresponding to the target control value Is of the discharge current is J, the value Vt (cnt) of the voltage detection value PRIVS that becomes the target control value Is is represented by the following equations (6) and (7). become that way

  Therefore, Vc (cnt) can be expressed by the following equation according to Equation 7.

(4) Setting of charging current level Subsequently, the charging current control signal PRICNT is set to the value of Vc (cnt) calculated by Equation 9 (step 515), and a series of processing is terminated (step 516).

  Through the series of processes described above, the discharge current Is can be set to a desired value.

Next, a life detecting device for the photosensitive drum 114 used in this embodiment will be described. The consumption value W of the photosensitive drum 114 is
W = K × Pt + α × Dt (Expression 10)
Calculated by Here, Pt is the charging application time, Dt is the drum rotation time, K is a coefficient determined according to the discharge current value, and α is an appropriate constant.

The value of K is determined according to the value of the discharge current Is and the charging frequency fs with reference to the table 1 stored in advance in the storage element 145. That is, the coefficient K is selected from at least two or more candidate value groups K ₁ , K ₂ ,... K _n stored in advance in the storage element 145, using the discharge current value Is as at least one condition. . Table 1 in this embodiment is shown in FIG.

  The integrated value of the consumption value W is stored in the recording element 145 as the integrated consumption value S. The recording element 145 also stores in advance a life limit value Z that defines the life of the photosensitive drum.

  FIG. 7 shows a flowchart showing the operation of the life detection apparatus used in this embodiment.

  The printer control unit 140 starts detecting the life of the photosensitive drum 114 at a predetermined timing such as when starting a printing operation (step 701). When the life detection is started, the printer control unit 140 reads the accumulated wear value S and the life specified value Z in addition to the table 1 for determining the value of K from the storage element 145 (step 702). Then, the accumulated consumption value S is compared with the life specified value Z (step 703). If S is larger than Z, it is determined that the photosensitive drum 114 has reached the end of its life, notifies the display panel 141 of the main body to that effect and warns the user, and prohibits the printing operation of the main body (step 705). . When S is smaller than Z, the printer control unit 140 continues the operation of the main body. When a voltage is applied to the photosensitive drum 114 or when the photosensitive drum 114 is driven, the printer control unit 140 calculates the consumption value W according to Equation 10 at a predetermined opportunity or sequentially (step 704), and the accumulated consumption value S. Is updated (step 706). The accumulated wear value S is updated by adding the wear value W to the value Sold before the wear value W is measured. Further, the accumulated consumption value S and the life limit value Z are compared at a predetermined timing, for example, immediately after the printing operation is completed (step 707). If S is greater than Z, it is determined that the photosensitive drum 114 has reached the end of its life, notifies the display panel 141 of the main body to that effect, warns the user, and prohibits the printing operation of the main body (step 708). . If S is smaller than Z, the printer control unit 140 updates the accumulated consumption value S stored in the storage element 145 and ends (step 710).

  Note that, when LINE-A and LINE-B are calculated (during pre-rotation), life detection and wear value W integration are performed as described above.

  In this embodiment, the discharge current Is is controlled so as to have different values in the printing process and the inter-sheet process. For image formation, it is necessary to uniformly charge the surface of the photosensitive drum 114. For this reason, a constant discharge current value is required. However, as the discharge current value increases, the consumption of the photosensitive drum 114 increases. For this reason, in order to extend the life of the photosensitive drum 114, the discharge current value is set lower in the inter-sheet process than in the printing process. However, if the discharge current value in the inter-sheet process is too low, an image printed in the subsequent printing process is adversely affected. Therefore, the discharge current value in the inter-sheet process needs to ensure a certain value or more. In addition, when printing on both sides of the recording sheet P, the gap between the sheets becomes longer, so the discharge current value in the gap process is set lower than that during single-sided printing. The set value of the discharge current in each of the above modes is shown in FIG.

  In this embodiment, the life of the photosensitive drum 114 is detected with the above-described configuration. Conventionally, the consumption value W is calculated according to the value of the charging total current It, that is, according to the value of the charging current control signal PRICNT. However, in this embodiment, the consumption value W is calculated according to the value of the discharge current Is. Because of the calculation, the error due to environmental conditions is smaller than the conventional method, and the life can be detected with higher accuracy.

  Note that a life warning value Y smaller than the life limit value Z may be set, and a warning may be displayed when the accumulated wear value S exceeds the life warning value Y. With this configuration, the user can know that the photosensitive drum has reached the end of its life, and can prepare an alternative cartridge before actually reaching the end of its life.

  Next, an “image forming apparatus” that is Embodiment 2 will be described with reference to FIGS. The hardware configuration of the present embodiment is the same as that of the first embodiment, but the control method of the charging high voltage circuit is different. The charging high-voltage circuit according to the first embodiment controls the discharge current to be a desired current, whereas in this embodiment, the charging total current is controlled to a desired value. Therefore, the description of the first embodiment is used for the hardware configuration, and the control method of the charging high voltage circuit will be described.

  FIG. 9 shows the set value of the total charge current value according to the printing mode in this embodiment. The charging current control signal PRICNT corresponding to the charging total current setting value in each mode is determined in advance, and the printer controller 140 outputs an appropriate charging current control signal PRICNT in each mode, so that a desired charging current and In this configuration, a charging voltage can be obtained.

  FIG. 10 is a flowchart showing the operation of the life detection apparatus used in this embodiment.

The printer control unit 140 calculates the characteristics of LINE-A and LINE-B at a predetermined timing such as a pre-multi-rotation process or a pre-rotation process (step 1102). Each characteristic is the same as in Example 1,
fa (x) = A × x + B (Formula 11)
fb (x) = C × x + D (Expression 12)
Is approximated by a linear expression.
The calculation method is the same as in the first embodiment.

Next, the life of the photosensitive drum 114 is determined at a predetermined timing such as when the printing operation is started. In addition to the table 2 for determining the value of K from the storage element 145, the printer control unit 140 reads the integrated wear value S and the specified life value Z (step 1103). FIG. 11 shows the table 2. Then, the accumulated consumption value S and the specified life value Z are compared (step 1104). If S is larger than Z, it is determined that the photosensitive drum 114 has reached the end of its life, notifies the device panel 141 of the main body to that effect and warns the user, and prohibits the printing operation of the main body (step 1105). . When S is smaller than Z, the printer control unit 140 continues the operation of the main body. When a voltage is applied to the photosensitive drum 114 or when the photosensitive drum 114 is driven, the printer control unit 140 sequentially calculates the discharge current Is from the characteristics of LINE-A and LINE-B calculated in step 1102. The calculation formula is
Is = fb (Vx) −fa (Vx) (Equation 13)
However, Vx is the value of the voltage detection signal PRIVS at that time.

  Further, the consumption value W is calculated from the discharge current Is obtained in step 1106 and the table 2 read in step 1103 (step 1107), and the integrated consumption value S is updated (step 1108). The accumulated wear value S is updated by adding the wear value W to the value Sold before the wear value W is measured. Further, the accumulated consumption value S and the specified life value Z are compared at a predetermined timing, for example, immediately after the printing operation is completed (step 1109). If S is greater than Z, it is determined that the photosensitive drum 114 has reached the end of its life, notifies the display panel 141 of the main body and notifies the user, and prohibits the printing operation of the main body (step 1111). . If S is smaller than Z, the printer control unit 140 updates the accumulated consumption value S stored in the storage element 145 (step 1110), and ends (step 1112).

  In the present embodiment, it has been shown that by detecting the life of the photosensitive drum 114 with the above-described configuration, it is possible to detect the life with high accuracy by the discharge current Is even when the discharge control is not performed.

  As in the first embodiment, a life warning value Y smaller than the life specified value Z may be set, and a warning may be displayed when the accumulated wear value S exceeds the life warning value Y. Needless to say.

The figure which shows the whole structure of Example 1. FIG. Circuit diagram of the charging high-voltage circuit The figure which shows the sequence of the image forming device The figure which shows the relationship between charging total current value and charging AC voltage peak value, and the relationship between the voltage detection signal PRIVS and the current control signal PRICNT. A flowchart showing an operation for obtaining a charging current control signal at which the discharge current level becomes a predetermined value. Figure showing table 1 The flowchart which shows operation | movement of the lifetime detection apparatus used in Example 1. FIG. The figure which shows the setting value of the discharge current in each mode The figure which shows the setting value of the charging total current value of Example 2 The flowchart which shows operation | movement of the lifetime detection apparatus used in Example 2. FIG. Figure showing table 2 The figure explaining the problem of the conventional example

Explanation of symbols

113 Process Cartridge 114 Photosensitive Drum 115 Charging Roller 139 High Voltage Power Supply 140 Printer Control Unit 145 Storage Element 201 MPU

Claims (9)

An image carrier life detection device in an image forming apparatus,
First computing means for computing a wear value W of the image carrier;
Second calculation means for calculating the cumulative consumption value S by integrating the consumption values W calculated by the first calculation means;
Storage means for storing the cumulative consumption value S calculated by the second calculation means;
Determination means for determining the life of the image carrier based on the accumulated consumption value S stored in the storage means;
With
The first calculation means calculates the wear value W by a function using K as a coefficient, and the coefficient K is calculated from a plurality of candidate values of the coefficient K stored in the storage means in advance. An apparatus for detecting a lifetime of an image carrier, wherein a discharge current value discharged to the image carrier is selected as at least one condition. In the image carrier life detecting device according to claim 1,
The storage means stores in advance a prescribed lifetime value Z of the image carrier, and the determining means compares the cumulative consumption value S with the prescribed lifetime value Z to determine the lifetime of the image carrier. An apparatus for detecting a life of an image carrier characterized by comprising: In the lifetime detection apparatus of the image carrier of Claim 1 or 2,
The lifetime detection device for an image carrier, wherein the coefficient K is selected from a plurality of candidate values of the coefficient K according to a plurality of conditions including the discharge current value and the charging frequency. In the lifetime detection apparatus of the image carrier in any one of Claims 1 thru | or 3,
The life detecting device for an image carrier, wherein the first computing means computes the wear value W by a function of the coefficient K and a time Pt during which a voltage is applied to the image carrier. In the lifetime detection apparatus of the image carrier according to claim 4,
The first calculating means calculates the wear value W,
W = K × Pt + α × Dt
Where K is a coefficient selected from the plurality of candidate values, Pt is a time during which a voltage is applied to the image carrier, α is an appropriate coefficient, and Dt is a time during which the image carrier is driven. An apparatus for detecting the life of an image carrier, characterized in that the calculation is performed based on the above.   6. An image forming apparatus, wherein the life of the image carrier is detected by using the image carrier life detecting device according to claim 1. The image forming apparatus according to claim 6.
An image forming apparatus, wherein a process cartridge including at least the image carrier and the storage unit is configured to be detachable from the apparatus main body. The image forming apparatus according to claim 6 or 7,
An image forming apparatus comprising warning means for warning the user of the life of the image carrier. The image forming apparatus according to claim 8.
The storage means stores in advance at least one life warning value Y having a value smaller than the specified life value Z, and compares the accumulated wear value S with the life warning value Y to compare the accumulated wear value. An image forming apparatus characterized in that a warning is given to a user by the warning means when S is larger.

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