JP5560634B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that arranges a uniform distribution state of a developer in a developing device at startup as early as possible.

  2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses include a type using a one-component developer (toner) and a type using a two-component developer. Since the method using a single component developer is relatively easy to handle and control, a single component toner has been dominant as a developer.

  However, as demand for faster printing (hereinafter also referred to as printing) increases in recent years, a method using a two-component developer can better cope with faster printing processing. Various developing devices (or developing devices) using a developer have been proposed.

  Such a two-component developer is composed of a toner and a carrier. The carrier is mixed and stirred together with the toner by the stirring and conveying member in the developing device. As a result, the toner is given a predetermined charge due to frictional charging. The charged toner temporarily adheres to the surface of the carrier and coats the surface of the carrier.

  The carrier is attracted to a magnetic developing roller and carries charged toner onto the photoreceptor. An electrostatic latent image is formed on the photoreceptor, and toner is transferred to the electrostatic latent image, and the toner image is developed on the electrostatic latent image.

  The carrier that has released the toner on the surface remains on the developing roller, returns to the inside of the developing device, is mixed and stirred again with new toner, charges the toner, and transports the toner onto the photoreceptor. Is done.

  In such a developing method using a two-component developer, in order to maintain a constant toner concentration with respect to the carrier of the developer, new toner is replenished into the developing device according to the amount of toner consumed.

  In recent years, a toner having a small particle diameter has been used to improve the image quality of images. As the toner particle size is reduced, the carrier particle size is reduced. As described above, when a toner having a small particle diameter and a carrier having a small particle diameter are used, an image with high image quality can be formed.

  However, a developer composed of toner or carrier having a reduced particle size has lower fluidity than a developer before the particle size is reduced. Therefore, once deviation occurs in the developer distribution in the developing unit, it becomes difficult to obtain a normal distribution state, which adversely affects the control of image unevenness, carrier flow out of the developing unit, toner density, etc. There was a bug.

  In order to cope with such problems, the temperature detection means provided in the developing device detects the temperature from the time of manufacture of the developing device to the transportation and storage environment to the user, and by this detected temperature history information, There has been proposed a process cartridge that changes the stirring time of a toner stirring member in a toner hopper of a process cartridge mounted on an image forming apparatus (see, for example, Patent Document 1).

  Similarly, in order to suppress the occurrence of abnormal images such as ring marks and point-like defects caused by an irregular distribution of developer, the humidity sensor is checked before printing to check whether the humidity is higher than a predetermined value. If the humidity is higher than a predetermined value, the developing device driving motor is driven for a predetermined time, and the developer is stirred for a predetermined time. On the other hand, a control method has been proposed in which a normal printing operation is performed immediately when the humidity is equal to or lower than a predetermined value (see, for example, Patent Document 2).

  In addition, in order to improve a developing operation failure caused by a deviation in developer distribution, etc., when there is a low-use developer having a driving amount accompanying a developing operation of a predetermined value or less, the deviation in developer distribution should be equalized. In addition, it is proposed that the low-use developer is idly driven for a predetermined time, and the developer replenishing mechanism is idly driven based on the measurement result of the replenishment driving amount of the developer replenishing mechanism (for example, Patent Document 3). reference).

JP 2003-263022 A JP-A-11-305528 JP 2008-233718 A

  By the way, the prior art of Patent Document 1 performs very time-consuming and time-consuming control of detecting the temperature from the time of manufacture of the developing device to the transportation and storage environment to the user by the temperature detection means. In particular, in order to detect the temperature from the time of manufacture of the developing device to the transportation and storage environment to the user, it is indispensable to dispose a built-in power source that drives the temperature detecting means for a long period of time, and there is a problem in economical efficiency.

  The prior art of Patent Document 2 tries to correct the irregular distribution of the developer in the developing device only by checking the humidity. However, the irregular distribution of the developer is not limited to being caused only by the humidity. An irregular distribution of the developer in the developing device also occurs due to the backlash of the entire apparatus due to replacement of the developer cartridge or the developing device itself.

  Assuming that the humidity is below a predetermined value, if printing is performed without stirring the developer for a certain period of time (developing the developer, that is, rotating the stirring member forward), the occurrence of abnormal images is suppressed. The problem that cannot be done is left.

  In addition, the prior art of Patent Document 3 improves the bias of the developer distribution that tends to occur when the developing device and the developer replenishment mechanism are low in use. There is a problem that the distribution cannot be dealt with when the distribution is not limited only by the low use of the developing device and the developer supply mechanism.

In order to solve the above-described problems, an image forming apparatus according to the present invention is provided in the developing device in an image forming apparatus including a developing device that develops an electrostatic latent image formed on an electrostatic latent image carrier. A developing section having a developing opening, a developer circulation path formed in the development section, a developer stirring and conveying screw disposed in the developer circulating path, and a driving torque of the developer stirring and conveying screw A torque detection unit that detects the torque, a torque value storage unit that stores the value of the driving torque detected by the torque detection unit, and a control unit that controls the driving of the developing device, The driving torque value at the time of power-on detected by the torque detection unit at the time of power-on is compared with the driving torque value at the time of the final printing stored in the torque storage unit at the time of the last final printing, and the driving at the time of the final printing than the torque value If towards the driving torque value at the time of serial power-on is large continues to rotate before the developer stirring and conveying Sukuryuu while detection by the torque detecting unit, the driving torque value which the torque detection unit detects said final printing When the driving torque value at the time of the final printing stored in the torque storage unit becomes less than the time, the pre-rotation is ended and the printing execution standby state is entered. If there is no change between the driving torque value at power-on or the driving torque value at power-on is smaller than the driving torque value at the time of final printing , the pre-rotation is immediately terminated. It is configured to enter a print execution standby state.

  In the image forming apparatus, the developing device is, for example, a two-component developing device. In addition, for example, the developer circulation path is divided into at least two paths having communication paths, the developer agitation transport screw is disposed in each of the divided paths, and the torque detection unit is configured to be the developer agitation transport. It is provided in any one drive part of a screw. Further, for example, the developing device is provided for each color of the developer.

  The present invention shortens the time for the pre-rotation of the developer agitating and conveying screw at the start-up, that is, the idle drive time of the developer as much as possible. There is an effect that it is possible to provide an image forming apparatus capable of entering a state.

1 is a schematic side sectional view schematically showing an internal configuration of a color image forming apparatus according to Embodiment 1 of the present invention. 1 is a block diagram illustrating a circuit configuration of a control system of a color image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is an enlarged view showing a detailed configuration of only the image forming unit of the color image forming apparatus according to Embodiment 1 of the present invention. (a), (b) is a figure which shows typically the detailed structure of the outside developer circulation path in the developing part of the color image forming apparatus concerning Example 1 of the present invention, and its developer stirring conveyance screw. (a) is a diagram showing a state in which a developer whose distribution is uniformed in the developer circulation path is being stirred and transported, and (b) is a developer whose shape is not yet uniform before stirring or during stirring and transporting. It is a figure which shows a state. 5 is a flowchart showing a pre-rotation control processing operation for shortening the pre-rotation time as much as possible in the color image forming apparatus according to Embodiment 1 of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail. In the following description, the electrostatic latent image carrier is composed of, for example, a photosensitive drum 7, the developing device is composed of, for example, a developing kit 15, and the torque storage unit is, for example, an EEPROM (electrically erasable programmable ROM) 34. The control unit includes a control system 30 and the like, for example.

  FIG. 1 is a schematic cross-sectional side view schematically showing the internal configuration of the image forming apparatus according to the first embodiment. The figure shows a tandem color image forming apparatus as an example.

  A color image forming apparatus 1 shown in FIG. 1 is a small color image forming apparatus having a size that can be placed on, for example, a desktop personal computer rack. A paper cassette 2 is detachably attached to the bottom of a main body base. I have. A large number of sheets 3 are placed and stored in the sheet cassette 2.

  An intermediate transfer belt 4 is arranged in a flat loop shape in the front and rear directions at substantially the center inside the color image forming apparatus 1. The intermediate transfer belt 4 is looped around the driving roller 5 and the driven roller 6 and circulates in the counterclockwise direction indicated by the arrow A in the figure. In the upper circulation portion of the intermediate transfer belt 4, four photosensitive drums 7 (7c, 7m, 7y, 7k) are arranged in a multistage manner from the upstream side to the downstream side in the image transport direction (from the right to the left in the figure). It is installed.

  Each of the photosensitive drums 7 is surrounded by a peripheral surface (hereinafter, only a peripheral device around the photosensitive drum 7k is representatively shown), and a cleaner 8, a charging roller 9, optical writing A head 11, a developing roller 13 of the image forming unit 12, and a primary transfer roller 14 are disposed. The developing roller 13 is a magnet roller.

  The four optical writing heads 11 are supported by the image forming apparatus main body frame via a support member (not shown). Further, the intermediate transfer belt 4, the driving roller 5, the driven roller 6, the primary transfer roller 14 and the like constitute a belt unit together with tension rollers 17 and 18 described later.

  From the image forming unit 12 corresponding to the photoconductive drum 7c to the image forming unit 12 corresponding to the photoconductive drum 7k, in the toner container 16 of the developing kit 15 of each image forming unit 12, cyan (which is a subtractive primary color, cyan ( c), magenta (m) and yellow (y) toners, and black (k) toner dedicated to printing of black portions of characters and images, respectively.

  In FIG. 1, the intermediate transfer belt 4 is always urged outward by a tension roller 17 that is in pressure contact with the back surface of the downstream end portion and a tension roller 18 that is in pressure contact with the back surface of the upstream end portion to maintain an appropriate tension. The intermediate transfer belt 4 transfers the toner image directly to the belt surface (primary transfer), and conveys the toner image to a transfer position to the paper for further transfer (secondary transfer) to the paper.

  The driven roller 6 disposed at the upstream end of the intermediate transfer belt 4 serves as a tension holding roller of the intermediate transfer belt 4 and a counter roller of the secondary transfer unit, and is driven as the counter roller. A secondary transfer roller 19 that is pressed and rotated via the intermediate transfer belt 4 is disposed opposite to the roller 6, and the secondary transfer unit 20 is driven by the driven roller 6, the intermediate transfer belt 4, and the secondary transfer roller 19. Is forming.

  Further, a paper take-out roller 21, a feeding roller 22, and a separating roller 23 are disposed in the vicinity of the sheet feeding opening (right side in the drawing) of the sheet cassette 2. A standby roller pair 24 is arranged in the middle of the sheet conveyance path up to the point.

  A belt-type fixing device 25 is disposed on the downstream side (upward in the drawing) of the secondary transfer unit 20. On the further downstream side of the belt-type fixing device 25, a pair of unillustrated unloading rollers for unloading the fixed paper from the belt-type fixing device 25, and a paper discharge tray 26 on which the unloaded paper is formed on the upper surface of the device. A paper discharge roller pair 27 that discharges the paper is disposed.

  As shown in FIG. 1, the color image forming apparatus 1 does not directly transfer a toner image onto a conventional sheet, but intermediate transfer is performed on a sheet that is conveyed vertically to a secondary transfer unit 20 by a pair of standby rollers 24. The toner image is transferred via the belt 4.

  Therefore, it is possible to cope with a maintenance process for recovering from a problem such as a paper jam occurring in the paper transport path by simply opening the right side of FIG.

  Since troubles such as paper jam do not occur in the arrangement section of the kits such as the image forming unit 12, the operation of attaching / detaching consumables such as the kits concentrated on the left side of FIG. It is configured so that a small space is sufficient for the replacement operation.

  Thereby, the dimension between each kit is reduced as much as possible, and size reduction of the whole apparatus main body is achieved. Further, the optical writing head 11 itself is also miniaturized and is configured to be closer to the photosensitive drum 7.

  FIG. 2 is a block diagram showing a circuit configuration of a control system in the color image forming apparatus 1 having the above configuration. As shown in the figure, in the control system 30, an I / F (interface) controller unit 32 and a head controller unit 33 are connected to the printer controller unit 31 via a data bus, with a printer controller unit 31 at the center. ing.

  Further, an EEPROM (electrically erasable programmable ROM) 34 and a ROM (read only memory) 35 are connected to the printer controller 31 via other data buses, and further, the high voltage unit 36, each motor via each signal line. A unit 37, a torque detection unit 38, a density sensor 39, a registration sensor 41, a toner sensor (CMYK) 42, and a temperature / humidity sensor 43 are connected.

  Further, an operation panel 44 (not shown in FIG. 1) is connected to the I / F controller unit 32. The I / F controller unit 32 includes a frame memory 45 having an image development area divided into four.

  Further, the head controller unit 33 includes optical writing heads 11 (11c, 11m, 11y, 11k) arranged to face the respective photosensitive drums 7 (7c, 7m, 7y, 7k) shown in FIG. It is connected.

  The printer controller unit 31 monitors and outputs output signals sent from each unit of the high-pressure unit 36 to the temperature / humidity sensor 43 while driving and controlling each unit based on the control program read from the ROM 43. Accordingly, the data is stored in the EEPROM 34 and saved.

  The I / F controller unit 32 receives print data RGB signals (or CMYK signals) downloaded via the Internet or sent from a host device (PC: personal computer) (not shown), and an image in the print data. The data is developed in the image development areas K, C, M, and Y divided into four in the frame memory 45 for each color.

  Then, the developed image data is output to the head controller unit 33, and the command in the print data is output to the printer controller unit 31. The printer controller unit 31 drives and controls each unit based on the above-described control program and the above commands.

  The head controller unit 33 controls each optical writing head 11 (11c, 11m, 11y, 11k) based on the image-developed image data transmitted from the I / F controller unit 32, and each photosensitive drum. 7 (7c, 7m, 7y, 7k), the respective electrostatic latent images are formed.

  The high-voltage unit 36 includes a plus or minus high-voltage power source that supplies a predetermined bias voltage to the charging roller 9, the developing roller 13, the primary transfer roller 14, the secondary transfer roller 19, and the like under the control of the printer controller unit 31. ing.

  Each motor unit 37 is controlled by the printer controller unit 31 under the control of the photosensitive drum 7, the driving roller 5, the paper take-out roller 21, the feeding roller 22, the separating roller 23, the standby roller pair 24, and the belt-type fixing device 25. The rotation timing of the drive source motor of the drive system connected to each drive gear such as the paper discharge roller pair 27 is controlled.

  As will be described in detail later, the torque detector 38 detects the rotational torque of the developer agitating and conveying screw disposed in the developer circulation path of the developing device, and sends a signal indicating the detected rotational torque information to the printer controller 31. Output.

  Although not shown in FIG. 1, the density sensor 39 is disposed at an appropriate location close to the surface of the intermediate transfer belt 4, and has a predetermined pattern formed on the intermediate transfer belt 4 as necessary. The density of the toner image is detected, and a signal indicating the detected density information is output to the printer controller unit 31.

  The registration sensor 41 detects the state of the leading edge of the sheet 3 fed from the sheet cassette 2 and entering the gripping portion of the standby roller pair 24 to detect whether the conveyance posture of the sheet 3 is correct. If the conveyance timing information after skew correction is not satisfied, the paper jam information is output to the printer controller 31.

  The toner sensor (CMYK) 42, which will be described in detail later, is disposed at the bottom of the developing unit of each image forming unit 12, and detects the toner concentration (mixing ratio of carrier and toner) in the developing unit, and the detected toner A signal indicating density information is output to the printer controller 31.

  The temperature / humidity sensor 43 is disposed at an appropriate location of the color image recording apparatus 1. The temperature / humidity sensor 43 detects the temperature / humidity inside the color image recording apparatus 1, and outputs a signal indicating the detected temperature / humidity to the printer controller 31.

  FIG. 3 is an enlarged view showing the detailed configuration of only the image forming unit 12 of the color image forming apparatus 1 having the above configuration. As shown in FIG. 1, the photosensitive drum 7 and the primary transfer roller 14 shown in FIG. 1 are also arranged to face each other with the intermediate transfer belt 4 interposed therebetween, and the front side of the drawing between the photosensitive drum 7 and the intermediate transfer belt 4 is shown. A primary transfer portion 50 is formed by a contact line to the far side.

  Further, a developing unit 46 is formed below the toner container 16 in the developing kit 15 of the image forming unit 12. The developing unit 46 has a developing opening 47, and the developing roller 13 is provided in the developing opening 47.

  Below the developing roller 13, two developer circulation paths 49 (49 a, 49 b) partitioned by a partition wall 48 are formed in two rows parallel to the axis of the developing roller 13 and horizontally. The toner sensor 42 described above is disposed at the bottom of the developer circulation path 49a on the outer side.

  In these two developer circulation paths 49 (49a, 49b), a predetermined amount of carrier is accommodated in advance, and toner is mixed into the carrier to constitute a developer. That is, the developing kit 15 of this example is a two-component developing device.

  Developer stirring and conveying screws 51 (51a and 51b) are disposed in the two developer circulation paths 49, respectively. The toner replenished from the toner container 16 to the developing unit 46 is first replenished to the developer circulation path 49a at a position far from the developing roller 13, that is, out of the two.

  Next, the operation of the color image forming apparatus 1 of this example having the above configuration will be briefly described. First, an image formation instruction is input from the operation panel 44 of FIG. 2, or print data downloaded via the Internet or sent from a host device (PC) is input.

  Therefore, the printer controller unit 31 starts driving control of the I / F controller unit 32 and the head controller unit 33, and on the one hand starts driving control of the high voltage unit 36 and each motor unit 37, and on the other hand, the torque detecting unit 38 is turned on. Monitor the output of each sensor.

  As a result, first, each photoconductor drum 7 is rotationally driven by each motor unit 37, and the surface of the photoconductor drum 7 uniformly cleaned by the cleaner 8 is uniformly initialized by the high-pressure unit 36 and the charging roller 9. Charged.

  The head controller unit 33 drives the optical writing heads 11 to emit light based on the image-developed print data transmitted from the I / F controller unit 32, and causes the photosensitive drums 7 of the image forming units 12 to respectively emit light. An electrostatic latent image corresponding to is formed.

  On the other hand, in the developing kit 15 of the image forming unit 12, toner is replenished from the toner container 16 to the developer circulation path 49 a outside the developing unit 46 as necessary based on the toner density detection information of the toner sensor 42.

  The developer agitating / conveying screw 51a in the developer circulation path 49a makes the developer a uniform distribution state without unevenness in the horizontal direction while agitating and conveying the developer. From the communicating path (sending port) formed at the end of the other side) to the adjacent developer circulation path 49b.

  The developer agitating / conveying screw 49b in the developer circulation path 49b removes the developer fed into the developer circulation path 49b from the outlet of the partition wall 51 (the front side in the depth direction of FIG. 3). The developer is supplied to the rotating peripheral surface of the developing roller 13 while agitating and conveying the developer to the communication path (return port) formed on the side end), and the supplied remaining developer is supplied from the return port. It is sent back to the developer circulation path 49a.

  The developing roller 13 supplied with toner from the developer agitating / conveying screw 49b in the developer circulation path 49b removes the developer toner from the photosensitive drum by a potential difference from the photosensitive drum 7 due to a bias voltage applied from the high voltage unit 36. 7 is transferred to an electrostatic latent image on the peripheral surface 7 to form a toner image (development).

  The toner image developed on the photosensitive drum 7 is rotated and conveyed to the primary transfer unit 50 as the photosensitive drum 7 rotates. In the primary transfer unit 50, the toner image on the photosensitive drum 7 is primarily transferred as an image image to the intermediate transfer belt 4 by a bias voltage applied to the primary transfer roller 14 from the high voltage unit 36.

  On the intermediate transfer belt 4, toner images of the respective color image images are sequentially transferred from the four photosensitive drums 7 c, 7 m, 7 y, and 7 k to form a full-color toner image. The full-color toner image primarily transferred to the intermediate transfer belt 4 is conveyed to the secondary transfer unit 20 by the circulating movement of the intermediate transfer belt 4.

  Prior to this, the sheet take-out roller 21, the feeding roller 22, and the separating roller 23 are driven by the drive control of each motor unit 37, and the sheets 3 are taken out from the sheet cassette 2 one by one. The leading end is stopped by the standby roller pair 24 and waits for the delivery timing.

  Then, at the timing when the leading edge of the first toner image primarily transferred to the intermediate transfer belt 4 is conveyed to the secondary transfer unit 20, the top of the image forming area of the sheet 3 corresponds to the secondary transfer unit 20. As described above, the waiting sheet 3 is sent out from the waiting roller pair 24.

  The full-color toner image is transferred from the intermediate transfer belt 4 by the bias voltage applied from the high voltage unit 36 to the secondary transfer roller 19 in the secondary transfer unit 20 on the paper 3 sent out from the standby roller pair 24.

  The sheet 3 on which the toner image is transferred passes through the belt-type fixing device 25, fixes the toner image on the sheet surface, is carried out by the discharge roller pair 27, and is sequentially stacked on the discharge tray 26.

  4A and 4B show the developer circulation path 49a of the developing section 46 in the developing kit 15 and the developer stirring and conveying screw 51a in the image forming unit 12 of the color image forming apparatus 1 operating as described above. It is a figure which shows typically a detailed structure.

  4A and 4B are views of the inside of the developer circulation path 49a in the direction of arrow C in FIG. 4 (a) and 4 (b), the same components as in FIG. 3 are given the same numbers as in FIG.

  As shown in FIG. 4A, in the developer circulation path 49a partitioned by the partition wall 48 from the developer circulation path 49b shown in FIG. Further, a developer stirring and conveying screw 51a composed of the fins 53 is provided.

  As shown in FIG. 4B, the drive unit 54 is engaged with one end (the right end in the figure) of the rotating shaft 52. The drive unit 54 is provided with the torque detection unit 38 shown in FIG. The drive unit 54 or the torque detection unit 38 is provided on any one of the rotation shafts or drive units of the two developer agitating / conveying screws 51a or 51b.

  The torque detection unit 38 shown in FIG. 4B constantly detects the drive torque when the drive unit 54 rotationally drives the developer agitating / conveying screw 51 a and notifies the printer controller unit 31 of the control system 30.

  The printer controller 31 stores the value of the drive torque immediately before the end of printing notified from the torque detector 38 at the time of final printing in the EEPROM 34 as the driving torque value at the time of final printing.

  In addition, the printer controller unit 31 uses the driving torque notified from the torque detection unit 38 as the driving torque at power-on when the developing unit 46 is rotated forward (i.e., idling without development). Each time it is notified from the detection unit 38, it is compared with the driving torque at the time of final printing, and based on the comparison result, the duration of the pre-rotation is controlled as will be described in detail later.

  The developer stirring and conveying screw 51a has a fin-shaped change point 55 at one end (the right end in FIGS. 4A and 4B and the other side in the depth direction in FIG. 3). Has been.

  The positions corresponding to the fin-shaped change points 55 of the partition wall 48 are not shown in FIGS. 4A and 4B, but the distribution is made uniform from the developer circulation path 49a to the developer circulation path 49b. A communication path is formed as a delivery port for delivering the developer.

  In addition, an end 56 opposite to the fin-shaped change point 55 of the partition wall 48 is not shown in FIGS. 4A and 4B, but from the developer circulation path 49b. A communication path is formed as a return port for returning the developer mixed with the carrier having a changed toner density to the circulation path 49a.

  FIG. 5 (a) shows a state in which the developer 57 having a uniform distribution is being stirred and conveyed in the developer circulation path 49a, and FIG. 5 (b) is still in the state before or during stirring. The state of the developer 57 having a non-uniform distribution is shown.

  The state shown in FIG. 5 (a) is a state where printing is in progress or immediately after the pre-rotation at the start of printing is sufficiently performed, and development is performed from the developer circulation path 49a with a uniform distribution. When the developer 57 is sent to the developer circulation path 49b, the developer 57 is adsorbed to the developing roller 13 as a uniform layer from the developer circulation path 49b, and the photosensitive drum 7 can be developed without unevenness. And a high-quality image can be formed on the paper 3.

  On the other hand, the state of FIG. 5B is a state in which the developer 57 is filled with the developer 57 at the time of shipment from the factory, and the distribution of the developer 57 becomes non-uniform due to rattling of the device during transportation or unpacking. Alternatively, the image forming unit 12, the developing kit 15, the toner container 16, and the like are replaced, and the apparatus has rattled and the distribution of the developer 57 becomes non-uniform.

  When printing is started in the state shown in FIG. 5B, the developer 57 having a non-uniform distribution is sent from the developer circulation path 49a to the developer circulation path 49b. The amount of the developer 57 adsorbed on the developing roller 13 is uneven, and the toner image developed on the photosensitive drum 7 has a density or other problems.

  In order to prevent this problem, a preparatory operation called pre-rotation (or also referred to as idle driving) has been conventionally performed in order to obtain a developer 57 having a uniform distribution as shown in FIG. It was mentioned before.

  And the problem of economics required to eliminate the non-uniform state, the problem of insufficient countermeasures depending only on the humidity to eliminate the non-uniform state, and other non-uniform states limited only to low use cannot be dealt with As described above, there are many problems left in the conventional method such as problems.

  In the developing unit 46 of this example, even if the developer 57 is unevenly distributed in any of the above states, the uniform distribution state of the developer 57 due to the pre-rotation of the developer stirring and conveying screw 51a at the time of start-up is quickly adjusted. Thus, the pre-rotation time is shortened as much as possible so that the print standby state can be entered at an early stage.

  FIG. 6 is a flowchart showing the processing operation of the pre-rotation control by the printer controller unit 31 of the control system 30 of this example for shortening the pre-rotation time as much as possible. In this process, the driving torque value at the time of final printing, which is detected by the torque detection unit 38 at the time of final printing described above and stored in the EEPROM 34, is used as data for determination.

  First, when the color image recording apparatus 1 is powered on or when the door of the main body apparatus is opened or closed for maintenance or the like, the I / F controller unit 32 starts a pre-rotation (step S1). This process is a process in which the developer stirring and conveying screw 51a is rotationally driven by the drive unit 54.

  Next, the printer controller unit 31 calls the torque value t1 at the time of final printing (step S2). In this process, the cyan (c), magenta (m), yellow (y) and black (k) developers are stored in the EEPROM 34 corresponding to the developing sections 46 of the four developing kits 15. The drive torque values Ct1, Mt1, Yt1, and Kt1 at the time of final printing are read by the printer controller unit 31.

  Subsequently, the printer controller unit 31 measures the current torque value t2 (step S3). In this process, the current drive torque values Ct2, Mt2, Yt2, and Kt2 notified from the torque detection unit 38 of the developing unit 46 of each developing kit 15 are referred to.

  Then, the printer controller unit 31 individually compares the drive torque values Ct1, Mt1, Yt1, and Kt1 at the time of final printing with the current drive torque values Ct2, Mt2, Yt2, and Kt2 (step S4).

  In this comparison processing, the printer controller unit 31 determines that the current drive torque value t2 is larger than the drive torque value t1 at the time of final printing, that is, if “t1 <t2”, at least one of CMYK. It is determined that the distribution of 57 is biased, and the pre-rotation is continued in order to make the distribution uniform (step S5).

  Then, the printer controller unit 31 returns to the process of step S3, and again refers to the current drive torque values Ct2, Mt2, Yt2, and Kt2 notified from the torque detection unit 38 of the developing unit 46 of each developing kit 15. In step S4, the four drive torque values t1 at the time of final printing and the current four drive torque values t2 are individually compared.

  If it is determined in step S4 that the current drive torque value t2 is equal to or less than the drive torque value t1 at the time of final printing, that is, “t1 ≧ t2” in all CMYK, the printer controller unit 31 determines that the developer 57 Judge that the distribution is uniform.

  The current drive torque values Ct2, Mt2, Yt2, and Kt2 are stored in the EEPROM 34 as the drive torque values Ct1, Mt1, Yt1, and Kt1 at the time of final printing (step S6). Then, the pre-rotation process is finished (step S7).

  The developing kit 15 of this example is a two-component developing device, and as soon as the toner concentration decreases, the toner is replenished from the toner container 16 to the developer circulation path 49a and mixed with the carrier having the same total amount. The position of the upper surface of the uniformized developer 57 toner in the developer circulation path 49a hardly changes.

  Therefore, the current drive torque value t2 hardly fluctuates until the end of printing. This is the reason why the current drive torque value t2 after the distribution is made uniform is stored in the EEPROM 34 as the drive torque value t1 at the time of final printing.

  Even when “t1 ≧ t2” is determined in the first step S4 of the above processing operation, the processes of steps S6 and S7 are immediately performed. As a result, the pre-rotation time is significantly shortened or the print standby state is entered with almost no pre-rotation.

  Thereafter, when a print start instruction is input together with print data from the operation panel 44, via the Internet, or from a host device (PC: personal computer) (not shown), the printer controller unit 31 executes print processing.

  in this way. According to the present embodiment, even when the developer distribution is uneven from any state, there is no problem of economic efficiency, there is no problem of insufficient countermeasures depending only on humidity, and the case of low use It is not possible to deal with other non-uniformity conditions limited to only, and the uniform distribution state of the developer can be adjusted early by simply referring to the torque value of the pre-rotation of the developer agitating and conveying screw at the start-up. Can do.

  As a result, it is possible to provide a color image recording apparatus capable of shortening the pre-rotation time as much as possible and entering the print standby state at an early stage.

  The present invention can be used in an image forming apparatus that arranges a uniform distribution state of a developer in a developing device at the time of startup as early as possible.

DESCRIPTION OF SYMBOLS 1 Color image forming apparatus 2 Paper cassette 3 Paper 4 Intermediate transfer belt 5 Drive roller 6 Driven roller (transfer opposing roller)
7 (7c, 7m, 7y, 7k) Photosensitive drum 8 Cleaner 9 Charging roller 11 (11c, 11m, 11y, 11k) Optical writing head 12 Image forming unit 13 Developing roller 14 Primary transfer roller 15 Developing kit 16 Toner container 17 , 18 Tension roller 19 Secondary transfer roller (transfer press roller)
DESCRIPTION OF SYMBOLS 20 Secondary transfer part 21 Paper extraction roller 22 Feeding roller 23 Rolling roller 24 Waiting roller pair 25 Belt type fixing device 26 Paper discharge tray 27 Paper discharge roller pair 30 Control system 31 Printer controller part 32 I / F (interface) controller part 33 Head controller 34 EEPROM (electrically erasable programable ROM)
35 ROM (read only memory)
36 High Voltage Unit 37 Each Motor Unit 38 Torque Detection Unit 39 Density Sensor 41 Registration Sensor 42 Toner Sensor (CMYK)
43 Temperature / Humidity Sensor 44 Operation Panel 45 Frame Memory 46 Developing Portion 47 Developing Opening 48 Bulkhead 49 (49a, 49b) Developer Circulating Path 50 Primary Transfer Portion 51 (51a, 51b) Developer Stirring Transport Screw 52 Rotating Shaft 53 Fin 54 Driving part 55 Change point of fin shape 56 End part 57 Developer

Claims (4)

In an image forming apparatus provided with a developing device for developing an electrostatic latent image formed on an electrostatic latent image carrier,
A developing unit provided in the developing device and having a developing opening;
A developer circulation path formed in the developing section;
A developer stirring and conveying screw disposed in the developer circulation path;
A torque detector for detecting a driving torque of the developer agitating and conveying screw;
A torque value storage unit for storing the value of the driving torque detected by the torque detection unit;
A control unit for controlling driving of the developing device;
Have
The controller is
Compare the driving torque value at the time of power-on detected by the torque detection unit at the time of power-on and the driving torque value at the time of final printing stored in the torque storage unit at the time of the last final printing,
When the driving torque value at the time of turning on the power is larger than the driving torque value at the time of the final printing, the developer agitating / conveying screw continues to rotate forward while performing detection by the torque detecting unit , and the torque detecting unit When the driving torque value detected by the motor becomes equal to or less than the driving torque value at the time of final printing stored in the torque storage unit at the time of the final printing, the pre-rotation is terminated and a printing execution standby state is entered.
When there is no variation between the driving torque value at the time of the final printing and the driving torque value at the time of turning on the power in the comparison , or the driving torque value at the time of turning on the power than the driving torque value at the time of the final printing If is smaller , immediately terminate the previous rotation and enter a print execution standby state.
An image forming apparatus.   The image forming apparatus according to claim 1, wherein the developing device is a two-component developing device.   The developer circulation path is divided into at least two paths having a communication path, the developer agitation transport screw is disposed in each of the divided paths, and the torque detection unit is one of the developer agitation transport screws. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided in the one drive unit.   The image forming apparatus according to claim 1, wherein the developing device is provided for each color of the developer.