JP2010091601A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for stably making a developing roller rotate, without significantly damaging the silence properties. <P>SOLUTION: This image forming apparatus includes a photoreceptor for forming an electrostatic latent image; a developing section for supplying toner to the photoreceptor via the developing roller and developing the electrostatic latent image; a developing motor for driving the developing roller; a determining means for determining whether the developing roller is in a high load state or in a non-high load state; and a drive control means for controlling the operation of the developing motor. The drive control means sets an input current Id to the developing motor, to a larger value (for example, Id=I53(>I50)), when the developing roller is determined in a high-load state than when the developing roller is determined in the non-high load state, and supplies the toner to the photoreceptor, by making the developing roller rotate by drive of the developing motor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer and an MFP (Multi Function Peripheral).

  For example, in an electrophotographic image forming apparatus, after an electrostatic latent image is formed on a photoconductor, toner is supplied to the photoconductor so that the electrostatic latent image becomes visible (development) as a toner image. ) The toner image is directly or indirectly transferred to the printing paper, thereby drawing a desired image on the printing paper.

  In such an image forming apparatus, toner is supplied to the photosensitive member by the developing roller. For example, in a four-cycle image forming apparatus, each developing roller provided in each of the four color developing units sequentially faces the photosensitive member, and the toner in each developing unit is supplied to the photosensitive member by each developing roller. (See Patent Document 1).

JP 2000-242067 A

  By the way, in such an image forming apparatus, when the stop time is long, the toner may aggregate around the developing roller due to the weight of the toner. When such agglomeration or the like occurs, the rotational load of the developing roller after the restart of operation increases. Therefore, when the printing operation is resumed after a relatively long stop period has elapsed, there is a problem in that the developing motor that drives the developing roller may step out and the rotation of the developing roller becomes unstable.

  In order to solve such a problem, in Patent Document 1, in a four-cycle image forming apparatus, a developing rack (rotary developing apparatus) in which a plurality of developing units are mounted is turned off. Describes rotation at a predetermined timing. In other words, the developing rack is additionally rotated at a time different from the printing time. According to this, since the toner in the developing unit (toner cartridge) is agitated when the power is turned off, toner aggregation can be suppressed.

  However, in the technique of Patent Document 1, since a large developing rack rotates, a loud operation sound is generated, and the quietness is greatly impaired. In particular, in an image forming apparatus installed in a relatively quiet room, when the developing rack suddenly starts to move when the power is turned off, an unexpectedly loud noise is generated, and the user may feel uncomfortable.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of stably rotating a developing roller without greatly impairing silence.

  In order to solve the above-mentioned problems, the invention of claim 1 is an image forming apparatus, wherein a toner is supplied to the photosensitive member via a photosensitive member on which an electrostatic latent image is formed and a developing roller, and the electrostatic latent image is formed. A developing unit that develops an image; a developing motor that drives the developing roller; a determination unit that determines whether the developing roller is in a high-load state or a non-high-load state; and controls the operation of the developing motor First drive control means, and when it is determined that the developing roller is in the high load state, the first drive control means determines that the developing roller is in the non-high load state. The input current to the developing motor is set to a larger value than the case, and the developing roller is rotated by driving the developing motor to supply toner to the photoconductor.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the image forming apparatus further includes a measuring unit that measures a temperature of a fixing device in the image forming apparatus, and the determination unit is configured to fix the fixing by the measuring unit. It is characterized in that it is determined that the developing roller is in the high load state on condition that the measured temperature of the container is not more than a predetermined value.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect of the present invention, the image forming apparatus further comprises detection means for detecting an environmental temperature and an environmental humidity related to the image forming apparatus, and the determination means is detected by the detection means. In addition, the developing roller is in the high load state on condition that the environmental temperature is equal to or lower than a first threshold value and the environmental humidity detected by the detecting means is equal to or lower than a second threshold value. It is characterized by determining.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the determination unit also determines a load level of the developing roller based on a detection result by the detection unit. The first drive control means changes an input current to the developing motor when toner is supplied to the photoconductor according to a determination result of the load level.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the first drive control unit is responsive to a driving time of the developing roller from a determination time point by the determination unit. The input current to the developing motor when the toner is supplied to the photoconductor is changed.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the first drive control unit determines that the cumulative usage time of the developing roller is greater than a predetermined value. In this case, the input current to the developing motor is set to a larger value than the case where it is determined that the accumulated usage time is smaller than the predetermined value, and the developing roller is rotated by driving the developing motor. It is characterized by supplying toner to the body.

  According to a seventh aspect of the present invention, there is provided an image forming apparatus, and a rotary developing rack that rotates around a predetermined axis with a plurality of developing units each having a photosensitive member on which an electrostatic latent image is formed and a developing roller. A developing motor that drives each developing roller of the plurality of developing units, a determination unit that determines whether each developing roller is in a high load state or a non-high load state, and controls the operation of the developing motor First driving control means, wherein the first driving control means determines that each developing roller is in the non-high load state when each developing roller is determined to be in the high load state. The input current to the developing motor is set to a larger value than in the case of determination, and the developing roller is rotated by driving the developing motor to supply toner to the photoconductor to develop the electrostatic latent image. With features That.

  According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect of the present invention, the image forming apparatus further includes a rack motor that drives the developing rack, and a second drive control unit that controls an operation of the rack motor. When it is determined that each of the developing rollers is in the high load state, the drive control unit is more sensitive than the case where each of the developing rollers is determined to be in a non-high load state. An input current to the rack motor at the time of supplying toner to the body is set to a large value, and a holding torque for maintaining the stopped state of the developing rack is generated.

  According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect of the present invention, the image forming apparatus further includes a measuring unit that measures a temperature of a fixing device in the image forming apparatus, and the determination unit is configured to fix the fixing by the measuring unit. It is characterized in that it is determined that each of the developing rollers is in the high load condition on condition that the measured temperature of the container is not more than a predetermined value.

  According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect of the present invention, the image forming apparatus further comprises detection means for detecting an environmental temperature and an environmental humidity related to the image forming apparatus, and the determination means is detected by the detection means. Further, each developing roller is in the high load state on condition that the environmental temperature is equal to or lower than the first threshold value and the environmental humidity detected by the detecting means is equal to or lower than the second threshold value. It is characterized by determining.

  According to an eleventh aspect of the present invention, in the image forming apparatus according to the tenth aspect, the determination unit also determines a load level of each developing roller based on a detection result by the detection unit, and the first drive control is performed. The means changes an input current to the developing motor at the time of supplying toner to the photoconductor according to the determination result of the load level, and the second drive control means is configured to change the current at the time of supplying toner to the photoconductor. The input current to the rack motor is changed according to the determination result of the load level.

  According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the eighth to eleventh aspects, the first drive control unit is configured to input current to the developing motor when toner is supplied to the photoconductor. Is changed according to the driving time of each developing roller from the time point of determination by the determining means, and the second drive control means changes the input current to the rack motor when the toner is supplied to the photoconductor. It changes according to time, It is characterized by the above-mentioned.

  According to the first to twelfth aspects of the present invention, the developing roller can be stably rotated without greatly impairing the quietness.

  In particular, according to the second and ninth aspects of the invention, it is easily determined whether or not the non-use state has been maintained for a long time, and it is easily determined that the developing roller is in a high load state. Is possible.

  In particular, according to the third and tenth aspects of the present invention, it can be determined easily and accurately that the developing roller is in a high load state by determining whether or not it has been left for a long time in a low temperature and low humidity environment. It is possible to determine.

  In particular, according to the invention described in claim 4, since the input current to the developing motor at the time of supplying the toner to the photosensitive member is changed according to the determination result of the load level, an appropriate torque is generated in the developing motor. Can be made.

  In particular, according to the fifth aspect of the present invention, since the input current to the developing motor when the toner is supplied to the photosensitive member is changed according to the driving time of the developing roller, an appropriate torque is generated in the developing motor. Can be made.

  In particular, according to the sixth aspect of the present invention, even when the developing roller deteriorates due to use, the developing motor can be driven with a relatively large torque to drive the developing roller more stably. .

  In particular, according to the eighth aspect of the present invention, the developing rack can be stopped by generating a sufficient holding torque.

  In particular, according to the invention described in claim 11, since the input current to the developing motor at the time of supplying the toner to the photosensitive member is changed according to the determination result of the load level, an appropriate torque is generated in the developing motor. Can be made. Further, since the input current to the rack motor at the time of supplying toner to the photosensitive member is changed according to the determination result of the load level, the rotary developing rack can be stopped more reliably.

  In particular, according to the twelfth aspect of the present invention, it is possible to generate an appropriate driving torque in the developing motor according to the driving time of the developing roller from the time point of determination by the determining means, and it is possible to generate an appropriate power in the rack motor. A holding torque can be generated.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<1. Device configuration>
FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus 1 (1A) according to the present embodiment. The image forming apparatus 1 is an apparatus that develops an electrostatic latent image on a photoreceptor (also referred to as an image carrier) to form an image. Here, as the image forming apparatus, an electrophotographic apparatus, more specifically, a 4-cycle full-color electrophotographic apparatus is illustrated.

  As shown in FIG. 1, the image forming apparatus 1 includes a photoconductor (image carrier) 11, a charger 12, an exposure device 13, and a rotary developing rack (rotary developing device) 20.

  The photoconductor 11 has a substantially cylindrical shape and is also expressed as a photoconductive drum. The charger 12 is a device that uniformly charges the outer peripheral surface of the photoconductor 11. The exposure device 13 is a device that selectively irradiates the outer peripheral surface of the photoconductor 11 with light.

  As shown in FIG. 2, the developing rack 20 includes a plurality (specifically, four) developing units 21 (specifically, 21Y, 21M, 21C, and 21K). Specifically, the developing rack 20 includes a yellow developing unit 21Y, a magenta developing unit 21M, a cyan developing unit 21C, and a black developing unit 21K. Each developing unit 21 has substantially the same configuration except that different color toners are stored.

  As shown in FIG. 3, each developing unit 21 includes a developing roller 14, a supply roller 15, and a toner storage unit 28. The toner storage unit 28 stores toner TN. Specifically, yellow toner is accommodated in the toner accommodating portion 28 of the developing unit 21Y, and magenta toner is accommodated in the toner accommodating portion 28 of the developing unit 21M. Similarly, cyan toner is accommodated in the toner accommodating portion 28 of the developing unit 21C, and black toner is accommodated in the toner accommodating portion 28 of the developing unit 21K. Each developing unit 21 is provided with a partition wall 29. By appropriately arranging the partition wall 29, the toner can be supplied more appropriately toward the supply roller 15 and the developing roller 14. Since each developing unit 21 is a replaceable member that also stores toner, it is also referred to as a toner cartridge. In order to reduce costs and the like, the toner container 28 is not provided with a stirring blade for stirring the toner.

  Refer to FIG. 2 again. The developing rack 20 is provided to be rotatable about a predetermined axis AX1. A motor (also referred to as “rack motor”) 22 for rotating the developing rack 20 and a rack docking gear 23 are provided in the vicinity of the developing rack 20 (on the lower side in the drawing).

  The rack docking gear 23 is provided so as to mesh with a gear fixed to one end surface of the developing rack 20 having a substantially cylindrical shape, and is also provided to mesh with a gear fixed to the rotation shaft of the rack motor 22. Yes.

  The rotational driving force of the rack motor 22 is transmitted to the developing rack 20 via the rack docking gear 23, and the developing rack 20 rotates about the axis AX1. Specifically, when the rack motor 22 rotates counterclockwise around the axis AX2, the rack docking gear 23 rotates clockwise around the axis AX3. As the rack docking gear 23 rotates, the developing rack 20 further rotates counterclockwise about the axis AX1.

  As the rack motor 22, for example, a two-phase excitation stepping motor is used. Adjusting the rotation direction and rotation speed of the rack motor 22, and consequently the rotation direction and rotation speed of the developing rack 20, by changing the input pulses to the stepping motor (specifically, the number of input pulses per unit time, etc.) Is possible.

  Further, a motor (also referred to as “developing motor”) 25 that rotates the developing roller 14 and a motor docking gear 24 are provided in the vicinity of the developing rack 20 (upper side in the drawing).

  The motor docking gear 24 is provided so as to mesh with a gear fixed to the rotation shaft of the developing motor 25. The motor docking gear 24 is provided so as to mesh with a gear fixed to one end surface of each of the substantially cylindrical developing rollers 14 when the developing rack 20 has a predetermined rotation angle.

  The rotational driving force of the developing motor 25 is transmitted to each developing roller 14 via the motor docking gear 24, and each developing roller 14 rotates about each rotating shaft. Specifically, when the developing motor 25 rotates counterclockwise around the axis AX5, the motor docking gear 24 rotates clockwise around the axis AX4. As the motor docking gear 24 rotates, the developing roller 14 located at the position facing the motor docking gear 24 rotates counterclockwise about the axis AX7.

  As the developing motor 25, for example, a two-phase excitation stepping motor is used. The rotational direction and rotational speed of the developing motor 25, and thus the rotational direction and rotational speed of the developing roller 14 are adjusted by changing the input pulses to the stepping motor (specifically, the number of input pulses per unit time). It is possible.

  The image forming apparatus 1 sequentially moves the four developing units 21 to a position facing the photoconductor 11 by rotating the developing rack 20. Then, the electrostatic latent image formed on the outer peripheral surface of the photoconductor 11 is developed using the corresponding color toner.

  Specifically, after the outer peripheral surface of the photoconductor 11 is charged by the charger 12 (see FIG. 1), the charge of the portion exposed by the exposure device 13 is reduced, so that the outer peripheral surface of the photoconductor 11 is statically exposed. An electrostatic latent image is formed. The electrostatic latent image is formed for each basic color component (specifically, each component of Y (yellow), M (magenta), C (cyan), and K (black)) in the final output image. .

  Each electrostatic latent image is developed by one of the plurality of development units 21 in the development rack 20. When an appropriate developing unit 21 among the plurality of developing units 21 is moved to a position facing the photoreceptor 11 and faces the photoreceptor 11, the developing roller 14 of the developing unit 21 is rotated by the developing motor 25. Then, the toner in the developing unit 21 is supplied to the photoconductor in accordance with the rotation operation of the developing roller 14. Thereby, the electrostatic latent image on the photoconductor 11 is developed.

  Specifically, the yellow component electrostatic latent image is developed by the yellow developing unit 21Y, and the magenta component electrostatic latent image is developed by the magenta developing unit 21M. Similarly, the cyan component electrostatic latent image is developed by the cyan developing unit 21C, and the black component electrostatic latent image is developed by the black developing unit 21K. Thus, each developing unit 21 forms a toner image of each basic color component by an electrophotographic method.

  In full-color printing, the above four-color toner image forming operations are sequentially executed. More specifically, first, an electrostatic latent image forming operation and a developing operation relating to the yellow component are executed, and then an electrostatic latent image forming operation and a developing operation relating to the magenta component are executed. Thereafter, an electrostatic latent image forming operation and a developing operation relating to the cyan component are executed, and finally, an electrostatic latent image forming operation and a developing operation relating to the black component are executed.

  The formed toner images are sequentially transferred to an intermediate transfer belt (also referred to as an intermediate transfer member) 31 (FIG. 1) and superimposed on the intermediate transfer belt 31. Then, the toner image of each basic color component superimposed on the intermediate transfer belt 31 is further transferred onto a paper (recording paper) PA, so that a full color image is formed on the paper PA.

  As shown in FIG. 1, the intermediate transfer belt 31 moves in the direction of the arrow AR <b> 1 by driving the drive roller 33. A secondary transfer roller 32 is provided at a position facing the drive roller 33 with the intermediate transfer belt 31 therebetween. Further, a paper feeding unit 40 is provided below the secondary transfer roller 32 and the like. The paper feed unit 40 is configured to supply the paper PA toward the secondary transfer roller 32 and the like on the upper side (downstream side) of the drawing.

  A fixing device 45 is provided on the downstream side (upper side in FIG. 1) of the paper PA that has passed the position of the secondary transfer roller 32, and a paper discharge unit 46 is provided on the downstream side in the transport direction. It has been. The toner image transferred onto the paper PA is heated by the fixing device 45 and fixed on the paper PA. Thereafter, the paper PA is discharged to the paper discharge unit 46 on the upper side of the image forming apparatus 1.

  A temperature measuring unit 51 that measures the temperature of the fixing device 45 is provided in the vicinity of the fixing device 45. For example, the temperature measurement unit 51 includes a thermistor. An environmental sensor 52 is provided between the secondary transfer roller 32 and the timing roller 42. The environmental sensor 52 detects environmental temperature and environmental humidity related to the image forming apparatus 1.

  The image forming apparatus 1 prints out an image based on image data transmitted from another information device (personal computer or the like) connected via a network or the like by using the printing mechanism as described above. Functions as a color page printer.

  FIG. 4 is a diagram illustrating functional blocks of the image forming apparatus 1.

  As illustrated in FIG. 4, the image forming apparatus 1 includes a CPU 61, a ROM 62, and a RAM 63. The computer system including the CPU 61 and the like implements various control functions in the image forming apparatus 1 by executing predetermined programs stored in the ROM 62 using the CPU 61 and the RAM 63. For example, the determination unit 61c and the operation control unit 61d are realized by software.

  The CPU 61 is electrically connected to the temperature measurement unit 51 and the environment sensor 52, respectively. The CPU 61 can acquire the measurement result by the temperature measurement unit 51 and the detection result by the environment sensor 52, respectively.

  The determination unit 61c determines whether each developing roller 14 is in a high load state based on the measurement result by the temperature measurement unit 51. In this embodiment, it is determined that each developing roller 14 is in a “high load state” on condition that the temperature measured by the temperature measuring unit 51 of the fixing device 45 is not more than a predetermined value TH10. Furthermore, in this embodiment, each developing roller 14 is in a “high load state” on condition that the temperature detected by the environmental sensor 52 is equal to or lower than the threshold TH11 and the humidity detected by the environmental sensor 52 is equal to or lower than the threshold TH21. Is determined. On the other hand, if either of the two conditions is not satisfied, it is determined that each developing roller 14 is not in a “high load state”, in other words, each developing roller 14 is in a “non-high load state (or normal state)”. Is done. Specifically, when the temperature measured by the temperature measuring unit 51 of the fixing device 45 is higher than a predetermined value TH10, it is determined that the state is “non-high load state”. Also, when the temperature detected by the environmental sensor 52 is higher than the threshold TH11, or when the humidity detected by the environmental sensor 52 is higher than the threshold TH21, it is determined that the state is “non-high load state”.

  Further, the CPU 61 is electrically connected to the developing motor 25 via the motor driver 65 and electrically connected to the rack motor 22 via the motor driver 66.

  The operation controller 61 d controls the operation of the developing motor 25 via the motor driver 65. That is, the operation control unit 61d and the motor driver 65 control the operation of the developing motor 25.

  In addition, the operation control unit 61 d controls the operation of the rack motor 22 via the motor driver 66. That is, the operation control unit 61 d and the motor driver 66 control the operation of the rack motor 22.

  The operation control unit 61d, the motor driver 65, and the motor driver 66 control the input current and the like of the developing motor 25 and the rack motor 22 based on the determination result of the determination unit 61c.

  For example, when it is determined that the developing roller 14 is in the “high load state”, the developing motor at the time of supplying the toner to the photoconductor is more than in the case where it is determined that the developing roller 14 is in the “non-high load state”. The input current to 25 is set to a relatively large value, and the developing motor 25 is rotated. That is, the input current to the developing motor 25 in the “high load state” is set to a value larger than the input current to the developing motor 25 in the “non-high load state (normal state)”. Such a control operation will be described in detail later.

<2. Outline of operation>
Next, the operation of the image forming apparatus 1 will be described in detail. First, an outline of the operation will be described.

In the image forming apparatus 1, when the power source is changed from the off state to the on state,
(A) a determination operation regarding the load state of the developing roller 14;
(B) initial rotation operation of the developing rack 20,
(C) printing operation according to the load state of the developing roller 14;
These operations are executed in this order. Below, it demonstrates according to this order.

<3. Judgment action>
As described above, if the image forming apparatus 1 is not used for a predetermined period, the toner may aggregate around the developing roller due to the weight of the toner. When such agglomeration or the like occurs, the rotational load of the developing roller after the restart of operation increases. In particular, when the image forming apparatus 1 is left in a “low temperature and low humidity environment”, this aggregating action is likely to occur. This is because, in a low-temperature and low-humidity environment, the degree of moisture absorption of the toner is small, the toner fluidity is high, and the toner easily enters a gap near the developing roller. As a result, the rotational load of the developing roller tends to increase particularly in a low temperature and low humidity environment.

  Therefore, in this image forming apparatus 1, it is determined as follows whether or not the phenomenon that the rotation load of the developing roller is increased due to the continuation of such a neglected state has occurred.

  Specifically, when the power source is changed from the off state to the on state, the determination operation by the determination unit 61c is executed in principle. For example, this determination operation is executed at a power-on time T20 (see FIG. 5).

  In this determination operation, the determination unit 61 c uses the temperature measurement unit 51 and the environment sensor 52 to determine whether the image forming apparatus 1 is left unattended.

  Specifically, first, it is determined whether or not a condition C1 that the measured temperature TE of the fixing device 45 by the temperature measuring unit 51 (FIG. 1) is equal to or lower than a predetermined value TH10 (for example, 50 ° C.) is satisfied.

  As shown in FIG. 5, the warm-up operation of the fixing device 45 is executed from the time T20 when the image forming apparatus 1 is turned on. A line LN1 in FIG. 5 shows an example of a change with time of the temperature of the fixing device 45.

  Specifically, when the energization of the heater in the fixing device 45 is started at the power-on time T20, the temperature of the fixing device 45 starts to rise. Then, after the temperature of the fixing device 45 rises to about 160 ° C., for example, the printing operation is performed. Note that the temperature of the fixing device 45 further rises to about 170 ° C. during the printing operation period.

  Thereafter, when the power is turned off at time T50, the temperature of the fixing unit 45 gradually decreases as the energization of the heater of the fixing unit 45 is stopped.

  At this time, the temperature of the fixing device 45 does not rapidly decrease. In order for the temperature of the fixing device 45 to decrease from about 160 ° C. to about 50 ° C., a time (for example, about one hour) from time T50 to time T60 is required. Therefore, when the measured temperature TE of the fixing device 45 is higher than 50 ° C., it is considered that one hour has not yet elapsed since the power was turned off after the warm-up operation of the fixing device 45 was performed. In other words, the image forming apparatus 1 is left for less than 1 hour.

  On the other hand, an increase in the rotational load of the developing roller is highly likely to occur when the image forming apparatus 1 is left unattended for a predetermined period (for example, about one and a half hours to two hours).

  Therefore, when the temperature measured TE of the fixing device 45 by the temperature measuring unit 51 is larger than a predetermined value TH10 (for example, 50 ° C.), it is determined that the image forming apparatus 1 is left for less than 1 hour, and the developing roller It is considered that the phenomenon of increase in rotational load has not occurred. That is, it is determined that the developing roller 14 is in the “non-high load state (normal state)”. Here, as measurement temperature TE, it is preferable to use a measurement result at a time immediately after power-on and before the start of fixing warm-up (for example, time T20).

  On the other hand, when the measured temperature TE of the fixing device 45 by the temperature measuring unit 51 is a predetermined value TH10 (for example, 50 ° C.) or less, it is determined that the image forming apparatus 1 is left for one hour or more, and the developing roller It is considered that there is a high possibility that an increase in the rotational load is occurring. However, here, a case where the threshold value TH10 is set with some allowance is illustrated. Specifically, it is determined that there is a high possibility that an increase in the rotational load of the developing roller is occurring even when the image forming apparatus 1 is left for about 1 hour to 1 and a half hours. As the threshold value TH10, a value corresponding to the apparatus configuration or the like may be determined as appropriate through experiments or the like.

  As described above, by using the measured temperature TE of the fixing device 45 by the temperature measuring unit 51, it is easily determined whether or not the non-use state (also referred to as the neglected state) of the image forming apparatus 1 has been continued for a long time. can do. As a result, it is possible to easily determine whether or not the developing roller is in a high load state.

  In the image forming apparatus 1, when the condition C1 that the measured temperature TE is equal to or lower than the predetermined value TH10 is satisfied, it is determined whether or not the next condition C2 is also satisfied. The condition C2 is that the temperature detected by the environmental sensor 52 (environmental temperature) TM is equal to or lower than the threshold TH11, and the humidity detected by the environmental sensor 52 (environmental humidity) HM is equal to or lower than the threshold TH21. Here, a value of 18 ° C. is used as the threshold value TH11 and 20% is used as the threshold value TH21. However, the present invention is not limited to this, and as the thresholds TH11 and TH21, values corresponding to the type of toner and the like may be appropriately determined by experiments or the like.

  When not only the condition C1 but also the condition C2 is satisfied, it is considered that the apparatus has been left for a long time in a “low temperature and low humidity environment”. In this case, it is determined that the developing roller 14 is in a “high load state”.

  On the other hand, when the condition C1 is satisfied but the condition C2 is not satisfied, it is considered that the leaving environment is not the “low temperature and low humidity environment”. In this case, it is determined that the developing roller 14 has not reached the “high load state”. Note that it is possible to grasp the load state of the developing roller 14 more accurately by considering the condition C2.

  As described above, when both the condition C1 and the condition C2 are satisfied, it is determined that the developing roller 14 is in the “high load state”. On the other hand, when either of the conditions C1 and C2 is not satisfied, it is determined that the state is “non-high load state”. By determining whether or not the developer roller 14 has been left for a long period of time in a low-temperature and low-humidity environment using the conditions C1 and C2 as described above, it is determined simply and more accurately that the developing roller 14 is in a high load state. It is possible.

  In this embodiment, when both the condition C1 and the condition C2 are satisfied, the level of the high load state of the developing roller 14 is further determined using the measurement result of the environment sensor 52.

  Specifically, as shown in FIG. 6, the degree of “low temperature and low humidity” of the environment is divided into three levels (levels L1, L2, and L3), and according to these levels, the level of the high load state ( Degree).

  Specifically, when the measured temperature TM by the environmental sensor 52 is less than the threshold TH13 (here 10 ° C.) and the measured humidity HM by the environmental sensor 52 is less than the threshold TH23 (here 10%), the determination unit 61c The low temperature and low humidity level of the environment is determined to be level L3.

  Further, when the measured temperature TM is lower than the threshold value TH12 (here, 15 ° C.) and the measured humidity HM is lower than the threshold value TH22 (here, 20%), the determination unit 61c sets the environmental low temperature and low humidity level to the level L2. Judge as. However, the determination of level L3 has priority over the determination of level L2. That is, even when the level L2 criterion is satisfied, when the level L3 criterion is satisfied, the low temperature and low humidity level is determined to be the level L3. The threshold value TH12 is a value greater than or equal to the threshold value TH13, and the threshold value TH22 is a value greater than or equal to the threshold value TH23.

  Further, when the measured temperature TM is lower than the threshold value TH11 (here 18 ° C.) and the measured humidity HM is lower than the threshold value TH21 (here 20%), the determination unit 61c sets the environmental low temperature and low humidity level to the level L1. Judge as. However, the determinations at levels L2 and L3 have priority over the determination at level L1. Note that the threshold TH11 is a value greater than or equal to the threshold TH12, and the threshold TH21 is a value greater than or equal to the threshold TH22 (here, TH21 = TH22).

  When the measured temperature TM is equal to or higher than the threshold TH11 (here 18 ° C.) or the measured humidity HM is equal to or higher than the threshold TH21 (here 20%), the determination unit 61c sets the low temperature and low humidity level of the environment at the level L0. Judge as there is. This level L0 means that it is not a “low temperature and low humidity environment”.

  In addition, when the equality between the temperature TM (or humidity HM) and each threshold value is established, the affiliation to each corresponding level may be determined in reverse to the above. For example, when the equal sign between the temperature TM (or humidity HM) and each threshold value is established, it may be determined that the temperature belongs to the corresponding level L3, L2, L1.

  The above-described levels L3, L2, and L1 indicating the degree of low temperature and low humidity also indicate the level of the developing roller 14 in a high load state (also referred to as “load level”). In other words, the determination unit 61c also determines the load level of the developing roller 14 based on the detection result by the environment sensor 52 and the like. As the value of the subscript i of the level Li increases, the level of low temperature and low humidity increases and the level of the developing roller 14 in a high load state (load level) also increases. That is, of the three levels L3, L2, and L1, level L3 indicates that the degree of “high load state” is the largest, and level L1 indicates that the degree of “high load state” is the smallest.

  The level L0 indicates that the environment is not the “low temperature and low humidity environment” and that the load state of the developing roller 14 is not the “high load state”.

<4. Initial rotation of developing rack>
Immediately after the determination operation as described above is executed, the initial rotation operation of the developing rack 20 is executed.

  In the image forming apparatus 1, a developing unit (toner cartridge) 21 is detachably mounted. In particular, when the power is turned off, there is a possibility that the developing unit (toner cartridge) 21 is taken out (detached) from the apparatus 1 for maintenance or the like.

  For this reason, in this image forming apparatus 1, after the power is turned on, the developing rack 20 is rotated to check whether or not all of the plural (here, four) developing units 21 are mounted. Such a rotation operation is referred to as an initial rotation operation.

  Specifically, as shown in FIG. 7, the motor driver 66 (FIG. 4) or the like rotates the rack motor 22 (FIG. 2) counterclockwise at a predetermined rotational speed R1 (eg, 1200 pps (pulses per second)). Specifically, a value I1 (for example, 1.0 A (ampere)) is set as the input current Ia to the rack motor 22. When the current I1 is input to the rack motor 22 and the rack motor 22 rotates, the developing rack 20 is driven to rotate counterclockwise about the axis AX1 (FIG. 2).

  By this rotational driving operation, the developing rack 20 is rotated to the reference position. The arrival at the reference position is detected by an optical sensor (not shown). More specifically, the optical sensor detects a hole provided at a predetermined position of the disk that rotates in synchronization with the developing rack 20 to detect that the developing rack 20 has reached the reference position.

  Thereafter, the rack motor 22 stops and the developing rack 20 stops at the initial position. During the stop, the rotation speed of the rack motor 22 is set to zero, and the input current Ia to the rack motor 22 is set to a value I7 (for example, 0.7 A (ampere)). When such a current Ia (= I7) is input, the rack motor 22 generates a torque (holding torque) for holding the developing rack 20 in a stopped state. As a result, the development rack 20 is prevented from moving (rotating) due to its own weight or the like.

  Next, the mounting confirmation operation of each developing unit 21K, 21Y, 21M, 21C is executed.

  Specifically, the current I1 is input again to the rack motor 22, and the rack motor 22 rotates. Then, when the developing rack 20 is rotated by a predetermined angle and the first developing unit 21 (for example, 21K) is moved to the position facing the photoconductor 11, the rotation of the developing rack 20 is stopped. During the stop, the rotational speed of the rack motor 22 is set to zero and the input current Ia to the rack motor 22 is set to a value I7 (for example, 0.7 A (ampere)) as described above.

  The mounting confirmation operation of each developing unit 21 is executed while the photosensitive member 11 is stopped at the opposite position. Specifically, the information stored in the memory provided in each developing unit 21 is read by a reading device (reader) installed in the vicinity of the photoconductor 11 to confirm the mounting of each developing unit 21. The When the reading process of the memory is successful (when communication is successful), it is determined that the corresponding developing unit 21 (for example, 21K) is attached. On the other hand, when the process is not successful (when communication fails), it is determined that the corresponding developing unit 21 is not attached. Here, a case where the presence or absence of the development unit 21 is confirmed based on the success or failure of the reading process from the memory in the development unit 21 is illustrated, but the present invention is not limited to this. For example, the developing unit 21 may be provided with a reflecting member, and the presence or absence of the developing unit 21 may be confirmed using a reflective sensor that detects the presence or absence of reflected light from the reflecting member with respect to the emitted light. . Or you may make it confirm the presence or absence of mounting | wearing of the developing unit 21 using the transmission type sensor which detects the presence or absence of the transmitted light with respect to an emitted light.

  When the mounting confirmation operation for the first developing unit 21 (for example, 21K) is completed, the current I1 is input again to the rack motor 22, and the rack motor 22 rotates. Then, when the developing rack 20 is rotated 90 (degrees: deg) and the next developing unit 21 (for example, 21Y) is moved to the position facing the photoconductor 11, the rotation of the developing rack 20 is stopped. Then, a mounting confirmation operation relating to the developing unit 21 (for example, 21Y) is executed. During stoppage, the rotational speed of the rack motor 22 is set to zero and the input current Ia to the rack motor 22 is set to a value I7 (for example, 0.7 A (ampere)) as described above. .

  Similarly, the mounting confirmation operation is sequentially executed for the remaining developing units 21 (for example, 21M and 21C). Thereafter, the developing rack 20 rotates and moves to a predetermined standby position.

  Here, in the above operation, each developing roller 14 (FIG. 2) moves on the outer peripheral side of the developing rack 20 according to the rotation of the developing rack 20, and each developing roller 20 rotates 90 degrees each time. 14 passes through a position facing the photoconductor 11. During this passage, the gear of each developing roller 14 meshes with the motor docking gear 24.

  At this time, if the motor docking gear 24 is stopped, an impact force is generated between the motor docking gear 24 and the gear of the developing roller 14, and a relatively large load is generated with respect to the rotation of the developing rack 20. The normal rotation operation of the rack 20 is hindered.

  In order to suppress the occurrence of such a load, in this embodiment, the developing motor 25 is rotated such that the motor docking gear 24 rotates at a speed synchronized with the moving speed of the developing roller 14 that moves on the outer periphery of the developing rack 20. Also rotate. Specifically, a current I2 (for example, 0.7 A (ampere)) is set as an input current Id to the developing motor 25, and the developing motor 25 is rotated at a speed R2 (for example, 600 pps (pulse per second)). Note that it is sufficient if the load on the developing rack 20 can be reduced. Therefore, it is sufficient that the current I2 is set to a relatively small value.

  When the mounting confirmation operation as described above is executed and it is confirmed that all the developing units 21 (21K, 21Y, 21M, and 21C) are mounted, the printable state is entered and the print job reception standby state is entered. Transition.

<5. Color printing operation>
Next, a case where a color printing command is received and a color printing operation is executed in a print job reception waiting state will be described.

  In the color printing operation, the developing rack 20 starts to rotate from the standby position by driving the rack motor 22. The developing rack 20 stops after the developing unit 21Y has moved to the position facing the photoconductor 11. Then, when the developing rack 20 is stopped, the developing roller 14 of the developing unit 21Y is rotated by the developing motor 25, and a yellow toner image is formed on the photoconductor 11.

  Thereafter, the developing rack 20 starts to rotate again by driving the rack motor 22. The developing rack 20 rotates 90 degrees counterclockwise about the axis AX1, and stops after the developing unit 21M has moved to the position facing the photoconductor 11. Then, when the developing rack 20 is stopped, the developing roller 14 of the developing unit 21M is rotated by the developing motor 25, and a magenta toner image is formed on the photoconductor 11.

  Further, the developing rack 20 starts to rotate again by driving the rack motor 22. The developing rack 20 rotates 90 degrees counterclockwise about the axis AX1, and stops after the developing unit 21C has moved to a position facing the photoconductor 11. When the developing rack 20 is stopped, the developing roller 14 of the developing unit 21 </ b> C is rotated by the developing motor 25 to form a cyan toner image on the photoconductor 11.

  Thereafter, similarly, the developing rack 20 starts to rotate again by driving the rack motor 22. The developing rack 20 rotates 90 degrees counterclockwise about the axis AX1, and stops after the developing unit 21K has moved to the position facing the photoconductor 11. When the developing rack 20 is stopped, the developing roller 14 of the developing unit 21K is rotated by the developing motor 25, and a black toner image is formed on the photoconductor 11.

  When the developing rack 20 is rotated in such an operation, a control operation similar to the initial rotation operation is performed.

  Specifically, a value I1 (for example, 1.0 A (ampere)) is set as the input current Ia to the rack motor 22. The current I1 is input to the rack motor 22 and the rack motor 22 is rotated counterclockwise at a speed R1 (for example, 1200 pps (pulses per second)), whereby the developing rack 20 is centered on the axis AX1 (FIG. 2). Rotated counterclockwise.

  Further, the developing motor 25 is driven so that the motor docking gear 24 rotates at a predetermined synchronous speed in the same manner as the initial rotation operation described above. Specifically, a current I2 (for example, 0.7 A (ampere)) is set as an input current Id to the developing motor 25, and the developing motor 25 is rotated at a speed R2 (for example, 600 pps (pulse per second)).

  Here, the control operation when rotating the developing rack 20 is common regardless of the above-described determination result regarding the load state of the developing roller 14 (see also FIGS. 8 to 11).

  On the other hand, when an image forming operation (forming operation) of each toner image is executed while the developing rack 20 is stopped, the following determination result regarding the load state of the developing roller 14 is used as follows. Different control actions are performed.

  First, the case where it is determined that the state is the “non-high load state (normal state)” will be described.

  At this time, as shown in FIG. 8, a current I50 (for example, 1.0 A (ampere)) is set as an input current Id to the developing motor 25 when toner is supplied to the photosensitive member, and a speed R5 (for example, 500 pps (pulse per second) is set. )), The developing motor 25 is rotated. During image formation, it is preferable to stably rotate the developing roller 14 so as not to cause a development failure. Therefore, a value that generates torque for stably rotating the developing roller 14 is set as the input current I50 to the developing motor 25. However, in order to suppress power consumption, the input current I50 is set to an appropriate value without being set to an excessively large value.

  Further, if the developing rack 20 is rotated by the rotational load of the developing motor 25 during image formation, the positional relationship between the developing roller 14 and the photoconductor 11 is shifted. In order to prevent such a situation, the rack motor 22 generates torque (holding torque) for maintaining (holding) the stopped state of the developing rack 20 here. Specifically, the set value I30 (for example, 0.7 A (ampere)) is input as the input current Ia to the rack motor 22 while the rotation of the rack motor 22 is stopped.

  As described above, during image formation in the “non-high load state (normal state)”, the current I50 (1.0 A) is input to the developing motor 25 to rotate the developing motor 25 at the speed R5, and the rack. A current I30 (0.7 A) is input to the motor 22 to maintain the rack motor 22 in a stopped state.

  Next, a case where it is determined that the state is a “high load state” will be described.

  In the high load state, the developing motor 25 is rotated at the same speed R5 as described above. On the other hand, as the input current Id to the developing motor 25, a current larger than the current I50 (1.0 A) in the normal state is input. Is done. As a result, the developing motor 25 can rotate each developing roller 14 more stably. In order to increase the holding torque of the developing rack 20, a current larger than the current I30 (0.7 A) in the normal state is input as the input current Ia to the rack motor 22. With such a relatively large input current, the rack motor 22 is more reliably maintained in a stopped state.

  Further, in this embodiment, the operation control unit 61d responds not only to the determination result regarding whether or not the state is the “high load state” but also to the determination result of the level of the “high load state” (that is, the load level Li). Thus, the current values Id and Ia when the toner is supplied to the photoconductor 11 are changed.

  For example, when the “high load state” is the maximum level L3, as shown in FIG. 9, the input current Id to the developing motor 25 is set to a value I53 (for example, 1.5 A) (I53> I50). Further, the input current Ia to the rack motor 22 is set to a value I33 (for example, 1.3 A) (I33> I30).

  When the “high load state” is level L2, as shown in FIG. 10, the input current Id to the developing motor 25 is set to a value I52 (eg, 1.3 A). This value I52 is larger than the value I50 and smaller than the value I53 (I50 <I52 <I53). Further, the input current Ia to the rack motor 22 is set to a value I32 (for example, 1.2 A). The value I32 is larger than the value I30 and smaller than the value I33 (I30 <I32 <I33).

  When the “high load state” is level L1, as shown in FIG. 11, the input current Id to the developing motor 25 is set to a value I51 (for example, 1.2 A) (I50 <I51 <I52). This value I51 is larger than the value I50 and smaller than the value I52 (I50 <I51 <I52). Further, the input current Ia to the rack motor 22 is set to a value I31 (for example, 1.0 A). This value I31 is larger than the value I30 and smaller than the value I32 (I30 <I31 <I32).

  As described above, when it is determined that each developing roller 14 is in the “high load state”, the current I50 (1) in the normal state is used as the input current Id to the developing motor 25 when the toner is supplied to the photosensitive member. Current (I53, I52, I51) larger than .0A) is input. According to this, even when the developing roller 14 is difficult to rotate due to toner aggregation or the like, it is possible to generate a larger torque in the developing motor 25 and to rotate the developing roller 14 more stably.

  Further, according to the image forming apparatus 1, it is not necessary to rotate the developing rack 20 when the power is turned off in order to stir the developing roller 14. Accordingly, it is possible to avoid greatly impairing silence.

  Further, when it is determined that each developing roller 14 is in the “high load state”, the input current Ia to the rack motor 22 when the toner is supplied to the photoconductor 11 by each developing roller 14 is the normal state. A current (I33, I32, I31) larger than the current I30 (0.7 A) is input. According to this, the holding torque for maintaining the stopped state of the developing rack 20 can be sufficiently generated.

  Further, since the input current values Id and Ia are changed according to the load level Li, the torque corresponding to the load level of the developing roller is appropriately generated by minimizing the increase of the input currents Id and Ia. It is possible to execute a more appropriate control operation. Specifically, since the input current Id at the time of supplying the toner to the photosensitive member 11 is changed according to the determination result of the load level Li, the developing motor 25 can apply an appropriate torque (corresponding to the load level of each developing roller 14 ( Driving torque). Further, since the input current Ia at the time of supplying the toner to the photoconductor 11 is changed according to the determination result of the load level Li, the rack motor 22 generates an appropriate torque (holding torque), and the rotary developing rack. 20 can be stopped more reliably. Furthermore, by suppressing an increase in current according to the load level Li, it is possible to suppress an increase in power consumption, motor heat generation, an increase in motor excitation sound, and the like.

  In this embodiment, the elapsed time after the operation of the image forming apparatus 1 that has been left unattended is resumed (specifically, the actual driving time of the developing roller 14 after the operation of the image forming apparatus is resumed). Assume that the input current values Id and Ia are changed.

  Specifically, as shown in FIG. 6, each driving time of the developing roller 14 after the operation of the image forming apparatus 1 is resumed (in other words, the driving time from the determination time point T20 by the determination unit 61c) TD Input current values Id and Ia are set. Here, for simplification, it is assumed that the driving times of the four developing rollers 14 are the same.

  More specifically, the input current values Id and Ia are set according to which of the periods PD1, PD2, PD3, and PD4 corresponds to the driving time TD. Here, the period PD1 is a period in which the driving time TD is 0 minute or more and less than 10 minutes. The period PD2 is the next period after the period PD1 elapses. Specifically, the period PD2 is a period in which the driving time TD is 10 minutes or more and less than 20 minutes. Furthermore, the period PD3 is a next period after the period PD2 has elapsed, and specifically, is a period in which the drive time TD is 20 minutes or more and less than 30 minutes. In addition, the period PD4 is a period after the period PD3 has elapsed, specifically, a period in which the drive time TD is 30 minutes or more.

  When the drive time TD corresponds to the period PD1 (when TD <10 (minutes)), the input current values Id and Ia are changed as described above according to the level (load level) of the “high load state”. Is done.

  Specifically, when the “high load state” is the maximum level L3, the input current Id for the developing motor 25 is set to the value I53, and the input current Ia to the rack motor 22 is set to the value I33. When the “high load state” is level L2, the input current Id to the developing motor 25 is set to the value I52, and the input current Ia to the rack motor 22 is set to the value I32. When the “high load state” is level L1, the input current Id to the developing motor 25 is set to the value I51, and the input current Ia to the rack motor 22 is set to the value I31.

  Here, when the developing roller 14 is rotated after the operation of the image forming apparatus 1 is resumed, the toner around the developing roller 14 is agitated as the developing roller 14 rotates, so that toner aggregation and the like are gradually eliminated. To go. Therefore, the load on the developing roller 14 is gradually reduced.

  Therefore, in this embodiment, the input currents Id and Ia are gradually reduced as the period elapses.

  Specifically, when it is determined that the “high load state” is the maximum level L3, when the period PD1 elapses, the input current Id to the developing motor 25 is set to the value I52, and the input current Ia to the rack motor 22 is set. Is set to the value I32. In other words, the input current Id in the period PD2 is reduced more than the input current Id in the period PD1, and the input current Ia in the period PD2 is reduced than the input current Ia in the period PD1.

  Thereafter, when the period PD2 elapses, the input current Id to the developing motor 25 is set to a value I51, and the input current Ia to the rack motor 22 is set to a value I31. In other words, the input current Id in the period PD3 is reduced more than the input current Id in the period PD2, and the input current Ia in the period PD3 is reduced than the input current Ia in the period PD2.

  Even when it is determined that the “high load state” is the maximum level L3, the load state of the developing roller 14 returns to the normal state in many cases when the period PD3 (here, 30 minutes) has elapsed. ing. Therefore, when the period PD3 elapses, the input current Id for the developing motor 25 is set to the value I50, and the input current Ia for the rack motor 22 is set to the value I30. That is, the input currents Id and Ia in the period PD4 are changed to normal input currents I50 and I30, respectively. In other words, the input current Id in the period PD4 is reduced more than the input current Id in the period PD3, and the input current Ia in the period PD4 is reduced than the input current Ia in the period PD3. According to this, it is possible to avoid unnecessarily increasing the torque and reduce power consumption.

  As described above, when it is determined that the “high load state” is the maximum level L3, the input currents Id and Ia are gradually reduced (in other words, stepwise) as time elapses.

  When it is determined that the “high load state” is the level L2, when the period PD1 elapses, the input current Id to the developing motor 25 is set to the value I51, and the input current Ia to the rack motor 22 is set to the value I31. Is set. In other words, the input currents Id and Ia in the period PD2 are reduced more than the input currents Id and Ia in the period PD1, respectively.

  When it is determined that the “high load state” is the level L2, the load state of the developing roller 14 returns to the normal state in many cases after the period PD2 (here, 20 minutes) has elapsed. Therefore, when the period PD2 elapses, the input current Id for the developing motor 25 is set to the value I50, and the input current Ia for the rack motor 22 is set to the value I30. That is, the input currents Id and Ia after the period PD3 are changed to normal input currents I50 and I30, respectively. According to this, it is possible to avoid unnecessarily increasing the torque and reduce power consumption.

  Thus, even when it is determined that the “high load state” is the level L2, the input currents Id and Ia are gradually reduced as time elapses.

  Further, when it is determined that the “high load state” is the level L1, when the period PD1 elapses, the input current Id to the developing motor 25 is set to the value I50, and the input current Ia to the rack motor 22 is set to the value I30. Is set. When it is determined that the “high load state” is the level L1, the load state of the developing roller 14 returns to the normal state in many cases when the period PD1 (here, 10 minutes) has elapsed. Therefore, in this way, by changing the input currents Id and Ia after the period PD2 to the input currents I50 and I30 at the normal time, respectively, it is possible to avoid unnecessarily increasing the torque and reduce power consumption. it can.

  As described above, the operation control unit 61d applies the developing roller 14 to the photosensitive member 11 in accordance with the driving time of the developing roller 14 from a predetermined determination time point regarding the load state of the developing roller 14 (for example, the operation restart time point T20 of the image forming apparatus). The input currents Id and Ia at the time of toner supply are changed. According to this, the torque (drive torque) of the developing motor 25 and the torque (holding torque) of the rack motor 22 can be appropriately generated at each time after the operation of the image forming apparatus 1 is resumed.

<6. Monochrome printing operation>
Next, the monochrome printing operation will be described with reference to FIGS.

  The monochrome printing operation is different from the color printing operation described above in that the developing rack 20 is not rotated after the developing unit 21K has moved to the position facing the photoconductor 11.

  On the other hand, for the input current and the like during image formation by the developing unit 21K, the same operation as described above is executed (see FIG. 6).

  Specifically, when it is determined that the state is “non-high load” immediately after the restart of the operation, the input current Id for the developing motor 25 is set to the value I50, and the input current Ia to the rack motor 22 is set to the value I30. (See FIG. 12). As a result, a normal driving operation is performed.

  On the other hand, when it is determined immediately after the operation is resumed that the state is a “high load state”, in principle, the input current Id to the developing motor 25 and the input current Ia to the rack motor 22 are values higher than normal values, respectively. Set to

  For example, when it is determined that the “high load state” is the maximum level L3 immediately after the operation is resumed, the input current Id to the developing motor 25 is set to the value I53 and the input current Ia to the rack motor 22 is the value during the period PD1. I33 is set (see FIG. 13). Thereafter, when the period PD1 elapses, the input current Id to the developing motor 25 is set to a value I52, and the input current Ia to the rack motor 22 is set to a value I32 (see FIG. 14). When the period PD2 elapses, the input current Id for the developing motor 25 is set to the value I51, and the input current Ia for the rack motor 22 is set to the value I31 (see FIG. 15). Further, when the period PD3 elapses, the input current Id to the developing motor 25 is set to a value I50, and the input current Ia to the rack motor 22 is set to a value I30 (see FIG. 12).

  When it is determined that the “high load state” is level L2 immediately after the operation is resumed, the input current Id to the developing motor 25 is set to the value I52 and the input current Ia to the rack motor 22 is set to the value I32 in the period PD1. (See FIG. 14). When the period PD1 elapses, the input current Id for the developing motor 25 is set to the value I51, and the input current Ia for the rack motor 22 is set to the value I31 (see FIG. 15). Further, when the period PD2 elapses, the input current Id to the developing motor 25 is set to a value I50, and the input current Ia to the rack motor 22 is set to a value I30 (see FIG. 12).

  When it is determined that the “high load state” is the level L1 immediately after the operation is resumed, the input current Id to the developing motor 25 is set to the value I51 and the input current Ia to the rack motor 22 is set to the value I31 in the period PD1. (See FIG. 15). Thereafter, when the period PD1 elapses, the input current Id to the developing motor 25 is set to a value I50, and the input current Ia to the rack motor 22 is set to a value I30 (see FIG. 12).

<7. Judgment when power is turned on again>
By the way, as described above, the determination operation regarding the load state of the developing roller 14 is performed immediately after the power-off state is changed to the power-on state in principle.

  However, if the temperature of the fixing device 45 rises to near 160 degrees in response to the turning on of the power, the power is turned off once before the developing roller 14 is driven for 30 minutes, and the power is turned on again immediately. Assuming that this is the case, the following inconvenience may occur. Specifically, since the temperature of the fixing device 45 is still maintained at a high temperature (for example, 80 ° C.) at the time when the power is turned on again, if the determination operation is performed again at the time when the power is turned on again, the measured temperature TE Is not satisfied with the condition C1 being equal to or less than a predetermined value TH10 (eg 50 ° C.). Therefore, even though the high load state of the developing roller 14 is still continued, it is determined that the developing roller 14 is in the “non-high load state”, and a correct determination result may not be obtained.

  Therefore, in this embodiment, after the determination operation is executed once, the determination result (including the load level) and the remaining time of the input current adjustment period based on the determination result are stored. For example, when the determination result is “level L3”, the non-volatile memory (not shown) in the image forming apparatus 1 indicates that the determination result and the remaining time of the adjustment period based on the determination result are “30 minutes”. Remember. Then, the remaining time of the adjustment period stored in the nonvolatile memory is decremented as the developing time of the developing roller 14 elapses.

  The previous determination result is referred to when the power is turned on again. Specifically, when the previous determination result indicates “non-high load state”, the determination operation as described above is newly executed. On the other hand, when the previous determination result indicates “high load state”, the value of “remaining time” regarding the adjustment period is used instead of executing a new determination operation. For example, when the remaining time is “25 minutes”, it is determined that the driving time TD of the developing roller 14 is “5 minutes” (= 30−25), that is, corresponds to the period PD1. If the previous determination result is “level L3”, the value I53 (see FIG. 6 and the like) corresponding to the period PD1 of the level L3 is set as the input current Id and corresponds to the period PD1 of the level L3. The value I33 is set as the input current Ia.

  In this way, particularly by using the previous determination result, even when the time until the power is turned on again is short, the load state of the developing roller 14 is determined more accurately and the developing motor 25 is driven more appropriately. It is possible. In addition, the holding torque of the rack motor 22 can be appropriately controlled.

<8. Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the contents described above.

  For example, in the above embodiment, the case where both the above conditions C1 and C2 are considered is illustrated, but the present invention is not limited to this, and only the condition C1 may be considered without considering the condition C2. . Alternatively, only the condition C2 may be considered without considering the condition C1.

  Further, in the above-described embodiment, the case is illustrated in which both of (a) the determination operation regarding the load state of the developing roller 14 and (b) the initial rotation operation of the developing rack 20 are performed in this order. It is not limited to this. For example, the execution order of both operations may be reversed. That is, after (b) the initial rotation operation of the developing rack 20 is executed, (a) the determination operation regarding the load state of the developing roller 14 may be executed.

  In the above embodiment, the case where the environmental sensor 52 is provided between the secondary transfer roller 32 and the timing roller 42 is illustrated, but the present invention is not limited to this, and the environmental sensor 52 is disposed at other positions. You may make it do. For example, as shown in FIG. 16, an environmental sensor 52 may be disposed in the vicinity of the photoconductor 11. Alternatively, the environmental sensor 52 may be disposed in the vicinity of the paper PA placement portion (paper feed portion 40).

  In the above embodiment, the case where the determination operation (determination operation regarding the load state of the developing roller 14) is performed when the power source is changed from the off state to the on state is illustrated, but the present invention is not limited to this. For example, the determination operation may be executed when the state of the cover that covers a part of the image forming apparatus 1 is changed from the open state to the closed state. According to this, the present invention can be applied even when the cover is opened for a long time for maintenance regardless of the state of the power source.

  In the above-described embodiment, the case where the rotational load of the developing roller 14 increases due to toner aggregation is mainly considered, but the present invention is not limited to this.

  For example, when the developing roller 14 is used for a long period of time, the shavings of the developing roller 14 may be mixed into the lubricating oil in the bearing portion of the developing roller 14 and the lubricity of the lubricating oil may be reduced. Such a factor can also increase the rotational load of the developing roller 14.

  Therefore, the following modifications can be made so as to cope with such an increase in rotational load.

  Specifically, when the cumulative number of prints by the developing roller 14 exceeds a predetermined number CT1 (for example, 5000 sheets), the input currents Id and Ia as shown in FIG. 17 are used instead of the input currents Id and Ia as shown in FIG. You may make it set. Here, it is assumed that an increase in the rotational load of the developing roller 14 is determined based on the cumulative number of prints. Specifically, when the cumulative number of printed sheets is larger than a predetermined value, it is assumed that the cumulative usage time of the developing roller 14 is longer than the predetermined value. This utilizes the characteristic that the cumulative usage time of each developing roller 14 increases and the rotational load of each developing roller 14 increases as the cumulative number of printed sheets increases.

  Specifically, when the cumulative number of printed sheets by the developing roller 14 exceeds the predetermined number CT1, the value I62 (1.4 (A)) is used instead of the value I52 (1.3 (A)), and the value I32 (1. Instead of 2 (A)), the value I42 (1.3 (A)) is used. The value I62 is slightly larger (0.1 (A)) than the value I52, and the value I42 is slightly larger (0.1 (A)) than the value I32.

  Similarly, when the cumulative number of printed sheets by the developing roller 14 exceeds the predetermined number CT1, the value I61 (1.3 (A)) is used instead of the value I51 (1.2 (A)), and the value I31 (1.0 Instead of (A)), the value I41 (1.1 (A)) is used. The value I61 is slightly larger (0.1 (A)) than the value I51, and the value I41 is slightly larger (0.1 (A)) than the value I31.

  The value I53 is a current that generates a sufficiently large torque, and can stably rotate the developing roller 14 against an increase in rotational load caused by a decrease in lubricity of the developing roller 14. Therefore, the value I53 is used as it is in FIG. However, the present invention is not limited to this. For example, the value I63 (1.6 (A)) may be used instead of the value I53, and the value I43 (1.4 (A)) may be used instead of the value I33. . The value I63 is slightly larger (0.1 (A)) than the value I53, and the value I43 is slightly larger (0.1 (A)) than the value I33.

  As described above, when the cumulative number of prints by the developing roller 14 exceeds the predetermined number CT1, the currents Id and Ia are larger values I62 and I42 (or I61 and I41) than when the cumulative print number is less than the predetermined number CT1. You may make it use. In other words, when it is determined that the accumulated usage time of the developing roller 14 is greater than the predetermined value, the input current Id, Ia may be set to a large value. According to this, even when the developing roller 14 deteriorates due to use, the developing motor 25 can be driven with a relatively large torque at the time of supplying the toner, so that the developing roller 14 can be driven more stably. It is.

  Moreover, although the case where this invention is applied to the color page printer of a 4-cycle system is illustrated in the said embodiment, it is not limited to this.

  For example, the present invention may be applied to a tandem color page printer (see FIG. 18). In the tandem type image forming apparatus 1 </ b> C of FIG. 18, a plurality of developing units 121 (121 </ b> Y, 121 </ b> M, 121 </ b> C, 121 </ b> K) are disposed on the upper side of the intermediate transfer belt 31. Each of the plurality of development units 121 includes a photoreceptor 11, a charger 12, an exposure device 13, a development roller 14, a development motor 25 (not shown), and the like. In such an image forming apparatus 1C, when the condition C1 and the like are satisfied, the input current to each developing motor 25 that drives each developing unit may be increased. According to this, even when the toner aggregates in the vicinity of each developing roller 14 due to the weight of the toner and the load on each developing roller 14 increases during the non-use period of the image forming apparatus 1C, each developing roller 14 is stably provided. Can be driven. Here, the case where each developing unit 121 has the developing motor 25 is illustrated, but the present invention is not limited to this, and a single developing motor 25 may be shared by a plurality of developing units 121. .

1 is a diagram illustrating a schematic configuration of an image forming apparatus. FIG. 2 is a schematic diagram showing a configuration near a developing rack. It is the schematic which shows the structure of a certain image development unit. It is a figure which shows the functional block of an image forming apparatus. It is a figure which shows the time-dependent change of the temperature of a fixing device. It is a figure which shows the relationship between a low temperature, low humidity level, and input current. 6 is a time chart showing an initial rotation operation of the developing rack. It is a time chart which shows the color printing operation in a normal state. It is a time chart which shows the color printing operation in level L3. It is a time chart which shows the color printing operation in level L2. It is a time chart which shows the color printing operation in level L1. It is a time chart which shows the monochrome printing operation in a normal state. It is a time chart which shows the monochrome printing operation in level L3. It is a time chart which shows the monochrome printing operation in level L2. It is a time chart which shows the monochrome printing operation in level L1. It is a figure which shows the image forming apparatus which concerns on a modification. It is a figure which shows the modification regarding the relationship between a low temperature, low humidity level, and input current. It is a figure which shows the image forming apparatus which concerns on another modification.

Explanation of symbols

1, 1A, 1B, 1C Image forming apparatus 11 Photoconductor 12 Charger 13 Exposure device 14 Developing roller 20 (Rotary) developing rack 21, 21K, 21Y, 21M, 21C Developing unit 22 Rack motor 23 Rack docking gear 24 Motor docking Gear 25 Developing motor 45 Fixing device 51 Temperature measuring unit 52 Environmental sensor PA Paper Ia Input current to rack motor 22 Id Input current to developing motor 25

Claims (12)

An image forming apparatus,
A photoreceptor on which an electrostatic latent image is formed;
A developing unit for supplying toner to the photoreceptor via a developing roller to develop the electrostatic latent image;
A developing motor for driving the developing roller;
Determination means for determining whether the developing roller is in a high load state or a non-high load state;
First drive control means for controlling the operation of the developing motor;
With
When the developing roller is determined to be in the high load state, the first drive control unit is configured to input to the developing motor more than in the case where it is determined that the developing roller is in the non-high load state. An image forming apparatus, wherein a current is set to a large value, and the developing roller is rotated by driving the developing motor to supply toner to the photosensitive member. The image forming apparatus according to claim 1,
Measuring means for measuring the temperature of the fixing device in the image forming apparatus;
Further comprising
The image forming apparatus according to claim 1, wherein the determination unit determines that the developing roller is in the high load state on condition that a temperature measured by the fixing unit is not more than a predetermined value. The image forming apparatus according to claim 2.
Detection means for detecting environmental temperature and environmental humidity relating to the image forming apparatus;
Further comprising
The determination means is also provided that the environmental temperature detected by the detection means is less than or equal to a first threshold value, and the environmental humidity detected by the detection means is less than or equal to a second threshold value, An image forming apparatus that determines that the developing roller is in the high load state. The image forming apparatus according to any one of claims 1 to 3,
The determination unit also determines a load level of the developing roller based on a detection result by the detection unit;
The image forming apparatus according to claim 1, wherein the first drive control unit changes an input current to the developing motor when toner is supplied to the photoconductor according to a determination result of the load level. 5. The image forming apparatus according to claim 1, wherein:
The first drive control unit changes an input current to the developing motor at the time of supplying toner to the photoconductor according to a driving time of the developing roller from a determination time point by the determining unit. Image forming apparatus. The image forming apparatus according to any one of claims 1 to 5,
When it is determined that the accumulated usage time of the developing roller is greater than a predetermined value, the first drive control unit applies the power to the developing motor more than when it is determined that the accumulated usage time is smaller than the predetermined value. An image forming apparatus, wherein an input current is set to a large value, and the developing roller is rotated by driving the developing motor to supply toner to the photosensitive member. An image forming apparatus,
A photoreceptor on which an electrostatic latent image is formed;
A rotary developing rack that is mounted with a plurality of developing units each having a developing roller and rotates around a predetermined axis;
A developing motor for driving each developing roller of the plurality of developing units;
Determination means for determining whether each of the developing rollers is in a high load state or a non-high load state;
First drive control means for controlling the operation of the developing motor;
With
When it is determined that each of the developing rollers is in the high load state, the first drive control unit moves the developing motor to the developing motor more than in the case where it is determined that each of the developing rollers is in the non-high load state. The image forming apparatus is characterized in that the input current is set to a large value, and each developing roller is rotated by driving the developing motor to supply toner to the photoconductor to develop the electrostatic latent image. The image forming apparatus according to claim 7.
A rack motor for driving the developing rack;
Second drive control means for controlling the operation of the rack motor;
Further comprising
The second drive control means is configured such that when each of the developing rollers is determined to be in the high load state, each of the developing rollers is more than when it is determined that each of the developing rollers is in a non-high load state. An image forming apparatus characterized in that an input current to the rack motor at the time of supplying toner to the photoconductor is set to a large value and a holding torque for maintaining the stopped state of the developing rack is generated. The image forming apparatus according to claim 8.
Measuring means for measuring the temperature of the fixing device in the image forming apparatus;
Further comprising
The image forming apparatus according to claim 1, wherein the determination unit determines that each of the developing rollers is in the high load state on condition that a temperature measured by the fixing unit is not more than a predetermined value. The image forming apparatus according to claim 9.
Detection means for detecting environmental temperature and environmental humidity relating to the image forming apparatus;
Further comprising
The determination means is also provided that the environmental temperature detected by the detection means is less than or equal to a first threshold value, and the environmental humidity detected by the detection means is less than or equal to a second threshold value, An image forming apparatus that determines that each of the developing rollers is in the high load state. The image forming apparatus according to claim 10.
The determination unit also determines a load level of each developing roller based on a detection result by the detection unit,
The first drive control means changes an input current to the developing motor at the time of supplying toner to the photoconductor according to a determination result of the load level,
The image forming apparatus according to claim 2, wherein the second drive control unit changes an input current to the rack motor when supplying toner to the photoconductor according to a determination result of the load level. 12. The image forming apparatus according to claim 8, wherein:
The first drive control unit changes an input current to the developing motor at the time of supplying toner to the photoconductor according to a driving time of each developing roller from a determination time point by the determination unit,
The image forming apparatus according to claim 2, wherein the second drive control unit changes an input current to the rack motor at the time of supplying toner to the photoconductor according to the drive time.

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