JP2016099541A - Image forming apparatus, speed control method, and speed control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can reduce the cumulative number of rotation of developing rollers to improve durability.SOLUTION: A control part 100 determines the amount of deceleration of developing rollers 7 on the basis of the correspondence between the amount of deceleration of the developing rollers 7 and the amount of correction for correcting image forming conditions of an image forming part 30 and upper limits of the image forming conditions of the image forming part 30. The control part 100 causes the image forming part 30 to form toner images in colors based on print data on a sheet by using the image forming conditions equal to or less than the upper limits and using an amount of deceleration equal to or less than the determined amount of deceleration, while the developing rollers 7 are decelerated.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus, a speed control method, and a speed control program.

  As an example of an image forming apparatus using an electrophotographic method, an apparatus including a photoconductor and a developing roller that supplies toner to the photoconductor and develops an electrostatic latent image formed on the photoconductor is known. Yes.

  In recent years, there has been a demand for a highly durable image forming apparatus capable of forming a desired image even when repeatedly printed. It has been conventionally known that the durability of an image forming apparatus depends on the cumulative number of rotations of the developing roller.

  For example, as an example of an image forming apparatus with high durability, the image forming apparatus described in Patent Document 1 reduces the rotation speed of the developing roller in accordance with the increase in the number of printed sheets, and the circumference of the developing roller with respect to the photosensitive member. Reduce the speed ratio.

JP 2012-247631 A

  However, the image forming apparatus described in Patent Document 1 still has room for improvement with regard to high durability. Specifically, there is room for improvement regarding reduction of the cumulative number of rotations of the developing roller.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of reducing the cumulative number of rotations of a developing roller and achieving high durability.

  In order to achieve the above object, an image forming apparatus of the present invention includes a photoconductor that carries a toner image, an exposure device that forms an electrostatic latent image on the photoconductor, and an electrostatic latent image formed by the exposure device. An image forming unit having a developing roller that supplies toner to the toner and develops the electrostatic latent image, a transfer unit that transfers the toner image carried on the photosensitive member to the recording sheet, and a control that controls the rotation speed of the developing roller And a control unit configured to decelerate based on a correspondence relationship between a deceleration amount with respect to the rotation speed of the developing roller and a correction amount for correcting the image forming condition of the image forming unit, and an upper limit value of the image forming condition. The toner image is formed on the recording sheet in the image forming unit in a state where the image forming condition is determined, the image forming condition equal to or less than the upper limit value is used, and the rotation speed of the developing roller is decreased using the deceleration amount equal to or less than the determined deceleration amount. .

  In the image forming apparatus, the image forming condition may be an absolute value of a developing bias applied to the developing roller when developing the electrostatic latent image.

  In the image forming apparatus, the control unit counts the number of recording sheets on which the toner image is formed by the image forming unit, and changes the absolute value of the developing bias according to the counted number of recording sheets. May be.

  The image forming apparatus may include a humidity detection unit that detects humidity in the apparatus, and the control unit may change the absolute value of the developing bias in accordance with the humidity detected by the humidity detection unit.

  In the image forming apparatus, the image forming condition may be an exposure intensity when the exposure apparatus forms an electrostatic latent image.

  In the image forming apparatus, the control unit may be configured to count the number of recording sheets on which the toner image is formed by the image forming unit, and to change the exposure intensity in accordance with the counted number of recording sheets. .

  The image forming apparatus may include a humidity detection unit that detects humidity in the apparatus, and the control unit may change the exposure intensity according to the humidity detected by the humidity detection unit.

  The invention disclosed in this specification includes various devices such as a control device, a control method, a printing device, a printing method, a computer program for realizing the functions of these methods or devices, and a recording medium on which the computer program is recorded. It is realizable with the aspect of.

  According to the present invention, the control unit determines the amount of deceleration, uses the image forming condition equal to or less than the upper limit value, and reduces the rotation speed of the developing roller using the amount of deceleration equal to or less than the determined deceleration amount. A toner image is formed on the forming unit. Therefore, the rotation speed of the developing roller can be reduced without the image forming condition exceeding the upper limit value. Thereby, it is possible to reduce the cumulative number of rotations of the developing roller and maintain high durability while maintaining appropriate image forming conditions.

1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment. It is a block diagram which shows the electric constitution of the control part which concerns on this embodiment. It is a flowchart which shows the procedure of a developing bias reduction process. It is a top view which shows the patch of each color formed in the conveyance belt. It is a flowchart which shows the procedure of the deceleration process which concerns on this embodiment. This is a subroutine for deceleration amount determination processing. 6 is a table showing a correspondence relationship between a deceleration amount of each developing roller and a developing bias correction amount corresponding to each developing roller.

  Embodiments will be described with reference to the drawings. After describing the overall configuration of the image forming apparatus 1, features of the present invention will be described in detail.

  As shown in FIG. 1, the image forming apparatus 1 includes an image forming unit 30, a paper feeding unit 9, and a control unit 100 in the apparatus main body 2.

  The image forming unit 30 includes a process unit 3 and an exposure device 4. The process unit 3 is provided corresponding to each color of black, yellow, magenta, and cyan, and is arranged in the order of yellow, magenta, cyan, and black in the conveyance direction of a sheet as an example of a recording sheet. The exposure device 4 is disposed above the process unit 3 and emits a laser beam corresponding to each color.

  Each process unit 3 includes a photoreceptor 5, a charger 6, a developing roller 7, a cleaning roller 8, and a transfer roller 13 as an example of a transfer unit. As the photoconductor 5 rotates, the surface of the photoconductor 5 is uniformly positively charged by the charger 6 and then selectively exposed by the laser beam from the exposure device 4. As a result, charges are selectively removed from the surface of the photoreceptor 5, and an electrostatic latent image is formed on the surface of the photoreceptor 5.

  Next, the developing roller 7 supplies toner to the electrostatic latent image formed on the surface of the photoreceptor 5 and develops the electrostatic latent image on the photoreceptor. At this time, a developing bias which is a voltage for developing the electrostatic latent image is applied to the developing roller 7.

  In this embodiment, positively charged toner is used, and a positive development bias is applied to the developing roller 7. In this embodiment, positively charged toner is used and a positive developing bias is applied to the developing roller 7. However, the present invention is not limited to this. Negatively charged toner is used and the developing roller 7 has a negative developing bias. The structure to be applied may be sufficient.

  In the present specification and drawings, when the process unit 3 and the developing roller 7 corresponding to each color are specified, the symbols K, Y, M, and C are associated with black, yellow, magenta, and cyan, respectively. Is attached.

  In the present embodiment, the surface of each photoconductor 5 is exposed by the laser beam emitted from the exposure device 4, but the present invention is not limited to this, and the light emitted from the LED, EL element, phosphor, or the like is used. The surface of each photoconductor 5 may be exposed.

  A paper feeding unit 9 that accommodates paper is disposed below the apparatus main body 2. The paper stored in the paper supply unit 9 is transported onto the transport belt 10 by various rollers.

  The conveyor belt 10 is stretched between a pair of driving rollers 11 and a driven roller 12 and is disposed to face the four photosensitive members 5 from below. A transfer roller 13 is disposed at each position facing each photoconductor 5 across the upper portion of the conveyance belt 10.

  The sheet transported on the transport belt 10 sequentially passes between the transport belt 10 and each photosensitive drum 5 as the transport belt 10 travels. Then, the toner image of each color carried by each photoconductor 5 is transferred to the paper by the transfer bias applied to each transfer roller 13, and a toner image is formed on the paper.

  The transferred toner image is heat-fixed on the sheet by the fixing unit 14 disposed on the downstream side in the sheet conveying direction with respect to the conveying belt 10. The sheet on which the toner image is fixed is discharged to a discharge tray 15 disposed on the upper surface of the apparatus main body 2 by various rollers.

  A belt cleaner 16 is disposed between the paper supply unit 9 and the conveyor belt 10, and the belt cleaner 16 removes toner and paper dust attached to the surface of the conveyor belt 10. A cleaning roller 8 is disposed corresponding to each photoconductor 5, and the toner remaining on the surface of each photoconductor 5 after the transfer of the toner image is removed from the surface of the photoconductor 5 by the cleaning roller 8. .

  A density sensor 17 that detects the density of a patch, which will be described later, is disposed at a position facing the drive roller 11. Further, a humidity sensor 150 that detects the humidity in the apparatus main body 2 is disposed above the sheet feeding unit 9.

  Next, the electrical configuration of the control unit 100 will be described. As shown in FIG. 2, the control unit 100 includes a CPU 101, a ROM 102, a RAM 103, and an NVRAM 104, and is electrically connected to the density sensor 17, the developing roller drive motor 70, the humidity sensor 150, and the developing bias generation circuit 200. ing.

  The ROM 102 stores various control programs and image processing programs for controlling the image forming apparatus 1, various settings, initial values, and the like.

  The RAM 103 is used as a work area from which various control programs are read, or as a storage area for temporarily storing print data such as image data sent via various interfaces.

  The NVRAM 104 is a non-volatile storage unit, and is used as a storage area for storing various settings, print data, and the like.

  The CPU 101 executes arithmetic operations for realizing various functions such as a printing function in the image forming apparatus 1 and is the center of control. The CPU 101 controls each component of the image forming apparatus 1 while storing the processing result in the RAM 103 or the NVRAM 104 according to the control program read from the ROM 102.

  The developing roller driving motor 70 is a driving source for driving the developing roller 7 corresponding to each color. The developing roller driving motor 70 includes a monochrome driving motor 71 that drives the developing roller 7K and a color driving motor 72 that drives the developing rollers 7Y, 7M, and 7C. The monochrome driving motor 71 and the color driving motor 72 are controlled. Each developing roller 7 is rotated according to the control of the unit 100.

  In the present embodiment, the monochrome driving motor 71 and the color driving motor 72 rotate each developing roller. However, the present invention is not limited to this, and a configuration in which one driving source rotates each developing roller 7, The drive source corresponding to the developing roller 7 may be configured to rotate each developing roller 7 individually.

  Detection results from the concentration sensor 17 and the humidity sensor 150 are output to the control unit 100. The detection result by the humidity sensor 150 is individually stored in the NVRAM 104 every time a sheet is detected by a paper discharge sensor (not shown).

  The developing bias generation circuit 200 generates a developing bias to be applied to the developing rollers 7K, 7Y, 7M, and 7C according to the control of the control unit 100. The developing bias is set for each color by the control unit 100.

  The development bias generation circuit 200 is a self-excited high voltage generation circuit including an oscillation transistor and a transformer, for example. The output voltage of the development bias generation circuit 200, that is, the development bias is controlled by, for example, a PWM signal from the control unit 100.

  In this embodiment, the development bias to be applied to each development roller 7 is generated by one development bias generation circuit 200. However, the present invention is not limited to this, and a configuration in which a development bias generation circuit is provided for each development roller 7 is provided. It may be.

  Next, the control performed by the control unit 100 will be described in detail. The controller 100 counts and accumulates the number of sheets on which toner images are formed after the photoreceptor 5 is replaced. In the present specification, the time when the photoconductor 5 is replaced means that an unused photoconductor 5 is mounted on the apparatus main body 2.

  Specifically, the control unit 100 sets the count value of the number counter provided in the NVRAM 104 to zero when the photosensitive member 5 is replaced. The number counter is provided corresponding to each photoconductor 5, and when the photoconductor 5 is replaced, the control unit 100 sets the number counter corresponding to the replaced photoconductor 5 to zero.

  The sheet counters corresponding to the respective photoreceptors 5 are provided on the downstream side of the fixing unit 14 in the sheet transport direction and in response to a detection operation of a sheet discharge sensor (not shown) that detects the sheet on which the toner image is formed. Increment the count value. As a result, the total number of printed sheets, which is the total number of sheets on which toner images are formed, is counted.

  The control unit 100 decreases the absolute value of the developing bias as an example of the image forming conditions of the image forming unit 30 in accordance with the increase in the cumulative number of printed sheets and the change in humidity in the apparatus main body 2. This is to keep the density of each color toner image formed by the image forming unit 30 constant.

  Specifically, as the cumulative number of printed sheets increases, the deterioration of each photoconductor 5 progresses, so that the chargeability of each photoconductor 5 decreases. For this reason, as the cumulative number of printed sheets increases, the amount of toner supplied from each developing roller 7 to each photoconductor 5 increases, and the density of each color toner image may change.

  In the present embodiment, in order to suppress such excessive supply of toner to each photoconductor 5, the control unit 100 decreases the absolute value of the developing bias as the cumulative number of printed sheets increases. As a result, the potential difference between each photoconductor 5 and each developing roller 7 is reduced, so that excessive supply of toner can be suppressed.

  Further, the chargeability of each photoconductor 5 changes according to the humidity in the apparatus main body 2. Specifically, when the humidity in the apparatus main body 2 is higher than a predetermined reference value, the chargeability of each photoconductor 5 is lower than when the humidity is lower than the predetermined reference value. Therefore, the amount of toner supplied from each developing roller 7 to each photoconductor 5 changes according to the change in humidity in the apparatus main body 2, and the density of the toner image of each color may change.

  Therefore, in the present embodiment, the control unit 100 sets the predetermined number of prints every time the total number of printed sheets reaches a predetermined number in order to suppress a change in density of the toner image due to an increase in the total number of printed sheets and a change in humidity. The developing bias corresponding to each developing roller 7 set at times is updated. The developing bias reduction process executed by the control unit 100 to update each developing bias will be described in detail with reference to FIG. The development bias reduction process is called at a predetermined time interval.

  As shown in FIG. 3, the control unit 100 determines whether or not the cumulative number of printed sheets has reached a predetermined number (S50). When determining that the total number of printed sheets has reached a predetermined number (S50: YES), the control unit 100 decreases the absolute value of each developing bias set based on the total number of printed sheets and humidity (S55).

  In the present embodiment, the predetermined number in S50 is set to a multiple of 5, but the present invention is not limited to this, and the predetermined number may be set to an arbitrary number. Further, a multiple of 5 in this specification includes 0. Here, S55 will be described in detail below.

  When the total number of printed sheets reaches a multiple of 5, the control unit 100 changes the absolute value of each developing bias according to the increase in the total number of printed sheets and the change in humidity. Specifically, the absolute value of each developing bias is changed according to the following equation (1). Equation (1) is shown where A is the absolute value of each developing bias for updating each developing bias that has been set.

A = absolute value of each developing bias that has been set−α × amount of increase in the total number of printed sheets−β × amount of decrease in humidity (1)
α and β are positive constants corresponding to each developing bias and predetermined in accordance with the cumulative number of printed sheets and humidity. Α and β may be constants obtained in advance by experiments or the like. In the present embodiment, α and β are constants, but the present invention is not limited to this, and any variable may be used.

  For example, when the total number of printed sheets reaches 100, the control unit 100 updates the previous developing bias from the absolute value of each developing bias set when the total number of printed sheets reaches 95, that is, here Then, the value obtained by multiplying 5 sheets, which is an increase amount of the cumulative number of printed sheets from when the total number of printed sheets reaches 95, is multiplied by a constant α.

  After that, based on the detection result of the humidity sensor 150 stored in the NVRAM 104, the humidity when the cumulative number of printed sheets reaches 100 is subtracted from the humidity when the cumulative number of printed sheets reaches 95. Determine the amount of reduction. Then, from the absolute value of each developing bias set when the cumulative number of printed sheets reaches 95, the numerical value obtained by multiplying the increase amount of the cumulative printed sheet number by the constant α, and the numerical value obtained by multiplying the decrease amount of the humidity by the constant β. By subtracting, the absolute value A of each developing bias is determined.

  Here, when the humidity when the cumulative number of printed sheets reaches 100 is higher than the humidity when the cumulative number of printed sheets reaches 95, the amount of decrease in humidity is a negative value.

  In the present embodiment, the constants α and β are set so that the absolute value A of each developing bias is smaller than the absolute value of each developing bias set in the above formula (1). . In other words, the absolute value of each set developing bias decreases every time the cumulative number of printed sheets reaches a predetermined number.

  Then, the control unit 100 controls the output voltage of the development bias generation circuit 200, and updates the absolute value of each development bias that has been set to the absolute value A of each development bias determined by Expression (1). The updated development biases are stored in the NVRAM 104.

  As a result, each time the cumulative number of printed sheets reaches a predetermined number, each development bias that has been set is updated to a developing bias that takes into account the increase in the total number of printed sheets and changes in humidity, and the increase in the total number of printed sheets and changes in humidity. Therefore, the density change of the toner image of each color can be kept constant.

  In the present embodiment, the control unit 100 is configured to decrease the absolute value of each set development bias when the cumulative number of printed sheets reaches a predetermined number. However, the present invention is not limited to this. The controller 100 may reduce the absolute value of each developing bias that has been set.

  In the present embodiment, the absolute value of each developing bias that has been set is decreased in accordance with an increase in the total number of printed sheets. However, the present invention is not limited to this, and it is in accordance with the total number of rotations of each photoconductor 5. The absolute value of each developing bias that has been set may be reduced.

  As shown in FIG. 3, when the controller 100 determines that the cumulative number of printed sheets has not reached the predetermined number (S50: NO), it ends the developing bias reduction process.

  Next, a patch forming process executed by the control unit 100 to detect the density of each color toner image formed by the image forming unit 30 will be described.

  In the patch forming process, the control unit 100 causes the image forming unit 30 to form patches corresponding to the colors shown in FIG. The patches of each color are formed on the transport belt 10 at a constant pitch and arranged in order of yellow, magenta, cyan, and black from the upstream side in the sheet transport direction. When the patch corresponding to each color is formed, a developing bias set individually for each color by the control unit 100 is applied to the developing roller 7 corresponding to each color.

  The control unit 100 controls known light emitting elements and light receiving elements (not shown) included in the density sensor 17 to detect the density of each color patch formed on the conveyance belt 10.

  Next, the deceleration process executed by the control unit 100 will be described in detail with reference to FIGS. In the present embodiment, in order to reduce the rotation speed of the developing roller 7 corresponding to each color while keeping the density of the toner image of each color constant, the control unit 100 reduces the cumulative number of rotations of each developing roller 7. The deceleration process is executed. The deceleration process is called at predetermined time intervals.

  By the way, it is known that the density of the toner image decreases as the rotation speed of the developing roller decreases. In consideration of this, in the deceleration process, the control unit 100 corrects each developing bias according to the deceleration of the rotation speed of each developing roller 7 so as to keep the density of the toner image of each color constant. . The correction of each developing bias means that the developing bias corresponding to each developing roller 7 is increased in accordance with the reduction in the rotation speed of each developing roller 7.

  As shown in FIG. 5, the control unit 100 determines whether or not it is time to execute the patch formation process (S100), and when it is determined that it is time to execute the patch formation process (S100: YES), deceleration is performed. A quantity determination process is executed (S105).

  The deceleration amount determination process is for determining a deceleration amount with respect to the rotation speed of each developing roller 7 when the rotation speed of the developing roller 7 corresponding to each color is decreased while keeping the density of the toner image of each color constant. It is processing. Hereinafter, the amount of deceleration with respect to the rotation speed of each developing roller 7 is simply referred to as the amount of deceleration of each developing roller 7. Note that the timing of executing the patch forming process in S100 is, for example, when the image forming apparatus 1 is turned on or when print data is sent to the control unit 100.

  By the way, as described above, by correcting each developing bias, when the rotational speed of each developing roller 7 is decelerated while keeping the density of each color toner image constant, the deceleration amount of each developing roller 7 and each developing roller There is a correspondence relationship with the correction amount (increase amount) of the developing bias corresponding to the roller 7. The correspondence relationship associates the deceleration amount of each developing roller 7 with the correction amount of each developing bias corresponding to the deceleration amount of each developing roller 7. In addition, what is necessary is just to obtain | require each said correlation by experiment etc. previously.

  Here, the correction amount of the developing bias corresponds to each developing roller 7 in order to keep the density of the toner image of each color constant as the control unit 100 decelerates the rotation speed of each developing roller 7. This is a numerical value for correcting the developing bias.

  In the deceleration amount determination process, each deceleration amount is determined based on the correspondence between the deceleration amount of each developing roller 7 and the correction amount of the developing bias corresponding to each developing roller 7 and the upper limit value of each developing bias. In the present embodiment, the upper limit value of each developing bias generated by the developing bias generation circuit 200 is set to 500V. In addition, the said upper limit is not limited to 500V, You may set to arbitrary numerical values.

  The deceleration amount determination process will be described in detail with reference to FIG. As shown in FIG. 6, the control unit 100 determines the correspondence between the deceleration amount of each developing roller 7 and the correction amount of the developing bias corresponding to each developing roller 7 shown in FIG. 7 and the upper limit value of each developing bias. Based on this, the maximum deceleration amount of each developing roller 7 is determined (S200).

  Specifically, for example, the control unit 100 sets the rotation speed of the development roller 7K to V1 and the development bias corresponding to the development roller 7K to 425V before reducing the rotation speed of the development roller 7K.

  In this state, in S200, for example, the control unit 100 reduces the rotation speed of the developing roller 7K so that the rotation speed becomes 96% of the rotation speed V1, in other words, the set deceleration of the developing roller 7K. When the amount is 4% of the rotational speed V1, in order to keep the density of the black toner image constant, based on the correspondence shown in FIG. 7A, the development bias is increased by 50V with respect to the development bias set to 425V. It is determined that correction is necessary so that

  In S200, for example, when the set deceleration amount of the developing roller 7K is 6% of the rotational speed V1, the control unit 100 corrects the developing bias to be increased by 75V with respect to the developing bias set to 425V. Judge that it is necessary.

  In this case, the control unit 100 determines that the development bias needs to be corrected to be 500V, but in this embodiment, the upper limit value of each development bias generated by the development bias generation circuit 200 is set to 500V. doing. Therefore, when the set deceleration amount of the developing roller 7K is 6% of the rotation speed V1, the developing bias is corrected so as to become the upper limit value.

  Next, the control unit 100 determines that the upper limit value of the correction amount of the developing bias corresponding to the developing roller 7K is 75V based on the upper limit value of the developing bias set in the developing bias generation circuit 200. Then, based on the upper limit value of the developing bias set in the developing bias generation circuit 200, the control unit 100 determines 6% of the rotational speed V1 that is the deceleration amount of the developing roller 7K when the developing bias reaches the upper limit value. Is the maximum value of the deceleration amount.

  In S200, the control unit 100 determines the maximum value of the deceleration amount of the developing rollers 7Y, 7M, and 7C as in the case of determining the maximum value of the deceleration amount of the developing roller 7K.

  For example, before the rotation speed of the developing rollers 7Y, 7M, and 7C is reduced, the control unit 100 sets the rotation speed of the developing rollers 7Y, 7M, and 7C to V2, and sets each developing bias corresponding to the developing rollers 7Y, 7M, and 7C. 400V, 440V and 460V are set.

  In this state, the control unit 100 determines that the upper limit value of the correction amount of the developing bias corresponding to the corresponding developing roller 7Y is 100 V based on the upper limit value of each developing bias set in the developing bias generation circuit 200 in S200. to decide.

  Then, based on the correspondence shown in FIG. 7B, the control unit 100 sets 10% of the rotation speed V2 that is the deceleration amount of the developing roller 7Y when the developing bias is the upper limit value to the maximum of the deceleration amount. Value.

  Similarly, based on the upper limit value of each developing bias set in the developing bias generation circuit 200, the control unit 100 sets the upper limit value of the developing bias correction amount corresponding to the developing rollers 7M and 7C to 60V and 40V, respectively. Judge.

  Then, the control unit 100 sets 6% of the rotational speed V2 and 4% of the rotational speed V2 to the maximum reduction amount of the developing rollers 7M and 7C based on the correspondence relationship shown in FIGS. 7C and 7D. Value.

  As described above, in S200, the control unit 100 determines the maximum deceleration amount of each developing roller 7 based on the corresponding relationships shown in FIGS. 7A to 7D and the upper limit value of each developing bias. Determine the value.

  Thereafter, as shown in FIG. 6, the control unit 100 sets 6% of the rotation speed V1 that is the maximum value of the deceleration amount of the developing roller 7K determined in S200 as the deceleration amount of the developing roller 7K (S205). The developing bias correction amount corresponding to the developing roller 7K is set to 75V. These settings are stored in the NVRAM 104.

  Thus, in the present embodiment, the control unit 100 sets 6% of the rotation speed V1 that is the maximum value of the determined deceleration amount as the deceleration amount of the developing roller 7K, and based on the above-described correspondence relationship, the deceleration amount 75V, which is the upper limit value of the developing bias correction amount corresponding to the maximum value, was set as the developing bias correction amount. However, the present invention is not limited to this, and the control unit 100 sets a deceleration amount smaller than 6% of the rotational speed V1 as the deceleration amount of the developing roller 7K, and responds to the set deceleration amount based on the correspondence relationship described above. The correction amount of the development bias may be set as the correction amount of the development bias.

  In other words, the control unit 100 sets an arbitrary deceleration amount that is less than or equal to the determined maximum deceleration amount as the deceleration amount of the developing roller 7K, and develops an arbitrary development bias that is less than or equal to the upper limit value of the development bias. It may be configured to set as a bias.

  In the present embodiment, the upper limit value of the developing bias correction amount corresponding to the developing roller 7K is set as the set developing bias correction amount, and therefore the upper limit value is not set as the developing bias correction amount. As compared with the above, the rotational speed of the developing roller 7K can be further reduced.

  Further, every time the cumulative number of printed sheets reaches a predetermined number, the control unit 100 updates each development bias that has been set to a development bias that takes into account the increase in the total number of printed sheets and a change in humidity. Is set as the correction amount of the set development bias. As described above, since the upper limit value of the correction amount of the developing bias is determined based on the developing bias considering the increase in the total number of printed sheets and the change in humidity, the rotation of the developing roller 7K can be performed while keeping the toner image density constant. The speed can be reduced.

  Next, the control unit 100 determines whether or not the maximum deceleration amounts of the developing rollers 7Y, 7M and 7C determined in S200 are equal to each other (S210), and determines that the maximum deceleration amounts are equal to each other. (S210: YES), the deceleration amount determination process is terminated.

  If the control unit 100 determines that the maximum values of the deceleration amounts of the developing rollers 7Y, 7M, and 7C determined in S200 are not equal to each other (S210: NO), the smallest one of the maximum values of the respective deceleration amounts is determined. Is set as the deceleration amount of the developing rollers 7Y, 7M and 7C (S215).

  Specifically, the control unit 100 determines the maximum deceleration amount of the developing rollers 7Y, 7M, and 7C determined in S200 of the present embodiment, which is 10% of the rotational speed V2, 6% of the rotational speed V2, and the rotational speed. It is determined whether or not the numerical values of 4% of V2 are equal to each other. If it is determined that they are not equal to each other, 4% of the smallest rotational speed V2 among the maximum values of the respective deceleration amounts is used as the developing rollers 7Y, 7M, and 7C. Set as the deceleration amount.

  Then, the control unit 100 sets the correction amount of each developing bias corresponding to the case where the deceleration amount is 4% of the rotational speed V2 based on the correspondence relationships shown in FIGS. 7B to 7D.

  Specifically, the control unit 100 sets the developing bias correction amounts corresponding to the developing rollers 7Y, 7M, and 7C to 40 V, and these settings are stored in the NVRAM 104. In this embodiment, 4% of the smallest rotational speed V2 among the maximum values of the respective deceleration amounts is set as the deceleration amount of the developing rollers 7Y, 7M, and 7C. However, the present invention is not limited to this, and 4% of the rotational speed V2 is set. The following arbitrary deceleration amount may be set.

  After setting the deceleration amounts of the developing rollers 7Y, 7M, and 7C in S215, the control unit 100 ends the deceleration amount determination process.

  As shown in FIG. 5, after executing the deceleration amount determination process in S105, the control unit 100 decelerates the rotation speed of each developing roller 7 based on each deceleration amount determined and set in S105, and determines in S105. The above-described patch forming process is executed in a state where each developing bias is corrected based on the developing bias correction amount corresponding to each developing roller 7 set (S115).

  Next, the control unit 100 determines whether or not the density of the patch is a predetermined density based on the density of the patch of each color detected in S115 (S120). When the control unit 100 determines that the density of the patch is a predetermined density (S120: YES), the control unit 100 determines whether there is print data in the control unit 100 (S140).

  If the control unit 100 determines that there is print data (S140: YES), the control unit 100 is in a state in which each development bias is corrected based on the development bias correction amount corresponding to each development roller 7 that has been set. In a state where the rotation speed of each developing roller 7 is decelerated based on each deceleration amount, the toner image of each color is formed on the sheet by the image forming unit 30 based on the print data (S145).

  Thereby, each developing roller 7 rotates in a state where the rotation speed of each developing roller 7 is decelerated, and the cumulative number of rotations of each developing roller 7 can be reduced, so that high durability can be achieved. In the present embodiment, when the control unit 100 determines the deceleration amount of each developing roller 7, the correspondence relationship that associates the deceleration amount of each developing roller 7 with the correction amount of the developing bias corresponding to each developing roller 7. And each deceleration amount is determined based on the upper limit value of the developing bias. As a result, the total number of rotations of each developing roller 7 can be reduced while keeping the density of the toner image of each color constant.

  Further, since the controller 100 reduces the rotation speed of the developing roller 7K without exceeding the upper limit value of the developing bias, the total rotation speed of the developing roller is reduced and high durability is maintained while maintaining appropriate image forming conditions. Can be achieved.

  When determining that there is no print data (S140: NO), the control unit 100 ends the deceleration process.

  If the control unit 100 determines that the density of each color patch is not a predetermined density (S120: NO), the controller 100 determines whether the density of the patch is higher than the predetermined density based on the density of the patch detected in S115. Is determined (S125).

  When determining that the density of the patch is higher than the predetermined density (S125: YES), the control unit 100 increases the deceleration amount of the developing roller 7 of the color corresponding to the patch determined to be higher than the predetermined density, in other words, S105. The deceleration amount of the developing roller set in step S is updated (S130). Note that the increase amount of the deceleration amount may be determined using a table or the like obtained in advance through experiments or the like.

  If the control unit 100 determines that the density of the patch is not higher than the predetermined density (S125: NO), the controller 100 decreases the deceleration amount of the developing roller 7 of the color corresponding to the patch determined not to be higher than the predetermined density, in other words. The deceleration amount of the developing roller set in S105 is updated (S135). Note that the amount of reduction in the deceleration amount may be determined using a table or the like obtained in advance through experiments or the like. After executing the processes of S130 and S135, the control unit 100 executes the process of S115 again.

  As described above, the control unit 100 decelerates the rotation speed of each developing roller 7 based on each deceleration amount determined in S105, and corrects each developing bias based on the correction amount of each developing bias determined in S105. The patch forming process is executed in the state, and the determined deceleration amounts are increased or decreased according to the detected density of each color patch. Thereby, compared with the case where the control unit 100 does not execute the patch forming process, it is possible to reduce the cumulative number of rotations of the developing rollers 7 while maintaining the density of the toner image of each color more reliably.

  If the control unit 100 determines that it is not time to execute the patch formation process (S100: NO), it executes the process of S140.

  In this embodiment, when the control unit 100 determines the deceleration amount of each developing roller 7, the correspondence between the deceleration amount of each developing roller 7 and the correction amount of the developing bias corresponding to each developing roller 7, and the development Although each deceleration amount is determined based on the upper limit value of the bias, the present invention is not limited to this, and the correspondence between the deceleration amount of each developing roller 7 and the exposure intensity correction amount of the exposure apparatus 4 corresponding to each color, The configuration may be such that each deceleration amount is determined based on the upper limit value of the exposure intensity. An example of this configuration will be described below.

  In the present embodiment, the control unit 100 suppresses a change in the density of the toner image due to an increase in the total number of printed sheets and a change in humidity, every time the total number of printed sheets reaches the predetermined number. The development bias corresponding to each set development roller 7 is updated. However, the present invention is not limited to this. Each time the cumulative number of printed sheets reaches a predetermined number, the image forming condition set when the predetermined number is reached. The structure which updates the exposure intensity | strength of the exposure apparatus 4 corresponding to each color as an example may be sufficient. In order to update each exposure intensity, the control unit 100 executes an exposure intensity reduction process.

  Specifically, in the exposure intensity reduction process, the control unit 100 determines whether or not the cumulative number of printed sheets has reached a predetermined number. When determining that the cumulative number of printed sheets has reached a predetermined number, the control unit 100 determines whether the cumulative number of printed sheets has reached a predetermined number. The exposure intensity of the exposure apparatus 4 corresponding to each color set to is reduced. The control unit 100 decreases each exposure intensity according to the following equation (2). Equation (2) is shown where B represents each exposure intensity for updating each set exposure intensity.

B = each set exposure intensity−θ × amount of increase in the total number of printed sheets−ζ × amount of decrease in humidity (2)
θ and ζ are positive constants determined in advance corresponding to each exposure intensity, and may be constants obtained in advance through experiments or the like. Further, θ and ζ may be arbitrary variables.

  If the control unit 100 determines that the cumulative number of printed sheets has not reached the predetermined number, the exposure intensity reducing process is terminated. The exposure intensity reduction process is called at a predetermined time interval.

  As a result, each time the cumulative number of printed sheets reaches a predetermined number, the set exposure intensity is updated to an optimum exposure intensity that takes into account the increase in the total number of printed sheets and changes in humidity. Therefore, the density change of the toner image of each color can be kept constant. In the present embodiment, the correspondence relationship between the deceleration amount of each developing roller 7 and the correction amount of the developing bias corresponding to each developing roller 7 is the same as that of each developing roller 7 while keeping the density of the toner image of each color constant. The predetermined relationship is established when the rotational speed is reduced. However, the present invention is not limited to this, and is established when the density of the toner image of each color is reduced by a predetermined density and the rotational speed of each developing roller 7 is reduced. It may be a predetermined relationship.

  As an example of this configuration, for example, the control unit 100 can be switched to a toner save mode that is a mode in which the image forming unit 30 forms a toner image while reducing toner consumption. Is a correspondence relationship that is established when the density of the toner image of each color is reduced by a predetermined density and the rotation speed of each developing roller 7 is reduced, and the amount of deceleration of each developing roller 7 and each developing roller 7 Each deceleration amount may be determined based on the correspondence relationship with the developing bias correction amount corresponding to the above and the upper limit value of the developing bias.

  As a result, even when the control unit 100 switches to the toner save mode, the cumulative number of rotations of the developing rollers 7 can be reduced and high durability can be achieved while maintaining appropriate image forming conditions.

  In this embodiment, although the example which the control part 100 performs each step was shown, it is not limited to this, The structure which another CPU performs at least one part or one or several ASIC performs It may be.

  The process unit 3 is provided corresponding to each color of black, yellow, magenta, and cyan. However, the present invention is not limited to this, and the process unit 3 may be provided only for black. Good.

  In the present embodiment, in the deceleration process, the control unit 100 corrects each developing bias according to the deceleration of the rotational speed of each developing roller 7, but is not limited thereto, and the rotational speed of each developing roller 7 is not limited thereto. A configuration in which each exposure intensity is corrected according to deceleration may be employed. Differences in the deceleration processing of this configuration from the present embodiment are mainly S105, S115, S145 in FIG. 5 and S200 in FIG. 6, and the others are the same as in the present embodiment. Therefore, the description of the part which overlaps with this embodiment is abbreviate | omitted, and only a different part is demonstrated.

  In the deceleration amount determination process in S105, the control unit 100 determines each deceleration amount based on the correspondence relationship that associates the deceleration amount of each developing roller 7 with the correction amount of each exposure intensity and the upper limit value of each exposure intensity. The structure to determine may be sufficient. It should be noted that the exposure intensity correction amount refers to the exposure device 4 corresponding to each color in order to keep the density of the toner image of each color constant as the controller 100 decelerates the rotation speed of each developing roller 7. It is a numerical value for correcting the exposure intensity.

  Next, the control unit 100 determines that the deceleration amount of each developing roller 7 when each exposure intensity reaches the upper limit value is the maximum value of each deceleration amount, and based on this determination, sets each maximum value to each maximum value. This is set as the deceleration amount of the developing roller 7. Further, the control unit 100 sets the correction amount of each exposure intensity to the upper limit value of the determined correction amount. These settings are stored in the NVRAM 104.

  Next, the control unit 100 decelerates the rotation speed of each developing roller 7 based on each deceleration amount determined in the deceleration amount determination process, and each exposure based on each exposure intensity correction amount determined in the deceleration amount determination process. The patch forming process is executed with the intensity corrected.

  Then, the control unit 100 decelerates the rotational speed of each developing roller 7 based on each determined deceleration amount, and corrects each exposure intensity based on the determined correction amount for each exposure intensity in the print data. Based on this, the toner image of each color is formed on the paper by the image forming unit 30.

  As a result, each developing roller 7 rotates while the rotation speed of each developing roller 7 is decelerated without the exposure intensity exceeding the upper limit value. Therefore, while maintaining appropriate image forming conditions, each developing roller 7 The cumulative number of revolutions can be reduced and high durability can be achieved. Further, when the control unit 100 determines the deceleration amount of each developing roller 7, the correspondence relationship between the deceleration amount of each developing roller 7 and the correction amount of each exposure intensity and the upper limit value of each exposure intensity Based on this, the respective deceleration amounts are determined. As a result, the total number of rotations of each developing roller 7 can be reduced while keeping the density of the toner image of each color constant.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Apparatus main body 3 Process part 4 Exposure apparatus 5 Photoconductor 7 Developing roller 13 Transfer roller 17 Density sensor 30 Image forming part 100 Control part 150 Humidity sensor 200 Development bias generation circuit

Claims (9)

A photosensitive member carrying a toner image, an exposure device for forming an electrostatic latent image on the photosensitive member, and supplying toner to the electrostatic latent image formed by the exposure device to develop the electrostatic latent image An image forming unit having a developing roller for transferring, and a transfer unit for transferring a toner image carried on the photosensitive member to a recording sheet;
A control unit for controlling the rotation speed of the developing roller,
The controller is
Determining the amount of deceleration based on the correspondence between the amount of deceleration with respect to the rotation speed of the developing roller and the amount of correction for correcting the image forming condition of the image forming unit, and the upper limit value of the image forming condition;
A toner image is formed on the recording sheet in the image forming unit in a state where the rotation speed of the developing roller is reduced using the image forming condition equal to or less than the upper limit value and the deceleration amount equal to or less than the determined deceleration amount. An image forming apparatus. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the image forming condition is an absolute value of a developing bias applied to the developing roller when the electrostatic latent image is developed. The image forming apparatus according to claim 2,
The controller is
An image forming apparatus that counts the number of recording sheets on which a toner image is formed by the image forming unit, and changes the absolute value of the developing bias according to the counted number of recording sheets. The image forming apparatus according to claim 2, wherein:
It has a humidity detector that detects the humidity inside the device.
The controller is
An image forming apparatus that changes the absolute value of the developing bias according to the humidity detected by the humidity detector. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the image forming condition is an exposure intensity when the exposure apparatus forms the electrostatic latent image. The image forming apparatus according to claim 5, wherein
The controller is
An image forming apparatus that counts the number of recording sheets on which a toner image is formed by the image forming unit and changes the exposure intensity in accordance with the counted number of recording sheets. The image forming apparatus according to claim 5, wherein:
It has a humidity detector that detects the humidity inside the device.
The controller is
An image forming apparatus that changes the exposure intensity according to the humidity detected by the humidity detector. A photosensitive member carrying a toner image, an exposure device for forming an electrostatic latent image on the photosensitive member, and supplying toner to the electrostatic latent image formed by the exposure device to develop the electrostatic latent image The image forming unit having a developing roller and a transfer unit that transfers a toner image carried on the photosensitive member to a recording sheet is corrected for a deceleration amount with respect to a rotation speed of the developing roller and an image forming condition of the image forming unit. A deceleration amount determination step for determining the deceleration amount based on the correspondence relationship with the correction amount for the image and the upper limit value of the image forming condition;
A toner image is formed on the recording sheet in the image forming unit in a state where the rotation speed of the developing roller is reduced using the image forming condition equal to or less than the upper limit value and the deceleration amount equal to or less than the determined deceleration amount. A speed control method including a decelerating step. A photosensitive member carrying a toner image, an exposure device for forming an electrostatic latent image on the photosensitive member, and supplying toner to the electrostatic latent image formed by the exposure device to develop the electrostatic latent image An image forming unit having a developing roller and a transfer unit that transfers the toner image carried on the photosensitive member to a recording sheet;
Deceleration amount for determining the deceleration amount based on the correspondence between the deceleration amount with respect to the rotation speed of the developing roller and the correction amount for correcting the image forming condition of the image forming unit and the upper limit value of the image forming condition The decision process,
A toner image is formed on the recording sheet in the image forming unit in a state where the rotation speed of the developing roller is reduced using the image forming condition equal to or less than the upper limit value and using the deceleration amount less than the determined deceleration amount. A speed control program for executing a deceleration process.

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