JP6304151B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus having a charging device arranged in contact with an image carrier.

In the image forming apparatus described in Patent Document 1, the photosensitive drum is charged by a charging roller. In this image forming apparatus, the charging application voltage (application voltage to the charging device) is changed according to the cumulative number of printed sheets, and the pace of the change is adjusted based on the output mode and the environment mode. The output mode is a mode representing whether monochrome or color image formation is performed. The environmental mode is a mode that is classified according to the temperature and humidity levels of the installation environment of the photosensitive drum.
In this image forming apparatus, there is a change in factors other than the number of printed sheets that affect the degree of film reduction of the photosensitive drum by adjusting the charging application voltage according to the output mode and the environmental mode as well as the cumulative number of printed sheets. Even in this case, it is possible to set the charging application voltage corresponding to the degree of film reduction of the photosensitive drum.

JP 2007-187832 A

  However, in the image forming apparatus described in Patent Document 1, even if a charging application voltage corresponding to the film reduction degree of the photosensitive drum is set, depending on the environment, the surface potential of the photosensitive drum applies the charging application voltage. In some cases, it may take a long time to reach an appropriate charging potential.

  For example, in a charging roller that has been in a low temperature and low humidity environment for a long time, the charging ability may be particularly deteriorated when the image forming apparatus main body is turned on or returned from the sleep mode. Therefore, since it takes time to restore the charging ability of the charging roller, it may take time for the surface potential of the photosensitive drum to reach an appropriate charging potential. As a result, image defects (for example, fogging) may occur until the surface potential of the photosensitive drum reaches an appropriate charging potential.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of shortening the return time of the charging ability of a charging unit that charges an image carrier in an environment of low temperature and low humidity. .

  According to one aspect of the present invention, an image forming apparatus includes an image carrier, a drive unit, a charging unit, a voltage application unit, a control unit, a fixing unit, a fixing temperature detection unit, and an environment detection unit. Is provided. An electrostatic latent image is formed on the image carrier. The drive unit rotates the image carrier. The charging unit charges the surface of the image carrier. The voltage application unit applies a charging voltage for charging the surface of the image carrier to the charging unit. The control unit controls the drive unit and the charging unit to execute warm-up of the image carrier and the charging unit. The fixing unit fixes an image based on the electrostatic latent image on the transfer material. The fixing temperature detection unit detects the temperature of the fixing unit. The environment detection unit detects the temperature and humidity of the environment where the image forming apparatus is installed. When executing warm-up of the image carrier and the charging unit, the control unit rotates the image carrier based on the temperature of the fixing unit, the temperature of the environment, and the humidity of the environment. The rotation time and the charging voltage are selected, and the drive unit is controlled so that the image carrier rotates during the selected rotation time, and the selected charging voltage is applied to the charging unit. In this manner, the voltage application unit is controlled.

  According to the present invention, it is possible to shorten the recovery time of the charging ability of the charging unit that charges the image carrier in a low temperature and low humidity environment.

1 is a cross-sectional view illustrating an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a part of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the temperature / humidity table of the image forming apparatus which concerns on embodiment of this invention. (A) It is a figure which shows the 1st control table of the image forming apparatus which concerns on embodiment of this invention. (B) is a diagram showing a second control table of the image forming apparatus according to the embodiment of the present invention. 5 is a flowchart showing a part of warm-up control executed by the image forming apparatus according to the embodiment of the present invention. 6 is a flowchart showing another part of the warm-up control executed by the image forming apparatus according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof is not repeated.

  An image forming apparatus 1 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing the image forming apparatus 1. The image forming apparatus 1 forms an image on the transfer material P. The transfer material P is, for example, a sheet such as paper. In the present embodiment, the image forming apparatus 1 is a multifunction machine. The multi-function peripheral includes, for example, at least two devices among a copying machine, a printer, a facsimile, and a scanner.

  The image forming apparatus 1 includes a feeding unit 10, a conveying unit 20, an image forming unit 30, a fixing unit 40, a discharging unit 65, a document conveying unit 70, an image reading unit 75, an operation unit 80, An environment detection unit 50 and a fixing temperature detection unit 55 are provided.

  The feeding unit 10 includes a plurality of cassettes 11 each containing a plurality of transfer materials P, and a manual feed tray 12. The transfer material P is made of, for example, paper or synthetic resin. The feeding unit 10 feeds the transfer material P from the cassette 11 or the manual feed tray 12 to the transport unit 20. The transport unit 20 transports the transfer material P to the image forming unit 30.

  The image forming unit 30 forms an image on the transfer material P. Specifically, the image forming unit 30 includes a photosensitive drum 31 (image carrier), a charging roller 32 (charging unit), an exposure unit 33, a developing unit 34, a transfer unit 35, and a cleaning unit 36. And a static elimination unit 37.

  The charging roller 32 is disposed in contact with the surface of the photosensitive drum 31. The charging roller 32 charges the surface of the photosensitive drum 31. Details will be described later. The exposure unit 33 irradiates the surface of the photosensitive drum 31 with light based on the image data. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 31.

  The developing unit 34 includes a developing roller 34a and develops the electrostatic latent image with toner (developer). Specifically, the developing unit 34 forms a toner image on the surface of the photosensitive drum 31 by attaching toner to the electrostatic latent image. The toner image is an image based on an electrostatic latent image. The transfer unit 35 transfers the toner image onto the transfer material P. The toner image transferred to the transfer material P may be referred to as “image”. The cleaning unit 36 removes toner remaining on the surface of the photosensitive drum 31. Details will be described later. The neutralization unit 37 removes residual charges on the surface of the photosensitive drum 31. The transport unit 20 transports the transfer material P to which the image is transferred to the fixing unit 40.

  The fixing unit 40 heats and pressurizes the transfer material P to which the image is transferred, and fixes the image on the transfer material P. Specifically, the fixing unit 40 includes a heating roller 41 and a pressure roller 42. The heating roller 41 heats the transfer material P. The pressure roller 42 is pressed against the heating roller 41. The transport unit 20 transports the transfer material P on which the image is fixed to the discharge unit 65.

  The discharge unit 65 discharges the transfer material P to the outside of the image forming apparatus 1. The document transport unit 70 transports the document toward the image reading unit 75. The image reading unit 75 reads an image of a document and generates image data. The operation unit 80 receives various user operations.

  The environment detection unit 50 detects the temperature (hereinafter referred to as “environmental temperature”) and humidity (hereinafter referred to as “environmental humidity”) in which the image forming apparatus 1 is installed. Specifically, the environmental temperature indicates the temperature outside the image forming apparatus 1, and the environmental humidity indicates the humidity outside the image forming apparatus 1.

  The fixing temperature detector 55 detects the temperature of the fixing unit 40 (hereinafter referred to as “fixing temperature”). Specifically, the fixing temperature detection unit 55 is disposed to face the heating roller 41. The fixing temperature detection unit 55 detects the temperature of the heating roller 41 without contacting the heating roller 41. Specifically, the temperature of the heating roller 41 is the fixing temperature.

  The charging roller 32 and the cleaning unit 36 will be described with reference to FIG. FIG. 2 is a diagram illustrating a part of the image forming apparatus 1. As shown in FIG. 2, the charging roller 32 includes a cored bar portion 32a and an elastic portion 32b. The elastic part 32b is formed on the outer peripheral surface of the cored bar part 32a and has conductivity. The elastic part 32b is, for example, conductive rubber.

  The cleaning unit 36 includes a cleaning blade 36a and a toner seal 36b. The cleaning blade 36 a is in pressure contact with the peripheral surface of the photosensitive drum 31 and removes toner remaining on the peripheral surface of the photosensitive drum 31. Specifically, the edge of the cleaning blade 36 a is in pressure contact with the peripheral surface of the photosensitive drum 31. The cleaning blade 36a is made of rubber, for example. The toner seal 36b is in contact with the peripheral surface of the photosensitive drum 31, and suppresses scattering of the toner removed by the cleaning blade 36a.

  With reference to FIG. 2, the warm-up of the photosensitive drum 31 and the charging roller 32 will be described. As shown in FIG. 2, the image forming apparatus 1 further includes a control unit 90, a voltage application unit 92, and a drive unit 94.

  The control unit 90 controls the driving unit 94 and the voltage application unit 92 to cause the photosensitive drum 31 and the charging roller 32 to warm up. The warm-up of the photosensitive drum 31 and the charging roller 32 is a preparatory operation of the photosensitive drum 31 and the charging roller 32 for setting the surface potential of the photosensitive drum 31 to a predetermined charging potential. Details are as follows.

  That is, the control unit 90 controls each element of the image forming apparatus 1. Specifically, the control unit 90 includes a processing unit 90a and a storage unit 90b. The processing unit 90a is a processor such as a CPU (Central Processing Unit), and executes various processes by executing a computer program stored in the storage unit 90b. The storage unit 90b includes a main storage device such as a semiconductor memory, and an auxiliary storage device such as a semiconductor memory and a hard disk drive. The storage unit 90b stores various computer programs and data.

  The voltage application unit 92 applies a charging voltage CV that charges the surface of the photosensitive drum 31 to the charging roller 32 under the control of the control unit 90. The charging roller 32 is in contact with the surface of the photosensitive drum 31. Accordingly, when the charging voltage CV is applied to the charging roller 32, the surface of the photosensitive drum 31 is charged.

  The drive unit 94 transmits driving force to the photosensitive drum 31, the charging roller 32, and the developing roller 34a under the control of the control unit 90, and rotates the photosensitive drum 31, the charging roller 32, and the developing roller 34a. . Specifically, the drive unit 94 includes a motor and a plurality of gears.

  When the control unit 90 performs warm-up of the photosensitive drum 31 and the charging roller 32, the fixing temperature detected by the fixing temperature detection unit 55, the environmental temperature detected by the environment detection unit 50, and the environment detection unit 50 Based on the detected environmental humidity, a rotation time RT for rotating the photosensitive drum 31 and a charging voltage CV are selected.

  Specifically, the control unit 90 selects the longer rotation time RT as the environmental temperature and the environmental humidity are lower. Further, the control unit 90 determines whether or not the fixing temperature is equal to or lower than the threshold Th. The rotation time RT selected when it is determined that the fixing temperature is higher than the threshold Th (that is, the rotation time RT selected when it is determined that the fixing temperature is not equal to or less than the threshold Th) is equal to or less than the threshold. It is shorter than the rotation time RT selected when it is determined that there is. Further, the control unit 90 selects a larger charging voltage CV as the environmental temperature and the environmental humidity are lower.

  The control unit 90 controls the driving unit 94 so that the photosensitive drum 31 rotates during the selected rotation time RT when the photosensitive drum 31 and the charging roller 32 are warmed up.

  If the selected rotation time RT is 0, the control unit 90 controls the drive unit 94 so that the photosensitive drum 31 does not rotate.

  The controller 90 performs a voltage application unit 92 so that the selected charging voltage CV is applied to the charging roller 32 during the selected rotation time RT when the photosensitive drum 31 and the charging roller 32 are warmed up. To control.

  In this case, the control unit 90 applies the first voltage as the charging voltage CV to the charging roller 32 during the predetermined time PT after the photosensitive drum 31 starts rotating in the selected rotation time RT. In addition, the voltage application unit 92 can be controlled. Further, the control unit 90 controls the voltage application unit 92 such that the second voltage as the charging voltage CV is applied to the charging roller 32 after the predetermined time PT has elapsed in the selected rotation time RT. You can also. The second voltage is greater than the first voltage. The controller 90 selects the first voltage and the second voltage as the charging voltage CV based on the fixing temperature, the environmental temperature, and the environmental humidity. The predetermined time PT can be determined experimentally and / or empirically, for example.

  When the selected rotation time RT is 0, the control unit 90 controls the voltage application unit 92 so that the selected charging voltage CV is applied to the charging roller 32 for a certain time.

  The control unit 90 controls the developing unit 34 so that the toner is discharged toward the photosensitive drum 31 when the photosensitive drum 31 and the charging roller 32 are warmed up. For example, the control unit 90 controls the developing unit 34 so that toner is intermittently ejected.

  Specifically, the control unit 90 controls the developing unit 34 by controlling the drive unit 94. That is, the control unit 90 controls the driving unit 94 so that the developing roller 34a rotates. As a result, the developing roller 34 a discharges toner toward the photosensitive drum 31.

  As described above with reference to FIG. 2, according to the present embodiment, the control unit 90 sets the rotation time RT and the charging voltage CV based on the fixing temperature, the environmental temperature, and the environmental humidity during the warm-up. Select. Therefore, even in a low temperature and low humidity environment, a suitable rotation time RT and a suitable charging voltage CV can be selected according to the low temperature and low humidity environment. As a result, the recovery time of the charging capability of the charging roller 32 can be shortened, so that the time until the surface potential of the photosensitive drum 31 becomes a predetermined charging potential (for example, an appropriate charging potential) can be shortened.

  The charging ability is an ability of the charging roller 32 to charge the surface potential of the photosensitive drum 31 to a predetermined charging potential. When the charging ability of the charging roller 32 is low, the time until the surface potential of the photosensitive drum 31 becomes a predetermined charging potential becomes longer. When the charging ability of the charging roller 32 is high, the surface potential of the photosensitive drum 31 becomes predetermined. The time until the charged potential is reduced. The rotation time RT, that is, the warm-up time, corresponds to the return time of the charging ability of the charging roller 32.

  For example, the charging roller 32 that has been in a low-temperature and low-humidity environment for a long time may have a reduced charging capability when the image forming apparatus 1 is turned on or returned from the sleep mode to the normal mode. . However, in this embodiment, since the recovery time of the charging ability of the charging roller 32 can be shortened even in a low temperature and low humidity environment, the time until the surface potential of the photosensitive drum 31 becomes a predetermined charging potential can be shortened. As a result, the occurrence of image defects (for example, fogging) can be suppressed.

  Note that the sleep mode is a mode in which power supply voltage is supplied only to the minimum necessary functions of the image forming apparatus 1 to minimize power consumption. The normal mode is a mode in which a power supply voltage is supplied to all functions of the image forming apparatus 1.

  In recent years, in order to realize energy saving, the time for lowering the fixing temperature is shortened after the image forming process (for example, printing process) is completed. Therefore, the environmental temperature tends to decrease relatively quickly in a low temperature and low humidity environment. Therefore, not only when the power is turned on, but also when returning from the sleep mode, reducing the return time of the charging ability of the charging roller 32 is effective in suppressing the occurrence of image defects (for example, fogging).

  Further, according to the present embodiment, the developing unit 34 discharges toner toward the photosensitive drum 31 during warm-up. Accordingly, the toner can be supplied to the edge of the cleaning blade 36 a via the photosensitive drum 31. As a result, the rotation time RT becomes long, and even when the rotating photosensitive drum 31 is rubbed for a long time by the cleaning blade 36a, an increase in stress applied to the photosensitive drum 31 by the cleaning blade 36a can be suppressed, and cleaning can be performed. It is possible to suppress the occurrence of chipping of the blade 36a. In addition, since an increase in stress from the cleaning blade 36a to the photosensitive drum 31 is suppressed, a decrease in charging property of the photosensitive drum 31 can be suppressed. In particular, in an environment of low temperature and low humidity, the elastic portion 32b of the charging roller 32 is easily cured, and therefore it is effective to supply toner from the developing portion 34 to the cleaning blade 36a via the photosensitive drum 31.

  Furthermore, according to the present embodiment, the developing unit 34 intermittently discharges toner during warm-up. Accordingly, it is possible to suppress the loss of the edge of the cleaning blade 36a and the increase in stress from the cleaning blade 36a to the photosensitive drum 31 while suppressing the consumption of toner.

  Further, according to the present embodiment, the control unit 90 selects a longer rotation time RT and a larger charging voltage CV as the environmental temperature and the environmental humidity are lower. Therefore, an appropriate rotation time RT and charging voltage CV can be selected according to the degree of low temperature and low humidity. As a result, excessive or insufficient rotation time RT and charging voltage CV can be suppressed.

  Furthermore, according to the present embodiment, the rotation time RT selected when the fixing temperature is higher than the threshold Th is shorter than the rotation time RT selected when the fixing temperature is equal to or lower than the threshold Th. Accordingly, when the fixing temperature is higher than the threshold value Th, the return time of the charging ability of the charging roller 32 can be further shortened. When the fixing temperature is higher than the threshold value Th, it is highly possible that the charging roller 32 has a relatively high charging capability because there is a high possibility that the image forming process has just been executed. Accordingly, the charging ability of the charging roller 32 can be restored even with a short rotation time RT, that is, a short warm-up time.

  Further, according to the present embodiment, the voltage application unit 92 applies a relatively small first voltage to the charging roller 32 for a predetermined time PT after the photosensitive drum 31 starts rotating, After the lapse of time, a relatively large second voltage is applied to the charging roller 32. As a result, the recovery time of the charging ability of the charging roller 32 can be shortened while suppressing the occurrence of pinholes on the photosensitive drum 31.

  The reason why the small first voltage is applied to the charging roller 32 during the predetermined time PT is to prevent the occurrence of pinholes on the photosensitive drum 31 due to the initial transient charging current. In addition, since the transient component disappears after the elapse of the predetermined time PT, a large second voltage is applied to the charging roller 32 to shorten the recovery time of the charging ability of the charging roller 32.

  Hereinafter, in the present embodiment, the rotation time RT to be selected by the control unit 90 is represented by the number of rotations of the photosensitive drum 31. Accordingly, the number of rotations representing the rotation time RT to be selected may be described as “number of rotations RT”. In the present embodiment, the time for which the photosensitive drum 31 rotates once is constant. That is, the rotation speed of the photosensitive drum 31 is constant. For example, the photosensitive drum 31 rotates at a rotation speed of 170 mm / second. According to the present embodiment, the rotation time RT is represented by the number of rotations of the photosensitive drum 31, thereby facilitating control for warming up the photosensitive drum 31 and the charging roller 32 and allowing the designer to intuitively Therefore, the rotation time RT can be recognized and the design work can be made more efficient.

  The warm-up of the photosensitive drum 31 and the charging roller 32 will be described in more detail with reference to FIGS. FIG. 3 is a diagram showing the temperature / humidity table 100. FIG. 4A shows the first control table 101. FIG. 4B is a diagram illustrating the second control table 102.

  As shown in FIGS. 2, 3, 4 (a), and 4 (b), the control unit 90 refers to the temperature / humidity table 100, the first control table 101, and the second control table 102. The photosensitive drum 31 and the charging roller 32 are warmed up. Details are as follows.

  That is, as shown in FIGS. 2 and 3, the storage unit 90 b stores a temperature / humidity table 100. The temperature / humidity table 100 is a table in which a temperature / humidity range A, a temperature / humidity range B, a temperature / humidity range C, and a temperature / humidity range D are determined from the environmental temperature and the environmental humidity. Each of the temperature / humidity range A to the temperature / humidity range D is a range defined by the environmental temperature and the environmental humidity.

  In comparison, the temperature / humidity range A is the lowest temperature / humidity environment, the temperature / humidity range B is the temperature / humidity environment next to the temperature / humidity range A, and the temperature / humidity range C is next to the temperature / humidity range B. The temperature / humidity range D is next to the temperature / humidity range C, and is a low temperature / humidity environment.

  In this embodiment, as shown in Table 1, a charging voltage CV that can be assigned to each of the temperature / humidity range A to the temperature / humidity range D, that is, a charging voltage CV that can be selected by the control unit 90 is prepared. Yes. In Table 1, the unit of voltage is shown in volts (V).

  As shown in Table 1, the charging voltage CV as a selection target by the control unit 90 is represented by the sum of the base voltage, the first correction voltage, and the second correction voltage. The base voltage is set to a voltage corresponding to the degree of film reduction of the photosensitive drum 31. Further, a larger first correction voltage is set as the temperature becomes lower and the humidity becomes lower. Furthermore, a larger second correction voltage is set as the temperature becomes lower and humidity becomes lower.

  At the time of warm-up in an environment (temperature / humidity range D in FIG. 3) that is not low temperature and low humidity, the control unit 90 performs base voltage (> 0V), first correction voltage (= 0V), and second correction voltage (= 0V). And select. That is, the control unit 90 sets the base voltage to the charging voltage CV. Further, the control unit 90 sets the base voltage to the charging voltage CV when the environmental temperature and the environmental humidity do not belong to any of the temperature / humidity range A to the temperature / humidity range D. In the present embodiment, the control unit 90 sets the base voltage to the charging voltage CV when the environmental temperature is 25 ° C. or higher.

  In the low-temperature and low-humidity environment of the temperature and humidity range C in FIG. 3, the control unit 90 performs the first correction voltage (> 0 V) and the second correction voltage (= 0 V) based on the fixing temperature, the environmental temperature, and the environmental humidity. And select. Then, the control unit 90 sets a voltage calculated by adding the first correction voltage to the base voltage (hereinafter sometimes referred to as “first addition voltage”) as the charging voltage CV. Hereinafter, adding the first correction voltage to the base voltage is defined as “first correction”.

  In the low-temperature and low-humidity environment of the temperature / humidity range A or B in FIG. 3, the control unit 90 performs the first correction voltage (> 0 V) and the second correction voltage (> 0V) is selected. Then, the control unit 90 adds a voltage calculated by adding the first correction voltage and the second correction voltage to the base voltage (hereinafter may be referred to as “second addition voltage”) as the charging voltage CV. Set to. Hereinafter, adding the first correction voltage and the second correction voltage to the base voltage is defined as “second correction”.

  For example, it is determined experimentally and / or empirically whether the control unit 90 performs the first correction or the second correction.

  Further, in this embodiment, as shown in Table 2, a rotation speed RT that can be assigned to each of the temperature / humidity range A to the temperature / humidity range D, that is, a rotation speed RT that can be selected by the control unit 90 is prepared. Has been. Further, a rotation speed RT that can be selected when the fixing temperature is equal to or lower than the threshold Th and a rotation speed RT that can be selected when the fixing temperature is higher than the threshold Th are prepared. In Table 2, the unit of the number of rotations is indicated by the number of rotations (times) of the photosensitive drum 31. The threshold value Th is, for example, 50 ° C.

  As shown in Table 2, the lower the temperature and humidity, the higher the rotation speed RT. In each of the temperature / humidity range A to the temperature / humidity range D, the rotation speed RT that can be selected when the fixing temperature is equal to or lower than the threshold Th is higher than the rotation speed RT that can be selected when the fixing temperature is higher than the threshold Th. Many.

  In the present embodiment, the first control table 101 and the second control table 102 are created based on Table 1 and Table 2.

  As illustrated in FIGS. 4A and 4B, the storage unit 90b stores a first control table 101 and a second control table 102. The unit of voltage is indicated by volts (V), and the unit of rotation number is indicated by the number of rotations (times) of the photosensitive drum 31. The threshold value Th is, for example, 50 ° C.

  The first control table 101 is referred to by the control unit 90 when the fixing temperature is equal to or lower than the threshold Th. The first control table 101 includes, for each of the temperature / humidity range A to the temperature / humidity range D, the first correction voltage and the second correction of the rotation speed RT of the photosensitive drum 31 and the charging voltage CV of the charging roller 32. 6 is a table in which voltages and information indicating whether or not toner is discharged during warm-up are assigned.

  The second control table 102 is referred to by the control unit 90 when the fixing temperature is higher than the threshold Th. The second control table 102 includes, for each of the temperature / humidity range A to the temperature / humidity range D, the first correction voltage and the second correction of the rotation number RT of the photosensitive drum 31 and the charging voltage CV of the charging roller 32. 6 is a table in which voltages and information indicating whether or not toner is discharged during warm-up are assigned.

  In each of the first control table 101 and the second control table 102, a higher rotation speed RT is assigned as the temperature becomes lower and humidity becomes lower. In each of the first control table 101 and the second control table 102, the first correction voltage and the second correction voltage are assigned so that the charging voltage CV increases as the temperature decreases and the humidity decreases. Further, it is determined that toner is discharged toward the photosensitive drum 31 during warm-up only in the temperature and humidity range A, which is the lowest temperature and humidity environment in the first control table 101 (with toner discharge).

  Further, when the first control table 101 and the second control table 102 are compared, in each of the temperature / humidity range A to the temperature / humidity range D, the rotation speed RT of the first control table 101 is equal to the rotation speed RT of the second control table 102. More than. Further, the first correction voltage and the first correction voltage are set so that the charging voltage CV of the first control table 101 is equal to or larger than the charging voltage CV of the second control table 102. Two correction voltages are assigned.

  In each of the first control table 101 and the second control table 102, the first correction voltage is 0V, so that the control unit 90 does not use both the first correction voltage and the second correction voltage. This means that the base voltage is set to the charging voltage CV. In addition, when the first correction voltage is other than 0V and the second correction voltage is 0V, it means that the control unit 90 executes the first correction without using the second correction voltage. Furthermore, the second correction voltage being other than 0V means that the control unit 90 executes the second correction.

  With reference to FIGS. 2-6, the process of the control part 90 which refers to the temperature / humidity table 100, the 1st control table 101, and the 2nd control table 102 is demonstrated. 5 and 6 are flowcharts showing the warm-up control executed by the control unit 90.

  As shown in FIGS. 2 and 5, in step S <b> 1, the control unit 90 determines whether the fixing temperature is equal to or lower than a threshold value Th. 5 and 6, the threshold value Th is, for example, 50 ° C.

  When it is determined that the fixing temperature is equal to or lower than the threshold Th (Yes in Step S1), the control unit 90 advances the process to Step S3.

  As shown in FIGS. 3 and 5, in step S <b> 3, the control unit 90 refers to the temperature / humidity table 100, and the temperature / humidity to which the environmental temperature and the environmental humidity belong from the temperature / humidity range A to the temperature / humidity range D. Determine the range.

  In step S5, the control unit 90 determines whether or not the temperature / humidity range determined in step S3 is the temperature / humidity range D.

  When it determines with a temperature / humidity range being the temperature / humidity range D (it is Yes at step S5), the control part 90 advances a process to step S7.

  As shown in FIG. 4A and FIG. 5, in step S <b> 7, the control unit 90 refers to the first control table 101, and the rotation speed RT (0 times) assigned to the temperature / humidity range D and the first The drive unit 94 and the voltage application unit 92 are controlled based on the correction voltage (0V), the second correction voltage (0V), information indicating the presence or absence of toner ejection (none), and the base voltage.

  That is, the control unit 90 controls the drive unit 94 so that the photosensitive drum 31 does not rotate. Further, the control unit 90 controls the voltage application unit 92 so that the charging voltage CV set to the base voltage is applied to the charging roller 32 for a certain period of time. Further, the control unit 90 controls the developing unit 34 so as not to discharge the toner.

  On the other hand, when it determines with a temperature / humidity range not being the temperature / humidity range D (it is No at step S5), the control part 90 advances a process to step S9.

  In step S9, the control unit 90 determines whether or not the temperature / humidity range determined in step S3 is the temperature / humidity range C.

  When it determines with a temperature / humidity range being the temperature / humidity range C (it is Yes at step S9), the control part 90 advances a process to step S11.

  In step S11, the control unit 90 refers to the first control table 101, and the rotation speed RT (11 times), the first correction voltage (100V), and the second correction voltage (100V) assigned to the temperature / humidity range C. The drive unit 94 and the voltage application unit 92 are controlled based on the information indicating whether or not toner is discharged (none) and the base voltage.

  That is, the control unit 90 controls the drive unit 94 so that the photosensitive drum 31 rotates 11 times. Further, the control unit 90 executes the second correction and controls the voltage application unit 92 so that the second addition voltage as the charging voltage CV is applied to the charging roller 32 while the photosensitive drum 31 rotates 11 times. . However, during the first two rotations of the photosensitive drum 31, the control unit 90 performs the first correction using the first correction voltage (100V) and uses the first addition voltage as the charging voltage CV as the charging roller. The voltage application unit 92 is controlled so that the voltage is applied to 32. Further, the control unit 90 controls the developing unit 34 so as not to discharge the toner.

  On the other hand, when it determines with the temperature / humidity range not being the temperature / humidity range C (it is No at step S9), the control part 90 advances a process to step S13.

  In step S13, the control unit 90 determines whether or not the temperature / humidity range determined in step S3 is the temperature / humidity range B.

  When it determines with a temperature / humidity range being the temperature / humidity range B (it is Yes at step S13), the control part 90 advances a process to step S15.

  In step S15, the control unit 90 refers to the first control table 101, and the rotation number RT (23 times), the first correction voltage (150V), and the second correction voltage (130V) assigned to the temperature / humidity range B. The drive unit 94 and the voltage application unit 92 are controlled based on the information indicating whether or not toner is discharged (none) and the base voltage.

  That is, the control unit 90 controls the drive unit 94 so that the photosensitive drum 31 rotates 23 times. Further, the control unit 90 executes the second correction and controls the voltage application unit 92 so that the second addition voltage as the charging voltage CV is applied to the charging roller 32 while the photosensitive drum 31 rotates 23 times. . However, during the first two rotations of the photosensitive drum 31, the control unit 90 performs the first correction using the first correction voltage (150V) and uses the first addition voltage as the charging voltage CV as the charging roller. The voltage application unit 92 is controlled so that the voltage is applied to 32. Further, the control unit 90 controls the developing unit 34 so as not to discharge the toner.

  On the other hand, if it is determined that the temperature / humidity range is not the temperature / humidity range B (No in step S13), that is, if it is determined that the temperature / humidity range is the temperature / humidity range A, the control unit 90 advances the process to step S17. .

  In step S17, the control unit 90 refers to the first control table 101, and the rotation speed RT (52 times), the first correction voltage (200V), and the second correction voltage (150V) assigned to the temperature / humidity range A. The drive unit 94 and the voltage application unit 92 are controlled based on the information (present) indicating whether or not toner is discharged and the base voltage.

  That is, the control unit 90 controls the drive unit 94 so that the photosensitive drum 31 rotates 52 times. In addition, the control unit 90 executes the second correction, and controls the voltage application unit 92 so that the second addition voltage as the charging voltage CV is applied to the charging roller 32 while the photosensitive drum 31 rotates 52 times. . However, during the first two rotations of the photosensitive drum 31, the control unit 90 performs the first correction using the first correction voltage (200V), and uses the first addition voltage as the charging voltage CV as the charging roller. The voltage application unit 92 is controlled so that the voltage is applied to 32. Further, the control unit 90 controls the developing unit 34 so that the toner is discharged toward the photosensitive drum 31.

  On the other hand, when it is determined that the fixing temperature is not lower than the threshold Th (No in step S1), that is, when it is determined that the fixing temperature is higher than the threshold Th, the control unit 90 advances the processing to step S21 in FIG.

  As shown in FIGS. 3 and 6, in step S <b> 21, the control unit 90 refers to the temperature / humidity table 100, and the temperature / humidity to which the environmental temperature and the environmental humidity belong from the temperature / humidity range A to the temperature / humidity range D. Determine the range.

  In step S23, the control unit 90 determines whether or not the temperature / humidity range determined in step S21 is the temperature / humidity range D.

  When it determines with a temperature / humidity range being the temperature / humidity range D (it is Yes at step S23), the control part 90 advances a process to step S25.

  As shown in FIGS. 4B and 6, in step S <b> 25, the control unit 90 refers to the second control table 102, and the rotation speed RT (0 times) assigned to the temperature / humidity range D and the first The drive unit 94 and the voltage application unit 92 are controlled based on the correction voltage (0V), the second correction voltage (0V), information indicating the presence or absence of toner ejection (none), and the base voltage. That is, the process of step S25 is the same as the process of step S7.

  On the other hand, when it determines with the temperature / humidity range not being the temperature / humidity range D (it is No at step S23), the control part 90 advances a process to step S27.

  In step S27, the control unit 90 determines whether or not the temperature / humidity range determined in step S21 is the temperature / humidity range C.

  When it determines with a temperature / humidity range being the temperature / humidity range C (it is Yes at step S27), the control part 90 advances a process to step S29.

  In step S29, the control unit 90 refers to the second control table 102, and the rotation speed RT (twice), the first correction voltage (100V), and the second correction voltage (0V) assigned to the temperature / humidity range C. The drive unit 94 and the voltage application unit 92 are controlled based on the information indicating whether or not toner is discharged (none) and the base voltage.

  That is, the control unit 90 controls the drive unit 94 so that the photosensitive drum 31 rotates twice. Further, the control unit 90 executes the first correction and controls the voltage application unit 92 so that the first addition voltage as the charging voltage CV is applied to the charging roller 32 while the photosensitive drum 31 rotates twice. . Further, the control unit 90 controls the developing unit 34 so as not to discharge the toner.

  On the other hand, when it determines with the temperature / humidity range not being the temperature / humidity range C (it is No at step S27), the control part 90 advances a process to step S31.

  In step S31, the control unit 90 determines whether or not the temperature / humidity range determined in step S21 is the temperature / humidity range B.

  When it determines with a temperature / humidity range being the temperature / humidity range B (it is Yes at step S31), the control part 90 advances a process to step S33.

  In step S33, the control unit 90 refers to the second control table 102, and the rotation speed RT (twice), the first correction voltage (150V), and the second correction voltage (130V) assigned to the temperature / humidity range B. The drive unit 94 and the voltage application unit 92 are controlled based on the information indicating whether or not toner is discharged (none) and the base voltage.

  That is, the control unit 90 controls the drive unit 94 so that the photosensitive drum 31 rotates twice. In addition, the control unit 90 executes the second correction and controls the voltage application unit 92 so that the second addition voltage as the charging voltage CV is applied to the charging roller 32 while the photosensitive drum 31 rotates twice. . Further, the control unit 90 controls the developing unit 34 so as not to discharge the toner.

  On the other hand, if it is determined that the temperature / humidity range is not the temperature / humidity range B (No in step S31), that is, if it is determined that the temperature / humidity range is the temperature / humidity range A, the control unit 90 advances the process to step S35. .

  In step S35, the control unit 90 refers to the second control table 102, and the rotation speed RT (three times), the first correction voltage (200V), and the second correction voltage (150V) assigned to the temperature / humidity range A. The drive unit 94 and the voltage application unit 92 are controlled based on the information indicating whether or not toner is discharged (none) and the base voltage.

  That is, the control unit 90 controls the drive unit 94 so that the photosensitive drum 31 rotates three times. Further, the control unit 90 executes the second correction and controls the voltage application unit 92 so that the second addition voltage as the charging voltage CV is applied to the charging roller 32 while the photosensitive drum 31 rotates three times. . Further, the control unit 90 controls the developing unit 34 so as not to discharge the toner.

  As described above with reference to FIGS. 5 and 6, according to the present embodiment, the degree of decrease in the charging ability of the charging roller 32 in the low temperature and low humidity environment is determined from the environmental temperature, the environmental humidity, and the fixing temperature. As a result, a suitable rotational speed RT and charging voltage CV are determined. Therefore, the recovery time of the charging ability of the charging roller 32 can be shortened even in a low temperature and low humidity environment. As a result, the surface potential of the photosensitive drum 31 can be made uniform in a short time, and image defects can be suppressed. That is, stable image formation is possible at an early stage. Further, the warm-up time, that is, the rotation speed RT can be shortened by increasing the charging voltage CV. On the other hand, even when the warm-up time is long, by discharging the toner, it is possible to suppress the loss of the edge of the cleaning blade 36a and the increase in stress from the cleaning blade 36a to the photosensitive drum 31.

  Next, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples.

  In the examples and reference examples of the present invention, a modified machine of FS-5250DN (A4 color) manufactured by Kyocera Mita was used as the image forming apparatus 1. Then, the photosensitive drum 31 and the charging roller 32 were warmed up to print a halftone image on A4 size paper. Then, the halftone image of the first printed sheet was evaluated.

  A case where fog did not occur in the halftone image and the density of the halftone image was appropriate was evaluated as “excellent”. “Excellent” indicates that the charging ability of the charging roller 32 has been satisfactorily restored.

  The case where fogging did not occur in the halftone image but the density change of the halftone image and / or the edge of the cleaning blade 36a was lost was evaluated as “good”. “Yes” indicates that the charging ability of the charging roller 32 is restored.

  A case where fog occurred in a halftone image was evaluated as “impossible”. “Not possible” indicates that the charging ability of the charging roller 32 has not fully recovered.

  Table 3 shows the evaluation of the halftone image when the fixing temperature is equal to or lower than the threshold Th.

  Table 4 shows the evaluation of the halftone image when the fixing temperature is higher than the threshold value Th.

  In Tables 3 and 4, “excellent” is indicated by “◯”, “permitted” is indicated by “Δ”, and “impossible” is indicated by “x”.

  In Tables 3 and 4, “Rotation speed” indicates the rotation speed of the photosensitive drum 31 during warm-up. “First correction” indicates that the first addition voltage was applied to the charging roller 32 as the charging voltage CV during warm-up. “Second correction” indicates that the second addition voltage was applied to the charging roller 32 as the charging voltage CV during warm-up.

  “First correction + toner discharge” indicates that the first addition voltage by the first correction is applied as the charging voltage CV to the charging roller 32 and the toner is discharged toward the photosensitive drum 31 during warm-up. Toner ejection was performed intermittently. Specifically, the toner is discharged every predetermined number of rotations of the photosensitive drum 31. In this case, the toner was ejected linearly along the axial direction of the photosensitive drum 31 with a toner amount having a line width of 1 mm in the circumferential direction of the photosensitive drum 31. “Second correction + toner discharge” indicates that the second addition voltage by the second correction is applied as the charging voltage CV to the charging roller 32 and the toner is discharged toward the photosensitive drum 31 during warm-up. The toner discharge is the same as the toner discharge in “first correction + toner discharge”.

  Moreover, environmental temperature and environmental humidity were classified into any of the temperature / humidity range A to the temperature / humidity range D of the temperature / humidity table 100 of FIG. The 1st correction voltage in 1st correction | amendment was determined with reference to Table 1 according to the temperature / humidity range (AD) to which environmental temperature and environmental humidity belong. The first correction voltage and the second correction voltage in the second correction were determined with reference to Table 1 according to the environmental temperature and the temperature and humidity range (A to D) to which the environmental humidity belongs. However, if it is determined that the second addition voltage is applied to the charging roller 32 as the charging voltage CV, the first addition voltage is applied to the charging roller 32 as the charging voltage CV during the first two rotations of the photosensitive drum 31. Applied.

  In the example of the present invention, in Table 3, the warm-up based on the rotation speed RT corresponding to “◯” and “Δ” and the first correction, the rotation speed RT corresponding to “◯” and “Δ”, and the second Warm-up based on correction, rotation speed RT corresponding to “◯” and “Δ” and first correction and warm-up based on toner discharge, and rotation speed RT corresponding to “◯” and “Δ” and second correction And warm-up based on toner discharge. In the embodiment of the present invention, the charging ability of the charging roller 32 could be restored in a short time without fogging in the halftone image. Note that the reference examples are the rotation speed RT corresponding to “x”, the first correction, the second correction, the first correction and toner discharge, and the second correction and toner discharge.

  In the embodiment of the present invention, in Table 4, the warm-up based on the rotational speed RT corresponding to “◯” and “Δ” and the first correction, and the rotational speed RT corresponding to “◯” and “Δ” Warm-up based on 2 corrections. In the embodiment of the present invention, the charging ability of the charging roller 32 could be restored in a shorter time than the embodiment shown in Table 3 without causing fogging in the halftone image. The reference example is the rotation speed RT corresponding to “x”, the first correction, and the second correction.

  When the rotational speed of the photosensitive drum 31 is 65 times in the temperature / humidity range A in Table 3 or when the rotational speed of the photosensitive drum 31 is 49 times in the temperature / humidity range B, the first correction is performed without discharging the toner. Alternatively, when the second correction is performed, a relatively high charging voltage CV is applied to the photosensitive drum 31 for a long time without supplying toner. As a result, the chargeability of the photosensitive drum 31 is lowered, and the density of the halftone image is increased.

  The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof (for example, (1) and (2) below). In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined. In order to facilitate understanding, the drawings schematically show each component as a main component, and the thickness, length, number, interval, etc. of each component shown in the drawings are actual for convenience of drawing. May be different. In addition, the material, shape, dimensions, and the like of each component shown in the above embodiment are merely examples, and are not particularly limited, and various changes can be made without departing from the effects of the present invention. is there.

  (1) As described with reference to FIG. 4A, FIG. 4B, FIG. 5, and FIG. 6, in the present embodiment and the present example, the first correction or the second correction is performed. However, in each of the first control table 101 and the second control table 102, the charging voltage CV after the first correction or the second correction is performed without determining the first correction voltage and the second correction voltage, respectively. It can also be determined. In this case, the processing for the first correction and the second correction is unnecessary, and the processing can be speeded up.

  (2) In the present embodiment, the image forming apparatus 1 is a multifunction peripheral, but may be a copier, a printer, or a facsimile. The image forming apparatus 1 may be monochrome compatible or color compatible.

  The present invention relates to an image forming apparatus and has industrial applicability.

1 Image forming apparatus 31 Photosensitive drum (image carrier)
32 Charging roller (Charging part)
34 Developing unit 36a Cleaning blade 40 Fixing unit 50 Environment detection unit 55 Fixing temperature detection unit 90 Control unit 92 Voltage application unit 94 Drive unit

Claims (8)

An image forming apparatus for forming an image on a transfer material,
An image carrier on which an electrostatic latent image is formed;
A drive unit for rotating the image carrier;
A charging unit disposed in contact with the surface of the image carrier and charging the surface of the image carrier;
A voltage applying unit for applying a charging voltage for charging the surface of the image carrier to the charging unit;
A control unit that controls the driving unit and the charging unit to perform warm-up of the image carrier and the charging unit;
A fixing unit for fixing an image based on the electrostatic latent image to the transfer material;
A fixing temperature detecting unit for detecting the temperature of the fixing unit;
An environment detection unit for detecting the temperature and humidity of the environment in which the image forming apparatus is installed,
When performing warm-up of the image carrier and the charging unit,
The controller is
Based on the temperature of the fixing unit, the temperature of the environment, and the humidity of the environment, a rotation time for rotating the image carrier and the charging voltage are selected,
Controlling the drive unit so that the image carrier rotates during the selected rotation time;
An image forming apparatus that controls the voltage application unit such that the selected charging voltage is applied to the charging unit. The controller is
As the charging voltage, a first voltage and a second voltage larger than the first voltage are selected,
Among the selected rotation times, the voltage application unit is controlled so that the first voltage is applied to the charging unit for a predetermined time after the image carrier starts to rotate. 2. The image forming apparatus according to claim 1, wherein the voltage application unit is controlled such that the second voltage is applied to the charging unit after the predetermined time has elapsed. A cleaning blade that is pressed against the peripheral surface of the image carrier and removes the developer remaining on the peripheral surface of the image carrier;
A developing section that develops the electrostatic latent image with a developer;
The control unit controls the developing unit so that the developer is discharged toward the image carrier when the image carrier and the charging unit are warmed up. The image forming apparatus according to claim 2.   The image forming apparatus according to claim 3, wherein the control unit controls the developing unit such that the developer is intermittently discharged. The controller determines whether the temperature of the fixing unit is equal to or lower than a threshold;
The rotation time selected when it is determined that the temperature of the fixing unit is higher than the threshold is shorter than the rotation time selected when it is determined that the temperature of the fixing unit is equal to or lower than the threshold. The image forming apparatus according to claim 1. The charging voltage as a selection target by the control unit is represented by a sum of a base voltage, a first correction voltage, and a second correction voltage,
The control unit selects the first correction voltage and the second correction voltage based on the temperature of the fixing unit, the temperature of the environment, and the humidity of the environment. The image forming apparatus according to any one of the above. The controller is
The lower the temperature of the environment and the humidity of the environment, the larger the charging voltage is selected,
The image forming apparatus according to claim 1, wherein the longer the rotation time is selected, the lower the temperature of the environment and the humidity of the environment.   The image forming apparatus according to claim 1, wherein the rotation time is represented by a rotation speed of the image carrier.

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