JP6490568B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that prevents occurrence of lateral stripes.

  Conventionally, an image forming apparatus described in Patent Document 1 is used as an image forming apparatus. An image forming apparatus described in Patent Document 1 forms a toner layer on a developing roller that rotates under the restriction of a toner regulating member, supplies the toner in the toner layer to an image carrier, and the image carrier A toner image is formed thereon. The image forming apparatus includes a counting unit that calculates the toner image formed on the image carrier in dot units, and a control that changes a voltage applied to the developing roller when the calculated value is equal to or greater than a predetermined reference value. Means.

  A conventional image forming apparatus calculates a toner image in units of dots, and when the print duty is high, the voltage applied to the developing roller is adjusted to increase the amount of toner supplied to the developing roller. When the amount of toner supplied to the developing roller is increased, the toner is sufficiently supplied even to a portion where the thickness dimension is low in the toner layer after supply. As a result, the energy of pressing the toner regulating member can be received by many toner particles, and this energy is dispersed by each toner particle to suppress vibration between the toner particles and suppress generation of frictional heat due to vibration. Can do. For this reason, the conventional image forming apparatus can prevent the toner temperature from rising.

JP 2011-39555 A

  However, recent contact developing type developers have been changed to low-temperature fixing toners, and there are cases where sufficient effects cannot be obtained by suppressing the toner temperature according to the prior art. In particular, a toner whose temperature has been increased by continuous printing in a high-temperature environment is fused at a portion where the element member is in contact and adheres with a decrease in temperature, so that a horizontal stripe is generated in a printed image. There is.

  Accordingly, an object of the present invention is to prevent horizontal stripes from occurring even when image formation is continuously performed in a high-temperature environment.

  An image forming apparatus according to an aspect of the present invention is an image forming apparatus that forms an image on a medium, and supplies a developer to the image carrier, and the developer image on the image carrier. A developing roller that contacts the developing roller, supplies a developer to the developing roller, a first temperature detecting unit that detects an internal temperature of the image forming apparatus, and the first roller After the temperature detected by the temperature detector becomes equal to or higher than a predetermined first threshold, the temperature detected by the first temperature detector is equal to or lower than a second threshold lower than the first threshold. And a controller that rotates the developing roller without forming an image on the medium.

  According to one embodiment of the present invention, horizontal stripes can be prevented from occurring even when image formation is continuously performed in a high-temperature environment.

1 is a cross-sectional view schematically showing a configuration of a printer according to Embodiments 1 to 3. FIG. 3 is a cross-sectional view schematically showing a configuration of a developing device in Embodiments 1 to 3. FIG. FIG. 3 is a block diagram schematically showing a configuration of a printer control system in the first to third embodiments. It is the schematic explaining the horizontal stripe which generate | occur | produces in the printing surface in Embodiment 1-3. It is the table | surface which showed the relationship between the temperature in Example 1-3, and a horizontal stripe. 4 is a flowchart illustrating an operation of the printer according to the first embodiment. 6 is a flowchart illustrating an operation of the printer according to the second embodiment. 10 is a flowchart illustrating the operation of the printer according to the third embodiment.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view schematically showing a configuration of a printer 100 as an image forming apparatus according to the first embodiment.
The printer 100 corresponds to toners that are developers of black (K), cyan (C), magenta (M), and yellow (Y), and toner cartridges 101K, 101C, 101M, and 101Y as developer containers. (Hereinafter, the toner cartridge 101 is referred to when there is no particular need to distinguish between them) and the developing devices 110K, 110C, 110M, 110Y (hereinafter referred to as the developing device 110 when there is no particular need to distinguish between them). ), Transfer rollers 120K, 120C, 120M, and 120Y (hereinafter referred to as transfer roller 120 when there is no need to distinguish between them), and LED (Light Emitting Diode) heads 121K, 121C, and 121M as exposure units. , 121Y (hereinafter, when there is no need to distinguish each of them) And a called LED head 121). The printer 100 also includes a paper feed cassette 122, a fixing unit 123, and a paper transport path 124.

The toner cartridge 101 stores toner as a developer for each color.
The developing device 110 forms a toner image. The developing device 110 is sequentially arranged in the direction of the arrow Z shown in FIG. 1 along a paper transport path 124 from the paper supply side to the paper discharge side as a medium. The developing devices 110K, 110C, 110M, and 110Y differ only in the color of the toner to be developed, and the other base configurations are the same.

FIG. 2 is a cross-sectional view schematically showing the configuration of the developing device 110.
The developing device 110 includes a photosensitive drum 111 as an image carrier, a charging roller 112 as a charging member, a developing roller 113 as a developing member, a developing blade 114 as a developer layer thickness regulating member, and a supply member. Supply roller 115, a cleaning blade 116 as a developer removing member, and a transport unit 117.

  The photosensitive drum 111 is an image carrier that carries an image. The photosensitive drum 111 is an organic photosensitive member constituted by a conductive support and a photoconductive layer. In the conductive support, a blocking layer is formed on a metal pipe such as aluminum. In the photoconductive layer, a charge generation layer and a charge transport layer are sequentially laminated.

  The charging roller 112 uniformly charges the surface of the photosensitive drum 111. The charging roller 112 includes a metal shaft and a semiconductive rubber layer such as epichlorohydrin rubber. Further, the charging roller 112 is in contact with the photosensitive drum 111 with a predetermined pressure contact amount, and is rotated by the rotation of the photosensitive drum 111.

  The developing roller 113 supplies toner to the photosensitive drum 111 and develops a toner image that is a developer image on the photosensitive drum 111. The developing roller 113 is composed of a metal shaft and a semiconductive urethane rubber layer. The developing roller 113 is in contact with the photosensitive drum 111 with a predetermined pressure contact amount, and rotates with a predetermined peripheral speed ratio in a direction opposite to the rotation direction around the rotation axis with respect to the rotation of the photosensitive drum 111.

  The developing blade 114 regulates the layer thickness of the toner supplied to the developing roller 113. The developing blade 114 is, for example, a metal thin plate member that has a thickness of 0.08 mm and has substantially the same length as the length of the developing roller 113 in the longitudinal direction, and regulates the toner layer thickness. One end side of the developing blade 114 in the longitudinal direction is fixed to a frame (not shown), and the other end side is arranged so that a portion slightly inside from the tip end portion is in contact with the developing roller 113.

  The supply roller 115 supplies toner to the developing roller 113. The supply roller 115 is composed of a metal shaft and a semiconductive foamed silicone sponge layer. The supply roller 115 is in contact with the developing roller 113 with a predetermined pressure contact amount, and rotates with a predetermined peripheral speed ratio in the counter direction at the contact portion with respect to the rotation of the developing roller 113.

  The cleaning blade 116 is a cleaning unit that removes residual toner remaining on the photosensitive drum 111 that has not been transferred to the sheet. The cleaning blade 116 is, for example, a urethane rubber member disposed at a position where one end thereof contacts the photosensitive drum 111 with a predetermined pressure contact amount.

  The transport unit 117 is a transport unit that transports residual toner removed by the cleaning blade 116 as waste toner. The transport unit 117 transports the residual toner and adhered matter removed by the cleaning blade 116 as waste toner toward the front side in the rotational axis direction of the photosensitive drum 111. Thereafter, the waste toner passes through the waste toner collecting path 125 shown in FIG.

  The toner cartridge 101 and the developing device 110 are both replacement units in the printer 100. Therefore, it is possible to replace the toner when the toner to be stored is consumed or when the component parts deteriorate.

  The transfer roller 120 shown in FIG. 1 is disposed at a position facing the photosensitive drum 111, and transfers the toner image formed on the photosensitive drum 111 onto the sheet conveyed by the transfer belt 127. The transfer belt 127 conveys the sheet by electrostatic attraction. The transfer belt 127 is stretched between a drive roller (not shown) that rotates by obtaining power from a drive motor described later, and a tension roller (not shown) that forms a pair with the drive roller.

  The LED head 121 irradiates the surface of the photosensitive drum 111 with light to form an electrostatic latent image. The LED head 121 includes, for example, an LED as a light emitting element and a lens array.

  The paper feed cassette 122 stores paper P. The paper feed cassette 122 accommodates the paper P in a stacked state and is detachably attached to the lower part of the printer 100. A paper feed unit (not shown) provided with a hopping roller for feeding and feeding the paper P one by one is disposed above the paper feed cassette 122.

  The fixing unit 123 fixes the toner image transferred onto the paper P by the transfer roller 120. The fixing unit 123 is disposed on the downstream side of the paper conveyance path 124 and includes a heating roller 123a, a pressure roller 123b, a thermistor (not shown), and a heater (not shown). The heating roller 123a covers, for example, a hollow cylindrical cored bar made of aluminum or the like with a heat-resistant elastic layer of silicon rubber, and a PFA (tetrafluoroethylene-perfluoroalkylalkyl vinyl ether copolymer) tube thereon. It is formed by. In the core bar, for example, a heater such as a halogen lamp is provided. The pressure roller 123b has a configuration in which, for example, a core metal made of aluminum or the like is covered with a heat-resistant elastic layer of silicon rubber, and a PFA tube is covered thereon, and a portion in pressure contact with the heating roller 123a is formed. It is arranged so that. The thermistor detects the surface temperature of the heating roller 123a. The thermistor is disposed in the vicinity of the heating roller 123a in a non-contact manner.

  The sheet conveyance path 124 is formed in an approximately S shape with respect to the lower frame of the printer 100.

As shown in FIG. 1, the printer 100 includes a first temperature sensor 128 as an apparatus internal temperature detection unit and a second temperature sensor 129 as a room temperature detection unit.
The first temperature sensor 128 is a first temperature detection unit that detects the temperature inside the printer 100. Here, the first temperature sensor 128 is in contact with the transfer belt 127 and detects the temperature of the developing device 110 (inside) by detecting the temperature of the transfer belt 127.
The second temperature sensor 129 is mounted in an OP (operation panel) (not shown), and is a second temperature detection unit that detects the temperature of the room in which the printer 100 is installed.

FIG. 3 is a block diagram schematically showing the configuration of the control system of the printer 100.
The printer 100 includes a control unit 130, a communication interface (hereinafter referred to as communication I / F) 140, an interface control unit (hereinafter referred to as I / F control unit) 141, a reception memory 142, and an image data editing memory 143. The operation unit 144 and the sensor group 145 are provided.

  The control unit 130 controls processing in the printer 100. For example, the control unit 130 includes a microprocessor, a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output port, a timer, and the like. The control unit 130 receives print data (image formation data) and control commands from a host device (not shown) via the communication I / F 140 and the I / F control unit 141, and controls the overall sequence of the printer 100. A printing operation (image formation data) is performed.

The control unit 130 includes a drum counter 131, a calculation unit 132, and a storage unit 133.
The drum counter 131 counts the number of rotations of the photosensitive drum 111 rotated during the printing operation.

The calculation unit 132 performs arithmetic based on the temperature read from the sensor group 145 or the rotation number of the drum counter 131 and determines whether or not a rotation flag is generated.
For example, the calculation unit 132 generates a rotation flag when a first condition in which the temperature detected by the first temperature sensor 128 is equal to or higher than a predetermined first threshold is satisfied.
Then, after the calculation unit 132 generates the rotation flag, the second condition in which the temperature detected by the first temperature sensor 128 is equal to or lower than the second threshold lower than the first threshold is satisfied. In this case, the developing roller 113 is rotated without forming an image on the medium.

Note that the calculation unit 132 desirably determines whether or not the first condition is satisfied after an image is formed on the medium using the photosensitive drum 111, the developing roller 113, and the supply roller 115.
In addition, the calculation unit 132 desirably determines whether or not the second condition is satisfied before the image is formed on the medium using the photosensitive drum 111, the developing roller 113, and the supply roller 115, for example.
Specifically, the calculation unit 132 determines whether the first condition is satisfied after forming an image on the medium based on the first print data, and is processed after the first print data. It is desirable to determine whether or not the second condition is satisfied based on the second print data before forming an image on the medium.
Here, the first threshold is a predetermined temperature. The second threshold is a temperature lower than the first threshold, may be a room temperature detected by the second temperature sensor 129, or may be a predetermined temperature.

  The storage unit 133 stores programs and data necessary for processing in the control unit 130. For example, the storage unit 133 stores the rotation flag generated by the calculation unit 132. The storage unit 133 may store the count value counted by the drum counter 131.

The communication I / F 140 communicates with a host device (not shown) and receives print data and control commands.
The I / F control unit 141 controls the communication I / F 140. For example, the I / F control unit 141 temporarily stores print data received by the communication I / F 140 in the reception memory 142 and gives the control command received by the communication I / F 140 to the control unit 130.
The communication I / F 140 and the I / F control unit 141 constitute a communication unit that communicates with another information processing apparatus such as a host device (not shown).
This communication unit can be realized by a NIC (Network Interface Card).

The reception memory 142 temporarily stores print data received from a host device (not shown) via the communication I / F 140 and the I / F control unit 141.
The image data editing memory 143 receives the print data stored in the reception memory 142 and stores image data formed by editing the print data.

The operation unit 144 includes a display unit such as an LED for displaying the status of the printer 100 and an input unit such as a switch for giving an instruction from the operator to the printer 100.
The sensor group 145 is various sensors for monitoring the operating state of the printer 100. The sensor group 145 includes, for example, a paper position detection sensor, a temperature / humidity sensor, a density sensor, and the like. The sensor group 145 includes the first temperature sensor 128 and the second temperature sensor 129 described above.

  The printer 100 also includes a charging roller power supply 150, a developing roller power supply 151, a supply roller power supply 152, a transfer roller power supply 153, a fuse power supply 154, a head drive control unit 155, and a fixing control unit. 156, a transport motor control unit 157, and a drive control unit 158. These are controlled by the control unit 130.

The charging roller power supply 150 applies a voltage to the charging roller 112 according to an instruction from the control unit 130 to charge the surface of the photosensitive drum 111.
The developing roller power supply 151 applies a predetermined voltage to the developing roller 113 in order to adhere toner to the electrostatic latent image formed on the surface of the photosensitive drum 111.
The supply roller power supply 152 applies a predetermined voltage to the supply roller 115 in order to supply toner to the developing roller 113.
The transfer roller power supply 153 applies a predetermined voltage to the transfer roller 120 in order to transfer the toner image formed on the photosensitive drum 111 onto the sheet P that is a recording casing.
The charging roller power supply 150, the developing roller power supply 151, and the supply roller power supply 152 can change voltages according to instructions from the control unit 130.

The fuse power supply 154 causes a current to flow through the fuse 160 that determines whether the developing device 110 is an unused product.
The head drive control unit 155 sends the image data stored in the image data editing memory 143 to the LED head 121 and drives the LED head 121.
The fixing control unit 156 applies a voltage to the fixing unit 123 serving as a fixing unit in order to fix the transferred toner image on the paper P.
The transport motor control unit 157 controls the paper transport motor 161 for transporting the paper P. The transport motor control unit 157 transports or stops the paper P at a predetermined timing according to an instruction from the control unit 130.
The drive control unit 158 drives a drive motor 162 for operating the photosensitive drum 111. When the drive motor 162 is driven by the drive controller 158, as shown in FIG. 2, the photosensitive drum 111 rotates in the direction of the arrow, and the charging roller 112, the developing roller 113, and the supply roller 115 rotate in the direction of the arrow, respectively. To do. Therefore, the drive control unit 158 and the drive motor 162 function as a drive unit 163 that rotates the developing roller 113. The drive control unit 158 includes a microprocessor, a ROM, a RAM, an input / output port, a timer, and the like.

Next, the operation of the printer will be described.
In the printer 100, the control unit 130 receives the print data via the communication I / F 140 and the I / F control unit 141, thereby controlling the entire sequence of the printer 100 and performing a printing operation.

  After receiving the print data, in the developing device 110, the drive motor 162 is rotated by the drive control unit 158, and the toner is replenished from the toner cartridge 101. Further, the transport motor control unit 157 drives the paper transport motor 161, so that the paper P in the paper feed cassette 122 is fed in the direction of the arrow X in FIG. The paper P is transported along the paper transport path 124 in the direction of arrow Z in FIG.

  The conveyed paper P sequentially passes under the developing devices 110K, 110C, 110M, and 110Y, and the toner images formed on the photosensitive drums 111K, 111C, 111M, and 111Y are transferred by the transfer rollers 120K, 120C, 120M, and 120Y. After being transferred and fixed by the fixing unit 123, it is discharged out of the printer 100.

Since the basic operations of the developing devices 110K, 110C, 110M, and 110Y are the same, only one developing device 110 will be described below.
The surface of the photosensitive drum 111 is uniformly and uniformly charged by the charging roller 112, and an electrostatic latent image is formed by the light emitted from the LED head 121.
A charging roller power supply 150 for applying a bias voltage having the same polarity as the toner is connected to the charging roller 112, and the surface of the photosensitive drum 111 is uniformly uniform by the bias voltage applied from the charging roller power supply 150. Is charged.

The developing roller 113 is connected to a developing roller power supply 151 that applies a bias voltage of the same polarity or opposite polarity as that of the toner. The toner charged by the bias voltage applied from the developing roller power supply 151 is connected to the developing roller 113. Adheres to the electrostatic latent image on the photosensitive drum 111.
The developing blade 114 is connected to a developing roller power source 151 or a supply roller power source 152 that applies a bias voltage of the same polarity or opposite polarity as that of the toner, and develops by the applied bias voltage and contact pressure. The toner on the roller 113 is charged and layer regulated.

  The supply roller 115 is connected to a supply roller power source 152 that applies a bias voltage of the same polarity or opposite polarity as that of the toner. The bias voltage applied from the supply roller power source 152 causes the toner roller 101 to The replenished toner is supplied to the developing roller 113. The supply roller 115 charges the toner by the contact frictional force with the developing roller 113 and scrapes off the undeveloped toner on the developing roller 113.

The cleaning blade 116 cleans the surface of the photosensitive drum 111 by scraping off the toner remaining on the surface of the photosensitive drum 111. In addition, the adhering matter adhering to the surface of the photosensitive drum 111 from the transfer belt 127 is also cleaned although the amount is small.
The transport unit 117 transports residual toner and deposits removed by the cleaning blade 116 as waste toner. The waste toner transported by the transport unit 117 is transported to the waste toner collecting unit 126 through the waste toner collecting path 125 shown in FIG.

  As shown in FIG. 2, a stirring supply mechanism 102 exists in the toner cartridge 101 and replenishes the developing device 110 with unused toner.

The transfer roller 120 is connected to a transfer roller power source 153 that applies a bias voltage having a polarity opposite to that of the toner. The toner image formed on the photosensitive drum 111 is transferred by the bias voltage applied from the transfer roller power source 153. Transfer to paper P.
The LED head 121 is controlled by the head drive control unit 155 based on the input image data, irradiates the surface of the photosensitive drum 111 with light, attenuates the potential of the light irradiation portion, and generates an electrostatic latent image. Form.

The paper P fed from the inside of the paper feed cassette 122 in the direction of the arrow X is transported under the developing device 110 by a transport roller (not shown).
In the fixing unit 123, the fixing controller 156 controls the heater based on the surface temperature of the heating roller 123a detected by the thermistor, so that the surface temperature of the heating roller 123a is maintained at a predetermined temperature. The sheet P on which the toner image is transferred passes through the pressure contact portion formed by the heating roller 123a and the pressure roller 123b maintained at a predetermined temperature, so that heat and pressure are applied, and the toner image is applied to the sheet P. It is fixed.

  By the way, if the printer 100 is left unattended after continuous printing (image formation) by the printer 100, there is a problem in that horizontal stripes occur on the printing surface (image forming surface) immediately after the start of the unattended operation. First, the horizontal stripe will be described.

FIG. 4 is a schematic diagram for explaining the horizontal stripes generated on the printing surface.
As shown in FIG. 4, the horizontal stripes are streaks L <b> 1 to L <b> 7 that periodically occur on the printing surface PS of the paper P. The period of the stripes L1 to L7 is mainly generated in the period in which the developing roller 113 rotates.

  The toner in the developing device 110 shown in FIG. 2 is subjected to great stress during continuous printing. In particular, at the contact pressure portion between the members of the developing device 110, the toner is easily melted by frictional heat due to contact charging. The streaks L1 to L7 are those in which the toner is fused and fixed to the member as the temperature decreases. The streaks L1 to L7 generated in the rotation cycle of the developing roller 113 are generated most strongly in the contact pressure portion between the developing roller 113 and the photosensitive drum 111, and then the contact pressure portion with the developing blade 114 and the contact with the supply roller 115 are generated. It occurs strongly in the order of pressure parts.

Further, the horizontal stripe does not occur every printing, but occurs in a certain environment. The environment is when both of the following two conditions are satisfied.
The first condition is that the temperature in the developing device 110 has risen and the printer 100 has performed continuous printing in a high temperature environment.
The second condition is that the developing device 110 whose temperature has risen is left unoperated for a certain period of time, and its temperature decreases.
When printing is continued with the temperature of the developing device 110 increased, or when the temperature of the developing device 110 is decreased, the horizontal streak does not occur, and two conditions such as a decrease from a high temperature increase are combined. Occur.

FIG. 5 is a table showing the relationship between temperature and horizontal stripes.
The belt temperature shown in FIG. 5 is a value read from the first temperature sensor 128 at the temperature of the transfer belt 127. The value here is the temperature of the transfer belt 127 when the temperature of the developing device 110 rises after continuous printing. In the first embodiment, the temperature of the transfer belt 127 is sensed. However, the temperature is not limited to this as long as the temperature in the developing device 110 can be determined. The first temperature sensor 128 may be attached to a specific part included in the developing device 110, and the first temperature sensor 128 is attached to another part that contacts the specific part included in the developing device 110. May be.

“O” and “X” plotted in FIG. 5 indicate the presence or absence of the occurrence of horizontal stripes. “◯” indicates that no horizontal stripes have occurred on the print surface, and “X” indicates that horizontal stripes have occurred on the print surface.
Then, printing is performed in a state where the temperature inside the developing device 110 that has risen returns to room temperature, thereby determining whether or not the horizontal stripes are generated.

As can be seen from the table shown in FIG. 5, the horizontal stripe occurs when the temperature of the transfer belt 127 after continuous printing (before leaving) exceeds a certain value. If the temperature at that time is the threshold value T1 (first threshold value), in this example, T1 = 35 ° C.
In this example, the temperature in the developing device 110, in particular, the temperature of the surface of the developing roller 113 changes at the temperature of the transfer belt 127 plus 10 ° C. Therefore, the temperature of the surface of the developing roller 113 at the threshold T1 is about 45 ° C.
Although the glass transition temperature of the toner alone is higher than 45 ° C. and does not melt alone, the toner that is in contact with the developing roller 113 is in contact with the pressure between the members and the pressure of the developing roller 113. It will be in the state which is easy to melt | fuse by the heat storage of the surface vicinity. For this reason, it is considered that the toner adheres to the outer periphery of the developing roller 113. The threshold temperature T1 obtained here is obtained experimentally, and the glass transition temperature of the toner alone minus 5 ° C. to 20 ° C. is a standard.

FIG. 6 is a flowchart illustrating the operation of the printer 100 according to the first embodiment.
First, the operation of the printer 100 is started, and the communication I / F 140 receives print data (S10). The received print data is sent to the reception memory 142 via the I / F control unit 141, further processed by the control unit 130, and stored in the image data editing memory 143 as image data.

  The calculating unit 132 determines whether or not a rotation flag is stored in the storage unit 133 (S11). If the rotation flag is stored (YES in S11), the process proceeds to step S12. If the rotation flag is not stored (NO in S11), the process proceeds to step S15.

  In step S <b> 12, the calculation unit 132 determines whether or not the temperature Ta of the transfer belt 127 detected by the first temperature sensor 128 is equal to or lower than the room temperature detected by the second temperature sensor 129. If the temperature Ta is not more than room temperature (YES in S12), the process proceeds to step S13. If the temperature Ta is higher than the room temperature, the process proceeds to step S15.

  In step S <b> 13, the calculation unit 132 performs an idling operation of the developing device 110 by instructing the drive control unit 158. The idling operation rotates the developing device 110 without performing printing (image formation). In the idling operation, it is sufficient to rotate at least the developing roller 113 in pressure contact with the supply roller 115. If the photosensitive drum unit is a separation type, only the developing unit needs to rotate. The purpose of the idling operation is to eliminate the generated horizontal stripe before printing. The toner adhered to the outer peripheral portion of the developing roller 113 can be scraped off when the supply roller 115 is pressed against and rotated in the counter direction.

In the idling operation, the voltage to the charging roller 112, the developing roller 113, the supply roller 115, and the transfer roller 120 may or may not be applied. Here, a voltage of −900 V to −1200 V (−1030 V in the first embodiment) is applied to the charging roller 112, and a voltage of −100 V to −500 V (in the first embodiment, is applied to the developing roller 113). −125 V) is applied, a voltage of −100 V to −500 V (−240 V in the first embodiment) is applied to the supply roller 115, and a voltage of 1000 V to 4000 V (an implementation voltage) is applied to the transfer roller 120. In the first embodiment, 2300 V) is applied.
Further, the application of voltage to the photosensitive drum 111 is also arbitrary.

  Next, the calculation unit 132 deletes the rotation flag stored in the storage unit 133 (S14). Then, the process proceeds to step S15.

In step S15, the control unit 130 controls each unit of the printer 100 to execute printing (image formation).
Then, the calculation unit 132 determines again whether or not the rotation flag is stored in the storage unit 133 (S16). If the rotation flag is stored (YES in S16), the process ends. If the rotation flag is not stored (NO in S16), the process proceeds to step S17.

  In step S <b> 17, the calculation unit 132 determines whether or not the temperature Ta of the transfer belt 127 detected by the first temperature sensor 128 is equal to or higher than a predetermined threshold T <b> 1 ° C. If the temperature Ta is equal to or higher than T1 ° C. (YES in S17), the process proceeds to step S18. If the temperature Ta is lower than T1 ° C. (NO in S17), the process ends.

  In step S18, the calculation unit 132 stores the rotation flag in the storage unit 133. And a process is complete | finished, and a process returns to step S10 after that.

  According to the first embodiment, the printer 100 reads the temperature in the developing device 110 that has risen in continuous printing with the transfer belt 127 and generates a rotation flag at the provided threshold temperature. Then, based on the rotation flag, the printer 100 rotates the developing device 110 idly before printing the next job under the condition that a horizontal stripe occurs. As a result, the toner adhering to the outer periphery of the developing roller 113 is scraped off by the supply roller 115, and the horizontal stripes can be eliminated before printing. As a result, a good image can be obtained even in a high temperature environment or after continuous durable printing. When the rotation flag is stored once, the calculation unit 132 receives the first temperature every time a job is received until the temperature detected by the first temperature sensor 128 is equal to or lower than the room temperature. It is determined whether or not the temperature detected by the sensor 128 is below room temperature.

Embodiment 2. FIG.
As shown in FIG. 1, the printer 200 according to the second embodiment is configured in the same manner as the printer 100 according to the first embodiment.
As shown in FIG. 3, the printer 200 according to the second embodiment includes a control unit 230, a communication I / F 140, an I / F control unit 141, a reception memory 142, an image data editing memory 143, and the like. The operation unit 144 and the sensor group 145 are provided. The printer 200 according to the second embodiment is configured in the same manner as the printer 100 according to the first embodiment except for the processing in the control unit 230.

  The control unit 230 includes a drum counter 131, a calculation unit 232, and a storage unit 133. The control unit 230 in the second embodiment is configured in the same manner as the control unit 130 in the first embodiment except for the processing in the calculation unit 232.

The calculation unit 232 performs arithmetic based on the temperature read from the sensor group 145 or the rotation number of the drum counter 131, and determines whether or not a rotation flag is generated.
The calculation unit 232 according to the second embodiment, the temperature detected by the first temperature sensor 128, in other words, the temperature detected by the first temperature sensor 128 decreases as the temperature decreases from the predetermined threshold T1. The developing device 110 is controlled so that the number of idling operations of the developing device 110 increases as the difference from the threshold T1 increases.

FIG. 7 is a flowchart illustrating the operation of the printer 100 according to the second embodiment.
In FIG. 7, processes similar to those in the flowchart of FIG. 6 are denoted by the same reference numerals as in FIG. 6.

  The processing in step S10 and step S11 in FIG. 7 is the same as the processing in step S10 and step S11 in FIG. However, in FIG. 7, when it is determined in step S11 that the rotation flag is stored (YES in S11), the process proceeds to step S22.

In step S22, the calculation unit 232 acquires the temperature Ta of the transfer belt 127 detected by the first temperature sensor 128, and the degree (difference) of the decrease in the temperature Ta from a predetermined threshold T1. Is calculated.
If the degree of this decrease is less than a predetermined threshold (here, 3 ° C.), the calculation unit 232 proceeds to step S15. Since the threshold value T1 is a predetermined temperature, the calculation unit 232 determines whether or not the temperature Ta of the transfer belt 127 is equal to or lower than a predetermined temperature (threshold value T1-3 ° C.). Judging.

  On the other hand, when the degree of the decrease is equal to or greater than a predetermined threshold, the calculating unit 232 increases the number of idling operations of the developing device 110 as the degree of the decrease increases. To control. For example, when the degree of the decrease is 3 ° C. or more and less than 6 ° C., the calculation unit 232 advances the process to step S23-1. Moreover, the calculation part 232 advances a process to step S23-2, when the grade of this fall is 6 degreeC or more and less than 9 degreeC. Furthermore, the calculation part 232 advances a process to step S23-3, when the grade of this fall is 9 degreeC or more.

In step S23-1, the calculation unit 232 instructs the drive control unit 158 to perform an idling operation for one sheet of a medium of a predetermined size (here, A4) in the developing device 110 in the vertical direction. Make it. Then, the process proceeds to step S14.
In step S <b> 23-2, the calculation unit 232 instructs the drive control unit 158 to perform the idling rotation operation for two sheets of a predetermined size medium (here, A4) in the developing device 110. Make it. Then, the process proceeds to step S14.
In step S23-3, the calculation unit 232 instructs the drive control unit 158 to perform an idle rotation operation for three sheets of a predetermined size medium (here, A4) in the developing device 110 in the vertical direction. Make it. Then, the process proceeds to step S14.

  As described above, the horizontal stripes are generated by a combination of temperature rise and fall, and the greater the temperature difference between the rise and the next action, the easier the toner adheres to the developing roller 113. The number of times increases. For this reason, in the second embodiment, the number of rotations of the developing device 110 is changed according to the temperature difference.

  The processing in steps S14 to S18 in FIG. 7 is the same as the processing in steps S14 to S18 in FIG.

  According to the second embodiment, the difference between the threshold temperature T1 at which the rotation flag is generated and the transfer belt 127 temperature Ta of the next JOB after the rotation flag is generated is calculated, and the number of idling rotations of the developing device 110 is determined based on the calculated value. . Accordingly, the printer 200 can cause the developing roller 113 to perform the minimum number of rotations necessary to eliminate the toner fixing streaks.

Embodiment 3 FIG.
As shown in FIG. 1, the printer 300 according to the third embodiment is configured in the same manner as the printer 100 according to the first embodiment.
As shown in FIG. 3, the printer 200 according to the third embodiment includes a control unit 330, a communication I / F 140, an I / F control unit 141, a reception memory 142, an image data editing memory 143, and the like. The operation unit 144 and the sensor group 145 are provided. The printer 300 according to the third embodiment is configured in the same manner as the printer 100 according to the first embodiment except for the processing in the control unit 330.

  The control unit 330 includes a drum counter 131, a calculation unit 332, and a storage unit 133. The control unit 330 in the third embodiment is configured in the same manner as the control unit 130 in the first embodiment except for the processing in the calculation unit 332.

The calculation unit 332 performs arithmetic based on the temperature read from the sensor group 145 or the rotation number of the drum counter 131, and determines whether or not a rotation flag is generated.
The calculation unit 332 according to Embodiment 3 controls the developing device 110 so that the number of idling operations of the developing device 110 increases as the rotational speed of the photosensitive drum 111 increases. Here, since the remaining life of the photosensitive drum 111 is shortened as the number of rotations of the photosensitive drum 111 is increased, the number of idling operations of the developing device 110 is increased as the remaining life of the photosensitive drum 111 is shortened.

FIG. 8 is a flowchart illustrating the operation of the printer 300 according to the third embodiment.
8, processes similar to those in the flowchart in FIG. 6 are denoted by the same reference numerals as in FIG.

  The processing in steps S10 to S12 in FIG. 8 is the same as the processing in steps S10 to S12 in FIG. However, in FIG. 8, when the temperature Ta is not more than room temperature (YES in S12), the process proceeds to step S32.

In step S <b> 32, the calculation unit 332 acquires a count value from the drum counter 131.
Then, the calculation unit 332 controls the developing device 110 so that the number of idling operations of the developing device 110 increases as the acquired count value increases. For example, if the count value is less than 10,000, the calculation unit 232 advances the processing to step S33-1. Moreover, the calculation part 332 advances a process to step S33-2, when this count value is 10,000 or more and less than 20,000. Furthermore, when the count value is 20,000 or more, the calculation unit 332 advances the process to step S33-3.

In step S33-1, the calculation unit 332 instructs the drive control unit 158 to perform the idling rotation operation for one sheet of a predetermined size medium (A4 in this case) in the developing device 110 in the vertical direction. Make it. Then, the process proceeds to step S14.
In step S <b> 33-2, the calculation unit 332 instructs the drive control unit 158 to perform idle rotation operation for two sheets of a predetermined size medium (here, A <b> 4) in the developing device 110. Make it. Then, the process proceeds to step S14.
In step S <b> 33-3, the calculation unit 332 instructs the drive control unit 158 to perform an idling operation for three sheets of a predetermined size medium (here, A4) in the developing device 110. Make it. Then, the process proceeds to step S14.

  As the count value increases, the number of idling revolutions of the developing device 110 also increases. However, as the count value increases, the toner deteriorates, and the deteriorated toner is more likely to adhere to the developing roller 113. This is because the number of times increases. Therefore, in the third embodiment, the number of rotations of the developing device 110 is changed according to the count value.

  The processing in steps S14 to S18 in FIG. 8 is the same as the processing in steps S14 to S18 in FIG.

  According to the third embodiment, the number of idling rotations of the developing device 110 when the rotation flag is executed is determined from the value of the drum counter 131, so that the idling rotation necessary for eliminating the toner fixing streaks is not excessively performed. It can be performed with the minimum number of rotations necessary for disappearance.

  In the first to third embodiments described above, the printers 100 to 300 have been described as examples of the image forming apparatus. However, the image forming apparatus is an apparatus such as an MFP (Multi Function Printer), a facsimile, or a copying apparatus. May be.

  100, 200, 300 Printer, 101 Toner cartridge, 110 Developing device, 111 Photosensitive drum, 112 Charging roller, 113 Developing roller, 114 Developing blade, 115 Supply roller, 116 Cleaning blade, 117 Conveying section, 120 Transfer roller, 121 LED head , 122 paper feed cassette, 123 fixing unit, 124 paper transport path, 130, 230, 330 control unit, 131 drum counter, 132, 232, 332 calculation unit, 133 storage unit, 140 communication I / F, 141 I / F control , 142 reception memory, 143 image data editing memory, 144 operation unit, 145 sensor group, 150 power supply for charging roller, 151 power supply for developing roller, 152 power supply for supply roller, 15 3 Power supply for transfer roller, 154 Power supply for fuse, 155 Head drive control unit, 156 Fixing control unit, 157 Conveyance motor control unit, 158 Drive control unit, 163 Drive unit

Claims (10)

An image forming apparatus for forming an image on a medium,
An image carrier;
A developing roller for supplying a developer to the image carrier and forming a developer image on the image carrier;
A supply roller that contacts the developing roller and supplies developer to the developing roller;
A first temperature detection unit for detecting the temperature inside the image forming apparatus;
After the temperature detected by the first temperature detection unit becomes equal to or higher than a predetermined first threshold, the temperature detected by the first temperature detection unit is lower than the first threshold. And a control unit that rotates the developing roller without forming an image on a medium when the threshold value is less than or equal to 2. The temperature detected by the first temperature detector after the image is formed on the medium using the image carrier, the developing roller, and the supply roller is compared with the first threshold value. The image forming apparatus according to claim 1. Before forming an image on a medium using the image carrier, the developing roller, and the supply roller, a temperature detected by the first temperature detection unit is compared with the second threshold value. The image forming apparatus according to claim 1 or 2. A second temperature detector for detecting a temperature of a room in which the image forming apparatus is installed;
The image forming apparatus according to claim 1, wherein the second threshold value is a temperature detected by the second temperature detection unit. The image forming apparatus according to claim 1, wherein the controller increases the number of rotations of the developing roller as the number of rotations of the image carrier increases. 5. The image forming apparatus according to claim 1, wherein the controller increases the number of rotations of the developing roller as the remaining life of the image bearing member is shorter. The image forming apparatus according to claim 1, wherein the second threshold value is a predetermined temperature lower than the first threshold value. The said control part increases the frequency | count of rotating the said developing roller, so that the difference of the temperature detected by the said 1st temperature detection part and the said 1st threshold value is large. Image forming apparatus. 9. The image formation according to claim 1, wherein the first temperature detection unit detects a temperature of a developing device including the image carrier, the developing roller, and the supply roller. apparatus. The image forming apparatus according to claim 9, wherein the first temperature detection unit detects a temperature of the developing device by detecting a temperature of a transfer belt in contact with the image carrier.

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