JP7342658B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus that forms an image on a recording medium.

In an image forming apparatus, a toner image is formed on a recording medium by applying a transfer voltage to a transfer roller. For example, Patent Document 1 discloses an image forming apparatus that controls a transfer voltage based on the estimated temperature of a transfer roller.

JP2017-215348A

By the way, in an image forming apparatus, for example, when performing an image forming operation, a transfer voltage is adjusted by performing current detection that detects a current flowing through a transfer roller. In such an image forming apparatus, for example, when it is sufficient to use a previously adjusted transfer voltage when performing an image forming operation, it is desirable to omit the process of adjusting the transfer voltage. By eliminating unnecessary processing, it is expected that the time required for image forming operations will be shortened.

It is desirable to provide an image forming apparatus that can shorten the time required for image forming operations.

An image forming apparatus according to an embodiment of the present invention includes a transfer belt, a transfer body, a first temperature sensor, and a control section. The transfer belt can be driven by a driving member and has an annular configuration. The transfer body is provided on the inner peripheral surface side of the transfer belt, and is configured to be applied with a transfer voltage. The first temperature sensor faces the transfer belt and detects a first temperature that is the surface temperature of the transfer belt when the amount of drive of the transfer belt after the transfer belt starts driving is one revolution or more. , is configured to detect a second temperature that is the surface temperature of the transfer belt when the amount of drive of the transfer belt after the transfer belt starts driving is less than one revolution. When determining whether to perform current detection to detect the current flowing through the transfer body, the control unit calculates a predetermined value and a difference between the second temperature and the first temperature at the time of the previous current detection. Based on the comparison, it is configured to determine whether to perform current detection. The predetermined value is a first threshold value in the first period after the transfer belt has stopped driving, and in the period after the transfer belt has stopped driving and before the first period and in the first period. A second threshold value for a second time period that includes a later time period.

In an image forming apparatus as an embodiment of the present invention, when determining whether to perform current detection, the difference between the second temperature and the first temperature at the time of previous current detection and a predetermined value are determined. By comparing the values, it is determined whether or not to perform current detection. Thereby, execution of current detection can be prevented when it is not necessary to carry out current detection.

An image forming apparatus according to an embodiment of the present invention includes a transfer belt, a transfer body, a temperature sensor, and a control section. The transfer belt can be driven by a driving member and has an annular configuration. The transfer body is provided on the inner peripheral surface side of the transfer belt, and is configured to be applied with a transfer voltage. The temperature sensor faces the transfer belt, detects a first temperature that is the surface temperature of the transfer belt when the transfer belt is driven one revolution or more after the transfer belt starts driving, and detects a first temperature that is the surface temperature of the transfer belt . The transfer belt is configured to detect a second temperature that is the surface temperature of the transfer belt when the amount of drive of the transfer belt after starting driving is less than one rotation. When determining whether or not to perform current detection of the transfer body, the control unit compares a predetermined value with a corrected temperature obtained by correcting the second temperature during the first period after the drive of the transfer belt stops. It is determined whether or not to perform current detection, and the second period is determined after the drive of the transfer belt is stopped and includes a period that is before the first period and a period that is after the first period. The device is configured to determine whether to perform current detection by comparing the temperature with a predetermined value.

In an image forming apparatus according to an embodiment of the present invention, when determining whether or not to perform current detection of the transfer member, a correction temperature obtained by correcting the second temperature in the first period after the transfer belt drive is stopped is used. By comparing with a predetermined value, it is determined whether or not to perform current detection, and a period after the transfer belt has stopped driving and before the first period and a period after the first period is determined. By comparing the second temperature with a predetermined value during the second period including the second period, it is determined whether or not current detection is to be performed. Thereby, execution of current detection can be prevented when it is not necessary to carry out current detection.

According to the image forming apparatus according to the embodiment of the present invention, it is possible to prevent the current detection from being performed when it is not necessary to perform the current detection, so that the time required for the image forming operation can be shortened.

1 is a configuration diagram showing a configuration example of an image forming apparatus according to an embodiment; FIG. 2 is a block diagram showing an example of a control system of the image forming apparatus shown in FIG. 1. FIG. FIG. 3 is an explanatory diagram showing an example of threshold data shown in FIG. 2; 2 is a flowchart representing an example of processing in the image forming apparatus shown in FIG. 1. FIG. 2 is another flowchart representing an example of processing in the image forming apparatus shown in FIG. 1. FIG. FIG. 2 is an explanatory diagram showing temperature changes of the transfer belt and transfer roller shown in FIG. 1. FIG. 2 is another explanatory diagram showing temperature changes of the transfer belt and transfer roller shown in FIG. 1. FIG. FIG. 2 is a block diagram illustrating an example of a control system of an image forming apparatus according to a comparative example. FIG. 7 is an explanatory diagram illustrating an example of threshold data of an image forming apparatus according to a comparative example. 7 is a flowchart illustrating an example of processing in an image forming apparatus according to a comparative example. FIG. 6 is an explanatory diagram showing temperature changes of a transfer roller and a transfer belt of an image forming apparatus according to a comparative example. FIG. 3 is a configuration diagram showing a configuration example of an image forming apparatus according to a modified example.

Embodiments of the present invention will be described in detail below with reference to the drawings. Note that the explanation will be given in the following order.
1. One embodiment 1.1 Configuration of image forming apparatus 1.2 Operation of image forming apparatus (A) Basic operation (B) Current detection execution judgment process (C) Current detection and transfer voltage adjustment (D) Threshold data adjustment Determination method 1.3 Function of image forming device 1.4 Effect 2. Variant

<1. One embodiment>
[1.1 Configuration of image forming apparatus 1]
FIG. 1 is a configuration diagram showing an example of the configuration of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 is, for example, a printer using an electrophotographic method, and is capable of forming a black and white image or a color image on a recording medium PM such as paper by performing an image forming operation using a developer such as toner. configured. At this time, the image forming apparatus 1 transfers the toner image onto the recording medium PM by applying a transfer voltage to a transfer roller 44 (described later) and causing a transfer current to flow. That is, variations in the current value of the transfer current affect the quality of the formed toner image. The current value of the transfer current is determined based on the voltage value of the transfer voltage and the resistance value of a combined resistance (hereinafter referred to as the resistance of the transfer roller 44) in the path of the current flowing through the transfer roller 44, and this resistance value is It changes depending on the temperature of the transfer roller 44. In order to suppress fluctuations in the current value of the transfer current, it is desirable that the transfer voltage be adjusted according to the temperature of the transfer roller 44. For this reason, the image forming apparatus 1 performs a current detection execution determination process for detecting the current flowing through the transfer roller 44, and based on the result of this determination, performs current detection and adjustment of the transfer voltage. Note that in this specification, a position close to the paper storage cassette 10 (described later) or a direction toward the paper storage cassette 10 when viewed from an arbitrary position on the transport path along which the recording medium PM is transported is referred to as upstream. Further, when viewed from any position on the conveyance path, a position close to a stacker 4 (described later) on which the recording medium PM is discharged and stacked, or a direction toward the stacker 4 is referred to as downstream.

The image forming apparatus 1 includes a paper storage cassette 10, a hopping roller 11, a registration roller 12, a pinch roller 13, four image forming units 20 (image forming units 20K, 20Y, 20M, 20C), and four toner cartridges. It includes a cartridge 27 (toner cartridges 27K, 27Y, 27M, 27C), four LED (Light Emitting Diode) heads 30 (LED heads 30K, 30Y, 30M, 30C), a transfer mechanism 40, and a fixing mechanism 50. There is.

The paper storage cassette 10 is, for example, a paper feed tray, and is a storage section that stores the recording medium PM. In the paper storage cassette 10, a plurality of recording media PM can be stacked. A hopping roller 11 is provided downstream of the paper storage cassette 10.

The hopping roller 11 is a rotating member that comes into pressure contact with the surface of the recording medium PM stacked on the paper storage cassette 10 and feeds out the recording medium PM downstream one by one. The hopping roller 11 is rotated by power transmitted from a hopping motor 86 (described later) about the central axis of the hopping roller 11 as a rotation axis. The hopping roller 11 is configured to convey the recording medium PM along a guide 2 that is a path for conveying the recording medium PM. A registration roller 12 and a pinch roller 13 are provided downstream of the hopping roller 11.

The registration rollers 12 and the pinch rollers 13 are configured to convey the recording medium PM toward the four image forming units 20 while sandwiching the recording medium PM. When the registration roller 12 and the pinch roller 13 convey the recording medium PM, the leading end of the recording medium PM abuts against the opposing portion of the registration roller 12 and the pinch roller 13, thereby correcting the skew of the recording medium PM. do. The registration roller 12 is a rotating member that rotates by power transmitted from a registration motor 87 (described later). The registration rollers 12 are configured to rotate about the center axis of the registration rollers 12 as a rotation axis. The pinch roller 13 is a rotating member that is arranged to face the registration roller 12 and applies pressure to the recording medium PM and rotates following the registration roller 12. The pinch roller 13 is configured to rotate about the central axis of the pinch roller 13 as a rotation axis. Four image forming units 20 are provided downstream of the registration rollers 12 and pinch rollers 13.

(Image forming unit 20)
The four image forming units 20 (image forming units 20K, 20Y, 20M, and 20C) are mechanisms that form toner images using toner based on instructions from a control section 72 (described later). Each of the four image forming units 20 includes a photosensitive drum 21, a static eliminator 22, a charging roller 23, a developing roller 24, a developing blade 25, and a supply roller 26. The photosensitive drum 21 is configured to carry an electrostatic latent image on its surface (surface layer portion). The photosensitive drum 21 is rotated by power transmitted from a drum motor 85 (described later). The photosensitive drum 21 is charged by a charging roller 23 and exposed to light by a corresponding LED head 30 . Specifically, the photosensitive drum 21 of the image forming unit 20K is exposed to light by the LED head 30K, the photosensitive drum 21 of the image forming unit 20Y is exposed to light by the LED head 30Y, and the photosensitive drum 21 of the image forming unit 20M is exposed to light by the LED head 30K. The photosensitive drum 21 of the image forming unit 20C is exposed by the LED head 30C. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 21. By supplying toner by the developing roller 24, a toner image corresponding to the electrostatic latent image is formed (developed) on the photosensitive drum 21. The static eliminating unit 22 is configured to eliminate static from the surface of the photosensitive drum 21 by irradiating the surface of the photosensitive drum 21 with light. The charging roller 23 is configured to charge the surface (surface layer portion) of the photosensitive drum 21. The charging roller 23 is arranged so as to be in contact with the surface (circumferential surface) of the photosensitive drum 21, and is also arranged so as to be pressed against the photosensitive drum 21 by a predetermined amount of pressing. The charging roller 23 rotates in accordance with the rotation of the photosensitive drum 21. A predetermined charging voltage is applied to the charging roller 23 by a charging voltage generation section 81 (described later). The developing roller 24 is configured to carry charged toner on its surface. The developing roller 24 is arranged so as to be in contact with the surface (circumferential surface) of the photosensitive drum 21, and is also arranged so as to be pressed against the photosensitive drum 21 by a predetermined pressing amount. The developing roller 24 is rotated by power transmitted from a drum motor 85 (described later). A predetermined developing voltage is applied to the developing roller 24 by a developing voltage generating section 82 (described later). The developing blade 25 is a member that scrapes off the toner carried on the surface of the developing roller 24. The developing blade 25 is adapted to adjust the thickness of the toner carried on the surface of the developing roller 24. The supply roller 26 is configured to supply the toner contained in the corresponding toner cartridge 27 to the developing roller 24 . The supply roller 26 is arranged so as to be in contact with the surface (circumferential surface) of the developing roller 24, and is also arranged so as to be pressed against the developing roller 24 by a predetermined amount of pressing. The supply roller 26 is rotated by power transmitted from a drum motor 85 (described later). As a result, friction occurs between the surface of the supply roller 26 and the surface of the developing roller 24, and the toner is charged by so-called frictional charging. A predetermined supply voltage is applied to the supply roller 26 by a supply voltage generation section 83 (described later).

The four toner cartridges 27 (toner cartridges 27K, 27Y, 27M, and 27C) are configured to contain toner. Specifically, the toner cartridge 27K contains black toner, the toner cartridge 27Y contains yellow toner, the toner cartridge 27M contains magenta toner, and the toner cartridge 27C contains cyan toner. It looks like this.

The four LED heads 30 (LED heads 30K, 30Y, 30M, 30C) irradiate light onto the photosensitive drums 21 of the four image forming units 20, respectively, based on instructions from the LED head control section 74 (described later). It is a mechanism to do this. The LED head 30 includes, for example, an LED array, a driving IC (Integrated Circuit) for driving the LED array, a lens for condensing light from the LED array, a substrate on which a group of registers for holding data is mounted, and the like. As the lens in the LED head 30, for example, a SELFOC (registered trademark) lens is preferably used.

(Transfer mechanism 40)
The transfer mechanism 40 transfers the toner images formed by the four image forming units 20K, 20Y, 20M, and 20C onto the transfer surface of the recording medium PM, and conveys the recording medium PM toward the fixing mechanism 50. It is configured as follows. The transfer mechanism 40 includes a transfer belt 41, a drive roller 42, a driven roller 43, and four transfer rollers 44 (transfer rollers 44K, 44Y, 44M, and 44C). The transfer belt 41 is, for example, an annular belt including a seamlessly formed high-resistance semiconductive plastic film. The transfer belt 41 can carry a toner image formed by the image forming unit 20. The transfer belt 41 is stretched by a driving roller 42 and a driven roller 43. The transfer belt 41 is configured to convey the conveyed recording medium PM while electrostatically attracting the conveyed recording medium PM. The drive roller 42 is a rotating member that rotates to convey the recording medium PM toward the fixing mechanism 50 by power transmitted from a belt motor 88 (described later), and is configured to rotate the transfer belt 41 in a circular manner. . That is, the transfer belt 41 can be driven by the drive roller 42. The driven roller 43 is a member that adjusts the tension applied to the transfer belt 41 while stretching the transfer belt 41 together with the drive roller 42 . The driven roller 43 is configured to rotate in the same direction as the drive roller 42. The four transfer rollers 44 are members that transfer the toner image formed on the surface of the photosensitive drum 21 of the corresponding image forming unit 20 onto the transfer surface of the recording medium PM. The transfer roller 44K is arranged to face the photosensitive drum 21 of the image forming unit 20K via the transfer belt 41, and the transfer roller 44Y is arranged to face the photosensitive drum 21 of the image forming unit 20Y via the transfer belt 41. The transfer roller 44M is arranged to face the photosensitive drum 21 of the image forming unit 20M via the transfer belt 41, and the transfer roller 44C is arranged to face the photosensitive drum 21 of the image forming unit 20C via the transfer belt 41. They are placed opposite each other. That is, the four transfer rollers 44 are provided on the inner peripheral surface side of the transfer belt 41. A transfer voltage determined by a calculation unit 77 (described later) is applied to each of the four transfer rollers 44 by a transfer voltage generation unit 80 (described later). Thereby, in the image forming apparatus 1, the toner image formed by the image forming unit 20 is transferred onto the transfer surface of the recording medium PM.

(Fixing mechanism 50)
The fixing mechanism 50 is a mechanism that applies heat and pressure to the toner image transferred onto the recording medium PM transported from the transfer mechanism 40, thereby fixing the toner image onto the recording medium PM. The fixing mechanism 50 includes a heat roller 51, a heater 52, a thermistor 53, and a pressure roller 54. The heat roller 51 is configured to apply heat to the toner on the recording medium PM. The heat roller 51 is configured to rotate by power transmitted from a heater motor 89 (described later). The heater 52 is configured to heat the heat roller 51 based on instructions from a mechanism control unit 75 (described later), and is configured using, for example, a halogen heater or a ceramic heater. The thermistor 53 is configured to detect the surface temperature of the heat roller 51. The pressure roller 54 is arranged so that a pressure contact portion is formed between it and the heat roller 51, and is configured to apply pressure to the toner on the recording medium PM. The recording medium PM conveyed by the fixing mechanism 50 is discharged to the stacker 4 along the guide 3 which is a path for conveying the recording medium PM. Here, the stacker 4 is a part on which the recording medium PM on which the toner image is fixed is stacked.

The image forming apparatus 1 further includes a density sensor 60, a cover 61, a thermistor 62, a cleaning blade 63, a waste toner tank 64, and transport sensors 65 to 68.

The concentration sensor 60 is, for example, a reflective optical sensor, and in this example, includes one light emitting sensor and two light receiving sensors. The density sensor 60 is arranged opposite to the transfer belt 41. The density sensor 60 detects the toner amount (density) of the toner image formed on the transfer belt 41 by measuring the intensity of reflected light in the toner image based on instructions from a mechanism control unit 75 (described later). It looks like this.

The cover 61 is a protective member that protects the density sensor 60 from toner, paper dust, and the like. The cover 61 is made of, for example, plastic. The cover 61 is disposed between the transfer mechanism 40 and the density sensor 60, covers the top of the density sensor 60 when the density sensor 60 is not used, and covers the top of the density sensor 60 when the density sensor 60 is used. The top is not covered.

The thermistor 62 is arranged to face the transfer belt 41 and is configured to detect the surface temperature of the transfer belt 41. Specifically, for example, when the amount of drive of the transfer belt 41 is one rotation or more, the thermistor 62 detects the temperature of the transfer belt 41. In this case, the contribution of heat advection between the transfer belt 41 and the thermistor 62 increases, and thermal equilibrium is maintained between the transfer belt 41 and each of the four transfer rollers 44. Therefore, the measured temperature value T detected by the thermistor 62 indicates the temperature of the transfer belt 41 and is substantially the same as the temperature of the four transfer rollers 44 . That is, the measured value T is an accurate measured value of the temperature of the transfer roller 44. Furthermore, when the amount of drive of the transfer belt 41 is less than one rotation, the thermistor 62 similarly detects the temperature of the transfer belt 41. That is, when the transfer belt 41 is stopped, or when the amount of drive of the transfer belt 41 is small even when the transfer belt 41 is driven, the contribution of heat advection between the transfer belt 41 and thermistor 62 is small. , thermal equilibrium is not maintained between the transfer belt 41 and each of the four transfer rollers 44. Therefore, the measured temperature value T detected by the thermistor 62 indicates the temperature of the transfer belt 41 and deviates from the temperature of the four transfer rollers 44 . That is, the measured value T is an estimated value that includes an error in the temperature of the transfer roller 44. When the image forming apparatus 1 performs current detection execution determination processing, the image forming apparatus 1 acquires the measurement value T when the transfer belt 41 is stopped, and the measurement value when the transfer belt 41 is driving. The current detection execution determination process can be performed more quickly than by acquiring the value T. Here, factors of heat advection include, for example, the heat of the heat roller 51 during the image forming operation, the frictional heat between the recording medium PM and the transfer belt 41, the airflow caused by a cooling fan (not shown), and the heat of the transfer belt 41 itself. This includes the difference between the heat transfer rate and the heat transfer rate of the transfer roller 44 itself.

The cleaning blade 63 includes, for example, a flexible rubber or plastic material, and is a member that scrapes and cleans the waste toner remaining on the surface of the transfer belt 41. The cleaning blade 63 is arranged opposite to the driven roller 43 with the transfer belt 41 interposed therebetween. The waste toner tank 64 is a member that collects and stores waste toner scraped off by the cleaning blade 63.

The conveyance sensors 65 to 68 are configured to detect the position of the conveyed recording medium PM and a paper jam. The conveyance sensor 65 is provided between the hopping roller 11, the registration roller 12, and the pinch roller 13. The conveyance sensor 66 is provided between the registration roller 12 and the pinch roller 13 and the four image forming units 20. The conveyance sensor 67 is provided between the four image forming units 20 and the fixing mechanism 50. Conveyance sensor 68 is provided downstream of fixing mechanism 50 .

(Control system of image forming apparatus 1)
FIG. 2 is a block diagram showing an example of a control system of the image forming apparatus 1. As shown in FIG. The image forming apparatus 1 includes a storage section 70 , a communication section 71 , a control section 72 , a transfer voltage generation section 80 , a charging voltage generation section 81 , a developing voltage generation section 82 , a supply voltage generation section 83 , and 4 It has four current measurement units 84, four drum motors 85, a hopping motor 86, a registration motor 87, a belt motor 88, and a heater motor 89.

The storage unit 70 is configured to store various data such as various settings used in the image forming apparatus 1. The storage unit 70 includes, for example, a nonvolatile memory. The storage unit 70 stores threshold data TD. Further, although not shown, a reference value TR (described later) of the temperature of the transfer belt 41 is stored.

FIG. 3 is an explanatory diagram showing an example of threshold data TD. The threshold value data TD includes information about a period in which a preset threshold value Tth regarding the temperature of the transfer roller 44 is used, and information about the threshold value Tth. That is, the threshold value Tth defines the temperature range of the transfer roller 44. In this example, the threshold value Tth is "Tth1" during a period in which the elapsed time t after the transfer belt 41 stops is equal to or greater than "0" minutes and the elapsed time t is less than "t1" minutes. Further, in a period in which the elapsed time t after the transfer belt 41 stops is more than "t1" minutes and the elapsed time t is less than "t2" minutes, the threshold value Tth is "Tth1+ΔTth1"°C. Further, in a period in which the elapsed time t after the transfer belt 41 stops is longer than "t2" minutes, the threshold value Tth is "Tth1"°C.

The communication unit 71 is configured to receive various data such as print data by communicating with a host device such as a personal computer. In this example, the communication unit 71 includes a connector, a communication IC, and the like. The communication unit 71 is configured to transmit the received print data to a command processing unit 73 (described later).

The control unit 72 is configured to control the operation of the image forming apparatus 1 by controlling the operation of each block. The control unit 72 can be configured using, for example, a processor capable of executing programs or a RAM (Random Access Memory). The functions of the control unit 72 may be realized by, for example, hardware or software. The control section 72 includes a command processing section 73 , an LED head control section 74 , a mechanism control section 75 , and a high pressure control section 79 .

The command processing unit 73 is configured to process print data sent from the communication unit 71. In this example, the command processing unit 73 includes a microprocessor, RAM, and middleware. Specifically, for example, the command processing unit 73 interprets a command included in the print data, and controls the mechanism control unit 75 based on the content of the command. Further, the command processing unit 73 is configured to develop the image data included in the print data into a bitmap, and transmit the image data developed into the bitmap to the LED head control unit 74.

The LED head control unit 74 is configured to control the four LED heads 30 based on the image data expanded into a bitmap transmitted from the command processing unit 73 and instructions from the mechanism control unit 75. . In this example, the LED head control section 74 includes a semi-custom LSI (Large Scale Integration) and a RAM. Specifically, for example, the LED head control unit 74 processes the image data expanded into a bitmap so that each of the four LED heads 30 can use it. Then, the LED head control section 74 controls the four LED heads 30 to emit light based on the processed image data and instructions from the mechanism control section 75. That is, the LED head control unit 74 inputs a black image data signal to the LED head 30K, inputs a yellow image data signal to the LED head 30Y, inputs a magenta image data signal to the LED head 30M, and inputs a cyan image data signal to the LED head 30M. A color image data signal is input to the LED head 30C. Thereby, the LED head control section 74 controls the four LED heads 30 so as to irradiate the photosensitive drum 21 of the image forming unit 20 with light.

The mechanism control section 75 controls the image forming apparatus 1 based on instructions from the command processing section 73 and output results of various sensors (thermistors 53 and 62, density sensor 60, conveyance sensors 65 to 68, and four current measurement sections 84). is configured to control the overall operation of. In this example, the mechanism control section 75 includes a semi-custom LSI (Large Scale Integration) or a microprocessor, and a RAM. Specifically, for example, the mechanism control section 75 controls the LED head control section 74 based on instructions from the command processing section 73 and output results from various sensors. Furthermore, the mechanism control section 75 controls the high pressure control section 79 based on instructions from the command processing section 73 and output results from various sensors. Furthermore, the mechanism control section 75 controls four drum motors 85, a hopping motor 86, a registration motor 87, a belt motor 88, and a heater motor 89 based on the instructions from the command processing section 73 and the output results of the conveyance sensors 65 to 68. control. Furthermore, the mechanism control section 75 controls the heater 52 based on the instruction from the command processing section 73 and the output result of the thermistor 53. Furthermore, the mechanism control section 75 controls the concentration sensor 60 based on instructions from the command processing section 73. Furthermore, the mechanism control unit 75 performs a current detection execution determination process for detecting the current flowing through the transfer roller 44 based on instructions from the command processing unit 73. When it is determined to perform current detection, the mechanism control unit 75 controls to perform current detection and adjustment of the transfer voltage. At this time, the mechanism control section 75 stores the measured value T of the temperature detected by the thermistor 62 in the storage section 70 as the reference value TR of the temperature of the transfer roller 44 . That is, the mechanism control unit 75 is configured to store an accurate measurement value of the temperature of the transfer roller 44 when the image forming apparatus 1 performs current detection and transfer voltage adjustment. The mechanism control section 75 includes a time measurement section 76, a calculation section 77, and a current detection section 78.

The time measurement unit 76 is configured to measure time and determine whether a predetermined time has elapsed based on instructions from the command processing unit 73. Specifically, for example, when the image forming apparatus 1 performs current detection execution determination processing, the time measurement unit 76 measures the elapsed time t after the transfer belt 41 stops. Furthermore, the time measuring unit 76 determines whether the elapsed time t is within "t1" minutes. Further, the time measuring unit 76 determines whether the elapsed time t is within "t2" minutes.

The calculation unit 77 is configured to perform various calculations in current detection execution determination processing, current detection, and transfer voltage adjustment based on instructions from the command processing unit 73. Specifically, for example, when the image forming apparatus 1 performs current detection execution determination processing, the calculation unit 77 calculates the measured value T when the amount of drive of the transfer belt 41 detected by the thermistor 62 is less than one revolution. Based on the reference value TR and the threshold value Tth in the threshold value data TD, it is configured to determine whether or not to perform current detection to detect the current flowing through the transfer roller 44. In this example, the calculation unit 77 determines the current by comparing the difference between the measured value T detected by the thermistor 62 and the reference value TR when the drive amount of the transfer belt 41 is less than one rotation with the threshold value Tth. Determine whether to perform detection. That is, the calculation unit 77 determines whether or not to perform current detection by comparing the difference between the measured value T as the estimated value of the temperature of the transfer roller 44 and the reference value TR with the threshold value Tth. Further, when the image forming apparatus 1 performs current detection and transfer voltage adjustment, the calculation unit 77 calculates the resistance value of the resistance of the transfer roller 44 corresponding to the current measurement unit 84 based on the measurement result of the current measurement unit 84. calculate. That is, the calculation unit 77 calculates the resistance value of the resistance of the transfer roller 44 according to the measurement value T as an accurate measurement value of the temperature of the transfer roller 44 . Then, the calculation unit 77 determines the voltage value of the transfer voltage to be applied to each of the four transfer rollers 44 based on this resistance value.

The current detection unit 78 is configured to control current detection based on the determination result of the calculation unit 77. Specifically, for example, when the image forming apparatus 1 performs current detection execution determination processing, the current detection unit 78 determines to perform current detection based on the determination result of the calculation unit 77. Further, when the image forming apparatus 1 performs current detection and transfer voltage adjustment, the current detection unit 78 performs high voltage control so as to apply a predetermined transfer voltage to each of the four transfer rollers 44 for current detection. 79. Further, the current detection unit 78 controls the current measurement unit 84 to measure the current flowing between the corresponding transfer roller 44 and the photosensitive drum 21.

The high voltage control section 79 is configured to control the generation of various voltages based on instructions from the mechanism control section 75. Specifically, for example, when the image forming apparatus 1 performs an image forming operation, the high voltage control section 79 controls the transfer voltage generation section 80 to generate the transfer voltage determined by the calculation section 77, and The charging voltage generating section 81 is controlled to generate a developing voltage, the developing voltage generating section 82 is controlled to generate a developing voltage, and the supply voltage generating section 83 is controlled to generate a supply voltage. At this time, the transfer voltage may be finely adjusted based on various parameters included in the print data, such as the thickness of the recording medium PM. Further, when the image forming apparatus 1 performs current detection, the high voltage control section 79 controls the transfer voltage generation section 80 to generate a predetermined transfer voltage for current detection.

The transfer voltage generation section 80 is configured to generate a transfer voltage and supply the transfer voltage to the four transfer rollers 44 based on instructions from the high voltage control section 79 . The charging voltage generation section 81 is configured to generate a charging voltage and supply the charging voltage to the charging rollers 23 of the four image forming units 20 based on instructions from the high voltage control section 79 . The developing voltage generation section 82 is configured to generate a developing voltage and supply the developing voltage to the developing rollers 24 of the four image forming units 20 based on instructions from the high voltage control section 79 . The supply voltage generation section 83 is configured to generate a supply voltage and supply the supply voltage to the supply rollers 26 of the four image forming units 20 based on instructions from the high voltage control section 79 .

Each of the four current measurement units 84 is, for example, a current sensor, and is configured to measure the current flowing through the corresponding transfer roller 44 based on an instruction from the current detection unit 78. Each of the four current measurement units 84 is provided on a path through which current flows between the transfer roller 44 and the photosensitive drum 21. Each of the four drum motors 85 is configured to transmit power to the photosensitive drum 21 of the corresponding image forming unit 20 based on instructions from the mechanism control section 75. The hopping motor 86 is configured to transmit power to the hopping roller 11 based on instructions from the mechanism control section 75. The registration motor 87 is configured to transmit power to the registration roller 12 based on instructions from the mechanism control section 75. Belt motor 88 is configured to transmit power to drive roller 42 based on instructions from mechanism control section 75 . The heater motor 89 is configured to transmit power to the heat roller 51 based on instructions from the mechanism control section 75.

Here, the drive roller 42 corresponds to a specific example of a "drive member" in the present invention. The transfer belt 41 corresponds to a specific example of the "transfer belt" in the present invention. The transfer rollers 44K, 44Y, 44M, and 44C correspond to a specific example of a "transfer body" in the present invention. The control unit 72 corresponds to a specific example of a “control unit” in the present invention.
[1.2 Operation of image forming apparatus 1]
(A. Basic movements)
In this image forming apparatus 1, a toner image is transferred onto the recording medium PM in the following manner.

First, the overall operation of the image forming apparatus 1 will be described with reference to FIGS. 1 and 2. In the image forming apparatus 1, when the communication unit 71 receives print data from the host device, the command processing unit 73 processes the print data and interprets the commands included in the print data based on instructions from the command processing unit 73. At the same time, the mechanism control section 75 is controlled based on the contents of the command. Further, the command processing section 73 develops the image data included in the print data into a bitmap, and transmits the image data developed into the bitmap to the LED head control section 74 . Mechanism control section 75 controls the overall operation of image forming apparatus 1 based on instructions from command processing section 73 and output results from various sensors. The LED head control unit 74 controls the four LED heads 30 based on the image data expanded into a bitmap transmitted from the command processing unit 73 and instructions from the mechanism control unit 75. High voltage control section 79 controls transfer voltage generation section 80 , charging voltage generation section 81 , development voltage generation section 82 , and supply voltage generation section 83 based on instructions from mechanism control section 75 . The image forming apparatus 1 thus includes four LED heads 30, a transfer voltage generating section 80, a charging voltage generating section 81, a developing voltage generating section 82, a supply voltage generating section 83, four drum motors 85, a hopping motor 86, and a resistor. By controlling the motor 87, belt motor 88, heater motor 89, and heater 52, an image forming operation is performed on the recording medium PM.

In the image forming apparatus 1, an electrostatic latent image is formed on the surface of the photosensitive drum 21 by the LED head 30 selectively irradiating light onto the photosensitive drum 21 whose surface is charged in the image forming unit 20. Ru. Then, a toner image is formed on the photosensitive drum 21 according to the electrostatic latent image.

The hopping roller 11 is driven by the hopping motor 86 to feed the recording medium PM loaded in the paper storage cassette 10 downstream. The recording medium PM is conveyed along the guide 2 toward the registration rollers 12 and the pinch rollers 13 . At this time, the front edge of the recording medium PM abuts against the opposing portion of the registration roller 12 and the pinch roller 13, so that the skew of the recording medium PM is corrected. Thereafter, the registration rollers 12 and the pinch rollers 13 transport the recording medium PM toward the image forming unit 20 by rotating while sandwiching the recording medium PM.

Thereafter, the transfer belt 41 conveys the recording medium PM toward the fixing mechanism 50 by rotating cyclically. At this time, the recording medium PM passes between the photosensitive drum 21 and the transfer roller 44. In the image forming apparatus 1, when a toner image is formed on the surface of the photosensitive drum 21 in the image forming unit 20, the transfer mechanism 40 performs a transfer process. At this time, in the transfer mechanism 40, the transfer belt 41 conveys the recording medium PM while the transfer roller 44 draws the toner image formed on the surface of the photosensitive drum 21. As a result, the toner image is transferred from the photosensitive drum 21 to the recording medium PM.

The fixing mechanism 50 performs a fixing process when the recording medium PM is conveyed. At this time, the fixing mechanism 50 applies heat and pressure to the toner image transferred to the surface of the recording medium PM, melts the toner image, and fixes the toner image on the recording medium PM. When the toner image is fixed on the recording medium PM, the image forming apparatus 1 conveys the recording medium PM toward the stacker 4 and discharges the recording medium PM onto the stacker 4.

The overall operation of the image forming apparatus 1 is as described above.

(B. Current detection execution judgment process)
The current detection execution determination process in the image forming apparatus 1 will be described in detail below. In this example, first, the power is turned on to the image forming apparatus 1, and the image forming apparatus 1 performs initialization processing. In the initialization process, the mechanism control section 75 controls the high voltage control section 79, four drum motors 85, and belt motor 88 based on instructions from the command processing section 73, thereby controlling the four image forming units 20 and The operation of the transfer mechanism 40 is controlled. That is, by rotating each roller of the image forming unit 20 and the transfer roller 44 and driving the transfer belt 41 one or more rotations, thermal equilibrium is maintained between the transfer belt 41 and the four transfer rollers 44 after a predetermined period of time has elapsed. It will be done. Then, the mechanism control unit 75 performs control to detect the current and adjust the transfer voltage. At this time, the mechanism control section 75 stores the measured value T of the temperature detected by the thermistor 62 in the storage section 70 as the reference value TR of the temperature of the transfer roller 44 . Then, the image forming apparatus 1 starts the current detection execution determination process.

FIG. 4 shows an example of the current detection execution determination process in the image forming apparatus 1. In the current detection execution determination process, the image forming apparatus 1 performs current detection based on the measured value T detected by the thermistor 62 when the drive amount of the transfer belt 41 is less than one revolution, the reference value TR, and the threshold value Tth. , determines whether or not to perform current detection, and determines to perform current detection based on this determination result. This operation will be explained in detail below.

First, the mechanism control section 75 controls the transfer belt 41 to stop based on an instruction from the command processing section 73 (step S101). Specifically, for example, the mechanism control unit 75 controls the four drum motors 85 and the belt motor 88 that were driven in the initialization process to stop based on instructions from the command processing unit 73. That is, the transfer belt 41 driven by the drive roller 42 stops. Then, the time measuring section 76 starts measuring the elapsed time t since the transfer belt 41 stopped.

Next, the communication unit 71 receives print data from the host device and transmits the print data to the command processing unit 73 (step S102).

Next, the time measurement section 76 determines whether the elapsed time t is within "t1" based on the instruction from the command processing section 73 (step S103). If the elapsed time t exceeds "t1" ("N" in step S103), the process advances to step S107.

If the elapsed time t is within "t1", the calculation unit 77 calculates the absolute value of the difference between the measured value T of the thermistor 62 and the reference value TR (step S104). Specifically, for example, the calculation unit 77 obtains the measured value T of the temperature measured from the thermistor 62 and also obtains the reference value TR stored from the storage unit 70, thereby calculating the measured value T and the reference value TR. Calculate the absolute value of the difference between

Next, the calculation unit 77 determines whether the absolute value of the difference between the measured value T and the reference value TR is greater than "Tth1" (step S105). Specifically, for example, the calculation unit 77 obtains “Tth1” which is the threshold value Tth from the threshold value data TD in the storage unit 70, and calculates the absolute value of the difference between the measured value T and the reference value TR and “Tth1”. Compare with. Thereby, the calculation unit 77 determines whether the absolute value of the difference between the measured value T and the reference value TR is greater than "Tth1". If the absolute value of the difference between the measured value T and the reference value TR is less than or equal to "Tth1" ("N" in step S105), this process ends.

If the absolute value of the difference between the measured value T and the reference value TR is greater than “Tth1” (“Y” in step S105), the current detection unit 78 performs current detection based on the determination result of the calculation unit 77. is determined (step S106).

If the elapsed time t exceeds "t1" ("N" in step S103), the time measuring unit 76 determines whether the elapsed time t is within "t2" (step S107). If the elapsed time t exceeds "t2" ("N" in step S107), the process proceeds to step S111.

If the elapsed time t is within "t2", similarly to step S104, the calculation unit 77 calculates the absolute value of the difference between the measured value T of the thermistor 62 and the reference value TR (step S108).

Next, the calculation unit 77 determines whether the absolute value of the difference between the measured value T and the reference value TR is greater than "Tth1+ΔTth1" (step S109). Specifically, for example, the calculation unit 77 obtains “Tth1+ΔTth1” which is the threshold value Tth from the threshold value data TD of the storage unit 70, and calculates the absolute value of the difference between the measured value T and the reference value TR and “Tth1+ΔTth1”. Compare with. Thereby, the calculation unit 77 determines whether the absolute value of the difference between the measured value T and the reference value TR is greater than "Tth1+ΔTth1". If the absolute value of the difference between the measured value T and the reference value TR is less than or equal to "Tth+ΔTth1" ("N" in step S109), this process ends.

If the absolute value of the difference between the measured value T and the reference value TR is greater than “Tth1+ΔTth1” (“Y” in step S109), the current detection unit 78, based on the determination result of the calculation unit 77, similarly to step S106. , it is determined to perform current detection (step S110).

If the elapsed time t exceeds "t2" ("N" in step S107), similarly to step S104, the calculation unit 77 calculates the absolute value of the difference between the measured value T of the thermistor 62 and the reference value TR ( Step S111).

Next, similarly to step S105, the calculation unit 77 determines whether the absolute value of the difference between the measured value T and the reference value TR is greater than "Tth1" (step S112). If the absolute value of the difference between the measured value T and the reference value TR is less than or equal to "Tth1" ("N" in step S112), this process ends.

If the absolute value of the difference between the measured value T and the reference value TR is greater than “Tth1” (“Y” in step S112), the current detection unit 78, based on the determination result of the calculation unit 77, similarly to step S106. , it is decided to perform current detection (step S113).

With this, this flow ends.

Note that in this example, the current detection execution determination process is started after the transfer voltage is adjusted in the initialization process, but the present invention is not limited to this. Alternatively, for example, the current detection execution determination process may be started after the transfer voltage is adjusted at a timing other than the initialization process.

(C. Current detection and transfer voltage adjustment)
FIG. 5 shows an example of current detection and transfer voltage adjustment. When the current detection unit 78 determines to perform current detection in steps S106, S110, and S113, the image forming apparatus 1 performs current detection and adjustment of the transfer voltage. This operation will be explained in detail below.

First, the control unit 72 controls the transfer belt 41 to be driven based on the determination by the current detection unit 78 (step S201). Specifically, for example, the mechanism control section 75 controls the high voltage control section 79, four drum motors 85, and belt motor 88 based on instructions from the command processing section 73, thereby controlling the four image forming units. 20 and the operation of the transfer mechanism 40. That is, by rotating each roller of the image forming unit 20 and the transfer roller 44 and driving the transfer belt 41 one or more rotations, thermal equilibrium is maintained between the transfer belt 41 and the four transfer rollers 44 after a predetermined period of time has elapsed. It will be done.

Next, the control unit 72 controls the transfer voltage generation unit 80 to apply a transfer voltage to the transfer roller 44 (step S202). Specifically, for example, the current detection section 78 instructs the high voltage control section 79 to apply a predetermined transfer voltage to each of the four transfer rollers 44 for current detection. High voltage control section 79 controls transfer voltage generation section 80 to generate a predetermined transfer voltage for current detection based on instructions from current detection section 78 . Then, the transfer voltage generation section 80 applies a transfer voltage to the transfer roller 44.

Next, the current detection unit 78 controls the current measurement unit 84 to measure the current flowing through the transfer roller 44 (step S203). Then, the current measuring section 84 measures the current.

Next, the calculation unit 77 calculates the resistance value of the resistance of the transfer roller 44 corresponding to the current measurement unit 84 based on the measurement results of the four current measurement units 84 (step S204). Specifically, for example, the calculation unit 77 calculates the ratio between the voltage value of the transfer voltage applied in step S202 and the current value of the current measured in step S203 as the resistance value of the resistance of the transfer roller 44. This resistance value correlates with temperature, and becomes smaller as the temperature increases.

Next, the calculation unit 77 determines the voltage value of the transfer voltage to be applied to each of the four transfer rollers 44 based on this resistance value (step S205). Specifically, for example, since the voltage value of the transfer voltage is proportional to the resistance value of the resistance of the transfer roller 44, the calculation unit 77 calculates the voltage of the transfer voltage by substituting the calculated resistance value into a predetermined linear equation. Determine the value.

Next, the mechanism control unit 75 stores the measured temperature value T detected by the thermistor 62 in the storage unit 70 as a new reference value TR of the temperature of the transfer roller 44 (step S206).

With this, this flow ends.

(D. Method for determining threshold data)
“ΔTth1”, “t1”, and “t2” in the threshold data TD are determined in advance, for example, by experiment. The method for determining "ΔTth1", "t1", and "t2" will be explained in detail below.

(When the temperature of the transfer belt 41 is lower than the temperature of the transfer roller 44)
FIG. 6 is an explanatory diagram showing temperature changes of the transfer belt 41 and the transfer roller 44. In this example, the temperature of the transfer belt 41 is the measured value T of the temperature detected by the thermistor 62, and the temperature of the transfer roller 44 is the temperature measured by the temperature sensor provided on the transfer roller 44 in order to determine "ΔTth1". It is a measured value. In FIG. 6, the horizontal axis represents time and the vertical axis represents temperature. Timing tm0 is the timing at which the transfer belt 41 stops. That is, in this example, the measured temperature value T detected by the thermistor 62 before timing tm0 indicates the temperature of the transfer belt 41 and is substantially the same as the temperature of the four transfer rollers 44. Further, the temperature measurement value T detected by the thermistor 62 after timing tm0 indicates the temperature of the transfer belt 41, and is deviated from the temperature of the four transfer rollers 44. lower than the temperature. The reference value TR of the temperature of the transfer roller 44 is, for example, the temperature at timing tm0, which is "TR1"°C. The timing tm1 is determined as the timing at which the difference between the reference value TR and the temperature of the transfer roller 44 becomes "Tth1". “ΔTth1” is determined as the difference between the temperature of the transfer roller 44 and the temperature of the transfer belt 41 at timing tm1. After timing tm0, as time passes, the difference between the temperature of the transfer roller 44 and the temperature of the transfer belt 41 gradually increases. As time further passes, the difference between the temperature of the transfer roller 44 and the temperature of the transfer belt 41 gradually decreases, and both the temperature of the transfer roller 44 and the temperature of the transfer belt 41 approach the environmental temperature. Timing tm2 is determined as a timing after timing tm1 when the difference between the temperature of the transfer roller 44 and the temperature of the transfer belt 41 becomes equal to or less than a predetermined temperature difference. In this case, in the threshold data TD, "t1" is the time from timing tm0 to timing tm1, and "t2" is the time from timing tm1 to timing tm2. That is, in a period in which the elapsed time t after the transfer belt 41 stops is more than "t1" minutes and the elapsed time t is less than "t2" minutes, the threshold value Tth is "Tth1+ΔTth1" and is less than "Tth1". It's also big.

(When the temperature of the transfer belt 41 is higher than the temperature of the transfer roller 44)
FIG. 7 is an explanatory diagram showing temperature changes of the transfer belt 41 and the transfer roller 44. In this example, the measured temperature value T detected by the thermistor 62 at a time after the timing tm0 indicates the temperature of the transfer belt 41, which deviates from the temperature of the four transfer rollers 44, and the temperature of the transfer belt 41 is The temperature becomes higher than that of the transfer roller 44. In this example, the reference value TR of the temperature of the transfer roller 44 is, for example, the temperature at timing tm0, which is "TR1"°C. The timing tm1 is determined as the timing at which the difference between the reference value TR and the temperature of the transfer roller 44 becomes "Tth1". “ΔTth1” is determined as the difference between the temperature of the transfer belt 41 and the temperature of the transfer roller 44 at timing tm1. After timing tm0, as time passes, the difference between the temperature of the transfer belt 41 and the temperature of the transfer roller 44 gradually increases. As time further passes, the difference between the temperature of the transfer belt 41 and the temperature of the transfer roller 44 gradually decreases, and both the temperature of the transfer roller 44 and the temperature of the transfer belt 41 approach the environmental temperature. Timing tm2 is determined as a timing after timing tm1 when the difference between the temperature of the transfer belt 41 and the temperature of the transfer roller 44 becomes equal to or less than a predetermined temperature difference. In this case, in the period in which the elapsed time t after the stop of the transfer belt 41 is more than "t1" minutes and the elapsed time t is less than "t2" minutes in the threshold value data TD, the threshold value Tth is "Tth1-ΔTth1". , which is smaller than “Tth1”.

[1.3 Operation of image forming apparatus 1]
Next, the operation of this embodiment will be explained in comparison with a comparative example. The image forming apparatus 1R according to this comparative example is configured to perform current detection execution determination processing based on a threshold value Tth that has the same magnitude regardless of time.

FIG. 8 is a block diagram showing an example of a control system of the image forming apparatus 1R. The image forming apparatus 1R includes a storage section 70R and a control section 72R. The storage unit 70R stores threshold data TDR.

FIG. 9 is an explanatory diagram showing an example of threshold data TDR of the image forming apparatus 1R. In FIG. 8, the horizontal axis represents elapsed time t, and the vertical axis represents temperature. In the image forming apparatus 1R, the threshold value Tth of the threshold value data TDR is "Tth1" regardless of time. On the other hand, in the image forming apparatus 1, the threshold value is The threshold value Tth of the data TD is "Tth1". Further, in a period in which the elapsed time t is more than "t1" minutes and the elapsed time t is less than "t2" minutes, the threshold value Tth is "Tth1+ΔTth1".

The control section 72R has a mechanism control section 75R. The mechanism control section 75R includes a time measurement section 76R and a calculation section 77R. The time measurement unit 76R measures time based on instructions from the command processing unit 73. When the image forming apparatus 1R performs current detection execution determination processing, the calculation unit 77R calculates a measured value T when the drive amount of the transfer belt 41 detected by the thermistor 62 is less than one revolution, a reference value TR, Based on the threshold value Tth in the threshold value data TDR, it is determined whether or not current detection for detecting the current flowing through the transfer roller 44 is to be performed.

FIG. 10 shows an example of the current detection execution determination process in the image forming apparatus 1R. This operation will be explained in detail below.

First, the mechanism control section 75R controls the transfer belt 41 to stop based on an instruction from the command processing section 73 (step S101). Next, the communication unit 71 receives print data from the host device and transmits the print data to the command processing unit 73 (step S102). Next, the calculation unit 77R calculates the absolute value of the difference between the measured value T of the thermistor 62 and the reference value TR (step S104). Specifically, for example, the calculation unit 77R obtains the measured temperature value T from the thermistor 62 and the reference value TR stored from the storage unit 70, thereby calculating the measured value T and the reference value TR. Calculate the absolute value of the difference between Next, the calculation unit 77R determines whether the absolute value of the difference between the measured value T and the reference value TR is greater than "Tth1" (step S105R). If the absolute value of the difference between the measured value T and the reference value TR is less than or equal to "Tth1" ("N" in step S105R), this process ends. If the absolute value of the difference between the measured value T and the reference value TR is greater than “Tth1” (“Y” in step S105R), the current detection unit 78 performs current detection based on the determination result of the calculation unit 77R. is determined (step S106). With this, this flow ends.

FIG. 11 is an explanatory diagram showing temperature changes of the transfer belt 41 and transfer roller 44 of the image forming apparatus 1R. In this example, the temperature of the transfer belt 41 is the measured value T of the temperature detected by the thermistor 62, and the temperature of the transfer roller 44 is unknown information in the image forming apparatus 1R. In FIG. 11, the horizontal axis represents time and the vertical axis represents temperature. Similar to FIG. 6, timing tm0 is the timing at which the transfer belt 41 stops. The measured temperature value T detected by the thermistor 62 before timing tm0 indicates the temperature of the transfer belt 41 and is substantially the same as the temperature of the four transfer rollers 44. Further, the temperature measurement value T detected by the thermistor 62 after timing tm0 indicates the temperature of the transfer belt 41, and is deviated from the temperature of the four transfer rollers 44. lower than the temperature. In this example, the reference value TR of the temperature of the transfer roller 44 is the temperature at the timing when the transfer voltage was adjusted before the timing tm0, and is "TR2"°C.

At timing tm3, the temperature of the transfer roller 44 is "T31" degrees Celsius, and the temperature of the transfer belt 41 is "T32" degrees Celsius. In this example, the difference between "T31", which is the temperature of the transfer roller 44, and "TR2", which is the reference value TR, is smaller than "Tth1", which is the threshold value Tth. Further, the difference between "T32", which is the temperature of the transfer belt 41, and "TR2", which is the reference value TR, is larger than "Tth1", which is the threshold value Tth. In this case, since the temperature of the transfer roller 44 is close to the reference value TR, it is desirable to use the already adjusted transfer voltage, but the calculation unit 77R calculates the difference between "T32" and "TR2" and "Tth1". For comparison, the current detection unit 78 decides to perform current detection. That is, the image forming apparatus 1R performs current detection and adjustment of transfer voltage.

On the other hand, in the image forming apparatus 1, for example, when the timing tm3 is after "t1" minutes from the timing tm0 and before "t2" minutes from the timing tm0, the calculation unit 77 calculates the measured value T "T32". ” and the reference value TR “TR2” and the threshold value Tth “Tth1+ΔTth1” are compared. If the difference between "T32" and "TR2" is smaller than "Tth1" but larger than "Tth1+ΔTth1", the current detection unit 78 does not decide to perform current detection and makes a decision to perform current detection. Processing ends. In this case, the image forming apparatus 1 does not need to perform current detection and transfer voltage adjustment. In this way, the image forming apparatus 1 can prevent current detection from being performed when it is desirable to use an already adjusted transfer voltage.

[1.4 Effect]
As described above, in the image forming apparatus 1 of the present embodiment, the calculation unit 77 calculates the measured value T when the drive amount of the transfer belt 41 detected by the thermistor 62 is less than one revolution, the previous current detection, and the transfer By comparing the difference from the reference value TR when the voltage is adjusted with the threshold value Tth, it is determined whether or not to perform current detection. The threshold value Tth is set to be "Tth1+ΔTth1"° C. during a period in which the elapsed time t after the transfer belt 41 stops is at least "t1" minutes and the elapsed time t is less than "t2" minutes. In a period including a period in which the elapsed time t is less than "t1" and a period in which it is greater than or equal to "t2" minutes, the threshold value Tth is set to be "Tth1"°C. As a result, for example, during a period in which the elapsed time t is more than "t1" minutes and the elapsed time t is less than "t2" minutes, the difference between the measured value T and the reference value TR is larger than "Tth1". If the current value is less than “Tth1+ΔTth1”, execution of current detection can be prevented. As a result, when re-driving the transfer belt 41 during, for example, an image forming operation, current detection and adjustment of the transfer voltage can be omitted, so that the time required for the image forming operation can be shortened. Therefore, user convenience can be improved. Furthermore, since current detection and transfer voltage adjustment can be omitted, power consumption can be suppressed.

Furthermore, in the image forming apparatus 1 of this embodiment, the calculation unit 77 determines the voltage value of the transfer voltage applied to the transfer roller 44 based on the current detected by current detection. Thereby, the transfer voltage can be set based on the resistance value of the resistance of the transfer roller 44 according to the temperature of the transfer roller 44. That is, for example, when estimating the resistance value of the transfer roller 44 according to the measured value T of the temperature of the thermistor 62 and setting the transfer voltage based on the estimated resistance value, the temperature of the thermistor 62 is equal to the temperature of the transfer roller 44. There is a possibility of deviation. In this case, the error in the estimated resistance value becomes large, and the quality of the transferred image may deteriorate. On the other hand, in the image forming apparatus 1, the resistance value of the transfer roller 44 is calculated based on the current detected by the current detection, for example, in accordance with the measured value of the temperature of the transfer roller 44. Since the voltage value of the applied transfer voltage can be determined, the quality of the transferred image can be improved.

<2. Modified example>
[Modification 1]
In the embodiment described above, the toner image formed by the image forming unit 20 is directly transferred onto the recording medium PM, but the invention is not limited to this. The formed toner image may be once transferred to an intermediate transfer belt, and the toner image transferred to the intermediate transfer belt may be transferred to the recording medium PM.

FIG. 12 is a configuration diagram showing a configuration example of an image forming apparatus 100 according to this modification. The image forming apparatus 100 includes a roll paper feeder 110, five image forming units 20 (image forming units 20W, 20Y, 20M, 20C, 20K), and five toner cartridges 27 (toner cartridges 27W, 27Y, 27M, 27C, 27K), five LED heads 30 (LED heads 30W, 30Y, 30M, 30C, 30K), a transfer mechanism 140, a fixing mechanism 50, and a rewinder 116. Note that in this example, the recording medium PM is roll paper.

The roll paper feeder 110 is a mechanism that feeds the recording medium PM. The roll paper feeder 110 includes a feeding roller 111 that feeds out the recording medium PM, a cutter 112 that cuts the recording medium PM, and a conveyance roller 113 that conveys the recording medium PM. The image forming unit 20W, like the other image forming units 20, includes a photosensitive drum 21, a static eliminator 22, a charging roller 23, a developing roller 24, a developing blade 25, and a supply roller 26. . The photosensitive drum 21 of the image forming unit 20W is exposed to light by the LED head 30W. The toner cartridge 27W stores white toner. The transfer mechanism 140 is configured to transfer the toner images formed by the five image forming units 20 onto the transfer surface of the recording medium PM. The transfer mechanism 140 includes an intermediate transfer belt 141, a drive roller 42, a driven roller 43, five transfer rollers 44 (transfer rollers 44W, 44Y, 44M, 44C, 44K), a secondary transfer opposing roller 145, and a secondary transfer roller 145. It has a next transfer roller 146. The intermediate transfer belt 141 is a seamlessly formed annular belt and can carry the toner image formed by the image forming unit 20. The intermediate transfer belt 141 is stretched by a drive roller 42 , a driven roller 43 , and a secondary transfer opposing roller 145 . The secondary transfer opposing roller 145 is arranged opposite to the secondary transfer roller 146 with the intermediate transfer belt 141 interposed therebetween. The transfer roller 44W is arranged to face the photosensitive drum 21 of the image forming unit 20W via the intermediate transfer belt 141. A predetermined transfer voltage is applied to the transfer roller 44W similarly to the other image forming units 20. The secondary transfer roller 146 is arranged to face the secondary transfer opposing roller 145 with the intermediate transfer belt 141 interposed therebetween. A predetermined transfer voltage is applied to the secondary transfer roller 146. The rewinder 116 accommodates the transported recording medium PM. The image forming apparatus 100 further includes a conveyance roller 114, a discharge roller 115, and a thermistor 162. The conveyance roller 114 conveys the recording medium PM conveyed by the roll paper feeder 110 toward the transfer mechanism 140. The discharge roller 115 discharges the recording medium PM conveyed by the fixing mechanism 50 toward the rewinder 116 . The thermistor 162 is arranged to face the intermediate transfer belt 141 and detects the surface temperature of the intermediate transfer belt 141.

In the image forming apparatus 100 , the recording medium PM fed by the roll paper feeder 110 is transported by the transport roller 114 and passes between the secondary transfer opposing roller 145 and the secondary transfer roller 146 in the transfer mechanism 140 . At this time, in the transfer mechanism 140, the toner images formed by the five image forming units 20 are transferred to the intermediate transfer belt 141 by the five transfer rollers 44, and the toner images transferred to the intermediate transfer belt 141 are further transferred to secondary transfer. The image is transferred onto the recording medium PM by the roller 146. As a result, a toner image is formed on the recording medium PM, and the toner image is fixed on the recording medium PM by the fixing mechanism 50. Then, the recording medium PM is discharged by the discharge roller 115 to the rewinder 116, and the rewinder 116 accommodates the recording medium PM. In the image forming apparatus 100 configured in this manner, the current detection execution determination process can be performed similarly to the image forming apparatus 1.

[Modification 2]
In the embodiment described above, when the communication unit 71 receives print data from the host device in step S102, the current detection execution determination process from step S103 onward is performed, but the present invention is not limited to this. Instead of this, for example, the current detection execution determination process from step S103 onward may be performed not only when the communication unit 71 receives print data. In this case, the transfer voltage is adjusted each time the absolute value of the difference between the measured value T of the thermistor 62 and the reference value TR is greater than the threshold value Tth. Therefore, when the communication unit 71 receives print data and performs an image forming operation, adjustment of the transfer voltage can be omitted, thereby improving convenience for the user.

[Modification 3]
In the embodiment described above, in step S109, the calculation unit 77 determines whether the absolute value of the difference between the measured value T and the reference value TR is greater than "Tth1+ΔTth1", but the invention is not limited to this. do not have. Instead of this, for example, it may be determined whether the absolute value of the difference between the measurement correction value corrected by adding "ΔTth1" to the measurement value T and the reference value TR is greater than "Tth1". In other words, the calculation unit according to the present modification performs the correction during a period in which the elapsed time t after the transfer belt 41 stops is more than "t1" minutes and the elapsed time t is less than "t2" minutes, for example. It may be determined whether or not to perform current detection by comparing the difference between the measured correction value and the reference value TR with a threshold value Tth.

[Other variations]
Furthermore, two or more of these modifications may be combined.

Although the present technology has been described above with reference to several embodiments and modifications, the present technology is not limited to these embodiments, and various modifications are possible.

For example, in the above embodiments, the image is formed on the recording medium PM using an electrophotographic method, but the present invention is not limited to this, and the image may be formed using any method. Further, in the above embodiments, the four image forming units 20 can form images in four colors, black, yellow, magenta, and cyan, but the present invention is not limited to this. Instead of this, for example, an arrangement may be made in which images can be formed by one or more image forming units.

For example, in the above embodiments, the present technology is applied to a single-function printer, but the present technology is not limited to this. The present invention may be applied to a so-called multi-function peripheral (MFP) having a multi-function peripheral (MFP).

1, 1R, 100... Image forming device, 2, 3... Guide, 4... Stacker, 10... Paper storage cassette, 11... Hopping roller, 12... Registration roller, 13... Pinch roller, 20, 20C, 20K, 20M, 20W , 20Y... Image forming unit, 21... Photosensitive drum, 22... Static elimination unit, 23... Charging roller, 24... Developing roller, 25... Developing blade, 26... Supply roller, 27, 27C, 27K, 27M, 27W, 27Y... Toner Cartridge, 30, 30C, 30K, 30M, 30W, 30Y... LED head, 40, 140... Transfer mechanism, 41... Transfer belt, 42... Drive roller, 43... Followed roller, 44, 44C, 44K, 44M, 44W, 44Y ...Transfer roller, 50...Fixing mechanism, 51...Heat roller, 52...Heater, 53, 62, 162...Thermistor, 54...Pressure roller, 60...Density sensor, 61...Cover, 63...Cleaning blade, 64...Waste toner Tank, 65, 66, 67, 68... Conveyance sensor, 70, 70R... Storage section, 71... Communication section, 72, 72R... Control section, 73... Command processing section, 74... LED head control section, 75, 75R... Mechanism Control unit, 76, 76R...Time measurement unit, 77, 77R...Calculation unit, 78...Current detection unit, 79...High voltage control unit, 80...Transfer voltage generation unit, 81...Charging voltage generation unit, 82...Development voltage generation unit , 83... Supply voltage generation section, 84... Current measurement section, 85... Drum motor, 86... Hopping motor, 87... Registration motor, 88... Belt motor, 89... Heater motor, 110... Roll paper feeder, 111... Feeding roller, 112... Cutter, 113, 114... Conveyance roller, 115... Discharge roller, 116... Rewinder, 141... Intermediate transfer belt, 145... Secondary transfer opposing roller, 146... Secondary transfer roller.

Claims (9)

an annular transfer belt that can be driven by a driving member;
a transfer body provided on the inner peripheral surface side of the transfer belt and to which a transfer voltage is applied;
detecting a first temperature that is a surface temperature of the transfer belt when the transfer belt is driven one rotation or more after the transfer belt starts driving ; a first temperature sensor that detects a second temperature that is a surface temperature of the transfer belt when the amount of drive of the transfer belt after the belt starts driving is less than one rotation;
When determining whether to perform current detection to detect the current flowing through the transfer body, a predetermined value and a difference between the second temperature and the first temperature at the time of the previous current detection are determined. A control unit that determines whether or not to perform the current detection by comparing,
The predetermined value is a first threshold value in a first period after the transfer belt has stopped driving, and is a first threshold value in a period after the transfer belt has stopped driving and before the first period and in the first period. The image forming apparatus has a second threshold value in a second period including a period after the first period. further comprising a second temperature sensor that measures the temperature of the transfer body,
If the second temperature is lower than the temperature of the transfer body measured by the second temperature sensor in the first period, the first threshold value is greater than the second threshold value;
The image forming apparatus according to claim 1, wherein when the second temperature is higher than the temperature of the transfer body in the first period, the first threshold value is smaller than the second threshold value. Image formation according to claim 1 or 2, wherein the difference between the temperature of the transfer body and the second temperature is equal to or less than a predetermined value in a period after the first period of the second period. Device. further comprising a second temperature sensor that measures the temperature of the transfer body,
The first threshold value is based on the first temperature when the current detection was performed last time, the temperature of the transfer body measured by the second temperature sensor, and the temperature when the current detection was performed last time. The image forming apparatus according to any one of claims 1 to 3, wherein the temperature difference from the first temperature is a temperature difference from the second temperature at a timing when the second temperature is the second threshold value. The image forming apparatus according to any one of claims 1 to 4, wherein the control unit determines a transfer voltage to be applied to the transfer body based on the current detected by the current detection. The image forming apparatus according to claim 5, wherein the first temperature is a temperature detected by the temperature sensor when the control unit determines the transfer voltage. It also includes a communications department that accepts print jobs.
The image forming apparatus according to any one of claims 1 to 6, wherein the control unit determines whether to perform the current detection when the communication unit receives the print job. The image forming apparatus according to any one of claims 1 to 7, wherein the transfer body is a transfer roller. an annular transfer belt that can be driven by a driving member;
a transfer body provided on the inner peripheral surface side of the transfer belt and to which a transfer voltage is applied;
detecting a first temperature that is a surface temperature of the transfer belt when the transfer belt is driven one rotation or more after the transfer belt starts driving ; a temperature sensor that detects a second temperature that is a surface temperature of the transfer belt when the amount of drive of the transfer belt after the belt starts driving is less than one rotation;
When determining whether or not to perform current detection of the transfer body, the correction temperature obtained by correcting the second temperature during the first period after the drive of the transfer belt is stopped is compared with a predetermined value. determining whether to perform current detection, and in a second period that is after the transfer belt has stopped driving and includes a period that is before the first period and a period that is after the first period; An image forming apparatus comprising: a control unit that determines whether or not to perform the current detection by comparing the second temperature and the predetermined value.

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