JP7413787B2 - Fixing device, image forming device - Google Patents

Description

The present invention relates to a fixing device that fixes a toner image to a sheet, and an image forming apparatus equipped with the fixing device.

An electrophotographic image forming apparatus includes a fixing device that heats and presses a toner image transferred to a sheet. Conventionally, a heater, a cylindrical fixing belt (heated member) heated by the heater, and a pressure roller (pressure member) forming a nip portion through which a sheet passes between the fixing belt and the fixing belt have been used. A fixing device is known (see Patent Document 1). For example, the heater is included in the fixing belt. When the pressure roller rotates, the fixing belt rotates in a driven manner, and the inner circumferential surface of the fixing belt slides in the sheet conveyance direction against the heat radiation surface of the heater.

When the fixing belt and the pressure roller are rotationally driven, the heater is heated and controlled so that the nip portion reaches a predetermined target temperature (fixing temperature). When the heating of the heater is controlled and heat is applied from the heater to the fixing belt, the heat is transmitted from the nip portion to the pressure roller via the fixing belt, and the pressure roller is also heated. .

Japanese Patent Application Publication No. 2017-116870

Generally, the pressure roller has an elastic layer made of silicone rubber or the like, and therefore has a relatively large heat capacity. Therefore, if the stopping time from when printing output ends and heating by the heater stops until heating starts again is short, the pressure roller maintains a high temperature state. In addition, if the stopping time is long, the pressure roller is in a low temperature state, which is lowered to ambient temperature. If heating is performed by a heater when the pressure roller is in the high temperature state, the time required for the temperature of the nip portion to rise to the target temperature is short, so the nip portion may exceed the target temperature. Heating continues, which not only wastes power, but also causes the sheet to curl after fixing. On the other hand, if heating is performed by a heater when the pressure roller is in the low temperature state, the time required to raise the temperature of the nip portion is long, so the fixing operation is not performed before the nip portion reaches the target temperature. , there is a risk of poor fixing.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device and an image forming apparatus that can stabilize the time required for a nip portion to become ready for fixing and prevent wasteful power consumption. be.

A fixing device according to one aspect of the present invention is configured to fix the toner image on the sheet by heating and pressurizing the toner image on the sheet at a fixing position on a sheet conveyance path. The fixing device includes a heater, a heated member, a pressure member, a temperature sensor, a heating control section, a temperature state determination section, and a heating temperature determination section. The member to be heated is a cylindrical member that is rotatably supported and includes the heater, and is a member whose inner circumferential surface is heated by the heater as it rotates. The pressure member is rotatably supported and is relatively biased toward the heated member, thereby forming a nip portion between the pressure member and the heated member through which the sheet passes. The temperature sensor measures the temperature of the heater. The heating control unit heats the heater to a predetermined set temperature based on the measured temperature acquired by the temperature sensor. The temperature state determination section includes temperature data including a plurality of temperature information regarding the heater corresponding to each of the plurality of temperature states of the pressure member, and temperature data that includes temperature information about the heater that is temporarily heated before heating by the heating control section. The temperature state of the pressurizing member is determined based on the actually measured temperature of the heater acquired by the temperature sensor. The heating temperature determining section determines the set temperature based on the temperature state determined by the temperature state determining section.

An image forming apparatus according to another aspect of the present invention includes a transfer device that transfers a toner image to a sheet, and the fixing device that fixes the toner image to the sheet.

According to the present invention, it is possible to stabilize the time required for the nip portion to become ready for fixing, and to prevent wasteful power consumption.

FIG. 1 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a configuration diagram of a fixing device in an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view showing a support mechanism for a pressure roller included in the fixing device. FIG. 4 is a block diagram showing the configuration of a control device in an image forming apparatus according to an embodiment of the present invention. FIG. 5 is a flowchart illustrating an example of the procedure of the heating temperature setting process executed by the control device. FIG. 6 is a flowchart illustrating an example of the procedure of the first temperature setting process executed by the control device. FIG. 7 is a flowchart illustrating an example of the procedure of the second temperature setting process executed by the control device. FIG. 8 is a flowchart illustrating an example of the procedure of the third temperature setting process executed by the control device. FIG. 9 is a diagram showing temperature data used in the first temperature setting process executed by the control device. FIG. 10 is a diagram showing temperature data used in the second temperature setting process executed by the control device. FIG. 11 is a diagram showing temperature data used in the third temperature setting process executed by the control device. FIG. 12 is a diagram showing temperature specification, with the horizontal axis representing time and the vertical axis representing the temperature measured by the temperature sensor.

Embodiments of the present invention will be described below with reference to the drawings. Note that the following embodiments are examples of embodying the present invention, and do not limit the technical scope of the present invention.

[Configuration of image forming apparatus 10]
The image forming apparatus 10 according to the present embodiment is an apparatus that performs print processing to form an image on a sheet 9. The image forming apparatus 10 performs the printing process using an electrophotographic method. The sheet 9 is an image forming medium such as paper or a sheet-like resin member.

As shown in FIG. 1, the image forming apparatus 10 includes a main body 1, a sheet conveying device 3, a printing device 40, a control device 8, an operating device 801, and a display device 802.

The sheet conveying device 3 includes a sheet feeding device 30 and a plurality of pairs of conveying rollers 31. The sheet delivery device 30 sends out the sheet 9 stored in the sheet storage section 2 to a conveyance path 300 within the main body section 1 .

The plurality of pairs of conveyance rollers 31 are rotationally driven by a motor, and convey the sheet 9 along the conveyance path 300 by rotating with the sheet 9 in between. Further, the plurality of conveyance roller pairs 31 discharge the sheet 9 from the exit 301 of the conveyance path 300 to the discharge tray 49 . In the following description, the direction in which the sheet 9 is transported along the transport path 300 will be referred to as a sheet transport direction D1. Further, a direction perpendicular to the sheet conveyance direction D1 and along the conveyance path 300 (a direction perpendicular to the paper surface of FIG. 1) is referred to as a width direction D2.

The printing device 40 forms a toner image on the sheet 9 that is conveyed along the conveyance path 300 by the sheet conveyance device 3 . The printing device 40 includes an image forming device 4, an optical scanning device 46, a transfer device 47, and a fixing device 48. The image forming device 4 includes a drum-shaped photoreceptor 41, a charging device 42, a developing device 43, a drum cleaning device 45, and the like.

The image forming apparatus 10 shown in FIG. 1 is a tandem color image forming apparatus. Therefore, the printing device 40 includes four image forming devices 4 corresponding to toners of four colors: yellow, cyan, magenta, and black. Further, the transfer device 47 includes an intermediate transfer belt 471, four belt transfer devices 472 corresponding to the four image forming devices 4, a sheet transfer device 473, and a belt cleaning device 474.

In the image forming device 4, the photoreceptor 41 rotates, and the charging device 42 charges the surface of the photoreceptor 41. Further, the optical scanning device 46 writes an electrostatic latent image on the surface of the photoreceptor 41 by scanning with laser light. The photoreceptor 41 is an example of an image carrier.

Furthermore, the developing device 43 supplies toner to the surface of the photoreceptor 41 to develop the electrostatic latent image as a toner image.

The transfer device 47 transfers the toner image onto the sheet 9 on the conveyance path 300 . In the transfer device 47 , a belt transfer device 472 transfers the toner image on the surface of the photoreceptor 41 to the surface of the intermediate transfer belt 471 . As a result, the color toner image is formed on the surface of the intermediate transfer belt 471.

The sheet transfer device 473 transfers the toner image formed on the intermediate transfer belt 471 onto the sheet 9 on the conveyance path 300 .

Note that when the image forming apparatus 10 is a monochrome image forming apparatus, the sheet transfer device 473 transfers the toner image on the photoreceptor 41 onto the sheet 9 in the conveyance path 300.

The drum cleaning device 45 removes toner remaining on the surface of the photoreceptor 41. Belt cleaning device 474 removes toner remaining on intermediate transfer belt 471 .

The fixing device 48 fixes the toner image onto the sheet 9 by heating and pressurizing the toner image transferred to the sheet 9 at the fixing position P<b>1 on the conveyance path 300 .

The fixing device 48 includes a heating device 5 , a sliding member 53 (an example of a heated member of the present invention), a pressure roller 6 (an example of a pressure member of the present invention), a motor 60 , and a motor drive circuit 61 . The heating device 5 includes a heater 51, a support member 52, and a heater power supply circuit 50.

The sliding member 53 is a flexible cylindrical member. Specifically, the sliding member 53 is an endless belt member. For example, the sliding member 53 is a cylindrical film member. The pressure roller 6 is a roller member in which an elastic layer (elastic member layer) made of a sponge member made of silicone rubber is formed on a base tube made of metal such as aluminum.

The heater 51 and the support member 52 are provided inside the sliding member 53. The heater 51 heats the sliding member 53, and specifically heats the inner circumferential surface 53a of the sliding member 53. The heater 51 is arranged along the width direction D2 at the fixing position P1. The heater 51 includes a plurality of heating resistors arranged along the width direction D2. For example, the heater 51 is a ceramic heater, and is formed into a planar shape or a narrow thin plate shape. Each of the heating resistors is a heating element that converts electricity into heat, and generates heat when electric power is supplied thereto. Note that the heater 51 is not limited to one composed of a heat generating resistor, and may be an IH heater using induction heating, for example.

The support member 52 is a member that supports the heater 51. The heater 51 and the support member 52 are arranged such that their longitudinal direction extends along the width direction D2.

As shown in FIG. 2, the sliding member 53 is rotatably supported while enclosing the heater 51 and the support member 52. As shown in FIG. For example, the fixing device 48 includes a pair of guide members 55 having an upright portion 55a along an arc.

The pair of guide members 55 are supported with their respective upright portions 55a facing both ends of the inner circumferential surface 53a of the sliding member 53 in the width direction D2. Thereby, the pair of guide members 55 rotatably support the sliding member 53.

As the sliding member 53 rotates around the heater 51 and the support member 52, the inner peripheral surface 53a of the sliding member 53 slides against the surface 51a (heat radiation surface) of the heater 51 along the sheet conveyance direction D1. move. The inner circumferential surface 53a of the sliding member 53 is coated with a lubricant in order to improve slidability with the surface 51a of the heater 51.

The heater 51 is a member that comes into contact with the inner peripheral surface 53a of the sliding member 53. That is, the heater 51 is a heat generating member that heats the sliding member 53 by radiating heat to the inner peripheral surface 53a of the sliding member 53, and is also a member that comes into contact with the inner peripheral surface 53a of the sliding member 53.

As shown in FIG. 3, the pressure roller 6 is rotatably supported while being biased toward the heater 51. As shown in FIG. Support shafts 6a are provided at both axial ends of the pressure roller 6, and the support shafts 6a are rotatably supported by a support mechanism 90. The support mechanism 90 includes a support frame 91 that is elongated in the axial direction of the pressure roller 6, a bearing member 93, and a biasing member 94. In addition, in FIG. 3, the support structure of the support shaft 6a on one side of the pressure roller 6 is illustrated, and the illustration of the support structure on the other side is omitted. The support frame 91 is a plate-shaped sheet metal member, and both longitudinal ends thereof are bent vertically. Support grooves 95 are formed in vertical portions at both ends of the support frame 91, into which the support shaft 6a can be inserted. The support shaft 6a is supported by a support groove 95 via a biasing member 94 such as a coil spring. In this embodiment, the pressure roller 6 is urged in the direction toward the heater 51 (see arrow D10) by the urging member 94. Note that the configuration is not limited to the configuration in which the pressure roller 6 is biased toward the heater 51; for example, the heater 51 and the support member 52 may be biased toward the pressure roller 6 by a biasing member such as a spring. good.

As shown in FIG. 2, the pressure roller 6 forms a nip portion Np1 with the sliding member 53 through which the sheet 9 passes. The position where the nip portion Np1 is formed is the fixing position P1.

The motor 60 drives the pressure roller 6 to rotate. The motor drive circuit 61 (see FIG. 1) supplies electric power to the motor 60 in accordance with a command from the control device 8 so that the motor 60 constantly rotates at a predetermined rotational speed. Thereby, the pressure roller 6 rotates at a predetermined constant speed. For example, the motor drive circuit 61 is an inverter drive circuit.

As the pressure roller 6 rotates, the sliding member 53 rotates as a result of the pressure roller 6 . That is, the pressure roller 6 rotates to cause the sliding member 53 to rotate.

The heater power supply circuit 50 supplies power to the heater 51 according to a command from the control device 8 . Further, the heater power supply circuit 50 adjusts the amount of power supplied to the heater 51 according to a command from the control device 8 .

As shown in FIG. 2, the heating device 5 includes a temperature sensor 56 that measures the temperature of the heater 51. Temperature sensor 56 is attached directly to the surface of heater 51. The temperature sensor 56 is a temperature sensor used for feedback control to maintain the temperature of the nip portion Np1 at a predetermined target temperature (fixing temperature). For example, temperature sensor 56 is a thermistor. Note that the target temperature is the temperature of the nip portion Np1 at which the toner image can be fixed on the sheet 9, and is, for example, 180°C.

The measured temperature measured by the temperature sensor 56 is a temperature that serves as a substitute index for the temperature of the fixing position P1, that is, the nip portion Np1. In other words, the temperature sensor 56 measures the temperature of the heater 51 as a temperature that is a substitute index for the temperature of the nip portion Np1.

The operating device 801 (see FIG. 1) is a device that accepts operations by an operator, and includes, for example, operating buttons and a touch panel. The display device 802 is a device that displays information, and includes, for example, a panel display device such as a liquid crystal display unit.

The control device 8 (see FIG. 1) performs various data processing and controls devices such as the sheet conveying device 3, the printing device 40, the display device 802, and the heating device 5.

As shown in FIG. 4, the control device 8 includes a CPU (Central Processing Unit) 81, and peripheral devices such as a RAM (Random Access Memory) 82, a secondary storage device 83, and a communication section 84.

The CPU 81 is a processor that performs various data processing and control by executing computer programs. RAM 82 is a computer readable volatile storage device. The RAM 82 temporarily stores the computer program executed by the CPU 81 and data output and referred to during the process of the CPU 81 executing various processes.

The CPU 81 includes a plurality of processing modules realized by executing the computer program. The plurality of processing modules include a main control section 8a, a heating control section 8b, a transport control section 8c, a print control section 8d, a temperature state determination section 8e, a heating temperature determination section 8f, and the like. In other words, the control device 8 includes a main control section 8a, a heating control section 8b, a transport control section 8c, a print control section 8d, a temperature state determination section 8e, a heating temperature determination section 8f, and the like.

The main control unit 8a executes various processes in response to operations on the operating device 801, signals input from the outside, etc., and also controls the display device 802.

The heating control unit 8b heats the heater 51 to a predetermined set temperature based on the measured temperature obtained by the temperature sensor 56. Specifically, the heating control unit 8b adjusts the amount of power supplied to the heating device 5 through feedback control based on a comparison between the measured temperature measured by the temperature sensor 56 and the preset temperature. The heating control unit 8b adjusts the amount of power supplied to the heater 51 by controlling the heater power supply circuit 50. In the present embodiment, the heating control unit 8b supplies power to the heater 51 to heat the heater 51 in the initial stage of heating so that the temperature measured by the temperature sensor 56 becomes a set temperature determined by a heating temperature determination unit 8f, which will be described later. Perform initial heat treatment. Further, after the initial stage of heating, the heating control unit 8b supplies power to the heater 51 to heat the heater 51 so that the temperature measured by the temperature sensor 56 becomes a predetermined fixed set temperature. Note that the fixed set temperature is set to 195°C when the target temperature of the nip portion Np1 is 180°C.

The conveyance control unit 8c controls the sheet conveyance device 3. The print control unit 8d causes the printing device 40 to execute the printing process in synchronization with the conveyance of the sheet 9.

The secondary storage device 83 is a computer-readable nonvolatile storage device. The secondary storage device 83 is capable of storing and updating the computer program and various data. For example, one or both of a flash memory and a hard disk drive may be employed as the secondary storage device 83.

The communication unit 84 is a signal interface, converts signals output from various sensors such as the temperature sensor 56 into digital data, and transmits the converted digital data to the CPU 81. Furthermore, the communication unit 84 converts the control command output by the CPU 81 into a control signal, and transmits the control signal to the device to be controlled.

By the way, since the pressure roller 6 has an elastic layer made of silicone rubber or the like, it has a relatively large heat capacity. Therefore, if the stopping time from when the printing output ends and the heating by the heater 51 stops until the heating starts again is short, the pressure roller 6 maintains a high temperature state. Further, if the stopping time is long, the pressure roller 6 is in a low temperature state where the temperature has dropped to the ambient temperature. If the initial heating by the heater 51 is performed when the pressure roller 6 is in the high temperature state, the temperature increase time for the temperature of the nip portion Np1 to reach the target temperature is short, so that the nip portion Np1 reaches the target temperature. Initial heating continues even when the temperature exceeds the temperature, which not only wastes power, but also causes the nip portion Np1 to become too high than the target temperature, which may cause curling of the sheet after fixing. On the other hand, if initial heating is performed by the heater 51 when the pressure roller 6 is in the low-temperature state, the temperature rising time of the nip portion Np1 is long, so the fixing operation is not performed before the nip portion Np1 reaches the target temperature. There is a risk that the image will be distorted, resulting in poor fixing.

Therefore, in this embodiment, the plurality of processing modules realized by the CPU 81 executing the computer program include a temperature state determination section 8e and a heating temperature determination section 8f. Thereby, in the fixing device 48, the CPU 81 can execute a heating temperature setting process (see FIG. 5), which will be described later. This makes it possible to stabilize the time required for the nip portion Np1 to become ready for fixing, and to prevent wasteful power consumption.

In the present embodiment, the temperature state determination unit 8e receives temperature data including a plurality of temperature information regarding the heater 51 corresponding to each of the plurality of temperature states of the pressure roller 6, and the temperature state determination unit 8e that determines the temperature of the heater 51 before initial heating by the heating control unit 8b. The temperature state of the pressure roller 6 is determined based on the actually measured temperature of the heater 51 obtained by the temperature sensor 56 after being temporarily heated.

Specifically, when the temperature data is the temperature data 101 shown in FIG. 9, the temperature state determination unit 8e determines the peak value ( The temperature state corresponding to the peak temperature) is extracted from the temperature data 101. Here, the preheating is, for example, heating the heater 51 at 850W for 0.5 seconds. Further, the temperature data 101 is acquired by the temperature sensor 56 after the heater 51 is temporarily preheated while the pressure roller 6 is in a plurality of temperature states (low temperature state, medium temperature state, high temperature state). This is the peak value of the measured temperature. In other words, the temperature data 101 indicates the relationship between a plurality of temperature states that the pressure roller 6 can take and the plurality of peak values corresponding to each temperature state. Note that the low temperature state is, for example, a state in which the temperature of the pressure roller 6 is less than 100°C. The medium temperature state is, for example, a state in which the temperature of the pressure roller 6 is 100°C or more and less than 150°C. The high temperature state is, for example, a state in which the temperature of the pressure roller 6 is 150° C. or higher.

Further, when the temperature data is the temperature data 102 shown in FIG. The temperature state corresponding to is extracted from the temperature data 102. Here, the temperature data 102 is acquired by the temperature sensor 56 after the heater 51 is temporarily preheated while the pressure roller 6 is in a plurality of temperature states (low temperature state, medium temperature state, high temperature state). is the attenuation slope of the measured temperature. In other words, the temperature data 102 indicates the relationship between a plurality of temperature states that the pressure roller 6 can take and a plurality of attenuation slopes corresponding to each temperature state.

Further, when the temperature data is the temperature data 103 shown in FIG. 11, the temperature state determination unit 8e temporarily preheats the heater 51, and then a predetermined time (0.5 seconds in this embodiment) elapses. After that, the temperature state corresponding to the actually measured temperature acquired by the temperature sensor 56 is extracted from the temperature data 103. Here, the temperature data 103 is obtained by temporarily preheating the heater 51 while the pressure roller 6 is in a plurality of temperature states (low temperature state, medium temperature state, high temperature state), and then for the predetermined period of time. This is the measured temperature acquired by the temperature sensor 56 after the elapsed time. In other words, the temperature data 103 indicates the relationship between a plurality of temperature states that the pressure roller 6 can take and the plurality of measured temperatures corresponding to each temperature state.

The above-mentioned temperature data 101, 102, and 103 are obtained in advance based on the temperature characteristics L1, L2, and L3 shown in FIG. 12. FIG. 12 is a diagram showing temperature specification, with the horizontal axis representing time and the vertical axis representing the temperature measured by the temperature sensor 56. As described above, the temperature data 101, 102, and 103 are reference data used in the determination process by the temperature state determination unit 8e, and are stored in the secondary storage device 83. Here, the temperature characteristic L1 is the temperature measured by the temperature sensor 56 when the heater 51 is temporarily preheated (heated at 850 W for 0.5 seconds) while the pressure roller 6 is in a high temperature state (150° C.). It is a characteristic of The temperature characteristic L2 is a characteristic of the temperature measured by the temperature sensor 56 when the heater 51 is temporarily preheated with the pressure roller 6 at 125°C. The temperature characteristic L3 is a characteristic of the temperature measured by the temperature sensor 56 when the heater 51 is temporarily preheated while the pressure roller 6 is kept at a low temperature (100° C.).

The heating temperature determining section 8f determines the set temperature used for the initial heating process by the heating control section 8b, based on the temperature state of the pressure roller 6 determined by the temperature state determining section 8e. Specifically, the heating temperature determination unit 8f sets the set temperature to a predetermined reference temperature (for example, 195°C) as the temperature indicated by the temperature state of the pressure roller 6 determined by the temperature state determination unit 8e is higher. The lower the temperature indicated by the temperature state is, the higher the set temperature is than the reference temperature (eg, 200°C).

[Heating temperature setting process]
Hereinafter, an example of the procedure of the heating temperature setting process executed by the CPU 81 of the control device 8 will be described with reference to the flowcharts of FIGS. 5 to 8. Note that in the following description, the temperature measured by the temperature sensor 56 will be referred to as an actual temperature. Further, the target temperature required for fixing when the sheet 9 passes through the nip portion Np1 is referred to as target fixing temperature Tx1. Further, in the following description, when the heating temperature setting process is started, the fixing device 48 is not driven and is in a non-operating state, and the heater 51 is stopped.

When the CPU 81 of the control device 8 determines that the image forming apparatus 10 has started (S11), the CPU 81 determines whether the heating stop time during which heating in the fixing device 48 was stopped is longer than a predetermined time T1 (S12). . Here, the image forming apparatus 10 is activated when the main power of the image forming apparatus 10 is turned on, when power saving mode is canceled, when an operation such as a copy start button is input on the image forming apparatus 10, or when an operation such as a copy start button is input on the image forming apparatus 10. This includes inputting a predetermined operation from the operating device 801. Note that the power saving mode is canceled when print job data is input to the communication unit 84 or when various operations are input in the power saving mode. Further, in the image forming apparatus 10, when the power saving mode is canceled, heating by the heating control section 8b is started.

The heating stop time includes a period during which the main power of the image forming apparatus 10 is turned off or a period during which the power saving mode is maintained.

The predetermined time T1 is the time required for the temperature of the pressure roller 6 to fall below the predetermined temperature Th1 after heating is stopped, and is information that is actually measured in advance. Information regarding the predetermined time T1 is stored in the secondary storage device 83. In the present embodiment, the predetermined temperature Th1 is a temperature lower than the target fixing temperature Tx1 (for example, 180° C.), but is a temperature that can be evaluated as the high temperature state (for example, 150° C.).

In step S12, if it is determined that the heating stop period is less than the predetermined time T1, the CPU 81 sets the initial heating temperature (set temperature) used for the initial heating process by the heating control section 8b to the temperature Th11 ( S13). After that, the series of processing ends.

The temperature Th11 is lower than a reference temperature Th12, which will be described later. When the target fixing temperature Tx1 is 180°C, the temperature Th11 is 190°C. When the heating stop period is less than the predetermined time T1, it can be estimated that the pressure roller 6 is in a high temperature state. In this case, the initial heating process is performed smoothly even if the initial heating temperature is not set to the reference temperature Th12 or set to the lower temperature Th11. Thereby, the temperature of the nip portion Np1 can be increased to the target fixing temperature Tx1 without consuming unnecessary power or excessively increasing the temperature of the nip portion Np1.

If it is determined in step S12 that the heating stop time is longer than the predetermined time T1, the CPU 81 rotates the pressure roller 6 by a predetermined angle (S14). The predetermined angle is larger than the angle corresponding to the nip width of the nip portion Np1 of the pressure roller 6. The predetermined angle is, for example, set within a range of 90 degrees to 180 degrees. When the heating of the heater 51 is stopped and the rotation of the pressure roller 6 is also stopped, the nip portion Np1 is a portion that is not in contact with air, and thus is less likely to radiate heat than other portions. Therefore, the pressure roller 6 is rotated by the predetermined angle in order to shift the position of the nip portion Np1 before the preheating treatment described below.

In the next step S15, the CPU 81 performs a preheating process on the heater 51. Specifically, 850 W of power is supplied to the heater 51 for only 0.5 seconds to temporarily heat the heater 51.

After starting the preheating process, the CPU 81 starts measuring the temperature of the heater 51 using the temperature sensor 56.

In the next step S16, the CPU 81 detects the peak value (maximum temperature) of the temperature actually measured by the temperature sensor 56. Thereafter, the CPU 81 determines whether development preparation is complete (S17). When it is determined that the development preparation is completed, the CPU 81 executes a first temperature setting process (S18) using the peak value. The first temperature setting process is an example of the first extraction process of the present invention. Note that the CPU 81 determines that the development preparation is completed when the development preparation in the image forming device 4 is completed. When the development preparation is completed, the heating control section 8b starts the heating process. Note that the completion of the development preparation corresponds to inputting an instruction to start the heating process to the heater 51.

As shown in FIG. 6, the first temperature setting process is executed by the CPU 81 according to steps S181 to S185. In step S181, the CPU 81 determines whether the peak value is a high temperature (90° C. or higher). In step S181, when it is determined that the peak value is a high temperature, the CPU 81 refers to the temperature data 101 (see FIG. 9) and determines that the pressure roller 6 is in a high temperature state. That is, the CPU 81 extracts the high temperature state from the temperature data 101 as the temperature state of the pressure roller 6 corresponding to the high temperature. After that, the CPU 81 sets the initial heating temperature (set temperature) to the temperature Th11 corresponding to the high temperature state (S182).

When the peak value is a high temperature (90° C. or higher), it can be estimated that the pressure roller 6 is in a high temperature state. In this case, even if the initial heating temperature is set to the temperature Th11 which is lower than the reference temperature Th12, the initial heating process is performed smoothly. Thereby, the temperature can be raised to the target fixing temperature Tx1 without consuming unnecessary power and without raising the temperature of the nip portion Np1 excessively.

If it is determined in step S181 that the peak value is not a high temperature, the CPU 81 determines whether the peak value is a low temperature (less than 60° C.) in the next step S183. In step S183, if it is determined that the peak value is low temperature, the CPU 81 refers to the temperature data 101 (see FIG. 9) and determines that the pressure roller 6 is in a low temperature state. That is, the CPU 81 extracts the low temperature state from the temperature data 101 as the temperature state of the pressure roller 6 corresponding to the low temperature. After that, the CPU 81 sets the initial heating temperature (set temperature) to the temperature Th13 corresponding to the low temperature state (S184). Here, the temperature Th13 is higher than a reference temperature Th12, which will be described later, and when the target fixing temperature Tx1 is 180°C, the temperature Th13 is 200°C.

When the peak value is a low temperature (less than 60° C.), it can be estimated that the pressure roller 6 is in a low temperature state. In this case, by setting the initial heating temperature to the temperature Th13 higher than the reference temperature Th12, it is possible to quickly raise the temperature of the nip portion Np1 in the initial heating process. This makes it possible to prevent fixing failure due to a delay in temperature rise.

In step S183, if it is determined that the peak value is not a low temperature, the CPU 81 determines that the peak value is within the reference temperature range (60° C. or higher and lower than 90° C.). In this case, in the next step S185, the CPU 81 refers to the temperature data 101 (see FIG. 9) and determines that the pressure roller 6 is in a medium temperature state (reference temperature state). That is, the CPU 81 extracts the medium temperature state from the temperature data 101 as the temperature state of the pressure roller 6 corresponding to the reference temperature. After that, the CPU 81 sets the initial heating temperature (set temperature) to the reference temperature Th12 corresponding to the medium temperature state (S185). Here, when the target fixing temperature Tx1 is 180°C, the temperature Th12 is 195°C.

As shown in FIG. 5, when it is determined in step S17 that the development preparation is not completed, in the next step S19, the CPU 81 calculates the attenuation slope of the characteristic after the peak value of the actually measured temperature of the temperature sensor 56. calculate. Thereafter, the CPU 81 determines whether development preparation is complete (S20). When it is determined that the development preparation is completed, the CPU 81 executes a second temperature setting process (S21) using the attenuation slope. The second temperature setting process is an example of the second extraction process of the present invention.

As shown in FIG. 7, the second temperature setting process is executed by the CPU 81 according to steps S211 to S215. In step S211, the CPU 81 determines whether the attenuation slope is smaller than a reference value. In step S211, when it is determined that the attenuation slope is smaller than the reference value, the CPU 81 refers to the temperature data 102 (see FIG. 10) and determines that the pressure roller 6 is in a high temperature state. That is, the CPU 81 extracts the high temperature state from the temperature data 102 as the temperature state of the pressure roller 6 corresponding to the attenuation slope. After that, the CPU 81 sets the initial heating temperature (set temperature) to the temperature Th11 corresponding to the high temperature state (S212).

If it is not determined in step S211 that the attenuation slope is smaller than the reference value, the CPU 81 determines whether the attenuation slope is larger than the reference value in the next step S213. If it is determined in step S213 that the attenuation slope is larger than the reference value, the CPU 81 refers to the temperature data 102 (see FIG. 9) and determines that the pressure roller 6 is in a low temperature state. That is, the CPU 81 extracts the low temperature state from the temperature data 102 as the temperature state of the pressure roller 6 corresponding to the attenuation slope. After that, the CPU 81 sets the initial heating temperature (set temperature) to the temperature Th13 corresponding to the low temperature state (S214).

In step S213, if it is determined that the attenuation slope is not larger than the reference value, the CPU 81 determines that the attenuation slope is within the allowable range of the reference value. In this case, in the next step S121, the CPU 81 refers to the temperature data 102 (see FIG. 10) and determines that the pressure roller 6 is in a medium temperature state (reference temperature state). That is, the CPU 81 extracts the medium temperature state from the temperature data 102 as the temperature state of the pressure roller 6 corresponding to the reference value. After that, the CPU 81 sets the initial heating temperature (set temperature) to the reference temperature Th12 corresponding to the medium temperature state (S215).

As shown in FIG. 5, when it is determined in step S20 that the development preparation is not completed, in the next step S22, the CPU 81 performs the preheating process for a predetermined period of time (for example, 2 seconds in this embodiment). After the elapsed time, the actual temperature measured by the temperature sensor 56 is measured. Thereafter, the CPU 81 executes a third temperature setting process (S23) using the measured temperature. The third temperature setting process is an example of the third extraction process of the present invention.

As shown in FIG. 8, the third temperature setting process is executed by the CPU 81 according to steps S231 to S235. In step S231, the CPU 81 determines whether the actually measured temperature is a high temperature (70° C. or higher) higher than the reference temperature. In step S231, when it is determined that the measured temperature is the high temperature, the CPU 81 refers to the temperature data 103 (see FIG. 11) and determines that the pressure roller 6 is in a high temperature state. That is, the CPU 81 extracts the high temperature state from the temperature data 103 as the temperature state of the pressure roller 6 corresponding to the measured temperature. After that, the CPU 81 sets the initial heating temperature (set temperature) to the temperature Th11 corresponding to the high temperature state (S232).

When it is determined in step S231 that the actually measured temperature is not the high temperature, the CPU 81 determines whether the actually measured temperature is a low temperature (less than 40 degrees) lower than the reference temperature in the next step S233. . In step S233, if the measured temperature is determined to be the low temperature, the CPU 81 refers to the temperature data 103 (see FIG. 11) and determines that the pressure roller 6 is in a low temperature state. That is, the CPU 81 extracts the low temperature state from the temperature data 103 as the temperature state of the pressure roller 6 corresponding to the measured temperature. After that, the CPU 81 sets the initial heating temperature (set temperature) to the temperature Th13 corresponding to the low temperature state (S234).

In step S233, if it is determined that the actually measured temperature is not the low temperature, the CPU 81 determines that the actually measured temperature is within the reference temperature range (40° C. or more and less than 70° C.). In this case, in the next step S235, the CPU 81 refers to the temperature data 103 (see FIG. 11) and determines that the pressure roller 6 is in a medium temperature state (reference temperature state). That is, the CPU 81 extracts the medium temperature state from the temperature data 103 as the temperature state of the pressure roller 6 corresponding to the reference temperature. After that, the CPU 81 sets the initial heating temperature (set temperature) to the reference temperature Th12 corresponding to the medium temperature state (S235). After that, the series of processing ends.

As described above, in the fixing device 48 of the present embodiment, temperature data including a plurality of pieces of temperature information regarding the heater 51 corresponding to each of a plurality of temperature states of the pressure roller 6, and temperature data before initial heating by the heating control unit 8b are provided. The temperature state of the pressure roller 6 is determined based on the actual measured temperature of the heater 51 obtained by the temperature sensor 56 after temporarily heating the heater 51, and the determined temperature state of the pressure roller 6. Based on this, the set temperature used for the initial heat treatment is set. Therefore, when it is determined that the pressure roller 6 is in a high temperature state, the initial heating process is smoothly performed even if the initial heating temperature is set to the temperature Th11, which is lower than the reference temperature Th12. Thereby, the temperature can be raised to the target fixing temperature Tx1 without consuming unnecessary power and without raising the temperature of the nip portion Np1 excessively. Further, when it is determined that the pressure roller 6 is in a low temperature state, the initial heating temperature is set to the temperature Th13 higher than the reference temperature Th12, so that the nip portion Np1 is quickly heated in the initial heating treatment. can do. Thereby, it is possible to prevent fixing failure due to a delay in temperature rise.

In the above-described embodiment, the first temperature setting process is performed when it is determined that the development preparation is completed immediately after the preheating process, and the predetermined time (2 seconds) after the preheating process is completed. ), the second temperature setting process is performed when it is determined that the development preparation is completed before the predetermined time has elapsed, and the third temperature setting process is performed when the predetermined time has elapsed. However, the present invention is not limited to such a processing example. The processing example may include at least one of the first temperature setting process, the second temperature setting process, or the third temperature setting process.

Further, the present invention can be regarded as an invention of the image forming apparatus 10 including the fixing device 48, or can be regarded as an invention of the fixing device 48 alone.

1 : Main body part 5 : Heating device 6 : Pressure roller 8 : Control device 8a : Main control part 8b : Heating control part 8c : Conveyance control part 8d : Print control part 8e : Temperature state determination part 8f : Heating temperature determination part 10 : Image forming device 50 : Heater power supply circuit 51 : Heater 56 : Temperature sensor 81 : CPU
82: RAM
83: Secondary storage device 84: Communication department

Claims (6)

A fixing device that fixes the toner image on the sheet by heating and pressurizing the toner image on the sheet at a fixing position on a conveyance path of the sheet,
heater and
a member to be heated, which is a cylindrical member that is rotatably supported and includes the heater, and whose inner peripheral surface is heated by the heater as it rotates;
a pressure member that is rotatably supported and relatively biased toward the heated member to form a nip portion between the heated member and the sheet through which the sheet passes;
a temperature sensor that measures the temperature of the heater;
a heating control unit that heats the heater to a predetermined set temperature based on the measured temperature obtained by the temperature sensor;
Temperature data including a plurality of temperature information regarding the heater corresponding to each of the plurality of temperature states of the pressure member, and temperature data obtained by the temperature sensor after temporarily heating the heater before heating by the heating control unit. a temperature state determination unit that determines the temperature state of the pressure member based on the measured temperature of the heater;
a heating temperature determining section that determines the set temperature based on the temperature state determined by the temperature state determining section;
The temperature data is
a peak value of the measured temperature obtained by the temperature sensor after temporarily heating the heater with the pressure member previously brought into the plurality of temperature states;
In the fixing device, the temperature state determination unit extracts from the temperature data the temperature state corresponding to the peak value of the actually measured temperature acquired by the temperature sensor after temporarily heating the heater. A fixing device that fixes the toner image on the sheet by heating and pressurizing the toner image on the sheet at a fixing position on a conveyance path of the sheet,
heater and
a member to be heated, which is a cylindrical member that is rotatably supported and includes the heater, and whose inner peripheral surface is heated by the heater as it rotates;
a pressure member that is rotatably supported and relatively biased toward the heated member to form a nip portion between the heated member and the sheet through which the sheet passes;
a temperature sensor that measures the temperature of the heater;
a heating control unit that heats the heater to a predetermined set temperature based on the measured temperature obtained by the temperature sensor;
Temperature data including a plurality of temperature information regarding the heater corresponding to each of the plurality of temperature states of the pressure member, and temperature data obtained by the temperature sensor after temporarily heating the heater before heating by the heating control unit. a temperature state determination unit that determines the temperature state of the pressure member based on the measured temperature of the heater;
a heating temperature determining section that determines the set temperature based on the temperature state determined by the temperature state determining section;
The temperature data is
The peak value of the measured temperature obtained by the temperature sensor after temporarily heating the heater in a state in which the pressure member is brought into the plurality of temperature states in advance, and the peak value of the measured temperature acquired by the temperature sensor after temporarily heating the heater. a degree of attenuation of the measured temperature obtained by the temperature sensor; and a measured temperature obtained by the temperature sensor after temporarily heating the heater and after a predetermined period of time has elapsed;
The temperature state determination section includes:
the temperature state corresponding to the peak value of the actually measured temperature acquired by the temperature sensor after the temporary heating, when an instruction to start heating processing by the heating control unit is input immediately after the temporary heating; Performing a first extraction process to extract from the temperature data,
The start instruction is not input immediately after the temporary heating, and the start is started before the predetermined time elapses after the degree of attenuation of the actually measured temperature acquired by the temperature sensor after the temporary heating is calculated. when an instruction is input, performing a second extraction process of extracting the temperature state corresponding to the attenuation degree from the temperature data;
After the predetermined time period has elapsed since the temporary heating ended, the temperature state corresponding to the measured temperature acquired by the temperature sensor after the predetermined time period has elapsed after the temporary heating is recorded as the temperature data. a fixing device that performs a third extraction process to extract from the image; The heating temperature determining section determines the set temperature to be lower than a predetermined reference temperature as the temperature indicated by the temperature state determined by the temperature state determining section is higher, and the temperature indicated by the temperature state becomes lower. The fixing device according to claim 1 , wherein the lower the set temperature, the higher the set temperature is than the reference temperature. The actual measured temperature is
Before heating by the heating control unit, the pressure member is rotated by a predetermined angle larger than an angle corresponding to the nip width of the nip portion, and then the heater is temporarily heated, and then the temperature is obtained by the temperature sensor. The fixing device according to any one of claims 1 to 3 , wherein the fixing device has a temperature of about 100%. Any one of claims 1 to 4 , wherein the heated member is a sliding member whose inner circumferential surface slides against a heat radiation surface of the heater along the sheet conveyance direction of the sheet passing through the conveyance path. The fixing device described in . a transfer device that transfers the toner image onto the sheet;
An image forming apparatus comprising: the fixing device according to claim 1 , which fixes the toner image on the sheet.

Images