JP2024047386A - Image forming device - Google Patents

Abstract

[Problem] To provide an image forming device that can properly detect the occurrence of an end temperature rise in which the non-paper passing portion of the fixing unit becomes hot, and can properly control the fixing unit, even when an openable cover is provided on the housing. [Solution] In an image forming device (1), a control unit (C) can execute a temperature reduction process to reduce the temperature of the heating roller (45HR) outside the area where the sheet (S) passes when executing a fixing process. In addition, when the control unit (C) determines that the rear cover (RC) is in the closed state and the open state, respectively, based on a sensor (K6), it executes a temperature reduction process based on the fact that the detected temperature of a second temperature sensor (ST) has reached a first threshold value and a second threshold value different from the first threshold value, respectively. [Selected Figure] Figure 1

Description

This disclosure relates to an image forming apparatus.

As an image forming apparatus such as an electrophotographic printer, there is known an apparatus equipped with a fixing device that heats a sheet on which an image is formed to fix a developer image. Such a fixing device is usually equipped with a heating section that heats the sheet and a temperature sensor that detects the temperature of the heating section, and in the fixing device, the fixing temperature by the heating section is controlled based on the detection result of the temperature sensor. In addition, as an example of a conventional image forming apparatus, the following Patent Document 1 proposes providing a second temperature sensor that detects the temperature of the non-paper passing portion of the fixing device in order to avoid problems caused by abnormally high temperatures in the non-paper passing portion of the fixing device.

JP 2001-282039 A

However, in the above-mentioned conventional technology, when an openable cover is provided on the housing of the image forming device, there is a possibility that the temperature sensor may not be able to properly detect the occurrence of end temperature rise in non-paper passing areas of the fixing unit, which may cause the temperature to rise depending on whether the cover is open or closed.

The present disclosure aims to provide an image forming device that can properly detect the occurrence of end temperature rise, in which the non-paper passing portion of the fixing unit becomes hot, and can properly control the fixing unit, even when an openable cover is provided on the housing.

In order to solve the above problem, the image forming apparatus of the present disclosure includes a housing, a process unit that forms a developer image on a sheet, a fixing unit that fixes the developer image on the sheet, a cover that is provided downstream of the fixing unit in the sheet transport direction and that can open and close a part of the housing, a cover sensor that detects the open/closed state of the cover, and a control unit. The fixing unit includes a heating unit that heats the sheet, and a temperature sensor that detects the temperature of the heating unit at one end side of the sheet width direction. The control unit is capable of performing a temperature reduction process that reduces the temperature of the heating unit outside the area through which the sheet passes when performing a fixing process to fix the developer image on the sheet. When it is determined based on the cover sensor that the cover is closed, the control unit performs the temperature reduction process based on the temperature detected by the temperature sensor reaching a first threshold value, and when it is determined based on the cover sensor that the cover is open, the control unit performs the temperature reduction process based on the temperature detected by the temperature sensor reaching a second threshold value different from the first threshold value.

According to the above configuration, the temperature sensor detects the temperature of the heating section at one end side in the width direction of the sheet. Furthermore, the temperature reduction process can reduce the temperature outside the area of the heating section through which the sheet passes. Furthermore, the temperature reduction process is executed based on the temperature detected by the temperature sensor reaching a first threshold value or a second threshold value that differs depending on whether the cover is open or closed. As a result, even if an openable cover is provided on the housing, the occurrence of an end temperature rise can be properly detected, and the fixing unit can be properly controlled.

The image forming device may further include a fan at the one end for exhausting air from inside the housing, and when the control unit determines that the cover is open based on the cover sensor, the control unit may execute the temperature reduction process based on the temperature detected by the temperature sensor reaching the second threshold value that is smaller than the first threshold value.

According to the above configuration, both the fan and the temperature sensor are provided on one end side in the width direction of the sheet. Furthermore, when the control unit determines that the cover is open, it executes a temperature reduction process based on the fact that the temperature detected by the temperature sensor has reached a second threshold value that is smaller than the first threshold value. This makes it possible to properly detect the occurrence of an end temperature rise even when an openable/closable cover is provided on the housing, and to more appropriately control the fixing unit.

The image forming device may further include a fan on the other end side in the width direction of the sheet that exhausts air from inside the housing, and when the control unit determines that the cover is open based on the cover sensor, the control unit may execute the temperature reduction process based on the temperature detected by the temperature sensor reaching the second threshold value that is smaller than the first threshold value.

According to the above configuration, the fan and the temperature sensor are provided on the other end side and one end side, respectively. Furthermore, when the control unit determines that the cover is open, it executes a temperature reduction process based on the fact that the temperature detected by the temperature sensor has reached a second threshold value that is greater than the first threshold value. This makes it possible to properly detect the occurrence of an end temperature rise even when an openable cover is provided on the housing, and to more appropriately control the fixing unit.

The image forming device may further include a fan that exhausts air from inside the housing, and when the control unit acquires speed information representing the rotation speed of the fan, the control unit may change at least one of the first threshold value or the second threshold value based on the acquired speed information.

According to the above configuration, in an image forming device having a fan, the control unit changes at least one of the first threshold value or the second threshold value based on the speed information. This allows the control unit to determine whether or not to execute a temperature reduction process depending on the rotation speed of the fan. As a result, the fixing unit can be more appropriately controlled in an image forming device having a fan.

The control unit may reduce the number of sheets processed per unit time when performing the fixing process as the temperature reduction process, compared to when the temperature reduction process is not performed.

The above configuration reduces the throughput of the image forming device, allowing for more appropriate control of the fixing device.

As part of the temperature reduction process, the control unit may increase the transport interval of the sheet transported to the fixing unit compared to when the temperature reduction process is not performed.

The above configuration allows the throughput of the image forming device to be reliably reduced, and the fixing device to be more appropriately controlled.

The control unit may interrupt the fixing process as the temperature reduction process.

The above configuration allows the throughput of the image forming device to be reliably reduced, and the fixing device to be more appropriately controlled.

When the cover is open, the image forming device may be capable of discharging a sheet to the outside of the housing through an opening formed in the housing.

With the above configuration, the sheet discharge path can be switched depending on whether the cover is open or closed.

According to one aspect of the present disclosure, an image forming device can be realized that can properly detect the occurrence of an edge temperature rise and properly control the fixing unit, even when an openable cover is provided on the housing.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present disclosure. FIG. 2 is a functional block diagram showing a configuration of a main part of the image forming apparatus. 3 is a diagram illustrating the installation positions of a fan, a first temperature sensor, and a second temperature sensor illustrated in FIG. 2. 3A to 3C are diagrams illustrating specific examples of detection results of a first temperature sensor and a second temperature sensor illustrated in FIG. 2 . 5A to 5C are diagrams illustrating the operation of the fan when the rear cover shown in FIG. 1 is in a closed state. 5A to 5C are diagrams illustrating the operation of the fan when the rear cover shown in FIG. 1 is in an open state. 5 is a flowchart showing an example of the operation of the image forming apparatus. 11A and 11B are diagrams illustrating installation positions of a fan, a first temperature sensor, and a second temperature sensor in an image forming apparatus according to a second embodiment of the present disclosure. 9A and 9B are diagrams illustrating the operation of a fan when the rear cover of the image forming apparatus illustrated in FIG. 8 is in a closed state. 9A and 9B are diagrams illustrating the operation of a fan when the rear cover of the image forming apparatus illustrated in FIG. 8 is in an open state.

[Embodiment 1]
A first embodiment of the present disclosure will be described below with reference to Figures 1 to 4. In this embodiment, a laser printer that forms an image on a sheet S using toner will be described as an example of an image forming apparatus 1.

[Configuration of image forming apparatus 1]
Fig. 1 is a diagram for explaining a schematic configuration of an image forming apparatus 1 according to a first embodiment of the present disclosure. Fig. 2 is a functional block diagram showing a configuration of a main part of the image forming apparatus 1. Fig. 3 is a diagram for explaining installation positions of a fan F, a first temperature sensor FT, and a second temperature sensor ST shown in Fig. 2. Fig. 4 is a diagram for explaining a specific example of detection results of the first temperature sensor FT and the second temperature sensor ST shown in Fig. 2.

In the following description, the up-down direction is defined with the installation surface side as the bottom, based on the state in which the image forming device 1 is installed and ready for use, as shown in FIG. 1. The front-rear direction is defined with the side on which the discharge tray TR is provided as the front. For example, as shown in FIG. 3, the right side in the width direction of the sheet SA is defined as one end of the housing 10, and the one end direction and the other end direction are defined.

In the following description, a monochrome printer that performs image formation processing for monochrome images is exemplified as the image forming device 1, but the present disclosure is not limited to this, and may be, for example, a color printer that performs image formation processing for full-color images. In addition, the present disclosure may be an MFP (Multi-Function Printer) that also has other functions such as a scanner function, a copy function, or a facsimile function, in addition to the image forming function, i.e., a print function.

As shown in Figures 1 and 2, the image forming device 1 includes a housing 10, a feed unit 3, a process unit 4, a fixing unit 45, and a discharge tray TR. The image forming device 1 also includes a control unit C, an operation panel 7, a display unit 8, a communication unit 20, a power supply circuit 21, a fan F, and a main motor M0. In this embodiment 1, the housing 10 constitutes the outer container of the image forming device 1, and houses the main components of the image forming device 1, such as the feed unit 3, the process unit 4, the fixing unit 45, and the control unit C.

The feeding unit 3 supplies the sheets S. The feeding unit 3 includes a feeding tray 31, a pickup roller 32, a pressure plate 33, a separation roller 34, a feeding roller 35, and a registration roller 36. The feeding tray 31 is a box-shaped member with an open top, and stores a predetermined amount of sheets S.

Note that the sheets S are not limited to paper media such as printing paper, but may also be resin media made of plastic, such as overhead projector sheets. As shown in Figures 3 and 4, the sheets S include sheets SA having the maximum paper width H1 that the image forming device 1 can handle, and sheets SI having the minimum paper width H2 that the image forming device 1 can handle.

The pickup roller 32 feeds out the sheet S stored in the feed tray 31. That is, when the sheet S is fed out, the sheet S stored in the feed tray 31 is brought to the pickup roller 32 by the pressure plate 33, and is fed to the separation roller 34 as the pickup roller 32 rotates. The separation roller 34 separates the sheets S picked up by the pickup roller 32 one by one. The feed roller 35 transports the sheet S toward the registration roller 36. The registration roller 36 aligns the leading edge of the sheet S, and then transports the sheet S toward the process unit 4.

The process unit 4 executes an electrophotographic process that forms a toner image as a developer image on the sheet S sent out by the feed unit 3. Specifically, the process unit 4 has an exposure unit 41, a charger 43, and a photosensitive drum 46. The process unit 4 also has a developer 44 that supplies toner onto the photosensitive drum 46, and a transfer unit 42 that has a transfer roller that transfers the toner supplied onto the photosensitive drum 46 to the sheet S.

The exposure device 41 exposes the photosensitive drum 46 by irradiating the photosensitive drum 46 with a predetermined light beam B shown by a dashed line in FIG. 1. Specifically, the exposure device 41 includes a laser light source (not shown), a polygon mirror 41G, a scanning lens 41L, a polygon motor 41M, and a reflecting mirror 41R.

The polygon mirror 41G is a rotating polygonal mirror with six reflecting surfaces on the side of a regular hexagonal prism. The polygon mirror 41G is used to deflect the light beam B emitted by the laser light source in a direction toward the photosensitive drum 46. The polygon motor 41M is a motor different from the main motor M0. The polygon motor 41M is also connected to the control unit C via a motor driver 41D, and drives the polygon mirror 41G to rotate independently of the main motor M0 based on operation instructions from the control unit C.

The exposure device 41 deflects the light beam B using a polygon mirror 41G, and emits the light beam B from the polygon mirror 41G to the surface of the photosensitive drum 46 via a scanning lens 41L and a reflecting mirror 41R. The exposure device 41 scans the surface of the photosensitive drum 46 with the light beam B to expose the photosensitive drum 46. As a result, an electrostatic latent image that constitutes a toner image is formed on the surface of the photosensitive drum 46. The polygon motor 41M is, for example, a brushless DC motor.

The transfer device 42 has a transfer roller that sandwiches the sheet S between itself and the photosensitive drum 46, and transfers the toner image from the photosensitive drum 46 to the sheet S. The charger 43 includes, for example, a scorotron type charger having a charging wire and a grid section (not shown). In this charger 43, a charging voltage is applied to the charging wire by a high voltage generating circuit (not shown), and a grid voltage is applied to the grid section, generating a corona discharge, and the surface of the photosensitive drum 46 is uniformly charged.

For example, the transfer device 42 may include a transfer belt instead of a transfer roller. Also, for example, the charger 43 may include a charging roller instead of a scorotron type charger.

The developing unit 44 includes a developing roller 44R for supplying toner as a developer onto the photosensitive drum 46, and a toner storage section 44A that stores the toner. The developing unit 44 is also configured such that the developing roller 44R and the toner storage section 44A are integrated into a developing cartridge.

The photosensitive drum 46 and the charger 43 are integrally configured as a drum cartridge 47. The drum cartridge 47 is detachable from the housing 10 through an opening 10B. Specifically, as shown by the two-dot chain line in FIG. 1, a front cover FC that can open and close the opening 10B is provided on the front side of the housing 10. When the front cover FC opens the opening 10B, the developer 44 or the drum cartridge 47 as a developing cartridge can be attached and detached. The front cover FC is provided with a sensor K5 that detects whether the front cover FC is open or closed, and is configured to output the detection result to the control unit C.

The above description concerns a case where a process cartridge is used in which the developer 44 and drum cartridge 47 as the developing cartridge are separable from each other. However, the present disclosure is not limited to this, and it is also possible to use, for example, an integrated process cartridge in which the developing cartridge and drum cartridge are inseparable.

In the process unit 4, the surface of the photosensitive drum 46 is uniformly charged by the charger 43, and then an electrostatic latent image based on the print data from the control unit C is formed on the surface of the photosensitive drum 46 by the light beam B from the exposure unit 41. In addition, the developing roller 44R supplies toner from inside the developing unit 44 to the surface of the photosensitive drum 46 on which the electrostatic latent image has been formed. This makes the electrostatic latent image visible, and a toner image is formed on the surface of the photosensitive drum 46. Thereafter, the sheet S fed from the feeding unit 3 is transported to a transfer position between the photosensitive drum 46 and the transfer unit 42, and the toner image formed on the surface of the photosensitive drum 46 is transferred onto the sheet S.

The sheet S onto which the toner image has been transferred is transported to the fixing device 45 by the photosensitive drum 46 and the transfer device 42. The fixing device 45 fixes the toner image formed on the sheet S. Specifically, the fixing device 45 thermally fixes the toner image on the sheet S transported from the photosensitive drum 46 and the transfer device 42. As a result, an image is printed and formed on the sheet S. In other words, in the image forming device 1, the electrophotographic process by the process unit 4 and the fixing process by the fixing device 45 are performed on the sheet S, thereby performing an image forming process that forms an image on the sheet S. The sheet S onto which the toner image has been thermally fixed is discharged onto the discharge tray TR by the intermediate discharge rollers 37, the upstream conveying rollers 40A, the discharge rollers 38, and the downstream conveying rollers 40B.

As shown by the solid line in FIG. 1, the discharge tray TR is a storage section for sheets S provided on the exposed portion of the top surface of the housing 10. Specifically, one end of the discharge tray TR is connected to the terminal end of the first transport path H10 at a connection point G4, which is an end exposed on the top surface side of the housing 10 and from which the user can collect the sheets S. In addition, the discharge tray TR constitutes a first discharge section for discharging the sheets S that have passed through the fixing unit 45.

The fixing device 45 includes, for example, a heating roller 45HR that contacts the sheet S on which the toner image is formed and heats the sheet S, a pressure roller 45PR that is pressed toward the heating roller 45HR by a pressing unit (not shown), and a heater 45H that heats the heating roller 45HR. The fixing device 45 also includes a first temperature sensor FT and a second temperature sensor ST. The fixing device 45 fixes the toner image to the sheet S with a predetermined pressure being applied between the heating roller 45HR and the pressure roller 45PR.

Inside the heating roller 45HR, for example, a heater 45H is disposed. This allows the heating roller 45HR to function as a heating section that heats the sheet S. The heater 45H is configured using, for example, a halogen lamp. Furthermore, the heater 45H emits light and generates heat when energized, and heats the heating roller 45HR from the inside by radiating heat.

Specifically, the control unit C controls the current supplied from the current supply circuit 21 to the heater 45H by controlling the current supply circuit 21 so that the temperature detected by the first temperature sensor FT becomes the fixing target temperature. This causes the control unit C to control the heating of the heating roller 45HR from the heater 45H. The control unit C also controls the rotational drive of the pressure roller 45PR by controlling the main motor M0. Then, in the fixing unit 45, the sheet S on which the toner image has been transferred is transported between the heating roller 45HR and the pressure roller 45PR, and the toner image is thermally fixed onto the sheet S.

Although the above description concerns a case where a fixing device 45 having a heating roller 45HR and a pressure roller 45PR is used, the fixing device 45 of the present disclosure is not limited in any way as long as it has a heating section that heats the sheet S. For example, instead of the heating roller 45HR, a heating unit equipped with a heater having a substrate and a resistance heating element provided on the substrate can be used as the fixing device. Also, for example, a pressure pad type fixing device can be used that is equipped with an endless belt that sandwiches the sheet S between the heating roller 45HR and a nip forming member having a pressure pad that presses the endless belt against the heating roller 45HR.

In addition, as shown in Figs. 3 and 4, the first temperature sensor FT and the second temperature sensor ST are disposed in the fixing device 45 at the center and one end side in the width direction of the sheet S, respectively. Specifically, as shown in Fig. 4, the first temperature sensor FT is disposed in the fixing device 45 at the center of the maximum paper width H1 of the sheet S so as to be symmetrical with respect to the center line CL in the one end and other end directions, and detects the temperature of the heating roller 45HR. Specifically, the first temperature sensor FT is disposed inside the minimum paper width H2 of the sheet S that can be printed by the image forming device 1. In addition, the second temperature sensor ST is disposed in the fixing device 45 outside the maximum paper width H1 of the sheet S that can be printed by the image forming device 1, and detects the temperature of the heating roller 45HR.

The first temperature sensor FT and the second temperature sensor ST are configured, for example, using a thermistor. The second temperature sensor ST is an example of a temperature sensor that detects the temperature of the heating section at one end side of the sheet S in the width direction.

In addition, as shown in FIG. 4, when the fixing process is performed on a sheet SI having the minimum paper width H2, the fixing unit 45 generates non-paper passing areas H3 and H4 where the sheet SI is not transported. Therefore, in the fixing unit 45, the temperature of the heating roller 45HR rises in the non-paper passing areas H3 and H4 compared to when the fixing process is performed on a sheet SA.

Specifically, when fixing is performed on sheet SA, the temperature distribution in the width direction of sheet S on heating roller 45HR becomes the waveform shown by dotted line 70 in FIG. 4. On the other hand, when fixing is performed on sheet SI, the heat of heating roller 45HR is not transferred to sheet SI in non-paper passing areas H3 and H4. As a result, the temperature of heating roller 45HR rises as shown by the arrow in FIG. 4, and the temperature distribution in the width direction of sheet S on heating roller 45HR becomes the waveform shown by solid line 80 in FIG. 4.

In FIG. 4, in the waveforms indicated by the dotted line 70 and the solid line 80, the horizontal axis X (position) indicates positions spaced apart from one end and the other end with the center line CL as the reference position. The vertical axis T (temperature) indicates specific examples of the detected temperatures at each position.

When performing the fixing process on sheet SI in this manner, the temperature rises on one end side of sheet S in the width direction, so the threshold value for determining the end temperature rise based on the temperature detected by second temperature sensor ST is set to a relatively large value compared to when performing the fixing process on sheet SA. This prevents the image forming device 1 from erroneously detecting an end temperature rise due to the temperature detected by second temperature sensor ST.

A second temperature sensor ST may be disposed in the non-paper passing portion H3 or H4 to detect the temperature of the heating portion at the end side in the width direction of the sheet S.

In addition, in the image forming device 1, as shown by the dotted line in FIG. 1, a fan F is provided between the process unit 4 and the fixing unit 45. Specifically, in the image forming device 1, the fan F is provided on one end side in the width direction of the sheet S, similar to the second temperature sensor ST, as shown in FIG. 3. The fan F is also attached to the side of the housing 10 and exhausts the air inside the housing 10.

In other words, the fan F has the function of exhausting the air between the process unit 4 and the fuser 45 in order to exhaust the heat generated by the process unit 4 itself and the heat given to the process unit 4 by the fuser 45. In addition, since the fan F is disposed in front of the fuser 45, as shown in FIG. 6 below, the air sucked in from the rear cover RC side cools a part of the fuser 45, and is then exhausted to the outside of the housing 10 by the fan F.

The image forming device 1 also has a rear opening 10C provided on the rear side of the housing 10. As illustrated by the two-dot chain line in FIG. 1, the housing 10 also has a rear cover RC on the rear side that can open and close the rear opening 10C. This rear cover RC constitutes a closing member that closes the rear opening 10C. Furthermore, the rear cover RC also constitutes a second discharge tray as a second discharge section for discharging the sheet S that has passed through the fixing device 45.

In other words, the rear cover RC can close the second discharge tray itself by closing the rear opening 10C. On the other hand, the rear cover RC can function as a second discharge tray that stores the sheet S that has been transported sequentially through the fixing unit 45 and the intermediate discharge rollers 37 by opening the rear opening 10C. In other words, when the rear cover RC is in the open state, the image forming apparatus 1 of this embodiment 1 is configured to be able to discharge the sheet S to the outside of the housing 10 through the rear opening 10C, which is an opening formed in the housing 10.

With the above configuration, the image forming device 1 can switch the discharge path of the sheet S depending on whether the rear cover RC is open or closed. Furthermore, the image forming device 1 can discharge the sheet S that has passed through the fixing device 45 to the second discharge tray without folding it. In addition, the rear cover RC is provided with a sensor K6 that detects whether the rear cover RC is open or closed, and is configured to output the detection result to the control unit C.

Furthermore, in the image forming device 1, the rear cover RC is an example of a cover that can open and close a portion of the housing 10. Also, the sensor K6 is an example of a cover sensor that detects whether the cover is open or closed.

The image forming apparatus 1 also includes a transport path, which is a space for transporting the sheet S, as shown by the dotted line in FIG. 1. Specifically, the image forming apparatus 1 includes a supply transport path H0 for transporting the sheet S from the feed unit 3 toward the process unit 4, and a first transport path H10 for transporting the sheet S that has passed through the fixing unit 45 toward the discharge tray TR.

In detail, in the supply conveying path H0, the location where the pickup roller 32 is installed is the start point of the conveying of the sheet S, and the location where the second sheet sensor K3 described below is installed is the end point of the conveying of the sheet S. In addition, in the supply conveying path H0, for example, the pickup roller 32, separation roller 34, feed roller 35, and registration roller 36 are installed as conveying rollers for conveying the sheet S. The pickup roller 32, separation roller 34, feed roller 35, and registration roller 36 are configured to rotate, for example, by the driving force from the main motor M0.

In addition, the supply conveying path H0 is provided with a branch path H00 on the front cover FC side. When the front cover FC has the opening 10B open, for example, a user can manually insert a sheet S into the branch path H00 from outside the image forming apparatus 1. This allows the user to transport a sheet S into the supply conveying path H0 via the branch path H00. In other words, the front cover FC can be used as a tray into which the user opens a portion to transport the sheet S, a so-called manual feed tray.

The supply conveying path H0 has a tray sensor K1, a first sheet sensor K2, and a second sheet sensor K3. The tray sensor K1 is provided near the feed tray 31. The tray sensor K1 detects the presence or absence of the feed tray 31. The tray sensor K1 is configured, for example, using an optical sensor. The tray sensor K1 is configured to output the presence or absence of the feed tray 31 to the control unit C.

The first sheet sensor K2 detects the sheet S. Similarly, the second sheet sensor K3 detects the sheet S. The first sheet sensor K2 and the second sheet sensor K3 can each be a sensor having an actuator that oscillates when the sheet S comes into contact with it, an optical sensor, or the like. Furthermore, the first sheet sensor K2 and the second sheet sensor K3 form a detection unit that can detect the length of the sheet S in the conveying direction.

The first sheet sensor K2 and the second sheet sensor K3 also output the detection results to the control unit C. Specifically, the first sheet sensor K2 outputs an ON signal to the control unit C from the time when the leading end of the sheet S reaches the position of the first sheet sensor K2 until the trailing end of the sheet S passes the position of the first sheet sensor K2, and outputs an OFF signal otherwise. Similarly, the second sheet sensor K3 outputs an ON signal to the control unit C from the time when the leading end of the sheet S reaches the position of the second sheet sensor K3 until the trailing end of the sheet S passes the position of the second sheet sensor K3, and outputs an OFF signal otherwise.

In the first conveying path H10, the conveying end point of the supply conveying path H0 is the conveying start point of the sheet S, and the connecting point provided downstream of the discharge rollers 38 in the conveying direction and connected to the discharge tray TR is the conveying end point of the sheet S. In other words, the first conveying path H10 is a conveying path between the installation point of the second sheet sensor K3 and the connecting point G4 connected to the discharge tray TR. In addition, the first conveying path H10 is provided with, for example, intermediate discharge rollers 37, upstream conveying rollers 40A, discharge rollers 38, and downstream conveying rollers 40B as conveying rollers for conveying the sheet S. These intermediate discharge rollers 37, upstream conveying rollers 40A, discharge rollers 38, and downstream conveying rollers 40B are configured to rotate, for example, by the driving force from the main motor M0.

The third sheet sensor K4 is provided in the first conveying path H10 between the fixing unit 45 and the intermediate discharge rollers 37. The third sheet sensor K4 is configured, for example, using an optical sensor. The third sheet sensor K4 is configured to detect the presence or absence of a sheet S between the fixing unit 45 and the intermediate discharge rollers 37. The third sheet sensor K4 is configured to output the presence or absence of a sheet S to the control unit C. In other words, the third sheet sensor K4 detects whether or not the sheet S has passed through the fixing unit 45 and notifies the control unit C.

Based on operational instructions from the control unit C, the main motor M0 drives the transport rollers provided on the supply transport path H0 and the first transport path H10 as described above. Based on operational instructions from the control unit C, the main motor M0 also drives, for example, the photosensitive drum 46, the developing roller 44R, the transfer roller of the transfer unit 42, or the pressure roller 45PR of the fixing unit 45. In other words, a transmission mechanism such as a gear that transmits the rotational force is connected to the main motor M0, and the main motor M0 functions as a power source for each part stored inside the housing 10. The main motor M0 is, for example, a brushless DC motor.

The operation panel 7 is provided with predetermined operation members such as operation buttons, and when operated by a user, it accepts instructions from the user for the image forming device 1 and notifies the control unit C.

The display unit 8 is equipped with an LED, a liquid crystal display, etc., and displays predetermined information to the user according to instructions from the control unit C. In addition to this description, for example, a touch panel may be integrally provided with the display unit 8, and the display unit 8 may function as an operation unit for the image forming device 1.

The communication unit 20 has a communication interface and performs two-way data communication with an external device (e.g., a computer terminal) of the image forming device 1 via a wired or wireless network.

The control unit C is a controller that controls each part of the image forming device 1, and has, for example, an ASIC (Application Specific Integrated Circuit) C1 and a memory unit C2. The control unit C executes various processes to cause the image forming device 1 to perform image formation processing and associated processes.

As described in detail below, the control unit C is also configured to be able to execute a temperature reduction process that reduces the temperature outside the area of the heating roller 45HR through which the sheet S passes, for example, the temperature of the non-paper passing areas H3 and H4, when executing a fixing process that fixes a toner image to the sheet S. Furthermore, the control unit C is configured to determine whether or not to execute the temperature reduction process using the detection result of the sensor K6 and the detected temperature of the second temperature sensor ST.

The memory unit C2 is a memory from which information can be read and written. The memory unit C2 is, for example, a RAM or NVM (non-volatile memory). The memory unit C2 stores predetermined information such as the number of printed sheets. The memory unit C2 also stores a first threshold value, which will be described later, and a second threshold value different from the first threshold value, which are used to determine whether or not to execute a temperature reduction process. As the first threshold value and the second threshold value, multiple types of first threshold value and second threshold value, each having different numerical values, are set in the memory unit C2 in advance according to the paper width of the sheet S and the rotation speed of the fan F. Furthermore, the first threshold value and the second threshold value may be stored in advance, for example, when the image forming device 1 is shipped from the factory, or may be updated as appropriate via the communication unit 20.

[Example of Operation of Image Forming Apparatus 1]
An example of the operation of the image forming apparatus 1 of the first embodiment will be specifically described below with reference to Figs. 5 to 7. Fig. 5 is a diagram for explaining the operation of the fan F when the rear cover RC shown in Fig. 1 is in a closed state. Fig. 6 is a diagram for explaining the operation of the fan F when the rear cover RC shown in Fig. 1 is in an open state. Fig. 7 is a flowchart showing an example of the operation of the image forming apparatus 1.

First, using Figures 5 and 6, we will specifically explain how the function of the fan F to exhaust air between the process unit 4 and the fixing unit 45 changes depending on whether the rear cover RC is open or closed.

As shown in FIG. 5, when the rear cover RC is in a closed state with the rear opening 10C closed, outside air does not flow into the inside of the housing 10 from the outside through the rear opening 10C. Therefore, when the rear cover RC is in a closed state and the fan F rotates, the fan F sucks in air near the fuser 45 from the other end side in the width direction of the sheet S and exhausts it, as shown by the arrow A1 in FIG. 5. As a result, a cooling area CS1 that is relatively cool is formed on the other end side in the width direction of the sheet S near the fuser 45, and a heating area HS1 that is relatively warm is formed on one end side in the width direction of the sheet S.

On the other hand, as shown in FIG. 6, when the rear cover RC is in an open state with the rear opening 10C open, outside air flows into the inside of the housing 10 from the outside of the housing 10 through the rear opening 10C. Therefore, when the rear cover RC is in an open state and the fan F rotates, the outside air that has passed through the rear opening 10C reaches the vicinity of the fixing device 45 at one end side of the width direction of the sheet S, as shown by the arrow A2 in FIG. 6. Furthermore, the outside air that has reached the rear opening 10C is sucked in from the vicinity of the fixing device 45 and exhausted, as shown by the arrow A3 in FIG. 6. As a result, in the vicinity of the fixing device 45, a cooling area CS2 that is relatively cooled is formed at one end side of the width direction of the sheet S, and a heating area HS2 that is relatively warm is formed at the other end side of the width direction of the sheet S.

In other words, when the rear cover RC is closed, a temperature rise area HS1 is formed in the detection area of the second temperature sensor ST by the function of the fan F, as shown in FIG. 5. In contrast, when the rear cover RC is open, a cooling area CS2 is formed in the detection area of the second temperature sensor ST by the function of the fan F, as shown in FIG. 6. For this reason, in the image forming device 1, when the rear cover RC is open, the second threshold value used to determine whether or not to perform a temperature reduction process when performing a fixing process is set to be smaller than the first threshold value used to determine whether or not to perform a temperature reduction process when performing a fixing process when the rear cover RC is closed.

With the above configuration, in the image forming device 1, when the rear cover RC is open, the second threshold value for the detected temperature of the second temperature sensor ST, which is relatively difficult to rise, is set smaller than the first threshold value. Therefore, even if an openable rear cover RC is provided on the housing 10, it is possible to properly detect the occurrence of an end temperature rise in the non-paper passing sections H3 and H4 of the fixing unit 45, and the fixing unit 45 can be controlled more appropriately.

In addition, in the image forming device 1, when the rear cover RC is closed, the first threshold value for the detected temperature of the second temperature sensor ST, which is relatively easy to rise, is set to be larger than the second threshold value. Therefore, even if an openable rear cover RC is provided on the housing 10, it is possible to prevent the detected temperature of the second temperature sensor ST from being erroneously detected as an end temperature rise.

Next, a basic operation example of the image forming device 1 of the present embodiment 1 will be specifically described with reference to FIG. 7. In the following description, the process of determining whether or not to execute the temperature reduction process and the temperature reduction process will be mainly described as a basic operation example.

As shown in S1 of FIG. 7, the control unit C determines whether or not a print job has been received for the image forming device 1. If the control unit C determines that a print job has not been received (NO in S1), the control unit C sets the image forming device 1 to a standby state.

On the other hand, when the control unit C determines that a print job has been received (YES in S1), the control unit C acquires the detected temperature of the second temperature sensor ST (S2) and stores the acquired detected temperature in the memory unit C2. Next, the control unit C acquires speed information indicating the rotation speed of the fan from the operation command to the fan F, and stores the acquired speed information in the memory unit C2.

Then, the control unit C determines whether the rear cover RC is open or not based on the detection result of the sensor K6 (S4). When the control unit C determines that the rear cover RC is closed based on the sensor K6 (NO in S4), the control unit C determines whether the detected temperature of the second temperature sensor ST stored in the memory unit C2 is equal to or higher than the first threshold value (S5).

The first threshold value used in the process of S5 is selected by the control unit C based on the information on the closed state of the rear cover RC, the paper width of the sheet S obtained from the received print job, and the acquired speed information. In other words, the control unit C refers to the memory unit C2 and selects a first threshold value corresponding to the information on the closed state, the paper width, and the speed information from among multiple types of first threshold values, and uses the selected first threshold value in the process of S5.

If the control unit C determines that the temperature detected by the second temperature sensor ST is equal to or higher than the first threshold (YES in S5), the control unit C proceeds to processing of S7. On the other hand, if the control unit C determines that the temperature detected by the second temperature sensor ST is lower than the first threshold (NO in S5), the control unit C proceeds to processing of S7.

On the other hand, when the control unit C determines that the rear cover RC is open based on the sensor K6 (YES in S4), the control unit C determines whether the detected temperature of the second temperature sensor ST stored in the memory unit C2 is equal to or higher than the second threshold value (S6).

The second threshold value used in the process of S6 is selected by the control unit C based on the information on the open state of the rear cover RC, the paper width of the sheet S obtained from the received print job, and the acquired speed information. In other words, the control unit C refers to the memory unit C2 and selects a second threshold value corresponding to the information on the open state, the paper width, and the speed information from among multiple types of second threshold values, and uses the selected second threshold value in the process of S6.

If the control unit C determines that the detected temperature of the second temperature sensor ST is equal to or higher than the second threshold (YES in S5), the control unit C executes a temperature reduction process (S7). Specifically, as the temperature reduction process, the control unit C reduces the number of sheets S processed per unit time when performing the fixing process compared to when the temperature reduction process is not executed. This allows the image forming device 1 to reduce the throughput of the fixing device 45 and, ultimately, the entire image forming device 1. As a result, the image forming device 1 can use the temperature reduction process to reduce the temperature outside the area of the heating roller 45HR through which the sheet S passes when performing the fixing process, allowing the fixing device 45 to be more appropriately controlled.

In addition, as a temperature reduction process, the control unit C may increase the transport interval of the sheet S transported to the fixing unit 45 compared to when the temperature reduction process is not performed. Note that the transport interval of the sheet S here refers to the distance between the rear end of the sheet S transported first and the front end of the sheet S transported subsequently, obtained from the detection results of the first sheet sensor K2 and the second sheet sensor K3.

In addition, because the conveying interval of the sheet S is increased during the temperature reduction process, the time during which the fixing device 45 operates without the sheet S passing through can be increased. This allows the amount of heat generated by the heater 45H per unit time to be smaller than when the conveying interval of the sheet S is small. As a result, in the image forming device 1, the temperature reduction process can reduce the temperature outside the area of the heating roller 45HR through which the sheet S passes when performing the fixing process, and can reduce the temperature difference between the temperature in the paper passing section through which the sheet S passes and the temperatures in the non-paper passing sections H3 and H4. Therefore, in the image forming device 1, the throughput of the fixing device 45, and therefore the entire image forming device 1, can be reduced, and the fixing device 45 can be controlled more appropriately.

In addition, the control unit C may interrupt the fixing process in the fixing unit 45 as the temperature reduction process. Specifically, the control unit C interrupts the fixing process until the temperature detected by the second temperature sensor ST falls below a predetermined threshold value previously set in the memory unit C2, for example. Furthermore, during the interruption period during which the fixing process is interrupted, the control unit C reduces the output of the heater 45H and continues the operation of the fixing unit 45 with the control target temperature of the paper passing unit reduced. In other words, the control unit C does not convey the sheet S to the fixing unit 45 during the interruption period. This allows the image forming device 1 to reduce the throughput of the fixing unit 45, and therefore the entire image forming device 1, and to more appropriately control the fixing unit 45.

Next, the control unit C executes an image forming process on the sheet S using the process unit 4 and the fixing unit 45 (S8). Specifically, the control unit C sequentially executes an electrophotographic process on the sheet S using the process unit 4 and a fixing process on the sheet S using the fixing unit 45, forming an image on the sheet S according to the received print job.

Next, the control unit C determines whether the received print job has been completed (S9). If the control unit C determines that the received print job has not been completed (NO in S9), it determines that image formation processing needs to be performed on the next sheet S, and proceeds to processing in S2.

On the other hand, when the control unit C determines that the received print job has been completed (YES in S9), it determines that there is no need to perform image formation processing on the next sheet S, and ends the process.

As described above, in the image forming apparatus 1 of the present embodiment 1, the second temperature sensor ST detects the temperature of the heating roller 45HR at one end side in the width direction of the sheet S. In addition, the temperature reduction process can reduce the temperature of the heating roller 45HR outside the area where the sheet S passes. Furthermore, the temperature reduction process is executed based on the fact that the detected temperature of the second temperature sensor ST has reached a first threshold value or a second threshold value that differs depending on whether the rear cover RC is open or closed. As a result, in the image forming apparatus 1 of the present embodiment 1, even if an openable cover is provided on the housing 10, it is possible to properly detect the occurrence of an end temperature rise in the non-paper passing portion H3 or H4 of the fixing unit 45, and to properly control the fixing unit 45.

In addition, in the image forming device 1 of this embodiment 1, as shown in Figures 5 and 6, the temperature reduction process can be performed under appropriate conditions by changing the first threshold value or the second threshold value that determines whether or not to perform the temperature reduction process depending on the change in the air flow near the fixing unit 45 due to the open/closed state of the rear cover RC.

In addition, in the image forming device 1 of the present embodiment 1, the control unit C executes the temperature reduction process under appropriate conditions. As a result, in the image forming device 1 of the present embodiment 1, the number of times the image forming process including the fixing process is performed, that is, the workload of the image forming device 1, can be optimized while suppressing the occurrence of an increase in temperature at the end of the fixing device 45.

In addition, in the image forming apparatus 1 of the present embodiment 1, it is possible to suppress the occurrence of temperature rise at the end of the fixing unit 45. As a result, in the image forming apparatus 1 of the present embodiment 1, it is possible to suppress the occurrence of malfunctions in the fixing unit 45, such as welding of the heating roller 45HR and the pressure roller 45PR in a high-temperature environment, malfunction of the bearing (not shown) that supports the heating roller 45HR, and activation of the thermostat (not shown) as a current-cutting member that is a safety device provided in the fixing unit 45.

In other words, in a typical image forming device, the above-mentioned malfunction may occur if the end temperature rise continues in the fixing unit. In contrast, the image forming device 1 of the present embodiment 1 can appropriately detect the end temperature rise and execute a temperature reduction process, thereby preventing the end temperature rise from continuing and suppressing the occurrence of the malfunction.

In addition, in the image forming device 1 of the present embodiment 1, when the control unit C acquires speed information indicating the rotation speed of the fan F, the control unit C changes the first threshold value and the second threshold value based on the acquired speed information. As a result, in the image forming device 1 of the present embodiment 1, the control unit C can determine whether or not to execute the temperature reduction process depending on the rotation speed of the fan F. As a result, in the image forming device 1 of the present embodiment 1, the fixing unit 45 can be more appropriately controlled.

In addition, when the control unit C acquires speed information representing the rotation speed of the fan F, at least one of the first threshold value and the second threshold value may be changed based on the acquired speed information.

[Embodiment 2]
A second embodiment of the present disclosure will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the first embodiment, and the description thereof will not be repeated.

Figure 8 is a diagram illustrating the installation positions of the fan F, the first temperature sensor FT, and the second temperature sensor ST of the image forming device 1 according to the second embodiment of the present disclosure.

In FIG. 8, the main difference between this embodiment 2 and embodiment 1 is that a fan F is provided on the other end side of the sheet S in the width direction.

As shown in FIG. 8, in the image forming device 1 of the second embodiment, the fan F is provided on the other end side in the width direction of the sheet SA, unlike in the first embodiment. In other words, in the image forming device 1 of the second embodiment, the second temperature sensor ST and the fan F are provided on one end side and the other end side, respectively, in the direction of one end and the other end of the housing 10.

[Example of Operation of Image Forming Apparatus 1]
An example of the operation of the image forming apparatus 1 of the second embodiment will be specifically described below with reference to Fig. 9 and Fig. 10. Fig. 9 is a diagram for explaining the operation of the fan F when the rear cover RC of the image forming apparatus 1 shown in Fig. 8 is in a closed state. Fig. 10 is a diagram for explaining the operation of the fan F when the rear cover RC of the image forming apparatus 1 shown in Fig. 8 is in an open state.

As shown in FIG. 9, when the rear cover RC is closed, outside air does not flow into the inside of the housing 10 from the outside through the rear opening 10C. Therefore, when the rear cover RC is closed and the fan F rotates, the fan F sucks in air near the fuser 45 from one end side of the width direction of the sheet S and exhausts it, as shown by arrow A4 in FIG. 9. As a result, near the fuser 45, a cooling area CS3 that is relatively cool is formed on one end side of the width direction of the sheet S, and a heating area HS3 that is relatively warm is formed on the other end side of the width direction of the sheet S.

On the other hand, as shown in FIG. 10, when the rear cover RC is open, outside air flows into the housing 10 from outside the housing 10 through the rear opening 10C. Therefore, when the rear cover RC is open and the fan F rotates, the outside air that passes through the rear opening 10C reaches the vicinity of the fuser 45 at the other end of the width of the sheet S, as shown by arrow A5 in FIG. 10. Furthermore, the outside air that has reached the rear opening 10C is sucked in from the vicinity of the fuser 45 and exhausted, as shown by arrow A6 in FIG. 10. As a result, a cooling area CS4 that is relatively cooled is formed near the other end of the width of the sheet S, and a heating area HS4 that is relatively warm is formed near the fuser 45 at one end of the width of the sheet S.

In other words, when the rear cover RC is closed, a cooling area CS3 is formed in the detection area of the second temperature sensor ST by the function of the fan F, as shown in FIG. 9. In contrast, when the rear cover RC is open, a temperature rise area HS4 is formed in the detection area of the second temperature sensor ST by the function of the fan F, as shown in FIG. 10. For this reason, in the image forming device 1, when the rear cover RC is open, the second threshold value used to determine whether or not to perform a temperature reduction process when performing a fixing process is set to be larger than the first threshold value used to determine whether or not to perform a temperature reduction process when performing a fixing process is when the rear cover RC is closed.

With the above configuration, the second embodiment achieves the same effects as the first embodiment. Furthermore, in the second embodiment, when the control unit C determines that the rear cover RC is open, it executes a temperature reduction process based on the fact that the detected temperature of the second temperature sensor ST has reached a second threshold value that is higher than the first threshold value. As a result, in the second embodiment, even if an openable cover is provided on the housing 10, it is possible to properly detect the occurrence of an end temperature rise in the non-paper passing section H3 or H4 of the fixing unit 45, and to more appropriately control the fixing unit.

In addition, in the image forming device 1 of the present embodiment 2, when the rear cover RC is in the open state, the second threshold value for the detected temperature of the second temperature sensor ST, which is relatively easy to rise, is set to be larger than the first threshold value. Therefore, even if an openable rear cover RC is provided on the housing 10, it is possible to prevent the detected temperature of the second temperature sensor ST from being erroneously detected as an end temperature rise.

Note that, as illustrated in FIG. 7, the control unit C has been described as performing the temperature reduction process regardless of the paper width of the sheet S. However, the present disclosure is not limited to this. For example, the control unit C may be configured in FIG. 7 to determine from the received print job whether the sheet S to be subjected to the image forming process is a sheet SI having the minimum paper width H2, and to perform the temperature reduction process when performing the fixing process only if it is determined that the sheet S is a sheet SI.

Also, a configuration has been described in which a second temperature sensor ST is provided on the same side or the opposite side of the width direction of the sheet S as the side on which the second temperature sensor ST is installed, and speed information of the fan F is used to determine whether or not to execute a temperature reduction process based on a first threshold value corresponding to the closed state of the rear cover RC or a second threshold value corresponding to the open state. However, the present disclosure is not limited to this. The present disclosure can also be applied, for example, to a configuration that does not include a fan F or a configuration in which the fan F is stopped.

Specifically, in the present disclosure, when the fan F is not functioning, a second threshold value smaller than the first threshold value is set. This makes it possible to reduce the risk of the temperature at the end on the side where the second temperature sensor ST is not installed becoming excessive by opening the rear cover RC, and makes it possible to properly detect an increase in end temperature in the non-paper passing section H3 or H4 of the fixing unit 45. Therefore, the fixing unit 45 can be properly controlled.

Furthermore, in this disclosure, the cover and cover sensor are not limited to the rear cover RC and the sensor K6, respectively. Specifically, in this disclosure, the cover is not limited in any way as long as it is provided near the fixing unit 45 and is a cover that can open and close a portion of the housing. Furthermore, the cover sensor may be one that detects the open/closed state of the cover provided near the fixing unit 45.

Specifically, for example, the front cover FC and the sensor K5 can be the cover and the cover sensor, respectively. In other words, if the front cover FC is provided near the fixing device 45, and when performing the fixing process, it is necessary to determine whether or not the temperature reduction process is to be performed using a first threshold value or a second threshold value different from the first threshold value depending on whether the front cover FC is open or closed, then the front cover FC is the cover within the scope of the claims.

This disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Configurations obtained by appropriately combining the technical means disclosed in each embodiment are also included in the technical scope of this disclosure.

REFERENCE SIGNS LIST 1 Image forming apparatus 4 Process unit 10 Housing 45 Fixing unit C Control unit F Fan ST Second temperature sensor (temperature sensor)
RC Rear Cover (Cover)
K6 Sensor (Cover Sensor)
S seat

Claims (8)

A housing and
a process unit for forming a developer image on a sheet;
a fixing device for fixing the developer image onto the sheet;
a cover that is provided downstream of the fixing unit in a sheet conveying direction and that is capable of opening and closing a part of the housing;
a cover sensor that detects whether the cover is open or closed;
A control unit,
The fixing device includes:
A heating unit that heats the sheet;
A temperature sensor that detects the temperature of the heating section at one end side in the width direction of the sheet,
The control unit is
A temperature lowering process can be performed to lower the temperature of the heating unit outside the area through which the sheet passes when performing a fixing process to fix a developer image on the sheet,
When it is determined that the cover is closed based on the cover sensor, the temperature reduction process is executed based on the fact that the temperature detected by the temperature sensor has reached a first threshold value;
When it is determined that the cover is open based on the cover sensor, the image forming apparatus executes the temperature lowering process based on the temperature detected by the temperature sensor reaching a second threshold different from a first threshold. A fan for exhausting air from inside the housing is provided at the one end portion.
The control unit is
2. The image forming apparatus according to claim 1, wherein when it is determined that the cover is open based on the cover sensor, the temperature lowering process is executed based on the detected temperature of the temperature sensor reaching a second threshold value which is lower than the first threshold value. A fan for exhausting air from inside the housing is further provided on the other end side in the width direction of the sheet,
The control unit is
2. The image forming apparatus according to claim 1, wherein when it is determined that the cover is open based on the cover sensor, the temperature lowering process is executed based on the detected temperature of the temperature sensor reaching a second threshold value which is lower than the first threshold value. Further comprising a fan for exhausting air from inside the housing,
2. The image forming apparatus according to claim 1, wherein the control unit, when acquiring speed information representing a rotation speed of the fan, changes at least one of the first threshold value or the second threshold value based on the acquired speed information. The control unit is
5. The image forming apparatus according to claim 1, wherein the temperature lowering process reduces the number of sheets processed per unit time when the fixing process is performed, as compared with a case where the temperature lowering process is not performed. The control unit is
The image forming apparatus according to claim 5 , wherein, as the temperature lowering process, a conveying interval of the sheet conveyed to the fixing unit is made longer than in a case where the temperature lowering process is not executed. The control unit is
The image forming apparatus according to claim 5 , wherein the temperature lowering process is performed by interrupting the fixing process. The image forming apparatus according to claim 1, wherein when the cover is in an open state, the sheet can be discharged to the outside of the housing through an opening formed in the housing.

Images