Image forming device

Abstract

To prevent unnecessary delay in the time required for image formation after solving paper jam, while preventing recurrence of paper jam.SOLUTION: When the occurrence of paper jam is determined, a controller 50 determines whether torque shortage occurs. When determining the occurrence of torque shortage, and when a temperature signal indicates a value higher than a predetermined temperature at the resumption of conveyance after the paper jam is resolved, the controller 50 sets the rotation speed of a motor so that the conveyance speed of a sheet becomes a first conveyance speed. On the other hand, when the temperature signal indicates a value equal to or less than the predetermined temperature, the controller sets the rotation speed of the motor so that the conveyance speed of the sheet becomes a second conveyance speed slower than the first conveyance speed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a technique for an image forming apparatus that is provided with a transport mechanism for transporting paper. [Background technology]

[0002] Patent Document 1 describes an image forming device that prevents reoccurrence of a jam after the jam is cleared by slowing down the paper transport speed until a predetermined number of sheets are printed. Note that a "jam" can also occur when paper gets stuck in the transport path of the image forming device, or when the transport mechanism does not transport the paper to the correct position. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-114766 A Summary of the Invention [Problem to be solved by the invention]

[0004] Some jams are more likely to reoccur than others, so if the conveying speed is uniformly slowed down after the jam is cleared, the time required to form an image after the jam is cleared may be unnecessarily delayed.

[0005] The present invention has been made in view of the above problems, and has an object to prevent the recurrence of a jam while suppressing unnecessary delays in the time required for image formation after the jam is cleared. [Means for solving the problem]

[0006] In order to solve the above problem, the present invention includes a temperature detection unit that outputs a temperature signal according to an environmental temperature, a transport mechanism that is provided in a transport path along which paper is transported and transports paper in response to the rotation of a motor, a paper detection unit that is located in the transport path and outputs a paper detection signal according to the presence or absence of paper, a transport control unit that controls the transport speed of paper by the transport mechanism by setting the rotation speed of the motor, a jam determination unit that determines whether a jam has occurred based on the paper detection signal, and a torque shortage determination unit that determines whether a torque shortage occurs when transporting paper by the transport mechanism when the jam determination unit determines that a jam has occurred. The transport control unit sets the rotation speed of the motor so that the paper transport speed becomes a first transport speed when the torque shortage determination unit determines that there is a torque shortage and the temperature signal indicates a value higher than a predetermined temperature when transport is resumed after the jam is cleared. On the other hand, when the temperature signal indicates a value lower than the predetermined temperature, the transport control unit sets the rotation speed of the motor so that the paper transport speed becomes a second transport speed slower than the first transport speed.

[0007] Some jams occur due to a lack of torque required by the transport mechanism to transport paper. The lack of torque can also occur due to changes in the environmental temperature, and when the temperature is below a certain level, it is more likely to occur due to, for example, an increase in the transport load caused by an increase in the viscosity of the lubricant or a decrease in the driving torque of the motor. Therefore, even after a jam caused by a lack of torque is cleared, the jam may reoccur due to the environmental temperature. On the other hand, if the environmental temperature is high after the jam is cleared, the possibility of the jam reoccurring is reduced. In the above configuration, when the jam determination unit determines that a jam has occurred, it is determined whether or not there is a lack of torque when the transport mechanism transports paper. If it is determined that there is a lack of torque and the temperature signal indicates a value higher than a predetermined temperature when transport is resumed after the jam is cleared, the rotation speed of the motor is set so that the transport speed of the paper is a first transport speed. Also, if the temperature signal indicates a value lower than the predetermined temperature, the rotation speed of the motor is set so that the transport speed of the paper is a second transport speed slower than the first transport speed. As a result, if a jam occurs and it is determined that the torque is insufficient, the paper conveying speed is slower only in situations where the jam is likely to reoccur after the jam is cleared than in situations where the jam is unlikely to reoccur. As a result, it is possible to prevent the jam from reoccurring while suppressing unnecessary delays in the time required to form an image after the jam is cleared.

[0008] The conveyance control unit is capable of switching between a first setting that sets the rotation speed of the motor so that the conveyance speed of the paper is a first conveyance speed, and a second setting that sets the rotation speed of the motor so that the conveyance speed of the paper is a second conveyance speed, and the torque shortage determination unit determines that a torque shortage is occurring as a condition that the paper is being conveyed at the first setting. This is because, since the required drive torque increases when the rotation speed of the motor is increased, an attempt to convey the paper at the first setting at which the rotation speed of the motor is increased is likely to result in a torque shortage. This makes it possible to prevent the conveyance speed from being unnecessarily slowed down when conveyance is resumed after a jam is cleared.

[0009] The torque shortage determination unit determines that a torque shortage has occurred as a condition that the temperature signal indicates a value equal to or lower than a predetermined temperature. Since the lower the environmental temperature, the more likely it is that a torque shortage will occur when transporting paper, the torque shortage determination unit determines that a torque shortage has occurred as a condition that the temperature signal indicates a value equal to or lower than a predetermined temperature. This makes it possible to prevent the transport speed from being unnecessarily slowed down when transport is resumed after a jam is cleared.

[0010] The torque shortage determination unit determines whether or not a torque shortage occurs based on the torque fluctuation of the motor over a predetermined period of time when the paper is transported. When a torque shortage occurs when transporting the paper, the torque fluctuation is larger than when a torque shortage does not occur, so the torque shortage determination unit determines whether or not a torque shortage occurs based on the torque fluctuation of the motor over a predetermined period of time. This makes it possible to efficiently determine whether or not a torque shortage occurs by using the existing phenomenon of the torque fluctuation of the motor.

[0011] If the torque shortage determination unit determines that there is no torque shortage, the conveyance control unit sets the motor rotation speed so that the paper conveyance speed will be the first conveyance speed when conveyance is resumed. If there is no concern about torque shortage, the possibility of a jam reoccurring after the jam is cleared is low. Therefore, if it is determined that there is no torque shortage, the conveyance control unit sets the motor rotation speed so that the paper is conveyed at the first conveyance speed. This makes it possible to prevent the conveyance speed from being unnecessarily slowed down when conveyance is resumed after the jam is cleared.

[0012] The device includes a user interface and a notification processing unit that notifies an error message through the user interface after the torque shortage determination unit determines that a torque shortage has occurred and until the jam is cleared. This allows the user to recognize the occurrence of a jam and shortens the time required to clear the jam.

[0013] The image forming apparatus may further include a non-volatile memory and a history storage unit that stores in the non-volatile memory the rotation speed of the motor corresponding to the first transport speed, the rotation speed of the motor corresponding to the second transport speed, and the result of the torque shortage determination unit as to whether or not there is a torque shortage. This allows the state of the image forming apparatus when a jam occurs to be stored as a history.

[0014] The conveyance control unit includes an input unit capable of receiving a selection instruction for the first setting or the second setting, and the conveyance control unit can switch between the first setting and the second setting according to the selection instruction received by the input unit. This makes it possible to prevent the recurrence of a jam while suppressing unnecessary delays in the time required for image formation after the jam is cleared, even in a configuration in which the first setting and the second setting can be switched according to the selection instruction received by the input unit.

[0015] The second conveying speed is half the first conveying speed, so that in situations where there is a possibility of a jam recurring, the paper conveying speed is reduced to half the speed, further preventing the jam from recurring. Effect of the Invention

[0016] According to the present invention, it is possible to prevent the recurrence of a jam and suppress an unnecessary delay in the time required to form an image after the jam is cleared. [Brief description of the drawings]

[0017] [Figure 1] FIG. [Diagram 2] FIG. [Diagram 3] 6 is a flowchart illustrating a process when printing is performed. [Figure 4] 4 is a flowchart for explaining the process of S16 in FIG. 3. [Diagram 5] FIG. 11 is a diagram illustrating the relationship between the transport speed and the temperature when transport is resumed. [Figure 6] 10 is a flowchart for explaining a process during printing according to the second embodiment. [Figure 7] FIG. 11 is a diagram illustrating the relationship between the transport speed and the temperature when transport is resumed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] (First embodiment) The following description will be given taking a printer as an example of an embodiment of an image forming apparatus. Fig. 1 is a cross-sectional view showing a schematic configuration of a printer 100. In Fig. 1, when the printer 100 is installed, the vertical directions are defined as the top and bottom, and in the horizontal direction perpendicular to the vertical directions, the front side where a user IF 55 (described later) and the like are arranged is defined as the front, and the opposite side is defined as the rear.

[0019] The printer 100 is a direct transfer tandem type color printer and mainly includes a housing 10, a feeder unit 12, a transport mechanism 20, an image forming unit 30, and a controller 50.

[0020] The housing 10 is generally box-shaped and has a top cover 11 that forms the upper portion. The top cover 11 is provided so as to be able to open and close around the upper rear end of the printer 100. By moving this top cover 11 to the open position, it becomes possible to pull out a part of the image forming unit 30 upward from inside the housing 10. The top cover 11 is formed with a paper output tray 11a into which paper M as a recording medium is discharged.

[0021] The feeder unit 12 is provided at the bottom of the housing 10. The feeder unit 12 has a paper feed tray 13, a paper feed roller 14, a separation roller 15, a pair of pinch rollers 16, a pair of registration rollers 17, and a manual tray 18. The paper feed tray 13 is a container that stores paper M, and is attached so as to be removable from the housing 10. A paper feed path R1 is formed on the front side of the paper feed tray 13, which is a path along which the paper M removed from the paper feed tray 13 is transported toward the image forming unit 30.

[0022] In the paper feed path R1, a paper feed roller 14, a separation roller 15, and a pinch roller 16 are arranged in this order. When the paper feed roller 14 rotates, the paper M in the paper feed tray 13 is pulled out toward the separation roller 15. The separation roller 15 rotates to send the paper M pulled out by the paper feed roller 14 toward the pinch roller 16. A registration roller 17 is arranged above the pinch roller 16. The registration roller 17 stops the paper M by hitting the leading edge of the paper M before it is supplied to the image forming unit 30, corrects the skew of the paper M, and adjusts the timing of image formation on the paper M. The manual tray 18 is provided on the front side of the housing 10. When the manual tray 18 is opened to the open position, the paper M can be manually fed toward the registration roller 17 in the housing 10.

[0023] An upstream path R2, which is a path through which the paper sheet M passes, is formed downstream of the paper feed path R1 within the housing 10. Specifically, the upstream path R2 is a path through which the paper sheet M passes from the registration rollers 17 to the paper discharge tray 11a.

[0024] The transport mechanism 20 includes a drive roller 21, a driven roller 22, a transport belt 23, and a pair of downstream transport rollers 24. In the upstream path R2, the drive roller 21, the driven roller 22, and the transport belt 23 of the transport mechanism 20 are located. The drive roller 21 is a roller that rotates in response to the rotation of a DC motor 61 described later. The transport belt 23 is an endless belt that is stretched between the drive roller 21 and the driven roller 22. The rotation of the drive roller 21 drives the transport belt 23 to circulate clockwise in FIG. 1. As a result, the paper M placed on the upper surface of the transport belt 23 is transported on the upstream path R2 from the upstream side (the registration roller 17 side) to the downstream side (the fixing unit 37 side described later) by the drive of the transport belt 23. A belt cleaner unit that removes adhesions such as a developer (hereinafter referred to as toner) that adheres to the transport belt 23 is disposed below the transport belt 23. The downstream transport rollers 24 will be described later.

[0025] In the upstream path R2, an image forming unit 30 is disposed at an image forming position where an image is formed on paper M. The image forming unit 30 is a unit that forms an image on paper M transported to the image forming position by the transport belt 23, and has a process section 31, an LED section 32, and a fixing section 37. The image forming unit 30 has four process sections 31 that are arranged side by side from the upstream side to the downstream side at the image forming position. Each process section 31 corresponds to a respective color of cyan (C), magenta (M), yellow (Y), and black (K).

[0026] Each process unit 31 has a developing unit 33, a photoconductor drum 34, a transfer roller 35, and a charger 36. The developing unit 33 contains toner of each color (C, M, Y, K) and supplies the toner to the outer peripheral surface of the photoconductor drum 34. In each process unit 31, the photoconductor drum 34 and the transfer roller 35 are disposed in contact with the conveyor belt 23 so as to sandwich the conveyor belt 23 from above and below. The charger 36 is disposed diagonally behind the photoconductor drum 34 at a predetermined distance so as not to come into contact with the photoconductor drum 34.

[0027] The LED section 32 is a well-known type that performs exposure using LEDs, and forms an electrostatic latent image on the outer circumferential surface of the corresponding photoconductor drum 34 based on image data and control commands input from the controller 50. The fixing section 37 is a unit that fixes the toner image formed on the paper M by the process section 31, and has a heating roller 38 and a pressure roller 39. The heating roller 38 has a heater therein that raises the temperature of the heating roller 38. The pressure roller 39 is disposed at a position where the paper M transported from the image forming position can be sandwiched between the heating roller 38 and the pressure roller 39 from above and below.

[0028] In the image forming unit 30 configured as described above, when the paper M passes through the image forming position on the upstream path R2, the photoconductor drum 34 is exposed to LED light emitted from the LED section 32, and development is performed in which a toner image is formed on the photoconductor drum 34 with toner supplied from the developing device 33. The paper M is sandwiched between the photoconductor drum 34 and the transfer roller 35 in each process section 31, so that the toner images of each color formed on the photoconductor drum 34 are transferred to the paper M. Thereafter, the paper M is sandwiched between the heating roller 38 and the pressure roller 39, so that the toner image formed on the paper M is fixed.

[0029] A downstream path R3 is formed downstream of the upstream path R2, i.e., downstream of the fixing unit 37, through which the paper M exiting the fixing unit 37 passes. The downstream path R3 includes downstream transport rollers 24, which are part of the transport mechanism 20, and discharge rollers 40. The paper M that has passed through the fixing unit 37 is sent by the downstream transport rollers 24 toward the discharge rollers 40. The discharge rollers 40 discharge the paper M onto the discharge tray 11a. In this embodiment, the upstream path R2 and the downstream path R3 are examples of transport paths.

[0030] A controller 50 that controls the operation of the printer 100 is provided on the rear side of the housing 10. As shown in Fig. 2, the controller 50 is a microcomputer that includes a CPU 51, a ROM 52, a RAM 53, and a non-volatile memory 54.

[0031] The controller 50 is connected to a user IF 55, an input IF 56, a temperature sensor 57, a sheet sensor 58, a fixing sheet sensor 59, and a motor drive circuit 60. The user IF 55 is an interface between the controller 50 and a user, and includes a display panel and operation keys. The user IF 55 may also be a touch panel that can accept touch operations by the user. The input IF 56 is an interface that communicates with a PC, which is an external device. For example, the input IF includes a network IF that connects the printer 100 to a wired or wireless network, and a USB interface that communicatively connects the printer 100 to a PC via a USB cable. Note that "IF" is an abbreviation for Interface.

[0032] The temperature sensor 57 detects the environmental temperature, which is the temperature inside the housing 10. The temperature sensor 57 is provided in the upper part of the inside of the housing 10, near the paper discharge roller 40. In this embodiment, the temperature sensor 57 is an example of a temperature detection unit.

[0033] The sheet sensor 58 is a sensor that detects the presence or absence of the paper M in the upstream path R2. The sheet sensor 58 is located downstream of the registration roller 17 and upstream of the drive roller 21 in the housing 10. That is, the sheet sensor 58 is located at an image forming position where an image is formed on the paper M in the upstream path R2. The fixing sheet sensor 59 is located downstream of the fixing unit 37, that is, in the downstream path R3. The sheet sensor 58 and the fixing sheet sensor 59 each include, for example, a rocking lever that is pressed by the passing paper M to rock, and an optical sensor that detects the rocking of the rocking lever. In this embodiment, when the paper M is passing, that is, when the rocking lever is tilted by the paper M, each sensor 58, 59 is ON. When the paper M is not passing, that is, when the rocking lever is not tilted by the paper M, each sensor 58, 59 is OFF. Note that the relationship between the attitude of the rocking lever and the ON / OFF of each sensor 58, 59 may be reversed. The number of sheet sensors 58, 59 in the printer 100 is not limited to two, and the printer 100 may have two or more sheet sensors 58 arranged on the upstream path R2. In this embodiment, the sheet sensor 58 and the fixing sheet sensor 59 are an example of a paper detection unit.

[0034] The DC motor 61 is a brushless DC motor, and is rotationally driven by a direct current. Power from the DC motor 61 is transmitted to the feed roller 14, separation roller 15, pinch roller 16, drive roller 21, downstream transport roller 24, and discharge roller 40 by a power transmission mechanism (not shown). Although only the DC motor 61 is shown in FIG. 2, the printer 100 also includes motors that provide power to the photoconductor drum 34, transfer roller 35, and further the developing roller of the developing unit 33.

[0035] The motor drive circuit 60 drives the DC motor 61 to rotate under the control of the controller 50. The motor drive circuit 60 has, for example, a switching element and is a circuit capable of controlling the power supplied to the DC motor 61. When the controller 50 drives the DC motor 61 to rotate, the controller 50 outputs a motor ON signal and a clock signal to the motor drive circuit 60. The motor ON signal is a signal that instructs the motor drive circuit 60 to drive / not drive the DC motor 61, and when the signal is "ON", the signal instructs the motor drive circuit 60 to drive the DC motor 61, and when the signal is "OFF", the signal instructs the motor drive circuit 60 to not drive the DC motor 61. The clock signal is a signal for instructing the motor drive circuit 60 to the rotation speed of the DC motor 61. When the motor ON signal input from the controller 50 is "ON", the motor drive circuit 60 controls the energization of a stator coil (not shown) of the DC motor 61 according to the duty of the input clock signal. This increases the rotation speed of the DC motor 61. Thereafter, when the rotation speed of the DC motor 61 reaches a predetermined rotation speed, the motor drive circuit 60 outputs a motor lock signal to the controller 50. The motor lock signal, when in the "ON" state, is a signal for causing the controller 50 to output a motor ON signal for maintaining the rotation speed of the DC motor 61 at a constant speed.

[0036] The controller 50 can switch between a full-speed print setting, in which the rotation speed of the DC motor 61 is controlled so as to transport the paper M at a full speed V1, and a half-speed print setting, in which the rotation speed of the DC motor 61 is controlled so as to transport the paper M at a half speed V2 slower than the full speed V1, as the transport speed of the paper M in the printing process. Specifically, when the print setting included in the print job specifies a general paper such as fine paper as the paper M, the full-speed print setting is switched to, and when the paper such as cardboard, postcard, or envelope is specified, the half-speed print setting is switched to. This is because pressure-sensitive paper has a large heat capacity and requires a large amount of heat for fixing, and the torque required to transport the paper M is larger than that of fine paper, etc., so that both requirements can be met by lowering the print speed. In the half-speed print setting, the duty of the clock signal output from the controller 50 is set to half the duty in the full-speed print setting, and the transport speed of the paper M is controlled to the half speed V2. In addition, the controller 50 also performs half-speed printing when a print mode requiring a print quality such as "photo printing" is set in the print settings. The non-volatile memory 54 stores the duty of the clock signal in the full-speed print setting and the duty of the clock signal in the half-speed print setting according to various print settings, and the controller 50 refers to each value from the non-volatile memory 54. In this embodiment, the full-speed print setting is an example of a first setting, and the half-speed print setting is an example of a second setting. Also, the full speed V1 is an example of a first conveying speed, and the half-speed V2 is an example of a second conveying speed.

[0037] In the printer 100 having the above configuration, a jam may occur due to a paper jam on the upstream path R2 in the housing 10. Some jams are likely to reoccur after the jam is cleared, while others are unlikely to reoccur. In particular, a jam is likely to reoccur when a torque shortage occurs due to the drive torque of the DC motor 61 being lower than the transport load for transporting the paper M. A torque shortage is also caused by a change in the environmental temperature, and when the temperature is below a certain temperature, for example, a transport load increases due to an increase in the viscosity of the lubricant or the drive torque of the DC motor 61 decreases. Therefore, in a jam that occurs when a torque shortage occurs, the jam may reoccur due to the environmental temperature even after the jam is cleared. On the other hand, if the environmental temperature is high after the jam is cleared, the possibility of the jam reoccurring is low. Therefore, in this embodiment, when the controller 50 resumes transport of the paper M after the jam is cleared, the transport speed of the paper M is changed to either full speed V1 or half speed V2 according to the environmental temperature, etc.

[0038] 3 is a flow chart showing the process executed by the controller 50 when the paper M is transported, and the main subject of the process is the controller 50. The process shown in FIG. 3 is executed when a print job and a print execution instruction for the print job are input to the controller 50 from a PC as an external device via the input IF 56. The print process is executed by the controller 50 as a process separate from that shown in FIG. 3. In the print process, the controller 50 sets the frequency of the clock signal according to the contents of the print settings included in the print job input via the input IF 56, and turns on the motor ON signal. This increases the rotation speed of the DC motor 61.

[0039] In step 11 (hereinafter, step will be simply referred to as S), the determination flag is set to an initial value of "0." The determination flag is information indicating whether or not there is a torque shortage in the transport mechanism 20 when a jam occurs, with "0" indicating that there is no torque shortage in the transport mechanism 20 when transporting the paper M, and "1" indicating that there is a torque shortage in the transport mechanism 20.

[0040] In S12, it is determined whether printing is complete. If printing is complete, an affirmative judgment is made in S12, and the process of FIG. 3 is terminated. If printing is not complete and an affirmative judgment is made in S12, then in S13, it is determined whether a jam has occurred. Specifically, the presence or absence of paper M passing through the upstream path R2 and the downstream path R3 is judged based on the output from the sheet sensor 58 and the fixing sheet sensor 59, and when the conveyance control of the paper M is in progress and the presence or absence of the paper M does not change for a predetermined time or more, that is, when the conveyance of the paper M has not progressed for a predetermined time or more, it is determined that a jam has occurred. If a negative judgment is made in S13, the process returns to S12. In this embodiment, the controller 50 executes the process of S13, thereby functioning as a jam judgment unit.

[0041] If an affirmative decision is made in S13, the process proceeds to S14. In S14, it is determined whether the current transport speed of the paper M is half speed V2. Specifically, it is determined whether the currently selected print setting is a full-speed print setting in which the paper M is transported at full speed V1, or a half-speed print setting.

[0042] If the transport speed of the paper M is half speed V2 and a positive judgment is made in S14, the process proceeds to S15, where a jam error is displayed on the user IF 55, and the process in FIG. 3 is terminated. Specifically, in S15, text or the like indicating that a jam has occurred is displayed on the user IF 55. Note that while the jam error is being displayed in S15, the process including the transport of the paper M is stopped. This is because a jam has occurred even though the transport speed of the paper M is half speed V2, and therefore driving must be stopped immediately.

[0043] On the other hand, if the conveying speed of the paper M is the full speed V1 and a negative judgment is made in S14, the process proceeds to S16. In S16, it is judged whether or not there is a torque shortage when conveying the paper M. That is, the controller 50 executes the process of S16 to function as a torque shortage judgment unit.

[0044] 4 is a flow chart for explaining the details of the process executed in S16. In S31, it is determined whether the DC motor 61 is in an unlocked state. In the unlocked state, the motor drive circuit 60 does not output a lock signal to the controller 50, and the DC motor 61 is not controlled at a constant speed. If there is no torque shortage, the torque fluctuation of the DC motor 61 is stable, and the rotation speed of the DC motor 61 eventually reaches a desired speed in a stable manner, and the motor lock signal is output from the motor drive circuit 60. On the other hand, if there is a torque shortage during the transport of the paper M, the torque fluctuation of the DC motor 61 is large, and the rotation speed of the DC motor 61 does not stably drive at the desired speed, and the motor lock signal is not output from the motor drive circuit 60.

[0045] If the DC motor 61 is in a locked state and is being controlled at a constant speed, a negative determination is made in S31 and the program proceeds to S35. In S35, the determination flag is set to "0", which indicates that no torque shortage occurs. After the process of S35 ends, the process proceeds to S36.

[0046] If an affirmative decision is made in S31, the process proceeds to S32, where a temperature signal detected in response to the environmental temperature is acquired. Specifically, the temperature signal currently output by the temperature sensor 57 detecting the environmental temperature is acquired.

[0047] In S33, it is determined whether the temperature signal acquired in S32 indicates a value equal to or lower than the first temperature TH1. The first temperature TH1 is the upper limit of the temperature that is likely to cause a torque shortage when the paper M is conveyed, and is, for example, 8°C. This is because, if a jam occurs when the environmental temperature is lower than the first temperature TH1, it is highly likely that a torque shortage has occurred due to factors such as an increase in the conveying load due to an increase in the viscosity of the lubricant or a decrease in the driving torque of the DC motor 61. If an affirmative determination is made in S33, the process proceeds to S34, where the determination flag is set to "1" indicating that a torque shortage has occurred. When the process of S34 is completed, the process proceeds to S36.

[0048] On the other hand, if the temperature signal indicates a value higher than the first temperature TH1, a negative judgment is made in S33, and the process proceeds to S35. In S35, the judgment flag is set to "0" indicating that there is no torque shortage. This is because if the environmental temperature is higher than the first temperature TH1, there is a high possibility that a jam has occurred due to a factor other than torque shortage.

[0049] In S36, the values ​​of the determination flags set in S34 and S35 are stored as history information in the non-volatile memory 54. At this time, the value of the lock signal corresponding to the current conveying speed is stored in the non-volatile memory 54 together with the value of the determination flag. When the process of S36 ends, the process proceeds to S17 in Fig. 3. In this embodiment, the controller 50 executes the process of S36, thereby functioning as a history storage unit.

[0050] In S17 of FIG. 3, a jam error is displayed on the user IF 55. The jam error displayed on the user IF 55 in S17 is the same as the image displayed on the user IF 55 in S15. In addition to this, in S17, text or the like indicating that a torque shortage is occurring may be displayed on the user IF 55. While the jam error is displayed in S17, processing including the transport of the paper M is stopped. In this embodiment, the controller 50 executes the processing of S17, thereby functioning as a notification processing unit.

[0051] The jam error display in S17 is removed when the user clears the jam. The jam is cleared, for example, by the user moving the top cover 11 to the open position and removing the paper M remaining in the upstream path R2 or the downstream path R3. At this time, the controller 50 may add the change of the top cover 11 from the open position to the closed position as a condition for clearing the jam. In addition, the controller 50 outputs a message to the display panel of the user IF 55 to prompt the user to input a restart instruction to resume transport of the paper M when the jam is cleared, and waits for input.

[0052] In S18, it is determined whether or not a restart instruction has been input to restart the transport of the paper M as the jam has been cleared. If a negative determination is made in S18, the process waits because the user has not yet cleared the jam. If a positive determination is made in S18, the process proceeds to S19.

[0053] In S19, it is determined whether the judgment flag is set to "1" indicating insufficient torque. If a negative judgment is made in S19, the process proceeds to S23, where the conveying speed of the paper M after conveying is resumed is set to full speed V1. This is because if there is no insufficient torque when the jam occurs, the jam is unlikely to reoccur after the jam is cleared.

[0054] If the result of S19 is affirmative, the process proceeds to S20, where a temperature signal corresponding to the environmental temperature is acquired. Specifically, the temperature signal currently detected by the temperature sensor 57 is acquired. In other words, in S20, the environmental temperature at the time when the conveyance of the paper M is resumed after the jam is cleared is detected.

[0055] In S21, it is determined whether the temperature signal acquired in S20 indicates a value equal to or lower than the first temperature TH1. The first temperature TH1 is the same value as that used in S33, for example, 8°C. FIG. 5 is a diagram for explaining the relationship between the conveying speed and temperature when conveying is resumed. The controller 50 changes the conveying speed in two stages according to the value of the temperature signal after the jam is cleared. Specifically, if the temperature signal indicates a value higher than the first temperature TH1, the controller 50 makes a negative judgment in S21, proceeds to S23, and controls the rotation speed of the DC motor 61 so that the conveying speed becomes full speed V1. This is because if the temperature is higher than the first temperature TH1, there is a low possibility that a jam will occur again after the conveying of the paper M is resumed, and by setting the conveying speed to full speed V1, a delay in the time required for printing after the conveying is resumed is suppressed.

[0056] On the other hand, if the temperature signal indicates a value equal to or lower than the first temperature TH1 and S21 is judged to be positive, the process proceeds to S21, where the rotation speed of the DC motor 61 is controlled so that the conveying speed becomes half speed V2, which is slower than full speed V1. This is because if the temperature is equal to or lower than the first temperature TH1, there is a high possibility that a jam caused by insufficient torque will reoccur after conveyance of the paper M is resumed, and therefore, by slowing down the conveying speed, the reoccurrence of the jam is suppressed.

[0057] When the process of S22 or S23 is completed, the process returns to S12. In S12, the processes of S13 to S23 are repeated until printing is completed. Thereafter, when printing is completed in S12, the process of Fig. 3 is terminated. In this embodiment, the controller 50 functions as a transport control unit by executing the processes of S18 to S23.

[0058] The above-described embodiment can provide the following advantages. If a torque shortage is determined after a jam is detected, and the temperature signal indicates a value higher than a predetermined temperature TH1 when the conveyance is resumed after the jam is cleared, the controller 50 sets the rotation speed of the DC motor 61 so that the conveyance speed of the paper M becomes full speed V1. On the other hand, if the temperature signal indicates a value equal to or lower than the first temperature TH1, the controller 50 sets the rotation speed of the DC motor 61 so that the conveyance speed of the paper M becomes half speed V2. As a result, in a situation where the likelihood of a jam recurring after the jam is cleared is high, the conveyance speed of the paper M becomes slower than in a situation where the likelihood of a jam recurring is low. As a result, it is possible to prevent the jam from recurring, while suppressing unnecessary delays in the time required for the printer 100 to form an image after the jam is cleared.

[0059] Since the driving torque of the DC motor 61 decreases as the conveying speed increases, the controller 50 determines whether the torque is insufficient on the condition that the first setting for conveying the paper M at full speed V1 is selected. This makes it possible to prevent the conveying speed from being unnecessarily lowered after a jam is cleared, thereby preventing a delay in the time required for image formation.

[0060] The controller 50 determines whether or not there is a torque shortage on the condition that the temperature signal indicates a value equal to or lower than the first temperature TH1. This makes it possible to prevent the conveying speed from being unnecessarily lowered and the time required for image formation from being delayed if the environmental temperature has risen after the jam is cleared.

[0061] The controller 50 determines whether or not there is a torque shortage when transporting the paper M, based on the torque fluctuation of the DC motor 61 over a predetermined period of time when the paper M is transported. This makes it possible to efficiently determine whether or not there is a torque shortage by using the existing phenomenon of the torque fluctuation of the DC motor 61.

[0062] If it is determined that there is no torque shortage, the controller 50 sets the rotation speed of the DC motor 61 so that the transport speed of the paper M becomes full speed V1 when transport is resumed after the jam is cleared. This makes it possible to prevent unnecessary delays in the time required for printing after the jam is cleared.

[0063] After it is determined that there is a torque shortage, the controller 50 notifies an error message via the user IF 55 until the jam is cleared. This allows the user to recognize the occurrence of a jam, and shortens the time required to clear the jam.

[0064] (Modification of the first embodiment) The determination of whether or not there is a torque shortage in S16 in Fig. 3 does not need to include a condition using a temperature signal. In this case, if an unlocked state is determined in S31 in Fig. 4, the process proceeds to S34, where the determination flag is set to "1." Therefore, the processes of S32 and S33 are omitted.

[0065] In the first embodiment, after the process of S22 is executed, the transport speed of the paper M is set to half speed V2 until it is determined in S12 that printing is completed. Alternatively, if the number of sheets to be printed specified by the print job is multiple, the transport speed of the paper M may be changed from half speed V2 to full speed V1 after the process of S22 is executed, on the condition that the number of printed sheets of paper M exceeds a predetermined number.

[0066] Second embodiment In the second embodiment, the configuration different from the first embodiment will be mainly described. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

[0067] In the first embodiment described above, when the environmental temperature after the jam is cleared is low, the transport speed of the paper M is set to half speed V2, which is one step lower. Instead of this, the transport speed of the paper M is changed to two different speeds depending on the environmental temperature after the jam is cleared.

[0068] FIG. 6 is a flowchart showing a process executed by the controller 50 when the paper M is transported in the second embodiment, and the main subject is the controller 50.

[0069] In the second embodiment, when the controller 50 determines in S13 that a jam has occurred, it makes a positive determination in S14, and then proceeds to S16 to determine whether or not there is a torque shortage. If the determination flag is set to "1" indicating a torque shortage in S19, the controller 50 proceeds to S20 to obtain a temperature signal.

[0070] In S40, it is determined whether the temperature signal indicates a value equal to or lower than the second temperature TH2. As shown in Fig. 7, the second temperature TH2 is lower than the first temperature TH1 (e.g., 8°C) and higher than the lower limit of the temperature at which the operation of the printer 100 is guaranteed. If a positive determination is made in S40, the process proceeds to S41, where the rotation speed of the DC motor 61 is set so that the transport speed of the paper M becomes low speed V3. As shown in Fig. 7, low speed V3 is lower than half speed V2 and higher than the lower limit of the possible transport speed.

[0071] On the other hand, if a negative decision is made in S40, the process proceeds to S21, where it is determined whether or not the temperature signal indicates a value equal to or lower than the first temperature TH1. If a positive decision is made in S21, the process proceeds to S22, where the rotation speed of the DC motor 61 is set so that the transport speed of the paper M is half speed V2. On the other hand, if a negative decision is made in S21, the process proceeds to S23, where the rotation speed of the DC motor 61 is set so that the transport speed of the paper M is full speed V1.

[0072] That is, in this embodiment, the conveying speed after the jam is cleared is changed to three stages depending on the environmental temperature as shown in Fig. 7. At this time, when the environmental temperature is equal to or lower than a first temperature TH1, the conveying speed of the paper M is changed to two stages depending on the temperature.

[0073] The above-described embodiment can achieve the same effects as the first embodiment. In addition, when the environmental temperature is equal to or lower than the second temperature TH2 that is lower than the first temperature TH1, the conveying speed is set to the low speed V3, so that the recurrence of jams caused by insufficient torque can be further suppressed.

[0074] (Other embodiments) The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the gist of the present invention. In the above embodiment, if it is determined that there is no torque shortage after the jam is cleared, the conveying speed is set to full speed V1. Alternatively, if it is determined that there is no torque shortage after the jam is cleared, the conveying speed may be set to half speed V2. In this case, in FIG. 3, the determination flag is set to "0", and if a negative determination is made in S19, the process proceeds to S22, where the rotation speed of the DC motor 61 is controlled so that the conveying speed becomes half speed V2.

[0075] In the above-described embodiment, the transport speed of the paper M after the jam is cleared is switched between two or three stages. Alternatively, the transport speed of the paper M after the jam is cleared may be switched between three or more stages according to the value indicated by the temperature signal. In this case, when the temperature signal acquired after the jam is cleared indicates a value equal to or lower than the first temperature TH1, the rotation speed of the DC motor 61 may be controlled so that the transport speed of the paper M becomes slower as the value indicated by the temperature signal becomes lower.

[0076] In the above-described embodiment, a brushless DC motor is used as the motor. However, instead of this, a brush motor or a stepping motor equipped with an encoder may be used as the DC motor, or an AC motor may be used.

[0077] In the above embodiment, the temperature inside the housing 10 is detected as the environmental temperature by the temperature sensor 57. Alternatively, the temperature sensor 57 may detect the temperature around the printer 100 outside the housing 10 as the environmental temperature.

[0078] In the above embodiment, a printer has been described as an example of an image forming apparatus, but the image forming apparatus may be a multifunction machine having both an image reading function and a printing function. [Explanation of symbols]

[0079] 10...housing, 20...transport mechanism, 30...image forming unit, 50...controller, 57...temperature sensor, 58...sheet sensor, 61...DC motor, 100...printer, M...paper, R2...upstream path, R3...downstream path, TH1...predetermined temperature, V1...full speed, V2...half speed

Claims

1. a temperature detection unit that outputs a temperature signal according to an environmental temperature; a transport mechanism that is provided on a transport path along which the paper is transported and transports the paper in response to rotation of a motor; a paper detection unit that is located on the transport path and outputs a paper detection signal according to the presence or absence of paper; a conveyance control unit that controls a conveyance speed of the paper by the conveyance mechanism by setting a rotation speed of the motor; a jam determination unit that determines whether a jam has occurred based on the paper detection signal; a torque shortage determination unit that determines whether or not a torque shortage occurs when the conveying mechanism conveys the paper when the jam determination unit determines that the jam has occurred; Equipped with The transport control unit is When the torque shortage determination unit determines that the torque shortage occurs and the sheet jam is cleared, When the temperature signal indicates a value higher than a predetermined temperature, the rotation speed of the motor is set so that the transport speed of the paper becomes a first transport speed; when the temperature signal indicates a value equal to or lower than a predetermined temperature, the rotation speed of the motor is set so that the transport speed of the paper becomes a second transport speed slower than the first transport speed. Image forming device.

2. The transport control unit is a first setting for setting the rotation speed of the motor so that the transport speed of the paper becomes the first transport speed, and a second setting for setting the rotation speed of the motor so that the transport speed of the paper becomes the second transport speed, The image forming apparatus according to claim 1 , wherein the condition for determining whether the torque deficiency occurs includes a condition in which the sheet is transported at the first setting.

3. 3. The image forming apparatus according to claim 1, wherein the condition for the torque shortage determining unit to determine that the torque shortage occurs includes a condition in which the temperature signal indicates a value equal to or lower than a predetermined temperature.

4. 4. The image forming apparatus according to claim 1, wherein the torque deficiency determination unit determines whether or not the torque deficiency occurs based on a torque fluctuation of the motor over a predetermined period of time when a sheet is transported.

5. The transport control unit is An image forming apparatus as described in any one of claims 1 to 4, wherein if the torque deficiency determination unit determines that no torque deficiency is occurring, the rotational speed of the motor is set so that the conveying speed of the paper becomes the first conveying speed when the conveying is subsequently resumed.

6. A user interface; and a notification processing unit that notifies an error message via the user interface after the torque deficiency determination unit determines that the torque deficiency has occurred, until the jam is cleared.

7. A non-volatile memory; An image forming apparatus according to any one of claims 1 to 6, further comprising a history memory unit that stores in the non-volatile memory the rotation speed of the motor corresponding to the first conveying speed, the rotation speed of the motor corresponding to the second conveying speed, and the determination result of whether or not there is a torque deficiency by the torque deficiency determination unit.

8. an input unit capable of receiving a selection instruction for the first setting or the second setting, 3. The image forming apparatus according to claim 2, wherein the transport control unit is capable of switching between the first setting and the second setting in response to a selection instruction received by the input unit.

9. 9. The image forming apparatus according to claim 1, wherein the second transport speed is half the first transport speed.

Images