JP2024029628A - Conveyance status detection sensor for print media conveyance - Google Patents

Abstract

In an image forming apparatus, it is possible to grasp the conveyance state of a print medium between an image bearing member and a fixing device using a conveyance state sensor unit. An image forming apparatus according to one aspect includes an image carrier that transfers a toner image to a print medium, and a fixing device that fixes the toner image to the print medium, and the image carrier and the fixing device are connected to the print medium. A conveying state sensor unit is arranged along the conveying path between the image carrier and the fixing device to detect the conveying state of the print medium in the conveying path between the image carrier and the fixing device, and the conveying state sensor unit detects an abnormality in the conveying state. It includes a conveyance abnormality detection sensor and an actuator that operates according to the conveyance state of the print medium between the image carrier and the fixing device. [Selection diagram] Figure 2

Description

2. Description of the Related Art Image forming apparatuses that form images on print media are known as devices that transport print media. An image forming apparatus includes an image carrier that carries a toner image on a print medium, and a fixing device that fixes the toner image on the print medium. The image carrier and the fixing device are arranged along the print medium conveyance path. In an image forming apparatus, a print medium may adhere to an image carrier. The image forming apparatus includes an optical sensor that detects a print medium attached to an image carrier.

FIG. 1 is a schematic diagram showing an example of an image forming apparatus. FIG. 2 is a schematic diagram showing an example of the configuration of an image carrier, a fixing device, a conveyance state sensor unit, and a clogging detection sensor. FIG. 3 is a schematic diagram showing the configuration of the conveyance state sensor unit of FIG. 2. FIG. 4 is a diagram showing an example of detection signals of the conveyance state sensor unit and the clogging detection sensor of FIG. 2. FIG. 5 is a schematic diagram showing a state in which the print medium is in contact with the movable part of the conveyance state sensor unit of FIG. 3. FIG. FIG. 6 is a schematic diagram showing a state in which the print medium is in contact with the print medium return section of the conveyance state sensor unit of FIG. 3. FIG. FIG. 7 is a schematic diagram showing an example of the conveyance abnormality detection sensor and actuator of the conveyance state sensor unit of FIG. 3. FIG. 8 is a schematic diagram showing a modification of the conveyance abnormality detection sensor and actuator. FIG. 9 is a schematic diagram showing a modification of the conveyance abnormality detection sensor and actuator. FIG. 10 is a schematic diagram showing a modification of the conveyance abnormality detection sensor and actuator. FIG. 11 is a schematic diagram for explaining the movement of the print medium between the image carrier and the fixing device. FIG. 12 is a diagram showing an example of the intensity of reflected light detected by a CTD sensor, which is an example of a conveyance abnormality detection sensor. FIG. 13 is a perspective view showing a photoreceptor unit of an image forming apparatus according to a comparative example.

An example of an image forming apparatus includes an image carrier that transfers a toner image to a print medium, and a fixing device that fixes the toner image to the print medium. The image carrier and the fixing device are arranged along the print medium conveyance path. The image forming apparatus includes a conveyance state sensor unit that detects the conveyance state of a print medium on a conveyance path between an image carrier and a fixing device. The conveyance state sensor unit can detect the conveyance state of the print medium on the conveyance path between the image carrier and the fixing device by operating the actuator.

For example, the image forming apparatus includes a clogging detection sensor disposed on the downstream side of the fixing device in the conveyance path. A detection time is set for the clogging detection sensor. The jam detection sensor detects a jam of the print medium between the image carrier and the fixing device in response to the fact that the print medium is not detected during the detection time. The image forming apparatus includes a control section that delays the detection time of the clog detection sensor when the print medium is detected by the conveyance state sensor unit. If an abnormality occurs in the conveyance state of the print medium in the conveyance path between the image carrier and the fixing device, the print medium may be delayed in reaching the clog detection sensor. Therefore, if a control section is provided that delays the detection time of the jam detection sensor when the print medium is detected by the conveyance state sensor unit, the control section delays the detection time so that the print medium reaches the jam detection sensor. to compensate for the delay. Therefore, by delaying the detection time of the clogging detection sensor, it is possible to suppress false detection of clogging by the clogging detection sensor.

Various examples of image forming apparatuses will be described below with reference to the drawings. In the description of the drawings, the same or corresponding elements are given the same reference numerals, and redundant description will be omitted as appropriate. For ease of understanding, some parts of the drawings may be simplified or exaggerated, and the dimensional ratios and the like are not limited to those shown in the drawings.

FIG. 1 is a schematic diagram showing an image forming apparatus 1 as an example. The image forming apparatus 1 includes a transport device 10, an image carrier 20, a developing device 30, a transfer device 40, and a fixing device 50. The conveyance device 10 conveys the print medium 2 on which an image is formed. As an example, the print medium 2 is paper. For example, the conveyance device 10 includes registration rollers 11, and the print medium 2 is conveyed to a transfer area, which will be described later, at a predetermined timing by the registration rollers 11.

The image carrier 20 may be an electrostatic latent image carrier or a photosensitive drum. The image carrier 20 forms an electrostatic latent image for forming a toner image. For example, the image forming apparatus 1 further includes a charging device 21 and a cleaning device 23. The charging device 21 and the cleaning device 23 are arranged at positions facing the surface 20b of the image carrier 20. The charging device 21 charges the surface 20b of the image carrier 20 to a predetermined potential.

The developing device 30 receives toner from the toner cartridge and forms a toner image on the surface 20b of the image carrier 20. The developing device 30 includes a developing roller 31 that supplies toner to the surface 20b of the image carrier 20. When the developing roller 31 supplies toner to the surface 20b of the image carrier 20, the electrostatic latent image formed on the surface 20b of the image carrier 20 is developed. As a result, a toner image corresponding to the electrostatic latent image, that is, a toner image corresponding to the image to be formed on the print medium 2 is formed on the surface 20b of the image carrier 20.

The transfer device 40 transfers the toner image developed on the image carrier 20 by the developing device 30 onto the print medium 2 . As an example, the transfer device 40 includes a transfer roller 41. The transfer roller 41 has, for example, an axis extending parallel to the axis of the image carrier 20. The surface 41b of the transfer roller 41 and the surface 20b of the image carrier 20 are in contact with each other, and a transfer area is formed between the transfer roller 41 and the image carrier 20. The transfer roller 41 applies an electric field to the print medium 2 conveyed to the transfer area so that the toner image formed on the surface 20b of the image carrier 20 is transferred to the print medium 2. The toner image is transferred by the transfer roller 41 onto the print medium 2 that is conveyed to the transfer area.

The cleaning device 23 collects toner remaining on the surface 20b of the image carrier 20 without being transferred to the print medium 2 as waste toner. The cleaning device 23 has a blade 24, for example. When the blade 24 scrapes off the toner remaining on the surface 20b of the image carrier 20, the cleaning device 23 removes the toner from the image carrier 20 and collects the toner. The blade 24 is fixed to the housing 3 of the image forming apparatus 1 so as to be in contact with the surface 20b of the image carrier 20.

The fixing device 50 fixes the toner image onto the print medium 2 by passing the print medium 2 through a fixing nip region that applies heat and pressure. The fixing device 50 includes a heating roller 51 that heats the print medium 2 and a pressure roller 52 that applies pressure to the heating roller 51 and drives the heating roller 51 to rotate. A fixing nip region of the fixing device 50 is formed between a heating roller 51 and a pressure roller 52.

FIG. 2 is an enlarged schematic diagram of the periphery of the image carrier 20 and the fixing device 50 in the image forming apparatus 1. As shown in FIG. As shown in FIG. 2, the image forming apparatus 1 includes, for example, a conveyance state sensor unit 70 (a first sensor unit). The conveyance state sensor unit 70 is disposed upstream of the fixing device 50 on the conveyance path 4 of the print medium 2 and detects the conveyance state of the print medium 2 on the conveyance path 4 .

For example, the image carrier 20 and the fixing device 50 are arranged along the first direction D1, which is the direction in which the conveyance path 4 extends. The image carrier 20 and the transfer roller 41 are arranged along a second direction D2 that intersects the first direction D1. The conveyance state sensor unit 70 is arranged between the image carrier 20 and the fixing device 50 along the conveyance path 4 and the second direction D2. The conveyance state sensor unit 70 is provided at a position closer to the image carrier 20 when viewed from the conveyance path 4 . In this case, the conveyance state sensor unit 70 can detect the print medium 2 that does not adhere to the surface 20b of the image carrier 20 but deviates from the conveyance path 4 toward the image carrier 20.

The conveyance state sensor unit 70 includes, for example, a conveyance abnormality detection sensor 71 that detects adhesion of the print medium 2 to the image carrier 20, and a conveyance state sensor 71 that detects adhesion of the print medium 2 to the image carrier 20, and detects the conveyance state of the print medium 2 between the image carrier 20 and the fixing device 50. and an actuator 72 that operates. The conveyance abnormality detection sensor 71 is a sensor that detects an abnormality in the conveyance state of the print medium 2 . The conveyance abnormality detection sensor 71 is an optical sensor that irradiates light 71b toward the surface 20b of the image carrier 20 and receives reflected light accompanying the irradiation of the light 71b. For example, the conveyance abnormality detection sensor 71 may be provided in advance and may be a density control optical sensor for controlling the density of the toner image on the surface 20b of the image carrier 20. In this case, the existing optical sensor for density control can be effectively used as the conveyance abnormality detection sensor 71. As an example, the conveyance abnormality detection sensor 71 may be a CTD (Color Toner Density) sensor. In this case, the conveyance abnormality detection sensor 71 acquires the intensity of light as a voltage value. In other words, the conveyance abnormality detection sensor 71 acquires the intensity of reflected light generated when the surface 20b of the image carrier 20 is irradiated with the light 71b as a voltage value.

The conveyance abnormality detection sensor 71 detects adhesion of the print medium 2 by emitting light 71b toward the surface 20b of the image carrier 20 and receiving reflected light from the print medium 2 adhering to the surface 20b. For example, the conveyance abnormality detection sensor 71 irradiates the surface 20b of the image carrier 20 with light 71b and detects that the print medium 2 is not attached to the surface 20b when it receives reflected light from the surface 20b. The conveyance abnormality detection sensor 71 irradiates light 71b toward the surface 20b of the image carrier 20, and detects that the print medium 2 is attached to the surface 20b when it receives reflected light from the print medium 2. . The intensity of the reflected light from the print medium 2 is smaller than the intensity of the reflected light from the surface 20b of the image carrier 20. Therefore, the conveyance abnormality detection sensor 71 detects adhesion of the print medium 2 to the surface 20b by receiving reflected light having a lower intensity than the reflected light from the surface 20b.

The actuator 72 includes, for example, a movable part 73 that moves as the print medium 2 comes into contact with it, and a print medium return part 74 that returns the print medium 2 to the transport path 4 . The conveyance state sensor unit 70 detects an abnormality in the conveyance state of the print medium 2 when the movable part 73 moves as the print medium 2 comes into contact with the movable part 73 . The image forming apparatus 1 includes a control section 80 that controls each section of the image forming apparatus 1, and the control section 80 is capable of communicating with the conveyance state sensor unit 70.

The control unit 80 detects an abnormality in the conveyance state of the print medium 2 according to a decrease in the intensity of the reflected light received by the conveyance abnormality detection sensor 71. For example, the image forming apparatus 1 has a display section 85, and when the control section 80 detects an abnormality in the conveyance state of the print medium 2, the control section 80 displays a message on the display section 85 indicating that an abnormality has occurred in the conveyance state of the print medium 2. It may be displayed.

The movable portion 73 has, for example, a first side 75 that the print medium 2 contacts, a second side 76 extending from the first side 75 toward the image carrier 20, and a second side 76 opposite to the first side 75. It has a shaft portion 77 located at the side end, and a support member 78 that rotatably supports the shaft portion 77. The shaft portion 77 extends parallel to the axis of the image carrier 20 (in a direction perpendicular to the paper surface of FIG. 2). The movable part 73 rotates around the shaft part 77. As an example, the movable portion 73 has an L-shape. In this case, the first side 75 and the second side 76 are linear, and the second side 76 extends from the end of the first side 75 on the image carrier 20 side in a direction that intersects with the first side 75. . The first side 75 extends from the shaft portion 77 toward the image carrier 20 .

The movable part 73 moves as the print medium 2 comes into contact with the print medium 2 and blocks the optical path of the light 71b from the conveyance abnormality detection sensor 71. For example, when the print medium 2 comes into contact with the first side 75, the first side 75 and the second side 76 rotate around the shaft portion 77, and the second side 76 blocks the optical path of the light 71b. In this case, the second side 76 is a light shielding part that blocks the optical path of the light 71b of the conveyance abnormality detection sensor 71 when the print medium 2 comes into contact with the first side 75.

The conveyance state sensor unit 70 detects an abnormality in the conveyance state of the print medium 2 when the movable part 73 interrupts the optical path from the conveyance abnormality detection sensor 71. For example, the inner wall of the second side 76 is blackened. The intensity of the reflected light from the second side 76 accompanying the irradiation of the light 71b from the conveyance abnormality detection sensor 71 is even smaller than the intensity of the reflected light from the print medium 2. For example, the conveyance abnormality detection sensor 71 outputs an abnormality signal indicating an abnormality in the conveyance state when the movable part 73 moves and the second side 76 blocks the optical path of the light 71b. The abnormality signal is a signal indicating a voltage value that decreases due to a decrease in the intensity of reflected light due to the movable part 73 blocking the optical path. On the other hand, a normal signal is a signal in which the intensity of reflected light does not decrease and shows a voltage value that does not decrease. When the movable part 73 is not in contact with the print medium 2, it returns to the position (original position) where it does not block the optical path of the light 71b. At this time, the conveyance abnormality detection sensor 71 outputs a normal signal. For example, the movable portion 73 may be returned to its original position by gravity, or may be returned to its original position by an urging force such as a spring.

For example, the print medium return section 74 extends from the movable section 73 toward the fixing device 50 . The print medium return unit 74 is provided to return the print medium 2 that has come into contact with the actuator 72 to the transport path 4 . The print medium return section 74 extends from the shaft section 77 toward the fixing device 50 . As an example, the print medium return section 74 has a curved shape that curves toward the conveyance path 4 as it becomes farther away from the shaft section 77 . For example, the image forming apparatus 1 may include a frame 79 between the print medium return unit 74 and the fixing device 50 to guide the print medium 2 to the fixing device 50.

The image forming apparatus 1 includes a clogging detection sensor 90 (second sensor unit) located downstream of the fixing device 50 in the transport path 4 . For example, the control unit 80 determines whether the print medium 2 is clogged using the transport state sensor unit 70, which is the first sensor unit, and the clog detection sensor 90, which is the second sensor unit. A predetermined time is set in the clog detection sensor 90, which is a time period during which the print medium 2 reaches the clog detection sensor 90. The predetermined time is an estimated arrival time for the print medium 2 to reach the clog detection sensor 90. The predetermined time is, for example, the period from when a sensor attached to the registration roller 11 (see FIG. 1) detects the print medium 2 to when the print medium 2 passes through the conveyance path 4 and reaches the jam detection sensor 90. This is the estimated time.

For example, the clog detection sensor 90 detects that the print medium 2 is clogged between the image carrier 20 and the fixing device 50 when the print medium 2 has not reached the clog detection sensor 90 at the predetermined time. . When the clogging detection sensor 90 detects clogging, for example, the clogging detection sensor 90 outputs a detection signal to the control unit 80. When the control unit 80 receives the detection signal, it causes the display unit 85 to display that the print medium 2 is jammed, and stops the operation of the image forming apparatus 1, for example.

However, even if the print medium 2 is not clogged between the image carrier 20 and the fixing device 50, if the print medium 2 deviates from the conveyance path 4, for example, the print medium 2 may reach the clog detection sensor 90. In such a case, if the clog detection sensor 90 detects a clog, it will result in an erroneous detection. In contrast, in the image forming apparatus 1, the control section 80 determines whether the print medium 2 is clogged using the conveyance state sensor unit 70, which is the first sensor unit, and the clog detection sensor 90, which is the second sensor unit. , the above-mentioned false detection can be suppressed.

Detection of the print medium 2 by the conveyance state sensor unit 70, the control section 80, and the jam detection sensor 90 will be described below. As shown in FIGS. 2, 3, and 4, in a state where the print medium 2 deviates from the conveyance path 4, it is assumed that the print medium 2 does not reach the clog detection sensor 90 within the predetermined time T1.

As shown in FIGS. 4 and 5, when the print medium 2 that has deviated from the transport path 4 comes into contact with the actuator 72, the movable part 73 rotates around the shaft part 77, causing the transport abnormality detection sensor 71 to emit light 71b. The optical path of When the optical path of the transport abnormality detection sensor 71 is blocked, the control unit 80 detects an abnormality in the transport state of the print medium 2 in response to a decrease in the intensity of the reflected light received by the transport abnormality detection sensor 71.

The control unit 80 calculates the time period Δ during which the movable unit 73 blocks the optical path of the conveyance abnormality detection sensor 71. During the time Δ, the movable part 73 moves as the print medium 2 comes into contact with the actuator 72, and the moved movable part 73 (second side 76) blocks the optical path of the light 71b, so that the conveyance abnormality detection sensor 71 is activated. This is the signal output time during which an abnormal signal is output. The signal output time is from the time when the moving part 73 interrupts the optical path of the light 71b and the conveyance abnormality detection sensor 71 starts outputting an abnormal signal until the movable part 73 returns to its original position and the conveyance abnormality detection sensor 71 is normal. This is the time until the signal starts to be output. The control unit 80 converts the signal output time Δ during which the abnormal signal is output from the conveyance abnormality detection sensor 71 or the time kΔ obtained by multiplying the signal output time Δ by a coefficient k into the expected time of arrival at the clogging detection sensor 90. By adding the predetermined time T1 to the predetermined time T1, the predetermined time T1 is delayed to the predetermined time T2.

After the print medium 2 contacts the movable part 73, the print medium 2 moves from the movable part 73 to the print medium return part 74, as shown in FIG. At this time, the movable part 73 returns to its original position. The print medium 2 that has moved to the print medium return section 74 is guided by the print medium return section 74 toward the conveyance path 4 . The print medium 2 that has returned to the conveyance path 4 has the toner image fixed in the fixing nip portion of the fixing device 50, and reaches the clog detection sensor 90 at a predetermined time T2. This prevents the clogging detection sensor 90 from erroneously detecting clogging.

Next, various examples of the conveyance state sensor unit (first sensor unit) will be described. FIG. 7 is a diagram showing the transport state sensor unit 70 described above. The conveyance state sensor unit 70 includes a conveyance abnormality detection sensor 71 and an actuator 72. For example, the conveyance abnormality detection sensor 71 is supported by a sensor support member 71c. The actuator 72 has a movable part 73 and a print medium return part 74 . The movable part 73 has a first side 75, a second side 76, and a shaft part 77, and blocks the optical path of the light 71b from the conveyance abnormality detection sensor 71 by rotating around the shaft part 77.

FIG. 8 is a diagram schematically showing a conveyance state sensor unit 70A according to a modification. The conveyance state sensor unit 70A includes a conveyance abnormality detection sensor 71A, which is a switch, and an actuator 72A. The conveyance abnormality detection sensor 71A is capable of communicating with the control unit 80, and outputs an abnormality signal to the control unit 80 when pressed by the actuator 72A. The conveyance abnormality detection sensor 71A includes, for example, a switch body 71d that is pushed by the actuator 72A when there is an abnormality in the conveyance state of the print medium 2, and a support portion 71f that supports the switch body 71d on a sensor support member 71c.

The actuator 72A includes, for example, a movable part 73A that comes into contact with the conveyance abnormality detection sensor 71A, a shaft part 77A that rotatably supports the movable part 73A, and a print medium return part that extends from the shaft part 77A to the side opposite to the movable part 73A. 74A. The movable portion 73A extends linearly from the shaft portion 77A toward the image carrier 20. The movable part 73A has a first surface 73b that presses the conveyance abnormality detection sensor 71A, and a second surface 73c that faces opposite to the first surface 73b.

The print medium 2 comes into contact with the second surface 73c. When the print medium 2 comes into contact with the second surface 73c, the movable portion 73A rotates around the shaft portion 77A, and the first surface 73b presses the conveyance abnormality detection sensor 71A (switch body 71d). Then, an abnormality signal is output from the conveyance abnormality detection sensor 71A to the control section 80, and the abnormality in the conveyance state of the print medium 2 is detected by the control section 80. As described above, in the conveyance state sensor unit 70A shown in FIG. 8, the conveyance abnormality detection sensor 71A has a switch that the movable part 73A comes into contact with when the movable part 73A moves, and the movable part 73A contacts the switch. When the contact occurs, an abnormality in the conveyance state of the print medium 2 is detected.

FIG. 9 is a schematic diagram showing a modification of the conveyance state sensor unit 70A of FIG. 8. As shown in FIG. 9, a conveyance state sensor unit 70B as a modified example has a weight 73f attached to a movable part 73A. That is, the movable portion 73A includes a contact portion 73g that contacts the conveyance abnormality detection sensor 71A, which is a switch, and a weight 73f fixed to the contact portion 73g. In the case of this transport state sensor unit 70B, the weight 73f can more reliably return the movable portion 73A to its original position when the print medium 2 is not in contact with it. Therefore, the behavior of the movable portion 73A can be made more stable.

FIG. 10 is a schematic diagram showing a conveyance state sensor unit 70C according to a further modification. As shown in FIG. 10, the conveyance state sensor unit 70C includes a conveyance abnormality detection sensor 71C and an actuator 72C. The conveyance abnormality detection sensor 71C includes, for example, a photointerrupter 71g and a sensor support member 71c that supports the photointerrupter 71g on the housing 3. The photointerrupter 71g includes, for example, a light emitting section 71h and a light receiving section 71k that receives light 71j from the light emitting section 71h.

The actuator 72C includes, for example, a movable portion 73C, a shaft portion 77A, and a print medium return portion 74A. The movable portion 73C moves as the print medium 2 comes into contact with the movable portion 73C and interrupts the optical path of the light 71j in the photointerrupter 71g. The conveyance state sensor unit 70C detects an abnormality in the conveyance state of the print medium 2 when the movable portion 73C interrupts the optical path of the photointerrupter 71g. For example, the movable portion 73C has an extending portion 73h extending from the shaft portion 77A toward the image carrier 20, and a protruding portion 73j protruding from the extending portion 73h to the side opposite to the conveyance path 4.

The protruding portion 73j protrudes toward the conveyance abnormality detection sensor 71C, for example, from a midway portion of the extending portion 73h. The protruding portion 73j is a portion that blocks the optical path of the photointerrupter 71g when the print medium 2 comes into contact with the movable portion 73C and the movable portion 73C moves. In this case, when the print medium 2 comes into contact with the movable part 73C, the movable part 73C moves around the shaft part 77A, and the protruding part 73j enters between the light emitting part 71h and the light receiving part 71k to change the optical path of the light 71j. interrupt. When the optical path of the light 71j is interrupted, the conveyance abnormality detection sensor 71C outputs an abnormality signal as the intensity of the light 71j received by the light receiving section 71k decreases. By outputting this abnormality signal to the control section 80, the control section 80 detects an abnormality in the conveyance state of the print medium 2. As described above, in the modified examples shown in FIGS. 8 to 10, the conveyance abnormality detection sensor 71, which is an optical sensor for density control, can be omitted.

As described above, by including the conveyance state sensor unit 70, the jam detection sensor 90, and the control section 80, the image forming apparatus 1 can detect the print medium 2 that has deviated from the conveyance path 4, as shown in FIG. . FIG. 12 shows actual measured values of a voltage value chart measured by a CTD sensor, which is an example of the conveyance abnormality detection sensor 71. The conveyance abnormality detection sensor 71 shown in FIG. 11 is a regular reflection type reflective sensor (KMEM008C manufactured by Kodenshi), and the actuator 72 is made of black ABS resin. The inner surface of the second side 76 of the movable portion 73 is subjected to a blackening treatment, and a light-absorbing sheet, for example, is pasted thereon. As the light-absorbing sheet, Fine Shut Pole manufactured by Koyo Orient Japan Co., Ltd. was used.

As shown in FIGS. 11 and 12, the print medium deviates from the transport path 4 and passes between the surface 20b of the image carrier 20 and the transport state sensor unit 70 (between 0 and a in FIGS. 11 and 12). 2 is detected when the reflected light to the conveyance abnormality detection sensor 71 becomes weaker than the reflected light from the surface 20b. When the conveyance abnormality detection sensor 71 is a CTD sensor, for example, the voltage value acquired by the conveyance abnormality detection sensor 71 by the print medium 2 passing between the surface 20b and the conveyance state sensor unit 70 (voltage according to the intensity of reflected light) value) is below the first threshold V1. At this time, the voltage value acquired by the conveyance abnormality detection sensor 71 varies depending on the type of print medium 2, but is, for example, 1.3V to 1.8V. The control unit 80 detects that the print medium 2 has moved between the front surface 20b and the conveyance state sensor unit 70 in response to the voltage value acquired by the conveyance abnormality detection sensor 71 falling below the first threshold value V1.

The print medium 2 that has deviated from the transport path 4 and moved to the transport state sensor unit 70 (the print medium 2 that has moved between a and b in FIGS. 11 and 12) comes into contact with the movable part 73 of the actuator 72. At this time, the movable part 73 moves as the print medium 2 comes into contact with the movable part 73, and the movable part 73 blocks the optical path of the light 71b from the conveyance abnormality detection sensor 71. When the conveyance abnormality detection sensor 71 is a CTD sensor, the voltage value (voltage value according to the intensity of reflected light) acquired by the conveyance abnormality detection sensor 71 by the print medium 2 in contact with the actuator 72 is smaller than the first threshold value V1. below the second threshold V2. At this time, the voltage value acquired by the conveyance abnormality detection sensor 71 is, for example, 0.1V, but if the inner surface of the second side 76 is subjected to blackening treatment, the voltage value becomes approximately 0V. . The control unit 80 detects that the print medium 2 has come into contact with the actuator 72 in response to the voltage value acquired by the conveyance abnormality detection sensor 71 falling below the second threshold value V2.

The print medium 2 that has deviated from the transport path 4 and moved between the transport state sensor unit 70 and the fixing device 50 comes into contact with the frame 79, for example. The print medium 2 is then guided to the fixing nip portion of the fixing device 50 by the frame 79. At this time, since the light 71b of the conveyance abnormality detection sensor 71 is reflected from the surface 20b of the image carrier 20, the voltage value acquired by the conveyance abnormality detection sensor 71 is equal to or higher than the first threshold value V1. At this time, the voltage value acquired by the conveyance abnormality detection sensor 71 is, for example, 3.0V. The control unit 80 detects that the print medium 2 is being transported normally in response to the voltage value acquired by the transport abnormality detection sensor 71 being equal to or higher than the first threshold value V1.

As described above, in the image forming apparatus 1, the transport state sensor unit 70 and the control section 80 can grasp the transport state of the print medium 2 between the image carrier 20 and the fixing device 50. Further, the control unit 80 determines the expected time for the print medium 2 to reach the clog detection sensor 90 in accordance with the signal output time Δ during which the conveyance abnormality detection sensor 71 outputs an abnormal signal when the print medium 2 deviates from the conveyance path 4. Delay (delay the predetermined time T1 to the predetermined time T2). Therefore, erroneous detection of a clog by the clog detection sensor 90 can be suppressed.

Next, an example of the image forming apparatus 1 will be described while comparing it with an image forming apparatus 100 according to a comparative example. FIG. 13 is a perspective view showing a photoreceptor unit 110 of an image forming apparatus 100 according to a comparative example. The photoreceptor unit 110 includes an image carrier 120 and a plurality of separation claws 130 that separate the print medium attached to the surface of the image carrier 120. On the other hand, the image forming apparatus 1 according to the embodiment includes the above-described conveyance state sensor unit 70, the control section 80, and the clogging detection sensor 90, but does not have the separation claw 130. In this way, the image forming apparatus 1 according to the embodiment can eliminate the need for the separation claw 130 by including the conveyance state sensor unit 70.

The image forming apparatus 1 according to the above embodiment and the image forming apparatus 100 according to the comparative example were examined to see if the print medium 2 was clogged. First, a test was conducted in which paper was continuously printed using each of the image forming apparatus 1 and the image forming apparatus 100 in an environment with a temperature of 22° C. and a humidity of 55%. The paper used was 60 g/m ² . As a result of this test, in the image forming apparatus 100 according to the comparative example, a jam of 1/5 kpv (one sheet out of 5000 sheets) was detected. On the other hand, no clogging was detected in the image forming apparatus 1 according to the example.

Further, a test was conducted in which paper was continuously printed using each of the image forming apparatus 1 and the image forming apparatus 100 under a low temperature and low humidity environment of an air temperature of 10° C. and a humidity of 10%. The paper used was 60 g/m ² and 70 g/m ² . As a result of this test, in the image forming apparatus 100 according to the comparative example, jams of 5/2 kpV (5 out of 2000 sheets of paper) were detected when the paper was 60 g/ ^m2 , and when the paper was 70 g/m2, jams were detected. ² , clogging of 3/2kpV (3 out of 2000 sheets) was detected. Some of the clogs detected were false positives.

In the image forming apparatus 1 according to the embodiment, no jam was detected when the paper was 70 g/ ^m2 , but when the paper was 60 g/ ^m2 , the jam was detected at 1/2kpV (one sheet out of 2000 sheets ) was detected. However, this blockage was not a false positive. In this manner, it has been found that the image forming apparatus 1 can reduce clogging and suppress false detection of clogging. Furthermore, since the image forming apparatus 1 does not require the separation claw 130, an increase in the cost of parts of the image forming apparatus 1 can be suppressed.

It is to be understood that not necessarily all aspects, advantages, and features described herein may be achieved or included by any one particular example or embodiment. Indeed, while various examples have been described and illustrated herein, it should be obvious that other examples may be modified in arrangement and detail.

Claims (15)

an image carrier that transfers the toner image to a printing medium;
a fixing device that fixes the toner image on the print medium,
The image carrier and the fixing device are arranged along the conveyance path of the print medium,
comprising a conveyance state sensor unit that detects the conveyance state of the print medium on the conveyance path between the image carrier and the fixing device;
The conveyance state sensor unit includes a conveyance abnormality detection sensor that detects an abnormality in the conveyance state, and an actuator that operates according to a conveyance state of the print medium between the image carrier and the fixing device.
Image forming device. The actuator has a movable part that moves as the print medium comes into contact with it,
The conveyance abnormality detection sensor outputs an abnormality signal indicating an abnormality in the conveyance state when the movable part moves.
The image forming apparatus according to claim 1. The actuator has a print medium return unit that returns the print medium to the transport path.
The image forming apparatus according to claim 1. The actuator has a movable part that moves as the print medium comes into contact with it,
The print medium return section extends from the movable section toward the fixing device.
The image forming apparatus according to claim 3. The conveyance abnormality detection sensor acquires the intensity of reflected light generated when the surface of the image carrier is irradiated with light as a voltage value,
The movable part moves as the print medium comes into contact with it and blocks the optical path of the light from the conveyance abnormality detection sensor,
The abnormal signal is a signal indicating a voltage value that has decreased due to a decrease in the intensity of the reflected light due to the movable part blocking the optical path.
The image forming apparatus according to claim 2. The conveyance abnormality detection sensor includes a switch that the movable part abuts when the movable part moves, and outputs the abnormality signal when the movable part abuts the switch.
The image forming apparatus according to claim 2. The movable part has a contact part that contacts the switch, and a weight provided on the contact part.
The image forming apparatus according to claim 6. The conveyance abnormality detection sensor has a photo interrupter,
The movable part moves as the print medium comes into contact with the movable part to interrupt the optical path of the photointerrupter,
The conveyance abnormality detection sensor outputs the abnormality signal when the movable part interrupts the optical path.
The image forming apparatus according to claim 2. The movable part has a first side that is in contact with the print medium, and a second side that extends from the first side toward the image carrier.
The image forming apparatus according to claim 2. The inner surface of the second side is subjected to a blackening treatment.
The image forming apparatus according to claim 9. The movable part has a shaft located at an end of the first side opposite to the second side, and rotates around the shaft.
The image forming apparatus according to claim 9. The actuator has a print medium return unit that returns the print medium to the transport path,
The print medium return section extends from the shaft section toward the fixing device.
The image forming apparatus according to claim 11. an image carrier that transfers the toner image to a printing medium;
a fixing device that fixes the toner image on the print medium;
a first sensor unit that is disposed upstream of the fixing device in the conveyance path of the print medium and detects a conveyance state of the print medium in the conveyance path;
a second sensor unit that detects a predetermined time during which the print medium passes on the downstream side of the fixing device;
The first sensor unit includes a conveyance abnormality detection sensor that detects an abnormality in the conveyance state, and an actuator that operates depending on the conveyance state of the print medium between the image carrier and the fixing device,
comprising a control unit that uses the first sensor unit and the second sensor unit to determine whether the print medium is clogged;
Image forming device. The control unit delays the predetermined time according to a signal output time during which the conveyance abnormality detection sensor outputs an abnormality signal indicating an abnormality in the conveyance state.
The image forming apparatus according to claim 13. The actuator has a movable part that moves as the print medium comes into contact with it,
The conveyance abnormality detection sensor irradiates light toward the surface of the image carrier,
The signal output time is a time during which the conveyance abnormality detection sensor outputs the abnormality signal due to the moved movable part blocking the optical path of the light.
The image forming apparatus according to claim 14.

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