JP2021096361A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that is suitable for achieving a more stable operation.SOLUTION: An image forming apparatus comprises: a main body that has a frame ground and a first electrical contact electrically connected with the frame ground; and a fixing device that is removably provided in the main body and has a second electrical contact. When the fixing device is mounted in the main body, the second electrical contact is electrically conducted to the first electrical contact, and subsequently the second electrical contact is isolated from the first electrical contact while the fixing device is mounted in the main body.SELECTED DRAWING: Figure 3C

Description

The present invention relates to an image forming apparatus including a fixing device.

So far, in an image forming apparatus such as an electrophotographic printer, an image forming apparatus in which a fixing apparatus for fixing a toner image on a recording medium is detachably configured has been proposed (see, for example, Patent Document 1).

JP-A-2019-124904

In such an image forming apparatus, a high quality image can be formed by holding the potential of the recording medium passing through the fixing apparatus at an appropriate value.

Therefore, it is desirable to provide an image forming apparatus suitable for realizing more stable operation.

An image forming apparatus according to an embodiment of the present invention includes a main body and a fixing device. The body has a frame ground and a first electrical contact that is electrically connected to the frame ground. The fixing device is detachably provided on the main body and has a second electrical contact. In the fixing device, the second electric contact conducts with the first electric contact in the process of being mounted on the main body, and the second electric contact is insulated from the first electrical contact in the mounted state mounted on the main body. It has become.

According to the image forming apparatus as one embodiment of the present invention, it is possible to avoid malfunction due to charging of the fixing device removed from the main body, and it is possible to realize a more stable image forming operation.
Therefore, according to this image forming apparatus, a high quality image can be formed.
It should be noted that this is an example of the effect of the present invention, and the effect of the present invention is not limited to this, and may be any of the effects described below.

It is a schematic diagram which shows the whole structure example of the image forming apparatus which concerns on one Embodiment of this invention. FIG. 3 is a block diagram schematically showing an example of internal configuration of the image forming apparatus shown in FIG. 1A. FIG. 3 is a perspective view showing the appearance of the image forming apparatus in a state where the image forming unit is removed from the main body of the image forming apparatus shown in FIG. 1A. FIG. 3 is a perspective view showing the appearance of the image forming apparatus in a state where the image forming unit and the fixing device are removed from the main body of the image forming apparatus shown in FIG. 1A. It is a schematic diagram which shows the fixing device attached to the image forming apparatus shown in FIG. 1A and the peripheral part thereof. FIG. 5 is a schematic view showing a state in which the fixing device shown in FIG. 1A is removed from the mounting slot of the image forming device. FIG. 5 is a schematic view showing a state in which the fixing device shown in FIG. 1A is being mounted in the mounting slot of the image forming device. FIG. 3 is a partially enlarged view showing a part of FIG. 3A in an enlarged manner. It is a partially enlarged view which shows by enlarging a part of FIG. 3B. FIG. 3 is a partially enlarged view showing a part of FIG. 3C in an enlarged manner. FIG. 5 is a schematic view showing a state in which a clogged recording medium is pulled out from the fixing device shown in FIG. 1A. It is a schematic diagram which shows the state which the fixing device as a reference example was removed from the mounting slot of the image forming apparatus as a reference example. It is a schematic diagram which shows the fixing device as a reference example attached to the image forming apparatus as a reference example, and the peripheral part thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description is a specific example of the present invention, and the present invention is not limited to the following aspects. Further, the present invention is not limited to the arrangement, dimensions, dimensional ratio, etc. of each component shown in each figure.

<1. Embodiment>
[Rough configuration of image forming apparatus 100]
FIG. 1A is a schematic view showing an overall configuration example of the image forming apparatus 100 according to the embodiment of the present invention. FIG. 1B is a block diagram corresponding to the internal configuration of the image forming apparatus 100 shown in FIG. 1A. The image forming apparatus 100 is an electrophotographic printer that forms an image (for example, a color image) on a recording medium (also referred to as a printing medium or a transfer material) such as paper. In the present specification, the medium transport direction in which the recording medium is transported in the image forming section 50, the transfer section 60, and the fixing device 70, which will be described later, is referred to as the X-axis direction, and the width direction orthogonal to the medium transport direction is referred to as the Y-axis direction. .. Further, the height direction orthogonal to both the X-axis direction and the Y-axis direction is defined as the Z-axis direction.

The image forming apparatus 100 includes, for example, a paper feeding unit 10, a medium conveying unit 20, an image forming unit 50, a transfer unit 60, a fixing device 70, and a discharging unit 80 inside the main body 3. .. The main body 3 of the image forming apparatus 100 is provided with a top cover 4 and a front cover 5.

(Paper feeding unit 10)
The paper feed unit 10 includes, for example, a paper feed tray 11, a pickup roller 12, a paper feed roller 13, and a separation roller 14. The paper feed tray 11 accommodates a plurality of recording media in a stacked state. The pickup roller 12 comes into contact with the uppermost recording medium among the plurality of recording media stacked on the paper feed tray 11 and rotates to take out the uppermost recording medium. The paper feed roller 13 and the separation roller 14 are arranged so as to face each other downstream of the pickup roller 12. The paper feed roller 13 and the separation roller 14 rotate to send the recording medium taken out by the pickup roller 12 to the downstream medium transport unit 20. Even when a plurality of recording media are taken out by the pickup roller 12, for example, the paper feed roller 13 and the separation roller 14 can separate the plurality of recording media one by one and send them out to the medium transport unit 20. ..

(Media carrier 20)
The medium transport unit 20 has, for example, a resist roller 21 and a pressure roller 22 arranged to face each other, and a transport roller 23 and a pressure roller 24 arranged to face each other in order from the upstream. The resist roller 21 and the pressure roller 22 rotate to correct the skew of the recording medium and convey the recording medium downstream. The transfer roller 23 and the pressure roller 24 transfer the skew-corrected recording medium to the downstream image forming section 50 and transfer section 60.

(Image forming unit 50)
The image forming unit 50 forms a toner image (developer image), and the transfer unit 60 transfers the toner image formed in the image forming unit 50 to a recording medium. The image forming unit 50 has, for example, four image forming units 51K, 51Y, 51M, and 51C that are detachably provided with respect to the housing. The four image forming units 51K, 51Y, 51M, and 51C may be collectively referred to as an image forming unit 51. The image forming units 51K, 51Y, 51M, and 51C have LED (Light Emitting Diode) heads 57K, 57Y, 57M, and 57C, respectively. The image forming units 51K, 51Y, 51M, and 51C further include a photoconductor drum 52, a charging roller 53, a developing roller 54, a toner supply roller 55, a cleaning blade 56, and a toner tank 58, respectively.

The LED heads 57K, 57Y, 57M, and 57C expose the surfaces of the photoconductor drums 52 facing each other to form an electrostatic latent image on the surface of each photoconductor drum 52.

The photoconductor drum 52 is a columnar member that supports an electrostatic latent image on a surface (surface layer portion), and is configured by using a photoconductor (for example, an organic photoconductor).

The charging roller 53 is a charging member that charges the surface layer portion of the photoconductor drum 52, and is arranged so as to be in contact with the surface of the photoconductor drum 52.

The developing roller 54 is a member that supports a toner for developing an electrostatic latent image on the surface, and is arranged so as to be in contact with the surface (peripheral surface) of the photoconductor drum 52.

The toner supply roller 55 is a supply member for supplying toner to the developing roller 54, and is arranged so as to be in contact with the surface of the developing roller 54.

The cleaning blade 56 is a cleaning member that cleans the surface of the photoconductor drum 52 by scraping and collecting the toner remaining on the surface of the photoconductor drum 52. The cleaning blade 56 is arranged so as to come into contact with the surface of the photoconductor drum 52 with a counter (protrude in the direction opposite to the rotation direction of the photoconductor drum 52).

The toner tank 58 is a container for storing toner inside, and has a toner discharge port at the lower portion thereof.

(Transfer unit 60)
The transfer unit 60 includes, for example, a transfer belt 61, a drive roller 62 for driving the transfer belt 61, a driven roller 63 driven by the drive roller 62, and image forming units 51K, 51Y, 51M, sandwiching the transfer belt 61. It has transfer rollers 67K, 67Y, 67M, 67C arranged so as to face each photoconductor drum 52 of 51C.

The transport belt 61 is an endless elastic belt made of a resin material such as polyimide resin, and is stretched (stretched) by a drive roller 62, a driven roller 63, and a transfer roller 67K, 67Y, 67M, 67C, and circulates and rotates. It has become like. The drive roller 62 drives the transfer belt 61 by the driving force from the transfer belt motor. The transfer rollers 67K, 67Y, 67M, 67C electrostatically transfer the toner images formed in the image forming units 51K, 51Y, 51M, 51C onto the recording medium while transporting the recording medium in the transport direction. It is a member for. The transfer rollers 67K, 67Y, 67M, 67C are made of, for example, a foamable semi-conductive elastic rubber material. The drive roller 62, the driven roller 63, and the transfer rollers 67K, 67Y, 67M, and 67C are rotatable substantially cylindrical members extending in the Y-axis direction perpendicular to the paper surface, respectively.

(Fixing device 70)
The fixing device 70 is a member for fixing the toner image on the recording medium by applying heat and pressure to the toner image transferred on the recording medium conveyed from the transfer unit 60. The fixing device 70 has, for example, a fixing belt 71, a pressure roller 72, a heater 73, and a thermistor 74 (FIG. 1B) inside the housing 75 (described later). The fixing device 70 is detachably provided with respect to the main body 3 of the image forming device 100. The image forming units 51K, 51Y, 51M, 51C and the transport belt 61 are driven in synchronization with each other, and the toner images of each color are sequentially superimposed and transferred to the recording medium electrostatically adsorbed on the transport belt 61. ..

The fixing belt 71 is a tubular endless elastic belt including an inner peripheral surface and an outer peripheral surface. The fixing belt 71 is made of a resin material such as a polyimide resin, or is formed by forming silicone rubber or the like on a metal base material such as stainless steel. The fixing belt 71 is provided so as to be able to circulate and rotate around an axis extending in the Y-axis direction as a rotation center.

The pressurizing roller 72 is a cylindrical or cylindrical rotating body extending in the Y-axis direction, and can rotate while sandwiching a recording medium between the pressurizing roller 72 and the fixing belt 71 by being urged by the fixing belt 71. It is provided. The pressure roller 72 has, for example, a shaft made of a rigid material such as a metal pipe extending in the Y-axis direction, and an elastic layer provided so as to surround the shaft. The pressure roller 72 is provided so as to come into contact with the outer peripheral surface of the fixing belt 71 and form a nip portion for sandwiching the recording medium.

The heater 73 is provided in an internal space extending in the Y-axis direction surrounded by the fixing belt 71. The heater 73 is provided so as to heat the fixing belt 71 from the inner surface by the control of the fixing control unit 790 (described later) based on the temperature information detected by the thermistor 74. The thermistor 74 is provided so as to detect the temperature of the central portion of the surface of the pressure roller 72 in the Y-axis direction, for example.

(Discharge unit 80)
The discharge unit 80 has a discharge roller pair 81 and a discharge roller pair 82 in this order. The discharge roller pair 81 and the discharge roller pair 82 discharge the recording medium discharged from the fixing device 70 to the outside.

As shown in FIG. 1B, the image forming apparatus 100 includes a print control unit 700, an I / F control unit 710, a reception memory 720, an image data editing memory 730, an operation unit 701, and a sensor group 702. The image forming apparatus 100 further includes a charging voltage control unit 740, a head drive control unit 750, a developing voltage control unit 760, a transfer voltage control unit 770, an image formation drive control unit 780, and fixing, which receive commands from the print control unit 700, respectively. It includes a control unit 790, a transfer belt drive control unit 800, and a paper feed / transfer drive control unit 810. Print control unit 700, I / F control unit 710, charging voltage control unit 740, head drive control unit 750, development voltage control unit 760, transfer voltage control unit 770, image formation drive control unit 780, fixing control unit 790, conveyor belt The drive control unit 800 and the paper feed / transport drive control unit 810 are both electric circuits composed of, for example, a microprocessor, a ROM, a RAM, an input / output port, and the like.

The print control unit 700 controls the entire processing operation in the image forming apparatus 100 by, for example, executing a predetermined program. Specifically, the print control unit 700 receives print data and control commands from the I / F control unit 710, and receives a charge voltage control unit 740, a head drive control unit 750, a development voltage control unit 760, and a transfer voltage control unit. The printing operation is performed by supervising the control of the 770, the image formation drive control unit 780, the fixing control unit 790, the transfer belt drive control unit 800, and the paper feed / transfer drive control unit 810.

The I / F control unit 710 receives print data and control commands from an external device such as a personal computer (PC), or transmits a signal relating to the state of the image forming device 100.

The reception memory 720 temporarily stores print data from an external device such as a PC via the I / F control unit 710.

The image data editing memory 730 receives the print data stored in the receiving memory 720, and stores the edited image data of the print data.

The operation unit 701 has, for example, an LED lamp for displaying information such as the state of the image forming apparatus 100, and an input unit (button or touch panel) for giving an instruction to the image forming apparatus by the user.

The sensor group 702 includes various sensors for monitoring the operating state of the image forming apparatus 100, for example, a position sensor for detecting the position of a recording medium, a temperature sensor for detecting the temperature inside the image forming apparatus 100, or an image forming unit 50 and a transfer unit. 60 includes a density sensor that detects the density of the toner image transferred onto the transport belt 61.

The charging voltage control unit 740 controls the surface of the photoconductor drums 52K, 52Y, 52M, and 52C by applying a charging voltage to each charging roller 53 according to the instruction of the printing control unit 700. ..

The head drive control unit 750 controls the exposure operation by the LED heads 57K, 57Y, 57M, 57C according to the image data stored in the image data editing memory 730.

The developing voltage control unit 760 applies a developing voltage to each developing roller 54 according to the instruction of the printing control unit 700, and applies toner to the electrostatic latent images formed on the surfaces of the photoconductor drums 52K, 52Y, 52M, and 52C. It controls to develop.

The transfer voltage control unit 770 applies a transfer voltage to the transfer rollers 67K, 67Y, 67M, 67C according to the instruction of the print control unit 700, and controls the transfer of the toner image to the recording medium.

The image formation drive control unit 780 controls the drive of the drive motors 781 to 784 according to the instruction of the print control unit 700. The drive motors 781 to 784 rotate the photoconductor drums 52K, 52Y, 52M, 52C, the charging roller 53, and the developing roller 54.

The fixing control unit 790 controls the fixing operation of the fixing device 70 according to the instruction of the printing control unit 700. Specifically, the voltage applied to the heater 73 is controlled. The fixing control unit 790 controls on / off of the voltage applied to the heater 73 based on the temperature of the fixing device 70 measured by the thermistor 74. The fixing control unit 790 also controls the operation of the fixing motor 793 based on the temperature of the fixing device 70 measured by the thermistor 74.

The transfer belt drive control unit 800 controls the operation of the transfer belt motor 801 provided in the image forming apparatus 100 according to the instruction of the print control unit 700. The transfer belt motor 801 drives the transfer belt 61 of the transfer unit 60.

The paper feed / transport drive control unit 810 controls the operation of the paper feed motor 811 and the transport motor 812 provided in the image forming apparatus 100 according to the instruction of the print control unit 700. The paper feed motor 811 rotates and drives the pickup roller 12, the paper feed roller 13 in the paper feed unit 10, and the separation roller 14. The transfer motor 812 rotates the resist roller 21 and the transfer roller 23 in the medium transfer unit 20.

FIG. 2A is an external perspective view showing a state in which the image forming unit 51 is removed from the main body 3 of the image forming apparatus 100. FIG. 2B is an external perspective view showing a state in which the image forming unit 51 and the fixing device 70 are removed from the housing of the image forming apparatus 100.

As shown in FIG. 2A, the top cover 4 is provided rotatably with respect to the main body 3, for example, on the upper portion of the main body 3 placed horizontally. The top cover 4 is configured to rotate from a horizontally extending closed position to an open position in a substantially vertical state and to be held at the open position. The LED heads 57K, 57Y, 57M, 57C are attached to the lower surface of the top cover 4, and show the printing operation positions shown in FIG. 1A and the printing operation positions shown in FIGS. 2A and 2B according to the rotational operation of the top cover 4. It is designed to be displaced from the retracted position. A part of the upper surface of the top cover 4 constitutes a stacker 90 on which the discharged recording medium is placed.

The front cover 5 is rotatably provided on the front portion of the main body 3 of the image forming apparatus 100 with respect to the main body 3. As shown in FIGS. 2A and 2B, the front cover 5 rotates to an open position inclined toward the front in a substantially vertical direction, and is locked at the open position. The front cover 5 is provided with, for example, an operation panel 5a.

As shown in FIG. 2A, the image forming unit 51 can be removed by pulling out in the direction of the arrow with both the top cover 4 and the front cover 5 in the open position. When the image forming unit 51 is removed, the image forming unit 51 moves along the guide groove 6 formed on the inner surface of the side wall of the main body 3. When the image forming unit 51 is attached to the main body 3, the image forming unit 51 moves along the guide groove 6 in the direction opposite to the arrow.

In the image forming apparatus 100, the fixing device 70 is also detachably provided in the mounting slot 3a formed in the main body 3. FIG. 2B shows a state in which the fixing device 70 is pulled out from the mounting slot 3a in the direction indicated by the arrow. At that time, the user can remove the fixing device 70 from the main body 3 by pulling while gripping the grip portion of the handle 75a of the fixing device 70. The fixing device 70 may be detachably provided with the top cover 4 closed, that is, with the top cover 4 in the closed position.

Further, the image forming apparatus 100 is provided with a duct 15 for releasing the heat of the fixing apparatus 70 to the outside. Air taken in from the outside of the image forming apparatus 100 flows through the duct 15. The air taken into the duct 15 is finally discharged to the outside of the image forming apparatus 100 through the ventilation holes 7 provided in the side wall portion of the main body 3.

[Structure of fixing device 70 and its peripheral parts]
Next, in addition to FIGS. 1A to 2B, a detailed configuration of the fixing device 70 and its peripheral portion will be described with reference to FIGS. 3A to 3C and FIGS. 4A to 4C. 3A to 3C schematically show the fixing device 70 mounted in the mounting slot 3a of the main body 3 and its peripheral portion. In particular, FIG. 3A shows a "mounting state" in which the fixing device 70 is mounted in the mounting slot 3a, FIG. 3B shows a "disengagement state" in which the fixing device 70 is detached from the mounting slot 3a, and FIG. 3C shows "a detached state". It represents an "intermediate state" between the "mounted state" and the "disengaged state". 4A to 4C correspond to FIGS. 3A to 3C, respectively, and are enlarged schematic views showing a part of the boundary portion between the fixing device 70 and the mounting slot 3a in an enlarged manner.

As shown in FIGS. 3A to 3C, the main body 3 has a frame 31 as a frame ground (FG) and an electric contact 32 electrically connected to the frame 31. The frame 31 is covered with a housing 33 made of, for example, a resin material. A mounting slot 3a in which the fixing device 70 is mounted is formed in a part of the housing 33. The mounting slot 3a is, for example, a groove having the Y-axis direction as the longitudinal direction and the substantially Z-axis direction as the depth direction, and the fixing device 70 is inserted in the substantially −Z direction. The electrical contact 32 is provided, for example, on the inner surface of the side wall of the mounting slot 3a so as to include a protruding portion protruding toward the fixing device 70 inserted into the mounting slot 3a (see FIGS. 4A to 4C). It is preferable that the electric contact 32 is formed of a strip-shaped metal made of a highly conductive material such as copper, and has elasticity so that the protruding portion is bent by an external force. The electrical contact 32 is a specific example corresponding to the "first electrical contact" of the present invention.

As described above, the fixing device 70 is provided with, for example, a housing 75 provided with a fixing belt 71, a pressure roller 72, a heater 73, a thermistor 74, and the like. However, in FIGS. 3A to 3C, the notation of the heater 73 and the thermistor 74 is omitted. The fixing device 70 is mounted in the mounting slot 3a of the main body 3 of the image forming apparatus 100, or can be removed from the mounting slot 3a. An electrical contact 76 is provided on the side surface of the housing 75 in the fixing device 70 so as to include a protruding portion protruding toward the inner surface of the side wall of the mounting slot 3a (see FIGS. 4A to 4C). The electrical contact 76 is preferably formed of a strip-shaped metal made of a highly conductive material such as copper, and has elasticity so that the protruding portion is bent by an external force. An electric contact 77 and an electric contact 78 are provided below the housing 75 of the fixing device 70, respectively. The electrical contact 76 is a specific example corresponding to the "second electrical contact" of the present invention.

On the bottom surface of the main body 3, for example, the mounting slot 3a, an electric contact 34 and an electric contact 35 are provided so as to be detachable from the electric contact 77 and the electric contact 78 provided in the lower part of the housing 75, respectively. In the "mounted state" of the fixing device 70 shown in FIG. 3A, the electric contact 34 and the electric contact 35 are connected to the electric contact 77 and the electric contact 78 provided on the bottom surface of the housing 75, respectively. ..

The main body 3 further has a resistor 8 having a first resistance value (for example, 500 MΩ). The resistor 8 is connected between the electrical contact 34 and the frame 31. Here, the second resistance value between the electrical contact 32 and the frame 31 may be sufficiently lower than, for example, the first resistance value. In the "mounted state" of the fixing device 70 shown in FIG. 3A, the resistor 8 is connected to the housing 75 of the fixing device 70 via the electric contact 34 and the electric contact 77. The electrical contact 34 is a specific example corresponding to the "third electrical contact" of the present invention.

The main body 3 further has an electric circuit 9. The electric circuit 9 constitutes, for example, the print control unit 700 and the fixing control unit 790 (both of which see FIG. 1B) described above. The electric circuit 9 is connected between the electric contact 35 and the frame 31. Here, the resistance value of the electric circuit 9 is, for example, about 10 kΩ, which is sufficiently lower than the first resistance value of the resistor 8. In the "mounted state" of the fixing device 70 shown in FIG. 3A, the electric circuit 9 is connected to the housing 75 of the fixing device 70 via the electric contact 35 and the electric contact 78.

When the fixing device 70 is mounted in the mounting slot 3a of the main body 3, the electrical contact 76 conducts with the electrical contact 32, and then the electrical contact 76 becomes the electrical contact 32 in the mounted state (FIG. 3A) mounted on the main body 3. It is designed to be insulated. Specifically, for example, by changing the relative position between the main body 3 and the fixing device 70 in the Z-axis direction, the electric contact 32 and the electric contact 76 come into contact with each other, and then the electric contact 32 and the electric contact 76 are separated from each other. It is designed to do. That is, for example, in the "disengaged state" shown in FIG. 3B, none of the electrical contacts 76 to 78 in the fixing device 70 is in contact with the electrical contacts 32 (see FIGS. 3B and 4B). When the fixing device 70 slides downward (-Z direction) from the "disengaged state", it eventually shifts to the "intermediate state" shown in FIG. 3C. In that "intermediate state", the electrical contacts 32 abut and conduct with the electrical contacts 76 (FIGS. 3C and 4C). However, in the "intermediate state", the electrical contacts 34 and 35 are separated from the electrical contacts 77 and 78, respectively (FIG. 3C). In the "intermediate state" of FIGS. 3C and 4C, it is the housing 75 of the fixing device 70 that the electrical contact 32 comes into contact with the electrical contact 76 before the electrical contacts 34 and 35 are connected to the electrical contacts 77 and 78. This is because the distance in the Z-axis direction from the bottom surface of the mounting slot 3a to the electrical contact 32 is longer than the distance in the Z-axis direction from the bottom surface to the electrical contact 76. When the fixing device 70 slides further downward (in the −Z direction) from the “intermediate state”, it eventually shifts to the “mounting state” shown in FIGS. 3A and 4A. With the transition from the "intermediate state" to the "mounted state", the electrical contacts 32 are separated from the electrical contacts 76, and then the electrical contacts 34 and 35 are connected to the electrical contacts 77 and 78, respectively (FIG. FIG. 3A and FIG. 4A). In the "mounted state" of FIGS. 3A and 4A, the electric contact 32 is separated from the electric contact 76 from the distance in the Z-axis direction from the bottom surface of the mounting slot 3a to the electric contact 76 in the "mounted state". This is because the distance in the Z-axis direction from the bottom surface of the mounting slot 3a to the electrical contact 32 is longer.

[Action / Effect]
(A. Basic operation)
In the image forming apparatus 100, the toner image is transferred to the recording medium as follows.

Specifically, as shown in FIG. 1A, first, the recording media stored in the paper feed tray 11 are picked up one by one from the top by the pickup roller 12, the paper feed roller 13, and the separation roller 14. It is fed in the direction of the downstream medium transport unit 20. Next, the recording medium fed out from the paper feed unit 10 is conveyed to the image forming unit 50 and the transfer unit 60 downstream while the skew is corrected by the resist roller 21, the pressure roller 22, and the like. In the image forming unit 50 and the transfer unit 60, the toner image is transferred onto the recording medium as follows.

When print image data and a print command are input to the print control unit 700 from an external device such as a PC to the activated image forming device 100 via the I / F control unit 710, the print control unit 700 sends the print command. In response to this, the print operation of the print image data is started in cooperation with the image formation drive control unit 780 and the like.

The image formation drive control unit 780 drives the drive motors 781 to 784 to rotate each of the photoconductor drums 52 in the four image formation units 51K, 51Y, 51M, and 51C in a predetermined direction at a constant speed. When the photoconductor drum 52 rotates, its power is transmitted to the toner supply roller 55, the developing roller 54, and the charging roller 53, respectively, via a drive transmission unit such as a gear train. As a result, the toner supply roller 55, the developing roller 54, and the charging roller 53 rotate in predetermined directions, respectively.

On the other hand, according to a command from the print control unit 700, the charge voltage control unit 740 applies a predetermined voltage to the charging roller 53 to uniformly charge the surface of the photoconductor drum 52.

Next, the head drive control unit 750 activates the LED head 57 and irradiates the photoconductor drum 52 with light corresponding to the printed image based on the image signal to form an electrostatic latent image on the surface of the photoconductor drum 52. Further, toner is supplied from the toner tank 58 to the toner supply roller 55. The toner is supported on the toner supply roller 55 and moves in the vicinity of the developing roller 54 as the toner supply roller 55 rotates. Therefore, the toner is negatively charged, for example, due to the potential difference between the potential of the developing roller 54 and the potential of the toner supply roller 55, and is supplied to the developing roller 54. The toner supplied to the developing roller 54 forms a toner layer regulated to a predetermined thickness by the developing blade.

Further, the toner layer on the developing roller 54 is developed according to the electrostatic latent image formed on the surface of the photoconductor drum 52, and the toner image is formed on the photoconductor drum 52. The toner image is transferred to a recording medium by an electric field between the photoconductor drum 52 and the transfer roller 67 to which a predetermined voltage is applied by the transfer voltage control unit 770.

After that, under the control of the fixing control unit 790, heat and pressure are applied to the toner image transferred on the recording medium in the fixing device 70, and the toner image is fixed on the recording medium. After that, the recording medium on which the toner image is fixed is discharged to the outside by the discharge unit 80.

(B. Detachment operation of fixing device 70)
In the image forming apparatus 100, for example, when the recording medium being fixed in the fixing apparatus 70 is clogged, that is, when a so-called jam of the recording medium occurs, the fixing apparatus 70 is removed from the main body 3 of the image forming apparatus 100 to perform restoration work. It can be performed. Specifically, when the printing operation of the image forming apparatus 100 is stopped while the recording medium is passing through the fixing device 70, as shown on the left side of FIG. 5, the fixing device is in a state where the recording medium PM is clogged. The 70 can be taken out from the mounting slot 3a. Therefore, as shown on the right side of FIG. 5, by pulling out the clogged recording medium PM from the fixing device 70, the jam of the recording medium can be resolved relatively easily. The fixing device 70 from which the clogged recording medium PM has been removed can be directly mounted in the mounting slot 3a of the main body 3 of the image forming device 100.

However, the fixing device 70 is charged by pulling out the clogged recording medium PM as shown on the right side of FIG. 5 from the state shown on the left side of FIG. This is because the toner before the fixing process is held on the surface of the recording medium PM, so that a charge (negative charge) having a polarity opposite to that of the toner (for example, a positive charge) is applied to the recording medium PM. For example, by pulling out the recording medium PM having a negative charge from the fixing device 70, the fixing device 70 is charged with a positive charge.

In mounting the fixing device 70 (on the right side in FIG. 5) charged with a positive charge in this way in the mounting slot 3a of the main body 3, for example, the electrical contacts 32 and electricity as in the configurations of FIGS. 6A and 6B as reference examples. Consider the case where the contact 76 does not exist. In this case, when shifting from the detached state of FIG. 6A to the mounted state of FIG. 6B, the path is not connected to the frame 31 via the resistor 8 which is the original discharge path, but via the electric circuit 9 having a lower resistance value. A discharge current flows through the path connected to the frame 31. In such a case, it may cause a malfunction of the electric circuit 9.

On the other hand, in the image forming apparatus 100 of the present embodiment, the electric contact 32 is provided in the main body 3 and the electric contact 76 is provided in the fixing device 70, and the electric contact 32 and the electric contact 76 are provided before reaching the mounted state. Are in contact with each other to conduct electricity. That is, the housing 75 of the fixing device 70 is configured so that the housing 75 of the fixing device 70 and the frame 31 are equipotential before conducting conduction with the resistor 8 and the electric circuit 9. Therefore, when the fixing device 70 is attached to the image forming device 100, the charged charge of the fixing device 70 is quickly discharged, and a discharge current flows through other components (for example, the electric circuit 9) other than the assumed path. Can be prevented.

(C. Effect)
As described above, in the image forming apparatus 100 as the present embodiment, since the fixing device 70 is detachably attached to the main body 3 of the image forming apparatus 100, the restoration work at the time of an abnormality such as a medium jam is simplified. The user can enjoy high convenience. Further, when the fixing device 70 is attached to the main body 3 of the image forming device 100, it is possible to prevent a malfunction due to a discharge current caused by the charged fixing device 70.

<2. Modification example>
Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above embodiments and can be modified in various ways. For example, in the above embodiment, an image forming apparatus for forming a color image has been described, but the present invention is not limited to this, and for example, an image forming that transfers only a black toner image to form a monochrome image. It may be a device. Further, in the above-described embodiment, the image forming apparatus of the primary transfer method (direct transfer method) has been described, but the present invention can also be applied to the secondary transfer method.

Further, in the above embodiment, the case where the fixing device 70 has a structure in which the electric contact 32 and the electric contact 76 come into contact with each other and then separate from each other in the process of sliding with respect to the main body 3 has been described, but the present invention is limited to this. It is not something that is done. For example, by changing the first position of the first electrical contact in the main body, by changing the second position of the second electrical contact in the fixing device, or by changing the first position of the first electrical contact in the main body. The first electric contact and the second electric contact may be separated from each other by changing both the position of the second electric contact and the second position of the second electric contact in the fixing device. Specifically, by operating the lever, the position of the first electric contact and the position of the second electric contact are changed, so that the first electric contact and the second electric contact are brought into contact with each other and separated from each other. May be adopted.

Further, in the present invention, for example, a relay may be provided in the main body or the fixing device to electrically conduct and separate the first electric contact and the second electric contact.

Further, in the above embodiment, the LED head using the light emitting diode as the light source is used as the exposure device, but for example, an exposure device using a laser element or the like as the light source may be used.

Further, in the above-described embodiment and the like, an image forming apparatus having a printing function has been described as a specific example of the "image forming apparatus" in the present invention, but the present invention is not limited thereto. That is, in addition to such a printing function, the present invention can be applied to, for example, an image forming apparatus that functions as a multifunction device having a scanning function and a fax function.

100 ... image forming device, 3 ... main body, 3a ... mounting slot, 31 ... frame, 32 ... electrical contact, 33 ... housing, 34, 35 ... electrical contact, 4 ... top cover, 5 ... front cover, 6 ... guide groove , 7 ... Vent, 8 ... Resistor, 9 ... Electric circuit, 10 ... Feeding unit, 20 ... Medium transport unit, 50 ... Image forming unit, 60 ... Transfer unit, 70 ... Fixing device, 80 ... Discharge unit, 51K , 51Y, 51M, 51C ... Image forming unit, 57K, 57Y, 57M, 57C ... LED head, 52K, 52Y, 52M, 52C ... Photoreceptor drum, 61 ... Conveying belt, 62 ... Drive roller, 63 ... Driven roller, 67K , 67Y, 67M, 67C ... Transfer roller, 71 ... Fixing belt, 72 ... Pressurizing roller, 73 ... Heater, 74 ... Thermista, 75 ... Housing, 76-78 ... Electrical contacts.

Claims (6)

A main body having a frame ground and a first electrical contact electrically connected to the frame ground,
A fixing device that is detachably provided on the main body and has a second electrical contact is provided.
When the fixing device is mounted on the main body, the second electrical contact conducts with the first electrical contact, and then the second electrical contact is attached to the main body in the mounted state. An image forming device that is insulated from the electrical contacts of the. The main body further includes a third electric contact that comes into contact with the fixing device in the mounted state, and a resistor that is connected between the third electric contact and the frame ground and has a first resistance value. Have and
The image forming apparatus according to claim 1, wherein the second resistance value between the first electric contact and the frame ground is lower than the first resistance value. By changing the relative position of the fixing device with respect to the main body, the first electric contact and the second electric contact come into contact with each other, and then the first electric contact and the second electric contact are separated from each other. The image forming apparatus according to claim 1 or 2. By changing the first position of the first electrical contact in the main body, by changing the second position of the second electrical contact in the fixing device, or by changing the first electric contact in the main body. By changing both the first position of the contact and the second position of the second electric contact in the fixing device, the first electric contact and the second electric contact are separated from each other. The image forming apparatus according to claim 1 or 2. The image forming apparatus according to claim 1 or 2, wherein the main body or the fixing device further includes a relay that conducts and separates the first electric contact and the second electric contact. The image forming apparatus according to any one of claims 1 to 5, wherein the main body further includes an electric circuit connected to the fixing device in the mounted state.

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