JP7545913B2 - Contact conduction mechanism and image forming apparatus - Google Patents

Description

This invention relates to a contact conduction mechanism and an image forming device, and in particular to a contact conduction mechanism and an image forming device that electrically connects a rotating shaft and a contact terminal by contacting them in the axial direction with a predetermined pressure.

One example of an image forming apparatus equipped with this type of conventional contact conduction mechanism is disclosed in Patent Document 1. The image forming apparatus of Patent Document 1 is equipped with a coupling means for driving the photosensitive drum, a non-rotating contact member (contact terminal) that fits into the rotation center hole of the coupling means and serves as an electrical contact for the photosensitive drum, and a biasing means for biasing the coupling means toward the developer cartridge side via the contact member. When the coupling means on the photosensitive drum side is engaged with the coupling of the image forming apparatus main body, the end face of the conductive member (rotating shaft) of the photosensitive drum comes into contact with the end face of the contact member, and the charge remaining on the photosensitive drum is released to the image forming apparatus main body.

JP 2000-112200 A

In the technology of Patent Document 1, the end faces of the rotating shaft and the contact terminal are in surface contact with each other. This makes it difficult to increase the contact pressure between the rotating shaft and the contact terminal, and therefore makes it difficult to ensure stable electrical continuity.

Therefore, the primary object of this invention is to provide a novel contact conduction mechanism and image forming device.

Another object of the invention is to provide a contact conduction mechanism and an image forming device that can ensure stable conduction between the rotating shaft and the contact terminal.

The first invention is a contact conduction mechanism that electrically connects a rotatably arranged rotating shaft and a rod-shaped contact terminal that is non-rotatably arranged coaxially with the rotating shaft by contacting them in the axial direction at a predetermined pressure, the contact conduction mechanism comprising: a tapered portion formed on one end of the contact terminal and having a diameter that decreases toward the tip side; a recess formed on one end of the rotating shaft and receiving the tip of the tapered portion ; a line contact portion formed on the opening edge of the recess and making line contact with the outer surface of the tapered portion ; and a groove portion formed on the outer surface of the tapered portion and extending in a direction intersecting the line contact portion so as to straddle the line contact portion .

According to the first invention, the linear contact between the linear contact portion of the rotating shaft and the tapered portion of the contact terminal can be increased in contact pressure and the risk of foreign matter getting caught between them can be reduced. Therefore, the electrical connection between the rotating shaft and the contact terminal can be stabilized. In addition, the groove can store a conductive lubricant, and the lubricant stored in the groove can be supplied (applied) to the linear contact portion, so that the electrical connection between the rotating shaft and the contact terminal can be further stabilized.

A second invention is according to the first invention, and further includes a guide portion that is formed on one end of the rotating shaft on the tip side of the recess and that increases in diameter toward the tip side.

According to the second aspect of the present invention, the tapered portion can be guided into the recess by the guide portion, so that the line contact portion and the tapered portion can be reliably brought into contact with each other.
The third invention is a contact conduction mechanism that electrically connects a rotatably arranged rotating shaft and a rod-shaped contact terminal that is non-rotatably arranged coaxially with the rotating shaft by contacting them in the axial direction at a predetermined pressure, the contact conduction mechanism comprising: a tapered portion formed at one end of the contact terminal and decreasing in diameter toward the tip side; a recess formed at one end of the rotating shaft and receiving the tip of the tapered portion; a line contact portion formed at the opening edge of the recess and making line contact with the outer surface of the tapered portion; and a guide portion formed at one end of the rotating shaft on the tip side of the recess and increasing in diameter toward the tip side, wherein the inclination angle of the guide portion with respect to the axial direction of the rotating shaft is greater than the inclination angle of the tapered portion with respect to the axial direction of the contact terminal.

The fourth invention is an image forming device equipped with a contact conduction mechanism according to any one of the first to third inventions.

The fifth invention is dependent on the fourth invention, and the rotating shaft is the shaft of the photosensitive drum.

According to this invention, the linear contact between the linear contact portion of the rotating shaft and the tapered portion of the contact terminal is achieved, so that the contact pressure between them can be increased and the risk of foreign matter becoming caught between them can be reduced. Therefore, the electrical continuity between the rotating shaft and the contact terminal can be stabilized.

The above and other objects, features and advantages of the present invention will become more apparent from the detailed description of the embodiments given below with reference to the drawings.

1 is a schematic cross-sectional view showing an internal structure of an image forming apparatus according to a first embodiment of the present invention. FIG. 13 is an illustrative view showing a state in which a process unit is attached to an apparatus main body. FIG. 2 is a perspective view showing a rear end portion of the process unit. FIG. 4 is a cross-sectional view showing the rear end portion of the process unit. 4 is an enlarged cross-sectional view showing a rear end portion of a drum shaft of a photosensitive drum. FIG. 2 is a perspective view showing a process unit driving device provided in the main body of the apparatus. FIG. 2 is a diagram illustrating a structure of a gear support shaft and its surroundings in the process unit driving device. 4 is a cross-sectional view showing a gear support shaft and its surroundings of the process unit driving device. FIG. 4 is an enlarged cross-sectional view showing a front end portion of a gear support shaft. FIG. 4 is a cross-sectional view showing a state in which the process unit driving device and the process unit are connected to each other; FIG. FIG. 4 is a cross-sectional view showing a state in which the drum shaft and the gear support shaft are connected. FIG. 11 is a cross-sectional view showing a state in which a drum shaft and a gear support shaft are connected in an image forming apparatus according to a second embodiment of the present invention.

[First embodiment]
1, an image forming apparatus 10 according to an embodiment of the present invention is a multifunction peripheral (MFP) having a copying function, a printer function, a scanner function, a facsimile function, etc., and forms a multicolor or monochrome image on paper (recording medium) by electrophotography. As will be described in detail later, the image forming apparatus 10 includes a contact conduction mechanism 200 (see FIG. 10) that electrically connects a drum shaft 76 of a photosensitive drum 36, which is an example of a rotating shaft, to a gear support shaft 108 of a drum drive gear 106, which is an example of a contact terminal, by contacting them in the axial direction, and dissipates electric charges remaining on the photosensitive drum 36 to the apparatus main body 12 via the contact conduction mechanism 200.

First, the basic configuration of the image forming device 10 will be briefly described. Note that in this first embodiment, the surface facing the position of the user who operates the image forming device 10, i.e., the surface on which the operation panel 28 (see FIG. 2) is provided, is defined as the front (front), and the front-to-rear direction (depth direction) of the image forming device 10 and its components are defined. In addition, the left-to-right direction (horizontal direction) of the image forming device 10 and its components are defined based on the state when the image forming device 10 is viewed from the front.

As shown in Figures 1 and 2, the image forming device 10 includes a device main body 12 equipped with an image forming unit 30 and the like, and an image reading device 14 disposed above the device main body 12.

The image reading device 14 has a document placement platform 16 made of a transparent material. A document pressing cover 18 is attached above the document placement platform 16 via a hinge or the like so that it can be opened and closed freely. This document pressing cover 18 is provided with an ADF (automatic document feeder) 24 that automatically feeds documents placed on a document placement tray 20 one sheet at a time to an image reading position 22. In addition, on the front side of the document placement platform 16, an operation panel 28 is provided that accepts input operations such as printing instructions from the user. This operation panel 28 is appropriately provided with a display, operation buttons, etc.

The image reading device 14 also has a built-in image reading unit 26 that includes a light source, multiple mirrors, an imaging lens, and a line sensor. The image reading unit 26 exposes the document surface to the light source, and guides the light reflected from the document surface to the imaging lens using multiple mirrors. The imaging lens then focuses the reflected light on the light receiving element of the line sensor. The line sensor detects the luminance and chromaticity of the reflected light focused on the light receiving element, and generates image data based on the image of the document surface. A CCD (Charge Coupled Device) or CIS (Contact Image Sensor) is used as the line sensor.

The device body 12 includes a control unit (not shown) including a CPU, memory, etc., and an image forming unit 30. The control unit transmits control signals to each part of the image forming device 10 in response to input operations on the operation panel 28, etc., and causes the image forming device 10 to perform various operations.

The image forming section 30 includes an exposure unit 32, a developing unit 34, a photoconductor drum 36, a cleaner unit 38, a charger 40, an intermediate transfer belt unit 42, a secondary transfer roller 44, and a fixing unit 46, and forms an image on paper conveyed from a paper feed tray 48 or a manual paper feed tray 50, and discharges the paper with the image formed on it to a paper discharge tray 52. Image data for forming an image on the paper is image data read by the image reading section 26 or image data sent from an external computer, etc.

The image data handled by the image forming device 10 corresponds to four color images of black (K), cyan (C), magenta (M) and yellow (Y). For this reason, four of each of the developing device 34, photosensitive drum 36, cleaner unit 38 and charger 40 are provided to form four types of latent images corresponding to each color, and these constitute four image stations. In addition, the photosensitive drum 36, cleaner unit 38 and charger 40 are unitized, and these constitute a process unit 70. In other words, the image forming section 30 is provided with four process units 70 equipped with the photosensitive drum 36, cleaner unit 38 and charger 40. Each of the process units 70 can be individually attached and detached from the front side of the device main body 12.

The apparatus main body 12 also has a process unit drive device 100 (see FIG. 6) fixedly mounted on its rear side. When the process unit 70 is mounted on the apparatus main body 12, the process unit 70 and the process unit drive device 100 are connected, and each photosensitive drum 36 can receive a rotational drive force from the process unit drive device 100. One end (rear end) of the drum shaft 76 of the photosensitive drum 36 and one end (front end) of the gear support shaft 108 of the drum drive gear 106 provided on the process unit drive device 100 come into contact with each other and are electrically connected. The specific configurations of the process unit 70 and the process unit drive device 100 will be described later.

The photoconductor drum 36 is an image carrier in which a photosensitive layer is formed on the surface of a cylindrical conductive base 74, and the charger 40 is a member that charges the surface of the photoconductor drum 36 to a predetermined potential. The exposure unit 32 is configured as a laser scanning unit (LSU) equipped with a laser emission section and a reflecting mirror, etc., and exposes the charged surface of the photoconductor drum 36 to light, thereby forming an electrostatic latent image on the surface of the photoconductor drum 36 according to the image data. The developer 34 visualizes the electrostatic latent image formed on the surface of the photoconductor drum 36 with four color (YMCK) toners. The cleaner unit 38 is equipped with a cleaning blade, etc., and removes foreign matter such as toner remaining on the surface of the photoconductor drum 36.

The intermediate transfer belt unit 42 includes an intermediate transfer belt 54, a drive roller 56, a driven roller 58, and four intermediate transfer rollers 60, and is disposed above the photosensitive drums 36. The intermediate transfer belt 54 is disposed so as to contact each photosensitive drum 36, and the intermediate transfer rollers 60 are used to transfer the toner images of each color formed on each photosensitive drum 36 to the intermediate transfer belt 54 in a sequentially overlapping manner, thereby forming a multi-color toner image on the intermediate transfer belt 54. In addition, a secondary transfer roller 44 is disposed near the drive roller 56, and the toner image formed on the intermediate transfer belt 54 is transferred to the paper by the paper passing through the nip area between the intermediate transfer belt 54 and the secondary transfer roller 44.

The fixing unit 46 includes a heat roller 62 and a pressure roller 64, and is disposed above the secondary transfer roller 44. The heat roller 62 is set to a predetermined fixing temperature, and when the paper passes through the nip area between the heat roller 62 and the pressure roller 64, the toner image transferred to the paper is melted, mixed, and pressed against the paper, thereby thermally fixing the toner image to the paper.

In the device main body 12, a first paper transport path L1 is formed for sending paper from the paper feed tray 48 or manual paper feed tray 50 to the paper output tray 52 via the registration rollers 68, secondary transfer roller 44, and fixing unit 46. In addition, when performing double-sided printing on the paper, a second paper transport path L2 is formed for returning the paper after single-sided printing is completed and the paper has passed through the fixing unit 46 to the first paper transport path L1 upstream of the secondary transfer roller 44 in the paper transport direction. In the first paper transport path L1 and the second paper transport path L2, a plurality of transport rollers 66 for applying a propulsive force to the paper are appropriately provided.

When performing single-sided printing (image formation) in the device main body 12, the paper is guided one by one by the paper feed tray 48 or manual paper feed tray 50 to the first paper transport path L1, and is transported by the transport roller 66 to the registration roller 68. The paper is then transported by the registration roller 68 to the secondary transfer roller 44 at a timing when the leading edge of the paper and the leading edge of the image information on the intermediate transfer belt 54 are aligned, and the toner image is transferred onto the paper. The paper then passes through the fixing unit 46, where the unfixed toner on the paper is melted and fixed by heat, and the paper is discharged onto the paper output tray 52.

On the other hand, when double-sided printing is performed, when the rear end of the paper that has passed through the fixing unit 46 after single-sided printing has been completed reaches the transport rollers 66 near the paper output tray 52, the transport rollers 66 are rotated in reverse, causing the paper to run in the opposite direction and be guided to the second paper transport path L2. The paper that has been guided to the second paper transport path L2 is then transported along the second paper transport path L2 and is guided to the first paper transport path L1 upstream of the registration rollers 68 in the paper transport direction. At this point, the front and back of the paper are inverted, and the paper then passes through the secondary transfer rollers 44 and the fixing unit 46, allowing printing to be performed on the back of the paper.

Next, the configuration of the process unit 70 will be described with reference to Figures 2 to 5. As shown in Figures 2 and 3, the process unit 70 includes a photosensitive drum 36, a cleaner unit 38, and a charger 40, which are integrally held in a predetermined arrangement by a process unit frame 72. The process unit 70 is detachable from the front side of the device body 12, and is attached to or detached from the device body 12 by sliding it in the depth direction (front-to-back direction) of the device body 12.

As shown in FIG. 4, the photosensitive drum 36 comprises a cylindrical base 74 with a photosensitive layer formed on its surface, and a metallic (i.e. conductive) drum shaft 76 that passes through the axial center of the base 74. Both ends of the drum shaft 76 are rotatably supported by first bearings 78 provided in the process unit frame 72, and the base 74 rotates in conjunction with the rotation of the drum shaft 76.

A photoconductor coupling 80 having external teeth is provided on the outer surface of the rear end of the drum shaft 76. The photoconductor coupling 80 is detachably engaged (connected) with a drive coupling 124 of the drum drive gear 106 described later, and transmits the rotational drive force of the drum drive gear 106 to the photoconductor drum 36. A second bearing 82 is provided between the first bearing 78 and the photoconductor coupling 80 on the outer surface of the rear end of the drum shaft 76. When the process unit 70 is attached to the device body 12, the second bearing 82 is fitted into a drum positioning portion 150 formed in a support holder 110 described later, and is used together with the drum positioning portion 150 to position the process unit 70 (centering the photoconductor drum 36).

In this first embodiment, a first connection portion 84 is formed on the rear end portion of the drum shaft 76 (the end surface on the gear support shaft 108 side), which is a connection portion with the gear support shaft 108. As can be clearly seen from FIG. 5, the first connection portion 84 includes a recess 86, a line contact portion 88, and a guide portion 90. The specific configuration of these will be described later.

Next, the configuration of the process unit drive device 100 will be described with reference to Figures 6 to 9. As shown in Figures 6 to 8, the process unit drive device 100 includes a drive device frame 102, a drive motor 104, a drum drive gear 106, a gear spindle 108, and a support holder 110. As described above, the process unit drive device 100 is fixedly mounted to the side wall on the rear side of the device main body 12, and applies a rotational drive force to each photosensitive drum 36. For this reason, four drum drive gears 106, four gear spindles 108, and four support holders 110 are provided corresponding to the four photosensitive drums 36 (process units 70), and are held in a predetermined arrangement by the drive device frame 102. However, only three of them are shown in Figure 6.

The drive unit frame 102 is made of metal and includes an outer plate 102a that is placed on the rear side, and an inner plate 102b that is placed a predetermined distance in front of the outer plate 102a.

A drive motor 104 is provided on the rear side of the outer plate 102a. The motor shaft of the drive motor 104 is provided so as to protrude forward from the outer plate 102a. In addition, a gear train including a gear portion 122 of the drum drive gear 106 and an idle gear (not shown), which will be described later, is housed between the outer plate 102a and the inner plate 102b. The rotational drive force from the drive motor 104 is transmitted to the drum drive gear 106 via an appropriate idle gear, and is transmitted from this drum drive gear 106 to the drum shaft 76 of the photosensitive drum 36 via a coupling (drive coupling 124 and photosensitive coupling 80).

The drum drive gear 106 includes a boss portion 120, a gear portion 122, and a drive coupling 124, which are integrally molded from synthetic resin or the like. The boss portion 120 is formed in a substantially cylindrical shape, and a disk-shaped gear portion 122 is formed at its base portion (rear end portion). Although not shown in the figure, external teeth are formed on the outer circumferential surface of the gear portion 122. In addition, a drive coupling 124 having internal teeth is formed at the tip portion (front end portion) of the boss portion 120. As described above, the drive coupling 124 is detachably fitted to the photoconductor coupling 80 attached to the drum shaft 76 of the photoconductor drum 36.

The boss portion 120 of the drum drive gear 106 is formed with a shaft hole 126, which is a cylindrical space that opens toward the rear. The gear support shaft 108 is inserted into this shaft hole 126 via the boss member 112, so that the drum drive gear 106 is rotatably supported relative to the gear support shaft 108.

The gear shaft 108 is a rod-shaped (approximately cylindrical) metallic (i.e. conductive) shaft member, and is arranged coaxially with the drum shaft 76 of the photosensitive drum 36. The gear shaft 108 is attached to the outer plate 102a in a non-rotatable state in which its rotation is restricted by a fixed holder 114. A boss member 112 is provided at the center of the gear shaft 108, and the drum drive gear 106 is attached to the boss member 112. A first stop member 130 is attached to the rear end of the gear shaft 108, and the first stop member 130 is engaged with the rear end surface of the fixed holder 114 to restrict the forward movement of the gear shaft 108. Furthermore, a second stop member 132 is attached to the gear shaft 108 at a position forward of the boss member 112. On the other hand, a spring stop portion 134 is formed at the front end of the boss member 112. A compression coil spring 136, which is an example of a biasing member, is provided so as to be sandwiched between the second anti-slip member 132 and the spring locking portion 134. This compression coil spring 136 restricts the rearward movement of the gear support shaft 108, and as described below, the gear support shaft 108 is pushed rearward by the drum shaft 76, so that the drum shaft 76 and the gear support shaft 108 come into contact with each other at a predetermined pressure.

In this first embodiment, the front end of the gear support shaft 108 is in axial contact with the rear end of the drum shaft 76 at a predetermined pressure, and is electrically connected to the rear end, so that the gear support shaft 108 is also used as a contact terminal for earthing the photosensitive drum 36. As can be clearly seen from FIG. 9, a second connection portion 140, which is a connection portion with the drum shaft 76, is formed at the front end of the gear support shaft 108 (the end surface on the drum shaft 76 side). The second connection portion 140 includes a tapered portion 142 and a groove portion 144. The specific configuration of these will be described later.

Returning to FIG. 6, the drum drive gear 106 described above is arranged so that the rear portion including the gear portion 122 is housed between the outer plate 102a and the inner plate 102b, and the front portion including the drive coupling 124 protrudes forward from the inner plate 102b. A support holder 110 is provided on the inner plate 102b so as to cover the protruding portion of the drum drive gear 106 from the inner plate 102b.

The support holder 110 is a holding member for positioning the photosensitive drum 36, and is formed of, for example, synthetic resin. The support holder 110 has a cylindrical drum positioning portion 150 that is concentric with the axial center of the gear support shaft 108 (i.e., the axial center of the drum drive gear 106). The support holder 110 rotatably supports the rear end of the drum shaft 76 of the photosensitive drum 36 at this drum positioning portion 150 via the second bearing 82 (see FIG. 10). This positions the photosensitive drum 36 (and therefore the entire process unit 70), and properly centers the drum drive gear 106 and the drum shaft 76 of the photosensitive drum 36.

In the image forming apparatus 10 as described above, when the process unit 70 is attached to the apparatus body 12, the process unit drive device 100 and the process unit 70 are connected as shown in FIG. 10. Specifically, the photosensitive coupling 80 is fitted into the drive coupling 124, and the second bearing 82 attached to the drum shaft 76 of the photosensitive drum 36 is fitted into the drum positioning portion 150 of the support holder 110, so that the photosensitive drum 36 is positioned by the support holder 110 and the second bearing 82. Then, the rotational driving force from the drive motor 104 is transmitted to the drum shaft 76 of the photosensitive drum 36 via the drum drive gear 106, so that the photosensitive drum 36 is rotated in a predetermined direction.

Furthermore, when the process unit 70 is attached to the device main body 12, the gear support shaft 108 is pushed rearward by the drum shaft 76, causing the gear support shaft 108 to move rearward slightly and compressing the compression coil spring 136. Then, with the gear support shaft 108 biased toward the drum shaft 76 by the compression coil spring 136, the rear end (first connection portion 84) of the drum shaft 76 and the front end (second connection portion 140) of the gear support shaft 108 come into contact with each other in the axial direction at a predetermined pressure and are electrically connected (i.e., the contact conduction mechanism 200 is connected).

Here, if the end faces of the drum shaft 76 and the gear support shaft 108 are simply butted together to make surface contact, it is difficult to increase the contact pressure, and so there is a risk of the electrical continuity becoming unstable. Furthermore, if the tip of the gear support shaft 108 is tapered to increase the contact pressure, even the slightest deviation from the axial center of the drum shaft 76 and the gear support shaft 108 will cause the drum shaft 76 and the gear support shaft 108 (drum drive gear 106) to dance, causing the rotation of the drum shaft 76 to become unstable.

In this first embodiment, a recess 86 is formed at the rear end of the drum shaft 76, and a tapered portion 142 formed at the front end of the gear support shaft 108 is fitted into this recess 86 to ensure rotational stability of the drum shaft 76, while the tapered portion 142 is brought into line contact with the recess 86 (specifically, the line contact portion 88) to ensure contact pressure and stabilize conduction. Below, the contact conduction mechanism 200 consisting of the first connection portion 84 and the second connection portion 140 will be specifically described with reference to Figures 5 and 8 to 11.

As shown in FIG. 5, a first connection portion 84 is formed at the rear end of the drum shaft 76. The first connection portion 84 includes a cylindrical recess 86. The recess 86 is a portion that receives the tip end of the tapered portion 142 of the gear support shaft 108, and has a diameter that is larger than the base end of the tapered portion 142 and smaller than the tip end of the tapered portion 142. An annular line contact portion 88 that makes line contact with the outer surface of the tapered portion 142 is formed at the opening edge of this recess 86.

In addition, a guide portion 90 is formed at the rear end of the drum shaft 76, closer to the tip side (toward the gear support shaft 108) than the recess 86. The guide portion 90 is a truncated cone-shaped hole whose diameter increases toward the tip side, and guides the tapered portion 142 of the gear support shaft 108 to the recess 86. The inclination angle α of the guide portion 90 with respect to the axial direction of the drum shaft 76 and the gear support shaft 108 is set to be larger than the inclination angle β of the tapered portion 142 (see FIG. 9). This is to prevent the guide portion 90 from contacting the tapered portion 142 when the contact conduction mechanism 200 is connected. The inclination angle α of the guide portion 90 is, for example, 45 degrees, and the inclination angle β of the tapered portion 142 is, for example, 30 degrees.

On the other hand, as shown in Figures 8 and 9, a second connection portion 140 is formed at the front end of the gear support shaft 108. The second connection portion 140 includes a tapered portion 142 that becomes smaller in diameter (i.e., has a tapered shape) toward the tip side (the drum shaft 76 side).

A groove 144 is formed on the outer surface of the tapered portion 142, extending in a direction intersecting the line contact portion 88 of the drum shaft 76. The groove 144 is formed so as to extend from the front end of the gear support shaft 108 across the line contact portion 88 of the drum shaft 76 to the axial center of the tapered portion 142 (see FIG. 11). In this first embodiment, two grooves 144 are formed at 180 degree intervals, and the two grooves 144 are connected to each other in the radial direction of the gear support shaft 108. However, the number of grooves 144 can be changed as appropriate, and when multiple grooves 144 are formed, it is not necessary to connect the grooves 144 to each other. In addition, although not shown, conductive grease (lubricant) is applied to the outer surface of the tapered portion 142, and the grease is stored in the grooves 144.

As shown in Figures 10 and 11, when the process unit 70 is attached to the device body 12 and the contact conduction mechanism 200 is connected, the tapered portion 142 of the gear support shaft 108 is guided into the recess 86 by the guide portion 90 of the drum shaft 76. This ensures that the line contact portion 88 of the drum shaft 76 and the tapered portion 142 of the gear support shaft 108 are in contact with each other.

In addition, when the contact conduction mechanism 200 is connected, the line contact portion 88 of the drum shaft 76 and the tapered portion 142 of the gear support shaft 108 are in line contact. This makes it possible to increase the contact pressure between the line contact portion 88 and the tapered portion 142, thereby stabilizing the conduction between the drum shaft 76 and the gear support shaft 108. It also reduces the risk of foreign matter getting caught between them. In other words, by making line contact between the line contact portion 88 and the tapered portion 142 (i.e., reducing the contact area), foreign matter is less likely to get caught between them, and even if foreign matter does get caught, it is less likely to remain between them (it is more likely to be pushed out and removed).

Furthermore, by storing grease in the groove portion 144, it is possible to supply (apply) grease from the groove portion 144 to the line contact portion 88 of the drum shaft 76, thereby making the electrical continuity more stable.

As described above, according to the first embodiment, the line contact portion 88 of the drum shaft 76 and the tapered portion 142 of the gear support shaft 108 are brought into line contact with each other, so that the contact pressure between them can be increased and the risk of foreign matter getting caught between them can be reduced. Therefore, the electrical connection between the drum shaft 76 and the gear support shaft 108 can be stabilized, and the charge remaining on the photosensitive drum 36 can be appropriately released to the device main body 12.

[Second embodiment]
Next, an image forming apparatus 10 according to a second embodiment of the present invention will be described with reference to Fig. 12. In this second embodiment, the configuration of the first connecting portion 84 of the drum shaft 76 is different from that of the first embodiment. Since the other parts are similar, the description that overlaps with the first embodiment will be omitted or simplified.

To put it simply, in the second embodiment, the first connection portion 84 of the drum shaft 76 does not include a guide portion 90. In other words, the rear end portion of the drum shaft 76 does not have a guide portion 90.

In this second embodiment, as in the first embodiment, the line contact portion 88 of the drum shaft 76 and the tapered portion 142 of the gear support shaft 108 are in line contact, so that electrical conduction between the drum shaft 76 and the gear support shaft 108 can be stabilized.

In each of the above-mentioned embodiments, the gear support shaft 108 itself is used as the contact terminal, but a rod-shaped contact terminal may be provided as a separate member at the front end of the gear support shaft 108.

In addition, in each of the above-described embodiments, the image forming device 10 is exemplified as a multifunction device that combines a copier, a facsimile, a printer, etc., but the image forming device 10 may be any one of a copier, a facsimile, a printer, etc., or a multifunction device that combines at least two of these.

Furthermore, in each of the above-described embodiments, the contact conduction mechanism 200 is applied to the drum shaft 76 of the photosensitive drum 36, but the contact conduction mechanism 200 can also be applied to other contact conduction parts of the image forming device 10. For example, the contact conduction mechanism 200 can also be applied to the contact conduction part of the secondary transfer roller 44 or the registration roller 68. The contact conduction mechanism 200 can also be applied to a contact conduction part provided in a device other than the image forming device 10.

Furthermore, the specific numerical values and part shapes given above are merely examples and can be changed as necessary according to the product specifications, etc.

REFERENCE SIGNS LIST 10 image forming apparatus 12 apparatus main body 14 image reading apparatus 30 image forming section 36 photosensitive drum 70 process unit 76 drum shaft (rotating shaft)
86: Recess 88: Line contact portion 90: Guide portion 100: Process unit drive device 106: Drum drive gear 108: Gear support shaft (contact terminal)
142 ... Tapered portion 144 ... Groove portion 200 ... Contact conduction mechanism

Claims (5)

A contact and conduction mechanism that electrically connects a rotatably provided rotating shaft and a rod-shaped contact terminal that is non-rotatably provided coaxially with the rotating shaft by contacting them with a predetermined pressure in the axial direction,
a tapered portion formed at one end of the contact terminal and having a diameter decreasing toward a tip end;
a recess formed at one end of the rotating shaft and configured to receive a tip end of the tapered portion ;
a line contact portion formed on an opening edge portion of the recess and in line contact with an outer surface of the tapered portion ;
a contact conduction mechanism including a groove formed on an outer surface of the tapered portion and extending in a direction intersecting the line contact portion so as to straddle the line contact portion ; 2. The contact and conduction mechanism according to claim 1 , further comprising a guide portion formed on one end of the rotating shaft on the tip side of the recess, the guide portion having a diameter increasing toward the tip side. A contact and conduction mechanism that electrically connects a rotatably provided rotating shaft and a rod-shaped contact terminal that is non-rotatably provided coaxially with the rotating shaft by contacting them with a predetermined pressure in the axial direction,
a tapered portion formed at one end of the contact terminal and having a diameter decreasing toward a tip end;
a recess formed at one end of the rotating shaft and configured to receive a tip end of the tapered portion;
a line contact portion formed on an opening edge portion of the recess and in line contact with an outer surface of the tapered portion;
a guide portion that is formed on one end of the rotating shaft on the tip side of the recess and that increases in diameter toward the tip side,
A contact and conduction mechanism, wherein an inclination angle of the guide portion with respect to an axial direction of the rotation shaft is larger than an inclination angle of the tapered portion with respect to the axial direction of the contact terminal. An image forming apparatus equipped with a contact conduction mechanism according to any one of claims 1 to 3. The image forming device according to claim 4, wherein the rotation shaft is the shaft of a photosensitive drum.

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