Screw fastening mechanism, drive transmission device, and image forming apparatus

Abstract

To prevent a screw fitting part from being damaged by stress generated by a screw part of a screw.SOLUTION: In a screw fastening mechanism 55, a screw part 51b of a screw 54 is fitted into a screw fitting part 54a of a first component 51, and a first surface of the first component and a second surface of a second component 52 are brought into contact with each other to screw fasten the first component and the second component. The screw fitting part of the first component is formed of a material in which chemical attack is caused by an adhesion liquid G adhering to the screw fastening mechanism, and gaps g1 and g2 where the first surface and the second surface are separated from each other are formed in a region closer to the screw fitting part than a contact region S between the first surface and the second surface so as to surround the screw fitting part.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a screw fastening mechanism, a drive transmission device, and an image forming apparatus. [Background technology]

[0002] Conventionally, there has been known a screw fastening mechanism in which a threaded portion of a screw is fitted into a threaded fitting portion of a first part, and a first surface of the first part and a second surface of a second part are brought into contact with each other, thereby fastening the first part and the second part together with the screw.

[0003] Patent Document 1 discloses a screw fastening mechanism in which a threaded portion of a screw inserted into a through hole in a glass substrate (second component) is screwed into a screw hole (screw-receiving portion) in a support (first component) to fasten the support and the glass substrate together. In this mechanism, a step portion is provided along the outer edge of the area surrounding the through hole in the glass substrate to prevent damage such as cracks and breaks in the glass substrate caused by stress generated near the through hole in the glass substrate due to the fastening of the screw from spreading. In this mechanism, when damage occurs in the area around the through hole in the glass substrate and the damage extends to the step portion at the outer edge of the area, the extension is stopped (terminated) at the step portion, preventing the damage from extending outside the area. Summary of the Invention [Problem to be solved by the invention]

[0004] However, when conventional screw fastening mechanisms are used in locations where liquids that cause chemical attacks adhere to the threaded engagement portion, the liquid can deteriorate the threaded engagement portion and cause damage such as cracks and breaks in the threaded engagement portion. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the present invention provides a screw fastening mechanism in which the threaded portion of a screw is fitted into the screw fitting portion of a first part, bringing a first surface of the first part into contact with a second surface of a second part, thereby screwing together the first part and the second part, wherein the screw fitting portion of the first part is formed from a material that is chemically attacked by an adhesive liquid that adheres to the screw fastening mechanism, and a gap that separates the first surface and the second surface is formed surrounding the screw fitting portion in an area closer to the screw fitting portion than the area of ​​contact between the first surface and the second surface. [Effects of the Invention]

[0006] According to the present invention, it is possible to suppress damage to the screw-fitting portion caused by chemical attack by the adhering liquid adhering to the screw fastening mechanism. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of a copying machine according to an embodiment. [Figure 2] A schematic diagram of the ADF in the same copier. [Figure 3] Block diagram of the ADF control system. [Figure 4] FIG. 2 is a schematic diagram of the document setting section of the ADF. [Figure 5] FIG. [Figure 6] 4 is a perspective view showing a drive device for lifting the bottom plate including a bottom plate lifting motor in the document setting unit of FIG. [Figure 7] FIG. 2 is a perspective view showing the internal structure of the drive device. [Figure 8] 4 is a cross-sectional view showing a screw fastening mechanism that fastens a case and a cover member together with screws in the drive device. FIG. [Figure 9] FIG. 10 is a cross-sectional view showing a modified example of the screw fastening mechanism. [Figure 10] 10A is a top view showing a case of a screw fastening mechanism according to another modified example, and FIG. 10B is a cross-sectional view showing the screw fastening mechanism. [Figure 11]FIG. 10 is a cross-sectional view showing still another modified example of the screw fastening mechanism. DETAILED DESCRIPTION OF THE INVENTION

[0008] BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below with reference to the drawings. It is to be noted that it is easy for a person skilled in the art to modify or alter the present invention within the scope of the claims to create other embodiments, and these modifications and alterations are included in the scope of the claims. The following description is an example of the best mode of the present invention and does not limit the scope of the claims.

[0009] FIG. 1 is a schematic diagram of a copying machine as an image forming apparatus according to an embodiment. As shown in FIG. 1, the copying machine 1 includes an automatic document feeder (ADF) 100, a paper feed unit 2 serving as a feeding device, and an image forming unit 3.

[0010] The paper feed section 2 has feed cassettes 21 and 22 that store transfer paper (paper) of different sizes as recording materials, and a feed means 23 consisting of various rollers that transport the transfer paper stored in the feed cassettes 21 and 22 to the image forming section 3.

[0011] The image forming unit 3 includes an exposure device 31, photosensitive drums 32 for each of four colors, a developing device 33, a transfer belt 34, and a fixing device 35. In the image forming unit 3, the exposure device 31 exposes each photosensitive drum 32 to light based on image data of a document read by the image reading unit of the ADF 100, forming a latent image of each color on each photosensitive drum 32. The developing device 33 for each color then supplies toner of each color to each photosensitive drum 32, and develops the latent image on each photosensitive drum 32 to form a toner image. The image forming unit 3 then transfers the toner image on each photosensitive drum 32 to recording paper supplied from the paper feed unit 2 using the transfer belt 34, and then the fixing device 35 melts the toner of the toner image transferred to the recording paper to fix the color image on the recording paper.

[0012] FIG. 2 is a schematic diagram of an automatic document feeder (ADF) 100 having a function as an image reading device, and FIG. 3 is a block diagram of a control system of the ADF 100. As shown in FIG. As shown in FIG. 2, the ADF 100 includes a document setting section A where a stack of documents is set, a separation and feeding section B that separates and feeds each document from the set document stack, and a registration section C that performs primary abutment alignment on the fed documents and pulls out and transports the aligned documents.

[0013] The ADF 100 also has a turning unit D that turns the transported document and transports the document surface toward the reading side (downward in the figure) by the first image reading unit 131. The ADF 100 also has a first reading and transporting unit E that reads the front surface image of the document from below the contact glass by the first image reading unit 131.

[0014] The ADF 100 also includes a second reading and conveying section F that reads the image on the back side of the document using the second image reading section 135 after the image on the front side has been read, a paper discharge section G that discharges the document outside the machine after the images on the front and back sides have been read, and a stack section H that holds and stacks the discharged documents.

[0015] 3, the ADF 100 includes motors 101 to 105 that drive the above-mentioned components, and a controller 150 that controls a series of operations. The controller 150 is connected via an I / F 107 to a main body control unit 10 that performs overall control of the copier 1. An operation unit 11 that allows a user to perform various operations is also connected to the main body control unit 10 via an I / F 106.

[0016] A document stack 110, which is a bundle of sheets to be read, is set in document setting section A. The document stack 110 is set on a document table 112 that includes a movable document table 111 as a sheet stacking section. The document stack 110 is set on the document table 112 with the document surface facing upward. At this time, the width direction of the document stack 110 is positioned by side fences 17 (see FIG. 5) in the sheet width direction, which is a direction perpendicular to the conveyance direction.

[0017] In addition, the setting of the document stack 110 is detected by a set filler 113 and a set sensor 114, and information indicating that the document stack 110 has been set is sent from the controller 150 to the main body control unit 10 via the I / F 107.

[0018] Furthermore, document length detection sensors 115 and 116 provided on the document table surface determine the approximate length of the document stack 110 in the transport direction. The document length detection sensors 115 and 116 may be, for example, reflective sensors or actuator-type sensors capable of detecting even a single document. The document length detection sensors 115 and 116 must be positioned so that they can at least determine whether the document is vertical or horizontal for the same document size.

[0019] 2 by a bottom plate lifting motor 105. When no document stack 110 is set on the document table 112, the movable document table 111 is in a lowered state, and this state is detected by a bottom plate HP sensor 117.

[0020] When the set filler 113 and the set sensor 114 detect that the document stack 110 has been set on the document table 112, the controller 150 raises the movable document table 111. Specifically, the bottom plate lifting motor 105 is rotated forward to raise the movable document table 111 so that the top surface of the document stack 110 comes into contact with the pickup roller 118 of the separation and feeding unit B.

[0021] 2 by the action of a cam mechanism driven by pickup motor 101. Also, when movable document table 111 rises and is pushed by the upper surface of document stack 110 on movable document table 111, pickup roller 118 rises in direction c in FIG. 2, and the upper limit can be detected by proper paper feed position sensor 119.

[0022] When the user presses the print key on the operation unit 11 and a document feed signal is sent from the main body control unit 10 to the controller 150 via the I / F 107, the pickup roller 118 is rotated by the forward rotation of the document feed motor 102. As the pickup roller 118 is rotated, it picks up several documents (ideally one document) on the document table 112. The rotation direction is the direction in which the top document is transported to the document feed slot.

[0023] The paper feed belt 120 is driven in the paper feed direction by the forward rotation of the paper feed motor 102. The reverse roller 121 is driven to rotate in the direction opposite to the paper feed direction by the forward rotation of the paper feed motor 102. This allows the topmost document to be separated from the documents below it, and only the topmost document can be fed.

[0024] To explain in more detail, the reverse roller 121 contacts the paper feed belt 120 with a predetermined pressure, and when it is in contact with the paper feed belt 120 directly or through a single document, it rotates counterclockwise in response to the rotation of the paper feed belt 120.

[0025] On the other hand, when two or more documents enter between the paper feed belt 120 and the reverse roller 121, the accompanying rotation force becomes less than the torque of the torque limiter. As a result, the reverse roller 121 rotates in the clockwise direction, which is its normal driving direction, and acts to push back the excess documents. This prevents double feeding of documents.

[0026] The document separated into one sheet by the action of the paper feed belt 120 and the reverse roller 121 is sent to the registration section C side by the paper feed belt 120, and after the leading edge is detected by the abutment sensor 122, it goes further and abuts against the stopped pull-out roller 123.

[0027] Thereafter, the document is fed a predetermined distance from the detection of abutment sensor 122, and when the document is pressed against pull-out roller 123 with a predetermined amount of deflection, paper feed motor 102 is stopped, thereby stopping the drive of paper feed belt 120. At this time, pickup motor 101 is rotated to move pickup roller 118 away from the top surface of the document, and the document is fed only by the conveying force of paper feed belt 120. As a result, the leading edge of the document enters the nip between the upper and lower roller pair of pull-out roller 123, and the leading edge is aligned (skew corrected).

[0028] The pull-out roller 123 has a skew correction function and is a roller for transporting the separated, skew-corrected document to the intermediate roller 124, and is driven by the reverse rotation of the paper feed motor 102. When the paper feed motor 102 is rotated in the reverse direction, the pull-out roller 123 and the intermediate roller 124 are driven, but the pickup roller 118 and the paper feed belt 120 are not driven.

[0029] 2, and detects the size of the document in the width direction perpendicular to the transport direction of the document transported by the pull-out rollers 123. The length of the document in the transport direction is detected from the motor pulses by reading the leading and trailing ends of the document with the abutment sensor 122.

[0030] When the document is transported from the registration section C to the turning section D by driving the pull-out roller 123 and the intermediate roller 124, the transport speed at the registration section C is set to be faster than the transport speed at the first reading transport section E. This makes it possible to shorten the processing time for sending the document to the image reading section.

[0031] When the leading edge of the document is detected by the reading entrance sensor 126, the document transport speed starts to be decelerated to be the same as the reading transport speed before the leading edge of the document enters the nip between the upper and lower roller pair of the reading entrance roller 127. At the same time, the reading motor 103 is driven in the forward direction to drive the reading entrance roller 127, the reading exit roller 128, and the CIS exit roller 129.

[0032] When the registration sensor 130 detects the leading edge of the document, the controller 150 reduces the transport speed of the document over a predetermined transport distance and temporarily stops the document just before the first image reading unit 131. The controller 150 also transmits a temporary stop signal to the main body control unit 10 via the I / F 107.

[0033] When a reading start signal is sent from the main body control unit 10 to the controller 150 via the I / F 107, the controller 150 accelerates the speed of the document that has been temporarily stopped so that the document reaches a predetermined conveying speed before the leading edge of the document reaches the position of the first image reading unit 131.

[0034] At this time, the position of the leading edge of the document is detected by counting pulses of the reading motor 103. Next, at the timing when the leading edge of the document reaches the first image reading unit 131, a gate signal indicating the effective image area in the sub-scanning direction (the same direction as the document transport direction) on the front side of the document is transmitted to the main body control unit 10. This gate signal is transmitted continuously until the rear end of the document leaves the first image reading unit 131. Then, while the document is transported by the drive of the reading entrance rollers 127 and the reading exit rollers 128, the image on the front side of the document is read by the first image reading unit 131.

[0035] In the case of single-sided document reading, the document, whose front side image has been read by first image reading unit 131 of first reading and conveying unit E, passes directly through second reading and conveying unit F and is conveyed to paper discharge unit G. At this time, when controller 150 detects the leading edge of the document with paper discharge sensor 132, controller 150 drives paper discharge motor 104 in the forward direction to rotate paper discharge roller 133 in the counterclockwise direction. Furthermore, based on the pulse count of paper discharge motor 104 from the detection of the leading edge of the document by paper discharge sensor 132, controller 150 detects the point immediately before the trailing edge of the document leaves the nip of the pair of upper and lower rollers of paper discharge roller 133. Then, just before the trailing edge of the document leaves the nip of the pair of upper and lower rollers of paper discharge roller 133, controller 150 decelerates the paper discharge motor drive speed to prevent the document from flying out when discharged onto paper discharge tray 134 of stack unit H.

[0036] On the other hand, when reading a double-sided document, the leading edge of the document is detected by the paper discharge sensor 132, and then the position of the leading edge of the document being conveyed is detected by counting pulses of the reading motor 103. Then, at the timing when the leading edge of the document reaches the position of the second image reading unit 135 of the second reading and conveying unit F, the controller 150 transmits a gate signal indicating the effective image area in the sub-scanning direction on the back side of the document to the second image reading unit 135. This gate signal is continuously transmitted until the trailing edge of the document leaves the second image reading unit 135.

[0037] Then, while the document is being transported by the drive of reading exit rollers 128 and CIS exit rollers 129, the image on the back side of the document is read by second image reading unit 135 using a document flow reading method (sheet-through reading). Note that second reading roller 136, which is disposed opposite second image reading unit 135, prevents the document from floating in second image reading unit 135 and also serves as a reference white area for acquiring shading data in second image reading unit 135.

[0038] Fig. 4 is a schematic diagram of the document setting unit A in this embodiment, and Fig. 5 is a perspective view of the main parts of the document setting unit A. Fig. 4(a) and Fig. 5(a) show a state in which the movable document table 111 is located at the lowest position, and Fig. 4(b) and Fig. 5(b) show a state in which the movable document table 111 is located at the highest position.

[0039] 5, a pair of side fences 17 are provided on the movable original table 111 so as to be movable in the width direction. The original MS set on the movable original table 111 is restricted in the width direction by the pair of side fences 17 so that the center of the original MS in the width direction is positioned at the center of the movable original table 111 in the width direction.

[0040] 4, the document setting unit A is provided with a lifting plate 140 that is rotatable about a rotation shaft 141 for raising and lowering the downstream end of the movable document table 111 in the transport direction. By rotating the bottom plate lifting motor 105 in the forward direction, the lifting plate 140 rotates clockwise in the figure about the rotation shaft 141 from the state shown in FIG. 4(a), and the movable document table 111 rotates clockwise in the figure. As a result, the downstream end of the movable document table 111 in the transport direction rises.

[0041] Furthermore, in this embodiment, a document pre-separator 152 is provided as an inclined surface that slopes upward from the top of document abutment surface 151 toward the downstream side in the document transport direction. Even if the leading edge of the top document of a document stack abuts against the inclined surface of document pre-separator 152, the document can easily climb up the inclined surface by the transport force of pickup roller 80. On the other hand, when the leading edge of the second or subsequent documents abuts against the inclined surface of document pre-separator 152, the force required to climb up this inclined surface exceeds the frictional force between the documents, so the documents can be separated.

[0042] In this embodiment, a friction plate 153 is provided in the widthwise center of the document pre-separator 152. This increases the force required to climb the inclined surface of the document pre-separator 152, thereby improving the separation ability of the document pre-separator 152.

[0043] In this embodiment, a relay member 40 is provided as a contact member that contacts the document abutment surface 151 at the center of the width direction of the downstream end of the movable document table 111 in the transport direction. The relay member 40 is attached to the movable document table 111 so as to be able to rotate freely.

[0044] 4(a), when the movable document table 111 is in the lowest position, the relay member 40 is in contact with the document abutment surface 151 in an inclined position such that the downstream end in the transport direction is positioned upward. This position allows the relay member 40 to come into contact with the document abutment surface 151 by its own weight.

[0045] The movable original table 111 is configured to rotate around its upstream end in the transport direction as a fulcrum, and the downstream end of the movable original table 111 in the transport direction moves up and down along an arc-shaped trajectory. Therefore, the gap between the original abutment surface 151 and the downstream end of the movable original table 111 in the transport direction changes as the table moves up and down.

[0046] In this embodiment, the relay member 40 is rotatably attached to the movable original table 111. As a result, even if the gap between the original abutment surface 151 and the downstream end of the movable original table 111 in the transport direction changes as the movable original table 111 is raised or lowered, the relay member 40 can rotate and maintain contact with the original abutment surface 151. Furthermore, by rotatably attaching the relay member 40 to the movable original table 111, an increase in the contact pressure with the original abutment surface 151 due to the rotation of the relay member 40 can be suppressed. This makes it possible to suppress an increase in the sliding resistance of the relay member 40 against the original abutment surface 151 when the movable original table 111 is raised or lowered. As a result, the movable original table 111 can be raised or lowered without any problems.

[0047] In this embodiment, the relay member 40 closes the gap between the downstream end of the movable document table 111 in the transport direction and the document abutment surface 151. This prevents the leading edge of the document from slipping into the gap between the movable document table 111 and the document abutment surface 151, thereby suppressing the occurrence of feeding failures.

[0048] FIG. 6 is a perspective view showing a drive device 50 for lifting the bottom plate including a bottom plate lifting motor 105 in this embodiment. FIG. 7 is a perspective view showing the internal structure of the drive device 50 for lifting the bottom plate.

[0049] The drive device 50 for lifting the bottom plate includes a case 51 as a first component made of a resin material, and a cover member 52 as a second component attached to the case 51. The case 51 houses a bottom plate lifting motor 105 and a drive transmission unit 53 including a plurality of gears that transmits the driving force of the bottom plate lifting motor 105. A rotating shaft 141 of the lifting plate 140 is connected to the output shaft of the drive transmission unit 53. As a result, when the bottom plate lifting motor 105 is rotated forward, the rotating shaft 141 rotates via the drive transmission unit 53, and accordingly, the lifting plate 140 rotates around the rotating shaft 141, lifting the downstream end of the movable document table 111 in the conveying direction.

[0050] FIG. 8 is a cross-sectional view showing a screw fastening mechanism 55 that fastens the case 51 and the cover member 52 of the drive device 50 together with the screw 54. As shown in FIG. The drive device 50 of this embodiment is provided with a screw fastening mechanism 55 that fastens the case 51 and the cover member 52 together with three screws 54. The screw fastening mechanism 55 for each screw 54 has a screw boss portion 51a formed at the fastening location where each screw 54 is fastened. The screw boss portion 51a is formed integrally with the case 51 made of a resin material, and has a screw hole 51b formed therein as a screw fitting portion into which the threaded portion 54a of the screw 54 is fitted.

[0051] Furthermore, the lid member 52, which is screwed to the case 51, has through holes 52a formed at fastening locations where the screws 54 are fastened, through which the threaded portions 54a of the screws 54 pass. With the lid member 52 set on the case 51, the threaded portions 54a of the screws 54 are fitted from the through holes 52a of the lid member 52 into the threaded holes 51b of the screw boss portions 51a of the case 51. In the screw fastening mechanism 55 of this embodiment, the screws 54 are self-tapping screws. Therefore, when the screws are fastened, the threaded portions 54a of the screws 54 are fitted into the threaded holes 51b while threading the inner walls of the threaded holes 51b of the screw boss portions 51a with the threaded portions 54a of the screws 54. Then, the screws 54 are fitted until the lid member 52 is sandwiched between the heads 54b of the screws 54 and the screw boss portions 51a of the case 51, thereby fastening the case 51 and the lid member 52 together with the screws.

[0052] In the drive unit 50 of this embodiment, grease or oil G is applied as a lubricant to each gear of the drive transmission unit 53. This grease G scatters around as the gears rotate. Therefore, to prevent the grease G from scattering outside the drive unit 50, the inside of the case 51 in which the gears are arranged is closed with a cover member 52.

[0053] Generally, in the screw fastening mechanism 55, when the threaded portion 54a of the screw 54 is fitted, stress is generated in the screw hole 51b of the screw boss portion 51a of the case 51 made of a resin material. This stress can cause damage such as cracks or breaks in the screw hole 51b of the screw boss portion 51a. In particular, in this embodiment, grease G (adherent liquid) used in the drive transmission unit 53 of the drive device 50 scatters and adheres to the screw fastening mechanism 55 of the drive device 50. If this grease G penetrates into the screw hole 51b of the screw boss portion 51a, the screw hole 51b of the screw boss portion 51a of the case 51 made of a resin material will be deteriorated by chemical attack. Therefore, in the screw fastening mechanism 55 of this embodiment, if the grease G penetrates into the screw hole 51b of the screw boss portion 51a, the stress from the threaded portion 54a of the screw 54 is likely to cause damage to the screw hole 51b of the screw boss portion 51a.

[0054] Here, in the screw fastening mechanism 55 of this embodiment, the upper surface 51c of the case 51 (first surface that is the surface on the lid member 52 side) and the lower surface 52b of the lid member 52 (second surface that is the surface on the case 51 side) are configured to abut against each other in an area S that surrounds the screw hole 51b of the screw boss portion 51a of the case 51. As a result, even if grease G that has scattered inside the case 51 adheres to the screw fastening mechanism 55, the grease G is prevented from penetrating into the screw hole 51b of the screw boss portion 51a.

[0055] However, as a result of research by the inventors, it was confirmed that even with this configuration, grease G moves by capillary action within contact area S between upper surface 51c of case 51 and lower surface 52b of lid member 52. Therefore, if contact area S continues to the opening edge of screw hole 51b, grease G that moves within contact area S by capillary action will seep out and penetrate into screw hole 51b, causing deterioration of the screw hole 51b portion of screw boss portion 51a made of a resin material due to chemical attack.

[0056] Therefore, in this embodiment, as shown in FIG. 8 , gaps g1 and g2 separating the upper surface of the case 51 and the lower surface of the lid member 52 are formed in a region closer to the screw hole 51b than the contact region S between the upper surface of the case 51 and the lower surface of the lid member 52, so as to surround the screw hole 51b. As a result, gaps g1 and g2 large enough to prevent capillary action are formed surrounding the screw hole 51b on the side closer to the screw hole 51b than the contact region S. As a result, the grease G that has moved within the contact region S by capillary action reaches the gaps g1 and g2 before reaching the screw hole 51b. Then, once the grease G reaches the gaps g1 and g2, it can no longer move further by capillary action, preventing the grease G from entering the screw hole 51b by capillary action. Therefore, it is possible to prevent the screw hole 51b of the screw boss portion 51a made of a resin material from being deteriorated by chemical attack by the grease G, and to prevent damage to the screw hole 51b of the screw boss portion 51a.

[0057] In particular, gaps g1 and g2 in this embodiment are formed by a separation portion of the upper surface of the case 51 that is shifted away from abutting portion 51c of the upper surface of the case 51 that abuts against the lower surface 52b of the cover member 52. This allows gaps g1 and g2 to be formed by processing the upper surface of screw boss portion 51a of case 51, which is made of an easily processable resin material, even if the lower surface 52b of the cover member 52 remains flat. This has the advantage of reducing manufacturing costs, particularly when cover member 52 is a non-resin product such as made of metal.

[0058] In this embodiment, as shown in Fig. 8, the gaps g1 and g2 are preferably formed closer to the screw hole 51b than the outer edge of the head 54b of the screw 54. If the gaps g1 and g2 were configured to extend outward beyond the outer edge of the head 54b of the screw 54, the cover member 52 would not be able to be sandwiched between the head 54b of the screw 54 and the top surface of the case 51, which could result in insufficient fastening force. Furthermore, if the screw 54 is overtightened in an attempt to increase the fastening force, the portion of the cover member 52 pressed by the head 54b of the screw 54 cannot be received by the top surface of the case 51, which could result in deformation of the cover member 52.

[0059] Furthermore, in this embodiment, gap g1 is configured as groove 51d, which is formed in a separated portion of the upper surface of case 51, which is separated from the lower surface of lid member 52, between a contact portion 51c of the upper surface of the case with the lower surface of the lid member and a surface portion of the upper surface of the case that is continuous with the opening edge of screw hole 51b (a surface portion corresponding to gap g2), so as to surround screw hole 51b. The presence of gap g1 formed by groove 51d makes it possible to store grease G that has migrated within contact region S by capillary action inside groove 51d. Therefore, even if a large amount of grease G has migrated within contact region S by capillary action, it can be captured inside groove 51d that forms gap g1, and the grease G can be prevented from penetrating into screw hole 51b.

[0060] In particular, if the groove 51d is formed downward in the direction of gravity, the grease G that has moved within the contact area S due to capillary action moves into the groove 51d due to its own weight. Therefore, more grease G can be captured inside the groove 51d, and the grease G can be prevented from penetrating into the screw hole 51b.

[0061] The region closer to the screw hole 51b than the groove 51d can be the contact region where the upper surface of the case 51 and the lower surface of the cover member 52 contact each other, because the groove 51d that forms the gap g1 prevents the grease G from entering the screw hole 51b. However, if more grease G enters than can be captured inside the groove 51d, the grease G may exceed the groove 51d and move by capillary action through the contact region closer to the screw hole 51b than the groove 51d, potentially reaching the screw hole 51b.

[0062] In this embodiment, in anticipation of such a case, in addition to the gap g1 formed by the groove 51d, a gap g2 formed by a recess 51e continuing to the opening edge of the screw hole 51b is formed on the side closer to the screw hole 51b than the groove 51d so as to surround the screw hole 51b. This prevents the grease G from moving to the screw hole 51b by capillary action even if the grease G exceeds the groove 51d, thereby preventing the grease G from reaching the screw hole 51b.

[0063] 9, the gap g1 formed by the groove 51d may be omitted, and only the gap g2 formed by the recess 51e continuing to the opening edge of the screw hole 51b may be formed to surround the screw hole 51b. Even in this configuration, the grease G that has moved within the contact region S by capillary action reaches the gap g2, and is no longer able to move further by capillary action, thereby preventing the grease G from penetrating into the screw hole 51b.

[0064] 10(a) and 10(b), the screw boss portion 51a of the case 51 may be formed with a communication passage 51f that connects the gap g2 defined by the groove 51d to the outside of the contact area S in the contact area S between the upper surface of the case 51 and the lower surface of the lid member 52. This allows the grease G stored inside the groove 51d to be discharged to the outside through the communication passage 51f. Therefore, even if a large amount of grease G reaches the groove 51d, the grease G can be prevented from moving beyond the groove 51d toward the screw hole 51b.

[0065] In this case, if a difference in elevation occurs inside groove 51d when drive device 50 is in use, communicating passage 51f is preferably configured to extend downward in the direction of gravity from gap g2 defined by groove 51d toward the outside. For example, if screw fastening mechanism 55 is in the state shown in Fig. 11 when drive device 50 is in use, communicating passage 51f is configured to extend downward in the direction of gravity from gap g2 defined by groove 51d toward the outside. With this configuration, grease G stored inside groove 51d is discharged to the outside from communicating passage 51f due to its own weight.

[0066] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and unless otherwise specifically limited in the above description, various modifications and variations are possible within the spirit and scope of the present invention as set forth in the claims.

[0067] For example, in this embodiment, the screw fastening mechanism 55 in the drive device 50 that drives the movable document table 111 of the ADF 100 has been described as an example, but it is also applicable to the screw fastening mechanism of other drive devices (drive transmission devices) in the ADF 100 or the copier 1. Furthermore, the screw fastening mechanism of this embodiment is applicable to screw fastening mechanisms of all kinds of devices, including home appliances, in addition to image forming devices and image reading devices.

[0068] The above description is merely an example, and each of the following aspects provides unique effects. [First aspect] The first aspect is a screw fastening mechanism 55 in which a first component (e.g., a case 51) has a threaded portion 54a of a screw 54 fitted into a threaded portion (e.g., a screw hole 51b) thereof, and a first surface (e.g., an upper surface of the case) of the first component is brought into contact with a second surface (e.g., a lower surface of the lid component) of a second component (e.g., a lid component 52), thereby screwing the first component and the second component together. The screw fastening mechanism 55 is characterized in that the screw fastening portion of the first component is formed from a material (e.g., a resin) that is chemically attacked by an adhesive liquid (e.g., grease G) that adheres to the screw fastening mechanism, and gaps g1 and g2 that separate the first surface and the second surface are formed so as to surround the screw fastening portion in an area closer to the screw fastening portion than the contact area S between the first surface and the second surface. In this type of screw fastening mechanism, stress generated by the threaded portion of the screw fitted into the screw-fitting portion of the first component can cause damage such as cracks and breaks in the screw-fitting portion. Furthermore, research by the inventors has revealed that if a liquid (adherent liquid) that deteriorates the screw-fitting portion through chemical attack adheres to the screw fastening mechanism, the screw-fitting portion can be deteriorated by the adhering liquid, and the thread-fitting portion can be damaged by stress generated by the threaded portion of the screw. For example, if a lubricant used in gears of a drive transmission device adheres to the screw fastening mechanism of the drive transmission device, and the screw-fitting portion of the first component is made of a resin or other material that is chemically attacked by the lubricant, the screw-fitting portion can be damaged. Specifically, in a typical screw fastening mechanism in which a first surface of a first component and a second surface of a second component abut in a region surrounding the thread-engaging portion of the first component, it was thought that the infiltration of adhering liquid from the outside into the thread-engaging portion would be suppressed. However, the present inventor confirmed that even in a configuration in which the abutment region between the first and second surfaces surrounds the periphery of the thread-engaging portion, adhering liquid moves within the abutment region due to capillary action and seeps into the thread-engaging portion. Therefore, in this aspect, a gap separating the first surface of the first component and the second surface of the second component is formed in a region closer to the thread-engaging portion than the contact region between these surfaces, surrounding the thread-engaging portion. This creates a gap that prevents capillary action from occurring, surrounding the thread-engaging portion, on the side closer to the thread-engaging portion than the contact region. As a result, the liquid that has migrated within the contact region by capillary action reaches the gap before reaching the thread-engaging portion. Once the liquid reaches the gap, it can no longer move by capillary action, preventing the liquid from penetrating into the thread-engaging portion due to capillary action. As described above, according to this aspect, even if the adhering liquid moves by capillary action within the contact area between the first surface of the first component and the second surface of the second component that surround the periphery of the threaded portion, the adhering liquid can be prevented from penetrating into the threaded portion. Therefore, the threaded portion of the first component can be prevented from being deteriorated by chemical attack by the adhering liquid, and therefore damage to the threaded portion caused by chemical attack by the adhering liquid adhering to the screw fastening mechanism can be prevented.

[0069] [Second mode] The second aspect is characterized in that, in the first aspect, the gap is formed by a separation portion of the first surface (e.g., groove 51d, recess 51e) that is shifted in a direction away from the second surface relative to the abutment portion 51c of the first surface that abuts against the second surface. This makes it easier to obtain the benefit of reduced manufacturing costs.

[0070] [Third aspect] The third aspect is characterized in that, in the second aspect, the separation portion on the first surface is a groove 51d formed to surround the screw fitting portion between the abutment portion of the first surface and a surface portion of the first surface that is continuous with the opening edge portion of the screw fitting portion. With this, even if a large amount of adhering liquid moves within the contact area S due to capillary action, the adhering liquid can be captured inside the groove 51d, and the adhering liquid can be prevented from penetrating into the screw fitting portion.

[0071] [Fourth aspect] The fourth aspect is characterized in that in the second aspect, the separated portion on the first surface is composed of a recess 51e that is continuous with the opening edge of the screw fitting portion so as to surround the screw fitting portion, and a groove 51d that is formed between the recess and the abutment portion of the first surface so as to surround the screw fitting portion. According to this, even if the adhering liquid exceeds the groove 51d, the recess 51e can prevent the adhering liquid from moving to the screw fitting portion by capillary action, so that the adhering liquid can be prevented from reaching the screw fitting portion.

[0072] [Fifth mode] A fifth aspect is the third or fourth aspect, characterized in that the groove is formed downward in the direction of gravity. This allows the adhering liquid that has moved within the contact area S due to capillary action to move into the interior of the groove 51d due to its own weight, so that more of the adhering liquid can be captured inside the groove 51d, and the adhering liquid can be prevented from penetrating into the screw insertion portion.

[0073] [Sixth aspect] A sixth aspect is the second aspect, wherein the separated portion on the first surface is a recess 51e that is continuous with the opening edge of the screw fitting portion so as to surround the screw fitting portion. This makes it possible to prevent the adhering liquid that has moved within the contact area S due to capillary action from infiltrating into the screw fitting portion with a simpler configuration.

[0074] [Seventh aspect] The seventh aspect is characterized in that, in any of the first to sixth aspects, a communication passage 51f is formed in the contact area S between the first surface and the second surface, connecting the gap to the outside of the contact area. This makes it possible to discharge the adhering liquid that has entered the gap to the outside through the communicating passage, so that even if a large amount of adhering liquid reaches the gap, the adhering liquid can be prevented from moving beyond the gap to the screw fitting portion.

[0075] [Eighth aspect] An eighth aspect is the seventh aspect, characterized in that the communication passage extends downward in the direction of gravity from the gap toward the outside. With this, the liquid accumulated inside the gap is discharged to the outside through the communication passage due to its own weight.

[0076] [Ninth aspect] A ninth aspect is characterized in that in any of the first to eighth aspects, the gap is formed closer to the screw fitting portion than the outer edge of the head of the screw. This makes it possible to obtain a sufficient screw fastening force while avoiding a situation in which the second component is deformed by fastening the screw.

[0077] [Tenth aspect] The tenth aspect is a drive transmission device (e.g., drive unit 50) in which a lubricant (e.g., grease G) is used in the drive transmission part 53, and is characterized in that it has a screw fastening mechanism 55 of any of the first to ninth aspects, and the screw fitting part in the screw fastening mechanism is formed from a resin material that is chemically attacked by the lubricant. This makes it possible to provide a drive transmission device in which damage to the screw-fitting portion due to stress generated by the threaded portion of the screw is suppressed.

[0078] [Eleventh aspect] An eleventh aspect is an image forming apparatus characterized by having the screw fastening mechanism of any one of the first to ninth aspects or the drive transmission device of the tenth aspect. This makes it possible to provide an image forming apparatus in which damage to the screw fitting portion due to stress generated by the threaded portion of the screw is suppressed. [Explanation of symbols]

[0079] 1: Copy machine 2:Paper feed section 3: Image forming unit 10: Main unit control section 50: Drive unit 51: Case 51a: Screw boss part 51b: screw hole 51c: Contact part 51d: Groove 51e: recess 51f: Communication path 52: Lid member 52a: Through hole 52b: Bottom surface 53: Drive transmission unit 54: Screw 54a: Threaded part 54b:Head 55: Screw fastening mechanism 100:ADF 105: Bottom plate lift motor 111: Movable manuscript table G: Grease S: Contact area g1, g2: gap [Prior art documents] [Patent documents]

[0080] [Patent Document 1] Japanese Patent Application Publication No. 2019-140226

Claims

1. A screw fastening mechanism in which a threaded portion of a screw is fitted into a thread fitting portion of a first component, and a first surface of the first component and a second surface of a second component are brought into contact with each other, thereby fastening the first component and the second component together with the screw, the screw-fitting portion of the first component is formed of a material that is chemically attacked by a liquid adhering to the screw-fastening mechanism, A screw fastening mechanism characterized in that a gap separating the first surface and the second surface is formed in a region closer to the screw fitting portion than the abutment region between the first surface and the second surface, so as to surround the screw fitting portion.

2. The screw fastening mechanism according to claim 1, A screw fastening mechanism characterized in that the gap is formed by a separation portion of the first surface that is shifted in a direction away from the second surface relative to the abutment portion of the first surface that abuts against the second surface.

3. The screw fastening mechanism according to claim 2, a screw fastening mechanism characterized in that the separation portion on the first surface is a groove formed to surround the screw fitting portion between the abutment portion of the first surface and a surface portion of the first surface that is continuous with the opening edge portion of the screw fitting portion.

4. The screw fastening mechanism according to claim 2, a recess formed between the recess and the abutting portion of the first surface so as to surround the screw fitting portion, the recess continuing to the opening edge of the screw fitting portion and surrounding the screw fitting portion;

5. The screw fastening mechanism according to claim 3 or 4, The screw fastening mechanism is characterized in that the groove is formed downward in the direction of gravity.

6. The screw fastening mechanism according to claim 2, The screw fastening mechanism is characterized in that the separated portion on the first surface is a recess that is continuous with an opening edge portion of the screw fitting portion so as to surround the screw fitting portion.

7. The screw fastening mechanism according to any one of claims 1 to 4 and 6, A screw fastening mechanism, characterized in that a communication passage is formed in the contact area between the first surface and the second surface, connecting the gap to the outside of the contact area.

8. The screw fastening mechanism according to claim 7, The screw fastening mechanism is characterized in that the communication passage extends downward in the direction of gravity from the gap toward the outside.

9. The screw fastening mechanism according to any one of claims 1 to 4 and 6, The screw fastening mechanism is characterized in that the gap is formed closer to the screw fitting portion than the outer edge of the head of the screw.

10. A drive transmission device in which a lubricant is used in a drive transmission part, A screw fastening mechanism according to any one of claims 1 to 4 and 6, The drive transmission device, wherein the screw fitting portion of the screw fastening mechanism is formed from a resin material that is chemically attacked by the lubricant.

11. An image forming apparatus, 7. An image forming apparatus comprising the screw fastening mechanism according to claim 1.

Images