JP2006091582A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of defects of image quality due to displacement of a developing vessel when using a coupling in a route for transmitting a driving force to the developing vessel in an image forming apparatus. <P>SOLUTION: A compression coil spring 52 is set so as to satisfy at least a relational expression (1) of F≥1.0(m×t/d)-m×G×cosθ, wherein m is a weight (kgf) of a developing vessel 32A of the developing unit 20; F is a pressing force (contact load)(kgf) energizing the developing vessel 32A toward a photoreceptor drum 16; d is a joint diameter (cm) of the coupling transmitting the driving force from an apparatus body to the developing vessel; t is a maximum value (kgfcm) of torque acting upon the coupling; θ is an angle (degrees) at which the arrangement position of the developing vessel 32A is inclined clockwise in a peripheral direction of the photoreceptor drum with an upward perpendicular direction as 0 degree when viewed from an axial direction of the photoreceptor drum 16; and G is a gravity acceleration. Thus, even in the case that axial deviation of the coupling is caused to vary the torque, the developing vessel 32A is not displaced, and an image of high quality can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that does not cause image quality defects due to blurring of internal components during driving.

  In an image forming apparatus that forms a toner image on a recording medium by a so-called electrostatic recording method, a photosensitive drum is charged by a charging device, and an electrostatic latent image is formed by laser light from an optical scanning device. The latent image is configured to be developed (visualized) by supplying toner from a developing roll.

  The visualized image toner is transferred and fixed to a recording medium such as paper, and a desired image is obtained on the recording medium.

  In the image forming apparatus having such a configuration, in order to obtain a high-quality image, it is desirable to narrow a gap between the photosensitive drum and the developing roll (hereinafter, this gap is referred to as “DRS”). Must be kept constant.

  On the other hand, an image forming apparatus such as a copying machine or a printer using an electrophotographic system is known in which an image carrier unit that is consumed due to wear or the like is replaced as a consumable item.

  At this time, if the developing device installed with a predetermined minute gap (DRS) on the image carrier is in the state of the minute gap, the image carrier unit is rubbed between the developing device and the image carrier when the image carrier unit is inserted and removed. Since the surface of the carrier and the developing roll of the developing device are damaged, causing an image defect, for example, in the apparatus disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 11-327267), the developing device can be brought into contact with and separated from the image carrier. The configuration is provided.

  However, as the problem described in Patent Document 1, it is known as a problem that when a developing device is brought into contact with the image carrier, a gear that receives driving with the image forming apparatus main body is damaged due to a contact operation or the like. In the technology, problems are solved by techniques such as rotating the gears slightly.

  However, as described in another prior art, for example, Japanese Patent Application Laid-Open No. 6-332285, even if the gear teeth do not collide, the positions of the gears of the image forming apparatus main body and the developing device are accurate. In this case, it was difficult to put out, and at that time, gear wear and image quality defect due to poor gear meshing were caused.

In this other prior art, a coupling mechanism is used as a means for solving the problem in order to absorb the displacement.
Japanese Patent Laid-Open No. 11-327267 JP-A-6-332285

  However, as described in this technology, it is difficult to accurately align the positions of the image forming apparatus main body and the driving unit of the developing device. This is difficult because positioning of the developing device is determined in advance as the image carrier.

  In order to transmit power even if there is a positional shift, there is a problem that the coupling causes a large fluctuation in torque in the rotation cycle when there is no center of rotation between the coupling on the driving side and the passive side.

  That is, as shown in FIG. 24A, the centers of the driving side coupling members 102 indicated by the two-dot chain line coincide with the centers of the driving side coupling members 100 indicated by the solid lines. When the protrusions 104 are engaged, torque fluctuation does not occur on the driven side. However, as shown in FIG. 24B, if the center of the coupling member 102 on the driven side is deviated, the distance from the rotation center on the driving side to the protrusion 100A of the driven coupling member 102 changes. (A-α and A-α), and there is a problem that torque fluctuation occurs on the driven side.

  Even if the driving device has sufficient power, the torque fluctuation causes the developing device to be twisted in a rotation cycle, thereby causing a DRS fluctuation and causing image quality defects.

  The present invention has been made to solve this problem. When a coupling is used in a path for transmitting a driving force to a developing device, an image without causing image quality defects by displacing the developing device. It is an object to provide a forming apparatus.

  According to the first aspect of the present invention, there is provided an image carrier that forms a latent image, and a developer that develops the latent image formed on the image carrier by receiving a load by an applied pressure load F (kgf) and contacting the image carrier. Including a developing unit having a weight of m (kgf), the image carrier and the developing unit, at least the developing unit being detachable, and movable in a direction of contacting and separating from the image carrier. An image forming apparatus main body, a driving device that is provided in the image forming apparatus main body and applies a rotational driving force to the developing device, a first coupling member attached to the driving device side, and a developing device side The second coupling member is configured to be engageable with the first coupling member, and when the first coupling member and the second coupling member are joined to each other, Rotate to developer An image forming apparatus including a coupling for transmitting power, wherein a coupling portion diameter of the coupling is d (cm), a maximum value of a torque acting on the coupling is t (kgfcm), and an axial direction When the arrangement position of the developing device with respect to the circumferential direction of the image carrier as viewed from the top is 0 degree in the vertical direction and θ degree in the clockwise direction, and G is the gravitational acceleration, The pressure load F at the time of abutting is satisfying F ≧ 1.0 (m × t / d) −m × G × cos θ.

  Next, the operation of the image forming apparatus according to the first aspect will be described.

  In order to obtain a good image quality, the detachable developing device needs to be pressed against the image carrier using a spring or the like to keep the distance between the developing device and the image carrier constant. For this reason, the developing device is held so as to be movable in a direction in which the developing device comes in contact with and separates from the image carrier, and a spring or the like urges the developing device toward the image carrier.

  By the way, when the rotational driving force for driving the developing device is obtained from the driving device through the coupling, the driving force is transmitted when the axial center on the developing device side does not coincide with the axial center on the driving device side. However, the developing device receives a force that varies in the radial direction of the shaft in response to a change in torque, and the distance between the developing device and the image carrier may vary depending on the setting of the biasing force.

  Here, by setting the pressure load F applied to the image carrier of the developing device so as to satisfy the above-described formula F ≧ 1.0 (m × t / d) −m × G × cos θ, the torque due to the shaft misalignment is set. Even when fluctuations occur, the developing device is not displaced, and a high-quality image can be obtained.

  The invention described in claim 2 is an image carrier that forms a latent image, and a developer that develops the latent image formed on the image carrier by receiving a load with a pressure load F (kgf) and contacting the image carrier. Including a developing device having a weight of m (kgf), the image carrier and the developing device, at least the developing device being detachable, and movable in a direction in which the image carrier is in contact with or separated from the image carrier. An image forming apparatus main body, a driving device that is provided in the image forming apparatus main body and applies a rotational driving force to the developing device, a first coupling member attached to the driving device side, and a developing device side The second coupling member is configured to be engageable with the first coupling member, and when the first coupling member and the second coupling member are joined to each other, Rotate to developer An image forming apparatus including a coupling for transmitting power, wherein a coupling portion diameter of the coupling is d (cm), a maximum value of a torque acting on the coupling is t (kgfcm), and an axial direction When the position of the developing device with respect to the circumferential direction of the image carrier as viewed from above is set to 0 degree in the vertical direction, θ degree in the clockwise direction and G as the gravitational acceleration, The pressure load F at the time of abutting is satisfying F ≧ 1.3 (m × t / d) −m × G × cos θ.

  Next, the operation of the image forming apparatus according to claim 2 will be described.

  By setting the pressure load F so as to satisfy the above-described formula F ≧ 1.3 (m × t / d) −m × G × cos θ, the torque fluctuation caused by the shaft misalignment can be reduced as compared with the case of claim 1. Become stronger.

  According to a third aspect of the present invention, there is provided the image forming apparatus according to the first or second aspect, wherein the cam is rotatably supported, and is arranged to face the cam in a direction away from the cam. A plunger that is supported so as to be movable and has a concave portion that abuts the outer peripheral surface of the cam at the cam-side end, a convex portion that is formed on at least one side of the concave portion, and a spring that biases the plunger. The spring is compressed by rotating the cam separated from the plunger and bringing the cam into contact with the plunger, and the developing device is brought into contact with the image carrier by the urging force of the spring. It is characterized by that.

  Next, the operation of the image forming apparatus according to the third aspect will be described.

  In the image forming apparatus according to the third aspect, when the cam separated from the plunger is rotated, the cam presses the convex portion, compresses the spring, and further rotates to overcome the convex portion and reach the concave portion. Since the convex portion is close to the cam and the concave portion is located far from the cam with respect to the convex portion, the spring is strongly compressed when the cam is in contact with the convex portion. When the cam passes over the convex portion and reaches the concave portion, the plunger biased by the spring moves to the differential cam side between the height of the convex portion and the concave portion, and the cam is fitted into the concave portion.

  When the cam is rotated to get over the convex portion, a click feeling can be obtained, so that it is easy to understand that the developing device is in contact with the image carrier, and the cam is unintentionally detached from the plunger even during the image forming operation. The effect which prevents is obtained.

  As described above, since the image forming apparatus of the present invention has the above-described configuration, it is possible to obtain a high-quality image without causing image quality defects by displacing the developing device even if the coupling is misaligned. It has the excellent effect of being able to.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the image forming apparatus 10 according to the present exemplary embodiment includes a paper cassette 12 for storing paper P, an optical scanning device 14, a photosensitive drum 16, a charger 18, a developing unit 20, a cleaning device 22, and a fixing device 24. A transfer roll 25, a paper transport device 27, and the like.

  Note that the photosensitive drum 16, the charger 18, the cleaning device 22, and the like are combined as one photosensitive unit 29.

  As shown in FIG. 2, the image forming apparatus 10 includes a box-shaped metal frame 26 inside.

  As shown in FIGS. 2 and 5, a developing unit loading unit 28 for detachably loading the developing unit 20 (see FIG. 5) and a photosensitive unit 29 (see FIG. 14) can be attached to and detached from the metal frame 26. A photosensitive unit loading section 31 for loading is provided.

  The developing unit 20 is detachable from the developing unit loading unit 28.

  In the developing unit loading section 28, a guide extending toward the front side of the apparatus and the rear image side in order to guide the developing unit 20 slidably toward the front side (arrow F direction) and the back side (arrow B direction) of the apparatus. A rail 30 is provided.

  As illustrated in FIG. 3, the guide rail 30 has an alphabetical J shape with a cross-sectional shape perpendicular to the longitudinal direction.

As shown in FIGS. 2 to 4, the developing unit 20 is provided with a guide plate 33 that is slidably inserted into the groove portion of the guide rail 30. The guide plate 33 has an L-shaped alphabetical cross-sectional shape in the longitudinal direction.
(Developer)
Next, the developing unit 20 will be described in detail.

  The developing unit 20 includes a developing device 32A and a support frame 32B that holds the developing device 32A by a predetermined amount.

  The developing unit 20 is a so-called trickle developing system (in order to prevent the developer charging performance from being lowered and to extend the developer replacement interval, the developer is gradually replenished with a replenishing developer (trickle developer). On the other hand, it is a developing method that develops while discharging excess developer (including many deteriorated carriers), so that the deteriorated developer is collected in a collection container (not shown). It has become.

  As shown in FIG. 6, the developing unit 20 includes a housing 116 that constitutes the developing device 32 </ b> A. The housing 116 opens toward the image bearing surface (outer peripheral surface) of the photosensitive drum 16. An opening 118 is formed.

  In the housing 116, a developing roll 120 is disposed near the opening 118. The housing 116 is provided with a main flow passage 122 and a double flow passage 124 for storing the developer D on the lower side thereof. The flow passages 122 and 124 are respectively open upward. The cross-sectional shape is a substantially semicircular shape opened upward.

  The main flow passage 122 and the return flow passage 124 are formed elongated along the axial direction of the photosensitive drum 16 (the front and back direction in FIG. 6).

  A partition wall 126 is erected from the bottom surface of the housing 116, and the partition wall 126 passes through the main flow passage 122 and the return flow passage 124 in the width direction of the developing device (in the direction of arrow W) perpendicular to the axial direction. It is divided along.

  The partition wall 126 is formed with a communication port (not shown) that communicates both at one end and the other end along the longitudinal direction of the flow passages 122 and 124.

  A screw shaft-like supply auger 132 and an admix auger 134 are rotatably disposed in the main flow passage 122 and the return flow passage 124, respectively.

  FIG. 7A is a side view showing the front side of the developing device 32A facing the front side of the device when the developing unit 20 is loaded in the developing unit loading section 28, and FIG. 7B is a view of the device of the developing device 32A. It is a side view which shows a back side. FIG. 8 is a perspective view of the developing device 32A.

  As shown in FIGS. 7A, 7B, and 8, a guide hole 34 and a groove 36 that are elongated in the horizontal direction are formed on the side surface of the developing device 32A, respectively.

  As shown in FIGS. 4 and 9 to 11, the support frame 32 </ b> B disposed outside the developing device 32 </ b> A is provided with guide holes 34 of the developing device 32 </ b> A and guide pins 40 that are movably inserted into the grooves 36. (The width of the guide hole 34 and the groove 36> the diameter of the guide pin 40).

  The guide pin 40 of the outer frame 32B is inserted into the guide hole 34 and the groove 36 which are elongated in the horizontal direction of the developing device 32A, so that the developing device 32A is in the horizontal direction with respect to the outer frame 32B and the photosensitive drum 16. Is supported so as to be movable by a predetermined length (the length of the long hole−the diameter of the guide pin) in the direction of contact with and away from the head.

  A camshaft 42 is rotatably supported on the exterior frame 32B along the longitudinal direction of the developing device 32A.

  A lever 44 is provided on the device front side of the exterior frame 32B. The lever 44 is connected to the camshaft 42 via a gear (not shown), and the camshaft 42 is configured to rotate by rotating the lever 44.

  The lever 44 is integrally provided with a plate 44A for preventing the photoreceptor unit 29 from being pulled out.

  Near both ends of the camshaft 42, a cam 46 and a hooking portion 47 (see FIG. 15) are attached.

  As shown in FIG. 12A, the shape of the distal end portion of the cam 46 includes a large radius portion (radius R) 46A and a small radius portion (radius r) 46B when viewed from the axial direction.

  As shown in FIGS. 13 and 8, the developing device 32 </ b> A is provided with a plunger 48 at a portion facing the cam 46.

  As shown in FIG. 12, the plunger 48 is slidably inserted into the hole 50 of the developing device 32A. A compression coil spring 52 that urges the plunger 48 in the direction of popping out is disposed in the hole 50.

  A large arc-shaped concave portion 54 is provided at the tip of the plunger 48, and small arc-shaped convex portions 55 are provided on both sides of the concave portion 54.

  The radius of curvature of the concave portion 54 (> the radius of curvature of the convex portion 55) has the same radius of curvature (radius R) as the large radius portion (radius R) of the cam 46.

  Here, as shown in FIG. 14, in the state where the lever 44 is standing, as shown in FIGS. 13 and 15, the hooking portion 47 contacts the downward projection 35 of the exterior frame 32B to expose the developing device 32A. Although the cam 46 is standing and separated from the plunger 48 with the tip 46 facing upward, the developing roller 120 is sufficiently separated from the photosensitive drum 16. When the lever 44 is rotated so as to incline toward the photosensitive drum as shown in FIG. 16, the hooking portion 47 is separated from the downward projection 35 although not shown in the drawing, and as shown in FIG. When the small radius portion pushes the plunger 48 and gets over the convex portion 55 on the side of the concave portion 54 and further rotates, as shown in FIG. 18 and FIG. Tip 6 is fitted completely into the recess 54.

  As a result, the compression coil spring 52 is compressed, and the developing device 32A that receives the reaction force of the compression coil spring 52 is urged toward the photosensitive drum (in the direction of arrow A).

  As a result, a part of the developing device 32A comes into contact with a part of the photosensitive unit 29 including the photosensitive drum 16, and the interval between the developing roll 120 and the photosensitive drum 16 can be set to an optimal minute interval.

  Further, when the lever 44 is tilted, the plate 44A attached to the lever 44 interferes with the drawing side of the photosensitive unit 29, so that the user is prevented from pulling out the photosensitive unit 29, and the photosensitive drum 16 is developed. It is possible to prevent the roll 120 from coming into contact and being damaged.

  When the photosensitive unit 29 is not pushed to the proper position, a part of the photosensitive unit 29 protrudes to the front side of the apparatus, and the plate 44A is exposed to the photosensitive member when the plate 44A is inclined. Since the unit 29 abuts against the protruding portion of the unit 29, it can be seen that the photosensitive unit 29 is not completely loaded.

The image forming apparatus 10 includes a coupling 56 for transmitting a driving force of a motor (not shown) provided on the metal frame 26 side to the developing unit 20.
(Coupling)
As shown in FIG. 20, the coupling 56 includes a first coupling member 56A attached to an output shaft (not shown) that outputs a rotational force from the motor on the metal frame 26 side, a first coupling member 56A, Is composed of a second coupling member 56B that can be contacted and separated in the axial direction.

  The second coupling member 56B is connected to the developing roll 120 of the developing unit 20.

  As shown in FIG. 21, each of the first coupling member 56A and the second coupling member 56B includes a pair of protrusions 58 protruding in the axial direction on both sides of the rotation center, and the first coupling member The projection 58 of 56A (shown by a solid line) is inserted and arranged between the projection 58 (shown by a two-dot chain line) of the second coupling member 56B so that the driving force is transmitted. ing.

  In the present coupling 56, the driving force can be transmitted even if the rotation center of the first coupling member 56A and the rotation center of the second coupling member 56B are slightly deviated in the radial direction.

  Note that the distance from the center of rotation to the center of each protrusion 58 (the center to which the driving force is transmitted) is set to be the same, and twice the distance corresponds to the joint portion diameter d of the present invention. .

  As shown in FIG. 6, in the developing unit 20, rotational force (torque) is transmitted to the supply auger 132 and the admixed auger 134 when the developing roll 120 rotates, and each rotates.

  At this time, the supply auger 132 rotates in a predetermined feeding direction, and the admix auger 134 rotates in the feeding direction opposite to the supply auger 132.

  Further, the main flow passage 122 and the return flow passage 124 are communicated with each other at both end portions via communication ports (not shown). As a result, in the housing 116 of the developing unit 20, the developer D circulates between the main flow passage 122 and the return flow passage 124 when the developing roll 120 rotates.

  The developing roll 120 is located above the main flow passage 122 and close to the outer peripheral portion of the supply auger 132.

  When the developing unit 20 is loaded in the developing unit loading unit 28, the developing roll 120 faces the image carrying surface of the photosensitive drum 16 as shown in FIG.

  The developing roll 120 has a built-in magnet 120A fixed in a columnar shape, and a cylindrical sleeve 121 is rotatably provided on the outer periphery thereof. The magnet 120A is provided with a plurality of N poles and S poles alternately in the circumferential direction. The sleeve 121 rotates in a direction (arrow RR direction) that follows the photosensitive drum 16 (hereinafter, the rotation of the developing roller 120 means the rotation of the sleeve 121 in this specification).

  When the photosensitive drum 16 rotates, the toner in the developer D flowing through the main flow passage 122 is adsorbed by the sleeve 121.

  A plate-shaped trimmer bar 80 is disposed in the housing 116 above the developing roll 120, and the trimmer bar 180 thins the toner adsorbed on the sleeve 121. When an electrostatic latent image is formed on the image bearing surface of the photoconductive drum 16, the toner charged to a predetermined polarity (usually negative (−) polarity) is developed at the developing position by electrostatic force. Thus, the toner image is transferred from the sleeve 121 of the developing roll 120 to the image carrying surface, and selectively adheres to the electrostatic latent image to form a toner image on the image carrying surface.

  An elastic plate-like sealing material 176 is attached to the peripheral portion of the opening 118 in the housing 116, and the sealing material 176 has its tip end in close contact with the image carrying surface of the photosensitive drum 16. .

  This prevents the toner that is peeled off from the developing roll 120 or the photosensitive drum 16 from being scattered and flows out from between the housing 116 and the photosensitive drum 16 to the outside.

  In the housing 116, a collecting roll 178 is rotatably disposed below the developing roll 120. The collecting roll 178 has a predetermined roll surface on the image carrying surface (outer peripheral surface) of the photosensitive drum 16. It is supported so as to face each other with a minute gap. The toner held on the outer peripheral surface of the developing roll 120 comes into contact with the collecting roll 178.

  A scraper 182 is disposed in the housing 116 between the collection roll 178 and the supply auger 132.

  The collecting roll 178 is also configured to rotate in the driven direction when the developing roll 120 rotates, and a voltage having a polarity opposite to that of the toner is applied to the cored bar portion via the scraper 182 when the developing unit 20 is operated. As a result, a voltage having the same potential as the developing bias is applied when the developing unit 20 is operated, thereby adsorbing the cloud toner of the opposite polarity that has peeled off and floated from the developing roll 120 and the photosensitive drum 16.

  Note that the scraper 182 makes its tip end abut against the roll surface of the collection roll 178 with a predetermined pressure, and peels and removes the toner adsorbed on the collection roll 178. The removed toner falls from the scraper 182 into the main flow path 122 and is collected.

  As shown in FIG. 6, a passage 60 that communicates between the photosensitive drum side and the opposite side of the photosensitive drum side is formed in the lower portion of the housing 116 of the developing unit 20.

  The end of the passage 60 on the photosensitive drum side opens below the collection roll 178.

  A hollow connecting portion 62 is slidably attached to the opposite side of the passage from the photosensitive drum side.

  As shown in FIG. 22, a duct 64 connected to a negative pressure suction device (not shown) is fixed to the metal frame 26 (not shown in FIG. 22) side. Note that an outward projection 64A is formed in the opening portion of the duct 64 in the vertical direction, and this projection 64A is hooked by an inward projection 62A formed in the opening portion of the groove 62B of the connecting portion 62, thereby developing. Although it can slide relatively in the longitudinal direction of the unit 20 (front and back in FIG. 22), both move in unison with respect to the sliding direction of the developing device 32A (arrow W direction in FIG. 22). There is no.

  For this reason, the duct 64 and the passage 60 are connected via the connecting portion 62, and the developing device 32A can be slid in the connected state.

By operating the negative pressure suction device to make the inside of the duct have a negative pressure, it is possible to suck ambient air from the end of the passage 60 on the photosensitive drum side and suck the toner cloud floating around the air together with the air It becomes.
(Function)
Next, the operation of the image forming apparatus 10 of this embodiment will be described.

  In the present embodiment, the weight of the developing device 32A of the developing unit 20 is m (kgf), the pressing force (current pressure load) for urging the developing device 32A toward the photosensitive drum 16 is F (kgf), and the coupling 56 The diameter of the joint portion is d (cm: see FIG. 21), the maximum value of the torque acting on the coupling 56 is t (kgfcm), and the photosensitive drum of the developing device 32A when viewed from the axial direction of the photosensitive drum 16. When the arrangement position with respect to the circumferential direction is set to 0 degree in the vertical direction, θ degree in the clockwise direction (see FIG. 18), and G as the gravitational acceleration, at least F ≧ 1.0 (m × t / d) − It is necessary to satisfy the relational expression (1) of m × G × cos θ, and it is preferable to satisfy the relational expression (2) of F ≧ 1.3 (m × t / d) −m × G × cos θ. . That is, when the developing device 32A is positioned above the side of the photosensitive drum 16, a part of its own weight of the developing device 32A corresponding to the position viewed from the photosensitive drum acts on the photosensitive drum side, so that the compression coil spring 52 is used. Therefore, when the developing device 32A is positioned below the side of the photosensitive drum 16, a force for pushing up the developing device 32A corresponding to the position viewed from the photosensitive drum is required. The force of the compression coil spring 52 must be increased accordingly.

  Here, the developing device 32A has a total weight m of 3 kgf and a torque t of 3 kgf · cm in which 0.75 kgf of developer is contained.

  In addition, the coupling 56 has a joint portion diameter (a diameter at a portion where a rotational driving force is applied from the driving device) d of 2 cm.

  In the present embodiment, the pressure load F is the urging force of two compression coil springs 52 in a state where the cam 46 is pressed by fitting the tip of the plunger 48 into the recess 54 (see FIG. 18). is there. In this state, the force per compression coil spring 52 of the present embodiment is 2.3 kgf.

  Further, the developing device 32A is positioned beside the photosensitive drum 16, and θ in the above formula is 270 °.

  Substituting the respective values into the relational expression (1), 2.3 × 2> 1.0 (3 × 3/2) −3 × G × cos 270 ° = 4.5, that is, 4.6> 4.5 It becomes.

  Incidentally, the state in which the pressing force F is changed is shown in the graph of FIG. 23. Under the conditions at this time, the shake of the developing device 32A can be suppressed to 60 μm or less. When the allowable deflection is 35 μm, the necessary pressing force F can be easily obtained by using the relational expression (2).

  The reason why the both sides of the developing device 32A in the longitudinal direction are pressed by the compression coil spring 52 is that the total runout of the developing roll 120 due to the load fluctuation from the coupling 56 can be more effectively suppressed than when pressing only at the center. is there.

  Further, in the present embodiment, since the concave portion 54 is formed at the tip of the plunger 48 and the cam 46 is fitted, the cam 46 is not easily detached from the plunger 48.

  Further, since a latch feeling is obtained when the cam 46 is fitted in the recess 54, erroneous operation is prevented.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an exemplary embodiment. It is a perspective view of a metal frame. It is a front view which shows the state which loaded the developing device in metal frames. It is a perspective view of the exterior frame of a developing device. It is a perspective view of a developing device. It is sectional drawing of a developing device and a photoconductive drum. (A) is a side view of the main body portion of the developing device on the apparatus front side, and (B) is a side view of the main body portion on the apparatus inside side. FIG. 6 is a perspective view of a main body of a developing device. It is a perspective view of the exterior frame of a developing device. It is a perspective view of the exterior frame of a developing device. It is a bottom view of the exterior frame of a developing device. (A) is a side view of the cam, and (B) is a sectional view of the vicinity of the plunger of the developing device. It is a side view of a developing device and a photosensitive drum. It is a side view of a developing device and a photosensitive drum. FIG. 6 is a perspective view of a main body of a developing device. It is a side view of a developing device and a photosensitive drum. It is sectional drawing of a developing device and a photoconductive drum. It is sectional drawing of a developing device and a photoconductive drum. FIG. 6 is a perspective view of a main body of a developing device. 2 is a perspective view of the vicinity of a coupling inside the image forming apparatus. FIG. It is the front view seen from the axial direction of the coupling. It is a side view of the developing device showing a connection state with a duct. 6 is a graph showing a relationship between total developing roll runout and pressing force. (A) is an action diagram of the force when the coupling axis is not displaced, and (B) is an action diagram of the force when the coupling axis is displaced.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 16 Photosensitive drum (Image carrier)
32A Developer 56 Coupling 56A First coupling member 56B Second coupling member

Claims (3)

An image carrier for forming a latent image;
A developer having a weight of m (kgf) including a developer that receives the load by the pressure load F (kgf) and abuts against the image carrier and develops the latent image formed on the image carrier;
An image forming apparatus main body that holds the image carrier and the developer, at least the developer is detachable, and is movable in a direction in which the image carrier is in contact with or separated from the image carrier;
A driving device that is provided in the image forming apparatus main body and applies a rotational driving force to the developing device;
A first coupling member attached to the drive device side; and a second coupling member attached to the developer side and configured to be engageable with the first coupling member. A coupling for transmitting the rotational driving force from the driving device to the developing device when a ring member and the second coupling member are joined;
An image forming apparatus comprising:
The coupling diameter of the coupling is d (cm),
The maximum value of torque acting on the coupling is t (kgfcm),
The arrangement position of the developing device with respect to the circumferential direction of the image carrier when viewed from the axial direction is set to θ degrees in the clockwise direction with the vertical upward direction being 0 degrees,
When gravity acceleration is G,
The image forming apparatus, wherein the pressure load F when the developing unit contacts the image carrier satisfies F ≧ 1.0 (m × t / d) −m × G × cos θ. An image carrier for forming a latent image;
A developer having a weight of m (kgf) including a developer that receives the load by the pressure load F (kgf) and abuts against the image carrier and develops the latent image formed on the image carrier;
An image forming apparatus main body that holds the image carrier and the developer, at least the developer is detachable, and is movable in a direction in which the image carrier is in contact with or separated from the image carrier;
A driving device that is provided in the image forming apparatus main body and applies a rotational driving force to the developing device;
A first coupling member attached to the drive device side; and a second coupling member attached to the developer side and configured to be engageable with the first coupling member. A coupling for transmitting the rotational driving force from the driving device to the developing device when a ring member and the second coupling member are joined;
An image forming apparatus comprising:
The coupling diameter of the coupling is d (cm),
The maximum value of torque acting on the coupling is t (kgfcm),
The arrangement position of the developing device with respect to the circumferential direction of the image carrier when viewed from the axial direction is set to θ degrees in the clockwise direction with the vertical upward direction being 0 degrees,
When gravity acceleration is G,
The image forming apparatus, wherein the pressure load F when the developing unit contacts the image carrier satisfies F ≧ 1.3 (m × t / d) −m × G × cos θ. A cam that is rotatably supported, a recess that is disposed opposite to the cam and is supported so as to be movable away from the cam, and that is in contact with the outer peripheral surface of the cam at an end on the cam side; A plunger having a convex portion formed on at least one side, and a spring for biasing the plunger;
Rotating the cam spaced apart from the plunger and bringing the cam into contact with the plunger compresses the spring, and the biasing force of the spring causes the developing device to contact the image carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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