JP6400324B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer (LBP) using a constant velocity joint.

2. Description of the Related Art Conventionally, an image forming apparatus in which a charger, an exposure unit, a developing device, and a transfer roller are provided around the outer periphery of a photosensitive drum that is rotated in one direction is known.
In these image forming apparatuses, after the entire outer periphery of the photosensitive drum is uniformly charged by a charger, image light based on image information is exposed by an exposure unit to form an electrostatic latent image. Then, toner is supplied from the developing unit to the electrostatic latent image to form a toner image, and the toner image is transferred onto a transfer material conveyed at the same speed as the peripheral speed of the photosensitive drum by a transfer roller. Yes.

In these image forming apparatuses, if an error occurs in the mounting position of the image forming unit including the photosensitive drum, the rotational speed during one rotation of the photosensitive drum may be uneven. For example, the drum shaft of the photosensitive drum and the drive shaft on the motor side are displaced in the vertical direction or the horizontal direction due to variations in accuracy of the image forming unit and the parts of the apparatus main body (frame, slide rail, etc.) that support the image forming unit. It is assumed that it will end up. Further, even if they are attached without error, it is assumed that such an error may occur afterwards while repeatedly attaching and detaching the image forming unit to and from the apparatus main body.
In these cases, the rotating drum shaft on the photosensitive drum side is inclined with respect to the driving shaft on the driving source side, that is, a state in which a declination is generated, which causes uneven rotation speed.

  If the rotational speed of the photosensitive drum during one rotation is uneven, the electrostatic latent image on the photosensitive drum expands and contracts during exposure by the exposure unit, and the image expands and contracts during transfer of the toner image onto the transfer material. Can cause image unevenness and a high-quality image cannot be formed. Therefore, it is necessary to always rotate the photosensitive drum at a constant speed.

  Therefore, in Patent Document 1, the rotating body shaft of the photosensitive drum and the driving shaft on the driving source side are connected by a tripod type constant velocity joint so as to prevent expansion and contraction of the image on the transfer material due to uneven rotation speed of the photosensitive drum. I have to.

JP 2007-256492 A

  The constant velocity joint of patent document 1 is comprised from the outer ring | wheel and the tripod member integrated inside the outer ring | wheel. The outer ring is formed with three track grooves extending in the axial direction on the inner circumference at intervals of 120 ° in the circumferential direction, and the tripod member is slidably inserted into each track groove so that the outer ring and the tripod member are mutually connected. Three protrusions for transmitting torque between them are provided. A pair of taper surfaces are formed at the tip of the bulging portion formed between adjacent track grooves of the outer ring, and a pair of taper surfaces are provided on the front side of the protruding portion of the tripod member. .

  According to this constant velocity joint, a state in which the axis of the rotating shaft that is not parallel and the axis of the drive shaft intersect in the vicinity of the joint portion where the tripod type constant velocity joint is arranged, a so-called declination (bending) occurs. It is easy to cope with a relatively large shift in the state. However, a state where the extension line of the axis of the rotating body axis and the extension line of the axis of the drive shaft intersect at a portion other than the joint, or the axis of the drum shaft and the axis of the drive shaft There is a problem that the range of deviation that can be dealt with is limited to the state of parallel and non-intersecting, that is, the so-called misalignment state.

In addition, in order to form a high-quality image on various rotating bodies other than the photosensitive drum used in the image forming apparatus, such as a charging roller, a developing roller, a stirring roller, and other rotating bodies that rotate around an axis by a driving force. It is desirable to suppress the unevenness of the rotation speed during one rotation as much as possible.
Furthermore, there is a problem that the connection between the rotating body shaft and the drive shaft must be smooth.

  Therefore, the present invention is used in an image forming apparatus and suppresses uneven rotation speed as much as possible in various rotating bodies involved in the formation of a toner image transferred to a transfer material by rotating around an axis by a driving force. Also, it is possible to cope with a larger declination and misalignment between the axis of the rotating body shaft and the axis of the driving shaft, and to make the connection between the rotating body shaft and the driving shaft smooth. To do.

  In order to solve the above problems, the present invention relates to a rotating body involved in forming a toner image transferred to a transfer material, a driving source for rotating the rotating body about an axis, and a driving force from the driving source. In the image forming apparatus including the drive transmission device that transmits to the rotating body, the drive transmission device connects a drive shaft extending from the drive source and a rotary body shaft extending from the rotary body, and the drive shaft. When the angle between the axis of the rotating body shaft and the axis of the rotating body shaft is other than 180 °, or the rotational speed fluctuation of the rotating body shaft that occurs when the misalignment occurs, the rotation of the drive shaft is suppressed. A connecting means for transmitting to the rotating body shaft, the connecting means comprising a pair of outer rings and a tripod member connecting between the pair of outer rings, and three axially extending on the inner circumferences of the outer rings; Keep track grooves at 120 ° intervals in the circumferential direction. The tripod member is accommodated at both axial ends of the tripod member so as to be slidable in the axial direction in the track grooves, thereby transmitting torque around the shaft between the outer rings and the tripod member. An image forming apparatus characterized in that it is a tripod type constant velocity joint provided with three possible projecting portions, respectively.

  By connecting the rotating shaft on the rotating body such as the photosensitive drum and developing roller involved in the formation of the toner image and the driving shaft on the driving source side with a tripod type constant velocity joint, the shaft center and driving of the rotating body shaft are driven. Even when the axis of the shaft is not on the same straight line, that is, even if there is a declination or misalignment between the two, the rotating body can be rotated at a constant speed without speed unevenness. For this reason, it is possible to prevent the toner image formed by the involvement of the rotating body from expanding and contracting and the image transferred to the transfer material from expanding and contracting, and an extremely high quality image can be formed. .

  Further, the tripod type constant velocity joint is composed of a pair of outer rings having three track grooves and a tripod member having three protrusions accommodated in the track grooves, respectively, at two locations on both ends of the tripod member. By providing the bending function and the swing function, it becomes possible to cope with larger declination and misalignment.

  In this configuration, it is possible to employ a configuration in which the tripod member and the both outer rings are synthetic resin molded products. Further, it is desirable that the tripod member and the both outer rings adopt a configuration in which the main material (base resin) of the synthetic resin is different.

  By making the tripod member and both outer rings a molded product of synthetic resin, a lubricant such as grease is unnecessary, and a lubricant leakage preventing member such as a boot is unnecessary. In addition, maintenance can be facilitated. Further, it is possible to prevent the disadvantage that the transfer material is soiled due to leakage of the lubricant, and it is possible to reduce the operation noise during torque transmission. Further, by adopting a structure in which the main material (base resin) of the synthetic resin of the tripod member and the outer rings is different, the resin adhesion phenomenon can be prevented, and the torque fluctuation and wear characteristics are effective.

  In each of these configurations, among the axial ends of the tripod member, the three protrusions at one end and the corresponding connection part with the one outer ring are the three protrusions at the other end and the three protrusions. It can be set as the structure which is easy to fall out to an axial direction rather than the connection part with the other said outer ring | wheel corresponding.

A rotating body such as a photosensitive drum and a developing roller involved in the formation of a toner image is, for example, for replacement of consumables such as toner or for replacement due to maintenance or deterioration of the parts themselves. There are many opportunities to attach and detach appropriately. For this reason, the rotating body shaft and the drive shaft are frequently connected (a state where the driving force is transmitted) and disconnected (a state where the driving force is not transmitted).
Therefore, as described above, by making one of the tripod member both ends in the axial direction easier to drop than the other, it is possible to specify the location where the rotating body shaft and the drive shaft are separated. That is, when the rotating body is moved away from the drive source side, the protruding portion is detached from the track groove, and one end portion in the axial direction of the tripod member is naturally separated from the outer ring. Further, when the rotating body is pushed into the drive source side, the projecting portion is accommodated in the track groove, and one end portion in the axial direction of the tripod member is naturally connected to the outer ring.

  In order to make one of the both ends in the axial direction of the tripod member easier to fall off than the other, for example, the fixed side, that is, the connecting portion between the other end in the axial direction of the tripod member and the other outer ring corresponding thereto. It is good to make it difficult to fall off in the axial direction, and to provide the outer ring or tripod member with dropout prevention means (prevention means). As a drop-off preventing means, there is a method in which the axial hole of the outer ring and the axial hole of the tripod member are coupled by a coupling member. Further, a retaining ring can be arranged on the inner periphery of the outer ring, and the tripod member can be prevented from coming off by the retaining ring. As another method, an opening at the opening side end of the outer ring on the fixed side may be provided with a protrusion bulging toward the inner diameter side, an undercut, or the like to narrow the outlet of the opening. Further, as another method, the gap between the fixed side tripod member and the outer ring is relatively narrow so that it does not easily fall off, and the non-fixed side, that is, one end in the axial direction of the tripod member, The gap at the time of fitting with the outer ring may be relatively wide so that one side is pulled out with priority over the other side against the pulling force in the axial direction.

  When one end of the tripod member in the axial direction is connected to the outer ring, a guide function can be provided in the vicinity of the entrance of the track groove of the outer ring so that the protrusion is smoothly accommodated in the track groove.

  That is, the configuration is such that the connecting portion between the three protruding portions at one end and the one outer ring is connected to the tip of the bulging portion formed between the adjacent track grooves of the one outer ring. A pair of tapered surfaces that are inclined in the direction opposite to the direction and form a top part in the middle of the circumferential width of the bulging part, and are formed on the front surface of the three protruding parts at one end of the tripod member. In this configuration, a pair of tapered surfaces are provided which are inclined toward the both sides from the center in the width direction of each protrusion and form a top in the middle of the width of the protrusion.

  According to this structure, even when the phase of the track groove and the projecting portion is deviated in the circumferential direction when the tripod member is inserted from the opening side end portion of the outer ring on the non-fixed side, the projecting portion is Contact is guided by a tapered surface formed at the tip, and the guide is guided to the tip opening of the track groove. For this reason, it is not necessary to perform phase alignment between the track groove and the protruding portion, and the tripod type constant velocity joint can be connected very easily.

  At this time, among the top portions of the three bulging portions of one of the outer rings, the axial position of the top portion of at least one bulging portion is different from the axial position of the top portion of the other bulging portion. can do. In particular, it is preferable that the top part of one bulge part among the top parts of the three bulge parts of one said outer ring | wheel protrudes ahead rather than the top part of two other bulge parts.

  Alternatively, among the tops of the three protrusions at one end of the tripod member, the axial position of the top of at least one of the protrusions is different from the axial position of the top of the other protrusions. can do. In particular, among the tops of the three protrusions at one end of the tripod member, it is preferable that the top of one protrusion protrudes more forward than the tops of the other two protrusions.

  For example, assuming that the positions of the tops of the three bulging parts of the outer ring in the axial direction are all the same and the positions of the tops of the protruding parts of the tripod member are all the same in the axial direction, When the phase of the top part of the part and the top part of the projecting part coincide with each other, it becomes a so-called three-point support, and not only can the guidance effect by the tapered surface be expected, but also when the pushing force exceeds the expected level There is also a risk of damage to the top. Therefore, in order to avoid the three-point support between the tops, it is desirable to adopt each of the above configurations.

  Further, in each of these configurations, curved surfaces that bend along the axial direction are provided on both side surfaces of the projecting portions facing the side surfaces of the track grooves, and the side surfaces of the track grooves and the curved surfaces are brought into contact with each other. A configuration can be employed. The curved surface provided on both side surfaces of each protrusion comes into contact with the side surface of the track groove, so that the bending function and the swing function of the outer ring and tripod member when the declination and misalignment occur smoothly work. Can do.

  According to the present invention, a rotating body shaft such as a photosensitive drum or a developing roller involved in the formation of a toner image is connected to a driving shaft on the driving source side by a tripod constant velocity joint. Even if there is a declination or misalignment with the drive shaft, the rotating body can be rotated at a constant speed without uneven speed. For this reason, it is possible to prevent the toner image formed by the involvement of the rotating body from expanding and contracting and the image transferred to the transfer material from expanding and contracting, and an extremely high quality image can be formed. .

  Further, the tripod type constant velocity joint is composed of a pair of outer rings having three track grooves and a tripod member having three protrusions accommodated in the track grooves, so that the rotating body shaft and the drive shaft Even if there is a larger declination or misalignment, the rotating body can be rotated at a constant speed without uneven speed.

The principal part enlarged view of the image forming apparatus which shows one Embodiment of this invention The detail of the components which comprise a connection means is shown, (a) is sectional drawing of a pair of outer ring | wheel, (b) is a BB arrow line view of (a). Cross section of connecting means Exploded perspective view of connecting means (A) cross-sectional view and (b) perspective view respectively showing modifications of the connecting portion Schematic diagram of full-color image forming device Schematic diagram of the main parts of a monochrome image forming apparatus

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a main part in an image forming unit 10 used in the image forming apparatus.
The image forming unit 10 includes a rotating body R that is involved in toner image formation, a driving source M that includes a motor that rotates the rotating body R about its axis, and a drive that transmits a driving force from the driving source M to the rotating body R. And a transmission device 20.

  The drive transmission device 20 includes a connecting means 30 that connects a drive shaft 21 extending from the drive source M and a rotating body shaft 22 extending from the rotating body R. The connecting means 30 is in a state where the axis of the rotating body shaft 22 and the axis of the drive shaft 21 are not on the same straight line, that is, when the angle formed between them is other than 180 ° (180 deg), or there is a misalignment. It has a function of suppressing the rotation speed fluctuation of the rotating body shaft 22 that occurs when it occurs and transmitting the rotation of the drive shaft 21 to the rotating body shaft 22. 2 to 4 show details of the connecting means 30. FIGS. 5A and 5B show modifications thereof.

  The drive transmission device 20 can be used for a rotating body R used in either a single color image forming apparatus or a full color image forming apparatus.

  FIG. 7 shows a monochrome image forming apparatus. In this image forming apparatus, a toner image is formed by a set of image forming units 10 including a photosensitive drum 1, a charger 2, an exposure unit 3, a developing unit 4, and a transfer roller 13, and the toner image is used as a transfer material. An image is formed by transferring onto the recording paper A.

  After the charger 2 uniformly charges the entire outer periphery of the photosensitive drum 1, the exposure unit 3 exposes image light based on the image information to form an electrostatic latent image. Then, toner is supplied from the developing device 4 to the electrostatic latent image, and a toner image is formed on the photosensitive drum 1. The toner image is transferred onto the recording paper A conveyed by the transfer roller 13 of the transfer unit 5 at the same speed as the peripheral speed of the photosensitive drum 1. In addition, the transferred image is fixed on the recording paper A by heat and pressure in the fixing unit 8. After the transfer, residual toner remaining on the peripheral surface of the photosensitive drum 1 is removed by the cleaning device 7.

  In the developing device 4, a developing roller 11, a stirring roller 12, and the like are provided as a rotating body R that rotates about the axis by a driving force from a driving source M. Further, the transfer unit 5 includes a photosensitive drum 1 and a transfer roller 13 as a rotating body R that similarly rotates around an axis by a driving force. The fixing unit 8 includes a fixing roller 14 and a pressure roller 15 as a rotating body R that rotates about an axis by a driving force. These rotators R are involved in the formation of a toner image transferred to the transfer material.

  FIG. 6 shows a full-color image forming apparatus. In this image forming apparatus, four sets of image forming units 10 are arranged in tandem along the moving direction of the intermediate transfer material 6. Each image forming unit 10 forms a toner image of each color of yellow, magenta, cyan, and black, and these toner images are transferred to the intermediate transfer material 6 in the transfer unit 9 and transferred to the transfer material in the secondary transfer unit 16. The color image is formed on the recording paper A.

  Hereinafter, in this embodiment, the drive transmission device 20 that connects the developing roller 11 as the rotating body R and the driving source M in each of the image forming apparatuses described above will be described. However, any other rotating body R is also described in the present invention. The drive transmission device 20 can be employed.

  As shown in FIG. 1, the rotator R (developing roller 11) has a rotator shaft 22 at both ends, and the rotator shaft 22 is supported by a pair of frames F ′ so as to be rotatable about a shaft via a bearing b. Has been. A drive source M for rotating the rotating body R is attached to the frame F on the apparatus main body side of the image forming apparatus, and is disposed to face the rotating body R in the axial direction. The frame F ′ is movable along the axial direction of the rotating body shaft 22 with respect to the frame F, and by this movement, the image forming unit 10 provided with the rotating body R can be attached to and detached from the apparatus main body. Yes.

The connecting means 30 connects the driving shaft 21 of the driving source M and the rotating body shaft 22 of the rotating body R, and includes a tripod type including a pair of outer rings 31 and 36 and a tripod member 40 connecting the pair of outer rings 31 and 36. It is a constant velocity joint. The tripod member 40 and both outer rings 31 and 36 are both molded products of synthetic resin. An appropriate synthetic resin is selected according to the use conditions of the tripod type constant velocity joint, and a synthetic resin that can be injection-molded is desirable. Any resin that can be injection-molded may be a thermoplastic resin or a thermosetting resin.
Here, the main resin of the synthetic resin forming the pair of outer rings 31 and 36 and the tripod member 40, that is, the base resin which is a component excluding the additive and the like, is composed of different resins, thereby causing an adhesion phenomenon. Can be prevented. The main material of the synthetic resin of the outer ring 31 and the tripod member 40 is preferably different from each other, and the main material of the synthetic resin of the other outer ring 36 and the tripod member 40 is also preferably different from each other. Thereby, it is possible to prevent torque fluctuation and improve wear resistance. For example, both outer rings 31 and 36 can be formed of nylon resin, and tripod member 40 can be formed of PPS resin (polyphenylene sulfide resin).

  The pair of outer rings 31, 36 are provided with shaft portions 31 a, 36 a at the closed side end portion of the cup portion where the end portion on either side opens. Three track grooves 32 and 37 extending in the axial direction are formed on the inner circumferences of the outer rings 31 and 36 at intervals of 120 ° (120 deg) along the circumferential direction. A pair of side surfaces 32a, 32a; 37a, 37a facing each other in the circumferential direction of the track grooves 32, 37 are flat surfaces having plane directions parallel to each other.

  The tripod member 40 is provided with three projecting portions 42 and 47 at both axial ends of the shaft-shaped main body 41. The three protrusions 42 and 47 are accommodated in the track grooves 32 and 37 of the corresponding outer rings 31 and 36, respectively. Further, the tip of one projecting portion 42 enters an accommodation recess 34 provided in the inner portion of the track groove 32 of the outer ring 31.

  The protrusions 42 and 47 are slidable in the axial direction in the track grooves 32 and 37. Further, both side surfaces 42 c and 47 b facing the side surfaces 32 a and 37 a of the track grooves 32 and 37 are respectively cylindrical surfaces that are bent along the axial direction of the tripod member 40. In this embodiment, the axial centers of the opposing cylindrical surfaces are directed in the radial direction of the tripod member 40 and coincide with the axial centers of the protruding portions 42 and 47 in the protruding direction. A spherical surface can be used instead of these cylindrical surfaces.

  In the protrusions 42 and 47, the side surfaces 42 c and 47 b on both sides engage with the side surfaces 32 a and 37 a of the track grooves 32 and 37 when a rotational torque is input to one of the drive shaft 21 and the rotating body shaft 22. Due to the engagement, rotation torque around the shaft is transmitted between the outer rings 31 and 36 and the tripod member 40.

  At this time, the side surfaces 32a and 37a of the track grooves 32 and 37 and the side surfaces 42c and 47b of the projecting portions 42 and 47 facing each other contact each other, and the contact portions are in sliding contact with each other. The bending function and the swinging function of the outer rings 31 and 36 and the tripod member 40 at the time are smoothly operated.

  Further, of the both ends of the tripod member 40 in the axial direction, the three protrusions 42 at the end on the rotating body R side and the corresponding connection part between the outer ring 31 are the three protrusions 47 at the end on the drive source M side. And the other outer ring 36 corresponding thereto, the structure is easier to fall off in the axial direction.

  In this embodiment, the connection portion between the tripod member 40 on the driving source M side, which is the fixed side, and the outer ring 36 has a structure that does not easily fall off in the axial direction. The structure is press-fitted with a structure that is relatively difficult to fall off. In addition, the connecting portion between the tripod member 40 on the non-fixed rotating body R side and the outer ring 31 has a structure in which a gap at the time of fitting is relatively wide and can be fitted with a relatively weak force. As a result, the non-fixed side is more preferentially removed than the fixed side with respect to the pulling force in the axial direction.

  As in this embodiment, it is desirable that the drive source M side is the fixed side and the rotating body R side is the non-fixed side, but the drive source M side is the non-fixed side and the rotary body R side is the fixed side. Configuration is also possible.

  As another means for making one of the both ends in the axial direction of the tripod member 40 easier to drop than the other, for example, a means for preventing a retaining ring or the like from falling off between the tripod member 40 on the fixed side and the outer ring, for example. It is good to provide. Specifically, a structure in which a C-shaped retaining ring having a part opened in the circumferential direction is attached to an engagement groove provided in the inner periphery of the opening end of the outer ring is conceivable. The retaining ring prevents the tripod member 40 from coming off from the opening side end of the outer ring. Further, as another method, a protrusion bulging toward the inner diameter side, an undercut (see reference numeral 38a in FIG. 4) or the like is provided at the opening side end of the track groove of the outer ring on the fixed side to narrow the outlet of the opening. Also good.

  A bulging portion 33 is formed between adjacent track grooves 32 of the outer ring 31 on the non-fixed side. A pair of tapered surfaces, which are inclined in a direction opposite to the circumferential direction and form a top portion 33b in the middle of the circumferential width of the bulging portion 33, at the distal end portion (tip portion facing the opening side) of the bulging portion 33. 33a and 33a are formed. The top 33 b is configured by a linear ridge line extending in the radial direction of the outer ring 31.

  A bulging portion 38 is also formed between adjacent track grooves 37 of the outer ring 36 on the fixed side. However, since the connecting portion on this side is not premised on frequent connection and disconnection, formation of a tapered surface and a top portion is provided. Can be omitted.

  At the end portion of the tripod member 40 on the non-fixed side, the front surfaces of the three projecting portions 42 are inclined from the center in the width direction of each projecting portion 42 toward both sides, and the middle of the projecting portion 42 in the width direction. A pair of tapered surfaces 42a are formed to form the top portion 42b. The top portion 42 b is configured by a linear ridge line extending in the radial direction of the tripod member 40.

  In these image forming apparatuses, it is assumed that an error occurs in the support position with respect to the apparatus main body such as the image forming unit 10. At this time, the shaft center of the rotating body shaft 22 on the rotating body R side and the shaft center of the driving shaft 21 on the driving source M side are shifted in the vertical direction, the lateral direction, or both directions. A declination or misalignment occurs between the 21 axial centers.

  When torque is transmitted in such a state, the protrusions 42 and 47 slide in the axial direction of the outer rings 31 and 36 along the track grooves 32 and 37 in both the fixed and non-fixed connection portions. . At this time, the contact between the side surfaces 42c and 47b of the projecting portions 42 and 47 and the side surfaces 32a and 37a of the track grooves 32 and 37 is a line contact (or a point contact when a spherical surface is used for the side surfaces 42c and 47b). The resistance is small, and the protrusions 42 and 47 slide smoothly along the track grooves 32 and 37.

  In this way, by providing the bending function and the swing function at the two positions on both ends of the tripod member 40, even if there is a large declination or misalignment between the rotating body shaft 22 and the drive shaft 21, The rotating body R can be rotated at a constant speed without causing uneven speed. For this reason, when forming a toner image on the photosensitive drum 1 from which the electrostatic latent image has been acquired, it is possible to maintain the constant speed of rotation of the developing roller 11 and prevent the toner image and the image from expanding and contracting. it can.

  FIG. 5 shows a modification. In the above-described embodiment, the axial positions of the top portions 33b of the three bulging portions 33 of the non-fixed outer ring 31 (positions with respect to the axial direction of the outer ring 31) are all the same, and the tripod member 40 corresponding thereto The axial positions of the top portions 42b of the three protruding portions 42 (the positions of the tripod member 40 with respect to the axial direction) are all the same.

  When the outer ring 31 and the tripod member 40 are assembled, the top portion 42b of the protruding portion 42 provided in the direction of every 120 ° around the axis is the same as the top portion 33b of the bulging portion 33 provided in the direction of every 120 °. First, the taper abuts against the taper surface 33a on either side, and is guided to the track groove 32 along the taper surface 33a.

  However, when the phases of the top portion 33b of the bulging portion 33 and the top portion 42b of the protruding portion 42 coincide with each other at the time of assembling, not only the guidance effect by the taper surface 33a can be expected, but also a so-called three-point support is assumed. For example, when the pushing force exceeds a certain value, the abutted top portions 33b and 42b may be damaged. Therefore, in order to avoid the three-point support between the top portions 33b and 42b, the following configurations can be adopted.

  As a first configuration, among the top portions 33 b of the three bulging portions 33 of the outer ring 31, the axial position of the top portion 33 b of at least one bulging portion 33 is the axial direction of the top portion 33 b of the other bulging portion 33. Set different from the position. Here, in order to avoid the three-point support, it is sufficient that the top portion 33b of at least one bulging portion 33 is different from the other, and the two top portions 33b are in the same axial position and the other one top portion 33b is relative to each other. The structure which is located in front (opening side end part side), and the two top parts 33b are the same axial direction position, and the other one is located relatively back (closed side end part side), Or the structure from which all the axial direction positions of the three top parts 33b differ can be considered. At this time, the top portions 42b of the three projecting portions 42 on the tripod member 40 side are set to positions that do not simultaneously contact the three top portions 33b of the bulging portion 33, for example, all at the same axial position. The

  For example, in FIG. 5A, among the top portions 33 b of the three bulging portions 33 of the outer ring 31, the top portion 33 b of one bulging portion 33 is more forward than the top portions 33 b of the other two bulging portions 33. A configuration protruding by a distance L is shown. The top portions 33b of the other two bulging portions 33 are at the same axial position, and the top portions 42b of the three protruding portions 42 on the tripod member 40 side are all set at the same axial position. For this reason, the three-point support between the top portions 33b and 42b can be avoided.

  In FIG. 5 (a), as means for making one of the both ends of the tripod member 40 in the axial direction easier to drop than the other, the three protruding portions 47 at the other end and the other outer ring corresponding thereto. The connecting portion with the inner portion 36 is structured to be difficult to fall off in the axial direction, and the outer ring 36 or the tripod member 40 is provided with a retaining means. As the retaining, there is a method in which the axial hole 36b of the outer ring 36 and the axial hole 41a of the tripod member 40 are coupled by a coupling member. For example, a coil spring 45 is interposed as a coupling member between the fixed tripod member 40 and the outer ring 36. Both ends of one coil spring 45 are fitted into an axial hole 41 a provided in the center of the tripod member 40 and an axial hole 36 b provided in the outer ring 36, and the tripod member 40 and the outer ring 36 are fitted by the coil spring 45. It is supported not to leave. In this state, the tripod member 40 and the outer ring 36 can be bent and swung, and are not separated unless pulled in the axial direction with a relatively strong force. For this reason, as in the above embodiments, when the outer ring 31 and the outer ring 36 are pulled in the direction away from the axial direction, the tripod member 40 and the outer ring 31 are separated first, and the tripod member 40 and the outer ring 36 are separated. Absent.

  As a second configuration, among the top portions 42 b of the three protrusion portions 42 of the tripod member 40, the axial position of the top portion 42 b of at least one protrusion portion 42 is the axial direction of the top portion 42 b of the other protrusion portion 42. It can be set differently from the position. Here, in order to avoid the three-point support, it is sufficient that the top portion 42b of at least one protrusion 42 is different from the others, and the two top portions 42b are in the same axial position, and the other one top portion 42b is relative. Or a configuration in which the two apex portions 42b are positioned at the same axial position and the other one is positioned relatively rearward (the closing side end side), or A configuration in which the axial positions of the three top portions 42b are all different is conceivable. At this time, the top portions 33b of the three bulging portions 33 on the outer ring 31 side are set to positions that do not contact the three top portions 42b at the same time, for example, all at the same axial position.

  For example, FIG. 5 (b) shows that the top 42b of one protrusion 42 (see symbol A in the figure) is the other two of the tops 42b of the three protrusions 42 at one end of the tripod member 40. The structure which protrudes ahead rather than the top part 42b (refer code | symbol B, C in a figure) of the one protrusion part 42 is shown. The top portions 42b of the other two projecting portions 42 are at the same axial position, and the top portions 33b of the three bulging portions 33 on the outer ring 31 side are all set at the same axial position. For this reason, the three-point support between the top portions 33b and 42b can be avoided.

  In these embodiments, the rotating roller shaft 22 of the developing roller 11 and the driving shaft 21 of the driving source M are connected by the connecting means 30 including a tripod type constant velocity joint, and the developing roller 11 is rotated at a constant speed. However, the present invention is not limited to this example, and is another rotating body R that rotates by obtaining the driving force from the driving source M and the driving shaft 21 and is attached to and detached from the apparatus main body due to the necessity of maintenance or the like. What is to be said can also be comprised according to the said example.

  For example, the rotating shaft of the photosensitive drum 1 as the rotating body R and the driving shaft of the driving source M are connected by the connecting means 30 formed of a tripod type constant velocity joint having any one of the above-described configurations. May be rotated at a constant speed.

  When the photosensitive drum 1 rotates at a constant speed, the electrostatic latent image formed on the photosensitive drum 1 by the exposure unit 3 is expanded or contracted, or the toner image on the photosensitive drum 1 is transferred by the transfer unit 5. Expansion and contraction of the image can be prevented. For this reason, a high quality image can always be formed. If the rotational speed of the photosensitive drum 1 is not uneven, the azimuth around the axis of the exposure unit 3 and the transfer unit 5 with respect to the photosensitive drum 1 can be freely set, and the degree of design freedom can be increased.

  Further, as the other rotator R, various rollers such as a stirring roller 12 and other toner supply rollers used in the developing unit 4 of the image forming apparatus, a transfer roller 13 used in the transfer unit 9 and the secondary transfer unit 16, fixing, and the like. The fixing roller 14 and the pressure roller 15 used in the section 8 may be used. In addition, a plurality of rotating bodies R selected from these rotating bodies R may be an image forming unit that is integrally supported rotatably on a casing, a frame, or the like.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charger 3 Exposure means 4 Developing device 5 Transfer part 6 Intermediate transfer material 7 Cleaning device 8 Fixing part 9 Transfer part 10 Image forming unit 11 Developing roller 12 Agitation roller 13 Transfer roller 14 Fixing roller 15 Pressure roller 16 Two Next transfer portion 20 Drive transmission device 21 Drive shaft 22 Rotating body shaft 30 Connecting means 31, 36 Outer rings 32, 37 Track grooves 32a, 37a Side surfaces 33, 38 Swelled portion 33a Tapered surface 33b Top portion 34 Recessed portion 40 Tripod member 41 Body portion 42, 47 Protruding part 42a Tapered surface 42b Top part 42c, 47b Side face 47a Top part R Rotating body A Recording paper F, F 'Frame M Drive source (motor)

Claims (9)

The rotating body (R) involved in the formation of the toner image transferred to the transfer material, the driving source (M) for rotating the rotating body (R) about the axis, and the driving force from the driving source (M) An image forming apparatus including a drive transmission device (20) for transmitting to a rotating body (R)
The drive transmission device (20) connects a drive shaft (21) extending from the drive source (M) and a rotating body shaft (22) extending from the rotating body (R), and also connects the driving shaft (21). The fluctuation of the rotational speed of the rotating body shaft (22) that occurs when the angle between the shaft center of the rotating body shaft and the shaft center of the rotating body shaft (22) is not 180 ° or when the center shift occurs is suppressed. And connecting means (30) for transmitting the rotation of the drive shaft (21) to the rotating body shaft (22).
The connecting means (30) includes a pair of outer rings (31, 36) and a tripod member (40) connecting the pair of outer rings (31, 36), and the inner circumference of the outer rings (31, 36). Three track grooves (32, 37) extending in the axial direction are formed at intervals of 120 ° in the circumferential direction, and the track grooves (32, 37) are formed at both ends in the axial direction of the tripod member (40). 37) Three projecting portions that allow torque transmission between the outer rings (31, 36) and the tripod member (40) between the outer rings (31, 36) and the tripod member (40) by being accommodated in the axial direction in the inner direction. 42, 47) are tripod type constant velocity joints provided respectively,
Of the one end portion and the other end portion in the axial direction of the tripod member (40), the connection portion between the three projecting portions (47) at the other end portion and the corresponding outer ring (36) at the other end falls off. A retaining structure in which the axial hole (36b) provided in the other outer ring (36) and the axial hole (41a) provided in the tripod member (40) are coupled by a coupling member. An image forming apparatus provided with means. The tripod member (40) and the image forming apparatus according to claim 1, wherein the outer ring (31, 36) is a molded product of synthetic resin. The image forming apparatus according to claim 2, wherein the tripod member (40) and the outer rings (31, 36) are different in the main material of the synthetic resin. The connecting portion between the three protrusions (42) at the end on the rotating body shaft (22) side and the outer ring (31) on the rotating body shaft (22) side is the connecting portion on the rotating body shaft (22) side. The circumferential width of the bulging portion (33) is inclined at the tip of the bulging portion (33) formed between the adjacent track grooves (32) of the outer ring (31) in a direction opposite to the circumferential direction. A pair of tapered surfaces (33a, 33a) forming a top portion (33b) are formed in the middle, and three protrusions (42) at the end of the tripod member (40) on the rotating body shaft (22) side. A pair of tapered surfaces (42b) that are inclined toward the both sides from the center in the width direction of each protrusion (42) on the front surface portion of the protrusion (42). the image forming apparatus according to any one of claims 1 to 3, characterized in that a 42a). The axial position of the top portion (33b) of at least one bulging portion (33) among the top portions (33b) of the three bulging portions (33) of the outer ring (31) on the rotating body shaft (22) side. an image forming apparatus according to claim 4, characterized in that different from the axial position of the top of the other of the bulging portion (33) (33b). Among the top portions (33b) of the three bulge portions (33) of the outer ring (31) on the rotating body shaft (22) side, the top portion (33b) of one bulge portion (33) is the other two The image forming apparatus according to claim 5 , wherein the image forming apparatus projects forward from the top (33b) of the bulging portion (33). The shaft of the top (42b) of at least one protrusion (42) among the tops (42b) of the three protrusions (42) at the end of the tripod member (40) on the rotating body shaft (22) side. The image forming apparatus according to claim 4 , wherein the directional position is different from the axial position of the top portion (42 b) of the other protruding portion (42). Of the tops (42b) of the three protrusions (42) at the end of the tripod member (40) on the rotating body shaft (22) side, the top (42b) of one protrusion (42) The image forming apparatus according to claim 7 , wherein the image forming apparatus protrudes forward from the top (42b) of the two protrusions (42). Provided on both side surfaces (42c, 47b) facing the side surfaces of the track grooves (32, 37) of the projecting portions (42, 47) are curved surfaces curved along the axial direction, The image forming apparatus according to any one of claims 4 to 8 , wherein the side surface (32a, 37a) of 37) and the curved surface are brought into contact with each other.

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