JP2005148319A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus preventing deterioration in image quality caused by vibration generated in an apparatus body by stabilizing the posture of a developing part in a developing step by a comparatively simple mechanism as an image forming apparatus using a revolver developing system which is freely rotatably equipped with a plurality of developing parts. <P>SOLUTION: The image forming apparatus is equipped with a rocking body S holding a rotary body R with which a plurality of developing parts 5Y, 5M, 5C and 5BK are rotationally moved, and also rocking between a developing position where it comes close to an image carrier 2 and a non-developing position where it retreats from the image carrier 2. It is constituted so that moment by the gravity F1 of the rocking body S may act in a direction where the rocking body S rocks from the non-developing position to the developing position in the developing stage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus using an electrophotographic process, such as a copying machine, a printer, a facsimile machine, or a complex machine thereof, and more particularly to an image forming apparatus using a revolver type (rotary type) color developing system. It is.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a color copying machine using a revolver type (rotary type) color developing system is known (for example, see Patent Document 1).

  Specifically, a rotating body in which developing units corresponding to four colors (yellow, magenta, cyan, and black) are rotatably held is installed on the swinging body. The oscillating body provided with the rotating body includes a position where the rotating body is close to the photosensitive drum (image carrier) (hereinafter referred to as a developing position), and a position where the rotating body is retracted from the photosensitive drum (hereinafter referred to as non-rotating body). (Referred to as “developing position”).

When the electrostatic latent image on the photosensitive drum is developed with a desired color by one of the four color developing units, the corresponding developing unit is the photosensitive member in the non-developing position. The rotating body is rotated so as to face the drum. Thereafter (or immediately before), the swinging body is swung from the non-developing position to the developing position by the biasing force of the cam. In this manner, the developing roller of the corresponding developing unit is held with a predetermined gap between the photosensitive drum and a desired developing process is performed.
At this time, the oscillating body holds the posture at the developing position by the urging force of the torsion coil spring installed on the cam shaft inserted in the elongated hole.

  After the development process is performed, the urging force of the cam is released, and the rocking body swings to the non-developing position by the moment due to the weight of the rocking body (a state where a plurality of developing units and a rotating body are mounted). Move. Then, preparation for developing other colors at that position (rotation of the developing unit by the rotating body) is performed.

JP 2003-15381 A

  In the conventional image forming apparatus described above, the posture of the developing unit during the developing process is not stable, and the image quality may be deteriorated.

Details are as follows.
During the developing process, the swinging body provided with a plurality of developing units and rotating bodies maintains the posture at the developing position by the biasing force of the torsion coil spring installed in the vicinity of the cam. The urging force of the torsion coil spring is set so as to overcome the moment (the moment due to the weight of the oscillating body) acting in the direction of retracting the oscillating body from the developing position. That is, a force obtained by subtracting the weight of the oscillating body from the biasing force of the torsion coil spring (a component force in the oscillating direction component) is a holding force for actually maintaining the attitude of the oscillating body at the developing position.

  Here, when the holding force for holding the posture of the rocking body at the developing position is small, the developing gap (the gap between the photosensitive drum and the developing roller) is caused by various vibrations generated in the main body of the image forming apparatus. Will vary. If the development gap varies, the intensity of the electric field formed there varies, and a problem in image quality occurs that the density of the toner image formed on the photosensitive drum becomes non-uniform.

Therefore, in order to avoid the deterioration of the image quality as described above, it is necessary to keep the holding force of the rocking body large. That is, the biasing force of the torsion coil spring is set to be large to some extent.
Further, since the weight of the swinging body equipped with the four developing units is not small, the urging force of the torsion coil spring is set to be larger in order to overcome it. In particular, in a developing unit that stores a large amount of developer, the weight is inevitably increased with the size of the developing unit. Therefore, the urging force of the torsion coil spring is set to be larger.

In addition, the biasing force of the torsion coil spring is set to be larger in consideration that the biasing force of the torsion coil spring changes due to environmental fluctuations (mainly temperature fluctuations) and temporal changes.
As described above, in order to set the biasing force of the torsion coil spring large, the wire diameter and the number of turns of the coil spring increase accordingly, the apparatus becomes larger, and the assemblability of the apparatus also decreases.

  The present invention has been made to solve the above-described problems, and is an image forming apparatus using a revolver developing system that includes a plurality of developing units rotatably, and the attitude of the developing unit during the developing process SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable image forming apparatus which is stable with a relatively simple mechanism and does not deteriorate image quality due to vibration generated in the apparatus main body.

  According to a first aspect of the present invention, an image forming apparatus includes an image carrier, a plurality of developing units, a rotating member that rotates the plurality of developing units, and a rotating member that is rotatable. And a swinging body that swings between a development position in which the rotating body is close to the image carrier and a non-development position that is retracted from the image carrier. When a latent image on the image carrier is developed by one developing unit, a moment due to the weight of the rocking body acts in a direction in which the rocking body swings from the non-development position to the development position. .

  The image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein when the latent image on the image carrier is not developed, the swinging body is moved from the developing position to the non-developing position. And a biasing member that biases the rocking body so as to rock.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the urging member is a cam.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects of the present invention, the moment due to the weight of the oscillating body is determined by the oscillating body from the non-developing position. It always acts in the direction of swinging to the developing position.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects of the present invention, the moment caused by the weight of the rocking body is such that the rocking body is in the non-developing position. In some cases, the swinging body changes its direction in a swinging direction from the developing position to the non-developing position.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect of the present invention, when the latent image on the image carrier is developed, the rocking body is moved from the non-development position to the development. A second urging member that urges the oscillating body to oscillate to a position is provided.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect of the present invention, the second urging member is a cam.

  An image forming apparatus according to an eighth aspect of the present invention is the movable balancer according to any one of the first to seventh aspects, wherein the oscillating body is a movable balancer that varies the position of the center of gravity of the oscillating body. It is equipped with.

  An image forming apparatus according to a ninth aspect of the present invention is the image forming apparatus according to any one of the first to eighth aspects, wherein the swinging body reaches the developing position or the non-developing position. A shock-absorbing member is provided for shock-absorbing the rocking body.

  An image forming apparatus according to a tenth aspect of the present invention is the image forming apparatus according to the ninth aspect, wherein the buffer member is a cam for adjusting a speed at which the rocking body swings.

  An image forming apparatus according to an eleventh aspect of the present invention is the image forming apparatus according to any one of the first to tenth aspects, wherein the plurality of developing units are detachably attached to the rotating body. It is configured.

  An image forming apparatus according to a twelfth aspect of the present invention is the developer container according to any one of the first to eleventh aspects, wherein each of the plurality of developing sections includes a developer. It is equipped with.

  The present invention relates to an image forming apparatus using a revolver developing system having a plurality of developing units rotatably, and without using a torsion coil spring or the like having a large spring force, the posture of a rocking body at a developing position by a moment due to its own weight. Is retained. As a result, it is possible to provide a highly reliable image forming apparatus in which the posture of the developing unit during the developing process is stable and image quality is hardly deteriorated due to vibration generated in the apparatus main body.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
A first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire color image forming apparatus will be described with reference to FIG.
As shown in FIG. 1, the image forming apparatus main body 1 is provided with a rotating body R so as to face a photosensitive drum 2 as an image carrier.
In addition to the rotating body R, a charging unit 3, a writing unit 4, an intermediate transfer belt 8, a cleaning blade 6 (cleaning unit), and the like are disposed on the outer periphery of the photosensitive drum 2.

  Here, four developing units (yellow developing unit 5Y, magenta developing unit 5M, cyan developing unit 5C, and black developing unit 5BK) are detachably installed on the rotator R, respectively. Each of the four developing units 5Y, 5M, 5C, and 5BK includes a developing roller 5a, a replenishing roller 5b, a toner bottle 5d (developer container), an agitator 5e, and the like. The toner bottles 5d of the four developing units 5Y, 5M, 5C, and 5BK store yellow toner, magenta toner, cyan toner, and black toner, respectively.

The four developing units 5Y, 5M, 5C, and 5BK rotate and move to positions facing the photosensitive drum 2 (development positions) by the rotation of the rotating body R, so that they are on the photosensitive belt 1. Each color toner image is sequentially formed. The developing position is determined by contacting rollers (not shown) inserted at both ends of the developing roller 5a in the axial direction with the photosensitive drum 2. The gap between the developing roller 5a and the photosensitive drum 2 determined by this roller is called a developing gap.
Here, the rotating body R is rotatably held by a swinging body S that swings between the developing position and the non-developing position. Then, each time a toner image of each color is formed by the four developing sections 5Y, 5M, 5C, and 5BK, the swinging body S swings.

  Specifically, the yellow developing unit 5Y is held at a position (development position) facing the photosensitive drum 2 (the state shown in FIG. 1), and a yellow toner image is formed on the photosensitive drum 2. Thereafter, the rocking body S is retracted from the developing position to the non-developing position by the operation of the cam 56 as the urging member (the state shown in FIG. 2). Then, the rotator R rotates about 90 degrees counterclockwise at the non-development position, and the black developing unit 5BK moves to the position where the yellow developing unit 5Y was located. Thereafter, the engagement between the engaging portion 65 and the cam 56 is released, and the rocking body S moves from the non-development position to the developing position by a moment due to the weight F1 of the rocking body S. Then, a black toner image is formed on the photosensitive drum 2 in a state where the black developing unit 5BK is in the developing position. The configuration and operation of the oscillator S will be described in detail later.

Then, the toner images of the respective colors formed on the photosensitive drum 2 are sequentially transferred on the intermediate transfer belt 8 in a superimposed manner.
Here, a driving roller, two driven rollers, and a first transfer roller 7 are disposed on the inner periphery of the intermediate transfer belt 8. The intermediate transfer belt 8 is stretched and supported by these rollers. A second transfer roller 9 and an intermediate transfer belt cleaning unit (not shown) are disposed on the outer periphery of the intermediate transfer belt 8.

  Here, the second transfer roller 9 and the intermediate transfer belt cleaning unit are configured to be able to contact and separate from the intermediate transfer belt 8, respectively. Then, the second transfer roller 9 and the intermediate transfer belt cleaning unit are retracted away from the intermediate transfer belt 8 until the desired toner image is superimposed on the intermediate transfer belt 8. Then, after the superposition of the toner images on the intermediate transfer belt 8 is completed, the second transfer roller 9 and the intermediate transfer belt cleaning unit move to a position where they contact the intermediate transfer belt 8.

Then, the color toner image on the intermediate transfer belt 8 is transferred to the transfer material P by the second transfer roller 9 in contact with the intermediate transfer belt 8.
Further, the untransferred toner remaining on the intermediate transfer belt 8 after the intermediate transfer process is collected by the intermediate transfer belt cleaning unit in contact with the intermediate transfer belt 8.

On the other hand, a plurality of transport rollers, a registration roller 11, a fixing unit 20, a paper discharge roller 25, and the like are disposed in the transport path of the transfer material P in the apparatus main body 1.
Here, the fixing unit 20 includes a fixing roller 21 as a heating unit and a pressure roller 22 as a pressure unit, and fixes an unfixed toner image on the transfer material P.

The image forming apparatus configured as described above operates as follows during image formation.
Referring to FIG. 1, the photosensitive drum 2 rotates in the direction of the arrow in the drawing. First, the surface of the photosensitive drum 2 is charged at a position facing the charging unit 3. Next, the surface of the photosensitive drum 2 reaches a portion facing the writing unit 4. An electrostatic latent image corresponding to image information of a desired color among yellow, magenta, cyan, and black is formed on the photosensitive drum 2 by the exposure light emitted from the writing unit 4.

Thereafter, the surface of the photosensitive drum 2 reaches a position (development position) facing the development unit corresponding to a desired color among the four development units 5Y, 5M, 5C, and 5BK. Then, the corresponding color toner is supplied from the developing unit to the latent image on the photosensitive drum 2. Thus, a one-color toner image is formed on the photosensitive drum 2.
Thereafter, the surface of the photosensitive drum 2 reaches a portion facing the intermediate transfer belt 8. The toner image formed on the photosensitive drum 2 is transferred onto the intermediate transfer belt 8 by the first transfer roller 7 to which a predetermined voltage is applied.

Here, untransferred toner that has not been transferred to the intermediate transfer belt 8 remains on the photosensitive drum 2 after passing through the portion facing the intermediate transfer belt 8.
Then, the surface of the photosensitive drum 2 to which the untransferred toner is attached reaches a portion facing the cleaning blade 6. At this position, the untransferred toner is collected in the cleaning unit.

  Such a series of processes on the photosensitive drum 2 is similarly performed for the other colors. The toner images formed on the photosensitive drum 2 by sequentially rotating and moving the four developing units 5Y, 5M, 5C, and 5BK along with the swinging of the swinging body S are transferred onto the intermediate transfer belt 8 in an overlapping manner. .

Thereafter, the color toner image formed over the intermediate transfer belt 8 reaches the portion facing the second transfer roller 9 as the intermediate transfer belt 8 travels in the direction of the arrow. At this position, the toner image is transferred onto the conveyed transfer material P.
Here, untransferred toner that has not been transferred to the transfer material P remains on the intermediate transfer belt 8 after passing through the portion facing the second transfer roller 9.
Then, the surface of the intermediate transfer belt 8 to which the untransferred toner adheres reaches a portion facing the intermediate transfer belt cleaning unit. At this position, the untransferred toner is collected in the intermediate transfer belt cleaning unit.
Thus, a series of processes on the intermediate transfer belt 8 is completed.

On the other hand, the transfer material P fed from the paper feeding unit 10 reaches the position of the registration roller 11 after passing through the transport roller. The transfer material P that has reached the position of the registration roller 11 is conveyed toward the position of the second transfer roller 9 in time so that the toner image formed on the intermediate transfer belt 8 is transferred.
Thereafter, the transfer material P that has passed the position of the second transfer roller 9 is transported to the position of the fixing unit 20 by the transport belt 12. At this position, the toner image on the transfer material P is fixed.
Then, the transfer material P as an output image passes through the fixing unit 20 and is then discharged out of the apparatus main body 1 through the discharge roller 25.
Thus, a series of image forming operations in the image forming apparatus is completed.

Next, with reference to FIGS. 3 to 5, the rocking body S that holds the rotating body R that houses the four developing units 5Y, 5M, 5C, and 5BK will be described in detail.
3 is a perspective view showing the oscillating body S, FIG. 4 is a front view in the direction of arrow C in FIG. 3, and FIG. 5 is a side view in the direction of arrow B in FIG. 3 to 5, the developing units 5Y, 5M, 5C, and 5BK that are detachably installed on the rotating body R are not shown.

  As shown in FIGS. 3 and 4, the rocking body S is provided with rocking plates 44 and 45 at both ends in the axial direction (the direction perpendicular to the paper surface of FIG. 1). The rotating body R, the swing shaft 48 provided with the idle gear 53, and the cam shaft 55 integrated with the cams 56 and 57 are sandwiched between the swing plates 44 and 45 at both ends. ing.

The rotating body R includes a rotating shaft 43 and rotating plates 41 and 42 provided integrally at both ends of the rotating shaft 43. A gear portion 41 a is provided on the outer periphery of one rotating plate 41. The gear portion 41a of the rotating plate 41 meshes with the idle gear 53 of the swing shaft 48 with reference to FIG.
Referring to FIGS. 3 and 4, bearings 46 and 47 are inserted at both ends of rotation shaft 43 (outside from the fixed positions of rotation plates 41 and 42). The bearings 46 and 47 are inserted into the holes of the swing plates 44 and 45. Thereby, the rotating body R is rotatably held by the swing plates 44 and 45 of the swing body S around the rotating shaft 43.

  At one end of the swing shaft 48, an idle gear 53 having the swing shaft 48 as a support shaft is rotatably provided. In addition, bearings 49 and 50 are inserted at both ends of the swing shaft 48. The bearings 49 and 50 are inserted into the holes of the swing plates 44 and 45. Further, referring to FIG. 4, both ends of rocking shaft 48 (further outside the insertion positions of bearings 49 and 50) are fixed to body side plates 71 and 72 of the apparatus body by caulking. As a result, the rocking body S is swingably held on the side plates 71 and 72 of the apparatus main body about the rocking shaft 48.

  Further, the idle gear 53 of the swing shaft 48 meshes with a drive gear 73 installed on a motor shaft of a drive motor 74 fixed to one main body side plate 71. Further, the idle gear 53 of the swing shaft 48 meshes with the gear portion 41a of the rotating body R. Then, the driving force of the drive motor 74 is transmitted to the gear portion 41a via the drive gear 73 and the idle gear 53, so that the rotating body R on which the developing portions 5Y, 5M, 5C, and 5BK are mounted has a desired rotation direction. Rotate.

  3 to 5, cams 56 and 57 are integrally provided at both ends of the cam shaft 55. Bearings 58 and 59 are inserted into both ends of the cam shaft 55 (further outside the fixed positions of the cams 56 and 57). The bearings 58 and 59 are inserted into the holes of the swing plates 44 and 45. Thereby, the cams 56 and 57 are rotatably held by the swing plates 44 and 45 of the swing body S around the cam shaft 55.

Here, one end of the cam shaft 55 is connected to a drive unit (not shown), and the swing body S swings when the cam shaft 55 is driven to rotate.
Specifically, when the rocking body S is brought close to the developing position (during the developing step), the cams 56 and 57 are engaged with the engaging portion 65 fixed to the apparatus main body 1 with reference to FIG. The cam shaft 55 is rotated so as not to match.

At this time, the moment due to the weight F1 of the rocking body S acts in the direction of rocking the rocking body S from the non-development position to the development position (clockwise in FIG. 1).
That is, as shown in FIG. 1, the center of gravity of the rocking body S on which the developing units 5Y, 5M, 5C, and 5BK are mounted substantially coincides with the center of the rotating body R. It can be considered that the total weight F1 of the rocking body S on which the developing units 5Y, 5M, 5C, and 5BK are mounted is added at this position. Therefore, from the positional relationship between the center of gravity of the rocking body S and the rocking center 48, the moment due to the weight F1 of the rocking body S acts in the clockwise direction in FIG.

  As described above, in the first embodiment, the postures of the developing units 5Y, 5M, 5C, and 5BK at the development position during the development process are held only by the moment due to the weight F1 of the oscillator S. In other words, a force that generates a moment in a direction different from the direction of the moment due to the weight F1 of the oscillating body S does not act on the oscillating body S of the first embodiment.

Unlike the holding force due to the torsion coil spring or the like, the holding force due to the own weight F1 of the rocking body S is stable with no environmental variation or temporal variation. Therefore, problems such as variations in the development gap due to various vibrations generated in the apparatus main body 1 are suppressed.
In the first embodiment, the approaching operation to the developing position is performed only by the moment due to the own weight F1 of the oscillator S without using a torsion coil spring or the like, so that the image forming apparatus is relatively inexpensive.

On the other hand, when the swinging body S is retracted from the development position to the non-development position (during the non-development process), the cams 56 and 57 are fixedly engaged with the apparatus main body 1 with reference to FIG. The cam shaft 55 is rotated so as to engage with the portion 65. At this time, the cams 56 and 57 function as a biasing member that biases the rocking body S so as to rock the rocking body S from the developing position to the non-developing position.
Then, after the oscillating body S is retracted to the non-developing position, or while the oscillating body S is retracted to the non-developing position, the drive motor 74 is driven to rotate the rotating body R in order to rotate the developing unit. Let

Thereafter, in order to carry out the developing process by the developing unit rotated and moved, the cam shaft 55 is rotated as described above, and the swinging body S is brought close to the developing position again.
Here, the outer peripheries of the cams 56 and 57 are formed such that the distance from the cam shaft 55 gradually decreases as the cam shaft 55 rotates at this time. As a result, the speed at which the swinging body S swings from the non-development position to the development position is adjusted, and the impact when reaching the development position is buffered. As described above, the cams 56 and 57 functioning as cushioning members alleviate the impact on the developing units 5Y, 5M, 5C, and 5BK as the swinging body S swings smoothly, so that the developing units 5Y, 5M, 5C, Toner scattering from 5BK is suppressed. The cams 56 and 57 similarly function as a buffer member when the rocking body S moves from the development position to the non-development position. Further, the buffer member is not limited to the cams 56 and 57, and a spring, a buffer material, or the like can be used.

  As described above, in the image forming apparatus configured as in the first embodiment, the posture of the rocking body S at the developing position is maintained by the moment due to its own weight without using a coil spring or the like. Accordingly, the postures of the developing units 5Y, 5M, 5C, and 5BK during the developing process are stabilized, and deterioration of image quality due to vibration generated in the apparatus main body 1 can be suppressed.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 6 is a configuration diagram illustrating the image forming apparatus according to the second embodiment, and corresponds to FIG. 1 according to the first embodiment. In the image forming apparatus according to the second embodiment, the position of the swing center of the swing body S is different from that of the first embodiment.

  As shown in FIG. 6, unlike the first embodiment, the rocking shaft 48 that is the rocking center in the rocking body S of the second embodiment is arranged at the lower right of the rocking plate. Yes. A cam 56 that functions as an urging member and a buffer member is disposed on the upper left of the swing plate.

As in the first embodiment, the oscillating body S is oscillated by rotating the cam shaft in which the cam 56 is integrated.
That is, when the swinging body S is brought close to the developing position, the cam shaft is rotated so that the cam 56 does not engage with the engaging portion 65 fixed to the apparatus main body 1 with reference to FIG. At this time, the moment due to the weight F1 of the rocking body S acts in the direction of rocking the rocking body S from the non-development position to the development position (counterclockwise in FIG. 6).

  On the other hand, when the oscillating body S is retracted from the development position to the non-development position, the camshaft is rotated so that the cam 56 is engaged with the engagement portion 65 fixed to the apparatus main body 1. At this time, the cam 56 functions as a biasing member that biases the swinging body S so as to swing the swinging body S from the developing position to the non-developing position.

  As described above, also in the image forming apparatus configured as in the second embodiment, the posture of the oscillating body S at the developing position is determined only by the moment due to the weight of the oscillating body S, as in the first embodiment. Retained. Accordingly, the postures of the developing units 5Y, 5M, 5C, and 5BK during the developing process are stabilized, and deterioration of image quality due to vibration generated in the apparatus main body 1 can be suppressed.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 7A is a configuration diagram showing a main part of the image forming apparatus according to Embodiment 3, and shows a state in which the rocking body S is held at the development position. FIG. 7B is a diagram showing a state in which the rocking body S of FIG. 7A is retracted to the non-developing position.
The image forming apparatus of the third embodiment is different from those of the above-described embodiments in that the rocking body S is held by the moment due to its own weight even in the non-developing position.

  As shown in FIGS. 7A and 7B, the rocking shaft 48 serving as the rocking center in the rocking body S of the third embodiment is different from the above embodiments in the vicinity of the lower center of the rocking plate. It is arranged. In other words, the swing shaft 48 is disposed at a position close to the lower position of the center of gravity of the swing body S (on the line of the arrow F1 in the drawing).

In addition to the urging member and the cam 56 (first cam) that function as a buffering member and the urging member disposed at the lower left of the swing plate, the cam 86 (second cam) that functions as the second urging member and buffering member. Cam) is disposed at the lower right of the swing plate.
Here, the second cam 86 is also provided integrally at both ends of the second cam shaft. The second camshaft is rotatably held by the swing plate of the swing body S via a bearing. Further, one end of the second cam shaft is connected to the drive unit, and the rocking body S is swung in the developing position direction when the second cam 86 is rotationally driven.

  Specifically, when the swinging body S is moved from the non-development position to the development position, the first engaging portion 65 fixed to the apparatus main body 1 is engaged with reference to FIG. 7A. The second cam 86 that has not been engaged with the second engagement portion 85 fixed to the apparatus main body 1 is engaged with the second engagement portion 85.

  At this time, the moment of action of the swinging body S due to its own weight F1 changes in the direction of swinging the swinging body S from the non-development position to the development position (counterclockwise in FIG. 7A). That is, the moment acting in the direction of swinging the swinging body S from the development position to the non-developing position (clockwise in FIG. 7B) at the non-development position causes the swinging body S to move at the development position. It changes so as to act in a swinging direction from the non-development position to the development position. This is because the rocking body S is biased by the second cam 86 and the positional relationship between the center of gravity of the rocking body S and the rocking shaft 48 is changed.

Thus, at the development position, the oscillator S is held only by the moment due to its own weight F1. Note that the second cam 86 is further rotated immediately before the rocking body S reaches the developing position, so that the second cam 86 and the second engaging portion 85 are slightly separated from each other.
Further, both the first cam 56 and the second cam 86 are formed such that the distance from the cam shaft to the outer periphery gradually decreases or gradually increases. Thereby, the impact when the rocking body S reaches the developing position from the non-developing position is alleviated.

On the other hand, when the oscillating body S is retracted from the development position to the non-development position, referring to FIG. 7B, the first cam 56 that is not engaged with the first engagement portion 65 is first engaged. The second cam 86 is rotated so that it engages with the portion 65 and does not engage with the second engagement portion 85.
At this time, the oscillating body S is urged by the first cam 56, and the acting direction of the moment due to the own weight F1 changes from a certain position to the direction in which the oscillating body S is oscillated from the developing position to the non-developing position. To do. At the non-development position, the rocking body S is stably held only by the moment due to its own weight F1.

  As described above, also in the image forming apparatus configured as in the third embodiment, the posture of the oscillating body S at the developing position is determined only by the moment due to the weight of the oscillating body S, as in the above embodiments. Retained. Accordingly, the postures of the developing units 5Y, 5M, 5C, and 5BK during the developing process are stabilized, and deterioration of image quality due to vibration generated in the apparatus main body 1 can be suppressed.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 8A is a configuration diagram showing a main part of the image forming apparatus according to Embodiment 4, and shows a state in which the rocking body S is held at the development position. FIG. 8B is a diagram illustrating a state in which the rocking body S of FIG. 8A is retracted to the non-developing position.
The image forming apparatus of the fourth embodiment is different from that of the third embodiment in that the position of the center of gravity of the oscillating body S varies due to the movement of the balancer 96.

As shown in FIGS. 8A and 8B, the rocking shaft 48 serving as the rocking center in the rocking body S of the fourth embodiment is arranged near the lower center of the rocking plate as in the third embodiment. Has been.
Further, unlike the third embodiment, the oscillator S of the fourth embodiment is not provided with cams 56 and 86. The swing body S is provided with a balancer 96 for changing the position of the center of gravity of the swing body S instead of the cams 56 and 86.

Here, the balancer 96 is installed on the upper part of the swing plate via the guide member 95.
Although not shown, the balancer 96 includes a motor on which a pinion is installed. The pinion of the balancer 96 meshes with the rack portion of the guide member 95. As a result, the balancer 96 travels on the guide member 95 in the direction of the arrow in the figure, and the swinging body S swings in the developing position direction or the non-developing position direction.

Specifically, when the rocking body S is moved from the non-development position to the development position, the balancer 96 is moved from the right side to the left side with reference to FIG. 8A. At this time, due to the movement of the balancer 96, the position of the center of gravity of the oscillating body S also moves from the right side to the left side.
As a result, the action direction of the moment due to its own weight F3 (= F2) changes from the non-developing position to the developing position in a direction where the momentum F3 (= F2) swings at a certain position in the movement path of the balancer 96 (see FIG. (This is a change from the arrow F3 in FIG. 8B to the arrow F2 in FIG. 8A.) That is, at this time, the balancer 96 functions as a second urging member.

On the other hand, when the oscillating body S is retracted from the developing position to the non-developing position, the balancer 96 is moved from the left side to the right side with reference to FIG. 8B. At this time, due to the movement of the balancer 96, the position of the center of gravity of the oscillating body S also moves from the left side to the right side.
As a result, the action direction of the moment due to its own weight changes from a certain position in the movement path of the balancer 96 to a direction in which the rocking body S is swung from the developing position to the non-developing position (from the arrow F2 in FIG. 8A). (Change to arrow F3 in FIG. 8B). That is, at this time, the balancer 96 functions as an urging member.
At the non-development position, the swinging body S is held in contact with a stopper (not shown) provided in the apparatus main body 1 so as to maintain its posture.

As described above, also in the image forming apparatus configured as in the fourth embodiment, the posture of the oscillating body S at the developing position is determined only by the moment due to the weight of the oscillating body S, as in the above-described embodiments. Retained. Accordingly, the postures of the developing units 5Y, 5M, 5C, and 5BK during the developing process are stabilized, and deterioration of image quality due to vibration generated in the apparatus main body 1 can be suppressed.
Further, in the fourth embodiment, it is possible to finely adjust the magnitude of the moment by adjusting the position of the balancer 96. As a result, even when the toner in the developing units 5Y, 5M, 5C, and 5BK is consumed and the weight of the rocking body S changes, the development is performed by adjusting the magnitude of the moment to be constant. The postures of the developing units 5Y, 5M, 5C, and 5BK at the positions can always be held with a stable force.

  It should be noted that the present invention is not limited to each of the above-described embodiments, and it is obvious that each embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in each embodiment. It is. Further, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiments, and the number, position, shape, and the like that are suitable for implementing the present invention can be used.

1 is a configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a schematic view showing a state in which a rocking body in the image forming apparatus of FIG. 1 is retracted to a non-developing position. FIG. 2 is a perspective view showing an oscillating body installed in the image forming apparatus of FIG. 1. It is a front view of the arrow C direction in the rocking body of FIG. It is a side view of the arrow B direction in the rocking body of FIG. It is a block diagram which shows the image forming apparatus in Embodiment 2 of this invention. It is the schematic which shows the state by which the rocking body installed in the image forming apparatus in Embodiment 3 of this invention was hold | maintained in the developing position. It is the schematic which shows the state which the rocking | fluctuation body of FIG. 7A was retracted | retreated to the non-development position. It is the schematic which shows the state by which the rocking body installed in the image forming apparatus in Embodiment 4 of this invention was hold | maintained at the developing position. It is the schematic which shows the state which the rocking | fluctuation body of FIG. 8A was evacuated to the non-development position.

Explanation of symbols

1 image forming apparatus body (apparatus body), 2 photosensitive drum (image carrier),
3 charging unit, 4 writing unit, 5Y, 5M, 5C, 5BK developing unit,
5a Development roller, 5b Supply roller,
5d toner bottle (developer container), 5e agitator,
6 cleaning blade (cleaning part), 7 first transfer roller,
8 Intermediate transfer belt, 9 Second transfer roller, 10 Paper feed unit,
11 Registration roller 12 Transport belt 20 Fixing unit
25 discharge roller, 41, 42 rotating plate, 41a gear section,
43 Rotating shaft, 44, 45 Swing plate,
46, 47, 49, 50, 58, 59 Bearing,
48 swing shaft, 53 idle gear, 55 camshaft,
56, 57, 86 Cam, 65, 85 Engagement part, 71, 72 Body side plate,
73 drive gear, 74 drive motor, 95 guide member,
96 Balancer, S rocking body, R rotating body.

Claims (12)

An image carrier;
A rotating body that holds the plurality of developing units and rotates the plurality of developing units;
A rotating body that rotatably holds the rotating body, and that swings between a developing position where the rotating body is close to the image carrier and a non-developing position where the rotor is retracted from the image carrier,
When the latent image on the image carrier is developed by one of the plurality of developing sections, the swinging body is moved in the direction in which the swinging body swings from the non-developing position to the developing position. An image forming apparatus characterized by the fact that a moment due to is exerted. And a biasing member that biases the swinging member so that the swinging member swings from the developing position to the non-developing position when the latent image on the image carrier is not developed. The image forming apparatus according to claim 1. The image forming apparatus according to claim 2, wherein the urging member is a cam. 4. An image forming apparatus according to claim 1, wherein the moment due to the weight of the rocking body always acts in a direction in which the rocking body rocks from the non-development position to the development position. apparatus. The moment due to the weight of the swinging body acts when the swinging body is in the non-development position, changing its direction in a direction in which the swinging body swings from the developing position to the non-developing position. The image forming apparatus according to claim 1. And a second urging member for urging the swinging member so that the swinging member swings from the non-development position to the development position when developing the latent image on the image carrier. The image forming apparatus according to claim 5. The image forming apparatus according to claim 6, wherein the second urging member is a cam. The image forming apparatus according to claim 1, wherein the oscillating body includes a movable balancer that varies a position of a center of gravity of the oscillating body. The image according to any one of claims 1 to 8, further comprising a buffer member that cushions an impact generated on the rocking body when the rocking body reaches the developing position or the non-developing position. Forming equipment. The image forming apparatus according to claim 9, wherein the buffer member is a cam that adjusts a speed at which the swinging body swings. The image forming apparatus according to claim 1, wherein each of the plurality of developing units is configured to be detachable from the rotating body. The image forming apparatus according to claim 1, wherein each of the plurality of developing units includes a developer container in which a developer is accommodated.

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