Patent Application
20150047459
This patent application is based on and claims priority pursuant to 35 U.S.C. §119(a) to Japanese Patent Application Nos. 2013-169020, filed on August 15, 2013, and 2013-268143, filed on Dec. 25, 2013, respectively, in the Japan Patent Office, the entire disclosures of which are hereby incorporated by reference herein.
1. Technical Field
Embodiments of this invention relate to a rotator driving system for a rotating a rotator, such as a photoconductive drum, a roller, etc., employed in an image forming apparatus or the like, and to an image forming apparatus with the same. In particular, embodiments of the present invention relate to a rotator driving system that has a dynamic vibration absorber to suppress fluctuation in rotational speed of the rotator, and the image forming apparatus with the same.
2. Related Art
Conventionally, when a rotational speed of a photoconductive drum employed in an image forming apparatus fluctuates, a scanning pitch accordingly changes in a sub-scanning direction, resulting in so-called banding, i.e., uneven density occurs in an image. To reduce such banding, a flywheel coaxial with the axis of the photoconductive drum is typically employed.
For such a configuration, however, since the fluctuation in rotational speed of the photoconductive drum is suppressed by using a larger flywheel, the size and weight of the apparatus is increased.
To suppress the fluctuation in rotational speed of the photoconductive drum without increasing the size of the flywheel, a configuration is known that includes a dynamic vibration absorber having an inertia body with a small diameter. One such system employs a dynamic vibration absorber that includes an annular inertia body disposed around a drive shaft with a ring of rubber interposed therebetween, which rotates together with a photoconductive drum.
In this configuration, design parameters of the dynamic vibration absorber, such as spring constant and viscous damping coefficient are determined by the rubber ring that supports the annular inertia body.
Other conventional systems include a dynamic vibration absorber, in which an inertia body is attached to a first rotator while sandwiching an elastic member therebetween. As in the above-described former conventional dynamic vibration absorber, spring constant and viscous damping coefficient design parameters are adjusted and set based on a single elastic member such as rubber, etc. The inertia body is supported on a support shaft (e.g., a rotary shaft of a photoconductive drum) via bearings.
In yet other conventional systems, a pair of inertia moment (herein below, simply referred to as inertia) adjusting devices is provided at different sections around an outer circumference of the inertia body to precisely set the spring constant to an optimal value, thereby omitting any fluctuation when it occurs therein by precisely adjusting the inertia.
To optimize the viscosity-providing component, the dynamic vibration absorber is generally made of rubber to utilize its large viscosity.
One aspect of the present invention provides a novel rotator driving system for driving a rotator with a motor that includes: a dynamic vibration absorber attached to a rotary shaft of the rotator. The dynamic vibration absorber includes: an inertia body; a viscosity-providing component to provide a viscosity; a torsion spring unit that includes a boss fixed to the rotary shaft, at least two spokes extending radially outward from the boss, and at least one seat provided at one of tips of the at least two spokes to fix the inertia body. The torsion spring unit is fixed by both the rotary shaft of the rotator and the boss fixed to the rotary shaft. The torsion spring unit also supports the inertia body via the at least one seat provided at one of tips of the at least two spokes.
Another aspect of the present invention provides a novel rotator driving system for driving a rotator with a motor that includes a dynamic vibration absorber attached to a rotary shaft of a rotator. The dynamic vibration absorber includes: a first inertia body not fixed to the rotary shaft in its rotational direction; at least two torsion spring units each extending radially outward from the rotary shaft while connecting to the first inertia body and the rotary shaft at its both ends, respectively; a viscosity-providing component supporting unit fixed to the rotary shaft; and a viscosity-providing component made of viscoelastic rubber connected to the first inertia body and the rotary shaft via the viscosity-providing component supporting unit. An amount of inertia and a spring constant of the dynamic vibration absorber are adjusted by moving a coupling position of the torsion spring unit coupled with the first inertia body in the radial direction in accordance with a variation in viscosity characteristics of the viscosity-providing component.
Yet another aspect of the present invention provides a novel image forming apparatus having a rotator driving system. The rotator driving system includes a dynamic vibration absorber attached to a rotary shaft of the rotator. The dynamic vibration absorber includes: an inertia body; a viscosity-providing component to provide a viscosity, a torsion spring unit that includes a boss fixed to the rotary shaft, at least two spokes extending radially outward from the boss, and at least one seat provided at one of tips of the at least two spokes to fix the inertia body. The torsion spring unit is fixed by the rotary shaft of the rotator and the boss fixed to the rotary shaft. The torsion spring unit supports the inertia body via the at least one seat provided at one of tips of the at least two spokes.
A more complete appreciation of the present invention and many of the attendant advantages thereof will be more readily obtained as substantially the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
In view of the above-described problems, one embodiment of the present invention establishes a dynamic vibration absorber capable of maintaining both spring and viscosity functions thereof while accurately supporting an inertia body coaxially with an axis of a rotary shaft. The other embodiments of the present invention provide a rotator driving system capable of reducing fluctuation in speed and an image forming apparatus with the rotator driving system as well.
Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views thereof and in particular to
Now, a first embodiment of the present invention is described with reference to
Now, an exemplary operation of forming a full-color image using the copier according to this embodiment of the present invention is described. First of all, when a photoconductive member driving system, not shown, drives and rotates the photoconductive drum 1Y in a direction as shown by arrow in the drawing, the photoconductive drum 1Y is uniformly charged by the electric charger 2Y. Subsequently, an optical device, not shown, irradiates a light beam LY and forms a Y-electrostatic latent image on the photoconductive drum 1Y. This Y-electrostatic latent image is subsequently developed by the developing device 9Y with Y-color toner included in the developer. During the development, a given developing bias is applied between a developing roller and the photoconductive drum 1Y, so that the Y-color toner on the developing roller electrostatically adheres onto a portion of a Y-electrostatic latent image on the photoconductive drum 1Y.
The Y-color toner image developed and formed in this way is conveyed to a primary transfer position, at which the photoconductive drum 1Y contacts the intermediate transfer belt 5, as the photoconductive drum 1Y rotates. At the primary transfer position, a predetermined bias voltage is applied to a backside of the intermediate transfer belt 5 from a primary transfer roller 6Y. Subsequently, a primary transfer field is caused by the predetermined bias voltage applied in this way, and the Y-color toner image on the photoconductive drum 1Y is attracted toward the intermediate transfer belt 5 and primarily transferred onto the intermediate transfer belt 5 under the primary transfer field. Subsequently, an M toner image, a C toner image, and a Bk toner image are primarily transferred similarly onto the Y-color toner image borne on the intermediate transfer belt 5 to sequentially overlap with each other. In
The overlapped four-color toner images on the intermediate transfer belt 5 in this way is subsequently conveyed to a secondary transfer position opposed to a secondary transfer roller 7 as the intermediate transfer belt 5 rotates. Toward the secondary transfer position, a transfer sheet P (simply indicated by arrow in the drawing) is conveyed at a predetermined time by the registration roller 10. At the secondary transfer position, the secondary transfer roller 7 applies a predetermined bias voltage onto the backside of the transfer sheet P. The secondary transfer electric field caused by the predetermined bias voltage when applied and a prescribed contacting pressure caused at the secondary transfer position allows the four-color toner image to be secondarily transferred from the transfer belt 5 to the transfer sheet P at once. Afterward, the secondarily transferred toner image on the transfer sheet P is discharged outside the image forming apparatus when completing a fixing process executed by a pair of fixing rollers 8.
The Y-color toner image developed and formed in this way is subsequently conveyed to the primary transfer position, in which the photoconductive drum 1Y and intermediate transfer belt 5 come into contact with each other as the photoconductive drum 1Y rotates. At the primary transfer position, the primary transfer roller 6Y applies the predetermined bias voltage onto the backside of the intermediate transfer belt 5. Subsequently, under a primary transfer field caused by the predetermined bias voltage applied, the Y-color toner image on the photoconductive drum 1Y is attracted toward the intermediate transfer belt 5 and is primarily transferred onto the intermediate transfer belt 5. Subsequently, an M toner image, a C toner image, and a Bk toner image are similarly primarily transferred onto the Y-color toner image on the intermediate transfer belt 5 to sequentially overlap with each other.
The toner images of the four color borne overlapped on the intermediate transfer belt 5 in this way is subsequently conveyed to the secondary transfer position opposed to the secondary transfer roller 7 as the intermediate transfer belt 5 rotates. Toward the secondary transfer position, a transfer sheet P is conveyed at a predetermined time by the registration roller 10. At the secondary transfer position, the secondary transfer roller 7 applies the predetermined bias voltage onto the backside of the transfer sheet P. Thus, a contacting pressure at the secondary transfer position and the secondary transfer electric field generated by the bias voltage when applied collectively allow the toner image on the transfer belt 5 to be secondarily transferred onto the transfer sheet P at once. Afterward, a secondarily transferred toner image on the transfer sheet P is discharged outside the image forming apparatus after completing a fixing process executed by a pair of fixing rollers 8.
Hence, according to this embodiment of the present invention, since the torsion spring unit and the viscosity-providing component respectively serving as design parameters for the dynamic vibration absorber 20 are secured by different parts respectively, each of these parameters can be easily optimized when designed. That is, since the torsion spring unit and the viscosity-providing component are conventionally constituted by a common single part by contrast such that the rubber provides both the torsion spring function and the viscosity function, for example, designing and setting of the parameter is cumbersome. According to the first embodiment of the present invention, however, the designing and setting of the parameter can be easily executed considerably. In addition, as described later more in detail, when the torsion spring unit is formed in spoke shape to exert a twisting function to twist the rotator, a space can be saved in a direction in parallel to the drum shaft 11. Hence, by simply forming the torsion spring unit in spoke shape, the spring constant can be easily set based only a length, a cross-sectional area, and the number of the spokes without changing a size of the dynamic vibration absorber 20. Further, the spring constant also can be set based only on an inner diameter, an outer shape, and a thickness of the cylinder of the viscosity-providing component as well.
Now, a dynamic vibration absorber according to one embodiment of the present invention is described with reference to
The viscosity-providing component 112 is preferably composed of a cylindrical viscoelastic material. The viscosity-providing component 112 maybe sandwiched and accordingly fixed by a supporting unit 117 and the inertia body 110 therebetween fixed to the rotary shaft 113.
Now, first of all, the torsion spring unit material is herein below described more in detail. The torsion spring unit 111 includes a boss 114 with a hole at its center, through which the rotary shaft penetrates, multiple spokes 115 extending radially outward from a perimeter of the boss 114 at even intervals, and an outer rim having contact surfaces on its outer circumference to contact and fix the inertia body. The torsion spring unit 111 is fixed to the rotary shaft at the boss 114. A fixing method of fixing the torsion spring unit 111 can be appropriate chosen. For example, a prescribed method can be adopted to stop rotation of the torsion spring unit 111, such as a screw fixing method, a D-shape or oval shape fitting method of fitting a shaft into a hole, etc. The other fixing method can be also employed as well.
The inertia body 110 is fixed to the outer rim of the torsion spring unit 111 with multiple screws 119 and is supported by an annular protrusion 118b in a floating condition not to directly contact the rotary shaft 113 as described later more in detail. Hence, while receiving weight and inertia of the inertia body 110, the spokes 115 exert a torsion spring function when the inertia body 110 rotates and vibrates. Here, a prescribed step is desirably formed in its cross section between the outer rim of the torsion spring unit 111 and the spokes 115 so that the spokes 115 do not contact the inertia body 110. With this, since the inertia body 110 does not interference with torsion spring function (i.e., motion to absorb the vibration of the inertia body 110 in its rotating direction), which is generally caused by the contact thereof, the torsion spring function is more considerably exerted precisely.
Here, although the number of spokes 115 is four in this embodiment as illustrated in the drawing, three or more spokes 115 other than four may be desirably employed when evenly disposed in a radial direction (i.e., placed at equal angular intervals). That is, when less than two spokes 115 having a relatively too small spring constant to support a weight of the inertia body 110 and are positioned horizontally, the spokes 115 likely deflect and change its rotational speed (i.e., awkwardly rotate).
Material of the torsion spring unit 111 can be made of metal. However, elongate spokes 115 are needed to obtain a desired spring constant thereof as a problem. Consequently, not to elongate spokes 115, plastic having less rigidity than the metal is desirable. For example, polyacetal, polycarbonate, and ABS (acrylonitrile-butadiene-styrene) or the like are preferably employed. Specifically, with the plastic having a relatively small rigidity, a smaller spring constant can be readily set. By contrast, when it is required, a greater rigidity can be set by enlarging either the number or a cross-sectional area of the spokes 115. The resin also allows mass production of spokes 115 using an injection molding method while improving its productivity at low cost.
Now, the viscosity-providing component 112 is described herein below more in detail. The viscosity-providing component 112 does not necessarily have a particular shape, but typically has a cylindrical shape in this embodiment of the present invention. The viscosity-providing component 112 is preferably made of viscoelastic rubber. For example, rubber, such as NBR (Nitrile butadiene rubber), EPDM (ethylene-propylene-diene-M), NR (Natural Rubber), etc., can be employed.
The viscosity-providing component 112 has prescribed planes at its both end faces. One of the planes is concentric with the inertia body 110 and is glued thereto. The other one of the planes is also concentric with the supporting unit 117 fixed to the rotator (i.e., the rotary shaft 113) and is glued thereto as well. To effectively assemble these members by gluing, a double-sided adhesive tape made of rubber is preferably used. Otherwise, the viscosity-providing component 112 may be glued to the supporting unit 117 by vulcanizing the rubber thereof, while it is glued to the inertia body with the double-sided adhesive tape.
The supporting unit 117 is composed of a boss fixed to the rotary shaft, a flange 118a glued to the viscosity-providing component 112, and the above-described annular protrusion 118b formed on an end face of the flange 118a to fit into an inner diameter portion (i.e., an inner wall) of the viscosity-providing component 112. Accordingly, when the protrusion 118b fits into the viscosity-providing component 112, the concentric precision with the rotary shaft is upgraded, and accordingly rotational fluctuation can be reduced.
Now, another example of the torsion spring unit 111 is described herein below with reference to
Now, yet another example of the torsion spring unit 111 capable of enhancing coaxial precision of the inertia body 110 in relation to the rotary shaft 113 by utilizing the torsion spring unit 111 is described with reference to
In
The optimal value of the torsion spring constant cannot be defined and set solely by the torsion spring unit 111, because the viscosity-providing component 112 made of viscoelastic material of rubber also includes a spring factor. Hence, the torsion spring constant needs to be optimized and designed based on material and shapes of the torsion spring unit 111 and the viscosity-providing component 112 as well. In such a situation, if a spring component of the viscosity-providing component 112 is reduced as minimum as possible while dominantly setting that of the torsion spring unit 111, the torsion spring constant can be readily optimized. Therefore, a rigidity of the viscosity-providing component 112 is desirably set to be smaller, while setting that of the torsion spring unit 111 to be larger enough than the rigidity of the viscosity-providing component 112. Hence, in this example, the result is obtained by preparing and utilizing the torsion spring unit 111 made of polyacetal resin having a Young's modulus of about 2500 MPA, and the viscosity-providing component 112 made of NBR having a Young's modulus of about 1 MPa.
Now, a second embodiment of the present invention is described with reference to
To another end face of the viscosity-providing component 112, an inertia body 110 of the dynamic vibration absorber 20 is glued coaxially with the rotary shaft 113 floating therefrom. The inertia body 110 is fixed and supported on a plane seat formed on an outer rim of the torsion spring unit 111 using screws 119. The torsion spring unit 111 has the similar shape as that of the example shown in
Accordingly, in such a situation, even though the rotational fluctuation of the rotator can be typically reduced by the flywheel 125, a change in speed (i.e., the rotational fluctuation of the rotator) increases, by contrast, at a prescribed resonant frequency determined based on respective inertias of the flywheel 125 and the rotator and a rigidity of spring of the drivetrain. However, even in such a situation, the change or fluctuation can be minimized by the dynamic vibration absorber 20 as well.
In a system that includes the above-described driving system with the flywheel 125 shown in
Now, yet another dynamic vibration absorber 20 according to a third embodiment of the present invention is described with reference to
Initially, various components of the dynamic vibration absorber 20 disposed around the rotary shaft 113 are described. The dynamic vibration absorber 20 includes a pair of inertia bodies, a torsion spring unit, and a viscosity-providing component as major components. Then, design parameters of these major components are optimized to work most effectively. Specifically, the inertia bodies of this embodiment include a disc-shaped first inertia body 110a and multiple second inertia bodies 110b fixed to the first inertia body 110a. These inertia bodies 110a and 110b are made of metal each to have a large inertia. There is provided a first inertia body hole 110c at a center of the first inertia body 110a as described later more in detail with reference to
The torsion spring unit 111 serves as a connecting part connecting the rotary shaft 113 with the inertia bodies 110a and 110b. Specifically, one end of the torsion spring unit 111 is connected to the rotary shaft 113 through a securing member (i.e., a boss 114), and the other end thereof is connected to the first inertia body 110a through a supporting bracket 121. Here, the torsion spring unit 111 is made of thin sheet metal. The supporting bracket 121 and the torsion spring unit 111 are roughly placed at the same position as each of the spokes 115 disposed in the above-described embodiment.
The viscosity-providing component 112 also serves as a connecting part to connect the rotary shaft 113 and the inertia bodies 110a and 110b with each other. Specifically, the viscosity-providing component 112 is connected to the rotary shaft 113 through the supporting unit 117, and is directly connected to the first inertia body 110a. The viscosity-providing component 112 is composed of rubber because higher viscosity can be set. For example, rubber, such as NBR, EPDM, NR, etc., is preferably employed.
The second inertia bodies 110b can be moved in a radial direction from a boss hole 114a acting as a rotational center thereby changing its fixed position. In
An aspect the viscosity-providing component 112 coupled to the first inertia body 110a and the rotatory shaft 113 through the supporting unit 117 is illustrated in
Now, a modification of the viscosity-providing component 112 is described with reference to
A front side view taken from an outside of the dynamic vibration absorber 20 is illustrated in
Now, the second inertia bodies 110b are described more in detail with reference to
Now, a modification of the torsion spring units 111 is described more in detail with reference to
In the other portion of the torsion spring unit 111 (i.e., a longer portion), the oblong hole 111a is formed as shown in
Now, a method of coupling the torsion spring unit 111 to the supporting bracket 121 is described more in detail with reference to
Here, the above-described inertia body can be made of metal having a heavy specific gravity. Although the inertia body has a circular shape in the above-described various embodiments as illustrated in the drawing, it is not limited thereto. Although the viscosity-providing component is made of viscoelastic material having the cylindrical shape as illustrated in the drawing, it is not limited thereto. Similarly, although four torsion spring units are provided as illustrated in the drawing, multiple torsion spring units may be acceptable and three or more torsion spring units may be more favorable. The torsion spring function member is preferably made of plastic. Further, the viscosity-providing component is preferably made of material capable of rendering its spring constant to be smaller than that of the torsion spring unit.
According to one aspect of the present invention, the inertia body can be coaxially held around a rotary shaft accurately, and accordingly the dynamic vibration absorber can effectively maintain prescribed spring and viscosity functions at the same time. That is, a novel rotator driving system for driving a rotator with a motor includes a dynamic vibration absorber attached to a rotary shaft of the rotator. The dynamic vibration absorber includes: an inertia body; and a viscosity-providing component to provide a viscosity; a torsion spring unit that includes a boss fixed to the rotary shaft, at least two spokes extending radially outward from the boss, and at least one seat provided at one of tips of the at least two spokes to fix the inertia body. The torsion spring unit is fixed by the rotary shaft of the rotator and the boss fixed to the rotary shaft. The torsion spring unit supports the inertia body via the at least one seat provided at one of tips of the at least two spokes.
According to another aspect of the present invention, the inertia body can be coaxially held around a rotary shaft more accurately, and accordingly the dynamic vibration absorber can more effectively maintain prescribed spring and viscosity functions at the same time. That is, a viscosity-providing component-supporting unit is connected to the rotary shaft, and the viscosity-providing component is sandwiched between and fixed to the viscosity-providing component-supporting unit and the inertia body.
According to yet another aspect of the present invention, the inertia body can be coaxially held around a rotary shaft more accurately, and accordingly the dynamic vibration absorber can more effectively maintain prescribed spring and viscosity functions at the same time. That is, the inertia body is supported by the torsion spring unit and the viscosity-providing component at its both end faces, respectively.
According to yet another aspect of the present invention, the inertia body can be coaxially held around a rotary shaft more accurately, and accordingly the dynamic vibration absorber can more effectively maintain prescribed spring and viscosity functions at the same time. That is, the inertia body is supported coaxially with the rotary shaft while floating above the rotary shaft.
According to yet another aspect of the present invention, the inertia body can be coaxially held around a rotary shaft more accurately, and accordingly the dynamic vibration absorber can more effectively maintain prescribed spring and viscosity functions at the same time. That is, each of the at least two spokes of the torsion spring unit includes a portion to enhance coaxial precision of the inertia body regarding the rotary shaft.
According to yet another aspect of the present invention, the inertia body can be coaxially held around a rotary shaft more accurately, and accordingly the dynamic vibration absorber can more effectively maintain prescribed spring and viscosity functions at the same time. That is, a flywheel is connected to the rotary shaft via a supporting unit fixed to the rotary shaft to suppress rotational fluctuation of the rotator. The inertia body is made of disc-shaped metal having a heavy specific gravity. The seat forms an outer ring extended over respective tips of the at least two spokes of the torsion spring unit. The viscosity-providing component is made of viscoelastic material having a cylindrical shape, and is sandwiched between and fixed to the flywheel and the inertia body.
According to yet another aspect of the present invention, the inertia body can be coaxially held around a rotary shaft more accurately, and accordingly the dynamic vibration absorber can more effectively maintain prescribed spring and viscosity functions at the same time. That is, the rotator driving system includes a dynamic vibration absorber attached to a rotary shaft of a rotator. The dynamic vibration absorber includes a first inertia body not fixed to the rotary shaft in its rotational direction, at least two torsion spring units each extending radially outward from the rotary shaft while connecting to the first inertia body and the rotary shaft at its both ends, respectively, a viscosity-providing component supporting unit fixed to the rotary shaft, a viscosity-providing component made of viscoelastic rubber connected to the first inertia body and the rotary shaft via the viscosity-providing component supporting unit. An amount of inertia and a spring constant of the dynamic vibration absorber are adjusted by moving a coupling position of the torsion spring unit coupled with the first inertia body in the radial direction in accordance with a variation in viscosity characteristics of the viscosity-providing component.
According to yet another aspect of the present invention, the inertia body can be coaxially held around a rotary shaft more accurately, and accordingly the dynamic vibration absorber can more effectively maintain prescribed spring and viscosity functions at the same time. That is, at least two second inertia bodies are attached to the first inertia body.
According to yet another aspect of the present invention, the inertia body can be coaxially held around a rotary shaft more accurately, and accordingly the dynamic vibration absorber can more effectively maintain prescribed spring and viscosity functions at the same time. That is, a torsion spring unit securing member is secured to the rotary shaft to secure the at least two torsion spring units at its one end. At least two inertia body supporting brackets are fixed to the first inertia body. Each of the at least two inertia body supporting brackets has a first slot with its longer axis extended in a radial direction. Each of the at least two torsion spring units is a metal plate spring extended in the radial direction forming a right angle with the first inertia body. The metal plate spring of each of the at least two torsion spring units has a second slot with its longer axis extended in the radial direction. Each of the at least two torsion spring units is fastened to corresponding one of the supporting brackets with a screw at an optional position in each of the first and second slots of each of the torsion spring units and that of the supporting brackets.
According to yet another aspect of the present invention, the inertia body can be coaxially held around a rotary shaft more accurately, and accordingly the dynamic vibration absorber can more effectively maintain prescribed spring and viscosity functions at the same time. That is, each of the second inertia bodies has a third slot with a longer axis extended in the radial direction. Each of the second inertia bodies is fastened to the first inertia body with a screw at an optional position in the third slot.
According to yet another aspect of the present invention, the inertia body can be coaxially held around a rotary shaft more accurately, and accordingly the dynamic vibration absorber can more effectively maintain prescribed spring and viscosity functions at the same time. That is, the torsion spring unit securing member and the viscosity-providing component supporting unit are integrally configured in a body.
Numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be executed otherwise than as specifically described herein. For example, the rotator driving system and the image forming apparatus with the same are not limited to the above-described various embodiments and may be altered as appropriate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-169020 | Aug 2013 | JP | national |
| 2013-268143 | Dec 2013 | JP | national |
