Patent Grant
8594534
The present invention relates to a corona discharger for generating corona discharge by applying a voltage to a charging wire and relates to an image forming apparatus using such a corona discharger.
An image forming apparatus in which a step of electrostatically transferring a toner image, electrostatically formed on a surface of an image bearing member, from the image bearing member onto a recording material such as paper is performed has been conventionally known. In such an image forming apparatus the surface of the image bearing member is uniformly charged, and an electrostatic latent image is formed on the charged surface and then is developed into the toner image with a toner. The toner image formed on the image bearing member is transferred onto the recording material under voltage application. The corona discharger is used as a charging means for charging such an image bearing member, a transfer means for transferring the toner image onto the recording material or a separating means for separating the recording material from the image bearing member.
The corona discharger generates the corona discharge by applying the voltage to the charging wire provided in a shield. The charging wire used in such a corona discharger is determined by deposition or erosion of an electric discharge product by the electric discharge for a long time, thus being less liable to cause the electric discharge. As a result, for example, in the case where the surface of the image bearing member is electrically charged, charging non-uniformity occurs. In order to prevent the occurrence of the charging non-uniformity, a corona charger (corona discharger) in which a plurality of wires of the charging wire are provided and thus a charging performance is improved has been devised. However, even in the case where such a plurality of wires of the charging wire are provided, when the corona charger is continuously used for a long time, with the result that the charging wire is deteriorated by the electric discharge and thus the charging non-uniformity occurs. Further, current leakage is liable to occur due to deposition of a contaminant such as the electric discharge product. In addition, in the case where the corona discharger is used as the transfer means or the separating means, there is a possibility of an occurrence of improper transfer or improper separation.
Therefore, in order to prevent the occurrence of such charging non-uniformity, a corona charger provided with a mechanism for feeding a fresh charging wire while performing winding-up of the deteriorated charging wire has been devised (Japanese Laid-Open Patent Application (JP-A) 2004-029504 and JP-A Hei 6-124036). In the case of structures described in JP-A 2004-029504 and JP-A Hei 6-124036, a single charging wire is turned back and used, thus being regarded as two charging wires. Then, by performing a winding-up operation, the charging performance is enhanced and the charging non-uniformity is less liable to occur.
As described above, in the case where the charging wire is wound up, the wire is successively superposed on a winding-up member (reel) for winding up the charging wire. For this reason, every (one) rotation of the reel, an apparent outer diameter of the reel is increased, so that a winding-up length of the charging wire wound up per (one) rotation of the reel is also increased. For this reason, irrespective of a winding-up amount of the charging wire, the apparent outer diameter of the reel is increased in the case where the wire winding-up operation is repeated by always rotating the reel with the same rotation amount, so that a winding-up amount is larger than that at an initial state. That is, a quantitative winding-up operation of the charging wire cannot be performed. As a result, in the case where the wire winding-up operation is repeated again and again, not only the used charging wire portion but also a fresh charging wire portion are collected, so that the whole area of the charging wire cannot be used, i.e., an unused portion occurs, so that the winding-up operation is not efficient.
A principal object of the present invention is to provide a corona discharger capable of reducing a degree of an increase of a winding-up amount of a charging wire more than necessary even when a winding-up of the charging wire is repeated.
Anther object of the present invention is to provide an image forming apparatus including the corona discharger.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
Parts (a) to (d) of
Parts (a) to (d) of
First Embodiment of the present invention will be described with reference to
[Image Forming Apparatus]
As shown in
The image forming portion P is constituted by a photosensitive drum 17, a primary charger 25, a laser scanner 16, a developing device 19, a transfer charger 20, a separation charger 21 and a cleaning member 26. The photosensitive drum 17 as an image bearing member is formed in a cylindrical shape and is rotationally driven. By the rotation, a toner image carrying surface is moved. The primary charger 25 as a charging means is constituted by a corona discharger (corona discharge device) disposed opposed to an outer peripheral surface of the photosensitive drum 17 and electrically charges the surface of the photosensitive drum 17 to a predetermined potential by corona discharge.
The laser scanner 16 as an exposure means (electrostatic latent image forming means) irradiates the surface of the photosensitive drum 17 charged by the primary charger 25 with laser modulated on the basis of an electric signal 37 (image data) described later, so that an electrostatic latent image is formed on the surface of the photosensitive drum 17. The developing device 19 as a developing means is disposed opposed to the surface of the photosensitive drum 17 to develop with a toner the electrostatic latent image formed on the surface of the photosensitive drum 17 into a toner image. The toner image carried on the photosensitive drum 17 is transferred at a transfer portion onto the recording material which is conveyed while being timed by the registration roller 15. At the transfer portion, the transfer charger 20 constituted by the corona discharger is disposed opposed to the photosensitive drum 17. By applying a predetermined transfer bias to the transfer charger 20, the toner image is transferred onto the recording material.
The recording material on which the toner image is transferred is separated from the photosensitive drum 17 by applying a predetermined separation bias to the separation charger constituted by the corona discharger, so that the recording material is conveyed to a fixing device 23 by a conveyer belt 22. The toner image is heat-fixed on the recording material by the fixing device 23. Thereafter, the recording material on which the toner image is fixed is discharged on a sorter 40.
Further, in
[Corona Discharger]
Next, the primary charger 25 as the corona discharger will be described more specifically with reference to
The charging wire 106 is provided so as to be turned back at least at one position. In this embodiment, the charging wire 106 is turned back at one position as shown in
Further, the shield 103 is formed to cover both sides of the wires 106a and 106b with respect to the photosensitive drum rotational direction and to cover a side opposite from the photosensitive drum 17 side. Further, an area which is surrounded by the shield 103 and opposes the photosensitive drum 17 is a discharge area in which the corona discharge is generated. On the other hand, an area outside the shield 103 is a non-discharge area.
Further, in this embodiment, the primary charger 25 is a charger of a scorotron type. That is, as shown in
Further, as shown in
The winding-up reel 110 in the drive-side case 101 is connected to a winding-up reel gear 123 as shown in
This rotation sensor 111 includes a photo-interrupter and a disk (encoder) which is fixed to the rotation shaft 107a and which is provided with slits at a plurality of positions of the disk with respect to a circumferential direction. The rotation sensor 111 detects a rotation amount such as a rotational angle, a rotation number (rotational frequency) or the like of the rotation shaft 107a. When the rotation amount of the rotation shaft 107a can be detected, from the number of teeth of the gears 107a and 123, it is possible to detect the rotation amount of the winding-up reel 110. A signal detected by the rotation sensor is sent to a winding-up controller 105 described later. Incidentally, such a rotation detecting means may also be provided on the rotation shaft of the winding-up reel 110.
Further, the winding-up reel 110 is provided with a reel winding-up groove (winding-up portion) 110a having a width (winding-up reel width) L1 which is substantially equal to a wired diameter d of the charging wire 106 as shown in
Further, upstream of the winding-up reel 110 with respect to the winding-up direction, a wire supporting member 137 for guiding the wire into the groove 110a is disposed. The wire supporting member 137 is urged in a rotational axis direction of the winding-up reel 110 to be shifted in the rotational axis direction of the groove 110a and the winding-up reel 110, so that the wire 106 entering the drive-side case 101 is guided into the groove 110a.
Further, about the feeding reel 108, the charging wire 106 is wound plural times and is fed successively by the feeding reel 108 depending on a winding-up amount of the winding-up reel 110. Incidentally, as an initial state, a fresh charging wire 106 is wound about the feeding reel 108 in an amount which is not less than an amount required until the primary charger 25 reaches the end of its lifetime. Further, as shown in
Further, as shown in
In this embodiment, a moving means for moving the charging wire 106 is constituted by the feeding reel 108, the winding-up reel 110, the driving motor 107 and the winding-up controller 105 (described later with reference to
The winding-up controller 105 includes, as shown in
The winding-up controller 105 controls the winding-up motor 107 to move the charging wire 106, e.g., in the following manner. That is, the wire fed from the feeding reel 108 is moved to a photosensitive drum rotational direction downstream position of a discharging area. The wire 106a provided at the photosensitive drum rotation direction downstream position of the discharging area is moved to a photosensitive drum rotational direction upstream position of the discharging area is wound up by the winding-up reel 110 in the driving-side case 101. Incidentally, such a constitution that the charging wire 106a located at the photosensitive drum rotational direction downstream position is wound up depending on a device characteristic and a fresh charging wire 106b is supplied to the photosensitive drum rotational direction upstream position may also be employed. Further, in order to obtain a more stable charging performance, it is also possible to employ a constitution in which the whole area of the used charging wires 106a and 106b is wound up.
By employing the above constitution, when the surface of the photosensitive drum 17 is charged, the single charging wire 106 can used as two charging wires consisting of the photosensitive drum rotational direction upstream wire 106a and the photosensitive drum rotational direction downstream wire 106b. As a result, the charging performance is improved, so that the charging non-uniformity is less liable to occur.
Further, as shown in
Incidentally, the cleaning member 113 for cleaning the charging wire 106 may also have a constitution as shown in
[Control of Charging Wire Winding-Up Amount]
As shown in
For this reason, in this embodiment, in order to suppress the increase of the winding-up amount, the rotation amount of the winding-up reel 110 driven by the winding-up motor 107 is controlled. That is, a cumulative rotation amount of the winding-up reel 110 is counted based on a detection result of the rotation sensor 111 and then the winding-up motor 107 is controlled so that the rotation amount of the reel 110 per unit winding-up length of the wire 106 is decreased with an increase of the number of laminations of the wire 106 with respect to a radial direction. Here, the lamination number with respect to the radial direction can be obtained from the cumulative rotation amount of the reel 110. Further, the unit winding-up length is a predetermined length of the wire 106. For example, a length of the wire 106 wound up in the case where the reel 110 is rotated one rotation (one full turn) from the initial state in which the wire 106 is not wound up by the reel 110 is taken as the unit winding-up length. In this case, in the initial state, the rotation amount of the winding-up reel 110 per unit winding-up length is 2π (one rotation) and is decreased, every increase of the winding-up number, correspondingly to the diameter of the wire 106.
Such control is effected by using a proper reel rotation angle θ at a cumulative (predetermined) rotation number n of the reel 110. Here, on the basis of the case where the reel diameter at the initial state in which the wire 106 is not wound up about the reel 110 is D0 and the reel 110 is rotated one rotation (2π) at the initial reel diameter D0, the rotational angle θ at the predetermined rotation number n of the reel 110 is obtained. That is, when the reel 110 is rotated at θ satisfying a ratio of 2π:D0=θ:(D0+2d×n), the winding-up amount of the wire 106 is always constant (irrespective of the cumulative rotation number). Therefore, θ is obtained by the following equation (1). Incidentally, a portion in parenthesis ([ ]) means that the numerical value is an integer obtained by dropping the functional portion of the numerical value.
θ=2πD0/(D0+2d×[n])[rad] (1),
wherein θ represents the proper reel rotation angle, D0 represents the initial reel diameter, d represents the diameter of the charging wire 106 and n represents the cumulative winding-up number.
From the equation (1), it is understood that the rotation angle (rotation amount) of the reel 110 is decreased with the increase of the cumulative rotation number n of the reel 110. A graph showing a relationship between the proper reel rotation angle θ and the cumulative winding-up number (cumulative rotation number or the lamination number of the wire 106 with respect to the radial direction) is shown in
[Charging Wire Winding-Up Operation]
The operation of the charging wire 106 during exchange will be described. As described above, by rotating the winding-up motor 107 in a predetermined amount, the winding-up reel 110 is rotated in the winding-up direction as shown in
By effecting such rotational control of the winding-up motor 107 in the following manner by the winding-up controller 105 during the deterioration due to the electric discharge of the charging wire 106 for a long time, an exchange process of the charging wire is performed.
The winding-up control is effected in an interruption manner during the print job. However, in order to reduce a printing time, the winding-up control may also be effected after the job without being effected during the job. In this embodiment, with reference to
Incidentally, as a condition of transition to the operation in the exchanging mode, different from the print image number, it is also possible to use an elapsed time in the case where an electric discharging time of the primary charger 25 is cumulatively added and reaches a predetermined time. In addition, the operation may also enter the exchanging mode in the case where a voltage applied to the charging wire 106 is measured and reaches a predetermined value or the case where a potential of the photosensitive drum surface is measured by a surface electrometer and reaches a value not more than a predetermined potential.
In the initial state, when the winding-up amount M is inputted into the winding-up controller 105 (S101), the cumulative rotation number n of the reel 110 and the rotation amount s of the reel 110 for winding up the wire in the winding-up amount M are reset in S102. Here, the initial state corresponds to, e.g., during product shipment, during exchange of the primary charger 25, and the like. Then, in S103, from the rotation number n (times) of the reel 110, the proper reel rotation angle θ and the apparent outer diameter D0 of the reel 110 are obtained. Then, in S104, the rotation amount s (rad) of the reel 110 is accumulated to calculate a remaining winding-up amount M. In S105, whether or not the reel 110 is rotated one rotation or more in the remaining winding-up amount M is judged. In the case where the reel 110 is rotated one rotation or more, the rotation number n of the reel 110 is increased by 1 in S106, the operation is returned to S103. On the other hand, when the rotation number of the reel is less than 1 in S105 and in other words, in the case where the remaining winding-up amount M is less than the winding-up amount when the reel 110 is rotated one rotation, the calculation is ended and the rotation amount s at that time is the rotation amount s to be obtained.
In the case where the winding-up operation of the wire is performed in a subsequent operation or later, the previous rotation amount s is reset and the operation starts S103 and the rotation amount s with respect to the winding-up amount M at that time is obtained. Incidentally, the rotation number n is accumulated on the basis of the previous numerical value (i.e., n is not reset).
Here, the reason why the calculation is ended in the case where the remaining winding-up amount M is less than the winding-up amount when the reel 110 is rotated one rotation is as follows. The diameter of the reel 110 is generally small and when the small diameter of the wire 106 is taken into consideration, the apparent diameter of the reel 110 at that time is also small. Therefore, the winding-up amount corresponding to one rotation of the reel 110 at that time is small and thus the remaining winding-up amount M smaller than the winding-up amount corresponding to one rotation of the reel 110 means that the remaining winding-up amount M is considerably small. Further, a part of the wire 106 is also disposed in the driving-side case 101 and the electrode-side case 102 which are undischarged areas, and do not influence on the electric discharge. For this reason, even when the wire is not wound up in a considerably small amount, the amount is absorbed in the undischarged area or is very small even when the part of the wire 106 enters the discharging area, so that the part of the wire 106 does not influence on the electric discharge. Therefore, in this embodiment, the calculation is ended at that time and then the rotation amount s is obtained.
Incidentally, when the length of the reel present in the undischarged area is constituted so as to be not less than the winding-up amount corresponding to one rotation of the reel during a maximum winding-up state of the wire by the reel 110 (when the wire 106 is wound up until its end), the part of the wire 106 in the remaining winding-up amount M enters the discharging area. Further, in the case where the remaining winding-up amount M is less than the winding-up amount when the reel 110 is rotated one rotation, the calculation is not ended and then the rotation angle of the reel corresponding to the remaining winding-up amount M is obtained and may also be added to the rotation amount s.
Thus, by effecting the exchanging process of the charging wire 106, the charging wire 106 can always be wound up in a stable winding-up amount. For that reason, the whole area or the almost whole area of the charging wire 106 can be used, so that the operation is very economical.
Second Embodiment of the present invention will be described with reference to
A winding-up reel 131 in the drive-side case 101 is connected to a winding-up reel gear 123 as shown in
In this embodiment, the winding-up reel 131 includes a reel portion 131a which is a winding-up portion at which a plurality of charging wires 105 can be arranged in the rotational axis direction. Further, the winding-up reel 131 includes a reel up-and-down motion (vertical motion) unit 140 which is a reciprocal movement means which reciprocates the winding-up reel 131 in the rotational axis direction during the winding-up of the charging wires 106 by the winding-up reel 131 and which arranges the charging wires 106, at the reel portion 131a, in the rotational axis direction in parallel to each other. Further, the winding-up controller 105 controls the winding-up motor 107 so that the rotation amount of the winding-up reel 131 is decreased so as to be smaller than that before the movement direction of the reel up-and-down motion unit 140 is changed in the case where the movement direction of the reel up-and-down motion unit 140 is changed. Incidentally, in this embodiment, “vertical” means a direction of the reciprocal motion along the rotational axis direction.
More specifically, first, the reel portion 131a is formed so that a length thereof in the rotational axis direction is sufficiently larger than that in the groove 110a in First Embodiment, so that the plurality of charging wires 106 can be arranged in the rotational axis direction. That is, the reel portion 131a has a winding-up reel width L2 which is sufficiently larger than the wire diameter d of each charging wire 106. For that reason, compared with First Embodiment, the charging wire 105 can be wound up in a larger amount by the winding-up reel 131, so that this embodiment has the advantages such as a service life extension of the primary charger 25 and an increase of an interval of maintenance for exchanging the charging wire 106.
Further, the reel up-and-down motion unit 140 includes a reel up-and-down motion gear 133, an upper cam and a lower cam which are provided coaxially with the winding-up reel 131, and includes an up-and-down motion intermediate gear 132a which is provided coaxially with the intermediate gear 132b. The rotation shaft of the up-and-down motion intermediate gear 132a and the intermediate gear 132b is parallel to the rotation shaft of the winding-up reel 131, so that the up-and-down motion intermediate gear 132a engages with the reel up-and-down motion gear 133 and the intermediate gear 132b engages with the winding-up reel gear 123.
Further, the up-and-down motion intermediate gear 132a and the intermediate gear 132b are different in number of teeth. Similarly, the reel up-and-down motion gear 133 and the winding-up reel gear 123 are different in number of teeth. Therefore, when the driving force is transmitted from the motor 107 and thus the up-and-down motion intermediate gear 132a and the intermediate gear 132b are rotated, the reel up-and-down motion gear 133 and the winding-up reel gear 123 engaging with the intermediate gears 132a and 132b, respectively, are rotationally driven at different rotational speeds. In this embodiment, the winding-up reel gear 123 is set so that its rotational speed is sufficiently larger than that of the reel up-and-down motion gear 133. That is, the winding-up reel gear 123 is larger in number of teeth than the reel up-and-down motion gear 133. In summary, the upper cam 134 is much slower in rotational speed than the winding-up reel 131.
Further, the upper cam 134 and the lower cam 135 have cam surfaces where they oppose each other, and are disposed so that their cam surfaces contact each other. In this embodiment, each of the cam surfaces is inclined with respect to a surface perpendicular to the rotational axis direction at the same inclination angle. Further, the upper cam 134 is connected to the reel up-and-down motion gear 133, and the lower cam 135 is provided on the winding-up reel gear 123. Further, the upper cam 134 is rotated together with the reel up-and-down motion gear 133 but the lower cam 135 is not rotated together with the winding-up reel gear 123. Therefore, as described above, by the rotational drive of the reel up-and-down motion gear 133, the cam surfaces of the cams 134 and 135 are shifted (deviated) from each other, so that the upper cam 134 and the lower cam 135 are moved relative to each other in the rotational axis direction.
In this embodiment, the upper cam 134 and the reel up-and-down motion gear 133 cannot be moved in the rotational axis direction but the lower cam 135 and the winding-up reel gear 123 can be moved in the rotational axis direction. As a result, the winding-up reel 131 is moved in the rotational axis direction while being rotated. Incidentally, the length of the intermediate gear 123b in the rotational axis direction is increased so as to prevent the reel gear 123 from being disengaged from the intermediate gear 123b even when the reel gear 123 is moved in the rotational axis direction in such a manner.
Further, at a side of the winding-up reel 131 opposite from the side where the upper cam 134 is provided (at a lower portion of
The reel up-and-down motion unit 140 will be described in detail with reference to
At the lower portion of the winding-up reel 131, the up-and-down motion urging spring 136 is disposed, and a stopping ring 139 provided under the urging spring 136 is fixed at a groove 138b of the winding-up shaft 138. As a result, a part group 150 located above the stopping ring 139, such as the reel up-and-down motion gear 133 and the upper cam 134, and the up-and-down motion urging spring 136 are rotatably slidably or non-rotatably supported by the winding-up shaft 138. Further, the part group 150 is urged in an arrow YA direction by the up-and-down motion urging spring 136. For that reason, the upper cam 134 and the lower cam 135 are always in the contact state. The upper cam 134 has an upper cam projection 134a where the upper cam 134 is most projected in an arrow YB direction, and the lower cam 135 has a lower cam projection 135a where the lower cam 135 is most projected in the arrow YA direction.
[Charging Wire Winding-Up Operation]
Next, with reference to (a) to (d) of
When the winding-up operation is started from the state of (a) of
The upper cam 134 is in a state of (c) of
When the upper cam 134 is further rotationally driven, the upper cam projection 134a is moved apart from the lower cam projection 135a and therefore the lower cam 135 and the winding-up reel 131 are urged in the arrow YA direction by the up-and-down motion urging spring 136, so that the state of the lower cam 135 and the winding-up reel 131 is returned to the state of (a) of
Next, the winding-up operation will be described based on numerical values used in this embodiment. The winding-up operation was performed under a condition that the charging wire diameter of the charging wire 106 was 0.1 mm, the reel width L2 of the winding-up reel 131 was 1 mm and the reel diameter was 15 mm. In this case, when the winding-up operation is started from the state of (a) of
Next, a series of winding-up operations of the charging wire 106 by the winding-up reel 131 will be described with reference to
In (a) of
Part (b) of
When the winding-up operation is further performed, as shown in (d) of
every time when the winding-up position of the charging wire 106 reaches the upper limit position or the lower limit position of the reel portion 131a. The charging wire 106 is gradually wound up while repeating the operations described above with reference to (a) to (d) of
Next, quantitative winding-up control of the charging wire 106 will be described. As described above, in the primary charger 25 in this embodiment, the reel diameter D(n) is increased every time when the winding-up position of the charging wire 106 reaches the upper limit position or the lower limit position of the reel portion 131a (with the winding-up width L2) of the winding-up reel 131. For that reason, in view of a relationship between the winding-up number and the reel diameter, there is a need to determine a proper rotation angle. The proper rotation number N of the winding-up reel 131 is obtained from the following equation (2). Incidentally, a portion in parenthesis ([ ]) means that the numerical value is an integer obtained by dropping the functional portion of the numerical value.
θ=2πD0/(D0+2d×[d×n/L2])[rad] (2),
wherein θ represents the proper reel rotation angle, D0 represents the initial reel diameter, L2 represents a winding-up reel width, d represents the charging wire diameter and n represents the cumulative reel rotation number.
Here, the equation (2) will be described more specifically. Basically, the equation (2) is similar to the equation (1) described above but is different from the equation (1) in that the reel width L2 is taken into consideration. That is, [n] in the equation (1) is changed to [d×n/L2] in the equation (2). Therefore, [d×n/L2] will be described.
First “d×n” represents the length of the charging wire 106 with respect to the rotational axis direction when the charging wire 106 is arranged in the rotational axis direction of the reel portion 131a at the cumulative winding-up number n. Therefore, [d×n/L2] is 1 when [d×n] is equal to L2. That is, [d×n/L2] corresponds to the winding-up number of 1 in the equation (1). As described above, the numerical value in [d×n/L2] is an integer obtained by dropping the fractional portion of the numerical value and therefore in the case where [d×n/L2] is an integral multiple of L2, the integer corresponds to the winding-up number in the equation (1). That is, [d×n/L2] means that the reel diameter is increased in the case where the winding-up position of the charging wire 106 reaches the upper limit position or the lower limit position to switch the movement direction. Accordingly, every proper reel rotation angle θ obtained from the equation (2), the winding-up motor 107 is controlled, so that it is possible to perform the wire feeding in a constant amount.
In the initial state, when the winding-up amount M is inputted into the winding-up controller 105 (S201), the cumulative rotation number n of the reel 131 and the rotation amount s of the reel 131 for winding up the wire in the winding-up amount M are reset in S202. Here, the initial state corresponds to, e.g., during product shipment, during exchange of the primary charger 25, and the like. Then, in S203, from the rotation number n (times) of the reel 131, the proper reel rotation angle θ and the apparent outer diameter D0 of the reel 131 are obtained. Then, in S204, the rotation amount s (rad) of the reel 131 is accumulated to calculate a remaining winding-up amount M. In S205, whether or not the reel 131 is rotated one rotation or more in the remaining winding-up amount M is judged. In the case where the reel 131 is rotated one rotation or more, the rotation number n of the reel 131 is increased by 1 in S206, the operation is returned to S203. On the other hand, when the rotation number of the reel is less than 1 in S205 and in other words, in the case where the remaining winding-up amount M is less than the winding-up amount when the reel 110 is rotated one rotation, the calculation is ended and the rotation amount s at that time is the rotation amount s to be obtained. Incidentally, the flow chart shown in
In this embodiment, compared with First Embodiment, the charging wire 105 can be wound up in a larger amount by the winding-up reel 131, so that this embodiment has the advantages such as a service life extension of the primary charger 25 and an increase of an interval of maintenance for exchanging the charging wire 106. Incidentally, in the above description, the winding-up reel 131 is moved by the reel up-and-down motion unit 140 but the charging wire 106 may also be moved relative to the winding-up reel 131. In summary, during the winding-up of the charging wire 106 by the winding-up reel 131, the winding-up reel 131 and the charging wire 106 may only be required to be reciprocated relative to each other in the rotational axis direction of the winding-up reel 131. Other constitutions and functions are similar to those in First Embodiment.
Third Embodiment of the present invention will be described with reference to
The primary charger 25 in this embodiment has a constitution in which a single charging wire 106 is used without being turned back. For this reason, the feeding reel 108 is disposed in the electrode-side case 102. Further, to the feeding reel 108, a high-voltage source 104 is connected. Further, similarly as in First and Second Embodiments, the feeding reel 108 incorporates therein the torque limiter 150 as shown in
Also in such a constitution, by the winding-up of the charging wire 106, the apparent outer diameter of the winding-up reel 110 is increased to increase the winding-up amount and therefore there is a possibility that the wire is not completely used, so that the application of the present invention is effective. As the wire winding-up control, it is also possible to employ the same control as in First or Second Embodiment based on the constitution of the winding-up reel 110.
In the embodiments described above, the constitution in which the present invention is applied to the primary charger is described, but the present invention is also applicable to other corona dischargers such as the transfer charger 20 and the separation charger 21. As a result, it is possible to suppress occurrences of the improper transfer and the improper separation. Further, in the above-described embodiments, the present invention is applied to a single color image forming apparatus, but is also applicable to an image forming apparatus for forming a plurality of color images, such as a full-color image forming apparatus.
While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purpose of the improvements or the scope of the following claims.
This application claims priority from Japanese Patent Application No. 259018/2010 filed Nov. 19, 2010, which is hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-259018 | Nov 2010 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3578970 | Michaud et al. | May 1971 | A |
| 4746796 | Heigl | May 1988 | A |
| 5337131 | Sagiv et al. | Aug 1994 | A |
| 6108504 | Dickhoff | Aug 2000 | A |
| 7149448 | Saito | Dec 2006 | B2 |
| 20070248379 | Onuma et al. | Oct 2007 | A1 |
| 20120128389 | Saito | May 2012 | A1 |
| Number | Date | Country |
|---|---|---|
| 6-124036 | May 1994 | JP |
| 2004-029504 | Jan 2004 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20120128390 A1 | May 2012 | US |
