JP2004310060A - Cleaning device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small sized and low cost cleaning device by which residual toner on the surface of an image carrier can be efficiently eliminated. <P>SOLUTION: A cleaning device 11 is provided with a conductive fur brush 37 coming in contact with a transfer belt 14, a conductive brush 42 coming in contact with the transfer belt 14 on a more upstream side of the feeding direction from the fur brush 37, and a single constant current power source 43. The fur brush 37 is connected to a constant current DC power source 43 and the conductive brush 42 is grounded. Current is caused to flow to the conductive brush 42 from the constant current DC power source 43 through the transfer belt 14. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cleaning device and an image forming device. In particular, the present invention is suitably applied to a cleaning device provided in an image forming apparatus such as a laser printer, a copying machine, a facsimile machine, and a multifunction peripheral thereof.

  The image forming apparatus collects toner remaining on the surface of a photoconductor (photoconductor drum or photoconductor belt) or an intermediate transfer body (intermediate transfer belt or intermediate transfer drum) as an image carrier even after transferring the toner image. Cleaning device. A part of the toner remaining on the surface of the image carrier after the transfer is charged to the opposite polarity, and the charge distribution is not uniform. Various cleaning devices have been proposed to efficiently collect such residual toner.

  Referring to FIG. 29, the cleaning device disclosed in Patent Literature 1 includes a pair of fur brushes 2A and 2B arranged so as to contact the surface of the photoconductor 1. Bias voltages of opposite polarities are applied to the fur brushes 2A, 2B by separate power supplies 3A, 3B. Residual toner having normal charging polarity (negative polarity) is collected by the fur brush 2A to which a positive voltage is applied by the power supply 3A. The residual toner having the opposite polarity (positive polarity) is collected by the fur brush 2B to which the negative voltage is applied by the power supply 3B.

  Referring to FIG. 30, the cleaning device disclosed in Patent Literature 2 includes one fur brush 5 arranged so as to contact the surface of photoconductor 4. A bias voltage having a polarity (negative polarity) opposite to the normal charge polarity (positive polarity) of the residual toner is applied to the fur brush 5 via a collection roller 6 having conductivity. A charger 8 connected to a power supply 7B is disposed upstream of the fur brush 5 in the rotation direction of the photoconductor 4. Before the residual toner is collected by the fur brush 5, the charge is removed or charged by the charger 8, and the charged polarity is made uniform. Patent Document 3 discloses a similar cleaning device.

  However, the conventional cleaning device requires a plurality of power supplies. More specifically, the cleaning device of FIG. 29 requires two power supplies 3A and 3B, one for each of the two fur brushes 2A and 2B. Similarly, the cleaning device of FIG. 30 requires two power supplies 7A and 7B, one for each of the fur brush 5 and the charger 8. Therefore, the size of the cleaning device increases, and the cost also increases.

  The amount of charge of the toner remaining on the surface of the image carrier varies depending on various conditions such as a current flowing in the transfer section. If a charger 8 for removing electricity is provided in front of the fur brush 5 as a cleaning member as in the cleaning device of FIG. 30, the charge polarity and charge amount of the toner reaching the fur brush 5 can be made uniform. However, since two power supplies are required as described above, the size of the cleaning device is increased. On the other hand, in a cleaning device such as the charger 8 that does not include a mechanism for removing static electricity, the voltage applied to the cleaning member may be set high in order to surely collect toner having different charging polarity and charge amount. However, this has the following problems. First, the image carrier is charged by an excessive cleaning current flowing through the image carrier, which causes an image defect. Further, the life of the image carrier is shortened by the excessive cleaning current. Further, when the charge amount of the toner is small, the toner is charged to the polarity opposite to the normal charge polarity due to the excessive cleaning current, and the cleaning performance is rather deteriorated. Similarly, the amount of toner remaining on the surface of the image carrier varies depending on various conditions.

No. 4-112274 (Fig. 1) JP-A-8-50437 (FIG. 1) Japanese Patent No. 2954812 (FIG. 1)

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a small-sized and low-cost cleaning device capable of efficiently removing residual toner on the surface of an image carrier. Another object of the present invention is to make it possible for the cleaning device to maintain appropriate cleaning performance even when the amount of charge of the residual toner or the amount of the residual toner changes.

  According to a first aspect of the present invention, there is provided a cleaning device that collects toner on the surface of an image carrier, comprising: a conductive rotating member that is driven to rotate while being in contact with the surface of the image carrier; Also, a conductive member that comes into contact with the image carrier on the upstream side in the transport direction of the image carrier, one of the rotating member and the conductive member is connected and the other is grounded, and the rotating member and A DC current flows through the image carrier between the conductive member and the conductive member, thereby causing a force between the rotating member and the image carrier to attract the toner having a normal charging polarity to the rotating member. A single DC power supply that generates a second electric field in a direction opposite to the first electric field between the conductive member and the image carrier while generating a first electric field in a direction in which Cleani characterized by comprising To provide a grayed apparatus.

  In the cleaning device according to the first aspect, the toner having the normal charging polarity on the surface of the image carrier is electrostatically attracted to the rotating member and collected by the first electric field generated between the rotating member and the image carrier. You. Further, since a second electric field opposite to the first electric field is generated between the conductive member and the image carrier, the conductive member functions as a charge removing member, and the toner charged to the opposite polarity on the surface of the image carrier. Has a regular charging polarity when passing through the conductive member. Therefore, the toner whose charging polarity is aligned with the regular charging polarity reaches the rotating member, so that the toner can be efficiently collected.

  One of the rotating member and the conductive member is connected to a DC power supply, while the other is grounded, and there is only one DC power supply for applying a charge or generating an electric field. Therefore, the size and cost of the device can be reduced. The rotating member may be connected to a DC power supply and the conductive member may be grounded, or the conductive member may be connected to a DC power supply and the rotating member may be grounded.

  The image carrier may be a photosensitive member including a photosensitive drum and a photosensitive belt, or may be an intermediate transfer member including an intermediate transfer belt and an intermediate transfer drum.

  The DC power supply is, for example, a constant current DC power supply. If a constant-current DC power supply is used as a power supply for generating an electric field, a constant amount of current can flow even if the resistance increases due to adhesion of toner to a rotating member or a conductive member or a change in durability of an image carrier. it can. Therefore, even if the resistance increases, the strength of the electric field generated by the rotating member or the conductive member can be maintained, and a decrease in the collection efficiency can be prevented.

  The DC power supply may be indirectly connected to the rotating member or the conductive member, or may be directly connected. For example, when the rotating member is a fur brush, a DC power supply may be indirectly connected via a flicker or a collection roller and a scraper. Alternatively, a DC power supply may be directly connected to the rotating shaft of the fur brush.

  The rotating member has conductivity, and rotates in a direction opposite to a conveying direction of the image carrier (a feeding direction in the case of a photosensitive belt or an intermediate transfer belt, a rotating direction in the case of a photosensitive drum or an intermediate transfer drum). Any material can be used as long as it can at least electrostatically adsorb and collect the residual toner on the surface of the image carrier. For example, the rotating member includes a fur brush, a conductive elastic roller, or a metal roller.

  The conductive member may be any as long as it has conductivity, makes uniform contact with the surface of the image carrier, and has low frictional resistance with the surface of the image carrier. For example, a conductive brush, a conductive film, a conductive rubber, or a fur brush can be used as the conductive member.

  Since the current supplied by the DC power supply flows between the rotating member and the conductive member via the image carrier, when the image carrier is an intermediate transfer belt stretched over a plurality of stretching rollers, the intermediate transfer belt is It is not necessary to ground the tension roller facing the rotating member via the intermediary member, and the roller can be electrically floated. Therefore, even when the image forming apparatus is downsized and the cleaning device is disposed close to the primary transfer unit and the secondary transfer unit, it is possible to prevent the transfer current from flowing from these transfer units to the cleaning device. In addition, it is possible to prevent a transfer failure caused by the flow of the transfer current and an image failure caused by the transfer failure.

  When the image carrier is an intermediate transfer member, the distance between the rotating member and the conductive member is set to be equal to the rotating member in order to more reliably prevent transfer current from flowing from the primary transfer portion and the secondary transfer portion. It is preferable that the distance be shorter than the distance between the primary transfer portion or the secondary transfer portion which is closest thereto. In other words, the conductive member is disposed at an interval from the rotating member, and the intermediate transfer member extends from a contact position of the rotating member to the intermediate transfer member to a contact position of the conductive member to the intermediate transfer member. Is shorter than the distance in the transport direction of the intermediate transfer member from the contact position of the rotating member to the intermediate transfer member to the nip portion of the intermediate transfer member and the primary transfer portion and the secondary transfer portion. preferable.

And the DC current I _c via the image carrier flowing between the conductive member and the rotary member _(.mu.A), the DC power supply output voltage V _C and _(V), relative to the image bearing member of the rotary member It is preferable that the distance L ₁ (mm) in the transport direction of the image carrier from the contact position to the contact position of the conductive member with the image carrier satisfies the following expression (1).

  Α and β are coefficients relating to the surface resistance of the image carrier. The coefficients α and β are defined by the following equations (2) and (3).

Right side of the equation (1), the cleaning failure so as to specify a condition for not generated by the surface potential V _s of the rotary member is excessively increased. This condition was obtained by experiment. The left side of the equation (1) defines a condition under which no gap discharge occurs between the rotating member and the conductive member. This condition was obtained by Paschen's rule. The DC current I _c flowing between the rotating member and the conductive member via the image carrier, the surface potential V _{s of} the rotating member, and the distance L ₁ between the rotating member and the conductive member are represented by the relationship of the formula (1). If satisfied, good cleaning performance can be obtained.

  The coefficient α is preferably in a range of −10.2 to −3.01 and the coefficient β is preferably in a range of 31.23 to 39.15.

  According to a second aspect of the present invention, there is provided an image forming apparatus including the above-described cleaning device.

  According to a third aspect of the present invention, there is provided an image carrier that carries a toner image on a surface thereof, and a transfer unit that transfers the toner image on the surface of the image carrier to a body to be transferred by power supplied from a first power supply. A current sensor configured to detect a current flowing through the transfer unit, and a rotation unit that is rotatably disposed downstream of the transfer unit in the transport direction of the image carrier so as to contact the surface of the image carrier, and has a conductivity. A member, a motor for rotating the rotating member, and a second power supply for supplying power to the rotating member, thereby electrostatically adsorbing toner remaining on the surface of the image carrier after transfer to the rotating member. And a controller that controls at least one of an output of the first power supply and a rotation speed of the motor based on a current value detected by the current sensor.

  In the image forming apparatus according to the third aspect, the output of the second power supply that supplies power to the rotating member that collects the toner remaining on the surface of the image carrier based on the current value flowing through the transfer unit detected by the current sensor And / or the speed of the motor driving the rotating member is adjusted. As the value of the current flowing to the transfer portion is larger, the amount of charge of the toner remaining on the image carrier increases, and the amount of the remaining toner tends to increase. Conversely, the smaller the current flowing in the transfer portion, the smaller the amount of charge of the toner remaining on the image carrier, and the amount tends to decrease. In the image forming apparatus according to the third aspect of the invention, the output of the second power supply and / or the speed of the motor for driving the rotating member is adjusted in accordance with the change in the amount of toner remaining on the image carrier, so that an appropriate Cleaning performance can be maintained.

  Specifically, the control unit increases the output of the second power supply as the current value detected by the current sensor increases. Also, the control unit increases or decreases the rotation speed of the motor as the current value detected by the current sensor increases, together with or instead of adjusting the output of the second power supply.

  The image forming apparatus may further include an environment sensor that detects an environmental condition. In this case, the control unit controls at least one of the output of the first power supply and the rotation speed of the motor based on an environmental condition detected by the environment sensor. The environment sensor detects, for example, at least one of temperature and humidity as the environmental condition.

  Further, the image forming apparatus may further include a dimension sensor for detecting a dimension of the transfer object. In this case, the control unit controls at least one of an output of the first power supply and a rotation speed of the motor based on a size of the transfer target detected by the size sensor.

  The image forming apparatus may further include a toner amount detection sensor that detects a toner amount on the surface of the image carrier. In this case, the control unit controls at least one of the output of the first power supply and the rotation speed of the motor based on the detected toner amount. The image forming apparatus may further include a jamming detection sensor that detects occurrence of jamming of the transfer medium. The control unit may control at least one of an output of the first power supply and a rotation speed of the motor based on a detection result of the jamming detection sensor. The control unit may control at least one of the output of the first power supply and the rotation speed of the motor in further consideration of other conditions such as the type of the transfer target.

  When the image carrier is an intermediate transfer belt, for example, the transfer unit forms a nip between the surface of the intermediate transfer belt and a nip portion through which an object to be transferred passes, and faces the secondary transfer roller. And a stretching roller that is arranged so as to be in contact with the back surface of the intermediate transfer belt, and the current sensor detects a current flowing through the stretching roller.

  According to the first and second aspects of the present invention, only one DC power supply is required for generating an electric field in the cleaning device. Therefore, the size and cost of the cleaning device can be reduced.

  According to the third aspect of the invention, the output of the second power supply for supplying power to the rotating member and / or the speed of the motor driving the rotating member are adjusted based on the current flowing through the transfer unit, so that the image is adjusted. Appropriate cleaning performance can be maintained even if the charge amount or the amount of toner remaining on the carrier changes.

(1st Embodiment)
FIG. 1 shows a tandem process type laser printer 12 which is an example of an image forming apparatus provided with a secondary cleaning device 11 (hereinafter, simply referred to as a cleaning device 11) according to the first embodiment of the present invention. In this embodiment, the normal charge polarity of the toner is assumed to be negative.

  The intermediate transfer belt 14 (hereinafter, simply referred to as the transfer belt 14) stretched between the pair of stretch rollers 13A, 13B is sent in the direction indicated by arrow A by the rotation of the stretch rollers 13A, 13B. Around the transfer belt 14, first to fourth image forming units 16A to 16D, a secondary transfer device 17, and a cleaning device 11 are provided.

  Each of the image forming units 16A to 16D transfers the yellow (Y), magenta (M), cyan (C), and black (Br) images to the transfer belt 14, respectively. The image forming units 16A to 16D have the same structure, and include a charging device 22, a developing device 23, a primary transfer device 24, and a primary cleaning device 25 around a photoreceptor drum 21. The surface of the photoreceptor drum 21 uniformly charged by the charging device 22 is exposed by a laser beam emitted from the laser unit 26 to form an electrostatic latent image. This electrostatic latent image is visualized by the toner supplied from the developing device 23 and becomes a toner image. This toner image is transferred to the front surface of the transfer belt 14 by a positive voltage applied to the back surface of the transfer belt 14 by the primary transfer device 24. The toner remaining on the surface of the photosensitive drum 21 even after the primary transfer is collected by the primary cleaning device 25.

  Each time the sheet passes through the image forming units 16A to 16D, the toner image is transferred onto the transfer belt 14 in a superimposed manner (however, in the case of a monochrome image, the toner image is transferred onto the transfer belt 14 only by the image forming unit 16D). Is done). The transferred toner image is transferred by a secondary transfer device 17 to a recording medium 28 such as paper conveyed from a paper feed cassette 27. Specifically, the toner image is transferred from the transfer belt 14 to the recording medium 28 by a positive voltage applied to the back surface of the recording medium 28. The toner 30 remaining on the transfer belt 14 even after the transfer by the secondary transfer device 17 includes a toner charged to the normal polarity (negative) and a toner charged to the opposite polarity (positive). The recording medium 28 onto which the toner image has been transferred is sent to the fixing device 31 and is fixed to the recording medium 28 by applying pressure and heat.

  The cleaning device 11 will be described with reference to FIGS. The cleaning device 11 includes a collection unit 35 that collects the toner 30, and a charge removal unit 36 that is located upstream of the collection unit 35 in the conveyance direction of the intermediate transfer belt 14 and that aligns the polarity of the toner 30 charged to the opposite polarity. It has.

The collection unit 35 includes a fur brush (rotating member) 37 that contacts the surface of the transfer belt 14. The fur brush 37 is obtained by implanting resin hair having a resistance of, for example, about 1 × 10 ⁴ to 1 × 10 ⁷ Ω / □ around the cored bar 37a. The fur brush 37 is rotationally driven by a motor 38A in a direction opposite to a feed direction of the transfer belt 14. A collection roller 39 made of metal and having conductivity is in contact with the fur brush 37. The collection roller 39 is driven to rotate in a direction opposite to the fur brush 37 by a motor 38B. Further, a scraper 41 that is made of metal and has conductivity and also functions as a contact member is in contact with the collection roller 39. Referring to FIG. 3, the width W1 of the fur brush 37 is wider than the maximum width W2 of the recording medium 28, but is smaller than the width W3 of the transfer belt 14. Therefore, irrespective of the size of the recording medium 28, there are areas ΔW on both sides of the transfer belt 14 where the fur brush 37 and the transfer belt 14 face each other without the transfer medium 28 interposed therebetween.

  On the other hand, the static elimination unit 36 includes a conductive brush (conductive member) 42 in which conductive resin bristles are implanted on a metal base having conductivity. The conductive brush 42 is in contact with the surface of the transfer belt 14.

  The fur brush 37 of the collection unit 35 is connected to a constant current DC power supply 43. Specifically, one end of the scraper 41 is connected to the constant current DC power supply 43, and the fur brush 37 is indirectly connected to the constant current DC power supply 43 via the scraper 41 and the collection roller 39. The constant current DC power supply 43 is connected to the fur brush 37 so as to generate a cleaning electric field having a polarity opposite to that of the toner 30 having the normal charging polarity. In this embodiment, since the regular charging polarity of the toner 30 is negative, the positive terminal of the constant current DC power supply 43 is connected to the fur brush 37 via the scraper 41 and the collection roller 39. On the other hand, the conductive brush 42 of the static elimination unit 36 is not connected to the power supply but is simply grounded.

  As shown in FIG. 4, the constant current DC power supply 43 includes a DC power supply 43a and a current detection element 43b connected in series to the DC power supply 43a, and controls a voltage to be output so that a current value is constant. Has functions.

As shown by a dotted line in FIG. 2, the scraper 41 from the constant-current DC supply 43, the collection roller 39, the fur brush 37, and a cleaning current I _C flows through the conductive brush 42 via the transfer belt 14. Referring also to FIG. 5A, in the collection unit 35, an electric field (cleaning electric field) E ₁ on the side opposite to the normal charging polarity of the toner 30 between the fur brush 37 and the transfer belt 14, that is, from the fur brush 37 to the transfer belt 14 An electric field is generated toward. Force for sucking electrostatically to the fur brush 37 to the toner 30 of the normal charge polarity of the surface of the transfer belt 14 as indicated by the cleaning electric field E ₁ in the arrow F _E (negative) is applied. The toner 30 is collected from the transfer belt 14 by being electrostatically attracted to the fur brush 37. Due to the potential difference between the fur brush 37 and the collection roller 39, the toner 30 adsorbed on the surface of the fur brush 37 moves to the collection roller 39, and is scraped off from the surface of the collection roller 39 by the scraper 41.

On the other hand, referring also to FIG. 5B, (field opposite to the cleaning electric field E ₁₎ and the conductive brush 42 in the discharger 36 field of normal charging polarity and same polarity of the toner 30 between the transfer belt 14 E ₂ is generated. The electric field E _2, charged toner 30 to the opposite polarity of the surface of the transfer belt 14, the normal charging polarity (negative) as it passes through the conductive brush 42. Therefore, the toner 30 whose charging polarity is aligned with the regular charging polarity reaches the fur brush 37 of the collecting unit 35, and the toner 30 can be efficiently collected from the transfer belt 14 by the fur brush 37.

Although by generating recovery unit 35 and the discharger 36 and the de-orientation different electric field E _1, E ₂ as described above, the recovery unit 35 these field E _1, E ₂ is connected to the constant-current DC supply 43 resulting in the cleaning current I _C flowing into the conductive brush 42 of the static eliminator 36 from the fur brush 37 via the transfer belt 14. Only the fur brush 37 of the collection unit 35 is connected to the constant current DC power supply 43, and the conductive brush 42 of the charge removal unit 36 is grounded. In other words, only a single constant-current DC power supply 43 is used as a power supply for applying charges or generating an electric field. Therefore, the size and cost of the device can be reduced.

The rated current of the constant current DC power supply 43 is, for example, 10 to 100 μA, and the maximum voltage is, for example, about 0.3 to 4 kV. In order to generate an electric field of sufficient strength in the collection unit 35 and the charge removal unit 36, the resistance of the transfer belt 14 is preferably, for example, not less than 1 × 10 ⁸ Ω / □ and not more than 1 × 10 ¹² Ω / □. Examples of the material of the transfer belt 14 include polyimide, polycarbonate, and polyphenylene sulfide.

  Further, since the constant current DC power supply 43 is used as a power supply for generating an electric field, the resistance increases due to the adhesion of the toner 30 to the fur brush 37, the collection roller 39, or the conductive brush 42, the durability change of the transfer belt 14, and the like. However, a certain amount of current can flow. Therefore, even if the resistance increases, the electric field strength of the collection unit 35 and the charge removal unit 36 is maintained, and a reduction in the collection efficiency can be prevented.

  Further, the current supplied by the constant current DC power supply 43 flows between the fur brush 37 of the collection unit 35 and the conductive brush 42 of the charge removing unit 36 via the transfer belt 14, and is collected with these by the transfer belt 14. It is not necessary to ground the stretching roller 13A facing the section 35 and the charge removing section 36. Therefore, in this embodiment, an electrically floating state is maintained by supporting the shaft of the stretching roller 13A, which is a conductive roller, with a bearing made of insulating resin. Therefore, even when the cleaning device 11 is arranged close to the primary transfer device 24 and the secondary transfer device 17 due to the miniaturization, the transfer current from the primary transfer device 24 and the secondary transfer device 17 is transferred via the transfer belt 14. It is possible to prevent the transfer from flowing into the tension roller 14, and it is possible to prevent a transfer failure due to the flow of the transfer current and an image failure due to the transfer failure.

The conductive brush 42 of the charge removing unit 36 needs to be arranged at a position where the conductive brush 42 does not contact the fur brush 37 of the collection unit 35. For example, the distance L _{1 in} the feed direction of the transfer belt 14 from the nip portion of the fur brush 37 to the transfer belt 14 to the contact position of the conductive brush 42 to the transfer belt 14 is set to be at least の the diameter of the fur brush 37. Just fine. The preferred setting range of the distance L ₁ will be described in detail later.

The primary in order to more reliably prevent the flow of transfer current from the primary transfer device 24 and the secondary transfer device 17, the distance L ₁ of the fur brush 37 and the conductive brush 42 that it is closest to the fur brush 37 It is preferable that the distance be shorter than the distance from the transfer device 24 or the secondary transfer device 17. In the present embodiment, since the primary transfer device 24 of the image forming unit 16A is arranged closest to the fur brush 37, the primary transfer device 24 of the image forming unit 16A is moved from the nip portion of the fur brush 37 to the transfer belt 14. than feed direction of the distance L ₂ to the nip portion, shorter the distance L _1.

(2nd Embodiment)
In the second embodiment of the present invention shown in FIG. 6, the collection unit 35 includes a conductive elastic roller 45 having a conductive rubber layer on the outer periphery of a cored bar, instead of the fur brush 37 (see FIG. 2). Other configurations and operations of the second embodiment are the same as those of the first embodiment.

(Third embodiment)
In the third embodiment of the present invention shown in FIG. 7, the fur brush 37 of the collecting unit 35 is electrically connected to the constant current DC power supply 43 via a flicker 46 which also functions as a contact member. The toner 30 collected by the fur brush 37 is scraped off by the flicker 46. Further, the charge removing section 36 includes a conductive film 47 instead of the conductive brush 42 (see FIG. 2). The conductive film 47 has a leading end contacting the transfer belt 14 and a base end supported by a conductive holder. The conductive film 47 is grounded via a holder. Cleaning current _{I C} flows in the conductive film 47 through the constant-current DC supply 43 flicker 46, the fur brush 37, and the transfer belt 14. Other configurations and operations of the third embodiment are the same as those of the first embodiment.

(Fourth embodiment)
In the fourth embodiment of the present invention shown in FIG. 8, a constant current DC power supply 43 is connected to the conductive brush 42 of the static elimination unit 36, and the fur brush 37 of the collection unit 35 is grounded via a flicker 46. Negative terminal is connected to the conductive brush 42 of the constant-current DC power supply 43, the cleaning current I _C flowing in the fur brush 37 through the constant-current DC supply 43 conductive brush 42, and the transfer belt 14, the fur brush 37 the cleaning electric field E ₁ in the regular charging polarity opposite side occurs in the toner 30, the conductive brush 42 field E ₂ in the opposite direction occurs and the cleaning electric field. Other configurations and operations of the fourth embodiment are the same as those of the first embodiment.

(Fifth embodiment)
In the fifth embodiment of the present invention shown in FIG. 9, the conductive brush 37 of the recovery unit 35 is connected to a constant current DC power supply 43 via a flicker 46. Further, the charge removing section 36 includes a fur brush 57 grounded via a flicker 56. The fur brush 57 is rotationally driven by a motor 38C in a direction opposite to the transfer direction of the transfer belt 14. Other configurations and operations of the fifth embodiment are the same as those of the first embodiment.

(Sixth embodiment)
In the sixth embodiment of the present invention shown in FIG. 10, the recovery unit 35 including the fur brush 37 connected to the constant current DC power supply 43 via the flicker 46 and the static elimination unit 36 including the grounded conductive film 47 include: It is arranged on the secondary transfer device 17 (upstream in the transport direction of the transfer belt 14) side of the first to fifth embodiments. As described above, in the cleaning device of the present invention, the distance (distance L ₁ ) from the collection unit 35 to the neutralization unit 36 is the distance from the collection unit 35 to the closest primary transfer device 9 or the secondary transfer device 17. As long as the condition that the distance is shorter than (distance L ₂ ) is satisfied, the transfer belt 14 can be arranged at an arbitrary position on the circumference.

(Seventh embodiment)
In the seventh embodiment of the present invention shown in FIG. 11, a cleaning blade 48 is provided on the downstream side in the feed direction of the transfer belt 14 in addition to the cleaning device 11 having the same configuration as the first embodiment. The tip of the cleaning blade 48 is in contact with the transfer belt 14, and the toner 30 that has passed through the collection unit 35 is removed from the surface of the transfer belt 14 by the cleaning blade 48. Other configurations and operations of the seventh embodiment are the same as those of the first embodiment.

(Eighth embodiment)
In the eighth embodiment of the present invention shown in FIG. 12, another conductive film 61 is disposed at an interval on the upstream side in the feed direction of the transfer belt 14 with respect to the conductive film 47 of the charge removing section 36. The front end of the conductive film 61 contacts the transfer belt 14, and the base end is supported by a conductive holder. The conductive film 61 is grounded.

  By providing the conductive film 61, the inside of the cleaning device 11 is sealed, and the smoke of the toner 30 generated by the fur brush 37 is prevented from diffusing to the outside of the cleaning device 11 and reattaching to the transfer belt 14. it can. In order to reliably seal the smoke of the toner 30, it is preferable that the conductive film 61 is rich in flexibility and the degree of close contact between the conductive film 61 and the transfer belt 14 is high. Therefore, it is preferable that the conductive film 61 be made of a material having a lower hardness than the conductive film 47 of the charge removing section 36 and be thinner than the conductive film 47.

Since the conductive film 61 is grounded, a portion of the cleaning current I _C flows in the conductive film 61 from the constant-current DC supply 43 flicker 46, via the fur brush 37 and the transfer belt 14. Due to this current, an electric field is generated between the conductive film 61 and the transfer belt 14 in the same direction as the electric field E ₂ (see FIG. 5B) generated between the conductive film 47 of the charge removing section 36 and the transfer belt 14. I do. Therefore, the conductive film 61 has a function of uniformly discharging the toner 30 remaining on the transfer belt 14 before reaching the charge removing section 36 to make the charged polarity uniform. Therefore, the provision of the conductive film 61 improves the static elimination performance of the cleaning device 11 as a whole. In order to adjust the intensity of the electric field generated between the conductive film 61 and the transfer belt 14, a resistor may be interposed between the conductive film 61 and the ground.

  An insulating film may be provided in place of the conductive film 61. Although this insulating film does not have a charge removing function, it can seal powder smoke of the toner 30 generated by the fur brush 37.

  Another conductive film 62 is provided at a distance from the fur brush 37 of the collection unit 36 in the feed direction of the transfer belt 14. The conductive film 62 has a leading end contacting the transfer belt 14 and a base end supported by a conductive holder. The conductive film 62 is grounded via a resistor 63.

  Similarly to the conductive film 61 disposed on the upstream side of the charge removing section 36, the conductive film 62 prevents the dust of the toner 30 generated by the fur brush 37 from diffusing out of the cleaning device 11.

Since the conductive film 62 is in contact with the transfer belt 14, a portion of the cleaning current I _C from the constant-current DC supply 43 flows into the transfer belt 14 via the conductive film 62. Due to this current, an electric field is generated between the conductive film 62 and the transfer belt 14 in the same direction as the electric field E ₂ (see FIG. 5B) generated between the conductive film 47 of the charge removing section 36 and the transfer belt 14. I do. Therefore, the conductive film 62 has a function of aligning the charging polarity of the toner 30 on the transfer belt 14 that has passed through the collecting unit 35 without being collected by the fur brush 37.

  A conductive brush 65 may be arranged as shown in FIG. 13 instead of the conductive film 61 on the upstream side in the feed direction of the transfer belt 14 from the charge removing section 35. In this case, although there is no function of sealing the smoke of the toner 30, the toner 30 remaining on the transfer belt 14 can be supplementarily discharged. Similarly, the conductive film 62 on the downstream side in the feed direction of the transfer belt 14 from the collection unit 36 may be replaced with a conductive brush. Further, as shown in FIG. 14, the cleaning device 11 of FIG. 12 may be arranged further upstream in the feed direction of the transfer belt 14. Furthermore, the cleaning device 11 may include only one of the conductive films 61 and 62.

  As a result of experiments and studies, the inventor has found that the cleaning devices 11 of the first to eighth embodiments exhibit appropriate cleaning performance when the conditions defined by the following expression (4) are satisfied. Was.

In the formula (4), the conductive member (conductive brush 42 of I _c is the rotation of the collecting portion 35 via the transfer belt 14 as an image bearing member (fur brush 37 or conductive roller 45) and the static eliminator 36, a conductive film 47 or the cleaning current (μA) flowing between the fur brushes 57). _VC is the output voltage (V) of the constant current DC power supply 43. Furthermore, L ₁ is the feed direction of the length of the transfer belt 14 from the contact position with respect to the transfer belt 14 of the rotary member to the contact position with respect to the transfer belt 14 of the conductive member (mm).

The α and β in equation (4) is a coefficient related to the surface resistivity [rho _s of the transfer belt 14. The coefficients α and β are defined by the following equations (5) and (6).

The right side of Expression (4) was obtained from experiments on the distance L ₁ , the cleaning current I _C , and the surface resistance ρ _S of the transfer belt 14. In this experiment, the cleaning device 11 of the first embodiment shown in FIGS. 1 to 3 was used. As described above, in the first embodiment, the rotating member provided in the collection unit 35 is the fur brush 37, and the conductive member provided in the charge removing unit 36 is the conductive member 42. The transfer belt 14 was made of polycarbonate, had a width W3 (see FIG. 3) of 350 mm, and a film thickness of 150 μm. The fur brush 37 had bristle made of conductive nylon, had an outer diameter of 15.4 mm, an axial length or width W1 of 310 mm, and had a resistance of 1 × 10 ⁹ Ω. Further, the conductive brush 42 was provided with bristle made of conductive nylon, had a bristle length of 5 mm, an axial length or width of 310 mm, and a resistance of 1 × 10 ⁹ Ω.

First, we examine the relationship between the output voltage V _C of the distance L ₁ and the constant-current DC supply 43 between the fur brush 37 and the conductive brush 42. Specifically, in the case the cleaning current _{I C} is 5 .mu.A, 10 .mu.A, and 20 .mu.A, was measured output voltage _{V C} at the time of changing the distance _{L 1.} The measurement results when the surface resistivity [rho _S of the transfer belt 14 is 1 × ^{10 10} Ω / □ shown in FIG. 15, the measurement results when the surface resistivity [rho _s is 1 × ^{10 11} Ω / □ in FIG. 16 Show. In FIGS. 15 and 16, the symbol “x” indicates that cleaning failure has occurred. The cleaning failure was determined as follows. First, the toner remaining on the transfer belt 14 even after passing through the cleaning device 11 was adhered to the adhesive tape. Next, the density of the toner adhered to the adhesive tape was measured, and when the measured value was higher than a predetermined threshold value, it was determined that the cleaning was defective.

Next, the relationship between the surface resistance ρs of the transfer belt 14 and the output voltage Vc of the constant current DC power supply 43 was examined. Specifically, to measure the output voltage _{V C} when the cleaning current _{I C} is 5 .mu.A, changing the surface resistance [rho _S for the case of 10μA and 20 .mu.A,. It was the distance L ₁ between the fur brush 37 and the conductive brush 42. FIG. 17 shows the measurement results. In FIG. 17, the symbol “x” indicates that cleaning failure has occurred, as in FIGS.

When the measurement results of FIGS. 15 to 17 are examined, it is determined whether or not cleaning failure occurs, or conversely, whether or not the cleaning device 11 exhibits proper cleaning performance is determined by the output voltage of the constant current DC power supply 43. It was found to be dependent on the V _C. In particular, from the measurement results shown in FIG. 17 from FIG. 15, it is less than the output voltage _{V C} of the constant-current DC power supply 43 is 5 kV, regardless of the value of the cleaning current _{I C,} the distance _{L 1,} and the surface resistivity [rho _S It was found that cleaning failure did not occur. Therefore, the surface resistance [rho _S is ^{1 × 10 8 Ω / □,} 1 × 10 9 Ω / □, 1 × 10 10 Ω / □, 1 × 10 11 Ω / □, and 1 × ^{10 12} Ω / □ when about , the output voltage _{V C} to obtain a 18 by plotting the cleaning current _{I C} and the distance _{L 1} which is a 5 kV. In FIG. 18, the measurement results shown in FIGS. 15 and 16 were used when the surface resistance ρ _S was 1 × 10 ¹⁰ Ω / □ and 1 × 10 ¹¹ Ω / □. The surface resistivity [rho _S is ^{1 × 10 8 Ω / □,} 1 × 10 9 Ω / □, and the 1 × ^{10 12} Ω / □ case likewise cleaning current _{I C} is 5 .mu.A, 10 .mu.A, and 20μA when measuring the output voltage V _C when the distance L ₁ was changed for the output voltage V _C from the result of the measurement to obtain a distance L ₁ which is a 5 kV.

There are eight graphs corresponding to the value ^{(10 12 Ω / □ 1 ×} 10 8 ~1 ×) of the surface resistance [rho _S in FIG. 18. When approximate curves are obtained by logarithmic approximation for each of these eight graphs, the result of FIG. 18 is given by the following equation (7).

The coefficients α and β are defined by the equations (5) and (6) as described above. Equation (7) was obtained from the measurement results where the surface resistance ρ _S was in the range of 1 × 10 ⁸ Ω / □ to 1 × 10 ¹² Ω / □. Therefore, by substituting ρ _s = 1 × 10 ⁸ and 1 × 10 ¹² into equations (5) and (6), the range of the coefficient α is not less than −10.2 and not more than −3.01 and the range of the coefficient β is not more than Is not less than 31.23 and not more than 39.15. Coefficients for the surface resistivity [rho _S alpha, a change in the value of β is shown in FIGS. 19 and 20.

Equation (7) shows a condition conditions the output voltage V _C is 5 kV, the cleaning in other words the output voltage V _C if is higher than this value failure. Thus, the rotating member (fur brush 37 or conductive roller 45) and the conductive member (conductive brush 42, conductive film 47, or the fur brush 57) a distance L ₁ between is less than the right side of the equation (7), a cleaning device 11 exhibits proper cleaning performance.

Surface resistivity [rho _S is ^{1 × 10 8 Ω / □,} 1 × 10 9 Ω / □, 10 Ω / □ 1 × 10, 1 × 10 11 Ω / □, and 1 × ^{10 12} Ω / □ when the formula ( 5μA as the cleaning current _{I C} to 7), 10 .mu.A, and the result of substituting 20μA shown in FIG. By comparing FIG. 18 with FIG. 21, it can be confirmed that Expression (7) closely approximates the result of FIG.

Next, the left side of Expression (4) will be described. Assuming that the gap between the two conductors is t (mm) and the gap breakdown voltage is V _B (V), Paschen's law is given by the following equation (8).

  When the equation (8) is arranged for the gap t, the following equation (9) is obtained.

Equation (9) shows the minimum gap t at which no gap discharge occurs between two conductors for a certain voltage. Therefore, the larger the distance L ₁ than equation obtained by replacing the air gap breakdown voltage V _B of the right side of equation (9) to the output voltage V _C, the rotation member (fur brush 37 or conductive roller 45) of the collection portion 35 No gap discharge is generated between the conductive member (conductive brush 42, conductive film 47, or fur brush 57) of the charge removing section 36, and a closed circuit can be formed between these members via the transfer belt 14. .

(Ninth embodiment)
FIG. 22 shows an image forming apparatus according to the ninth embodiment of the present invention. Although only a part of the image forming apparatus of FIG. 1 is shown in FIG. 22 for convenience of description, the image forming apparatus of the present embodiment is different from FIGS. Has the same configuration as the first embodiment shown in FIG. Therefore, the image forming apparatus of the present embodiment also includes elements not shown in FIG. 22 but shown in FIGS. 1 to 3. In the following description, FIG. 1 to FIG. 3 will be referred to in addition to FIG. 22.

Constant current DC power supply 43 of the cleaning device 11 includes a DC power source 43a, and a current detecting element 43b connected in series to the DC power source 43a, the output voltage so that the current value of the cleaning current I _C becomes constant It has a control function. The constant-current DC supply 43 is configured a cleaning current I _C to be set to various values.

  The primary transfer device 24 of each of the image forming units 16A to 16D includes a conductive roller 24a facing the photosensitive drum 21 with the transfer belt 14 interposed therebetween. A constant voltage power supply 101 is connected to the conductive roller 24a. On the conductive roller 24a, a primary transfer voltage having a polarity (positive polarity) opposite to the normal charge polarity (negative in this embodiment) of the toner 30 forming a toner image on the surface of the photosensitive drum 21 is applied by the constant voltage power supply 101. Applied. The constant voltage power supply 101 includes a DC power supply 101a and a voltage detecting element 101b connected in parallel with the DC power supply 101a, and has a function of controlling a current output so that the primary transfer voltage is constant. A semiconductive roller may be used instead of the conductive roller 24a.

The secondary transfer device 17 includes a conductive roller 17a opposed to the tension roller 14B with the transfer belt 14 interposed therebetween. Like the conductive roller 24a of the primary transfer device 24, the conductive roller 17a is connected to a constant voltage power supply 102 having a DC power supply 102a and a voltage detecting element 102b connected in parallel to the DC power supply 102a. The constant voltage power supply 102a has a function of controlling a current to be output so that the voltage is constant. A semi-conductive roller may be used instead of the conductive roller 17a. On the other hand, the tension roller 13B is grounded, and a secondary transfer current sensor 104 is interposed between the ground portion and the tension roller 13B. A closed circuit is formed from the constant voltage power supply 102 to the ground via the conductive roller 17a, the transfer belt 14, the tension roller 13B, and the secondary transfer current sensor 104. To the conductive roller 17a, a secondary transfer voltage having a polarity (positive) opposite to the normal charging polarity (negative) of the toner 30 forming a toner image on the surface of the transfer belt 14 is applied by a constant voltage power supply 102. As a result, the toner image on the surface of the transfer belt 14 is transferred to the recording medium 28 passing through the nip formed between the transfer belt 14 and the conductive roller 24a. Current flowing through the closed circuit during the secondary transfer voltage is applied, the current flowing through the other words during the secondary transfer voltage applying secondary transfer device 17 (secondary transfer current I _t2) is detected by the secondary transfer current sensor 104. The secondary transfer current sensor 104 outputs a detected value of the secondary transfer current _It2 to the control unit 105.

  An environment sensor 106 is provided in the image forming apparatus. The environment sensor 106 detects the humidity H and outputs the detected value to the control unit 105.

  A paper size sensor 107 that detects the size of the recording medium 28 is provided in a transport path between the paper cassette 27 (see FIG. 1) and the secondary transfer device 17. The paper size sensor 107 outputs the detected size of the paper, that is, the size of the recording medium 28, to the control unit 105.

  An AIDC (Auto Image Density Control) sensor 109 is provided between the secondary transfer device 17 and the image forming unit 16D located at the most downstream side in the feed direction of the transfer belt 14 among the image forming units 16A to 16D. ing. The image forming units 16A to 16D form toner patches in an area ΔW (see FIG. 3) of the transfer belt 14 where the recording medium 28 is not arranged. The AIDC sensor 109 detects the toner density in the toner patch, and outputs a detected value to the control unit 105.

  In the image forming apparatus, a jam sensor 110 for detecting jamming or jamming of the recording medium 28 is provided. The jam sensor 110 outputs a signal indicating the occurrence of jamming to the control unit 105.

The control unit 105 includes elements such as a CPU, a RAM, and a ROM, and controls the cleaning device 11 based on inputs from the secondary transfer current sensor 104, the environment sensor 106, the paper size sensor 107, the AIDC sensor 109, and the jam sensor 110. adjusting the cleaning current I _C of the constant-current DC power supply 43 is outputted.

Next, with reference to the flowchart of FIG. 23A and 23B, will be described adjustment of the cleaning current _{I C} of the control unit 105 executes. First, in step S23-1, if the image formation of a new job is set to an initial value the cleaning current _{I C} in step S23-2. Next, the secondary transfer current sensor 104 at step S23-3 to detect the secondary transfer current _{I t2.} More specifically, a secondary transfer voltage is applied to the conductive roller 17 by the constant voltage power supply 102 in a state where the recording medium 28 does not exist in the nip portion between the conductive roller 17 and the transfer belt 14, and the current flowing through the stretching roller 13B at that time is It is measured by the secondary transfer current sensor 104.

When the secondary transfer current _It2 is small, the toner 30 on the transfer belt 14 is hardly affected by the secondary transfer, and thus tends to maintain the normal charging polarity (negative). In this case, since the less necessary to invert the cleaning device 11 the charging polarity of the toner 30 from the reverse polarity (positive) to the normal charging polarity, an electric field E ₂ in the cleaning electric field E ₁ and discharger 36 of the recovery unit 35 is low Strength is good. Therefore, when the small secondary transfer current I _t2, the cleaning current I _C can be a small current. On the other hand, when the secondary transfer current _It2 is large, the toner 30 on the transfer belt 14 is strongly affected by the secondary transfer, and thus the charging polarity tends to reverse to the normal charging polarity. In this case, the intensity of the electric field E ₂ is set sufficiently high with need to align the charging polarity of the toner 30 of the static eliminator 36, it is preferably higher cleaning electric field E ₁ in the recovery section 35. Therefore, when the secondary transfer current I _t2 is small, it is necessary to increase the cleaning current I _C. Therefore, if the secondary transfer current _{I t2} detection value is the threshold value _{I T2th} than the predetermined in at step S23-4, the set value of the cleaning current _{I C} to be output of the constant-current DC supply 43 in step S23-5 It is increased by a predetermined amount ΔI _C1 .

Next, in step S23-6, the environment sensor 106 detects the humidity H in the image forming apparatus. If the humidity H is high, the conductivity of the paper increases due to moisture absorption, so that the transfer efficiency in the secondary transfer device 17 decreases, and the amount of the toner 30 remaining on the transfer belt 14 tends to increase. Therefore, if the threshold value _{H th} or the detected value of the humidity H is predetermined in step S23-7, it is increased by an amount [Delta] I _c2 defined set value of the cleaning current _{I C} in advance in step S23-8.

In step S23-9, the detection value of the paper size sensor 107 is read. Referring to FIG. 3, since the width W3 of the transfer belt 14 is wider than the maximum width W2 of the paper or the recording medium 28, there are areas ΔW on both sides of the transfer belt 14 that do not face the paper. Ideally, no toner adheres to this area ΔW, but actually, a phenomenon (so-called toner fogging) occurs in which the toner adheres thinly to the area ΔW in the primary transfer device 24 of each of the image forming units 16A to 16D. As the size of the paper is smaller, the area of the area ΔW on the transfer belt 14 where the paper is not present increases, so that the amount of toner due to fogging tends to increase. Therefore, in this case, it is necessary to increase the recovery efficiency of the toner by setting a cleaning electric field E ₁ in the recovery section 35 of the cleaning device 11 to a high strength. Conversely, the area of the region ΔW larger the size of the paper decreases, the amount of residual NATO by the head tends to decrease, the cleaning electric field E ₁ in the recovery section 35 may be a relatively low intensity. Therefore, when the paper size detected by sheet size sensor 107 is smaller than the A4 size or A4 size in step S23-10, a cleaning current _{I C} of the set values constant current DC power supply 43 is outputted at step S23-11 Is increased by a predetermined amount ΔI _C3 .

In step S23-12, the output of AIDC sensor 109 is read. As described above, the AIDC sensor 109 detects the toner density D in the toner patch on the transfer belt 14. When the detected toner density is high, the toner density of the toner image on the transfer belt 14 is high, and the amount of the toner remaining on the transfer belt 14 even after the secondary transfer tends to be large. Therefore, in this case, it is necessary to increase the recovery efficiency of the toner by setting a cleaning electric field E ₁ in the recovery section 35 of the cleaning device 11 to a high strength. Conversely, when the detected toner density is low, the toner density of the toner image on the transfer belt 14 tends to be low, and the amount of toner remaining on the transfer belt 14 even after the secondary transfer tends to be small. Accordingly, the cleaning electric field E ₁ in the recovery section 35 in this case may be a relatively low intensity. Therefore, if the threshold _{D th} or the detected value of the toner density D is predetermined in step S23-13, a predetermined set value of the cleaning current _{I C} of the constant-current DC power supply 43 is outputted at step S23-14 only amount [Delta] I _C4 increases.

When jamming occurs, the image forming apparatus stops in a state where the toner image not transferred to the recording medium 28 adheres to the transfer belt 14 as it is. Thus configured, upon restart after jamming occurs, i.e., the jamming first after the occurrence job remaining large amount of the toner on the transfer belt 14, a cleaning electric field E ₁ in the recovery section 35 of the cleaning device 11 to the high-strength It is necessary to increase the toner collection efficiency. Therefore, if the first job after detection jamming by the jam sensor 110 in step S23-15, is increased by an amount [Delta] I _C5 defined set value of the cleaning current _{I C} in advance in step S23-16. Specifically, the job starts after the transfer belt 14 for a period of time required for at least one revolution, thereby temporarily increasing the cleaning current I _C.

After the processing shown in FIGS. 23A and 23B ends, the actual job is executed. Constant current DC power supply 43 of the cleaning device 11, the toner charge quantity and charge polarity remaining on the transfer belt 14, and outputs the adjusted cleaning current I _C in accordance with the amount of toner remaining on the transfer belt 14. Therefore, the cleaning device 11 exhibits proper cleaning performance, and can reliably and efficiently remove the toner remaining on the transfer belt 14. The initial value of the cleaning current I _C and the adjustment amounts ΔI _{C1 to} ΔI _C5 are set so that, for example, the cleaning current I _C changes within a range of 3 μA or more and 50 μA or less.

  The control unit 105 may execute the control shown in FIGS. 23A and 23B for each sheet or recording medium 28 instead of for each job.

Although the control of FIGS. 23A and 23B are adjusted cleaning current _{I C,} as shown in FIGS. 24A and 24B, the rotational speed of the fur brush 37 to the recovery unit 35 of the cleaning device 11 is provided (rotation member), specifically Specifically, the rotation speed of the motor 38A that drives the fur brush 37 to rotate may be adjusted. The higher the rotation speed of the fur brush 37, the higher the toner collection efficiency of the cleaning device 11. Conversely, the lower the rotation speed of the fur brush 37, the lower the toner collection efficiency of the cleaning device 11.

If an image of a new job is to be formed in step S24-1, the rotation speed R of the motor 38A is set to an initial value in step S24-2. If the secondary transfer current _{I t2} detected by the secondary current sensor 104 at step S24-3 that the threshold value _{I T2th} above in step S24-4, a defined set value of the rotational speed R advance in step S24-5 by an amount ΔR ₁ increase. Then, if the humidity H detected by the environment sensor 106 is a threshold value _{H th} or more in the step S24-7 In step S24-6, the amount [Delta] R ₂ defined the set value of the rotational speed R advance in step S24-8 Just increase. Further, if the detected value of the paper size sensor 107 read in step S24-9 is smaller than the A4 size or the A4 size in step S24-10, the set value of the rotation speed R is set to a predetermined amount in step S24-11. only ΔR ₃ increase. Furthermore, the detected concentration D of the toner patch by the AIDC sensors 109 read in step S24-12 is equal threshold _{D th} or more in the step S24-13, a defined set value of the rotational speed R advance in step S24-14 Increase by an amount ΔR ₄ . If the first job after jamming detected in step S24-15, the increase amount [Delta] R ₅ is the period required for at least the transfer belt 14 rotates one round defined a set value of the rotational speed R advance in step S24-16 Let it.

  After the processing shown in FIGS. 23A and 23B ends, the actual job is executed. The fur brush 37 provided in the collection unit 35 of the cleaning device 11 rotates at a rotation speed adjusted according to the charge amount and the charge polarity of the toner remaining on the transfer belt 14 and the amount of the toner remaining on the transfer belt 14. I do. Therefore, the cleaning device 11 exhibits proper cleaning performance, and can reliably and efficiently remove the toner remaining on the transfer belt 14.

Regulation of the cleaning current _{I C} (FIG. 23A and FIG. 23B), may be applied in combination with regulation of the rotational speed R of the motor 38A (FIG. 24A and 24B). The environment sensor 106 may detect the temperature inside the image forming apparatus in addition to or instead of the humidity. In this case, as the detected temperature is high, the cleaning current I _C is set larger, the rotational speed R of the motor 38A is set to be faster. Conversely, the lower the detected temperature, the cleaning current I _C is set smaller, the rotational speed R of the motor 38A is set smaller. Further, the configuration of the second embodiment to the seventh embodiment (see FIGS. 7 to 14) may be adopted as the cleaning device 11 in the ninth embodiment. Further, the cleaning device 11 in the ninth embodiment may have a configuration in which the removing roller 36 is not provided as shown in FIG. 25, but the collection roller 35 and the tension roller 13A opposed to the transfer belt 14 are grounded. . Furthermore, the control of the present embodiment can be applied to a primary transfer device for collecting the residual toner on the photoconductor.

(Tenth embodiment)
FIG. 26 shows an image forming apparatus according to the tenth embodiment of the present invention. For convenience of explanation, FIG. 26 shows only a part of the image forming apparatus of FIG. The image forming apparatus of the tenth embodiment has the same configuration as that of the first embodiment shown in FIGS. 1 to 3 except that various sensors and the like described later are provided. Accordingly, the image forming apparatus according to the present embodiment also includes elements not shown in FIG. 26 but shown in FIGS. 1 to 3. In the following description, FIGS. 1 to 3 will be referred to in addition to FIG.

Constant current DC power supply 43 of the cleaning device 11 includes a DC power supply 43a, the voltage output to a current detecting element 43b connected in series to the DC power source 43a, becomes the current value of the cleaning current I _C is a constant Has the function of controlling A feedback current sensor 201 is interposed between the neutralizing unit 36 and the ground unit. The feedback current sensor 201 outputs a detected value of the detected current (feedback current I _R ) to the control unit 203.

The primary transfer device 24 of each of the image forming units 16A to 16D includes a conductive roller 24a facing the photosensitive drum 21 with the transfer belt 14 interposed therebetween. A constant voltage power supply 202 is connected to the conductive roller 24a. To the conductive roller 24a, a primary transfer voltage _Vt1 having a polarity (positive) opposite to a normal charging polarity (negative) of the toner 30 forming a toner image on the surface of the photosensitive drum 21 is applied by a constant voltage power supply 202. . The constant voltage power supply 202 includes a DC power supply 202a and a voltage detecting element 202b connected in parallel with the DC power supply 202a, and has a function of controlling a current output so that the primary transfer voltage _Vt1 is constant. Further, in the present embodiment, the constant voltage power supply 202 includes a current detection element 202c connected in series with the DC power supply 202a, and can control the output voltage so that the current becomes constant as necessary. In other words, the constant voltage power supply 202 can also function as a constant current power supply. A semiconductive roller may be used instead of the conductive roller 24a.

Control unit 203 sets the primary transfer voltage _{V t1} of the primary transfer device 24 of the image forming units 16 A- 16 D. In particular, the control unit 203 based on the primary transfer voltage _{V t1} of the four image forming units most cleaning device 11 the image forming unit 16A of the first transfer device 24 disposed proximate to one of 16A~16D the feedback current _{I R} Adjust.

In the cleaning device 11, a closed circuit is formed from the constant current DC power supply 43 to the ground via the scraper 41, the collection roller 39, the fur brush 37, the transfer belt 14, the conductive brush 42, and the feedback current sensor 201. . This is in closed circuit through the cleaning current I _C from the constant-current DC supply 43. Therefore, usually the value of the feedback current I _R and the cleaning current I _C is equal. However, when the resistance of the transfer belt 16 is reduced due to durability or when the humidity in the image forming apparatus is high, the image forming unit arranged closest to the cleaning device 11 among the four image forming units 16A to 16D is used. Current may flow from the primary transfer device 24 of the unit 16A to the cleaning device 11. When flow of the current is generated, the feedback current I _R is larger than the cleaning current I _C. In detail, the constant voltage power supply 202 of the primary transfer device 24 controls the current so that the primary transfer voltage _Vt1 is constant. Therefore, when the resistance decreases, the current becomes excessively large. Through the cleaning device 11. For example, the feedback current _{I R} output to the cleaning current _{I C} is in a 10μA constant current DC power supply 43 of the cleaning device 11 if 12 .mu.A, the primary transfer device 24 of the image forming unit 16A of 2μA to the cleaning device 11 This means that current is flowing. When an excessive primary transfer current generated in the primary transfer device 24 flows through the transfer belt 14, the transfer belt 14 is damaged and its life is shortened. Therefore, the control unit 203 in the feedback current I to determine the presence or absence of excessive primary transfer current generated from the values of _R in the primary transfer device 24 of the image forming apparatus 16A, the primary transfer device 24 of the image forming units 16A based on the determination The primary transfer voltage _Vt1 is adjusted.

The processing executed by the control unit 203 will be specifically described with reference to the flowchart in FIG. First, if an image is to be formed for a new job in step S27-1, a current having a constant value is simultaneously supplied to the primary transfer units 24 of the four image forming units 16A to 16D in step S27-2. Specifically, the constant voltage power supply 202 of the primary transfer unit 24 of each of the image units 16A to 16D is caused to function as a constant current power supply, and a constant current is output. Then, in step S27-3, measured by the voltage detecting element 101b of the primary transfer voltage _{V t1} that the primary transfer device 24 of the image forming units 16A~16D is output when that current of a constant value flows. The primary transfer voltage _Vt1 measured by each primary transfer device 24 is output to the control unit 203. At step S27-4, on the basis of the measured primary transfer voltage _{V t1,} to determine a set value of the primary transfer voltage _{V t1} of each image unit 16A~16D used during an actual image forming. Specifically, the control unit 203 stores the set value of the primary transfer voltage V _t1 corresponding to the primary transfer voltage V _t1 measured in step S27-3 in the form of a table, measurement of the primary transfer voltage V _t1 The set value of the primary transfer voltage _Vt1 during image formation is uniquely determined with respect to the value.

Since excessive primary transfer current generated at the primary transfer device 24 of the image forming units 16B~16D flows into other image forming units mostly adjacent, almost does not contribute to an increase in the feedback current I _R. Therefore, it is used for actual image formation without adjusting the set value of these image forming units primary transfer device 16b to 16d 24 primary transfer voltage V _t1 determined in step S27-4 for. On the other hand, closest to the image forming knit 16A disposed in the further adjusted to the set value of the primary transfer voltage _{V t1} at step S27-5~S27-9 applied to the cleaning device 11.

First, in step S27-5, it applies a primary transfer voltage _{V t1} set in step S27-4 to the primary transfer device 24 of the image forming unit 16A. Specifically, the voltage output from the constant voltage power supply 202 of the primary transfer device 24 is set as the set value of the primary transfer voltage _Vt1 . Then, in step S27-6, detects the feedback current _{I R} at the time of primary transfer device 24 is outputting the set value of the primary transfer voltage _{V t1} at feedback current sensor 201. If the detected value of the feedback current I _R is equal to or higher than the threshold value I _Rth predetermined in step S27-7, i.e. excessive primary transfer current generated by the primary transfer device 24 of the image forming units 16A are flowing into the cleaning device 11 and if it is determined lowers by an amount [Delta] V _t1 that the set value predetermined primary transfer voltage V _t1 determined in step S27-4. To the set value of the feedback current _{I R} is less than the threshold _{I Rth} in step S27-7, the process of step S27-5~S27-8 is repeated. If the set value of the feedback current _{I R} in step S27-7 is less than the threshold value _{I Rth,} setting value of the primary transfer voltage _{V t1} of the image forming unit 16A is fixed at the value at that point in step S27-8.

After the processing shown in FIG. 27 ends, the actual job is executed. The primary transfer voltage _Vt1 output from the constant voltage power supply 202 of the image forming unit 16A is adjusted so that an excessive primary transfer current flowing into the cleaning device 11 is not generated. Therefore, it is possible to prevent an excessive current from flowing to the transfer belt 14 and prolong the life of the transfer belt 14.

  The control unit 203 may execute the control shown in FIG. 27 for each sheet or recording medium 28 instead of for each job.

  The configuration of the second to seventh embodiments (see FIGS. 7 to 14) may be adopted as the cleaning device 11 in the tenth embodiment. Further, the cleaning device 11 in the tenth embodiment may have a configuration in which the removing roller 36 is not provided as shown in FIG. 28 and the tension roller 13A opposed to the collection unit 35 with the transfer belt 14 interposed therebetween is grounded. . In this case, the feedback current sensor 201 is interposed between the tension roller 13A and the ground.

  The present invention is not limited to the above embodiment, and various modifications are possible. For example, the core metal 37 a of the fur brush 37 of the collection unit 35 (see FIGS. 2 and 7 to 11) or the core metal of the conductive elastic roller 45 (see FIG. 6) may be directly connected to the constant current DC power supply 43. Good. Further, a metal roller may be used as a rotating member of the collection unit 35.

  A conductive rubber is used instead of the conductive brush 42 (see FIGS. 2, 6, 8, and 11), the conductive film 47 (see FIGS. 7 and 10), and the fur brush 57 (see FIG. 9). Is also good. The conductive brush 42, the conductive film 47, and the fur brush 57 may be grounded via a resistor. By adjusting the resistance value of the resistor, the present invention can be applied to a transfer belt having various resistance values and characteristics.

  When the normal charging polarity of the toner is opposite (positive) to that in the above-described embodiment, the polarity of the voltage applied from the constant current source to the collection unit 35 or the charge removal unit 36 may be reversed. For example, if the normal charging polarity of the toner is positive in the first embodiment, the scraper 41 may be connected to the negative terminal of the constant current DC power supply 43.

  Further, the present invention can be applied to a cleaning device for an intermediate transfer drum and a photoconductor such as a photoconductor drum.

  Further, in addition to the laser printer, the present invention can be applied to an image carrier cleaning device provided in another image forming apparatus such as a copying machine, a facsimile machine, and a multifunction peripheral thereof.

FIG. 1 is a schematic diagram illustrating a laser printer including a cleaning device according to a first embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a cleaning device according to the first embodiment of the present invention. FIG. 2 is a partial plan view showing the cleaning device according to the first embodiment of the present invention. It is a schematic circuit diagram which shows a constant current DC power supply. FIG. 5 is a schematic diagram illustrating a cleaning electric field generated in a collection unit. It is the schematic which shows the electric field which generate | occur | produces in a charge removal part. It is a schematic diagram showing a cleaning device according to a second embodiment of the present invention. It is a schematic diagram showing a cleaning device according to a third embodiment of the present invention. It is a schematic diagram showing a cleaning device according to a fourth embodiment of the present invention. It is a schematic diagram showing a cleaning device according to a fifth embodiment of the present invention. It is a schematic diagram showing a cleaning device according to a sixth embodiment of the present invention. It is a schematic diagram showing a cleaning device according to a seventh embodiment of the present invention. It is a schematic diagram showing a cleaning device according to an eighth embodiment of the present invention. It is a schematic diagram showing a cleaning device concerning a modification of an 8th embodiment of the present invention. It is a schematic diagram showing a cleaning device concerning a modification of an 8th embodiment of the present invention. The surface resistance of the transfer belt is a graph showing a relationship between 1 × ¹⁰ 10 Ω / □ distance L ₁ and the voltage in the case of. The surface resistance of the transfer belt is a graph showing a relationship between 1 × 10 ¹¹ Ω / □ distance L ₁ and the voltage in the case of. 5 is a graph illustrating a relationship between a surface resistance of a transfer belt and a voltage. Output voltage is a graph showing the relationship between the applied current and the distance L ₁ in the case of 5 kV. 6 is a graph showing a change in a value of a coefficient α with respect to a logarithmic value of a surface resistance of a transfer belt. 6 is a graph showing a change in a value of a coefficient β with respect to a logarithmic value of a surface resistance of a transfer belt. 9 is a graph showing the results of substituting the surface resistance and cleaning current of various transfer belts into the conditional expressions according to the present invention. It is a schematic diagram showing a cleaning device according to a ninth embodiment of the present invention. It is a flow chart for explaining operation of a cleaning device concerning a 9th embodiment of the present invention. It is a flow chart for explaining operation of a cleaning device concerning a 9th embodiment of the present invention. It is a flow chart for explaining operation of a cleaning device concerning a modification of a 9th embodiment of the present invention. It is a flow chart for explaining operation of a cleaning device concerning a modification of a 9th embodiment of the present invention. It is a schematic diagram showing the cleaning device concerning the modification of a 9th embodiment of the present invention. It is a schematic diagram showing an image forming apparatus according to a tenth embodiment of the present invention. 21 is a flowchart for explaining an operation of the image forming apparatus according to the tenth embodiment of the present invention. FIG. 19 is a schematic diagram illustrating an image forming apparatus according to a modification of the tenth embodiment of the present invention. FIG. 9 is a schematic diagram illustrating an example of a conventional cleaning device. FIG. 11 is a schematic diagram illustrating another example of a conventional cleaning device.

Explanation of reference numerals

Reference Signs List 11 cleaning device 12 laser printer 13A, 13B stretching roller 14 transfer belt 16A, 16B, 16C, 16D image forming unit 17 secondary transfer device 21 photoconductor drum 22 charging device 23 developing device 24 primary transfer device 25 primary cleaning device 26 laser Unit 27 Paper feed cassette 28 Recording medium 30 Toner 31 Fixing device 35 Collection unit 36 Static elimination unit 37 Fur brush 37a Core bar 38A, 38B Motor 39 Collection roller 41 Scraper 42 Conductive brush 43 Constant current DC power supply 45 Conductive elastic roller 46 Flicker 47 Conductive film 48 Cleaning blade 57 Fur brush 56 Flicker 101, 102, 202 Constant voltage power supply 104 Primary transfer current sensor 105, 203 Control unit 106 Environment sensor 107 Paper sheet Zusensa 109 AIDC sensors 110 jam sensor 201 feedback current sensor

Claims (16)

A cleaning device for collecting toner on the surface of the image bearing member,
A rotating member having conductivity that is driven to rotate while being in contact with the image carrier surface,
A conductive member that comes into contact with the image carrier on the upstream side in the transport direction of the image carrier from the rotating member;
One of the rotating member and the conductive member is connected and the other is grounded, thereby generating a DC current flowing through the image carrier between the rotating member and the conductive member, A first electric field is generated between the rotating member and the image carrier in a direction in which a force for adsorbing the toner having a normal charging polarity to the rotating member acts, and the conductive member and the image carrier. And a single DC power supply that generates a second electric field opposite to the first electric field.   The cleaning device according to claim 1, wherein the rotating member is connected to the DC power supply, and the conductive member is grounded.   The cleaning device according to claim 1, wherein the conductive member is connected to the DC power supply, and the rotating member is grounded.   The cleaning device according to any one of claims 1 to 3, wherein the DC power source is a constant current DC power source. And the DC current I _c via the image carrier flowing between the conductive member and the rotary member _(.mu.A), and the DC power supply output voltage V _{c (V),} relative to the image bearing member of the rotary member The distance L ₁ (mm) in the transport direction of the image carrier from the contact position to the contact position of the conductive member with the image carrier satisfies the following relationship;

2. The cleaning apparatus according to claim 1, wherein said α and β are coefficients relating to a surface resistance of said image carrier.   The cleaning device according to claim 5, wherein the coefficient α is in a range from -10.2 to -3.01.   The cleaning device according to claim 5, wherein the coefficient β is in a range of 31.23 to 39.15. An image carrier, a transfer unit for transferring a toner image to the image carrier, and a transfer unit downstream of the transfer unit in the conveyance direction of the image carrier, collecting toner remaining on the surface of the image carrier An image forming apparatus comprising: a cleaning device;
The cleaning device includes:
A rotating member having conductivity that is driven to rotate while being in contact with the image carrier surface,
A conductive member that is in contact with the image carrier on the upstream side in the transport direction of the image carrier from the rotating member;
One of the rotating member and the conductive member is connected and the other is grounded, thereby generating a DC current flowing through the image carrier between the rotating member and the conductive member, whereby the A first electric field is generated between the rotating member and the image carrier in a direction in which a force for adsorbing the toner having the normal charging polarity to the rotating member acts, and the conductive member and the image carrier are And a single DC power supply that generates a second electric field opposite to the first electric field. And the DC current I _c via the image carrier flowing between the conductive member and the rotary member _(.mu.A), the DC power supply output voltage V _C and _(V), relative to the image bearing member of the rotary member distance L ₁ in the conveying direction of the image bearing member from the contact position to the contact position with respect to said image bearing member of the conductive member satisfies the following relationship,

The image forming apparatus according to claim 8, wherein α and β are coefficients relating to a surface resistance of the image carrier.   The image forming apparatus according to claim 9, wherein the coefficient α is in a range from −10.2 to −3.01.   The image forming apparatus according to claim 9, wherein the coefficient β is in a range from 31.23 to 39.15. An image carrier that carries a toner image on its surface;
A transfer unit that transfers the toner image on the surface of the image bearing member to a transfer target body using power supplied from a first power supply;
A current sensor for detecting a current flowing through the transfer unit;
A rotatable member that is rotatably disposed downstream of the transfer unit in the transport direction of the image carrier so as to contact the image carrier surface, and has conductivity.
A motor for rotating the rotating member,
A second power supply that supplies power to the rotating member, thereby electrostatically adsorbing toner remaining on the surface of the image carrier after transfer to the rotating member;
An image forming apparatus comprising: a control unit that controls at least one of an output of the second power supply and a rotation speed of the motor based on a current value detected by the current sensor.   13. The image forming apparatus according to claim 12, wherein the control unit increases the output of the second power supply as the current value detected by the current sensor increases.   13. The image forming apparatus according to claim 12, wherein the control unit increases the rotation speed of the motor as the current value detected by the current sensor increases. It further includes an environmental sensor that detects environmental conditions,
15. The control unit according to claim 12, wherein the control unit further controls at least one of an output of the first power supply and a rotation speed of the motor based on an environmental condition detected by the environment sensor. The image forming apparatus according to claim 1. Further comprising a dimension sensor for detecting the dimension of the transfer object,
13. The apparatus according to claim 12, wherein the control unit further controls at least one of an output of the first power supply and a rotation speed of the motor based on a size of the transfer target detected by the size sensor. The image forming apparatus according to claim 14.

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