JP4701661B2 - Developing device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a printer, and more particularly to a developing device using a non-magnetic one-component developer and an image forming apparatus using the developing device.

  Development devices used in conventional image forming apparatuses such as an electrophotographic system include a non-magnetic one-component development method using a non-magnetic one-component developer (toner) composed only of toner and a two-component development composed of toner and a carrier. A two-component development system using an agent is known. Above all, the non-magnetic one-component developing system developing device does not require mixing with the carrier, stirring, and toner concentration control, so the size of the device can be reduced and the cost can be reduced. And the like are unnecessary, and are increasingly used mainly in printers that are required to be maintenance-free.

In the non-magnetic one-component development method, how to form a toner layer having a predetermined toner amount and toner charge amount on the developing roll is an important factor. For this reason, usually, after a certain amount of toner has adhered to the developing roll while a toner supply roll using a foam bite into the developing roll, the toner on the developing roll is regulated by a regulating blade provided on the developing roll side. A method of regulating the layer thickness and applying charging is adopted.
However, in this method, the toner is subject to mechanical stress in the nip area between the toner supply roll and the developing roll and the nip area between the developing roll and the regulating blade, and the toner is liable to be deteriorated. There is a problem that heat is generated by pressure for regulating the thickness, and toner sticks to the regulating blade. This problem is particularly serious in a developing device used in an image forming apparatus for forming a color image. That is, in order to form a color image, it is necessary to develop the color by completely melting the toner of each color. Therefore, the binder resin used for the toner tends to have a low melting point, and the toner is not fixed to the regulating blade. It tends to occur more easily.
Furthermore, due to the great stress applied to the toner particles, the external additive particles on the toner surface may be peeled off or embedded inside, resulting in the initial fluidity, cohesiveness, chargeability, etc. of the toner particles. Will also change.

JP-A-7-234583 (Example, FIG. 2) JP-A-8-179608 (Example 1, FIG. 1) Japanese Patent Laid-Open No. 9-62088 (Embodiment of the Invention, FIG. 3)

In order to solve such a problem, a system in which a developing roll and a toner supply roll are disposed apart from each other has been proposed (see, for example, Patent Documents 1 to 3).
Patent Document 1 describes that the gap between the developing roll and the toner supply roll is made larger than the thickness of the toner layer on the developing roll. Patent Document 2 provides an example in which a developing roll and a toner supply roll are spaced from each other, and a regular polygonal column-shaped roll is used as the toner supply roll.
However, in each of these technologies, although the developing roll and the toner supply roll are spaced apart from each other, the toner stress at the opposite portion of the both is reduced. Since the toner is charged at the same time as the excess toner is scraped off, it is necessary to press the layer thickness regulating blade strongly against the developing roll to some extent (increase the pressure contact force). The problems of toner adhesion and toner stress remain unsolved.

  Further, Patent Document 3 proposes a configuration in which a toner collection roll is provided in addition to the toner supply roll. In Patent Document 3, as shown in FIG. 12, a configuration is described in which two supply rolls 83 and 84 and one collection roll 85 are both arranged away from the development roll 82 so as to face the development roll 82. ing. Further, the developing roll 82 and the two supply rolls 83 and 84 are rotated in the same direction (Whith) at the mutually facing portions, and are rotated in the opposite direction (Against) from the collection roll 85. . Further, the gap between the developing roll 82, the collecting roll 85, and the two supply rolls 83 and 84 is configured to decrease in the downstream direction in the toner conveyance direction on the developing roll 82. Therefore, by gradually narrowing the gap with the developing roll 82, the rubbing force with the developing roll 82 is increased, and the toner is peeled (collected) from the developing roll 82 and the toner is efficiently supplied to the developing roll 82. It can be done well. Reference numeral 81 denotes a photoconductor.

  However, after the toner layer is formed on the developing roll 82, the excess toner existing around the supply roll 83 is covered on the toner layer on the developing roll 82. On the developing roll 82, excessive toner adheres more unevenly on the layered toner layer, resulting in uneven toner layer thickness. For this reason, a layer thickness regulating blade 86 for scraping off the excess toner is required, and a large pressure contact force is required. As a result, the problem that the toner sticks easily to the layer thickness regulating blade 86 is not solved.

  For this reason, the present inventors have studied a developing device as shown in FIG. 13, for example, which does not affect the toner supplied onto the developing roll. In this case, the developing roll 91 and the toner supply roll 92 are rotated in the same direction at the opposite portions so that the toner blown from the opposite portions does not affect the toner layer supplied to the developing roll 91 side. In addition, a method is assumed in which both are arranged and the distance to the wall surface 93a of the developing housing 93 is increased (corresponding to the length of L in the drawing).

  However, with this With configuration, a large space is required in the vicinity of the outlet of the facing portion between the developing roll 91 and the toner supply roll 92 so that the toner does not stay, and there is a concern that the apparatus may be increased in size. It has also been found that even when such a large space is provided, the formation of a uniform toner thin layer on the developing roll 91 is limited to toner with good fluidity. In the case of a toner with poor fluidity, it was confirmed that excess toner adhered in a streak pattern in the circumferential direction on the formed toner thin layer, resulting in a narrow degree of freedom in toner selection.

  On the other hand, as shown in FIG. 14, when the blowing of the developing roll 91 and the toner supply roll 92 is arranged upward, the toner is sent out below the toner supply roll 92 even though there is sufficient space in the upper part. For this reason, it was confirmed that only a narrow space was provided, and it was difficult to continuously supply toner in the direction of arrow D in the figure.

  The present invention has been made in order to solve the above technical problem, further uniformizing the developer amount and the developer charge amount of the developer layer formed on the developer carrier, The present invention provides a developing device having stable development characteristics over a long period of time and an image forming apparatus using the same.

That is, as shown in FIGS. 1 (a) and 1 (b), the basic configuration of the present invention is such that a developer carrying is carried on the surface which can rotate and face an image carrying body carrying an electrostatic latent image. A developer supply member 2 that is capable of supplying the developer carrier 1 with a developer that is spaced apart from the developer carrier 1 and supported on the surface thereof, and a developer carrier from the developer supply member 2. The developer supplied onto the developer supply member 2 before the supply of the developer to the body 1 is preliminarily regulated, and the developer preregulation amount α to be preliminarily regulated is set to the developer carrier 1. And a preliminary regulating means 3 for adjusting the regulated supply amount β to an amount corresponding to the sum of the developer residual amount γ on the developer supply member 2 side.

In such technical means, the developing device according to the present application uses a non-magnetic one-component developer (developer), and the developer carrier 1 may be any drum as long as it can carry the developer. Shape, including belt shape. Further, from the viewpoint of effective development, the developer carrier 1 is preferably arranged in contact with the image carrier on which the electrostatic latent image is carried, but may be non-contact. Further, the developer carrier 1 may be an elastic body or a rigid body.
The developer supply member 2 is preferably a rigid body from the viewpoint of stably maintaining a gap with the developer carrier 1, but is not particularly limited as long as it can carry and transport the developer.

In the present invention, the developer carrier 1 and the developer supply member 2 are configured to move in the same direction (with configuration) even if they are configured to move in opposite directions (Against configuration) at opposite portions of both. However, the Against configuration is preferable. In this case, there is an advantage that the developer regulation supply amount β can be easily stabilized by adjusting the gap between the two.
Further, by adjusting the developer preliminary regulation amount α so as to be the sum of the developer regulation supply amount β and the developer residual amount γ by the preliminary regulation means 3, the developer carrier 1 and the developer supply member 2. The developer regulation supply amount β supplied to the developer carrier 1 is stabilized.
Therefore, the amount of the developer on the developer carrier 1 can be optimized in advance. For example, the developer layer thickness regulation at the charging member 5 or the like that is disposed opposite to the developer carrier 1 and charges the developer is regulated. The charging member 5 can be made to have a pressure that is merely in contact with the charging member 5, or the charging member 5 can be disposed in non-contact with the developer carrier 1 or the developer layer. It will be possible to prevent unnecessary stress.

In the present invention , the AC is provided between the developer carrier 1 and the developer supply member 2 and promotes the movement of the developer from at least the developer supply member 2 to the developer carrier 1 in one cycle. A developer supply member including an action region that contains an electric field component and acts on the movement of the developer between the developer carrier 1 and the developer supply member 2 and a non-working region that does not act on the movement of the developer; Supply bias applying means for applying a supply bias 4 for supplying the developer from 2 to the developer carrying member 1 is provided. Such a supply bias 4 makes it possible to further control the developer regulation supply amount β on the developer carrier 1.

By the way, as a technique approximating the supply bias applied between the developer carrier 1 and the developer supply member 2, the prior art documents (Japanese Patent Laid-Open Nos. 9-311539 and 10-26882) are disclosed. There is a proposed method.
In these documents, as a developing bias applied between the image carrier and the developer carrier 1, one period is composed of a portion where the potential changes alternately and a portion where the potential remains constant without changing. The one which intends to apply the alternating electric field (blank pulse) is proposed. At the same time, as a bias to be applied to the developer supply member 2, there has been proposed a system in which an alternating electric field similar to the development bias is applied. Here, in order to suppress the influence of the phase shift between the bias applied to the developer supply member 2 and the development bias, the frequency of the bias applied to the developer supply member 2 is made larger than the frequency of the development bias. Further, it is also disclosed that the interference is prevented and the influence of the phase shift is reduced.
However, in such a system, the supply bias and the development bias are individually applied, and the supply bias is not applied in a form superimposed on the development bias. However, the supply bias creates a supply electric field based on a difference from the development bias, and depending on the timing, there is a concern that the developer supply itself from the developer supply member 2 to the developer carrier 1 cannot be performed.

At this time, there has also been proposed a system in which an electric field similar to a developing bias is formed between the developer carrier 1 and the developer supply member 2 by keeping the potential of the developer supply member 2 constant. Even when a supply bias consisting of a blank pulse is applied between the developer carrier 1 and the developer supply member 2, the developer is reciprocated at a portion where the potential of the supply bias reciprocates alternately, and is constant. In the portion where the potential is maintained, the developer is positively returned to one side. Such an action can be easily understood in these patent documents because it corresponds to the same effect as the action of the blank pulse in the development region.
Therefore, in the methods described in these documents, all electric field components in one cycle act as an active region that acts on the developer, and a non-acting region is provided in a part of one cycle of the supply bias. There is no suggestion about the point of installation.
Further, when such a DC electric field (a portion that maintains a constant potential) is applied, the developer on the developer supply member 2 is usually in an uncharged (almost uncharged) state. Unnecessary charging is caused by the above, and the variation in charge amount is increased. For this reason, even if an attempt is made to supply the developer from the developer supply member 2 to the developer carrier 1, the amount of developer supplied tends to fluctuate with variations in the charge amount, and a certain amount in the developer carrier 1. It becomes impossible to control the formation of the developer thin layer.
As described above, it is stated that the blank pulse is applied to secure the coating amount (supply amount) of the developer, but the point of controlling the developer supply amount by controlling the time of the active region and the non-active region is described. Is not suggested at all. In other words, a technique for increasing the developer supply adhesion amount from the developer supply member 2 to the developer carrier 1 has been described, but the developer supply adhesion amount is such that the regulation member does not require layer thickness regulation. There is no suggestion of a technique for reducing and making uniform.

The preliminary regulating means 3 in the present invention is preferably an auxiliary supply member that is arranged upstream of the developer supply member 2 and that supplies the developer to the developer supply member 2 in a regulated manner. 2 is adjusted. In addition, the auxiliary supply member may be disposed apart from or in contact with the developer supply member 2. However, from the viewpoint of life, the auxiliary supply member is disposed apart from the developer supply member 2. A roll-shaped member is preferable. Therefore, the preliminary restricting means 3 of the present invention is disposed in the upstream side of the developer supply member 2 so as to be separated from the developer supply member 2 and is a roll-shaped auxiliary member that restricts and supplies the developer to the developer supply member 2. It has a supply member.

  Further, in the embodiment using the auxiliary supply members that are spaced apart from each other, the average adhesion amount of the developer layer on the auxiliary supply member is A, and the average adhesion amount of the developer layer on the developer supply member 2 is B. The average deposition amount of the developer layer on the developer carrier 1 is preferably set to satisfy the relationship C <B <A, where C on the developer carrier 1 The developer regulated supply amount β is more stable.

In the present invention, the developer adhesion amount on the developer supply member 2 is 50 to 80 g / m ² , and the developer adhesion amount on the developer carrier 1 is 7 g / m ² or less. By doing so, the amount of developer on the developer carrier 1 can be made small and uniform, the charging member 5 can be charged, and stress applied to the developer is further reduced. can do.
Furthermore, as an aspect of the image forming apparatus according to the present invention, an image carrier on which an electrostatic latent image is carried,
As a developing device for developing the electrostatic latent image on the image carrier, the above-described developing device is provided.

According to the present invention, the developer carrier and the developer supply member are spaced apart from each other, and the developer supplied onto the developer supply member is preliminarily regulated, and the developer carrier and the developer supply member are Since the supply bias applied between them is devised, the developer stays between the developer carrier and the developer supply member, and a uniform developer thin layer can be formed on the developer carrier. Become.
In addition, the degree of freedom in selecting the developer increases, and stress applied to the developer during charging of the developer on the developer carrier is reduced, thereby preventing sticking of the developer and the like.
Furthermore, since a roll-shaped auxiliary supply member is provided on the upstream side of the developer supply member and spaced apart from the developer supply member, and the developer is regulated and supplied to the developer supply member, The developer preliminary regulation amount is adjusted, and the lifetimes of the developer supply member and the auxiliary supply member are extended.
Therefore, it is possible to provide a developing device that can maintain good image quality over a long period of time, and by using these developing devices, an image forming apparatus that can form a stable image over a long period of time can be easily obtained. Can be built.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 2 shows an image forming apparatus according to the first embodiment to which the present invention is applied.
In the figure, reference numeral 21 denotes a photoconductor that carries an electrostatic latent image made of an organic photoconductor that rotates in the direction of the arrow. The photoconductor 21 is charged by a charging device 22 such as a charging roll, and a laser writing device or the like. An electrostatic latent image is written by the exposure device 23 having an LED array. The written electrostatic latent image is formed as a potential image based on contrast with a high potential portion not exposed to light because the surface potential of the photosensitive member 21 exposed to light decreases.
Further, the developing device 30 accommodates toner, which is a non-magnetic one-component developer, in a developing housing 31, and supports the toner on a developing roll 32 as a developer carrying member. By applying a developing bias in which an AC voltage is superimposed on the voltage, the developing roll 32 is held at an intermediate potential between the high potential portion and the low potential portion of the electrostatic latent image, and the image portion of the electrostatic latent image is charged. The toner is developed with toner.

Further, a toner supply roll 34 that supplies toner to the development roll 32 is disposed behind the development roll 32 at a position separated from the development roll 32, and the developer is supplied from the toner supply roll 34 to the development roll 32. It is like that.
Further, the transfer device 26 is constituted by, for example, a transfer roll disposed in contact with the photoconductor 21, and applies a transfer bias in a direction in which the toner image on the photoconductor 21 is attracted by the bias power source 27, thereby causing the photoconductor 21 to be applied. The upper toner image is transferred to the recording material 28.
Further, the toner remaining on the photosensitive member 21 is removed by, for example, a doctor blade type cleaning device 29.

In this embodiment, the recording material 28 onto which the toner image on the photosensitive member 21 is transferred is conveyed to the fixing device 50, and the toner image is fixed to the recording material 28 by the fixing device 50.
The fixing device 50 has, for example, a heat roll method, and includes a heating roll 51 and a pressure roll 52, and a toner image is recorded on the recording material by passing the recording material 28 between the heating roll 51 and the pressure roll 52. 28 is fixed.

Here, the developing device 30 which is a feature of the present invention will be described in detail with reference to FIG. In the drawing, a developing device 30 has a developing housing 31 that opens toward the photosensitive member 21, and a developing roll 32 is rotatable at a position facing the opening of the developing housing 31 with a gap from the photosensitive member 21. Contained.
The developing roll 32 in the present embodiment is constituted by a metal roll having a mirror-finished surface of stainless steel (SUS), for example.

Behind the developing roll 32 is a toner supply roll 34 made of a metal roll having a mirror-finished stainless steel (SUS) surface that supplies toner as a developer to the developing roll 32 at a position spaced apart from the developing roll 32. The developing roll 32 and the toner supply roll 34 are configured so as to rotate in opposite directions (Against direction) at opposite portions of the developing roll 32 and the toner supply roll 34.
The toner supply roll 34 may be any as long as it can supply toner to the developing roll 32, and may be in the form of a roll, a belt, or a brush.
In the present embodiment, a bias power supply 35 is connected to the toner supply roll 34, and the other end of the bias power supply 35 is connected to the developing roll 32.

Further, an auxiliary supply roll 36 for supplying toner to the toner supply roll 34 is provided behind the toner supply roll 34 at a position away from the toner supply roll 34. Similar to the toner supply roll 34, the auxiliary supply roll 36 in the present embodiment is configured by a metal roll having a mirror-finished stainless steel surface, and a bias power source 37 is connected between the toner supply roll 34 and the auxiliary supply roll 36. Has been.
Further, a toner hopper 38 for containing toner is provided behind the auxiliary supply roll 36, and the toner is stirred by an agitator (not shown), for example, so that the toner is conveyed to the auxiliary supply roll 36 side.

Further, in the present embodiment, a charging member 41 that charges the toner on the developing roll 32 is disposed at a position facing the developing roll 32 and downstream of the facing portion between the developing roll 32 and the toner supply roll 34. It is installed.
The charging member 41 is obtained by fixing the conductive film 41a to the conductive support member 41b. The conductive support member 41b is fixed to the developing housing, and the conductive film 41a side is free. The conductive film 41a is connected to a bias power source controlled at a constant current (not shown) to control toner charging.

The conductive film 41a in the present embodiment is not particularly limited as long as it can control the charge of the toner. For example, by using a resin sheet using an ionic conductive material as a conductive agent, for example, as a conductive agent, an electronic conductive material can be used. The toner on the developing roll 32 can be uniformly charged as compared with the resin sheet using the active substance.
At this time, examples of the resin sheet include polyamide (PA) and polyvinylidene fluoride (PVdF). Examples of the ion conductive substance include perchlorates (for example, lithium perchlorate, sodium perchlorate, ammonium perchlorate, etc.), quaternary ammonium salts, and the like.

  Furthermore, in the present embodiment, toner on the toner supply roll 34 (toner that has not been supplied to the development roll 32) is placed at a position facing the toner supply roll 34 and downstream of the nip area with the development roll 32. A cleaning blade 42 is provided with one end fixed to the developing housing 31 or the like. The blade 42 is made of, for example, a PET sheet having a thickness of 0.1 mm, and refreshes the toner supply roll 34, thereby contributing to suppression of electric field fluctuation between the nip between the developing roll 32 and the toner supply roll 34.

Here, the supply bias applied between the toner supply roll 34 and the developing roll 32 in the present embodiment will be described.
FIG. 4 shows an example of the voltage waveform of the supply bias in the present embodiment. The operation time (corresponding to the operation region) in which the trapezoidal wave (rectangular wave) has a large voltage fluctuation and the subsequent non-zero voltage zero are shown. The voltage waveform forms one cycle with the action time (corresponding to the non-action area). The bias power supply 35 is configured so that this voltage waveform is applied. The toner supply roll 34 is applied with a waveform superimposed on the developing bias applied to the developing roll 32.
In other words, in the present embodiment, toner flying from the toner supply roll 34 to the developing roll 32 is performed during an operation time with a large fluctuation of the sine wave, and development is performed by changing the ratio (duty ratio) of the operation time in one cycle. The amount of toner supplied to the roll 32 can be controlled. Further, the toner is not charged unnecessarily. If this operation time is continued, the amount of toner to be supplied becomes too large to control the supply amount.
In this embodiment, a bias waveform similar to the supply bias is applied to the bias power source 37.

Next, the operation of the developing device 30 according to the present embodiment will be described with reference to FIG.
In the drawing, the toner stirred by the agitator in the toner hopper 38 is supplied to the auxiliary supply roll 36 side. The toner supplied to the auxiliary supply roll 36 is supplied with a predetermined amount of preliminarily regulated toner by the bias power source 37 to the toner supply roll 34 side.
The toner supplied to the toner supply roll 34 side is supplied with a predetermined amount of toner to the development roll 32 side by a supply bias by a bias power source 35 between the development roll 32 and the toner supply roll 34.
At this time, in the present embodiment, a bias having a voltage waveform shown in FIG. 4 is applied as a supply bias between the developing roll 32 and the toner supply roll 34. A bias is also applied between the auxiliary supply roll 36 and the toner supply roll 34 by a bias power source 37 so as to have a bias waveform similar to that in FIG. In order to apply such a bias, for example, a waveform generation circuit based on a CPU or the like is used, a development bias in which a DC component and an AC component are superimposed is applied to the bias power source 33, and a supply bias is shown in FIG. After such a waveform is synthesized, it may be applied to the bias power source 35 and the bias power source 37. In the present embodiment, the duty ratios of the bias power supply 35 and the bias power supply 37 are changed so that the respective supply amounts become predetermined values.
Further, since the peripheral speed of the toner supply roll 34 is 1.5 times the peripheral speed of the developing roll 32, a predetermined amount of toner is deposited on the developing roll 32. As a result, the toner amount on the developing roll 32 is stabilized.

The toner supplied in the form of a thin layer on the developing roll 32 is charged to a predetermined charge amount by the subsequent charging member 41, then conveyed on the developing roll 32, and developed in the developing area with the photoreceptor 21. To be served.
On the other hand, the toner that has not been supplied to the developing roll 32 side on the toner supply roll 34 is scraped off by the blade 42.

In the present embodiment, since toner that is preliminarily regulated and supplied to the developing roll 32 does not cause excessive toner adhesion, the toner adhesion amount (layer thickness) on the developing roll 32 is stabilized and charged. Since the member 41 can be charged only, the load on the developing roll 32 by the charging member 41 can be reduced, the deterioration of the developing roll 32 can be prevented, and at the same time, development with a very low stress applied to the toner is possible. Further, by providing the toner supply roll 34 with a peeling member (specifically, a blade 42), the toner supply roll 34 is refreshed, and an inter-nip electric field fluctuation that is a concern when toner remains on the toner supply roll 34 is prevented. In addition, since the supply bias between the developing roll 32 and the toner supply roll 34 is further stabilized, the amount of toner supplied to the developing roll 32 can be further stabilized. Furthermore, since the toner adhesion amount can be controlled by the supply bias, the image density can be adjusted and stabilized.
Accordingly, it is possible to ensure the uniformity of toner supply to the developing roll 32 and to suppress fluctuations in toner supply conditions even for long-term use.
In addition, it is especially when the gap is 50 μm or more that it is easily influenced by the electric field fluctuation between the nips. If the gap is about 50 μm, the electric field is affected by the mechanical rubbing force between the nips. The impact is reduced.

In this embodiment, similarly to the blade 42 disposed opposite to the toner supply roll 34, a toner peeling member may be provided on the developing roll 32 and the auxiliary supply roll 36. The toner adhesion amount is stabilized. Further, as these peeling members, a means for electrical recovery may be provided instead of the blade form, and in this case, the same effect can be obtained.
Further, in the present embodiment, since the surfaces of the developing roll 32, the toner supply roll 34, and the auxiliary supply roll 36 are mirror-finished, residual toner is mechanically peeled off from these roll surfaces, There is also an effect that it is easy to recover electrically. That is, since the operation of rubbing the toner against the roll surface is not used by separating the rolls from each other, the toner slip phenomenon on the roll surface that occurs when the roll is brought into pressure contact is not a concern. It is possible to use a mirror roll. As an effect, the toner can be easily peeled and collected mechanically by a scraping blade or the like from a roll surface having a small friction coefficient and the toner slipping on the surface. In addition, since the mechanical adhesive force is small, it can be electrically recovered by a recovery roll or the like with a smaller electric field.

5 and 6 show other waveforms of the supply bias in the present embodiment, and a sine wave as shown in FIG. 5 or a triangular wave as shown in FIG. 6 is the same as the supply bias shown in FIG. The effect of. In particular, in these waveforms (FIGS. 5 and 6), the voltage during the non-operation time is zero, and the electric field does not reliably affect the movement of the toner during the non-operation time.
In both cases, the toner moves during the operation time, and in the non-operation time, a zero electric field is used to prevent unnecessary charging and adhesion of the toner exceeding the specified amount. It becomes possible.

  On the other hand, FIG. 7 shows a supply bias different from the supply bias described above in the present embodiment. In this figure, the waveform is such that a triangular wave voltage is applied only to one side (in this example, a negative voltage) during the action time, and during the non-action time, a triangle wave having an area equal to the area of the triangular wave of the action time is the action time. They are formed on different positive voltage sides.

The operation when such an electric field is applied as a supply bias will be described.
The negatively charged toner in the toner hopper is hardly charged, but individual toner particles are slightly negatively charged or positively charged, or these toner particles are mixed. Further, at the stage of being carried on the toner supply roll, the toner particles come into contact with each other, and one is negatively charged and the other is positively charged.
When toner particles having such various charge amounts exist, the supply bias shown in FIG. 7 is applied between the developing roll and the toner supply roll (the negative peak is large on the toner supply roll side). ) And the negatively charged toner particles are strongly attracted to the developing roll side, and the force of the positively charged toner particles toward the developing roll side can be reduced.

For this reason, the toner on the developing roll has a large number of negatively charged toner particles, and the polarity is easily aligned. In addition, since a certain amount of toner is supplied on the developing roll, when the charging is performed with the charging member thereafter, for example, the contact pressure (linear pressure) is reduced to reduce the stress on the toner. Even if it is reduced, the target toner charge amount can be obtained. As a result, it is possible to provide a developing device capable of extending the life.
In the present embodiment, the developing roll 32 and the toner supply roll 34 have an Against configuration in which they move in different directions at opposite portions, but may have a With configuration in which they move in the same direction, for example. In this case, the amount of toner ejected from the nip area between the developing roll 32 and the toner supply roll 34 can be reduced, and the ejected toner does not adhere to the developing roll 32 even if the space on the downstream side of the nip area is narrowed. The developing device can be downsized. In the present exemplary embodiment, the rotation direction of the toner supply roll 34 and the auxiliary supply roll 36 may be either the Gainst configuration or the With configuration.
Further, in the present embodiment, the bias power supply 35 and the bias power supply 37 are connected between the developing roll 32 and the toner supply roll 34 and between the toner supply roll 34 and the auxiliary supply roll 36, respectively. 34 and the auxiliary supply roll 36 may be connected to a power source in which a bias waveform similar to that of the bias power sources 35 and 37 described above is applied.

Embodiment 2
FIG. 8 shows an outline of the developing device 30 according to the second embodiment to which the reference invention related to the present invention is applied. In the figure, the present embodiment is configured in substantially the same manner as the developing device 30 in the first embodiment, but the configuration of the auxiliary supply roll 36 is different from that in the first embodiment. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and the detailed description is abbreviate | omitted.

In the present embodiment, the auxiliary supply roll 36 is a roll having an elastic foam on the surface, and is configured in a contact state (the amount of biting is almost zero) that makes point contact with the toner supply roll 34.
Therefore, the toner conveyed on the auxiliary supply roll 36 on the surface of the elastic foam is supplied to the toner supply roll 34 side due to a potential difference with the toner supply roll 34 and a mechanical rubbing force. At this time, since the auxiliary supply roll 36 hardly bites into the toner supply roll 34, the stress applied to the toner is extremely small.
At this time, the toner layer supplied to the toner supply roll 34 has some thickness unevenness different from that in the first embodiment. However, when the toner supply roll 34 is supplied to the developing roll 32, the supply bias is reduced. As a result, the toner vibrates, and a uniform toner thin layer is formed on the developing roll 32.

Therefore, the same effect as in the first embodiment is obtained.
In this embodiment, the auxiliary supply roll 36 is made of an elastic foam. However, the present invention is not limited to this. For example, a brush roll, a rubber roll, a flexible tube roll, or the like is brought into light contact with the toner supply roll 34. Even if it is the structure used, it does not interfere.

Embodiment 3
FIG. 9 shows an outline of the developing device 30 according to the third embodiment to which the reference invention related to the present invention is applied. In this figure, the present embodiment is configured in substantially the same manner as the developing device 30 in the first embodiment, but unlike the first embodiment, a plate-like rigidity regulating member 43 is supplied with toner instead of the auxiliary supply roll 36. It arrange | positions so that the roll 34 may be opposed. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and the detailed description is abbreviate | omitted.

In the present embodiment, a plate-like rigidity regulating member 43 is provided on the upstream side of the portion facing the developing roller 32 facing the toner supply roll 34. The gap between the plate-like rigidity regulating member 43 and the toner supply roll 34 is 500 μm.
In such a configuration, the toner replenished from the toner hopper 38 passes through the gap between the toner supply roll 34 and the plate-like rigidity regulating member 43 and is supplied onto the toner supply roll 34. At this time, since the gap is 500 μm, the stress applied to the toner passing through the gap is small, and a thick toner film having some unevenness is formed on the toner supply roll 34.
Thereafter, as in the first embodiment, a predetermined supply bias is applied at the nip portion between the developing roll 32 and the toner supply roll 34, and the toner vibrates, whereby a uniform toner thin layer is formed on the developing roll 32. Is formed.
Therefore, the present embodiment has the same effect as the first embodiment.

Embodiment 4
FIG. 10 shows an outline of the developing device 30 according to the fourth embodiment to which the reference invention related to the present invention is applied. In this figure, the present embodiment is configured in substantially the same manner as the developing device 30 in the third embodiment, but a film-like seal member 44 is used instead of the plate-like rigidity regulating member used in the third embodiment. This is different from the third embodiment. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 3, and the detailed description is abbreviate | omitted.

One end of the film-like seal member 44 in the present embodiment is fixed to the developing housing 31 and the other end is free. Therefore, when the toner replenished from the toner hopper 38 is supplied to the toner supply roll 34 and is conveyed on the toner supply roll 34, the toner moves in a direction to spread the film-like seal member 44, so that the toner layer is leveled. It works like this. As a result, a thick toner film having some unevenness is formed on the toner supply roll 34.
Thereafter, as in the first embodiment, a predetermined supply bias is applied at the nip portion between the developing roll 32 and the toner supply roll 34, and the toner vibrates, whereby a uniform toner thin layer is formed on the developing roll 32. Is formed.
Therefore, the present embodiment has the same effect as the first embodiment.
The film-like sealing member 44 in the present embodiment is preferably a conductive film from the viewpoint of avoiding excessive charging to the toner, but is not limited to this, and if there is a certain amount of waist, for example, a metal foil-like member or the like It may be.

Example 1
In this example, the amount of toner supplied to the developing roll is evaluated using the trapezoidal wave (rectangular wave) shown in FIG. 4 as the supply bias in the configuration in the first embodiment.
Specifically, when the gap between the developing roll and the toner supply roll is 100 μm, the peripheral speed ratio of the toner supply roll / developing roll is 1.5, and the peripheral speed of the developing roll is 100 mm / s, the supply bias is By applying a sine wave of 1 to 2 kV _pp at a frequency of 1 to 2 kHz and changing the duty ratio, the toner adhesion amount (supply amount) on the developing roll was measured.
As a result, as shown in FIG. 11, when the duty ratio was increased, the supply amount M / A increased in proportion thereto. Therefore, it was confirmed that the toner supply amount can be easily changed depending on the duty ratio. In particular, it was confirmed that the supply amount can be stably controlled even in a small region of 10 g / m ² or less.

Furthermore, in this example, the peripheral speed of the developing roll was set in the range of 100 to 250 mm / s, and the peripheral speed ratio of the toner supply roll was varied from 0.5 to 3, and the same evaluation was performed. In both cases, it was confirmed that the supply amount increased in proportion to increasing the duty ratio as in FIG.
Furthermore, the same effect was confirmed by using a sine wave and a triangular wave instead of the trapezoidal wave (rectangular wave) in the present embodiment.

Example 2
In this example, the toner adhesion amount on the developing roll and the toner supply roll is measured and evaluated under the following various conditions in the configuration of the first embodiment.
The toner used was a non-magnetic one-component toner produced by a pulverization method and had a volume center particle size of 7 μm. The peripheral speed of the developing roll is 100 mm / sec, the peripheral speed of the toner supply roll is 200 mm / sec, the peripheral speed of the auxiliary supply roll is 200 mm / sec, the gap between the developing roll and the toner supply roll is 100 μm, the toner supply roll and the auxiliary supply roll The gap was 250 μm.
Further, as a charging member on the developing roll, a polyamide sheet having a modulus of elasticity of 1.2 × 10 ⁹ Pa, a resistance value adjusted with an ion conductive substance, a volume resistivity of 1 × 10 ⁸ Ω · cm, and a thickness of 100 μm ( Specifically, nylon 66 was used, one end was fixed to a conductive support member, and the free end side was applied so as to lightly contact the toner layer on the developing roll. The pressure contact force at this time was set to a linear pressure of 0 g / cm (adjusted to such a small value that it cannot be measured).
The supply bias applied between the developing roll and the toner supply roll was adjusted so that the duty ratio was 0.07 in the voltage waveform of FIG. The bias waveform formed between the toner supply roll and the auxiliary supply roll was adjusted so that the duty ratio was 0.05 in the waveform of FIG.

The results, in the auxiliary supply roll and the toner supply on the roll, uneven thickness and coating weight unevenness been observed, in the auxiliary supply roll 150~500g / ^{m 2,} is on the toner supply roll of 50 to 80 g / ^{m 2} Toner Amount of adhesion was obtained. These variations were assumed to be due to the amount of adhesion changing depending on the environmental atmosphere (temperature and humidity), the amount of toner in the toner hopper, and the like.
However, even in such a state, it was confirmed that the toner adhesion amount on the developing roll was 7 g / m ² and a uniform thin layer was formed. In this example, after passing through the charging member, it became 5 g / m ² and was used for development in this state.

Further, after that, the toner was changed to one having a volume center particle diameter of 5.7 μm produced by an emulsion polymerization aggregation method, and the same evaluation was performed, but the same result as described above was obtained.
The evaluation was repeated with the peripheral speed of the developing roll in the range of 100 to 250 mm / sec, but similar results were obtained. Further, the evaluation was performed by changing the peripheral speed ratio of the toner supply roll in the range of 0.5 to 3.0, and this result was the same. At this time, the peripheral speed of the auxiliary supply roll was fixed at 200 mm / sec.
From the above, it was confirmed that the toner thin layer control on the developing roll in this case is sufficiently effective.

(A) (b) is explanatory drawing which shows the outline | summary of the image development apparatus concerning this invention. 1 is an explanatory diagram showing Embodiment 1 of an image forming apparatus to which the present invention is applied. FIG. 2 is an explanatory diagram illustrating a developing device according to the first embodiment. FIG. 4 is an explanatory diagram illustrating a supply bias waveform according to the first embodiment. 6 is an explanatory diagram showing a second waveform of a supply bias according to Embodiment 1. FIG. FIG. 6 is an explanatory diagram showing a third waveform of a supply bias according to the first embodiment. FIG. 10 is an explanatory diagram showing a fourth waveform of the supply bias according to the first embodiment. FIG. 10 is an explanatory diagram illustrating an overview of a developing device according to a second embodiment. FIG. 10 is an explanatory diagram illustrating an outline of a developing device according to a third embodiment. FIG. 10 is an explanatory diagram showing an outline of a developing device as a modification of the third embodiment. FIG. 6 is an explanatory diagram illustrating a relationship between a supply bias and a supply amount according to the first embodiment. It is explanatory drawing which shows the outline | summary of the image development apparatus as a prior art example. It is explanatory drawing which shows the outline | summary of the image development apparatus as a comparative example. It is explanatory drawing which shows the modification of a comparative example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Developer carrying body, 2 ... Developer supply member, 3 ... Preliminary regulation means, 4 ... Supply bias, 5 ... Charging member, α ... Developer preliminary regulation amount, β ... Developer regulation supply amount, γ ... Developer Residual amount

Claims (6)

A developer carrying body which is rotatable and opposed to an image carrying body on which an electrostatic latent image is carried;
A developer supply member that is spaced apart from the developer carrier and capable of supplying the developer carried on the surface to the developer carrier;
An AC electric field component that is provided between the developer carrying member and the developer supplying member and includes at least an AC electric field component that promotes the movement of the developer from the developer supplying member to the developer carrying member in one cycle. A developer is supplied from the developer supply member to the developer carrier including an action area that affects the movement of the developer between the carrier and the developer supply member and a non-action area that does not affect the movement of the developer. Supply bias applying means for applying a supply bias for
The developer supplied onto the developer supply member before the developer is supplied from the developer supply member to the developer carrier is pre-regulated, and the developer pre-regulation amount to be pre-regulated is determined as the developer. Preliminary regulation means for adjusting the amount to a sum corresponding to the sum of the developer regulation supply amount to the carrier and the developer residual amount to the developer supply member side ,
The preliminary regulating means, that has the developer is disposed apart from the supply member and the developer of the developer supply member in regulating supply roll of the auxiliary supply member on the upstream side of the developer supplying member A developing device. The developing device according to claim 1 ,
The average adhesion amount of the developer layer on the auxiliary supply member is A, the average adhesion amount of the developer layer on the developer supply member is B, and the average adhesion amount of the developer layer on the developer carrier is C. Sometimes, the developing device is set such that C <B <A. The developing device according to claim 1,
The developing device according to claim 1, wherein the developer carrying member and the developer supply member rotate in different directions at mutually opposed portions. The developing device according to claim 1 ,
A developing device characterized in that the developer adhesion amount on the developer supply member is 50 to 80 g / m ² and the developer adhesion amount on the developer carrier is 7 g / m ² or less. The developing device according to claim 1,
Further, the developing is provided with a charging member that is disposed to face the developer carrying member and that is provided downstream of the facing portion between the developer carrying member and the developer supply member in the developer transport direction to impart charge to the developer. apparatus. An image carrier for carrying an electrostatic latent image;
An image forming apparatus comprising the developing device according to any one of claims 1 to 5 for developing an electrostatic latent image on the image carrier.

Images