JP2006099022A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of preventing lowering in the concentration of toner included in two-component developer carried on a developer carrier. <P>SOLUTION: The developing device 1 comprises a developing container 15 in which the developer including magnetic carrier and non-magnetic toner is stored, stirring screws 11 and 12 stirring the developer while making it circulate in the developing container 15; a developing roller 5 positioned above the stirring screws 11 and 12 and supplying the developer stirred by the stirring screws 11 and 12 to a photoreceptor drum 4 in order to develop an electrostatic latent image formed on the photoreceptor drum 4; and a vibration generating member 10 vibrating the developer conveyed to circulate below the developing roller 5 by the stirring screws 11 and 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a developing device that supplies a developer to an image carrier, and more particularly to a developing device that uses a two-component developer.

  A two-component developer containing a magnetic carrier and a non-magnetic toner has the advantage that toner charge control and developer transport are relatively easy, and it is easy to cope with colorization and high speed. Further, in the two-component developer, it was possible to cope with higher resolution by using a non-magnetic toner having a small particle diameter.

  However, when the particle size of the toner is reduced, there is a disadvantage that the binding between the toner particles and the binding between the toner and the carrier become strong and the developer is likely to be condensed.

Therefore, in a conventional developing device, an electrode whose spacing with respect to the developer carrying member continuously changes along the moving direction of the developer is installed on the upstream side of the developing region, and the developer carrying member and the electrode are Some have a power supply circuit that applies an oscillating voltage between them (see, for example, Patent Document 1). According to this developing device, even when the particle size of the developer is small, the developer is prevented from agglomerating to facilitate charge control of the developer, and good development can be performed.
JP-A-3-55581

  However, in the developing device according to Patent Document 1 described above, the toner concentration in the developer supplied to the image carrier via the developing roller may be reduced. This decrease in toner density occurs when the toner amount attracted to the developing roller decreases due to the decrease in toner density around the developing roller. For this reason, it is important to maintain a high toner concentration in the developer near the developing roller.

  An object of the present invention is to provide a developing device that can prevent a decrease in the concentration of toner contained in a two-component developer carried on a developer carrying member.

(1) A developing device according to the present invention includes:
A developer container containing a developer containing a magnetic carrier and a non-magnetic toner;
Stirring means for stirring while circulating the developer in the developer container;
A developer carrier that is located above the stirring means and that carries the developer stirred by the stirring means to develop the electrostatic latent image formed on the image carrier and supplies the developer to the image carrier. When,
Vibration transmitting means for vibrating the developer circulated and conveyed under the developer carrying member by the stirring means;
It is provided with.

  The developing device according to the present invention includes a developing container, a stirring means, a developer carrier, and a vibration transmitting means. Toner is supplied to the developing container through a toner supply port. The toner supplied to the developing container is mixed with the magnetic carrier while being circulated through the developing container by the stirring means. The developer stirred by the stirring means is carried on the developer carrier by magnetic force, and is supplied to the image carrier via the developer carrier.

  The vibration transmitting means vibrates the developer located below the developer carrier. Of the magnetic carrier and non-magnetic toner constituting the developer, the non-magnetic toner usually has a smaller particle diameter and lighter specific gravity. Therefore, when the developer vibrates, the non-magnetic toner easily moves upward. As a result, more non-magnetic toner is collected near the developer carrier.

(2) The developing device according to (1),
The vibration transmitting means is arranged at the bottom of the developing container located below the stirring means.

  In this configuration, the vibration transmitting means is disposed at the bottom of the developing container. By arranging the vibration transmitting means at the bottom, the vibration is easily transmitted to the developer staying at the bottom of the developing container. As a result, the toner staying at the bottom of the developing container easily moves upward, and more toner is collected near the developer carrier.

(3) The developing device according to (2),
The vibration transmitting means includes a piezoelectric element, two electrodes arranged so as to sandwich the piezoelectric element, and a vibration power supply unit that applies an AC voltage to the two electrodes.

  In this configuration, the piezoelectric element vibrates by applying an AC voltage to the electrodes arranged on both sides of the piezoelectric element, and the vibration is transmitted to the developer. The vibration frequency of the piezoelectric element is arbitrarily set by changing the AC voltage value applied to the electrode from the vibration power supply unit.

(4) The developing device according to (3),
The two electrodes are arranged in the vertical direction, and the upper electrode is made of an elastic body.

  In this configuration, the piezoelectric element comes into contact with the developer via the elastic electrode. For this reason, the elastic body vibration is superimposed on the vibration of the piezoelectric element.

(5) The developing device according to (3) or (4),
The AC voltage value of the vibration power supply unit is set so that the developer in the developer container is not separated into a carrier layer and a toner layer.

  In this configuration, in consideration of the possibility that the developer in the developer container may be separated into the carrier layer and the toner layer if the vibration of the piezoelectric element is too strong, the voltage from the vibration power supply unit to the piezoelectric element is considered. Is applied.

(6) The developing device according to any one of (1) to (5),
The apparatus further comprises stop means for stopping the operation of the stirring means while the vibration transmitting means is in operation.

  In this configuration, when the vibration transmitting means vibrates the developer, the development is not stirred by the stirring means. The stop means is provided because if the stirring means is always operated, the toner moved upward by the vibration transmitting means may be pushed down again. A typical example of the stopping means is a clutch disposed between the stirring means and the drive source.

(1) According to the first aspect of the invention, it is possible to prevent a decrease in the concentration of toner contained in the two-component developer carried on the developer carrying member.

(2) According to the invention of claim 2, more toner can be collected in the vicinity of the developer carrier, and the concentration of toner contained in the two-component developer carried on the developer carrier is reduced. Can be prevented.

(3) According to the third aspect of the present invention, it is easy to set the strength of vibration given to the developer by the vibration means.

(4) According to the invention of claim 4, the vibration efficiency of the vibration means for vibrating the developer can be improved.

(5) According to the invention of claim 5, the carrier and the toner can be appropriately mixed in the developing container, and the occurrence of image formation defects in the image forming apparatus can be suppressed.

(6) According to the invention of claim 6, the toner can be easily collected near the developer carrying member.

  Hereinafter, embodiments of the developing device of the present invention will be described with reference to the drawings.

  First, a schematic configuration of the developing device 1 will be described with reference to FIGS. 1 and 2. The developing device 1 includes a developing roller 5 and stirring screws 11 and 12 inside a developing container 15. The developing roller 5 constitutes the developer carrying member of the present invention. The developing roller 5 includes a magnet roller 7 that is fixedly supported by a support shaft, and a developing sleeve 6 that is rotatably supported along the peripheral surface of the magnet roller 7. The magnet roller 7 includes a plurality of magnetic poles along the peripheral surface. The circumferential surface of the magnet roller 7 is disposed so as to face the circumferential surface of the photosensitive drum 4. In this embodiment, the magnet roller 7 is composed of two S poles and three N poles, and conveys the developer while restraining it. The developing sleeve 6 has a cylindrical shape made of stainless steel having a thickness of 0.4 mm, and is connected to a developing power supply unit 13 having an AC power supply 13B and a DC power supply 13A. The developing power supply unit 13 applies to the developing sleeve 6 a DC superimposed AC voltage in which a DC is superimposed on the AC voltage.

  Above the developing roller 5 in the developing container 15, a spike height regulating member 2 that adjusts the height of the developer layer 3 laminated on the peripheral surface of the developing roller 5 is disposed. Below the developing roller 5, stirring screws 11 and 12 constituting the stirring means of the present invention are arranged.

  The agitation screws 11 and 12 are connected to the motor 20 and circulate and convey the developer supplied from a toner container (not shown) via the developer supply port 19. A partition plate 22 is disposed between the stirring screw 11 and the stirring screw 12. The developer is circulated around the partition plate 22 in the developing container 15 by the stirring screws 11 and 12. The direction in which the developer is circulated is as shown by the arrows in FIG.

  The vibration generating member 10 is disposed at the bottom of the developing container 15 located below the stirring screw 11. The vibration generating member 10 is connected to a vibration power supply unit 14 having an AC power supply. As shown in FIG. 3, the vibration generating member 10 is a stacked piezoelectric element. In addition, a piezoelectric element is an element which produces mechanical distortion by applying a voltage. The vibration generating member 10 is a Rajban type having two metal electrodes 10A and 10C and a vibrator 10B sandwiched between them. A high frequency voltage is applied to the metal electrodes 10 </ b> A and 10 </ b> C of the vibration generating member 10 from the vibration power supply unit 14.

  In this embodiment, fine ceramics such as barium titanate and lead zirconate titanate ceramics are used as the material of the vibrator 10B. However, as a material of the vibrator 10B, a single crystal such as lithium niobate or lithium tantalate, or a zinc oxide sputtered thin film can be used as appropriate depending on the vibration frequency and the life of the apparatus.

  The vibration power supply unit 14 applies an alternating voltage to the vibration generating member 10 so that the minute amplitude vibration frequency generated by the vibration generating member 10 is in an ultrasonic range of 10 kHz or more. At this time, the vibration power supply unit 14 causes the vibration of the vibration generating member 10 to be a sine wave having a frequency of 1 MHz or less. This is because when the vibration frequency increases, the heat generation in the metal electrodes 10A and 10C and the vibrator 10B cannot be ignored, and the degree of vibration attenuation increases. In this embodiment, an alternating voltage having a frequency of 20 kHz and 20 Vpp is applied from the vibration power supply unit 14 to the developing roller 5 so that the vibration of the vibration generating member 10 becomes a sine wave of 20 kHz.

  FIG. 4 is a block diagram illustrating a schematic configuration of the developing device 1. As shown in FIG. 4, the developing device 1 includes a microcomputer 8, and a developing power supply unit 13, a vibration power supply unit 14, a motor 20, a density sensor 17, a clutch 21, and a connector 18 are connected to the microcomputer 8. . The density sensor 17 detects the toner density in the developing container 15. The clutch 21 switches power transmission from the motor 20 to the developing sleeve 6 or the stirring screws 11 and 12 on / off. The connector 18 is used to connect the image forming apparatus and the developing device 1. The microcomputer 8 comprehensively controls the operation of each part of the developing device 1.

  The developer circulated and conveyed through the developing container 15 by the stirring screws 11 and 12 is carried on the peripheral surface of the developing roller 5 in the state of a magnetic brush by the magnetic force of the magnet roller 7. The developer carried on the circumferential surface of the developing roller 5 is transported to a developing area which is a position facing the photosensitive drum 4 based on the rotation of the developing sleeve 6. The developer layer held in the state of a magnetic brush on the peripheral surface of the developing roller 5 is cut off by the head height regulating member 2, and the amount of developer conveyed to the developing region is properly maintained.

  Here, the operation of each magnetic pole of the magnet roller 7 will be described. The developer circulated and conveyed by the stirring screw 11 is restrained by the magnetic force of the pumping pole S2. Subsequently, the developer restrained by the rotation of the developing sleeve 6 is conveyed to the developer reservoir 3. The developer conveyed to the developer reservoir 3 is sufficiently restrained by the cut pole N2. The developer cut off by the head height regulating member 2 is transported to the developing region by the transport magnetic pole S1. In the development area, the developer is restrained by the development pole N1. When a bias voltage is applied to the developing sleeve 6 via the developing power supply unit 13, the nonmagnetic toner in the developer moves toward the photosensitive drum 4, and the electrostatic latent image formed on the peripheral surface of the photosensitive drum 4. The image is developed.

  In the present embodiment, the vibration generating member 10 is used to increase the toner concentration of the developer conveyed just below the developing roller 5 by the stirring screw 11. That is, the vibration generating member 10 is used to supply a developer having a sufficient toner concentration between the stirring screw 11 and the developing roller 5.

  When the operation of the developing device 1 starts, the microcomputer 8 controls the vibration power supply unit 14 to apply an alternating voltage with a frequency of 20 kHz and 20 Vpp from the vibration power supply unit 14 to the vibration generating member 10. The vibrator 10B having a thickness of about 1 mm connected to the metal electrode 10A vibrates in the vertical direction by application of the alternating electrode. The vibration of the vibrator 10B is transmitted to the developer through the metal electrode 10C. At this time, if the metal electrode 10C is made of an elastic member, the vibration efficiency is improved because the elastic body vibration of the metal electrode 10C is superimposed on the vibration of the vibrator 10B. In the present embodiment, the magnitude of vibration of the vibration generating member 10 is adjusted so that the carrier layer and the toner layer are not separated in the developing container 15.

  According to the present embodiment, by causing the developer to slightly vibrate at a high frequency in the developing container 15, toner having a small specific gravity among the developers can easily rise to the developer surface. For this reason, it becomes possible to supply the developing roller 5 with a developer having a sufficient toner concentration.

  In the above-described embodiment, the stirring screws 11 and 12 are driven even when the vibration generating member 10 is vibrating. However, the microcomputer 8 controls the clutch 21 during the vibration of the vibration generating member 10 to control the stirring screws 11 and 12. 12 may be stopped. In this way, the toner that has risen to the vicinity of the developing roller 5 due to the vibration of the vibration generating member 10 is not pushed down again toward the bottom of the developing container 15 by the stirring screw 11.

  Finally, the description of the above-described embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

FIG. 2 is a side sectional view showing a schematic configuration of a developing device of the present invention. 1 is a plan sectional view showing a schematic configuration of a developing device of the present invention. It is a figure which shows an example of a structure of the vibration transmission means of this invention. 1 is a block diagram illustrating a schematic configuration of a developing device of the present invention.

Explanation of symbols

1-developing device 5-developing roller 6-developing sleeve 7-magnet roller 11, 12-stir screw

Claims (6)

A developer container containing a developer containing a magnetic carrier and a non-magnetic toner;
Stirring means for stirring while circulating the developer in the developer container;
A developer carrier that is located above the stirring means and that carries the developer stirred by the stirring means to develop the electrostatic latent image formed on the image carrier and supplies the developer to the image carrier. When,
Vibration transmitting means for vibrating the developer circulated and conveyed under the developer carrying member by the stirring means;
A developing device comprising:   The developing device according to claim 1, wherein the vibration transmitting unit is disposed at a bottom portion of the developing container located below the stirring unit.   The vibration transmission means includes a piezoelectric element, two electrodes arranged so as to sandwich the piezoelectric element, and a vibration power source unit that applies an AC voltage to the two electrodes. 2. The developing device according to 2.   The developing device according to claim 3, wherein the two electrodes are arranged in a vertical direction, and an upper electrode is formed of an elastic body.   5. The developing device according to claim 3, wherein an AC voltage value of the vibration power supply unit is set so that the developer in the developing container is not separated into a carrier layer and a toner layer.   The developing device according to claim 1, further comprising a stopping unit that stops the operation of the stirring unit while the vibration transmitting unit is in operation.

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