JP3893237B2 - Developing device and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developing device that attaches a developing material in a liquid developer carried on a developer carrying member to a latent image carried on a latent image carrying member of an image forming apparatus and develops the same, and a facsimile machine including the developing device The present invention relates to an image forming apparatus such as a printer and a copying machine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a developing device that uses a liquid developer containing a liquid carrier and a developing material such as toner is known as a developer. In this type of developing device, after a liquid developer contained in an agent containing portion as a liquid tank is carried on a developer carrying member such as a developing roller, a latent image on a latent image carrying member such as a photosensitive drum is obtained. The latent image is developed by adhering to the surface. In such a developing device and an image forming apparatus including the same, the liquid level of the liquid developer in the agent container may be detected by a float type liquid level sensor, and predetermined control may be performed based on the detection result.
[0003]
As this type of float type liquid level sensor, a magnetic force generator such as a magnet, magnetic force detection means such as a Hall element or a magnetic switch, and a float member that moves up and down as the liquid level in the agent container is increased or decreased. What you have is known. In such a float type liquid level sensor, one of the magnetic force generator and the magnetic force detection means is connected to the float member and moves up and down, and the other is fixed to the liquid tank side, and as the float member moves up and down, The distance between the two changes. Along with this change, the magnetic force detection means may or may not detect the magnetic force, so that the magnetic force detection means can detect the liquid level in the agent container based on the detection result.
[0004]
[Problems to be solved by the invention]
By the way, in such a conventional float type liquid level sensor, the float member may be positioned at a level different from the level corresponding to the actual liquid level.
[0005]
For example, normally, the upper surface of the float member is positioned above the liquid surface of the liquid developer, but the liquid developer adheres by being waved or swirled by the liquid developer. When only the liquid component in the attached liquid developer evaporates or falls along the side surface of the float member, a developing substance such as toner remains on the upper surface of the float member. When such adhesion of the liquid developer and evaporation and dropping of the liquid are repeated, the developing material gradually accumulates on the upper surface of the float member, and the float member gradually sinks due to its weight. . Due to such sinking, the float member is gradually positioned at a level different from the level corresponding to the actual liquid level. In particular, when a so-called thixotropic liquid developer is used, the developing material is easily deposited on the upper surface of the float member. This thixotropic liquid developer has a relatively high viscosity of 100 to 1000 [mPa · s], contains a developing substance at a relatively high concentration of 5 to 40 [%], and with the application of shearing force. The liquid developer has such a property that the viscosity is gradually lowered and the viscosity is gradually increased as it is allowed to stand.
[0006]
Also, for example, during the developing operation, a liquid flow usually occurs in the liquid developer in the agent container due to stirring, and the liquid level of the liquid developer is greatly undulated or gradually increased from the stirring center toward the outside. Or the liquid level becomes non-uniform. If the liquid level at the float member is different from the actual liquid level (the liquid level at rest) when the liquid level is not uniform, the float member will correspond to the actual liquid level. It is positioned at a different level from the level to be performed.
[0007]
If the float member is located at a different level, naturally, the magnetic force generator or the magnetic force detection means connected to the float member will also be located at a different level. An error occurs in the detected liquid level of the position sensor.
[0008]
The present invention has been made in view of the above background, and an object of the present invention is to reduce an error between the actual liquid level in the agent container and the detected liquid level of the float type liquid level sensor. A developing device and an image forming apparatus including the developing device are provided.
[0009]
[Means for Solving the Problems]
  In order to achieve the above object, an invention according to claim 1 is directed to an agent container that contains a liquid developer containing a developing substance and a liquid carrier, and a developer that carries a liquid developer supplied from the agent container. And a float type liquid level sensor for detecting the liquid level of the liquid developer in the agent container. The developer in the liquid developer carried on the developer carrier is transferred to the latent image of the image forming apparatus. In the developing device for developing the latent image attached to the latent image carried on the image carrier, as the float type liquid level sensor, a magnetic force generator, and a magnetic force detecting means for detecting the magnetic force of the magnetic force generator, A spherical float member that moves up and down as the liquid level increases and decreases, and changes the distance between the magnetic force generator and the magnetic force detection means as the float member moves up and down. Provided to detect the liquid level based on the detection resultIn addition, the agent accommodating portion is used as a stirring body that rotates and stirs the liquid developer in the agent accommodating portion in the horizontal direction by rotating around a position shifted from the center of the plane section of the agent accommodating portion. A flexible agitator that rotates while flexibly bending in contact with the inner wall of the side wall, and non-flexible that generates a flow of liquid developer that moves along the axis of rotation by rotation on the same axis With a stirrerIt is characterized by that.
[0010]
  In this developing device, the developer in the liquid developer adhering to the upper part of the spherical float member descends along the spherical surface of the float member together with the liquid carrier, and the liquid developer in the agent container is discharged. Since it reaches the liquid level and is taken in, it is difficult to deposit on the float member. Accordingly, sinking of the float member due to the deposition of the developing substance can be reduced, and an error between the actual liquid level in the agent container and the detected liquid level of the float type liquid level sensor can be reduced.
Further, in this developing device, the developing agent such as toner is uniformly dispersed in the liquid developer by stirring the liquid developer in the agent container by the stirring member, and the developing substance concentration of the liquid developer is Can be made uniform.
Further, in this developing device, the stirrer rotates around the position shifted from the center of the flat cross section of the agent container in the horizontal direction. Along with this rotation, the liquid developer located closer to the rotation shaft side of the stirring body (hereinafter referred to as the stirring shaft side) than the center in the agent container is positively rotated to make the liquid surface undulate. On the other hand, the liquid developer located on the opposite side of the stirring shaft from the center is rotated relatively slowly by the convection of the liquid developer that is rotated in contact by the stirring member, so that the liquid surface has ripples. It can be suppressed. In such a configuration, if the liquid level of the liquid developer is detected at a position where the ripple is suppressed in this way, that is, at a position opposite to the stirring shaft side, the float type liquid level sensor may cause a float caused by the ripple. The liquid level detection error of the liquid level sensor can be further reduced.
However, the liquid developer cannot be sufficiently moved in the rotation axis direction, and the liquid developer may be insufficiently stirred in the vertical direction. Further, the liquid developer on the side opposite to the agitation shaft cannot be brought into contact with the agitator, and horizontal agitation in the horizontal direction may be insufficient. As a result, the developing substance such as toner cannot be uniformly dispersed throughout the liquid developer, and there is a possibility that the developing substance concentration of the liquid developer becomes non-uniform.
Therefore, in this developing device, the non-flexible stirrer generates a so-called axial flow of the liquid developer that moves along the rotation axis while stirring the liquid developer in the horizontal direction by the rotation, The liquid developer is stirred up and down by this axial flow. On the other hand, the flexible stirrer rotates while flexing flexibly due to contact with the inner wall of the side wall of the agent container. Such a flexible stirring body can be rotated along a trajectory that traces the entire region in the agent container in the horizontal direction, for example, as indicated by reference numeral 116 in FIG. The flexible stirrer (wing member 116) that rotates in such a locus directly rotates the liquid developer by directly contacting the liquid developer located on the side opposite to the stirrer side. Can do. Further, by rotating while flexibly bending, the liquid developer located on the side opposite to the stirring shaft side is given a rotational force weaker than that of the flexible stirring body to suppress the ripple. In the above configuration, the liquid developer can be stirred in the horizontal direction and also in the vertical direction by the rotation of the non-flexible positive stirring body. Further, the rotation of the flexible stirrer can surely rotate the liquid developer located on the side opposite to the stirrer side and stir in the horizontal direction while suppressing undulations due to stirring. As a result, it is possible to suppress unevenness in the developer concentration of the liquid developer due to insufficient horizontal stirring and insufficient vertical stirring while suppressing the undulation of the liquid developer due to stirring.
[0011]
  According to a second aspect of the present invention, there is provided an agent container that contains a liquid developer containing a developing substance and a liquid carrier, a developer carrier that carries a liquid developer supplied from the agent container, and the agent container. And a float type liquid level sensor for detecting the liquid level of the liquid developer in the unit, and the developer in the liquid developer carried on the developer carrying member is transferred to the latent image carrier carried on the latent image carrier of the image forming apparatus. In a developing device for developing the latent image by attaching it to an image, MagnetismA force generator, a magnetic force detection means for detecting the magnetic force of the magnetic force generator, a float member that moves up and down as the liquid level increases and decreases, is formed in a horizontally long shape, and the float member is fixed at both ends, Either one of the magnetic force generator or the magnetic force detection means is fixed at an intermediate position between both ends, and a ring holding member that holds the ring portion between the end portion and the intermediate position, and is inserted into each ring portion. And a plurality of guide rods for guiding the vertical movement of the float member, and detecting the magnetic force detection means by changing the distance between the magnetic force generator and the magnetic force detection means as the float member moves up and down. Detecting the liquid level based on the resultAs the float type liquid level sensorEstablishmentIn addition, the agent accommodating portion is used as a stirring body that rotates and stirs the liquid developer in the agent accommodating portion in the horizontal direction by rotating around a position shifted from the center of the plane section of the agent accommodating portion. A flexible agitator that rotates while flexibly bending in contact with the inner wall of the side wall, and non-flexible that generates a flow of liquid developer that moves along the axis of rotation by rotation on the same axis With a stirrerIt is characterized by that.
[0012]
  In this developing device, the float members supported at both ends of the ring holding member float at a level corresponding to the liquid level at that position. A magnetic force generator or magnetic force detection means is fixed to the ring holding member at an intermediate position of these float members, and this support position is a liquid level detection position of the float type liquid level sensor. When each float member fixed at both ends of the ring holding member floats at different liquid level levels due to the undulation of the liquid level, the magnetic force generator or magnetic force detection means fixed to the ring holding member is at both liquid level levels. Located in the middle. In the magnetic force generator or the magnetic force detection means positioned in this way, level fluctuations associated with the undulation of the liquid level are reduced. The above operation will be described as follows using an example using a ring pin as a ring holding member, a guide rod as a guide rod, and a Hall element as a magnetic force generating means. 18A and 18B are schematic views showing a float type liquid level sensor according to the present developing device, respectively. In each figure, the ring pin 141 has a spherical float member 140 fixed to both ends thereof, a magnetic force generator 144 fixed to an intermediate position of both ends, and between the intermediate position and each float member 140. The ring portion 141a is held. A guide bar 139 is inserted into each of the two ring portions 141a, and these guide bars 139 are fixed in a region not shown. The Hall element 143 that detects the magnetic force of the magnetic force generator 144 is disposed so as to face the magnetic force generator 144 that moves up and down when it is positioned at a predetermined level. When the liquid developer 7 is agitated from a stationary state (FIG. 18A) and the liquid level is made to wave, both float members 140 have different liquid level as shown in FIG. 18B. And the ring pin 141 is inclined. When the ring pin 141 is inclined as described above, the magnetic force generator 144 fixed at an intermediate position thereof is positioned at an approximately intermediate level between the respective liquid surface levels. Here, assuming that X1 which is the level of the float member 140 on the right side in the drawing is the original liquid level, only the float member 140 on the left side in the drawing is lowered from the original liquid level by the distance L1 in the illustrated example. It will be floating at the position. When only one float member 140 is provided, the lowering distance of the magnetic force generator 144 is also set to L. However, in the example shown in the drawing, only half L / 2 is lowered. On the other hand, assuming that X2 which is the level of the float member 140 on the left side in the drawing is the original liquid level, in the example shown in the drawing, the distance L1 from the original liquid level is also set to the distance L1. The magnetic force generator 144 is raised only by L / 2. Further, when one float member 140 is lowered and the other float member 140 is raised from the original liquid level, the magnetic force generator 144 is floated at a level close to the original liquid level. be able to. As a result, the level fluctuations of the magnetic force generator and the magnetic force detection means accompanying the wave of the liquid level are reduced. As a result, the error between the actual liquid level in the agent container and the detected liquid level of the float type liquid level sensor can be reduced.
Further, in this developing device, the developing agent such as toner is uniformly dispersed in the liquid developer by stirring the liquid developer in the agent container by the stirring member, and the developing substance concentration of the liquid developer is Can be made uniform.
Further, in this developing device, the stirrer rotates around the position shifted from the center of the flat cross section of the agent container in the horizontal direction. Along with this rotation, the liquid developer located closer to the rotation shaft side of the stirring body (hereinafter referred to as the stirring shaft side) than the center in the agent container is positively rotated to make the liquid surface undulate. On the other hand, the liquid developer located on the opposite side of the stirring shaft from the center is rotated relatively slowly by the convection of the liquid developer that is rotated in contact by the stirring member, so that the liquid surface has ripples. It can be suppressed. In such a configuration, if the liquid level of the liquid developer is detected at a position where the ripple is suppressed in this way, that is, at a position opposite to the stirring shaft side, the float type liquid level sensor may cause a float caused by the ripple. The liquid level detection error of the liquid level sensor can be further reduced.
However, the liquid developer cannot be sufficiently moved in the rotation axis direction, and the liquid developer may be insufficiently stirred in the vertical direction. Further, the liquid developer on the side opposite to the agitation shaft cannot be brought into contact with the agitator, and horizontal agitation in the horizontal direction may be insufficient. And this As a result, a developing substance such as toner cannot be uniformly dispersed throughout the liquid developer, and there is a possibility that the developing substance concentration of the liquid developer becomes non-uniform.
Therefore, in this developing device, the non-flexible stirrer generates a so-called axial flow of the liquid developer that moves along the rotation axis while stirring the liquid developer in the horizontal direction by the rotation, The liquid developer is stirred up and down by this axial flow. On the other hand, the flexible stirrer rotates while flexing flexibly due to contact with the inner wall of the side wall of the agent container. Such a flexible stirring body can be rotated along a trajectory that traces the entire region in the agent container in the horizontal direction, for example, as indicated by reference numeral 116 in FIG. The flexible stirrer (wing member 116) that rotates in such a locus directly rotates the liquid developer by directly contacting the liquid developer located on the side opposite to the stirrer side. Can do. Further, by rotating while flexibly bending, the liquid developer located on the side opposite to the stirring shaft side is given a rotational force weaker than that of the flexible stirring body to suppress the ripple. In the above configuration, the liquid developer can be stirred in the horizontal direction and also in the vertical direction by the rotation of the non-flexible positive stirring body. Further, the rotation of the flexible stirrer can surely rotate the liquid developer located on the side opposite to the stirrer side and stir in the horizontal direction while suppressing undulations due to stirring. As a result, it is possible to suppress unevenness in the developer concentration of the liquid developer due to insufficient horizontal stirring and insufficient vertical stirring while suppressing the undulation of the liquid developer due to stirring.
[0013]
According to a third aspect of the present invention, in the developing device according to the first or second aspect, the magnetic force generating body and the magnetic force detecting means are arranged so as to move up and down together with the float member. Thus, the distance is changed.
[0014]
In this developing device, the entanglement of the electric wires of the magnetic force detection means accompanying the vertical movement of the float member can be eliminated. Specifically, as a configuration for changing the distance between the magnetic force generator and the magnetic force detection means as the float member moves up and down, the magnetic force generator is moved up and down together with the float member, and the magnetic force detection means is moved to a liquid tank or the like. There is a configuration in which the magnetic force detection means is moved up and down together with the float member, and a magnetic force generator is fixed to a liquid tank or the like. However, in the latter configuration, it is necessary to extend the power supply of the magnetic force detection means and the electric wires for signals long in the liquid so that the float member can follow the vertical movement of the float member, and the float moves along with the vertical movement of the float member. There is a risk of being entangled with the supporting member for use. Therefore, in this developing device, the distance between the magnetic force generator and the magnetic force detection means is changed by the former configuration. In such a configuration, by moving the magnetic force generator that does not require wiring together with the float member, it is not necessary to extend the wire of the magnetic force detection means into the liquid for a long time. can do.
[0015]
According to a fourth aspect of the present invention, in the developing device according to the third aspect, a plurality of the magnetic force detecting means are arranged in the vertical direction.
[0016]
In this developing device, a plurality of magnetic level detection means for detecting the magnetic force of the magnetic force generator that moves up and down together with the float member are arranged in the vertical direction, so that a plurality of liquid levels are generated based on the vertical movement of one magnetic force generator. Can be detected.
[0017]
A fifth aspect of the present invention is the developing apparatus according to the first, second, third, or fourth aspect, wherein the float member is floated by a foamed resin.
[0018]
In this developing device, it is possible to avoid floating loss caused by damage to the air sealing outer wall of the float member. Specifically, as the float member, there are those in which air is enclosed in an outer wall for air encapsulation made of resin or the like, and those made of foamed resin, etc., but in the former one, the air enclosure outer wall is damaged. If it is received, the air inside may be released and the floating property may be lost. On the other hand, in the latter type used in the float type liquid level sensor, even if the outer wall is damaged, among the innumerable cells constituting the main body, the air in the extremely small foam cell existing in the damaged part It will not be lost, only lost.
[0024]
  Claim6The invention of claimAny one of 1 to 5In the developing device, the non-flexible stirring member is provided that generates a flow of a liquid developer that moves toward the bottom of the agent container along the rotation axis direction. It is what.
[0025]
In this developing device, the liquid developer is moved from the upper side to the lower side of the agent container by the axial flow generated by the rotation of the non-flexible stirring member, and then hits the bottom of the agent container. Is moved from the lower side to the upper side and stirred in the vertical direction. In such agitation, the liquid developer is made to reach the liquid surface from the lower side to the upper side of the agent container, and then moved in the reverse direction so as to move from the upper side to the lower side. , Can suppress the rise and swell of the liquid level.
[0026]
  Claim7The invention of claim6In this developing apparatus, a taper is provided at the bottom corner of the agent container, and the liquid developer that has hit the bottom by the movement along the rotation axis is guided upward by the taper on the side opposite to the axis deviation direction. It is characterized by doing so.
[0027]
In this developing device, after colliding with the bottom of the agent container by the axial flow, the liquid developer which is going to spread along the bottom surface is guided upward on the side opposite to the stirring shaft side by the taper. In such a configuration, in the agent container, the liquid developer flows from the upper side to the lower side on the stirring shaft side, and the liquid developer flows from the lower side to the upper side on the side opposite to the stirring shaft side. Let me. By such a flow, the liquid developer moves horizontally from the liquid surface to the bottom on the stirring shaft side and spreads on the opposite side while rotating in the horizontal direction as the stirring member rotates, It moves in the vertical direction following the path of moving from the bottom to the liquid level on the side and reaching the stirring shaft side again. The vertical rotation of the liquid developer can be performed more smoothly by this vertical rotation.
[0028]
  Claim8According to the present invention, a latent image carrier that carries a latent image, a latent image forming unit that forms the latent image on the latent image carrier, and a developing material in a liquid developer is attached to the latent image. An image forming apparatus comprising: a developing device that develops an image;Or 7The developing device is provided.
[0029]
Also in this image forming apparatus, an error between the actual liquid level in the agent container of the developing apparatus and the detected liquid level of the float type liquid level sensor is reduced by the same action as the developing apparatus of claim 1 or 2. Can do.
[0030]
  Claim9The invention of claim8In the image forming apparatus, a density detecting unit that detects a developing substance concentration of the liquid developer in the agent storage unit, a recovery unit that recovers the liquid developer used for development and returns the liquid developer to the agent storage unit, Replenishing means for replenishing the concentration adjusting agent in the agent containing portion, and based on the detection results of the concentration detecting means and the float type liquid level sensor, the driving of the replenishing means is controlled to control the liquid developer in the agent containing portion. And a control means for adjusting the developing substance concentration.
[0031]
In this image forming apparatus, the “liquid developer after being used for development” means that the developed image on the latent image carrier is transferred paper or the like in addition to the liquid developer remaining on the surface of the developer carrier after development. And a liquid developer remaining on the surface of the latent image carrier after the transfer process transferred to the recording member.
In this image forming apparatus, the developed liquid developer is collected by the collecting unit and returned to the agent containing unit, and the developing substance concentration of the liquid developer in the agent containing unit is detected by the concentration detecting unit. On the other hand, the control means replenishes the liquid developer in the agent container with an appropriate amount of a concentration adjusting agent such as a developing substance or a liquid carrier based on the detection result of the concentration detection means and the detection result of the float type liquid level detection sensor. The replenishing means is controlled to adjust the developing material concentration. The liquid developer whose developer concentration is adjusted in this way is supplied from the agent container to the developer carrier and contributes to development. In such a configuration, even when the developing substance concentration of the developed liquid developer is different from that before development, it can be adjusted to the concentration before development and reused for development. Further, by controlling the replenishment means based on not only the detection result of the concentration detection means but also the detection result of the float type liquid level sensor, the liquid developer concentration can be maintained while maintaining the liquid level in the agent container appropriately. Can be adjusted.
[0032]
  Claim10The invention of claim9In the image forming apparatus, the control unit is configured to detect the presence or absence of the concentration adjusting agent in the replenishing unit based on the driving time of the replenishing unit and the detection result of the float type liquid level sensor. It is characterized by this.
[0033]
In this image forming apparatus, the presence or absence of the concentration adjusting agent in the replenishing unit can be detected by the control unit without providing a special sensor for detecting the presence or absence of the concentration adjusting agent. Specifically, replenishment of a concentration adjusting agent such as a liquid developer or a liquid carrier is performed by driving a replenishing unit. If the liquid level does not rise no matter how many times this driving is repeated, The adjustment agent is gone. Therefore, the control means can detect the presence or absence of the concentration adjusting agent in the replenishing means based on the driving time of the replenishing means and the detection result of the float type liquid level sensor.
[0034]
  Claim 12The invention of claim8, 9 or 10In this image forming apparatus, a liquid developer having a developing material dispersed at a concentration of 5 to 40 [%] and a viscosity adjusted to 100 to 10000 [mPa · s] is used. Is.
[0035]
In this image forming apparatus, by using a liquid developer containing a developing material such as toner at a relatively high concentration of 5 to 40%, a liquid developer containing a developing material at a lower concentration is used. A high density image can be formed with a smaller amount of liquid than in the case. Further, unlike the case of using a liquid developer exceeding the viscosity of 10,000 [mPa · s], which increases the production cost due to the reason that stirring of the carrier and the developing material becomes extremely difficult, an image with a high density at a relatively low price. Can be formed. Further, image density unevenness due to the dispersion unevenness can be suppressed as compared with the case of using a liquid developer having a viscosity of less than 100 m [Pa · s], which easily causes uneven dispersion of the developing substance.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to an electrophotographic printer as an image forming apparatus will be described.
First, a basic configuration of the printer according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram of a printer according to the present embodiment. In the figure, a charging unit 2, a developing unit 100 as a developing device, an intermediate transfer drum 3, a drum cleaning unit 4 for cleaning the photosensitive drum 1, and the like are disposed around the photosensitive drum 1 as a latent image carrier. Has been. A transfer roller 5 is disposed on the right side of the intermediate transfer drum 3 in the drawing so as to form a transfer nip having a predetermined width in contact therewith.
[0037]
The photosensitive drum 1 is driven to rotate in a direction indicated by an arrow (clockwise) in the drawing at a constant speed during printing by a driving unit such as a motor (not shown). Then, after the rotation, the peripheral surface is uniformly charged by the charging unit 2, and then the writing light LB based on the image information is irradiated and imaged by the optical writing unit (not shown) to carry the electrostatic latent image. To do. The electrostatic latent image is developed by the developing unit 100 to become a visible image with a liquid developer, and then moves to a contact position with the intermediate transfer drum 3 as the photosensitive drum 1 rotates.
[0038]
The intermediate transfer drum 3 is rotated at the same peripheral speed as the photosensitive drum 1 in the direction of the arrow (counterclockwise) in the figure by a driving means (not shown), and the visible image is a peripheral surface of the intermediate transfer drum 3. Intermediate transfer. As the intermediate transfer drum 3 rotates, the intermediate transfer drum 3 moves to the transfer nip.
[0039]
On the other hand, a sheet feeding device (not shown) feeds the transfer paper 6 toward the transfer nip at a timing at which the transfer paper 6 can be superimposed on the visible image. The transfer paper 6 superimposed on the visible image at the transfer nip is transferred from the intermediate transfer drum 3 to a fixing device (not shown) after the visible image is transferred from the intermediate transfer drum 3. Then, after the visible image is fixed by heating or the like, it is discharged outside the printer.
[0040]
The liquid developer remaining on the photosensitive drum 1 without being transferred to the intermediate transfer drum 3 is mechanically scraped and removed by the cleaning blade 4a of the drum cleaning unit 4 and then recovered by the screw member 4b. 8, falls in the collection pipe 8 by its own weight, and reaches a second tank described later.
[0041]
The surface of the intermediate transfer drum 3 that has passed through the transfer nip is removed from the liquid developer remaining without being transferred to the transfer paper 6 by an intermediate transfer drum cleaning unit (not shown) and then to the contact position with the photosensitive drum 1. Move again.
[0042]
The surface of the photosensitive drum 1 that has passed through this contact position is moved to a position facing a neutralization lamp (not shown) and the residual potential is removed to prepare for the next printing.
[0043]
The developing unit 100 mainly includes a developing unit 101, a collecting unit 102 that is a collecting unit, an agent adjusting unit 103, and a replenishing unit 104 that is a density adjusting unit.
[0044]
The developing unit 101 includes a developing roller 105 as a developer carrying member, a coating roller 106, a regulating blade 107, a first stirring screw 108, a second stirring screw 109, a first tank 110 as an agent storage unit, and the like. . In this first tank 110, a liquid developer 7 containing toner as a developing substance and a liquid carrier is accommodated in an amount of about 100 to 150 [cc].
[0045]
This liquid developer 7 has a viscosity adjusted to 100 to 10,000 [mPa · s] and a toner concentration adjusted to 5 to 40 [%]. More specifically, in the present embodiment, those adjusted to viscosity = about 300 [mPa · s] and toner concentration = 15 [%] are used.
[0046]
In the first tank 110, the application roller 106 is disposed above the liquid developer 7, so that the liquid level of the liquid developer 7 does not contact the application roller 106 in a standby state. Further, the first stirring screw 108 and the second stirring screw 109 are horizontally arranged so as to be arranged in parallel.
[0047]
When the printing operation is started, these screws are rotated in opposite directions by driving means (not shown), and the liquid developer 7 above the screws is raised and brought into contact with the application roller 106 to be supplied. The liquid developer supplied in this manner adheres to the application roller 106 rotated counterclockwise in the drawing by a driving means (not shown) and passes through the position facing the regulating blade 107 to have a layer thickness. Is regulated and thinned. Then, after a part of the toner is applied to the developing roller 105 rotating while being in contact with the application roller 106 at an amount of about 30 [cc] per minute, the development at the position facing the photosensitive drum 1 together with the development roller 105 is performed. It moves to the position and contributes to development. At this development position, the used liquid developer 7 that remains on the developing roller 105 without moving to the electrostatic latent image on the photosensitive drum 1 is collected in accordance with the rotation of the developing roller 105. It moves to the opposite position and is collected.
[0048]
The collection unit 102 includes a collection roller 111, a collection blade 112, a collection screw 113, and a collection pipe 114. The collecting roller 111 rotates while contacting the surface of the developing roller 105 after passing through the developing position, and collects the used liquid developer 7 adhering to the surface. The liquid developer 7 collected in this manner is mechanically scraped off from the surface of the collection roller 112 by the collection blade 112 and then conveyed into the collection pipe 114 by the collection screw 113. The recovery pipe 114 falls by its own weight and reaches a second tank described later.
[0049]
The agent adjusting unit 103 includes a second tank 115 as an agent storage unit, two wing members 116 and 117 as stirring bodies, a concentration signal output means 118, a transfer pump 120, a transfer pipe 121, and the like. The second tank 115 also contains the liquid developer 7 therein, and a tank lid 119 is attached to the opening.
[0050]
The density signal output means 118 constitutes a density detection means together with a control unit (not shown).
[0051]
In the second tank 115, the wing members 116, 117 are rotated by a stirring motor (not shown), whereby the liquid developer 7 is rotated in a substantially horizontal direction and stirred. While the liquid developer 7 is agitated in this manner, the toner density is detected by the density detection means comprising the density signal output means 118 and the control unit.
[0052]
The transport pipe 121 has one end connected to the bottom of the second tank 115 and the other end connected to the drain pipe 122 of the first tank. In the middle of the transfer pipe 121, the transfer pump 120 is provided. The liquid developer 7 in the second tank 115 is transported and supplied into the first tank 115 by the transport pump 120. When an excessive amount of the liquid developer 7 is supplied into the first tank 115 by the transport pump 120, the excess liquid developer overflows due to the rise in the liquid level of the liquid developer 7 in the first tank 115. The pipe attachment position is reached, and it returns to the second tank 115 through this overflow pipe.
[0053]
The replenishing unit 104 includes a carrier bottle 123 that contains a replenishing liquid carrier, a developer bottle 124 that contains a replenishing liquid developer, and a carrier for transporting the liquid carrier from the carrier bottle 123 to the second tank. A pump 147, a developer pump 146 for conveying the liquid developer from the developer bottle 124 to the second tank, and the like are provided, and are controlled by a control unit which is a control means (not shown).
[0054]
The liquid developer in the developer bottle 124 has its toner concentration adjusted to 15 [%], which is desirable for development. This density is the standard density in this printer.
[0055]
The control unit controls the driving of the developer pump 146 and the carrier pump 147 based on the output signal from the concentration signal output means 118 of the agent adjusting unit 103, so that an appropriate amount of liquid carrier is contained in the second tank 115. Or by replenishing the liquid developer, the toner concentration of the liquid developer 7 in the second tank 115 is adjusted. By such control, the liquid developer before the liquid toner collected from the developing roller 105 and the liquid developer collected from the photosensitive drum 1 are mixed is used. Even in the case where the toner density is different from the toner density of 7, the water can be returned to the second tank 115 and reused.
[0056]
1, the developing unit 100 includes a developing cartridge (enclosed by an alternate long and short dash line in the drawing) of the developing unit 101, the collecting unit 102, the agent adjusting unit 103, and the replenishing unit 104. It can be separated from other parts. For this reason, it is easily removed from the printer main body during maintenance when a failure or life is reached. The drain pipe 122 of the developing cartridge is connected to the transport pipe 121 of the agent adjusting unit 103 by a coupling 136.
[0057]
It is desirable to remove the developer cartridge having such a configuration from the printer main body in the following procedure. That is, first, the transport pump 120 of the agent adjusting unit 103 is driven in reverse to return the liquid developer 7 in the first tank 110 of the developing unit 101 to the second tank 115 of the agent adjusting unit 103. Then, after closing the drain valve 137 provided on the drain pipe 122, the coupling 136 is operated to separate the drain pipe 122 on the developing cartridge side and the transport pipe 121 on the agent adjusting section 103 side. By closing the drain valve 137 before separating the two pipes, the liquid developer 7 remaining in the first tank 110 and the drain pipe 122 is not leaked and wasted. Since the transport pipe 121 is provided in the transport pipe 121, the liquid developer 7 in the second tank 115 is not leaked from the separated portion when the two pipes are separated. In order to avoid it reliably, a coupling 121 having a valve function may be used.
[0058]
FIG. 2 is a top view showing the developing device 100 with the tank lid 119 removed from the direction of arrow A in FIG. FIG. 3 is an exploded perspective view of the agent adjusting unit 103. In FIG. 3, reference numeral 118 denotes a density signal output means, which constitutes a density detection means together with a control unit (not shown).
[0059]
The density detection means 118 includes a support plate 129 protruding from the lower surface of the tank lid 119 and an optical sensor 132 disposed above the tank lid 119. Further, a disk unit rotatably held on the support plate 129 and a disk motor 133 for rotating the disk unit are also provided.
[0060]
The disk unit is composed of two outer disks 131a and 131b and a middle disk 130 sandwiched between them. The middle disk 130 has a smaller diameter than the two outer disks 131a, and rotates at a position eccentric from the rotation center of the outer disks 131a and 131b. Further, the circumferential surface is mirror-finished. When the disk unit is rotated with its peripheral surface partially immersed in the liquid developer 7, the liquid development is performed in the recess formed in the circumferential direction by the step between the middle disk 130 and the two outer disks 131a and 131b. Agent 7 is filled. The recesses have different depths in the circumferential direction because the middle disk 130 is disposed at a position eccentric from the two outer disks 131a and 131b. A regulating blade (not shown) is in contact with the peripheral surfaces of the two outer disks 131a and 131b, and a liquid development having a thickness gradient in the circumferential direction is formed in the concave portion that has passed through the position facing the regulating blade. A liquid film of the agent 7 is formed.
[0061]
The optical sensor 132 includes a light emitting element and a light receiving element (not shown), and irradiates the liquid film with light from the light emitting element through the opening 134e of the tank lid 119. The irradiated light is transmitted through the liquid film and then reflected by the mirror surface of the middle disk 130 serving as the bottom of the recess. Then, after passing through the liquid film again, it passes through the opening 134 e and is received by the light receiving element of the optical sensor 132. The light receiving element outputs a signal having a value corresponding to the amount of received light to the control unit.
[0062]
The amount of light transmitted through the liquid film varies depending on the concentration of the developing material. However, in the thixotropic liquid developer 7 containing toner at a high concentration, the variation rate of the amount of transmitted light with respect to the toner concentration is remarkably large, and if the liquid film has a constant thickness, the transmitted light can be transmitted with only a slight change in the toner concentration. May be obtained or not. Therefore, the concentration signal output means 118 shown in the figure forms a liquid film having a thickness gradient in the circumferential direction in the concave portion and transmits light with various thicknesses, so that the disk unit is transmitted until it rotates once. It is configured to reliably obtain light.
[0063]
The light receiving element continuously changes its output value according to the rotation angle (liquid film thickness) of the disk unit. The integration result of this output value per rotation of the disk unit corresponds to the total amount of light received by the light receiving element. There is a correlation with the toner concentration of the liquid developer 7. Therefore, the control unit integrates the output value that continuously changes in this way while the disk unit makes one rotation, and calculates the toner concentration of the liquid developer 7 based on the integration result.
[0064]
According to the density detecting means having the above configuration, the toner density can be detected even with the thixotropic liquid developer 7 containing toner at a high density.
[0065]
Although the example in which the reflection type optical sensor 132 is provided in the density signal output unit 118 has been described, a transmission type optical sensor may be provided instead. Specifically, the middle disk 130 is formed of a transparent member such as glass or resin, and a light receiving element or a light emitting element of an optical sensor is installed therein, and a light emitting element or a light receiving element that is paired with an internal element outside. Install the element. Then, the light emitted from the light emitting element is transmitted through the liquid film only once, and the transmitted light is received by the light receiving element.
[0066]
Next, a characteristic configuration of the printer according to the present embodiment will be described.
FIG. 4A is a perspective view showing a float type liquid level sensor attached to the agent adjusting unit 103. In the figure, a float type liquid level sensor 135 includes two float members 140, two guide rods 139 for guiding the vertical movement of the float member 140, a ring pin 141, four Hall elements 143 as magnetic force detection means, a magnetic force. It consists of the generator 144 and the like. The ring pin 141 has two ring portions 141a, and two guide rods 139 protruding from the lower surface of the tank lid (not shown) are inserted into the ring portions 141a.
[0067]
The two float 140 members floating in the liquid developer (not shown) move up and down as the liquid level increases and decreases while being held at the opposite ends of the ring pins 141. This vertical movement is guided by the two guide rods 139 so as not to flow in the rotation direction of the liquid developer. The magnetic force generator 144 is fixed to the center of the ring pin 141.
[0068]
In addition to the two guide rods 139, a support plate 129 of the concentration signal output means 118 protrudes from the tank lid (not shown) so as to be positioned between the guide rods 139 and is fixed to the float member 140. It faces the generated magnetic force generator 144. The four hall elements 143 are fixed to the support plate 129 so as to be aligned in the vertical direction.
[0069]
These four Hall elements 143 are mounted in order from the top to the height corresponding to the upper limit liquid level, the standard liquid level, the lower limit liquid level, and the emergency stop liquid level.
[0070]
When the liquid level falls below the lower limit liquid level or exceeds the upper limit liquid level, the disk unit is not immersed in the liquid developer 7, or all of the disk unit is immersed in the liquid developer 7, and the liquid film is formed. As a result, the toner density cannot be detected.
[0071]
Each Hall element 143 is configured to output a detection signal of 0 [V] to a replenishment control unit, which will be described later, when a magnetic force of S pole or N pole is detected while 5 [V] power is supplied, for example. Yes. When the float member 140 moves up and down as the liquid level of the liquid developer increases and decreases, among the four Hall elements 143, the one at the height position of the float member 140 generates the magnetic force fixed to the float member 140. The magnetic force of the body 144 is detected.
[0072]
By fixing each Hall element 143 not to the float member 140 but to the support plate 129, electric wires (not shown) for power supply and signals connected to each Hall element 143 are fixed without extending in the liquid developer for a long time. Can be arranged. Therefore, the wire is not entangled with the float member 140, the ring pin 141, and the guide rod 139 as the float member 140 moves up and down.
[0073]
The material of the float member 140 is lighter than the specific gravity of the liquid developer, and it is desirable to use a foamed resin such as polystyrene, polyethylene, or polypropylene. In the printer of this embodiment, 0.02 to 0.6 [g / cm³The specific gravity of polystyrene (styrene foam) was used.
[0074]
As for the shape of the float member 140, it is desirable to use a shape that exhibits good floating properties while reducing the surface area as much as possible. As the plane area on the side that receives the flow of the rotating liquid developer increases, the float member 140 is affected by the rotational force of the liquid developer, and the vibration is increased, or turbulence is generated in the liquid developer. Because. Further, the larger the plane area, the larger the floating resistance in the high viscosity liquid developer and the worse the floating response.
[0075]
In the float type liquid level sensor 135 shown in FIG. 4A, the toner in the liquid developer (not shown) adhering to the upper part of the spherical float member 140 appears along the spherical surface of the float member 140 together with the liquid carrier. To descend. Then, the liquid developer reaches the liquid level in the second tank (not shown) and is taken in. This makes it difficult for toner to accumulate on the float member 140 and reduces the sinking of the float member due to the deposition of the developing material, and the actual liquid level in the second tank and the detected liquid level of the float type liquid level sensor. And the error can be reduced. Further, the spherical float member 140 without corners reduces the liquid flow resistance received from the liquid developer and lessens the subtle vertical movement caused by receiving the flow of the liquid developer than the corner float member. Can do.
[0076]
Further, in this float type liquid level sensor, as described above with reference to FIGS. 18A and 18B, the level fluctuation of the magnetic force generator 144 due to the undulation of the liquid surface is reduced, and the second The error between the actual liquid level in the tank and the detected liquid level can be reduced. Note that the maximum inclination angle of the ring pin 141 when the two float members 140 are floated at different liquid level levels, the distance between the two ring portions 141a, the inner wall of the ring portion 141a and the guide rod 139. It can be set finely by adjusting the clearance.
[0077]
In the printer of this embodiment, the type of the liquid developer 7 to be used by the user is specified. Specifically, it is specified by clearly specifying, for example, “Please use XX of XX Company for the liquid developer” in the instruction manual of the apparatus. A foamed resin having a specific gravity lighter than that of the designated type of liquid developer 7 is used for the float member 140. Therefore, as long as the designated type of liquid developer 7 is used, the float member does not sink in the liquid developer 7.
[0078]
The detection signal from each hall element 143 is output to a supply control unit described later. This replenishment control unit determines whether or not there is at least one hall element 143 that outputs a detection signal, and if “not present”, displays an error message on a display unit such as a display (not shown). In the case of “Yes”, it is next determined whether or not an output is made from the second Hall element 143 from the bottom (below the lower limit liquid level). It determines with it being below a minimum liquid level.
[0079]
In the present printer, each of the Hall elements 143 is arranged at an interval so as not to generate a detection dead space between the Hall elements 143, and the float type liquid level sensor 135 is set so as to detect a liquid level fluctuation range of 20 [mm]. It is composed.
[0080]
As shown in FIG. 4B, the float type liquid level sensor 135 is configured so as to form one unit with the concentration signal output means 118, and these means are compactly arranged in the second tank 115. It can be arranged.
[0081]
FIGS. 5A and 5B are perspective views showing a comparative example of the float type liquid level sensor 135. In this comparative example, the float member 140 is formed in a square block shape. In the float member 140 having such a shape, toner easily accumulates on the upper surface thereof, so that the float member 140 floats at a level lower than the original floating level due to the weight of the deposited toner. Further, the illustrated float type liquid level sensor 135 has only one float member 140, and the ring pin 141 cannot be tilted as shown in FIG. The level fluctuation of the magnetic force generator 144 cannot be reduced.
[0082]
FIG. 6 is a block diagram showing a part of the electric circuit of the printer. In the figure, a control unit 200 that is a control unit includes a density detection control unit 200, a replenishment control unit 202, and a storage unit 203 configured by a hard disk, a RAM, or the like.
[0083]
The concentration detection control unit 201 and the replenishment control unit 202 are connected so as to be able to communicate data with each other, and the storage unit 203 is also connected thereto.
[0084]
The density detection control unit 201 is also connected to the disk motor 113 of the density signal output means 118, the optical sensor 132, and the like so as to control the drive thereof and to communicate with the optical sensor 132. It has become.
[0085]
The replenishment control unit 202 is also connected to the transport pump 120, the developer pump 146, the carrier pump 147, the float type liquid level sensor 135, the stirring motor (for the blade members 116 and 117) 148, and the like. Or communicate with the float type liquid level sensor 135.
[0086]
FIG. 7 is a flowchart showing the density detection control of the density detection control unit 201. In the figure, the density detection control unit 201 starts density detection control at a predetermined cycle, first starts driving the disk motor (133), and rotates the disk unit of the density signal output means (118). (Step 1: Hereinafter, step is denoted as S). By this rotation, a liquid film made of the liquid developer in the second tank (115) is formed on the disk unit.
[0087]
Next, the density detection control unit 201 integrates a continuously changing output value sent from the light receiving element of the optical sensor (132) for a predetermined time (S2). This predetermined time is the time required for one rotation of the disk unit, and is about 7 seconds in the printer of this embodiment.
[0088]
When the integration process is completed, the density detection control unit 201 calculates the toner concentration of the liquid developer in the second tank (115) based on the integration result (S3). Specifically, for example, from a database that associates each integrated value with the toner density, the toner density corresponding to the integrated result is specified, or the integrated result is substituted into an algorithm that indicates the relationship between the integrated value and the toner density. Then, the toner density is calculated. Then, after updating the toner density data stored in the storage means 203 to the value of the calculation result (S4), it is determined whether or not the control should be continued (S5).
[0089]
If it is determined that the control should be continued because the developing operation is in progress (Y in S5), the control flow is looped to S2 and the integration process is performed again. If it is determined that the control should not be continued (N in S5), the drive of the disk motor 133 is stopped (S6), and the control is terminated.
[0090]
In such density detection control, when the control is started, the integration process is repeated until the stop of the disk motor 133 is confirmed in S5, and the toner density data stored in the storage means 203 is repeatedly updated. The Note that the processing time of about 7 seconds is spent in the above S2, but since the other is almost instantaneous calculation processing, the toner density calculation time (processing time from S2 to S5) per time is 7 A little over a second.
[0091]
FIG. 8 is a flowchart showing the density adjustment control of the replenishment control unit 202. This density adjustment control is based on the liquid level of the liquid developer 7 in the second tank 115 and the toner density data stored in the storage means 203. In this control, one of the developers is supplied to adjust the toner density of the liquid developer 7.
[0092]
The outline of the density adjustment control shown in FIG. 8 is as follows. That is, first, the liquid level in the second tank 115 (hereinafter simply referred to as the liquid level) is determined (S1), and when the liquid level is lower than the standard liquid level (Y in S2), the liquid carrier or the liquid development is performed. After replenishing the agent into the second tank 115 for a predetermined time (S11 or S14), the process returns to the control of S1 again to determine the liquid level. If the liquid level is equal to or higher than the standard liquid level (N in S2), the control is terminated without replenishing the liquid carrier or the liquid developer. Therefore, the concentration adjustment control is started at a predetermined cycle, and once it is determined that “liquid level <standard liquid level”, the liquid carrier or the liquid developer is replenished until the liquid level rises to the standard liquid level. The
[0093]
When “liquid level = standard liquid level”, the control proceeds in the order of S1, S2, S3, S4, and S17. In S17, it is determined whether or not the control should be continued. If it is determined that the control should be continued because the developing operation is in progress (Y in S17), the control is shifted to S1. Looped. Further, when it is determined that it should not be continued (N in S17), a series of control ends.
[0094]
By such replenishment, the liquid level fluctuates between the standard liquid level and a level slightly below it, so that it is kept near the standard liquid level unless there is any abnormality. However, liquid level abnormalities such as the liquid level falling below the lower limit liquid level or exceeding the upper limit liquid level may occur due to failure of each pump or the float type liquid level sensor 135, out of the concentration replenishment agent, or the like.
[0095]
Therefore, the replenishment control unit 202 confirms whether or not there is such a liquid level abnormality (S4, S5), and if the liquid level is abnormal (Y in S4 or S5), a “water level error” is displayed on a display unit (not shown). "Is displayed and the control is terminated.
[0096]
Further, it is confirmed whether the density adjusting agent is lost, that is, whether the developer bottle 124 and the carrier bottle 123 are empty. Display “bottle empty error” or “carrier bottle empty error” to end the control. Specifically, the liquid developer and the liquid carrier are replenished by driving the developer pump 146 and the carrier pump 147 for a predetermined time (S11, S15). This driving is repeated several times. However, if the liquid level does not rise, these bottles are empty. In this embodiment, after the developer pump 146 and the carrier pump 147 are driven for 2 seconds per time, the control flow is returned to S1 to determine the liquid level, and the liquid level does not reach the standard liquid level. Further, the control for driving these pumps for 2 seconds is repeated. In such a series of steps, each time the pump is driven once, 1 is added to the developer pump driving frequency C1 and the carrier pump driving frequency C2 (S12, S16), and each reaches 10 times. It is determined whether or not (S9, S13), and if it has been reached (Y in S9 or S13), a bottle empty error is displayed (S10, S149). When the liquid level reaches the standard liquid level, the developer pump driving frequency C1 and the carrier pump driving frequency C2 are reset to zero (S3), and the control is terminated.
[0097]
Whether to replenish the liquid developer or the liquid carrier is determined by reading the toner density data and the target density from the storage means 203 (S7) and comparing them (S8). . If “target density> toner density data” (Y in S8), the liquid developer is supplied, and if “target density ≦ toner density data” (N in S8), the liquid carrier is supplied. . In this embodiment, since the target density is set to 18 [%], the liquid carrier is replenished when the toner density becomes 18 [%]. The toner concentration desirable for development is 15 [%] equivalent to the liquid developer for replenishment (in the developer bottle 124), but if it is within the range of 15 ± 3 (12 to 18) [%]. The development density does not fluctuate.
[0098]
Here, since the toner concentration of the replenishing liquid developer is 15% of the standard concentration, the toner concentration of the liquid developer 7 in the second tank 115 exceeds 15% and 18%. If it is less, the liquid developer 7 is actually diluted even if the replenishing liquid developer is replenished. However, it is possible to suppress a decrease in density due to replenishment in the region of 15 to 18 [%], and to suppress a development density shortage due to a toner density shortage, compared to a case where the target density is set to 15 [%]. A replenishing liquid developer having a toner density higher than 15% may be used.
[0099]
In the pump drive 9 in S11 and S15, a processing time of 2 seconds is spent. However, since this is almost instantaneous calculation processing, the processing time from S1 to S12 or S1 to S16 is slightly over 2 seconds. It becomes. On the other hand, as described above, in the density detection control, the toner density calculation time per time is just over 7 seconds, and the toner density data is not updated during this time. For this reason, in the density adjustment control by the replenishment control unit 202, when replenishment is repeatedly performed, the same toner density data is read and used in S7 at least three times.
[0100]
According to the above density adjustment control, control can be performed based on the toner density data stored in advance in the storage unit 203 without waiting for the calculation of the toner density by the density detection control unit 201.
[0101]
In addition, although the example which provided the density | concentration detection control part 201 which is a density | concentration calculating means, and the replenishment control part 202 which implements the said density | concentration adjustment control was demonstrated individually, these were comprised by one CPU etc., and the said density | concentration detection The control flow of control and the control flow of density adjustment control may be performed in parallel.
[0102]
Although not shown in FIG. 8, when the emergency stop liquid level is detected, the replenishment control unit 202 stops the wing member 116 from being immersed in the liquid developer and sprays the liquid developer around it. Since there is a risk of scattering, the operation of the entire printer is urgently stopped.
[0103]
FIG. 9 is a perspective view showing the agent adjusting unit 103 in a state where the tank lid 119 is attached to the second tank 115. FIG. 9 shows the second tank 115 provided with the float type liquid level sensor 135 shown in FIGS. 4 (a) and 4 (b). In FIG. 9, the second tank 115 is formed so that its plane cross section is not a perfect circle but an ellipse. The term “oval” here is not an ellipse in terms of geometry, but a land track shape in which a square such as a square or rectangle is interposed between a half circle and a half circle divided by a center line of a perfect circle. It is the shape.
[0104]
A shaft rod 138 as a shaft member is rotatably supported by a waterproof structure bearing (not shown) provided on the bottom surface of the second tank 117, and rotates at a position shifted to the left in the figure from the center (center of gravity) of the bottom surface. To do. On the peripheral surface of the shaft rod 138, a wing member 116 made of a flexible member, and a wing member 117 arranged on the lower side in the drawing and made of an inflexible member, Is fixed.
[0105]
The flexible wing member 116 is adjusted in length so as to touch the inner peripheral surface of the second tank 115 at any rotational position, and the shaft 138 rotates in the direction of the arrow in the figure. Along with this, it rotates in the same direction while bending so as to lick the inner peripheral surface of the tank. Internal members such as a support plate 129 and an outer disk 131 are disposed on the rotating track of the flexible wing member 116. When the flexible wing member 116 comes into contact with these internal members as it rotates, as shown in FIG. 10, the flexible wing member 116 is further bent in the direction opposite to the rotation direction so as to avoid this. Then, in a bent state, the surface of these internal members is licked and continues to rotate. As shown in FIG. 11, after rotating to a position where the internal members can be separated, the tank is again shown in FIG. Continue to rotate to lick the inner surface. Even if such a blade member 116 is provided with an internal member such as a support plate 129 or an outer disk 131 on its rotating track, the entire area of the liquid developer 7 existing on the rotating track is contacted with a low viscosity. It can be rotated while being distorted. In such a configuration, even a high-viscosity thixotropic liquid developer 7 that hardly generates convection can be rotated well and stirred in the horizontal direction at the height position of the wing member 116.
[0106]
On the other hand, the non-flexible wing member 117 is provided at a position below the wing member 116 in the shaft rod 138 as shown in FIG. 9, and the axial direction of the shaft rod 138 is similar to a ship screw. It is composed of four fan-shaped wing members that can twist. When the liquid developer 7 rotates as the wing member 117 rotates, an axial flow of the liquid developer 7 that moves from the upper side to the lower side in the figure is generated. The liquid developer hitting the bottom of the second tank 115 due to the axial flow rebounds at the bottom and moves from the lower side to the upper side this time. Unlike the wing member 116, the wing member 117 is configured such that the rotational track does not reach the entire area of the second tank plane at the height position, but the liquid developer 7 having a reduced viscosity on the rotational track is used. By this rebounding, it is possible to efficiently move to a region where the rotational trajectory does not reach. For this reason, a difference in viscosity between the liquid developer 7 on the rotation path and the liquid developer 7 in a region that does not reach the rotation path hardly occurs, and deterioration of the stirring efficiency due to the difference in viscosity is suppressed.
[0107]
As for the direction of the axial flow, as shown in FIG. 9, the direction from the upper side to the lower side in the figure is desirable. In the axial flow in this direction, the undulation of the liquid surface can be suppressed compared to the axial flow in the direction from the lower side to the upper side in the drawing, and the liquid developer 7 is stronger due to the rebound at the bottom of the second tank 115. This is because a shearing force can be applied to lower the viscosity of the liquid developer 7 more efficiently.
[0108]
In this printer, since the stirring force of the non-flexible wing member 117 is higher than the stirring force of the flexible wing member 116, the liquid developer 7 at the height position of the wing member 117 is better. Reduce viscosity quickly. The low-viscosity liquid developer 7 rises to the height position of the wing member 116 by the above-described rebound. For this reason, the wing member 117 moves the liquid developer 7 having a lower viscosity to the rotational orbit of the wing member 116 by the axial flow, and assists the stirring by the wing member 116. The liquid developer 7 in the vicinity of the center of the rotation track of the wing member 116 is pulled downward in the figure by the axial flow generated by the rotation of the wing member 117 and descends to the rotation position of the wing member 117.
[0109]
In the above configuration, the liquid developer 7 in the second tank 115 is positively rotated in the rotation direction of the shaft rod 138 and sufficiently stirred in the horizontal direction. In addition, while the vicinity of the center of rotation moves downward, the vertical movement of the outer side moves upward also causes sufficient stirring in the vertical direction.
[0110]
By the way, if the entire area of the liquid developer 7 is simply brought into contact with the flexible wing member 116 and rotated at the height position of the internal members such as the support plate 129 and the outer disk 131, the second state. There is no need to provide a complicated configuration in which the planar shape of the tank 115 is oblong and the rotation center of the wing member 116 is shifted from the center of the planar shape. Specifically, as shown in FIG. 13, it is sufficient to make the planar shape of the second tank 115 a regular circle and rotate the flexible wing member 116 at the center position of the planar shape. However, in this configuration, as shown in FIG. 14, the non-flexible wing member 117 having a strong stirring force is also rotated at this center position, and the liquid developer 7 by the wing member 117 is relatively fast. The liquid level is greatly rippled by rotation and axial flow. Such a large wave causes a large error between the liquid level detection result of the float type liquid level sensor 135 and the actual liquid level in a stationary state. In addition, since the float member 140 is sucked into the vortex generated in the vicinity of the shaft rod 138 and is vigorously shaken up and down, a large error is caused by this shaking.
[0111]
Therefore, in the printer of this embodiment, the shaft rod 138 is provided at a position shifted from the center (center of gravity) of the second tank 115, and the blade members 116, 117 are rotated around the position shifted from the center. Yes. In such a configuration, as the blade member 117 rotates, the liquid developer located on the side of the shaft rod 138 from the center of the second tank 115 is positively rotated to make the liquid surface undulate. On the other hand, the liquid developer located on the opposite side of the shaft 138 from the center of the second tank 115 is convected by the liquid developer rotated by the wing member 117 or stirred more than the wing member 117. By rotating the weak wing member 116, the wing member 116 is rotated relatively slowly. Since the float type liquid level sensor 135 detects the liquid level at a position where the ripple is suppressed in this way, it is possible to reduce a liquid level detection error due to the ripple.
[0112]
At the bottom of the second tank 115, as shown in FIG. 15, the liquid developer 7 spreads along the bottom surface toward the center of the tank after hitting the bottom by the axial flow generated by the rotation of the blade member 117. It is desirable to provide a taper 145 that leads upward. In this configuration, in the second tank 115, the liquid developer 7 flows from the upper side to the lower side on the shaft rod 138 side from the tank center, and at the opposite side to the shaft rod 138, from the lower side to the upper side. The flow of the liquid developer 7 heading is actively generated. With such a flow, the liquid developer 7 can be more reliably stirred in the vertical direction.
[0113]
In this printer, the toner density of the liquid developer 7 guided upward from the bottom of the second tank by the taper 145 is detected by the density detection means comprising the density signal output means 118 and the control unit. Further, as shown in FIG. 16, the concentration adjusting agent (replenishment liquid carrier or liquid developer) and the recovered developer (recovered from the photosensitive drum or the developing roller) are disposed closer to the shaft rod 138 than the center of the tank. It is made to fall to the liquid level. More specifically, the concentration adjusting agent and the collected developer are dropped on the upper side of the rotation track of the wing member 117. In such a configuration, the concentration adjusting agent and the collected developer are supplied to the liquid developer surface that is actively rotated by the blade member 117 on the shaft rod 138 side of the tank center. Then, it is caught in the axial flow generated with the rotation of the blade member 117 and is moved from the liquid surface to the bottom of the second tank 115, and the horizontal stirring and the vertical stirring are sufficiently performed. Further, at the bottom of the second tank 115, the taper 145 guides upward while spreading from the shaft rod 138 side to the opposite side along the bottom surface. This time, in the liquid developer 7 on the opposite side, the horizontal agitation and the agitation in the vertical direction are further promoted with the upward movement and the rotation of the blade member 136. In this configuration, the density detecting means detects the toner density of the liquid developer 7 in which the density adjusting agent and the collected developer are sufficiently agitated in the horizontal direction and the agitation in the vertical direction. .
[0114]
FIG. 17 is a side view showing a modification of the wing member 116 shown in FIG. In FIG. 17, in addition to the flexible wing member 116a that rotates above the non-flexible wing member 117, a flexible wing member 116b that rotates below the wing member 117 is provided. In such a configuration, the toner precipitated on the bottom of the second tank 115 due to being left for a long period of time or the like can be agitated by the lower wing member 116b, so that the toner can be more reliably dispersed in the liquid developer. .
[0115]
Note that metal powder may accumulate in the liquid developer in the first tank 110 and the second tank 115. This metal powder is generated, for example, by friction between rollers and blades (collection roller 111, collection blade 112, application roller 106, regulation blade 107, etc.) made of metal, or by meshing of a gear (not shown). Or fall into the second tank. The liquid developer containing metal powder may cause a development bias or a transfer bias to leak at the development position or the transfer nip, thereby impairing the development performance or the transfer performance. Further, a discharge from the developing roller 105 to the photosensitive drum 1 may be generated at the developing position, and the surface of the photosensitive member may be damaged by the discharge. Further, each disk of the disk unit may be damaged or the light transmittance of the liquid film may be changed. When these occur, of course, the image quality is degraded. Therefore, when metal powder accumulates in the liquid developer, a magnet is detachably disposed in the first tank 110, the second tank 115, or a pipe for transporting the liquid developer. Is desirable. This is because metal powder can be magnetically deposited on the arranged magnet and removed from the liquid developer.
[0116]
Further, a magnet may be arranged between the developing roller 105 and the developing roller 105 so as to face the developing roller 105 with a predetermined gap between the developing position and the developing position. More preferably, as the magnet, a magnetic roller that is driven to rotate is disposed through a gap of 10 to 200 [μm] with the developing roller 105, and a scraping blade for scraping the metal powder is applied to the magnetic roller. It is desirable to arrange them in close contact. In such a configuration, the metal powder contained in the liquid developer immediately before use for development is magnetized on the magnetic roller to be removed from the liquid developer, and the metal powder magnetized on the magnetic roller is scraped off with a scraping blade. Can be recovered.
[0117]
【The invention's effect】
  Claims 1, 2, 3, 4, 5, 6Or 7According to the invention, since the sink of the float member due to the deposition of the developing material is reduced, or the level fluctuation of the magnetic force generator and the magnetic force detection means due to the undulation of the liquid surface is reduced, And the detected liquid level of the float type liquid level sensor can be reduced.
In addition, there is also an excellent effect that the developing substance concentration of the liquid developer can be made uniform in the agent container.
In addition, there is also an excellent effect that the liquid level detection error of the float type liquid level sensor due to the undulation of the liquid developer in the agent container can be further reduced.
Furthermore, there is an excellent effect that the unevenness of the developing material concentration due to insufficient horizontal agitation of the liquid developer and insufficient agitation of the vertical direction can be suppressed while suppressing the ripple of the liquid developer due to the agitation.
[0118]
In particular, according to the invention of claim 3 or 4, there is an excellent effect that the entanglement of the electric wires of the magnetic force detection means accompanying the vertical movement of the float member can be eliminated.
[0119]
Particularly, according to the invention of claim 4, there is an excellent effect that a plurality of liquid levels can be detected based on the vertical movement of one magnetic force generator.
[0120]
In particular, according to the invention of claim 5, there is an excellent effect that it is possible to avoid floating loss caused by damage to the outer wall for air sealing of the float member.
[0123]
  In particular, the claims6 or 7According to the invention, after the liquid developer is made to reach the liquid surface from the lower side to the upper side of the agent container, this time, compared to the case of performing the reverse stirring such that the liquid developer is moved from the upper side to the lower side this time. However, there is an excellent effect that the rise and undulation of the liquid level can be suppressed.
[0124]
  In particular, the claims7According to the invention, since the liquid developer is more smoothly stirred in the vertical direction, there is an excellent effect that the concentration of the developing substance of the liquid developer can be made more uniform.
[0125]
  Claim8, 9, 10 or 11According to the invention, there is an excellent effect that an error between the actual liquid level in the agent container of the developing device and the detected liquid level of the float type liquid level sensor can be reduced.
[0126]
  In particular, the claims9 or 10According to the invention, even when the developed substance concentration of the developed liquid developer is different from that before development, there is an excellent effect that it can be adjusted to the concentration before development and reused for development. Further, there is an excellent effect that the concentration of the liquid developer can be adjusted while appropriately maintaining the liquid level in the agent container.
[0127]
  In particular, claim 10According to the invention, there is an excellent effect that the presence or absence of the concentration adjusting agent in the replenishing means can be detected by the control means without providing a special sensor.
[0128]
  In particular, claim 11According to the invention, a liquid developer containing a developing material at a relatively high concentration of 5 to 40 [%] is used, which is less than when a liquid developer containing a developing material at a lower concentration is used. There is an excellent effect that a high-density image can be formed with a liquid amount. Further, unlike the case of using a liquid developer exceeding the viscosity of 10,000 [mPa · s], which increases the production cost, there is an excellent effect that a high density image can be formed at a relatively low price. Further, there is an excellent effect that unevenness in image density due to the dispersion unevenness can be suppressed as compared with the case of using a liquid developer having a viscosity of less than 100 m [Pa · s] which easily causes uneven dispersion of the developing substance.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a printer according to an embodiment.
FIG. 2 is a plan view showing a developing unit of the printer.
FIG. 3 is an exploded perspective view of an agent adjusting unit of the developing unit.
FIG. 4A is a perspective view showing a float type liquid level sensor of the agent adjustment unit.
(B) is a perspective view showing the float type liquid level sensor together with a concentration signal output means.
FIGS. 5A and 5B are perspective views showing a float type liquid level sensor of a comparative example. FIGS.
FIG. 6 is a block diagram showing a part of an electric circuit of the printer.
FIG. 7 is a flowchart showing density detection control of a density detection control unit of the printer.
FIG. 8 is a flowchart showing density adjustment control of a replenishment control unit of the printer.
FIG. 9 is a perspective view showing the same agent adjusting unit in a state where a tank lid is attached to the second tank.
FIG. 10 is a plan view showing a state of a flexible wing member in the second tank.
FIG. 11 is a plan view showing a state of the wing member that has rotated slightly more than in FIG. 10;
12 is a plan view showing a state of the wing member whose rotation has further advanced than in FIG. 11; FIG.
FIG. 13 is a plan view showing a second tank configured in a regular cylindrical shape together with the wing member.
FIG. 14 is a cross-sectional view showing a stirring state of the liquid developer in the right cylindrical second tank.
FIG. 15 is a perspective view showing a second tank having a taper at the bottom.
FIG. 16 is a plan view showing the flow of the liquid developer in the developing unit.
17 is a side view showing a modification of the flexible wing member (116) shown in FIG. 9. FIG.
FIGS. 18A and 18B are schematic views showing a float type liquid level sensor according to the present invention, respectively.
[Explanation of symbols]
1 Photosensitive drum (latent image carrier)
100 Development unit (developing device)
102 Collection unit (collection means)
105 Development roller (developer carrier)
115 Second tank (agent storage part)
116, 117 Wing member (stirring body)
118 Concentration detection means
135 Float type liquid level sensor
138 Shaft bar (shaft member)
139 Guide rod (guide rod)
141 Ring pin (ring holding member)
140 Float member
143 Hall element (magnetic force detection means)
144 Magnetic generator
145 taper
200 Control unit (control means)

Claims (11)

An agent container that contains a liquid developer containing a developing substance and a liquid carrier, a developer carrier that carries the liquid developer supplied from the agent container, and a liquid developer liquid in the agent container A float type liquid level sensor for detecting the position of the developer, and the developer contained in the liquid developer carried on the developer carrier is attached to the latent image carried on the latent image carrier of the image forming apparatus. In a developing device for developing an image,
The float type liquid level sensor includes a magnetic force generator, magnetic force detecting means for detecting the magnetic force of the magnetic force generator, and a spherical float member that moves up and down as the liquid level increases and decreases, and the float member of with the vertical movement varying the distance between the magnetic force generating member and the magnetic force detecting means, provided that detects the liquid level based on the detection result of the magnetic force detecting means Rutotomoni,
The inner wall of the side wall of the agent container as a stirrer that rotates and stirs the liquid developer in the agent container horizontally by rotating around the position shifted from the center of the plane section of the agent container. A flexible stirrer that rotates while flexibly in contact with the surface, and a non-flexible stirrer that generates a flow of liquid developer that moves along the rotational axis by rotation on the same axis developing apparatus is characterized in that a and body. An agent container that contains a liquid developer containing a developing substance and a liquid carrier, a developer carrier that carries the liquid developer supplied from the agent container, and a liquid developer liquid in the agent container A float type liquid level sensor for detecting the position of the developer, and the developer contained in the liquid developer carried on the developer carrier is attached to the latent image carried on the latent image carrier of the image forming apparatus. In a developing device for developing an image ,
A magnetic force generating member, and magnetic force detecting means for detecting the magnetic force of the magnetic force generating member, a float member which moves vertically along with the decrease of the liquid level, the whole is horizontally formed, the float member is fixed to both , Either one of the magnetic force generator or the magnetic force detection means is fixed at an intermediate position between both ends, and a ring holding member for holding the ring portion between the end portion and the intermediate position, and each ring portion A plurality of guide rods that are inserted to guide the vertical movement of the float member, and change the distance between the magnetic force generator and the magnetic force detection means with the vertical movement of the float member, Rutotomoni provided which detects the liquid level based on the detection result, as the float type liquid level sensor,
The inner wall of the side wall of the agent container as a stirrer that rotates and stirs the liquid developer in the agent container horizontally by rotating around the position shifted from the center of the plane section of the agent container. A flexible stirrer that rotates while flexibly in contact with the surface, and a non-flexible stirrer that generates a flow of liquid developer that moves along the rotational axis by rotation on the same axis developing apparatus is characterized in that a and body. The developing device according to claim 1 or 2,
The developing device characterized in that the distance is changed by arranging the magnetic force generator and the magnetic force detection means so as to move up and down together with the float member. . The developing device according to claim 3.
A developing device comprising a plurality of the magnetic force detecting means arranged in a vertical direction. The developing device according to claim 1, 2, 3 or 4,
A developing apparatus using the float member floating by a foamed resin . In any of the developing apparatus 請 Motomeko 1 to 5,
A developing device, characterized in that a non-flexible stirring member is provided that generates a flow of liquid developer that moves toward the bottom of the agent container along the rotational axis direction . The developing device 請 Motomeko 6,
A taper is provided at the bottom corner of the agent container, and the liquid developer that has collided with the bottom due to the movement along the rotation axis is guided upward by the taper on the side opposite to the axis deviation direction. A developing device. A latent image carrier that carries a latent image, a latent image forming unit that forms the latent image on the latent image carrier, and a developing material in a liquid developer that adheres to the latent image to develop the latent image. In an image forming apparatus comprising a developing device,
An image forming apparatus comprising the developing device according to claim 1, wherein the developing device according to claim 1, 2, 3, 4, 5, 6 or 7 is provided. The image forming apparatus according to claim 8 .
Concentration detecting means for detecting the developer concentration of the liquid developer in the agent containing portion, a collecting means for collecting the liquid developer after use for development and returning it to the agent containing portion, and adjusting the concentration in the agent containing portion Based on the detection results of the supply means for supplying the agent, the concentration detection means, and the float type liquid level sensor, the drive of the supply means is controlled to adjust the developer concentration of the liquid developer in the agent storage portion. And an image forming apparatus. The image forming apparatus according to claim 9 .
An image characterized in that the control means is configured to detect the presence or absence of a concentration adjusting agent in the replenishing means based on the driving time of the replenishing means and the detection result of the float type liquid level sensor. Forming equipment. The image forming apparatus according to claim 8, 9 or 10 ,
An image forming apparatus using a liquid developer in which a developing substance is dispersed at a concentration of 5 to 40 [%] and a viscosity is adjusted to 100 to 10,000 [mPa · s].

Images