JPH0511589A - Developing device using one-component developer - Google Patents

Abstract

PURPOSE:To stably regulate a developer layer to prescribed thickness on a developing device developing an electrostatic latent image held on an image carrier with a one-component developer. CONSTITUTION:The developing device is provided with a developer container 16a, the developing roller 16b of an elastic body provided so as to rotate and drive inside the container 16a, and a leaf spring member 16c for regulating the thickness of the developer layer, the leaf spring member is integrally supported by a rigid supporting member 16d capable of turning, on one end side of the leaf spring member, and is elastically brought into press-contact the developing roller to regulate the thickness of the one-component developer layer of the developing roller, on the other end side of the plate spring member, and the top end part of the other end side of the leaf spring member is chamfered to have roundness. The center of the turn of the rigid supporting member is actually positioned at the tangent of the leaf spring member and the developing roller, and the leaf spring member is supported by the rigid supporting member so as to give deflection length within 4mm to the other end side of the leaf spring member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing an electrostatic latent image held on an image bearing member such as a photoconductor or a dielectric with a one-component developer.

[0002]

2. Description of the Related Art In an electrostatic recording device such as an electrophotographic copying machine or an electrophotographic printer, an electrostatic latent image is written on an image carrier such as a photoconductor or a dielectric, and the electrostatic latent image is charged with a developer. The toner image is electrostatically developed, and then the charged toner image is electrostatically transferred to a recording medium such as recording paper and then fixed on the recording medium by heat, pressure, light or the like. As the developer used in the developing process, generally, two-component developer composed of powder fine particles of a colored resin, so-called toner, and magnetic carrier is widely known. A developing device using a two-component developer includes a stirrer that stirs the two-component developer to frictionally charge a toner and a magnetic carrier with each other,
A magnetic roller, that is, a developing roller that attracts a part of the magnetic carrier with a magnetic force to form a magnetic brush is provided, and a part of the developing roller is exposed and faces the image carrier. Toner electrostatically adheres to the magnetic brush formed around the developing roller, and the toner is conveyed by the rotation of the developing roller along with the magnetic brush to the area facing the image carrier, that is, the developing area. The electrostatic latent image is developed. In short, the magnetic carrier in the two-component developer has two functions, that is, the function of charging and rubbing the toner and the function of transporting the toner to the developing area.

A developing device using such a two-component developer has the advantage that the toner transportability, which affects the quality of the developed toner image, that is, the recording quality, is relatively good, but on the other hand, the toner transportability is good. In order to maintain it, it is necessary to maintain the component ratio of the toner and the magnetic carrier within a predetermined range, and the magnetic carrier must be regularly replaced, which is troublesome maintenance. It becomes a problem. That is, since the toner is consumed by the development, the toner must be replenished as appropriate, and when the magnetic carrier deteriorates, it must be replaced.

Therefore, as a developing device which does not require troublesome maintenance as in the case of a two-component developer, a developing device using a one-component developer consisting of powder fine particles of a colored resin, so-called toner, has been attracting attention. However, in the case of a one-component developer, particularly a non-magnetic type one-component developer, how to charge the toner and how to convey the toner to the developing area is an important issue. This is because the quality of the developed toner image, that is, the recording quality, is greatly affected by the charging and conveyance of the toner.

In a conventional developing device using a one-component developer, an elastic developing roller made of conductive synthetic rubber or conductive porous synthetic rubber is used as a developer carrying body for carrying toner to a developing area. The elastic developing roller is placed in the toner holding container and a part of the elastic developing roller is exposed to be brought into contact with the image carrier.
When the elastic developing roller is rotated, toner adheres to the surface around the rotation by frictional force to form a toner layer, which causes the toner to be conveyed to the developing area. In order to carry out the development of No. 2 at a uniform development density, it is necessary to regulate the layer thickness of the toner layer uniformly. Therefore, a layer thickness regulating member such as a blade or a roller is applied to the elastic developing roller to remove excess toner from the toner layer to make the toner layer uniform. On the other hand, for charging the toner, frictional charging with respect to the elastic developing roller and the layer thickness regulating member is also used, but since such frictional charging is easily affected by environmental fluctuations such as temperature and humidity,
It is also possible to form the layer thickness regulating member from a conductive material and apply a voltage of a predetermined polarity thereto to positively inject charges into the toner when regulating the layer thickness of the toner. Of course, when using triboelectrification, the work function between the toner, the elastic developing roller and the layer thickness regulating member is taken into consideration in order to give a predetermined amount of electric charge to the toner with a desired polarity, and charge injection is also required. When used, the material of the layer thickness regulating member is limited to a conductive material.

By the way, as a problem of the developing device for a one-component developer as described above, it is unexpectedly difficult to maintain the toner layer thickness uniform by the layer thickness regulating member stably over a long period of time. That point is pointed out. For example, as a layer thickness regulating member capable of injecting charges, for example, a sharp edge portion is formed on a metal blade, and the edge portion is elastically engaged with an elastic developing roller to remove excess toner. It has been proposed to make the layer thickness uniform, but in this case, in order to guarantee the uniform toner layer thickness, the processing accuracy of the sharp edge of the metal blade is 2 μm.
It is necessary to do the following. This is because the toner particle size is generally about 5 to about 10 μm, which is extremely fine. Therefore, if the processing accuracy of the edge portion is 2 μm or more,
This is because uneven streaks remain as traces on the layer thickness control surface of the toner, and the traces also appear as white streaks or black streaks in the recorded image. Even if the processing accuracy of the sharp edge part of the metal blade can be set to 2 μm or less, such an edge part is not only easily damaged, but also the processing cost is very high. It is practically impossible to put this into practical use.

It has also been proposed to regulate the toner layer thickness by pressing the flat surface of a metal blade or the rotating surface of a metal roller against an elastic developing roller. in this case,
Although it is possible to perform highly accurate processing on such a flat surface or a rotating surface at a relatively low cost, in order to regulate the toner layer thickness to a predetermined thin thickness, the metal blade or metal for the elastic developing roller is used. The pressure contact force of the roller must be increased considerably, which causes the toner particles to be crushed and physically fixed to the flat surface or the rotating surface. Of course, when the toner particles adhere to the flat surface of the metal blade or the rotating surface of the metal roller, uneven streaks remain as traces on the toner layer thickness regulation surface, and the traces are recorded on the recorded image as in the case described above. Will appear. Although a hard polymer material or the like can be considered as the material of the layer thickness regulating member, in this case, the advantage of controlling the charging of the toner by the charge injection cannot be obtained.

[0008]

Therefore, a leaf spring member is used as a metal layer thickness regulating member capable of stably regulating the toner layer thickness for a long period of time and capable of performing highly accurate processing at a relatively low cost. It has been proposed, an example of which is shown in FIG. In the figure, L is a leaf spring member, S is a support for the leaf spring member L, and D is an elastic developing roller. The leaf spring L is formed of a suitable metal material such as stainless steel, phosphor bronze, cold rolled steel sheet, etc., and its characteristic point is that the edge portion on the tip side is chamfered and rounded (so-called. R chamfer). As is clear from FIG. 14, the leaf spring member L is held by the support S in such a manner that the chamfered tip edge thereof is elastically pressed against the elastic developing roller D. That is, the leaf spring member L is pressed by the elastic developing roller D by its own spring force, and when the elastic developing roller D is rotated as shown by the arrow in the figure, the elastic developing roller D causes the leaf spring member L to rotate. Since most of the excess toner from the carried toner layer is removed by the chamfered leading edge of the leaf spring member L, the toner layer thickness is regulated by the pressing force on the flat surface of the leaf spring member L. The pressing force of the flat surface with respect to the elastic developing roller D can be made relatively small, so that the toner particles can be prevented from sticking to the flat surface.
On the other hand, it is possible to perform the high-precision machining of the flat surface of the leaf spring member L and the high-precision chamfering of the tip edge thereof at a relatively low cost, and the chamfered tip edge is higher than the edge portion described above. Far less susceptible to damage.

However, as a problem of the leaf spring member L as described above, when the toner layer thickness is regulated, vibration is easily generated in the leaf spring member L and the toner layer thickness fluctuates periodically. It has been pointed out. That is, the leaf spring member L
Receives a frictional force F in the tangential direction during the rotation of the elastic developing roller D, so that the leaf spring member L fluctuates in the direction indicated by arrow A ₁ and at the same time vibrates in the direction indicated by arrow A ₂ . When the leaf spring member L vibrates in this way, the elastic developing roller D
The upper toner layer thickness naturally fluctuates, and this fluctuation of the toner layer thickness affects the development density of the electrostatic latent image, and at the portion where the toner layer thickness is thick, the toner charge amount is insufficient and so-called fog ( (Toner contamination in the background area of the electrostatic latent image) occurs. Therefore, the present invention uses a metal leaf spring member as a layer thickness regulating member in a developing device using a one-component developer consisting only of toner so that charge can be injected into the toner. An object of the present invention is to provide a structure in which the layer thickness of the toner layer can be stably regulated to a predetermined thickness without vibrating when regulating the layer thickness of the layer.

[0010]

In order to achieve the above object, according to the present invention, there is provided a developing device for developing an electrostatic latent image held on an image bearing member with a one-component developer, comprising: There is provided a developing device having a configuration as described in 1. That is, it is provided with a developer holding container for containing a one-component developer and an elastic developing roller rotatably provided in the developer holding container. It is arranged so as to be exposed from the holding container so as to be in contact with the image carrier, and the one-component developer is attached to the rotation surface of the container to form a one-component developer layer, and the area where it is in contact with the image carrier by its rotation. And a leaf spring member for regulating the layer thickness of the one-component developer layer of the elastic developing roller, the leaf spring member being rotatable at one end thereof. The elastic support roller is integrally supported by the rigid support member, and is elastically pressed into contact with the elastic development roller to regulate the layer thickness of the one-component developer layer of the elastic development roller on the other end side. The other end of the leaf spring member is chamfered In the developing device provided with a single component developer layer, the rotation center of the rigid support member is substantially positioned on a tangent line between the leaf spring member and the elastic developing roller, and the spring member has a layer thickness of the one-component developer layer. There is provided a developing device characterized in that the developing device is supported by a rigid support member so as to give a bending length of 4 mm or less to the other end side so as to stably regulate the toner to a predetermined thickness.

[0011]

As apparent from the above construction, in the developing device according to the present invention, since the center of rotation of the rigid support member is positioned on the tangent line between the leaf spring member and the elastic developing roller, the elastic member The frictional force applied to the leaf spring member by the developing roller is directed to the center of rotation of the rigid support member, so that no rotational moment acts on the rigid support member, thus substantially preventing vibration of the leaf spring member. Can be done. Further, since the leaf spring member is supported by the rigid support member so as to give the bending length within 4 mm to the other end side in order to stably regulate the layer thickness of the one-component developer layer to a predetermined thickness, electrostatic latent Good development quality can be obtained during image development.

[0012]

Embodiments of the present invention will now be described with reference to FIGS. 1 to 13 of the accompanying drawings. First, Fig. 1
2, a basic configuration of a laser printer is schematically shown as an example of an electrostatic recording device to which the developing device according to the present invention is applied. In this laser printer, a photosensitive drum 10 is used as an image carrier. The photosensitive drum 10 is formed by forming a photoconductive material layer, that is, a photosensitive material layer on the surface of a cylindrical base body made of, for example, aluminum. Examples of such photosensitive materials include organic photosensitive materials, selenium-based photosensitive materials, and
Although an amorphous silicon photosensitive material or the like is used, in this embodiment, the photosensitive drum 10 is an OPC photosensitive drum using an organic photosensitive material. During the recording operation, the photosensitive drum 10 is rotated in the direction indicated by the arrow a so that the peripheral speed of the photosensitive drum 10 is 70 mm / s.

A negative charge is applied to the photosensitive material layer of the photosensitive drum 10 by a suitable charger such as a scorotron charger 12, and the surface potential of the charged region is set to -650V, for example. In this embodiment, since the organic photosensitive material is used as the photosensitive material, the photosensitive drum 10 is given a negative charge, but the selenium-based photosensitive material is given a positive charge. In the case of an amorphous silicon photosensitive material, negative or positive charges are given. An electrostatic latent image is written on the charged area of the photoconductor drum 10 by the laser beam scanning unit 14, and the electrostatic latent image is written by using the laser beam LB emitted from the laser beam scanning unit 14 as a bus line of the photoconductor drum 10. This is performed by repeatedly scanning the laser beam along the direction and blinking the laser beam LB based on binary image data from, for example, a word processor or a microcomputer. That is, the electric charge at the portion irradiated with the laser beam LB is released (the aluminum cylindrical base of the photoconductor drum 10 is grounded), whereby a binary electrostatic latent image is formed by the potential difference in the charging area. Will be. Incidentally, a portion where the electric charge is removed by the irradiation of the laser beam LB is called a charge well, and its potential is increased from about −650V to about −100V (decreased in absolute value).

The electrostatic latent image written by the laser beam scanning unit 14 is developed as a charged toner image by the developing device 16. The developing device 16 includes a developer container 16a containing a one-component developer consisting of only toner, and a developing roller 16b arranged in the developer container 16a and rotated in the direction of the arrow shown in the drawing. As shown in the drawing, a part of the developing roller 16b is a developer container 16
It is exposed from a and is brought into contact with the photosensitive drum 10. The shaft of the developing roller 16b is drivingly connected to the same drive source (not shown) as the photosensitive drum 10 via an appropriate transmission gear train (not shown), and the peripheral speed thereof is 70 mm / mm. It is rotated to 175 mm / s, which is about 2.5 times s. The developing roller 16b can be configured as a conductive elastic roller, but is preferably formed of a conductive porous rubber material, and examples of such a conductive porous rubber material include polyurethane sponge,
Carbon black or the like may be mixed as a conductivity-imparting agent into urethane rubber / sponge, silicon rubber / sponge, or the like. In this embodiment, a porous urethane sponge (trade name of Rubycell made by Toyo Polymer) is used,
The average pore diameter of this porous urethane sponge is 10 μm,
The number of pore cells is 200 cells / inch, and the volume resistance is 10 ⁴ to 10
⁷ Ωcm and Asker C hardness is 23 degrees. The developing roller 16b made of such a material has a good toner-conveying property, and when the developing roller 16b is rotated, the toner adheres to the rotating surface of the developing roller 16b to sequentially form a toner layer. At the time of developing the electrostatic latent image, a developing bias voltage of -300 V is applied to the developing roller 16b, so that the charged toner is electrostatically attached to the electrostatic latent image area, but is attached to the background area. Is blocked. The non-magnetic type one-component developer used here has a volume resistance of 4 × 10 ¹⁴ Ωcm and an average particle size of 12
A polyester negative electrode toner having a particle size of 0.5 μm and 0.5% external addition of silica is used.

Further, the developing device 16 is provided with a layer thickness regulating member 16c for regulating the layer thickness of the toner layer formed on the developing roller 16b to a predetermined thickness, and this layer thickness regulating member 16c is made of a suitable metal material. However, in the present embodiment, the leaf spring member is made of stainless steel (SUS304-CSP-3 / 4H) and has a thickness of 0.1 mm. The layer thickness regulating member, that is, the leaf spring member 16c is integrally supported by a rotatable rigid support member 16d at one end thereof, and the rigid support member 16d is rotatably supported between both walls of the developer container 16a. It is mounted on the shaft 16e. As shown in FIG. 1, a suitable spring means, for example a coil spring 16f, is applied to the rigid support member 16d, whereby the rigid support member 16d is elastically biased in the direction of rotation indicated by the arrow in the figure, and The leaf spring member 16c is elastically brought into pressure contact with the developing roller 16b at a line pressure of, for example, 35 gf / cm at the other end side thereof, so that the layer thickness of the toner layer on the developing roller 16b can be regulated. Further, the tip end edge on the other end side of the leaf spring member 16c is chamfered and rounded (so-called R chamfer),
The radius R of the rounded tip is, for example, 0.05 mm.
The leaf spring member 16c is positioned by its rounded tip so as to scrape off the excess toner from the developing roller 16b, and the rounded tip of the leaf spring member 16c is preferably the contact point between the leaf spring member 16c and the developing toner 16c. It is located in the vicinity. When the developing device 16 is operated, a charge injection voltage of, for example, −400 V is applied to the leaf spring member 16c. Therefore, when the layer thickness of the toner layer is regulated by the leaf spring member 16c, negative charge injection to the toner is positively performed. The toner is then charged with a predetermined amount of negative charge.

The point to be noted here is that, as shown in FIG. 2, when the pressing force of the coil spring 16f against the rigid support member 16d is released, the center of rotation of the rigid support member 16d, that is, the center of the shaft 16e. The leaf spring member 16c is positioned on the tangent line between the developing roller 16b, and therefore, when the leaf spring member 16c regulates the toner layer thickness, the frictional force F received from the developing roller 16b by the leaf spring member 16e is equal to that of the rigid support member 16d. Since it is directed to the center of motion, there is no component force that causes a rotational moment to act on the rigid support member 16d from the frictional force F, and thus the leaf spring member 1
The vibration of 6c can be substantially prevented.
Further noteworthy is that in the present embodiment, the leaf spring member 16c is
Flexing length FL, that is, the distance from the supporting tip of the rigid supporting member 16d to the leaf spring member c to the rounding tip of the leaf spring member 16c is about 4 mm or less and the developing roller 16
The contact width of the leaf spring member 16c with respect to b is 2.4 mm or more, which allows the toner layer thickness to be stably regulated to a predetermined thin thickness. Note that this will be described later in detail.

The developing device 16 further includes a toner collecting / supplying roller 16g, a paddle rotating blade 16h, and a toner stirring blade 16i.
It is equipped with. The toner collecting and supplying roller 16g is preferably a conductive sponge, for example, the number of pore cells is about 40 cells / inch,
The developing roller 16b is made of a conductive sponge with a volume resistance of 10 ⁴ Ωcm (Bridgestone Everlite TS-E).
And is rotated in the same direction as the developing roller 16b. In addition, the toner collecting and supplying roller 16g
Is rotated so that its peripheral speed is 228 mm / s. The toner collecting / supplying roller 16g scrapes off toner not used for development from the developing roller 16b on one side of the pressure contact area with the developing roller 16b, that is, on the right side of FIG. 1, and on the other side, that is, the developing roller on the right side of FIG. 1
It functions to positively supply and adhere toner to 6b. A bias voltage of -400V is applied to the toner collecting / supplying roller 16g, which prevents the toner particles from entering the sponge material of the toner collecting / supplying roller 16g, and the toner is electrostatically developed on the developing roller. Will be supplied to 16b. The paddle rotating blade 16h is rotated so as to send the toner in the developer container 16a to the toner supply side of the toner collecting and supplying roller 16h, and the toner stirring blade 16i eliminates dead stock of toner in the developer container 16a. It functions as appropriate to send the toner to the paddle rotor 16h. Note that reference numeral 16
j is a deformable seal material such as a soft sponge, and the seal material 16j prevents the toner from flowing out.

The charged toner image obtained in the developing process is then electrostatically transferred onto a recording medium such as recording paper P by a suitable transfer device such as a corotron transfer device 18. That is, the corotron transfer device 18 gives the recording paper P an electric charge having a polarity opposite to that of the charged toner image, that is, a positive electric charge, whereby the charged toner image is transferred from the photosensitive drum 10 to the recording paper P.
It is electrostatically transferred onto. The recording paper P is temporarily stopped at the pair of registration rollers 20 after being fed from a paper feed cassette (not shown), and then the pair of registration rollers is driven at a predetermined timing. The recording paper P is introduced into the contact area between the photoconductor drum 10 and the corotron transfer device 18, so that the charged toner image can be transferred onto the recording paper P at the predetermined position. Immediately after passing through such a transfer process, a negative charge is applied to the recording paper P by the static eliminator 22, thereby neutralizing a part of the positive charges of the recording paper P, and thus the recording paper P and the photosensitive drum. The electrostatic attraction between the recording paper P and the recording paper P is weakened so that the recording paper P is electrostatically attracted by the photoconductor drum 10 and is not caught therein. Subsequently, the recording paper P is sent to the thermal fixing device 24, where the transferred toner image is thermally fixed on the recording paper P. That is, the heat fixing device 52 comprises a heat roller 52a and a backup roller 52b, and when the recording paper P is passed between them, the transferred toner image is melted by heat and firmly fixed onto the recording paper P. In FIG. 1, reference numeral 26 indicates a toner scraping blade for removing the residual toner from the photosensitive drum 26. The toner removed by the toner scraping blade 54 is stored in a toner reservoir 56. Further, reference numeral 30 indicates an LED array functioning as a charge eliminating lamp. The LED array 30 removes the residual charge from the photoconductor drum 10, and the charge eliminating region is given a negative charge again by the scorotron charger 12.
The above recording cycle is repeated.

In the embodiment described above, the leaf spring member 16
Although stainless steel was used as the metal material of c, the leaf spring member 16c may be formed of other metal materials such as phosphor bronze, elastic spring alloy, beryllium copper alloy, and cold rolled steel plate. Further, in the present invention, the center of rotation of the rigid support member 16d is substantially positioned on the tangent line between the leaf spring member 16c and the developing roller 16b. The term "target" means that if the vibration of the leaf spring member 16c is prevented, the center of rotation of the rigid support member 16d is the leaf spring member 16c.
Should be interpreted as meaning that it may be slightly displaced from the tangent line between the elastic developing roller 16b and the elastic developing roller 16b. In short, when the leaf spring member 16c receives a frictional force in the tangential direction from the developing roller 16b, the leaf spring member 1 is caused by the component force.
It should be interpreted as meaning that vibration does not occur in 6c.

As described above, in this embodiment, the bending length FL of the leaf spring member 16c is about 4 mm or less and the developing roller 1
By setting the contact width of the leaf spring member 16c with respect to 6b to be 2.4 mm or more, the toner layer thickness can be stably regulated to a predetermined thin thickness, which was confirmed by the following experiment. It is a thing. First, prior to the experiment, a leaf spring member support mechanism as shown in FIG. 3 was created. In this leaf spring member support mechanism, the shaft 32
A rigid support member 34 that is detachable from the rigid support member 34 is provided, and the leaf spring member 16c is supported by the rigid support member 34. A coil spring 36 acts on the rigid support member 34, whereby the leaf spring member 16c moves to the developing roller 16b.
Is elastically pressed against a predetermined pressure. The rotation center of the rigid support member 34, that is, the center of the shaft 32 is located on the tangent line between the leaf spring member 16c and the developing roller 16b, so that the frictional force F (FIG. 4) acting on the leaf spring member 16c is the shaft. Since it goes to the center of 32, the leaf spring member 1
The component force that vibrates 6c is not generated from the frictional force F. In short, the leaf spring member support mechanism of FIG. 3 is equivalent to the leaf spring member support mechanism shown in FIG.

In the experiment, FIG. 5, FIG. 6, FIG. 7 and FIG.
4 types of rigid support parts 34 ₁ , 34 ₂ , 34
₃ and 34 ₅ were prepared, and a leaf spring member 16c having the same size was attached to each of these rigid supporting members. That is, in FIG. 5, the distance from the center of rotation of the rigid support member 34 ₁ to its supporting tip is 23 mm, the distance from the supporting tip to the leaf spring member 16c, that is, the bending length is 2 mm, and in FIG. distance to the support from the tip 34 _{and second} turning center is a 22 mm, distance or bending length of the leaf spring member 16c from the support tip is a 3 mm, from its rotational center in FIG. 7, the rigid support member 34 ₃ The distance to the support tip is 21 mm, and the leaf spring member 16c is provided from the support tip.
8 is 4 mm, and in FIG. 8 the distance from the center of rotation of the rigid support member 34 ₄ to its supporting tip is 20 mm, and the distance from the supporting tip to the leaf spring member 16c, that is, the bending length is 5 mm. It is said that. In short, the rigid support members 34 ₁ , 34 ₂ , 34 ₃ and 34 ₄ are similar except that the position of the supporting tip with respect to the leaf spring member 16 c is different.

The developing process was carried out for each of the cases shown in FIGS. 5 to 8, and the layer thickness of the toner layer at that time was measured. The layer thickness of the toner layer was measured by using a laser scanning micro measuring device 38 as shown in FIG. The measurement procedure there will be described below. (1) After performing the developing process with each set protrusion amount, the developing roller 16b was gently taken out from the developing device 16, and the developing roller 16b was installed in the laser scanning micro measuring device 38 of FIG. Laser Scan Micro Measuring Device 38
A light emitting portion 38a and a light receiving portion 38b are provided in the center, and a reference shield wall 38c that shields a part of the laser beam emitted from the light emitting portion 38a is provided in the center between them. In Figure 9,
The toner layer formed around the developing roller 16b is exaggeratedly illustrated and is indicated by reference numeral TL. Developing roller 16b for the laser scanning micro measuring device 38
With respect to the setting, the toner layer thickness is regulated by a leaf spring member 16c when the developing roller 16b is taken out of the developing device 16, that is, in a predetermined area in the circumferential direction of the developing roller 16b, and on the photosensitive drum 10 side. Area that has not yet reached (in short, in FIG. 1, an upper arc area of the developing roller 16b, which is an area between the contact point with the leaf spring member 16c and the contact point with the photoconductor drum 10). Is positioned above the reference shielding wall 40c. (2) The distance L1 was measured in such an installed state. (3) Then, the developing roller 16b is attached to the laser scanning micro-measuring device 38, and nitrogen gas is blown to the developing roller 16b to completely remove the toner layer, and the distance L2 is measured there. (4) Then, the calculation of L2-L1 was performed to calculate the toner layer thickness. (5) The above measurement was repeated 5 times for each of the cases of FIGS. 4 to 8 to obtain a macroscopic toner layer thickness average value and the variation degree thereof.

The above measurement results are shown as a graph in FIG. As is clear from the graph, when the bending length of the leaf spring member 16c is set to 5 mm (FIG. 8), the macroscopic average layer thickness of the toner layer is 12.7 μm, which is relatively large, and the variation degree is 3σ ( The standard deviation (σ) is also large at 5.4 μmm. The reason for this is that as the bending length of the leaf spring member 16c increases, its flexibility increases, so that the layer thickness regulation force of the toner layer becomes weaker and vibration easily occurs, and thus the toner layer macroscopically averages. Not only the layer thickness but also the degree of variation becomes large. As shown in the graph of FIG. 10, when the degree of variation is 5.4 μm, the layer thickness of the toner layer often exceeds the upper limit value of 14.5 μm, which is considered to maintain good developing quality. When the layer thickness of the toner layer exceeds the upper limit value of 14.5 μm, the charge amount of the normal toner decreases, which means that some toner particles may be almost uncharged. Since such uncharged toner particles are not constrained by the developing bias voltage applied to the developing roller 16c, they can be attached to the background area of the photosensitive drum 10, which causes fog.

Next, 20,000 sheets of recording paper (A4 size) were subjected to running recording for each of the cases shown in FIGS. 5 to 8 to evaluate the recording quality. At this time, all black recording (so-called solid black), all white recording (no electrostatic latent image is formed) on the recording paper, and parallel oblique pattern recording of 1-dot diagonal line with an angle of 45 ° (the pitch between horizontal diagonal lines is 8 dots). ), The evaluation target is the first recorded one, and the recording paper (A
(4 size) After running recording of 20,000 sheets. The evaluation result is shown in the graph of FIG. In the graph, the black circles represent the fog density OD measured by an optical reflection densitometer for the entire white recording, and the open squares represent the maximum value of the average optical reflection density OD in the area of 4 mm in diameter for the parallel inclined pattern (black. The density difference ΔOD between the stripe) and the minimum value (white stripe) is shown. As is clear from the graph of FIG. 11, when the bending length of the leaf spring member 16c is 3 mm (FIG. 5) or less, the concentration difference ΔOD rapidly increases. Only when the bending length of the leaf spring member 16c is 2 mm (FIG. 5), black streaks and white streaks with a large density difference ΔOD0.08, which were not initially seen in the parallel oblique line pattern recording, are observed. It was well above the possible concentration difference ΔOD 0.03. Then, when the developing device is disassembled and the cause is investigated, the toner particles are fixed to the layer thickness regulating surface of the leaf spring member 16c, and the fixed portion is the rigid support member 34 located on the back side of the layer thickness regulating surface. Matched the support tip of ₁ . The reason for this is that the leaf spring member 16c has a short bending length, so its flexibility is small, and the supporting tip of the rigid support member 34 ₁ makes contact with the leaf spring member 16c and the developing roller 16b as shown in FIG. The developing roller reaches the area width (2.4 mm in this embodiment), so that the flexure of the leaf spring member 16c is pushed between the developing roller 16b and the developing roller 16b during running recording of 20,000 recording sheets. It is bent so that it is a little far from, and the toner is pressed down in the meantime. That is, the toner thus pressed down is pressed against the layer thickness regulating surface of the leaf spring member 16c and fixed there. on the other hand,
When the bending length of the leaf spring member 16c was 4 mm or less and the contact area width between the leaf spring member 16c and the developing roller 16b was 2.4 mm or more, the evaluation of the recording quality was good. That is, a sufficient recording density OD1.4 was obtained even after running recording of 20,000 sheets of recording paper, density unevenness was as small as 0.10 even in the case of full black recording, and the fog density was a small value (fog density OD ≦ 0.01). : The value obtained by subtracting OD0.1 of the recording paper). In short, in the above embodiment, the flex length of the leaf spring member 16c should be in the range of 2.4 mm to about 4 mm.

By the way, as described above, in the above embodiment, the leading edge of the leaf spring member 16c, that is, the leading edge on the toner layer thickness regulation side is chamfered and rounded (so-called R chamfer). The radius R of the rounded tip is, for example, 0.05
However, this rounded tip can also be a free factor in obtaining good recording quality, and the following experiment was conducted for this.

0.2 mm thick stainless steel plate material (SUS 631-CSP
-4 / 3H), 4 leaf spring members are prepared, and 3 of them are rounded and chamfered with a super grindstone, and the radius of the rounded tip is R = 0.10 mm, R =
0.07 mm and R = 0.03 mm, and the remaining one sheet was not rounded and chamfered. Recording operation was actually performed using each of these four types of leaf spring members, and the recording quality on recording paper was evaluated. The outline of each recording operation is as follows. (1) The bending length of the leaf spring member 16c was set to 3 mm. (2) Each leaf spring member was pressed against the developing roller 16b with a linear pressure of 35 gf / cm. (3) Each recording operation was performed in an environment where the temperature was 40 ° and the relative humidity was 80% RH, which was likely to cause fog. (4) In each recording operation, full black recording (so-called black solid), full white recording (without forming an electrostatic latent image) and 1-dot diagonal parallel oblique line pattern recording (horizontal direction) on the recording paper. The pitch between the shaded lines was 8 dots), and the evaluation targets were the first recorded one and the one after running recording of 20,000 recording sheets (A4 size).

The evaluation results are shown in the graph of FIG. In addition,
The horizontal axis of the graph is the radius R of the rounded tip of the leaf spring member.
The right vertical axis shows the diameter of the parallel diagonal pattern recording 4 mm.
The difference between the maximum value (black streaks) and the minimum value (white streaks) of the average optical reflection density OD in the area of is shown, and the left vertical axis thereof is the fog density of the entire white recording measured with an optical reflection densitometer. .. As is clear from this graph, in the case of the parallel oblique line pattern recording in the case of using the leaf spring member (R = 0) having no rounding tip, the difference in average recording density is as large as 0.08 and the distinguishable density difference is 0.03. , And black streak-like and white streak-like unevenness in the recording density was observed on the recording paper. On the contrary,
Leaf spring member with rounded chamfer (R = 0.10 mm, R =
In the case of 0.07 mm and R = 0.03 mm), it is understood that the recording density difference can be suppressed to 0.03 or less. In addition, high temperature and high humidity (40 degrees / 8
In the whole white recording performed under the environment of 0% RH), when the leaf spring member of R = 0.10 mm is used, the density difference of the discrimination limit is 0.01
(The value obtained by subtracting the optical reflection density OD0.10 of the recording paper) was exceeded, indicating that fog is likely to occur. In short, when the rounded chamfering process is applied to the tip of the leaf spring member 16b, that is, the tip on the toner layer thickness regulation side, the radius R should be within the following range. 0.03mm ≤ R ≤ 0.07mm

Further, regarding three types of rounded chamfered leaf spring members (R = 0.10 mm, R = 0.07 mm, R = 0.03 mm), linear pressure (that is, toner layer thickness regulating pressure) against the developing roller 16b. Experiments were also conducted to see how the toner layer thickness changes when V is changed. The result is shown in the graph of FIG. As is clear from the graph, as a general tendency, as the radius R of the rounded tip of the leaf spring member becomes smaller, the toner layer thickness can be regulated to be thin with a smaller linear pressure. For example, looking at the upper limit value (0.07 mm) of the radius R of the rounded tip of the leaf spring member, it can be seen that the linear pressure on the developing roller 16b needs to be 30 gf / cm or more. For the three types of round chamfered leaf springs, the linear pressures on the developing roller 16b were set to 12 gf / cm, 30 gf / cm, 45 gf / cm and 60 gf / cm, respectively, and the same recording as above was performed. Paper (A4 size) was subjected to a running recording test 20,000 times, and then the recording quality was evaluated. As a result, when the linear pressure was 60 gf / cm 2, the toner particles adhered to all the leaf spring members as if they were crushed, and black lines and white lines with a maximum density difference of 0.16 were generated in the parallel oblique line pattern recording. From the above, the linear pressure of the leaf spring member 16c against the developing roller 16b is about 30 gf / cm to about 45 gf.
It can be seen that it is preferable to set it within the range of / cm 2.

[0029]

As is apparent from the above construction, in the developing device according to the present invention, a metal leaf spring capable of injecting electric charges in order to regulate the layer thickness of the one-component developer layer on the image carrier. It is possible to apply the member to the image carrier without vibrating, and the plate spring member is given a predetermined bending length, which stabilizes the layer thickness of the one-component developer layer to a predetermined thickness. Therefore, the development quality of the electrostatic latent image, that is, the recording quality can be favorably maintained.

[Brief description of drawings]

FIG. 1 is a schematic view of a laser printer to which a developing device according to the present invention is applied.

FIG. 2 is an enlarged view showing a developing roller, a leaf spring member and a rigid support member taken out from the developing device of FIG.

FIG. 3 is a schematic view showing a leaf spring member support mechanism configured so that a rigid support portion of a leaf spring member in a developing device can be replaced.

FIG. 4 is a partially enlarged view showing a contact portion between a plate spring member and a developing roller of the plate spring member support mechanism shown in FIG. 3 in an enlarged manner.

5 is a schematic view in which a rigid support member that supports the leaf spring member so that the bending length of the leaf spring member is 2 mm is attached to the leaf spring member support mechanism of FIG.

6 is a schematic view in which a rigid support member that supports the leaf spring member so that the bending length of the leaf spring member is 3 mm is attached to the leaf spring member support mechanism of FIG.

7 is a schematic view in which a rigid support member that supports the leaf spring member so that the bending length of the leaf spring member is 4 mm is attached to the leaf spring member support mechanism of FIG.

8 is a schematic view in which a rigid support member that supports the leaf spring member so that the bending length of the leaf spring member is 5 mm is attached to the leaf spring member support mechanism of FIG.

FIG. 9 is an explanatory diagram of a measuring method for measuring the layer thickness of the toner layer on the developing roller with a laser scanning micro measuring device.

10 shows the measurement results when the layer thickness of the toner layer on the developing roller is measured according to the measuring method of FIG. 9 when the bending length of the leaf spring member as shown in FIGS. 5 to 8 is set. It is a graph.

FIG. 11 is a graph showing evaluation of recording quality when running recording of 20,000 recording papers was performed for each of the bending lengths of the leaf spring members shown in FIGS. 5 to 8.

FIG. 12 is a graph showing the relationship between the radius of the rounded tip of the leaf spring member and the layer thickness of the toner layer.

FIG. 13 is a graph showing the relationship between the contact pressure of the leaf spring member against the developing roller and the layer thickness of the toner layer, with the radius of the rounded tip portion of the leaf spring member appropriately changed.

FIG. 14 is a schematic view showing a conventional example in which a leaf spring member is used as a layer thickness regulating member for regulating the layer thickness of the toner layer on the developing roller.

[Explanation of symbols]

 10 ... Photosensitive drum 12 ... Scorotron charger 14 ... Laser beam scanning unit 16 ... Developer 16a ... Developer container 16b ... Developing roller 16c ... Leaf spring member 16d ... Rigid support member 16e ... Shaft 16f ... Coil spring 16g ... Toner recovery Supply roller 18 ... Corotron transfer device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Nishio 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (1)

Claims: What is claimed is: 1. A developing device for developing an electrostatic latent image held on an image carrier (10) with a one-component developer, the developer holding device containing the one-component developer. A container (16a) and an elastic developing roller (16b) rotatably provided in the developer holding container are provided. The elastic developing roller exposes a part of the elastic developing roller from the developer holding container. Is arranged so as to be in contact with the image carrier, and a one-component developer is adhered to the rotation surface of the image carrier to form a one-component developer layer, and the toner is conveyed to a region in contact with the image carrier by its rotation. And a leaf spring member (16) for regulating the layer thickness of the one-component developer layer of the elastic developing roller.
c), the leaf spring member is integrally supported by a rigid support member (16d) rotatable at one end side thereof, and the leaf spring member of the one-component developer layer of the elastic developing roller is provided at the other end side thereof. In the developing device, which is elastically pressed into contact with the elastic developing roller to regulate the layer thickness, and the tip end portion of the leaf spring member on the other end side is chamfered and rounded, the rigid support member The rotation center of (16d) is substantially positioned on the tangent line between the leaf spring member (16c) and the elastic developing roller (16b), and the leaf spring member has a predetermined thickness of the one-component developer layer. A developing device, which is supported by the rigid support member so as to give a bending length of 4 mm or less to the other end side so as to stably control the thickness.