JPH0511588A - Developing device using one-component developer - Google Patents

Abstract

PURPOSE:To prevent a leaf spring member from being vibrated at the time of regulating the thickness of a developer layer by using the leaf spring member made of metal as a layer thickness regulating member, so as to inject a charge into a one-component developer. CONSTITUTION:In the developing device, a developing roller 16b is disposed so as to oppositely contact with an image carrier 10 in such a manner that a part of the developing roller 16b is exposed from a developer container 16a, sticks the one- component developer to the rotary face of the developing roller 16b to form a one- component developer layer and simultaneously, carry it to a region oppositely contacting with the image carrier by the rotation of the developing roller 16b, further, the leaf spring member 16c for regulating the thickness of the one-component developer layer of the developing roller is provided, integrally supported by a rigid supporting member 16d capable of turning, on one end side of the plate spring member, and elastically press-contacted to the developing roller to regulate the thickness of the one-component developer layer of the developing roller, on the other end side of the leaf spring member, and the center of the turn of the rigid supporting member 16d is actually positioned at the tangent of the leaf spring member 16c and the developing roller 16b.

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 development process, generally, a powdery fine particles of a colored resin, that is, a two-component developer including a toner and a 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 is given two functions, that is, the function of charging and rubbing the toner and the function of transporting the toner to the developing area.

In a developing device using such a two-component developer, there is an advantage that the toner transportability that affects the quality of the developed toner image, that is, the recording quality is relatively good, but the good toner transportability is In order to maintain it, it may be necessary to maintain the component ratio of the toner and the magnetic carrier within a predetermined range, and the magnetic carrier may have to be replaced regularly, 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, greatly depends on the charging and the transportation 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. This elastic developing roller is placed in the toner holding container and a part of the developing roller is exposed and brought into contact with the image carrier.
When the elastic developing roller is rotated, the toner adheres to the peripheral surface of the rotation due to 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 uniformly regulate the layer thickness of the toner layer. Therefore, a layer thickness regulating member such as a blade or a roller is applied to the elastic developing roller, whereby excess toner is removed from the toner layer to make the toner layer uniform. On the other hand, as for the charging of 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 changes 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 surprisingly 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 electric 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 ensure 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 diameter is generally about 5 to about 10 μm, which is extremely fine, so that the processing accuracy of such an 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 of the metal blade can be set to 2 μm or less, such an edge is not only susceptible to damage, 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 regulated. 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 over a long period of time and capable of performing highly accurate processing at a relatively low cost. It has been proposed that two typical examples are 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, or the like, and is characterized in that the edge portion on the tip side is chamfered and rounded (so-called. R chamfer).
As is apparent 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, in the example of FIG. 14A, the leaf spring member L is pressed against the elastic body developing roller D by its own spring force, and
In the example of (b), the support S receives elastic rotational force from the direction shown by the arrow A ₁ , and the leaf spring member L is pressed against the elastic developing roller D by this. Thus, when the elastic developing roller D is rotated as shown by the arrow in the drawing, most of the excess toner from the toner layer carried by the elastic developing roller D is the chamfered leading edge of the leaf spring member L. Since the toner layer thickness is regulated by the pressing force on the flat surface of the leaf spring member L after being removed by the above, the pressing force of the flat surface on the elastic developing roller D can be made relatively small. Therefore, it is possible to prevent the toner particles from sticking to the flat surface. On the other hand, the leaf spring member L
The high-precision machining of the flat surface and the high-precision chamfering of its tip edge can be performed at a relatively low cost, and its chamfered tip edge is much less susceptible to damage than the above-mentioned edge part. .

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, FIG. 14 (a)
In the example shown in FIG. 3, the leaf spring member L receives a tangential frictional force F ₁ during rotation of the elastic developing roller D, so that the leaf spring member L fluctuates in the direction indicated by arrow A ₂ and at the same time arrow A
Vibrate in the direction indicated by _3, also in the example shown in FIG. 14 (b), the leaf spring member L is subjected to tangential friction force F ₂ during the rotation of the elastic developing roller D, the frictional force F ₂ min Force component F
₃ causes a rotational moment of the support S, which causes the support S to vibrate about its rotation axis (arrow A ₄ ),
This vibration naturally extends to the leaf spring member L as well. When the leaf spring member L vibrates in this way and the toner layer thickness fluctuates, not only the development density of the electrostatic latent image is affected, but also the toner charge amount becomes insufficient at the portion where the toner layer thickness becomes thick. So-called fog (toner contamination in the background area of the electrostatic latent image) will occur. 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. The purpose is to prevent vibration when the layer thickness is regulated.

[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. 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 rotation thereof causes the contact region with the image carrier. 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 only the rigid supporting member, the rotation center of the rigid support member is substantially positioned on the tangent line between the leaf spring member and the elastic developing roller. .

[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.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment according to the present invention will now be described with reference to FIGS. 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 area 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 provided with a negative charge, but the selenium-based photosensitive material is provided with a positive charge. In the case of an amorphous silicon photosensitive material, a negative or positive charge is 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 the laser beam LB emitted from the laser beam scanning unit 14.
Is repeatedly scanned along the generatrix direction of the photoconductor drum 10 and the laser beam LB is blinked based on binary image data from a word processor or a microcomputer, for example. That is, the electric charge is discharged at the portion irradiated with the laser beam LB (the aluminum cylindrical base body 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. The laser beam L
The portion where the charge is removed by the irradiation of B is called a charge well, and its potential is increased from about −650V to about −100V (absolute value is lowered).

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 is provided with a developer container 16a for containing a one-component developer made 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, 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 may 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 example, 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
^{It has 7} Ωcm and Asker C hardness of 23 degrees. The developing roller 16b formed 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 and a toner layer is sequentially formed. 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 rigid support member 16d that is rotatable 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 pressed and brought into contact with the developing roller 16b at a line pressure of, for example, 35 gf / cm at the other end side thereof to regulate the layer thickness of the toner layer on the developing roller 16b. 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 point to be noted here is that as shown in FIG.
When the pressing force of the coil spring 16f with respect to 6d is released, the rotation center of the rigid support member 16d, that is, the shaft 1
The center of 6e is positioned on the tangent line between the leaf spring member 16c and the developing roller 16b, so that the frictional force F received from the developing roller 16b by the leaf spring member 16e is rigidly supported when the toner layer thickness is regulated by the leaf spring member 16c. Since the rigid support member 16d is directed toward the center of rotation of the member 16d, no rotational moment acts on the rigid support member 16d.
The vibration of 6c can be substantially prevented.
When the developing device 16 is in operation, a charge injection voltage of, for example, −400 V is applied to the leaf spring member 16c, so that 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 developing unit 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,
Formed from conductive sponge (Everlite TS-E made by Bridgestone) with volume resistance of 10 ⁴ Ωcm, and developing roller 16b
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 respect to the developing roller 16b, that is, on the right side in FIG. 1, and at the opposite side, that is, the developing roller on the right side in FIG. 1
It functions to positively supply and adhere the toner to 6b. A bias voltage of -400 V 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 electrostatically develops the toner. 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 the dead stock of toner in the developer container 16a. It functions to send the toner to the paddle rotor 16h by being operated appropriately. 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 and 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, whereby 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 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 that functions as a static elimination lamp. The LED array 30 removes the residual charge from the photoconductor drum 10, and the static elimination area 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 was used as the metal material of c, the leaf spring member 16c may be formed of other metal materials such as phosphor bronze, cupronickel, cold rolled steel plate, elastic spring alloy, beryllium copper alloy, and the like. it can. Further, in the present invention, the rotation center 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" may be such that the center of rotation of the rigid support member 16d may be slightly deviated from the tangent line between the leaf spring member 16c and the elastic developing roller 16b as long as the vibration of the leaf spring member 16c is prevented. Should be interpreted as meaning. In short, the leaf spring member 16c is the developing roller 1
It should be understood that it is sufficient that the leaf spring member 16c does not vibrate due to the component force when a tangential frictional force is applied from 6b.

As described above, in the developing device 16 according to the present invention, the vibration of the leaf spring member 16c is substantially prevented, so that the layer thickness of the toner layer on the developing roller 16b does not change and is constant. Therefore, the quality of the charged toner image, that is, the quality of the recorded image can be maintained, and the present inventors conducted various experiments in order to actually confirm this. This will be described in detail below.

First, as shown in FIG. 3, the shaft 16e
Is supported by a mounting seat 33 that can be displaced in the horizontal direction, and the rigid support member 16d is detachable from the mounting seat 32. That is, the long holes 32a are formed in the mounting seat 32, and the long holes 3a are formed.
Rigid support member 16 with set screw 32b through 2a
d is fixed to the mounting seat 32 so that the shaft 16e can be displaced in the horizontal direction with respect to the rigid support member 16d. First, the developing process was actually performed in a state where the tangent line between the leaf spring member 16c and the developing roller 16b passed through the center of the shaft 16e, that is, the state shown in FIG. 3B (the present invention). Then the shaft 16
3 by displacing e away from the rigid support member 16.
The state shown in (a) was set, and the developing process was similarly performed in this state. In the state of FIG. 3A, the tangent line between the leaf spring member 16c and the developing roller 16b forms an angle of 5 ° with the line connecting the contact point between them and the center of the shaft 16e. Shifting angle of shaft 16e −
Defined as 5 °. Subsequently, the shaft 16e was displaced so as to approach the rigid support member 16 to obtain the state shown in FIG. 3C, and the developing process was similarly performed in this state. Even in the state of FIG. 3C, the tangent line between the leaf spring member 16c and the developing roller 16b is the contact point between them and the shaft 1.
An angle of 5 ° is formed with respect to the line connecting the center of 6e, and this angle is also defined as the shift angle + 5 ° of the shaft 16e for convenience. In addition, when obtaining the respective states of FIG. 3A, FIG. 3B, and FIG. 3C, the coil spring 16
The elastic action of f does not reach the rigid support member 16d.

3 (a), 3 (b) and 3 (c)
The fluctuation of the toner layer thickness in each state was measured, and the variation degree of the fluctuation of the layer thickness was calculated. The variation of the toner layer thickness was measured by the following procedure. That is, (1) After performing the developing process in each of the states of FIG. 3A, FIG. 3B, and FIG. 3C, the developing roller 16b is gently taken out from the developing device 16, and the developing roller 16b is removed.
b was installed in a laser scanning micro measuring device 34 as shown in FIG. Laser Scan Micro Measuring Device 34
A light emitting portion 34a and a light receiving portion 34b are provided in the, and a reference shield wall 34c that shields a part of the laser beam emitted from the light emitting portion 34a is provided in the center between them. In Figure 4,
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 34
With respect to the installation, a predetermined area in the circumferential direction of the developing roller 16b, that is, an area where the toner layer thickness is regulated by the leaf spring member 16c when the developing roller 16b is taken out of the developing device 16, 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 shield wall 34c. (2) The distance L1 was measured in such an installed state. (3) Subsequently, the developing roller 16b is attached to the laser scanning micro-measuring device 34, 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 carried out in FIG. 3 (a), FIG. 3 (b) and FIG.
Repeat 5 times for each state of (c),
A macroscopic toner layer thickness average value was obtained and the degree of variation was obtained.

The above measurement results are shown as a graph in FIG. As is clear from the graph, in the state of FIG. 3A, that is, when the shift angle of the shaft 16e is −5 °, the macroscopic toner layer average thickness is 13.8 μm, and the variation degree 3σ (σ is standard deviation). ) Became as large as 7.3 μm. Further, in the state of FIG. 3C, that is, when the shift angle of the shaft 16e is + 5 °, the macroscopic toner layer average thickness is 8.7 μm, and the variation degree 3σ is 4.5 μm. Further, in the state of FIG. 3B, that is, when the shift angle of the shaft 16e is 0 (the present invention), the macroscopic toner layer average thickness is 10.2 μm,
The degree of variation 3σ was 2.2 μm.

Next, FIG. 3 (a), FIG. 3 (b) and FIG.
The state of occurrence of vibration of the leaf spring member 16c in each state of (c) was observed. By the way, since the vibration of the leaf spring member 16c, which is a problem here, is a minute one which cannot be visually recognized, such an observation is indirectly performed by the method shown in FIG. That is, as shown in FIG. 7, after removing the photoconductor drum 10 from the developing device 16 and installing the surface potential difference meter 36 at a position corresponding to the developing area,
By operating the developing device 16 and measuring the surface potential of the developing roller 16b, it is possible to observe the occurrence of vibration of the leaf spring member 16c. In FIG. 7, V _b is the developing bias voltage −30 of the developing roller 16b.
0V, _Vbl is the charge injection voltage of the leaf spring member 16c -400V
The, V _r denotes a bias voltage -400V of the toner recovery and supply roller 16g.

If the leaf spring member 16c does not vibrate,
If it is determined that the developing device 16 shown in FIG.
V_b, V_blAnd V_rIs the developing roller 16
b, leaf spring member 16c, and toner recovery / supply roller 1
6 is applied, the surface potential of the developing roller 16b becomes
Immediately as shown in_bsShould rise and stabilize there
Is. Because the leaf spring member 16c is the developing roller 1
6b only in contact with the toner layer of a predetermined thickness
Therefore, the surface potential V_bsIs mainly applied to the developing roller 16b.
Generated by the toner layer,
Small electric potential V_tIt consists of and. this
On the other hand, if the leaf spring member 16c is vibrating,
In this case, the leaf spring member 16c is thin on the developing roller 16b.
The toner layer is constantly moving back and forth.
In the meantime, there is a situation where it can be said that it is almost direct contact.
This may partially occur, and at this time, the developing roller 16b
Not only the developing bias voltage but also a part of the charge injection voltage
Applied and thus the surface potential V _bsIs extremely unstable
It should be in a state. When the developing device 16 is stopped, V
_b, V_blAnd V_rReturns to ground level (zero volts)
And the surface potential is V_bsTo toner layer potential V_tDrop to
It should be.

3 (a), 3 (b) and 3 (c)
8 shows the results of measuring the surface potential of the developing roller 16b in each of the above states. Note that in FIG. 8A, the reference width indicated by the arrow SL corresponds to 10 seconds, and the same applies to FIGS. 8B and 8C.
As is clear from the graphs of FIG. 8A and FIG. 8C, the surface potential of the developing roller 16b is in the case where the shift angle of the shaft 16e is −5 ° and the shift angle of the shaft 16e is + 5 °. It is unstable in the peak region, which indicates that the leaf spring member 16c is vibrating, but in the state of FIG. 3B, that is, when the displacement angle of the shaft 16e is 0 ° (the present invention )
In, the surface potential of the developing roller 16b is stable in its peak region, which means that the leaf spring member 16c is not vibrating.

When the shift angle of the shaft 16e is -5 °, when the leaf spring member 16c receives a frictional force in the tangential direction from the developing roller 16b, one of the component forces is the leaf spring member 1.
6c acts to separate the developing roller 16b from the developing roller 16b, and the separating action vibrates the leaf spring member 16c. Such vibration of the leaf spring member 16b weakens the regulation force of the toner layer thickness, so that the toner layer thickness becomes relatively thick, which agrees with the result of the graph of FIG. When the thickness of the toner layer is increased, the average charge amount of the toner is reduced, which means that some toner particles may be almost uncharged, which may cause so-called fog. Actually, when the recording operation was performed under the environment of high temperature and high humidity (40 degrees, relative humidity 80% RH), with the displacement angle of the shaft 16e set to -5 °, the optical reflection density OD0. Fog of 04 or more occurred, the recording density fluctuated, a line break of 1 dot appeared, and the recording quality was poor.

Further, the shift angle of the shaft 16e is + 5 °
In this case, when the leaf spring member 16c receives a frictional force in the tangential direction from the developing roller 16b, one component force thereof causes the leaf spring member 16c to bite into the developing roller 16b. This means that the leaf spring member 16c vibrates. Such vibration of the leaf spring member 16b strengthens the regulation force of the toner layer thickness, so that the toner layer thickness becomes relatively thin, which agrees with the result of the graph of FIG. When the recording operation was actually performed with the shaft 16e having a displacement angle of + 5 °, a fog having an optical reflection density of OD 0.04 or more was generated on the recording paper. This results in a contradiction with the above description, but immediately after the leaf spring member 16c bites into the developing roller 16b, the leaf spring member 16c.
It is presumed that c is repelled, and at this time, the toner layer thickness varies and a thick toner layer portion is locally formed, and the average charge amount of the toner in that portion drops.

In the case where the shift angle of the shaft 16e is + 5 ° (the present invention), the leaf spring member 16c does not vibrate, the developing operation is stably performed, and a good recording quality is actually obtained. Was given. That is, OD1.4 was obtained for the recording density measured using the optical reflection densitometer, the density unevenness was small at 0.1 or less, and the fog density on the background portion of the recording paper was not identifiable (fog density OD ≦ 0.01: Of recording paper
It was the value obtained by subtracting OD0.1).

In the example shown in FIG. 3, the leaf spring member 13c is fixed and the position of the shaft 16e is changed, but the same experiment was conducted also when the installation angle of the leaf spring member 13c was changed. That is, as shown in FIG. 9, the leaf spring member 16c was attached to the rigid support member 16d via the attachment seat 38 which is capable of angular displacement. That is, elongated holes 38a are formed in the mounting seat 38, and the leaf spring member 16c is fixed to the rigid support member 16 through the elongated holes 38a by the set screw 38b.
so that it can be fixed to the leaf spring member 16c.
The angular position of can be changed. First, the tangent line between the leaf spring member 16c and the developing roller 16b is the shaft 16e.
The developing process was actually executed in a state of passing through the center of the drawing, that is, a state as shown in FIG. 9B (the present invention). Then
The mounting seat 38 is angularly displaced by 5 ° in the counterclockwise direction, as shown in FIG.
The state shown in (a) was set, and the developing process was similarly performed in this state. In the state of FIG. 9A, the tangent line between the leaf spring member 16c and the developing roller 16b forms an angle of 5 ° with respect to the line connecting the contact point between them and the center of the shaft 16e. Displacement angle of leaf spring member 16c-
Defined as 5 °. Subsequently, the mounting seat 38 was angularly displaced by 5 ° in the clockwise direction to obtain the state shown in FIG. 9C, and the developing process was similarly performed in this state. Figure 9
In the state of (c), the leaf spring member 16c and the developing roller 16 are
The tangent to b forms an angle of 5 ° with the line connecting the contact point between them and the center of the shaft 16e, and this angle is also defined as the displacement angle of the leaf spring member 16c + 5 ° for convenience. Note that the elastic action of the coil spring 16f is prevented from reaching the rigid support member 16d when obtaining the respective states of FIG. 9A, FIG. 9B, and FIG. 9C.

9 (a), 9 (b) and 9 (c)
3 (a) and 3 (b) for each state of
As in the case of FIG. 3C, the variation in the toner layer thickness was measured, and the variation degree of the variation in the layer thickness was calculated. The result is shown in FIG. Furthermore, using the method of FIG.
The surface potential of the developing roller 16b was also measured in each of the states of (a), FIG. 9 (b), and FIG. 9 (c). The result is shown in FIG. In addition, in FIG. 11A, the reference width indicated by the arrow SL corresponds to 10 seconds, and the same applies to FIG. 11B and FIG. 11C.

When the displacement angle of the leaf spring member 16c was -5 °, the macroscopic toner layer average thickness was 7.8 μm, and the variation degree 3σ was as large as 6.2 μm. When the recording operation is actually performed, a thin portion with an optical reflection density of OD1.3 or less occurs in the recording density, and the optical reflection density of the fog is OD.
As it was over O.O3, the background on the recording paper became dark. On the other hand, as shown in FIG.
The surface potential of b also fluctuates sharply in the peak region, which is shown in FIG.
It is very similar to (c). In short, when the displacement angle of the leaf spring member 16c is −5 °, when the leaf spring member 16c receives a frictional force in the tangential direction from the developing roller 16b, as in the case of FIG. Component force is leaf spring member 1
6c acts on the developing roller 16b,
This means that the leaf spring member 16c vibrates.

When the displacement angle of the leaf spring member 16c is + 5 °, the macroscopic toner layer average thickness is 18.4 μm, and the variation 3σ is as large as 4.6 μm. When the recording operation was actually performed, the recording density varied, the optical reflection density OD of 0.04 or less was generated, and the line of one dot was broken. On the other hand, as shown in FIG. 11C, the surface potential of the developing roller 16b is also unstable in the peak region, which is very similar to that in FIG. 8A. in short,
When the displacement angle of the leaf spring member 16c is + 5 °,
Similarly to the case of (a), when the leaf spring member 16c receives a tangential frictional force from the developing roller 16b, one component force acts to separate the leaf spring member 16c from the developing roller 16b. This causes the leaf spring member 16c to vibrate.

When the displacement angle of the leaf spring member 16c is 0 ° (in the present invention), the macroscopic toner layer average thickness is 10.2 μm, and the variation degree 3σ is 2.2 μm, and these numerical values show good recording quality. Is within the range of the toner layer thickness. Even in the actual recording operation, the optical reflection density OD1.4 was obtained as the print density, the density unevenness was as small as 0.1 or less, and the background fog density on the recording paper could not be identified (fog density OD ≦ 0.01: It was the value obtained by subtracting OD0.1).

As described above, in the above-described 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), and the rounded tip. The radius R of the portion is set to, for example, 0.05 mm, but this rounded tip portion can also be an important 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 and R = 0.07, respectively.
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 experiment is as follows. (1) The center of the shaft 16e of the rigid support member 16d is positioned on the tangent line between each leaf spring member and the developing roller 16b. (2) Each leaf spring member was pressed against the developing roller 16b with a linear pressure of 40 gf / cm. (3) Each recording operation was performed in an environment where the temperature was 40 ° and the relative humidity was 80% RH, where fog was likely to occur. (4) In each recording operation, the entire black recording (so-called black solid), the entire white recording (state in which no electrostatic latent image is formed), and the parallel diagonal pattern recording of the 1-dot diagonal line at the angle of 45 ° (horizontal direction) 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 sheets of recording paper (A4 size).

The evaluation results are shown in the graph of FIG. In addition,
The horizontal axis of the graph represents the radius R of the rounded tip of the leaf spring member, and the right vertical axis thereof is the maximum value (black streak) and the minimum value (black line) of the average optical reflection density OD in the area of 4 mm diameter in the parallel oblique line pattern recording ( (White streaks), and the vertical axis on the left thereof is the value of the fog density of the entire white recording measured by an optical reflection densitometer. As is clear from this graph, in the case of the parallel oblique line pattern recording when the leaf spring member (R = 0) having no rounded tip portion is used, the average recording density difference is as large as 0.08, and the distinguishable density difference is 0.03. The recording density was greatly exceeded, and black and white streaky recording density irregularities were found on the recording paper. On the other hand, a rounded chamfered leaf spring member (R = 0.10 mm, R = 0.07 m)
It can be seen that the recording density difference can be suppressed to 0.03 or less when m and R = 0.03 mm). Also, high temperature and high humidity (40 degrees / 80% R
In the whole white recording performed under the environment of H), when the leaf spring member of R = 0.10 mm was used, the density difference of 0.01 (the value obtained by subtracting the optical reflection density OD0.10 of the recording paper) was recognized. Has exceeded
It can be seen that fog is likely to occur. In short, when rounded chamfering 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 regulation pressure) against the developing roller 16b. An experiment was 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 thinner 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. In addition, regarding the three types of round chamfered leaf springs, the linear pressure on the developing roller 16b is 12 gf each.
Set to / cm, 30gf / cm, 45gf / cm and 60gf / cm,
The same recording paper (A4 size) as the above case 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 leaf spring member 1 for the developing roller 16b
It can be seen that the linear pressure of 6c is preferably in the range of about 30 gf / cm 2 to about 45 gf / cm 2.

[0038]

As is apparent from the above description, in the electrostatic recording apparatus according to the present invention, the metal plate spring member is applied to the developing roller and the rigid support member of the plate spring member is rotated. By substantially positioning the center on the tangent line between the leaf spring member and the developing roller, the charge amount of the toner can be properly controlled regardless of environmental changes, and a good recording operation can be maintained for a long period of time. It becomes possible.

[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 shows a case where a developing roller, a leaf spring member and a rigid supporting member of a developing device are arranged according to the present invention (FIG. 3 (b)).
And those components are arranged in other manners (see FIG. 3).
It is a comparison figure which shows the example with (a) and FIG.3 (c).

FIG. 4 is an explanatory diagram of a measuring method for measuring a layer thickness of a toner layer on a developing roller by laser microscanning.

5 is a graph showing the measurement results when the layer thickness of the toner layer on the developing roller is measured according to the measurement method of FIG. 4 in each case of FIG.

FIG. 6 is an explanatory diagram of a measuring method for measuring a surface potential of the developing roller with a surface electrometer while a toner layer is formed on the surface of the developing roller.

FIG. 7 is a graph for explaining the output tendency of the surface potential meter when the surface potential of the developing roller is measured by the surface potential meter according to the measuring method of FIG.

8 is a graph showing the measurement results when the surface potential of the developing roller is actually measured according to the measurement method of FIG. 7 in each case of FIG.

FIG. 9 shows a case where a developing roller, a leaf spring member and a rigid support member of a developing device are arranged according to the present invention (FIG. 9 (b)).
And those components are arranged in another manner (see FIG. 9).
FIG. 10A is a comparative diagram showing another example of FIG. 9C and FIG.

10 is a graph showing the measurement results when the layer thickness of the toner layer on the developing roller is measured according to the measurement method of FIG. 4 in each case of FIG.

11 is a graph showing the measurement results when the surface potential of the developing roller is actually measured according to the measurement method of FIG. 7 in each case of FIG.

FIG. 12 is a graph showing the relationship between the radius of the rounded tip of the leaf spring member and the recording quality.

FIG. 13 is a graph showing the relationship between the pressing force of the leaf spring member against the developing roller and the layer thickness of the toner layer, with the radius of the rounded tip 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 a toner layer on a 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 and supply roller 18 ... Corotron transfer device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yukio Nishio             1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture             Within Fujitsu Limited

Claims (2)

[Claims] 1. A developing device for developing an electrostatic latent image held on an image carrier (10) with a one-component developer, the developer holding container (16a) containing the one-component developer, An elastic developing roller (16a) rotatably driven in the developer holding container is provided, and a part of the elastic developing roller is exposed from the developer holding container to the image carrier. It is arranged so as to be in contact with each other, and a one-component developer is attached to the rotation surface thereof to form a one-component developer layer, and the rotation thereof is conveyed to a contact area with the image carrier, Further, a leaf spring member (16) for regulating the layer thickness of the one-component developer layer of the elastic developing roller is provided.
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 at the other end side thereof. In a developing device which is elastically pressed into contact with the elastic developing roller so as to regulate the layer thickness, the center of rotation of the rigid support member (16d) is the leaf spring member (16c) and the elastic developing roller. A developing device characterized in that it is positioned substantially on a tangent to (16b). 2. The developing device according to claim 1, wherein the rigid support member (16d) is released when the elastic pressing contact state of the leaf spring member (16c) with respect to the elastic body developing roller (16b) is released. The developing device is characterized in that the center of rotation of (1) coincides with the tangent line between the spring member (16c) and the elastic developing roller (16b).