JPH0216917B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a casing for storing a developer made of a mixture of magnetic carrier powder and non-magnetic toner powder, and a casing for storing a developer made of a mixture of magnetic carrier powder and non-magnetic toner powder, and a casing for transporting the developer by adsorbing it to an outer peripheral surface. a sleeve in which a magnetic body is arranged; a regulating member that regulates the height of the developer adhering to the sleeve;
The present invention relates to a developing device for an electrophotographic device, including a toner concentration control device that controls the toner concentration of the developer.

One such device was published as a patent application in 1985.
It is disclosed in Publication No. 161261. This device scrapes and circulates developer material from its rotating sleeve by effectively controlling changes in the thickness of developer material flowing over a scraper plate that slopes downward from its tip in contact with the sleeve. Detected in a location where there is no
The device is configured to thereby detect a change in toner concentration. However, this device has a problem in that it is relatively difficult to detect changes in toner concentration with high accuracy.

It is an object of the present invention to solve the problems of the conventional apparatus and to provide a simple and convenient developing apparatus for an electrophotographic apparatus.

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

In FIG. 1, reference numeral 11 is a rotating drum having a suitable photoreceptor 12 mounted on its circumferential surface, and is rotated in the direction indicated by arrow A during operation by being connected to a suitable driving means. During rotation, the photoreceptor 12 is subjected to the action of known electrostatic latent image forming means such as corona discharge and optical image irradiation, thereby forming an electrostatic latent image, that is, a potential difference image, in accordance with the original on its surface. This electrostatic latent image is then converted into a visible toner image by development device 13 and transferred to a suitable support.

The developing device 13 has a casing 15 having an opening 14 on the side facing the photoreceptor 12, and inside the casing are magnetic carrier powder such as iron powder (hereinafter simply referred to as carrier) and a non-containing material such as colored synthetic resin. A developer 16 made of a mixture of magnetic toner powder (hereinafter simply referred to as toner) is stored. The toner and carrier are sufficiently agitated by the rotation of the agitating member 17, and are sufficiently adhered to each other by the frictional electricity generated at this time. Opening 1 of casing 15
A sleeve 18 made of non-magnetic material is partially exposed from 4.
is rotatably provided. A magnet assembly 20 having a plurality of magnet pieces 19 is fixedly arranged within the sleeve 18 and is independent of the rotation of the sleeve 18 . The magnet pieces 19 are alternately arranged so that the SN polarity of the adjacent magnet pieces is reversed in the circumferential direction. The sleeve 18 is connected to a drive source (not shown) and rotates in the direction indicated by arrow B during operation. Casing 1
A part of the developer stored in the sleeve 5 is attracted to the outer peripheral surface of the sleeve 18 by the magnetic force of the magnet piece 19.
As the sleeve 18 rotates, it is transported in the direction of arrow B. During this conveyance, the developer adhering to the sleeve 18 is trimmed to a predetermined brush height (hair length) by a regulating member, ie, a doctor blade 21, which is arranged to maintain a gap with the outer peripheral surface of the sleeve 18. It will be done. The developer then comes into contact with or comes close to the electrostatic latent image on the photoreceptor 12 and is electrostatically attracted onto the photoreceptor 12, forming a visible toner image corresponding to the electrostatic latent image. Last magnet piece 19
The developer outside the range a of the magnetic force is removed from the sleeve 18 by the scraping plate 22, mixed into the stored developer again, and reused.

Reference numeral 23 in the figure represents a toner storage container, which is located above the casing 16. Toner storage container 23
has a supply roller 24 therein which stores replenishment toner and below which is connected to a suitable drive. The supply roller 24 has an axial circumferential groove 25, and rotates as appropriate in response to a command from a toner concentration detection device, which will be described later, to replenish the developer with toner in the groove 25. The supply roller 24 is connected to a constantly rotating drive source through a clutch means such as an electromagnetic clutch or a spring clutch, and rotates or stops depending on whether the clutch means is energized or deenergized. For the supply roller 24 and its driving means, for example, the structure described in the above-mentioned publication can be adopted.

The toner concentration detection device of the present invention has a scooping member 30 whose lower end is located close to the sleeve 18. The scoop member 30 is made of a non-magnetic material such as aluminum, brass, or synthetic resin, and preferably has a smooth upper surface 30a. The scoop member 30 is disposed such that its lower end is spaced apart from the circumferential surface of the sleeve 18 and buried in the developer on the sleeve, and extends an appropriate length in the generatrix direction of the sleeve 18 and extends from the upper surface of the scoop member 30. That is, the developer scooping surface lies substantially on a plane extending radially upward from the axis of the sleeve, or is inclined with respect to the plane so as to open upwardly.
Furthermore, the lower end of the scooping member 30 is disposed at a position where the developer near the lower end is substantially affected by the magnetic force of the magnet piece 19. A portion of the developer conveyed on the sleeve 18 due to the rotational force of the sleeve 18 and the magnetic force of the magnet piece 19 is scooped up by the scooping member 30 . This scooped developer swells up along the upper surface of the scooping member 30, and the height level h of the swelled portion changes depending on the change in toner concentration.
change in a positive relationship. That is, when the toner concentration is lower than the height for a developer having a desired toner concentration, the height level is lowered.

A suitable sensing device 32 is provided, for example on the scoop member 30, to detect changes in the developer height level. The sensing portion of the sensing device 32 is mounted at a height such that it comes into contact with the raised developer when the developer has a desired toner concentration, but does not come into contact when the developer has a lower toner concentration. . As the detection device 32, a commercially available piezoelectric element (eg, TMS type toner sensor manufactured by Tokyo Denki Kagaku Kogyo Co., Ltd.) can be used. In this case, as shown in FIG. 2, it is preferable that the sensing surface (vibrator) 32a of the piezoelectric element be slightly protruded from the upper surface of the scoop member 30 or be located on the same plane. Further, as the detection device 32, a detection device using a change in inductance of a coil element as described in the above-mentioned publication, or a known optical device consisting of a lamp and a photoelectric element as shown in Utility Model Application Publication No. 22182 of 1982 can be used. It is also possible to adopt means of detecting the target. The scooping member 30 is preferably disposed approximately at the center of the sleeve 18 in the longitudinal direction, but is not limited to this position.

Referring to FIG. 3, the developer detection operation when the piezoelectric element 32 is used as the detection device will be described. The piezoelectric element 32 includes an oscillation circuit 32b that oscillates an output at a predetermined frequency, and a sensing section 32c that receives the output from the oscillation circuit 32b. The sensing section 32c includes a vibrator 32a that resonates with the output of the oscillation circuit 32b.
has. As described above, the vibrator 32a is exposed on the upper surface of the scoop member 30, and when the developer raised along the member 30 comes into contact with it, it reduces the amplitude due to the pressure of the developer, and when it does not come into contact with it, it reduces the amplitude. Make it large. The magnitude of this amplitude is detected by the detection/output circuit 32d and output as either a high level or low level signal. This signal is sent to the clutch means of the toner supply roller 24 to energize or de-energize the clutch means.

When the toner concentration of the developer drops below a predetermined value,
The height level h of the developer scooped up by the scooping member 30 on the sleeve 18 decreases, and the developer no longer reaches the vibrator 32a of the piezoelectric element 32.
As a result, the detection/output circuit 32d outputs a low level signal indicating insufficient toner concentration.
Therefore, the supply roller 24 is energized to scatter replenishment toner onto the developer. The scattered toner is immediately mixed with the developer by the action of the stirring member 17. When the toner concentration reaches a predetermined value due to toner replenishment, the level of the developer on the member 30 rises to a height where it contacts the vibrator 32a again, and as a result, the detection/output circuit 32d outputs a high level indicating that the toner concentration is normal. A signal is output, and the supply roller 2
4 stops, and toner replenishment ends. By repeating these operations, the developer in the developing device is always maintained within a predetermined toner concentration range.

In the experiment, a magnet of 600 to 800 G was used as the magnet piece 19 near the lower end of the scoop member 30, the scoop member 30 was inclined at an angle of 60° to 70° with respect to the tangent to the sleeve 18, and the lower end was attached to the sleeve 1.
A piezoelectric element that responds to a pressure of 30 to 50 mmg was used as a detection element, facing the outer peripheral surface of the sleeve at a distance of about 1/3 of the thickness of the developer attached to the sleeve (approximately 2 to 3 mm). For example, when the sensing portion of the piezoelectric element was placed in a position where it could come into contact with a bulge of developer with a toner concentration of 8%, the toner concentration in the developer could be controlled with an accuracy within a range of 8±0.5%.

FIG. 4 shows another embodiment of the developing device according to the present invention. In this example the rake member 30 has a limited height H. That is, when trying to hold the developer at a toner concentration of 8%, for example, the height H of the scooping member 30 is set such that the developer can climb over the member 30 and fall backward when the toner concentration is 8% or more. Set. In this configuration, a detection means 40 is provided behind the member 30 in order to detect the presence (presence or absence) of developer falling from the member 30. As the detection means, a piezoelectric element, a coil body, an optical detection means, etc. as described above can be used. In the example shown in FIG. 4, an inclined flat plate member 41 is arranged at a position to receive the developer falling over the member 30. The upper surface of the plate member 41 is preferably smooth so that the developer can flow smoothly. The center of the plate member 41 is cut out in a substantially circular hole shape, and the sensing surface (vibrator) of the piezoelectric element 32 having the above-mentioned configuration is exposed from there toward the upper surface of the member 41. The sensing surface protrudes slightly from the top surface of the plate member 41, or is preferably located flush with the top surface. In such a configuration, when the developer has a predetermined toner concentration, that is, when the developer falls from the scooping member 30, the developer flows down on the member 41, and the detection device 32 detects that the developer falls from the scoop member 30. Falling is detected. Such detection causes the output circuit 32d to generate a signal indicating that the toner concentration is normal, as in the case described in the first embodiment. On the other hand, if the detection device 32 does not detect the developer falling, the toner supply roller is energized and replenishes the developer with toner until the detection device 32 detects the developer falling again. In order to reliably guide the developer falling from the member 30 onto the device 32, a guide member such as a funnel may be provided on the member 30 or between the member 30 and the sensing surface of the device 32.

The energization timing of the detection device 32 will be explained with reference to FIG. Generally, in an electrophotographic apparatus, a developing device operates only when performing development. For this reason, the height level h of the developer material scooped by the member 30 becomes approximately stable after a certain period of time t1 has elapsed from the time when the developing device is started (when the rotation of the sleeve 18 starts). Therefore, the detection device 32 detects the period from the time t1 has elapsed until the sleeve 18 stops.
Only t2 is energized.

As described above, the present invention provides a developing device that can control toner density with high precision.

In the above-mentioned embodiments, a magnetic brush type developing device with a rotating sleeve and a fixed magnet was explained, but the present invention is also applicable to a developing device with a fixed sleeve and a rotating magnet or a rotating sleeve and a magnet. It is possible.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing an embodiment of the developing device according to the present invention, FIG. 2 is a perspective view of a portion of the device shown in FIG. 1, and FIG. 3 is a toner concentration incorporated in the developing device according to the present invention. A block diagram for explaining the function of the detection device, FIG. 4 is a schematic vertical cross-sectional view showing another embodiment of the developing device according to the present invention, and FIG. 5 is a toner concentration detecting device incorporated in the developing device according to the present invention. This is a timing chart showing the timing of energization. 18... Sleeve, 19... Magnet piece, 21...
Regulating member, 30... scooping member, 32... detection device.

Claims (1)

[Scope of Claims] 1. A casing that stores a developer made of a mixture of magnetic carrier powder and non-magnetic toner powder, and a magnet arranged inside to attract and transport the developer to the outer peripheral surface. In the developing device for an electrophotographic apparatus, the developing device includes: a sleeve having a flat surface, a regulating member that regulates the height of the developer adhering to the sleeve, and a toner concentration control device that controls the toner concentration of the developer; , a lower end is buried in the developer on the sleeve at a position downstream of the regulating member when viewed in the developer transport direction and at a position where the magnetic force of the magnet body is applied to the developer on the sleeve, and the developer is transported. a scooping member arranged upright or inclined with respect to the direction; a detection device for detecting the height level of the developer scooped by the scooping member; and a detection device for detecting the height level of the developer scooped by the scooping member; 1. A developing device for an electrophotographic device, comprising: means for replenishing toner powder. 2. In the device according to item 1, the detection device is disposed on the scooping member at a predetermined distance from the outer circumferential surface of the sleeve, and determines whether or not the scooped developer comes into contact with the scooping member. A developing device for an electrophotographic device, characterized in that the height level of the image is detected. 3. In the device according to item 2 above, the detection device comprises a piezoelectric element that emits a predetermined output signal in response to the pressure caused by the scooped developer, and the pressure sensing surface of the element is set when the scooping member is scooped. A developing device for an electrophotographic apparatus, characterized in that the developing device is located on the same plane as a surface that comes into contact with a developer. 4. A casing that stores a developer made of a mixture of magnetic carrier powder and non-magnetic toner powder, a sleeve that has a magnetic body arranged inside and that attracts and conveys the developer to its outer peripheral surface, and the sleeve. In a developing device for an electrophotographic apparatus, the toner concentration control device includes a regulating member that regulates the height of the developer that adheres to the developer, and a toner concentration control device that controls the toner concentration of the developer. The lower end is buried in the developer on the sleeve at a position downstream of the regulating member when viewed in the direction and at a position where the magnetic force of the magnet body is applied to the developer on the sleeve, and is inclined with respect to the conveyance direction of the developer. a scoop member having a predetermined height; a detection device that detects the presence of developer falling over the scoop member;
A developing device for an electrophotographic device, comprising means for replenishing a developer with toner powder in response to an output signal of the detection device.