JPH045191B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a detector for detecting the level of magnetic toner contained in a developing device used in an electronic copying machine, a printer, or the like.

In general, dry development methods for electrostatic latent images in electrophotography, electrostatic recording, electrostatic printing, etc. are two-component development methods that use a mixed powder of non-magnetic toner and magnetic carrier as the developer, and one-component development methods that use a mixed powder of non-magnetic toner and magnetic carrier as the developer. It is broadly divided into one-component development method using magnetic toner.

Two-component development requires control of toner density, uniform mixing with carrier, etc., and the developing device is complicated and large, making it unsuitable for maintenance-free use.
On the other hand, the one-component development method requires only toner replenishment, making it suitable for maintenance-free use. However, with the magnetic toner method, if there is a shortage of toner, the copy density will drop rapidly, so it is necessary to detect the remaining amount of toner in the toner storage tank of the developing device in advance and maintain the toner storage level above a predetermined value. There is.

Conventionally, methods for detecting the storage level of magnetic toner include methods that place a coil close to the magnetic toner and utilize changes in the inductance of the coil, methods that use electrodes to detect the electrical resistance of the toner, and methods that use acoustic elements to detect the toner. Various methods have been proposed, including one that detects toner as a powder, but in all of them, the detection object is placed along the wall of the toner storage tank of the developing device, and no special measures have been taken for the shape of the detection object. It had not been done.

Therefore, in the one-component development method using magnetic toner, an electrostatic latent image formed on a photoconductor is developed using a conductive magnetic toner, such as that described in Japanese Patent Laid-Open No. 49-4532. In addition to the so-called CPU method, which fixes directly, there is also the so-called CPU method, which involves the process of transferring the developed image onto a transfer sheet such as plain paper.
It has also been adopted and put into practical use in the PPC method. However, the magnetic toner used in the PPC method has a high volume resistivity (for example, Japanese Patent Publication No. 56-46596,
(Refer to JP-A No. 53-31136, JP-A No. 55-126266, etc.) Furthermore, since the particle size distribution is made up of small particles with a particle size distribution of approximately 5 to 30 μm, fluidity is poor, and the inside of the toner storage tank is It tends to stick to walls and remain there. Therefore, when such a magnetic toner with poor fluidity is used, if the sensitivity of the detection body is increased in order to improve the accuracy of the detection level, a problem arises in that malfunctions are likely to occur. especially,
In order to simplify and downsize the structure of the developing device,
A toner storage tank having a popper-like shape is generally used, but as described in Japanese Patent Application Laid-open No. 54-61939, a detection object is often placed on the slope of the toner storage tank. Toner adhesion and residue on the inner wall of the storage tank will become significant.
There has been a problem in that the amount of toner remaining in the toner storage tank cannot be detected with sufficient reliability.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above and to provide a magnetic toner detector capable of detecting the remaining amount of magnetic toner in a toner storage tank with sufficient reliability.

The magnetic toner detector of the present invention is characterized most in that it has a shape that makes it difficult for toner to remain around the detector.

The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a sectional view showing an example of a developing device equipped with the magnetic toner detector of the present invention. In the figure, a magnetic toner detector 1 is installed on the slope of a wall plate 2' of a toner storage tank 2 via a mounting plate 1'. The magnetic toner 3 in the toner storage tank 2 is attracted to the magnet roll 4. The magnet roll 4 has a non-magnetic sleeve 5 disposed facing the photosensitive drum 8.
A permanent magnet roll 6 having a plurality of magnetic poles on its surface is disposed inside the permanent magnet roll 6. The magnetic toner 3 adsorbed onto the non-magnetic sleeve 5 is transported by the relative rotation of the non-magnetic sleeve 5 and the permanent magnet roll 6, and is transported by the doctor member 7 attached to the wall plate 2'' of the toner storage tank 2. It is transported in the direction of the arrow shown in the figure with its thickness regulated, and when it passes through the opposing gap between the non-magnetic sleeve 5 and the surface of the photoreceptor drum 8, it adheres to the surface of the photoreceptor drum 8.
The electrostatic latent image (not shown) formed on the surface is visualized. Note that FIG. 1 shows the case where both the non-magnetic sleeve 5 and the permanent magnet roll 6 are rotated counterclockwise, and the ratio of their rotational speeds is appropriately selected (for example, as disclosed in Japanese Patent Application Laid-Open No. 126266/1983). ), the toner can be transported in the same direction as these.

When development is repeatedly performed as described above, the storage level of the magnetic toner 3 in the toner storage tank 2 gradually decreases from the initial position x (indicated by a dashed line in the figure). When the storage level reaches position y (indicated by a two-dot chain line in the figure), which corresponds to the approximate center of the detection object 1, the detection object 1 generates an electrical signal, for example, a lamp connected to the detection object 1. A display device (not shown) can notify that toner needs to be replenished.

In the above-mentioned developing device, the detector 1 is greatly different in its arrangement and shape from the conventional one, and has its tip 1a protruding into the toner tank 2 and facing the sleeve 5 at the tip 1a, as shown in FIG. The detector is installed on the wall plate 2' so that the surface 1b to be detected is a substantially vertical surface, and the tip 1a of the detector is formed so that its upper part is wedge-shaped. Therefore, according to the detection body 1, the magnetic toner 3 in the toner storage tank 2 easily falls from the surface of the tip of the detection body, thereby reliably preventing it from adhering to or remaining on the top of the tip of the detection body. I can do it. In this case, since the ease with which magnetic toner falls from an inclined surface is generally proportional to its inclination angle, it is preferable that θ in FIG. 2 be 90° or less. Further, the surface 1b at the tip of the detection body does not necessarily have to be vertical, but it is necessary that the angle between it and the perpendicular be less than ±30°.

In order to improve the accuracy of detecting the toner storage level by the detector, it has been proposed to place the detector on the back side of the tractor member (on the side of the toner storage tank) so that the tip of the detector is vertical. (Refer to Japanese Unexamined Patent Publication No. 57-2066), the permissible mounting space for the detection object cannot be made large, it is unfavorable for the precision of doctor parts that require high dimensional precision, and it is easily affected by the external magnetic field of the permanent magnet roll. There are other problems. Therefore, the mounting position of the detection body needs to be on the slope of the wall plate of the toner storage tank as in the present invention.

As described above, according to the present invention, the detection body is configured such that its arrangement and shape can substantially prevent toner from adhering and remaining on its surface, so that the toner storage level is set to the reference value. In other words, it is possible to accurately detect when the toner level has fallen below the detection object, thereby preventing malfunctions due to toner adhering to or remaining on the detection object, and making it possible to detect the toner storage level with sufficient reliability. . Furthermore, if the detector is simply placed along the slope of the wall of the toner storage tank as in the past, the fluidity of the magnetic toner decreases, especially under high temperature and humid environmental conditions, resulting in malfunction of the detector. However, according to the present invention, the toner storage level can be detected with sufficient reliability even under such environmental conditions.

The detection method of the object to be detected according to the present invention includes, for example, a method using a change in the inductance of a detection coil as described in Japanese Patent Laid-Open No. 54-61939, a method using a Hall element, and a method using an electrode to detect the toner's electricity. A known method such as a method of detecting resistance can be applied.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a developing device equipped with the magnetic toner detector of the present invention, and FIG. 2 is a perspective view of the magnetic toner detector of the present invention in FIG. 1: Magnetic toner detector, 2: Toner storage tank,
3: Magnetic toner.

Claims (1)

[Claims] 1. In order to detect the storage level of the magnetic toner in the toner storage tank that stores the magnetic toner, in a magnetic toner detection body disposed on the slope of the toner storage tank, the tip portion for detecting the storage level is located in the toner storage tank. A magnetic toner detector, which penetrates into a tank, and has an end surface of the tip portion that is a substantially vertical surface, and the tip portion is formed in a wedge shape that points upward when viewed from the end surface side.