JPS6319684A - Image forming device - Google Patents

Abstract

PURPOSE:To maintain an image carrier and a developing sleeve at an invariably constant interval by providing a means which displaces one of the image carrier and developing sleeve so that the interval between the both is specified. CONSTITUTION:The cam surface of a cam 8 is so formed that the position that a pin 6 abuts on is displaced in a sine curve shape between + or -75mum at a place where phi=3.00. Variation in deflection quantity due to the eccentricity of a photosensitive body is made to correspond to a sine curve at the time of the equal-speed rotation of a photosensitive body, and the period of the deflection of the surface of the photosen sitive body and the swing quantity of a sleeve 3 based on the rotation of the cam is made coincident with the deflection quality; and the both are rotated synchronously to hold the internal between the both constant. The synchronism between the photosentivie body and motor is brought under rotation control of the same driving source by equalizing the number of poles and the number of phases between a photosen sitive driving motor and a cam driving motor. In another way, a discoid encoder which has one slit is arranged on the photosensitive body and cam motor and a photosensor outputs one signal in every turn to control the cam surface motor. Conse quently, the influence of the deflection due to the eccentricity of the image carrier and others and vibration transmitted from a driving system is eliminated.

Description

Detailed Description of the Invention (1) Object of the Invention (Field of Industrial Application) This invention relates to a developing device of an image forming apparatus using an electrostatic recording means, such as an electrostatic copying machine or a printer, and particularly to an image bearing device thereof. The present invention relates to a device for maintaining a distance between a body and a developing sleeve.

(Prior art and issues to be solved WU) Toner is supplied by a developing device to the static TrL latent image formed on the photosensitive layer on the surface of a moving image carrier to form a transferable toner image, and this is transferred onto a sheet-like sheet such as paper. Image forming apparatuses configured to transfer images onto materials are well known in the art.

This type of image forming apparatus includes a rotating cylindrical image bearing member (referred to as a photoreceptor) having a photosensitive layer on its surface, a rotating cylindrical image bearing member (referred to as a photoreceptor), which is placed close to the image bearing member, and contains toner therein. A magnetic drum is provided to supply the electrostatic latent image formed on the photosensitive layer to make it visible, and a sleeve is provided which rotates around the magnetic drum and is arranged with a small gap from the photosensitive layer. Those equipped with a developing device are widely used.

In such devices, the distance between the photoconductor and the sleeve is usually about 300 μm, and the tolerance is ±30 to obtain a good quality image by supplying the appropriate amount of toner to Hsa' on the photoconductor surface. l OOgm, which is quite severe.

As can be easily surmised, if the interval is too small, toner will adhere to areas where it should not be attached, resulting in the so-called capri phenomenon; if it is too large, it will cause a decrease in density, blurring of fine lines, etc. Image quality cannot be avoided.

However, since the deflection due to eccentricity during one rotation of the photoreceptor is normally about 1004 tb, it is difficult to maintain the above-mentioned distance within a predetermined range.

For this reason, conventionally, the above-mentioned distance has been maintained by means as shown in FIG. 6, for example.

This is schematically illustrated in FIG. 6, which is a schematic side view of the main parts of the image forming apparatus, showing a cylindrical photoreceptor 10 extending perpendicularly to the plane of the paper and a developing device 20 disposed close to the cylindrical photoreceptor 10. A sleeve 30 is disposed inside the developing device,
Spacer rollers 40 (only one of which is shown in the figure) made of a self-lubricating material such as Teflon (trade name) are arranged at both ends of the spacer rollers 40, and the developing direction is in the direction of arrow 50. The spacer roller 40 is pressed against the photoreceptor by applying elastic force.

With this configuration, even if the photoreceptor shakes, the rollers 40 follow it, so that the distance between the photoreceptor and the sleeve can be maintained.

However, when W1 is established in this way, the vibrations and rotational irregularities of the developing device drive system are transmitted to the photoreceptor, and the exposure position changes periodically, resulting in uneven density and deterioration of image quality. .

The present invention has been made in order to deal with such a situation, and is an image forming apparatus that has a developing device including a rotating cylindrical photoreceptor and a sleeve for supplying toner to the photoreceptor. without direct contact with the body,
It is an object of the present invention to provide an image forming apparatus that can maintain a constant distance between the two at all times.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention provides an image forming apparatus as described above, in which a photoreceptor and a The present invention is characterized in that means is provided for displacing at least one of the developing sleeve and the developing sleeve in a direction in which the distance between the two changes in synchronization with the rotation of the photoreceptor.

With this configuration, it is possible to always maintain a constant interval between the two without making them come into direct contact with each other, and it is possible to always supply an appropriate amount of toner to the surface of the photoreceptor to obtain a high-quality image.

(Description of Embodiments) FIG. 1 is a plan view of essential parts of an image forming apparatus to which the present invention is applied, showing the relative arrangement of a photoreceptor 1 and a developing device 2. It is indicated by a chain line.

The developing device is provided with a hollow sleeve 3 that is rotated by a drive source (not shown), and inside the sleeve 3, a magnetic roller 4 having a plurality of magnetic poles on its circumferential surface is mounted on a shaft while being prevented from rotating. As shown in the figure, the sleeve 3 is attached to a bearing disposed on the sleeve 5 of the magnetic roller 4, so the shaft 5,
By displacing the magnetic opening, the sleeve 3
It is assumed that the developing device 2 is moved toward or away from the photoreceptor 1, and that the developing device 2 is always biased away from the photoreceptor by a spring or the like (not shown).

Both ends of the vehicle 5 protrude outside the developing device, and a bottle 6.6 is attached to each of the protruding portions, and the tip of each pin 6 is placed in an appropriate position within the neck mount due to the aforementioned deflection tendency. , is in contact with a cam 8.8 disposed on the output shaft of a motor 7.7 fixed to a frame F or the like.

The cam 8 is preferably made of a material that is highly self-lubricating and has good processing accuracy, such as polyacetal or PPS resin.

As shown in FIG. 2a, the cam 8 has a substantially disk-shaped configuration in which the surface on which the pin 6 comes into contact is formed into an inclined surface.

As shown expanded in FIG. 2b, the cam surface of the cam 8 is
For example, the position where pin 6 contacts is φ=30,
It is formed so that it is displaced in a sine curve shape between ±75 mm (the cam surface that the pin 6 comes into contact with is
(It will be immediately understood that a sine curve-shaped cam surface with an arbitrary maximum displacement can be formed by forming a plane having an appropriate angle with respect to the output shaft of the cam surface and rotating the shaft at a constant speed).

This is because the deflection due to the eccentricity of the photoreceptor corresponds to the fact that when the photoreceptor rotates at a constant speed, the change in the amount of deflection exhibits a sine curve.

Therefore, by matching the period and amount of vibration of the photoconductor surface and the amount of vibration of the pin 6, that is, the amount of vibration of the sleeve 3 during the rotation of the cam, and rotating them synchronously, the distance between the two can be reduced. can be maintained constant.

There is almost no change in the runout of the photoreceptor over time, so if it is adjusted at the time of assembly, there is no need for subsequent adjustment as a general rule.

Variations in the amount of runout of the photoconductor are normally concentrated within a certain range depending on the model, so if the inclination angle of the cam surface of the cam is set to one, then, for example, the above-mentioned cam 8, la in the axial direction of the sleeve of the cam
Since the movement in m is ±54 m, the adjustment can be made in units of lam, and the adjustment is easy.

The photoconductor and the motor can be synchronized, for example, by making the photoconductor drive motor and the cam drive motor have the same number of poles and phases and controlling their rotations with the same drive source, or by controlling the rotation of the photoconductor and cam drive motor by the same drive source. This can be achieved by arranging a disc-shaped encoder with slits and controlling the cam motor by using a photo sensor to extract one signal per revolution.

If the part that supports the photoreceptor and the part that supports the motor 7 are integrated into a unit, such as a so-called cartridge system, adjustment will be easier, but there will also be the problem of readjustment when replacing the photoreceptor. do not have.

Although not shown, in the apparatus shown in FIG. 1, the casing of the developer is fixed and the sleeve 3
A shaft 5 supporting the magnetic roller 4 is loosely fitted into a long hole formed in the casing portion so that the sleeve moves toward and away from the photoreceptor, and is normally biased elastically in a direction away from the photoreceptor. Thus, the adjustment of the distance between the photoreceptor and the sleeve may be limited to only the sleeve portion including the shaft 5 and the magnetic roller 4.

FIG. 3 shows another embodiment of the present invention, which is a schematic oblique view of the developing device seen from behind, and the same reference numerals are given to the parts corresponding to those of the previous embodiment. This is an indication.

The developing device 2 is moved in the direction of arrow A by a spring member 9 engaged therewith.
The motor 7. is elastically biased in the direction opposite to the side where the photoreceptor is located, and a pressing member 10 is in contact with the back thereof, and is fixed to a fixed position in a fixed position such as a panel part (not shown). By controlling the motor in synchronization with the deflection of the photoconductor using the feed screws 11, 11 attached to the output shaft of 7, as in the case of the previous embodiment, the distance between the photoconductor and the sleeve is maintained at a predetermined distance. can be maintained as follows.

Incidentally, instead of the feed screw, a cam such as shown in FIG. 3A and FIG. 3B, which shows the expanded view thereof, may be used and rotated while reading the amount of deflection to control one interval.

Furthermore, although not shown, an eddy current type,
It is also possible to provide an appropriate distance sensor such as a capacitive type or an optical type, and use a step motor to rotate the cam and swing the developing device.

With this configuration, it is possible to synchronize the vibration of the photoconductor with the pre-rotation during image writing or power-on, and during printing, so that it is possible to synchronize the fluctuation of the photoconductor with the pre-rotation during image writing, power-on, and printing. It can also handle vibrations other than normal vibrations.

FIG. 4 shows still another embodiment of the present invention, in which the developing device is fixed and the photoreceptor is brought into contact with and separated from it.

The figure is viewed from the axial direction of the photoreceptor. FIG. 3 is a side view of the photoreceptor support section, and the pair of support plates 13 (only one of which is shown in the figure) has two elongated holes 16 in the case shown in the figure.
pins 13a and 16b are formed, and pins 13a and 13b, which are attached to appropriate positions on immovable parts such as panels (not shown), are loosely fitted into these pins 13a and 16b, so that the support plate 13 is disposed so as to be freely displaceable in the left and right directions shown in the figure. , the shaft 1 of the photoreceptor is attached to the bearing 15 arranged on this support plate.
4 is rotatably supported.

A developer (not shown) is shown to the right of support plate 13, which is biased to the left by spring 17 to separate the photoreceptor from the developer.

Each support plate has a screw 12a attached to the output shaft of the motor 12.
By rotating the motor 12, the distance between the photoreceptor and the sleeve can be maintained at a predetermined distance.

As mentioned above, it is easy to understand that the motor can be controlled by rotating the motor a predetermined amount based on the pre-measured deflection of the photoreceptor or the distance to the photoreceptor surface detected by a sensor. I guess it's possible.

It should be noted that the sensor is not necessarily limited to one that measures the absolute value of distance; for example, as shown in FIG. The sensor may receive reflected light from an appropriate non-image area of the photoreceptor, compare the outputs of the image area, and displace the photoreceptor so that the outputs are equalized.

As described above, according to the present invention, the distance between the image bearing member and the developing sleeve of an image forming apparatus can be maintained constant without direct contact between the two, and the eccentricity of the image bearing member can be maintained constant. It is not affected by other vibrations or vibrations transmitted from the drive system.

(3) Effects of the Invention Since the present invention has the configuration described above, it is possible to always maintain a predetermined distance between the image carrier and the developing sleeve regardless of processing or assembly errors of various parts of the device, and the image carrier This has the effect of supplying an appropriate amount of toner to the static `rrL latent image on the body surface to obtain a high quality image.

[Brief explanation of drawings]

Fig. 1 is a plan view of essential parts showing an embodiment in which the present invention is applied to an image forming apparatus equipped with a rotating cylindrical image carrier, and Figs. 2a and 2b are cams used in the above device and their development views. , FIG. 3 is a perspective view showing another embodiment, FIG. 3A is a cam used in place of the feed screw in the device of FIG. FIG. 5 is a perspective view showing an example of a sensor, and FIG. 6 is a side view of a main part illustrating a known device. 1... φ photoreceptor, 2... fat developing device, 3... ψ developing sleeve, 4... magnetic roller, 5φ... shaft, 6-- meeting bottle,
7.12---Motor 3 @ II 6 cam, 13・
... Support plate, 14... Photoconductor shaft, 17.e. Spring. □ Drawing 0 Purity (No change in content) 'Figure 1, Section 2d, Figure 2b, hand-based sales, E7 (method) 1985, 11B2'; Commissioner of the Japanese Patent Office Kuro III Akio (1) ) 2
19 Indication Patent Applications No. 162945/1983 (2) Name of the invention Image forming neck (3) Relationship with the 5 amendments Applicant address name Canon Co., Ltd. (4) Agent address Minato-ku, Tokyo Nishi-Shinbashi l-9-11 (6) Number of inventions increased by amendment 0 (7) Subject of amendment Documents and drawings proving power of representation

Claims (1)

[Claims] (1) An image forming apparatus comprising: an image carrier that carries an electrostatic latent image and travels; and a developing sleeve that is disposed close to the image carrier and supplies toner to the latent image to develop the latent image. An image forming apparatus comprising means for displacing at least one of a developing sleeve and a developing sleeve so that the distance between the two becomes a predetermined value in accordance with a detected output.