JPS63128380A - Magnet roll - Google Patents

Abstract

PURPOSE:To prevent image fogging, image nonuniformity, the lowering of picture density, and void from occurring, by specifying the peak position of flux density held by a permanent magnet confronting with a photosensitive drum, the peak value of the flux density, the width of the flux density value of 90% of the peak value, and the peak position of the flux density held by an adjacent permanent magnet. CONSTITUTION:When a line connecting between the central point of the photosensitive drum 1 and that of a magnet roll 2 is set as a reference line, and a position on the line is set at 0 deg., the aberration from the reference line of the peak position point (a) of the flux density held by the permanent magnet 4a confronting with the photosensitive drum 1 is set within a range of + or -2 deg.. Also, the peak value (b) of the flux density is set at 700-1,400G on the surface of a nonmagnetic sleeve 5, and furthermore, the width of the flux density value of 90% of the peak value is set within a range of + or -8 deg.-+ or -18 deg. from the reference line, and the flux density peak positions (d) and (d') held by the adjacent permanent magnet is constituted so that it exceeds + or -45 deg. from the reference line. In such way, the problem of the image fogging, the image nonuniformity, the lowering of the picture density, or the void, etc., can be evaded, and the image with high quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a magnet roll used in a developing device using magnetic brush development, and more specifically to a magnetic roll used in a developing device that uses magnetic brush development.
It relates to a magnetic roll that provides high-quality images without uneven image density, reduced image density, white spots, etc.

"Prior Art and Problems" Conventionally, a magnet roll used in a developing device has a magnetic flux density peak position of a permanent magnet facing a photoreceptor drum,
Since the relationship between the peak value, 90% width of the peak value, and developability is not clear, there are problems such as image fogging, image density unevenness, image density reduction, and white spots, making it impossible to obtain high-quality images.

"Means for Solving the Problems" In view of the above-mentioned circumstances, the present inventors have conducted intensive research and have arrived at the present invention which can solve the above-mentioned problems.

That is, the present invention includes a plurality of permanent magnets in a cylindrical non-magnetic sleeve that is disposed facing a photoreceptor drum, a box containing magnetic developer, and a doctor blade that controls the thickness of the magnetic developer. It is possible to adsorb and transport a magnetic developer to the outer periphery of the non-magnetic sleeve, control the thickness of the magnetic developer with a doctor blade, and supply the magnetic developer to the electrostatic latent image formed on the surface of the photoreceptor drum. In a magnet roll used in a developing device for producing a visual image, a reference line is defined as a line connecting the center of the photoreceptor drum and the center of the magnet roll, and the position of the peak of the magnetic flux density of the permanent magnet facing the photoreceptor drum is used as a reference line. Positional deviation from reference line is ±2°
and the peak value of the magnetic flux density is 700 to 1400G on the surface of the non-magnetic sleeve, and the width of the magnetic flux density value of 90% of the peak value is ±8 from the reference line.
The magnet roll is characterized in that the magnetic flux density peak position of adjacent permanent magnets is ±450 or more from the reference line.

``Embodiment'' To explain the present invention based on the drawings, FIG. 1 is a schematic diagram of the main parts of a copying machine, in which (1) is a photosensitive drum, (2) is a magnet roll, (3) is a toner box, The magnet roll (2) has permanent magnets (4a) to (
4d) and its outer periphery is covered with a non-magnetic sleeve (5). (6) is a doctor blade, (
7) is a magnetic developer (toner). In the figure, 01 is the center point of the photoreceptor drum (1), 02 is the magnet roll (2
), the line connecting O3 and 0□ is the reference line.

In the second session, the permanent magnet (4a) facing the photoreceptor drum (1)
) and the magnetic flux density distribution on the surface of the nonmagnetic sleeve of the permanent magnets (4b) and (4d) adjacent thereto. As mentioned above, the reference line is a line connecting the center point of the photoreceptor drum (1) and the center point of the magnet roll (2), and the line is 0°.
shall be. Point a is a permanent magnet (4a) facing the photoreceptor drum.
b indicates the peak position of the magnetic flux density of the adjacent permanent magnet (
4b) shows the magnetic flux density peak position of (4d).

In the present invention, positional deviations of three peak positions of magnetic flux density of the permanent magnet (4a) facing the photoreceptor drum (1) from the reference line O≦θ1≦+2@, 0≧02≧−2°,
That is, it is within the range of ±2'', and the peak value of the magnetic flux density on the surface of the non-magnetic sleeve (5) is between 700 and 1400.
0, and the width of 90% of the magnetic flux density value is within the range of ±8° to ±18° from the reference line, and furthermore, the magnetic flux density peak positions d and d' of adjacent permanent magnets are within the reference line. It is configured to be at least ±45° from the line. Above a
If the point exceeds the range of ±2'', the toner (7) will not adhere to the photoreceptor drum (1) sufficiently, resulting in a decrease in copy density, density unevenness, etc., and a good image will not be obtained. In addition, if the value of b is less than 700G, the toner will not stand up enough and the toner will not adhere to the photoreceptor drum sufficiently, resulting in a decrease in density, white spots, etc., and it will be difficult to obtain a good image. If the value of b exceeds 1400, excess toner may adhere or strong magnetic force may prevent toner from adhering, resulting in image fogging, density unevenness, etc., resulting in poor image quality. is not obtained.

Additionally, if the width of C is less than 16' (8°
If the angle exceeds 18°×2), image fog etc. will occur and good image quality will not be obtained. Furthermore, if d and d' are less than 45°, it is difficult to set the value of b to 700G or more, and even if
Even if a magnetic force of 00 G or more is obtained, the width of C may be less than 16° or the toner spikes may be bent, and as a result, the density of the copy may be reduced, unevenness, etc. may occur, and a good image may not be obtained.

Figure 3 shows a permanent magnet (4a) facing the photoreceptor drum (1).
) is a distribution diagram of the peak value (b) of magnetic flux density in the axial direction. h is the variation in magnetic flux density in the entire axial direction,
e is the maximum variation in magnetic flux density in the entire axial direction, and g
(mm)/f (G) is the magnetic force change rate.

In the present invention, the variation h in the magnetic flux density in the entire axial direction
is preferably within 70G and within 15G at 1ON (excluding both ends Ion). If h exceeds 70G, toner deviation will occur, causing density unevenness, and if g/f exceeds 1.5, toner deviation will occur locally, which will also cause density unevenness. .

"Operations and Effects" As described above, according to the present invention, high-quality images without image fog, image unevenness, reduction in image density, white spots, etc. can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic view of the main parts of the copying apparatus, FIG. 2 is a magnetic flux density distribution diagram on a non-magnetic sleeve, and FIG. 3 is a distribution diagram of the magnetic flux density peak value in the axial direction. 1... Photosensitive drum 2... Macnet roll 3... Toner boxes 4a to 4d... Permanent magnet 5... Non-magnetic sleeve

Claims (1)

[Claims] 1. A plurality of cylindrical non-magnetic sleeves are disposed facing the photoreceptor drum, a box containing magnetic developer, and a doctor blade that controls the thickness of the magnetic developer. It has a permanent magnet, attracts and conveys the magnetic developer to the outer periphery of the non-magnetic sleeve, controls the thickness of the magnetic developer with a doctor blade, and applies the magnetic developer to the electrostatic latent image formed on the surface of the photoreceptor drum. In a magnet roll used in a developing device that supplies a visible image, a reference line is defined as a line that connects the center of the photoreceptor drum and the center of the magnet roll, the position of the peak of the magnetic flux density of the permanent magnet facing the photoreceptor drum. The positional deviation from the reference line is within ±2°, the peak value of the magnetic flux density is 700 to 1400G on the surface of the non-magnetic sleeve, and 90% of the peak value
The width of the magnetic flux density value in % is ±8° or more ±1 from the above reference line.
8 degrees or less, and the magnetic flux density peak positions of adjacent permanent magnets are ±45 degrees or more from the reference line. 2. The peak value of the magnetic flux density of the permanent magnet facing the photoconductor drum is such that the change in magnetic flux density in the entire axial direction is within 70G and within 15G at 10mm (however, at both ends 1
(excluding 0 mm) The magnetic roll according to claim 1.