Electrophotography – Image formation – Transfer
Reexamination Certificate
2002-01-31
2004-01-06
Tran, Hoan (Department: 2852)
Electrophotography
Image formation
Transfer
Reexamination Certificate
active
06674988
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toner density and toner misregistration detection sensor for use in image formation of color image forming apparatuses such as a color copier and a color printer, and a color image forming apparatus using the same, and to a method for toner misregistration detection.
2. Description of the Related Art
Conventionally, a color image forming apparatus such as a color copier or a color printer is provided with a toner density detection sensor and a toner misregistration detection sensor separately. The toner density detection sensor is disclosed, for example, in Japanese Unexamined Patent Publications JP-A 9-89769 (1997), JP-A 10-62340 (1998), JP-A 10-186827 (1998), and JP-A 11-84768 (1999). The toner density detection disclosed in the publications is performed based on a difference in reflection rate resulting from irradiating toner with infrared light.
A toner misregistration detection sensor, as shown in
FIG. 7A
, utilizes as a light source
21
an LED in which a light pencil is narrowed by a laser or lens. The detection by the toner misregistration detection sensor is performed in such a manner that a photosensitive drum
30
is irradiated with collimated light. The photosensitive drum
30
is thereby rotated at uniform rotating speed, and reflection light reflected from each of yellow (Y) toner, magenta (M) toner, cyan (C) toner, and black (K) toner is detected by a light receiving element
22
to detect a toner misregistration by measuring time intervals between detections of the reflection light from the respective toners.
A toner misregistration sensor
20
as shown in
FIG. 7A
, for example, measures a time interval t
1
between detection of reflection light from Y toner and detection of reflection light from K toner, a time interval t
2
between detection of reflection light from M toner and detection of reflection light from K toner, and a time interval t
3
between detection of reflection light from C toner and detection of reflection lights of K toner, as shown in
FIG. 7B
, thereby detecting Y toner, M toner, and C toner misregistrations with reference to K toner position. When the time interval t
1
between the detection of the Y toner reflection light and the detection of the K toner reflection lights is longer than a predetermined value, the Y toner deviates from the K toner. When the time interval t
2
between the detections of the M toner and K toner reflection lights is shorter than a predetermined value, the M toner deviates from the K toner. Furthermore, according to a difference between the time interval t
1
and the time interval t
2
, a toner misregistration between the Y toner and the M toner can be detected. In this way, toner misregistration can be detected in accordance with differences between the time intervals between the detections of reflection light from the respective Y, M, and C toners and the detection of reflection light from the K toner.
The conventional toner density sensor detects only toner densities. Further, the conventional toner misregistration sensor detects only toner misregistrations. Therefore, in order to detect toner densities and toner misregistrations, two sensors such as a toner density sensor and a toner misregistration sensor are necessary. Therefore, there arises a problem that costs of the color image forming apparatus increases and sufficient space is necessary in the color image forming apparatus to arrange these two sensors therein.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a toner misregistration detection sensor, capable of detection of both toner density and toner misregistration with a signal detected by one light emitting element and one light receiving element, a color image forming apparatus provided with the same, and a method for toner misregistration detection.
The invention relates to a toner misregistration detection sensor for use in a color image forming apparatus, comprising:
a light emitting element for irradiating a predetermined area on an object to be detected with light;
a light receiving element for receiving reflection light which is emitted from the light emitting element and reflected on a surface of the object to be detected;
toner density detection means for detection of toner density based on a signal outputted from the light receiving element; and
toner misregistration detection means for detection of toner misregistration based on a signal outputted from the light receiving element.
According to the invention, the detection functions of a toner density detection means and a toner misregistration detection means are performed based on signals from a light receiving element which receives light which is emitted from a light emitting element and is reflected on a surface of an object to be reflected. Therefore, the space occupied by the such a sensor can be smaller in comparison with that occupied with different sensors for detection of toner density and toner misregistration, with the result that cost reduction can be achieved.
In the invention, it is preferable that the toner misregistration detection means detects a misregistration of each of the yellow toner, magenta toner and cyan toner to the black toner.
According to the invention, the toner misregistration detection means utilizes the difference in the reflection rate of light between color toners such as yellow, magenta and cyan, and a black toner, thereby detecting a misregistration of each of the color toners to the black toner.
In the invention, it is preferable that the toner misregistration detection means detects a misregistration of a pattern of each of yellow toner, magenta toner and cyan toner, to a pattern of black toner.
According to the invention, the toner misregistration detection means can detect misregistration of the respective color toners to the black toner from their patterns.
In the invention, it is preferable that the toner misregistration detection means detects a misregistration of a pattern of each of yellow toner, magenta toner and cyan toner to a pattern of black toner which are placed so as to be misregistered from each other by half of a width of either of the patterns.
According to the invention, the toner misregistration detection means can detect a misregistration of a pattern of each of yellow toner, magenta toner and cyan toner to a pattern of black toner which are disposed so as to be misregistered from each other by half of a width of either of the patterns.
In the invention, it is preferable that the toner misregistration detection means detects a misregistration of a pattern of each of yellow toner, magenta toner and cyan toner to a pattern of black toner, which patterns are disposed so as to form stripes arranged at regular intervals.
According to the invention, since the toner misregistration detection means detects a misregistration of a pattern of each of yellow toner, magenta tone and cyan toner to a pattern of black toner which patterns are disposed so as to form stripes arranged at regular intervals, the toner misregistration detection means can easily detect the direction of the misregistration.
In the invention it is preferable that the toner misregistration detection means detects a misregistration of a pattern of each of yellow toner, magenta toner and cyan toner to a pattern of black toner which is disposed so as to overlap part of the pattern of each of the color toners.
According to the invention, the black toner pattern is disposed so as to overlap part of each of the color toner patterns, thus, the toner misregistration detection means can detect a misregistration of the color toner pattern to the black toner pattern.
In the invention it is preferable that the toner misregistration detection means detects a misregistration of a pattern of each of yellow toner, magenta toner and cyan toner to a pattern of black toner which is disposed so as to be partly overlapped by the pattern of each of the color toners.
According to the invention, since the black toner pattern is
Sharp Kabushiki Kaisha
Tran Hoan
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