JP2011191657A - Reflective optical sensor and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an array-type reflective optical sensor capable of prolonging the life thereof, and to provide an image forming apparatus including the reflective optical sensor. <P>SOLUTION: The reflective optical sensor includes: a plurality of light emitters arrayed in a predetermined direction to irradiate a toner pattern with detection light; and a plurality of light receivers disposed corresponding to the plurality of light emitters to receive the detection light reflected by the toner pattern; wherein the density of the toner pattern and/or the position of the toner pattern are detected. The density of the toner pattern and/or the position of the toner pattern are detected by using at least one light emitter of the plurality of light emitters and the corresponding light receiver, and after a lapse of predetermined time, the density of the toner pattern and/or the position of the toner pattern are detected by using a light emitter and the corresponding light receiver other than the one light emitter and the corresponding light receiver. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a reflective optical sensor and an image forming apparatus. More specifically, the present invention relates to a reflective optical sensor used for a toner density detection sensor for detecting a toner density in a toner pattern on an image carrier or a medium, and the reflective optical sensor. The present invention relates to an image forming apparatus including an optical sensor.

  2. Description of the Related Art Image forming apparatuses that form images using toner are widely implemented as analog or digital monochrome or color copiers, printers, plotters, facsimile machines, and recently multifunction printers (MFPs). The image formed by such an image forming apparatus is a toner image. As is well known, in order to obtain a good image, the amount of toner used for developing an electrostatic latent image must be appropriate. I must. There are various known development methods, such as a method using a two-component developer including toner and carrier, and a mono-toner development method using a developer composed only of toner. The amount of toner supplied to the developing unit where the toner is developed is referred to as “toner density”.

  When the toner density is too low, a sufficient amount of toner is not supplied to the electrostatic latent image, and the resulting toner image is an image with insufficient density. On the other hand, when the toner density is too high, the density distribution of the image to be formed is biased toward the high density side, and the toner image is also difficult to see. Thus, in order to form a proper toner image, the toner density must be in an appropriate range. Conventionally, in order to control the toner density within an appropriate range, a method of forming a toner pattern for detecting toner density, irradiating it with detection light, and detecting a change in reflected light has been widely used. An optical device that irradiates a toner pattern with detection light and receives reflected light is called a reflective optical sensor.

  Various reflection type optical sensors have been proposed and known for a long time (see, for example, Patent Documents 1 to 6). These conventionally known reflection type optical sensors include one or two light emitting units, or three light emitting units (LEDs) having different wavelength characteristics, and one or two light receiving units for receiving reflected light. Part (photodiode or phototransistor). As described above, the LED is generally used as the light emitting unit, but the detection light emitted from the LED is irradiated to the toner pattern for detecting the toner concentration as a spot having a size smaller than that of the toner pattern. For example, the toner pattern is formed on the transfer belt and moves as the transfer belt rotates. At this time, the moving direction of the toner pattern is referred to as a “sub-direction”. A direction perpendicular to the sub direction on the transfer belt is referred to as a “main direction”. If an electrostatic latent image to be visualized as a toner image is formed by optical scanning, the main direction corresponds to the main scanning direction in the optical scanning, and the sub direction corresponds to the sub scanning direction.

  The toner pattern is written in an electrostatic latent image forming unit by optical scanning or the like, and is visualized by development to become a toner pattern. In the above case, the toner pattern is transferred onto the transfer belt, moved in the sub direction, and reflected by the reflective optical sensor. It moves to a detection part and is irradiated with the spot of detection light. The spot size of the detection light is usually about 2 to 3 mm in diameter. Ideally, the position in the main direction where the spot of the detection light from the reflective optical sensor is irradiated is the central portion in the main direction of the toner pattern. However, there are fluctuations in the optical scanning area in the electrostatic latent image forming unit, meandering of the transfer belt, displacement of the attachment position of the reflective optical sensor in the main direction, and changes in the attachment position in the main direction over time. For this reason, the positional relationship between the toner pattern and the reflective optical sensor in the main direction is not necessarily an ideal state.

  If the spot of detection light protrudes from the toner pattern due to the positional relationship between the toner pattern and the reflective optical sensor in the main direction, the reflected light received by the light receiving means is not appropriate, and the toner density Proper detection is not possible.

  For example, in a method of irradiating one spot, receiving reflected light by one light receiving unit, and detecting the toner density based on the difference between regular reflected light and diffuse reflected light, the spot protrudes outside the toner pattern. Consider the case of irradiation. At this time, a part of the spot is specularly reflected at the part without the toner pattern and diffusely reflected at the part of the toner pattern. Therefore, if the light receiving part is arranged to receive the specularly reflected light, the light receiving part The intensity of the specularly reflected light received by the light source is reduced by diffuse reflection, but such a decrease in the specularly reflected light intensity can occur even when the toner amount in the toner pattern is small. There is a problem in that it cannot be distinguished whether the toner is caused by a small amount of toner or if the spots are caused by protruding from the toner pattern.

  In order to avoid such a problem, conventionally, the toner is such that the spot of the detection light is located in the toner pattern in the main direction regardless of the presence of a positional deviation in the main direction of the toner pattern and the reflective optical sensor. The main direction width and the sub direction width of the pattern are set to about 15 mm to 25 mm so that the spot of the detection light does not protrude outside the toner pattern even if the positional relationship is shifted.

  Density detection using a reflective optical sensor and a toner pattern is to adjust the image forming apparatus so that the image forming process is properly performed in order to ensure and maintain high image quality in an image forming apparatus, particularly a color image forming apparatus. Since the process is performed separately from the output of the image to be formed, the original image cannot be formed while the toner density is being detected.

  When the electrostatic latent image to be a toner pattern is written by optical scanning, the optical scanning time increases in proportion to the size of the toner pattern, which causes a reduction in work efficiency for original image formation.

  Further, the toner forming the toner pattern is consumed as non-contributing toner that does not contribute to the original image formation, and the consumption amount of non-contributing toner increases in proportion to the size (area) of the pattern.

  That is, the conventionally known toner concentration detection methods have a problem that it is difficult to improve work and a problem that the consumption of non-contributing toner is large.

In view of the above-described circumstances, Patent Document 7 proposes an array-type reflective optical sensor.
This reflective optical sensor has M (≧ 3) detection light emitting portions for emitting detection light, and a support member can be irradiated with detection light spots at M locations in a direction orthogonal to the sub-direction. , The irradiation means is arranged in one direction intersecting the sub-direction so that the space between adjacent spots is equal to or smaller than the size of the toner pattern in the orthogonal direction, and N (≧ 3) light-receiving portions are the support members. In order to receive the reflected light of the detection light by the toner pattern, the light receiving means is arranged in one direction so as to correspond to the irradiation means and face the support member. The M light emitting portions of the irradiating means are caused to emit light, and the toner density is arithmetically detected based on the outputs of the N light receiving portions of the light receiving means.

  By the way, in the toner density detection, since the toner pattern is output to the same main scanning position, the same light emitting unit is used. When an LED is used for the light emitting part, there is a problem in that the amount of emitted light decreases due to element deterioration when it is used for a long time, so that accurate toner concentration detection cannot be performed. However, it is not sufficient, and further improvement is desired.

  The present invention has been made in view of the above problems, and an object thereof is to provide an array-type reflective optical sensor capable of achieving a long life and an image forming apparatus including the reflective optical sensor.

In order to solve the above problems, a reflective optical sensor according to the present invention and an image forming apparatus provided with the reflective optical sensor have the technical features described in the following (1) to (6). .
(1): A plurality of light emitting units that are arranged in a predetermined direction and irradiate the toner pattern with detection light, and the detection light that is provided corresponding to the plurality of light emitting units and reflected by the toner pattern is received. A reflection-type optical sensor that detects the density of the toner pattern and / or the position of the toner pattern, and includes at least one light-emitting unit and a corresponding one of the plurality of light-emitting units. The density of the toner pattern and / or the position of the toner pattern is detected by using the light receiving unit, and after a predetermined time has elapsed, the light emitting unit other than the one light emitting unit and the corresponding light receiving unit and the corresponding light receiving unit A reflection type optical sensor that detects the density of the toner pattern and / or the position of the toner pattern using a section.

  According to the configuration described in (1) above, the light emitting unit used for detecting the toner density or the toner pattern position, and the light receiving unit are used after the predetermined time has elapsed. Thus, the life of the reflective optical sensor can be extended.

(2) The reflection type optical sensor according to (1), wherein the predetermined time is the number of times the density of the toner pattern and / or the position of the toner pattern is detected.

  According to the configuration described in (2) above, it is possible to extend the life of the reflective optical sensor by switching between the light emitting unit and the light receiving unit according to the number of times the toner density or toner pattern position is detected.

(3) The reflection type optical sensor according to (1), wherein the predetermined time is a cumulative lighting time of the one light emitting unit.

  According to the configuration described in (3) above, it is possible to extend the life of the reflective optical sensor by switching between the light emitting unit and the light receiving unit according to the cumulative lighting time of the light emitting unit.

(4): The density of the toner pattern and / or the position of the toner pattern is detected by using at least one light emitting unit and the corresponding light receiving unit among the plurality of light emitting units, and the one light emitting unit When the amount of light received by the corresponding light receiving unit is out of the reference range, the density of the toner pattern and / or the toner pattern using the one light emitting unit, the light emitting unit other than the corresponding light receiving unit, and the corresponding light receiving unit. The reflection type optical sensor according to (1) above, wherein the position is detected.

  According to the configuration described in (4) above, when the amount of light received by the light receiving unit is out of the reference range, it is possible to extend the life of the reflective optical sensor by switching between the light emitting unit and the light receiving unit. did.

(5): an image carrier, an optical scanning device that scans the image carrier in the main scanning direction with a light beam modulated in accordance with image information, and attaches toner to the latent image. A developing device that generates a toner image, a transfer device that directly transfers the toner image to a medium on a support member, or transfers the toner image to a medium via an intermediate transfer member, the image carrier, the support member, or The reflective optical sensor according to any one of (1) to (4), wherein the reflective optical sensor detects the density and / or position of the toner pattern formed on the intermediate transfer member. An image forming apparatus.

  According to the configuration described in (5) above, it is possible to realize an image forming apparatus equipped with the reflective optical sensor described in (1) to (4) above.

  The image forming apparatus according to claim 5, wherein the image information is multicolor image information.

  According to the configuration described in (6) above, it is possible to realize a color image forming apparatus equipped with the reflective optical sensor described in (1) to (4) above.

  According to the present invention, it is possible to provide an array-type reflective optical sensor that can achieve a long life and an image forming apparatus including the reflective optical sensor.

1 is a schematic diagram for explaining a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a schematic diagram for explaining a configuration example of a toner pattern and an arrangement configuration example of the toner pattern and a reflective optical sensor. FIG. 10 is an explanatory diagram for describing detection of a toner pattern by a reflective optical sensor. It is a graph which shows the part for regular reflection contribution from the transfer belt in each light-receiving part D1-D5 of a reflection type optical sensor. It is a graph which shows the regular reflection contribution part and diffuse reflection contribution part from the toner pattern in each light-receiving part D1-D5 of a reflection type optical sensor. It is a graph which shows the part for regular reflection contribution from a transfer belt which has a toner pattern in each light-receiving part D1-D5 of a reflection type optical sensor, and a diffuse reflection contribution part. It is a graph which shows the output by the transfer belt in each light-receiving part D1-D5 of a reflection type optical sensor from the transfer belt which has a toner pattern, the output by a toner pattern, and the sum total in all the light-receiving parts. FIG. 6 is an explanatory diagram for explaining toner pattern density detection after a predetermined time has elapsed by a reflective optical sensor. FIG. 10 is an explanatory diagram for describing detection of the position of a toner pattern after a predetermined time has elapsed by a reflective optical sensor.

The reflective optical sensor according to the present invention is arranged in a predetermined direction, and is provided corresponding to a plurality of (M) light emitting units that irradiate the toner pattern with detection light, and the plurality of light emitting units, A plurality of (N) light receiving portions that receive detection light reflected by the toner pattern, and detects the density of the toner pattern and / or the position of the toner pattern, and at least one of the plurality of light emitting portions After detecting a density of the toner pattern and / or a position of the toner pattern by using one light emitting unit and a corresponding light receiving unit, and after a predetermined time has passed, other than the one light emitting unit and the corresponding light receiving unit The density of the toner pattern and / or the position of the toner pattern is detected using the light emitting unit and the corresponding light receiving unit.
An image forming apparatus according to the present invention includes an image carrier, an optical scanning device that forms a latent image by scanning the image carrier with a light beam modulated according to image information in a main scanning direction, and A developing device that attaches toner to the latent image to generate a toner image; a transfer device that directly transfers the toner image to a medium on a support member or an intermediate transfer member; And a reflective optical sensor according to the present invention for detecting the density and / or position of the toner pattern formed on the body, the support member, or the intermediate transfer member.
Next, the reflective optical sensor according to the present invention and the image forming apparatus including the reflective optical sensor will be described in more detail.
Although the embodiments described below are preferred embodiments of the present invention, various technically preferable limitations are attached thereto, but the scope of the present invention is intended to limit the present invention in the following description. Unless otherwise described, the present invention is not limited to these embodiments.

Embodiments of the invention will be specifically described below.
First, an embodiment of an image forming apparatus will be described with reference to FIG. The image forming apparatus shown in FIG. 1 forms a “color image”. A color image is formed by toners of four colors of yellow: Y, magenta: M, cyan: C, and black: K.

In FIG. 1, a portion indicated by reference numeral 20 is an “optical scanning device”. As the optical scanning device 20, various publicly known devices can be used.
Reference numerals 11Y to 11K are drum-shaped photoconductors that are “photoconductive latent image carriers”, and the photoconductor 11Y is used for forming a toner image with yellow toner, and the photoconductors 11M, 11C, and 11K are respectively Used to form a toner image with magenta toner, cyan toner, and black toner.
That is, the optical scanning device 20 performs “image writing by optical scanning” on the four photoconductors 11Y, 11M, 11C, and 11K.

  Each of the photoconductors 11Y to 11K is rotated at a constant speed in the clockwise direction, is uniformly charged by the charging rollers TY, TM, TC, and TK that form a charging unit, and receives “each corresponding optical scanning” by the optical scanning device 20, and yellow. , Magenta, cyan, and black are written to form a corresponding electrostatic latent image (negative latent image).

  These electrostatic latent images are reversed and developed by developing devices GY, GM, GC, and GK, respectively, and a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are formed on the photoreceptors 11Y, 11M, 11C, and 11K, respectively. Is done.

  These color toner images are transferred to a recording sheet (not shown) (transfer paper or a plastic sheet for an overhead projector). A transfer belt 17 is used for transfer. The recording sheet is fed from a sheet placement portion (not shown) (provided at the lower portion of the transfer belt 17), supplied to the upper peripheral surface on the right side of the transfer belt 17 in FIG. Then, the transfer belt 17 is conveyed counterclockwise by rotating counterclockwise. While being conveyed in this manner, the yellow toner image is transferred from the photoreceptor 11Y to the recording sheet by the transfer unit 15Y, and the magenta toner image and cyan are transferred from the photoreceptors 11M, 11C, and 11K by the transfer units 15M, 15C, and 15K, respectively. The toner image and the black toner image are sequentially transferred.

  A part of each color toner image remaining after transfer by the transfer units 15Y, 15M, 15C, and 15K on the surface of each of the photoreceptors 11Y, 11M, 11C, and 11K is cleaned by the cleaning blades BY, BM, BC, and BK. Is done. After the cleaning, the photoconductors 11Y, 11M, 11C, and 11K are rotated again to positions facing the charging rollers TY, TM, TC, and TK, and used for the next image forming process.

  In this way, a yellow toner image to a black toner image are superimposed on the recording sheet to compose a color image synthetically. On the recording sheet, the carried color image is fixed by the fixing device 19 and discharged out of the device. Instead of the above, an intermediate transfer belt is used, and the four color toner images are superimposed on the intermediate transfer belt and transferred to obtain a color image. May be transferred and fixed.

  In FIG. 1, reference numerals OS1 to OS4 denote reflection type optical sensors of the present invention. In the image forming apparatus shown in FIG. 1, image writing is performed by optical scanning as described above, and the main scanning direction in optical scanning is a direction orthogonal to the drawing of FIG. 1 (the same direction as the rotation axis of the photoconductor 11). This direction is called “main direction”. The toner density detection is performed as follows using the reflective optical sensors OS1 to OS4.

  That is, the toner pattern for detecting the toner density is an electrostatic latent image that is to be formed by individually writing on the photoconductors 11Y to 11K by the optical scanning device 20, and the developing devices GY, GM, GC, The toner image is reversed and developed by GK, and further transferred directly to the surface of the transfer belt 17 to become a toner pattern. (In other words, it is not transferred to the recording sheet.)

  As is apparent from this description, the transfer belt 17 is a support member in the embodiment being described. Therefore, hereinafter, the transfer belt 17 is also referred to as a “support member 17”. The toner pattern is formed on the transfer belt 17 as a support member, and is moved by the rotation of the transfer belt 17, and the toner density detection and position detection are performed by the reflective optical sensors OS1 to OS4.

  The toner pattern formed on the transfer belt 17 is removed from the surface of the transfer belt 17 by a cleaning device (not shown) on the right side of the reflective optical sensors OS1 to OS4 in FIG. 1, that is, on the downstream side of these sensors. The

  FIG. 2 illustrates the relationship between the toner pattern formed on the transfer belt 17 as a support member and the reflective optical sensors OS1 to OS4. As shown in FIG. 2, the vertical direction in FIG. 2 is the main direction and corresponds to the direction orthogonal to the drawing in FIG. Further, the left-right direction in FIG. 2 is the sub direction, and the left direction is the moving direction of the surface of the transfer belt 17 (indicated by an arrow A in FIG. 2).

  In FIG. 2, reference numerals PP1 to PP4 indicate position detection patterns for detecting the positions of the yellow toner image to the black toner image on the transfer belt 17, and reference numerals DP1 to DP4 indicate toner patterns for toner density detection.

  The toner pattern DP1 is a pattern for detecting the density of yellow toner, and the toner patterns DP2, DP3, and DP4 are patterns for detecting the density of magenta toner, cyan toner, and black toner, respectively.

  That is, the reflective optical sensors OS1 to OS4 detect the position of each color toner image at four locations in the main scanning direction, and the reflective optical sensor OS1 detects the density of yellow toner, and the reflective optical sensors OS2 to OS4. Detects the density of magenta toner to black toner.

  As a modification, for example, four patterns of toner patterns DP1 to DP4 are formed on the upstream side in the sub-direction following the toner pattern DP1 in FIG. 2, and these are sequentially detected by the reflective optical sensor OS1. Can also be provided. In this case, for example, the reflection type optical sensor OS4 may be omitted, and the position detection patterns PP1 to PP3 may be detected at three locations in the main scanning direction by the three reflection type optical sensors OS1 to OS3.

  As shown in FIG. 2, the position detection patterns PP1 to PP4 are formed at positions corresponding to the reflective optical sensors OS1 to OS4 on the transfer belt 17, and are formed in a line pattern parallel to the main direction and the main direction. It is comprised by the linear pattern inclined diagonally. These line-shaped patterns are parallel to the main direction and are inclined with respect to the main direction to form a pair, and each pair is formed of yellow, magenta, cyan, and black toners.

  In the above, an example in which the toner pattern formed on the transfer belt 17 for conveying and transferring the recording sheet is detected has been described. However, depending on the form of the image forming apparatus, a photosensitive member as a latent image carrier or intermediate The toner pattern formed on the transfer belt (or intermediate transfer member) can also be detected by a reflective optical sensor.

Hereinafter, the detection of the reflective optical sensor and the toner pattern will be described through embodiments.
In FIG. 3A, the symbol OS1 indicates the reflection type optical sensor described above. Since the four reflective optical sensors OS1 to OS4 described above are structurally identical, the reflective optical sensor OS1 will be described as an example.

In FIG. 3A, the vertical direction is the “main direction” and the horizontal direction is the “sub direction”. In the reflective optical sensor OS1, as shown in FIG. 3A, detection light emitting parts E1 to E10 (M = 10) for emitting detection light are arranged at regular intervals at a predetermined pitch in parallel to the main direction. On the other hand, the light receiving units D1 to D10 (N = 10) that receive the reflected light are arranged at equal intervals in parallel with the main direction to form “light receiving unit”. In this configuration, the light receiving means is associated with the appropriate housing. The housing is arranged in a predetermined positional relationship at “a position below the transfer belt 17” shown in FIG.
Here, M is preferably 6 (= 3 × 2) or more. N is preferably 6 (= 3 × 2) or more. Furthermore, it is preferable that M and N are the same number.

  The light emitting units E1 to E10 forming the irradiation unit and the light receiving units D1 to D10 forming the light receiving unit are located at the same position in the main direction. That is, the arrangement pitch of the light receiving parts D1 to D10 is equal to the arrangement pitch of the light emitting parts E1 to E10.

  The surface of the transfer belt 17 is smooth, and the specularly reflected light on the surface of the transfer belt of the detection light radiated from each light emitting unit is reflected between the corresponding light receiving unit and the two light receiving units adjacent to the corresponding light receiving unit. It is assumed that light is received by a total of three light receiving units. Accordingly, in FIG. 3B, when the light emitting unit E3 is lit, the specularly reflected light on the transfer belt surface of the detection light emitted from the light emitting unit E3 is D2 adjacent to the light receiving units D3 and D3 corresponding to E3. And D4 receive light, but D1 and D5 to D10 do not receive light. That is, the outputs from the three light receiving units D2, D3, and D4 are not zero, but the outputs from the remaining light receiving units D1 and D5 to D10 are zero.

  The light emitting units E1 to E10 are specifically LEDs, and the light receiving units D1 to D10 are specifically PDs (photodiodes).

  The arrangement pitch of the light emitting portions E1 to E10 is such that the detection light emitted from each light emitting portion irradiates the surface of the transfer belt 17 as 10 spots arranged in the main scanning direction as spots, and between adjacent spots (non-irradiation region). Is smaller than the “width in the main direction” of the toner pattern DP1.

  As described above, the toner patterns DP1 to DP4 for detecting the toner density are formed for each color toner of yellow, magenta, cyan, and black, but the toner pattern DP1 shown in FIG. 3A is composed of yellow toner. . The toner pattern DP1 is obtained by changing the density to a plurality of gradations (5 gradations in the example of FIG. 3) and forming individual patterns in a rectangular shape. That is, the toner pattern DP1 is a set of five “rectangular toner patterns” having different density gradations. These rectangular toner patterns with different density gradations can be formed by adjusting the laser power or light emission duty in optical scanning or adjusting the developing bias.

  As shown in FIGS. 3A and 3B, the toner pattern DP1 is formed on the surface of the transfer belt 17 as a support member and moves in the sub-direction, and approaches the detection distance of the reflective optical sensor OS1. To go. The time at which the toner pattern DP1 is formed is determined, and the time to reach the detection region after the toner pattern DP1 is formed is also determined approximately.

  Therefore, the light emitting unit (LED) is controlled to blink at an appropriate timing when the toner pattern DP1 approaches the detection distance. Here, the light emitting unit to be controlled to blink does not need to control all the light emitting units E1 to E10 to blink, and only controls the light emitting units near the toner pattern DP1 to blink.

  Here, it is assumed that the toner pattern DP1 passes near the light emitting portion E3, and the light emitting portions E1 to E5 are sequentially blinked.

  The size of the spot formed on the surface of the transfer belt 17 by the detection light emitted from the light emitting portions E1 to E5 is smaller (for example, 2 mm) than the pitch (for example, 3 mm) of the light emitting portions E1 to E5. Five spots are arranged adjacent to each other in the main direction on the transfer belt.

  The “individual rectangular toner patterns” in the toner pattern DP1 are formed such that the size in the main direction is smaller than the pitch (3 mm) of the light emitting portions (for example, 2.5 mm). At this time, since the distance between adjacent spots in the main direction is 1 mm, the size of the toner pattern in the main direction is smaller than 2.5 mm. The lighting of the light emitting unit is sequentially performed from the light emitting unit E1 toward the light emitting unit E5. That is, first, the light emitting unit E1 is turned on and turned off, and then the light emitting unit E2 is turned on and turned off. Next, the light emitting unit E3 is turned on / off, and the light emitting unit E4 and the light emitting unit E5 are turned on / off in this order. These light emitting units are repeatedly turned on and off at high speed. Therefore, the surface of the transfer belt 17 is repeatedly scanned in the main direction with five spots of detection light. This is hereinafter referred to as “spot scanning with detection light”.

  As described above, when the surface of the transfer belt 17 is smooth and the detection light is irradiated to the portion where the toner pattern is not formed, the reflected light is regular reflected light.

  The specularly reflected light on the surface of the transfer belt 17 of the detection light emitted from each light emitting part is incident only on the corresponding light receiving part and two adjacent light receiving parts (the remaining light receiving parts not corresponding to the light emitting part). It is supposed to be. This will be described with reference to FIG. FIG. 4 shows the detection output at each light receiving portion of the specularly reflected light by the transfer belt 17 of the detection light emitted from the light emitting portion E3 when only the light emitting portion E3 is turned on. The horizontal axis indicates the light receiving unit, and the vertical axis indicates the magnitude of the detection output. Here, the detection outputs of the light receiving part D1 and the light receiving part D5 are zero.

Under such conditions, for example, when the central portion of the toner pattern DP1 in the main direction is transported to the position irradiated with the spot of the detection light from the light emitting unit E3 (however, the position still irradiated is reached). Is not in the state.)
The detection light emitted from the light emitting part E1 is regularly reflected on the surface of the transfer belt 17 and received by the light receiving part D1 and the light receiving part D2. At this time, when only the light emitting unit E1 is blinking, the detection output in the corresponding light receiving unit D1 is approximately the same as the detection output of the light receiving unit D3 when only the light emitting unit E3 is emitting light, and in the light receiving unit D2. The detection output is substantially the same as the detection output of the light receiving unit D4 when only the light emitting unit E3 emits light.
Similarly, the detection light emitted from the light emitting unit E2 is regularly reflected on the surface of the transfer belt 17 and received by the light receiving unit D1, the light receiving unit D2, and the light receiving unit D3, and the detection light emitted from the light emitting unit E4 is transferred to the transfer belt 17. Is regularly reflected on the surface of the transfer belt 17 and received by the light receiving unit D3, the light receiving unit D4, and the light receiving unit D5, and the detection light emitted from the light emitting unit E5 is regularly reflected on the surface of the transfer belt 17 and received by the light receiving unit D4 and the light receiving unit D5. The
When only the light emitting unit E2 is lit, the detection output in the corresponding light receiving unit D2 is almost the same as the detection output of the light receiving unit D3 when only the light emitting unit E3 emits light, and the detection in the light receiving units D1 and D3. The outputs are almost the same as the detection outputs of the light receiving parts D2 and D4 when only the light emitting part E3 emits light. When only the light emitting unit E4 is blinking, the detection output in the corresponding light receiving unit D4 is almost the same as the detection output of the light receiving unit D3 when only the light emitting unit E3 emits light, and the detection in the light receiving units D3 and D5. The outputs are almost the same as the detection outputs of the light receiving parts D2 and D4 when only the light emitting part E3 emits light.
When only the light emitting unit E5 is blinking, the detection output in the corresponding light receiving unit D5 is almost the same as the detection output of the light receiving unit D3 when only the light emitting unit E3 emits light, and the detection output in the light receiving unit D4 is This is almost the same as the detection output of the light receiving unit D2 when only the light emitting unit E3 emits light.

On the other hand, consider a case where the toner pattern DP1 is conveyed to the detection position of the reflective optical sensor OS1.
When the light emitting unit E3 is turned on and the detection light irradiates the toner pattern DP1, the detection light is specularly reflected and diffusely reflected by the toner pattern DP1, as shown in FIG.
At this time, the detection output distribution in each light receiving unit is shown in FIG. The detection outputs at D1 and D5 are only the diffuse reflection contribution due to the toner pattern, and the detection outputs at D3 are only the regular reflection contribution due to the toner pattern, but the detection outputs at D2 and D4 are the diffuse reflection contribution due to the toner pattern. Regular reflection contributions are mixed.

  Therefore, looking at the outputs of the light receiving portions D1 to D5 when the detection light irradiation object is the toner pattern DP1 on the transfer belt 17, the amount of light received by the light receiving portion D3 is the case where the irradiation object is the transfer belt 17 alone. The output at other light receiving units is a value other than 0. From this result, it can be seen that the toner pattern DP1 (one rectangular toner pattern thereof) is at the position of the light emitting portion E3. When the toner pattern is between the light emitting units E3 and E4, the output of the light receiving unit D3 is low when the light emitting unit E3 is lit, and the output of the light receiving unit D4 is low when the light emitting unit E4 is lit. Become. Thus, it can be seen that the toner pattern is between the light emitting portions E3 and E4 in the main direction. When the light emitting unit E4 is turned on, if the output of the light receiving unit D3 is smaller than the output of the light receiving unit D4, the toner pattern may be “on the side closer to the light emitting unit E4 than the light emitting unit E3”. Recognize.

  In this way, the position in the main direction of the toner pattern DP1 can be detected with an accuracy of “the arrangement pitch of the light emitting portions Ei (i = 1 to 5)”.

  If this is spread, if M is set to 100, for example, and 100 light emitting parts E1 to EM are arranged in the main direction at a pitch of 100 μm, for example, the arrangement width is 10 mm. Similarly, when N = 100, 100 light receiving portions D1 to DN are arranged in a main direction at a pitch of 100 μm, and the size of the spot formed on the surface of the support member by the detection light from the light emitting portions Ei (i = 1 to 100). Is 80 μm, and is regularly reflected by the support member and received by the light receiving portion Dj (j = i−1, i, i + 1), and the size of the toner pattern in the main direction is equal to the light emitting portion pitch: 100 μm. To do. At this time, while the light emitting unit Ei is blinking sequentially from i = 1 to 100, the change in the output of the light receiving unit Di (i = 1 to 100) is examined, and when the light emitting units Ei and Ei + 1 are turned on, the light receiving unit Di and If the output of Di + 1 is low, it can be seen that the toner pattern is “position between the light emitting portions Ei and Ei + 1” in the main direction. That is, the position in the main direction of the toner pattern with the size in the sub direction: 100 μm can be detected with an accuracy of 100 μm.

  As described above, for example, arranging 100 light emitting units in the main direction at a pitch of 100 μm can be easily realized by using an LED array, and arranging 100 light receiving units in the main direction at a pitch of 100 μm is a PD. This can be easily realized by using an array, and an arrangement pitch of several tens of μm to several hundreds of μm can be easily realized depending on the LED array or PD array.

  The reflective optical sensor in the example described with reference to FIG. 3 has a high density of independent LEDs as the light emitting parts E1 to E5 and PDs as the light receiving parts D1 to D5, for example, resin mold type or surface mount type. It can be integrated and configured. If ultra-compact LEDs or PDs are used, the size of each element is on the order of mm, and mounting with an arrangement pitch of about 1 mm is possible. Therefore, in that case, the position in the main direction of the “toner pattern of about 1 mm in the main direction” can be detected with 1 mm accuracy.

  As described above, the toner pattern DP1 is a pattern for detecting the density of yellow toner, and a rectangular toner pattern whose density changes in five levels is arranged and formed at a predetermined pitch in the sub direction.

  As described above, when the light emitting units E1 to E5 are sequentially blinked and the light spot of the detection light from the light emitting unit E3 irradiates the toner pattern, for example, the incident amount of specularly reflected light is reduced in the light receiving unit D3. The output is small, and the output is increased in other light receiving units due to the incidence of diffusely reflected light. The regular reflection light in the reflection of the toner pattern monotonously decreases as the toner density increases, and the diffuse reflection light monotonously increases as the toner density increases.

  The toner density detection method is based on the difference in reflection characteristics between the transfer belt 17 and the toner pattern DP1, and therefore pays attention to the above-described regular reflection light and diffuse reflection light. If attention is paid to the diffuse reflected light, the diffuse reflected light in the reflection of the toner pattern monotonously increases as the toner density increases. In addition, since all the reflected light in the reflection of the transfer belt is regular reflected light, the contribution of the reflected light due to the diffuse reflected light is zero.

  Therefore, the difference in reflection characteristics between the pattern having a low toner density and the transfer belt 17 is small, and the difference in reflection characteristics between the pattern having a high toner density and the transfer belt 17 is large.

  Here, an algorithm for improving the toner density detection efficiency in the toner density detection method using the toner pattern DP1 shown above will be described with reference to FIGS.

  When the toner pattern DP1 does not exist on the transfer belt 17, the reflected light from the surface of the transfer belt 17 when the light-emitting portion E3 is turned on and the detection light irradiates the surface of the transfer belt 17 is five light beams D1 to D5. When detected by the light receiving unit, the detection outputs at the three light receiving units D2 to D4 are not 0, but the detection outputs at D1 and D5 are 0. Here, when the detection output at D2 is a, the detection output at D3 is b, and the detection output at D4 is c, the reflection characteristic of the transfer belt 17 can be expressed as (a + b + c).

  In addition, the detection output in the light receiving unit D3 corresponding to the light emitting unit E3 that is lit, and each light receiving unit (here, the light receiving unit D2 and the light receiving unit D3 located within the reach of regular reflection light from the transfer belt excluding the light receiving unit D3) The ratio with the detection output of the light receiving part D4) can be derived. Ratio of D3 and D2: V is V = a / b, ratio of D3 and D4: V ′ is V ′ = c / b.

  When a toner pattern is present on the transfer belt 17, when the light emitting portion E3 is turned on and the detection light irradiates the toner pattern DP1 on the transfer belt 17, the detection light is regularly reflected and diffusely reflected by the toner pattern. . Since the light receiving unit of D3 detects only the specular reflection light of the irradiation object, it includes only the contribution of specular reflection light, but all the detection outputs in the four light receiving units except D3 include the contribution of diffuse reflection light. Yes.

  However, the detection outputs in the two light receiving portions D1 and D5 include only the contribution due to the diffuse reflected light. This can be easily understood from the result that the regular reflection light from the transfer belt 17 is received only by the three light receiving portions D2 to D4 when the irradiation object is the transfer belt 17. On the other hand, in the detection outputs in the two light receiving portions D2 and D4, the regular reflection contribution due to the toner pattern and the diffuse reflection contribution are mixed.

  The calculation of the mixing ratio will be described with reference to FIG. When the detection output at the light receiving portion D2 when the detection light from the light emitting portion E3 is reflected by the toner pattern on the transfer belt is d, the detection output at the light receiving portion D3 is e, and the detection output at D4 is f, the detection at D2 In the output d, V · e is the regular reflection contribution due to the toner pattern, and the remaining (d−V · e) is the diffuse reflection contribution due to the toner pattern. Similarly, in the detection output f at D4, V ′ · e is the regular reflection contribution due to the toner pattern, and the remaining (f−V ′ · e) is the diffuse reflection contribution due to the toner pattern. Thus, the detection outputs at D2 and D4 can be divided into regular reflection contributions and diffuse reflection contributions.

  Therefore, when only the light emitting unit E3 is turned on, if the object of the detection light to be irradiated is a toner pattern, the sum of the regular reflected light contributions by the toner patterns of all the light receiving units D1 to D5 is e · (1 + V + V ′), and the output value increases by e · (V + V ′) as compared with the case where only the light receiving portion at D3 is used for toner density detection. Similarly, the sum of the diffuse reflection contribution due to the toner patterns of all the light receiving portions D1 to D5 is expressed as (g + h + (d−V · e) + (f) where g is the detection output at D1 and h is the detection output at D5. −V ′ · e)), and the output value increases by (d−V · e) + (f−V ′ · e) compared to the case where only the light receiving portions at D1 and D5 are used for toner density detection. .

  That is, the detection outputs at D2 and D4 are divided into regular reflection contributions and diffuse reflection contributions, and as shown in FIG. 7, the sum of the regular reflection contributions by the toner patterns at all the light receiving portions D1 to D5 and the diffuse reflection contributions. The sum of the specular reflection contributions of the detection output at each light receiving part is added to all the light receiving parts, and the sum of the diffuse reflection contributions of the detection output at each light receiving part is added to all the light receiving parts. The toner density is arithmetically detected based on the difference between the two reflection characteristics and the above-described reflection characteristic of the transfer belt 17.

When the density of the toner pattern is high, the sum of the regular reflection contributions of the detection output at each light receiving part over all the light receiving parts becomes small, and the diffuse reflection contribution of the detection output at each light receiving part is added over all the light receiving parts. The sum is larger.
When the density of the toner pattern is low, the sum of the regular reflection contributions of the detection output at each light receiving part over all the light receiving parts becomes large, and the diffuse reflection contribution of the detection output at each light receiving part is added over all the light receiving parts. The sum is smaller.

Next, position detection by the position detection pattern PP1 will be described.
FIGS. 3D to 3F schematically illustrate “position detection by the position detection pattern PP1”.
As shown in FIG. 3, the position detection pattern PP1 includes linear patterns LPY1, LPM1, LPC1, and LPB1 parallel to the main direction, and linear patterns LPY2, LPM2, LPC2, and LPB2 that are inclined with respect to the main direction. It is comprised by. The line patterns LPY1 and LPY2 form a pair and are formed of yellow toner. Similarly, the line patterns LPM1 and LPM2 are paired and formed with magenta toner, the line patterns LPC1 and LPC2 are paired and formed with cyan toner, and the line patterns LPB1 and LPB2 are paired with black toner. Formed with.

  Parallel line patterns LPY1, LPM1, LPC1, and LPB1 of these toners are formed so as to form a constant interval in the sub direction (vertical direction in FIGS. 3D to 3F). That is, if these parallel line patterns LPY1, LPM1, LPC1, and LPB1 are arranged at a constant interval (desired interval) in the sub direction, the yellow to black toner images have an appropriate positional relationship in the sub direction. Eggplant.

  In order to detect whether or not the positional relationship in the sub-direction is appropriate, as shown in FIG. 3 (f), the timing at which the position detection pattern PP1 approaches the reflective optical sensor is measured, for example, at an appropriate timing. The light emitting unit E3 is continuously turned on. As the position detection pattern PP1 moves, the detection light from the light emitting portion E3 is displaced in the sub direction with respect to the support member 17, and the detection light spots sequentially irradiate the line patterns LPY1 to LPB1.

  Then, when the detection light irradiates the line pattern, by tracking the output of the light receiving parts D1 to D5 in time, it is possible to detect the time interval at which the detection light irradiates the four line patterns, If this time interval is equal, the positional relationship between the toner images in the sub-direction is appropriate. If the time interval is not equal, there is a shift in the positional relationship between the toner images, and the amount of shift can be known. The timing of the optical scanning start can be controlled so as to correct.

  Further, the deviation in the main direction between the toner images can be detected as follows. The detection in this case will be described with reference to FIGS. 3E and 3F for a yellow toner image.

  FIG. 3E shows a case where the yellow toner image is at an appropriate position in the main direction (left and right direction in FIG. 3E). At this time, the spot line pattern LPY1 of the detection light from the light emitting unit E3 is irradiated. Then, T is the time from when the line-shaped pattern LPY2 is irradiated. FIG. 3F shows a case where the yellow toner image is shifted by ΔS in the main direction. Since the line pattern LPY2 is inclined with respect to LPY1, the time from when the spot of the detection light from the light emitting unit E3 irradiates the line pattern LPY1 to the line pattern LPY2 is T + ΔT, which is appropriate. The amount of deviation in the main direction can be known from the time at a correct position: difference from T: ΔT.

That is, if the angle formed by the line pattern LPY2 in the main direction is θ and the moving speed of the transfer belt 17 as a support member in the sub direction is V,
ΔS · tanθ = V · ΔT
Therefore, the deviation amount ΔS in the main direction is
ΔS = V · ΔT · cotθ
Can know as

  Next, a method for extending the lifetime of the reflective optical sensor described above will be described in detail with reference to FIGS.

  In the above, the toner pattern density detection and the pattern position detection are performed using the light emitting units E1 to E5. However, if the toner pattern density detection and the pattern position detection are performed a predetermined number of times, as shown in FIGS. The positions where the toner pattern and the position detection pattern are formed are changed, and the toner pattern density detection and the pattern position detection are performed using the light emitting units E6 to E10. If the number of detections to be specified is set to be the number of times that the light emitting units E1 to E5 are expected to deteriorate, the reflective optical sensor can be used for a longer time.

  As another embodiment, the lighting time is accumulated in each of the light emitting units E1 to E5, and if the accumulated time of any of the light emitting units E1 to E5 reaches a predetermined time, the toner The position where the pattern and the position detection pattern are formed is changed, and the toner pattern density detection and the pattern position detection are performed using the light emitting units E6 to E10. If the specified accumulated time is set to a time when the light emitting unit is expected to deteriorate, the reflective optical sensor can be used for a longer time. Further, since the lighting time is accumulated, it is possible to grasp the time when it will deteriorate more accurately.

  As another embodiment, when the detection value when the toner pattern density detection and the pattern position detection are performed using the light emitting units E1 to E5 deviates from a preset allowable value, the toner pattern, the position The position where the detection pattern is formed is changed, and the toner pattern density detection and the pattern position detection are performed using the light emitting units E6 to E10. In this way, it is possible to use the reflective optical sensor for a longer time since another light emitting unit is used after confirming that the light emitting unit has deteriorated.

  In yet another embodiment, each time toner pattern density detection and pattern position detection are performed, the positions where the toner pattern and the position detection pattern are formed are changed, and the light emitting units E1 to E5 and the light emitting units E6 to E10 are alternately arranged. You may make it switch to.

  Thus, for example, in the case of M = 10 and N = 10 (when there are 10 light emitting units and 10 light receiving units, respectively), a combination of 1 ≦ m, n ≦ 5 light emitting units and corresponding light receiving units, 6 ≦ m, n ≦ 10 and the combination of the corresponding light receiving portions are not used at the same time (for detecting the density and / or position of the same toner pattern) but at different times (different toner pattern densities and By selectively using it only for (// detecting the position), the lifetime of the reflective optical sensor can be extended.

  In addition, this invention is not limited to the above-mentioned embodiment at all, and does not prevent adding a well-known and usual technique suitably. In other words, for example, an illumination optical system (illuminating condensing lens) and a light receiving system (light receiving condensing lens) as described in Patent Document 7 may be provided.

OS1 to OS4 Reflective optical sensor E1 to E10 Light emitting part (LED)
D1 to D10 Light receiving part (PD)
DP1 to DP4 Toner pattern for toner density detection 17 Support member (transfer belt)

JP 2008-064953 A JP-A 64-35466 JP 2004-21164 A JP 2002-72612 A JP 2004-309292 A JP 2004-309293 A JP 2009-258601 A

Claims (6)

A plurality of light emitting units arranged in a predetermined direction and irradiating the toner pattern with detection light;
A plurality of light receiving portions provided corresponding to the plurality of light emitting portions and receiving the detection light reflected by the toner pattern,
A reflective optical sensor for detecting the density of the toner pattern and / or the position of the toner pattern,
The density of the toner pattern and / or the position of the toner pattern is detected using at least one light emitting unit and a corresponding light receiving unit among the plurality of light emitting units, and after a predetermined time has passed, the 1 A reflection type optical sensor that detects the density of the toner pattern and / or the position of the toner pattern using a light emitting unit other than the light emitting unit and the corresponding light receiving unit and a corresponding light receiving unit.   The reflective optical sensor according to claim 1, wherein the predetermined time is the number of times the density of the toner pattern and / or the position of the toner pattern is detected.   The reflective optical sensor according to claim 1, wherein the predetermined time is a cumulative lighting time of the one light emitting unit.   The density of the toner pattern and / or the position of the toner pattern is detected using at least one light emitting unit and the corresponding light receiving unit among the plurality of light emitting units, and the light receiving unit corresponding to the one light emitting unit. When the amount of light received by the sensor is out of the reference range, the density of the toner pattern and / or the position of the toner pattern is detected using the light emitting unit other than the one light emitting unit and the corresponding light receiving unit and the corresponding light receiving unit. The reflective optical sensor according to claim 1, wherein: An image carrier;
An optical scanning device that scans the image carrier with a light beam modulated in accordance with image information in a main scanning direction to form a latent image;
A developing device that attaches toner to the latent image to generate a toner image;
A transfer device for transferring the toner image directly to a medium on a support member or transferring the toner image to a medium via an intermediate transfer member;
The reflective optical sensor according to any one of claims 1 to 4, which detects the density and / or position of a toner pattern formed on the image carrier, the support member, or the intermediate transfer member. And an image forming apparatus.   The image forming apparatus according to claim 5, wherein the image information is multicolor image information.

Images