JP2011175151A - Image forming apparatus and toner density measurement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow an image forming apparatus to measure toner density in a short period of time. <P>SOLUTION: A sensor 8 includes a plurality of light-receiving elements 42 configured to detect measurement light from a plurality of detection positions arrayed vertically with respect to the advancing direction of an intermediate transfer belt 4. Among the plurality of detection positions, the first detection position is a position through which a test pattern 32 on the intermediate transfer belt 4 passes, the second detection position is a position through which the test pattern 32 on the intermediate transfer belt 4 does not pass. A correction calculation part 21 corrects the output value of the light-receiving element 42C corresponding to the first detection position by the output value of the light-receiving element 42R and/or 42L corresponding to the second detection position, then, specifies the toner density of the test pattern. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a toner density measuring method.

  In image forming apparatuses such as printers, copiers, facsimiles, and complex machines using electrophotography, the toner amount (toner density) of a toner image formed on a photoreceptor such as a photoreceptor drum is the quality of the printed image. Directly affect. This toner density changes depending on various conditions such as the environment in which the image forming apparatus is used. For example, if the charging characteristics of the developer change due to a change in the environmental atmosphere, the toner is less likely to fly from the developing unit to the photoconductor in a state where the developing bias applied to the photoconductor is kept constant.

  As the number of image formations increases, the thickness of the photosensitive layer decreases due to the cleaning blade for cleaning the photosensitive member and polishing due to contact with the intermediate transfer member, and it is difficult to keep the surface charged potential of the photosensitive member constant. Become. When the surface charging potential is gradually lowered, the toner image density is increased and the image quality is lowered.

  In particular, in a color image forming apparatus having a tandem configuration in which photoconductors corresponding to a plurality of colors to be used are arranged along the traveling direction of the intermediate transfer member, an image is formed with a color different from a desired one. There is.

  Therefore, a toner image for adjusting the toner density (hereinafter referred to as a test pattern) is carried on a predetermined area such as an intermediate transfer belt for primary transfer of the toner image formed on the photoconductor, and the density of the test pattern is detected by a sensor. The toner image density is adjusted by controlling the process conditions such as the developing bias voltage according to the measurement result. For example, the test pattern is formed so as to include regions having different toner concentrations in stages.

  The measurement result of this test pattern is affected by the reflectance of the background on which the test pattern is formed. The surface of the intermediate transfer member such as the intermediate transfer belt in the tandem type color image forming apparatus described above is caused by rubbing by the cleaning member or a transfer roller that secondarily transfers the toner image to a recording medium such as printing paper. As a result, dirt, scratches, adhesion of toner external additives and the like occur. For this reason, the measured toner concentration may not be accurate. Therefore, the surface state of the intermediate transfer body before the test pattern is formed is measured by a sensor, and the toner density is corrected based on the sensor value (see, for example, Patent Document 1).

Japanese Patent No. 3272768

  In the above-described technique, since it is necessary to measure the reflectance of the background of the intermediate transfer member, it is necessary to rotate (circulate) the intermediate transfer member a plurality of times, and it takes time to measure the toner density. In particular, in the case of a color image forming apparatus, this tendency becomes remarkable because the toner density is adjusted for each of a plurality of color toners to be used.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and a toner concentration measuring method for measuring a toner concentration in a short time.

  In order to solve the above problems, the present invention is configured as follows.

  An image forming apparatus according to the present invention detects a photoconductor, a developing unit for developing a toner image on the photoconductor, a transfer body to which the toner image on the photoconductor is transferred, and measurement light from the surface of the transfer body. And a correction unit that corrects the toner density based on the output value of the sensor. The sensor includes a plurality of light receiving elements that detect measurement light from a plurality of detection positions arranged perpendicular to the traveling direction of the transfer body, and the first detection position of the plurality of detection positions is the transfer body. The position where the upper test pattern passes, and the second detection position among the plurality of detection positions is a position where the test pattern does not pass on the transfer body. The correction unit outputs the output value of the first light receiving element corresponding to the first detection position among the plurality of light receiving elements as the second light reception corresponding to the second detection position among the plurality of light receiving elements. The toner density of the test pattern is specified by correcting with the output value of the element.

  Accordingly, in order to identify the toner density by regarding the measurement value of the second detection position as the measurement value on the background of the transfer body at the first detection position, the transfer body is simply rotated (turned) once. The toner density of the test pattern can be measured. Therefore, the toner concentration can be measured in a short time. In addition, since the contamination of the transfer body is caused by the transfer roller or the like for secondary transfer, the transfer body is attached along the transfer roller or the like (that is, in a direction perpendicular to the moving direction of the transfer body), so the first detection position The measurement value of the second detection position in that direction as viewed from the side can be regarded as the measurement value of the background of the transfer body at the first detection position.

  In addition to the image forming apparatus described above, the image forming apparatus according to the present invention may be configured as follows. In this case, the third detection position among the plurality of detection positions is a position where the test pattern does not pass on the transfer body, and is located in a direction opposite to the second detection position when viewed from the first detection position. To do. And a correction | amendment part makes the output value of a 1st light receiving element the output value of a 2nd light receiving element, and the output value of the 3rd light receiving element corresponding to the 3rd detection position among several light receiving elements. The toner density of the test pattern is specified by correcting with the average value.

  Accordingly, since the average value of the measurement values of the second and third detection positions adjacent to both sides of the first detection position is regarded as the measurement value of the background of the transfer body at the first detection position, the toner of the test pattern The concentration is calculated more accurately.

  The image forming apparatus according to the present invention may be configured as follows in addition to any of the image forming apparatuses described above. In this case, the first detection position is a position through which the center of the test pattern passes, and the distance from the first detection position to the second detection position and the distance from the first detection position to the third detection position. Are the same.

  Thereby, the average value of the measurement values of the second and third detection positions adjacent to both sides of the first detection position can be made close to the measurement value of the background of the transfer body at the first detection position.

  The image forming apparatus according to the present invention may be configured as follows in addition to any of the image forming apparatuses described above. In this case, the plurality of light receiving elements are light receiving elements in the charge coupled device.

  The toner concentration measuring method according to the present invention includes a first detection position through which a test pattern on a transfer body arranged perpendicular to the traveling direction of the transfer body passes by a plurality of light receiving elements of the sensor, and on the transfer body. A step of detecting measurement light from one or a plurality of second detection positions through which the test pattern does not pass, and a plurality of output values of the first light receiving elements corresponding to the first detection positions among the plurality of light receiving elements. And correcting the output value of one or a plurality of second light receiving elements corresponding to the second detection position of the light receiving elements, and specifying the toner density of the test pattern.

  Accordingly, in order to identify the toner density by regarding the measurement value of the second detection position as the measurement value on the background of the transfer body at the first detection position, the transfer body is simply rotated (turned) once. The toner density of the test pattern can be measured. Therefore, the toner concentration can be measured in a short time.

  According to the present invention, the toner density can be measured in a short time in the image forming apparatus.

FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a part of the electrical configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a diagram illustrating an example of a test pattern formed on the intermediate transfer belt in the image forming apparatus illustrated in FIGS. 1 and 2. FIG. 4 is a diagram illustrating an example of a sensor in the image forming apparatus illustrated in FIGS. 1 and 2. FIG. 5 is a diagram illustrating an example of an output waveform of the sensor 8 at the time of toner density adjustment in the image forming apparatus illustrated in FIGS. 1 and 2.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus is an apparatus having a printing function, such as a printer, a facsimile machine, a copier, and a multifunction machine.

  The image forming apparatus of this embodiment has a tandem color developing device. The color developing device includes photosensitive drums 1a to 1d, an exposure device 2, and developing units 3a to 3d. The photoconductor drums 1a to 1d are four-color photoconductors of cyan, magenta, yellow, and black. The exposure apparatus 2 is an apparatus that forms an electrostatic latent image by irradiating the photosensitive drums 1a to 1d with laser light. The exposure apparatus 2 includes a laser diode that is a light source of laser light and optical elements (lens, mirror, polygon mirror, etc.) that guide the laser light to the photosensitive drums 1a to 1d.

  Further, around the photosensitive drums 1a to 1d, a charger such as a scorotron, a cleaning device, a static eliminator and the like are arranged. The cleaning device removes residual toner on the photosensitive drums 1a to 1d after the primary transfer, and the static eliminator neutralizes the photosensitive drums 1a to 1d after the primary transfer.

  The developing units 3a to 3d are filled with toners of four colors, cyan, magenta, yellow, and black, and the developing units 3a to 3d attach the toner to the electrostatic latent images on the photosensitive drums 1a to 1d. To form a toner image. The toner constitutes a developer together with the carrier, and an external additive such as titanium oxide is further added.

  The photosensitive drum 1a and the developing unit 3a develop magenta, the photosensitive drum 1b and the developing unit 3b develop cyan, and the photosensitive drum 1c and the developing unit 3c develop yellow. Then, black development is performed by the photosensitive drum 1d and the developing unit 3d.

  The intermediate transfer belt 4 is an annular image carrier that contacts the photosensitive drums 1a to 1d and primarily transfers the toner images on the photosensitive drums 1a to 1d. The intermediate transfer belt 4 is a kind of transfer body. The intermediate transfer belt 4 is stretched around the driving roller 5 and is rotated by the driving force from the driving roller 5 in the direction from the contact position with the photosensitive drum 1a to the contact position with the photosensitive drum 1d.

  The transfer roller 6 brings the conveyed paper into contact with the transfer belt 4 and secondarily transfers the toner image on the transfer belt 4 to the paper. The sheet on which the toner image has been transferred is conveyed to the fixing device 9 and the toner image is fixed on the sheet.

  The roller 7 has a cleaning brush. The roller 7 is brought into contact with the intermediate transfer belt 4 to remove the toner remaining on the intermediate transfer belt 4 after the toner image is transferred onto the paper.

  The sensor 8 irradiates the intermediate transfer belt 4 with a light beam and detects the reflected light. When adjusting the toner density, the sensor 8 irradiates a predetermined detection position of the intermediate transfer belt 4 with a light beam, detects reflected light (measurement light) of the light beam, and outputs an electrical signal corresponding to the light amount. This detection position is a position through which a test pattern described later passes.

  FIG. 2 is a block diagram showing a part of the electrical configuration of the image forming apparatus according to the embodiment of the present invention. In FIG. 2, the print engine 11 controls a toner source, a transfer source (not shown) that drives the above-described roller, a bias application circuit that applies a development bias and a primary transfer bias, and an exposure device 2 to develop, transfer, And a processing circuit that executes fixing, feeding, printing, and discharging. The developing bias is applied between the photosensitive drums 1a to 1d and the developing units 3a to 3d, respectively, and the primary transfer bias is applied between the photosensitive drums 1a to 1d and the intermediate transfer belt 4, respectively.

  FIG. 3 is a diagram illustrating an example of a test pattern formed on the intermediate transfer belt 4 in the image forming apparatus illustrated in FIGS. 1 and 2. The print engine 11 adjusts the toner density when the apparatus is activated. In the toner density adjustment, the print engine 11 develops a test pattern (toner image) 32 in the test pattern area 31 of the intermediate transfer belt 4. The test pattern 32 includes a plurality of patch images that are developed with a plurality of stepwise toner density setting values. The test pattern 32 is formed for each color of the developing device (here, cyan, magenta, yellow, and black). The print engine 11 identifies the toner density of the test pattern 32 based on the output signal of the sensor 8, and processes such as the developing bias and the primary transfer bias based on the measured value of the toner density of the test pattern 32. Adjust the setting value of the condition.

  Here, details of the sensor 8 and the print engine 11 will be described.

  FIG. 4 is a diagram illustrating an example of the sensor 8 in the image forming apparatus illustrated in FIGS. 1 and 2. The sensor 8 includes one or a plurality of light emitting elements such as a light emitting diode (not shown) that causes a light beam to enter a detection position described later, and a light receiving element array 41 that receives reflected light of the light beam from the detection position. The light receiving element array 41 has a plurality of light receiving elements 42 arranged in a line at equal intervals. For the light receiving element 42, a photodiode, a phototransistor, or the like is used. A charge coupled device (CCD) may be used for the light receiving element array 41. The plurality of light receiving elements 42 detect measurement light (reflected light described above) from a plurality of detection positions on the intermediate transfer belt 4 arranged perpendicularly to the traveling direction of the intermediate transfer belt 4. Therefore, the plurality of light receiving elements 42 are also arranged perpendicular to the traveling direction of the intermediate transfer belt 4. The first detection position among the plurality of detection positions is a position through which the test pattern 32 on the intermediate transfer belt 4 passes, and the second detection position among the plurality of detection positions is on the intermediate transfer belt 4. This is a position where the test pattern 32 does not pass.

  In this embodiment, the print engine 11 includes a correction calculation unit 21 and a bias control unit 22.

  The correction calculation unit 21 corrects the output value of the first light receiving element corresponding to the first detection position described above with the output value of the second light receiving element corresponding to the second detection position described above, to thereby test the test pattern. A toner density of 32 (that is, a toner density corresponding to each patch image) is specified.

  In particular, in this embodiment, the correction calculation unit 21 calculates the output value of the first light receiving element, the output value of the second light receiving element, and the output value of the third light receiving element corresponding to the third detection position. The toner density of the test pattern 32 is specified by correcting with the average value. The third detection position is one of the plurality of detection positions described above, and is a position where the test pattern 32 does not pass on the intermediate transfer belt 4, and the second detection position as viewed from the first detection position. Located in the opposite direction to the position. Therefore, in this embodiment, the width of the test pattern 32 is narrower than the width of the light receiving element array 41.

  Further, in this embodiment, the first detection position is a position through which the center of the test pattern 32 passes, and the distance from the first detection position to the second detection position and the first detection position to the third detection position. The distance to the detection position is the same. In this embodiment, the first light receiving element is the light receiving element 42C at the center of the light receiving element array 41, the second light receiving element is the light receiving element 42R at one end of the light receiving element array 41, and the third light receiving element 42C. The light receiving element is a light receiving element 42L at the other end of the light receiving element array 41.

  When the first and second light receiving elements are used for toner density adjustment, for example, the output signals of the plurality of light receiving elements 42 are input to the print engine 11 via an analog circuit such as an amplifier and sampled simultaneously. The value of the sampled output signal is input to the correction calculation unit 21 of the print engine 11. The correction calculation unit 21 acquires the output values of the first and second light receiving elements at the same timing, and specifies the toner density of the test pattern 32 from the difference between the output values of the first and second light receiving elements. Alternatively, the difference between the output signals of the first and second light receiving elements is calculated by an analog circuit, the calculation result is sampled by the print engine 11, and the correction calculation unit 21 specifies the toner density of the test pattern 32 from the difference. You may make it do.

  When the first, second, and third light receiving elements are used for toner density adjustment, for example, the output signals of the plurality of light receiving elements 42 are input to the print engine 11 through analog circuits such as amplifiers and simultaneously sampled. The The value of the sampled output signal is input to the correction calculation unit 21 of the print engine 11. The correction calculation unit 21 acquires the output values of the first, second, and third light receiving elements at the same timing, and averages the output values of the first light receiving element and the output values of the second and third light receiving elements. The toner density of the test pattern 32 is specified from the difference from the value. Alternatively, the average of the output signals of the second and third light receiving elements is calculated by an analog circuit, the difference between the output signal of the first light receiving element and the average is calculated, and the calculation result is sampled by the print engine 11 Then, the correction calculation unit 21 may specify the toner density of the test pattern 32 from the difference.

  The bias controller 22 controls the developing bias applied to the photosensitive drums 1 a to 1 d and the primary transfer bias applied to the intermediate transfer belt 4 during normal printing and toner density adjustment.

  Next, toner density adjustment in the image forming apparatus will be described.

  First, the print engine 11 rotates the intermediate transfer belt 4 with the driving roller 5. Then, the bias controller 22 applies a development bias and a primary transfer bias, and performs toner development of the test pattern. As a result, toner images of the respective colors are formed on the photosensitive drums 1a to 1d, and the toner images are transferred to the intermediate transfer belt 4 to form test patterns 32 of the respective colors.

  After the test pattern 32 is formed, the output signal of the light receiving element 42 is sampled, and the correction calculation unit 21 calculates the toner density of each patch image in the test pattern 32 from the output signal of the light receiving element 42.

  FIG. 5 is a diagram illustrating an example of an output waveform of the sensor 8 at the time of toner density adjustment in the image forming apparatus illustrated in FIGS. 1 and 2. In FIG. 5, VC is an output waveform of the light receiving element 42C, VR is an output waveform of the light receiving element 42R, and VL is an output waveform of the light receiving element 42L.

  Regarding VR and VL, since the test pattern 32 does not pass through these detection positions, reflected light from the background portion of the intermediate transfer belt 4 is continuously detected. On the other hand, with respect to VC, the reflectance decreases according to the toner density when the test pattern 32 passes the detection position, so the VC level is lower than VR and VL.

  Therefore, the correction calculation unit 21 corrects the value corresponding to each patch image in VC (the value of each stepped flat portion in FIG. 5) with VR or VL or the average value of VR and VL, The actual value of the toner density of the patch image is calculated.

  In this way, the correction calculation unit 21 measures the toner density of the test pattern 32 and then changes the process condition such as the bias condition such as the developing bias voltage based on the measured value of the toner density to thereby change the toner image density. Adjust. If a gamma table for toner density correction is used, the correction calculation unit 21 may update the gamma table based on the measured value of the toner density. Further, the correction calculation unit 21 may update the exposure condition of the exposure apparatus 2 based on the measured value of the toner density.

  As described above, according to the above-described embodiment, the sensor 8 includes the plurality of light receiving elements 42 that detect measurement light from the plurality of detection positions arranged perpendicular to the traveling direction of the intermediate transfer belt 4. The first detection position of the plurality of detection positions is a position through which the test pattern 32 on the intermediate transfer belt 4 passes, and the second detection position of the plurality of detection positions is on the intermediate transfer belt 4. Is a position where the test pattern 32 does not pass. Then, the correction calculation unit 21 corrects the output value of the light receiving element 42C corresponding to the first detection position with the output value of the light receiving element 42R and / or the light receiving element 42L corresponding to the second detection position. The toner density is specified.

  As a result, the test pattern 32 passes through the measurement value at the detection position where the test pattern 32 does not pass, which exists in the direction perpendicular to the traveling direction of the intermediate transfer belt 4 as viewed from the detection position through which the test pattern 32 passes. The toner density is specified by regarding the measured value on the background of the intermediate transfer member at the detection position. Therefore, the toner density of the test pattern can be measured by rotating the intermediate transfer member once (around). That is, the toner density can be measured in a short time.

  The above-described embodiments are preferred examples of the present invention, but the present invention is not limited to these, and various modifications and changes can be made without departing from the scope of the present invention. is there.

  For example, in the above embodiment, the center of the light receiving element array 41 and the light receiving elements 42C, 42R, and 42L at the both ends are used for toner density adjustment, but instead of the light receiving element 42C, a plurality of light receiving elements 42 are used. A light receiving element that detects measurement light from another detection position through which the test pattern 32 passes may be used. Similarly, instead of the light receiving elements 42R and 42L, a light receiving element that detects measurement light from another detection position through which the test pattern 32 does not pass may be used among the plurality of light receiving elements 42.

  In the embodiment described above, the correction calculation unit 21 acquires the output values of all the light receiving elements 42 of the light receiving element array 41, and uses a plurality of detection positions through which the test pattern 32 passes these output values, such as a threshold value. And those corresponding to a plurality of detection positions through which the test pattern 32 does not pass, the respective average values are calculated, and the average values of those corresponding to the plurality of detection positions through which the test pattern 32 passes are obtained. As described above, the toner density of the test pattern 32 may be calculated by correcting with the average value corresponding to a plurality of detection positions through which the test pattern 32 does not pass.

  In the above embodiment, the output value of the light receiving element 42C for the first detection position and the light receiving element 42R (or 42L) for the second detection position when the test pattern 32 does not pass the detection position. A difference from the output value (an average value at a predetermined timing or a predetermined period) may be calculated, and the output value of the light receiving element 42C at the first detection position may be further corrected based on the difference. Similarly, when the test pattern 32 does not pass through the detection position, the output value of the light receiving element 42C for the first detection position and the output value of the light receiving elements 42R and 42L for the second and third detection positions. It is also possible to calculate a difference (average value for a predetermined timing or a fixed period) with respect to the average value of the light and further correct the output value of the light receiving element 42C for the first detection position.

  In the above-described embodiment, the present invention is applied to a color image forming apparatus. However, the present invention can also be applied to a monochrome image forming apparatus.

  In the above embodiment, the reflective sensor 8 is used. However, a transmissive sensor may be used according to the configuration of the intermediate transfer member.

  In the above-described embodiment, the intermediate transfer belt 4 is used as an intermediate transfer member. However, other forms of intermediate transfer member may be used.

  The present invention is applicable to, for example, toner density adjustment of an image forming apparatus.

1a to 1d Photosensitive drum (an example of a photosensitive member)
3a to 3d Developing unit 4 Intermediate transfer belt (an example of a transfer member)
8 Sensor 21 Correction calculation part (an example of a correction part)
22 Bias controller 32 Test pattern 41 Light receiving element array 42 Light receiving element 42C Light receiving element (an example of a first light receiving element)
42L light receiving element (an example of a second light receiving element, an example of a third light receiving element)
42R light receiving element (an example of a second light receiving element, an example of a third light receiving element)

Claims (5)

A photoreceptor,
A developing unit for developing a toner image on the photoreceptor;
A transfer member to which a toner image on the photosensitive member is transferred;
A sensor for detecting measurement light from the surface of the transfer body;
A correction unit that corrects the toner density based on the output value of the sensor,
The sensor has a plurality of light receiving elements for detecting measurement light from a plurality of detection positions arranged perpendicular to the traveling direction of the transfer body,
The first detection position of the plurality of detection positions is a position through which the test pattern on the transfer body passes, and the second detection position of the plurality of detection positions is the position on the transfer body. Where the test pattern does not pass,
The correction unit outputs an output value of a first light receiving element corresponding to the first detection position of the plurality of light receiving elements to a second detection position corresponding to the second detection position of the plurality of light receiving elements. Correcting the output value of the light receiving element of 2 to identify the toner density of the test pattern;
An image forming apparatus. A third detection position of the plurality of detection positions is a position where the test pattern does not pass on the transfer body, and is opposite to the second detection position when viewed from the first detection position. Located in
The correction unit outputs an output value of the first light receiving element, an output value of the second light receiving element, and an output of a third light receiving element corresponding to the third detection position of the plurality of light receiving elements. The toner density of the test pattern is specified by correcting with an average value of the value,
The image forming apparatus according to claim 1.   The first detection position is a position through which the center of the test pattern passes, and the distance from the first detection position to the second detection position and the third detection position from the first detection position. The image forming apparatus according to claim 2, wherein the distances to the same are the same.   The image forming apparatus according to claim 1, wherein the plurality of light receiving elements are light receiving elements in a charge coupled device. In a toner concentration measurement method for measuring a toner concentration on a transfer body of an image forming apparatus,
A first detection position through which the test pattern on the transfer body that is arranged perpendicular to the traveling direction of the transfer body passes by the plurality of light receiving elements of the sensor, and the test pattern does not pass on the transfer body. Or detecting measurement light from a plurality of second detection positions;
The output value of the first light receiving element corresponding to the first detection position of the plurality of light receiving elements is set to one or more second corresponding to the second detection position of the plurality of light receiving elements. Correcting the output value of the light receiving element and specifying the toner density of the test pattern;
A toner concentration measuring method comprising:

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