JP2011227451A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly measure the toner density and/or the position of a toner pattern on an intermediate transfer belt even when the toner density is high.SOLUTION: In a image forming apparatus, a sensor 8 makes an S-wave incident as a measuring beam to an intermediate transfer belt 4 (a substrate of the intermediate transfer belt 4 or a toner pattern 41 on the intermediate transfer belt 4), and detects a P-wave component and an S-wave component of reflected light from the intermediate transfer belt 4. The toner density and/or the position are calculated based on the P-wave component and the S-wave component detected by the sensor 8.

Description

  The present invention relates to an image forming apparatus.

  Many image forming apparatuses such as printers, copiers, facsimiles, and complex machines that form images by an electrophotographic process develop a toner image on a photosensitive drum, transfer the toner image to an intermediate transfer belt, Then, the toner image is transferred from the intermediate transfer belt to the printing paper, and the toner image is fixed on the printing paper.

  In such an image forming apparatus, toner density correction and color misregistration correction are performed as necessary or periodically (see, for example, Patent Document 1).

  In general, in the density correction process, a reference toner pattern (patch image) is developed and transferred to an intermediate transfer belt, and the toner density of the toner pattern on the intermediate transfer belt is specified using an optical sensor. Density correction is performed based on the toner density. Further, in the case of a color image forming apparatus, the position of the toner pattern on the intermediate transfer belt is specified using an optical sensor, and color misregistration correction is performed based on the position.

  As another method, there is a method for specifying the toner density on the photosensitive drum, as described in Japanese Patent Application Laid-Open No. H10-228707.

JP-A-6-250480

  In the technique described in Patent Document 1, P-wave (P-polarized) measuring light is incident on a photosensitive drum on which a toner image is formed, and the P-wave component and the S-wave component of the reflected light from the photosensitive drum are used. Are separately detected, and the toner density is calculated from the difference between the detected value of the P wave component (sensor output value) and the detected value of the S wave component (sensor output value).

  In this technique, since the difference between the P wave component and the S wave component of the reflected light from the photosensitive drum is large, the toner density on the photosensitive drum can be specified. However, the intermediate transfer belt is different from the photosensitive drum. Therefore, even if the toner density is measured by the above-described technique, the difference between the P wave component and the S wave component of the reflected light is reduced and the toner density can be accurately detected even if the toner density is increased. It becomes difficult.

  FIG. 7 is a diagram illustrating an example of a correspondence relationship between the actual toner density and the detected values (sensor output values) of the P wave component and the S wave component when the toner density is measured by the technique described in Patent Document 1. It is. FIG. 7A shows the correspondence when the glossiness of the intermediate transfer belt is 15, and FIG. 7B shows the correspondence when the glossiness of the intermediate transfer belt is 1 or less. The toner density is a value where the maximum density is 100 percent.

  As shown in FIG. 7, when the toner concentration is high, the difference between the sensor output value of the P wave component and the sensor output value of the S wave component is small, so that it is difficult to detect an accurate toner concentration (that is, a detection error). Becomes larger). In particular, when the glossiness is 1 or less, the tendency becomes more prominent. In such an image forming apparatus, since the toner external additive or the like adheres to the intermediate transfer belt as the apparatus is used, the glossiness decreases with time. For this reason, the measurement accuracy of the toner concentration decreases with time.

  The present invention has been made in view of the above problems, and can accurately measure the toner concentration and / or position of a toner pattern on a transfer body such as an intermediate transfer belt even when the toner concentration is high. The object is to obtain a forming device.

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

  An image forming apparatus according to the present invention includes a photoconductor, a developing unit that develops a toner pattern on the photoconductor, a transfer body to which the toner pattern on the photoconductor is transferred, and measurement light incident on the transfer body to transfer A sensor that detects reflected light from the body, and a pattern detection unit that identifies the toner density and / or position of the toner pattern on the transfer body from the output of the sensor. Then, the sensor causes an S wave to enter the transfer body as measurement light, and detects the P wave component and the S wave component of the reflected light from the transfer body. The pattern detection unit derives the toner density and / or position from the P wave component and the S wave component detected by the sensor.

  As a result, since the S wave (S polarized light) is used as the measurement light, the intensity of the reflected light detected by the sensor increases, and the difference between the P wave component and the S wave component is large even when the toner concentration is high. Thus, the toner density and / or position of the toner pattern on the transfer member can be accurately measured.

  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 sensor includes a light emitting element, a first beam splitter that separates light from the light emitting element into a P wave and an S wave, a second beam splitter that separates reflected light into a P wave component and an S wave component, A first light receiving element for detecting a P wave component emitted from the second beam splitter; and a second light receiving element for detecting an S wave component emitted from the second beam splitter, wherein the S wave emitted from the first beam splitter is The measurement light is incident on the transfer body. Then, the pattern detection unit derives the toner density and / or position from the output of the first light receiving element and the output of the second light receiving element.

  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 pattern detection unit calculates a value based on the difference between the output of the first light receiving element and the output of the second light receiving element as the toner density.

  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 dynamic microhardness of the transfer body is any value of 0.04 or more and less than 0.1.

  When a P wave is used for the measurement light, a transfer body having a hardness of 0.1 or more with little surface contamination with time is used. However, when an S wave is used for the measurement light, the intensity of the reflected light is high. In addition, since the difference between the P wave component and the S wave component becomes large, it is possible to form a transfer body with a material having low hardness, and the choice of materials increases.

  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 surface roughness of the transfer body is any value that is 1.0 μm or more and less than 6.0 μm.

  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 toner used for the toner pattern is added with an external additive containing 0.5% or more and less than 2.0% of titanium oxide.

  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 relative permittivity of the photosensitive member is any value of 5.0 or more and less than 13.0.

  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 transfer body is formed of thermoplastic polyurethane or chloroprene rubber and is surface-coated with a fluororesin.

  An image forming apparatus according to the present invention includes a photoconductor, a developing unit that develops a toner pattern on the photoconductor, a transfer body to which the toner pattern on the photoconductor is transferred, and measurement light incident on the transfer body to transfer A sensor that detects reflected light from the body, and a pattern detection unit that specifies the position of the toner pattern on the transfer body from the output of the sensor. The sensor includes: a light emitting element; a polarizing element that separates an S wave in light from the light emitting element; a polarizing plate that separates an S wave component in reflected light; and a light receiving element that detects an S wave component emitted from the polarizing plate. The S wave emitted from the polarizing element is incident on the transfer body as measurement light. The pattern detection unit derives the position of the toner pattern from the output of the light receiving element.

  According to the present invention, in the image forming apparatus, even when the toner concentration is high, the toner concentration and / or position of the toner pattern on the transfer body can be accurately measured.

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 for explaining concentration measurement by the sensor in the first embodiment. FIG. 4 is a diagram illustrating an example of a patch image. FIG. 5 shows an example of a correspondence relationship between the actual toner density and the detected values (sensor output values) of the P wave component and the S wave component when the toner density is measured by the image forming apparatus according to the first embodiment. FIG. FIG. 6 is a diagram for explaining a dynamic microhardness measurement system. FIG. 7 is a diagram illustrating an example of a correspondence relationship between the actual toner density and the detected values (sensor output values) of the P wave component and the S wave component when the toner density is measured by the technique described in Patent Document 1. It is. FIG. 8 is a diagram for explaining the position measurement of the toner pattern by the sensor according to the second embodiment.

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

Embodiment 1 FIG.

  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 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.

  In this embodiment, the dynamic micro hardness of the intermediate transfer belt 4 may be any value that is 0.04 or more and less than 0.1. Further, the intermediate transfer belt 4 may have any surface roughness of 1.0 μm or more and less than 6.0 μm. Further, the proportion of titanium oxide contained in the external additive added to the toner is any value that is 0.5% or more and less than 2.0% with respect to the total weight of the external additive. May be. Further, the relative permittivity of the photosensitive drums 1a to 1d may be any value that is 5.0 or more and less than 13.0. Further, for example, the intermediate transfer belt 4 is made of thermoplastic polyurethane or chloroprene rubber, and is surface-coated with a fluorine resin such as polytetrafluoroethylene (PTFE).

  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 (measurement light) and detects the reflected light. When adjusting the toner density, the sensor 8 irradiates a predetermined region of the intermediate transfer belt 4 with a light beam, detects reflected light of the light beam, and outputs an electric signal corresponding to the light amount.

  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 the development of a toner image by controlling a driving source (not shown) that drives the above-described roller, a bias applying circuit that applies a developing bias and a primary transfer bias, and the exposure device 2. This is a processing circuit for executing transfer and fixing, as well as paper feeding, printing and paper ejection. 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.

  The print engine 11 calculates the toner density and / or position of the toner pattern from the P wave component and the S wave component of the reflected light detected by the sensor 8.

  FIG. 3 is a diagram for explaining concentration measurement by the sensor 8 in the first embodiment.

  As shown in FIG. 3, in the first embodiment, the sensor 8 includes a light source 51 that emits a light beam, a beam splitter 52 on the light source side, a light receiving element 53 on the light source side, a beam splitter 54 on the light receiving side, One light receiving element 55 and a second light receiving element 56 are provided.

  The light source 51 is, for example, a light emitting diode. The beam splitter 52 transmits the S-polarized component and reflects the P-polarized component among the light rays from the light source 51. The light receiving element 53 on the light source side is, for example, a photodiode, detects the P-polarized light component from the beam splitter 52, and outputs an electric signal corresponding to the amount of light. This electric signal is used for stable control of the output light amount of the light source 51.

  The light of the S-polarized component that has passed through the beam splitter 52 on the light source side is incident on the surface (the toner pattern 41 or the ground) of the intermediate transfer belt 4 and reflected. The reflected light at this time has a regular reflection component and a diffuse reflection component, and the regular reflection component is S-polarized light. Note that the incident angle of the measurement light to the intermediate transfer belt 4 is less than the Brewster angle, and is preferably any angle in the range of 20 degrees to 40 degrees.

  The beam splitter 54 transmits the P-polarized component of the reflected light and reflects the S-polarized component (that is, the regular reflection component). The first light receiving element 55 is, for example, a photodiode, detects the P-polarized light component transmitted through the beam splitter 54, and outputs an electric signal having a voltage corresponding to the light amount. The second light receiving element 56 is, for example, a photodiode, has light detection characteristics similar to those of the first light receiving element 55, detects light of the S-polarized component reflected by the beam splitter 54, and has a voltage corresponding to the amount of light. Outputs electrical signals.

  In the first embodiment, the print engine 11 specifies a measured value of toner density based on the output of the first light receiving element 55 and the output of the second light receiving element 56, and corrects the toner density based on the measured value. I do. An amplifier or the like is provided between the light receiving elements 55 and 56 and the print engine 11 as necessary.

  The toner density is calculated based on the following equation, for example.

  (Toner concentration [percent]) = {1− (PS) / (Po−So)} × 100

  Here, P is a sensor output value (voltage) of the P-polarized component, S is a sensor output value (voltage) of the S-polarized component, and Po is a portion where there is no toner image (that is, the intermediate transfer belt 4). Is the sensor output value (voltage) of the P-polarized component at the background of the toner, and So is the sensor output value (voltage) of the S-polarized component at the location where there is no toner image (that is, the background of the intermediate transfer belt 4). .

  Next, the operation of the above apparatus will be described.

  First, the operation at the time of toner density correction will be described.

  The print engine 11 operates the sensor 8 to adjust the light amount of the sensor 8 and determines whether the sensor 8 is abnormal. When there is no abnormality in the sensor 8, the following processing is performed.

  The print engine 11 rotates the intermediate transfer belt 4 with the driving roller 5 and controls the exposure device 2 to form a toner pattern (patch image) in a predetermined region on the surface of the intermediate transfer belt 4. FIG. 4 is a diagram illustrating an example of a patch image. As shown in FIG. 4, the patch image 61 is formed with a plurality of densities (for example, 25 percent, 50 percent, 75 percent, and 100 percent).

  The print engine 11 samples the outputs of the light receiving elements 55 and 56 of the sensor 8 in a predetermined area on the surface of the intermediate transfer belt 4, and measures the toner density of each patch image 61 from the values as described above. The value is calculated, and the toner density is corrected by adjusting the development bias and the primary transfer bias based on the density measurement values for the background and the patch image of each density.

  In this way, the toner density is corrected.

  FIG. 5 shows an example of a correspondence relationship between the actual toner density and the detected values (sensor output values) of the P wave component and the S wave component when the toner density is measured by the image forming apparatus according to the first embodiment. FIG. FIG. 5A shows the correspondence when the glossiness of the intermediate transfer belt is 15, and FIG. 5B shows the correspondence when the glossiness of the intermediate transfer belt is 1 or less. As shown in FIG. 5, in the image forming apparatus, the difference between the P wave component and the S wave component becomes larger than when the technique described in Patent Document 1 is used (FIG. 7).

  Next, the operation at the time of color misregistration correction will be described.

  In the case of color misregistration correction, the print engine 11 forms a patch image on the intermediate transfer belt 4 for each color, specifies the timing at which the patch image is detected from the output of the sensor 8, and adjusts the toner development timing for each color. To eliminate color misregistration.

  In this way, color misregistration is corrected. The color misregistration correction may be performed simultaneously with the density correction (that is, using the same patch image).

  As described above, according to the first embodiment, the sensor 8 causes the S wave to be incident on the intermediate transfer belt 4 as the measurement light, and the P wave component and the S wave component of the reflected light from the intermediate transfer belt 4 are obtained. To detect. The print engine 11 calculates the toner density and / or position from the P wave component and the S wave component detected by the sensor 8.

  As a result, since the S wave (S polarized light) is used as the measurement light, the intensity of the reflected light detected by the sensor 8 increases, and the difference between the P wave component and the S wave component is high even when the toner concentration is high. The toner density and / or position of the toner pattern on the intermediate transfer belt 4 can be accurately measured.

  Further, according to the first embodiment, the intermediate transfer belt 4 has a dynamic microhardness in the vicinity of the surface (thickness of about 3 microns) of any value of 0.04 or more and less than 0.1. It may be formed as follows.

  When P waves are used as measurement light, an intermediate transfer belt having a dynamic micro hardness of 0.1 or more is used. On the other hand, when the S wave is used as the measurement light, the intensity of the reflected light is high and the difference between the P wave component and the S wave component is large, so that the intermediate transfer belt 4 can be formed with a material having low hardness. , The choice of materials increases.

  More specifically, when the dynamic microhardness of the intermediate transfer belt 4 is 0.1 or more, the surface characteristics of the belt 4 hardly change over time, and the initial surface characteristics are maintained, so that the measurement accuracy is also high. Less likely to change over time. Similarly to the case where the P wave is used as the measurement light, the intermediate transfer belt 4 having a dynamic micro hardness of 0.1 or more can be used even when the S wave is used as the measurement light. On the other hand, when the dynamic microhardness of the intermediate transfer belt 4 is less than 0.1, the surface characteristics may change somewhat with time. As described above, by using the S wave as the measurement light, The toner density can be measured satisfactorily. On the other hand, if the P wave is used as the measurement light for the intermediate transfer belt 4 having a dynamic micro hardness of less than 0.1, the reflected light cannot be obtained sufficiently and the difference between the P wave component and the S wave component is not sufficient. Since it is not, it is not preferable.

  Further, when the dynamic micro hardness of the intermediate transfer belt 4 is less than 0.04, the surface hardness of the intermediate transfer belt 4 is considerably low, so that the surface becomes rough due to polishing with toner or adhesion of a toner external additive. Thus, even if the S wave is used as the measurement light, the sensor 8 cannot sufficiently receive the reflected light from the intermediate transfer belt 4. Therefore, the dynamic micro hardness of the intermediate transfer belt 4 is preferably 0.04 or more.

  Here, the dynamic micro hardness will be described. FIG. 6 is a diagram for explaining a dynamic microhardness measurement system. The dynamic micro hardness can be measured by, for example, DUH-200 manufactured by Shimadzu Corporation.

  In measuring the dynamic microhardness, the triangular pyramid indenter is pressed against the sample with a load P [mN], the indentation depth D [μm] at that time is measured, and the measured value DUH of the dynamic microhardness is obtained based on the following equation.

  DUH = α × P / (D × D)

  Here, the coefficient α is 3.858 (when the ridge line angle of the triangular pyramid indenter is 115 degrees).

  Further, according to the first embodiment, the intermediate transfer belt 4 has a surface roughness in the vicinity of the surface (thickness of about 3 microns) of any value that is 1.0 μm or more and less than 6.0 μm. It may be formed as follows.

  When a P wave is used as measurement light, an intermediate transfer belt having a surface roughness of less than 1.0 μm is used. On the other hand, when the S wave is used as the measurement light, the intensity of the reflected light is high and the difference between the P wave component and the S wave component is large, so that the intermediate transfer belt 4 is formed of a material having a rough surface. It becomes possible and the choice of material increases.

  More specifically, when the surface roughness of the intermediate transfer belt 4 is less than 1.0 μm, the surface characteristics of the belt 4 hardly change over time, and the initial surface characteristics are maintained, so that the measurement accuracy is also high. Less likely to change over time. Similarly to the case where the P wave is used as the measurement light, the intermediate transfer belt 4 having a surface roughness of less than 1.0 μm can be used even when the S wave is used as the measurement light. On the other hand, when the surface roughness of the intermediate transfer belt 4 is 1.0 μm or more, the surface characteristics may slightly change over time. As described above, by using the S wave as the measurement light, The toner density can be measured satisfactorily. On the other hand, if the P wave is used as measurement light for the intermediate transfer belt 4 having a surface roughness of 1.0 μm or more, the reflected light cannot be obtained sufficiently and the difference between the P wave component and the S wave component is not sufficient. Since it is not, it is not preferable.

  Further, when the surface roughness of the intermediate transfer belt 4 is 6.0 μm or more, the sensor 8 cannot sufficiently receive the reflected light from the intermediate transfer belt 4 even when the S wave is used as the measurement light. Accordingly, the surface roughness of the intermediate transfer belt 4 is preferably less than 6.0 μm.

  Further, according to the first embodiment, the proportion of titanium oxide contained in the external additive added to the toner is 0.5% or more and 2.0% with respect to the total weight of the external additive. Any value that is less than may be used.

  When a P wave is used as measurement light, an external additive having a titanium oxide content of less than 0.5% is used so that surface contamination with time is reduced. On the other hand, when the S wave is used for the measurement light, the intensity of the reflected light is high and the difference between the P wave component and the S wave component is large, so that an external additive having a high titanium oxide content (in other words, oxidation) Toner with a large amount of titanium added) can be used, and the choice of materials increases.

  More specifically, when the proportion of titanium oxide contained in the external additive is less than 0.5%, the surface characteristics of the belt 4 hardly change over time, and the initial surface characteristics are maintained. Measurement accuracy is also difficult to change over time. Similarly to the case where the P wave is used as the measurement light, even when the S wave is used as the measurement light, it is possible to use a toner in which the proportion of titanium oxide contained in the external additive is less than 0.5%. On the other hand, when the proportion of titanium oxide contained in the external additive is 0.5% or more, the surface characteristics may slightly change over time. As described above, S waves are used as measurement light. By doing so, the toner concentration can be measured satisfactorily. On the other hand, when the P wave is used as the measurement light for the intermediate transfer belt 4 using toner in which the proportion of titanium oxide contained in the external additive is 0.5% or more, sufficient reflected light cannot be obtained. Moreover, since the difference between the P wave component and the S wave component is not sufficient, it is not preferable.

  Further, when the proportion of titanium oxide contained in the external additive is 2.0% or more, the sensor 8 cannot sufficiently receive the reflected light from the intermediate transfer belt 4 even when the S wave is used as the measuring light. Therefore, the proportion of titanium oxide contained in the external additive is preferably less than 2.0%.

  Further, according to the first embodiment, the photosensitive drums 1a to 1d may be formed so that the relative dielectric constant is 5.0 or more and less than 13.0.

  When a P wave is used as measurement light, a photosensitive drum having a relative dielectric constant of less than 5.0 is used. On the other hand, when the S wave is used for the measurement light, the intensity of the reflected light is high and the difference between the P wave component and the S wave component is large, so that the photosensitive drums 1a to 1d are made of a material having a high relative dielectric constant. Forming becomes possible and the choice of material increases. Note that the difference in relative permittivity between the photosensitive drums 1a to 1d causes a difference in density at the edge of the image. When the relative permittivity is large, the difference in relative permittivity tends to be large. Therefore, when the difference between the P wave component and the S wave component is not sufficient, the measurement error increases. Therefore, when the relative permittivity is large, if the difference between the P wave component and the S wave component is made sufficiently large by using the S wave as measurement light, the position of the toner pattern can be accurately measured with little measurement error. Can be measured.

  More specifically, when the relative permittivity of the photosensitive drums 1a to 1d is less than 5.0, even when the S wave is used as the measurement light, similarly to the case where the P wave is used as the measurement light, The photosensitive drums 1a to 1d can be used. On the other hand, when the relative permittivity of the photoconductive drums 1a to 1d is 5.0 or more, the position of the toner pattern can be satisfactorily measured by using the S wave as the measurement light as described above. On the other hand, when the P wave is used as the measurement light for the photosensitive drums 1a to 1d having a relative dielectric constant of 5.0 or more, the reflected light is not sufficiently obtained, and the difference between the P wave component and the S wave component is large. This is not preferable because it is not sufficient.

  Further, when the relative permittivity of the photosensitive drums 1 a to 1 d is 13.0 or more, the sensor 8 cannot sufficiently receive the reflected light from the intermediate transfer belt 4 even when the S wave is used as the measurement light. Therefore, it is preferable that the relative permittivity of the photosensitive drums 1a to 1d is less than 13.0.

Embodiment 2. FIG.

  The image forming apparatus according to the second embodiment of the present invention includes a sensor 8 having a configuration different from that of the first embodiment. Since the other configuration and operation of the image forming apparatus according to the second embodiment are the same as those of the first embodiment, the description thereof is omitted.

  FIG. 8 is a diagram for explaining the position measurement of the toner pattern by the sensor 8 according to the second embodiment.

  As shown in FIG. 8, in the second embodiment, the sensor 8 includes a light source 101 that emits light, a light source side polarizing plate 102, a light receiving side polarizing plate 103, and a light receiving element 104.

  The light source 101 is, for example, a light emitting diode. The polarizing plate 102 separates the S wave in the light beam from the light source 101 by transmitting the S polarization component.

  The S-polarized light component that has passed through the polarizing plate 102 on the light source side is incident on the surface of the intermediate transfer belt 4 (the toner pattern 41 or the base) and reflected. The reflected light at this time has a regular reflection component and a diffuse reflection component, and the regular reflection component is S-polarized light. Note that the incident angle of the measurement light to the intermediate transfer belt 4 is less than the Brewster angle, and is preferably any angle in the range of 20 degrees to 40 degrees.

  The polarizing plate 103 separates the S wave in the reflected light by transmitting the S polarization component. The light receiving element 104 is, for example, a photodiode, detects the S-polarized light component transmitted through the polarizing plate 103, and outputs an electric signal having a voltage corresponding to the light amount.

  In the second embodiment, the print engine 11 specifies the position of the toner pattern based on the output of the light receiving element 104, and corrects the development position of the toner image based on the position. An amplifier or the like is provided between the light receiving element 104 and the print engine 11 as necessary.

  As described above, according to the second embodiment, since the S wave (S polarized light) is used as the measurement light, the intensity of the reflected light detected by the sensor 8 is increased, and the toner on the intermediate transfer belt 4 is increased. The position of the pattern can be measured accurately.

  Each embodiment described above is a preferred example 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. It is.

  For example, in the first embodiment, the measurement light may be generated using another optical element that transmits or reflects only the S wave instead of the beam splitter 52.

  In each of the above embodiments, the color image forming apparatus has been described. However, the present invention can also be applied to a monochrome image forming apparatus.

  The present invention is applicable to, for example, an image forming apparatus.

1a to 1d photoconductor drum (example of photoconductor)
3a to 3d Developing unit 4 Intermediate transfer belt 8 Sensor 11 Print engine (an example of a pattern detection unit)
41 Toner pattern 51, 101 Light source (an example of a light emitting element)
52 Beam splitter (example of first beam splitter)
54 Beam splitter (example of second beam splitter)
55 1st light receiving element 56 2nd light receiving element 102 Polarizing plate (an example of a polarizing element)
103 Polarizing plate 104 Light receiving element

Claims (9)

A photoreceptor,
A developing unit for developing a toner pattern on the photoreceptor;
A transfer body to which a toner pattern on the photoreceptor is transferred;
A sensor that makes measurement light incident on the transfer body and detects reflected light from the transfer body;
A pattern detection unit that specifies the toner density and / or position of the toner pattern on the transfer body from the output of the sensor;
The sensor makes an S wave incident on the transfer body as the measurement light, detects a P wave component and an S wave component of reflected light from the transfer body,
The pattern detection unit derives the toner density and / or the position from the P wave component and the S wave component detected by the sensor;
An image forming apparatus. The sensor includes: a light emitting element; a first beam splitter that separates light from the light emitting element into a P wave and an S wave; a second beam splitter that separates the reflected light into a P wave component and an S wave component; A first light-receiving element that detects a P-wave component that is emitted from the second beam splitter; and a second light-receiving element that detects an S-wave component that is emitted from the second beam splitter, and which is emitted from the first beam splitter. A wave is incident on the transfer body as the measurement light,
The pattern detection unit derives the toner density and / or the position from the output of the first light receiving element and the output of the second light receiving element;
The image forming apparatus according to claim 1.   The image forming apparatus according to claim 2, wherein the pattern detection unit calculates a value based on a difference between an output of the first light receiving element and an output of the second light receiving element as the toner density.   The image forming apparatus according to claim 1, wherein the dynamic microhardness of the transfer body is any value of 0.04 or more and less than 0.1.   The image forming apparatus according to claim 1, wherein the surface roughness of the transfer body is any value of 1.0 μm or more and less than 6.0 μm.   2. The image forming apparatus according to claim 1, wherein the toner used in the toner pattern is added with an external additive containing 0.5% or more and less than 2.0% titanium oxide.   2. The image forming apparatus according to claim 1, wherein the relative permittivity of the photosensitive member is any value of 5.0 or more and less than 13.0.   6. The image forming apparatus according to claim 4, wherein the transfer body is made of thermoplastic polyurethane or chloroprene rubber and is surface-coated with a fluororesin. A photoreceptor,
A developing unit for developing a toner pattern on the photoreceptor;
A transfer body to which a toner pattern on the photoreceptor is transferred;
A sensor that makes measurement light incident on the transfer body and detects reflected light from the transfer body;
A pattern detection unit that identifies the position of the toner pattern on the transfer body from the output of the sensor;
The sensor detects a light emitting element, a polarizing element that separates an S wave in the light from the light emitting element, a polarizing plate that separates an S wave component in the reflected light, and an S wave component emitted from the polarizing plate. A light receiving element, and the S wave emitted from the polarizing element is incident on the transfer body as the measurement light,
The pattern detection unit derives the position of the toner pattern from the output of the light receiving element;
An image forming apparatus.

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