JP2015055842A - Surface state detection apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface state detection apparatus configured to increase sensor output without increasing an inrush current to a light-emitting unit or an amplification factor of an amplifier, while contributing to extending the service life and improving detection accuracy.SOLUTION: A surface state detection apparatus 70 includes: a reflective optical sensor 200 arranged opposite a portion of a fixing belt 61 supported by a heating roller 62; and detection information processing means 300. The reflective optical sensor 200 includes: a light-receiving system formed by at least two light-receiving units; and a light-receiving optical system for guiding a light flux reflected by an object to be detected to the light-receiving system. As for an area between arbitrary two adjacent light-receiving units among the light-receiving units, an output to be obtained when a light-receiving unit of a size corresponding to the area is arranged in the area is estimated from outputs in the arbitrary adjacent two light-receiving units. The estimated output is used for detecting the object to be detected.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, a plotter, or a multi-function machine equipped with at least one of them. Specifically, the surface state of a member is detected to replace the member or form an image. The present invention relates to an image forming apparatus provided with a surface state detection device for determining whether to stop the operation or the like.

In this type of image forming apparatus, an electrostatic latent image is written on the surface of an image carrier based on image data, and a developer such as toner is attached to the electrostatic latent image to form a visible image.
The visualized image is transferred directly to a recording medium such as paper or indirectly via an intermediate transfer member.
The recording medium holding the image is passed through a fixing device having fixing means such as a fixing belt to fix the image.
By repeatedly fixing the image, the surface of the fixing belt may be worn or scratched.

For example, when A4 size paper is transported vertically as a recording medium and fixing is repeated, vertical streak is generated on the surface of the fixing belt at positions where both ends in the paper width direction are located. .
This occurs because the surface of the fixing belt is worn by paper dust adhering to both ends of the paper. Paper dust is waste such as additives generated by cutting paper.
With such vertical streaks formed on the fixing belt, when the A4 size paper is transported horizontally and fixed, the image surface corresponds to the vertical streaks. Luster streaks appear.
The appearance of the gloss streaks causes image quality degradation.
In order to prevent deterioration of image quality, it is necessary to accurately determine the wear state of the surface of the fixing belt and replace the fixing belt, or to interrupt or stop the image forming operation.

In order to prevent such deterioration of image quality, Patent Document 1 discloses a configuration in which the surface of the fixing roller is irradiated with light from a light source and the reflected light is received by an optical sensor.
Based on the intensity of the reflected light captured by the optical sensor, the reflectance of the surface of the fixing roller is calculated by the control means.
When the reflectance is below a predetermined value, it is judged that a flaw on the surface of the fixing roller, an offset, surface deterioration, a decrease in the amount of oil retained, etc., and a warning alarm is transmitted. .
For example, when the reflectance reaches 20%, a toner offset danger message and a fixing roller replacement request message are displayed on the operation panel, so that the fixing roller can be replaced at an appropriate time.

A conventional reflective optical sensor used for detecting the surface state of a member has a configuration capable of irradiating a specimen such as the fixing belt and the fixing roller exemplified above with an arbitrary spot diameter and a minute pitch. Yes.
That is, a light receiving / emitting integrated device is used instead of a general-purpose light emitting element such as a surface mount type or a shell type, and a light receiving element.
Since the light emission intensity in any one light emitting part of the light receiving / emitting integrated device is smaller than that of a general light emitting element such as a surface mount type or a shell type, the sensor output cannot be said to be sufficient.
In order to compensate for this disadvantage, by increasing the injection current to the light emitting part or increasing the amplification factor of the amplifier, the reflection characteristics when the test object (fixing belt) is not damaged and when there is a scratch The difference is increased.

  However, when the injection current to the light emitting portion is increased, there is a problem that the life of the light emitting portion is shortened, and when the amplification factor of the amplifier is increased, noise is increased.

  The present invention has been made in view of such a situation, and can increase the sensor output without increasing the injection current to the light emitting unit or the amplification factor of the amplifier, extending the service life and improving the detection accuracy. The main object is to provide a surface state detection device that can contribute to the above.

  In order to achieve the above object, the present invention comprises a reflective optical sensor that detects the surface of a test object, and a surface that detects the surface state of the test object based on detection information from the reflective optical sensor. In the state detection device, the reflective optical sensor includes an irradiation system including at least one light emitting unit, an irradiation optical system that guides light emitted from the irradiation system to a test object, and an emission optical system that is emitted from the irradiation system and the target. A light receiving system comprising at least two light receiving parts for receiving light reflected by the test object, and a light receiving optical system for guiding the light beam reflected by the test object to the light receiving system; For an area sandwiched between any two light-receiving sections, the output that can be received when a light-receiving section having a size corresponding to the area is placed in the area is output from any two adjacent light-receiving sections. Estimate from the estimate Characterized by using the output of the detection of the test object.

  According to the present invention, the sensor output can be increased without increasing the injection current to the light emitting unit or the amplification factor of the amplifier, so that the lifetime can be extended and the detection accuracy can be improved. .

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention, where (a) is an overall configuration diagram, (b) is a main configuration diagram of an image forming unit, and (c) is a schematic configuration diagram of a fixing device. It is. FIG. 6 is a schematic plan view for explaining a fixing operation of the fixing device. It is sectional drawing of the transversal direction of a reflection type optical sensor. It is sectional drawing seen from the LED side in the longitudinal direction of a reflective optical sensor. It is sectional drawing seen from PD side in the longitudinal direction of a reflective optical sensor. It is a top view in the longitudinal direction of a reflective optical sensor. It is a schematic plan view which shows the arrangement structure of an opening member. It is a flowchart which shows the detection operation | movement of a reflection type optical sensor. It is a figure which shows PD output value of a reflection type optical sensor in a state without a fixing belt. It is a figure which shows the state in which the divergent light beam from LED reflects and scatters by an aperture member. It is a figure which shows PD output value of a reflection type optical sensor in the state with a fixing belt. It is sectional drawing of the transversal direction of the reflective optical sensor in a specific example. It is sectional drawing seen from the LED side in the longitudinal direction of the reflection type optical sensor. It is sectional drawing seen from PD side in the longitudinal direction of the reflection type optical sensor. It is a top view in the longitudinal direction of the reflective optical sensor. It is the schematic of the spot shape which the reflected light from a fixing belt when a certain LED lights on makes on PD. It is a figure which shows PD output value light-received by each light-receiving part. FIG. 7 is an enlarged view of FIG. It is a figure which shows the part which is not light-received. FIG. 7 is a partially enlarged view of FIG. It is a figure which shows the approximated curve based on PD output value light-received by each light-receiving part when a certain LED lights. It is a figure which shows an interpolation polynomial. It is a figure which shows a part of approximate curve obtained from the interpolation polynomial. It is a figure which shows an interpolation polynomial. It is a figure which shows a part of approximate curve obtained from the interpolation polynomial. It is a figure which shows an interpolation polynomial. It is a figure which shows distribution of the light-receiving part output which added the virtual output estimated by the polynomial interpolation. It is a figure which shows the example of selection of the light-receiving part which does not estimate a virtual output. The figure which shows the PD output value which added the output which is virtually estimated, (a) is the figure when the output which is virtually estimated in all, (b) is the case where the part which is less than 10% is not estimated FIG. It is sectional drawing of the transversal direction of the reflective optical sensor in 2nd Embodiment. It is sectional drawing seen from the LED side in the longitudinal direction of the reflection type optical sensor. It is sectional drawing seen from PD side in the longitudinal direction of the reflection type optical sensor. It is a top view in the longitudinal direction of the reflective optical sensor. It is the schematic of the spot shape which the reflected light from a fixing belt when a certain LED lights on makes on PD. It is a figure which shows PD output value light-received by each light-receiving part. It is a figure which shows the calculation result of the virtual output by linear interpolation. It is a figure which shows the light reception output distribution which added the virtual output estimated by the linear interpolation. It is a figure which shows the light reception output distribution which added the virtual output estimated by linear interpolation, and is a figure when the part which is less than 10% is not estimated. is there. It is sectional drawing of the transversal direction of the reflective optical sensor in 3rd Embodiment. It is sectional drawing seen from the LED side in the longitudinal direction of the reflection type optical sensor. It is sectional drawing seen from PD side in the longitudinal direction of the reflection type optical sensor. It is a top view in the longitudinal direction of the reflective optical sensor. It is sectional drawing of the transversal direction of the reflective optical sensor in 4th Embodiment. It is sectional drawing seen from the LED side in the longitudinal direction of the reflection type optical sensor. It is sectional drawing seen from PD side in the longitudinal direction of the reflection type optical sensor. It is a top view in the longitudinal direction of the reflective optical sensor. It is sectional drawing of the transversal direction of the reflective optical sensor in 5th Embodiment. It is sectional drawing seen from the LED side in the longitudinal direction of the reflection type optical sensor. It is sectional drawing seen from PD side in the longitudinal direction of the reflection type optical sensor. It is sectional drawing seen from the LED side in the longitudinal direction of the reflection type optical sensor. It is a schematic plan view showing an arrangement configuration of a reflection type optical sensor with respect to an A4 size sheet. FIG. 5 is a schematic plan view showing an arrangement configuration of a reflective optical sensor for an A5 size sheet. It is a schematic plan view showing an arrangement configuration of a reflection type optical sensor with respect to an A6 size sheet. FIG. 3 is a schematic plan view showing an arrangement configuration and shape of a reflective optical sensor for an A1 size sheet.

Embodiments of the present invention will be described below with reference to the drawings.
The first embodiment will be described with reference to FIGS.
FIG. 1 is a schematic configuration diagram of a color printer as an image forming apparatus according to the present embodiment.
FIG. 1A illustrates only a main part of the color printer 100 in an explanatory manner. The color printer 100 is a so-called tandem type printer.
A transfer belt, which is an intermediate transfer member denoted by reference numeral 11, is an endless belt, is provided around a plurality of rollers (three in the drawing), and is driven by a driving roller that is one of these rollers. It rotates in the counterclockwise direction.

A lower portion of the transfer belt 11 in the drawing is stretched in a planar manner, and image forming units UY, UM, UC, and UB are disposed in this portion.
Here, Y, M, C, and B in the reference numerals represent yellow, magenta, cyan, and black, respectively.
The image creating unit UY creates a yellow image, the image creating unit UM creates a magenta image, the image creating unit UC creates a cyan image, and the image creating unit UB creates a black image. Is a unit.
Below the image forming units UY to UB, an optical scanning device 13 as an image writing device is arranged, and further below that a cassette 15 is arranged.

Since the image forming units UY to UB are structurally the same, the image forming unit UY is taken as an example and will be briefly described with reference to FIG.
The image forming unit UY includes a photoconductive drum 20Y as a photoconductive photoconductor (image carrier), and a charger 30Y, a developing unit 40Y, a transfer roller 50Y, and a cleaning unit 60Y are provided around the photoconductive drum 20Y. It has an arranged structure.
The charger 30Y is a contact type charging roller.
A space between the charger 30Y and the developing unit 40Y is set as an image writing unit using the scanning light LY.
The transfer roller 50 </ b> Y is disposed on the side opposite to the photosensitive drum 20 </ b> Y via the transfer belt 11 and is in contact with the back surface of the transfer belt 11.

The image forming units UM to UB have the same configuration as the image forming unit UY. When necessary, the photoconductor drums 20M to 20B, the chargers 30M to 30B, the developing units 40M to 40B, and the transfer rollers 50M to 50B are used. , Written as cleaning units 60M-60B.
Such a color image printing process by the color printer 100 is well known, but will be briefly described below.
In addition, the rectangle shown with the broken line in FIG.1 (b) shows the unit of the image formation unit UY collectively, and does not necessarily show entities, such as a casing.

When the color image forming process starts, the photosensitive drums 20Y to 20B and the transfer belt 11 start to rotate. The rotation direction of each of the photosensitive drums 20Y to 20B is clockwise, and the rotation direction of the transfer belt 11 is counterclockwise.
The photosensitive surfaces of the photosensitive drums 20Y to 20B are uniformly charged by the chargers 30Y to 30B, respectively.
The optical scanning device 13 writes an image on each of the photosensitive drums 20Y to 20B by optical scanning with the scanning lights LY to LB based on the image information.
Various types of optical scanning devices 13 for performing such image writing are well known in the art, and these well-known devices are appropriately used as the optical scanning device 13.

The photosensitive drum 20Y is optically scanned using a laser beam whose intensity is modulated according to the yellow image as the scanning light LY, and the yellow image is written to form an electrostatic latent image corresponding to the yellow image. .
The formed electrostatic latent image is a so-called negative latent image, and is visualized as a yellow toner image by reversal development using yellow toner by the developing unit 40Y.
The visualized yellow toner image is electrostatically primarily transferred onto the surface side of the transfer belt 11 by the transfer roller 50Y.

The photosensitive drum 20M is optically scanned using a laser beam whose intensity is modulated in accordance with the magenta image as the scanning light LM, and the magenta image is written, and the electrostatic latent image (negative latent image) corresponding to the magenta image ) Is formed.
The formed electrostatic latent image is visualized as a magenta toner image by reversal development using magenta toner by the developing unit 40M.

The photosensitive drum 20C is optically scanned using a laser beam whose intensity is modulated according to the cyan image as the scanning light LC, and the cyan image is written, and an electrostatic latent image (negative latent image) corresponding to the cyan image is written. ) Is formed.
The formed electrostatic latent image is visualized as a cyan toner image by reversal development using cyan toner by the developing unit 40C.

The photosensitive drum 20B is optically scanned using a laser beam whose intensity is modulated in accordance with the black image as the scanning light LB, the black image is written, and an electrostatic latent image (negative latent image) corresponding to the black image is written. ) Is formed.
The formed electrostatic latent image is visualized as a black toner image by reversal development using black toner by the developing unit 40B.

The magenta toner image is electrostatically primary-transferred to the transfer belt 11 side by the transfer roller 50M. At this time, the magenta toner image is superimposed on the yellow toner image previously transferred onto the transfer belt 11.
Similarly, the cyan toner image is primary-transferred by the transfer roller 50C so as to be superimposed on the yellow toner image and magenta toner image previously superimposed on the transfer belt 11.
The black toner image is primarily transferred to the yellow, magenta, and cyan color toner images on the transfer belt 11 by the transfer roller 50B.
In this manner, the toner images of four colors of yellow, magenta, cyan, and black are superimposed on the transfer belt 11 to form a color toner image.

The photosensitive drums 20Y to 20B are cleaned by the cleaning units 60Y to 60B, respectively, after the toner image is transferred, and residual toner, paper dust, and the like are removed.
The color toner image formed on the transfer belt 11 is finally secondarily transferred from the transfer belt 11 onto the transfer sheet S, which is a sheet-like recording medium, by the secondary transfer roller 17, and the fixing device 19. As a result, the toner image is fixed on the transfer paper S and discharged out of the printer.
The transfer paper S is stacked and accommodated in the cassette 15, and is fed by a well-known paper feeding mechanism (not shown).
The fed transfer sheet S waits with its leading end held by a timing roller pair (registration roller pair) (not shown), and a secondary transfer unit in synchronization with the movement of the color toner image on the transfer belt 11. It is sent to.
The secondary transfer portion is a contact portion between the transfer belt 11 and the secondary transfer roller 17 that rotates in contact with the transfer belt 11.

The transfer sheet S is sent to the secondary transfer portion by the pair of timing rollers at the timing when the color toner image on the transfer belt 11 reaches the secondary transfer portion.
Thus, the color toner image and the transfer paper S are superimposed, and the color toner image is electrostatically transferred onto the transfer paper S.
The transfer sheet S on which the color toner image is transferred by the secondary transfer is subsequently fixed on the color toner image when passing through the fixing device 19, and is then discharged onto the tray TR on the upper side of the color printer 100.

  The above is a schematic description of the color image printing process by the color printer 100.

Next, the fixing device 19 will be described with reference to FIG.
The fixing device 19 is a so-called belt fixing system. As shown in the drawing, the fixing unit 19 includes a fixing belt 61 as a fixing member, a heating roller 62, a fixing unit roller 64, a pressure roller 63, a tension roller 65, a peeling roller. It has a claw 66 and the like.
The fixing belt 61 has a structure in which a release layer made of PFA, PTFE or the like is provided on a base material such as nickel or polyimide, and an elastic layer such as silicone rubber is provided between the base material and the release layer. is there.
Therefore, the surface of the fixing belt 61 is a resin such as PFA or PTFE forming a release layer, and information on the surface is a detection target.
The fixing belt 61 is an endless belt and is wound around a heating roller 62 and a fixing roller 64 and is given a necessary tension by a tension roller 65.

The heating roller 62 is a hollow roller made of aluminum or iron and includes a heat source H such as a halogen heater. The heat source H heats the fixing belt 61 via the heating roller 62.
Although not shown, a temperature sensor such as a thermopile for detecting the surface temperature of the fixing belt 61 is provided on the surface of the fixing belt 61 in a non-contact manner.
The fixing roller 64 has a metal core metal surrounded by silicone rubber to give elasticity.
The fixing roller 64 rotates the fixing belt 61 in the counterclockwise direction.
The pressure roller 63 is provided with an elastic layer such as silicone rubber on a metal core such as aluminum or iron, and the surface layer is constituted by a release layer such as PFA or PTFE.

The pressure roller 63 is in pressure contact with the fixing belt 61 at a position corresponding to the fixing roller 64. This pressure contact deforms the fixing roller 64 to form a nip portion. This nip portion becomes a fixing portion.
The tension roller 65 is a metal core provided with silicone rubber.
A plurality of peeling claws 66 are arranged in the axial direction (direction perpendicular to the paper surface) of the fixing roller 64 so that the pointed portion thereof is in contact with the surface of the fixing belt 61.

As described above, the non-contact temperature sensor for detecting the surface temperature of the fixing belt 61 is provided, but a contact-type temperature sensor such as a thermistor may be used instead.
When fixing is performed, the fixing belt 61 rotates counterclockwise and the pressure roller 63 rotates clockwise while being heated by the heat source H.
When the surface temperature of the fixing belt 61 reaches a fixable temperature, the transfer sheet S on which the color toner image is transferred is conveyed in the direction of the arrow and enters the fixing unit.
The color toner image receives heat from the fixing belt 61 side in the fixing unit, is pressed against the fixing belt 61 by the pressure roller 63, receives pressure, and is fixed on the transfer paper S.

Although not shown, the color printer 100 has a cleaning device for cleaning the transfer belt 11.
This cleaning device is arranged on the left side of the image forming unit UY in FIG.
The cleaning device includes a cleaning brush and a cleaning blade which are disposed so as to contact the transfer belt 11 so as to face a portion where the fixing belt 61 is wound around a roller.
The transfer belt 11 is cleaned by scraping and removing foreign matters such as residual toner and paper dust on the transfer belt 11 with the cleaning brush and the cleaning blade.
The cleaning device also has discharge means (not shown) for carrying out and discarding the residual toner removed from the transfer belt 11.

In the example of the image forming apparatus shown in FIG. 1, the transfer method is an intermediate method in which each color toner image is primarily transferred onto the transfer belt 11 as described above, and then collectively transferred onto the transfer paper S by the secondary transfer roller 17. However, the transfer method is not limited to this.
For example, the transfer paper S is carried on the transfer belt 11 and conveyed, the transfer paper S is brought into contact with each photosensitive drum, and the toner images of the respective colors are directly superimposed on the transfer paper S and transferred. It is also possible to do.
Also in this case, the fixing of the color toner image may be the same as described above.

As shown in FIG. 1C, the fixing device 19 has a surface state detection device 70 that detects the surface state of the fixing belt 61 as a test object with a fixing member.
The surface state detection device 70 irradiates and detects a plurality of light spots in a direction crossing the conveying direction on the surface of the fixing member, receives and detects reflected light at each light spot, and based on the plurality of detection results It detects the surface condition.
The surface state detection device 70 includes a reflective optical sensor 200 and detection information processing means 300.
A light shielding member 400 is movably provided between the reflective optical sensor 200 and the fixing belt 61. The drive mechanism of the light shielding member 400 is omitted.
The light blocking member 400 is for blocking the optical path between the reflective optical sensor 200 and the fixing belt 61, and the light blocking member 400 moves as necessary to open and close the optical path.

The reflective optical sensor 200 is disposed to face a portion of the fixing belt 61 that is wound around the heating roller 62.
The reflective optical sensor 200 includes a light emitting unit that emits a plurality of light spots toward the surface of the fixing belt 61 in a direction crossing the conveying direction on the surface of the fixing belt 61, and a light receiving unit that receives reflected light from the fixing belt 61. And.
Since the direction intersecting with the conveyance direction on the surface of the fixing belt 61 corresponds to the main scanning direction when writing an image by optical scanning, it will be simply referred to as the main scanning direction below.

The detection information processing unit 300 is electrically connected to the reflective optical sensor 200 and is disposed in the color printer 100.
The detection information processing unit 300 receives the detection signal from the reflective optical sensor 200 and detects the surface state of the fixing belt 61 as surface information.
The surface of the fixing belt 61 is initially intact, but as the fixing operation is repeated, the above-described offset, scratches due to contact with the peeling claws 66, and streak-like scratches due to the sheet-like recording member are generated.
The state of the surface where such a flaw or offset occurs, that is, the presence or absence of offset, the degree, the state or position of the flaw is the surface state and is surface information.

In the following, detection of surface information for mainly line-like wounds will be described.
FIG. 2 is a diagram illustratively showing fixing by the fixing device 19.
The vertical direction in FIG. 2 corresponds to the direction (main scanning direction) intersecting the transport direction TRD on the surface of the fixing belt 61.
Reference numeral S indicates a transfer sheet having a color toner image to be fixed. In this example, the transfer sheet S is A4 size, and can be conveyed in the longitudinal direction and the width direction.
Symbol A4T indicates the paper width when the A4-size transfer paper S is conveyed in the longitudinal direction, and symbol A4L indicates the paper width when the A4-size transfer paper S is conveyed in the width direction (short direction). .

The paper width A4L is substantially equal to the width of the fixing belt 61 (the length in the vertical direction in the figure). Therefore, when the A4 size transfer paper S is conveyed in the width direction (short direction), it is generated at the end in the longitudinal direction. A streak scar is hardly a problem in practice.
On the other hand, the paper width A4T is shorter than the width of the fixing belt 61, and the line-shaped scratches are generated inside the paper width A4L, which may cause the above-described problem.
Reference numerals W1 and W2 in FIG. 2 indicate margins of movement of the transfer paper width end portion in the main scanning direction when the A4-size transfer paper S is conveyed in the longitudinal direction.

Even if the A4-sized transfer paper S is transported in the longitudinal direction, the transport position in the main scanning direction cannot be made completely coincident with each transfer paper. Fluctuates slightly in the scanning direction.
Alternatively, when a so-called belt deviation occurs in the fixing belt 61 itself, the surface of the fixing belt fluctuates with respect to both end portions of the transfer sheet S in the main scanning direction.
The margin widths W1 and W2 take into account such fluctuations.
If the variation width of the position where the transfer sheet S and the fixing belt 61 are in contact is narrow, streak-like scratches are concentrated in a narrow range. Therefore, when the transfer sheet is conveyed, the transfer sheet is intentionally moved in the main scanning direction. In some cases, the transfer position at the position is shifted.
The margin widths W1 and W2 are also considered in such a case. However, the margin width is about 10 mm at most.

As described above, when the margin widths W1 and W2 are taken into account, when the A4-size transfer sheet S is fed in the longitudinal direction, if the presence or absence of a streak is detected as the surface state, the detection region A is larger than the margin width. Must be set larger.
In the example of FIG. 2, the detection area A is set so as to include the margin width W2 among the margin widths W1 and W2, and is not provided on the side where the margin width W1 is present.
It is considered that the occurrence of the streak is likely to occur in the same manner in the area of the margin width W1 and the area of the margin width W2, and it is practically sufficient to detect within one margin width. It is possible.
Of course, a detection region may be set for each of the marginal widths W1 and W2, and further, the size of the detection region may be set to cover the entire width of the transfer belt 61.

The reflective optical sensor 200 irradiates a plurality of light spots in the main scanning direction. The region irradiated with the plurality of light spots forms a detection region A.
Since the reflective optical sensor 200 can form a long detection region A, the relative positional relationship in the main scanning direction between the reflective optical sensor 200 and the end in the width direction of the transfer paper may be relatively rough.
The detection information processing unit 300 can detect the surface state of the fixing belt in the detection area A that is long in the main scanning direction in response to the detection signal from the reflective optical sensor 200.
When the width direction end of the transfer paper is included in the detection area A, at least one of the flaw level, which is information of streak flaws formed by the width direction end of the transfer paper, and the position of the flaw in the main scanning direction The surface information of the fixing belt 61 is quantified.
This point will be described later.

Here, the scratch level refers to the extent of the scratch, that is, the depth (roughness) of the scratch and the width (size) of the scratch.
Supplement about the depth of the wound.
When the surface of the fixing member is scratched by contact with the thermistor or the peeling claw or has a line-shaped scratch, the contact pressure between the fixing member and the toner image is weakened at the scratched portion as described above.
Fixation failure occurs in response to a scratch, and an image abnormality called white spot, which is a phenomenon in which the image density decreases, occurs in the fixed image.
Here, the depth of the flaw and the correlation between such a flaw and the image abnormality caused by the flaw are quantitatively captured and expressed as a parameter representing the degree of the image abnormality.

Next, a specific example of the reflective optical sensor 200 will be described.
FIG. 3 is a diagram for explaining a specific example of the reflective optical sensor 200.
The X, Y, and Z directions are determined as shown in FIGS.

The X direction is a direction that intersects the transport direction in the above description, and is the main scanning direction in the example being described.
The Y direction corresponds to the transport direction. The Z direction is a direction orthogonal to both the X and Y directions.
Reference numeral 61S denotes a surface portion including a detection region (detection region A) of the fixing belt 61.
Therefore, the Z direction is a direction from the reflective optical sensor 200 toward the surface portion 61S.

3A and 3B, reference numeral 210 denotes a substrate, reference numeral 240 denotes a side plate in the width direction (Y direction), and reference numeral 220 denotes a lens element as an irradiation optical system.
FIG. 3D shows an arrangement state of a light emitting diode (hereinafter referred to as “LED”) as a light emitting portion and a photodiode (hereinafter referred to as “PD”) as a light receiving portion on the substrate 210.
Reference numeral 211 denotes an LED, and reference numeral 212 denotes a PD.
A plurality of LEDs 211 are arranged at equal intervals in the X direction, which is the longitudinal direction of the substrate 210.
N LEDs 211 are drawn here for convenience of explanation, and the number of LEDs 211 arranged is determined by design conditions, and can generally be set to several tens to several hundreds.

A plurality of PDs 212 are arranged at equal intervals in the X direction. In this illustrative example, the number of PDs 212 is the same as the number of LEDs 211.
Numbers are sequentially assigned to the LEDs 211 one by one from the left side of FIG. 3B, and the N-th LED 211-N is denoted.
All the LEDs 211 are a sequential arrangement of LEDs 211-1, 211-2, 211-3, 211-4, ..., 211- (N-2), 211- (N-1), 211-N. .
The LEDs 211-1 to 211-N constitute an irradiation system.

The PDs 212 are sequentially numbered one by one from the left side of FIG. 3C, and the nth one counted from the left side of the figure is represented as PD212-n.
The total number of PDs 212 is N, and all PDs 212 are a sequential array of 212-1, 212-2, ..., 212-n, ... 212-N.
Next, the lens element 220 will be described with reference to FIGS. 3 (A), 3 (B), and 3 (C).
The lens element 220 is composed of two region portions.
That is, as shown in FIGS. 3A and 3B, an irradiation lens array area in which irradiation lenses 220-p (p = 1 to N) are arrayed, and a light receiving lens 220C area. It is.
The region of the irradiation lens array constitutes an irradiation optical system, and the region of the light receiving lens 220C constitutes a light receiving optical system.

In this embodiment, the number of irradiation lenses 220-p is N, which is the same as the number of LEDs 211, and one LED 211-p and one irradiation lens 220-p are 1 above the LED 211 in the Z direction. They are arranged in the X direction so as to correspond to the pair 1.
That is, the irradiation optical system includes a plurality of irradiation lenses that exist in the arrangement direction of the light emitting units, and individually correspond to each light emitting unit.
As shown in FIG. 3A and FIG. 3C, the light receiving lens 220C is a single cylindrical lens, and corresponds to the PDs 212-1 to 212 -N, and is located above the PD 212 in the Z direction. Be placed.
The cylindrical lens focuses light only in one axial direction.

FIG. 3C is a diagram of the reflective optical sensor 200 as viewed from the positive direction of the Y axis toward the negative side.
The light receiving lens 220C has a positive power only in the Y direction.
The region of the irradiation lens array and the light receiving lens 220C are integrally formed, and these can be integrally formed by resin molding.

In FIG. 3B, reference numerals 230-0, 230-1,... 230-p,..., 230-P denote a set of one LED 211-p and one irradiation lens 220-p. An opening member for preventing flare light between adjacent groups is shown.
A reference numeral 231 illustrated in FIG. 3A indicates an opening member for mainly preventing flare light between the array of the LEDs 211-p and the array of the PD 212-p.
These opening members are restricting members that restrict light leakage to other regions.

FIG. 3E shows a state in which the opening members 230 and 231 are integrated when N = 28.
Thus, the opening member is provided corresponding to the set of one LED 211-p and one irradiation lens 220-p.
By providing the aperture member, light for irradiation other than the lens for irradiation corresponding to an arbitrary LED to be lit, or light (flare light) that passes through the light receiving lens 220C and irradiates the fixing belt directly enters the PD. To prevent you from doing.
Further, direct reflected light (flare light) from the lens surface of the irradiation lens other than the irradiation lens corresponding to the arbitrary LED to be lit or the irradiation lens corresponding to the arbitrary LED to be lit is directly incident on the PD. It prevents that.

Reference numeral 241 in FIG. 3A denotes a side plate in the main scanning direction (X direction). The side plates 240 and 241 are integrated to form a case of the reflective optical sensor 200.
The opening members 230 and 231 can be integrated with the case by resin molding.
As shown in FIG. 3B, when an arbitrary LED 211-p is turned on, the emitted divergent light beam is condensed by the irradiation lens 220-p corresponding to the LED 211-p, and the surface of the fixing belt. 61S is irradiated as a light spot.
The reflected light at the portion irradiated with the light spot on the surface 61S of the fixing belt is condensed only in the Y direction by the light receiving lens 220C as shown in FIG. Incident.

  Reflection by the surface 61S of the fixing belt is not specular reflection, and since it is not condensed in the X direction by the light receiving lens 220C, the PD that receives the reflected light is not limited to the PD 212-n but a plurality of PDs. Cross.

Next, the operation of the reflective optical sensor 200 will be described using the flowchart shown in FIG.
The LEDs 211 are lit from the LED 211-1 to the LED 211-N so that the light spot scans from the left end S-1 to the right end SN in FIG. Repeatedly turns off. This is so-called sequential lighting.
In synchronization with the lighting of the LED 211-p, the reflected light from the surface 61S of the fixing belt is collected only in the Y direction by the light receiving lens 220C and received by a plurality of PDs including the PD 212-n.

In this example, for simplicity of explanation, it is assumed that the number of PDs to be received is an odd number, and m is an integer (2m + 1).
That is, the reflected light when the LED 211-p is lit is received by the PD 212-n and m PDs on both sides thereof.
For example, if m = 2, there are five PDs that receive the reflected light: PD212-n-2, PD212-n-1, PD212-n, PD212-n + 1, and PD212-n + 2.

The plurality of PDs photoelectrically convert the amount of received light. The photoelectrically converted signal is amplified and becomes a detection signal.
Each detection signal for each PD is sent to the detection information processing means 300 for each detection.
Of course, the value of m is not necessarily 2, but it is good. What is necessary is just to obtain | require experimentally the correlation with an image beforehand and to select favorable m.
However, if m is as small as 0, there is only one PD output value, and since the value is small, detection variation becomes large.
Further, when m is large and corresponds to the sum of PDs, the contrast of the streak-like wound to be detected is lowered. Good m is about 2 to 6.

When the sequential lighting is repeated and p = N, and the final LED 211-N is turned on / off, the lighting is finished sequentially with this as one cycle.
In some cases, in order to increase detection accuracy, sequential lighting may be performed over a plurality of cycles, and an average value processing of detection results in each cycle may be performed.

In the case of the above description, when the light spot is on the left side S-1 or S-2 on the surface 61S of the fixing belt, that is, when the LED 211-1 or LED 211-2 is lit, the illumination lens is an inverted magnification system. Therefore, the number of PDs that receive light is less than five.
The same applies when the light spot is located at S- (N-1) or S-N near the right end.
In view of such circumstances, in this case, the number of LEDs that are sequentially turned on is not N, but two LEDs whose light spots on the surface 61S of the fixing belt are close to the left end and right end are removed, and N− You may make it light up sequentially about four.
That is, in general, it is not necessary to use all N LEDs 211 to be turned on / off, and any N ′ (≦ N) of them may be used.

FIG. 5 shows the experimental results when the reflective optical sensor shown in FIG. 3 is operated according to FIG.
In FIG. 5A, each of the LEDs 211-p (p = 1 to 28) is turned on in the absence of the fixing belt 61, that is, in the absence of an object that reflects the light beam emitted from the reflection type optical sensor. The PD output value of PDn (n = 1 to 28) is shown.
In the absence of a fixing belt, the PD output is ideally zero, but as shown in this result, a mountain-shaped PD output centering on PD14 and PD15 is obtained. I understand.
When the present inventors investigated the cause of the PD output, as shown in FIG. 5 (B), when the LED 211-p is turned on, a part of the divergent luminous flux is part of the opening members 230-p and 231. It was found that the light was reflected and scattered by the front surface (surface facing the LED) of the light and received by a plurality of PDs 212-n.

Therefore, in order to create a state without the fixing belt 61 in the image forming apparatus, the light shielding member 400 shown in FIG.
When the fixing belt is present, the PD output including the reflected light from the front surface of the opening member in addition to the reflected light from the fixing belt to be originally detected is detected.
Therefore, it is possible to obtain only the reflected light from the fixing belt by detecting the PD output with the light shielding member 400 closed, and then detecting the PD output with the light shielding member opened, and taking the difference therebetween. It becomes.

5C is obtained from the PD output obtained with the fixing belt 61 in a state where the light shielding member is opened, in a state where the fixing belt 61 in FIG. 5A is not present, that is, with the light shielding member closed. This is the PD output when the PD output is subtracted.
That is, the signal is only the reflected light from the fixing belt 61.
Focusing on the peak of the peak of the PD output for this result, the PD number at which the PD output peaks when the LED 211-13, LED 211-14, LED 211-15, and LED 211-16 are sequentially turned on. It turns out that it shifts from the smaller one to the larger one.

This is also clear from the fact that the light spot on the fixing belt surface 61S is scanned from left to right when the LEDs 211-13, LED 211-14, LED 211-15, and LED 211-16 are sequentially turned on. .
In FIG. 5A, since the light emitted from the LED is directly reflected by the aperture member and received by the PD, if the shape of the front surface of the aperture member when viewed from each LED is the same, the PD light reception proportional to the LED light emission amount The amount is considered detectable.
Since the pitch of the opening members is the same as the arrangement pitch of the LEDs, the distribution in FIG. 5A is also similar for each LED, which is considered to represent the variation in the amount of emitted LED light at the time of detection.

Next, a case where the fixing belt 61 is damaged will be described.
In general, when the fixing belt 61 is damaged, the regular reflection component of the reflected light from the fixing belt surface 61S is decreased and the diffuse reflection component is increased as compared with the case where there is no damage.
In the form of the reflective optical sensor 200 shown in FIG. 3, the amount of light received by the PD 212 decreases by the amount of regular reflection components, and the amount of light received by the PD 212 increases by the amount of diffuse reflection components. Part of it increases.
As a result, when there is a scratch, the amount of light received by the PD 212 is reduced compared to when there is no scratch.

FIG. 6 shows a reflective optical sensor 200a according to this embodiment.
The x direction is the main scanning direction, the y direction is the sub scanning direction, z is the direction perpendicular to the xy plane, and the reflective optical sensor 200a faces the fixing belt 61a. The test object is a fixing belt as a fixing member.
The size and arrangement of the individual light receiving parts constituting the light receiving system are the same as those of the reflective optical sensor 200 shown in FIG.
In addition, the size and arrangement of the individual light emitting units constituting the irradiation system are the same as those of the reflective optical sensor 200 shown in FIG.

As shown in FIG. 6A, the reflective optical sensor 200a is disposed so as to irradiate a light spot on the surface of the fixing belt 61a with a light emitting diode (LED) 211a that emits near-infrared light. The irradiated lens 220a, the light receiving lens 220aC arranged to guide the reflected light reflected from the fixing belt 61a, and the photodiode (PD) for receiving the reflected light guided by the light receiving lens 212a, a substrate 210a that supports the LEDs 211a and the PD 212a, and side plates 240a and 241a that hold the substrate 210a, the irradiation lens 221a, and the light receiving lens 220aC.
The irradiation lens 220a and the light receiving lens 220aC are anamorphic lenses having different curvatures in the main scanning direction and the sub-scanning direction.

FIG. 6B is a view of the reflective optical sensor 200a of FIG. 6A viewed from the LED 211a side in the y direction.
FIG. 6C is a diagram of the reflective optical sensor 200a of FIG. 6A viewed from the PD 212a side in the y direction.
FIG. 6D is a diagram of the substrate 210a that supports the LEDs 211a and the PD 212a as viewed in the z direction.
FIG. 6E is a schematic diagram of spots formed on the PD by reflected light from the test object (fixing belt) when the LED 211a-14 is turned on.

FIG. 6F shows a PD output value received by each light receiving unit.
The PD output value is a relative value normalized by the maximum value (here, the output value in the PD 212a-14).

PD_ALL in FIGS. 6F and 6A indicates the sum of the PD output values in all 28 PDs.
PD_12 in FIGS. 6 (F) and 6 (b) represents a total of 12 PD output sums of PD 212a-9 to PD 212a-20.
PD_10 in FIGS. 6F and 6C indicate the total PD output sum of PD212a-10 to PD212a-19.
PD_9 in FIGS. 6F and 6D indicate the total PD output sum of PD 212a-10 to PD 212a-18.
PD_8 in FIGS. 6 (F) and 6 (e) indicate the total PD output sum of PD 212a-11 to PD 212a-18.

Each PD in PD_12 pieces, PD_10 pieces, PD_9 pieces, and PD_8 pieces is 12 pieces, 10 pieces, 9 pieces, and 8 pieces of PDs selected in descending order of the PD output value among all 28 PDs.
From FIG. 6F, the PD output caused by the reflected light from the test object (fixing belt) does not need to be the sum of all 28 PDs, and at least 8 selected PD outputs in descending order. It can be seen that the output sum of PDs may be used.
In the present invention, the output sum of 12 PDs selected in descending order of the PD output value is used as the output for detecting the test object.

FIG. 6G is an enlarged view of FIG. 6E over the region of PD 212a-9 to PD 212a-20.
FIG. 6 (H) shows a portion which is not received by PD 212a-9 to PD 212a-20 in FIG. 6 (G) by hatching with hatching.
Here, an area sandwiched between PD 212a-9 and PD 212a-10 is 213a-9-10, and an area sandwiched between PD 212a-10 and PD 212a-11 is 213a-10-11.
Similarly, 213a-11-12, 213a-12-13,... 213a-18-19 are regions sandwiched between two adjacent light receiving sections in the range of PD212a-9 to PD212a-20, respectively. 213a-19-20.

FIG. 6 (I) is an enlarged view of FIG. 6 (H) over the region of PD 212a-13 to PD 212a-16.
Here, assuming that the width in the X direction of each PD is dm_PD and the width in the X direction of the region sandwiched between any two PDs is dm_N, the arrangement pitch of adjacent PDs in the X direction is given by dm_PD + dm_N.

Next, a method for calculating a virtual output in a region sandwiched between two arbitrary light receiving units will be described with reference to FIGS. 6 (J) and 6 (K).
FIG. 6J is a PD output distribution in each light receiving unit of the PD 212a-9 to PD 212a-20 when the LED 211a-14 is turned on.
The PD output value is a relative value normalized by the maximum value (here, the PD output value in the PD 212a-14).

In order to estimate an output (hereinafter referred to as “virtual output”) that can be received when a light receiving unit having a size corresponding to the area is disposed between areas adjacent to any two adjacent PDs. First, an interpolation polynomial is obtained.
The interpolation polynomial is obtained by solving a linear equation system.
And the output in the area | region between arbitrary two PD can be estimated from the result calculated | required from the interpolation polynomial, and the ratio of dm_PD and dm_N.

When it takes time to solve the linear equation system, for example, the number of target light receiving units may be reduced, and the order of the equation may be reduced.
6 (L) and FIG. 6 (M) are 213a-9, which is an area sandwiched between the light receiving parts 212a-9 and 212a-10 by obtaining an interpolation polynomial with four light receiving parts as the object. It is an example which calculates the virtual output in -10.
6 (N) and FIG. 6 (O) obtain an interpolation polynomial with the number of target light receiving units being four, and 213a-13, which is an area sandwiched between the light receiving units 212a-13 and 212a-14. 14 is an example of calculating a virtual output in FIG.
When the virtual output between each light reception is calculated by the method shown in FIGS. 6L to 6O, the time required for the calculation process is shortened.

FIG. 6 (P) shows a polynomial for 213a-9-10 to 213a-19-20, which is an area sandwiched between two arbitrary light receiving parts, in the PD output of each light receiving part of PD 212a-9 to PD 212a-20. The light receiving unit output distribution to which the virtual output estimated by interpolation is added is shown.
213a-9-10 to 213a-19- in total of 12 PD outputs of PD212a-9 to PD212a-20 and 12 PD output sums of 212a-9 to (PD) 212a-20 Comparing PD_12 + α with the total value of the virtual outputs estimated for 20, the output of the latter was about 20% larger than the former.
In this way, for a region sandwiched between two arbitrary light receiving units, an output (virtual output) that can be received when a light receiving unit having a size corresponding to the region is arranged is estimated, and the estimated result is measured. By using this for object detection, the sensor output was increased without increasing the injection current into the light emitting part and the amplification factor of the amplifier.
When the sensor output increases, the difference in reflection characteristics increases between the case where the test object (fixing belt) is not scratched and the case where the test object is flawed, so that the flaw can be detected with higher accuracy.

  FIG. 6 (P) shows the difference in the display of the output at each light receiving unit and the virtual output between the light receiving units, but the same applies to other drawings.

In the above description, the test object is a fixing belt as a fixing member. However, for example, a semiconductor substrate or paper may be the test object.
Further, although the case where an irradiation lens is used as the irradiation optical system and a light reception lens is used as the light reception optical system has been described as an example, it is needless to say that an irradiation mirror is used as the irradiation optical system and a light reception mirror is used as the light reception optical system.
Furthermore, although the present invention has been described with respect to the case where there are a plurality of light emitting units, for example, only one light emitting unit is provided and a reflection optical sensor is provided with a drive mechanism to detect a scratch on an object at an arbitrary position. It is also possible.

As an example, the light emitting portion has a rectangular shape of □ 100 μm × 100 μm. As an example, the light receiving portion has a rectangular shape of □ 500 μm × 2000 μm.
The arrangement pitch of the light emitting part and the light receiving part is 600 μm as an example. The arrangement pitch P of the plurality of light spots on the test object (fixing belt) is 600 μm as an example.

Hereinafter, the lens shape will be described.
The lens parameters are specifically described. The radius of curvature of the irradiation lens in the main scanning direction is 4.6 mm, the cone constant in the main scanning direction is 0, and the radius of curvature of the irradiation lens in the sub-scanning direction is 4.3 mm.
The conical constant of the irradiation lens in the sub-scanning direction is −2.0, the lens diameter of the irradiation lens in the main scanning direction is 0.6 mm, the lens diameter of the irradiation lens in the sub-scanning direction is 9.2 mm, and the irradiation lens The lens thickness is 6.6 mm.
The radius of curvature of the light receiving lens in the main scanning direction is 30 mm, the cone constant in the main scanning direction is -1.5, the radius of curvature of the light receiving lens in the sub scanning direction is 4.8 mm, and the cone constant in the sub scanning direction of the light receiving lens. Is -1.6.
The lens diameter of the light receiving lens in the main scanning direction is 17 mm, the lens diameter of the light receiving lens in the sub scanning direction is 11.2 mm, and the lens thickness of the light receiving lens is 6.1 mm.

  The distance between the irradiation lens and the light receiving lens in the sub-scanning direction is 2.53 mm, the distance between the irradiation system and the irradiation lens in the optical axis direction is 10.37 mm, and the light receiving system to the light receiving lens in the optical axis direction. The distance between them is 10.87 mm.

In the above, with respect to a region sandwiched between any two adjacent light receiving units among at least two light receiving units, all light receiving outputs that can be received when a light receiving unit having a size corresponding to the region is arranged in the region. Estimated across departments.
The total value of all the estimated outputs is used for the detection of the test object. For example, there is a method that does not calculate a plurality of light receiving units with low outputs.
FIG. 6 (Q) shows a change in the scale of the vertical axis in FIG. 6 (P).
From FIG. 6 (Q), for a light receiving part having a small PD output value, such as PD 212a-9, PD 212a-19, PD 212a-20, etc., the absolute output can be obtained even if the virtual output in the region sandwiched between the light receiving parts is estimated. The value is small.
For this reason, it is difficult to say that there is a great merit for the detection of the test object.

Therefore, in the present invention, among the light receiving parts that can receive the reflected light, the light receiving part that is less than 10% of the output in the light receiving part where the output in the light receiving part has the maximum value is in the region sandwiched between the light receiving parts. Do not estimate virtual output.
In this way, the time required for the calculation processing of the detection information processing means 300 can be shortened accordingly.

In FIG. 7, the PD outputs at the respective light receiving portions of PD 212a-9 to PD 212a-20 are virtually estimated for 213a-10-11 to 213a-17-18, which are regions sandwiched between two arbitrary light receiving portions. The light receiving part output distribution to which the output is added is shown.
A total of 12 PD output sums of PD212a-9 to PD212a-20 and 12 PD output sums of 212a-9 to PD212a-20 are virtualized for 213a-10-11 to 213a-17-18. Comparing PD_12 + α ′ to which the total estimated output is added is compared with the case where no hypothetical output is estimated for a light receiving unit that is less than 10% (FIG. 7B). Compared to the case (FIG. 7A), the output increased by about 19%.
As described above, the virtual output is estimated with respect to the region sandwiched between any two light receiving portions of the specific light receiving portion among the at least two light receiving portions that receive the light reflected by the test object, and the estimated result is By using it for detecting an object to be detected, the sensor output can be increased while reducing the time required for the calculation process.

A second embodiment will be described based on FIGS. 8 and 9.
Note that the same parts as those in the above embodiment are denoted by the same reference numerals, and unless otherwise specified, description of the configuration and functions already described is omitted, and only the main part will be described (the same applies to other embodiments below).
In the above-described embodiment, the light receiving / emitting device for the reflective optical sensor in which one irradiation lens corresponds to one light emitting portion and the sensor optical system are used.
In this case, the intensity of the reflected light from the fixing belt is not sufficient, and there is a concern that the detection accuracy of the scratch on the belt surface using the reflective optical sensor may be lowered.

In the present embodiment, the light receiving and emitting device for the reflective optical sensor and the optical system for the sensor are optimized so that one irradiation lens having a large lens diameter corresponds to the plurality of light emitting units.
Thereby, the reflected light intensity from the test object (fixing belt) was further increased, and the detection accuracy of the scratch on the surface of the test object (fixing belt) was improved.

FIG. 8 shows a reflective optical sensor 200a ′ of this embodiment.
The x direction is the main scanning direction, the y direction is the sub scanning direction, z is the direction perpendicular to the xy plane, and the reflective optical sensor 200a ′ is the direction facing the fixing belt 61a ′.
The test object is a fixing belt as a fixing member.
As shown in FIG. 8A, the reflective optical sensor 200a ′ irradiates a light spot on the surface of the fixing belt 61a ′ with a light emitting diode (LED) 211a ′ that emits near infrared light and the emitted light. The receiving lens 220a ′ disposed in the light receiving portion, the light receiving lens 220a′C disposed so as to guide the reflected light reflected from the fixing belt 61a ′, and the reflected light guided by the light receiving lens are received. Photo diode (PD) 212a ′, substrate 210a ′ supporting LED 211a ′ and PD 212a ′, and substrate 210a ′, irradiation lens 220a ′, and side plates 240a ′ and 241a ′ holding light receiving lens 220a′C. Composed.

The irradiation lens 221a ′ and the light receiving lens 220a′C are anamorphic lenses having different curvatures in the main scanning direction and the sub-scanning direction.
FIG. 8B is a view of the reflective optical sensor 200a ′ of FIG. 8A viewed from the LED 211a ′ side in the y direction.
FIG. 8C is a view of the reflective optical sensor 200a ′ of FIG. 8A viewed from the PD 212a ′ side in the y direction.
FIG. 8D is a view of the substrate 210a ′ supporting the LEDs 211a ′ and PD 212a ′ as viewed in the z direction.

First, referring to FIG. 8D, this figure is a diagram for explaining the arrangement state of LEDs and PDs on the substrate 210a ′, where reference numeral 211a ′ indicates LEDs and reference numeral 212a ′ indicates PDs.
The LEDs 211a ′ have a plurality (four in the figure) as a set in the X direction which is the longitudinal direction of the substrate 210a ′, and each set is arranged at equal intervals. Each set is an irradiation system.
The number of LEDs 211a ′ is 28 (4 × 7) in the figure, but this is for convenience of explanation. The number of LEDs 211a ′ is determined by design conditions, and generally several tens to several hundreds. Can be set.

A plurality of PDs 212 a ′ are arranged at equal intervals in the X direction. In this example, the number of PDs 212a ′ is the same as the number of LEDs 211a ′.
For each LED 211a ′, four sets from the left side of FIG. 8B are set as one set p (p = 1 to P), and the numbers are sequentially numbered from the left side of FIG. 8B in each set. , And the q-th set of p sets counted from the left side of the figure is represented as LED 211a′-pq.
All LEDs 211a ′ are LEDs 211a′-1-1, 211a′-1-2, 211a′-1-3, 211a′-1-4, 211a′-2-1,..., 211a′-2-4 ,..., 211a′-pq,... 211a′-P-4.
When the total number of LEDs 211a ′ is N, N = 4P.
In this embodiment, since P = 7, N = 28. As an example, the LED 211a ′ has a rectangular shape of □ 100 μm × 100 μm, and a total of four LEDs are arranged at an array pitch of 120 μm in one set.

The PDs 212a ′ are sequentially numbered one by one from the left side of FIG. 8C, and the nth one counted from the left side of the figure is represented as PD 212a′-n.
The total number of PDs 212 is N, and all PDs 212a 'are a sequential arrangement of 212a'-1, 212a'-2, ..., 212a'-n, ... 212a'-N.
For example, the PD 212a ′ has a rectangular shape of □ 500 μm × 2000 μm, and N (= 28) are arranged at an arrangement pitch of 600 μm.

Next, the lens element 220a ′ will be described with reference to FIGS. 8A, 8B, and 8C.
The lens element 220a ′ is composed of two region portions.
That is, as shown in FIGS. 8A and 8B, an irradiation lens array area in which irradiation lenses 220a′-p (p = 1 to P) are arrayed and a light receiving lens 220a′C. And the area.
In this embodiment, the number of the irradiation lenses 220a′-p is the number obtained by dividing the number of the LEDs 211a ′ by 4 (P = N / 4 = 7), and the four LEDs 211a ′ are arranged above the LEDs 211a ′ in the Z direction. -Pq (q = 1 to 4) and irradiation lenses 220a'-p are arranged in the X direction so as to correspond to each other on a one-to-one basis.

The light receiving lens 220a′C is a single cylindrical lens as shown in FIGS. 8A and 8C, and corresponds to the PD 212a′-1 to 212a′-N in common with the PD 212a ′. Arranged upward in the Z direction.
FIG. 8C is a diagram of the reflective optical sensor 200a ′ viewed from the positive direction of the Y axis toward the negative side.
The light receiving lens 220a′C has a positive power only in the Y direction.
The region of the irradiation lens array and the light receiving lens 220a′C are integrally formed, and these can be integrally formed by resin molding.

Next, the operation of the reflective optical sensor 200a ′ will be described.
The LEDs 211a ′ are arranged from the LEDs 211a′-p-4 in the LEDs 211a′-p so that the light spot scans on the fixing belt surface 61Sa ′ from the left end Sa′-1 to the right end Sa′-28 in FIG. Lights up to LEDs 211a′-p−1.
p is turned on and off one by one in order from 1 to P. This is so-called sequential lighting.
This is because the irradiation lens 220a′-p is an inverted system.
The LED 211a ′ considers the magnification of the sensor optical system so that the arrangement pitch P of the plurality of light spots on the object to be tested (fixing belt) is equal to that of the first embodiment even when the exit beam is oppositely incident. In addition, they are arranged at positions symmetrical to each other with respect to the optical axis of the irradiation lens.
The arrangement pitch P of the light spots is 600 μm as an example.

In synchronization with the lighting of the LEDs 211a′-p, the reflected light from the fixing belt surface 61Sa ′ is condensed only in the Y direction by the light receiving lens 220a′C in synchronization with the lighting of the LEDs 211a′-pq. Light is received by a plurality of PDs including the PD 212a′-n.
FIG. 8E is a schematic diagram of spots formed on the PD by reflected light from the test object (fixing belt) when the LED 211a′-4-2 is turned on.
FIGS. 8F and 8A show PD output values received by each light receiving unit when the LED 211a′-4-2 is lit.
FIGS. 8F and 8B show PD output values received by each light receiving unit when the LED 211a-14 is turned on in the reflective optical sensor 200a.

The PD output values in FIGS. 8F and 8A are relative values normalized by the PD output values in the PD 212a-16 when the LED 211a-14 is turned on by the reflective optical sensor 200a.
8 (F) (a) and FIG. 8 (F) (b), the reflective optical sensor 200a ′ has a PD output value that is about four times that of the reflective optical sensor 200a.
In this way, by arranging the light emitting portions at positions symmetrical to each other with respect to the optical axis of the irradiation lens so that one irradiation lens having a large lens diameter corresponds to the plurality of light emitting portions, While maintaining the arrangement pitch P of a plurality of light spots on the (fixing belt), the reflected light intensity from the fixing belt is increased as compared with the conventional sensor, and the detection accuracy of the surface of the test object (fixing belt) is detected. Can be further improved.

Hereinafter, the lens shape will be described.
The lens parameters are specifically described. The radius of curvature of the irradiation lens in the main scanning direction is 4.6 mm, the cone constant in the main scanning direction is 0, and the radius of curvature of the irradiation lens in the sub-scanning direction is 4.3 mm.
The conical constant of the irradiation lens in the sub-scanning direction is −2.0, the lens diameter of the irradiation lens in the main scanning direction is 2.4 mm, the lens diameter of the irradiation lens in the sub-scanning direction is 9.2 mm, and the irradiation lens The lens thickness is 6.6 mm.
The radius of curvature of the light receiving lens in the main scanning direction is 30 mm, the cone constant in the main scanning direction is -1.5, the radius of curvature of the light receiving lens in the sub scanning direction is 4.8 mm, and the cone constant in the sub scanning direction of the light receiving lens. Is -1.6.

The lens diameter of the light receiving lens in the main scanning direction is 17 mm, the lens diameter of the light receiving lens in the sub scanning direction is 11.2 mm, and the lens thickness of the light receiving lens is 6.1 mm.
The distance between the irradiation lens and the light receiving lens in the sub-scanning direction is 2.53 mm, the distance between the irradiation system and the irradiation lens in the optical axis direction is 10.37 mm, and the light receiving system to the light receiving lens in the optical axis direction. The distance between them is 10.87 mm.

In the first embodiment, polynomial interpolation is used to calculate a virtual output in a region sandwiched between any two adjacent light receiving units. However, a method for obtaining a coefficient of a polynomial is very troublesome and complicated.
Therefore, in this embodiment, the time required for the interpolation process is shortened by using linear interpolation which is first-order polynomial interpolation.
FIG. 9A shows a result of calculating a virtual output in a region sandwiched between any two adjacent light receiving units using linear interpolation.
The target reflection type optical sensor is the reflection type optical sensor 200a shown in the first embodiment.
When linear interpolation is used, calculation can be performed by a much simpler method than by solving the equation system shown in FIGS. 6 (K), 6 (M), and 6 (O).

9B and 9C, the PD output in each of the light receiving units PD212a-9 to PD212a-20 is 213a-9, which is a region sandwiched between any two adjacent light receiving units. The light-receiving part output distribution which added the virtual output estimated by linear interpolation about -10-213a-19-20 is shown.
Note that the output increase was equivalent to the case where polynomial interpolation was used.
Thus, by using linear interpolation for calculation of the virtual output in the region sandwiched between any two adjacent light receiving units, it is possible to calculate the virtual output by a simpler method.

FIG. 10 shows a third embodiment.
In FIG. 8, the light receiving lens 220a′C of the reflective optical sensor 200a ′ is an anamorphic lens, but it may be a cylinder lens having no power in the arrangement direction of the irradiation lenses (here, the main scanning direction).
FIG. 10 shows a reflective optical sensor 200b of this embodiment.
As shown in FIG. 10A, the reflective optical sensor 200b is arranged so as to irradiate a light spot on the surface of the fixing belt 61b with a light emitting diode (LED) 211b that emits near-infrared light. The irradiated lens 220b-q, the light receiving lens 220bC arranged so as to guide the reflected light reflected from the fixing belt 61b, and a photodiode for receiving the reflected light guided by the light receiving lens ( PD) 212b, a substrate 210b that supports LED 211b and PD 212b, and side plates 240b and 241b that hold substrate 210b and lens array 220b.

FIG. 10B is a diagram of the reflective optical sensor 200b of FIG. 10A viewed from the LED 211b side in the y direction.
FIG. 10C is a view of the reflective optical sensor 200b of FIG. 10A viewed from the PD 212b side in the y direction.
FIG. 10D is a view of the substrate 210b that supports the LEDs 211b and the PD 212b in the z direction.

As shown in FIG. 6, the reflective optical sensor 200a has a configuration in which a plurality of PDs are arranged in the arrangement direction of each irradiation lens.
Therefore, in the direction orthogonal to the arrangement direction of the irradiation lenses and the optical axis direction of the irradiation lenses (in this case, the sub-scanning direction), light rays incident on the PD are taken into consideration in consideration of the PD position and the PD size. It is necessary to squeeze in a direction orthogonal to each.
However, since a plurality of PDs are arranged with respect to the arrangement direction of each irradiation lens, it is not necessary to squeeze the light for the light receiving lens by applying power in the arrangement direction of each irradiation lens.
In addition, regarding the light receiving lens, when power is provided in the arrangement direction of each irradiation lens, the irradiation system is different, but a plurality of detection lights (for example, LEDs 211a′-2) that are incident on the test object at substantially the same incident angle. -2, LED 211a′-3-2, LED 211a′-4-2, LED 211a′-5-2, LED 211a′-6-2, etc.) through each end of the light receiving lens in the arrangement direction. Between the light reaching the LED (for example, the LED 211a-2-2) and the light (for example, the LED 211a-4-2) that transmits near the center in the arrangement direction and reaches each PD (for example, the LED 211a-4-2). It will occur.
The incident angle here refers to the optical axis direction of the irradiation lens, the lens apex of the arbitrary irradiation lens, and the center of gravity of the light emitted from any one light emitting unit corresponding to the irradiation lens on the test object. It is the angle formed by the direction connecting the positions.

If the light receiving lens is a cylinder lens having no power in the arrangement direction of the irradiation lenses, a plurality of detection lights incident on the test object at substantially the same incident angle have substantially the same PD received light amount distribution.
For this reason, compared with the case of an anamorphic lens, it is possible to suppress a change in the PD received light amount distribution due to the difference in the LED to be lit, and to detect the surface state of the fixing belt with higher accuracy.
The lens parameters are specifically described. The radius of curvature of the irradiation lens in the main scanning direction is 4.6 mm, the cone constant in the main scanning direction is 0, and the radius of curvature of the irradiation lens in the sub-scanning direction is 4.3 mm.
The conical constant of the irradiation lens in the sub-scanning direction is −2.0, the lens diameter of the irradiation lens in the main scanning direction is 2.4 mm, the lens diameter of the irradiation lens in the sub-scanning direction is 9.2 mm, and the irradiation lens The lens thickness is 6.6 mm.

The radius of curvature of the light receiving lens in the main scanning direction is ∞, the cone constant in the main scanning direction is 0, the radius of curvature of the light receiving lens in the sub scanning direction is 4.8 mm, and the cone constant of the light receiving lens in the sub scanning direction is −1. .6.
The lens diameter of the light receiving lens in the main scanning direction is 17 mm, the lens diameter of the light receiving lens in the sub scanning direction is 11.2 mm, and the lens thickness of the light receiving lens is 6.1 mm.
The distance between the irradiation lens and the light receiving lens in the sub-scanning direction is 2.53 mm, the distance between the irradiation system and the irradiation lens in the optical axis direction is 10.37 mm, and the light receiving system to the light receiving lens in the optical axis direction. The distance between them is 10.87 mm.

FIG. 11 shows a fourth embodiment.
In the reflection type optical sensor lens shown in the above embodiment, the irradiation lens and the light receiving lens are arranged at respective desired positions. However, as shown in FIG. 11, the irradiation lens and the light receiving lens are integrated. Alternatively, the lens array 220c may be used.
FIG. 11 shows a reflective optical sensor 200c of this embodiment. The reflective optical sensor 200c of this embodiment is based on the reflective optical sensor 200b.

As shown in FIG. 11A, the reflective optical sensor 200c is arranged so as to irradiate a light spot on the surface of the fixing belt 61c with a light emitting diode (LED) 211c that emits near-infrared light. The lens array 220c integrated with the irradiated lens 221c and the light receiving lens 222c arranged so as to guide the reflected light reflected from the fixing belt 61c, and the reflection guided by the light receiving lens It includes a photodiode (PD) 212c that receives light, a substrate 210c that supports the LEDs 211c and PD 212c, a substrate 210c, an irradiation lens 221c, and side plates 240c and 241c that hold the light receiving lens 222c.
The irradiation lens 221c is an anamorphic lens having different curvatures in the main scanning direction and the sub-scanning direction, while the light receiving lens 222c is a cylinder lens having no power in the main scanning direction.

FIG. 11B is a diagram of the reflective optical sensor 200c of FIG. 11A viewed from the LED 211c side in the y direction.
FIG. 11C is a view of the reflective optical sensor 200c of FIG. 11A viewed from the PD 212c side in the y direction.
FIG. 11D is a view of the substrate 210c supporting the LEDs 211c and PD 212c as viewed in the z direction.

By integrating the irradiating lens and the light receiving lens, it is possible to improve the workability when assembling each lens to the reflective optical sensor, and to improve the arrangement accuracy between the lens surfaces.
Therefore, the light receiving unit output fluctuation (PD light receiving quantity fluctuation) is suppressed, and the surface state of the fixing belt can be detected with higher accuracy.

FIG. 12 shows a fifth embodiment.
As shown in FIG. 12, an opening member (light-shielding wall) 230d as a regulating member for preventing flare light may be arranged.
The reflective optical sensor 200d according to the present embodiment is obtained by arranging an opening member 230d on the reflective optical sensor 200c shown in FIG.
As shown in FIG. 12A, the reflective optical sensor 200d is arranged so as to irradiate a light spot on the surface of the fixing belt 61d with a light emitting diode (LED) 211d that emits near-infrared light. The lens array 220d in which the irradiated lens 221d and the light receiving lens 222d arranged so as to guide the reflected light reflected from the fixing belt 61d are integrated, and the reflection guided by the light receiving lens A photodiode (PD) 212d that receives light, a substrate 210d that supports the LEDs 211d and PD 212d, side plates 240d and 241d that hold the substrate 210d and the lens array 220d, and a light shielding wall 230d that prevents flare light. Is done.

FIG. 12B is a view of the reflective optical sensor 200d of FIG. 12A viewed from the LED 211d side in the y direction.
FIG. 12C is a view of the reflective optical sensor 200d of FIG. 12A viewed from the PD 212d side in the y direction.
FIG. 12D is a diagram of the substrate 210d that supports the LEDs 211d and PD 212d as viewed in the z direction.

By providing the opening member, light (flare light) that irradiates the fixing belt through the irradiation lens other than the irradiation lens corresponding to any LED to be lit or the light receiving lens is directly incident on the PD. Can be prevented.
Further, direct reflected light (flare light) from the lens surface of the irradiation lens other than the irradiation lens corresponding to the arbitrary LED to be lit or the irradiation lens corresponding to the arbitrary LED to be lit is directly incident on the PD. Can be prevented.
Thereby, the surface state of the fixing belt can be detected with high accuracy.
The opening member 230d and the case (240d, 241d) can be integrated by resin molding.

By disposing the reflective optical sensor described above in the image forming apparatus, it is possible to detect flaws on the fixing belt in real time and to detect the position and width of the flaws on the fixing belt, which was impossible in the past. It becomes.
Furthermore, by calculating the output in the region sandwiched between any two light receiving parts and using the calculation result for detection of the test object, an increase in the injection current to the light emitting part and the amplification factor of the amplifier is suppressed. be able to.

In the image forming apparatus, the length of the detection area A in the main scanning direction is shortened by placing the reflective optical sensor described above in the vicinity of the edge of the small paper width as shown in FIG. In addition, the sheet width end portion can be included in the detection area A.
That is, the fact that the detection area A can be shortened has an advantage that the reflective optical sensor 200 can be miniaturized particularly in the main scanning direction.
Since the width of the flaw is about several hundred μm to several mm and the fluctuation range as the position of the flaw is about several mm, the detection region A is preferably about 5 mm to 15 mm in the main scanning direction.
The image forming apparatus can use sheets of a plurality of sizes such as A3 size, A4 size, and A5 size.

In FIG. 13A to FIG. 13C, the reflection type optical sensor has an end portion of a small-sized recording medium and a fixing belt in a direction perpendicular to the advancing direction of the fixing belt within the surface of the fixing belt. It is partially arranged with respect to the contact position or its vicinity.
In general, there are a large number of sheets that can be passed through the maximum length in the A3 vertical direction. Therefore, the small size sheet width here refers to the sheet size excluding the A3 sheet.
If the image forming apparatus is capable of A2 portrait paper, paper sizes other than A2 paper are targeted.
Further, since there are two small-size paper width end portions on both ends, one reflection type optical sensor can be arranged on each end of the paper, that is, two in total in the main scanning direction.
However, the vertical streak caused by the end face of the paper occurs on both sides of the paper, and generally there is no significant difference between the scratch levels.

Further, by using a fixing belt as the fixing member, it is possible to detect the surface state of the fixing belt with high accuracy using the above-described reflective optical sensor.
Further, in the image forming apparatus, the reflective optical sensor described above may be enlarged in the main scanning direction as shown in FIG. 13D so as to be compatible with various paper sizes.
That is, the recording medium is arranged over the entire length of the fixing belt in the direction orthogonal to the traveling direction of the fixing belt so as to correspond to various sizes of the recording medium.
For example, in the case of an image forming apparatus capable of A1 longitudinal paper, each of the A2 size, A3 size, A4 size, A5 size, B3 size, B4 size, B5 size, and B6 size paper width ends is a reflective optical sensor. The reflection type optical sensor is enlarged in the main scanning direction so that irradiation can be performed.
By making it large enough to accommodate various paper sizes, it is possible to prevent undetected scratches appearing at different locations on the fixing belt depending on the paper size.

The form of the reflective optical sensor is not limited to the reflective optical sensor described in the above embodiment.
It is sufficient that a plurality of light spots can be irradiated on the surface of the fixing belt in the main scanning direction and the reflected light can be received.
The reflective optical sensor described in the above embodiment is an array type in which a plurality of LEDs and a plurality of PDs face each other in a one-to-one relationship. However, the laser is deflected by an optical deflector, and the reflected light from the surface of the fixing belt is 1 Alternatively, an optical deflection type in which light is received by a plurality of PDs may be used.
Further, a sensor driving type in which an optical sensor composed of one LED and one PD is moved in the main scanning direction by a driving means may be used.

  In the above-described embodiment, the fixing belt is illustrated as an example of the test object. However, the fixing belt can be similarly applied to other members that cause deterioration with time in the image forming apparatus.

DESCRIPTION OF SYMBOLS 19 Fixing device 20 Photosensitive drum as an image carrier 61 Fixing belt as a test object 200 Reflective optical sensor 211 LED as light emitting part
212 PD as light receiving unit
220 Lens Element as Irradiation Optical System 220C Light Receiving Lens as Light Receiving Optical System S Transfer Paper as Recording Medium

Japanese Patent Laid-Open No. 05-113739

Claims (10)

In a surface state detection device comprising a reflective optical sensor for detecting the surface of a test object, and detecting the surface state of the test object based on detection information from the reflective optical sensor,
The reflective optical sensor is
An irradiation system consisting of at least one light emitting part;
An irradiation optical system for guiding the light emitted from the irradiation system to the test object;
A light receiving system comprising at least two light receiving parts for receiving light emitted from the irradiation system and reflected by the test object;
A light receiving optical system for guiding the light beam reflected by the test object to the light receiving system;
With
For an area sandwiched between any two adjacent light receiving sections among the light receiving sections, an output that can be received when a light receiving section having a size corresponding to the area is disposed in the area, A surface state detection apparatus characterized by estimating from outputs from two light receiving sections and using the estimated output for detection of the test object. The surface state detection apparatus according to claim 1,
The surface state detection device characterized in that the light-receiving unit that receives less than 10% of the output in the light-receiving unit having the maximum output among the light-receiving units is not used for calculation of an estimate. . In the surface state detection apparatus according to claim 1 or 2,
The irradiation system consists of at least two light emitting units,
The irradiation optical system includes a plurality of irradiation lenses that exist in a plurality in the arrangement direction of the light emitting units and individually correspond to the light emitting units,
The surface condition detecting device, wherein the light receiving optical system comprises one light receiving lens. In the surface state detection apparatus according to claim 3,
The surface condition detection device according to claim 1, wherein the light receiving lens is a cylindrical lens that focuses light only in one axial direction. In the surface state detection apparatus according to claim 3 or 4,
The surface state detection apparatus, wherein the irradiation lens and the light receiving lens are integrated. In the surface state detection apparatus according to any one of claims 1 to 5,
The output capable of receiving light is calculated using polynomial interpolation. In the surface state detection apparatus according to claim 6,
The surface condition detecting device according to claim 1, wherein the output capable of receiving light is calculated using linear interpolation which is first-order polynomial interpolation. In the surface state detection apparatus according to any one of claims 1 to 7,
A surface state detection apparatus comprising a regulating member for regulating leakage of light to another region between the irradiation system and the irradiation optical system. An image forming apparatus that finally transfers a toner image formed on an image carrier based on image information to a recording medium, and passes the recording medium through a fixing device having a fixing belt to fix the toner image to the recording medium. In
An image forming apparatus comprising the surface state detection device according to claim 1 as a surface state detection device for detecting a surface state of the fixing belt. The image forming apparatus according to claim 9.
The reflection-type optical sensor is located in a direction perpendicular to the advancing direction of the fixing belt within the surface of the fixing belt, or a position where the end of the small-sized recording medium contacts the fixing belt or the vicinity thereof. Partially arranged,
Alternatively, the image forming apparatus is disposed over the entire longitudinal direction of the fixing belt with respect to a direction orthogonal to the traveling direction of the fixing belt so as to correspond to various sizes of the recording medium. .

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