JP2014178572A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which can detect a surface condition of a fixing member with high accuracy regardless of the size or a flaw position of a recording medium to be used and which can maintain excellent image qualities.SOLUTION: The image forming apparatus comprises a photoreceptor drum 101, a charging unit 301, an exposure unit 200, a developing unit 102, a primary transfer unit 106, a photoreceptor cleaning unit 308, a fixing unit 111 having a fixing belt 67, a reflective optical sensor 68 which irradiates a surface of the fixing belt 67 with N pcs of light spots SP at an irradiation pitch P, a main body control unit 400 determining a surface condition of the fixing belt 67, moving means 70, and the like. The reflective optical sensor 68 is moved by the moving means 70 in such a manner that a passing position of a sheet end on the fixing belt 67 is disposed within an irradiation region P(N-1) of the light spot SP.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, a facsimile machine, a plotter apparatus, and a complex machine thereof.

  2. Description of the Related Art Conventionally, image forming apparatuses that form color images using a plurality of color toners have been widely implemented as analog or digital color copiers, printers, facsimile machines, and the like, and recently, as multifunction printers (MFPs), etc. Widely implemented (see, for example, Patent Documents 1 to 3). In this image forming apparatus, an electrostatic latent image is written on the surface of an image carrier, and a developer such as toner is attached to the electrostatic latent image to make an image. Next, the image forming apparatus transfers the image-formed image onto a recording medium such as paper, and fixes the image transferred onto the recording medium by fixing means such as a fixing belt.

  By repeatedly fixing the image, scratches may occur on the surface of the fixing unit. Specifically, for example, in an image forming apparatus that can use A4 size paper and A3 size paper as a recording medium, fixing is repeated in a state in which A4 size paper is vertically fed (referred to as sending the paper vertically long). Can be mentioned. Due to the repeated fixing of A4 size paper, vertical streak may occur on the surface of the fixing belt as a fixing means at the positions where both end portions of the A4 longitudinal paper in the paper width direction are located. This occurs because the surface of the fixing belt is roughened and worn by paper dust (debris such as additives generated by cutting the paper) adhering to both ends of the paper. When such vertical streak-like scratches are formed on the fixing belt, fixing is performed using A4 landscape paper (referred to as sending the paper in landscape orientation) or A3 portrait paper. A glossy streak appears on the surface of the image corresponding to the vertical streak-like scratches caused by A4 vertical paper. The appearance of this gloss streak may cause image quality degradation.

  In the inventions described in Patent Documents 1 to 3, measures for preventing such deterioration in image quality are disclosed. For example, in the image forming apparatus described in Patent Document 1, an optical sensor that detects the damage state is installed on the surface of a rotating body such as a fixing belt. As this optical sensor, a line sensor, a point detection type photosensor, or the like is used. The line sensor has a length substantially the same as the length of the fixing belt, and detects a damage state of substantially the entire length of the fixing belt based on the density of reflected light. The point detection type photosensor is configured to be movable in the axial direction over substantially the entire length of the fixing belt, and detects a damage state of the substantially entire length of the fixing belt while moving.

  However, Patent Document 1 detects damage caused to the fixing belt by the separation claw that separates the paper from the surface of the fixing belt, and is provided for the purpose of detecting scratches or the like generated on the fixing belt due to the edge of the paper. Not a thing. In addition, since a line sensor that is substantially the same as the length of the fixing belt is used, production costs and power consumption are increased, which may increase costs. In addition, in the point detection type photosensor, since the whole length is detected while moving, the time for passing through the damaged portion is short, and the detection accuracy may be lowered.

  On the other hand, the image forming apparatus described in Patent Document 2 includes a detection device that detects a scar on the surface of the fixing roller, which is a fixing member, and the periphery thereof in order to detect the surface state of the fixing member. The exposure apparatus is controlled so that a larger amount of developer is attached to the portion corresponding to the scar portion according to the degree of the scar of the scar portion detected by the detection device. Such control makes it possible to keep the image quality high by making the unevenness of streaky gloss in the image after completion of fixing unnoticeable.

  In the prior art described in Patent Document 3, the surface roughness of the abutting member that abuts the fixing member is made rougher than the surface roughness of the fixing member to roughen the surface of the fixing member. Patent Document 3 proposes a method in which the entire surface layer of the fixing member is roughened in this way so that the contrast of the glossiness between the end position of the recording medium and the position other than the end position does not change significantly. ing. As described above, in recent years, an image forming apparatus that can detect the occurrence of a flaw on the fixing member and the state of the flaw with higher accuracy and respond quickly, and can maintain high image quality. Development is required.

  The present invention has been made in view of the above circumstances, and when detecting the surface state of a carrier that moves while closely contacting a recording medium such as a fixing member, the surface of the fixing member is changed by changing the size of the paper. Even if the position of the scratch generated on the surface of the fixing member changes or the position of the scratch on the surface of the fixing member is displaced due to the meandering of the fixing member, the surface condition of the fixing member can be changed with higher accuracy. An object of the present invention is to provide an image forming apparatus that can detect and maintain high image quality.

  In order to achieve the above object, an image forming apparatus according to the present application forms an electrostatic latent image on the surface of an image carrier, charging means for charging the surface of the image carrier, and the charged image carrier. An exposure unit, a developing unit that causes developer to adhere to the electrostatic latent image on the surface of the image carrier, and an image that is visualized on the surface of the image carrier, and a transfer that transfers the image that is visualized on the surface of the image carrier to a recording medium Fixing means having a fixing member for fixing the image transferred to the recording medium and the fixing member when the moving direction of the fixing member is a first axis direction and the direction orthogonal to the moving direction is a second axis direction. A reflection-type optical detection means for irradiating a plurality of lights toward the surface of the member, forming a plurality of light spots in the second axis direction of the surface of the fixing member, receiving the reflected light and detecting it as a detection value; , A moving means for moving the reflective optical detection means in the second axis direction, and reflective light Surface state determination means for determining the surface state of the fixing member based on the detection value from the detection means, and the number of light spots formed in the second axis direction on the surface of the fixing member is N (N is 3), and the irradiation pitch between the light spots is P, the moving means is P (N−1) of the irradiation areas of the N light spots formed on the surface of the fixing member. The reflection type optical detection means is configured to move in the second axial direction so that the passing position of the end of the fixing medium in the second axial direction of the recording medium is disposed within the range. .

  According to the present invention, when detecting the surface state of a conveying member such as a fixing member that moves while closely contacting the recording medium, the reflective optical detection means is moved in the main scanning direction in accordance with the size of the recording medium. Thus, it is possible to detect the surface state in the vicinity of the passing position of the end portion by irradiating the passing position of the end portion of the recording medium with the light spot. As a result, it is possible to accurately determine a change in the surface state of the conveyance body, and to obtain an image forming apparatus capable of maintaining high image quality.

1 is a schematic diagram of a process engine unit of an image forming apparatus according to a first embodiment. It is explanatory drawing for demonstrating an image forming unit. It is explanatory drawing for demonstrating an exposure unit, Comprising: It is a top view of the whole exposure unit. It is explanatory drawing for demonstrating an exposure unit, Comprising: The arrangement | positioning state of the member from the light source of a K and M station to a polygon mirror is shown. It is explanatory drawing for demonstrating an exposure unit, Comprising: The arrangement | positioning state of the member from the light source of a C and Y station to a polygon mirror is shown. It is explanatory drawing for demonstrating an exposure unit, Comprising: It is a side view of the whole exposure unit. FIG. 4 is an explanatory diagram for explaining transfer of a toner image, and is a perspective view showing an intermediate transfer belt and a support roller. FIG. 6 is an explanatory diagram for explaining a configuration of a fixing unit. It is explanatory drawing for demonstrating the basic composition of the conventional reflective optical sensor which has one light emission part and one light-receiving part, (a) is a side view, (b) is a top view. . It is explanatory drawing for demonstrating the structure of the reflection type detection sensor of the 1st example which irradiates a some light spot, (a) is a side view, (b) is a top view. It is explanatory drawing for demonstrating the procedure which detects a surface state using two reflection type optical sensors of FIG. 9, (a) shows the installation state of a reflection type optical sensor, (b) is the light spot of FIG. Indicates the irradiation position. It is explanatory drawing for demonstrating the procedure which moves the reflective optical sensor of FIG. 9, and detects a surface state, Comprising: (a) shows the moving direction of a reflective optical sensor, (b) is a some light spot. The moving direction of the irradiation area corresponding to is shown. It is explanatory drawing for demonstrating the procedure which detects a surface state using the reflection type optical sensor of FIG. 11, (a) shows the installation state of a reflection type optical sensor, (b) shows several light spots. The corresponding irradiation area is shown. It is explanatory drawing for demonstrating the structure of the reflection type detection sensor of the 2nd example which irradiates a some light spot, Comprising: (a) shows the schematic sectional drawing which observed the reflection type optical sensor in the main scanning direction, (B) shows the schematic sectional drawing which observed LED and the lens for irradiation in the subscanning direction. It is the schematic sectional drawing which observed PD and the lens for light reception of the reflection type optical sensor of Fig.14 (a) in the subscanning direction. It is a top view of the board | substrate which supports LED and PD of the reflective optical sensor of FIG. It is explanatory drawing for demonstrating in detail the structure of the lens element of the reflection type optical sensor of FIG. It is explanatory drawing for demonstrating the influence of PD output by the error of the design position of the reflection type optical sensor of FIG. It is a flowchart which shows operation | movement of the reflection type optical sensor of FIG. FIG. 6 is an explanatory diagram for explaining a case where a reflective optical sensor is installed at a passing position of each paper edge in the main scanning direction. It is the schematic which shows the reflective optical sensor which made it movable to a main scanning direction by the moving means based on 1st Example of this application, Comprising: (a) shows the top view of a reflective optical sensor and a moving means, (B) shows these sectional views. It is explanatory drawing for demonstrating the positional relationship of the irradiation area | region of the light spot from the reflective optical sensor of 1st Example, and a damage | wound part, (a) is only the light spot of one end irradiating a damage | wound part. (B) shows a state where the light spot near the center is irradiating the scratched part, and (c) shows a state where only the light spot at the other end is irradiating the scratched part. It is explanatory drawing for demonstrating the state moved to the main scanning direction so that the reflective optical sensor of 1st Example may irradiate the passage position of the one edge part of a paper corresponding to the size of a paper, (A) shows L5, (b) shows L4, (c) shows L3, (d) shows L2, and (e) shows the state moved to each wound part (end part passing position) of L1. It is explanatory drawing for demonstrating the state moved to the main scanning direction so that the reflective optical sensor of 1st Example may irradiate the passage position of the other edge part of a paper corresponding to the size of a paper, (A) is L1 ′, (b) is L2 ′, (c) is L3 ′, (d) is L4 ′, and (e) is moved to each wound part (end passage position) of L5 ′. Indicates. It is explanatory drawing for demonstrating the 3rd Example which each installed two reflection type optical sensors in the passage position of the paper edge part to detect, (a) is the position of L1 and L1 ', (b) is (C) shows a state in which the reflective optical sensor is moved to the positions L1 and L4 at the positions L3 and L5. It is explanatory drawing for demonstrating the 4th Example which each installed two reflection type optical sensors in the passage position of the both ends of a paper, (a) is the position of L5 and L5 ', (b) is L4 and The reflective optical sensor is moved to the position of L4 ′, (c) is moved to the positions of L3 and L3 ′, (d) is moved to the positions of L2 and L2 ′, and (e) is moved to the positions of L1 and L1 ′. Indicates. It is explanatory drawing for demonstrating the 5th-8th Example which provided the light-shielding member, (a) shows the state which is detecting in the passage position of a paper edge part with a reflection type optical sensor, (b) ) Shows a state where detection is performed at the position of the light shielding member. The reflective optical sensor is set to (a) to (a) to be arranged so that the passing position of the end of the fixing belt in the main scanning direction of the paper is within the irradiation area P (N-1) of the N light spots. It is explanatory drawing for demonstrating the state which has moved to the position of (c). FIG. 9 is an explanatory diagram for explaining a change in a PD output value due to an error in a design position of a reflective optical sensor in a second embodiment, and (a) shows a PD when there is no error in the design position of the reflective optical sensor. The graph of an output value is shown, (b) shows the PD output when an error occurs in the design position. FIG. 20 is an explanatory diagram for explaining experimental results when the reflective optical sensor shown in FIG. 14 is operated according to the flow of FIG. 19 in the fifth and sixth examples, and (a) is a fixing belt. 2 is a graph showing a PD output value in a state where no is present, and (b) is a graph showing a PD output value from the fixing belt. In 5th Example, it is explanatory drawing for demonstrating that a part of light beam from LED is reflected and scattered by an aperture member, and is received by PD. In 6th Example, it is explanatory drawing for demonstrating PD output value at the time of dispersion | variation in the emitted light amount of LED, (a) is a graph which shows the sum total of PD output value, (b) is It is a graph which shows the light quantity of a light spot. It is a graph which shows the sensor output of each LED at the time of correcting light quantity in 6th Example. In 7th Example, it is a flowchart which shows the light quantity correction | amendment procedure at the time of providing a light-shielding member.

  In describing the embodiment of the present invention, the surface state of a scratched portion and a scratch-free portion formed on a fixing belt (fixing member), which is an example of a conveyance body, is detected using FIGS. 9 to 17. An example will be described. In this specification, the spot-like light emitted from the light emitting unit is referred to as “spot light”, and an image formed on the surface of the carrier such as a fixing member by the spot light is referred to as “light spot”. An area occupied by the light spot on the surface of the fixing member is referred to as an “irradiation area”. Further, the moving direction of the fixing belt is defined as “first axis direction”, and the direction intersecting with the moving direction is defined as “second axis direction”. In this specification, the first axis direction is the “sub-scanning direction”, and the second axis direction is the “main scanning direction”.

  FIG. 9A shows a side view of a reflective optical sensor 68a (68b) having one light emitting portion E1 and one light receiving portion D1, and FIG. 9B shows a plan view. FIG. 10A shows a side view of a reflective optical sensor 68c having five light emitting parts E1 to E5 and seven light receiving parts D0 to D6, and FIG. 10B shows a plan view. FIG. 11A shows the installation state of the two reflective optical sensors 68a and 68b of FIG. 9, and FIG. 11B shows the light spots SP1 and SP2. FIG. 12A shows a state in which one reflective optical sensor 68a in FIG. 9 is installed so as to be movable in the direction of the arrow, and FIG. 12B shows the moving direction of the plurality of light spots SP1. FIG. 13A shows the installation state of the reflective optical sensor 68c of FIG. 10, and FIG. 13B shows the light spots SP1 to SP5. 14 to 17 show a lens configuration of the reflective optical sensor 68c of FIG.

  First, as shown in FIG. 11, a method for detecting a scratch 80 on the upper surface of the fixing belt 67 at the passing position (near the scratch 80) at the end of the sheet when the two reflective optical sensors 68 a and 68 b are used. Will be described. As shown in FIGS. 9A and 9B, the reflective optical sensors 68a and 68b used here have one light emitting portion E1 and one light receiving portion D1, and the fixing belt 67. It is installed on the top surface. Further, the light emitting unit E1 has one irradiation lens LE1, and the light receiving unit D1 has one light receiving lens LD1. These two reflective optical sensors 68a and 68b are installed side by side in the main scanning direction so as to form light spots SP1 and SP2 in the main scanning direction on the surface of the fixing belt 67, as shown in FIG. 11B. Has been. In addition, the reflective optical sensor 68a irradiates an area without a scratch (hereinafter referred to as “scratch-free part 81”), and the reflective optical sensor 68b performs an area with a scratch (hereinafter referred to as “scratched part 80”). It is installed to irradiate.

  With the reflection-type optical sensors 68a and 68b installed as described above, it is possible to detect the surface state of the scratched portion 80 and the scratchless portion 81 at substantially the same position in the sub-scanning direction. Then, by comparing the detection value of the scratch-free portion 81 acquired by the reflective optical sensor 68a with the detection value of the scratch portion 80 acquired by the reflective optical sensor 68b, it is possible to determine the surface state of the scratched portion. it can.

  However, the fixing belt 67 meanders for a few seconds after starting driving, and after a few seconds, the fixing belt 67 does not meander. Due to the meandering of the fixing belt, the position of the flaw 80 may fluctuate (displace) in the main scanning direction. Therefore, every time the fixing belt 67 is driven, the position of the scratch 80 may be shifted in the main scanning direction, and the scratch 80 may be removed from the irradiation area of the light spot SP2. Therefore, there is a case where the scratched part 80 cannot be detected by a method in which only two light spots are used to obtain detection values at only two places.

  As another detection means, as shown in FIG. 12, one reflection type optical sensor 68a is installed, and the reflection type optical sensor 68a is moved in the main scanning direction as indicated by an arrow. There are means for detecting the surface condition. In such a means, the detection value when the light spot SP1 irradiates the scratched part 80 (scratch generated at the passing position of the end of the paper) is compared with the detection value when the scratchless part 81 is detected. I can. However, as in the case of the point detection type photosensor disclosed in Patent Document 1, since the time for the light spot SP1 to pass through the scratch 80 is short, the number of data points when detecting the scratch 80 is reduced. As a result, the average state of the scratch 80 generated in the sub-scanning direction cannot be detected, and it is difficult to perform highly accurate detection.

  In order to solve this problem, it is preferable to use a reflective optical sensor that emits a plurality of light spots in the main scanning direction on the surface of the fixing belt 67 as shown in FIG. A first example using such a reflective sensor will be described with reference to FIGS. As shown in FIG. 10, the reflective optical sensor 68c has five light emitting units E1 to E5 and seven light receiving units D0 to D6 installed in series in the main scanning direction. Irradiation lenses LE1 to LE5 installed corresponding to the light emitting portions E1 to E5 collect the light from the light emitting portions E1 to E5 and irradiate the surface of the fixing belt 67 with spot-like light, thereby producing a light spot. SP (SP1-SP6) is formed. Further, the light receiving lenses LD0 to LD6 installed corresponding to the light receiving portions D0 to D6 collect the scattered light reflected by the fixing belt 67 and cause the light receiving portions D0 to D6 to receive the light.

  When performing detection using the reflective optical sensor 68c, if a plurality of light spots are irradiated simultaneously, the light spots are irradiated in a time-sharing manner because they are affected by the scattered light of the adjacent light spots. Specifically, first, the light emitting unit E1 is caused to emit light, and the reflected light when the light spot SP1 is irradiated is received by the light receiving units D0, D1, and D2, and the detection value is acquired. Next, the light emitting unit E2 is caused to emit light, and the reflected light when the light spot SP2 is irradiated is received by the light receiving units D1, D2, and D3, and the detection value is acquired. Similarly, when the light emitting portions E3 to E5 are caused to emit light, the three adjacent light receiving portions receive the reflected light from the light spots SP3 to SP5 and acquire the detection values.

  As described above, when a plurality of light spots are irradiated in a time-sharing manner, light reception by a plurality of adjacent light receiving units (D0 to D6) is possible. Therefore, there is an advantage that the light receiving area can be increased and the light use efficiency can be improved.

  Further, as shown in FIG. 13A, the reflective optical sensor 68c is installed so as to irradiate a light spot also on the scratch-free portions 81 on both sides in the main scanning direction with the scratch 80 interposed therebetween. That is, it is installed so as to sandwich the passage position of the paper edge. With this installation, as shown in FIG. 13B, the light spot from the reflective optical sensor 68c is irradiated to a wide range including the scratched portion 80 and the scratch-free portions 81 on both sides thereof (light spots SP1 to SP1). SP5). In this way, by using the reflective optical sensor 68c that irradiates a plurality of light spots, even if the position of the scratch 80 is shifted in the main scanning direction due to the meandering of the fixing belt 67, any one of the reflective optical sensors 68c is used. By this light spot, the flawed portion 80 of the fixing belt 67 can be detected.

  Next, a second example of a reflective optical sensor that irradiates a plurality of light spots in the main scanning direction on the surface of the fixing belt will be described with reference to FIGS. 14-17 is explanatory drawing for demonstrating the specific structure of the reflection type optical sensor 68d of a 2nd example. As shown in FIGS. 14 to 17, x, y, and z directions are determined. The “x direction” corresponds to the “direction intersecting the conveyance direction (movement direction) of the fixing belt 67”, that is, the “second axis direction”, and is the “main scanning direction” in the example described below. The “y direction” corresponds to the “conveying direction (moving direction) of the fixing belt 67”, that is, the “first axis direction”, and is the “sub-scanning direction” in the example described below. The “z direction” is “a direction perpendicular to both the x and y directions”.

  14 and 15, “Detection area A” indicates an area where the light spot SP on the fixing belt 67 is irradiated. Reference numeral 67S denotes a “surface portion including the detection region (the detection region A described above)” of the fixing belt 67. Therefore, the “z direction” is a direction from the reflective optical sensor 68d toward the “surface portion 67S”.

  Hereinafter, the configuration of the reflective optical sensor 68d will be described. FIG. 14A is a cross-sectional view of the reflective optical sensor 68d observed from the positive direction in the x direction (main scanning direction) toward the negative direction. FIG. 14B is a schematic cross-sectional view of the LED 211 and the irradiation lens 221 of the reflective optical sensor 68d observed from the negative direction in the y direction (sub-scanning direction) toward the positive direction. FIG. 15 is a schematic cross-sectional view of the PD 212 and the light receiving lens 222 of the reflective optical sensor 68d observed from the negative direction in the y direction (sub-scanning direction) toward the positive direction. As shown in these drawings, the reflective optical sensor 68d includes a substrate 210, side plates 240 and 241, a lens element 220 supported by the side plate 240, and the like.

  FIG. 16 is a plan view of the substrate 210. As shown in FIG. 16, on a substrate 210, a light emitting diode (hereinafter referred to as “LED”) 211 as a light emitting portion and a photodiode (hereinafter referred to as “PD”) 212 as a photosensor (light receiving portion). Are arranged in the main scanning direction (x direction).

  As shown in these drawings, the reflective optical sensor 68d includes an irradiation optical system having an LED 211 and an irradiation lens 221, a light reception optical system having a light reception lens 222 and a PD 212, a substrate 210, side plates 240 and 241, and , And is configured. Further, a flat portion 223 made of a flat surface parallel to the optical axis direction is formed at the boundary between the irradiation lens 221 and the light receiving lens 222. The reflective optical sensor 68d includes opening members 230 and 231 for preventing flare light.

  The LEDs 211 are arranged at equal intervals in the x direction which is the longitudinal direction of the substrate 210, with a plurality (four in FIG. 16) as one set. In FIG. 16, four sets of 16 LEDs 211 are drawn. However, this is for convenience of explanation, and the number of the LEDs 211 arranged is appropriately determined according to design conditions. A plurality of PDs 212 are arranged at equal intervals in the x direction of the substrate 210. In the following description, it is assumed that the number of PDs 212 is the same as the number of LEDs 211.

  14 (b) and FIG. 16, that is, four LEDs from the start point side in the x direction are individually set as one set p (p = 1 to P ′, P ′ is the total number of sets), Numbers are assigned sequentially one by one from the left in the set, and this number is set to q (q = 1 to 4). The p sets of the q-th LEDs 211 counted from the left side of FIG. 16 are represented as LEDs 211-pq. Therefore, as shown in FIG. 16, all LEDs 211 are LED 211-1-1, LED 211-1-2, LED 211-1-3, LED 211-1-4, LED 211-2-1,. 2-4, ..., LED 211-pq, ..., LED 211-P'-1, LED 211-P'-2, LED 211-P'-3, LED 211-P'-4 Become. If the total number of LEDs 211 is N, N = 4P ′.

  On the other hand, the PDs 212 are sequentially numbered one by one from the left side of FIG. 16, and the nth one counted from the left side of FIG. 16 is represented as PD212-n. The total number of PDs 212 is N, and all the PDs 212 are sequentially arranged in the order of PD 212-1, PD 212-2, ..., PD 212-n, ..., PD 212- (N-1), PD 212-N. is there.

  Next, with reference to FIGS. 14A, 14B, and 15, the configuration of the lens element 220 will be described in detail. The lens element 220 is composed of two region portions. That is, as shown in FIGS. 14A and 14B, it is composed of an area of the irradiation lens array in which the irradiation lenses 221 are arranged and an area of the light receiving lens 222.

  As shown in FIG. 14B, a plurality of irradiation lenses 221 are provided in the x direction, and each is denoted by reference numeral 221-p (p = 1 to P ′). In FIG. 14B, the irradiation lenses 221-1, ..., 221-P 'are arranged. Further, one irradiation lens 221-p is provided corresponding to the four LEDs 211p-q. That is, the number P of irradiation lenses 221-p is a number obtained by dividing the number N of LEDs 211 by 4 (P = N / 4). As shown in FIG. 14 (b), the irradiation lens 221-p has a one-to-one correspondence with the four LEDs 211-pq (q = 1 to 4) at the upper part of the LED 211 in the z direction. They are arranged in the x direction.

  The light receiving lens 222 is a “single cylindrical lens” as shown in FIGS. As shown in FIG. 15, the light receiving lens 222 is installed above the PD 212 in the z direction so as to correspond to the PDs 212-1 to 212 -N. The light receiving lens 222 has a positive power only in the y direction.

  The region of the irradiation lens array and the light receiving lens 222 are integrally formed, and these can be integrally formed by resin molding.

  As shown in FIG. 14B, the opening member 230 is installed on both sides of the irradiation lens 221. From the left side of the drawing, the opening member 230-0, the opening member 230-1,. -P,..., Are sequentially arranged as opening members 230-P ′. The opening member 230 is provided to prevent “flare light” between adjacent groups of “a set of four LEDs 211-pq (q = 1 to 4) and an irradiation lens 221-p”. It has been. Moreover, the opening member 231 shown in FIG. 14A mainly prevents “flare light” between “the array of LEDs 211-pq (q = 1 to 4) and the array of PD212-p”. Is to do.

  FIG. 17 shows a state in which the opening member 230 and the opening member 231 are integrated when P ′ = 7. As shown in FIG. 17, an opening O is provided corresponding to each of the irradiation lenses 221-p (2211-1, 221-2,...). That is, one opening O is provided corresponding to a set of four LEDs 211-pq (q = 1 to 4) and one irradiation lens 221-p. By providing the opening O in this way, light that passes through the irradiation lens 221 other than the irradiation lens 221 corresponding to the arbitrary LED 211 to be lit and irradiates the fixing belt 67 or irradiation corresponding to the arbitrary LED 211 that is lit. Direct reflected light from the lens surface of the irradiation lens 221 other than the irradiation lens 221 corresponding to the lighting lens 221 or the arbitrary LED 211 to be lit (these light is “flare light”) is directly incident on the PD 212. To prevent it.

  As shown in FIG. 14B, a pair of side plates 240 are installed at both ends in the longitudinal direction (x direction) on the substrate 210. As shown in FIG. 14A, a pair of side plates 241 is installed at both ends in the width direction (y direction) on the substrate 210 so as to be long in the x direction. These side plates 240 and 241 are integrated to form a case 243. The opening members 230 and 231 described above and the case 243 can be integrated by resin molding.

  Further, as shown in FIG. 14B, when the LED 211-pq is turned on, the emitted “divergent light flux” is condensed by the irradiation lens 221-p corresponding to the LED 211-pq. Then, the fixing belt surface 67S is irradiated as a light spot SP. Reflected light at the “part irradiated with the light spot SP (irradiation region)” on the fixing belt surface 67S is condensed only in the y direction by the light receiving lens 222 as shown in FIGS. Then, it enters one of the PDs 212-n. Reflection by the fixing belt surface 67S is not specular reflection, and since it is not condensed in the x direction by the light receiving lens 222, the PD 212 that receives the reflected light is not “PD 212-n alone”. The PDP 212 receives the light.

  Next, the operation of the reflective optical sensor 68d of the second example will be described using the flowchart shown in FIG. The LED 211 scans from the LED 211-p-4 to the LED 211-p- in the LED 211-p so that the light spot scans on the fixing belt surface 67S from the leftmost light spot SP1 to the rightmost light spot SPN in FIG. Turn on and off one by one in the order of 1. This operation is repeated from p = 1 to P ′. So-called “sequential lighting” is performed. This is because the irradiation lens 221-p is an inverted system.

  Hereinafter, an operation from lighting of the LED 211 to detection by the PD 212 will be described. First, in step S10 of FIG. 19, p = 1 (1 ≦ p ≦ P ′) is set as an initial value of the set p of the LEDs 211. Next, in step S11, q = 4 (1 ≦ q ≦ 4) is set as a counter for managing the lighting order of the LEDs 211-pq in the set p.

  Next, the process of lighting and light reception is entered. First, in step S12, the LED 211-pq is turned on. For example, in the first processing, that is, when p = 1 and q = 4, the first set of LEDs 211-1-4 is turned on. Next, in step S <b> 13, the reflected light reflected by the fixing belt surface 67 </ b> S is received by the PD 212.

  In synchronization with the lighting of the LEDs 211-pq, the reflected light from the fixing belt surface 67S is collected only in the y direction by the light receiving lens 222 and received by a plurality of PDs 212 including the PD 212-n. Here, for the sake of simplicity of explanation, it is assumed that the number of light-receiving PDs is “odd”, and that m is an integer (2m + 1). That is, the reflected light when the LED 211-pq is lit is received by the PD 212-n and “m PDs on both sides” (PD212- (nm) to PD212- (n + m)).

  For example, if m = 2, the plurality of PDs that receive the reflected light are PD212- (n-2), PD212- (n-1), PD212-n, PD212- (n + 1), PD212- ( n + 2). The plurality of PDs 212- (nm) to PD212- (n + m) photoelectrically convert the amount of received light. The photoelectrically converted signal is amplified and becomes a “detection signal”. The detection signal for each PD 212 is sent to a surface state determination means (not shown) for determining the surface state at each detection in step S15 described later.

  Of course, the value of m may not be 2, but it does not matter. A correlation with the image data may be experimentally obtained in advance, and a suitable m may be selected. However, if m is small as 0, there is only one sensor output value (hereinafter referred to as “PD output value”), and since the value is small, detection variation increases, which is not preferable. Further, when m is large and corresponds to the sum of PDs 212, the contrast of the streak-like wound to be detected is lowered, which is not preferable. Accordingly, m is more preferably about 2 to 6.

  When the light reception by the PD 212 is completed, the LED 211-pq is turned off in step S14. Thereafter, in step S15, detection signals of the respective PDs 212- (nm) to PD212- (n + m) are transmitted to the surface state determination means.

  In step S16, it is determined whether q> 1, that is, whether the processing in steps S12 to S15 has been executed for all four LEDs 211 in the set p. If q> 1 is yes, there is an LED 211 that is not lit, etc., so that q is counted down (q = q-1) in step S17, and the process returns to step S12. Then, the processing of steps S12 to S15 is repeated for the next LED 211-pq.

  On the other hand, if q> 1 is NO, the process is completed for all the LEDs 211 in the set p, and the process proceeds to step S18. For example, in the set of p = 1, when a series of processing of turning on, turning off, and detecting signal transmission is completed for the LEDs 211-1-4 to 2111-1-1 at the left end of the page of FIG. It is determined that the processing for the LED 211 has been completed.

  In step S18, it is determined whether p <P ', that is, whether the processing in steps S11 to S17 has been executed for all sets p (p = 1 to P'). If p <P ′ is YES, there is a set p that has not been processed, and therefore p is incremented (p = p + 1) in step S19, and the process returns to step S11. On the other hand, if p <P ′ is no, the process is completed for all the sets p, and the process proceeds to step S20. As described above, the LEDs 211-p-q are sequentially turned on repeatedly so that p = P ′ and q = 1, and when the final LED 211-P′-1 “lights on / off”, this is sequentially set as one cycle. The lighting and PD output value acquisition ends.

  Thereafter, in step S20, it is determined whether the series of processes is repeated for another cycle. If YES, the process returns to step S10 and the processes of steps S11 to S19 are repeated. In this way, it is also possible to perform sequential lighting over a plurality of cycles, and perform an average value processing of detection results in each cycle. Such processing can improve detection accuracy. If the determination in step S20 is NO, the entire process is terminated.

  Heretofore, the detection example of the fixing belt surface 67S by the reflective optical sensor 68d has been described. In this example, as shown in FIG. 14B, when the light spot SP that illuminates the surface of the fixing belt 67S is at the left end SP1 or SP2, that is, the LED 211-1-3 or the LED 211-1-4. When the light is lit, the irradiation lens 221 is an inverted magnification system, so that the number of PDs 212 that receive light is less than five. The same applies when the light spot SP is closer to 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 211 whose light spots SP on the fixing belt surface 67S are closer to the left end and the right end are removed two by two. -4 pieces may be turned on sequentially. That is, generally, it is not necessary to use all N LEDs 211 that are turned on and off, and any N ′ (≦ N) of them may be used.

  As described above, by using the reflective optical sensors 68c and 68d of the first and second examples that form the light spot SP by irradiating a plurality of spot lights in the main scanning direction of the fixing belt surface 67S, Even if the position of the flaw is displaced in the main scanning direction, the flaw on the fixing belt 67 can be detected with high accuracy.

  However, in actuality, papers of various sizes pass on the fixing belt, so that scratches occur at various positions in the main scanning direction (passing position of the paper edge). Therefore, it is necessary to detect a flaw at the passing position of each paper edge. Therefore, as shown in FIG. 20A, it is also possible to arrange the reflection type optical sensor 68c (or 68d) that irradiates a plurality of spot lights at the passing position of the end of each sheet in the main scanning direction. It is done. As a result, as shown in FIG. 20 (b), one of the light spots SP1 to SP5 of each reflective optical sensor 68c is irradiated to the scratch 80 formed by the passage of both ends of each size of paper. . However, due to the size and space problems of the reflective optical sensor 68c, there are many cases where the reflective optical sensor 68c cannot be disposed at the passing position of each paper edge. In addition, the number of reflective optical sensors is increased, which increases the cost and is not realistic.

  Therefore, in the image forming apparatus according to the present application, the above-described problem is solved, and the scratched part 80 generated at the passing position of the end of various sizes of paper on the fixing belt is detected by the reflective optical sensor. I was able to.

<First embodiment>
The image forming apparatus according to the first embodiment of the present application will be described below with reference to the drawings. In this embodiment, the image forming apparatus is applied to a tandem type full-color printer (hereinafter simply referred to as “printer”). The printer of this embodiment forms an image using toners of four colors of yellow, cyan, magenta, and black, and is provided with members corresponding to the respective colors. Hereinafter, in this specification, in FIGS. 1 and 2 and the description thereof, at the end of the reference numeral, Y is a member for yellow, C is a member for cyan, M is a member for magenta, and a member for black. Is described with K. Also, in FIGS. 3 to 6 and the description thereof, “a” is attached to the black member, “b” is attached to the magenta member, “c” is attached to the cyan member, and “d” is attached to the yellow member. I will explain. Further, the right direction (the longitudinal direction of the intermediate transfer belt 105) in FIG. 1 is defined as the X direction, the front direction (the short direction of the intermediate transfer belt 105) in the Y direction, and the lower direction is defined as the Z direction. 2 to 6, arrows indicating the directions of X, Y, and Z are attached in correspondence with FIG. 1.

  First, the outline of the configuration of the printer of this embodiment will be described. FIG. 1 is a schematic configuration diagram (hereinafter referred to as a “process engine unit 100”) showing an image forming process portion for performing exposure, charging, development, transfer, and fixing in the printer of this embodiment. In the printer of this embodiment, in addition to the process engine unit 100 shown in FIG. 1, a print controller (not shown) that processes image data sent from a PC or the like and converts it into exposure data, controls the image forming operation. A main body control unit 400, a paper feeding unit (not shown) for supplying transfer paper 115 as a recording medium, a manual feed tray (not shown) for manually feeding the transfer paper 115, and an image formed A paper discharge tray (not shown) for discharging the transfer paper 115 is provided.

  The main body control unit 400 drives and controls each unit of the printer, and includes a CPU (Central Processing Unit) that executes various calculations and drive control of each unit. Furthermore, a ROM (Read Only Memory) that stores fixed data such as a computer program in advance, a RAM (Random Access Memory) that functions as a work area that stores various data in a rewritable manner, and the like are provided. The main body control unit 400 also has a function as surface state determination means for determining the surface state of the fixing belt 67 based on a detection value from a reflection type optical sensor 68 described later.

  As shown in FIG. 1, the process engine unit 100 of the printer of this embodiment includes image forming units 1Y, 1C, 1M, and 1K that form toner images of yellow, cyan, magenta, and black, and exposure as exposure means. Unit 200, intermediate transfer belt 105 as transfer means, primary transfer units 106Y, 106C, 106M, 106K and secondary transfer roller 108, fixing unit 111 as fixing means, and reflection type as reflection type optical detection means The optical sensor 68 (refer FIG. 21) and the main body control part 400 as the above-mentioned surface state judgment means are provided.

  As the first transfer means, an endless belt-like intermediate transfer belt 105 (also functioning as a second image carrier) is provided. The intermediate transfer belt 105 is stretched around four support rollers 112, 113, 114, and 119 (the stretch refers to a state where the belt is stretched around the four support rollers under tension). In this stretched state, the intermediate transfer belt 105 is driven to rotate counterclockwise as indicated by an arrow in FIG. 1 by the support roller 112 that also functions as a drive roller.

  The image forming units 1Y, 1C, 1M, and 1K are provided on a stretched portion of the intermediate transfer belt 105. The image forming units 1Y, 1C, 1M, and 1K include the photosensitive units 103Y, 103C, 103M, and 103K, charging units 301Y, 301C, 301M, and 301K as charging units, and developing units 102Y, 102C as developing units. , 102M, 102K. The developing units 102Y, 102C, 102M, and 102K are supplied with toners of yellow, cyan, magenta, and black from the toner bottles 104Y, 104C, 104M, and 104K, respectively. The photosensitive units 103Y, 103C, 103M, and 103K are provided with photosensitive drums 101Y, 101C, 101M, and 101K as first image carriers.

  As shown in FIG. 1, an exposure unit 200 as an exposure unit is provided below the image forming units 1Y, 1C, 1M, and 1K. The exposure unit 200 emits writing light Lb by driving a semiconductor laser (light sources 2200a, 2200b, 2200c, 2200d in FIGS. 4 and 5) provided inside the exposure unit 200 based on the image information. To do. The writing light Lb forms an electrostatic latent image on the photoconductive drums 101Y, 101C, 101M, and 101K. Here, the emission of the writing light Lb is not limited to the laser, but may be, for example, an LED (Light Emitting Diode).

  Next, the configuration of the image forming units 1Y, 1C, 1M, and 1K will be described with reference to FIG. In the following description, the image forming unit 1Y that forms a yellow toner image will be described as an example, but the other image forming units 1C, 1M, and 1K have the same configuration. About these, each member of the image forming unit 1Y in the following description is replaced with each member of the other image forming units 1C, 1M, and 1K (the end Y of the code is replaced with C, M, and K, respectively). Description and explanation are omitted.

  As shown in FIG. 2, in the image forming unit 1Y, a charging unit (charging unit) 301Y, a developing unit (developing unit) 102Y, and a photosensitive member cleaning unit 308Y are provided around the photosensitive drum 101Y. Further, a primary transfer unit 106Y is provided at a position facing the photosensitive drum 101Y with the intermediate transfer belt 105 interposed therebetween.

  The charging unit 301Y is of a contact charging type employing a charging roller, and uniformly charges the surface of the photosensitive drum 101Y by applying a voltage in contact with the photosensitive drum 101Y. As the charging unit 301Y, a non-contact charging type using a non-contact scorotron charger or the like can be used.

  The developing unit 102Y has a function of developing the image by attaching a developer to the electrostatic latent image formed by the exposure unit 200. As shown in FIG. 2, the agitating unit provided in the developing case 302Y. Mainly composed of a portion 303Y and a developing portion 304Y. The developing unit 102Y uses a two-component developer (hereinafter simply referred to as “developer”) made of a magnetic carrier and a non-magnetic toner supplied from the toner bottle 104Y shown in FIG. The developer is not limited to a two-component developer, and a one-component developer can also be used. The developer is supplied from the toner bottle 104Y to the agitation unit 303Y, conveyed while being agitated by the agitation unit 303Y, and supplied onto the developing sleeve 305Y as a developer carrier. The stirring unit 303Y is provided with two parallel screws 306Y, and a partition plate 311Y is provided between the two screws 306Y and partitioned from each other. The partition plate 311Y is provided so that the inside of the stirring unit 303Y is partitioned at the center and communicated at both ends of the screw 306Y.

  Further, a TC sensor 312Y for detecting the toner density of the developer in the developing unit 102Y is attached to the developing case 302Y. In the developer used in this embodiment, since the carrier is a magnetic material and the toner is a non-magnetic material, the TC sensor 312Y adopts a magnetic permeability method. Therefore, the toner concentration in the developing unit 102Y appears in the magnetic permeability of the developer, that is, the magnetic resistance of the developer per unit volume.

  On the other hand, the developing unit 304Y is provided with a developing sleeve 305Y that faces the photosensitive drum 101Y through the opening of the developing case 302Y. A magnet (not shown) is fixedly arranged in the developing sleeve 305Y. A doctor blade 307Y is provided so that the tip approaches the developing sleeve 305Y. In the developing unit 304Y, among the developer attached to the developing sleeve 305Y, nonmagnetic toner is transferred to the photosensitive drum 101Y.

  In such a developing unit 102Y, the developer in the stirring unit 303Y is conveyed and circulated while being stirred by the two screws 306Y, and is supplied to the developing sleeve 305Y. The two-component developer supplied to the developing sleeve 305Y is pumped up and held by a magnet in the developing sleeve 305Y. The developer pumped up by the developing sleeve 305Y is conveyed along with the rotation of the developing sleeve 305Y, and is regulated to an appropriate amount by the doctor blade 307Y. The regulated developer is returned to the stirring unit 303Y. Thus, the developer conveyed to the area facing the photosensitive drum 101Y (hereinafter referred to as “development area”) is brought into a spiked state by the magnet in the developing sleeve 305Y, and a magnetic brush is applied to the surface of the developing sleeve 305Y. Form. In the developing region, a developing electric field is formed by moving the toner in the developer to the electrostatic latent image portion on the photosensitive drum 101Y by the developing bias applied to the developing sleeve 305Y.

  As a result, the toner in the developer is transferred to the electrostatic latent image portion on the photosensitive drum 101Y, and the electrostatic latent image on the photosensitive drum 101Y is visualized to form a toner image. The developer that has passed through the developing region is transported to a portion where the magnetic force of the magnet is weak, thereby leaving the developing sleeve 305Y and returning to the stirring unit 303Y. When the toner density in the stirring unit 303Y becomes light by repeating such an operation, the TC sensor 312Y detects this, and based on the detection result, the toner is replenished from the toner bottle 104Y to the stirring unit 303Y.

  The primary transfer unit 106Y has a function of transferring the toner image formed on the photosensitive drum 101Y to the intermediate transfer belt 105. In this embodiment, a primary transfer roller is employed as the primary transfer unit 106Y, and is installed so as to be pressed against the photosensitive drum 101Y with the intermediate transfer belt 105 interposed therebetween. Of course, the primary transfer unit 106Y is not limited to a roller shape, and may be a conductive brush shape, a non-contact corona charger, or the like.

  The photoreceptor cleaning unit 308Y is arranged so that the tip is pressed against the photoreceptor drum 101Y. A cleaning blade 309Y made of, for example, polyurethane rubber is provided on the tip side. Further, in order to improve the cleaning performance, a conductive fur brush 310Y that is in contact with the photosensitive drum 101Y is used in combination. A bias is applied to the fur brush 310Y from a metal electric field roller (not shown), and a tip of a scraper (not shown) is pressed against the electric field roller. The toner removed from the photosensitive drum 101Y by the cleaning blade 309Y and the fur brush 310Y is accommodated in the photosensitive member cleaning unit 308Y and recovered by a waste toner recovery unit (not shown).

  In the image forming unit 1Y of FIG. 2 configured as described above, first, the surface of the photosensitive drum 101Y is uniformly charged by the charging unit 301Y as the photosensitive drum 101Y rotates. Next, based on the image information from the print controller, the exposure unit 200 irradiates laser writing light Lb to form an electrostatic latent image on the photosensitive drum 101Y. Thereafter, the electrostatic latent image is visualized by the developing unit 102Y to form a toner image. This toner image is primarily transferred onto the intermediate transfer belt 105 by the primary transfer unit 106Y. The transfer residual toner remaining on the surface of the photosensitive drum 101Y after the primary transfer is removed by the photosensitive member cleaning unit 308Y and used for the next image formation.

  Next, the configuration of the exposure unit 200 provided below the paper surface of the image forming units 1Y, 1C, 1M, and 1K will be described with reference to FIGS. FIG. 3 is a plan view of the entire exposure unit 200. FIG. 4 is a view observed in the m1 direction shown in FIG. 3 and shows the installation state of members from the light source for yellow and cyan to the polygon mirror. FIG. 5 is a view observed from the m2 side shown in FIG. 3, and shows the installation state of members from the light source for magenta and black to the polygon mirror. FIG. 6 shows a side view of the exposure unit 200. For convenience of explanation, the exposure unit 200 shown in FIGS. 3 to 6 is displayed upside down and horizontally reversed from the exposure unit 200 shown in FIG.

  The exposure unit 200 used in this embodiment includes four light sources 2200a, 2200b, 2200c, 2200d made of semiconductor lasers, four coupling lenses 2201a, 2201b, 2201c, 2201d, four aperture plates 2202a, 2202b, 2202c, 2202d, Four cylindrical lenses 2204a, 2204b, 2204c, 2204d (see FIGS. 4 and 5 above), polygon mirror 2104 (see FIGS. 3 to 6), four fθ lenses 2105a, 2105b, 2105c, 2105d, and eight folding mirrors 2106a, 2106b, 2106c, 2106d, 2108a, 2108b, 2108c, 2108d, 4 toroidal lenses 2107a, 2107b, 2107c, 2107d, 4 light detection sensors 2205a, 205b, 2205c, 2205d, 4 one light detection mirror 2207a, 2207b, 2207c, 2207d (or, see FIG. 6), and, a like scan controller (not shown). These members are assembled at predetermined positions of the optical housing 2300 (see FIG. 6).

  3 to 6, for convenience, “direction corresponding to the main scanning direction” is abbreviated as “main scanning corresponding direction”, and “direction corresponding to the sub scanning direction” is referred to as “sub scanning corresponding direction”. It is briefly described. 3 and 4, for convenience, the direction along the optical axis of the coupling lens 2201a and the coupling lens 2201b is referred to as “w1 direction”, and the main scanning corresponding direction in the light source 2200a and light source 2200b is referred to as “m1 direction”. . Further, the direction along the optical axis of the coupling lens 2201c and the coupling lens 2201d is referred to as “w2 direction”, and the main scanning corresponding direction in the light source 2200c and the light source 2200d is referred to as “m2 direction”. Note that the sub-scanning corresponding direction in the light source 2200a and the light source 2200b and the sub-scanning corresponding direction in the light source 2200c and the light source 2200d are both the same direction as the Z-axis direction in the drawing.

  As shown in FIG. 3, the light source 2200b and the light source 2200c are arranged at positions separated from each other in the X-axis direction. The light source 2200a is disposed on the −Z side of the light source 2200b (below the light source 2200b in FIG. 4). The light source 2200d is disposed on the −Z side of the light source 2200c (below the light source 2200c in FIG. 5).

  As shown in FIG. 4, the coupling lens 2201a is disposed on the optical path of the light beam emitted from the light source 2200a, and makes the light beam a substantially parallel light beam. The coupling lens 2201b is disposed on the optical path of the light beam emitted from the light source 2200b, and makes the light beam a substantially parallel light beam. As shown in FIG. 5, the coupling lens 2201c is disposed on the optical path of the light beam emitted from the light source 2200c, and makes the light beam a substantially parallel light beam. The coupling lens 2201d is disposed on the optical path of the light beam emitted from the light source 2200d, and makes the light beam a substantially parallel light beam.

  As shown in FIG. 4, the aperture plate 2202a has an opening (not shown), and shapes the light beam that has passed through the coupling lens 2201a. The aperture plate 2202b has an aperture (not shown), and shapes the light beam that has passed through the coupling lens 2201b. As shown in FIG. 5, the aperture plate 2202c has an opening (not shown), and shapes the light beam that has passed through the coupling lens 2201c. The aperture plate 2202d has an aperture (not shown) and shapes the light beam that has passed through the coupling lens 2201d.

  As shown in FIG. 4, the cylindrical lens 2204 a forms an image of the light beam that has passed through the opening of the aperture plate 2202 a in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the Z-axis direction. The cylindrical lens 2204 b forms an image of the light beam that has passed through the opening of the aperture plate 2202 b in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the Z-axis direction. As shown in FIG. 5, the cylindrical lens 2204 c forms an image of the light beam that has passed through the opening of the aperture plate 2202 c in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the Z-axis direction. The cylindrical lens 2204d forms an image of the light beam that has passed through the opening of the aperture plate 2202d in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the Z-axis direction.

  As shown in FIG. 6, the polygon mirror 2104 has four-stage mirrors 2104ad and 2104bc having a two-stage structure, and each mirror serves as a deflection reflection surface. Then, as shown in FIGS. 4 and 5, in the first stage (the lower stage in FIG. 4, FIG. 5 and FIG. 6) of the four-sided mirror 2104ad, the light beam from the cylindrical lens 2204a and the light beam from the cylindrical lens 2204d. Each light beam is deflected. The quadrilateral mirror 2104bc of the second stage (the upper stage in FIG. 4, FIG. 5, and FIG. 6) is arranged so that the light beam from the cylindrical lens 2204b and the light beam from the cylindrical lens 2204c are respectively deflected. As shown in FIG. 6, the first-stage four-sided mirror 2104ad and the second-stage four-sided mirror 2104bc rotate with the axis I as the rotation axis and are shifted from each other by 45 °, and the writing scan is performed at the first stage. And the second stage are alternately performed.

  As shown in FIG. 6, the light beams from the cylindrical lens 2204a and the cylindrical lens 2204b are deflected in the direction of the fθ lenses 2105a and 2105b on the −X side of the polygon mirror 2104 (the left side in FIG. 6). Light beams from the cylindrical lens 2204c and the cylindrical lens 2204d are deflected toward the fθ lenses 2105c and 2105d on the + X side of the polygon mirror 2104 (to the right in FIG. 6).

  As shown in FIG. 6, each fθ lens 2105a, 2105b, 2105c, 2105d causes a light spot on the surface of the corresponding photosensitive drum 101Y, 101C, 101M, 101K as the polygon mirror 2104 rotates. It has a non-circular arc shape with power that moves at a constant speed in the main scanning direction. The fθ lens 2105a and the fθ lens 2105b are disposed on the −X side of the polygon mirror 2104, and the fθ lens 2105c and the fθ lens 2105d are disposed on the + X side of the polygon mirror 2104.

  The fθ lens 2105a and the fθ lens 2105b are stacked in the Z-axis direction, the fθ lens 2105a is opposed to the first-stage four-sided mirror 2104ad of the polygon mirror 2104, and the fθ lens 2105b is the second-stage four-sided mirror 2104bc. Opposite to. Further, the fθ lens 2105c and the fθ lens 2105d are stacked in the Z-axis direction, the fθ lens 2105c is opposed to the second-stage tetrahedral mirror 2104bc, and the fθ lens 2105d is opposed to the first-stage tetrahedral mirror 2104ad. Yes.

  Therefore, the light beam from the cylindrical lens 2204a deflected by the polygon mirror 2104 passes through the fθ lens 2105a, the folding mirror 2106a, the toroidal lens 2107a, and the folding mirror 2108a as a spot-like light drum 101K for black. And a light spot is formed on the surface of the photosensitive drum 101K. The light spot moves in the longitudinal direction of the photosensitive drum 101K as the polygon mirror 2104 rotates. That is, the photosensitive drum 101K is scanned. The moving direction (Y direction) of the light spot at this time is the “main scanning direction” on the photosensitive drum 101K, and the rotational direction (X direction) of the photosensitive drum 101K is “sub-scanning” on the photosensitive drum 101K. Direction.

  The light beam from the cylindrical lens 2204b deflected by the polygon mirror 2104 passes through the fθ lens 2105b, the folding mirror 2106b, the toroidal lens 2107b, and the folding mirror 2108b as spot-like light, and the photosensitive drum 101M for magenta. And a light spot is formed on the surface of the photosensitive drum 101M. The light spot moves in the longitudinal direction of the photosensitive drum 101M as the polygon mirror 2104 rotates. That is, the photosensitive drum 101M is scanned. The moving direction (Y direction) of the light spot at this time is the “main scanning direction” on the photosensitive drum 101M, and the rotational direction (X direction) of the photosensitive drum 101M is “sub-scanning” on the photosensitive drum 101M. Direction.

  In addition, the light beam from the cylindrical lens 2204c deflected by the polygon mirror 2104 passes through the fθ lens 2105c, the folding mirror 2106c, the toroidal lens 2107c, and the folding mirror 2108c as spot-like light, and the photosensitive drum 101C for cyan. And a light spot is formed on the surface of the photosensitive drum 101C. The light spot moves in the longitudinal direction of the photosensitive drum 101C as the polygon mirror 2104 rotates. That is, the photosensitive drum 101C is scanned. The moving direction (Y direction) of the light spot at this time is the “main scanning direction” on the photosensitive drum 101C, and the rotational direction (X direction) of the photosensitive drum 101C is “sub-scanning” on the photosensitive drum 101C. Direction.

  Further, the light beam from the cylindrical lens 2204d deflected by the polygon mirror 2104 passes through the fθ lens 2105d, the folding mirror 2106d, the toroidal lens 2107d, and the folding mirror 2108d as spot-like light, and the photosensitive drum 101Y for yellow. And a light spot is formed on the surface of the photosensitive drum 101Y. The light spot moves in the longitudinal direction of the photosensitive drum 101Y as the polygon mirror 2104 rotates. That is, the photosensitive drum 101Y is scanned. The moving direction (Y direction) of the light spot at this time is the “main scanning direction” on the photosensitive drum 101Y, and the rotational direction (X direction) of the photosensitive drum 101Y is “sub-scanning” on the photosensitive drum 101Y. Direction.

  By the way, the scanning area in the main scanning direction in which image information is written on each of the photosensitive drums 101K, 101M, 101C, and 101Y is called an “effective image area”. The folding mirrors 2106a to 2106d and 2108a to 2108d are arranged so that the optical path lengths from the polygon mirror 2104 to the photosensitive drums 101K, 101M, 101C, and 101Y coincide with each other. Further, the photosensitive drums 101K, 101M, 101C, and 101Y are arranged so that the incident positions and incident angles of the respective light beams are equal to each other.

  Further, the cylindrical lenses 2204a to 2204d (see FIGS. 3 to 5) and the toroidal lenses 2107a to 2107d (see FIG. 6) corresponding thereto correspond to the deflection points and the photosensitive drums 101K, 101M, 101C, and 101Y corresponding thereto. A surface tilt correction optical system having a conjugate relationship with the surface in the sub-scanning direction is configured.

  An optical system disposed on the optical path between the polygon mirror 2104 and each of the photosensitive drums 101K, 101M, 101C, and 101Y is also called a scanning optical system. In the present embodiment, the fθ lens 2105a, the toroidal lens 2107a, and the folding mirrors 2106a and 2108a constitute a K station optical scanning optical system (referred to as a scanning optical system for the black image forming unit 1K). The fθ lens 2105b, the toroidal lens 2107b, and the folding mirrors 2106b and 2108b constitute a scanning optical system for the M station (referred to as a scanning optical system for the magenta image forming unit 1M). The fθ lens 2105c, the toroidal lens 2107c, and the folding mirrors (2106c, 2108c) constitute a scanning optical system for the C station (referred to as a scanning optical system for the cyan image forming unit 1C). Further, the f-theta lens 2105d, the toroidal lens 2107d, and the folding mirrors 2106d and 2108d constitute the Y station scanning optical system (referred to as the yellow image forming unit 1Y scanning optical system).

  Of the light beam deflected by the polygon mirror 2104 and passed through the scanning optical system of the K station, a part of the light beam before starting writing enters the light detection sensor 2205a via the light detection mirror 2207a. The light detection sensor 2205b is deflected by the polygon mirror 2104, and a part of the light beam before the start of writing out of the light beam via the scanning optical system of the M station enters through the light detection mirror 2207b.

  The light detection sensor 2205c is deflected by the polygon mirror 2104, and a part of the light beam before the start of writing out of the light beam via the scanning optical system of the C station enters through the light detection mirror 2207c. A part of the light beam before the start of writing out of the light beam deflected by the polygon mirror 2104 and passed through the scanning optical system of the Y station enters the light detection sensor 2205d via the light detection mirror 2207d.

  Each of the light detection sensors 2205a to 2205d outputs a signal (photoelectric conversion signal) corresponding to the amount of received light. Control such as scanning of these light detection sensors 2205 a to 2205 d is performed by a scanning control device (not shown) under the control of the main body control unit 400. This scanning control device detects the scanning start timing of the corresponding photosensitive drums 101K, 101M, 101C, and 101Y based on the output signals of the respective light detection sensors 2205a to 2205d.

  Next, details of the intermediate transfer belt 105 will be described with reference to FIG. As shown in FIG. 7, a secondary transfer roller 108, which is a secondary transfer unit, is provided at a position facing the support roller 112 among the four support rollers 112, 113, 114, and 119. When the toner image on the intermediate transfer belt 105 is secondarily transferred onto the transfer paper 115, the secondary transfer roller 108 is pressed against the portion of the intermediate transfer belt 105 wound around the support roller 112. . A roller cleaning unit 116 that cleans toner adhering to the secondary transfer roller 108 is in contact with the secondary transfer roller 108 (see FIG. 1). The secondary transfer unit is not limited to the configuration using the secondary transfer roller 108, and may be configured using, for example, a transfer belt or a non-contact transfer charger.

  As shown in FIG. 7, a test pattern for checking image density and image position and a pattern for image formation are formed near the center of the intermediate transfer belt 105 in the main scanning direction (Y direction). Further, a photo sensor (not shown) for detecting the density and position of the test pattern may be provided at a position facing the support roller 112 among the support rollers of the intermediate transfer belt 105. A belt cleaning unit 110 is provided at a position facing the support roller 113 among the support rollers 112, 113, 114, and 119 of the intermediate transfer belt 105. The belt cleaning unit 110 is for removing residual toner remaining on the intermediate transfer belt 105 after the toner image on the intermediate transfer belt 105 is transferred to the transfer paper 115.

  The fixing unit 111 is a fixing unit for fixing the toner image transferred onto the transfer paper 115. As shown in FIG. 1, the fixing unit 111 is located downstream of the transfer paper 115 conveyed by the secondary transfer roller 108 in the conveyance direction. Is provided. As shown in FIG. 8, the fixing unit 111 includes a pressure roller 63 as a pressure body, a fixing belt 67 as a fixing body, a fixing roller 66 and a heating roller 64 around which the fixing belt 67 is wound, And a tension roller 65 that applies tension to the fixing belt 67. In addition, the fixing roller 66 and the pressure roller 63 form a nip portion 69 that sandwiches and conveys the transfer paper 115.

  The pressure roller 63 is formed by providing an elastic layer such as silicone rubber on the surface of a core metal such as aluminum or iron, and a release layer formed of PFA or PTFE is provided on the surface layer. The fixing belt 67 is configured by a base material such as nickel or polyimide having a release layer such as PFA or PTFE, or an intermediate layer provided with an elastic layer such as silicone rubber. The fixing belt 67 is wound around a fixing roller 66, a heating roller 64, and a tension roller 65, and is maintained at an appropriate tension by the tension roller 65. The fixing roller 66 is formed with silicone rubber on the surface of a metal core. The heating roller 64 is an aluminum or iron hollow roller and has a heat source such as a halogen heater (not shown) inside.

  When the transfer paper 115 enters the fixing unit 111 including such a member toward the nip portion 69 composed of the fixing roller 66 and the pressure roller 63, a predetermined pressure and heat are generated in the nip portion 69. To fix the image on the transfer paper 115.

  When the fixing unit 111 repeatedly fixes, for example, A4 size paper in the state of longitudinal paper, both ends of the A4 longitudinal paper on the surface of the fixing belt 67 in the paper width direction (hereinafter referred to as “edge portion”). In some cases, a vertical streak may occur at the position where the This occurs when the surface of the fixing belt 67 is roughened by paper dust adhering to the end face of the edge portion. At this time, when A4 landscape paper or A3 portrait paper is fixed after fixing A4 portrait paper, glossy streaks appear on the image surface corresponding to the vertical streak, and the image quality is reduced. It will cause deterioration.

  In order to prevent this deterioration in image quality, in the printer of the first embodiment according to the present application, as shown in FIG. 8, a reflective optical sensor 68 that irradiates a plurality of light spots is installed in the fixing unit 111. . The reflection type optical sensor 68 is configured to be movable in accordance with the passage position of the sheet end portion of the fixing belt 67, and the state of scratches (scratch density) at the sheet end portion position of the fixing belt 67. Can be accurately determined.

  Hereinafter, the configuration of the reflective optical sensor 68 used in the first embodiment will be described in detail with reference to FIG. The reflective optical sensor 68 used in the first embodiment has the same basic configuration as the reflective optical sensor 68c shown in FIG. 10, and includes five light emitting portions E1 to E5, five irradiation lenses LE1 to LE5, and 7 The light receiving units D0 to D6 and seven light receiving lenses LD0 to LD6 are provided. The reflective optical sensor 68 of this embodiment emits a plurality of lights toward the fixing belt 67, and irradiates N light spots SP (where N is an integer of 3 or more) in the main scanning direction. Irradiation is performed at a pitch P. In this embodiment, N = 5 light spots SP1 to SP5 can be irradiated. The reflection type optical sensor 68 is configured to be movable in the main scanning direction so that the passing position of the end of the paper is arranged within the irradiation area P (N−1) of the N light spots SP. Yes.

  The irradiation region P (N-1) is, for example, the range shown in FIG. 14B, which is a range narrower than the entire irradiation region R of the N light spots SP1 to SPN. Originally, if the passing position of the paper edge is within the entire irradiation region R, the scratched part 80 generated at the passing position can be detected by the reflective optical sensor 68. However, since the passing position of the sheet end portion is arranged within the irradiation area P (N−1) narrower than the entire irradiation area R, the installation error of the reflective optical sensor 68 and the meandering of the fixing belt 67 are detected. The surface state can be detected with higher accuracy without being affected by the above.

  FIG. 21 shows a moving means 70 for moving the reflective optical sensor 68 having such a configuration in the main scanning direction, a positioning means for positioning the paper end on the fixing belt 67, and a reflective optical sensor 68. An example with a fixing means is shown. FIG. 21A is a plan view observed from the z direction, and FIG. 21B is a cross-sectional view observed from the y direction.

  As shown in FIGS. 21A and 21B, the moving means 70 includes a long rail-shaped guide 71, a ball bearing 72, and a stage 73. The guide 71 is arranged long in the main scanning direction of the fixing belt 67. A stage 73 is connected to the guide 71 so as to be movable in the main scanning direction by a ball bearing 72. A reflective optical sensor 68 is fixed on the stage 73 by a fixing screw 74 as a fixing means. Then, by sliding the stage 73 with respect to the guide 71, the reflective optical sensor 68 moves in the main scanning direction (for example, see FIG. 28).

  In this way, by moving the reflective optical sensor 68 in the main scanning direction, the passing position of the end of the sheet, that is, the passing position, is within the irradiation area P (N−1) of the N light spots SP. It is possible to arrange a wound 80 that occurs at a position. For example, as shown in FIG. 22, belt scratches L <b> 1 to L <b> 1 generated at the passing position of one end (one side) of each of the scratches 80 generated on the fixing belt 67 by using a plurality of sizes of sheets. Let L5 be the belt scratches that occur at the passing position of the other end (the other side) L1 ′ to L5 ′. In this case, the irradiation range P (N-1) of the light spot SP is controlled so as to irradiate the belt scratches L1 to L5 and L1 ′ to L5 ′ at any passing position by the movement of the reflective optical sensor 68. Can do. Then, based on the output signal of the reflection type optical sensor 68, the main body control unit 400 as the surface state detecting means detects the surface state of the fixing belt, and thereby the end portions of the sheets of all sizes on the fixing belt 67. It is possible to measure the state of the scratch 80 generated at the passing position of the.

  Further, a positioning mark 75 is formed at one position of the stage 73 as positioning means. The guide 71 is provided with five positioning marks 76 (76a, 76b, 76c, 76d, 76e, 76a ′, 76b ′, 76c ′, 76d ′, 76e ′) on both sides in the main scanning direction. Yes. The positioning marks 75 and 76 may be formed by printing or the like on the surface of the stage 73 or the guide 71, or may be formed by providing concave grooves or protrusions. Further, the positioning mark 76 of the guide 71 is one side in the width direction of the guide 71 and is formed on the object in the longitudinal direction by five each, but the present application is not limited to this and is used. An appropriate number of positioning marks 76 can be formed at an appropriate position according to the number and direction of sheets. Further, the guide 71 may be formed on both sides in the width direction.

  Then, the positioning mark 75 on the stage 73 is aligned with any positioning mark 76 on the guide 71. Thus, for example, as shown in FIG. 22B, the designated sheet is within the range of P (N−1) of the irradiation areas of the five light spots SP1 to SP5 irradiated on the fixing belt 67. The reflection type optical sensor 68 can be moved so that the passage position at the end in the main scanning direction is arranged. Therefore, the reflective optical sensor 68 can be easily and accurately moved.

  As described above, by moving the reflection-type optical sensor 68, at least one of the flaws 80 (for example, the belt flaw L5 in FIG. 22) on the fixing belt 67 at the passing position of the sheet end of the designated size is provided. The light spot SP is irradiated. In the main body control unit 400, the detected value from the light spot SP irradiated to the belt scratch L5 at the passing position of the paper edge and the position deviated from the belt scratch L5 at the passing position of the paper edge (the scratch-free portion 81). ) And the detected value from the spot SP irradiated. By this comparison, the state of the belt scratch L5 generated at the passing position of the sheet end on the fixing belt 67 can be determined from the sensor output value (PD output value).

  In addition, it is desirable that the stage 73 moves on the guide 71 so that the position of the reflective optical sensor 68 in the main scanning direction does not change even if there is vibration of the image forming apparatus. Therefore, in this embodiment, the fixing screw 74 that fixes the reflective optical sensor 68 to the stage 73 is tightened, and the tip 74 a of the fixing screw 74 is abutted against the surface of the guide 71. By this abutment, the stage 73 is fixed to the guide 71 to prevent the reflection type optical sensor 68 from moving due to vibration or the like. In addition, when it is desired to move the reflective optical sensor 68 due to a change in paper or the like, the reflective optical sensor 68 can be moved to a target position by loosening the fixing screw 74.

  Further, in this embodiment, as shown in FIGS. 23 and 24, the reflective optical sensor 68 is slid in the main scanning direction, and the end portions of various sizes of paper on the fixing belt 67 in the main scanning direction are detected. It can be fixed at the passing position. 23 and 24, only the reflective optical sensor 68 is drawn on the fixing belt 67, and the display of the moving means 70 and the like is omitted. The same applies to the following embodiments. FIGS. 23A to 23E show a state in which the reflective optical sensor 68 is moved to the belt scratches L1 to L5 at the passing positions of one end of the paper, respectively. 24A to 24E show a state in which the reflective optical sensor 68 is moved to the belt scratches L1 'to L5' at the passing positions of the other end of the paper, respectively. The reason why each of the end portions is movable is that the scratches may occur to the same extent at the passing positions of the end portions on both sides of the paper, but one of the end portions is more In some cases, scratches are likely to occur. In such a case, by installing the reflection type optical sensor 68 at the passing position of the end where damage is likely to occur, it is possible to more quickly detect the damage that may affect the image quality. Then, by acquiring the detection value based on the output signal from the reflective optical sensor 68 at each fixed position, the state of the wound 80 occurring at each passing position can be accurately determined.

  The reflective optical sensor 68 may be formed to be movable over the entire length of the fixing belt 67. That is, the guide 71 is formed to have substantially the same length as the fixing belt 67 in the axial direction, and the reflective optical sensor 68 can be moved to any position of the belt scratches L1 to L5 and L1 ′ to L5 ′. Yes. Thereby, not only the position can be moved in accordance with the paper size, but also the reflection type optical sensor at the passing position of the end portion where the scratches easily occur among the belt scratches L1 to L5 and L1 ′ to L5 at the passing positions of both end portions. 68 can be installed to detect the surface condition. In addition, since the reflection type optical sensor 68 that is shorter than the fixing belt 67 is moved, it is necessary to provide a reflection type optical sensor having substantially the same length as the entire length of the fixing belt 67 and to provide a light source or the like over the entire length. And can be implemented at low cost.

  Further, as a modification, the reflective optical sensor 68 has only belt scratches L1 to L5 generated at one passing position shown in FIG. 23 or belt scratches L1 ′ to L5 generated at the other passing position shown in FIG. It may be configured to be movable only within the range of '. In this case, the moving range is halved compared to the moving means that can move the reflective optical sensor 68 to the belt scratches L1 to L5 and L1 ′ to L5 at the passing positions of both ends in the main scanning direction of all size sheets. It can be suppressed to a degree. Therefore, the moving means 70 can be made compact and the installation space for the moving means 70 and the reflective optical sensor 68 can be reduced. For example, in the example shown in FIGS. 23 and 24, the belt scratches L1 to L5 at the passing positions of one end in the main scanning direction of sheets of various sizes passing on the fixing belt 67 and the other side are used. This method is effective when the difference between the belt scratches L1 ′ to L5 ′ at the end passing position is small, that is, when the same level of scratching occurs at the passing positions at both ends, and only one of them needs to be detected. is there.

  Note that the reflective optical sensor 68 may be manually performed by the operator sliding the reflective optical sensor 68 together with the stage 73 on the guide 71 of the moving means 70. Further, the reflective optical sensor 68 may be automatically moved by adding a suitable drive mechanism such as an electric actuator to the moving means 70 and transmitting a signal from the main body control unit 400.

  In the case of manual movement, for example, when the user performs copying or the like with A4 longitudinal paper, the reflective optical sensor 68 is moved and arranged at the passing position of the end of the A4 longitudinal paper. Thereafter, by performing processing such as copying, it is possible to accurately detect the occurrence of scratches or the like on the fixing belt 67 due to A4 longitudinal paper. In the case of automatic movement, the image forming apparatus automatically detects the paper size used for image formation, and the main body control unit 400 transmits a signal corresponding to the detected paper size. Good. In response to this signal, the driving mechanism of the moving means 70 is actuated to move the reflective optical sensor 68 to the passing position of the end of the paper of that size. As a result, the operator can perform copying or the like without moving the reflective optical sensor 68.

  In any case, the fixing belt 67 is easily damaged by arranging the reflective optical sensor 68 at a position corresponding to the frequently used paper size such as A4 paper, B5 paper, etc. The surface condition of the location can be detected. After that, for example, even when a large size paper such as B4 or A3 is used, if the level of scratches does not affect the image quality by monitoring the surface condition, streaks, unevenness, etc. are transferred to the large size paper. Therefore, it is possible to maintain good image quality. Further, when the degree of scratches becomes large, for example, by transmitting the fact to the user through a buzzer or a message, the user can take measures such as replacement of the fixing belt 67 and maintenance. As a result, it is possible to satisfactorily prevent the influence on the image quality of a large size paper. Further, unnecessary replacement of the fixing belt 67 can be prevented, and the cost of consumables can be reduced.

  As described above, according to the reflective optical sensor 68 of the first embodiment, the stage 73 is slid along the guide 71, and the reflective optical sensor 68 is moved to the irradiation region P (N-1) of the N light spots. The passing position of the paper edge is arranged. Further, the reflection type optical sensor 68 can be arranged at the passing position of the paper edge of any size corresponding to the paper size. At this position, the surface state of the fixing belt 67 is detected by the reflective optical sensor 68, so that at least one of the N light spots can be generated at the end passing position, that is, the scratch 80. The state of the wound 80 can be detected by irradiating the position. Furthermore, it is possible to detect the surface state of the scratch-free portion 81 with any of the other light spots, and it is also possible to detect a change in the state of the scratch by comparing these. As described above, it is possible to measure the belt scratch L generated at the passing positions of the end portions of all size sheets on the fixing belt 67.

  In the first embodiment, the reflective optical sensor 68c shown in FIG. 10 or the like is used, but the present application is not limited to this. As long as it can irradiate a plurality of light spots, any other one may be used, or a reflective optical sensor 68d shown in FIG. 14 or the like may be used.

<Second embodiment>
The second embodiment will be described below. In the image forming apparatus of the second embodiment, the reflective optical sensor 68d of the second example shown in FIGS. 14 to 17 is used as the reflective optical sensor 68 connected to the moving means 70 shown in FIG. The unit 70 has the same basic configuration as that of the image forming apparatus of the first embodiment except that a fine adjustment unit is provided. Therefore, detailed description of the same configuration as in the first embodiment is omitted. The same applies to the following embodiments. In the second embodiment, the same reflective optical sensor 68c as in the first embodiment may be used.

  In the second embodiment, when the reflective optical sensor 68 is moved to the passing position of the end of the paper on the fixing belt 67 in the main scanning direction with an accuracy of ± P (N−1), the reflective optical sensor is further used. A fine adjustment mechanism (not shown) that can finely adjust the position of the sensor 68 in the main scanning direction within a range of ± P (N−1) / 2 or less is provided. By this fine adjustment mechanism, the main body control unit 400 finely adjusts the position of the reflective optical sensor 68 in the main scanning direction within the range of ± P (N−1) / 2 while acquiring the PD output value from the PD 212. To do. By the fine adjustment within the range of ± P (N−1) / 2, the light spot SP near the center of the N light spots SP1 to SPN formed on the fixing belt 67, the passing region L, that is, The belt wound can be irradiated.

  Such fine adjustment means is not particularly limited as long as it can move the reflective optical sensor 68 within a range of ± P (N−1) / 2 or less. For example, fine adjustment may be performed manually, or automatic adjustment may be performed under the control of the main body control unit 400 or the like. Further, as a member constituting the fine adjustment means, a known member capable of fine adjustment such as a fine adjustment screw (adjuster) can be used.

  Next, changes in the PD output depending on the presence or absence of the design position error of the reflective optical sensor 68 will be described with reference to FIGS. FIG. 18 is a schematic diagram showing the tilt direction of the lens element 220 of the reflective optical sensor 68. “Α” indicates a tilt error in the sub-scanning direction, and “β” indicates a tilt error in the main scanning direction. See also FIGS. 14 and 15 for the directions of α and β. FIG. 29A shows a graph of the PD output value when there is no error in the design position of the reflective optical sensor 68, and FIG. 29B shows the PD output when an error occurs in the design position. In FIG. 29, N = 18 light spots SP1 to SP18 are irradiated on the fixing belt 67, and detection values from the respective light spots SP1 to SP18 are shown.

  An example of detecting the surface state by comparing the scratched portion 80 on the fixing belt 67 with the scratchless portion 81 using the PD output value obtained by the light spots SP1 to SP18 using the reflective optical sensor 68. explain. In FIG. 29A, for example, among the PD output values (detected values) from the light spots SP1 to SP18, the minimum value is the PD output value from the scratched portion 80, and the maximum value is the PD output value from the scratchless portion 81. And Then, the state of scratches that occur at the passing position of the end of the sheet on the fixing belt 67 can be determined from the difference in PD output values between the scratched part 80 and the scratchless part 81. In FIG. 29A, the PD output value from the light spot SP1 is the PD output value from the scratch-free portion 81, and the PD output value from the light spot SP9 is the PD output value from the scratch portion 80. The greater the difference between the PD output value of the light spot SP1 and the PD output value of the light spot SP9, the more severe the scratched portion 80 is.

  However, an error may occur in the PD output value when there is an error in the design position accuracy of the reflective optical sensor 68. For example, when the reflective optical sensor 68 is installed in the β direction in FIG. 18 at an inclination from the design position, the PD from the end light spot SP (light spot SP1) as shown in FIG. 29B. The output value may decrease. Therefore, in the case as shown in FIG. 29 (b), if this is the case, the PD output value from the light spot SP1 whose output has decreased due to the installation error of the reflective optical sensor 68 is minimized, and the state of the belt scratch is correctly determined. You may not be able to. In order to eliminate this, for example, the PD output value from the SP6 to SP13 light spot, which is a spot near the center of the 18 spots, is used as the PD output value of the wound 80. If the minimum value of the PD output value from the light spot of SP6 to SP13 is the PD output value from the wound part 80, the PD output value from the wound part 80 is correctly selected as the PD output value from SP9. be able to.

  Thus, in order to avoid the influence of the installation error of the reflective optical sensor 68, it is necessary to locate the scratch 80 near the center of the N light spots SP. Therefore, in the second embodiment, a fine adjustment mechanism is provided that can finely adjust the position of the reflective optical sensor 68 in the main scanning direction within a range of ± P (N−1) / 2 or less. Thereby, the position of the scratch 80 can be moved to the vicinity of the center in the irradiation area of the N light spots SP, and the influence of the installation error of the reflective optical sensor 68 is reduced, and the scratch is accurately obtained. 80 states can be detected.

<Third embodiment>
The third embodiment will be described below with reference to FIG. The image forming apparatus of the third embodiment has the same basic configuration as that of the image forming apparatus of the first embodiment, except that two reflective optical sensors 68 are provided. In the third embodiment, FIGS. 25A to 25C show a state in which the reflection type optical sensors 68A and 68B are installed at the passing positions of the end portions of two sizes of paper.

  For example, when there are two sizes of paper that are frequently used, it is assumed that the belt scratches at the passing position of one end of these sheets in the main scanning direction are L5 and L3. In this case, as shown in FIG. 25B, one reflective optical sensor 68B is installed at each of the positions of the scratches L5 and L3, that is, at the position of the belt scratch L5, and the reflective optical sensor is positioned at the position of the belt scratch L3. A sensor 68A is installed. Then, the surface state of the fixing belt 67 is determined from the PD output values at the positions of the belt scratches L5 and L3. By detecting in this way, it is not necessary to move the reflective optical sensor 68 from the position of the belt scratch L5 to the position of the belt scratch L3 and acquire a PD output value, and a plurality of belt scratches can be collectively collected. It can be acquired and the usability can be improved.

  Further, a case will be described in which the size of the frequently used paper is changed and the belt scratch at the passing position of one end of the two sizes of paper in the main scanning direction is changed to the positions of L4 and L1. In this case, as shown in FIG. 25C, the reflection type optical sensors 68B and 68A may be moved to the respective positions of the belt scratches L4 and L1, and the same effect as described above can be obtained.

  Further, as shown in FIG. 25A, the belt scratch L1 at the passing position of one end in the main scanning direction of the paper passing over the fixing belt 67 and the belt scratch generated at the passing position of the other end. Reflective optical sensors 68A and 68B may be installed on both sides of L1 ′ to obtain PD output values. As a result, the surface states of the belt scratches L1 and L1 'on both sides can be determined, so that the influence of the belt scratches L1 and L1' on the image can be accurately determined. As described above, a method of detecting the surface state at a line-symmetrical position of the fixing belt 67 such as the belt scratches L1 and L1 ′ is, for example, in the main scanning direction of sheets of various sizes passing on the fixing belt 67. This method is effective when the difference between the belt scratches L1 to L5 at the passing position of one end and the belt scratches L1 ′ to L5 ′ generated at the passing position of the other end is large. In such a case, a method for efficiently detecting the state of a flaw will be described in a fourth embodiment below.

<Fourth embodiment>
In the fourth embodiment, as in the third embodiment, two reflective optical sensors 68A and 68B are installed at different positions of the fixing belt 67 in the main scanning direction. In the third embodiment, the two reflective optical sensors 68A and 68B are installed at arbitrary positions corresponding to the passing positions of one end portions of two frequently used sheets. On the other hand, in the fourth embodiment, the reflection type optical sensors 68A and 68B are installed at the passing positions of both ends of one sheet.

  In the fourth embodiment, one reflective optical sensor 68A is moved to the passing position (for example, the position of the belt scratch L5 in FIG. 26A) of one end of the paper on the fixing belt 67 in the main scanning direction. Let Then, the other reflection type optical sensor 68B includes a mechanism that simultaneously moves to the passing position of the other end (L5 ′ in the example of FIG. 26A), and constitutes the moving means 70. With the moving means 70 having such a mechanism, first, as shown in FIGS. 26A to 26E, at one end portion in the main scanning direction of sheets of various sizes passing on the fixing belt 67. One reflective optical sensor 68A is moved to the belt scratches L1 to L5 at the passing position. By only performing this operation, another reflective optical sensor 68B is automatically moved to the belt scratches L1 'to L5' at the passing position of the other end at the same time. Therefore, the PD output values at the passing positions of the paper edge portions on both sides can always be obtained, and the usability can be improved.

  In the third and fourth embodiments, two reflective optical sensors 68A and 68B are installed in the main scanning direction. However, the present application is not limited to this. In consideration of the degree of scratches, the number of frequently used sheets, the budget, the size of the apparatus, etc., three or more reflective optical sensors 68 may be installed. Further, for example, when an even number of reflective optical sensors 68 are installed, it is possible to detect the passing positions of the end portions on both sides of the paper by installing them on both sides in the main scanning direction. Also, in the case of an odd number, it may be installed on both sides in the same manner to detect the passing positions of both ends, or may be installed at one passing position of each end of each paper to be used. Alternatively, the paper may be installed only at the passing position of one end portion with respect to one of the sheets, and the paper that most needs to detect the scratch may be placed at the passing positions of both end portions. In these cases as well, detection accuracy and ease of use can be achieved by moving each reflective optical sensor 68 in the main scanning direction by the moving means 70 in response to the change of the sheet, the position of the flaw, the meandering of the fixing belt 67, and the like. Can be improved.

<Fifth embodiment>
Hereinafter, the fifth embodiment will be described with reference to FIGS. 27, 30, and 31. FIG. The image forming apparatus of the fifth embodiment has the same basic configuration as that of the image forming apparatus of the first embodiment except that a light shielding member 90 is provided on the movement path of the reflective optical sensor 68. In the fifth embodiment, the reflective optical sensor 68 having 28 PDs 212 and 28 LEDs 211 (that is, p = 7 sets) is used. 27A shows a state in which the PD output value at the belt scratch L5 is acquired by the reflective optical sensor 68, and FIG. 27B shows the PD output from the light shielding member 90 by the reflective optical sensor 68. FIG. Indicates that the value is being acquired.

  Before describing the fifth embodiment, first, the experimental results when the reflective optical sensor 68 shown in FIG. 14 is operated according to the flowchart shown in FIG. 19 to detect the surface state will be described. The experimental results at this time are shown in FIG.

  FIG. 30A shows each LED 211 -pq (q = 1 to 4) in a state where there is no fixing belt 67 (that is, a state where there is no object reflecting the light beam emitted from the reflective optical sensor 68). PD output value of PD212-n (n = 1 to 28) when) is turned on. In FIG. 30A, the LED code 211 and the PD code 212 are omitted, and “LED-pq” and “PDn” are used.

  If the fixing belt 67 is not present, the PD output value is ideally “zero”. However, it can be seen from the experimental results shown in FIG. 30A that mountain-shaped PD output values are obtained centering on PD 212-14 and PD 212-15. The inventor investigated the cause of the PD output value. As a result, when the LED 211-pq is turned on, as shown in FIG. 31, a part of the divergent light beam is reflected and scattered on the front surface of the opening member 230-p and the opening member 231 (surface facing the LED). As a result, it has been found that the light is received by a plurality of PDs 212-n.

  Therefore, in this embodiment, in order to create a state in which the fixing belt 67 is not present in the image forming apparatus, a light shielding member 90 is provided as shown in FIG. However, when the fixing belt 67 is present, the PD output value including the reflected light from the front surfaces of the opening members 230 and 231 in addition to the reflected light from the fixing belt 67 to be detected is detected. Become.

  Therefore, first, as shown in FIG. 27B, the PD output value is detected in a state where the reflective optical sensor 68 is moved onto the light shielding member 90. Subsequently, as shown in FIG. 27A, the reflection type optical sensor 68 is moved to the passing position (for example, L5) of the end of the sheet on the fixing belt 67 to detect the PD output value. Then, the surface state of the fixing belt 67 is determined based on the PD output value from the light shielding member 90 and the PD output value from the fixing belt 67. As a result, the surface state of the fixing belt 67 can be accurately determined without being affected by noise of reflected light inside the reflective optical sensor 68 such as reflected light from the opening members 230 and 231.

  In this embodiment, more specifically, the difference between the PD output value at the light shielding member 90 and the PD output value at the fixing belt 67 is taken. By subtracting the PD output value from the light shielding member 90, it is possible to acquire the PD output value of only the reflected light from the fixing belt 67, and the detection accuracy by the reflective optical sensor 68 can be improved.

  In FIG. 30B, the PD output value obtained in the absence of the fixing belt 67 in FIG. 30A (that is, on the light shielding member 90) is subtracted from the PD output value obtained in the presence of the fixing belt 67. PD output value at the time. That is, the PD output value in FIG. 30B is a signal of only the reflected light from the fixing belt 67. With regard to this result, attention was paid to the peak of the PD output value. Then, when the LED 211-p-4, LED 211-p-3, LED 211-p-2, and LED 211-p-1 are sequentially turned on, the PD number at which the PD output value peaks is from the smallest to the largest. It turns out that it shifts toward. When the LED 211-p-4, the LED 211-p-3, the LED 211-p-2, and the LED 211-p-1 are sequentially turned on, the light spot on the fixing belt surface 67S is changed as shown in FIG. It is also clear from the fact that the paper is scanned from the left to the right of FIG.

<Sixth embodiment>
Hereinafter, the sixth embodiment will be described with reference to FIGS. 30, 32, and 33. FIG. In the sixth embodiment, the light amount of the LED 211 is adjusted using the PD output value of FIG. 30A acquired in the fifth embodiment.

  Hereinafter, a light amount adjustment method using the PD output value shown in FIG. 30A in the sixth embodiment will be described. In FIG. 30A, light emitted from the LED 211 is directly reflected by the opening members 230 and 231 and received by the PD 212. Therefore, if the shape of the front surface of the opening members 230 and 231 when viewed from each LED 211 is the same, the amount of light received by the PD 212 proportional to the amount of light emitted from the LED can be detected.

  In this regard, the pitch of the opening members 230-p is sufficiently larger than the interval between the LEDs 211-p-1 to 211-p-4, and therefore can be regarded as having substantially the same shape when viewed from any of the LEDs 211. For this reason, the distribution of FIG. 30A is also similar for each LED 211, and is considered to represent the variation in the amount of emitted LED light at the time of detection.

  In the sixth example, PD output values were obtained when 20 of the 28 LEDs 211 from the LED 211-2-4 to the LED 211-6-1 on the light shielding member 90 were sequentially lit. FIG. 32A shows the result of obtaining the sum of PD output values from PD 212-1 to PD 212-28 when each LED 211 is lit. Further, FIG. 32B shows a result when the light amount of the light spot SP irradiating the fixing belt 67 from the reflective optical sensor 68 is measured with an optical power meter.

  The trends in the two graphs of FIGS. 32 (a) and (b) are very similar. That is, even if the LED light emission amount (the light amount of the light spot SP) is not used, the PD output value acquired on the light shielding member 90 can be substituted. Even if the amount of light emitted from the LED, which is affected by time and environment (especially temperature), is not known, if the PD output value in a state where the reflective optical sensor 68 is moved on the light shielding member 90 is detected, it is sometimes. The value according to the LED light emission amount can be known. Therefore, each time the surface state is detected by the reflective optical sensor 68, this means that the light amount can be corrected using the detected value.

  In FIG. 32A, the sum of the PD output values is used, but the number of PDs 212 that take the sum can be reduced within a range in which practical light quantity correction is possible. However, it is preferable to use as many PD output values as possible in order to equalize the light amount of the light spot SP. Therefore, the PD output value of only the reflected light from the fixing belt 67 obtained in FIG. 30B is divided by the PD output value shown in FIG. As a result, as shown in FIG. 33, it is possible to obtain a PD output value of only the reflected light from the fixing belt 67 that has been corrected for the amount of light and in which each LED light emission amount is equal. As described above, by performing the light amount correction, the surface state of the fixing belt 67 can be accurately determined without being affected by the variation in the light emission amount of the plurality of light spots SP.

  As shown in FIG. 32A, the LED 211-4-2 has a smaller PD output value than the LEDs 211-4-1 and LED 211-4-3. That is, the light emission amount of the LED 211-4-2 is small. FIG. 30B is a PD output value acquired in a state where the light emission amount of the LED 211-4-2 is small. Therefore, by dividing this PD output value by the relative output of FIG. 32A, the LED 211-4- The PD output value corresponding to 2 increases. FIG. 33 is a graph showing the results. Compared with the graph of FIG. 30B, it can be seen that the PD output value for the LED 211-4-2 has increased. This is a PD output value whose light amount has been corrected, which eliminates the influence of time and environment (particularly temperature), and can improve the detection accuracy of the reflective optical sensor 68 without being affected by these effects. it can.

<Seventh embodiment>
The seventh embodiment will be described below. In the seventh embodiment, as in the fifth embodiment, an image forming apparatus including a light shielding member 90 is used. Further, as in the fifth embodiment, the difference between the PD output value from the fixing belt 67 and the PD output value from the light shielding member 90 is taken. In the seventh embodiment, the difference is the same as in the sixth embodiment. In addition, the amount of light is adjusted.

  Hereinafter, the procedure for detecting the surface state of the fixing belt 67 when the light shielding member 90 of the seventh embodiment is used will be described with reference to the flowchart of FIG. First, in step S <b> 30, the reflective optical sensor 68 is moved onto the light shielding member 90. In this state, in step S31, the LEDs 211-pq are sequentially turned on, and in step S32, the PD output value is acquired by the PD 212-n (PD output value 1). The detailed operation of the LED lighting and PD output value acquisition is the same as the flowchart shown in FIG. Note that the PD output value 1 obtained here is used in the light amount correction in the subsequent step S37.

  Next, in step S <b> 33, the reflection type optical sensor 68 is moved to the passing position of the sheet end on the fixing belt 67. In this state, in step S34, the LEDs 211-pq are similarly turned on sequentially, and in step S35, the PD output value is acquired by the PD 212-n (PD output value 2). Similarly to the above, the detailed operation of this LED lighting and PD output value acquisition is the same as the flowchart shown in FIG.

  Next, in step S36, the difference between the PD output value 1 and the PD output value 2 acquired above is obtained. Specifically, it is calculated by the following expression “PD output value 2−PD output value 1”. In addition, the value as obtained in step S32 is a result including variations in the amount of emitted LED light at the time of operation of the reflective optical sensor 68. Therefore, in step S37, the light amount correction is performed using the PD output value 1 acquired in step S32. As a specific example, after summing up and standardizing the PD output value for each LED 211p-q as in the sixth embodiment, the difference processing result is removed as in the sixth embodiment. To do. As described above, the PD output value of only the reflected light from the fixing belt 67 whose light amount has been corrected can be obtained, and the detection accuracy by the reflective optical sensor 68 can be improved.

<Eighth embodiment>
The eighth embodiment will be described below. In the eighth embodiment, as in the sixth embodiment, the PD output value 1 of the reflective optical sensor 68 on the light shielding member 90 and the PD output value 2 of the reflective optical sensor 68 on the fixing belt 67 are obtained. Have acquired.

  In the eighth embodiment, when the PD output value 1 and the PD output value 2 are acquired, the LEDs 211 are sequentially turned on a plurality of times sequentially as described in the flowchart of FIG. The plurality of PD output values 1 and 2 thus obtained may be averaged by the number of periods, or a median value may be used to remove abnormal values. The detection accuracy by the reflective optical sensor 68 can be improved by taking the difference between the PD output value 1 and the PD output value 2 and performing light amount correction based on such an average value or median value.

  Then, it is preferable to sequentially turn on the LEDs 211 over a plurality of periods over one rotation of the fixing belt 67. In this case, errors due to fluctuations during rotation of the fixing belt 67 such as meandering can be reduced. In particular, it is more preferable to light up sequentially for 5 cycles or more, and it is also possible to remove abnormal values by using data for 3 cycles or more excluding the maximum value and the minimum value of the PD output value. . As a result, the detection accuracy by the reflective optical sensor 68 can be further improved.

  The image forming apparatus of each embodiment of the present application has been described above. However, the image forming apparatus used in these embodiments is an example, and the present application is not limited to this image forming apparatus. Regardless of the size of the paper used, the reflective optical sensor is moved so that the P (N-1) region of the light spot irradiation region is irradiated to the passing position of the end portion of the fixing member. As long as the surface state can be determined, an image forming apparatus having another configuration may be used. In addition, any size paper on the fixing member can be used as long as it can reliably detect a scratched part at the end passage position and accurately determine the surface state. It is possible to solve this problem.

  In each embodiment, detection of the surface state of the fixing belt (fixing member) is described. In particular, since the fixing belt uses a material having a high surface hardness such as PFA for the surface layer, the fixing belt is easily damaged. Therefore, by applying the present application and detecting the surface state using the reflective optical sensor, it is possible to prevent the influence on the image quality and to efficiently use the fixing belt. However, the present application is not limited to detection of the surface state of the fixing member. The present invention can be applied to the detection of the surface state other than the fixing member as long as it is a conveyance body that closely contacts and conveys a recording medium such as paper. The transport body may be, for example, a photosensitive drum, an intermediate transfer body, etc., and by applying the present application, by detecting these surface states, it is possible to quickly cope with the occurrence of scratches and to improve image quality. Can be maintained in high quality.

67 Fixing belt (fixing member, carrier)
68 Reflective optical sensor (reflective optical detection means)
80 Scratched part 81 Scratchless part 101Y, 101C, 101M, 101K Photosensitive drum (image carrier, conveying body)
102Y, 102C, 102M, 102K Development unit (developing means)
105 Intermediate transfer belt (transfer means, image carrier, carrier)
106Y, 106C, 106M, 106K Primary transfer unit (transfer means)
108 Secondary transfer roller (transfer means)
111 Fixing unit (fixing means)
115 Transfer paper (recording medium)
200 Exposure units 301Y, 301C, 301M, 301K Charging units (charging means)
400 Main body control unit (surface condition judging means)
70 moving means 71 guide 72 ball bearing 73 stage 74 fixing screw 74a tip 90 light blocking member SP, SP1 to SPn light spot P irradiation pitch

JP 2010-262203 A Japanese Patent No. 4632820 JP 2007-34068 A

Claims (11)

An image carrier;
Charging means for charging the surface of the image carrier;
Exposure means for forming an electrostatic latent image on the surface of the charged image carrier;
Developing means for visualizing the image by attaching a developer to the electrostatic latent image on the surface of the image carrier;
Transfer means for transferring the image visualized on the surface of the image carrier to a recording medium;
Fixing means having a fixing member for fixing the image transferred to the recording medium;
When the moving direction of the fixing member is the first axial direction and the direction orthogonal to the moving direction is the second axial direction, a plurality of lights are irradiated toward the surface of the fixing member, and the surface of the fixing member A reflection type optical detection means for forming a plurality of light spots in the second axis direction and receiving the reflected light and detecting it as a detection value;
Moving means for moving the reflective optical detection means in the second axis direction;
Surface state determination means for determining the surface state of the fixing member based on the detection value from the reflection type optical detection means,
When the number of light spots formed in the second axis direction on the surface of the fixing member is N (N is an integer of 3 or more), and the irradiation pitch between the light spots is P,
The moving means has a second axial direction of the recording medium in the fixing member within a range of P (N−1) of the irradiation areas of the N light spots formed on the surface of the fixing member. An image forming apparatus, wherein the reflection type optical detection means is configured to move in the second axial direction so that a passing position of the end of the second optical axis is arranged.   The moving means is the reflection-type optical detection means so that a passing position of the end of the recording medium is disposed within a range of P (N−1) in the irradiation area of the N light spots. 2. The apparatus according to claim 1, wherein the reflection type optical detection means is further moved in the second axis direction within a range of ± P (N-1) / 2 or less after the movement of the first and second movements. The image forming apparatus described in 1.   The moving means moves the reflection-type optical detection means within one end of the recording medium in the second axis direction within a range of P (N−1) in the irradiation region of the N light spots. 3. The image forming apparatus according to claim 1, wherein the reflection type optical detection means is moved so that only a passing position is arranged.   The image forming apparatus according to claim 1, wherein a plurality of the reflective optical detection units are installed in the second axis direction. A first reflective optical detection means and a second reflective optical detection means are installed at different positions in the second axial direction,
The moving means has the P on the fixing member within a range of P (N−1) in the irradiation area of the N light spots formed on the fixing member by the first reflective optical detection means. The second reflective optical detection means is moved to the second reflective optical detection means by moving the first reflective optical detection means so that the passing position of one end of the recording medium in the second axial direction is arranged. The passing position of the other end of the recording medium in the second axis direction on the fixing member is within a range of P (N−1) in the irradiation region of the N light spots of the reflective optical detection means. The image forming apparatus according to claim 4, wherein the image forming apparatus is configured to move in the second axial direction so as to be disposed. A light-shielding member that is disposed on a movement path of the reflection-type optical detection unit in the second axis direction and that blocks light irradiation from the reflection-type optical detection unit to the fixing member;
The moving means is configured to move the reflective optical detection means so that N light spots are formed on the light shielding member by irradiation of light from the reflective optical detection means,
The surface state determination means includes the detection value acquired when the reflective optical detection means is moved onto the light shielding member;
Passing position of the reflection type optical detection means within the range of P (N-1) in the irradiation area of the N light spots and passing the end portion of the recording medium on the fixing member in the second axis direction 6. The image forming apparatus according to claim 1, wherein a surface state of the fixing member is determined based on a detection value acquired when moving so as to be disposed.   The surface state determination unit is based on a value obtained by subtracting the detection value acquired when the reflection type optical detection unit is moved onto the light shielding member from the detection value acquired when the reflection type optical detection unit is moved onto the fixing member. The image forming apparatus according to claim 6, wherein the surface state of the fixing member is determined.   Based on the detection value acquired when the reflective optical detection means is moved onto the light shielding member, the surface state determination is configured to correct the amount of light emitted from the reflective optical detection means. The image forming apparatus according to claim 6, wherein the unit determines a surface state of the fixing member based on the detection value after the light amount correction.   The reflection-type optical detection means is placed on the fixing member within a range of P (N−1) in an irradiation area of the N light spots irradiated on the fixing member from the reflection-type optical detection means. Acquisition of a detection value when the recording medium is moved so that the passing position of the end portion in the second axis direction is arranged, and detection value when the reflective optical detection means is moved onto the light shielding member The surface state determination means determines the surface state of the fixing member based on a plurality of detection values acquired from the detection results of the plurality of times. The image forming apparatus according to 6 to 8.   The image forming apparatus according to claim 1, wherein the fixing member is an endless belt-shaped fixing belt. An image forming apparatus including a transport body that transports a recording medium in close contact, and forms an image on a previous recording medium,
When the moving direction of the transport body is the first axial direction and the direction orthogonal to the moving direction is the second axial direction, a plurality of lights are irradiated toward the surface of the transport body, and the surface of the transport body A reflection type optical detection means for forming a plurality of light spots in the second axis direction and receiving the reflected light and detecting it as a detection value;
Moving means for moving the reflective optical detection means in the second axis direction;
Surface state determination means for determining the surface state of the carrier based on the detection value from the reflective optical detection means,
When the number of light spots formed in the second axis direction on the surface of the carrier is N (N is an integer of 3 or more), and the irradiation pitch between the light spots is P,
The moving means has a second axial direction of the recording medium in the carrier within a range of P (N−1) of the irradiation areas of the N light spots formed on the surface of the carrier. An image forming apparatus, wherein the reflection type optical detection means is configured to move in the second axial direction so that a passing position of the end of the second optical axis is arranged.