JP7010133B2 - Image forming device and sensor unit - Google Patents

Description

The present invention relates to an image forming apparatus and a sensor unit.

In an image forming apparatus using an electrophotographic method, sensors for detecting the density of a pattern or the like are arranged facing each other under a belt member such as an intermediate transfer belt. A shutter is provided between the sensor and the belt member so that foreign matter (dust, toner, etc.) does not adhere to the light receiving surface of the sensor. Further, a film-shaped cleaning member for removing foreign matter adhering to the light receiving surface of the sensor is attached to the shutter (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2006-208645 (see FIG. 4)

However, when opening and closing the shutter, the contact load between the cleaning member and the edge of the sensor may hinder the operation of the shutter.

The present invention has been made to solve the above problems, and an object of the present invention is to suppress malfunction of the shutter due to a contact load between the cleaning member and the sensor.

The image forming apparatus of the present invention includes an image forming portion that forms a developer image, a belt member on which the developer image formed by the image forming portion is transferred, a sensor having a light receiving surface facing the belt member, and a sensor. A shutter arranged between the sensor and the belt member and having an engaging portion, an open position where the shutter allows light from the belt member to enter the light receiving surface of the sensor, and a closed position which covers the light receiving surface of the sensor. It has a guide portion having a guide groove that guides between them and engages with the engaging portion, and a cleaning member that is attached to the shutter and cleans the light receiving surface of the sensor. The guide portion guides the shutter in a predetermined region between the open position and the closed position so as to be displaceable in a direction away from the light receiving surface of the sensor. The guide grooves are the first groove portion that engages with the engaging portion when the shutter is in the open position, the second groove portion that engages with the engaging portion when the shutter is in the closed position, the first groove portion, and the second groove portion. It has a third groove portion provided between the groove portion and the groove portion. The groove width of the third groove portion is wider than the groove width of the first groove portion and the groove width of the second groove portion.

In the present invention, when the cleaning member comes into contact with the sensor, the shutter can be displaced in a direction away from the light receiving surface, so that the contact load between the cleaning member and the sensor can be reduced, which causes the shutter to malfunction. It can be suppressed.

It is a figure which shows the whole structure of the image forming apparatus of 1st Embodiment. It is a schematic diagram which shows the structural example of the process unit of 1st Embodiment. It is a figure which shows the sensor of 1st Embodiment. It is a schematic diagram for demonstrating the role of the light emitting element and the light receiving element of the sensor of 1st Embodiment. It is a schematic diagram which shows the relationship between the optical input to a sensor, and a sensor output. It is a figure which shows the sensor and the cleaning member of 1st Embodiment. It is a schematic diagram which shows the sensor unit of 1st Embodiment. It is a perspective view which shows the sensor unit of 1st Embodiment. It is a perspective view which shows the shutter of 1st Embodiment. It is a perspective view which shows the state which the shutter was removed from the sensor unit of 1st Embodiment. It is a perspective view which shows the base of the sensor unit of 1st Embodiment. It is a perspective view which shows the guide part of 1st Embodiment. It is a schematic diagram (A)-(C) which shows the change of the engagement state between a guide groove and a guide protrusion with the movement of a shutter of 1st Embodiment. It is a block diagram which shows the control system of the image forming apparatus of 1st Embodiment. It is a schematic diagram (A)-(C) which shows the opening operation of the sensor unit of 1st Embodiment. It is a schematic diagram (A)-(C) which shows the closing operation of the sensor unit of 1st Embodiment. It is a schematic diagram (A) to (D) which shows the opening and closing operation of the sensor unit of the comparative example. It is a schematic diagram for demonstrating the overlap amount of the sensor of 1st Embodiment and a cleaning member.

The first embodiment.
<Structure of image forming apparatus>
FIG. 1 is a diagram showing an overall configuration of an image forming apparatus 1 according to the first embodiment of the present invention. The image forming apparatus 1 transfers the toner image formed by the image forming unit 100 forming the toner image as the developer image, the medium supply unit 101 for supplying the medium P, and the image forming unit 100 to the medium P. It has a belt unit 20, a fixing device 105 for fixing a toner image on the medium P, and discharge rollers 106, 107, 108 for discharging the medium P on which the toner image is fixed.

The medium supply unit 101 includes a medium cassette 102 as a medium accommodating unit accommodating the medium P, a feed roller 103 as a paper feed mechanism for feeding the media P in the medium cassette 102 one by one, and a fed medium. It has a transport roller 104 as a transport mechanism for transporting P.

The medium cassette 102 accommodates a plurality of media P such as printing paper in a laminated state, and is detachably attached to the main body of the image forming apparatus 1. The feed roller 103 is arranged so as to come into contact with the medium P in the medium cassette 102, and is rotated by the medium transfer motor 131 (FIG. 14) to feed the media P one by one.

The transfer roller 104 is rotated by the medium transfer motor 131 (FIG. 14) to transfer the medium P toward the secondary transfer unit 25 (described later) of the transfer belt unit 20. The transfer roller 104 is configured here by three pairs of rollers arranged along the transfer path of the medium P, but is not limited to such a configuration.

The image forming unit 100 includes a process unit 10Y, 10M, 10C, 10K, 10W for forming a toner image of yellow, magenta, cyan, black, and white, and an LED head 11Y, 11M, 11C, 11K, 11W as an exposure apparatus. Has. The process units 10Y, 10M, 10C, 10K, and 10W are arranged in a row from left to right in the figure along the traveling direction of the intermediate transfer belt 21 (described later) of the transfer belt unit 20.

Since the process units 10Y, 10M, 10C, 10K, and 10W have a common configuration except for the toner, they will be described as "process unit 10" when it is not necessary to distinguish them. Similarly, the LED heads 11Y, 11M, 11C, 11K, and 11W will be described as "LED head 11" when it is not necessary to distinguish them.

FIG. 2 is a schematic diagram showing a configuration example of the process unit 10. The process unit 10 includes a photoconductor drum 12 as an image carrier, a charging roller 13 as a charging member, a developing roller 14 as a developing agent carrier, a supply roller 15 as a supply member, and a layer regulating member. A layer regulation blade 16 and a toner cartridge 17 as a developer accommodating body are provided.

The photoconductor drum 12 has a photosensitive layer (charge generation layer and charge transport layer) formed on the surface of a cylindrical conductive support. The photoconductor drum 12 is rotated counterclockwise as shown by an arrow in FIG. 2 by a drive motor 134 (FIG. 14).

The charging roller 13 is arranged so as to be in contact with the surface of the photoconductor drum 12, and rotates following the rotation of the photoconductor drum 12. A charging voltage is applied to the charging roller 13 by the charging voltage power supply 123 (FIG. 14) to uniformly charge the surface of the photoconductor drum 12.

The LED head 11 includes an LED array in which a plurality of LED elements (light emitting elements) are arranged, and a lens array in which a plurality of lenses are arranged. The LED head 11 irradiates the surface of the photoconductor drum 12 with light under the control of the head control unit 119 (FIG. 14), and exposes the photosensitive layer of the photoconductor drum 12 to form an electrostatic latent image.

The developing roller 14 is arranged so as to be in contact with the surface of the photoconductor drum 12, and the rotation is transmitted from the photoconductor drum 12 via a gear in a direction opposite to the rotation direction of the photoconductor drum 12 (clockwise in the figure). Rotate to. A developing voltage is applied to the developing roller 14 by a developing voltage power supply 124 (FIG. 14), and an electrostatic latent image on the surface of the photoconductor drum 12 is developed with toner.

The supply roller 15 is arranged so as to abut on the surface of the developing roller 14 and rotates in the same direction as the rotation direction of the developing roller 14 (clockwise in the figure). A supply voltage is applied to the supply roller 15 by the supply voltage power supply 125 (FIG. 14) to supply toner to the developing roller 14.

The layer regulation blade 16 is a blade made of metal (for example, stainless steel) arranged so as to abut on the surface of the developing roller 14. The layer regulation blade 16 is applied with a layer regulation voltage by the layer regulation voltage power supply 126 (FIG. 14), and regulates the thickness of the toner layer formed on the surface of the developing roller 14 to a constant thickness.

The toner cartridge 17 is detachably attached to the upper part of the main body of the process unit 10 to supply toner to the developing roller 14 and the supply roller 15. The portion of the process unit 10 that contributes to the development of the electrostatic latent image (that is, the portion including the developing roller 14, the supply roller 15, and the layer limiting blade 16) is referred to as a developing unit.

Returning to FIG. 1, the transfer belt unit 20 contains the intermediate transfer belt 21 as a belt member (or intermediate transfer body) and the photoconductor drums of the process units 10Y, 10M, 10C, 10K, and 10W sandwiching the intermediate transfer belt 21. It has four primary transfer rollers 22 arranged so as to be in contact with 12 and a secondary transfer unit 25 that secondarily transfers the toner image of the intermediate transfer belt 21 to the medium P.

The intermediate transfer belt 21 is a film made of a resin such as polyimide. The intermediate transfer belt 21 is arranged so as to pass between the photoconductor drums 12 of the process units 10Y, 10M, 10C, 10K, and 10W and the primary transfer roller 22 (that is, the primary transfer nip).

A primary transfer voltage is applied to the primary transfer roller 22 by the primary transfer voltage power supply 127 (FIG. 14). By this primary transfer voltage, the toner images of the photoconductor drums 12 of the process units 10Y, 10M, 10C, 10K, and 10W are primarily transferred to the intermediate transfer belt 21.

A drive roller 23, a driven roller 24, and a secondary transfer backup roller 26 are arranged on the inner peripheral side of the intermediate transfer belt 21. The drive roller 23 is rotated by a belt drive motor 132 (FIG. 14) to drive the intermediate transfer belt 21 in the direction indicated by the arrow T. The driven roller 24 applies tension to the intermediate transfer belt 21. Further, a guide roller 28 for guiding the traveling of the intermediate transfer belt 21 is provided between the secondary transfer backup roller 26 and the driven roller 24.

A secondary transfer roller 27 is arranged on the outer peripheral side of the intermediate transfer belt 21 so as to sandwich the intermediate transfer belt 21 with the secondary transfer backup roller 26. The secondary transfer roller 27 and the secondary transfer backup roller 26 constitute a secondary transfer unit 25. The nip portion between the secondary transfer roller 27 and the secondary transfer backup roller 26 is referred to as a secondary transfer nip.

A secondary transfer voltage is applied to the secondary transfer roller 27 by the secondary transfer voltage power supply 128 (FIG. 14). Due to this secondary transfer voltage, the toner image of the intermediate transfer belt 21 is secondarily transferred to the medium P transferred from the transfer roller 104 to the secondary transfer unit 25.

The fixing device 105 applies heat and pressure to the medium P on which the toner image is transferred by the secondary transfer unit 25, and fixes the toner image on the medium P. In the fixing device 105 shown in FIG. 1, two sets of three rollers are arranged so as to sandwich the transport path of the medium P, and a belt is hung on each of them. At least one roller of the fixing device 105 is rotated by the fixing drive motor 133 (FIG. 14). The fixing device 105 is not limited to the configuration shown in FIG. 1, and may have, for example, a configuration having one fixing roller and one pressure roller.

Discharge rollers 106, 107, and 108 constituting the discharge unit are arranged on the downstream side of the fixing device 105 in the transport direction of the medium P. The discharge rollers 106, 107, and 108 rotate by rotation transmission from the fixing drive motor 133 (FIG. 14), and discharge the medium P on which the toner image is fixed to the outside of the image forming apparatus 1. A stacker portion 109 on which the discharged medium P is placed is provided on the upper portion of the image forming apparatus 1.

<Sensor unit configuration>
The sensor unit 5 is arranged so as to face the lower side of the intermediate transfer belt 21. Although the sensor unit 5 is arranged between the drive roller 23 and the secondary transfer unit 25 here, it may be arranged at another position. The sensor unit 5 has a sensor 3 (3A, 3B) facing the surface (outer peripheral surface) of the intermediate transfer belt 21 and a shutter 4 arranged between the sensor 3 and the intermediate transfer belt 21.

In FIG. 1, the direction parallel to the moving direction of the intermediate transfer belt 21 at the position facing the sensor unit 5 is the Y direction, and the width direction of the intermediate transfer belt 21 is the X direction. The direction parallel to both the X direction and the Y direction is defined as the Z direction.

Regarding the Y direction, the moving direction of the intermediate transfer belt 21 is the + Y direction, and the opposite direction is the −Y direction. Regarding the Z direction, the direction from the sensor unit 5 toward the intermediate transfer belt 21 is the + Z direction, and the opposite direction is the −Z direction.

FIG. 3 is a schematic diagram showing the sensor 3. The sensor unit 5 (FIG. 1) has two sensors 3 in the width direction (that is, the Y direction) of the intermediate transfer belt 21, that is, a density sensor 3A and a color shift sensor 3B.

The density sensor 3A emits light to a density detection pattern formed on the surface of the intermediate transfer belt 21 and detects the reflected light. The color shift sensor 3B emits light to a pattern for detecting color shift formed on the surface of the intermediate transfer belt 21 and detects the reflected light. Further, the sensors 3A and 3B emit light to the back surface of the shutter 4 or the surface surface of the intermediate transfer belt 21 at the time of calibration, and detect the reflected light.

Both the sensors 3A and 3B have a light receiving surface 30 inclined by an angle θ with respect to the surface (that is, the XY surface) of the intermediate transfer belt 21. Each of the sensors 3A and 3B has a light emitting element 31 such as an LED (light emitting diode) and light receiving elements 32 and 33 such as a photodiode. The light receiving elements 32 and 33 are arranged on both sides of the light emitting element 31 in the X direction. Since the sensors 3A and 3B have a common configuration, they will be described as "sensor 3" when it is not necessary to distinguish them.

4A and 4B are schematic views for explaining the roles of the light emitting element 31 and the light receiving elements 32 and 33 of the sensor 3. FIG. 4A shows a case where the light emitted from the light emitting element 31 is diffusely reflected, and FIG. 4B shows a case where the light emitted from the light emitting element 31 is specularly reflected.

The light emitting element 31 emits light to a pattern formed on the intermediate transfer belt 21. When the light is diffusely reflected like a pattern of a color other than black, the reflected light L1 is incident on the light receiving element 32 as shown in FIG. 4A. On the other hand, when the light is specularly reflected as in the black pattern, the reflected light L2 is incident on the light receiving element 33 as shown in FIG. 4 (B).

FIG. 5 is a diagram showing the relationship between the optical input to the sensor 3 and the output of the sensor 3. The sensor 3 outputs a voltage proportional to the intensity of the input light. The lower the density of the pattern, the more reflected light, so the output of the sensor 3 is large. On the other hand, the higher the density of the pattern, the smaller the reflected light, so that the output of the sensor 3 is small.

Since there are individual differences in the output characteristics of the sensor 3 as shown by V1 and V2 in FIG. 5, calibration is performed. Black calibration is performed using the back surface of the shutter 4, and color calibration is performed using the front surface of the intermediate transfer belt 21, which will be described later.

FIG. 6 is a diagram showing sensors 3A and 3B, a shutter 4 covering the sensors 3A and 3B, and cleaning films 9A and 9B provided on the shutter 4. The shutter 4 is arranged on the intermediate transfer belt 21 side (upper side in FIG. 6) of the sensors 3A and 3B.

The cleaning films 9A and 9B as cleaning members are films formed of an elastic body. For example, the cleaning films 9A and 9B are Mylar (registered trademark) films made of polyester resin, and have a thickness of, for example, 0.2 to 0.3 mm.

The upper end portion 91 of the cleaning film 9A is attached to the shutter 4. The lower end portion 92 of the cleaning film 9A abuts on the light receiving surface 30 of the density sensor 3A with a predetermined overlap amount in the Z direction. The lower end portion 92 of the cleaning film 9A is inclined at the same angle θ as the light receiving surface 30 of the density sensor 3A.

Similarly, the upper end 91 of the cleaning film 9B is attached to the shutter 4. The lower end portion 92 of the cleaning film 9B abuts on the light receiving surface 30 of the color shift sensor 3B in the Z direction with a predetermined overlap amount. The lower end portion 92 of the cleaning film 9B is inclined at the same angle θ as the light receiving surface 30 of the color shift sensor 3B. Since the cleaning films 9A and 9B have the same configuration, they will be described as "cleaning film 9" when it is not necessary to distinguish them.

FIG. 7 is a schematic diagram showing the sensor unit 5. The sensor unit 5 has a sensor 3, a shutter 4, and a cleaning film 9. The shutter 4 can move in the Y direction between the closed position that covers the light receiving surface 30 of the sensor 3 and the open position that opens the light receiving surface 30 of the sensor 3.

The sensor unit 5 also has a cam 70 as a drive unit for moving the shutter 4 from the closed position to the open position (that is, in the + Y direction) and an urging unit for urging the shutter 4 from the open position to the closed position. With a spring 75 of.

FIG. 8 is a perspective view showing the sensor unit 5. As shown in FIG. 8, the sensor unit 5 as a whole has a long shape in the X direction (that is, the width direction of the intermediate transfer belt 21). The sensor unit 5 has a base 6 as a substrate. The base 6 is made of, for example, sheet metal.

FIG. 9 is a perspective view showing the shutter 4. As shown in FIG. 9, the shutter 4 has a rectangular flat plate portion 40 long in the X direction, a pair of side plate portions 45 formed at both ends of the flat plate portion 40 in the X direction, and end portions of the flat plate portion 40 in the −Y direction. It has a back surface portion 46 formed on the surface.

In the flat plate portion 40, openings 43 are formed at two locations corresponding to the sensors 3A and 3B (FIG. 10). When the two openings 43 of the shutter 4 overlap the sensors 3A and 3B in the Z direction, the light from the intermediate transfer belt 21 can be incident on the light receiving surfaces 30 of the sensors 3A and 3B.

On the other hand, when the two openings 43 of the shutter 4 do not overlap the sensors 3A and 3B in the Z direction, the flat plate portion 40 of the shutter 4 covers the sensors 3A and 3B, and the light from the intermediate transfer belt 21 is the sensor 3A. , 3B does not enter the light receiving surface 30.

Further, cleaning films 9A and 9B for cleaning the surfaces of the sensors 3A and 3B are attached to the edges of the two openings 43 of the shutter 4. The cleaning films 9A and 9B are fixed to the edge of the opening 43 in the + Y direction.

An opening 47 is formed at a portion corresponding to the cam 70 (FIG. 8) in the central portion of the flat plate portion 40 in the X direction. The end face of the opening 47 in the + Y direction constitutes a contact surface 49 that abuts on the cam 70. Openings 48 for mounting the spring 75 on the base 6 are formed at two locations near both ends of the flat plate portion 40 in the X direction.

Guide protrusions 41 and 42 as engaging portions that engage with the guide groove 80, which will be described later, are formed so as to project in the X direction on each side plate portion 45 of the shutter 4. The guide protrusions 41 and 42 are arranged side by side in the Y direction and are at the same height in the Z direction. Of the guide protrusions 41 and 42, the guide protrusion 41 (first engaging portion) is located in the −Y direction, and the guide protrusion 42 (second engaging portion) is located in the + Y direction. The guide protrusions 41 and 42 have a rectangular shape having a long side in the Y direction and a short side in the Z direction.

FIG. 10 is a perspective view showing the shutter 4 removed from the sensor unit 5. As shown in FIG. 10, sensors 3A and 3B, a guide member 8, a cam 70, and a spring 75 are attached to the inside of the base 6 made of sheet metal.

FIG. 11 is a perspective view showing the base 6 of the sensor unit 5. The base 6 has a substantially rectangular bottom plate portion 60 long in the X direction, a rear wall 59 extending along the −Y end portion of the bottom plate portion 60, and a + Y direction end portion of the bottom plate portion 60. It has an existing front wall 61 and a pair of side walls 62 extending along both ends of the bottom plate portion 60 in the X direction.

At the center of the bottom plate portion 60 in the X direction, a cam holding portion 65 having a plate surface parallel to the YZ surface is formed by cutting and raising. The cam holding portion 65 is formed with a through hole 65a through which the cam shaft 73 penetrates.

As shown in FIG. 10, the camshaft 73 extends in the X direction, penetrates the through hole 62a (FIG. 11) formed in one side wall 62, and projects to the outside of the base 6. A transmission gear 72 that receives rotational transmission of the motor 74 (FIG. 14) is attached to the protruding end of the camshaft 73.

A cam 70 is fixed to the opposite end of the camshaft 73. The cam 70 has a substantially cylindrical shape centered on the central axis in the X direction, and a fan-shaped notch 71 is formed in a part thereof in the circumferential direction. The notch 71 abuts on the contact surface 49 (FIG. 9) of the opening 47 of the shutter 4.

Spring holding portions 64 having plate surfaces parallel to the XZ surface are formed by cutting and raising at two locations near both ends of the bottom plate portion 60 in the X direction. An annular protrusion 64a (FIG. 11) is formed on the surface of the spring holding portion 64 on the −Y side. The annular protrusion 64a (FIG. 11) is a portion that engages with the inner peripheral side of the spring 75.

The spring 75 is a compression coil spring whose axial direction is the Y direction. Here, two springs 75 are provided at intervals in the X direction. The + Y direction end of the spring 75 is held by the spring holding portion 64 of the base 6. A protruding portion 44 (FIG. 7) protruding in the −Z direction from the flat plate portion 40 of the shutter 4 is in contact with the end portion of the spring 75 in the −Y direction. That is, the spring 75 is sandwiched and held in the Y direction between the spring holding portion 64 of the base 6 and the protruding portion 44 of the shutter 4.

As shown in FIG. 11, fixing plates 66 and 67 are formed at both ends of the front wall 61 of the base 6 in the X direction, and fixing plates 68 are formed at the center of the front wall 61 in the X direction. These fixing plates 66, 67, 68 are portions for fixing the sensor holders 51, 52 (FIG. 10) for holding the sensors 3A, 3B.

The fixing plate 66 has an engaging hole 66a that engages with an engaging pin 55a (FIG. 10) described later, and a screw hole 66b that penetrates the screw S3 (FIG. 10). The fixing plate 68 has a locking portion 68a for locking the sensor holder 51 (FIG. 10) and a screw hole 68b for passing the screw S4 (FIG. 10). The fixing plate 67 has a locking portion 67a for locking the sensor holder 52 (FIG. 10) and an engaging hole 67b for engaging with the engaging pin 55b (FIG. 10) described later.

Returning to FIG. 10, the sensor holder 51 holds the sensor 3A in an inclined state with respect to the XY plane. A locked portion 51a to be locked to the locking portion 68a of the fixing plate 68 described above is formed at the end of the sensor holder 51 in the + X direction, and a screw hole 51b is formed at the end in the −X direction. It is formed.

The sensor holder 52 holds the sensor 3B in an inclined state with respect to the XY surface. A locked portion 52a to be locked to the locking portion 67a of the fixing plate 67 described above is formed at the end of the sensor holder 52 in the + X direction, and a screw hole 52b is formed at the end in the −X direction. It is formed.

A front frame 55 is attached to the front (+ Y direction) of the fixing plates 66, 67, 68. The front frame 55 has an engaging pin 55a that engages with the engaging hole 66a of the fixing plate 66 and an engaging pin 55b that engages with the engaging hole 67b of the fixing plate 67. Further, the front frame 55 has a female screw portion (not shown) into which the above-mentioned screws S3 and S4 are screwed.

A screw S3 penetrates through the screw hole 51b of the sensor holder 51, and the screw S3 is screwed into the female screw portion of the front frame 55. Further, the locked portion 51a of the sensor holder 51 is locked to the locking portion 68a. As a result, the sensor holder 51 is attached to the base 6.

A screw S4 penetrates through the screw hole 52b of the sensor holder 52, and the screw S4 is screwed into the female screw portion of the front frame 55. Further, the locked portion 52a of the sensor holder 52 is locked to the locking portion 67a. As a result, the sensor holder 52 is attached to the base 6.

At the upper ends of the pair of side walls 62 of the base 6, a guide holding portion 63 having a plate surface parallel to the XY surface is formed by bending. A guide member 8 that guides the shutter 4 is attached to each guide holding portion 63, and is fixed by a screw S5.

The pair of guide members 8 each have a guide groove 80 on the opposite side (that is, inside in the X direction) and a base 88 on the opposite side. The base 88 of the guide member 8 is formed with a screw hole through which the screw S5 is passed. The guide member 8 is fixed to the guide holding portion 63 by screwing the screw S5 penetrating the screw hole of the base portion 88 into the screw hole 63a (FIG. 11) of the guide holding portion 63.

The base 6 to which each component is attached as described above is fixed to the main body of the image forming apparatus 1 by screws S1 and S2 (FIG. 8) at both ends in the X direction.

FIG. 12 is a perspective view showing the guide member 8. Although only one of the pair of guide members 8 is shown in FIG. 12, the pair of guide members 8 have a shape symmetrical with respect to the center of the sensor unit 5 in the X direction.

The guide member 8 has a guide groove 80 (guide portion) long in the Y direction. The guide groove 80 is a portion that slidably engages with the guide protrusions 41 and 42 (FIG. 7) of the shutter 4 and guides the shutter 4 in the Y direction.

The guide groove 80 includes a first groove portion 81 located at the end in the −Y direction, a second groove portion 82 located at the end in the + Y direction, and an intermediate groove portion 83 (third groove portion) located between them. Have.

The groove width (dimension in the Z direction) of the first groove portion 81 and the second groove portion 82 is substantially equal to or slightly wider than the dimension in the Z direction of the guide protrusions 41 and 42 (FIG. 7) of the shutter 4. That is, the first groove portion 81 and the second groove portion 82 regulate the positions of the guide protrusions 41 and 42 of the shutter 4 in the Z direction.

On the other hand, the groove width of the intermediate groove portion 83 is wider than the groove width of the first groove portion 81 and the second groove portion 82. In other words, the groove width of the intermediate groove portion 83 is wider than the dimension of the guide protrusions 41 and 42 of the shutter 4 in the Z direction. That is, the intermediate groove portion 83 allows the displacement of the guide protrusions 41 and 42 of the shutter 4 in the Z direction (that is, has a degree of freedom).

Further, the first groove portion 81 has a groove upper surface 81a which is an end surface in the + Z direction and a groove lower surface 81b which is an end surface in the −Z direction. Similarly, the second groove portion 82 has a groove upper surface 82a and a groove lower surface 82b, and the intermediate groove portion 83 has a groove upper surface 83a and a groove lower surface 83b.

The groove upper surface 83a of the intermediate groove portion 83 is located above the groove upper surface 81a of the first groove portion 81 and the groove upper surface 82a of the second groove portion 82 (that is, in the + Z direction). Therefore, the intermediate groove portion 83 allows the shutter 4 to be displaced upward from the guide protrusions 41 and 42.

The groove lower surface 83b of the intermediate groove portion 83 is located slightly below the groove lower surface 81b of the first groove portion 81 and the groove lower surface 82b of the second groove portion 82 (that is, in the −Z direction). However, the present invention is not limited to such a configuration, and these groove lower surfaces 81b, 82b, 83b may have the same height.

The intermediate groove portion 83 has an inclined portion 84 whose groove width gradually changes between the intermediate groove portion 83 and the first groove portion 81. Further, the intermediate groove portion 83 has an inclined portion 85 whose groove width gradually changes between the intermediate groove portion 83 and the second groove portion 82.

13 (A) to 13 (C) are schematic views showing changes in the engagement state between the guide groove 80 and the guide protrusions 41 and 42 with the movement of the shutter 4. As shown in FIG. 13A, when the shutter 4 is located at the end in the −Y direction of the moving range, the guide protrusion 41 is located at the first groove portion 81 of the guide groove 80, and the guide protrusion 42 is in the middle. It is located in the groove 83.

Since the guide protrusion 41 is engaged with the first groove portion 81, the position of the shutter 4 is restricted in the Z direction. That is, the shutter 4 is in a state where it is hardly displaced in the Z direction. In this state, the flat plate portion 40 (FIG. 8) of the shutter 4 covers the sensors 3A and 3B. Therefore, the position of the shutter 4 shown in FIG. 13A is referred to as a closed position.

As shown in FIG. 13B, when the shutter 4 moves from the closed position in the + Y direction, the guide protrusions 41 and 42 move in the guide groove 80, and the guide protrusion 41 moves from the first groove portion 81 to the intermediate groove portion 83. do. On the other hand, the guide protrusion 42 is still located in the intermediate groove portion 83.

Since the groove width of the intermediate groove portion 83 is wider than that of the first groove portion 81, the guide protrusions 41 and 42 can be displaced in the Z direction. In this state, the cleaning film 9 (FIG. 8) of the shutter 4 is in contact with the edges of the sensors 3A and 3B.

In the example shown in FIG. 13B, when the guide protrusion 42 reaches the end portion (inclined portion 85) of the intermediate groove portion 83, a part of the guide protrusion 41 remains in the first groove portion 81. Therefore, the shutter 4 swings upward as shown by the arrow U with the portion remaining in the first groove portion 81 of the guide protrusion 41 as the center (fulcrum).

As shown in FIG. 13C, when the shutter 4 further moves in the + Y direction, the guide protrusion 42 moves from the intermediate groove portion 83 to the second groove portion 82. Since the guide protrusion 42 engages with the second groove portion 82, the position of the shutter 4 is restricted in the Z direction. That is, the shutter 4 is in a state where it is hardly displaced in the Z direction. In this state, the opening 43 (FIG. 8) of the shutter 4 is located above the sensors 3A and 3B, and the light receiving surface 30 of the sensors 3A and 3B is opened. Therefore, the position of the shutter 4 shown in FIG. 13C is referred to as an open position.

<Control system>
Next, the control system of the image forming apparatus 1 will be described. FIG. 14 is a block diagram showing a control system of the image forming apparatus 1. The image forming apparatus 1 includes a print control unit 110, an interface control unit 111, a reception memory 112, an image data editing memory 113, an operation unit 114, a sensor group 115, a position sensor 116, a density sensor 3A, and a color shift sensor 3B. The print control unit 110 also includes a high-voltage power supply control unit 117, a shutter control unit 118, a head control unit 119, a fixing control unit 120, a motor control unit 121, and a drive control unit 122.

The print control unit 110 includes, for example, a microprocessor, ROM, RAM, input / output ports, timers, and the like. The print control unit 110 receives print data and control commands via the interface control unit 111, and controls the overall operation of the image forming apparatus 1.

The interface control unit 111 receives print data and control commands from a host device (external computer or the like). The reception memory 112 temporarily stores the print data received by the interface control unit 111. The image data editing memory 113 edits the print data stored in the reception memory 112 to generate and store image data (image data).

The operation unit 114 has a display unit (for example, an LED) for displaying the state of the image forming apparatus 1 and an operation input unit (switch, display panel, etc.) for receiving the input of the operator. The sensor group 115 includes various sensors that monitor the state of the image forming apparatus 1, for example, a medium position sensor that detects the position of the medium P, a temperature / humidity sensor that detects the ambient temperature and humidity, and a toner residue that detects the remaining amount of toner. It has a quantity sensor and the like.

The density sensor 3A optically detects the density detection pattern transferred to the intermediate transfer belt 21 by the process units 10Y, 10M, 10C, 10K, 10W. The color shift sensor 3B optically detects the pattern for color shift detection transferred to the intermediate transfer belt 21 by the process units 10Y, 10M, 10C, 10K, and 10W.

The high-voltage power supply control unit 117 includes a charging voltage power supply 123 that applies a charging voltage to the charging roller 13, a development voltage power supply 124 that applies a development voltage to the development roller 14, and a layer regulation voltage power supply that applies a layer regulation voltage to the layer regulation blade 16. 126, supply voltage power supply 125 that applies supply voltage to supply roller 15, primary transfer voltage power supply 127 that applies primary transfer voltage to primary transfer roller 22, and secondary transfer voltage applied to secondary transfer roller 27. The secondary transfer voltage power supply 128 is controlled.

The shutter control unit 118 drives a motor 74 that moves the shutter 4 based on a control signal from the print control unit 110. The head control unit 119 controls the light emission of the LED head 11 based on the image data output from the image data editing memory 113 to the print control unit 110.

The fixing control unit 120 supplies the heating element (for example, a halogen lamp) of the fixing device 105 based on the control signal from the printing control unit 110 and the detection temperature of the temperature sensor (for example, thermistor) provided in the fixing device 105. Control the current.

The motor control unit 121 controls the medium transfer motor 131, the belt drive motor 132, and the fixing drive motor 133 based on the control signal from the print control unit 110. The drive control unit 122 controls the drive motor 134 based on the control signal from the print control unit 110.

<Basic operation of image forming apparatus>
Next, the basic operation of the image forming apparatus 1 in this embodiment will be described with reference to FIGS. 1 and 14. The print control unit 110 of the image forming apparatus 1 starts an image forming operation (printing operation) when it receives a print command and print data from a higher-level apparatus.

First, the feed roller 103 rotates to feed one medium P housed in the medium cassette 102. Further, the transport roller 104 rotates, and the medium P fed by the feed roller 103 is conveyed toward the secondary transfer unit 25.

In each process unit 10 (FIG. 2) of the image forming unit 100, the photoconductor drum 12 rotates, and the charging roller 13 rotates following the photoconductor drum 12. Further, the developing roller 14 and the supply roller 15 are rotated by the rotation transmission from the photoconductor drum 12. Further, the drive roller 23 rotates to run the intermediate transfer belt 21.

In each process unit 10, a charging voltage is applied to the charging roller 13 to uniformly charge the surface of the photoconductor drum 12. Further, the LED head 11 exposes the surface of the photoconductor drum 12 based on the image data of each color to form an electrostatic latent image.

Further, a supply voltage is applied to the supply roller 15, and toner is supplied to the developing roller 14. The layer regulation blade 16 thins the toner held on the surface of the developing roller 14. A developing voltage is applied to the developing roller 14, and the electrostatic latent image on the photoconductor drum 12 is developed with toner to form a toner image (developer image).

When the toner image formed on each photoconductor drum 12 reaches the vicinity of the primary transfer roller 22, the primary transfer voltage is applied to the primary transfer roller 22. As a result, the toner image is primarily transferred from each photoconductor drum 12 to the intermediate transfer belt 21. The toner image on the intermediate transfer belt 21 moves toward the secondary transfer unit 25 due to the running of the intermediate transfer belt 21.

The toner image on the intermediate transfer belt 21 and the medium P conveyed by the transfer roller 104 reach the secondary transfer unit 25 at the same time. A secondary transfer voltage is applied to the secondary transfer roller 27, whereby the toner image of the intermediate transfer belt 21 is secondarily transferred to the medium P.

The medium P on which the toner image is transferred by the secondary transfer unit 25 is conveyed to the fixing device 105. In the fixing device 105, the toner image transferred to the medium P is heated and pressurized to be fixed to the medium P. The medium P on which the toner image is fixed is carried out by the discharge rollers 106, 107, 108 and placed on the stacker portion 109. As a result, the image forming operation is completed.

<Color shift correction processing and density correction processing>
Here, the color shift correction process and the density correction process will be described. The image forming apparatus 1 performs a color shift correction process after the device power is turned on and before the above-mentioned image forming operation is started. That is, the print control unit 110 controls the high-voltage power supply control unit 117 and the head control unit 119 after moving the shutter 4 to the open position, and the process units 10Y, 10M, 10C, 10K, and 10W control each color pattern (color shift). A pattern for detection) is formed and transferred to the intermediate transfer belt 21. Then, the pattern on the intermediate transfer belt 21 is detected by the color shift sensor 3B.

Each pattern formed of yellow, magenta, cyan, black and white toner has a different light reflectance. The color shift sensor 3B outputs a voltage signal having a waveform corresponding to the color of each pattern on the intermediate transfer belt 21. The print control unit 110 detects the amount of deviation of each pattern on the intermediate transfer belt 21 based on the voltage signal output from the color shift sensor 3B, and the LED heads 11Y, 11M, according to the detected amount of deviation. Adjust the light emission timing of 11C, 11K, 11W. When the color shift correction process is completed, the print control unit 110 moves the shutter 4 to the closed position.

Further, since the density of the toner image fluctuates depending on environmental conditions such as temperature and humidity, the density correction processing is performed periodically. First, color calibration and black calibration necessary for density correction are performed.

Color calibration is performed with the shutter 4 closed, that is, with the back surface of the shutter 4 facing the density sensor 3A. The light emitted from the light emitting element 31 of the density sensor 3A is diffusely reflected by the back surface of the shutter 4 (resin molded body) and is incident on the light receiving element 32 as shown in FIG. 4 (A). The print control unit 110 adjusts the light emission current of the light emitting element 31 (LED) so that the output of the density sensor 3A is within the set range.

Further, the black calibration is performed in a state where the shutter 4 is open, that is, in a state where the surface of the intermediate transfer belt 21 faces the density sensor 3A. The light emitted from the light emitting element 31 of the density sensor 3A is specularly reflected by the surface (smooth and glossy) of the intermediate transfer belt 21 and incident on the light receiving element 33 as shown in FIG. 4 (B). The print control unit 110 adjusts the light emission current of the light emitting element 31 (LED) so that the output of the density sensor 3A is within the set range.

Subsequently, the print control unit 110 controls the high-voltage power supply control unit 117 and the head control unit 119 to form a pattern (pattern for density detection) of each color with the process units 10Y, 10M, 10C, 10K, and 10W, and intermediate. Transfer to the transfer belt 21. Then, the pattern on the intermediate transfer belt 21 is detected by the density sensor 3A.

The density sensor 3A outputs a voltage signal corresponding to the density of each pattern on the intermediate transfer belt 21. The print control unit 110 transmits an instruction for adjusting parameters and the like to the process units 10Y, 10M, 10C, 10K, and 10W based on the voltage signal output from the density sensor 3A.

<Opening and closing operation of shutter 4>
Next, the opening / closing operation of the shutter 4 will be described. 15 (A) to 15 (C) are schematic views showing the opening operation (that is, the movement from the closed position to the open position) of the shutter 4.

In the state shown in FIG. 15A, the shutter 4 is at the end (that is, the closed position) in the −Y direction of the moving range. The guide protrusion 41 of the shutter 4 is located in the first groove portion 81 of the guide groove 80, and the guide protrusion 42 is located in the intermediate groove portion 83.

The spring 75 is held between the protrusion 44 of the shutter 4 and the spring holding portion 64 of the base 6, but when the shutter 4 is in the closed position, the spring 75 is in the most extended state. The light receiving surface 30 of the sensor 3 is covered with the flat plate portion 40 of the shutter 4, and the light from the intermediate transfer belt 21 does not enter the light receiving surface 30 of the sensor 3.

With the shutter 4 in the closed position in this way, the color calibration described above is performed. Since the Z-direction position of the shutter 4 is restricted by the engagement between the guide protrusion 41 and the first groove portion 81, color calibration can be performed with high accuracy.

When starting the opening operation of the shutter 4, the print control unit 110 drives the motor 74 (FIG. 14) in the forward direction. The rotation of the motor 74 is transmitted to the cam 70 via the transmission gear 72 and the camshaft 73. As a result, the cam 70 rotates counterclockwise in the drawing, and the notch 71 of the cam 70 presses the shutter 4 in the + Y direction. The shutter 4 moves in the + Y direction while compressing the spring 75.

As shown in FIG. 15B, when the shutter 4 moves in the + Y direction, the cleaning film 9 reaches the sensor 3. The edges 34, 35 surrounding the light receiving surface 30 of the sensor 3 project upward from the light receiving surface 30, and the cleaning film 9 first rides on the edge 34.

At this time, the guide protrusions 41 and 42 of the shutter 4 are located in the intermediate groove portion 83 of the guide groove 80, and therefore the shutter 4 can be displaced in the Z direction. Therefore, the shutter 4 is displaced in the + Z direction (that is, the direction away from the light receiving surface 30 of the sensor 3) due to the contact between the cleaning film 9 and the edge portion 34 of the sensor 3.

More specifically, since the guide protrusion 42 reaches the end portion (inclined portion 85) of the intermediate groove portion 83 and a part of the guide protrusion 41 remains in the first groove portion 81, the shutter 4 is the guide protrusion 41. It swings upward as shown by the arrow U about the portion remaining in the first groove portion 81.

Then, when the shutter 4 further moves in the + Y direction, the cleaning film 9 moves so as to sweep the light receiving surface 30 of the sensor 3 and removes foreign matter on the light receiving surface 30. As shown in FIG. 15C, when the shutter 4 reaches the + Y direction end portion (that is, the open position) of the moving range, the cleaning film 9 passes through the light receiving surface 30 of the sensor 3 and reaches the edge portion 35.

At this time, the opening 43 (FIG. 8) of the shutter 4 overlaps the light receiving surface 30 of the sensor 3 in the Z direction, and the light from the intermediate transfer belt 21 is incident on the light receiving surface 30 of the sensor 3. Further, the guide protrusion 42 of the shutter 4 reaches the second groove portion 82 of the guide groove 80. The Z direction of the shutter 4 is restricted by the engagement between the guide protrusion 42 and the second groove 82. The spring 75 is in the most compressed state.

With the shutter 4 in the open position as described above, the above-mentioned black calibration, density correction processing, and color shift correction processing are performed.

16 (A) to 16 (C) are schematic views showing a closing operation (that is, movement from an open position to a closed position) of the shutter 4. The state shown in FIG. 16A is the same as the state shown in FIG. 15C, and the shutter 4 is located at the open position. Further, the guide protrusion 42 is located in the second groove portion 82, and the guide protrusion 41 is located in the intermediate groove portion 83.

When starting the closing operation of the shutter 4, the print control unit 110 drives the motor 74 (FIG. 14) in the reverse direction and rotates the cam 70 clockwise.

When the shutter 4 is in the open position, the cylindrical surface of the cam 70 is in contact with the contact surface 49 of the shutter 4, but as shown in FIG. 16B, the cam 70 rotates and the cam 70 is notched. When the portion 71 faces the contact surface 49 of the shutter 4, the shutter 4 moves in the −Y direction due to the restoring force of the compressed spring 75.

When the shutter 4 moves in the −Y direction, the cleaning film 9 moves while contacting the light receiving surface 30 of the sensor 3 and rides on the edge portion 34 of the sensor 3. At this time, the guide protrusions 41 and 42 of the shutter 4 are both located in the intermediate groove portion 83 of the guide groove 80 and can be displaced in the Z direction. Therefore, the shutter 4 is displaced in the + Z direction (that is, the direction away from the light receiving surface 30 of the sensor 3) due to the contact between the cleaning film 9 and the edge portion 34 of the sensor 3.

More specifically, when the guide protrusion 41 reaches the end portion (inclined portion 84) of the intermediate groove portion 83, a part of the guide protrusion 42 remains in the second groove portion 82, so that the shutter 4 has a guide protrusion. It swings upward as shown by the arrow U about the portion remaining in the second groove 82 of 42.

Then, when the shutter 4 further moves in the −Y direction, the cleaning film 9 passes over the edge portion 34 and passes through the sensor 3. When the shutter 4 reaches the −Y direction end portion (that is, the closed position) of the moving range, the guide protrusion 41 of the shutter 4 reaches the first groove portion 81 of the guide groove 80. The Z direction of the shutter 4 is restricted by the engagement between the guide protrusion 41 and the first groove portion 81.

The opening 43 (FIG. 8) of the shutter 4 moves to a position where it does not overlap with the light receiving surface 30 of the sensor 3, whereby the light receiving surface 30 of the sensor 3 is covered with the flat plate portion 40 of the shutter 4. That is, the light from the intermediate transfer belt 21 does not enter the light receiving surface 30 of the sensor 3.

As described above, in the sensor unit 5 of this embodiment, when the cleaning film 9 comes into contact with the sensor 3 (more specifically, when it gets over the edge portion 34), the guide protrusions 41 and 42 of the shutter 4 guide. It is guided to the intermediate groove portion 83 (that is, the portion having a wide groove width) of the groove 80. Therefore, the shutter 4 is displaced in the + Z direction, and the contact load between the cleaning film 9 and the sensor 3 can be reduced.

In particular, when the shutter 4 is moved by the urging force of the spring 75 (FIG. 16B), if the contact load between the cleaning film 9 and the sensor 3 is large, the shutter 4 is stopped halfway (that is, malfunction). Is likely to occur. By reducing the contact load as described above, it is possible to prevent the shutter 4 from malfunctioning.

17 is a schematic diagram (A) to (D) for explaining the opening / closing operation of the shutter 4 in the sensor unit of the comparative example. In this comparative example, the width of the guide groove 80 of the guide member 8 is constant over the entire area. That is, the shutter 4 is guided by the guide groove 80 so as not to be displaced in the Z direction. For convenience of explanation, the components of the comparative example will also be described with the same reference numerals as the components of the present embodiment.

FIG. 17A shows a state in which the shutter 4 is in the closed position. When the shutter 4 is opened, the cam 70 rotates counterclockwise as described above, and the shutter 4 starts moving in the + Y direction. The guide protrusions 41 and 42 of the shutter 4 move in the guide groove 80 in the + Y direction, and the spring 75 is gradually compressed.

As shown in FIG. 17B, when the shutter 4 moves in the + Y direction, the cleaning film 9 rides on the edge portion 34 of the shutter 4. At this time, since the shutter 4 is not displaced in the Z direction due to the engagement between the guide protrusions 41 and 42 and the guide groove 80, the contact load between the cleaning film 9 and the edge portion 34 of the shutter 4 increases. However, since the driving force of the motor 74 exceeds the contact load, the shutter 4 is unlikely to stop.

As shown in FIG. 17C, when the shutter 4 further moves in the + Y direction, the cleaning film 9 moves so as to sweep the light receiving surface 30 of the sensor 3, and when the shutter 4 reaches the open position, the shutter 4 opens. The unit 43 (FIG. 8) is located on the light receiving surface 30 of the sensor 3.

When the shutter 4 is closed, the cam 70 rotates clockwise, and the restoring force of the spring 75 causes the shutter 4 to move in the −Y direction. The guide protrusions 41 and 42 of the shutter 4 move in the guide groove 80 in the −Y direction.

As shown in FIG. 17D, when the shutter 4 moves in the + Y direction, the cleaning film 9 rides on the edge portion 34 of the shutter 4. Since the shutter 4 is not displaced in the Z direction due to the engagement between the guide protrusions 41 and 42 and the guide groove 80, the contact load between the cleaning film 9 and the edge portion 34 of the shutter 4 increases.

The shutter 4 is moved by the restoring force of the spring 75, but since the restoring force of the spring 75 is limited, there is a possibility that a malfunction may occur in which the movement of the shutter 4 is stopped halfway due to an increase in the contact load. That is, the light receiving surface 30 of the sensor 3 may not be sufficiently covered by the shutter 4 (that is, it may be in a half-open state).

On the other hand, in the sensor unit 5 of this embodiment, when the cleaning film 9 comes into contact with the sensor 3, the shutter 4 is guided so as to be displaceable in the + Z direction. Therefore, the shutter 4 is displaced in the + Z direction, and the contact load between the cleaning film 9 and the sensor 3 can be reduced. That is, it is possible to prevent a malfunction in which the shutter 4 is stopped due to a contact load.

FIG. 18 is a schematic diagram for explaining the amount of overlap between the sensor 3 and the cleaning film 9. As described above, in the sensor 3, the light receiving surface 30 is inclined by an angle θ with respect to the XY surface (that is, the surface parallel to the surface of the intermediate transfer belt 21).

The cleaning film 9 has a shape in which the upper end portion 91 is fixed to the shutter 4 and the lower end portion 92 is in contact with the sensor 3. Here, the lower end portion 92 of the cleaning film 9 is inclined in parallel with the light receiving surface 30 of the sensor 3, that is, by an angle θ with respect to the XY surface.

A predetermined overlap amount is set between the cleaning film 9 and the sensor 3. The overlap amount refers to the amount of overlap of the cleaning film 9 and the sensor 3 in the Z direction (indicated by reference numeral B in FIG. 18) in a state where the cleaning film 9 extends straight in the Z direction. The overlap amount is, for example, 1.3 mm.

By setting the overlap amount in this way, when the cleaning film 9 moves along the light receiving surface 30 of the sensor 3, the cleaning film 9 moves so as to sweep the light receiving surface 30 and efficiently scrapes off foreign matter. be able to. Therefore, the cleaning effect of the light receiving surface 30 by the cleaning film 9 can be enhanced.

Further, as shown in FIGS. 15B and 16B, when the cleaning film 9 gets over the edge portion 34 of the sensor 3, the shutter 4 is moved upward by the action of the intermediate groove portion 83 of the guide groove 80. Displace, for example, 0.9 mm in the (+ Z direction). Therefore, the amount of overlap between the cleaning film 9 and the edge portion 34 of the sensor 3 is 0.4 mm (= 1.3 mm-0.9 mm). As a result, the contact load is significantly reduced as compared with the case where the shutter 4 is not displaced in the Z direction.

<Effect of the first embodiment>
As described above, in the first embodiment of the present invention, the shutter 4 arranged between the sensor 3 and the intermediate transfer belt 21 and the guide for guiding the shutter 4 between the open position and the closed position. It has a member 8 and a cleaning film 9 attached to the shutter 4. Further, the guide member 8 guides the shutter 4 in a predetermined region between the open position and the closed position so as to be displaceable in a direction away from the light receiving surface 30 of the sensor 3. Therefore, the contact load when the cleaning film 9 comes into contact with the sensor 3 can be reduced, and the malfunction of the shutter 4 can be suppressed.

Further, since it has a cam 70 (that is, a driving unit) that moves the shutter 4 from the closed position to the open position and a spring 75 (that is, the urging unit) that urges the shutter 4 from the open position to the closed position, it is a spring. When the shutter 4 is moved by the urging force of the 75, the effect of suppressing the malfunction of the shutter 4 is particularly remarkable.

Further, since the cleaning film 9 is provided so as to overlap the light receiving surface 30 of the sensor 3 in the direction orthogonal to the moving direction of the shutter 4, the cleaning film 9 effectively removes foreign matter from the light receiving surface 30 of the sensor 3. Can be removed.

Further, since the sensor 3 has a light emitting element 31 that emits light toward the intermediate transfer belt 21 and light receiving elements 32 and 33 that receive light from the intermediate transfer belt 21, the sensor 3 is formed on the surface of the intermediate transfer belt 21. The pattern etc. can be read optically. Further, since the sensor 3 is arranged so as to be inclined with respect to the surface of the intermediate transfer belt 21, it is possible to configure the diffusely reflected light and the specularly reflected light to be received by separate light receiving elements 32 and 33.

Further, the guide groove 80 includes a first groove portion 81 that engages with the guide protrusion 41 when the shutter 4 is in the open position, and a second groove portion 82 that engages with the guide protrusion 42 when the shutter 4 is in the closed position. It has an intermediate groove portion (third groove portion) 83 between the first groove portion 81 and the second groove portion 82, and the width of the intermediate groove portion 83 is wider than the width of the first groove portion 81 and the width of the second groove portion 82. .. Therefore, the intermediate groove portion 83 can guide the shutter 4 so as to be displaceable in the + Z direction, and the first groove portion 81 and the second groove portion 82 can position the shutter 4 in the Z direction. Therefore, it is possible to accurately perform calibration using the back surface of the shutter 4 while suppressing malfunction of the shutter 4.

Further, since the guide groove 80 has inclined portions 84 and 85 between the first groove portion 81 and the intermediate groove portion 83 and between the second groove portion 82 and the intermediate groove portion 83, the guide protrusions 41 and 42 are provided. It can be smoothly moved in the guide groove 80. Further, it is also possible to swing the shutter 4 around the first groove portion 81 or the second groove portion 82.

Further, since the guide protrusions 41 and 42 have a rectangular shape, the shutter is in a state where the guide protrusion 41 is engaged with the first groove portion 81 and a state where the guide protrusion 42 is engaged with the second groove portion 82. 4 can be held in a stable posture.

Further, since the cleaning film 9 is a film formed of an elastic body, it can move so as to sweep the light receiving surface 30 of the sensor 3 and can be efficiently cleaned.

Further, since the shutter 4 has an opening 43 facing the light receiving surface 30 when the shutter 4 is in the open position, and the cleaning film 9 is arranged adjacent to the opening 43, the sensor 3 has an opening. It can be cleaned with the cleaning film 9 just before the light receiving surface 30 is opened.

Further, at least of the density sensor 3A for detecting the density of the image formed on the surface of the intermediate transfer belt 21 and the color shift sensor 3B for detecting the positional deviation of the images of a plurality of colors formed on the surface of the intermediate transfer belt 21. Since it has one, it is possible to perform density correction processing, color shift correction processing, or both.

Although the intermediate transfer type image forming apparatus has been described in the above-described embodiment, the present invention may be applied to the direct transfer type image forming apparatus. The image forming apparatus of the direct transfer method has a transport belt (belt member) for transporting the medium P on which the image formed by the image forming unit 100 is transferred, instead of the intermediate transfer belt 21.

Even in the case of the direct transfer type image forming apparatus, the density detection pattern and the color shift detection pattern (that is, the developer image) formed by the image forming unit 100 are transferred to the surface of the transport belt. The sensor unit 5 is arranged under the conveyor belt so that the sensor 3 faces the surface of the conveyor belt.

Further, in the above-described embodiment, the light receiving surface 30 of the sensor 3 (sensors 3A, 3B) is arranged in an inclined manner, but the light receiving surface of the sensor 3 may be parallel to the belt surface. Further, the sensor 3 is not limited to the density sensor and the color shift sensor, and other types may be used.

Further, in the above-described embodiment, the cam 70 is used as the driving unit for driving the shutter 4, but the cam 70 is not limited to the cam 70, and for example, a solenoid or the like may be used.

Further, in each of the above-described embodiments, the printer has been described as an example of the image forming apparatus, but the printer is not limited to the printer, and a copying machine, a facsimile apparatus, an MFP (Multifunction Peripheral), or the like may be used. Further, the image forming apparatus is not limited to the one that forms a color image, and may be one that forms a monochromatic image.

Although the preferred embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various improvements or modifications are made without departing from the gist of the present invention. be able to.

1 image forming device, 3,3A, 3B sensor, 4 shutter, 5 sensor unit, 6 base, 8 guide member, 9,9A, 9B cleaning film (cleaning member), 10,10Y, 10M, 10C, 10K, 10C process Unit, 11, 11Y, 11M, 11C, 11K, 11W LED head (exposure device, exposure unit), 12 Photoconductor drum (image carrier), 13 Charging roller (charging member), 14 Developing roller (developer carrier, Development unit), 15 Supply roller (supply member), 16 Layer regulation blade (layer regulation member), 17 Toner cartridge (developer container), 20 Transfer belt unit (transfer unit), 21 Intermediate transfer belt (belt member, intermediate) Transfer), 22 Primary transfer roller (primary transfer), 23 Drive roller, 24 Driven roller, 25 Secondary transfer unit, 26 Secondary transfer backup roller, 27 Secondary transfer roller, 30 Light receiving surface, 31 Light emitting element (Light emitting part), 32, 33 Light receiving element (light receiving part), 34, 35 edge part (convex part), 40 flat plate part, 41 guide protrusion (engaging part, first engaging part), 42 guide protrusion (engagement part) Joint part, second engagement part), 43 opening part, 44 protrusion part, 45 side plate part, 46 back part, 47,48 opening part, 49 contact surface, 51, 52 sensor holder, 63 guide holding part, 64 Spring holding part, 65 cam holding part, 70 cam (drive part), 71 notch part, 72 transmission gear, 74 motor (drive source), 75 spring (urging member), 80 guide groove, 81 first groove part, 82 2nd groove, 83 intermediate groove (3rd groove), 84,85 inclined part, 88 base part, 91 upper end part, 92 lower end part, 100 image forming part, 101 medium supply part, 102 medium cassette (medium accommodating part), 103 Feed roller, 104 transport roller, 105 fixing device, 106, 107, 108 discharge roller, 110 print control unit.

Claims (12)

The image forming part that forms the developer image and
A belt member to which the developer image formed in the image forming portion is transferred, and
A sensor having a light receiving surface facing the belt member and
A shutter arranged between the sensor and the belt member and having an engaging portion ,
The shutter is guided between an open position that allows light from the belt member to enter the light receiving surface of the sensor and a closed position that covers the light receiving surface of the sensor, and engages with the engaging portion. A guide part with a guide groove to be used, and
It has a cleaning member attached to the shutter and cleans the light receiving surface of the sensor.
The guide portion guides the shutter in a predetermined region between the open position and the closed position so as to be displaceable in a direction away from the light receiving surface of the sensor .
The guide groove is
A first groove portion that engages with the engaging portion when the shutter is in the open position, and a first groove portion.
A second groove that engages with the engaging portion when the shutter is in the closed position,
With a third groove portion provided between the first groove portion and the second groove portion
Have,
The groove width of the third groove portion is wider than the groove width of the first groove portion and the groove width of the second groove portion.
An image forming apparatus characterized in that. A drive unit that moves the shutter from the closed position to the open position,
The image forming apparatus according to claim 1, further comprising an urging portion for urging the shutter from the open position to the closed position. The image forming apparatus according to claim 1 or 2, wherein the cleaning member is provided so as to overlap the light receiving surface in a direction orthogonal to the moving direction of the shutter. The sensor has a light emitting portion that emits light toward the belt member and a light receiving portion that receives light from the belt member, and is arranged so as to be inclined with respect to the surface of the belt member. The image forming apparatus according to any one of claims 1 to 3, wherein the image forming apparatus is characterized. 1 to 4, wherein the guide groove has an inclined portion between the first groove portion and the third groove portion and between the second groove portion and the third groove portion, respectively. The image forming apparatus according to any one of the above items. The image forming apparatus according to any one of claims 1 to 5 , wherein the engaging portion has a rectangular shape. The image forming apparatus according to any one of claims 1 to 6 , wherein the cleaning member is a film formed of an elastic body. The shutter has an opening facing the light receiving surface when in the open position.
The image forming apparatus according to any one of claims 1 to 7 , wherein the cleaning member is arranged adjacent to the opening. The sensor according to any one of claims 1 to 8 , wherein the sensor has at least one of a density sensor for detecting the density of the developer image and a color shift sensor for detecting the misalignment of the developer images of a plurality of colors. The image forming apparatus according to item 1. The image forming apparatus according to any one of claims 1 to 9 , wherein the two sensors are arranged at intervals in the width direction of the belt member. The image forming part is
An image carrier that supports a developer image and an image carrier
A charging member that uniformly charges the surface of the image carrier,
An exposure apparatus that exposes the surface of the image carrier to form a latent image,
The image forming apparatus according to any one of claims 1 to 10 , further comprising a developing unit for developing a latent image on the surface of the image carrier. A sensor unit that is placed facing the belt member.
A sensor having a light receiving surface facing the belt member and
A shutter arranged between the sensor and the belt member and having an engaging portion ,
The shutter is guided between an open position that allows light from the belt member to enter the light receiving surface of the sensor and a closed position that covers the light receiving surface of the sensor, and engages with the engaging portion. A guide part with a guide groove to be used, and
It has a cleaning member attached to the shutter and cleans the light receiving surface of the sensor.
The guide portion guides the shutter in a predetermined region between the open position and the closed position so as to be displaceable in a direction away from the light receiving surface of the sensor.
The guide groove is
A first groove portion that engages with the engaging portion when the shutter is in the open position, and a first groove portion.
A second groove that engages with the engaging portion when the shutter is in the closed position,
With a third groove portion provided between the first groove portion and the second groove portion
Have,
The groove width of the third groove portion is wider than the groove width of the first groove portion and the groove width of the second groove portion.
A sensor unit characterized by that.

Images