JP7135784B2 - MEDIUM THICKNESS DETECTION DEVICE, MEDIUM CONVEYING DEVICE, AND IMAGE FORMING APPARATUS - Google Patents

Description

The present invention relates to a medium thickness detection device, a medium conveying device, and an image forming apparatus.

2. Description of the Related Art Some image forming apparatuses are equipped with a medium thickness detection device that detects the thickness of a medium such as printing paper. A conventional medium thickness detection device has a medium support member (stage) and a medium pick-up member, and detects the thickness of the medium when the medium is transported between them (see, for example, Japanese Unexamined Patent Application Publication No. 2002-100003).

Japanese Patent No. 4579312 (see FIGS. 25-26, paragraphs 0121-0127)

However, in the above configuration, the medium contacts the medium pick-up member while moving, so the surface of the medium may be damaged. When the surface of the medium is damaged in this way, it causes image unevenness such as vertical streaks.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a medium thickness detecting device, a medium conveying device, and an image forming apparatus capable of suppressing the occurrence of scratches on the medium surface. do.

A medium thickness detecting device according to the present invention includes a conveying section that conveys a medium, a medium supporting member that is arranged in a medium conveying path and supports the medium, and a medium supporting member that faces the medium supporting member across the conveying path and measures the thickness of the medium. It has a stylus that can be displaced in a direction, a detection unit that detects the thickness of the medium based on the displacement of the stylus, and a contact/separation mechanism that moves the stylus toward and away from the medium support member. The contact/separation mechanism is capable of swinging about a swing shaft, and includes a lever member having an action portion that acts on the stylus on one side of the swing shaft, and a lever member with respect to the swing shaft. It has a driving part provided on the side opposite to the action part and swinging the lever member. The detecting section is arranged between the driving section and the swing shaft so as to face the lever member, and the thickness of the medium is detected based on the distance from the lever member detected by the detecting section. The acting portion has a first portion that abuts the probe in a direction toward the medium support member and a second portion that abuts the probe in a direction away from the medium support member. When the transport unit is transporting the medium, the contact/separation mechanism separates the stylus from the medium, and when the transport unit stops transporting the medium, the contact/separation mechanism brings the stylus into contact with the medium and detects detects the thickness of the media.

A medium conveying device of the present invention includes the medium thickness detecting device described above and at least one conveying roller that conveys the medium. Further, an image forming apparatus of the present invention includes the medium thickness detecting device and an image forming section that forms an image on the medium whose thickness is detected by the medium thickness detecting device.

In the present invention, since the stylus comes into contact with the medium while the transportation of the medium is stopped, it is possible to suppress the occurrence of scratches on the surface of the medium. Therefore, it is possible to suppress the occurrence of image unevenness caused by scratches on the surface of the medium.

1 illustrates an image forming apparatus according to a first embodiment; FIG. 2 is a perspective view showing a medium thickness detector of the image forming apparatus according to the first embodiment; FIG. 4 is a front view showing the medium thickness detection section of the first embodiment; FIG. 3 is a perspective view showing a medium thickness detection section according to the first embodiment; FIG. FIG. 2 is a schematic diagram showing a medium thickness detection unit according to the first embodiment; FIG. FIG. 4 is an enlarged view of a part of a lever member, a stylus, and a medium support member of the medium thickness detector according to the first embodiment; 4A and 4B are diagrams showing the operation of the medium thickness detection unit according to the first embodiment; FIG. 2 is a block diagram showing a control system of the image forming apparatus according to the first embodiment; FIG. 5 is a flow chart showing medium thickness detection operation of the first embodiment. 7A to 7E are schematic diagrams showing the medium thickness detection operation of the first embodiment; FIG. FIG. 11 is a block diagram showing a control system of an image forming apparatus according to a second embodiment; FIG. 5 is a flow chart showing medium thickness detection operation of the first embodiment. 7A to 7C are schematic diagrams showing a medium thickness detection operation according to the first embodiment; FIG.

First embodiment.
<Configuration of Image Forming Apparatus>
FIG. 1 is a diagram showing the overall configuration of an image forming apparatus 1 according to the first embodiment of the invention. The image forming apparatus 1 includes a medium transport mechanism (medium transport device) 40 that transports a medium P such as printing paper, an image forming unit 100 that forms a toner image as a developer image, and a toner image that is transferred onto the medium P. It has a transfer unit 20, a fixing device 30 that fixes the toner image on the medium P, and a housing 1A that accommodates them. An openable and closable upper cover 1B is provided on the upper portion of the housing 1A.

The medium transport mechanism 40 includes a paper feed tray 41 containing the medium P, a pickup roller 42 arranged to contact the medium P contained in the paper feed tray 41, and a pickup roller 42 arranged adjacent to the pickup roller 42. It has a feed roller 43 and a retard roller 44 arranged to face the feed roller 43 .

The paper feed tray 41 accommodates media P such as printing paper in a stacked state. The pickup roller 42 rotates in contact with the uppermost medium P among the media P in the paper feed tray 41 and feeds out the medium P from the paper feed tray 41 . The feed roller 43 feeds the medium P fed out by the pickup roller 42 to the transport path. The retard roller 44 rotates in a direction opposite to the feeding direction of the feed roller 43, and provides conveyance resistance to the medium P to prevent double feeding.

The medium transport mechanism 40 also has a registration roller 45, a first transport roller 51, and a second transport roller 52, which are a pair of rollers, along the transport path of the medium P. As shown in FIG. The registration rollers 45 start rotating at a predetermined timing after the leading edge of the medium P comes into contact with the nip portion between the rollers, correct the skew of the medium P, and convey the medium. The first transport rollers 51 and the second transport rollers 52 transport the medium P from the registration rollers 45 to the secondary transfer section 25 (described later) of the transfer unit 20 . The first transport rollers 51 and the second transport rollers 52 constitute a transport section that transports the medium P. As shown in FIG.

A first medium sensor 53 as a medium position sensor is arranged upstream of the first conveying roller 51 in the medium P conveying direction. A second medium sensor 54 is arranged on the downstream side of the second conveying roller 52 . Both the first medium sensor 53 and the second medium sensor 54 detect passage of the leading edge of the medium P.

The image forming section 100 includes process units (image forming units) 10Y, 10M, 10C, and 10K that form yellow, magenta, cyan, and black toner images, and LED heads 11Y, 11M, 11C, and 11K as exposure devices. have. The process units 10Y, 10M, 10C, and 10K are arranged in a line from left to right in the drawing along the traveling direction of an intermediate transfer belt 21 (described later) of the transfer unit 20. FIG.

Since the process units 10Y, 10M, 10C, and 10K have a common configuration except for the toner, they will be referred to as the "process unit 10" unless they need to be distinguished from each other. Similarly, the LED heads 11Y, 11M, 11C, and 11K will be described as "LED heads 11" unless they need to be distinguished from each other.

The process unit 10 includes a photosensitive drum 12 as an image bearing member, a charging roller 13 as a charging member, a developing roller 14 as a developer bearing member, a supply roller 15 as a supply member, and a developer containing member. and a toner cartridge 16 of

The photoreceptor drum 12 is formed by forming a photoreceptor layer (charge generation layer and charge transport layer) on the surface of a cylindrical conductive support. The photosensitive drum 12 is rotated in the direction indicated by the arrow in FIG. 1 (counterclockwise in the drawing) by a drum motor 18 (FIG. 8).

The charging roller 13 is arranged to contact the surface of the photoreceptor drum 12 and rotates following the rotation of the photoreceptor drum 12 . A charging voltage is applied to the charging roller 13 by a charging voltage power source 202 (FIG. 8) to uniformly charge the surface of the photosensitive 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 is attached to the upper cover 1</b>B of the image forming apparatus 1 . The LED head 11 irradiates the surface of the photoreceptor drum 12 with light under the control of the head control unit 207 (FIG. 8) to expose the photosensitive layer of the photoreceptor drum 12 to form an electrostatic latent image.

The developing roller 14 is arranged to contact the surface of the photoreceptor drum 12 , and rotates in a direction (clockwise in the drawing) opposite to the rotational direction of the photoreceptor drum 12 due to rotation transmission from the photoreceptor drum 12 . The developing roller 14 is applied with a developing voltage by a developing voltage power supply 203 (FIG. 8), and develops the electrostatic latent image on the surface of the photosensitive drum 12 with toner.

The supply roller 15 is arranged to contact the surface of the developing roller 14 and rotates in the same direction as the rotating direction of the developing roller 14 (clockwise in the drawing). The supply roller 15 is supplied with a supply voltage from a supply voltage source 204 (FIG. 8) and supplies toner to the developing roller 14 .

The toner cartridge 16 is detachably attached to the upper portion of the process unit 10 and supplies toner to the developing roller 14 and the supply roller 15 . A portion of the process unit 10 that contributes to the development of the electrostatic latent image (that is, a portion including the developing roller 14 and the supply roller 15) is called a developing section.

The transfer unit 20 includes an intermediate transfer belt 21 as an intermediate transfer body, and four primary rollers 10Y, 10M, 10C, and 10K which are arranged to contact the photosensitive drums 12 of the process units 10Y, 10M, 10C, and 10K with the intermediate transfer belt 21 interposed therebetween. It has a transfer roller 22 and a secondary transfer portion 25 that secondarily transfers the toner image on the intermediate transfer belt 21 onto the medium P.

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

A primary transfer voltage is applied to the primary transfer roller 22 by a primary transfer voltage power source 205 (FIG. 8). This primary transfer voltage causes the toner images on the photosensitive drums 12 of the process units 10Y, 10M, 10C, and 10K to be primarily transferred onto 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 motor 29 (FIG. 8) and causes the intermediate transfer belt 21 to run in the direction indicated by arrow B. As shown in FIG. The driven roller 24 applies tension to the intermediate transfer belt 21 . A guide roller 28 is provided between the secondary transfer backup roller 26 and the driven roller 24 to guide the running of the intermediate transfer belt 21 .

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 a secondary transfer backup roller 26 . A secondary transfer portion 25 is configured by the secondary transfer roller 27 and the secondary transfer backup roller 26 . A nip portion between the secondary transfer roller 27 and the secondary transfer backup roller 26 is called a secondary transfer nip.

A secondary transfer voltage is applied to the secondary transfer roller 27 by a secondary transfer voltage power source 206 (FIG. 8). Due to this secondary transfer voltage, the toner image on the intermediate transfer belt 21 is secondarily transferred onto the medium P conveyed to the secondary transfer portion 25 .

The fixing device 30 applies heat and pressure to the medium P onto which the toner image has been transferred by the secondary transfer section 25 to fix the toner image onto the medium P. As shown in FIG. The fixing device 30 has a fixing roller 31 containing a heater 33 ( FIG. 8 ) and a pressure roller 32 pressed against the fixing roller 31 . The fixing roller 31 is rotated by a fixing motor 35 (FIG. 8).

Discharge rollers 46 , 47 , and 48 constituting a discharge section are arranged downstream of the fixing device 30 in the direction in which the medium P is conveyed. The ejection rollers 46 , 47 , 48 are rotated by rotation transmission from the fixing motor 35 ( FIG. 8 ), and eject the medium P on which the toner image is fixed to the outside of the image forming apparatus 1 . A stacker unit 49 on which the ejected medium P is placed is provided in the upper part of the image forming apparatus 1 .

In FIG. 1, the moving direction of the medium P when passing through the secondary transfer portion 25 is the Y direction (more specifically, the +Y direction), and the width direction of the intermediate transfer belt 21 is the X direction. The X direction is parallel to the axial direction of each roller (including the photosensitive drum 12 ) of the process unit 10 , each roller of the medium transport mechanism 40 , the primary transfer roller 22 and the secondary transfer roller 27 . Let the direction parallel to both the X direction and the Y direction be the Z direction. Here, the X and Y directions are parallel to the horizontal plane and the Z direction is vertical.

<Structure of Medium Thickness Detector 50>
FIG. 2 is a partial cross-sectional perspective view showing the medium thickness detection unit 50 as the medium thickness conveying device of the present embodiment, cut at substantially the center in the X direction. The medium thickness detection unit 50 has the first conveying roller 51, the second conveying roller 52, the first medium sensor 53, and the second medium sensor 54 described above.

The first transport roller 51 is composed of an upper roller 51a and a lower roller 51b which are arranged with the transport path of the medium P interposed therebetween. Upper roller 51 a and lower roller 51 b are rotatably attached to frame 101 fixed to housing 1 A of image forming apparatus 1 . A nip portion is formed between the upper roller 51a and the lower roller 51b.

A guide plate 301 that guides the medium P from the registration roller 45 to the first transport roller 51 is provided on the upstream side (−Y direction) of the first transport roller 51 in the transport direction of the medium P. The guide plate 301 has a curved guide surface along the transport path of the medium P from the registration rollers 45 .

The first medium sensor 53 is a swing lever protruding into the transport path of the medium P from the guide plate 301 toward the first transport roller 51 . When the first medium sensor 53 comes into contact with the leading edge of the medium P, the first medium sensor 53 swings around the support shaft 53a. The swinging motion of the first medium sensor 53 is detected by a photosensor 53b arranged below the support shaft 53a (in the -Z direction).

An upper guide 303 and a lower guide 302 that guide the medium P from both sides in the Z direction are provided on the downstream side (+Y direction) of the first conveying roller 51 in the medium P conveying direction. After passing through the first transport rollers 51 , the medium P is guided by the upper guide 303 and the lower guide 302 and transported to the second transport rollers 52 .

The second conveying rollers 52 are composed of an upper roller 52a and a lower roller 52b arranged with the medium P conveying path interposed therebetween. The upper roller 52a and the lower roller 52b are rotatably attached to the frame 101, and a nip portion is formed between the upper roller 52a and the lower roller 52b.

The second medium sensor 54 is a swing lever that protrudes into the conveying path of the medium P from the second conveying roller 52 toward the secondary transfer portion 25 . The second medium sensor 54 abuts on the leading edge of the medium P and swings about the support shaft 54a. The swinging motion of the second medium sensor 54 is detected by a photosensor 54b arranged below the support shaft 54a (in the -Z direction).

3 and 4 are a front view and a perspective view showing the medium thickness detector 50. FIG. FIG. 5 is a schematic diagram showing the main part of the medium thickness detection unit 50 cut at substantially the center in the X direction.

As shown in FIGS. 3 and 4, the frame 101 made of sheet metal includes a support plate 102 that covers the upper roller 51a from above (+Z direction), and a support plate 102 that extends downward (−Z direction) from the end of the support plate 102 in the +Y direction. ). The frame 101 also has a bottom plate 104 located below the lower roller 51b (-Z direction) and a wall portion 105 extending upward (+Z direction) from the end of the bottom plate 104 in the +Y direction.

As shown in FIG. 4, a medium support member 55 that contacts one surface (here, the back surface) of the medium P is arranged downstream (+Y direction) of the first conveying roller 51 in the conveying direction of the medium P. . The medium support member 55 is arranged at the center of the first transport roller 51 in the X direction (that is, the center of the transport path of the medium P).

As shown in FIG. 5 , the medium support member 55 has a contact surface 55 a that contacts the medium P that has passed through the nip portion of the first transport roller 51 . The contact surface 55a is generally parallel to the XY plane, and the side closer to the first conveying roller 51 is curved toward the -Z side. The medium support member 55 is made of resin and has an aluminum deposition film formed on the contact surface 55a.

Media support member 55 has a fixed portion 56 that is secured to wall 105 of frame 101 with screws 107 . The wall portion 105 is formed with a longitudinal groove 106 through which a screw 107 is inserted so that the position of the fixing portion 56 in the Z direction can be adjusted. Thereby, the Z-direction position of the medium support member 55 can be adjusted.

A probe 70 (displacement member) that contacts the other surface (here, the surface) of the medium P is provided in the +Z direction (above) of the medium support member 55 . The probe 70 is arranged so as to sandwich the transport path of the medium P between the medium support member 55 and the probe 70 . The probe 70 has a contact portion 71 on the side facing the medium support member 55 . The contact portion 71 is made of resin, and the surface that comes into contact with the medium P is coated with an aluminum vapor deposition film.

A shaft portion 72 protrudes in the +Z direction from the +Z direction end of the tracing stylus 70 (the end on the side opposite to the medium support member 55). The shaft portion 72 is inserted through a circular hole 108 formed in the support plate 102 and protrudes in the +Z direction from the support plate 102 . The shaft portion 72 has a large-diameter portion 73 (contact portion) having an outer diameter larger than the inner diameter of the hole 108 near the projecting tip. The stylus 70 can be displaced in the Z direction, in other words, in the thickness direction of the medium P, with the shaft portion 72 inserted through the hole 108 .

A lever member 60 for displacing the tracing stylus 70 in the Z direction is provided in the +Z direction of the support plate 102 . The lever member 60 is made of resin such as ABS (acrylonitrile-butadiene-styrene) resin and has a shape elongated in the X direction. The lever member 60 has an action portion 62 that biases the stylus 70 at the end in the -X direction. In addition, the lever member 60 has, at its +X direction end, a contact portion 66 that is pressed by a cam member 80 to be described later.

The lever member 60 has a swing shaft 61 at a position adjacent to the acting portion 62 in the +X direction. The lever member 60 is swingable about the central axis C1 in the Y direction by the swing shaft 61 . The swing shaft 61 is attached to a wall portion 112 (FIG. 2) formed by cutting and raising the frame 101 .

FIG. 6 is a schematic diagram showing the positional relationship between the acting portion 62 of the lever member 60, the stylus 70, and the medium support member 55. As shown in FIG. The action portion 62 of the lever member 60 has a first portion 63 and a second portion 65 that face each other in the Z direction, and a connecting portion 64 that connects these ends in the +X direction. It has a rectangular cross-sectional shape.

The first portion 63 faces the end surface of the shaft portion 72 in the +Z direction. The second portion 65 has a groove portion 65a through which the shaft portion 72 of the stylus 70 is inserted. When the acting portion 62 moves in the -Z direction, the first portion 63 abuts on the end surface of the shaft portion 72 in the +Z direction and biases it in the -Z direction. When the action portion 62 moves in the +Z direction, the second portion 65 abuts on the -Z direction end surface of the large diameter portion 73 as a contact portion and biases it in the +Z direction. Also, the first portion 63 of the action portion 62 is biased in the -Z direction by a spring 68 as a biasing member.

A cam member 80 is provided so as to face the contact portion 66 of the lever member 60 in the +Z direction. The cam member 80 rotates around the rotation axis C2 in the X direction. The cam member 80 has an outer circumferential surface 80a extending in the circumferential direction centered on the rotation axis C2, but a retracted portion 80b without the outer circumferential surface 80a over a certain angular range centered on the rotation axis C2. have.

When the outer peripheral surface 80 a of the cam member 80 faces the contact portion 66 of the lever member 60 , the outer peripheral surface 80 a presses the contact portion 66 , but the retracting portion 80 b faces the contact portion 66 of the lever member 60 . During this time, the retracting portion 80b does not press the contact portion 66. As shown in FIG. The cam member 80 is rotated by a measuring motor 85 (FIG. 8), and is switched between a state in which the lever member 60 is pressed and a state in which the lever member 60 is not pressed.

Returning to FIG. 5, a medium thickness sensor 90 as a detection section is provided between the contact section 66 of the lever member 60 and the pivot shaft 61 so as to face each other. Media thickness sensor 90 is a reflective micro-displacement sensor. More specifically, the medium thickness sensor 90 irradiates the surface of the lever member 60 (here, the surface on the +Z side) with light, receives the reflected light, and optically detects the distance to the surface. Media thickness sensor 90 is secured to sensor housing 111 ( FIG. 2 ) attached to frame 101 .

FIGS. 7A and 7B are schematic diagrams showing the rocking motion of the lever member 60. FIG. FIG. 7A shows a state in which the lever member 60 is not pressed by the cam member 80. FIG. FIG. 7B shows a state where the lever member 60 is pressed by the cam member 80. FIG.

As shown in FIG. 7A, when the lever member 60 is not pressed by the cam member 80, the biasing force of the spring 68 biases the acting portion 62 of the lever member 60 in the -Z direction. As a result, the first portion 63 of the action portion 62 comes into contact with the end surface of the shaft portion 72 of the probe 70 and biases it in the -Z direction. As a result, the contact portion 71 of the tracing stylus 70 moves toward the medium support member 55 and contacts the medium P on the medium support member 55 . The position of the stylus 70 at this time is called the measurement position.

The rotational position of the lever member 60 about the pivot shaft 61 changes depending on the thickness of the medium P between the medium support member 55 and the stylus 70 . Therefore, by detecting the distance between the medium thickness sensor 90 and the lever member 60 with the medium thickness sensor 90, the thickness of the medium P can be detected based on the distance.

On the other hand, as shown in FIG. 7B, when the lever member 60 is pressed in the -Z direction by the cam member 80, the lever member 60 swings counterclockwise in the drawing. Therefore, the acting portion 62 of the lever member 60 moves in the +Z direction against the biasing force of the spring 68 . As a result, the second portion 65 of the action portion 62 comes into contact with the large-diameter portion 73 of the stylus 70 and biases it in the +Z direction. As a result, the contact portion 71 of the probe 70 is separated from the medium P on the medium support member 55 . The position of the stylus 70 at this time is called a standby position. The distance between the measurement position and the retracted position (that is, the amount of displacement of the probe 70) is, for example, 2 to 3 mm.

The cam member 80 presses the lever member 60 as shown in FIG. 7B except when the medium thickness is detected, and the stylus 70 is at the standby position away from the medium P in the +Z direction. The lever member 60 and the cam member 80 constitute a contact/separation mechanism that causes the tracing stylus 70 to approach and separate from the medium support member 55 .

In the above configuration, the conveying rollers 51 and 52, the medium sensors 53 and 54, the medium support member 55, the stylus 70, the lever member 60, the cam member 80, and the medium thickness sensor 90 detect the medium thickness. A unit 50 (medium thickness detection device) is configured.

<Control system>
Next, a control system of the image forming apparatus 1 will be described. FIG. 8 is a block diagram showing the control system of the image forming apparatus 1. As shown in FIG. The image forming apparatus 1 includes a control device 200 , an interface control section 221 , a reception memory 222 , an image data editing memory 223 , an operation section 224 , a sensor group 225 , a first medium sensor 53 , a second medium sensor 54 and a medium thickness sensor 90 . have. The control device 200 also includes a high-voltage power supply control unit 201, a head control unit 207, a drive control unit 208, a belt drive control unit 209, a fixing control unit 210, a fixing drive control unit 211, a paper feed/conveyance control unit 212, and a medium thickness measurement unit. It has a control unit 215 .

The control device 200 includes, for example, a microprocessor, ROM, RAM, input/output ports, timers, and the like. The control device 200 receives print data and control commands via the interface control section 221 and controls the overall operation of the image forming apparatus 1 .

The interface control unit 221 receives print data and control commands from a host device (computer, etc.). The reception memory 222 temporarily stores print data received by the interface control unit 221 . The image data editing memory 223 edits the print data stored in the reception memory 222 to generate and store image data.

The operation unit 224 is provided on, for example, the operation panel 1C (FIG. 1), and includes a display unit (e.g., LED) for displaying the state of the image forming apparatus 1, and an operation input unit (switches and display panel) for receiving input from the operator. etc.). The sensor group 225 includes various sensors that monitor the state of the image forming apparatus 1, such as a temperature/humidity sensor that detects environmental temperature and humidity, and a toner remaining amount sensor that detects the remaining amount of toner.

A high-voltage power supply control unit 201 includes a charging voltage power supply 202 that applies a charging voltage to the charging roller 13, a development voltage power supply 203 that applies a development voltage to the developing roller 14, and a supply voltage power supply 204 that applies a supply voltage to the supply roller 15. A primary transfer voltage power source 205 that applies a primary transfer voltage to the secondary transfer roller 22 and a secondary transfer voltage power source 206 that applies a secondary transfer voltage to the secondary transfer roller 27 are controlled.

The head control unit 207 controls light emission of the LED head 11 based on the image data output from the image data editing memory 223 to the control device 200 . The drive control unit 208 controls rotation of the drum motor 18 that rotates the photosensitive drum 12 . A belt drive control unit 209 controls rotation of a belt motor 29 that rotates the drive roller 23 .

The fixing control unit 210 controls current supplied to the heater 33 (for example, a halogen lamp) of the fixing device 30 based on the detected temperature of the thermistor 34 as a temperature sensor provided in the fixing device 30 . A fixing drive control unit 211 controls rotation of a fixing motor 35 that rotates the fixing roller 31 .

The paper feed transport control unit 212 controls rotation of a paper feed motor 213 that rotates the pickup roller 42 and feed roller 43 and a transport motor 214 that rotates the registration roller 45 and transport rollers 51 and 52 . Both the pickup roller 42 and the feed roller 43 are connected to the paper feed motor 213 via a clutch, and can individually control the rotation timing. Similarly, the registration roller 45 and the transport rollers 51 and 52 are both connected to the transport motor 214 via clutches, and can individually control their rotation timings.

The medium thickness measurement control unit 215 controls rotation of a measurement motor 85 as a drive source for rotating the cam member 80 for swinging the lever member 60 .

<Operation of Image Forming Apparatus>
Next, operations of the image forming apparatus 1 will be described with reference to FIGS. 1 and 8. FIG. The control device 200 of the image forming apparatus 1 starts an image forming operation (printing operation) upon receiving a print command and print data from a host device.

First, the pickup roller 42 rotates to feed the medium P accommodated in the paper feed tray 41, and the feed roller 43 sends out the medium P to the transport path. The retard roller 44 provides conveyance resistance to the medium P to prevent double feeding. Further, the registration rollers 45 start rotating a predetermined time after the leading edge of the medium P reaches the nip portion of both rollers, correct the skew of the medium P, and convey the medium.

When the leading edge of the medium P reaches the first medium sensor 53 and further reaches the downstream side of the medium support member 55, the medium thickness detection operation is performed. This will be described later. The first conveying roller 51 and the second conveying roller 52 convey the medium P whose thickness has been detected toward the secondary transfer section 25 .

On the other hand, in each process unit 10 of the image forming section 100 , the photosensitive drum 12 rotates, and the charging roller 13 rotates following the photosensitive drum 12 . Further, the developing roller 14 and the supply roller 15 are rotated by rotation transmission from the photosensitive drum 12 . Further, the drive roller 23 rotates to cause the intermediate transfer belt 21 to run.

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

A supply voltage is applied to the supply roller 15 to supply toner to the developing roller 14 . A developing roller 14 is applied with a developing voltage and develops the electrostatic latent image on the photosensitive drum 12 with toner to form a toner image (developer image).

A primary transfer voltage is applied to the primary transfer roller 22 when the toner image formed on each photosensitive drum 12 reaches the vicinity of the primary transfer roller 22 . As a result, a toner image is primarily transferred from each photosensitive drum 12 to the intermediate transfer belt 21 . The toner image on the intermediate transfer belt 21 moves toward the secondary transfer portion 25 as the intermediate transfer belt 21 runs.

The toner image on the intermediate transfer belt 21 and the medium P transported by the transport rollers 51 and 52 reach the secondary transfer portion 25 . At this time, the conveying rollers 51 and 52 are rotated based on the detection timing of the second medium sensor 54 so that the leading edge of the toner image on the intermediate transfer belt 21 and the leading edge of the medium P reach the secondary transfer portion 25 at the same time. Rotation is controlled. Further, a secondary transfer voltage is applied to the secondary transfer roller 27 and the toner image on the intermediate transfer belt 21 is secondarily transferred onto the medium P.

The medium P onto which the toner image has been transferred by the secondary transfer portion 25 is conveyed to the fixing device 30 . In the fixing device 30 , the toner image transferred to the medium P is heated and pressed by the fixing roller 31 and the pressure roller 32 to be fixed on the medium P. The medium P on which the toner image is fixed is carried out by the discharge rollers 46 , 47 and 48 and placed on the stacker section 49 . This completes the image forming operation.

In the image forming operation described above, the thickness of the medium P is detected before the secondary transfer of the toner image is performed, and the image forming conditions are adjusted according to the detected thickness. Specifically, the secondary transfer voltage in the secondary transfer section 25 or the fixing temperature in the fixing device 30 is adjusted according to the thickness of the medium P detected.

<Medium thickness detection operation>
Next, the medium thickness detection operation will be described. FIG. 9 is a flow chart showing the medium thickness detection operation. 10A to 10E are schematic diagrams showing the medium thickness detection operation. Note that FIG. 9 also shows the step of feeding and transporting the medium P from the paper feed tray 41 (step S101), which is performed before the medium thickness detection operation.

The control device 200 first rotates the paper feed motor 213 and the transport motor 214 by the paper feed transport control unit 212, and starts transporting the medium P by the pickup roller 42, the feed roller 43, the registration roller 45, and the transport rollers 51 and 52. (step S101, FIG. 10A).

When the leading edge of the medium P reaches the first medium sensor 53 (step S102), the control device 200 causes the paper feeding/conveying control unit 212 to rotate the conveying motor 214 by a predetermined number of revolutions, and then stops to convey the medium P. is stopped (step S103). As a result, as shown in FIG. 10B, the transportation of the medium P stops when the leading edge of the medium P reaches the downstream side of the medium support member 55 . That is, the medium P stops while being supported on the medium support member 55 .

Next, the control device 200 drives the measuring motor 85 by means of the medium thickness measurement control section 215 to rotate the cam member 80, release the pressure of the lever member 60, and move the probe 70 to the measuring position. (Step S104). That is, as shown in FIG. 10(C), the tracing stylus 70 moves in the -Z direction and contacts the surface of the medium P on the medium support member 55 .

In this state, the control device 200 uses the medium thickness sensor 90 to detect the distance from the medium thickness sensor 90 to the lever member 60, and based on this, detects the thickness of the medium P (step S105).

Next, the control device 200 drives the measuring motor 85 by the medium thickness measurement control section 215 to rotate the cam member 80 and press the lever member 60 to move the stylus 70 to the standby position (step S106). That is, as shown in FIG. 10D, the tracing stylus 70 moves in the +Z direction and separates from the surface of the medium P on the medium support member 55 .

Next, the control device 200 causes the sheet feeding/conveying control section 212 to start rotating the conveying motor 214 . As a result, as shown in FIG. 10E, the medium P is started to be transported by the first transport rollers 51 and the second transport rollers 52 (step S107).

Image formation in the process unit 10 and primary transfer onto the intermediate transfer belt 21 are performed in parallel with the operations of steps S101 to S107.

After that, when the leading edge of the medium P passes through the second medium sensor 54 (step S108), the paper feeding/conveyance control section 212 controls the rotation of the conveyance rollers 51 and 52 based on this timing, and the intermediate transfer in the secondary transfer section 25 is performed. The toner image on the transfer belt 21 and the medium P are aligned (step S109). After that, as described above, secondary transfer and fixing of the toner image onto the medium P and ejection of the medium P are performed.

<Effects of the first embodiment>
As described above, in the first embodiment, the stylus 70 is separated from the medium P while the medium P is being conveyed by the conveying rollers 51 and 52 (conveying section). Further, when the conveyance of the medium P is stopped, the stylus 70 comes into contact with the medium P, and the medium thickness sensor 90 (detection section) detects the thickness of the medium P. Since the stylus 70 contacts the medium P while the medium P is stopped, the occurrence of scratches on the surface of the medium P can be suppressed. Since the occurrence of scratches on the surface of the medium before secondary transfer is suppressed, the occurrence of image unevenness such as vertical streaks can be suppressed, and the image quality can be improved.

Further, based on the detection signal of the first medium sensor 53, when the medium P reaches a predetermined position (that is, when the leading edge of the medium P reaches the downstream side of the medium support member 55), the medium P is transported. Since it is stopped and the probe 70 is brought into contact with the medium P, the probe 70 can be reliably brought into contact with the surface of the medium P and its thickness can be detected.

In addition, since the lever member 60 has the action portion 62 on one side of the swing shaft 61 and the cam member 80 (driving portion) is provided on the side opposite to the action portion 62 with respect to the swing shaft 61, , the actuation portion 62 can be moved by the cam member 80 using the principle of leverage.

In addition, since the medium thickness sensor 90 is arranged between the cam member 80 and the swing shaft 61 so as to face the lever member 60, the medium thickness sensor 90 detected by the medium thickness sensor 90 and the lever member 60 The thickness of the medium P can be detected based on the distance of .

In addition, the acting portion 62 of the lever member 60 has a first portion 63 that abuts the probe 70 in the −Z direction (the direction toward the medium support member 55) and a first portion 63 that contacts the probe 70 in the +Z direction (the direction away from the medium support member 55). Since the lever member 60 has the second portion 65 that abuts in the direction of rotation), the rocking motion of the lever member 60 can be converted into movement of the tracing stylus 70 in the Z direction (thickness direction of the medium P) with a simple configuration.

Further, since the axial direction (Y direction) of the swing shaft 61 of the lever member 60 is orthogonal to the width direction (X direction) of the medium P, the lever member 60 is arranged substantially parallel to the first transport roller 51. be able to. That is, the elongated lever member 60 can be efficiently arranged in the space around the first conveying roller 51 .

In addition, since the medium support member 55 and the probe 70 are arranged in the central portion of the transport path in the width direction of the medium P, the thickness of both the medium P with a narrow width and the medium P with a wide width can be detected. can.

Further, since the lever member 60 is driven by the cam member 80, it is possible to keep the stylus 70 in contact with the medium P only when detecting the thickness of the medium, and keep the stylus 70 away from the medium P at other times with a simple configuration. can be maintained.

Second embodiment.
Next, a second embodiment of the invention will be described. FIG. 11 is a block diagram showing the control system of the image forming apparatus according to the second embodiment. The image forming apparatus according to the second embodiment has the same configuration as the image forming apparatus according to the first embodiment except that it has a medium type input section 120 (medium type setting section).

The medium type input unit 120 is a part where the user inputs the type of medium P. FIG. The type of medium P is, for example, plain paper, thick paper, film medium, transfer paper, and the like. The medium type input unit 120 is provided, for example, on the operation panel 1C (FIG. 1) of the image forming apparatus 1, but is not limited to this.

In this second embodiment, a first operation mode in which thickness detection is performed by bringing the stylus 70 into contact with the medium P while transport of the medium P is stopped; and a second operation mode in which thickness detection is performed by contacting the medium P. Either the first operation mode or the second operation mode is selected according to the type of medium P set by the medium type input unit 120 .

Here, the first operation mode is selected when the medium P is a medium that is easily damaged (also called a special medium) such as a film medium or transfer paper. The second operation mode is selected when the medium P is a medium that is not easily damaged, such as plain paper or thick paper.

FIG. 12 is a flow chart showing the medium thickness detection operation of the second embodiment. FIGS. 13A to 13C are schematic diagrams showing the second operation mode of the medium thickness detection operation. The control device 200 of the image forming apparatus determines whether or not the type of medium P set by the medium type input unit 120 is a preset special medium (that is, a medium that is easily scratched) (step S201). In the case of a special medium, steps S101 to S109 (first operation mode) similar to those in the first embodiment are executed.

On the other hand, if the type of medium P set by the medium type input unit 120 is not a special medium, the process proceeds to step S202 to execute the second operation mode. In step S202, the control device 200 drives the measurement motor 85 by means of the medium thickness measurement control section 215 to rotate the cam member 80 and move the probe 70 to the measurement position. The operation of moving the stylus 70 to the measurement position is as described in step S104 (FIG. 9) of the first embodiment.

Next, the control device 200 starts transporting the medium P by the pickup roller 42, the feed roller 43, the registration roller 45, and the transport rollers 51 and 52, as described in the first embodiment (step S203, FIG. 13 ( A)).

When the leading edge of the medium P reaches the first medium sensor 53 (step S204), the distance from the medium thickness sensor 90 to the lever member 60 is measured by the medium thickness sensor 90 when the transport motor 214 rotates a predetermined number of times. The thickness of the medium P is detected based on this (step S205). That is, unlike the first operation mode, the thickness is detected while the medium P is conveyed.

After that, when the leading edge of the medium P passes the second medium sensor 54 (step S108), the toner image on the intermediate transfer belt 21 and the toner image on the intermediate transfer belt 21 are transferred to the secondary transfer portion 25 based on this timing, as described in the first embodiment. Control for alignment with the medium P is performed (step S109). After that, secondary transfer and fixing of the toner image onto the medium P, and ejection of the medium P are performed.

As described above, in the second embodiment, when the medium P is a special medium (that is, a medium that does not easily get scratched), the medium P is brought into contact with the stylus 70 to reduce the thickness. Since the detection is performed, the occurrence of scratches on the surface of the medium P can be suppressed, and the image quality can be improved. In addition, when the medium P is not a special medium (that is, a medium that is not easily scratched), the thickness is detected by bringing the stylus 70 into contact while conveying the medium P, thereby shortening the time required for image formation. be able to.

Here, the type of the medium P is set based on the user's input in the medium type input unit 120 (FIG. 11), but the setting is not limited to this example. For example, the control device 200 may set the type of the medium P based on an instruction from a host device.

In each of the above-described embodiments, the lever member 60 is used to displace the probe 70. However, not only the lever member 60 but also the probe 70 can be displaced between the measurement position and the retracted position. I wish I had.

Further, in each of the above-described embodiments, the cam member 80 is used to swing the lever member 60, but the cam member 80 is not a limitation, and another actuator such as a solenoid may be used.

Further, in each of the embodiments described above, the cam member 80 is rotated by the measurement motor 85, but other drive sources may be used. For example, the cam member 80 is connected via a one-way clutch to a rotation transmission mechanism from the paper feed motor 213 to the registration rollers 45, and when the paper feed motor 213 rotates in the reverse direction, the rotation is not transmitted to the registration rollers 45. , may be transmitted to the cam member 80 .

Moreover, although the medium thickness sensor 90 detects the thickness of the medium P by optically detecting the distance from the lever member 60, for example, a contact-type detection method may be used.

In each of the embodiments described above, an intermediate transfer type image forming apparatus has been described, but the present invention may be applied to a direct transfer type image forming apparatus. Instead of the intermediate transfer belt 21, the direct transfer type image forming apparatus has a transport belt for transporting the medium P onto which the image formed by the image forming section 100 is transferred.

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

Although the preferred embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the scope of the present invention. be able to.

Reference Signs List 1 image forming apparatus 1A housing 1C operation panel 10, 10Y, 10M, 10C, 10K process unit 11, 11Y, 11M, 11C, 11K LED head 12 photoreceptor drum (image carrier) 13 charging roller (charging member) 14 developing roller (developer carrier) 15 supply roller (supply member) 16 toner cartridge (developer container) 20 transfer unit 21 intermediate transfer belt (intermediate transfer member) 22 primary Transfer Roller (Primary Transfer Member) 25 Secondary Transfer Section 26 Secondary Transfer Backup Roller 27 Secondary Transfer Roller (Secondary Transfer Member) 30 Fixing Device 40 Medium Conveying Mechanism (Medium Conveying Device) 50 Medium Thickness detector (medium thickness detector) 51 First conveying roller (conveying unit) 52 Second conveying roller (conveying unit) 53 First medium sensor (medium position sensor) 54 Second medium sensor (medium position sensor ( hole portion), 66 contact portion, 68 spring, 70 probe, 71 contact portion, 72 shaft portion, 73 large diameter portion (contact portion), 80 cam member (contact/separation mechanism, driving portion), 85 motor for measurement (driving source) 90 medium thickness sensor (detecting section) 100 image forming section 101 frame 120 medium type input section (setting section) 200 control device.

Claims (10)

a transport unit that transports the medium;
a medium support member arranged in the medium transport path and supporting the medium;
a probe that faces the medium support member across the transport path and is displaceable in the thickness direction of the medium;
a detection unit that detects the thickness of the medium based on the displacement of the probe;
a contact/separation mechanism that causes the probe to approach and separate from the medium support member;
The contact/separation mechanism is
a lever member that is swingable about a swing shaft and has an action portion that acts on the stylus on one side with respect to the swing shaft;
a driving portion provided on the side opposite to the action portion with respect to the swing shaft of the lever member and swinging the lever member;
The detecting unit is arranged between the driving unit and the swing shaft so as to face the lever member, and detects the thickness of the medium based on the distance from the lever member detected by the detecting unit. is detected and
The acting portion has a first portion that contacts the probe in a direction toward the medium support member and a second portion that contacts the probe in a direction away from the medium support member,
When the conveying unit conveys the medium, the contact/separation mechanism separates the probe from the medium,
The contact/separation mechanism brings the stylus into contact with the medium, and the detecting unit detects the thickness of the medium when the conveying unit stops conveying the medium. detection device. further comprising a medium position sensor that detects that the medium has reached a predetermined position on the transport path;
2. The medium thickness detection according to claim 1, wherein the conveying unit stops conveying the medium based on the detection result of the medium position sensor, and the contact/separation mechanism brings the stylus into contact with the medium. Device. The second portion has a hole,
The probe includes a shaft portion extending through the hole portion of the second portion and extending toward the first portion, and a shaft portion provided on the shaft portion that contacts the periphery of the hole portion of the second portion. 3. The medium thickness detection device according to claim 1, further comprising a contact portion that makes contact. 4. The medium thickness detection device according to claim 1 , wherein the direction of said swing axis is perpendicular to the width direction of said medium. further comprising a setting unit for setting the type of the medium;
Based on the setting of the setting unit,
When the conveying unit is conveying the medium, the contact/separation mechanism separates the probe from the medium, and when the conveying unit stops conveying the medium, the contact/separation mechanism causes the a first operation mode in which the sensing element is brought into contact with the medium and the detection unit detects the thickness of the medium;
5. The method according to any one of claims 1 to 4 , characterized in that switching is performed between a second operation mode in which the detecting unit detects the thickness of the medium while the conveying unit is conveying the medium. A media thickness detection device as described. The medium thickness detection device according to claim 5 , wherein the setting unit is an input unit through which a user inputs the type of the medium. The medium thickness detection device according to any one of claims 1 to 6 , wherein the probe and the medium support member are arranged in a central portion of the transport path in the width direction of the medium. . The medium thickness detection device according to any one of claims 1 to 7 , wherein the driving portion is a cam member. A medium conveying device comprising the medium thickness detecting device according to any one of claims 1 to 8 . A medium thickness detection device according to any one of claims 1 to 8 ;
and an image forming unit that forms an image on the medium whose thickness is detected by the medium thickness detecting device.

Images