JP5685949B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that detects the presence or absence of a recording medium in a conveyance path.

  There has been proposed a technique for determining that a recording medium is present in a detection area when the detection area provided on the transport path is irradiated with detection light and the light receiving unit receives the reflected light (see Patent Document 1). . In Patent Document 1, a roller is provided outside a detection region in a direction orthogonal to the conveyance direction for conveying a recording medium. By providing a roller outside the detection area in the direction orthogonal to the transport direction, the posture of the recording medium can be stabilized in the detection area without the roller interfering with detection light or reflected light.

JP 2001-97608 A

However, there is a problem that wrinkles and slack cannot be prevented from propagating to the detection area along the conveyance direction by the roller of Patent Document 1 provided outside the detection area in the direction orthogonal to the conveyance direction. When wrinkles or slack in the recording medium propagates to the detection area, the detection light is reflected in a direction different from the direction in which the light receiving unit can receive light, and there is no recording medium even though the recording medium exists in the detection area. Will be misjudged.
The present invention has been made in view of the above problems, and an object of the present invention is to stably detect a recording medium even when wrinkles and slack propagate along the conveyance direction.

  In order to achieve the above object, an image forming apparatus of the present invention includes a recording medium support unit that supports a recording medium in at least a part of a conveyance path for conveying the recording medium in the conveyance direction. The detection unit includes a light emitter and a light receiver, and the light emitter irradiates detection light on a detection region provided in the transport path. The light receiver receives reflected light of the detection light from the recording medium present in the detection area. The pressing roller presses the recording medium toward the recording medium support portion in a pressing area provided in the conveyance path. Here, the position where the pressing area is provided in the conveyance direction of the recording medium is upstream of the detection area. Furthermore, the range in which the pressing area is provided in the direction orthogonal to the transport direction includes the entire range in which the detection area is provided in the orthogonal direction.

  By pressing the recording medium against the recording medium support by the pressing roller, wrinkles and slack of the recording medium can be eliminated in the pressing area. Here, since the pressing area is located upstream of the detection area in the transport direction, wrinkles or slack of the recording medium can be prevented from propagating along the transport direction from the upstream of the transport direction to the detection area. Furthermore, since the range in which the pressing area is provided in the direction orthogonal to the transport direction includes the entire range in which the detection area is provided, wrinkles and slack propagate from the upstream in the transport direction along the transport direction over a wide range of the detection area. Can be prevented. Therefore, the recording medium can be kept flat in the detection area, and the reflection angle of the reflected light in the detection area can be stabilized. That is, the light receiver of the detection unit can stably receive the reflected light. In addition, when the leading end of the recording medium is located in the detection area, the recording medium can be pressed against the recording medium support in the pressing area upstream from the detection area, and the reflection angle of the reflected light at the leading end is stable. Can be

  Furthermore, a downstream pressing roller that presses the recording medium against the recording medium support portion in the downstream pressing area downstream of the detection area may be provided. Thereby, it is possible to prevent wrinkles or slack of the recording medium from propagating along the transport direction from the downstream in the transport direction to the detection area. In addition, when the rear end of the recording medium is located in the detection area, the recording medium can be pressed against the recording medium support in the pressing area downstream from the detection area, and the reflection angle of the reflected light at the rear end can be stabilized. Can be

  Further, a roller support portion that supports the pressing roller so as to allow separation from the recording medium support portion, and an elastic member that urges the pressing roller so as to approach the recording medium support portion may be provided. Here, since the pressing roller presses the recording medium against the recording medium support portion, the recording medium is conveyed between the pressing roller and the recording medium support portion. That is, when the recording medium is conveyed, it is necessary to insert the recording medium between the pressing roller and the recording medium support unit. On the other hand, by providing the roller support portion, the pressing roller can be separated from the recording medium support portion, and the recording medium can be inserted between the pressing roller and the recording medium support portion. Further, by providing an elastic member that urges the pressing roller so as to approach the recording medium support portion, the recording medium can be pressed against the recording medium support portion by the pressing roller.

  In the pressing area, the recording medium is flattened by the pressing roller. However, when the recording medium is deformed between the detection area and the pressing area, the angle of the recording medium in the detection area becomes unstable. When the recording medium is provided with a supply unit that unwinds the recording medium wound around the winding core and supplies the recording medium to the conveying path, the recording medium is detected in the conveying direction so as to restore the shape wound around the winding core. Try to bend between the area and the pressing area. In particular, the higher the rigidity of the recording medium, the stronger the restoring force to the shape wound around the core, and the smaller the diameter of the core, the more the recording medium tends to bend with a smaller radius of curvature. Therefore, the higher the rigidity of the recording medium and the smaller the diameter of the supply roll, the shorter the distance between the detection area and the pressing area in the transport direction and the curving of the recording medium between the detection area and the pressing area is prevented. It is desirable to do.

1 is a block diagram illustrating a circuit configuration of an image forming apparatus. (2A) is a side view of the image forming apparatus, and (2B) is a front view of a recording medium support. (3A) to (3D) are side views of the pressing roller, and (3E) is a schematic diagram of the recording medium.

Hereinafter, embodiments of the present invention will be described in the following order with reference to the accompanying drawings.
(1) Configuration of image forming apparatus:
(2) Conveyance path configuration:
(3) Distance between detection area and pressing area:
(4) Other embodiments:

(1) Configuration of image forming apparatus:
FIG. 1 is a block diagram showing a circuit configuration of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 includes a control unit 10, a detection circuit 20, a print head control circuit 30, and a conveyance control circuit 40. The control unit 10 includes a CPU, a ROM, a RAM, an ASIC, and the like, and executes various arithmetic processes for controlling the detection circuit 20, the print head control circuit 30, and the conveyance control circuit 40.

  The detection circuit 20 is connected to a detection unit 21 including a light emitter 22 and a light receiver 23. The detection circuit 20 generates a drive current for causing the light emitter 22 of the detection unit 21 to emit light based on the control signal from the control unit 10, and outputs the drive current to the light emitter 22. The light emitter 22 includes, for example, a light emitting diode that emits visible light having a predetermined wavelength toward a predetermined detection region when a drive current is supplied. The light receiver 23 includes a photodiode that generates a direct current corresponding to the received light intensity of the received visible light, for example, and outputs the direct current to the detection circuit 20 as a detection signal. The detection circuit 20 acquires the detection signal output from the light receiver 23, and determines whether the light reception intensity in the light emitter 22 is larger than a predetermined threshold based on the detection signal. The detection circuit 20 outputs determination data indicating whether the received light intensity is greater than a threshold value to the control unit 10.

  When the determination data indicating that the received light intensity in the light emitter 22 is larger than the threshold value is acquired, the control unit 10 determines that the recording medium exists in the detection area. Conversely, when the determination data indicating that the received light intensity is equal to or less than the threshold value is acquired, the control unit 10 determines that there is no recording medium in the detection area. Furthermore, when the state where the determination data indicating that the received light intensity is less than or equal to the threshold value is changed to the state where the determination data indicating that the received light intensity is greater than the threshold value is obtained, the control unit 10 It is determined that the leading end has passed the detection area. On the other hand, when the state where the determination data indicating that the received light intensity is larger than the threshold value is changed to the state where the determination data indicating that the received light intensity is equal to or less than the threshold value is changed, the control unit 10 records the recording medium. It is determined that the rear end portion of has passed the detection region.

  The print head control circuit 30 generates a drive signal for driving the print head 31 based on the control signal from the control unit 10 and outputs the drive signal to the print head 31. The image forming apparatus 1 of the present embodiment is a so-called line printer, and the print head 31 has a width that is greater than the width of the recording medium in a direction orthogonal to the conveyance direction of the recording medium. The print head 31 includes a plurality of discharge nozzles arranged in a direction perpendicular to the conveyance direction of the recording medium. The print head 31 includes a driving element corresponding to each of the plurality of ejection nozzles, and ink droplets are ejected from the plurality of ejection nozzles when the driving element is driven based on the driving signal. Ink droplets ejected from the plurality of ejection nozzles land on the recording medium, and dots arranged in the direction perpendicular to the transport direction are formed on the recording medium.

  The transport control circuit 40 generates a drive signal for driving the transport motor 41 based on the control signal from the control unit 10 and outputs the drive signal to the transport motor 41. The driving force of the transport motor 41 is transmitted to the transport drive roller 41a via a gear and a belt (not shown), and the transport drive roller 41a is rotationally driven. When the conveyance drive roller 41a is rotationally driven, a force for conveying the recording medium is transmitted to the recording medium, and the recording medium is conveyed in the conveyance direction. Further, the transport control circuit 40 generates a drive signal for driving the supply motor 42 based on the control signal from the control unit 10 and outputs the drive signal to the supply motor 42. The driving force of the supply motor 42 is transmitted to a supply roll 42a as a supply unit via a gear and a belt (not shown), and the supply roll 42a is rotationally driven. As the supply roll 42a rotates, the recording medium is unwound to the transport path.

(2) Conveyance path configuration:
FIG. 2A is a side view schematically showing the conveyance path of the image forming apparatus 1. The image forming apparatus 1 conveys the recording medium M wound around the core 42a1 of the supply roll 42a to the space between the print head 31 and the platen 54 in the main body casing 1a, and the print head 31 faces the recording medium M. Thus, dots are formed on the recording medium M by ejecting ink droplets. The conveyance direction of the recording medium M is a direction from the supply roll 42a toward the print head 31 (a direction toward diagonally lower left in FIG. 2A). The recording medium M has a certain width in the direction orthogonal to the transport direction (width direction).

  The supply roll 42a located at the uppermost stream of the transport path includes a winding core 42a1 and a recording medium M wound along the side surface of the winding core 42a1. The winding core 42a1 is formed in a columnar shape, and the direction of the central axis of the winding core 42a1 coincides with the direction orthogonal to the conveyance direction of the recording medium M. The recording medium M is unwound to the downstream conveyance path when the supply roll 42a rotates around the central axis. The recording medium M of the present embodiment is formed by laminating a plurality of films formed of different materials in the thickness direction. For example, the recording medium M is processed into a packaging bag by performing welding molding after printing. Further, for example, in order to protect the contents of the bag from light rays or the like, metal is deposited on a part of the film, and the recording medium M has a high reflectance.

  The recording medium support unit 50 is provided downstream of the supply roll 42 a in the conveyance direction of the recording medium M. The recording medium M unwound from the supply roll 42 a is supported from below by the recording medium support unit 50. The recording medium support unit 50 is substantially plate-shaped, and the recording medium M is in contact with the planar upper surface of the recording medium support unit 50 in parallel, and is conveyed downstream while sliding on the upper surface. . Thereby, the recording medium M can be stably conveyed on the upper surface of the recording medium support part 50. The recording medium M is not limited to the case where the recording medium M is unwound and supplied from the supply roll 42 a, but the single-sheet recording medium M cut in a predetermined length unit in the transport direction is placed on the recording medium support unit 50. Is also supplied. In FIG. 2A, a direction perpendicular to the upper surface of the recording medium support 50 is indicated as a Z direction.

  The transport driving roller 41 a and the transport driven roller 41 b are provided downstream of the recording medium support unit 50 in the transport direction of the recording medium M. The recording medium M conveyed along the upper surface of the recording medium support unit 50 is sandwiched between the lower conveyance driving roller 41a and the upper conveyance driven roller 41b. The transport driving roller 41a and the transport driven roller 41b are formed in a cylindrical shape in which the axial direction of each central axis coincides with the orthogonal direction of the transport direction of the recording medium M, and rotate around the central axis. The driving force of the transport motor 41 is transmitted to the transport driving roller 41a, and the transport driving roller 41a is rotationally driven by the driving force. When the conveyance driving roller 41a is rotationally driven, the recording medium M sandwiched between the conveyance driving roller 41a and the conveyance driven roller 41b is conveyed downstream in the conveyance direction. As the recording medium M is transported by the transport driving roller 41a, the transport driven roller 41b is driven to rotate.

  The print head 31 and the platen 54 are provided downstream of the transport driving roller 41a and the transport driven roller 41b in the transport direction of the recording medium M. That is, the recording medium M transported further downstream from the transport driving roller 41 a and the transport driven roller 41 b is supplied between the print head 31 and the platen 54. Further, when the recording medium M is conveyed downstream, the recording medium M is discharged out of the main body housing 1a.

  FIG. 2B is a diagram illustrating the top surface of the recording medium support unit 50 as viewed from the Z direction. The recording medium support 50 is formed with a through hole 51 that passes through the recording medium support 50 in the Z direction. The through hole 51 is formed in the recording medium support unit 50 in the transport direction of the recording medium M (broken line) and at the center position in the orthogonal direction. As shown in FIG. 2A, the detection unit 21 is provided above the through hole 51 in the Z direction, and the light emitter 22 irradiates the detection light L <b> 1 toward the through hole 51. In the recording medium M, the detection light L1 is irradiated to a portion existing at a position where the through hole 51 is blocked from above in the Z direction, and the detection region A (circular shape) that is the region irradiated with the detection light L1 in the portion. Hatching) is formed. The detection light L1 irradiated to the detection area A is totally reflected (mirror reflection) on the recording medium M and becomes reflected light L2.

  Here, when the recording medium M is supported in parallel with the upper surface of the recording medium support unit 50, the incident angle of the detection light L1 with respect to the recording medium M (difference between the Z direction and the optical axis direction of the detection light L1). Is set to be equal to or greater than the critical angle of the recording medium M. The light receiving optical axis of the light receiver 23 coincides with an axis obtained by rotating the light emitting optical axis of the light emitter 22 by 180 degrees around the axis in the Z direction passing through the center of the detection region A. As a result, when the recording medium M exists at a position where the through hole 51 is blocked from above and the recording medium M is supported at an angle close to parallel to the upper surface of the recording medium support 50, the detection light L1 is generated. The totally reflected light L 2 is received by the light receiver 23. The detection area A is smaller than the through hole 51.

  Here, when the recording medium M does not exist at a position blocking the through hole 51 from above, the detection light L1 passes through the through hole 51, and the light receiver 23 does not receive the reflected light L2. Accordingly, it is determined that the light reception intensity of the light receiver 23 is equal to or less than a predetermined threshold, and the control unit 10 determines that the recording medium M does not exist in the detection area A. Further, when the recording medium M exists at a position where the through hole 51 is blocked from above, the reflected light is reflected when the angle of the recording medium M is not parallel to the upper surface of the recording medium support 50 at the through hole 51. The optical axis of L2 is deviated from the received optical axis of the light receiver 23. Here, since the detection area A has a predetermined range (for example, a circle having a diameter of 1 mm) and the light receiver 23 has a predetermined allowable range in the angle of the light receiving optical axis, the recording medium M in the detection area A and the recording medium Even if the upper surface of the support portion 50 is not strictly parallel, the light receiver 23 receives the reflected light L2. However, the greater the angle difference between the recording medium M and the upper surface of the recording medium support 50 in the detection area A, the smaller the received light intensity of the reflected light L2 received by the light receiver 23. That is, when the angular difference between the recording medium M in the detection area A and the upper surface of the recording medium support unit 50 is smaller than a predetermined angle, the control unit 10 determines that the recording medium M exists in the detection area A. On the other hand, when the angle difference between the recording medium M and the upper surface of the recording medium support unit 50 in the detection area A is equal to or larger than a predetermined angle, the control unit 10 determines that the recording medium M does not exist in the detection area A. .

  As shown in FIGS. 2A and 2B, a pressing roller 52 is provided upstream of the detection area A in the conveyance direction of the recording medium M. Further, a downstream pressing roller 53 is provided downstream of the detection area A in the conveyance direction of the recording medium M. The pressing roller 52 and the downstream pressing roller 53 are each formed in a columnar shape in which the direction of the central axis coincides with the orthogonal direction of the conveyance direction of the recording medium M, and rotates about the central axis. The lengths of the pressing roller 52 and the downstream pressing roller 53 in the direction orthogonal to the conveyance direction of the recording medium M are equal to each other and longer than the width of the detection area A in the direction orthogonal to the conveyance direction of the recording medium M. The center position of the pressing roller 52 and the downstream pressing roller 53 in the direction orthogonal to the transport direction matches the position of the center of the detection area A in the direction orthogonal to the transport direction.

  3A and 3B are side views showing the pressing roller 52 as viewed from the outside in the direction orthogonal to the conveyance direction of the recording medium M. FIG. Since the downstream pressing roller 53 has the same configuration as the pressing roller 52, the illustration and description of the downstream pressing roller 53 are omitted. The pressing roller 52 is connected to the lower end of the swing member 52a via the rotation shaft P1. At the upper end of the swing member 52a, there is provided a rotation shaft P2 whose axial direction coincides with the direction orthogonal to the conveyance direction of the recording medium M. The upper end of the swing member 52a and the connecting member 52b are connected via the rotation shaft P2. Are connected. The connecting member 52b is rigidly joined to the fixing member 52c. Although not shown, the fixing member 52c is rigidly joined to the main body housing 1a. Since the swinging member 52a can rotate about the rotation axis P2 at the upper end, the pressing roller 52 connected to the lower end of the swinging member 52a is separated from the state in which the pressing roller 52 approaches the upper surface of the recording medium support 50 (FIG. 3A) ( 3B) is allowed. Further, the fixed member 52c and the swing member 52a are connected via a spring 52d as an elastic member, and the swing member 52a has a pressing roller 52 connected to the lower end by an elastic force that the spring 52d tries to extend. The recording medium support unit 50 is urged to approach.

  With the configuration of the roller support portions (52a to 52d) described above, as shown in FIG. 3B, the pressing roller 52 is separated from the recording medium support portion 50 against the elastic force of the spring 52d. The leading end of M can be inserted between the transport driving roller 41a and the transport driven roller 41b. Similarly, the downstream pressing roller 53 can be separated from the recording medium support 50.

  On the other hand, when the recording medium M is transported on the upper surface of the recording medium support unit 50 as shown in FIG. 3A, the recording medium M is recorded by the pressing roller 52 biased to approach the recording medium support unit 50. It can be pressed against the medium support 50. Of course, since the pressing roller 52 is rotated freely around the rotation axis P <b> 1 orthogonal to the conveyance direction of the recording medium M, the influence of the frictional resistance of the pressing roller 52 on the conveyance of the recording medium M can be suppressed. The pressing roller 52 and the downstream pressing roller 53 press the recording medium M toward the recording medium support portion 50, so that the pressing area B1 where the pressing roller 52 and the downstream pressing roller 53 press the recording medium M as shown in FIG. 2B. (Rectangular hatching) and downstream pressing area B2 (rectangular hatching) are formed on the recording medium M. Here, as indicated by a thick line on the horizontal axis (conveying direction) in FIG. 2B, the pressing area B1 corresponding to the pressing roller 52 is located upstream from the detection area A, and the downstream pressing area corresponding to the downstream pressing roller 53. B2 is a position downstream of the detection area A. 2B, the range in which the pressing area B1 and the downstream pressing area B2 are provided in the direction orthogonal to the conveyance direction of the recording medium M is indicated by the orthogonal line. The entire range in which the detection area A is provided in the direction is included.

  As described above, since the pressing area B1 and the downstream pressing area B2 are respectively provided upstream and downstream of the detection area A in the transport direction, wrinkles and slack of the recording medium M from the upstream and downstream in the transport direction along the transport direction. Can be prevented from propagating to the detection region A. Furthermore, since the range in which the pressing area B1 and the downstream pressing area B2 are provided in the direction orthogonal to the transport direction includes the entire area in which the detection area A is provided, the upstream of the transport direction along the transport direction in the wide range of the detection area A. And it is possible to prevent wrinkles and slack from propagating from the downstream. Therefore, the recording medium M can be kept flat and parallel to the recording medium support 50 in the detection area A, and the reflection angle of the reflected light L2 reflected by the detection area A can be stabilized. That is, the light receiver 23 of the detection unit 21 can receive the reflected light L2 stably. Accordingly, it can be determined that the recording medium M does not exist even though the recording medium M exists in the detection area A. That is, it is possible to prevent problems such as prompting replenishment or replacement of the recording medium M or issuing a conveyance abnormality warning even though the recording medium M exists in the detection area A.

  For example, when the recording medium M is transported obliquely (when the edge in the width direction of the recording medium M is transported so as not to be orthogonal to the axial direction of the central axis of the transport driving roller 41a), The edge comes into contact with a guide portion (not shown) that guides the recording medium M from the outside in the width direction at the recording medium support portion 50, and the recording medium M may be wrinkled in the width direction. In this way, even when wrinkles occur, wrinkles and slack can be prevented from propagating to the detection area A from the upstream and downstream in the transport direction along the transport direction. Further, since the pressing area B1 and the downstream pressing area B2 are wider than the detection area A in the direction orthogonal to the transport direction, even when wrinkles occur outside the detection area A in the direction orthogonal to the transport direction, It is possible to prevent wrinkles from propagating to the detection area A inside the pressing area B1 and the downstream pressing area B2.

  In the transport path of the present embodiment, the transport drive roller 41 a and the supply roll 42 a transmit external force to the recording medium M. Therefore, the conveyance drive roller 41a and the supply roll 42a are likely to be a starting point for causing wrinkles and slack in the recording medium M. For example, when the unwinding amount of the recording medium M by the supply roll 42a is larger than the conveyance amount of the recording medium M by the transport driving roller 41a, the recording medium M may be slackened starting from the supply roll 42a. Propagation to the detection area A beyond the area B1 can be prevented. On the other hand, when the unwinding amount of the recording medium M by the supply roll 42a is smaller than the conveyance amount of the recording medium M by the conveyance driving roller 41a, excessive tension is applied to the recording medium M between the conveyance driving roller 41a and the supply roll 42a. And non-uniform slip occurs in the width direction at the transport drive roller 41a. In this case, since the tension of the recording medium M is not uniform in the width direction, wrinkles that undulate in the width direction may occur from the transport driving roller 41a, but the wrinkles propagate to the detection area A beyond the downstream pressing area B2. Can be prevented.

  3C and 3D are side views showing a state in which the end of the recording medium M in the transport direction is located in the detection area A. FIG. As shown in FIG. 3C, when the leading end of the recording medium M is located in the detection area A, the recording medium M exists upstream from the detection area A. Accordingly, the recording medium M can be pressed against the recording medium support 50 in the pressing area B1 upstream from the detection area A, and the leading end of the recording medium M can be detected stably. Further, as shown in FIG. 3D, when the rear end of the recording medium M is located in the detection area A, the recording medium M exists downstream from the detection area A. Therefore, the recording medium M can be pressed against the recording medium support 50 in the downstream pressing area B2 downstream of the detection area A, and the rear end of the recording medium M can be detected stably.

(3) Distance between detection area and pressing area:
As shown in FIGS. 3C and 3D, the recording medium M is in contact with the recording medium support portion 50 in parallel in the section from the detection area A to the pressing area B1 and the section from the detection area A to the downstream pressing area B2. If so, the leading end and the trailing end of the recording medium M can be detected stably. However, since the recording medium M is curved in these sections, the reflection angle of the reflected light L2 in the detection area A is greatly deviated from the light receiving optical axis of the light receiver 23, and the leading end and the rear end of the recording medium M are displaced. It cannot be detected stably. In particular, when the recording medium M is supplied from the supply roll 42a, the recording medium M tends to be curved so as to be convex upward in the Z direction in an attempt to restore the shape wound around the supply roll 42a. Note that the recording medium M formed by laminating a plurality of films formed of different materials in the thickness direction as in the present embodiment has non-uniform mechanical properties in the thickness direction. Easy to bend.

  FIG. 3E is a schematic diagram illustrating a state in which the recording medium M is curved in a section from the detection area A to the pressing area B1. As shown in FIG. 3E, the recording medium M curves upward in the Z direction from the edge of the pressing area B1, and the recording medium M curves again so that the leading end contacts the recording medium support 50 again. Here, as the rigidity EI of the recording medium M is higher, the shape wound around the supply roll 42a is maintained against the gravity and the tension between the transport driving roller 41a and the supply roll 42a. The recording medium M is greatly curved. Further, as the diameter of the supply roll 42a is smaller, the recording medium M can be deformed with a smaller radius of curvature, so that the recording medium M is greatly curved as indicated by a broken line. The radius of the supply roll 42a can be reduced to the radius r (FIG. 2A) of the core 42b1. That is, the higher the rigidity EI of the recording medium M and the smaller the radius r of the core 42b1, the greater the angle difference between the leading end located in the detection area A and the upper surface of the recording medium support 50. Here, when the angle difference between the recording medium M and the upper surface of the recording medium support 50 in the detection area A is equal to the limit angle α, the received light intensity of the reflected light L2 received by the light receiver 23 is equal to the threshold value. To do. That is, when the angle difference between the recording medium M in the detection area A and the upper surface of the recording medium support 50 is larger than the limit angle α, it is determined that the recording medium M does not exist in the detection area A.

  In the present embodiment, the distance D1 from the detection area A to the pressing area B1 is set by the following procedure. That is, among the supply rolls 42 a that can be mounted on the image forming apparatus 1, the supply roll 42 a having the highest rigidity EI of the recording medium M and the smallest radius r of the core 42 b 1 is mounted on the image forming apparatus 1. Note that a supply roll 42a having a remaining amount of the recording medium M smaller than a predetermined amount is mounted on the image forming apparatus 1 so that the recording medium M wound near the winding core 42b1 is unwound. Then, while changing the distance d from the detection area A to the pressing area B1, the angle difference between the leading end of the recording medium M located in the detection area A and the upper surface of the recording medium support section 50 is investigated, thereby determining the angle. The distance d that makes the difference equal to the limit angle α is specified. Note that the smaller the distance d from the detection area A to the pressing area B1, the smaller the angle difference between the leading end of the recording medium M and the upper surface of the recording medium support 50. When the distance d is specified, a distance obtained by subtracting a predetermined safety distance (for example, 0.1 × d) from the distance d is set as an upper limit value of the distance D1 from the detection area A to the pressing area B1. Thereby, the leading end of the recording medium M can be stably detected regardless of the supply roll 42a mounted on the image forming apparatus 1. Furthermore, the pressing area B1 and the downstream pressing area B2 do not interfere with the through hole 51, and the pressing roller 52 and the downstream pressing roller 53 are detected both in the state of approaching the recording medium support unit 50 and in the separated state. The distance that does not interfere with the light L1, the reflected light L2, and the detection unit 21 itself is set as the lower limit value of the distance D1. The distance D1 belonging to the range from the lower limit value to the upper limit value set as described above is set. The distance D2 between the detection area A and the downstream pressing area B2 is also set by the same method.

(4) Other embodiments:
The image forming apparatus 1 of the embodiment includes the pressing roller 52 and the downstream pressing roller 53. However, even when the image forming apparatus 1 includes only the pressing roller 52, wrinkles or slack in the detection area A from the upstream in the transport direction. Can be prevented from propagating. The pressing roller 52 and the downstream pressing roller 53 are only required to be able to press the recording medium M against the recording medium support unit 50. For example, the recording medium M is recorded by its own weight with the pressing roller 52 and the downstream pressing roller 53. You may press against the support part 50. FIG. The pressing roller 52 and the downstream pressing roller 53 may be biased by an elastic member other than the spring 52d, and may be biased by a highly elastic resin such as rubber, for example. The spring 52d is not limited to a coil spring as shown in FIGS. 3A and 3B, and may be a leaf spring, a torsion spring, or the like. Further, it is only necessary not to prevent the recording medium M from being inserted from the upstream side, and the downstream pressing roller 53 is not necessarily supported so as to be separated from the recording medium support unit 50. That is, only the pressing roller 52 may be supported so as to be separated from the recording medium support unit 50.

  Further, in the direction orthogonal to the transport direction, the range in which the pressing area B1 and the downstream pressing area B2 are provided may include the entire area in which the detection area A is provided, and the pressing area B1 and the downstream pressing area B2 are provided. The range where the detection area A is provided may be equal. The range in which the pressing area B1 and the downstream pressing area B2 are provided in the orthogonal direction is preferably as wide as possible. For example, the range where the frictional resistance generated by the pressing roller 52 and the downstream pressing roller 53 does not hinder the conveyance of the recording medium M is wide. May be. Of course, the ranges in which the pressing area B1 and the downstream pressing area B2 are provided may be different from each other in the direction orthogonal to the transport direction. The recording medium support unit 50 desirably supports the recording medium M widely. However, in the present invention, the recording medium support unit 50 may be provided at least in a region facing the pressing region B1 and the downstream pressing region B2.

  Furthermore, the present invention can be applied to any image forming apparatus 1 as long as it is a transport image forming apparatus 1 that detects the recording medium M transported in the transport path. For example, the present invention can be applied to other recording type image forming apparatuses such as an inkjet type serial printer and a laser printer other than the inkjet type. Further, the pressing roller 52 may be provided in the image forming apparatus 1 provided with the supply roll 42a that only follows the rotation, or the supply unit that does not include the supply roll 42a and supplies only the single sheet recording medium M. The pressing roller 52 may be provided in the image forming apparatus 1 provided.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 10 ... Control part, 20 ... Detection circuit, 21 ... Detection part, 22 ... Light emitter, 23 ... Light receiver, 30 ... Print head control circuit, 31 ... Print head, 40 ... Conveyance control circuit, 41 DESCRIPTION OF SYMBOLS ... Conveyance motor, 41a ... Conveyance drive roller, 41b ... Conveyance driven roller, 42 ... Supply motor, 42a ... Supply roll, 42a1 ... Core, 50 ... Recording medium support part, 51 ... Through-hole, 52 ... Pressing roller, 52a ... Oscillating member, 52b ... connecting member, 52c ... fixing member, 53 ... downstream pressing roller, A ... detection area, B1 ... pressing area, B2 ... downstream pressing area, L1 ... detection light, L2 ... reflected light, M ... recording medium .

Claims (3)

A recording medium support unit for supporting the recording medium in at least a part of a conveyance path for conveying the recording medium in the conveyance direction;
A detector including a light emitter that emits detection light to a detection region provided in the transport path, and a light receiver that receives reflected light of the detection light from the recording medium present in the detection region;
A pressing roller for pressing the recording medium toward the recording medium support portion in a pressing area provided in the transport path;
A supply unit for feeding the recording medium to the transport path by unwinding the recording medium wound around a winding core;
With
The position where the pressing area is provided in the transport direction is upstream of the detection area,
The range in which the pressing region are provided in the direction orthogonal to the conveying direction, viewed contains the entire range of the detection area in the orthogonal direction is provided,
The distance between the detection area and the pressing area in the transport direction is shortened as the rigidity of the recording medium is high and the diameter of the winding core is small.
Image forming apparatus. A downstream pressing roller that presses the recording medium toward the recording medium support portion in a downstream pressing area downstream of the detection area in the transport direction;
The image forming apparatus according to claim 1. A roller support portion that supports the pressing roller so as to allow separation from the recording medium support portion;
An elastic member for urging the pressing roller so as to approach the recording medium support;
The image forming apparatus according to claim 1, further comprising:

Images