JP2007001185A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which surely detects the floating of a recording medium without causing erroneous detection, which may collide with a printing head to cause damages to the printing head, irrespective of the shape of floating nor the type of the recording medium. <P>SOLUTION: In the image forming apparatus, a collision detection mechanism 20, which is constituted of a plurality of detection devices arranged in the sheet width direction comprising a sensing member 21 of the floating of a recording medium, a rotary shaft 22, a rotary transmission part 23, a rocking piece 24 and a detection sensor 26, is provided on the upper stream side of the sheet transferring direction of a carriage 16 which supports the plurality of printing heads 15 of an image recording section 4. The respective detecting sensitivity of the floating sheet of the plurality of detection devices can be differently set corresponding to the quality and size of the sheet and the shape of floating sheet. The sensitivity can be set by the positional movement of the detection sensor or the change of the length by the sensing member 21 of the floating of the recording medium, or by the setting change of the output level of the detection sensor or the effective position. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention can reliably detect the lift of the recording medium that does not detect the lift of the recording medium that collides with the print head and causes damage to the print head regardless of the shape of the lift from the recording medium transport mechanism or the type of the recording medium. The present invention relates to an image forming apparatus that detects an image.

  In general, in an inkjet image forming apparatus, in order to accurately and accurately record an image on a recording medium, a plurality of recording nozzles of the print head are recorded while the print head records an image on the recording medium. It is necessary to keep the distance between the recording medium and the recording medium at an optimum distance for recording.

  However, the recording medium often floats from the recording medium transport unit for various reasons. If the floating of the recording medium is large, the interval between the recording medium and the recording head is out of the set interval, so that the recording as set on the recording medium cannot be performed. In addition, the recording medium may collide with the recording head and the recording nozzle may be damaged.

As a method for preventing the collision between the recording medium and the recording head, a collision warning sensor is arranged over the entire recording width of the image forming apparatus, that is, the entire width of the ink jet nozzle row of the printing head, and the recording medium that causes the collision is used. A device that detects the lift is known. (For example, refer to Patent Document 1.)
JP 2001-328246 A ([Summary], FIG. 1)

  However, if the type of recording medium to be used is different, for example, the recording medium is hard, soft, the surface is rough and the frictional resistance is high, the surface is well-prepared and the frictional resistance is low, etc. If they are different, even if the floating height of the recording medium is the same, the contact resistance to the detection member of the collision detection sensor that detects the floating of the recording medium is different.

  Therefore, if the collision detection sensor is adjusted according to the recording medium with high contact resistance, the recording medium with low contact resistance cannot be detected, and the recording medium floating at an inconvenient height is conveyed to the print head as it is. End up.

  On the other hand, if the collision detection sensor is adjusted according to the recording medium with low contact resistance, the collision detection sensor reacts sensitively, and it detects even the floating within the appropriate range that does not require detection of the recording medium, There was a possibility of canceling printing.

  In addition, the shape of the lift of the recording medium is not constant.For example, when both ends of the recording medium are lifted depending on the type and storage state of the recording medium, the usage environment, etc. In the case where a plurality of lifts occur in the width direction, a difference occurs in the shape of the lifts.

  As an example, when both ends of the recording medium are lifted, the suction height of the recording medium transport mechanism is attracted to the recording medium transport mechanism, and the height of the lift is reduced, but in the case of a hard recording medium or a stiff recording medium Then, it is not attracted to the recording medium transport mechanism and remains in a lifted state.

  In this case, since the floating recording medium has a degree of freedom in the vertical direction, if a physical force is applied such that the detection member of the collision detection sensor comes into contact with the recording medium from above, recording is performed. The lifted shape of the medium escapes downward, and depending on the adjustment of the collision detection sensor, the lift of the recording medium may not be detected and may pass through.

  As another example, when both sides are adsorbed and the central part is lifted, both sides are adsorbed, so that the physical strength of the lifted part is increased regardless of the type of the recording medium, such as flexibility or thickness. Tend. That is, if this raised portion collides with the print head, the possibility of damaging the print head increases.

  Therefore, it is necessary to reliably detect the height at which the raised shape of the central portion of such a recording medium collides with the print head. If the collision detection sensor is made sensitive in order to reliably detect the floating of the center of the recording medium, the collision detection sensor reacts to the floating parts on both sides that do not collide with the print head. There was a possibility that the printing would be stopped due to the detection.

  SUMMARY OF THE INVENTION In view of the above-described conventional situation, an object of the present invention is to provide a recording medium that collides with the print head and causes damage to the print head regardless of the shape of the lift from the recording medium conveyance mechanism of the recording medium or the type of the recording medium. It is an object of the present invention to provide an image forming apparatus that reliably detects the rising of the image without erroneous detection.

  The configuration of the image forming apparatus according to the present invention will be described below.

  An image forming apparatus according to the present invention includes a recording medium conveyance mechanism that conveys a recording medium, a recording head that is fixed to the apparatus main body and is conveyed by the recording medium conveyance mechanism, and a recording head that includes the recording head. A collision warning sensor located upstream of the recording medium conveyance mechanism in the recording medium conveyance direction, and the collision warning sensor includes a recording medium floating sensing member for sensing a floating portion of the recording medium. And a detection sensor that detects a change in the state of the recording medium floating detection member, and the recording medium floating detection member extends in a direction perpendicular to the conveyance direction of the recording medium and in the width direction of the recording medium, and The sensitivity for detecting the rising of the recording medium is configured to have at least two values in the width direction.

  The recording head may be an inkjet head, for example. Further, for example, a plurality of the detection sensors may be provided.

  Further, in this image forming apparatus, the recording medium floating detection member is formed so as to have at least two values as a distance from the recording medium, for example. In this case, for example, the recording medium floating detection member is configured such that the gap between the recording medium at the center in the width direction is smaller than the gap with the recording medium at the end in the width direction. Is done.

  In the image forming apparatus, the recording medium floating detection member may be divided into a plurality of parts. In this case, the recording medium floating sensing member may be configured to have, for example, at least two values as the distance from the recording medium, and has, for example, at least two values as detection sensitivity for the recording medium. In addition, for example, the detection amplitude for the recording medium may be configured to have at least two values.

  According to the present invention, it is possible to reliably detect the floating of the recording medium that collides with the print head and causes damage to the print head without erroneous detection.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the recording medium includes, for example, paper 9 and the like, the recording medium transport mechanism includes, for example, a paper feeding unit 2 and a platen unit 3, and the collision warning sensor includes, for example, a collision It consists of a detection mechanism 20 and the like.

  FIG. 1 is a side view schematically showing a configuration of a main part of the image forming apparatus according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 includes a paper feeding unit 2, a platen unit 3, an image recording unit 4, and a recording medium discharge unit 5.

  The paper feed unit 2 includes a paper tray 6, a pickup roller 7, and a registration roller pair 8. The paper tray 6 can store at least one cut sheet-like paper 9 as a recording medium. In this example, a plurality of sheets 9 are stored in the sheet tray 6.

  In FIG. 1, the direction along the conveyance direction of the paper 9 is shown as the Y axis, and the direction orthogonal to the Y axis on the surface on which the image of the paper 9 is formed during image recording is shown as the X axis. The direction orthogonal to the Y axis is shown as the Z axis.

  The pickup roller 7 is a paper take-out mechanism that takes out the paper 9 from the paper tray 6 one by one. The pickup roller 7 is rotatably supported by a frame of a main body device (not shown) (image forming apparatus 1, the same applies hereinafter).

  The registration roller pair 8 is rotatably supported by the frame of the main unit. The registration roller pair 8 is a conveyance direction adjustment unit that corrects the skew of the sheet 9 taken out by the pickup roller 7, that is, aligns the sheet 9 with the conveyance direction (Y-axis direction).

  The registration roller pair 8 is also a paper feeding unit that feeds the aligned paper 9 to the platen unit 3 in accordance with the timing of image formation on the paper 9 in the image recording unit 4.

  The platen unit 3 is a transport device that transports the paper 9 fed from the paper feed unit 2 during image recording. As shown in FIG. 1, the platen unit 3 includes a platen belt 10, a plurality of platen belt rollers 11, a driven roller 12, a platen frame 13, and a platen suction unit 14.

  The platen belt 10 and the plurality of platen belt rollers 11 cooperate to constitute a belt conveyor that conveys the paper 9 along the Y axis. The sheet 9 is conveyed by the platen belt 10 between the platen sheet conveyance areas a and b.

  The platen belt 10 and the platen belt roller 11 are assembled with their conveying directions set so as to convey the paper 9 along the Y axis throughout the image recording.

  The driven roller 12 is disposed at a position facing the platen belt roller 11 in the Z-axis direction across the platen belt 10 at the upstream end of the platen belt 10 in the sheet conveyance direction, and prevents the sheet 9 from lifting up. Yes. The platen frame 13 and the platen suction part 14 will be described later.

  The image recording unit 4 disposed close to the platen belt 10 is an ink ejection device for ejecting ink onto the paper 9. The image recording unit 4 includes a plurality of print heads 15 (15c, 15k, 15m, and 15y) and a carriage 16 that supports these print heads 15.

  The print head 15 is composed of an aggregate of image recording heads for recording images. The print head 15 is provided for each color. For example, in this example, the print heads 15c, 15k, 15m, and 15y eject inks of cyan, black, magenta, and yellow, respectively.

  Further, the print head 15 is formed to have the same size as or larger than the maximum width of the paper 9 used in the image forming apparatus 1. That is, when the image forming apparatus 1 is set to record on a maximum of A3 size paper, the width of the print head 15 is set to be equal to or larger than the width of the A3 size paper.

  The recording medium discharge unit 5 is disposed on the downstream side of the platen belt 10 and the image recording unit 4 in the sheet conveyance direction. The recording medium discharge unit 5 is a mechanism for discharging the sheet 9 on which the image is recorded by the image recording unit 4 to the outside of the main body apparatus. As shown in FIG. 1, the recording medium discharge unit 5 includes a discharge unit conveying roller pair 17, a discharge unit discharge roller pair 18, and a discharge tray 19.

  The discharge unit conveyance roller pair 17 takes over the conveyance of the sheet 9 conveyed from the platen unit 3 and conveys the sheet 9 toward the discharge unit discharge roller pair 18. The discharge unit discharge roller pair 18 discharges the sheet 9 conveyed from the discharge unit conveyance roller pair 17 to the discharge tray 19.

  Here, as an embodiment of the present invention, a collision detection mechanism 20 is installed between the paper feeding unit 2 and the image recording unit 4. The collision detection mechanism 20 includes a recording medium floating detection member 21, a rotation shaft 22, a rotation transmission unit 23, a swing piece 24, a support unit 25, and a detection sensor 26. Details of these configurations and functions will be described later.

  FIG. 2 is a top view schematically showing the platen portion 3. In FIG. 2, the platen belt 10 is shown by cutting away a substantially right half of the drawing in the Y-axis direction for convenience of explaining the configuration of the platen portion 3.

  As shown in FIG. 2, the plurality of platen belt rollers 11 are arranged so that the platen belt 10 is parallel to the X axis and the Y axis between the platen sheet conveyance areas a and b where the platen belt 10 and the image recording unit 4 face each other. Further, the platen belt 10 is supported.

  A belt roller drive motor 27 that rotates the platen belt roller 11 is connected to at least one of the platen belt rollers 11. In the example shown in the figure, a belt roller drive motor 27 is connected to the rotation shaft 11-1 of the platen belt roller 11 at the downstream end of the platen belt 10 in the sheet conveying direction.

  Further, the platen belt 10 is provided with a plurality of suction holes 28 formed throughout. A platen frame 13 shown in FIG. 1 for supporting the platen belt 10 in a planar manner is provided below the platen belt 10.

  The platen frame 13 rotatably supports the platen belt roller 11 and holds a platen suction part 14 (see FIG. 1). The platen frame 13 has a surface along the X-axis and Y-axis directions, and a plurality of grooves 29 extending in the Y-axis direction are formed over the entire region facing the platen belt 10.

  A suction hole 31 is provided in a substantially central portion of each groove 29. A platen suction portion 14 shown in FIG. 1 is fixedly disposed on the platen frame 13. The platen suction part 14 is provided with a platen chamber (not shown). The suction hole 31 communicates with the platen chamber.

  The platen chamber has a negative pressure generating source for making a negative pressure in its own chamber. This negative pressure generating source is a known negative pressure generating device such as a fan. The platen chamber sucks air from the suction hole 31 by the negative pressure of the negative pressure generation source, and sucks the paper 9 being conveyed through the platen belt 10. That is, the platen suction unit 14 is a negative pressure generating device that generates a negative pressure for attracting the paper 9 to the platen belt 10.

  Next, the collision detection mechanism 20 that constitutes a main part of the present invention will be described. As shown in FIG. 1, the collision detection mechanism 20 is installed between the paper feeding unit 2 and the image recording unit 4.

  FIG. 3 is a perspective view showing in detail the collision detection mechanism 20 of the image forming apparatus 1 according to the present embodiment. In FIG. 3, the same components as those shown in FIG. 1 are denoted by the same reference numerals as those in FIG.

  As shown in FIG. 3, the support part 25 is fixed to the carriage 16 (see FIG. 1) whose upper end is not shown in FIG. Both end portions have support arms 25-1 projecting substantially at right angles, and the recording medium floating detection member 21 and the rotation transmission portion 23 are connected to the tips of the support arms 25-1 via the rotation shaft 22. Is rotatably supported.

  Note that the recording medium floating detection member 21 and the rotation transmission unit 23 are configured integrally. Further, the recording medium floating detection member 21 is disposed so as to extend perpendicularly to the conveyance direction (Y-axis direction) of the paper 9 (Z-axis direction) and in the width direction (X-axis direction) of the paper 9.

  A swing piece 24 is attached to one end portion (left end portion in FIG. 3) of the rotation transmitting portion 23 at a substantially right angle. The swinging piece 24 is provided with a swinging claw 24-1 formed by bending a portion extending sideways to a substantially right angle.

  When the recording medium floating detection member 21 rotates in a pendulum shape in the Y-axis direction as indicated by a double-sided arrow c in the figure with the rotation shaft 22 as a fulcrum, the rotation is oscillated through the rotation transmission unit 23. 24, the swing piece 24 rotates like a pendulum, and the swing claw 24-1 of the swing piece 24 rotates like a pendulum in the Z-axis direction (pendulum motion) as shown by an arrow d in the figure. )

  A detection sensor 26 is disposed at the pendulum movement position of the swinging claw 24-1. The detection sensor 26 is a transmissive photosensor, and is fixed to the notch bent portion 25-2 of the support portion 25. The detection sensor 26 is a detection sensor that turns on and off the switch by the pendulum movement of the swinging claw 24-1, and its detection output is transmitted to a platen unit drive control unit (not shown) via a wiring (not shown).

  In the configuration of the collision detection mechanism 20 described above, when the sheet 9 is a sheet that collides with the print head 15, the collision detection mechanism 20 detects the sheet 9 before the sheet 9 is conveyed under the print head 15. Is done.

  When detected by the collision detection mechanism 20, a detection signal output from the detection sensor 26 is transmitted to the platen unit drive control unit. The platen unit drive control unit stops the driving of the belt roller drive motor 27, for example, and prevents the occurrence of a problem that the sheet 9 collides with the print head 15.

  As an example of the method for detecting the paper 9 having a shape that collides with the print head 15, the distance between the print head 15 and the platen belt 10 is measured, and the thickness tl of the object that collides with the print head 15 is clarified.

  Next, when the sheet 9 having the thickness tl tries to pass under the collision detection mechanism 20, the sheet 9 comes into contact with the recording medium floating detection member 21 and passes through the recording medium floating detection member 21 and the rotation transmission unit 23. The interval t2 between the recording medium floating detection member 21 and the platen belt 10 is set such that the swing piece 24 is swung, and the switch of the detection sensor 26 is turned on or off by the pendulum movement of the swung swing piece 24. Set.

  Thereby, when the sheet 9 having the thickness tl passes under the collision detection mechanism 20, the recording medium floating detection member 21 contacts the sheet 9 and rotates (or swings), and the rotation transmitting unit 23. The swinging piece 24 swings, the pendulum motion of the swinging piece 24 is detected by the detection sensor 26, the detection signal is transmitted to the platen unit drive control unit, and the driving of the belt roller drive motor 27 is stopped. The paper 9 is prevented from colliding with the print head 15.

  In the above description, the thickness of the paper 9 is detected. However, this thickness is not actually the thickness of the paper 9 itself, but the height of lifting from the surface of the platen belt 10.

  FIG. 4 is a diagram for explaining typical shapes of various types of paper that cause the paper 9 to lift from the surface of the platen belt 10.

  As shown in FIG. 4, the paper 9 (9-1, 9-2, 9-3) is like a paper 9-1 shown in the upper part of FIG. 4 on a surface perpendicular to the paper transport direction (Y-axis direction). And a shape in which the center is convex upward like the paper 9-2 shown in the center of FIG. 4, or a warp of both ends like the paper 9-3 shown in the lower part of FIG. Various unique shapes occur depending on the type of paper and the storage environment, such as a shape combined with a central convex shape.

  The heights p and p 'from the platen belt 10 surface where both ends warp upward, the height q from the platen belt 10 surface where the center is convex upward, both ends and the center are both up The heights r, r ′, r ″, etc., from the surface of the platen belt 10 of the convex portion become the “floating portion” of the paper 9 from the surface of the platen belt 10.

  FIG. 5 is a diagram showing a detailed shape of the recording medium floating detection member 21 as the first embodiment of the collision detection mechanism 20 in the image forming apparatus 1 of the present embodiment. FIG. 5 shows two types of recording medium floating sensing members 21-1 and 21-2 having different shapes on the upper and lower sides.

  In this example, the shape of the end surface of the recording medium floating detection member 21 (21-1, 21-2) facing the sheet 9 (not shown in FIG. 5) is detected on the sheet 9 (9-1, 9-2, The uneven shape is formed in accordance with the floating shape of 9-3), and detection according to the floating shape of the paper 9 is performed.

  For example, in the case of the floating shape of the sheet 9-3 shown in the lower part of FIG. 4, the recording medium floating detection member 21-1 having the shape shown in the upper part of FIG. 5 is used. The lower end surface of the recording medium floating detection member 21-1 facing the sheet 9 is divided into three regions: a lower end surface 21-1a at the center and a lower end surface 21-1b at both ends.

  The distance between the lower end surface 21-1a at the center and the paper 9 is not uniform in the width direction of the paper 9, but is different, and has two distance values. In other words, the lower end surface 21-1a at the center is a convex shape having a step from the lower end surfaces 21-1b at both ends.

  Thereby, the detection sensitivity of the sheet 9 floating by the lower end surface 21-1a at the center of the recording medium floating detection member 21-1 is set higher than the detection sensitivity of the sheet 9 floating by the lower end surface 21-1b at both ends. be able to. That is, it is possible to detect the height of the warp at both ends of the sheet 9-3 and the height of the central corrugated convex at different detection levels.

  By the way, the floating height of the paper 9 that collides with the print head 15 differs depending on the type of curl of the paper 9 such as warpage or corrugated convex shape.

  For example, since the height of the curl that starts to collide with the print head 15 is higher than that of the corrugated convex shape, warpage is caused by using the shape of the recording medium floating sensing member 21-2 shown in the lower part of FIG. Thus, it is possible to correctly detect the dangerously-shaped paper 9 without detecting the printable paper 9 sensitively or detecting the paper 9 colliding with the print head. .

  The shape of the sheet detection end face of the recording medium floating detection member 21-1 shown in FIG. 5 is a stepped shape, but there may be a plurality of steps, and the value of the step is not two but three. There may be more than one. Further, as shown in the lower part of FIG. 5, the sheet detection end face has a continuously changing shape with a substantially arc shape at the center, and the interval between the lower end of the recording medium floating detection member 21-2 and the sheet 9 is as follows. It may be a curve that is not uniform in the width direction of the paper 9 and that the interval value has an infinite number of continuous values.

  As described above, the shape of the sheet detection end face of the sensing member 21 can be appropriately determined depending on the type of the sheet 9 to be used and the floating state.

  For example, when the influence of the floating of the central portion of the sheet 9 is smaller than that of the end portion, the central portion of the sheet detecting end surface is opposite to the shape of the recording medium floating detecting member 21-1 shown in FIG. A concave shape may be used. Further, the sheet detection end face may be divided into any number as long as it is two or more instead of three areas.

  Further, the continuously changing shape such as the recording medium floating sensing member 21-2 shown in the lower part of FIG. 5 is not limited to an arc, and may be a more complicated curve. Also, the arc shape and the figure shown in the lower part of FIG. It is also possible to combine with a shape having a step shown above 5.

  FIG. 6 is a diagram showing a detailed shape of the recording medium floating detection member according to the second or fourth embodiment to be described later of the collision detection mechanism 20 in the image forming apparatus 1 of the present embodiment.

  In this example, the recording medium floating detection member of the collision detection mechanism 20 is divided into a plurality of pieces as shown in FIG. In the example shown in FIG. 6, the recording medium floating sensing member of this example has eight recording medium floating sensing members 32 (32-1, 32-2, 32-3, 32-4, 32-5, 32-6). , 32-7, 32-8).

  Further, the eight detection transmission pieces 33 (33-1, 33-2, 33-3, 33-4, 33-5, 33-) are also integrated with the eight recording medium floating detection members 32. 6, 33-7, 33-8).

  Individual detection of the recording medium floating sensing member 32 (32-1, 32-2, 32-3, 32-4, 32-5, 32-6, 32-7, 32-8) divided as described above. The sensitivities are not the same and are non-uniformly adjusted to have at least two detection sensitivities.

  As a method for adjusting the detection sensitivity of the individual recording medium floating detection member 32, with respect to a portion where sensitivity is desired to be sensitive, the interval t2 between the recording medium floating detection member 32 and the platen belt 10 described with reference to FIG. Narrower than.

  On the other hand, with respect to the part where the detection sensitivity is to be made insensitive, the interval t2 between the recording medium floating detection member 32 and the platen belt 10 is adjusted to be wider than the other parts.

  As another method, with respect to a part where sensitivity is to be made sensitive, the amplitude of the pendulum motion of the swing piece 24 (see FIGS. 1 and 3) of the recording medium floating sensing member 32 at that part is the other part. The detection sensor 26 is installed to be turned on or off in a state shorter than the swing width of the pendulum motion.

  On the other hand, with respect to a portion where the detection sensitivity is to be made insensitive, the amplitude of the pendulum motion of the swing piece 24 of the recording medium floating sensing member 32 at that portion is longer than the amplitude of the pendulum motion of the other portion. By setting the switch of the detection sensor 26 to be turned on or off, the detection sensitivity is adjusted to be insensitive.

  In order to adjust the detection sensitivity in accordance with the correspondence relationship between the swing width of the pendulum motion of the swing piece 24 and the detection sensor 26, the adjustment is performed when the detection sensitivity is made sensitive or insensitive. The detection sensor 26 can be easily adjusted by moving the position of the detection sensor 26 relative to the member 32 in either the vertical direction.

  For example, when it is desired to positively detect the sheet 9-3 having a shape in which the warpage of both ends shown in FIG. 4 and the convex shape at the center are combined, the recording medium floating detection member at the center of FIG. The detection sensitivity of 32-3, 32-4, 32-5, and 32-6 is made more sensitive than the recording medium rest detection pieces 32-1, 32-2, 32-7, and 32-8 on both sides. Adjust to.

  In addition, when it is desired to positively detect the sheet 9-1 having both ends warped upward as shown in FIG. 4, the recording medium rest detection pieces 32-1, 32-2, and 32-7 at both ends, and The detection sensitivity of 32-8 is adjusted to be more sensitive than the detection sensitivity of the recording medium floating detection members 32-3, 32-4, 32-5, and 32-6 at the center.

  As described above, according to the recording medium floating detection member 32 of this example, it is possible to perform detection according to the floating shape of the paper 9 to be detected.

  Also, depending on the difference in detection purpose, such as detecting even a slight float of the paper 9, or detecting only a wide float, or detecting only a long float, the on-time of the detection sensor 26 or By setting the length (period) of the off time, the sensitivity of the recording medium floating sensing member 32 can be adjusted to arbitrarily detect the shape abnormality of the paper 9 to be detected.

  FIG. 7 is a diagram for explaining the detailed configuration and operation of the collision detection mechanism as the third embodiment in the image forming apparatus of the present embodiment.

  In FIG. 7, for convenience of illustration and description, the recording medium floating detection member 21, the rotation shaft 22, and the detection transmission piece 23 provided in the collision detection mechanism 20 shown in FIG. The mounting position of the swing piece 24 integrated with the detection transmission piece 23 is shown on the opposite side to the case of FIG. 1, but the function and operation of this example described below includes the swing piece 24. The orientation of the mounting position is not relevant.

  Further, the structural relationship between the swing piece 24 and the two detection sensors 26 in the collision detection mechanism 20 described below is the first and second embodiments shown in FIGS. 5 and 6 described above and the fourth described later. This embodiment can also be applied.

  As shown on the left side of FIG. 7, in the collision detection mechanism 20 of this example, two detection sensors 26 (26-1 and 26-2) are arranged with respect to the swing piece 24.

  Also in the case of the recording medium floating detection member 21 in this configuration, the entire recording medium floating detection member 21, the detection transmission piece 23, and the swing piece 24 are brought into contact when the lower end surface 21 a is in sliding contact with a shape abnormality portion of the sheet 9 (not shown). As shown in the center of FIG. 7, the rotary shaft 22 is rotated in the counterclockwise direction with the rotary shaft 22 as a fulcrum.

  With this rotation, the swing piece 24 rotates from the position corresponding to the upper detection sensor 26-1 toward the lower detection sensor 26-2. With such a configuration, it is possible to perform detection corresponding to the quality of the paper 9 such as hardness, waist strength, and shape.

  For example, when the sheet 9 is hard, when the floating portion of the sheet 9 comes into contact with the lower end surface 21 a of the recording medium floating detection member 21, the recording medium floating detection member 21 swings greatly. Along with the swing, the swing piece 24 swings greatly.

  The hard paper 9 is individually detected by arranging the positions of the switches 26-1a and 26-2a of the detection sensor 26 (26-1, 26-2) at a position corresponding to the swing width of the swing piece 24. It becomes possible.

  Alternatively, when the paper 9 is soft, even if the floating portion of the paper 9 comes into contact with the recording medium floating sensing member 21, the weight of the recording medium floating sensing member 21 and the detection transmission piece 23 and the bottom of the recording medium floating sensing member 21 Since the sheet 9 loses the resistance from the end face 21a, the shape of the floating portion of the sheet 9 changes, and the recording medium floating sensing member 21 cannot be swung greatly. It will be minute.

  Accordingly, by installing the detection sensor 26-1 so that the position of the switch 26-1 a of the detection sensor 26-1 is aligned with the swing width of the small swing piece 24, the soft paper 9 Can be detected individually.

  As described above, according to this example, it is possible to perform detection according to the detailed floating shape of the paper 9.

  The state shown on the left in FIG. 7 is a state in which the recording medium floating detection member 21 does not detect the sheet 9, the switch 26-1a of the detection sensor 26-1 is on, and the switch 26- of the detection sensor 26-2. 2a shows an off state.

  Further, the state shown in the center of FIG. 7 is a state in which the recording medium floating detection member 21 detects, for example, the soft paper 9 (or starts to detect an abnormal shape), and the swinging width of the swinging piece 24 is small. The moving piece 24 is located between the switch 26-1a of the detection sensor 26-1 and the switch 26-2a of the detection sensor 26-2, and the switches 26-1a and 26-2a of the detection sensors 26-1 and 26-2 are both together. The state is turned off.

  The state shown on the right side of FIG. 7 is a state in which the recording medium floating detection member 21 detects, for example, the hard paper 9 (or starts to detect a large abnormal shape), and the swinging width of the swing piece 24 is large. The swing piece 24 is moved from the position of the detection sensor 26-1 to the position of the detection sensor 26-2. As a result, the switch 26-1a of the detection sensor 26-1 is turned off, and the switch 26-2a of the detection sensor 26-2 is turned on.

  As described above, since the combination of three types of outputs can be obtained by the two detection sensors, which detection sensor is used to detect the sheet 9 is used by an input from an operation panel (not shown) by the operator. The type of the paper 9 may be selected and adjusted so that detection is performed by a detection sensor that matches the selected paper 9 as described above.

  Of course, as shown in FIG. 7, the number of detection sensors 26 is not limited to two, and it is possible to detect the floating shapes of various types of sheets 9 by installing the number corresponding to the sheet 9 to be detected. .

  Further, the collision detection mechanism 20 that does not use a plurality of detection sensors 26 performs adjustments suitable for the respective sheets 9 before being incorporated into the image forming apparatus 1, and after being incorporated, the adjustment state before incorporation is maintained. However, if a plurality of detection sensors 26 are used as described above, the sheet 9 to be used is selected from the operation panel without removing the collision detection mechanism 20 from the image forming apparatus 1 and readjustment. It is possible to detect the floating shapes of various types of paper 9 simply by doing so.

  If a sensor capable of analog output with respect to the swing width of the swing piece 24 is used as the detection sensor 26, the detection sensitivity can be changed by changing the detection level with respect to the output value of one detection sensor. In this case, it is possible to freely control the detection level at any time from the controller of the image forming apparatus 1, and it is possible to freely correspond to various sheets 9 and floating.

  In the configuration shown in FIG. 6, the detection method according to the floating shape of the sheet 9 has been described, but in this example, the dimension in the width direction perpendicular to the conveyance direction of the sheet 9 is the recording medium floating detection member 32. The detection of the floating shape of the sheet 9 when the dimension is smaller than the dimension in the array width direction will be described.

  As an example of the case where the width dimension with respect to the conveyance direction of the sheet 9 is smaller than the dimension in the arrangement width direction of the recording medium floating sensing members 32, for example, the dimension in the conveyance width direction of the sheet 9 is the recording medium. A case where the floating sensing member 32 is half the dimension in the array width direction will be described.

  First, the detection of the floating shape of the sheet 9 when the sheet 9 is conveyed with the center of the sheet 9 in the conveyance width direction aligned with the center of the platen unit 3 in the conveyance width direction will be described. To do.

  In this case, the shape of the sheet 9 is set by an input from the operation panel (not shown) by the operator, so that the recording medium floating sensing members 32-3, 32-4, 32-5, and 32-6 are displayed. The sheet 9 is set to be detected by the two recording medium floating detection members 32.

  As described above, when the size of the sheet 9 in the transport width direction is half, the shape of the sheet 9 to be positively detected is, for example, that of the sheet 9-1 having a shape in which both ends warp upward as shown in FIG. In such a case, in the configuration of FIG. 6, the desired detection can be performed by adjusting the recording medium floating detection members 32-3 and 32-6 to be more sensitive than others.

  In addition, for the detection of a limited location such as detecting only the convex shape of the central portion of the paper 9, for example, by setting the detection sensor of the portion desired to be detected from the operation panel (not shown) by the operator to a usable state, It is also possible to detect only a limited part.

  Next, when the supply method of the sheet 9 is conveyed toward the end of the platen unit 3, that is, the alignment of the sheet 9 with respect to the platen unit 3 is performed at any end in the conveyance width direction of the sheet 9 (for example, downstream in the conveyance direction (The right end toward the side) is aligned with any end in the transport width direction of the platen unit 3 (for example, the right end toward the downstream side in the transport direction) and the sheet 9 is floated The detection of will be described.

  First, also in this case, the conveyance method of the paper 9 and the width dimension perpendicular to the conveyance direction of the paper 9 are set on an operation panel (not shown). Depending on the setting, when the size of the paper 9 is half of the dimension in the arrangement width direction of the recording medium floating sensing member 32 as described above, the recording medium floating sensing members 32-1, 32-2, 32-3, 32- Adjustment is performed so that up to four recording medium floating detection members 32 detect the recording medium.

  Next, when it is desired to detect the floating shape of the paper 9 to be used with high sensitivity, for example, to detect the floating of the central portion, the detection sensitivity of the recording medium floating detection members 32-2 and 32-3 is made sensitive. Set by input from the operation panel.

  Contrary to the above, when it is desired to detect the floating of both ends of the paper 9, the detection sensitivity of the recording medium floating detection members 32-1 and 32-4 is set by input from the operation panel so as to be sensitive. Do.

  As described above, regardless of whether the paper 9 having a small width dimension is transported at the center position, aligned at the edge, or has a plurality of paper 9 shapes, the paper 9 can be transported only by setting the operation panel. 9 floating shapes can be detected.

  As described above in detail, according to the present invention, it is possible to detect the lifting shape of the paper 9 from a predetermined position such as the platen surface according to the type of the paper 9 and the lifting shape. Before the paper 9 collides with the print head, it is possible to detect a floating shape that may cause a collision and prevent the print head from being damaged.

  As shown in the above embodiments, according to the present invention, the recording medium floating detection member is configured such that the sensitivity for detecting the rising of the recording medium differs in the width direction. Regardless of the shape of the lift from the medium transport mechanism and the type of the recording medium, it is possible to reliably detect the lifting of the recording medium that collides with the print head and causes damage to the print head without erroneous detection.

1 is a side view schematically showing a configuration of a main part of an image forming apparatus according to an embodiment. FIG. 3 is a top view schematically showing a platen portion of the image forming apparatus in the present embodiment. FIG. 2 is a perspective view showing in detail a collision detection mechanism of the image forming apparatus in the present embodiment. FIG. 5 is a diagram illustrating various types of paper shapes that cause the paper to lift from the platen belt surface, taking up typical ones. FIG. 3 is a diagram illustrating a detailed shape of a recording medium floating detection member as a first embodiment of a collision detection mechanism in the image forming apparatus of the present embodiment. It is a figure which shows the detailed shape of the recording medium floating detection member concerning 2nd or 4th embodiment of the collision detection mechanism in the image forming apparatus of this embodiment. It is a figure explaining the detailed structure and operation | movement of the collision detection mechanism as 3rd Embodiment in the image forming apparatus of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper feed part 3 Platen part 4 Image recording part 5 Recording medium discharge part 6 Paper tray 7 Pickup roller 8 Registration roller pair 9 (9-1, 9-2, 9-3) Paper (recording medium)
DESCRIPTION OF SYMBOLS 10 Platen belt 11 Platen belt roller 11-1 Rotating shaft 12 Driven roller 13 Platen frame 14 Platen suction part 15 (15c, 15k, 15m, 15y) Print head 16 Carriage 20 Collision detection mechanism 21, 21-1, 21-2 Recording Media floating detection member 21a, 21-1a, 21-1b Lower end surface 22 Rotating shaft 23 Detection transmission piece 24 Oscillating piece 24-1 Oscillating claw 25 Support portion 25-1 Support arm 25-2 Notch bent portion 26 ( 26-1, 26-2) Detection sensor 27 Belt roller drive motor 28 Suction hole 29 Groove 31 Suction hole 32 (32-1, 32-2, 32-3, 32-4, 32-5, 32-6, 32) -7, 32-8) Recording medium floating detection member 33 (33-1, 33-2, 33-3, 33-4, 33-5, 33-6, 33-7, 3-8) detects transmission piece

Claims (9)

A recording medium transport mechanism for transporting the recording medium;
A recording head for recording an image on the recording medium fixed to the apparatus main body side and conveyed by the recording medium conveyance mechanism;
A collision warning sensor located upstream of the recording head in the recording medium conveyance direction of the recording medium conveyance mechanism;
Have
The collision warning sensor is composed of a recording medium floating detection member for detecting a floating part of the recording medium, and a detection sensor for detecting a state change of the recording medium floating detection member,
The recording medium floating detection member extends in a direction perpendicular to the recording medium conveyance direction and in the width direction of the recording medium, and has at least two values in the width direction as a sensitivity for detecting the floating of the recording medium. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the recording head is an inkjet head.   The image forming apparatus according to claim 1, wherein a plurality of the detection sensors are provided.   The image forming apparatus according to claim 1, wherein the recording medium floating detection member has at least two values in the width direction as an interval between the recording medium and the recording medium.   5. The recording medium floating detection member is characterized in that an interval with the recording medium at a central portion in the width direction is smaller than an interval with the recording medium at an end portion in the width direction. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the recording medium floating detection member is divided into a plurality of parts.   The image forming apparatus according to claim 6, wherein the recording medium floating detection member has at least two values as a distance from the recording medium.   The image forming apparatus according to claim 6, wherein the recording medium floating sensing member has at least two values as detection sensitivity for the recording medium. The image forming apparatus according to claim 6, wherein the recording medium floating detection member has at least two values as a detection amplitude for the recording medium.

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