JP2000326576A - Ink jet image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep a distance between the image forming portion of a recording medium and an ink emitting surface constant even if the thickness of the recording medium changes and to smoothly feed even a recording medium hard to bend. SOLUTION: The position of a platen holding member 670 is determined by the contact position of the cam outer peripheral surface of the platen height variable cam 681 fixed to a platen height changeover shaft 680 with a platen reinforcing stay 690. The platen height variable cam 681 has function for changing over the height of a platen 130 to change the position thereof and the outer peripheral surface distance thereof is changed to change over the height of the platen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink jet image forming apparatus such as a copying machine, a printer, and a plotter.

[0002]

2. Description of the Related Art Conventionally, an ink jet type image forming apparatus for forming an image by discharging ink onto a recording medium has been widely known. A conventional ink jet type image forming apparatus will be described with reference to FIGS.

FIG. 11 is a schematic structural view schematically showing a printer which is an example of a conventional ink jet type image forming apparatus. FIG. 12 is a schematic view showing a carriage and a print head of the printer shown in FIG. It is a schematic block diagram.
FIG. 13A is a schematic diagram illustrating a state in which a bearing fixed to a carriage is held in a posture by a guide plate, and FIG. 13B is a diagram illustrating a second bearing fixed to a posture switching lever. FIG. 4 is a schematic diagram showing a state where the posture is held by the circumstance.

[0004] The printer 18 has a predetermined main scanning direction (see FIG. 1).
1 and a carriage 1 that reciprocates in a direction perpendicular to the paper surface of FIG. A print head 2 for ejecting ink is removably mounted on the carriage 1. The print head 2 reciprocates in the main scanning direction together with the carriage 1. The printer 18 also includes a transport roller 3 that transports (paper feed) a recording medium such as the recording paper 4 in a sub-scanning direction (a direction orthogonal to the main scanning direction). A driven roller 5 that is driven and rotated while pressing and nipping the recording paper 4 against the conveying roller 3 is disposed on the conveying roller 3.

[0005] A platen 6 on the downstream side of the driven roller 5 in the recording medium transport direction and below the print head 2 guides the recording paper 4 in the recording medium transport direction and places the recording paper 4 thereon. ing. A discharge roller 7 for discharging the recording paper 4 is disposed downstream of the platen 6 in the recording medium conveyance direction. A spur 8 that discharges the recording paper 4 while nipping the recording paper 4 in cooperation with the discharge roller 7 is disposed on the discharge roller 7. Further, a cutter 9 for cutting the recording paper 4 into a predetermined length is disposed downstream of the spur 8 in the recording medium transport direction. The recording paper 4 cut by the cutter 9 is discharged through the discharge port 10.

Incidentally, the transport roller 3 and the driven roller 5
The platen 6 is slightly higher than a position on a straight line connecting a first holding position for holding the recording paper 4 by both sides and a second holding position for holding the recording paper 4 by both the discharge roller 7 and the spur 8. It is fixed to. In this manner, the distance between the platen 6 and the print head 2 is kept constant, and the distance between the portion (image forming portion) of the recording paper 4 placed on the platen 6 and the print head 2 becomes constant. Thus, the image quality is kept constant.

In the case where the distance between the platen 6 and the print head 2 is kept constant as described above, when the thickness of the recording paper 4 changes, the distance between the image forming portion of the recording paper 4 and the print head 2 increases. There is a problem that the image quality cannot be kept constant. Further, when conveying a recording medium having high rigidity (hard to bend) irrespective of the thickness of the recording paper 4, there is also a problem that the leading end collides with the platen 6 during the conveyance and the conveyance cannot be performed.

In the configuration in which the platen 6 is fixed, the distance between the print head 2 and the recording paper 4 changes according to the thickness of the recording paper 4 being conveyed. For this reason, when the interval between the print head 2 and the recording paper 4 is narrow, they may come into contact with each other. When the recording paper 4 comes into contact with the print head 2, the image formed on the recording paper 4 becomes dirty (print dirt), and the print quality is reduced. On the other hand, if these intervals are too wide so that the recording paper 4 does not contact the print head 2, satellite dots are generated, and the position where the ink ejected from the print head 2 adheres to the recording paper 4 changes. For this reason, the print quality deteriorates as in the case where the interval between the print head 2 and the recording paper 4 is narrow.

Therefore, in order to solve such a problem, in a conventional ink jet type image forming apparatus such as a printer 18, the attitude of the carriage 1 is changed (switched) in accordance with the thickness of the recording medium, and The distance between the mounted print head 2 and the recording paper 4 is kept constant.

A guide shaft 1 for guiding the carriage 1 in the main scanning direction is provided around the carriage 1 as shown in FIG.
1 and a guide plate 12 for guiding the carriage 1 and holding the posture of the carriage 1 are arranged. A bearing 1 for sliding the guide plate 12 in the main scanning direction.
3 is fixed to the carriage 1. A second bearing 14 for sliding the guide plate 12 in the main scanning direction when the posture of the carriage 1 is changed is provided at a position adjacent to the bearing 13.
Is arranged. The second bearing 14 is fixed to a posture switching lever 15 operated when switching the posture of the carriage 1.

As shown in FIG. 13, the attitude switching lever 15 has two projections 15a. On the other hand, the carriage 1 is formed with two long holes 1a, 1a into which the two protrusions 15a, 15a are fitted respectively. The positions of both ends of the long holes 1a, 1a are different from each other, and one end is higher than the other end. Therefore,
When the attitude switching lever 15 moves in the direction of arrow A, the two protrusions 15a, 15a are located at either end of the elongated holes 1a, 1a, whereby the attitude of the carriage 1 is switched and the carriage 1 is moved to the platen. 6 (see FIG. 12).

A procedure when the posture of the carriage 1 is switched with the movement of the posture switching lever 15 will be described.

The recording paper 4 inserted into the printer 18 is supplied to a paper feeding unit having a detector for detecting the thickness (paper thickness) of the recording medium.
It is transported (not shown), and the paper thickness is detected here. Thereafter, the sheet is conveyed to the platen 6 while being nipped by the conveying roller 3 and the driven roller 5, and reaches the sheet discharging roller 7. When a predetermined time elapses after the leading end of the recording paper 4 has passed the paper discharge roller 7, the conveyance of the recording paper 4 stops.

Based on the output value carrying the paper thickness detected by the detector described above, a control device (not shown) controls the recording paper 4
The distance between the position and the print head 2 is calculated, and the position of the attitude switching lever 15 is determined so that the distance falls within the tolerance range. The position of the attitude switching lever 15 obtained in this way is compared with the current position of the attitude switching lever 15, and if both are the same, the apparatus is in a state of waiting for a recording operation (image forming operation). Are different from each other, the position of the attitude switching lever 15 is displayed on the display unit of the operation panel (not shown). The user moves the posture switching lever 15 to the position displayed on the operation panel to move the carriage 1.
Switch the posture of. Since the position of the attitude switching lever 15 changes, the changed position is set as the current position,
This current position is compared again with the position of the attitude switching lever 15 such that the distance between the recording paper 4 and the print head 2 is within the tolerance range. If the two are the same, a recording operation (image forming operation) wait state is set. If they are different, the above procedure is repeated.

[0015]

As described above, the technique for switching the attitude of the carriage 1 to keep the distance between the print head 2 and the image forming portion of the recording paper 4 constant has the following problems.

In this technique, the carriage 1 rotates about the guide shaft 11 in accordance with the position of the attitude switching lever 15. By this rotation, the attitude of the print head 2 mounted on the carriage 1 changes. The print head 2 usually has a surface (ink ejection surface) on which a plurality of nozzles for ejecting ink are formed. The plurality of nozzles are formed side by side in the transport direction of the recording paper 4. That is, the plurality of nozzles are arranged in a line from the transport roller 3 to the paper discharge roller 7.

When the carriage 1 rotates as described above and the attitude of the print head 2 changes, the ink ejection surface of the print head 2 is inclined with respect to the recording paper 4. As a result, of the plurality of nozzles formed on the ink ejection surface,
There is a difference in the distance between the recording paper 4 and the nozzle closest to the recording paper 4 (first nozzle position) and the nozzle closest to the paper discharge roller 7 (second nozzle position). This difference increases in proportion to the amount of inclination (change amount) of the attitude of the print head 2 and also increases in proportion to the range (image forming area) from the first nozzle position to the second nozzle position. . When the distance between the nozzle and the recording paper 4 changes in accordance with the position of the nozzle in this way, the ink ejected from these nozzles becomes
An error occurs due to a change in the position where the image is adhered to. As a result, the quality (print quality) of the image formed on the recording paper 4 decreases.

In order to prevent such a decrease in print quality and to keep print quality within an allowable range, a guide shaft 11 (see FIG. 12) serving as a rotation center of the carriage 1 is arranged as far away from the print head 2 as possible. The difference between the distance from the first nozzle position to the recording paper 4 and the distance from the second nozzle position to the recording paper 4 is reduced. However, in this case, there is a problem that the size of the apparatus (printer 18) is increased and its cost is increased.

According to the present invention, in consideration of the above circumstances, the distance between the image forming portion and the ink ejection surface can be kept constant even if the thickness of the recording medium changes, and the recording medium can be smoothly conveyed even if the recording medium is hardly bent. An object of the present invention is to provide an inkjet type image forming apparatus.

[0020]

In order to achieve the above object, an ink jet type image forming apparatus according to the present invention is directed to a printing head having an ink discharge surface formed with a plurality of ink discharge ports for discharging ink in a predetermined direction. The recording medium is reciprocated and the recording medium is conveyed in an intersecting direction intersecting the predetermined direction. (1) a first transport member that is disposed upstream of the image forming area in the transport direction of the recording medium and transports the recording medium while nipping the recording medium; (2) a second transport member that is disposed downstream of the image forming area in the recording medium transport direction and transports the recording medium while nipping the recording medium;
The first transport member and the second transport member, which regulate a position of the image forming portion so that a distance between the ink ejection surface located above the image forming region and the image forming portion is a predetermined distance; And (4) switching means for moving the recording medium position regulating member to switch its position.

Here, (5) the recording medium position regulating member may be composed of a plurality of members.
(6) The switching means may move the recording medium position regulating member such that the recording medium position regulating member rotates or horizontally moves with respect to the ink ejection surface.

(7) The switching means is provided on a straight line connecting a first holding position where the first conveying member holds the recording medium and a second holding position where the second conveying member holds the recording medium. The recording medium position regulating member may be moved to a position or a lower limit position moved in a direction away from the ink ejection surface with respect to the straight line.

Further, (8) the above-mentioned ink jet type image forming apparatus is provided with a thickness detecting means for detecting the thickness of the recording medium, and (9) the switching means is provided for detecting the thickness of the recording medium detected by the thickness detecting means. The position of the recording medium position regulating member may be switched based on the thickness.

Furthermore, (10) the thickness detecting means includes:
It may have a displacement sensor that changes according to the thickness of the recording medium.

(11) The switching means may include a switching lever for selectively switching the position of the recording medium position regulating member.

Furthermore, (12) the switching means may include a driving means for moving the recording medium position regulating member.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ink jet type image forming apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of an ink jet printing apparatus (hereinafter, referred to as a printer) as one embodiment of the ink jet type image forming apparatus of the present invention, as viewed from the front (front). 1 is a perspective view of the printer viewed from the back. Here, a printer has been described as an embodiment of the inkjet type image forming apparatus of the present invention, but a plotter, a copying machine, a facsimile, etc.,
It can be applied to technologies in other fields that have similar problems.

The printer 100 includes a pair of legs 20, and a main body 30 supported by the legs 20. On the front surface of the main body 30, (F) a manual feed port 200 is formed, and a discharge port 500 is formed slightly above the (F) manual feed port 200. Also, the main body 30
The (S) manual paper feed port 300 is formed on the back surface of. A roll-shaped recording medium 102 is provided below the main body 30.
A roll-shaped recording medium feeding section (not shown) that supports (see FIG. 3) and feeds the recording medium is provided.

The roll-shaped recording medium 102 is fed from one end by a paper feed roller 420 (see FIG. 3) to form an image, and then discharged from the discharge port 500 to the outside of the apparatus. . A cut sheet (recording medium in the form of a cut sheet) 101 (see FIG. 3) is fed from the (F) manual paper feed port 200 or (S) manual paper feed port 300 to form an image. The air is discharged from the outlet 500 to the outside of the machine. An openable / closable upper cover 60 is attached to the main body 30, and an operation panel 70 is disposed on the right side of the upper cover 60.

Referring to FIG. 3, the internal structure of printer 100 will be described.

FIG. 3 is a schematic diagram showing the internal structure of the printer.

The printer 100 includes an image forming section for forming an image on a recording medium, and a cut sheet 101 in the image forming section.
Paper feed unit and roll-shaped recording medium feeding unit for feeding and transporting the roll-shaped recording medium 102 and the cut paper 101 or roll-shaped recording medium 102 on which an image is formed. It is composed of a paper discharge unit that discharges outside the machine. Further, the printer 100 has a recording medium height switching mechanism (consisting of a recording medium position regulating member, switching means, and the like according to the present invention) for maintaining a constant distance between the print head 151 and the recording medium. are doing.

First, the above-described image forming section will be described.

The image forming section is provided with a carriage 150 on which each print head 151 is mounted in order to form an image on the cut sheet 101 or the roll-shaped recording medium 102.
The carriage 150 includes a pair of slide rails 152, 1
53 slidably supports in the main scanning direction, and reciprocates in the main scanning direction by a timing belt (not shown) and a carriage motor (not shown). In order to perform color printing on the cut sheet 101 or the roll-shaped recording medium 102, the carriage 150 has a BK (black) head 151a (not shown) and a C (cyan) head 151b.
(Not shown), M (magenta) head 151c (not shown), Y (yellow) head 151d (not shown)
Are mounted.

In forming an image, first, a cut sheet 101 (or roll-shaped recording medium 102) fed and conveyed from a manual sheet feeding section (or a roll-shaped recording medium feeding section) is transported by a conveying roller. 110 and driven pressure roller 120
(This is an example of a first conveying member according to the present invention.) The sheet is conveyed to a predetermined recording start position while being sandwiched between the recording members, and is stopped at this position (print standby). Image forming operation (printing operation)
In the first embodiment, while the carriage 150 is scanning in one direction, print control is performed based on image data and a signal output from an encoder (not shown) attached in the main scanning direction, and a recording medium height variable mechanism is provided. The printing is performed on a platen 130 (an example of a recording medium position regulating member according to the present invention). When one scan of the carriage 150 is completed, the cut paper 101 or the roll-shaped recording medium 102 is conveyed by a predetermined amount in the sub-scanning direction while being nipped by the conveyance roller 110 and the driven pressure roller 120. Thereafter, the carriage 150 starts scanning again to perform an image forming operation,
The above operation is repeated until printing is completed.

The manual paper feed unit will be described.

The manual paper feed unit conveys and feeds a commonly used recording medium (F) a manual paper feed unit, and (F) a thick paper or a plate that cannot be conveyed by the manual paper feed unit. Conveys recording media with high rigidity (hard to bend)
It is composed of two paper feeding units of a manual paper feeding unit (S) for conveying.

(F) Cut paper 101
(F) A manual paper feed port 200 is formed. (F) It is determined whether or not a recording medium has been inserted downstream of the manual paper feed port 200 in the recording paper transport direction. (F) The manual paper feed sensor 210 and the cut paper 101 are transported. A paper roller 220 and a plurality of driven roller units (not shown) are provided. The driven roller unit is provided with (F) a driven roller 231 that rotates following the rotation of the sheet feeding roller 220, and a leaf spring (not shown) that applies a predetermined pressing force to both ends of the driven roller 231. Also, above the driven roller 231, (F) the recording medium thickness detection sensor 24
0 (which is an example of the thickness detecting means according to the present invention) is arranged. This (F) recording medium thickness detection sensor 240
Detects the height displacement of the driven roller 231 caused by the insertion of the cut sheet 101 during conveyance while nipping the cut sheet 101 between the (F) paper feed roller 220 and the driven roller 231 to detect the height of the recording medium. Detect the thickness.

On the other hand, the (S) manual paper feed port 300 is formed in the (S) manual paper feed section. (S) It is determined whether a recording medium has been inserted downstream of the manual paper feed port 300 in the recording paper transport direction (S). The manual paper feed sensor 310 and the cut paper 101 are transported (S). A paper roller 320 and a plurality of driven roller units (not shown) are provided. The driven roller unit is provided with a driven roller 331 that rotates following the rotation of the (S) paper feed roller 320, and a leaf spring (not shown) that applies a predetermined pressing force to both ends of the driven roller 331. Both the (F) manual paper feed unit and (S) manual paper feed unit feed and transport the cut paper 101 to the same image forming unit.

The roll-shaped recording medium feeding section will be described.

The roll-shaped recording medium feeding section has a roll-shaped recording medium support section 400 for supporting the roll-shaped recording medium 102. A roll-shaped recording medium feed sensor 410 for detecting the position of the recording medium, a roll-shaped recording medium 1
2, a roll-shaped recording medium feeding roller 420 for transporting the recording medium 02 and a plurality of driven roller units (not shown) are provided. The driven roller unit includes a driven roller 431 that rotates following the rotation of the roll-shaped recording medium feeding roller 420;
A leaf spring (not shown) for applying a predetermined pressing force to both ends
Is provided. Further, a roll-shaped recording medium paper thickness detection sensor 440 is disposed above the driven roller 431, and the roll-shaped recording medium paper thickness detection sensor 440 is
While the roll-shaped recording medium 102 is being transported while being held between the roll-shaped recording medium feed roller 420 and the driven roller 431, the height displacement of the driven roller 431 caused by the insertion of the roll-shaped recording medium 102 is detected.

The paper discharge section will be described.

The paper discharge unit has a paper discharge roller 510 and a plurality of spur units 520 that rotate following the rotation of the paper discharge roller 510. The discharge roller 510 and the spur unit 520 are examples of the second transport member according to the present invention. The spur unit 520 is attached to a spur stay 550. The spur unit 520 is configured to apply a predetermined pressure to the spur. Also, the discharge rollers 510
, The rotation of the transport roller 110 is transmitted, and the discharge roller 510 also rotates.

A cutter unit 540 that cuts the recording medium 102 into a predetermined length is disposed downstream of the paper discharge roller 510 in the recording paper conveyance direction. When the image forming operation is completed in the image forming unit, the cut sheet 101 or the recording medium 102 is moved to the discharge roller 510 and the spur unit 52.
0, and the discharge guide 530 and the discharge stay 5
The sheet is discharged outside the apparatus while being guided by the lower surface of the sheet 50. When the recording medium 102 is a roll paper, the recording medium 102 is conveyed while being sandwiched between the discharge roller 510 and the spur unit 520, and a portion of the recording medium 102 where an image is formed (a print image end portion) is cut by a cutter. Stops at a position beyond the position, the round blade of the cutter unit 540 cuts the recording medium 102 while moving and rotating in the main scanning direction, and the print image end portion is guided by the lower surface of the paper discharge guide 530 and the paper discharge stay 550. While being discharged outside the aircraft.

Referring to FIG. 4, the recording medium height switching mechanism will be described.

FIG. 4 is a perspective view showing a recording medium height switching mechanism, and the same components as those in FIG. 3 are denoted by the same reference numerals.

The recording medium height switching mechanism is provided with a cut sheet 10 fed by each sheet feeding section such as (F) a manual sheet feeding section, (S) a manual sheet feeding section, and a roll-shaped recording medium sheet feeding section.
1 and a transport roller 110 for transporting the roll-shaped recording medium 102 to the image forming unit. Further, the recording medium height switching mechanism includes a driven roller 120 (see FIG. 3), a transport motor 620 for rotating the transport roller 110, and a transport motor 620.
A drive gear 630 fastened to the transport motor 620 and a transport roller gear 640 fastened to the end of the transport roller 110
It has.

The transport rollers 110 are provided on both sides 700a, 7
00b (see FIG. 3)
It is rotatably held at 50a and 650b. The tangent connecting the outer circumference of the transport roller 110 and the outer circumference of the paper discharge roller 510 is indicated by each print head 151a, 151b, 151c, 1
It is arranged parallel to the ink ejection surface 51d. Also,
A platen 130 is provided between the transport roller 110 and the paper discharge roller 510, and the upper part of the platen 130 is an image forming area. The platen 130 is connected to the transport roller 1
The print heads 151a, 151b, 151c, 1 are slightly smaller than the tangent connecting the outer circumference of the paper discharge roller 10 and the outer circumference of the paper discharge roller 510.
It is held high on the 51d side. The platen 130 keeps a constant distance between the print heads 151a, 151b, 151c, 151d and the cut sheet 101 (and the roll-shaped recording medium 102).

A platen holding member 670 for holding the platen 130 is provided below both ends in the longitudinal direction of the platen 130.
Is provided. An inclined surface 670a is formed in a portion of the platen 130 facing the transport roller 110. The inclined surface 670a is connected to the conveying roller bearing 65.
0 is in contact with the outer peripheral surface. Below the sheet discharge roller 510, a platen height switching shaft 680 rotatably held by both side plates 700a and 700b is arranged. In the vicinity of the platen height switching shaft 680, a 670b having the same inclined surface as the inclined surface 670a of the platen holding member 670 is provided.
Are formed. These two inclined surfaces 670a, 67
The platen 130 is held by 0b.

A platen reinforcing stay 690 for reinforcing the platen 130 is fixed to a portion of the platen 130 other than both ends where the platen holding member 670 is fixed. One end of a tension spring 691 is fixed to both ends in the longitudinal direction of the platen reinforcing stay 690, and the other end of the tension spring 691 is fixed to a body stay 710 fixed to both side plates 700a, 700b. As a result, the platen holding member 670 fixed to the platen 130 is constantly urged in a downward direction along the two inclined surfaces 670a and 670b.

The position of the platen holding member 670 is
It is determined by the contact position between the cam outer peripheral surface of the variable platen height cam 681 fixed to the platen height switching shaft 680 and the platen reinforcing stay 690. The variable platen height cam 681 is for switching the height of the platen 130 to change its position. The platen height is switched by changing the outer peripheral surface distance of the variable platen height cam 681.

Rotary shaft 51 to which discharge roller 510 is fixed
A platen height switching lever 682 for switching the height of the platen 130 is rotatably fixed to one end in the longitudinal direction. This platen height switching lever 682
, A semilunar gear 683 is fixed. On the other hand, a gear 684 meshing with the gear 683 is fixed to a portion of the platen height switching shaft 680 below the gear 683. Gear 68 of the platen height switching shaft 680
Next to 4, a platen height switching cam 681 for switching the height of the platen 130 is formed. By rotating the platen height switching lever 682, the platen height switching cam 681 rotates, and the height of the platen 130 changes by a fixed amount.

Further, a shielding plate (slipper) 685 is fastened and fixed to the platen height switching shaft 680.
Near plate 85, platen height position sensors 686a and 686b for detecting the position of platen 130 are arranged. As the platen height switching shaft 680 rotates, the fly 685 also rotates. Therefore, the platen height switching cam 6
The rotation position of 81 is determined by the sensor 686
a, 686b is detected based on the position. The switching means according to the present invention includes a platen height switching shaft 680, a platen height switching cam 681, a platen height switching lever 682, gears 683, 684, and the like.

Referring to FIG. 5, FIG. 6, and FIG.
The procedure for switching the height of 30 will be described.

FIG. 5 shows the first holding position where the recording paper is held by both the transport roller 110 and the driven roller, and the discharge roller 5.
10 and a higher position than a position on a straight line connecting the second holding position for holding the recording paper by the spurs and the print head 1
FIG. 3 is a schematic diagram showing a platen 130 held at a position closest to 51 and components around the platen 130. FIG. 6 is a schematic diagram showing the platen 130 held at a position slightly higher than the position on the straight line and components around the platen 130. FIG.
FIG. 5 is a schematic diagram showing the platen 130 and components around the platen 130 held at a position slightly lower than the position on the straight line. In these drawings, the same components as those shown in FIG. 4 are denoted by the same reference numerals.

Here, a straight line connecting a first holding position where the recording sheet is held by both the transport roller 110 and the driven roller 120 and a second holding position where the recording sheet is held by both the discharge roller 510 and the spur 520 are shown. The distance from the position to the surface of the platen 130 is defined as the height of the platen 130 (platen height).

The platen height h1 shown in FIG. 5 is determined based on the thickness of a thin recording medium among the recording media usable in the printer 100. In addition, the distance between the surface of the recording medium and the print head 151 is set in a range where the print quality is not deteriorated (does not deteriorate). Platen 130
However, at the position shown in FIG. 5, the rotation position of the switching cam 681 is detected by a part 685a of the flyer 685 blocking the platen height position sensor 686a.

The platen height h2 shown in FIG. 6 is determined based on the thickness of a thick recording medium among the recording media usable in the printer 100. In addition, the distance between the surface of the recording medium and the print head 151 is set in a range where the print quality is not deteriorated (does not deteriorate). Platen 130
However, when the position is as shown in FIG. 6, the rotation position of the switching cam 681 is
6a and 686b are unshielded positions.

The platen height h3 shown in FIG. 7 is a position slightly lower than the position on the straight line connecting the first holding position and the second holding position (an example of the lower limit position in the present invention). ) Is the height when the platen 130 is located. When the platen 130 is located at this position, the platen 130 functions as a guide member for the recording medium. Therefore,
For example, the platen 1 is an effective conveyance guide for conveying a rigid (hard to bend) recording medium such as a plate.
30 works. The rotation position of the switching cam 681 at this time is detected by a part 685b of the flyer 685 blocking the platen height position sensor 686b.

Referring to FIGS. 8 and 9, switching for switching the position (height) of platen 130 in each of (F) manual paper feeding, (S) manual paper feeding, and roll-shaped recording medium paper feeding. The operation will be described.

FIG. 8 is a flowchart showing the operation up to the start of printing in the case of (F) manual paper feeding and roll-shaped recording medium paper feeding. FIG. 9 is a flowchart showing the operation up to the start of (S) manual paper feed printing.

As shown in FIG. 8, when a recording medium is inserted, (F) manual feed sensor 210
(Or the roll-shaped recording medium feeding sensor 410) is turned on (S801). Accordingly, (F) the manual feed roller 220 (or the roll-shaped recording medium feed roller 420) starts to be driven (S802), and the recording medium starts to be conveyed.
Based on the amount of displacement (displacement) of the driven roller 231 (or the driven roller 431), (F) the recording medium thickness detection sensor 240 (or the roll-shaped recording medium paper thickness detection sensor 44)
0), the paper thickness of the recording medium is detected (S80).
3). The height (position) of the platen 130 at this time is compared with the platen height at the current shielding position of the platen height position sensors 685a and 685b (S804). If the heights are the same, printing is started. The print medium is conveyed to the position and stopped (S805), and a print start waiting state is set (S806).

On the other hand, when the heights are different from each other, (F) the manual feed roller 220 (or the roll-shaped recording medium feed roller 420) is stopped, and a message indicating the correct platen height position is displayed. It is displayed (S807). Subsequently, when it is confirmed that the platen height switching lever 682 has been switched to the correct position (S808), the process returns to S803.

FIG. 9 is a flow chart showing the operation up to the start of printing of (S) manual paper feed.

As shown in FIG. 9, when a recording medium is inserted, the insertion causes the (S) manual paper feed sensor 310 to be turned on (S901). Thereby, the platen height is detected based on the shielding positions of the platen height position sensors 686a and 686b at this time, and it is determined whether or not the platen height position sensor 686b is shielded (S90).
2). When the platen height position sensor 686b is blocked, the (S) paper feed roller 320 is driven (S90).
3) Convey the recording medium to the print start position and stop it (S904). As a result, a print start waiting state is set (S
905).

On the other hand, if it is determined in step S902 that the platen height position sensor 686b is not shielded, (S) the sheet feed roller 320 is stopped and the lever position of the platen height position sensor 686b is closed. A message is displayed (S906). Subsequently, when it is confirmed that the platen height switching lever 682 has been switched to the correct position (S907), the process returns to S901.

With reference to FIG. 10, another embodiment of the recording medium height switching mechanism will be described.

FIG. 10 is a perspective view showing another embodiment of the recording medium height switching mechanism, and the same components as those shown in FIG. 4 are denoted by the same reference numerals.

The recording medium height switching mechanism of the above-described embodiment is configured to rotate the gear of the switching cam by rotation of the gear of the platen height switching lever. However, FIG.
In another embodiment, a gear 800 is fastened and fixed to a platen height switching shaft 680, and a gear 820 meshing with the gear 800 is connected to a platen height switching shaft rotating motor 810.
The switching cam 681 is rotated by rotating the switching cam 681 (which is an example of the driving means according to the present invention). With such a configuration, the same effect as in the above embodiment can be obtained.

[0071]

As described above, according to the ink jet type image forming apparatus of the present invention, the position of the recording medium position regulating member is appropriately switched by the switching means so that the image can be formed even when the thickness of the recording medium changes. Since the distance between the formation portion and the ink ejection surface can be kept constant, the printing quality can be improved. Further, when a thick and less flexible recording medium is conveyed, the position of the recording medium position regulating member is switched so that the recording medium is not obstructed by the recording medium position regulating member, so that the recording medium is thick and less flexible. Even if there is, it can be transported smoothly.

Here, when the recording medium position regulating member is constituted by a plurality of members, the recording medium position regulating member switched by the switching means by appropriately changing the combination of the plurality of members. Can be easily changed.

The switching means may move the recording medium position regulating member such that the recording medium position regulating member rotates or moves horizontally with respect to the ink ejection surface. Since the distance between the ink and the ink ejection surface can be easily maintained constant, the print quality can be more reliably improved.

Further, the switching means is provided at a position on a straight line connecting a first holding position where the first conveying member holds the recording medium and a second holding position where the second conveying member holds the recording medium. Alternatively, in a case where the recording medium position regulating member is moved to a lower limit position moved in a direction away from the ink ejection surface than this straight line, the recording medium position regulating member is moved to the position on the straight line or the lower limit position. , The conveyance of the recording medium is not hindered even if the recording medium is thick and hard to bend.

Further, there is provided a thickness detecting means for detecting the thickness of the recording medium, wherein the switching means determines the position of the recording medium position regulating member based on the thickness of the recording medium detected by the thickness detecting means. In the case of switching, the position of the recording medium position regulating member is switched based on the thickness of the recording medium, so that the distance between the image forming portion of the recording medium and the ink ejection surface can be more accurately kept constant.

Further, when the thickness detecting means is provided with a displacement sensor that changes according to the thickness of the recording medium, a simple structure of the thickness detecting means can be obtained.

Further, when the switching means has a switching lever for selectively switching the position of the recording medium position regulating member, the position of the recording medium position regulating member is changed by operating the switching lever. Can be easily switched.

Further, when the switching means has a driving means for moving the recording medium position regulating member, the position can be easily switched by moving the recording medium position regulating member by the driving means. .

[Brief description of the drawings]

FIG. 1 is a perspective view of an inkjet printing apparatus, which is an embodiment of an inkjet type image forming apparatus of the present invention, as viewed from the front.

FIG. 2 is a perspective view of the printer of FIG. 1 as viewed from the back.

FIG. 3 is a schematic diagram showing an internal structure of the printer of FIG.

FIG. 4 is a perspective view illustrating a recording medium height switching mechanism.

FIG. 5 is a diagram showing a position higher than a linear position connecting a first holding position for holding a recording sheet by both a conveying roller and a driven roller and a second holding position for holding a recording sheet by both a discharge roller and a spur. FIG. 3 is a schematic diagram showing a platen held at a position closest to a print head and components around the platen.

FIG. 6 is a schematic diagram showing a platen held at a position slightly higher than the position on the straight line and components around the platen.

FIG. 7 is a schematic diagram showing a platen held at a position slightly lower than the position on the straight line and components around the platen.

FIG. 8F is a flowchart showing an operation up to the start of printing in the case of manual sheet feeding and roll-shaped recording medium feeding.

FIG. 9 is a flowchart showing an operation up to the start of (S) manual feed printing.

FIG. 10 is a perspective view showing another embodiment of a recording medium height switching mechanism.

FIG. 11 is a schematic configuration diagram schematically illustrating a printer as an example of a conventional inkjet type image forming apparatus.

12 is a schematic configuration diagram schematically showing a carriage, a print head, and the like of the printer shown in FIG.

13A is a schematic diagram illustrating a state in which a bearing fixed to a carriage is held in a posture by a guide plate, and FIG. 13B is a schematic diagram illustrating a second bearing fixed to a posture switching lever. FIG. 4 is a schematic diagram showing a state where the posture is held by a guide plate.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 printer 101 cut paper 102 roll-shaped recording medium 110 transport roller 120 driven roller 130 platen 151a, 151b, 151c, 151d print head 510 discharge roller 620 transport motor 630 drive gear 640 transport roller gear 650 transport roller bearing 670 platen holding member 680 platen Height switching shaft 681 Platen height variable cam 682 Platen height switching lever 682a, 682b Platen height position sensor 810 Platen height switching shaft rotating motor

Claims (8)

[Claims] 1. A print head having an ink ejection surface formed with a plurality of ink ejection ports for ejecting ink is reciprocated in a predetermined direction, and a recording medium is conveyed in an intersecting direction intersecting the predetermined direction. An ink jet type image forming apparatus which forms an image by discharging ink from the ink discharge port to an image forming portion located in an image forming region in front of the ink discharge surface of the recording medium, wherein the recording medium is larger than the image forming region. A first transport member disposed on the upstream side in the transport direction and transporting while nipping the recording medium; and a second transport member disposed on the downstream side in the recording medium transport direction than the image forming area and transporting while nipping the recording medium. A conveying member, and a position of the image forming portion such that a distance between the ink ejection surface located above the image forming region and the image forming portion is a predetermined distance. A recording medium position regulating member disposed between the first transport member and the second transport member, and switching means for switching the position by moving the recording medium position regulating member. An ink-jet type image forming apparatus characterized by the above-mentioned. 2. The ink jet image forming apparatus according to claim 1, wherein the recording medium position regulating member is constituted by a plurality of members. 3. The switching device according to claim 2, wherein the switching unit moves the recording medium position regulating member such that the recording medium position regulating member rotates or horizontally moves with respect to the ink ejection surface. Item 3. An inkjet image forming apparatus according to item 1 or 2. 4. The switching means includes: a linear position connecting a first holding position where the first conveying member holds a recording medium and a second holding position where the second conveying member holds a recording medium; 4. The ink jet system according to claim 1, wherein the recording medium position regulating member is moved to a lower limit position moved in a direction away from the ink ejection surface with respect to the straight line. Image forming device. 5. A printing apparatus, comprising: a thickness detecting unit configured to detect a thickness of a recording medium, wherein the switching unit switches a position of the recording medium position regulating member based on a thickness of the recording medium detected by the thickness detecting unit. The inkjet image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. 6. The ink jet image forming apparatus according to claim 5, wherein said thickness detecting means includes a displacement sensor that changes according to the thickness of a recording medium. 7. The apparatus according to claim 1, wherein said switching means has a switching lever for selectively switching a position of said recording medium position regulating member. Inkjet type image forming apparatus. 8. The ink-jet image according to claim 1, wherein the switching unit includes a driving unit that moves the recording medium position regulating member. Forming equipment.