JPH09207401A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus wherein clamping and releasing of a recording medium is easy. SOLUTION: This image forming apparatus consists of a printing head for performing printing on a recording medium, a belt member 26 being hung on a drive pulley 24 and a turn pulley 25, a clamp member 28 provided on a holding member 27 connected with this belt member 26 and clamping the recording medium and a cam member 64 being brought into contact with and being separated from this cramp member 28 and as the clamp member 28 moves and the cam member 64 is brought into out of contact with it, the end part of the imaging medium is clamped by means of the clamp member 28 and printing is performed on the printing medium by means of the printing head and after printing is performed, clamping of the recording medium is released by bringing the clamp member 28 is brought into contact with the cam member 64 to discharge the paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus in which a recording medium is clamped by a clamp member held by a belt member, conveyed along a print head, and printed by the print head. Regarding

[0002]

2. Description of the Related Art Conventionally, as an example of an image forming apparatus of this type, various types of color printing are performed by one-pass scanning of a recording member having a print head corresponding to each color (yellow, magenta, cyan, black, etc.). Has proposed a multi-head printer. For example, JP-A-60-7388
There is one disclosed in Japanese Patent No. 5 as "image forming apparatus". FIG. 11 shows an example of the configuration. A platen roller 1 is arranged in the central portion, and four image forming units 2 to 5 are arranged around the platen roller 1. Each of the image forming units 2 to 5 is provided with a thermal head 6 as a printing head, and a thermal transfer ribbon (ink ribbon) 7 interposed between the thermal head 6 and the platen roller 1. In such a structure, the recording member 9 set in the paper feed cassette 8 is fed by the paper feed roller 10 and sent to the platen roller 1 via the pair of registration rollers 11. As the platen roller 1 rotates, the image is transferred from the first image forming unit 2 to the fourth image forming unit 5 so that each color is sequentially transferred in an overlapping manner, thereby completing the printing process. The sheet is discharged onto the sheet discharge tray 13 via the sheet discharge roller 12.

[0003]

However, in the structure in which four thermal heads 6 (printing heads) are circularly arranged around one platen roller 1 as described above, the platen having a large diameter is used. The roller 1 is required, which leads to an increase in size of the entire device. Further, the thermal head 6 having a shape retracted from the curvature shape of the platen roller 1 having such a large diameter is required, and further, the driver IC mounted on the head portion is located at a considerable distance from the heater line. Therefore, the size of the ceramic substrate on which the head portion is mounted is increased, which increases the cost of the device.

As another example of the multi-head printer, there is a configuration in which the print heads are arranged in a straight line in the print order. However, in such a configuration, since the four printing heads are arranged in series, the length in the arrangement direction becomes long, and as a result, the size of the entire apparatus becomes large. Also,
A platen roller or the like corresponding to each printing head is required, increasing the number of parts and increasing the cost of the apparatus.

[0005]

According to the first aspect of the present invention,
A printing head for printing on a recording medium, a belt member suspended on a drive pulley and a turn pulley, a clamp member provided on a holding member connected to the belt member for clamping the recording medium, and a clamp A cam member that comes into contact with and separates from the member, and the clamp member moves to release the contact with the cam member, thereby causing the clamp member to clamp the end portion of the recording medium, Printing is performed by the printing head, and after printing, the clamp member comes into contact with the cam member to release the clamp of the recording medium so that the recording medium can be discharged.

According to the second aspect of the invention, the clamp member held by the belt member is arranged so as to pass through the position outside the printing head.

According to a third aspect of the invention, an elastic member for urging the clamp member in the direction of clamping the recording medium is provided.
The unclamping performed by the clamp member coming into contact with the cam member is performed against the urging force of the elastic member.

[0008]

According to the first aspect of the invention, the recording member clamped by the clamp member can be smoothly moved with respect to the printing head in conjunction with the rotational movement of the drive pulley and the turn pulley, and the belt member is also provided. The recording member can be clamped and released sequentially and continuously by contact and separation of the clamp member and the cam member accompanying the movement of the recording medium. As a result, unevenness in printing density in the sub-scanning direction and image quality It is possible to prevent deterioration.

According to the second aspect of the invention, the moving structure of the recording member with respect to the printing head can be simplified.

According to the third aspect of the invention, the operation of clamping and releasing the recording member by the clamp member accompanying the movement of the belt member can be easily performed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A first example of an image forming apparatus which is the basis of an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the configuration of a four-head mounted color printing mechanism for four colors of Y (yellow), M (magenta), C (cyan), and B (black) in a multi-head printer. Two platen rollers 14 and 15 are arranged in the left-right lateral direction in the central portion. In the up-down direction (vertical direction) of the platen roller 14, the Y-color printing head 16 (thermal head) and the B-color printing head 1 are provided.
7 (thermal head) is arranged to face it. An M-color printing head 18 is provided above and below the platen roller 15.
And the C-color printing head 19 are arranged to face each other. Each printing head 16 to 19 has a single color ink sheet 2
0 are in contact with each other, and the ink sheet 20 is
It is stretched between the winding roller 21 and the supply roller 22. Each of the printing heads 16 to 19 has a head pressure contact cam 23a.
The head pressure contact release unit 23 including the cam follower 23b and the pressure spring 23c performs the pressure contact / release operation with respect to the platen rollers 14 and 15.

A pair of drive pulleys 24 are arranged on the sheet feeding / discharging side (right side) of the platen roller 14, and the platen roller 15 at a position opposite to the drive pulley 24.
A pair of turn pulleys 25 is arranged on the side (left side) (see FIG. 9 described later for details). Two belt members 2 in total are provided between the drive pulley 24 and the turn pulley 25.
6 have been bridged. A holding member 27 is connected between the two belt members 26, and a clamp member 28 as two clamp members is attached to the holding member 27. A tensioner 25 a for optimizing the tension of the belt member 26 is attached to the turn pulley 25. Also, at the paper feed position on the drive pulley 24 side,
A paper feed roller 30 for feeding the recording member 29 and a paper feed tray 31 are arranged. A pair of paper ejection rollers 32 and a paper ejection tray 33 are provided at the paper ejection position below the paper feed position.
And are arranged. The base plate 34 of the apparatus body is arranged below the series of mechanical components as described above.

Here, one platen roller 14 and two printing heads 1 arranged vertically are provided.
Reference numerals 6 and 17 constitute the recording unit A. Also,
Similarly, one platen roller 15 and the two printing heads 18 and 19 arranged in the vertical direction constitute a recording unit B. The recording medium unit A and the recording medium unit B are arranged in the left-right direction which is a direction parallel to the base plate 34 on the bottom surface with respect to the arrangement mechanism of the entire printer.

In such a structure, the recording member 29 is sent to the position of the belt member 26 on the drive pulley 24 via the paper feed roller 30, so that the leading end of the paper is clamped by the clamp member 28. After that, the recording member 29 changes the printing heads 16, 1 of Y → M → C → B.
By sequentially sending the image to each of the pages 8, 19, and 17, the overlapping transfer is completed by the scanning process of one rotation through the printing process of each color, and the sheet is discharged to the sheet discharge tray 33 via the sheet discharge roller 32. Therefore, the upper and lower recording body units A and B
By arranging two heads in the lateral direction, the lateral width can be shortened by almost half as compared with the configuration of the head unit arranged in a horizontal row as in the related art, and the space can be omitted. Further, with such an arrangement configuration, the number of parts required for assembly can be reduced, so that the device cost and the weight can be reduced.

FIG. 2 shows an example in which the recording medium units A and B are arranged vertically. That is, the platen rollers 14 and 15 are arranged in the vertical direction, and the printing heads 16 to 19 are arranged on the left and right of the platen rollers 14 and 15, respectively. In this case, the paper feed roller 30 is arranged at the upper left, and the paper discharge roller 32 is arranged at the upper right. By adopting such a vertical arrangement form, the space of the installation area can be reduced as compared with the case of the horizontal configuration of FIG. Further, as a result, all the components in the recording medium units A and B are arranged in the same posture, so that it is possible to obtain a merit that no difference appears in the transfer quality between the units.
As an example, the heat from the radiation fins provided on the thermal head is naturally convectively radiated upward in the same condition,
It is not necessary to change the control of the influence of the individually accumulated heat.

Next, a second example of the image forming apparatus which is the basis of the embodiment of the present invention will be described with reference to FIGS. 3 and 4. The description of the same parts as those shown in FIG. 1 and FIG. 2 is omitted, and the same reference numerals are used for the same parts (hereinafter the same).

In the first example of the image forming apparatus described above, an ink cassette (not shown) is constructed by individually disposing the monochromatic ink sheets 20 corresponding to the respective printing heads 16 to 19. Here, the internal structure of the ink cassette is changed. That is, as shown in FIG. 3, the Y print head 16 and the M print head 18 are housed in the same ink cassette 35, and two colors common to the Y and M print heads 16 and 18 are used. Painted ink sheet 3
6 was used. In the same manner, the B print head 17 and the C print head 19 are housed in the same ink cassette 35, and the two-color coating ink shared by the B and C print heads 17 and 19 is used. Sheet 36 was used. Although these two ink cassettes 35 are detachably provided, they are located at the center of the ink sheet 36, and an intermediate drive roller 37 that assists the movement of the two color ink sheets 36.
And a pinch roller 38 that is in contact with the intermediate drive roller 37. A gear 39 is fixed to the intermediate drive roller 37, and idle gears 40, 41, 42 are sequentially meshed with each other to transmit a rotational driving force to the gear 39. The idle gear 42 meshes with a gear 44 that drives the ink sheet take-up spool 43. The gear 44 is a gear 45 attached to a motor 46.
And are engaged. The two-color ink sheet 36 is wound between the ink sheet take-up spool 43 and the ink sheet supply spool 47. A back tension portion 35a which is formed integrally with the case of the ink cassette 35 and applies a frictional load to the supply spool shaft is in pressure contact with the supply spool shaft of the ink sheet supply spool 47. Further, a marker 48 for discriminating the cassette is attached to the outer peripheral surface of the ink cassette 35, and a reading sensor 49 for reading the marker is arranged in the vicinity of the marker 48.

FIGS. 4A and 4B show a coating form on the surface of the two-color coating ink sheet 36 mounted in the ink cassette 35. (A) shows a state of the ink sheet 36 for Y and M colors, and a marker 50 is formed at the boundary between Y and M to determine the printing position start position. (B) shows a state of the ink sheets 36 for B and C colors, and a marker 50 is formed at the printing position start position at the boundary between B and C.

In such a structure, first, recording is performed by bringing the Y and M color ink sheets 36, which move leftward, into contact with the two printing heads 16 and 18 in the upper ink cassette 35. After sequentially transferring the colors Y and M to the member 29, the ink sheets 36 for the colors C and B that move rightward are brought into contact with the two printing heads 19 and 17 in the lower ink cassette 35. As a result, C and B are applied to the recording member 29.
Colors are sequentially transferred to complete transfer of all four colors. As described above, the two printing heads 16 and 18 (or the printing heads 17 and 19) are arranged in one ink cassette 35, and the printing process is performed using the two-color ink sheet 36. By doing so, the ink cassette configuration can be made common regardless of the difference in the internal configuration of the cassette, and thus the mechanism can be simplified.

Next, a third example of the image forming apparatus which is the basis of the embodiment of the present invention will be described with reference to FIGS. Here, when the recording member 29 is moved in a state where the printing heads 16 to 19 are pressed against the platen rollers 14 and 15, a rotational driving force weaker than the force required to move the recording member 29 is applied to the platen rollers 14 and 15. The recording member conveying force control means for applying to the recording medium is provided. FIG. 5 shows an example of the structure of the recording member conveying force control means 51. The rotational driving force of the motor 52 is transmitted from the worm 53 attached to the motor shaft to the idle gear 54, and the driving force transmitted to the idle gear 54 is transmitted to the gear 55 integrated with the drive pulley 24. Furthermore, this gear 55
Is transmitted from the idle gear 56 to the idle gear 57 to the gear 58. The gear 58 transmits the driving force to the platen rollers 14 for Y and B colors, and at the same time, transmits the driving force to the roller 60 integrated with the platen roller 15 for M and C colors via the timing belt 59. . Thereby, by controlling the rotational driving force of the motor 52,
The rotation driving force of the platen rollers 14 and 15 is controlled by the set torque of the torque limiter 61 attached to the platen rollers 14 and 15.

FIG. 6 shows the basic operation principle for controlling the conveyance of the recording member 29 by using the recording member conveying force control means 51. Here, the force f required to move the recording member 29 when focusing on one Y-color printing head 16
The relationship between ₂ and its resistance to movement is described. Now, assuming that the ink sheet 20 and the recording member 29 move as a unit, the force f ₂ required to start the movement of the recording member 29 is f ₂ ≧ (P × μ ₁ × r + μ ₂ × P) -f ₁ (1) f ₁ : Ink sheet driving force f ₂ : Force required to move recording member P: Printing head pressure contact force μ ₁ : Platen shaft friction coefficient μ ₂ : Between printing head and ink sheet Friction coefficient r: The radius of the platen roller. Of these, the term of P × μ ₁ × r is the load resistance of the platen roller 14, and the platen roller 14 having such load resistance is given a rotational driving force by using the recording member conveyance force control means 51 of FIG. Then, the value of the load resistance is set to almost 0 and the value of f ₁ is reduced. Therefore, from this, by applying a rotational driving force weaker than the force f ₂ required for the movement of the recording member 29 to the platen rollers 14 and 15, the pulling drive of the recording member 29 can be easily performed. Therefore, it is possible to prevent an overload from being applied to the clamp portion at the leading end of the sheet to cause the sheet misalignment, and to prevent the color superposition misalignment due to the sheet elongation due to the excessive tensile force acting on the recording member 29.

Next, a fourth example of the image forming apparatus which is the basis of the embodiment of the present invention will be described with reference to FIGS. 7 and 8. Here, a sheet position detection sensor S1 that detects the moving position of the leading end of the recording member 29, the clamp member 28 that clamps and pulls the leading end of the recording member 29, or the belt member 26 that holds the clamp member 28 is moved. To S4 are arranged on the downstream side of the printing heads 16 to 19 of the respective colors. Specifically, in a multi-head printer using a two-color coating ink sheet 36 as shown in FIG. 7, it is located on the downstream side of each of the printing heads 16 to 19,
Y-color operation start sensor S1 as a paper position detection sensor
And M color operation start sensor S2 and C color operation start sensor S
3 and the M-color operation start sensor S4 are arranged. In addition to this, a home position sensor S0 is arranged at the paper feed position, and a Y-color ink sheet cue sensor S5 is provided at a position close to the ink sheet 36 on the downstream side of each of the printing heads 16 to 19. M color ink sheet cue sensor S6, C
A color ink sheet cue sensor S7 and a B color ink sheet cue sensor S8 are arranged.

Further, in the process of continuously moving the recording member 29 at the printing speed, the printing heads 17 to 19 for the respective colors of the second and subsequent colors are sequentially brought into pressure contact with each other, and the printing operation is sequentially carried out after the predetermined step movement. Printing scanning control means (not shown)
Was provided. Further, a head release scanning control means (not shown) is provided for sequentially releasing the first color printing heads 16 to 19 for which printing has been completed, while the recording member 29 is continuously moved at the printing speed. .

In such a configuration, the specific operation of each sheet position detection sensor, the print scan control means, and the head release scan control means will be described by taking the drive timing for print scan as an example. Now, the marker 62 (see FIG. 9) provided in the center of the clamper holder 27 holding the clamper 28 is detected by the home position sensor S0, and the leading edge of the sheet stands by at the home position. Then, after the paper is fed, the recording medium 29 starts to move by the motor 52, and the recording medium 29 is moved at the printing speed at the timing when the marker 62 sequentially passes through the operation start sensors S1 to S4 of the Y to B colors and is detected. In the process of continuous movement, the printing heads 16 to 19 of the respective colors are sequentially brought into pressure contact with the platen rollers 14 and 15, and after a certain step of movement from the time of the press contact, printing is started (print scanning control means). ). In addition, after the printing operation of a certain number of printing lines for each color is completed based on the program stored in the CPU (not shown), the recording medium 29 can be moved without interruption this time. In the process of continuously moving the printing head 29 at the printing speed, the printing heads 16 to 19 for the first color are printed.
The heads are sequentially released (head release scanning control means).
Even when the final B color is printed, the head releasing operation is performed while performing the continuous paper discharging operation.

FIG. 8 shows the shape of the dot 63 when printing is performed using a thermal head as the printing heads 16 to 19. Now, the movement in the sub-scanning direction X is the position X ₁
If there is a time interval after the printing is temporarily stopped, the heat storage of the thermal head decreases, and the printing density becomes thin in the next few lines after the start of movement, resulting in deterioration of image quality. Further, such a deterioration phenomenon cannot be completely uniformized and corrected even by using a conventional thermal correction technique for a thermal head. However, as in the present embodiment, during the process of continuously moving the recording medium 29 at the printing speed, the printing heads 16 to
Such a deterioration phenomenon of image quality can be prevented by performing control such that 19 is sequentially pressed and released.

Next, an embodiment of the present invention will be described with reference to FIGS. 9 and 10. This embodiment can be applied to each of the first to fourth image forming apparatuses described above. First, in FIG. 9, between the drive pulleys 24,
A cam 64 as a cam member is provided which has a substantially semi-cylindrical shape and is elongated along the sub-scanning direction X. The cam 64 is composed of a clamp member detaching portion 64a formed of a substantially flat region on the upper surface of the cylindrical surface and a clamp releasing portion 64b formed of a curved region on the lower surface of the cylindrical surface. Paper separation projections 65 are attached to the unclamping portion 64b at two locations. The cam 64 is fixed to the holder 66 at both ends thereof and is held in the space. Cam 6
4 and the holder 66 form a cam portion 67. Further, the cam portion 67 as described above, the doglegged clamper 28 for pulling and driving the tip of the recording medium 29, the clamper holder 27 for holding the clamper 28, and the clamper holder 27 are connected. Two clamp belts 26 and this clamp belt 26
Drive pulley 24 and turn pulley 2 around which
5 constitutes the clamp opening / closing cam mechanism 68.

With such a structure, the clamp setting / releasing operation of the recording medium 29 using the clamp opening / closing cam mechanism 68 will be described with reference to FIG. In this state, the piece 28a of the clamper 28 causes the cam 6 to
4 is in contact with the clamp member detaching portion 64a, and when the state moves from this state to a state where the tip of the clamp member detaching portion 64a is passed as the clamp belt 26 advances, it acts as an elastic member in the central portion of the clamper 28. Spring 2
The piece 28b is pressed against the surface of the clamper holder 27 by the urging force of 8c, whereby the recording medium 29 is held between the piece 28b and the clamper holder 27. afterwards,
In the state of, the color printing process is completed, the clamp belt 26 advances, and the state shifts to. In this state, the piece 28a is the clamp release portion 64b of the cam 64.
Against the urging force of the spring 28c, the piece 28b
Is released from the surface of the clamper holder 27, whereby the recording medium 29 is released from the clamped state and is ejected to the paper ejection tray 33 (see FIG. 1) via the paper ejection roller 32. By using the clamp opening / closing cam mechanism 68 in this way, one scan can be completed, and as a result,
Mechanically simple structure and continuous clamp setting
The releasing operation can be easily performed.

[0028]

According to the first aspect of the present invention, the printing head for printing on the recording medium, the belt member suspended on the drive pulley and the turn pulley, and the holding member connected to the belt member are provided. And a cam member that comes into contact with and separates from the clamp member. When the clamp member moves and the contact with the cam member is released, the end of the recording medium by the clamp member is formed. After the portion is clamped, printing is performed on the recording medium by the printing head, and after the printing, the clamp member comes into contact with the cam member to release the clamp of the recording medium and the sheet can be discharged. Therefore, the recording head of the recording member clamped by the clamp member is interlocked with the rotating movement of the drive pulley and the turn pulley. The recording member can be smoothly clamped and released by the contact and separation of the clamp member and the cam member accompanying the movement of the belt member. Therefore, it is possible to increase the accuracy of holding the paper, and to prevent uneven printing density in the sub-scanning direction and deterioration of image quality.

According to the second aspect of the present invention, since the clamp member held by the belt member is disposed so as to pass through the position outside the printing head, the structure for moving the recording member with respect to the printing head is simplified. It has the effect of being able to.

According to a third aspect of the invention, an elastic member for urging the clamp member in the direction of clamping the recording medium is provided.
Since the clamp release which is performed by the clamp member coming into contact with the cam member is performed against the biasing force of the elastic member, the clamp member releases and clamps the recording member with the movement of the belt member. This has an effect that the operation can be easily performed.

[Brief description of drawings]

FIG. 1 is a front view showing a first example of an image forming apparatus which is a basis of an embodiment of the invention.

FIG. 2 is a front view showing a configuration example in which recording body units are arranged in two vertical stages.

FIG. 3 is a front view showing a second example of the image forming apparatus which is the basis of the embodiment of the present invention and showing an example of an ink cassette configuration when two-color ink sheets are used.

FIG. 4 is a plan view showing a coating form of a two-color coating ink sheet.

FIG. 5 is a front view showing a third example of the image forming apparatus which is the basis of the embodiment of the invention and showing a configuration example of a recording medium carrying force control means.

FIG. 6 is a front view showing a force relationship that acts when a recording medium is conveyed.

FIG. 7 is a front view showing a fourth example of the image forming apparatus which is the basis of the embodiment of the invention.

FIG. 8 is a schematic diagram showing how the image quality is deteriorated.

FIG. 9 is a perspective view showing the configuration of the clamp opening / closing cam mechanism according to the embodiment of the present invention.

FIG. 10 is an explanatory diagram showing the operating principle of clamp setting / releasing in the cam portion.

FIG. 11 is a front view showing a configuration example of a conventional multi-head.

[Explanation of symbols]

 16 to 19 printing head 24 drive pulley 25 turn pulley 26 belt member 27 holding member 28 clamp member 29 recording medium 64 cam member

Claims (3)

[Claims] 1. A print head for printing on a recording medium, a belt member suspended between a drive pulley and a turn pulley, and a clamp provided on a holding member connected to the belt member for clamping the recording medium. A member and a cam member that comes into contact with and separates from the clamp member, and after the clamp member moves to release the contact with the cam member, the clamp member clamps the end portion of the recording medium. Printing is performed on the recording medium by the printing head, and after the printing, the clamp member comes into contact with the cam member to release the clamp of the recording medium so that the recording medium can be discharged. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the clamp member held by the belt member is arranged so as to pass an outside position of the printing head. 3. An elastic member for urging the clamp member in a direction for clamping the recording medium is provided, and the unclamping performed by the clamp member coming into contact with the cam member is performed against the urging force of the elastic member. The image forming apparatus according to claim 1, wherein: