JPH0382580A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To stably remove the wrinkles or slackening of an ink ribbon, in performing the contact and separation between a thermal recording means and a rotary means, by limiting the movement of a transfer material along the running direction thereof in synchronous relation to the separation of both means and releasing the limit of the movement of said transfer material in synchronous relation to the pressure contact of both means. CONSTITUTION:In such a case that a thermal head 24 comes into pressure contact with a platen drum 22, when torque is applied to a winding core 31 on a taking-up side in the taking-up direction thereof in such a state that the rotation of a winding core 30 on a feed-out side is limited, an ink ribbon 26 is tensioned. When a thermal head pressure contact cam 101 is revolved in this state, the thermal head 24 is brought into pressure contact with the platen drum 22 and an ink ribbon roll brake lever 103 is displaced by an ink ribbon roll brake cam 102 revolved at the same time and an ink ribbon roll brake 104 is separated from an ink ribbon roll brake roller 105 and the winding core 30 on the feed-out side becomes rotatable. Therefore, by properly selecting the shape and phase difference of two cams 101, 102, the pressure contact of the thermal head 24 becomes possible without generating wrinkles or slackening in the ink ribbon 26.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an image forming apparatus, such as a thermal transfer printer or a thermal transfer copying machine, which forms a full-color image on paper according to image information.

(Prior Art) In recent years, color copying machines have been developed and put into practical use as image forming apparatuses using digital technology and thermal transfer ink ribbons. FIG. 10 shows the structure of the main part of the image forming section of such an image forming apparatus. That is, the platen drum 22 rotates around a sheet of paper as an image forming medium, and the ink ribbon 26 stretched so as to be in contact with the platen drum 22 moves at the same speed as the circumferential speed of the platen drum 22. It is supposed to be done. The thermal head 24, which is provided so as to be able to approach and separate from the platen drum 22 via the ink ribbon 26, selectively responds to image information sent from a control section (not shown) while being in pressure contact with the platen drum 22. This generates heat and thermally transfers the ink from the ink ribbon 26 onto the paper wound around the platen drum 22. A full-color image is formed by performing such thermal transfer using inks of multiple colors.

The thermal head 24 is brought into contact with and separated from the platen drum 22 by a thermal head pressure contact cam 101 attached to a camshaft 100. Further, the movement of the ink ribbon 26 is achieved by rotationally driving a DC motor 120 connected to the feeding-side winding core 30 and a DC motor 121 connected to the winding-side winding core 31 at a predetermined timing and with a predetermined torque. It is about to be done.

In the image forming apparatus configured as described above, when the thermal head 24 is brought into pressure contact with the platen drum 22,
In order to prevent the ink ribbon 26 from being wrinkled or loosened, which may cause transfer defects, two motors 120 and 1211 are installed in the direction in which tension is applied to the ink ribbon 26 (in the direction of the arrow in the figure).
;It is designed to generate torque. At this time, in order to keep the ink ribbon 26 in a tensioned state, it is necessary that the forces pulling the ink ribbon 26 from both sides be balanced.

However, since the outer diameters of the winding cores 30 and 31 on the winding side and the feeding side of the ink ribbon 26 change every moment according to the winding amount, the two motors 120,
It is necessary to change the torque of 121. To do this accurately requires a complex and large-scale control circuit and control program, so there is a method of setting the torque of the DC motor 120, 121 in several stages and applying an appropriate value from among them. However, the drawback was that the pulling force from both sides became unstable.

In addition, two DC motors are required just to move the ink ribbon 26, which is an obstacle to miniaturizing the device, increases power consumption, and increases the cost of the device. .

(Problems to be Solved by the Invention) As described above, the present invention provides an ink ribbon in order to prevent the ink ribbon from being wrinkled or loosened, which may cause transfer defects, when the thermal heater is brought into pressure contact with the platen drum. The method that pulls the ink ribbon by generating torque in two motors in the direction of tension on the ink ribbon has the disadvantage that the pulling force from both sides becomes unstable, and two DC motors are required just to move the ink ribbon. This was done in order to eliminate the drawbacks that hinder the miniaturization of the ink ribbon, increase power consumption, and increase the cost of the ink ribbon. It is an object of the present invention to provide an image forming apparatus that can be removed, and furthermore, can be made smaller, have lower power consumption, and lower cost.

[Structure of the Invention] (Means for Solving the Problems) The image forming apparatus of the present invention includes a rotating means for wrapping and rotating an image forming medium around the outer periphery, and a rotating means for rotating the image forming medium by winding the image forming medium around the outer periphery, and a rotating means for rotating a pair of cores while being in contact with the rotating means. An image forming apparatus comprising a traveling transfer material and a thermal recording means for transferring an image while pressing the transfer material against an image forming medium wound around the rotating means, the thermal recording means and the rotating means. A contact/separation means for press contacting and separating from the
When the thermal recording means and the rotating means are separated, the movement of the transfer material in the running direction is restricted, and when the thermal recording means and the rotating means are brought into pressure contact, the movement of the transfer material is restricted in the running direction. The invention is characterized by comprising a means for canceling the restriction on movement along the .

(Function) When the thermal recording means and the rotating means are brought into contact with each other, the present invention restricts the movement of the transfer material along the traveling direction in synchronization with the separation between the thermal recording means and the rotating means, and the thermal recording means The restriction on the movement of the transfer material along the traveling direction is released in synchronization with the pressure contact between the transfer material and the rotating means. As a result, when the thermal recording means and the rotating means are separated, tension is generated in the transfer material so that no wrinkles or slack occur, and when they are brought into pressure contact, they are pressed together from the above state, and the transfer material is transferred at the same time. Since the movement of the material along the running direction is released, the transfer material has no wrinkles or slack when the image forming operation starts, and it is possible to start forming a good image.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. Note that the same parts as in the conventional configuration shown in FIG. 10 will be described with the same reference numerals.

FIG. 2 shows, as an example of the image forming apparatus of the present invention, a thermal transfer type color copying machine capable of selectively making multicolor copies. That is, 1 is a main body of a copying machine, and an operation panel (not shown) is provided at the front of the upper surface of the main body 1. The upper part of the main body 1 is an original scanning section 3 that scans and reads an original set on an original table (transparent glass) 2, and the lower part is an image forming section 4. In addition, 5
is a document cover provided on the document table 2 so as to be openable and closable. Further, the document table 2 is fixed to the main body 1.

At the longitudinal end of the document table 2, as shown in FIGS.
As shown in FIG. 2, a fixed scale 50 is provided as a reference for setting the original. The fixed scale 50 is composed of a transparent part and a white opaque part. Pointers 51 and 52 as size indicators are opposed to the transparent portion. This guideline 51.52 is shown in Figure 3 (
As shown in b), it is fixed to a belt 57 that is stretched between pulleys 54 and 55. The pulley 55 is rotated by a motor 58, and the distance between the pointers 51 and 52 is changed by driving the rotation of the motor 58 according to the set paper size, magnification, etc. It looks like this. The range indicated by the pointers 51 and 52 is the width in the vertical direction as the copyable range.

Further, a white reference plate 59 is provided on the upper surface of the end of the document table 2 below the fixed scale 50 .

The document scanning section 3 is configured as shown in FIG. 4, for example. That is, the first lamp is equipped with the illumination lamp 6 as a light source.
A carriage 7, a second carriage 8 that bends the optical path with a mirror, a lens 9, and a photoelectric converter 1 that converts the reflected light from the document tray.
1, and a mirror part 10 that corrects the optical path length when changing the magnification;
It is comprised of a photoelectric converter 11 that receives reflected light from a document plate, and a drive system (not shown) that changes the positions of these parts.

The first carriage 7 includes an illumination lamp 6 that irradiates light onto the document tray, a glue deflector 12 that serves as a reflector that collects the light from the illumination lamp 6 onto the document surface, and a second carriage that directs the reflected light from the document tray. A mirror 13 that guides the camera to the 8 side is mounted.

The second carriage 8 is equipped with mirrors 8a and 8b that guide the light guided by the mirror 13 to the lens 9. The first and second carriages 7.8 are connected to each other by a timing belt (not shown).
are arranged to move in the same direction at a speed of 172 as the first carriage 7. This makes it possible to scan while keeping the optical path length up to the lens 9 constant.

The lens 9 has a fixed focal length and is moved in the optical axis direction when changing the magnification. This lens 9 may be composed of a variable focal length lens such as a zoom lens.

The mirror part 10 has two mirrors 10a.

10b, and those mirrors 10a according to the change in optical path length corresponding to the selected magnification ratio.

The position of the lens 10b is changed, and by bending the optical path of the light from the lens 9 with the two mirrors 10a and 10b, the light is guided to the charging converter 11.

The photoelectric converter 11 photoelectrically converts the light reflected from the original scraps and separates and outputs the image on the original scraps as color signals of cyan, green, and yellow (or red, green, and blue) light. For example, it is mainly composed of a CCD type line image sensor. In this case, one pixel of the document is divided into three consecutive elements of the CCD sensor (C1G
,Y.

or R, G, B). The photoelectric converter 11
The output is supplied to an A/D converter 91, which will be described later.

The above first and second cartridges 7.8, lens 9, mirror 1
0g and 10b are each moved using a stepping motor (not shown) as a driving source. As shown in FIG. 5, the first and second carriages 7.8 actuate a timing belt 19 that is stretched between a drive pulley 14 connected to the rotating shaft of the stepping motor and idler pulleys 15 and 16. It will be moved accordingly. The mirrors 10a, 10b and lens 9
are separate stepper motors (not shown)
It is moved by A spiral shaft (not shown) is rotated by a corresponding stepping motor, and the lens 9 is moved in the optical axis direction by this spiral movement.

The image forming section 4 is configured as shown in FIG. 2, for example. That is, the platen drum 22 is disposed approximately at the center of the image forming section 4 . The platen drum 22 has a periphery made of an elastic material such as rubber, and functions as a platen roller for the thermal head 24. The platen drum 22 rotates in the direction of arrow A in the figure to wrap the paper P around its circumferential surface, thereby preventing the paper P from shifting during overlapping printing.

Around the platen drum 22, sheets of paper P are placed at predetermined intervals.
Pressure rollers 25, . The circumference of the platen drum 22 is slightly longer than the length in the longitudinal direction of the maximum paper size.

A thermal head 2 is located below the platen drum 22.
4 are arranged. The thermal head 24 is attached to a heat radiator integrally formed on the rear end surface of the holder.

An ink ribbon 26 as an image forming medium is interposed between the platen drum 22 and the thermal head 24. Core 3 of the ink ribbon 26
0.degree. 31 is connected to a drive shaft of a motor (not shown) via a drive force transmission mechanism (not shown), and is rotated as required.

FIG. 1 is a diagram showing the structure of the main parts of the image forming section. In the illustrated state, the thermal head 24 is in pressure contact with the platen drum 22. From this state, when the camshaft 100 is rotationally driven to rotate the thermal head pressure contact cam 101, the thermal head 24 is separated from the platen drum 22 according to the cam shape. At this time, the ink ribbon roll brake cam 1 fixed to the camshaft 100
02 also rotates at the same time to displace the ink ribbon roll brake lever 103, whereby the ink ribbon roll brake 104 attached to the end of the ink ribbon roll brake lever 103 is pressed against the ink ribbon roll brake roller 105. The rotation of the ink ribbon roll brake roller 105 is restricted. The ink ribbon roll brake roller 105 is connected to the winding core 30 on the feeding side via a drive train, and therefore, the rotation of the ink ribbon 26 on the feeding side is restricted in synchronization with the release of the thermal head 24 from pressure contact.

On the other hand, when the thermal head 24 is in pressure contact with the platen drum 22, if torque is applied in the winding direction to the winding core 31 on the winding side while the rotation of the winding core 30 on the feeding side is restricted, the ink ribbon 26 When the thermal head pressure contact cam 101 is rotated in this state, the thermal head 24 is brought into pressure contact with the platen drum 22, and
Ink ribbon roll brake cam 102 rotating at the same time
As a result, the ink ribbon roll brake lever 103 is displaced and the ink ribbon roll brake 104 is separated from the ink ribbon roll brake roller 105. In other words, rotation of the winding core 30 on the feeding side becomes possible in synchronization with the pressure contact of the thermal head 2. In such a configuration, by appropriately selecting the shape and phase difference of the two cams 101 and 102, it is possible to press the thermal head 26 into contact with the ink ribbon 26 without causing wrinkles or slack.

The ink ribbon roll brake roller 105 and the feeding-side winding core 30 may be directly connected, but by increasing the rotation speed of the feeding-side winding core 30 by a drive train, the braking torque at the ink ribbon roll brake roller 105 can be reduced. It is possible to do so. Further, although the two cams 101 and 102 are connected by the same camshaft 100, camshafts in a row connected by a drive train may be used.

As shown in FIG. 2, a paper feed roller 41 is provided at the lower right portion of the main body 1, and takes out sheets of paper P as an image forming medium stored in the paper feed cassette 20 one by one. It looks like this. The paper P taken out by the paper feed roller 41 is transported toward the platen drum 22 by a conveyance roller 42 via a guide 43, and is wrapped around the platen drum 22 by a gripper 23, a pressing roller 25, and so on. This makes it possible to convey the paper accurately. Here, the paper feed cassette 20 is attached to the main body 1.
It can be attached and detached from the side. Note that 46 in FIG. 2 is a manual paper feeding device for manually feeding paper P and the like. The paper P fed from the manual paper feeder 46 is also wound around the platen drum 22 in the same manner as described above.

The paper P, whose leading end is fixed by the gripper 23, is wound around the platen drum 22 by rotation in the direction of arrow A in the figure, and after the leading end passes through the printing area, the thermal head 24 is pressed against the platen drum 22, and printing is performed. will be held.

- When the color printing is completed, the platen drum 22 has made approximately one rotation. Here, the thermal head 24 is once released, the ink ribbon 26 is wound up, and the next color is located.

Then, the platen drum 22 is again indicated by the arrow in the figure.

It starts rotating in the direction A, and the thermal head 24 prints, and the next color is printed in an overlapping manner.

In this manner, in the case of full-color copying, image formation is performed by four operations of yellow, magenta, cyan, and black, or three operations of yellow, magenta, and cyan.

In the case of a single color such as black, it is performed in one operation.

When discharging paper, the platen drum 22 is rotated in the direction of arrow A in the figure until the rear end of the paper P reaches the paper discharge guide 27, and when it reaches the guide 27 for paper discharge, the platen drum 22 is rotated in the direction of arrow B in the figure. The rear end of the paper P is separated from the platen drum 22 by a separation claw (not shown), and the paper discharge guide 27 is rotated.
lead to. Finally, the tip of the paper P is held by the gripper 23.
The paper P, on which copies have been made, is released and transported by the paper ejection guide 27 and is ejected onto the paper ejection tray 28.

FIG. 6 schematically shows the overall control system, which includes a main control section 81, a first sub-control section 82, and a second sub-control section 83. The main control unit 81 includes an operation panel 80, a memory 9
9, each connected to a correction circuit 84, a luminance/color difference separation circuit 85, an image quality improvement circuit 86, a color signal conversion circuit 87, a binarization circuit 88, a first sub-control unit 82, and a second sub-control unit 83;
It is designed to control these things.

The first sub-control section 82 includes a light source control section 89, a motor drive section 90. It is connected to the photoelectric converter 11, A/D converter 91, and resolution converter 92, respectively, and controls these. The light source control unit 89 is connected to the illumination lamp 6 and controls its lighting and light amount. That is,
The illumination lamp 6 is turned on during normal image reading operation. The motor drive unit 90 includes the scanning motor 18
drive.

The second sub-control unit 83 includes a thermal head temperature control unit 93,
It is connected to the thermal head 24, various detection switches 94, and drive section 95, respectively, and controls these. The drive unit 95 is connected to a drive system 96 such as a motor and a solenoid, and drives the drive system 96 .

The memory 99 stores reference data obtained by A/D converting the light reflected by the white reference plate 59.

The correction circuit 84 performs standardization (shading correction, etc.) using image data (after resolution conversion) obtained by A/D converting the reflected light from the original document and reference data stored in the memory 99 (shading correction, etc.). correction).

Further, the color signal conversion circuit 87 will be explained in more detail with reference to FIG. Luminance signal (■), color difference signal 1 (CI), and color difference signal 2 sent from the image quality improvement circuit 86
Each signal (C2) is sent to a color signal conversion circuit 87, and the color signal conversion circuit 87 sends out any one of Y, MSC, and B color signals to a binarization circuit 88. At this time, the selection of the Y, MSC, and B color signals is performed by the main control section 81. That is, as shown in the table below, the main control unit 81 selects the Y and M%C1B color signals sent to the binarization circuit 88 based on the combination of the signals a and b. Note that the color signals are automatically selected in sequence (for example, in the order of YMC→B).

Table 1 Next, the operation in the above configuration will be explained. For example, the operator now specifies copying conditions such as magnification using the operation panel. Then, the main control unit 81 determines the copyable range (
The width of the motor 5 is determined based on the result of this determination.
Drive 8.

As a result, the pointers 51 and 52 are moved to indicate the copyable range determined by the specified copying conditions and the size of the paper P.

In response to this instruction, the operator places the document plate L7 and presses a copy start key (not shown). Then, the main control section 81 drives the motor 58 to move the pointer 51.degree. 52 to a position equal to or larger than the maximum document width (for example, 297 mm for A3 size), that is, to a non-image area. The main controller 81 also turns on the illumination lamp 6 and controls the first and second carriages 7.8.
move. Thereby, the light from the illumination lamp 6 is irradiated onto the white reference plate 59 and the document plate via the document table 2.

The reflected light from these white reference plate 59 and the original plate is reflected by mirror 13.8al 8b% lens 9, mirror 10a, 10
b in order to be guided to the photoelectric converter 11. This photoelectric converter 11 converts the light into cyan (C), green (G),
Yellow (Y), red (R), green (G),
It is separated into a blue (B) analog color signal and sent to the A/D converter 91. The A/D converter 91 converts each analog color signal into a digital signal. This A/D
The signal from the white reference plate 59 from the converter 91 is stored in nine memories as reference data.

The original signal from the A/D converter 91 is output to the resolution converter 92.

The resolution conversion unit 92 performs resolution conversion to match the resolution of the photoelectric converter 11 and the resolution of the thermal head 24, and sends the result to the correction circuit 84. At this time, if the resolutions of the photoelectric converter 11 and the thermal head 24 are the same, the above resolution conversion process is omitted. Correction circuit 8
4 are C, G, Y, sent from the resolution converter 92;
Alternatively, each color signal of RlG and B is standardized using the reference data stored in the memory 99, that is, correction processing (shading correction) is performed to correct variations in the photoelectric converter 11, and the results are used as luminance. Color difference separation circuit 8
Send to 5. The luminance color difference separation circuit 85 receives C and G signals sent from the correction circuit 84.

Various calculation processes are performed on each color signal of Y, R, G, and B to produce a luminance signal (I), color difference signal 1 (CI), and color difference signal 2.
(C2) and sent to the image quality improvement circuit 86. The image quality improvement circuit 86 analyzes the luminance signal, color difference signal 1, and color difference signal 2 sent from the luminance color difference separation circuit 85,
Image quality improvement processing such as edge emphasis and character identification is performed on the signal, and the signal is sent to the color signal conversion circuit 87. The color signal conversion circuit 87 receives a luminance signal, a color difference signal 1, and a color difference signal 2 that have been subjected to image quality improvement processing.
Performs color conversion based on yellow (Y), magenta (
A binarization circuit 88 send to

The binarization circuit 88 receives the color signals (Y, M, etc.) sent from the color signal conversion circuit 87.

C, B) is subjected to area gradation conversion, that is, binarization, by a dither method or the like, and the binarized signal is sent to the thermal head temperature control section 93. The thermal head temperature control section 93 sends a print signal to the thermal head 24 based on the binarized signal supplied from the binarization circuit 88 .

Further, in response to the input of the copy start key (not shown), the paper P in the paper feed cassette 20 is taken out by the paper feed roller 41, and this taken out paper P is transferred to the transport roller 42.
is conveyed by the platen drum 2 via the guide 43.
2, and its tip is fixed by a gripper 23. As a result, the paper P is wound around the platen drum 22.

In response to this state, the thermal head 24 is brought into pressure contact with the platen drum 22, and prints (that is, forms an image) on the paper P wound around the platen drum 22 in accordance with the print signal. Then, repeat the above operation as Y,
A full-color image is formed by repeating the process for each of the M, C, and B colors.

When the printing is finished, the main control section 81 turns off the illumination lamp 6, discharges the paper P wound around the platen drum 22, and ends the copying operation.

As described above, when the thermal head 24 and the platen drum 22 are brought into contact with each other, the ink ribbon 26 moves along the running direction in synchronization with the separation between the thermal head 24 and the platen drum 22, and the side winding core 30 The thermal When the head 24 and the platen drum 22 are separated from each other, tension is generated in the ink ribbon 26 so that no wrinkles or slack occur. Since the movement along the direction is released, the ink ribbon 26 has no wrinkling or slack when the image forming operation starts, and it is possible to start forming a good image. Furthermore, as a drive source for moving the ink ribbon 26, it is sufficient to have one motor that drives the winding core 31 on the take-up side, and the device can be made smaller, lower in power consumption, and lower in cost. It has become something that can be done.

FIG. 8 shows another embodiment of the invention. ink ribbon 2
As a means for restricting the movement along the running direction of the first
A latch wheel 105a is used instead of the ink ribbon roll brake roller 105 shown in the figure, and instead of pressing the ink ribbon roll brake 104, a claw provided at the tip of the ink ribbon roll brake lever 103 is hooked onto the latch wheel 105a. With this configuration, it is possible to produce the same effects as in the above embodiment.

FIG. 9 shows yet another embodiment of the invention. As a means for releasing the restriction on the movement of the ink ribbon 26 along the running direction, a solenoid 108 and a ratchet lever 109 are used in place of the ink ribbon roll brake lever 103 and the ink ribbon roll brake cam 102 shown in FIG. An interrupter 10 rotates in conjunction with a photo interrupter 106 and a thermal head pressure contact cam 101 as means for synchronizing the pressure contact of the thermal head 24 and the release of restrictions on the movement of the ink ribbon 26 along the running direction.
7, and the solenoid 108 sucks and releases the ratchet lever 109 in synchronization with the output signal of the thermal head pressure detection means. It is also possible to produce effects similar to those in the example.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to stably remove wrinkles and slack from an ink ribbon, and furthermore, it is possible to reduce the size, power consumption, and cost of the apparatus. It is possible to provide an image forming apparatus that can perform

[Brief explanation of drawings]

1 to 9 are for explaining the present invention in detail. FIG. 1 is a diagram showing the structure of the main part of the image forming section, and FIG. 2 is a cross-sectional view schematically showing the overall configuration. Figure 3 is a diagram for explaining the arrangement of the pointer and the white reference plate;
The figures are for explaining the main parts of Fig. 2, Fig. 5 is a schematic perspective view showing a part of the configuration, Fig. 6 is a block diagram schematically showing the overall control system, and Fig. 7 is a block diagram for explaining the color signal conversion circuit in detail, FIGS. 8 and 9 are diagrams showing the structure of the main parts of the image forming section in other embodiments, and FIG. 10 is a block diagram for explaining the color signal conversion circuit in detail. FIG. 2... Original table, 3... Original scanning unit, 4... Image forming unit, 22... Platen drum (rotating means), 24...
... Thermal head (thermal recording means), 26 ... Ink ribbon (transfer material), 100 ... Camshaft, 10
1... Thermal head pressure contact cam (contact/separation means), 102
... Ink ribbon roll brake cam, 103...
Ink ribbon roll brake lever 104... Ink ribbon roll brake, 105... Ink ribbon roll brake roller, D... Document, P... Paper (image forming medium).

Claims (1)

[Scope of Claims] A rotating means for rotating an image forming medium wrapped around its outer periphery; a transfer material running between a pair of cores while in contact with the rotating means; and a transfer material being wound around the rotating means. an image forming apparatus comprising: a thermal recording means for transferring an image while being pressed against an image forming medium; When the thermal recording means and the rotating means are separated, the movement of the transfer material in the running direction is restricted, and when the thermal recording means and the rotating means are brought into pressure contact, the movement of the transfer material is restricted. An image forming apparatus comprising: means for releasing restrictions on movement along a traveling direction.