JPH01108078A - Image forming device - Google Patents

Abstract

PURPOSE:To contrive higher printing accuracy and superimposing accuracy, by providing a medium-restricting means using a sheet-shaped member for pressing an image-forming medium against a feeding body and for releasing the medium from the pressed state. CONSTITUTION:A medium-restricting means 5 comprises a first pressing part 5A disposed on the lower side of a platen drum 2 and a second pressing part 5B disposed on the upper side of the drum 2. During printing on a paper, both sheet-shaped members 21, 26 of the medium-restricting means 5 remain pressed against the outer peripheral surface of the drum 2 by elastic forces of first and second energizing members 21, 25, respectively, whereby the paper being printed is inserted between the drum 2 and the sheet-shaped members 21, 26 in satisfactory close contact with the outer periphery of the drum 2. After superimposing printing in e plurality of colors is conducted by reciprocating the drum 2 in the directions of arrows alpha1, alpha2 a plurality of times, first and second rotary brackets 19, 24 at the first and second pressing parts 5A, 5B are turned to release the sheet-shaped members 21, 26 from the pressed state.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus, and more particularly, to an image forming apparatus, and more particularly, to The present invention relates to an image forming apparatus that wraps the paper around a conveyance member and forms images of multiple colors on the paper using a thermal transfer method in this state.

(Prior Art) An overview of a conventional image forming apparatus using a thermal transfer method will be explained with reference to FIGS. 6 to 10.

FIG. 6 shows a thermal transfer type color copying machine as an example of an image forming apparatus, and an image reading means 150 is provided on the upper surface of the main body 1 of the apparatus. The image reading means 10 is provided with a document cover 103 that can be opened and closed, and a document table 102 made of transparent glass on which a document is placed is provided below the document cover 103. The image reading unit 150 optically scans a document set on the document table 102 by reciprocating a scanner section including an exposure optical system along the lower surface of the document table 102, and photoelectrically converts this optical information. It is something to do. This image reading means 15
The information converted in 0 is supplied to an image forming means 200 provided inside the apparatus body 100, and this image forming means 2
At step 00, an image is formed on paper P as an image forming medium in accordance with the converted information.

Here, the image reading means 150 will be briefly described in detail.

The image reading unit 150 includes a first carriage 151 configured to be movable along the document table 102 and a second carriage 152 configured to be movable along the document table 102 similarly to the first carriage 151. , imaging lens 15
3, and a first correction mirror 154 and a CCD that correct the optical path length when magnifying and reading image information attached to a document.
a light receiving means 160 consisting of a line sensor 155; Second carriage 151, 152, imaging lens 15
3. It has a drive system that changes the position of the light receiving means 160.

The first carriage 151 includes a light source lamp 156 as a linear light source, a deflector 157 that focuses the light from the light source lamp onto the document surface, and a second carriage that receives reflected light from the document surface. 152 first mirror 15
It is equipped with 8.

The second carriage 152 changes the optical path of the light from the first mirror 158 and sends it to the imaging lens 153. It includes third mirrors 161 and 162.

The imaging lens 153 is of a fixed focal length type,
During zooming, this imaging lens 153 is moved in the optical axis direction.

The light receiving means 160 can change its position with respect to the imaging lens 153 in response to a change in optical path length caused by a preselected magnification ratio. Light receiving means 160
captures the reflected light from the original through the optical system mentioned above, converts it photoelectrically, and separates and outputs the image information attached to the original as cyan, green, and yellow (or red, green, and blue) color signals. It is something to do.

The imaging lens 153 and the light receiving means 160 are driven in the optical axis direction by a spiral shaft 16 driven by a stepping motor (not shown), as shown in FIG.
4 and a bracket 165 screwed onto this spiral shaft 164, the bracket 16
This is done by moving the imaging lens 153 and the light receiving means 160 connected to the lens 5 in the optical axis direction.

As shown in FIG. 4, the image forming means 200 includes a thermal print head 142 that approaches and separates from the outer circumferential surface of the platen drum 140 with a fulcrum 141 as the rotation center, and a head surface of the thermal print head 142 and a surface of the platen drum 140. An ink ribbon 143 interposed between the paper P that is wrapped around the outer periphery and conveyed, and a supply roller 144 that supplies and winds up the ink ribbon 143.
It includes a take-up roller 145 and guide rollers 146 and 147 that guide the ink ribbon 143 so as to come into sliding contact with the outer peripheral surface of the platen drum 140.

Incidentally, the ink ribbon 143 is prepared in a plurality of colors or in a single color depending on color copying or monochrome copying. The outer periphery of the platen drum 140 is made of an elastic material such as rubber, and the outer periphery is set to be slightly larger than the length of the maximum paper size (for example, A3).

Additionally, a paper feed cassette 130 is provided in the apparatus main body 100.
A paper feed side conveyance path 170 is provided between the platen drum 140 and the platen drum 140, and a paper discharge side conveyance path 171 is provided to perform a discharge operation of the paper P discharged from the platen drum 140.

The paper feed side conveyance path 170 is for forming a moving path for the paper P between the paper feed cassette 130 and the platen drum 140, and along the way there is a registration roller 131 that aligns and pressure-feeds the copy paper. Equipped with:

Further, the paper discharge side conveyance path 171 is connected to the platen drum 14.
This is for forming a moving path for the paper P on which an image has been formed between the sheet P and the paper ejection tray 190, and is provided with a paper ejection roller 191 in the middle and at the end.

On the outer periphery of the platen drum 140, three pressure rollers 201, 202, and 203TFI rollers are arranged so as to be in sliding contact with the D7 platen drum 140, and the platen drum 1
The paper P, one end of which is held by a gripper 120 provided on the platen drum 140, is brought into pressure contact with the circumferential surface of the platen drum 140.

Next, the operation of the apparatus having the above configuration will be explained with reference to FIGS. 7 to 10, and the image forming means 200. Platen drum 14
0 and the operation of the gripper 120 will be mainly explained.

When this device starts copying a document, the image reading unit 150 reads and scans the document and feeds paper from the paper feed cassette 130 to the paper feed side transport path 170.

After the paper P taken out from the paper feed cassette 130 is aligned by the registration roller] 31, it is transferred to the platen drum 14.
As shown in FIG. 8, the gripper 120 placed at
Fixed to 0.

Next, the platen drum 140 starts normal rotation (clockwise rotation in FIG. 16).
Wrap paper P around the outer peripheral surface of 0 itself. The wound paper P is pressed against the outer circumferential surface of the platen drum 140 by pressure rollers 201, 202, and 203, thereby preventing misalignment during overlapping printing.

The paper P, whose leading end P1 is fixed by the gripper 120, is rotated clockwise and wound around the platen drum 140, and then its leading end P1 is attached to the thermal print head 1.
42, this thermal print head 142 is pressed against the platen drum 140 side to perform printing.

At this time, if the gripper 120 is protruding outside the circumference of the platen drum 140 as shown in FIG.
Since the thermal print head 142 cannot be pressurized until after the paper P has sufficiently escaped, the leading edge P of the paper P
The width of 1 becomes large. Therefore, as shown in FIG.
It is preferable that the gripper 120 enters inside the circumferential surface of the platen drum 140, as shown in FIG.

Furthermore, as shown in FIG. 9, the gripper 120 extends in the length direction (axial direction) of the platen drum 140.
If alignment is performed using the contact surface of the paper P in the gripper 120, the registration rollers 131 can be omitted.

At the stage when printing of the first color is completed by the above-described printing operation, the platen drum 140 has completed approximately one revolution.

At this stage, the printing operation of the thermal print head 142 is temporarily canceled. Then, the ink ribbon 143 is wound up, and the cue for the second color is performed. Then, the platen drum 140 starts rotating clockwise again, and the tip end P1
When the color passes through the printing area, the thermal print head 142 is again pressurized to print the next color in an overlapping manner.

When discharging the printed paper P, the platen drum 1
40 rotates clockwise until the rear end of the paper P reaches a paper guide provided in the paper discharge side conveyance path 171, and then rotates in the opposite direction.

As a result, the paper P is conveyed to the paper discharge tray 190 via the paper guide and the paper discharge roller 191, as shown in FIG. 7(b). At this time, the gripper 120 releases the paper P.

As shown in FIG. 9, if the gripper 120 is configured to be slightly buried inward from the outer periphery of the platen drum 140, the non-image area can be made smaller to some extent.

However, in the conventional apparatus with the above configuration, the paper P
is pressed against the platen drum 140 by three pressure rollers 201, 202 and 203, so the area where the paper P and the platen roller are in close contact is in a line contact state, and the contact area is small, so the paper P is pressed against the platen drum 140. There is a high possibility that it will float up from the outer periphery of the drum 140, resulting in a problem that the printing accuracy by the thermal print head 142 and the overlay accuracy in multicolor printing deteriorate.

On the other hand, if the number of pressure rollers is increased in an attempt to increase the contact area, there is a problem in that the manufacturing cost increases and the weight of the device increases.

(Problems to be Solved by the Invention) As described above, in the conventional apparatus, there is a problem in that the adhesion of the paper P to the platen roller is poor, resulting in a decrease in printing accuracy 1 overlay accuracy.

Therefore, although the present invention has a simple configuration, it is possible to obtain high adhesion between the paper and the conveying body, thereby achieving printing accuracy of 1.
This is necessary because the object is to provide an image forming apparatus that can improve overlay accuracy. .

[Structure of the Invention] (Means for Solving the Problems) The present invention provides an image forming apparatus in which an image forming medium is conveyed while being wrapped around a conveying member, and the image forming medium is subjected to image formation by an image forming means. The image forming apparatus includes a medium restraining means using a sheet-like member that presses the image forming medium against the conveyance body and releases the image forming medium from the pressed state.

(for production) The operation of the apparatus having the above configuration will be explained below.

In this apparatus, when forming an image by the image forming means, the image forming medium is transported while being wound around a transport member. At this time, the sheet-like member of the medium restraining means presses the image forming medium against the conveying body in surface contact. This improves the adhesion between the image forming medium and the conveying body.

On the other hand, after image formation, the medium restraining means releases the image forming medium from the pressed state.

(Example) Examples of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 shows an image forming means 1, a platen drum 2 as a conveyor, and a platen drum 2 as a conveying member in an embodiment of the apparatus. A gripper 31 provided on the outer periphery of the platen drum 2, a paper feed/discharge mechanism section 4 for paper P as an image forming medium, and a medium restraining means 5 arranged facing the outer periphery of the platen drum 2 are shown.

The image forming means 1 includes a thermal print head 6 and an ink ribbon 7, as in the case of the conventional apparatus shown in FIG.
A supply roller 8 and a take-up roller 9 supply and take up the ink ribbon 7, and guide rollers 10, 11, 12, and 13 guide the ink ribbon 7 so as to be in full contact with the outer peripheral surface of the platen roller 2. It is equipped with.

The platen drum 2 is driven by a drive motor (not shown).
Arrow α1 shown in FIG. It is designed to be driven in the α2 direction.

The paper feed/discharge mechanism section 4 includes guide members 14 and 15 that guide the paper P toward the outer periphery of the platen drum 2, receive and discharge the paper P after printing from the platen drum 2, and this guide member. a triangular gate 16 which is rotatably arranged at the ends of the paper P and sets the conveyance direction when feeding and discharging the paper P; and both guide members 1.
A paper feed roller 1 whose outer periphery is in contact with the movement area of the paper P of 4°15 and performs paper feeding and paper ejection operations of the paper P.
7 and 18.

The gate 16 is designed to rotate to the solid line position shown in FIG. 1 when feeding the paper P, and to the dotted line position shown in the figure when discharging the paper P.

The medium restraining means 5 is a platen drum 2 shown in FIG.
The platen drum 2 includes a first pressure contact portion 5A disposed on the lower surface side of the platen drum 2, and a second pressure contact portion 5B disposed on the upper surface side of the platen drum 2.

The first pressure contact portion 5A includes a first fixing bracket 17 fixed to the end of the one guide member 14, and a first fixing bracket 17 that is rotatably arranged around a fulcrum 18 in the vicinity of the idle roller 12. 1 rotation bracket 19 and this first
A first biasing member (tension spring) 20 that biases one rotating bracket in the direction of arrow β1, and the first fixed bracket 17
and the first rotation bracket 20 and the first biasing member 2
A sheet-like member 21 made of a polyester film or plain paper that is in surface contact with the platen drum 2 under pressure due to an elastic force of 0, and a rotating member that resists the elastic force of the first biasing member 20 against the first rotating bracket 19. The platen roller 2 is provided with a driving means (not shown, such as an electromagnetic plunger) that imparts dynamic motion and presses the sheet-like member 21 against the platen roller 2 at this time.

The second pressure contact portion 5B includes a second fixing bracket 22 fixed to the end of the other guide member 15, and a second fixing bracket 22 that is rotatably arranged around a fulcrum 23 in the vicinity of the other guide roller 13. 2 rotation bracket 24 and this second
A second biasing member (tension spring) 25 that biases the rotating bracket 24 in the direction of arrow β2, and the second fixed bracket 22
and the second rotation bracket 24, the second biasing member 2
5, a sheet-like member 26 made of polyester film or plain paper that is in pressure contact with the upper surface of the platen drum 2; and the second rotating bracket 2.
4 is provided with a driving means (for example, an electromagnetic plunger), not shown, which imparts a rotational movement to the platen roller 2 against the elasticity of the second biasing member 25 and presses the sheet-like member 26 against the platen roller 2 at this time.

Here, regarding the configuration and operation of the gripper 3, the second
This will be explained with reference to FIGS. 3(a) and 3(b).

The gripper 3 shown in the figure has a slide piece 31a and a pressing piece 3.
1b is integrally molded into a single-shape shape.The slide piece 31a of this sandwich member 31 is fitted into the slide groove 33 provided in the platen drum 2, and the suppressing piece 31b is fitted into the slide groove 33 provided on the platen drum 2. facing the outer circumferential surface of the

An engaging piece 3 protruding outward is provided on the side edge of the pressing piece 31b.
1c is formed. Further, the slide piece 31a is urged toward the center of the platen drum 2 by a button 234 arranged on the side surface of the platen drum 2.

Further, a gripper opening/closing mechanism section 35 is provided facing the rotation area of the engagement piece 31c.

The gripper opening/closing mechanism section 35 has a pawl 36a that engages with the engaging piece 31G, a rocking body 37 that rocks about a fulcrum 38, and an urging force that applies a biasing force in the Y1 direction to the rocking body 37. The first spring 39 controls the position of the oscillating body 37. It is provided with second regulation pins 40a and 40b.

The operations of the gripper 3 and the gripper opening/closing mechanism 35 will be described with reference to FIGS. 6(a> and 6(b)).

When the platen drum 2 with the gripper 3 attached rotates in the X1 direction shown in FIG. 2 and the engaging piece 31G of the holding member 31 engages with the pawl 36a as shown in FIG. slides toward the outside of the platen drum 2 against the biasing force of the spring 34, thereby creating a gap 41 between the suppressing piece 31k) and the outer periphery of the platen drum 2. After the end of the paper P is inserted into this gap 41, when the platen drum 2 further rotates in the X1 direction, the engagement piece 31
G separates from the pawl 36a. At this moment, the clamping member 31 is pulled toward the center of the platen drum 2 by the spring 34, so that the pressing piece 31b strongly presses and clamps the edge of the paper P against the outer periphery of the platen drum 2.

After this, the platen drum 2 is reversed in the X2 direction and moves to the next process.

Next, an outline of the electrical control system of the embodiment apparatus and the principle of multicolor image formation will be explained.

As shown in FIG. 4, this embodiment device includes an overall control section 40 that controls the entire device, - image reading means 44,
The values of each color component of green (G), yellow (Y), and cyan (C) included in the image information read by the image reading means 44 are taken in, and the values are transferred to the printing medium of the ink ribbon 7, that is, the color of the ink. magenta (M) and yellow (Y).

A color conversion unit 41 that converts the color to cyan (C), and a color conversion unit 4
5. A memory section 42 stores the color information that has been color-converted in step 1 along with positional information on the document (not shown), and reads the color information and positional information stored in this memory section 42, and uses the values of the color information as shown in FIG. Magenta (M) and yellow (Y) on the ink ribbon 7 as shown in (a) and (b).

It is equipped with a thermal print head 6 that melts and transfers cyan (C) and black (B) ink onto the paper P. still,
The black (B) color component mentioned above is obtained from the output of an AND gate 43 connected between the memory section 42 and the thermal print head, as shown in FIG.

Next, the operation of the apparatus configured as described above will be described, mainly with respect to the operation of the medium restraining means 5 that presses the paper P against the platen drum 2 or releases the pressed state.

When the gate 16 is in the solid line position shown in FIG. 1, the paper MP passes through the gate 16 and between the guide members 14 and 15, and is installed on the outer periphery of the platen drum 2 by the rotation of the paper feed roller 17°18. It is sent to gripper 3.

The gripper 3 grips the leading end of the paper P in the manner described above, and in this state rotates the platen drum 2 in the direction of the arrow α1. Then, this paper P is conveyed to the print leading edge position. At this time, the ink ribbon 7 is also fed to the print leading edge position.

In this state, attach the thermal print head to platen drum 2.
Pressure is applied to the side, and the platen drum 2 is rotated in the direction of the arrow α1 to perform a printing operation on the paper P.

During the printing operation on such paper P, the medium restraining means 5
Both sheet-like members 21 and 26 of the first . The elasticity of the second biasing member 20.25 maintains the state in which it is in pressure contact with the outer peripheral surface of the platen drum 2, and as a result, the paper P being printed enters between the platen drum 2 and both sheet-like members 21.26. As a result, the paper P is brought into complete contact with the outer periphery of the platen drum 2.

Then, move the platen drum 2 to the arrow α1. After reciprocating in the α2 direction multiple times and performing a single overlapping print of multiple colors on the paper P, a drive means (not shown) moves the first pressure contact portion 5A and the second pressure contact portion 5A.
1st degree second rotation bracket 19.2 in pressure contact part 5B
4 to release the pressed state of the sheet-like members 21 and 26. As a result, the paper P is loosely wound around the outer periphery of the platen drum 2.

Thereafter, the platen drum 2 is rotated in the direction of arrow α1, and the rear end of the paper P is placed on the guide member 14. Next, the platen drum 2 is rotated in the direction of arrow α2, and the paper feed rollers 17 and 18 are rotated in the opposite direction to the direction in which paper is fed, and at this time, the gate 16 is rotated to the position shown by the dotted line. , the paper P in the print groove is discharged in the direction of the arrow.

The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the invention.

[Effects of the Invention] According to the present invention described in detail above, since the image forming medium is brought into close contact with the conveying body by the medium restraining means having a simple structure using a sheet-like member, the image forming medium It is possible to provide an image forming apparatus that can improve adhesion to a conveying body, and improve printing accuracy 2 and overlay accuracy.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing a device according to an embodiment of the present invention, FIG. 2 is an enlarged perspective view showing a gripper of the device, FIG. 3(a),
(b) is an explanatory diagram of the same operation as above, FIG. 4 is a block diagram showing the electrical control system of the embodiment device, and FIGS. 5(a) and (
b) is an explanatory diagram showing the image forming principle of the same device, FIG. 6 is an overall sectional view of the conventional device, FIGS. 7(a) and (b) are explanatory diagrams showing the paper conveyance state of the conventional device, respectively, Fig. 8 is an enlarged explanatory diagram showing the state in which paper is held in the conventional device, Fig. 9 is an enlarged omitted cross-sectional view showing the state in which the paper is wrapped around the platen drum in the conventional device, and Fig. 10 is a positional relationship between the paper and the gripper. FIG. DESCRIPTION OF SYMBOLS 1... Image forming means, 2... Platen drum, 5...
...Medium restraining means, 21.26... Sheet-like member. (G) Figure 5 Figure 7 Figure 8 Figure 9 Figure 10

Claims (2)

[Claims] (1) In an image forming apparatus in which an image forming medium is conveyed while being wrapped around a conveying body, and the image forming medium is subjected to image formation by an image forming means, the pressing operation and the pressing state of the image forming medium against the conveying body are controlled. An image forming apparatus characterized by having a medium restraining means using a sheet-like member that performs an operation of releasing an image forming medium. (2) The image forming apparatus according to claim 1, wherein the sheet-like member is selected from polyester film and plain paper.