JPH04261880A - Image forming device - Google Patents

Abstract

PURPOSE:To make the blank space of a paper narrow and effect an efficient printing without increasing the size of a carriage driving mechanism or ribbon cassette. CONSTITUTION:A paper 1 is held against the surface of a platen 20 by a bail bar 50 and the right end part of a recording head 40 in its paper feed direction is formed into a curved surface contour extending continuously from the surface of a recording head to the rear face of a radiating plate 41 in order to prevent the recording head 20 from being caught by an end part 1a of the raised paper. The recording head 40 is moved to the side of the paper 1 with its head facing downward to a raised face 23 of the platen 20 separated a suitable distance from the left edge of the paper 1 and the printing is started at a point at which the speed becomes constant.

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 such as a printer used as a print output device for a word processor or a personal computer.

0002

2. Description of the Related Art An example of this type of printer is a thermal transfer type serial thermal printer, and the image forming apparatus of this printer is constructed as shown in FIG. In FIG. 4, 100 is a paper feed roller that conveys the paper 101 upward, and a rubber platen 200 is disposed near the upper side of this paper feed roller 100. A carriage 30 faces the paper feed roller 100 and the platen 200.
0, and this carriage 300 has a guide shaft 350 parallel to the support shaft of the paper feed roller 100.
and a carriage base 310 that is reciprocatably provided on the guide shaft 350.

Platen 200 of carriage base 310
A recording head 400 is provided in a portion facing the recording head 400 . The recording head 400 is mounted on the carriage base 310 during printing.
An ink ribbon (not shown) of a ribbon cassette 320 set above is brought into contact with the paper 101 on the platen 200, and the ink of the ink ribbon is thermally transferred to the paper 101 to perform printing (image recording).

0004

By the way, in the above configuration, when the paper 101 is inserted into the paper feed roller 100,
When the paper feed roller 100 is rotated to convey the paper 101, the elastic restoring force of the paper 101, which is conveyed while being wrapped around the paper feed roller 100, causes the paper feed roller 1 to rotate.
The leading edge of the paper 101 that has left the paper 101 collapses toward the carriage 300, and the paper 101 rises from the surface of the platen 200 at the upper end of the platen 200, as shown in FIGS. 4 and 5.

In this state, when the recording head 400 is lowered onto the platen 200 in order to print on the paper 101 and moved in the direction of arrow C shown in FIG. Since the left end of the paper 101 in the figure gets caught and the paper 101 is not pressed against the surface of the platen 200, normal printing operation cannot be performed. In order to eliminate such drawbacks, as shown in FIG. 6, the head down position of the recording head 400 is set to
Select the position shown in , press the left end of the paper 101 with the recording head 400, and from this state move the recording head in the direction of arrow C.
It is sufficient to print by moving it in the direction. However, this method has the following drawbacks. That is, as shown in FIG. 7, when the recording head 400 is activated and accelerates until the speed of the recording head 400 reaches a predetermined speed,
Since stable printing cannot be performed, the acceleration area D (=
P0 to P1), the printing operation cannot be started. Therefore, the area from the left edge of the paper 101 to P1 becomes a blank area E where no printing is performed, and there is a drawback that the blank area E becomes large.

[0006] In order to reduce the above-mentioned margin E, it is necessary to increase the driving force for moving the recording head 400, improve the acceleration performance, and relatively reduce the acceleration time, that is, the acceleration area D. . However, this method requires a large motor, resulting in an increase in the size and cost of the device.

Another method for reducing the margin E is to lower the recording head 400 to a position P3 where the end of the recording head 400 in the moving direction can press the paper 101, as shown in FIG. There is a method that can be considered, but according to this method, the margin E1 can only be made slightly smaller than the margin E, and it cannot be said to be an effective method. In addition, as another method, as shown in FIG.
A heat sink 41 provided on the back side of the head substrate 410 of 0
By making 0a wider, when the head is down, this heat sink 41
A possible method is to press the paper 101 at the end of the moving direction side of 0a to reduce the margin to E2 and print. However, according to this method, the heat dissipation plate 410a, that is, the recording head 400 becomes larger, so the ribbon cassette must also become larger, and the carriage 300 becomes larger.
This has the disadvantage that the entire printer becomes large in size.

SUMMARY OF THE INVENTION The present invention has been made to solve the various drawbacks of the prior art, and aims to provide an image forming apparatus that can reduce the size and cost of the apparatus and reduce the margins.

[0009]

[Means for Solving the Problems] The image forming apparatus of the present invention includes a carriage having a recording head facing the platen, which is movable back and forth in a direction perpendicular to the paper feeding direction with respect to the platen. In an image forming apparatus that forms an image on a sheet, the corner of the recording head in the paper feeding direction is configured with a continuous curved surface from the recording head surface to a heat dissipation plate formed on the back surface of the recording head, and the sheet to be recorded is placed on the platen. The recording head is provided with a guide member that is brought into contact with the recording head so that the operation of the recording head can be started from outside the starting edge of the paper,
This achieves the above objective.

0010

[Operation] According to the above structure, the guide member allows the paper to be aligned with the surface of the platen. Since the right end of the recording head, which is the corner on the side in the paper feed direction, is composed of a continuous curved surface from the recording head surface to the heat sink, when the recording head moves, the recording head catches the edge of the paper. No problems occur. In addition, since there is no need for the recording head to press down on the axial end of the paper when the head is down, the main acceleration area of the recording head can be set to the outside of the paper. Therefore, since printing can be performed immediately from the widthwise end of the paper, the margin can be made smaller.

[0011]

[Examples] Examples of the present invention will be described below.

FIGS. 2 and 3 show a thermal transfer type serial thermal printer to which the present invention is applied, and a paper feed roller 10 is rotatably supported in a predetermined position of the printer in the direction of arrow B. A paper guide 11 having a radius of curvature slightly larger than the radius of the paper feed roller 10 is provided below the paper feed roller 10 . In addition, guide rollers 12,
12 is provided in contact with the surface of the paper feed roller 10.

A platen holder 25 is disposed near the upper side of the paper feed roller 10, and has a platen holding portion 25a bent downward at its tip.
A rubber platen 20 is fixed to the platen holder 25 over substantially the entire length thereof. In addition, a carriage 30 is provided opposite the paper feed roller 10 and the platen 20, and this carriage 30 is parallel to the support axis of the paper feed roller 10, but has a guide shaft 35,
The carriage base 31 is movable back and forth in the longitudinal direction of the guide shaft 35. A recording head 40 comprising a heat sink 41a on the back side of a head substrate 41 is disposed at the upper part of the carriage base 31 facing the platen 20. The recording head 40 is in a head-down position where it is pressed against the surface of the platen 20;
It is rotatable to a head-up position away from the surface, and this rotational movement is controlled by a control circuit 60 shown in FIG. The control circuit 60 includes a drive unit such as a motor and a control unit that controls the drive unit, and in addition to the above control, controls the carriage base 31 to reciprocate in the direction shown by arrow C in FIG. Heating control is performed. Note that heating control of the recording head 40 and more specifically the head substrate 41 is performed in accordance with serial print data transferred to the control circuit 60 from a print data transfer section (not shown).

A sheet of paper 1 is conveyed between the recording head 40 and the platen 20 described above. The paper 1 is conveyed by the above-described paper feed roller 10 and guide rollers 12, 12 working together, and the paper 1 is conveyed upward while being wrapped around the surface of the paper feed roller 10.

A ribbon cassette 32 that supports an ink ribbon 33 in a movable manner is set above the carriage base 31, and when the recording head 40 is lowered, the ink ribbon 33 is pulled out from the ribbon cassette 32, and the recording head 40 and the platen are pulled out. Paper 1 conveyed between 20 and 20
be contacted. At this time, the portions of the ink ribbon 33 located on both sides of the recording head 40 are held by guide plates 42 and 43 erected from the carriage base 31. On the other hand, when the recording head 40 is raised, the ink ribbon 33 is released from contact with the paper 1.

In addition, above the recording head 40, a bail bar 50 is arranged as a conveyance guide member that causes the paper feed roller 10 to press the leading end of the paper 1 against the surface of the platen 20. As shown in FIG. 3, the bail bar 50 is arranged with its lower end side inclined toward the ribbon cassette 32, and the leading end of the paper 1 is pressed against the surface of the platen 20 by the guiding action of the inclined surface 51. Therefore, the paper feed roller 10
Despite the elastic restoring force of the paper 1 being conveyed while being wrapped around the paper 1, the leading end of the paper 1 can be brought into reliable contact with the surface of the platen 20.

The paper 1 that comes into contact with the surface of the platen 20 is as shown in FIG. The recording head 40 that prints on the paper 1 has a head chip surface on the left end 40a in contact with the paper 1 to improve contact with the paper 1, and a right end 40b separated from the paper 1. It is in a top-down and right-down state. Such a recording head 40 is provided with a heat dissipation plate 41 on the back surface to prevent heat from accumulating in the recording head 40 and improve print quality. The right corner 40 of the heat dissipation plate 41 on the paper feeding direction side is located at a position P4 slightly deviated leftward from the left edge of the paper 1 as a home position before printing starts.

In such a configuration, the substrate head 41
When a printing operation is performed in which the ink of the ink ribbon 33 is thermally transferred to the paper 1 by heating the recording head 40 and moving the recording head 40 in the direction of the arrow C, the end of the recording head 40 protrudes in front of the paper 1. This not only prevents the recording head 40 from catching the left edge of the paper even if the left edge 1a, which is the recording start edge, of the paper 1 is raised, but also prevents the recording head 40 from catching the left edge of the paper. E can be made smaller.

That is, as shown in FIG. 1, the recording head 40 is moved down to a position P4 that is an appropriate distance away from the left edge of the paper 1, and is started from this position to reach an acceleration area D (=P
4 to P5), the speed reaches a steady state, and printing starts at position P5. Therefore, the margin E3 in this case is
This corresponds to the length from the left edge position P6 of the paper to the print start position P5. Here, the acceleration region D is the same as in the case of the conventional example shown in FIGS. 7 to 9. Therefore, since the head-down position P4 is set farther from the left edge position P6 of the paper 1 compared to the conventional example, the margin E3 can be made smaller than the margins E and E1 of the conventional example, resulting in improved efficiency. Printing becomes possible. In addition, since there is no need to narrow the acceleration region D, there is no need to use a large motor for the drive section of the carriage base 31.

In the above embodiment, the present invention is applied to a thermal transfer type serial thermal printer that uses an ink ribbon. The present invention can be similarly applied to an image forming apparatus using a thermal recording method that records an image.

[0021]

As described above, according to the present invention, the paper is brought into contact with the platen by the guide member, and the corner of the recording head in the paper feeding direction is recorded so that the recording head does not get caught on the edge of the paper that rises above the platen. Since the curved surface is continuous from the surface to the back surface of the heat sink, the moving speed of the recording head can be easily set to a low speed state at one end in the width direction of the paper. Therefore, since printing can be performed immediately from one end in the width direction of the paper, the margin can be reduced. Therefore, efficient printing can be performed.

[0022] Furthermore, there is no possibility of the recording head catching the widthwise end of the paper during movement. Furthermore, since there is no need to move the recording head using a drive system with a large driving force, it is convenient for miniaturizing the device configuration and reducing costs.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing the shape and printing conditions of a recording head of an image forming apparatus according to the present invention.

FIG. 2 is a perspective view of an image forming apparatus according to the present invention.

FIG. 3 is a view in the direction of arrow A in FIG. 2.

FIG. 4 is a side view of a conventional image forming apparatus.

FIG. 5 is a schematic plan view of FIG. 4;

FIG. 6 is a schematic plan view showing another conventional example.

FIG. 7 is a drawing showing a printing situation in a conventional example.

FIG. 8 is a drawing showing a printing situation of another conventional example.

FIG. 9 is a drawing showing a printing situation in another conventional example.

[Explanation of symbols]

1 Paper 10 Paper feed roller 20 Platen 30 Carriage 31 Carriage base 32 Ribbon cassette 40 Recording head 40a Recording head chip 41 Heat sink 41c Tapered surface 50 veil bar 60 Control circuit

Claims (1)

[Claims] 1. An image forming apparatus in which a carriage having a recording head facing a platen is provided so as to be movable back and forth in a direction perpendicular to a paper feeding direction with respect to the platen, and the recording head forms an image on paper. The corner on the side in the paper feed direction is made up of a continuous curved surface from the recording head surface to the heat dissipation plate formed on the back surface of the recording head, and is provided with a guide member that brings the recording paper into contact with the platen, and the recording head is connected to the paper An image forming apparatus characterized in that an operation can be started from outside the starting end.