JPH0335569Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a paper width detection device for a printer, and more particularly to a paper width detection device suitable for detecting the width of printing paper in a laser beam printer.

A fuser for a laser beam printer that has a heat roll and a heat plate generally has an inlet of the heat plate in order to bring the printing paper into close contact with the heat plate so that heat can be efficiently transferred from the heat plate to the print paper. There is an air suction section on the side. However, unless the air suction section moves the air shutter in accordance with the printing paper width and changes the air suction width, air leaks from areas outside the printing paper, and the air suction section cannot fully demonstrate its function. Therefore, in general, in a laser beam printer, the printing paper width is detected by a printing paper conveyance tractor in a transfer section, and an air shutter is moved in accordance with the output.

Figure 1 is a perspective view of a conventional paper width detection device;
3 are schematic diagrams of the paper width detection section. 1
a, 1b are tractors, 2 is printing paper, 3 is a magnet that moves in conjunction with the tractor 1a, 4 is a plurality of Hall elements, 5 is a sensor plate for fixing the Hall elements 4, 6 is the tractors 1a, 1b A drive shaft 7 is a shaft for rotating the paper and conveying the paper, and the paper width detection section is composed of a magnet 3 and a Hall element 4.

Although the tractor 1b is fixed to a laser beam printer main body (not shown),
a is adapted to move along the drive shaft 6 and shaft 7 according to the paper width of the printing paper 2, and in conjunction with this, the magnet 3 also moves according to the paper width of the printing paper 2.

A plurality of Hall elements 4 are arranged at equal intervals at positions facing the magnets 3 according to the paper width of the printing paper 2, and are fixed to the main body of the laser beam printer via a sensor plate 5. Generally, the paper width of printing paper 2 is in units of 0.5 inches, and the moving position of the air shutter mentioned above is also in units of paper width.
Since it is controlled in units of 0.5 inches or in units of 1 inch, which is a multiple thereof, the distance between the Hall elements is arranged in units of 0.5 inches.

However, in the printing paper 2 used in laser beam printers, 147/8 inches, etc.
Paper widths that are not in units of 0.5 inch are often used. In this case, the third
As shown in the figure, when the tractor 1a is moved according to the paper width of the printing paper 2, the magnet 3 is located between the Hall elements 4, and the magnet 3 and the Hall element 4 do not face each other, so that the paper width Detection becomes impossible.

Therefore, depending on the paper width of the printing paper 2 used, it becomes necessary to change the arrangement position of the Hall elements 4 or to reduce the arrangement interval to 1/4", 1/8", etc. In either case, there were drawbacks such as poor versatility and an increase in the number of Hall elements 4, making them expensive.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-described drawbacks of the prior art and to provide an inexpensive paper width detection device that can detect paper widths of all printing paper widths.

The present invention has the following features: (1) If the length of the magnet of the paper width detection device is made slightly longer than the 0.5 inch interval between Hall elements,
Since the magnet can always be opposed to the Hall element for paper of any paper width, undetectability can be avoided.

(2) Paper width [0.5 inch x 2 + α] (n; integer, 0
Even if the position of the air shutter for paper with paper width (<α<0.5 inch) is the same as that for paper with a paper width of [0.5 inch x n], there is no significant difference in the adhesion between the hot plate and the paper.

Focusing on these two points, this method has been devised so that it can be applied to paper whose width is not an integral multiple of 0.5 inch, without increasing the number of Hall elements.

An embodiment of the present invention is shown below in Figs. 4 and 5.
This will be explained in detail using FIG.

FIG. 4 is a schematic diagram of a paper width detecting section showing an embodiment of the present invention, which is arranged in the tractor section shown in FIG. 1 similarly to FIGS. 2 and 3. Components that are the same as those in FIG. 1 are designated by the same reference numerals, and their explanation will be omitted here.

The Hall elements 4 are arranged at regular intervals in the paper width direction of the printing paper 2. In this example
The spacing is 0.5 inch. A magnet 3 that moves in the paper width direction of the printing paper 2 in conjunction with the tractor 1a.
The length is slightly larger than the arrangement interval (0.5 inch) of the Hall elements 4. In this configuration, when the magnet 3 is moved in the paper width direction (in the direction of the arrow in FIG. 4), it always faces one or more Hall elements 4 regardless of the position of the magnet 3. When the magnet 3 straddles and faces multiple Hall elements 4, signals are output from the multiple Hall elements 4, and the output signals from these Hall elements 4 are ranked in order as shown in FIG. A control circuit 8 that sends out the lower one output of the attached signals.
Among the output signals from the plurality of Hall elements 4, only the output signal indicating the smallest paper width is extracted as a paper width detection signal. As a result, it is possible to obtain a paper width detection signal of a value (y) obtained by rounding down the paper width to the nearest 0.5 inch for any paper width, that is, for any position (x) of the magnet 3.

The functions of the control circuit 8 can be realized using commercially available integrated circuits. Alternatively, it can also be realized with a software configuration using a microcomputer.

In the embodiment, the arrangement interval of the Hall elements 4 is
0.5 inch, and the control circuit 8 was used to determine the output signal from the plurality of Hall elements 4, and the smallest signal was used as the paper width detection signal. , and by rounding down the detected paper width to 0.5 inch units, this is to prevent air leakage due to the air shutter moving to a position larger than the actual paper width of the printing paper 2. Therefore, depending on the intended use of the paper width detection signal, the arrangement interval of the Hall elements 4 may be set to 1 inch or the like, but the present invention is basically the same.

In this embodiment, the magnet 3 is linked to the tractor 1a, and the Hall element 4 is linked to the sensor plate 5.
Although it is fixed to the main body of the laser beam printer via a , this may be reversed and the effect will be the same.

In addition, in the above embodiment, a laser beam printer was described, but in an impact printer that forms characters by striking type or colliding wires, it is actually The present invention can also be applied to prevent characters from being omitted or damage to the printing hammer when the width of printing paper mounted on a tractor is narrow, and the main effects are the same.

Further, in the present invention, a Hall element is used as a magnetic proximity switch, but the effect is the same when a reed switch is used.

According to the present invention, it is possible to detect the paper width of any printing paper width, so it is possible to use paper whose paper width is not an integral multiple of 0.5 inch even in printers equipped with a paper width detection device. become.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a paper width detection device, FIGS. 2 and 3 are schematic diagrams of a conventional paper width detection section, and FIG. 4 is a schematic diagram of a paper width detection section showing an embodiment of the present invention. FIG. 5 is a block diagram of a circuit for extracting one detection signal from a plurality of output signals, and FIG. 6 is a graph showing the relationship between paper width and detection signal when the circuit of FIG. 5 is used. In the figure, 1a and 1b are tractors, 2 is printing paper, 3 is a magnet, 4 is a Hall element, 5 is a sensor plate, 6 is a drive shaft, 7 is a shaft,
Reference numeral 8 denotes a control circuit that selects and determines the lower one output of the ranked inputs.

Claims (1)

[Claims for Utility Model Registration] A printer comprising a tractor movable in the width direction of printing paper and a mechanism section for holding the tractor, wherein a plurality of sensors are arranged at equal intervals in the mechanism section, A control circuit for disposing a detected object having a length wider than the arrangement interval of the sensors on the tractor, and outputting a smaller value with respect to the paper width when two or more of the sensors output an output. A paper width detection device for a printer, characterized in that it is provided with a paper width detection device.