JPH0223410Y2 - - Google Patents

Description

[Detailed description of the invention] Purpose of the invention (industrial application field) This invention is based on a sensor made of pressure-sensitive conductive rubber whose electrical resistance changes according to external pressure, which can be moved toward and away from the platen. By bringing the sensor into pressure contact with the printing paper supported on the platen, the gap between the printing paper and the printing head is adjusted based on the amount of movement of the sensor when the electrical resistance of the sensor reaches a certain reference value. The present invention relates to a printing gap adjustment device for a printing device.

(Prior Art) Generally, in this type of printing gap adjustment device, in order to obtain an accurate printing gap, it is desirable to appropriately change the pressure force of the sensor against the printing paper in accordance with the paper thickness of the printing paper. In other words, in the case of thick printing paper such as thick paper or multiple sheets stacked on top of each other, it is necessary to set the pressure force of the sensor to be large to remove warping or lifting of the printing paper. In particular, when printing paper such as copy paper is used, it is necessary to set the pressing force small to prevent contact traces of the sensor from remaining on the printing paper.

However, in conventional sensors of this type, the same force as the pressure of the sensor on the printing paper is applied to the pressure-sensitive conductive rubber as a reaction. In the case of detecting the pressure-sensitive conductive rubber, a strong force acts on the pressure-sensitive conductive rubber, and in the case of copying paper, a weak force acts on the pressure-sensitive conductive rubber. Therefore, if a strong force of more than a predetermined value is applied, the structure of the pressure-sensitive conductive rubber will be destroyed, leading to a risk of false detection.On the other hand, if a weak force of less than a predetermined value is applied, the characteristic graph shown in Figure 5 will change. As is clear from comparing each line, a problem arises in that the repeatability of the pressure-sensitive conductive rubber deteriorates.

(Problems to be solved by the invention) This invention was made in view of the above-mentioned conventional technology, and the problems to be solved by the invention are as follows.
The purpose is to ensure that appropriate external pressure is always applied to the pressure-sensitive conductive rubber so that the sensor operates accurately and stably for a long period of time.

Configuration of the Invention (Means for Solving the Problems) In order to solve the above problems, this invention adopts a means of arranging a surface pressure converting member between the sensor and the platen.

(Function) By the above means, when the thickness of the printing paper is large, the side area of the printing paper side of the surface pressure converting member is set smaller than the side area of the pressure-sensitive conductive rubber. If it is paper, do the opposite,
Appropriate external pressure can always be applied to the pressure-sensitive conductive rubber, allowing the sensor to operate accurately and stably for a long period of time without causing tissue destruction or deterioration of the repeatability of the pressure-sensitive conductive rubber. can.

(Example) Hereinafter, an example that embodies this invention will be described based on the drawings.

As shown in FIG. 1, a platen 3 is fixed between a pair of left and right side plates 1 and 2 that constitute the frame of the printing device, and a printing paper 4 is supported on the platen 3. Bearings 7 and 8 are rotatably inserted into a pair of through holes 5 and 6 formed at opposing positions in side plates 1 and 2 in front of the platen 3, and both bearings 7 and 8 are A shaft support hole 9 is provided eccentrically from the rotation center.

A guide shaft 10 is arranged in front of the platen 3 so as to extend between the side plates 1 and 2, and a support shaft 11 protruding from both ends of the guide shaft 10 is connected to the shaft support hole 9 of the both bearings 7 and 8.
are inserted in each. A step motor 14 is operatively connected to the right bearing 8 via a driven gear 12 and a driving gear 13. When the motor 14 is driven, the bearings 7 and 8 are rotated at predetermined angles, and the guide shaft 10 eccentrically supported by the bearings 7 and 8 moves toward and away from the platen 3. It is becoming more and more common. Further, a reference position detection sensor 15 made of a photo interrupter is disposed on the outer surface of the left side plate 1, and detects a detected piece 16 which can rotate integrally with the left bearing 7, so that the guide shaft 10 is aligned with the platen 3. It is possible to detect that the object is located at the reference position farthest from the object.

A carriage 19 carrying a wire-type printing head 18 facing the dot matrix platen 3 is supported on the guide shaft 10 so as to be able to reciprocate from side to side, and its rear end is supported by a guide rail 20. An endless timing belt 21 driven by a carriage drive motor 22 is connected to the carriage 19, and as the timing belt 21 is rotated between a pair of left and right pulleys 17, the carriage 19 is moved to the platen 3.
While reciprocating along the front surface of the printer, the printing head 18 can print on the printing paper 4 on the platen 3.

On the other hand, a paper thickness detection sensor 24 is fixed to the upper surface of the front end of the carriage 19 via a mounting piece 23, and is moved together with the print head 18 in both directions toward and away from the platen 3 by driving the step motor 14. It is becoming more and more common. As shown in FIG. 2, this paper thickness detection sensor 24 includes a pressure-sensitive conductive rubber 25 made of silicone rubber mixed with graphite, and pressure-sensitive conductive rubber fixed to both the front and rear sides of the pressure-sensitive conductive rubber 25. A pair of electrode plates 26 and 27 having the same area as 25, and a surface pressure conversion member 28 made of synthetic resin or the like fixed to the front surface of the front electrode plate 26.
It is composed of. Note that the surface pressure conversion member 28
protrudes slightly toward the platen 3 side than the print head 18, and the amount of protrusion is set smaller than the minimum printing gap between the print paper 4 and the print head 18 so that it does not interfere with printing. There is.

When the carriage 19 moves toward the platen 3, the front end surface of the surface pressure converting member 28 is pressed against the printing paper 4 on the platen 3, and the surface pressure as a reaction acts on the pressure-sensitive conductive rubber 25. The electrical resistance of the pressure-sensitive conductive rubber 25 changes depending on the surface pressure.

By the way, the surface pressure converting member 28 of this embodiment
is formed into a tapered shape, and the side area of the pressure-sensitive conductive rubber 25 is set larger than the area of the side that contacts the printing paper 4. Therefore, the paper thickness detection sensor 24
When pressed against the printing paper 4, the pressure-sensitive conductive rubber 25
The surface pressure per unit area acting on the printing paper 4 is smaller than the surface pressure per unit area acting on the printing paper 4.

Next, the electric circuit of the printing gap adjusting device of this embodiment will be explained based on FIGS. 2 and 3.

A central processing unit (hereinafter referred to as CPU) 31 is connected to the step motor 14, carriage drive motor 22, reference position detection sensor 15, comparator 29, RAM 32, and ROM 33, respectively. The CPU 31 inputs the signal from the reference position detection sensor 15 and counts the amount of movement of the paper thickness detection sensor 24 from the reference position as the number of steps of the step motor 14. A variable resistor 34 is connected to the comparator 29, and a change in the electrical resistance value of the pressure-sensitive conductive rubber 25 in the paper thickness detection sensor 24 is applied as a voltage change to the inverting input terminal 29a of the comparator 29. A variable resistor 3 is connected to the inverting input terminal 29b.
An arbitrarily settable reference voltage value is applied based on the operation in step 4. Then, when the paper thickness detection sensor 24 is pressed against the printing paper 4 and the voltage accompanying the change in the electrical resistance value of the pressure-sensitive conductive rubber 25 reaches the reference voltage value, the output terminal 29C of the comparator 29
A paper thickness detection signal is output to the CPU 31, and based on this, the CPU 31 calculates the amount of movement of the paper thickness detection sensor 24 from the reference position to the pressure contact position in the RAM.
32 to be memorized.

In the ROM 33, a constant distance from the front surface of the platen 3 to the reference position is set by the step motor 14.
The number of steps is stored in advance as the number of steps, and when paper is detected, the CPU 31 reads the stored data and the RAM 32.
The amount of movement of the paper thickness detection sensor 24 is read out.
By calculating these values, the paper thickness of the printing paper 4 can be detected. Furthermore, the ROM 33 stores a plurality of data on the appropriate printing gap corresponding to the paper thickness of the printing paper 4, that is, the distance between the front surface of the printing paper 4 and the front end surface of the printing head 18, and the CPU 3
1 is the appropriate printing gap corresponding to the calculated value of paper thickness.
The information is read from the ROM 33 and the step motor 14 is driven in the opposite direction by the number of steps corresponding to the printing gap.

Next, the operation of the printing gap adjusting device configured as above will be explained.

Now, when the power is turned on, the paper thickness detection sensor 24 is placed together with the carriage 19 at the reference position farthest from the platen 3, and the reference position is detected by the reference position detection sensor 15. When the step motor 14 is driven in this state, the carriage 19, print head 18, and paper thickness detection sensor 24 are moved together toward the platen 3 as the guide shaft 10 eccentrically rotates, and the paper thickness detection sensor The surface pressure converting member 28 of 24 is connected to the platen 3.
It is pressed against the upper printing paper 4.

Then, as a reaction to the pressure contact force, a predetermined surface pressure acts on the pressure-sensitive conductive rubber 25 via the surface pressure converting member 28, and a voltage based on the electrical resistance value of the pressure-sensitive conductive rubber 25 changes according to the surface pressure. is input to the comparator 29. When the voltage value reaches a reference voltage value arbitrarily set by the variable resistor 34, the CPU 31 stops driving the step motor 14 and detects the paper thickness of the printing paper 4.

When the paper thickness of the printing paper 4 is detected, the step motor 1 is operated in a predetermined number of steps according to the paper thickness value.
4 is driven in the reverse direction, and the printing head 18 is moved together with the carriage 19 in the direction away from the platen 3, and there is a gap between the front surface of the printing paper 4 and the front end of the printing head 18 corresponding to the paper thickness of the printing paper 4. A sufficient printing gap is ensured. Therefore, in this state, the carriage drive motor 22 is started to move the carriage 19.
print head 1 while reciprocating along platen 3.
By activating the printing wire 8, it is possible to apply an appropriate impact force to the printing paper 4 and perform clear printing.

By the way, the paper thickness detection sensor 24
When the pressure-sensitive conductive rubber 25 side area of the surface pressure converting member 28 is different from the surface area of the printing paper 4 side, the surface pressure acting on the pressure-sensitive conductive rubber 25 and the surface pressure acting on the printing paper 4 are different. The surface pressure applied to each case will have different values. In other words, the paper thickness detection sensor 2
4 presses the printing paper 4 as F, the surface area of the pressure-sensitive conductive rubber 25 of the surface pressure converting member 28 as A, which is equal to the area of action of the pressure-sensitive conductive rubber 25, and the area of the printing paper 4 as B. , the pressure-sensitive conductive rubber 25 has an F/A
A surface pressure of F/B acts on the printing paper 4.

Therefore, as shown in FIG.
If the lateral area A of the pressure-sensitive conductive rubber 25 of No. 8 is set larger than the lateral area B of the printing paper 4, the pressure-sensitive conductive rubber 25
It is possible to apply a surface pressure greater than the surface pressure applied to the printing paper 4, and for example, when detecting thick printing paper 4 made of thick paper or multiple sheets stacked on top of each other, the strong Print paper 4 due to surface pressure
Warpage, floating, etc. are eliminated, and erroneous detection can be prevented. On the other hand, at the same time, a smaller surface pressure acts on the pressure-sensitive conductive rubber 25 compared to the surface pressure that acts on the printing paper 4, so the structure of the rubber 25 may be destroyed or its repeatability may deteriorate. There is no risk of this happening.

Further, as shown in FIG. 4, contrary to the case described above, the surface area A of the pressure-sensitive conductive rubber 25 of the surface pressure converting member 28 is
If you set B to be smaller than the area B on all four sides of the printing paper,
Since a surface pressure smaller than the surface pressure acting on the pressure-sensitive conductive rubber 25 acts on the printing paper 4, even when detecting the printing paper 4 such as copy paper, there is no contact trace of the paper thickness detection sensor 24 on the paper. There is no risk of any residue remaining, and since a surface pressure stronger than the surface pressure acting on the printing paper 4 acts on the pressure-sensitive conductive rubber 25, the problem of deterioration of repeatability due to too weak surface pressure can be avoided. Can be done.

Note that this invention is not limited to the configuration of the above embodiment; for example, the paper thickness detection sensor 24
The shape of the surface pressure converting member 28 can be arbitrarily changed, the paper thickness detection sensor 24 can be movably provided at any location facing the platen 3 other than on the carriage 19, or the surface pressure converting member 28 can be changed to a pressure-sensitive conductor. It is also possible to change the structure of each part arbitrarily and embody it without departing from the spirit of the invention, such as attaching it to the rubber 25 so that it can be replaced.

Structure of the invention As detailed above, according to this invention, by arranging the surface pressure converting member between the sensor and the platen, it is possible to always apply an appropriate external pressure to the pressure-sensitive conductive rubber. This has the excellent effect of allowing the sensor to operate accurately and stably for a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a plan view of essential parts of a printing device showing an embodiment embodying this invention, Fig. 2 is a side view showing the configuration of a paper thickness detection sensor, Fig. 3 is an electric circuit diagram of the printing device, and Fig. 3 is a side view showing the configuration of a paper thickness detection sensor. FIG. 4 is a side view of a paper thickness detection sensor equipped with different surface pressure converting members, and FIG. 5 is a graph showing the repetition characteristics of pressure-sensitive conductive rubber. In the figure, 3 is a platen, 4 is printing paper, 24
is a paper thickness detection sensor, 25 is a pressure-sensitive conductive rubber, 28
is a surface pressure converting member.

Claims (1)

[Claims for Utility Model Registration] A sensor 24 made of pressure-sensitive conductive rubber 25 whose electrical resistance changes due to external pressure is attached to the platen 3.
The sensor 2 is provided so that it can be approached and isolated from the
4 is pressed against the printing paper 4 supported on the platen 3, the gap between the printing paper 4 and the printing head is determined based on the amount of movement of the sensor 24 when the electrical resistance of the sensor 24 reaches a certain reference value. A printing gap adjusting device for a printing device, characterized in that a surface pressure converting member 28 is disposed between the sensor 24 and the platen 3.