JPH0576595B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION Field of Industrial Application This invention relates to a sensor that detects an object such as printing paper by being pressed against the object.

Problems to be Solved by the Invention In this type of sensor made of pressure-sensitive conductive rubber, only a slight pressing force is required to apply compressive strain by a predetermined stroke from an unpressurized state.

When this sensor is installed in a carriage to detect the paper thickness of a printing device, the paper thickness detection is
Since the detection must be performed at a short distance between the print head and the platen, the detection operation must be performed by applying a compressive strain of a small stroke to the sensor from a non-pressure state.

Therefore, if the printing paper is floating with respect to the platen, the sensor will be compressed by a predetermined stroke due to the slight contact force on the printing paper from the non-pressure state, which may cause malfunction. .

"Structure of the Invention" Means for Solving the Problems In order to solve the above problems, the present invention uses a pressure-sensitive conductive rubber sensor that changes its own electrical resistance when pressed by a detected object. The main body is provided on a support member, and an initial pressure applying means is provided between the sensor main body and the support member for applying a predetermined amount of compressive strain to the sensor main body prior to detection.

Function As mentioned above, by applying a predetermined initial pressure to the sensor body and applying a predetermined amount of compressive strain, even if a slight pressing force is applied from the outside, it will not be able to perform the initial detection operation. To avoid generating compressive strain corresponding to the stroke.

Embodiment Hereinafter, an embodiment in which the present invention is embodied in a paper thickness detection device for a printing device will be described with reference to FIGS. 1 to 6. As shown in FIG.
Printing paper 1 is placed between the left and right side walls 10a and 10b of 0.
A platen 12 made of prismatic metal is installed to support the platen 1 . The both side walls 10 are arranged so as to face each other in front of the platen 12.
Through holes 13 and 14 are formed in a and 10b, respectively, and an eccentric shaft support hole 15 is provided in the through holes 13 and 14.
A pair of left and right eccentric bodies 16 and 17 are rotatably supported, and a platen 1 is attached to both eccentric bodies 16 and 17.
A guide shaft 18 extending parallel to the eccentric bodies 16 and 1 is fitted and fixed by small-diameter support shafts 19 at both ends of the guide shaft 18, and each eccentric body 16, 1
7 and a guide shaft 18 are integrated.

On the right side of the right eccentric body 16 is the eccentric body 16.
A driven gear 20 is fixedly located concentrically with the driven gear 20, and a drive motor 22, which is a step motor, is provided on the right side of the right side wall 10a and has a drive gear 21 that meshes with the driven gear 20.
Therefore, when the drive motor 22 is rotated in the forward and reverse directions, the eccentric bodies 16 and 17 are integrally rotated on the same axis via the guide shaft 18 via the drive gear 21 and the driven gear 20. 16,17
Due to the eccentric action of the guide shaft 18, the guide shaft 18 is moved back and forth toward and away from the platen 12.

A reference position detection piece 23 is attached and fixed at the base end to the outer surface of the left eccentric body 17, and a photo sensor including a light emitting element and a light receiving element is provided on the outer surface of the left side wall 10b. The reference position detection sensor 24 is attached, and as the eccentric body 17 rotates, the reference position detection piece 23 moves to the reference position detection sensor 2.
When the optical path is interrupted by passing between the four light emitting and receiving elements, the reference position detection sensor 24 outputs a detection signal.

A carriage 25 is fitted and supported on the guide shaft 18 so as to be movable along the platen 12, and an endless timing belt 27 and a pair of pulleys 2 are partially fixed to the lower surface of the carriage 25.
8 along the platen 12 by a drive motor (not shown). The timing belt 27, pulley 28, and drive motor (not shown) constitute a carriage moving device 41 shown in FIG. or,
At the front of the carriage 25, both side walls 10a, 1
A guide rail 29 extending parallel to the guide shaft 18 is installed between the carriage 25 and a pair of upper and lower protruding pieces 26 that protrude from the front end of the carriage 25. The carriage 25 is moved left and right along the guide shaft 18 and the guide rail 29 while being loosely fitted on the end side.

As shown in FIGS. 1 and 2, the carriage 25
On the left side of the print head 30 on which the print head 30 is mounted and fixed, a bracket 31 whose side surface is approximately L-shaped as a supporting member is fixedly attached to the upper surface of the carriage 25, as shown in FIG. A block body 32 is fixed to the side surface of the upright portion of the bracket 31 on the platen side. Further, an adjustment screw 33 serving as a pressing member that extends back and forth through the block body 32 is screwed into the upright portion. A flat mounting part 33a is integrally formed at the tip of the adjustment screw 33, and a detector 40 consisting of a sensor body 35 and a pair of electrode plates 34a and 34b sandwiching the sensor body 35 is attached to the mounting part 33a. is fixed with adhesive.

The detector 4 is mounted on the upright portion of the bracket 31.
A cap-shaped cover 36 that covers the detector 0 and the block body 32 is fixedly attached at the base end, and an opening 36a is formed at the tip of the cover 36 to allow the detector 40 to enter. Further, a leaf spring 37 is clamped and fixed at its base end between the lower base end of the cover 36 and the block body 32, and a tip bent portion 38 serving as a receiving portion is attached to the outer electrode plate 34b.
is fitted externally. The outer surface of the bent portion 38 is placed in a position that slightly protrudes toward the platen 12 through the opening 36a, and is located between the tip end surface of the print head 30 and the platen 12. There is.

The sensor main body 35 is made of pressure-sensitive conductive rubber whose electrical resistance gradually decreases from an insulating state to a conductive state in response to external pressure, and the pressure-sensitive conductive rubber is made of silicone rubber with graphite. It is used in the form of a thin film formed by blending a fixed amount. This pressure-sensitive conductive rubber has almost no change in characteristics due to temperature, so it
Suitable for printing devices with 0. The detector 40, the adjusting screw 33, the leaf spring 37, the cover 36, etc. constitute a pressure sensor 39, and the adjusting screw 33 and the leaf spring 37 constitute an initial pressure applying means.

Then, based on the eccentric rotation of the guide shaft 18, the pressure sensor 39 is moved together with the carriage 25 and the printing head 30 in a direction approaching the platen 12, that is, toward the rear, and the bent portion 3 of the leaf spring 37 is moved.
8 is brought into pressure contact with the printing paper 11 on the platen 12, the detector 40 is compressed based on the pressure, and the resistance value of the sensor body 35 decreases as shown in FIG.

Further, by rotating the adjustment screw 33, the detector 40 is pushed toward the bent portion 38 of the leaf spring 37, and the sensor body 35 is moved toward both electrode plates 3.
4a and 34b, an initial pressure can be applied to the sensor main body 35, and the pressure can be changed and set.

Next, the control circuit of this printing device will be explained according to FIG. 6. 42 is a central processing unit (CPU) to which the output terminals of the reference position detection sensor 24 and the operational amplifier 43 are respectively connected. has been done. Further, between the power supply and the inverting input terminal of the operational amplifier 43, each of the electrode plates 34a and 3 is provided.
The pressure sensor 39 is connected to the pressure sensor 39 through the 4b, and a variable resistor 44 is connected between the power supply and the non-inverting input terminal of the operational amplifier 43, and the reference resistance value can be set according to the paper thickness of the printing paper 11. is connected. The CPU 42 also has the print head 3.
0, drive motor 22 and carriage moving device 41
is connected, and print interval data corresponding to the paper thickness of each type of printing paper 11, interval data between the pressure-sensitive sensor 39 at the reference position and the platen 12, and a program for controlling the operation of the entire printing apparatus. A read-only memory (ROM) 45 in which information such as information is stored, and a random access memory (RAM) 46 in which information such as the rotation angle of the drive motor 22 at the time of paper thickness detection are stored are connected.

Next, the operation of the printing device configured as described above will be explained. In this embodiment, an initial pressure F1 corresponding to the resistance value R1 shown in FIG. 5 is applied to the sensor body 35 based on the rotation operation of the adjusting screw 33 shown in FIG. Now, when the printing device is powered on in this state, the CPU 42 drives the carriage moving device 41 to move the printing head 30 to the first position.
Place it in the home position shown in the figure. At the same time, the drive motor 22 is driven. As the drive motor 22 rotates, the pair of eccentric bodies 16 and 17 and the guide shaft 18 are rotated together via the drive gear 21 and the driven gear 20, and the reference position detection piece on the left eccentric body 17 is rotated. 23 is the reference position detection sensor 2
Immediately after crossing the optical path No. 4, the rotation of the drive motor 22 is stopped. As a result, the carriage 25, print head 30, and pressure sensor 39, together with the guide shaft 18, are arranged at a position farthest from the platen 12 depending on the shape of the eccentrics 16, 17.

When the printing paper 11 is mounted on the platen 12 in this state, its lower end is detected by a printing paper detection switch (not shown), and a paper detection signal is output from the switch. Then, the CPU 42 drives the drive motor 22 based on the paper detection signal. As the motor 22 rotates in the forward direction, the guide shaft 18 is eccentrically rotated via the drive gear 20, etc., and the print head 30, pressure sensor 39, etc. are moved toward and backward toward the platen 12 together with the guide shaft 18. . Along with this, the pressure sensor 39
The bent portion 38 of the leaf spring 37 is pressed against the printing paper 11, and the bent portion 38 is displaced forward against the elastic force of the leaf spring 37, and pressure is applied to the sensor body 35.

The operational amplifier 43 is connected to the sensor main body 3.
5 and a preset reference resistance value R2, and when the resistance value of the sensor body 35 reaches the reference resistance value R2, a predetermined signal is output to the CPU 42. do.
It goes without saying that this reference resistance value R2 is larger than the resistance value R1 corresponding to the initial pressure F1. Based on this, the CPU 42 stops normal rotation of the drive motor 22, and calculates the rotation angle data of the drive motor 22 from the reference position, that is, the movement amount data of the pressure sensor 39, and temporarily stores it in the RAM 46. .

Next, the CPU 42 uses the distance data between the pressure sensor 39 and the platen 12 stored in the ROM 45.
The paper thickness of the printing paper 12 is calculated by comparing it with the movement amount data of the pressure sensor 39 stored in the RAM 46. Then, depending on the paper thickness of the printing paper 11, the CPU 42 rotates the drive motor 22 in the opposite direction by a required angle, thereby moving the printing head 30 to a position at an appropriate distance from the surface of the printing paper 11.
move.

As described above, in this embodiment, the printing paper 11 is
The thickness of the paper is detected, and the print head 3 is moved according to the paper thickness.
Since the printing interval between 0 and the printing paper 11 can be appropriately changed and maintained properly, clear printing can be performed regardless of the paper thickness. Furthermore, when the pressure sensor 39 is pressed against the printing paper 11, compressive strain occurs in the sensor body 35, but the amount of strain is very small, approximately 0.05 mm, so that the printing head There is no possibility that the paper 30 will come into contact with the printing paper 11.

Furthermore, in this embodiment, the printing paper 11
When the detector 40 is set on the platen 12 in a floating state, even if the detector 40 comes into contact with the printing paper 11, if the initial pressure is set higher than the contact pressure, the contact pressure will be small. Even if the sensor body 35 is twisted, the sensor body 35 will not be distorted by the stroke for detecting the paper thickness. Therefore, the sensor body 3
5 is stabilized, there is no risk of the paper thickness detection operation of the printing paper 11 being performed incorrectly, and the paper thickness detection operation of the printing paper 11 is stabilized.
1 between the platen 12 and the detector 40, the thickness of the printing paper 11 can be accurately detected.

Furthermore, the configuration for this purpose is extremely simple since it only includes a leaf spring 37 that receives the detector 40 and an adjustment screw 33 that presses the detector 40.

Effects of the Invention As described in detail above, the present invention has an excellent effect of being able to prevent the possibility of malfunction occurring when detecting an object, despite the extremely simple configuration.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway plan view of a printing device embodying the present invention, and FIG. 2 is an A-A in FIG. 1.
3 is an enlarged sectional view along the line B-B of FIG. 1, FIG. 4 is an enlarged side sectional view showing the mounting configuration of the pressure sensor, and FIG. 5 is a characteristic diagram of the sensor body. FIG. 6 is a block circuit diagram of the printing device. In the figure, 11 is a printing paper as an object to be detected;
31 is a bracket constituting a support member, 33 is an adjustment screw, 35 is a sensor body, 37 is a leaf spring, 3
Reference numeral 8 denotes a bent portion constituting a receiving portion (the above-mentioned 33 and 38 constitute initial pressure applying means).

Claims (1)

[Claims] 1. A sensor body 35 made of pressure-sensitive conductive rubber whose electrical resistance changes when pressed by the object to be detected 11 is provided on the support member 31, and the sensor body 35 and the support member 31 are connected to each other. In between, an initial pressure applying means 33 is provided for applying a predetermined amount of compressive strain to the sensor main body 35 prior to detection;
A sensor characterized by having 38. 2 The initial pressure applying means includes a receiving portion 38 that receives the surface of the sensor main body 35 on the detected object 11 side.
and a pressing member 33 for pressing the sensor main body 35 toward the receiving portion 38 on the opposite side thereof. 3. The sensor according to claim 1, wherein the initial pressure applying means is capable of changing its pressing force.