JPS61122740A - Coordinate input device - Google Patents

Abstract

PURPOSE:To obtain a highly accurate stress detecting device by using load detectors provided with plural distortion sensors and reduced at their sensitivity to horizontal force. CONSTITUTION:If external force is applied to a proper position 2 of an input board 1a, the force is applied to the load detectors 3a-3d and an elastic plate 4 is deflected. Since one of the resistance values of the distortion sensors 5a, 5b is increased and the other is decreased by the same value, the output Vf1 of a subtractor 8 is proportional to the external force. If force parallel with the input board 1a is applied, both the ends of the elastic plate 4 are deflected in the different directions and the distortion sensors 5a, 5b are increased or decreased by the same value, the Vf1 is not almost changed. The coordinate can be obtained by applying a prescribed equation to the obtained load.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a coordinate input device for inputting the coordinates of a position indicated by a finger or a pointer stick into a computer or the like.

2. Description of the Related Art Conventionally, so-called digitizers have been used as coordinate input devices for computers and the like, which are expensive but capable of inputting coordinates with high accuracy and are used for inputting figures. Recently, however, computers have become commonplace, and there has been a demand for input devices that can input coordinates at low cost. In particular, there is a need for a see-through type input device that allows data to be input by looking through a display and pressing a figure shown on the display with a finger or the like. This is done by preparing several options in advance so that people who are not familiar with computer operations can easily create the Nosaku, displaying these on the display, and pressing one of the options with a finger. This is because more and more methods are being used to automatically perform processing. A light pen was a typical type of perspective coordinate input device, but devices that allow input with a finger or a ballpoint pen without using a special pen are more convenient, and several methods have been developed to date. is proposed.

Typical methods include a switch matrix method using a transparent conductive sheet, a voltage and current division method using a transparent resistance sheet, a method using laser light, and a method that measures the propagation time of surface waves.

(For example, Nikkei Electronics, P122 (j981
゜6.8)) However, all of these devices are complicated and expensive, and their displays are difficult to see and maintenance is difficult, so they have not become popular.

Instead of these methods, a stress detection type coordinate input device that detects the coordinates of a point to which a force is applied by detecting the component force of a force applied to one point on the input panel uses a glass plate or acrylic as an input panel. Since it can use a homogeneous and completely transparent material such as a plate and has a simple configuration, it becomes a low-cost coordinate input device.

The principle of detecting coordinates by this stress detection type is disclosed in Japanese Patent Application No. 58-1
This is shown in No. 01122, and will be explained using FIG. 11.

In FIG. 11, 1 is an input panel, 2 is an application point of an external force F perpendicular to the input panel 1, and 12a to 12d are load detection points. The coordinates of the load detection points 12a to 12d are respectively (xl
,yl)+("2+72)+("3゜y3),(x4
．． y4), and the magnitude of the load perpendicular to the input panel 1 is fl, f2. f3. Assuming f4, the coordinates (x, y) of the point of application of external force can be obtained from the balance of moments in the plane using the following equation.

However, F=f1+f2+f3+f4...
- (3) In this way, the coordinates (X, Y) of the external force application point can be detected by determining the magnitude of the load if the coordinates of the load detection point are known in advance. FIG. 12 shows a specific configuration. In FIG. 12, 1 is an input panel, 2 is an external force application point, and 13a to 13d are load detectors. FIG. 13 shows an enlarged view of the load detectors 13a to 13d. In FIG. 13, 14 is an elastic body made of stainless steel, and 15 is a strain sensor. One end of the elastic body 14 is fixed to the input panel 1, and the other end is fixed to a fixed frame (not shown). Next, this operation will be briefly explained. First, when an external force is applied to the input panel 1, the elastic body 14 is strained according to its position, and this is reflected by the strain sensor 5.
The load at four points on the input panel 1 is determined by the change in resistance, and the coordinates are detected using equations (1) 2 to (3) above.

Problems to be Solved by the Invention However, the above configuration has a drawback in that accurate coordinates cannot be detected if an external force is applied in a direction other than perpendicular to the input panel. This drawback is not a problem in applications where the input panel is flat and menus are selected using a finger, but it must be resolved in applications where the input panel is curved or more precise applications such as inputting figures are required. It is. The cause of this drawback lies in the structure of the load detectors 13a to 13d. In other words, since the load detector has a cantilevered structure as shown in FIG. 13, the elastic body 14 is also distorted when a horizontal force is applied.

In view of the above problems, the present invention provides a stress detection type coordinate input device with higher accuracy.

Means for Solving the Problems To achieve this object, the present invention uses a load detector that is equipped with a plurality of strain sensors and has reduced sensitivity to horizontal forces.

Effect With this configuration, when an external force is applied in a direction other than perpendicular to the input panel, the horizontal force component does not affect the output of the load detector, so the direction of the external force applied to the input panel is Coordinates can be detected with high accuracy regardless of the

EXAMPLE A first example of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an input panel and a load detector of a coordinate input device according to a first embodiment of the present invention. In FIG. 1, 1a is 188n in length and 252111 in width. thickness 3
111 plate glass input panel, 2 external force application point, 3a
3d are load detectors provided at the four corners of the input panel 1a. FIG. 2 is a plan view of the load detector, and FIG. 3 is a front view of the load detector. In Figures 2 and 3, 4 is the length g
oioa.

A rectangular stainless steel elastic plate with a width of 1 am and a thickness of INI+, 5a and 5b are strain gauges made of semiconductor strain gauges, and 6a and eb are input to both ends of the elastic plate 4! ! ! L
1 is a spacer made of silicone rubber with a thickness of 2 mm, and 7 is a spacer made of stainless steel with a thickness of 2 mm for connecting the elastic plate 4 and a fixed frame (not shown).

Although the spacers 6a, 6b, and 7 have a prismatic shape, there is no problem even if they have a cylindrical shape.

As shown in FIGS. 2 and 3, a strain gauge 5a.

6b is a point P to the front surface 4a and back surface 4b of the elastic plate 4, respectively.
It is arranged so that it is symmetrical about the center.

FIG. 4 is a circuit diagram for determining the load value from the resistance change of the strain sensors 6a and sb. 6a in Figure 4.

6b is a strain resistor, 9a and 9b are resistors connected in series with the strain sensors sa and sb, respectively, between the power supply and the ground, and 8 is a connection point between the strain sensors 6a and 6b and the resistors 9a and 9b. Voltage va1. This is a subtracter that outputs the difference between υb1 as an output vf1.

The operation of the first embodiment configured as above will be described below. First, when an external force is applied to an appropriate part of the input panel 1a, force is applied to the load detectors 3a to 3d located between the input panel 1 and the fixed frame, causing the elastic plate 4 to bend. If the external force is perpendicular to the input panel 1a, the elastic plate 4 deforms symmetrically in FIG. 3.

Therefore, one of the resistance values of the strain sensors 5a and 5b increases by the same value, and the other decreases. Therefore, the voltage ' in Figure 3 is
1) One of al and vbl increases and the other decreases, and as a result, the output vf1 of the subtracter 8 is proportional to the magnitude of the external force. If we consider the case where a parallel force is applied to the input board 1a, the input board 1 tries to rotate due to the parallel force, so both ends of the elastic board 4 are distorted in different directions as shown in Figure 3. . Therefore, the resistance values of the strain sensors 5a and sb both decrease or increase. Therefore, the output vf1 of the subtractor 8
will hardly change, and the influence of the force parallel to the input panel 1 will hardly be exerted on the output vf1.

Then, the coordinates can be obtained by applying Equations (1) to (3) above to the obtained load.

As described above, according to the first embodiment, it is possible to detect only the vertical component of the external force regardless of the direction of the external force applied to the input panel 1a, and it is possible to use a spherical input panel 1a. , accuracy is improved.

Furthermore, the influence of the change in resistance value of the strain sensor 1 due to temperature and the expansion and contraction of the elastic plate 4 can also be eliminated.

Next, a second embodiment of the present invention will be described with reference to the drawings. The configurations of the input panel and load detector are almost the same as in the first embodiment, so the different parts will be explained. 6th
6 are a plan view and a front view of the load detector. 5 and 6, 4 is an elastic plate, 6a, 6
b is a spacer for connecting the input panel 1a and the elastic board 4;
7 is a spacer for connecting the elastic plate 4 to the fixed frame, 10
a.

1ob is a strain sensor, which is placed on one of the widest surfaces of the elastic plate 4.
They are fixed so that they are symmetrical. FIG. 7 is a circuit diagram for obtaining a voltage proportional to the load based on the resistance change of the strain sensor. What is different in FIG. 7 from FIG. 4 is the strain sensor 10a.
are connected in series between the ground and the resistor 9a as in FIG. 4, but strain sensor 1obf′i is connected in series between
a and the resistor 9b, the strain sensor 10
a and 10b, the voltage 7 and a2.
``The sign of the change in b2 is reversed.

The operation of the second embodiment configured as described above will be explained, but parts similar to the first embodiment will be omitted. If the external force is perpendicular to the input panel 1a, the strain sensors 10a and 10b will both decrease or increase due to the deformation of the elastic plate 4. Therefore, the voltages Z'a2 and '1)b2 in Fig. 7
One of them increases and the other decreases, so the output vf2 of the subtractor 8 is proportional to the magnitude of the external force. When the external force is parallel to the input panel 1a, one of the strain sensors 10a and 10b increases and the other decreases. Therefore, the voltage va□, v
Both b2 change in the same way, the output vf2 does not change, and the influence of the force parallel to the input board is almost not exerted on the output vf2.

As described above, according to the second embodiment, it is possible to detect only the vertical component of the external force, regardless of the direction of the external force applied to the input panel, it is possible to use a spherical input panel, and the accuracy is will improve. Furthermore, in the second embodiment, since the strain sensors are on the same plane, the load can be accurately detected even if the neutral plane of the deformation of the elastic plate does not pass through the center of gravity. It can be taken widely.

Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a plan view of the load detector, and FIG. 9 is a front view. Here, the difference from the first embodiment is that the strain sensor 11
Four a to 11d are used, two each on the two widest surfaces of the elastic plate 4, that is, the front surface 4& and the back surface 4b, at the same position so as to be symmetrical with respect to the center line perpendicular to the longitudinal direction of the surface. This is the point that is fixed to . FIG. 10 is a circuit diagram for obtaining a voltage proportional to the load from the resistance change of the strain sensor. The difference in FIG. 10 from the first embodiment shown in FIG. 4 is that there is no resistor, and a bridge circuit is formed by strain sensors 11a to 11d.

Strain sensors 11c and 11a, 11b and 11d are connected in series to a power source and ground. Here, the same effect can be obtained even if the strain sensors 11h and 11a and the strain sensors 11c and 11d are replaced at the same time.

The operation of the third embodiment configured as described above is a combination of the first embodiment and the second embodiment, and its effects are also the same, so a description thereof will be omitted.

Although glass is used as the input panel 1a in each embodiment of the present invention, any material with a certain degree of rigidity, such as an acrylic plate or an aluminum plate, can be used. Further, as a strain sensor, not only one whose resistance value changes depending on strain, but also one which generates a voltage and which can detect strain as a voltage change can be used. Further, the elastic plate is not limited to stainless steel, as long as it has appropriate rigidity to support the input panel and elasticity to detect the load.

Effects of the Invention As described above, the present invention uses a plurality of strain sensors as load detectors with reduced sensitivity to horizontal forces, thereby making it possible to use a curved surface as an input panel. , it is possible to obtain a highly accurate coordinate input board.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the configuration of a coordinate input device according to a first embodiment of the present invention, Fig. 2 is a plan view of the same load detector, Fig. 3 is a front view of the same, and Fig. 4 is a diagram of the same device. A circuit diagram for obtaining an output proportional to the load, FIG. 5 is a plan view of the load detector of the coordinate input device in the second embodiment, and FIG. 6 is a front view of the same.
Section 7 is a circuit diagram for obtaining an output proportional to the load of the device, FIG. 8 is a plan view of the load detector of the coordinate input device in the third embodiment, FIG. 9 is a front view of the same, and FIG. The figure is a circuit diagram for obtaining an output proportional to the load of the device, Figure 11 is a principle diagram of a conventional example, and Figure 12 is a perspective view showing the configuration of the input panel and load detector of a conventional coordinate input device. , FIG. 13 is an enlarged perspective view of a conventional load detector. 1a...Input panel, 2...External force application point, 3a-3d...Load detector, 4...
Elastic plate, s a ', s b... strain sensor,
6a, 6b, 7...Spacer. Name of agent: Patent attorney Toshio Nakao and 1 other person +
4 for -jealousy
Part 19, Part 11, Part 2

Claims (5)

[Claims] (1) Each of the load detectors provided at a plurality of positions on the input panel is provided with a plurality of strain sensors, and the input panel is configured to be insensitive to forces in a horizontal direction, and A coordinate input device that detects the coordinates of the load application point based on the applied load. (2) The load detector is made of a rectangular elastic plate, and at least two strain sensors are provided on the center line along the longitudinal direction of the widest surface of the elastic plate, and one of the center and both ends of the elastic plate is connected to the center line of the elastic plate. 2. The coordinate input device according to claim 1, wherein the other is fixed to the input panel via a spacer to a fixed frame. (3) Strain sensors are placed on different sides of the widest surface of the elastic plate, and located parallel to the widest surface of the elastic plate and symmetrical to a straight line passing through the center of gravity of the elastic plate perpendicular to the longitudinal direction. 3. The coordinate input device according to claim 2, wherein the coordinate input device is provided in a coordinate input device. (4) The coordinate system according to claim 2, characterized in that two strain sensors are provided on one of the widest surfaces of the elastic plate at positions symmetrical with respect to the center line in the longitudinal direction of the surface. Input device. (5) Two strain sensors are installed on each of the two widest surfaces of the elastic plate, at symmetrical positions with respect to the center line in the longitudinal direction of the surfaces, and at the same position on the two surfaces. A coordinate input device according to claim 2, characterized in that: