FR3086777A1 - CAPACITIVE KEYBOARD - Google Patents

Abstract

The present invention relates to a capacitive keyboard (100) comprising: • an electronic layer (1) comprising at least one capacitive sensor, • a metal layer (2) on the electronic layer, comprising a bearing surface (20) accessible to a user, • a spacer (3) arranged between the metallic layer (2) and the electronic layer (1), configured to maintain a determined distance between the metallic layer and the electronic layer, the capacitive keyboard (100) being mainly characterized in that that the bearing surface (20) of the metal layer comprises at least one bearing zone (21) capable of being deformed by a pressure exerted by the user so as to reduce the distance between the metal layer (2) and the electronic layer (1) plumb with said support zone, and in that the electronic layer (1) is configured to detect the reduction of said distance plumb with said support zone (21).

Description

CAPACITIVE KEYBOARD

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a capacitive keyboard, in particular a keyboard for an industrial machine.

STATE OF THE ART

Known capacitive keyboards typically consist of a printed circuit, called "printed circuit board" (PCB) in English, comprising capacitive sensors. Each capacitive sensor is connected to a suitable signal processing system.

By definition, capacitive sensors are conductive elements electrically connected to the electronic tracks of the printed circuit. Each sensor corresponds to a keyboard key that can be operated by a user.

The sensors generate an electric field. When the user presses a given key, the user's finger disturbs the electric field of the corresponding sensor, i.e. changes the capacity of the sensor.

The signal processing system receives the signals from the sensors as input. It is therefore informed of the sensor whose field has been modified, and outputs a signal corresponding to the key pressed.

A non-electrically conductive layer, called "dielectric layer", is arranged on the printed circuit. This layer includes a decoration made up of patterns associated with the different keys and which represent the function of each respective key, and is generally made of glass or plexiglass. It plays the role of the user interface.

Thus, in known capacitive keyboards, the detection of the actuated key is carried out by means of the dielectric layer, which limits the sensitivity of the keyboard, in particular if the user is wearing gloves.

In addition, the dielectric layer does not protect the printed circuit and its capacitive sensors. Known keyboards are therefore very sensitive to the external environment as well as to mechanical shocks, and are sources of electromagnetic compatibility (EMC) constraints in that they generate and / or are sensitive to electromagnetic disturbances making them hardly compatible. with other electronic devices located in their immediate environment.

BRIEF DESCRIPTION OF THE INVENTION

An object of the invention is to provide a capacitive keyboard enabling the drawbacks described above to be overcome.

To this end, the invention relates to a capacitive keyboard comprising:

• an electronic layer comprising at least one capacitive sensor, • a metallic layer on the electronic layer, comprising a bearing surface accessible to a user, • a spacer arranged between the metallic layer and the electronic layer, configured to maintain a determined distance between the metallic layer and the electronic layer, the capacitive keyboard being mainly characterized in that the bearing surface of the metallic layer comprises at least one bearing zone capable of being deformed by a pressure exerted by the user so as to reducing the distance between the metal layer and the electronic layer plumb with said support area, and in that the electronic layer is configured to detect the reduction of said distance plumb with said support area.

According to the capacitive keyboard according to the invention, the user exerts pressure directly on the metal plate, which is electrically conductive, at a determined support area. The electronic layer then detects the variation in distance corresponding to the plumb of the support zone between the metal layer and said electronic layer. Consequently, the detection of the support zone requested by the user is carried out by variation of distance between the metal layer and the electronic layer, and not by simple detection of the user's finger through a dielectric layer. in accordance with state of the art keyboards. Detection is then reliable and the keyboard has good sensitivity, especially in the case where the user's hand is covered with a glove.

The glove is not an electrical conductor. Thus, when the glove covers the user's finger, the interaction between the covered finger and the sensor is less, as is the sensitivity of the keyboard vis-à-vis the covered finger. This drawback is nonexistent with the keyboard of the invention, with which a pressure of the user's finger on the desired support area causes a deformation of said support area, whether or not the finger is covered with a glove , then resulting in recognition of the key actuated by the electronic layer.

The capacitive keyboard of the invention allows the detection of a low pressure of the user on a key of the keyboard, it being understood that the sensitivity of each key, that is to say the threshold value of pressure exerted by the user on the key from which the corresponding distance variation is detected by the capacitive sensor, is adjustable.

Likewise, the present keyboard advantageously makes it possible to detect a prolonged pressure over time by the user, for example of a few seconds, on a determined key. Indeed, the detection of the key requested by the electronic layer is carried out as long as the reduction of the distance plumb with said key is maintained.

Furthermore, the metal layer is rigid, although deformable, and thus makes it possible to protect the electronic layer from mechanical shock and from external stresses.

In the present text, the capacitive keyboard is considered from its rear face to its front face, the front face being that which is accessible to a user. The indication that a first part is "on" a second part therefore means that the first part is closer to the front face than the second part. However, unless expressly stated, the term "on" does not necessarily imply direct contact between the parts, a third part possibly being able to be interposed between said parts.

Similarly, the different layers making up the capacitive keyboard can be described with reference to their so-called "front face" and "rear face" faces, the front face being located above the rear face during current use of the keyboard. wherein said keyboard rests on a support or is integrated into such a support.

According to other aspects, the proposed capacitive keyboard has the following different characteristics taken alone or according to their technically possible combinations:

the support surface of the metallic layer is continuous. By “continuous support surface” is meant the fact that the metal layer does not include any opening in the central zone situated opposite the capacitive sensors; the metal layer is therefore in the form of a solid sheet or plate, which may however include openings in a peripheral zone for its attachment to the other constituent layers of the keyboard; these openings make it possible to add a backlighting function.

the capacitive keyboard further comprises a guide layer on the metal layer, said guide layer comprising at least one through orifice situated directly above a corresponding support zone of the metal layer, said orifice being suitable for passage of a user's finger. The holes in the guide layer allow the user's fingers to be guided precisely to the keys on the keyboard, making it easier to use the keyboard. The mechanical deformation of the metal layer is thus channeled precisely at the level of each key, which avoids accidentally deforming other neighboring keys, in particular when strong pressure is exerted on a key. The guide layer also allows the user to easily locate the keys on the keyboard. In addition, the guide layer strengthens the structure of the keyboard, the thickness of the guide layer is preferably greater than or equal to 1 mm. This minimum thickness further improves the comfort of using the keyboard.

each through hole of the guide layer has a chamfered edge. The user's finger is then guided by the chamfer towards the center of the key. In addition, the chamfer clears the protruding edge of the edge of the hole which could be unpleasant to the touch.

the keyboard further comprises a double-sided adhesive layer arranged between the guide layer and the metal layer. Such an adhesive layer constitutes a simple and effective bonding means and makes it possible to obtain uniform retention of the guide layer on the metal layer, that is to say bonding with the same effectiveness at all points of the interface. bonding between these layers.

said at least one support zone of the metal layer comprises a visual pattern formed on the support surface of the metal layer. This visual motif represents the function of the key, and allows the user to know the function of the key without having to press it beforehand.

the spacer comprises at least one through orifice located plumb with a corresponding support zone of the metal layer, to allow a deformation of the support zone in the orifice.

the spacer is configured to deform with the metal layer plumb with a support area.

the spacer is a double-sided adhesive layer for bonding the metal layer and the electronic layer. The adhesive layer constitutes a simple and effective bonding means and makes it possible to obtain a uniform hold of the metal layer on the electronic layer, while preserving a determined distance between these layers.

The invention also relates to a system comprising:

• a capacitive keyboard as described above, and • a processor configured to receive as input a detection signal from the electronic layer, and to determine which support area has been deformed by the user.

BRIEF DESCRIPTION OF THE FIGURES

Other advantages and characteristics of the invention will appear on reading the following description given by way of illustrative and nonlimiting example, with reference to the appended figures:

Figure 1 is a perspective view of an embodiment of the capacitive keyboard according to the invention;

Figure 2 is an exploded view of the capacitive keyboard of Figure 1;

FIG. 3A is a side view in section of the capacitive keyboard of FIG. 1, the metal plate not being deformed;

FIG. 3B is an enlargement of a part of the keyboard of FIG. 3, which illustrates the deformation of the metal plate during a pressure applied by a user on a key of the capacitive keyboard.

DETAILED DESCRIPTION OF THE INVENTION

The capacitive keyboard 100 according to the invention comprises a multilayer structure, one embodiment of which is shown in FIGS. 1 and 2.

With reference to FIGS. 1 and 2, the multilayer structure successively comprises, from the rear face to the front face of the keyboard, an electronic layer 1, a spacer 3 arranged on and in contact with the electronic layer 1, and a metal layer 2 arranged on and in contact with the spacer 3. According to this embodiment, the structure optionally comprises a guide layer 4 arranged on the metal layer 2.

The electronic layer 1 comprises a printed circuit provided with one or more capacitive sensors. The number of capacitive sensors is chosen according to the number of keys on the keyboard, which will be described below, it being understood that a key on the keyboard corresponds to a capacitive sensor.

Each capacitive sensor is connected to a suitable signal processing system (not shown). This signal processing system is preferably integrated in the electronic layer, in particular in the printed circuit, but can alternatively be separated from said electronic layer while being able to communicate with the capacitive sensors.

The metal layer 2 is in the form of a plate or a sheet. Preferably, the metal layer is a plate or sheet whose thickness is usually between 0.2 mm (millimeters) and 0.6 mm, but this can change depending on the diameter of the button.

The metal layer 2 includes a support surface 20 which is physically accessible to a user. For this purpose, the support surface 20 is located on the front surface of the metal layer.

The bearing surface 20 of the metal layer 2 is provided with one or more bearing zone (s) 21. Each bearing zone 21 constitutes a key on the capacitive keyboard which is configured to be actuated by pressure exerted by the user so as to distort it.

The support zones 21 preferably include a visual pattern formed on the support surface of the metal layer. This visual motif represents the function of the key, and allows the user to know the function of the key without having to press it beforehand. It can be for example a letter, a number, or a symbol. In FIGS. 1 and 2, the first key of the first row comprises for example a pattern comprising stripes.

The metal layer 2 is positioned on the electronic layer 1 at a determined distance, denoted D, from said electronic layer. This distance D is preserved by the spacer 3 arranged between the metal layer 2 and the electronic layer 1.

The metal layer 2 is relatively rigid, although deformable at least at the level of the support zones 21. It gives rigidity to the structure of the keyboard, in addition to providing shielding which reduces the constraints of electromagnetic compatibility (EMC) .

According to a preferred embodiment, the support surface 20 of the metal layer 2 is continuous. Thus, the central area of the support surface of the metal layer 2, which is the area located opposite the capacitive sensors, rests at all points on the front surface of the spacer 3. This improves the rigidity of said metal layer , while allowing its deformation at the support zones, and allows a better distribution of forces on the metal layer. The keyboard structure is then stiffened and more resistant to external stresses, in particular to mechanical shock.

The spacer 3 is preferably in the form of a plate whose thickness corresponds to the determined distance, represented by the double arrow D1 in FIG. 3A, between the metal layer 2 and the electronic layer 1.

According to one embodiment, the spacer 3 is configured to be deformed with the metal layer 2. In detail, when a bearing zone 21 of the metal layer 2 undergoes pressure exerted by the user, represented by the arrow F in FIG. 3B, it deforms under the effect of this pressure in the direction of the spacer 3 until it pushes an area of the spacer located directly above the support area 21 in an integral manner in the direction of the electronic layer 1.

According to one embodiment, the spacer 3 comprises at least one through hole 30 located plumb with a corresponding support zone 21 of the metal layer

2. In other words, the spacer zone described in the previous paragraph is crossed by this opening. Such an orifice 30 is configured to allow the deformation of the support zone 21 in said orifice. In detail, when the support zone 21 deforms in the direction of the electronic layer, it passes through the corresponding orifice 30 of the spacer. The presence of this orifice directly above the support zones 21 makes it possible to limit the mechanical losses that may occur in the case of a full spacer, when the force is transmitted from the metal layer 2 to the spacer 3, and thus improves the sensitivity of the keyboard keys.

According to one embodiment, the spacer 3 is a double-sided adhesive layer for bonding the metal layer 2 and the electronic layer 1. Thus, the spacer allows to maintain a determined distance between the metal layer and the electronic layer, while ensuring the bonding of these two layers.

The guide layer 4 is advantageously in the form of a rigid plate.

The guide layer 4 comprises at least one through hole 40 located plumb with a corresponding support zone 21 of the metal layer. Such an orifice 40 is configured to allow the passage of a finger of the user coming to exert pressure on the support area. The user's finger is then guided via the orifice 40 towards the support area 21, which prevents him from inadvertently pressing on other areas of the support surface 20 distinct from the support areas 21 , and thus improves the user comfort of the keyboard.

The thickness of the guide layer 4 is adjusted according to the desired comfort. A thickness preferably less than or equal to 2 mm, makes it possible to obtain satisfactory guidance of the user's fingers.

According to one embodiment, the orifices 40 of the guide layer have a chamfered edge 41. The chamfer smoothes the protruding edge of the holes, and further improves user comfort.

The guide layer 4 is preferably bonded to the metal layer 2 by means of a double-sided adhesive layer 5 arranged between the guide layer 4 and the metal layer 2. Such an adhesive layer 5 constitutes a simple and effective bonding means. and makes it possible to obtain uniform maintenance of the guide layer 4 on the metal layer 2.

In addition to its function of guiding the fingers, the guide layer 2 makes it possible to strengthen the structure of the keyboard, which on the one hand improves the resistance of the structure to external mechanical stresses, and on the other hand channels the deformation of the metallic layer during pressing of the keys by limiting mechanical losses in the structure.

The keyboard 100 further comprises a fixing system allowing the different layers of the structure described above to be fixedly connected together.

In FIGS. 1 and 2, the fastening system comprises screws 61 and nuts 62. The screws 61 are inserted from the front face of the structure into through holes 42 formed in the periphery of the guide layer 4, and pass through successively through holes 51 formed in the periphery of the adhesive layer 5, the through holes 22 of the metal layer 2, the through holes 31 of the spacer 3, and the through holes 10 of the electronic layer 1, preferably formed in the corners of these layers.

It is specified that the term "periphery" refers to an area of the different layers which is located around a central area of these layers, opposite the support areas 21 (the central area of the guide layer 4, of the adhesive layer 5, the spacer 3, and the electronic layer 1) or containing the support zones 21 (the central zone of the metal layer 2). The nuts 62 are screwed onto the threads of the screws 61 and come into contact with the rear face of the keyboard 100.

The operation of the keyboard will now be described with reference to FIGS. 3A and 3B which illustrate the arrangement of the layers of the structure respectively without deformation and with deformation of the metal plate during pressure applied by a user to a key on the keyboard.

With reference to FIG. 3A, no pressure is exerted by the user on the keyboard. The metal layer 2 is separated from the electronic layer 1 by a determined distance D1. The metal layer extends along a straight line L1 in dotted lines substantially parallel to the underlying electronic layer.

With reference to FIG. 3B, when the user presses a key on the keyboard, his finger crosses the orifice 40 of the guide layer 4 until it comes into contact with the corresponding support zone 21 constituting the key. The pressure exerted by the user's finger on the support zone 21 causes a deformation of the metal layer 2 at the level of said support zone. By deforming, the metallic layer 2 approaches the electronic layer 1, and the distance D1 between these two layers decreases until reaching a value D2. This deformation of the metal layer is represented by the curved line L2 in dotted lines.

According to the embodiment of Figures 3A and 3B, the metal layer 2 is deformed in an orifice 30 of the spacer. Alternatively, in the case of a solid spacer (not shown), the spacer deforms with the metal layer.

The capacitive sensor of the electronic layer located directly above the deformed support zone 21 detects the decrease in distance D, and sends an output signal to a processor (not shown) which is processed by a system signal processing suitable for this purpose. From the sensor output signal, the processor determines which support area has been deformed by the user and therefore which keyboard key has been pressed.

The user can press several keys at the same time, in which case all the corresponding support zones will become distorted. The reduction in distances will be detected by the various sensors, which will each output a corresponding signal.

The determination of the button actuated by the user is thus carried out by deformation of the mechanical layer and corresponding reduction of the distance D, and not by detection of the presence of the user's finger.

Therefore, by using capacitive technology, the keyboard of the invention is capable of detecting the keys actuated in a sensitive manner when the user places his finger on the key in question. Unlike known capacitive keyboards with which the detection is done by the approach of the finger through a dielectric at the front face of the keyboard which must necessarily be electrically non-conductive, the keyboard of the invention detects a very slight deformation of the metal layer on front 5 generated by the user.

Therefore, in addition to being sensitive, the metal layer provides significant advantages in terms of protection of the keyboard against the external environment, in particular by providing protection against mechanical shock but also sealing against liquids as well as EMC constraints. .

In addition, this type of detection by reduction of distance makes it possible to minimize the size of the sensors.

The keyboard of the invention is also based on a multilayer structure which is simple to manufacture, which makes it very advantageous in the context of industrial manufacturing.

Claims (11)

1. Capacitive keyboard (100) comprising: • an electronic layer (1) comprising at least one capacitive sensor, • a metal layer (2) on the electronic layer, comprising a bearing surface (20) accessible to a user, • a spacer (3) arranged between the layer metallic (2) and the electronic layer (1), configured to maintain a determined distance between the metallic layer and the electronic layer, the capacitive keyboard (100) being characterized in that the bearing surface (20) of the metallic layer comprises at least one support zone (21) capable of being deformed by pressure exerted by the user so as to reduce the distance between the metal layer (2) and the electronic layer (1) directly above said zone support, and in that the electronic layer (1) is configured to detect the reduction of said distance directly below said support area (21). 2. Capacitive keyboard (100) according to claim 1, in which the support surface (20) of the metallic layer is continuous. 3. Capacitive keyboard (100) according to one of claims 1 or 2, further comprising a guide layer (4) on the metal layer (2), comprising at least one orifice (40) through located at the base of 'A support zone (21) corresponding to the metal layer, said orifice (40) being adapted for the passage of a finger of the user. 4. Capacitive keyboard (100) according to claim 3, wherein the thickness of said guide layer (4) is less than or equal to 2 mm. 5. Capacitive keyboard (100) according to one of claims 3 or 4, wherein each through hole (40) of the guide layer (4) has a chamfered edge (41). 6. Capacitive keyboard (100) according to one of claims 3 to 5, further comprising an adhesive layer (5) double-sided arranged between the guide layer (4) and the metal layer (2). 7. Capacitive keyboard (100) according to any one of the preceding claims, in which said at least one support zone (21) of the metal layer comprises a visual pattern formed on the support surface of the metal layer. 8. Capacitive keyboard (100) according to any one of the preceding claims, in which the spacer (3) comprises at least one through hole (30) situated directly above a support zone (21) corresponding to the metal layer (2), to allow deformation of the support zone in the orifice. 9. Capacitive keyboard (100) according to any one of the preceding claims, in which the spacer (3) is configured to deform with the metal layer (2) perpendicular to a support area (21) . 10. Capacitive keyboard (100) according to any one of the preceding claims, in which the spacer (3) is a double-sided adhesive layer for bonding the metal layer and the electronic layer. 11. System comprising: • a capacitive keyboard (100) according to any one of the preceding claims, and • a processor configured to receive as input a detection signal from the electronic layer, and to determine which support area has been deformed by the user.