JP5028824B2 - Capacitance detection type switch device and wristwatch provided with the same - Google Patents

Description

The present invention relates to a capacitance detection type switch device that is turned on when a human body comes into contact with or close to the human body, and a wristwatch including the same.

Conventionally, a capacitance detection type switch device is known. This capacitance detection type switching device is a touch sensor that utilizes the change in capacitance by bringing a finger into contact with or approaching an electrode, and is composed of an electrode, a CR oscillation circuit, a counter, and the like. . When the electrode is touched, the capacitance is changed and the oscillation frequency of the CR oscillation circuit is lowered. Therefore, the CR oscillation is counted for a certain time by the counter, and the lowered oscillation frequency value is detected. A change from off to on is detected by comparing the calculated oscillation frequency value with a base frequency value at the time of off which is a reference value stored in advance (see, for example, Patent Document 1).
Japanese Utility Model Publication No. 52-164565

  However, in the capacitance detection type switch device, the electrode changes the capacitance by contact or proximity of a human body, but the capacitance also changes due to stray capacitance. For this reason, when the stray capacitance changes with a change in the electrode arrangement environment, the capacitance also changes and the oscillation frequency of the CR oscillation circuit changes. For this reason, an error occurs between the actual off-time frequency value and the off-time base frequency value used as the reference value, and as a result, on / off detection cannot be performed properly. In addition, when a plurality of electrodes are arranged, there is a possibility that sensitivity may vary or malfunction may occur.

The present invention has been made in view of such conventional problems, and includes a capacitance detection type switch device capable of appropriately performing on / off detection without being affected by changes in environmental conditions, and the same. An object is to provide a wristwatch .

  In order to solve the above-mentioned problem, in the capacitance detection type switching device according to the first aspect of the present invention, a plurality of electrodes with which a human body is brought into contact or close to each other and reference values corresponding to the respective electrodes are provided. A reference value storage means for storing; an oscillation circuit whose oscillation frequency is changed by a capacitance coupled to the electrode; a detection means for detecting an oscillation frequency value of each electrode; and a detection means for each electrode detected by the detection means. Based on the oscillation frequency value and the corresponding reference value stored in the reference value storage means, for each electrode, a calculation means for calculating a change amount of the oscillation frequency due to the capacitance coupled to the electrode, and the calculation means A discriminating unit that discriminates for each electrode whether or not the calculated change amount of the oscillation frequency of the electrode is larger than a predetermined value, and by this discriminating unit, all the change amounts of the plurality of electrodes are larger than the predetermined value. A reference value changing means for changing all reference values corresponding to the plurality of electrodes stored in the reference value storage means based on the oscillation frequency values detected by the detecting means. When the discriminating means discriminates that the change amount of the oscillation frequency is smaller than the predetermined value among the plurality of electrodes, the human body is brought into contact with or close to the electrode whose change amount of the oscillation frequency is larger than the predetermined value. Judgment means for judging that the

  In other words, if all of the calculated changes in the oscillation frequency of the plurality of electrodes are determined to be greater than the predetermined value, it is not the case that the human body is in contact with or close to a specific electrode, but the stray capacitance that accompanies changes in environmental conditions. It can be assumed that it is caused by the change of Therefore, in this case, by changing all reference values corresponding to a plurality of electrodes stored in advance based on the detected oscillation frequency values, reference values adapted to changes in environmental conditions are set. can do. Therefore, it is possible to appropriately perform on / off detection without being affected by changes in environmental conditions.

  In addition, when it is determined that there is an electrode whose variation in oscillation frequency is smaller than a predetermined value among the plurality of electrodes, an electrode whose variation in oscillation frequency is larger than a predetermined value has a stray capacitance due to a change in environmental conditions. It can be assumed that the human body is in contact with or in close proximity to the electrode, not due to the change. Therefore, in this case, it is possible to detect ON properly by determining that the human body is in contact with or close to an electrode whose oscillation frequency change amount is larger than a predetermined value.

  As described above, the invention according to claim 1 corresponds to a plurality of electrodes stored in advance when all of the calculated variation amounts of oscillation frequencies of the plurality of electrodes are determined to be larger than a predetermined value. All the reference values to be changed are changed based on each detected oscillation frequency value. Therefore, if all of the calculated changes in the oscillation frequency of the plurality of electrodes are determined to be greater than the predetermined value, it is not the case where the human body is in contact with or close to the specific electrode, but the stray capacitance associated with the change in environmental conditions. Because it can be assumed that it is caused by a change in environmental conditions, it is possible to set a reference value according to changes in environmental conditions, so that on / off detection can be performed appropriately without being affected by changes in environmental conditions. It becomes possible.

(First embodiment)
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, the present invention is applied to a wristwatch. As shown in the vertical sectional view of FIG. 1, a watch glass 20 is attached to an upper portion of a synthetic resin watch case 100, and a watch module 30 is accommodated in the watch case 100. A back cover 4 made of conductive metal is attached to the lower surface of the watch case 100. The back cover 40 is electrically connected to the circuit ground.

  The timepiece module 30 includes an upper housing 5 and a lower housing 6. A circuit board 7 is provided between the upper housing 5 and the lower housing 6. On this circuit board 7, various electronic components necessary for the clock function such as the LSI 8 and the detection circuit 9 are mounted. In this case, the detection circuit 9 is for detecting a change in capacitance of a touch switch described later.

  The upper housing 5 is provided with a liquid crystal display panel 10 electrically connected to the circuit board 7 in correspondence with the watch glass 20, and the battery 11 is connected to the circuit board 7 in the lower housing 6. It is stored in an electrically connected state.

  As shown in FIG. 2, a plurality of electrode portions 12 to 15 are provided on the inner surface of the synthetic resin watch case 100. Each of the plurality of electrode portions 12 to 15 is a metal screw, and is screwed into screw holes 16a to 16d provided on the inner surface of the watch case 100 corresponding to 2 o'clock, 4 o'clock, 8 o'clock, and 10 o'clock. Thus, it is embedded in the inner surface of the watch case 100. Further, the plurality of electrode portions 12 to 15 are elastically contacted by contact plates 17 provided at the edge portions corresponding to 2 o'clock, 4 o'clock, 8 o'clock and 10 o'clock on the circuit board 7 of the timepiece module 30, respectively. The circuit board 7 is electrically connected. Each of the plurality of contact plates 17 is electrically connected to a detection circuit 9 described later on the circuit board 7.

  Further, as shown in FIG. 2, touch portions 18 are provided corresponding to the plurality of electrode portions 12 to 15 on the outer surface of the portions corresponding to 2 o'clock, 4 o'clock, 8 o'clock and 10 o'clock in the wristwatch case 100, respectively. It has been.

  FIG. 3 is a block diagram showing a configuration of the detection circuit 9. In a normal state, that is, in a state where a part of a human body such as a finger is not in contact with the touch unit 18, the CR oscillation circuits 91 to 94 oscillate at frequencies determined by the internal capacitors Ci1 to Ci4 and the internal resistors Ri1 to Ri4, respectively. To do. When a part of a human body such as a finger comes into contact with the touch part 18, the electrode part 15 has a capacitance Ct between the electrode part 15 and the touch part 18, and the touch part 18 and the circuit ground G (the back of the watch). Capacitance Ce with the lid) is coupled. Therefore, the electrostatic capacity C of the CR oscillation circuit is a parallel capacity of the combined capacity of Ct and Ce and the built-in capacity Ci. That is, when the touch unit 18 is touched with a finger, the capacitance C of the CR oscillation circuits 91 to 94 increases by the combined capacitance of Ct and Ce, and the frequency becomes slower. By picking up the change in frequency, it is determined that the touch switch is turned on when the finger touches the touch unit 18 corresponding to the electrode unit 15.

  In order to detect the frequencies of the CR oscillation circuits 91 to 94, the outputs of the CR oscillation circuits 91 to 94 are supplied to the counter 96 through the OR gate 95, and the outputs of the CR oscillation circuits 91 to 94 are output for a certain time. What is necessary is to measure how many are counted. For this reason, a fixed time is created by the timer 97, and the outputs of the CR oscillation circuits 91 to 94 are counted by the counter 96. At this time, the counter 96 starts counting with the signal a from the control circuit 98 and the timer 97 starts. When the timer 97 counts for a certain period of time, it outputs a signal b and stops the counting of the counter 96. When receiving the signal b, the control circuit 98 reads the data of the counter 96 and outputs the key input signal c when it is smaller than a reference value (base count values Y1 to Y4 described later). When the timer 97 counts the CPU and its peripheral circuits and the CPU operation program for a certain period of time, the control circuit 98 outputs the signal b and stops the counter 96 counting. When the control circuit 98 receives the signal b, the control circuit 98 is composed of a ROM that reads and stores the data of the counter 96, a RAM that is used as a work area of the CPU, and the like.

  FIG. 4 is a flowchart showing a processing procedure of the control circuit 98 in the present embodiment. In the following flowchart, as indicated in FIG. 3, the switches configured by the touch unit 18, the electrode unit 15, and the CR oscillation circuits 91 to 94 are referred to as switches 1 to 4.

  The control circuit 98 first detects the count value X1 of the switch 1 in order to detect the count values of the switches 1 to 4 in a time division manner (step S101). That is, as described above, the control circuit 98 outputs the signal a to start counting of the counter 96 and starts the timer 97. When the timer 97 counts for a certain period of time, it outputs the signal b and stops counting of the counter 96. Let When receiving the signal b, the control circuit 98 reads the data of the counter 96, detects this as the detection value X of the switch 1, and stores it in the internal RAM.

  Next, it is determined whether or not the detection of the count value X of all the switches 1 to 4 has been completed (step S102). If not completed, the value of the register I for specifying the switches 1 to 4 is incremented (step S103), and the processing from step S101 is repeated. Therefore, when the determination in step S102 is YES and the count values of all the switches 1 to 4 are detected, the RAM of the control circuit 98 corresponds to the switches 1 to 4 as shown in FIG. The respective detection values X1 to X4 are stored. In the figure, Y1 to Y4 are base count values (reference values) of the switches 1 to 4, and I is a value of the register I for specifying the switches 1 to 4.

  Subsequently, by “(Y−X)> α”, it is determined whether or not there is a switch in which the difference between the base count value Y and the count value X detected this time is equal to or greater than a predetermined value α (step S104). If this determination is NO and there is no switch in which the difference between the base count value Y and the count value X is α, it is assumed that none of the switches 1 to 4 has changed, and steps S105 to S107 are performed. Return without processing.

  However, if there is a switch in which the difference between the base count value Y and the count value X is α, it is determined whether all the switches 1 to 4 have changed by α or more (step S105). If the determination in step S105 is YES and all the switches 1 to 4 have changed by α or more, the user does not touch any one of the touch portions 18 to turn on a specific switch, It can be assumed that the capacitance Ce or the like has changed due to a change in stray capacitance accompanying a change in environmental conditions. Therefore, in this case, the base count value Y of all the switches 1 to 4 is changed to the current count value X (step S106). Accordingly, the current count values X1 to X4 are stored as Y1 to Y4 in the RAM shown in FIG.

  On the other hand, if the determination in step S105 is NO and all the switches 1 to 4 have not changed by α or more, and there is a switch whose change is less than α, it is determined that the switch that has changed by α or more is ON. (Step S107). That is, when it is determined that there is a change amount (YX) of the oscillation frequency smaller than α among the plurality of switches 1 to 4, the switch with the change amount (YX) being α or more is an environmental condition. It can be assumed that the finger is touched to the switch, not due to the change in the stray capacitance due to the change in. Therefore, it is determined that the switch is ON, and the key input signal c is output from the control circuit 98.

  (Second Embodiment)

  FIG. 6 is a flowchart showing a processing procedure of the control circuit 98 in the second embodiment of the present invention. The control circuit 98 first detects the count value X1 of the switch 1 a plurality of times (step S201) and stores it in the RAM in order to detect the count values of the switches 1 to 4 a plurality of times in a time division manner. In the present embodiment, detection is performed four times for each of the switches 1 to 4, and therefore, when the process of step S201 ends, the count value X1 (1 for four times of the switch 1 as shown in FIG. ) To X1 (4) are stored. Y1 is the base count value of the switch 1.

  Next, based on “(Y1-X1)> β”, it is determined whether or not the amount of change (Y1-X1) is equal to or greater than a predetermined value β (step S202). If this determination is NO and (Y1-X1)> β has not been satisfied even once in a plurality of detections, even if there is a change in the oscillation frequency in the CR oscillation circuit 91, the change in the oscillation frequency is It can be assumed that the switch 1 is not touched with a finger but is caused by a change in stray capacitance accompanying a change in environmental conditions. Therefore, in this case, the base count value Y1 of the switch 1 stored in the RAM is changed to the count value X1 (4) detected in the last time (fourth time) (step S203). As a result, a base count value (reference value) adapted to changes in environmental conditions can be set.

  In the present embodiment, the base count value Y1 is changed to the count value X1 (4) detected in the last time (fourth time) in step S203. However, for example, the average value of the four count values is changed to the average value. Instead of using the count value as it is, such as changing the count value or correcting the count value, the count value may be changed as appropriate.

  On the other hand, if (Y1-X1)> β is satisfied even once as a result of the determination in step S202, the change in the oscillation frequency in the CR oscillation circuit 91 is caused by the change in the stray capacitance accompanying the change in the environmental conditions. Instead, it can be assumed that the finger is in contact with the switch 1. Therefore, in this case, it is determined that the switch 1 is ON (step S107). As a result, the key input signal c is output from the control circuit 98.

  Similarly, the processes of steps S201 to S204 described above are executed for switch 2 (step S205), switch 3 (step S206), and switch 4 (step S207). As a result, the base count value is changed or ON is determined for all the switches 2 to 4.

(Third embodiment)
FIG. 8 is a diagram showing a storage state of the RAM included in the control circuit 98 according to the third embodiment of the present invention. As shown in the figure, the RAM stores the following values for each of the switches 1 to 4.
OFF state count value Z1
ON count value W1
Count value change width A1
Threshold value range B1

  Here, the count value Z1 in the OFF state is a count value when the switch is in the OFF state, and the count value W1 in the ON state is a count value when the switch is in the ON state. The count value change width A1 is the difference between the count value Z1 in the OFF state and the count value W1 in the ON state, Z1−W1 = A1, and the threshold count value width B1 is 80% of the count value change width A1. A1 × 0.8 = B1.

  FIG. 9 is a flowchart showing a processing procedure of the control circuit 98 in the present embodiment. The control circuit 98 first detects the count value X1 of the switch 1 a plurality of times in order to detect the count values of the switches 1 to 4 in a time division manner (step S301). Next, it is determined whether or not the difference between the detected current count value X1 and the count value Z1 in the off state is equal to or greater than the threshold count value width B1, that is, “Z1−X1> B1”. (Step S302). If it is determined that Z1-X1> B1 is not satisfied, that is, if the amount of change (Z1-X1) is not B1 or more, the switch 1 is determined to be OFF (step S303). Therefore, the key input signal c is not output from the control circuit 98.

  However, if Z1-X1> B1, that is, if the amount of change (Z1-X1) is greater than or equal to B1, the switch 1 is determined to be ON (step S304). That is, in this embodiment, the count value Z1 of the OFF state, which is the oscillation frequency value of the CR oscillation circuit 91 in the actually detected OFF state, and the oscillation frequency value of the CR oscillation circuit 91 in the actually detected ON state. Based on the count value W1 in a certain ON state, the threshold count value width B1 is calculated. Therefore, since the threshold count value width B1 that is the reference change amount is calculated based on the oscillation frequency values Z1 and W1 detected under a certain environmental condition, the calculated threshold count value width B1 takes the environmental condition into consideration, It will be taken into consideration. Therefore, the threshold count value width B1 taking this environmental condition into consideration and the detected change amount (Z1-X1) are compared, and when the detected change amount (Z1-X1) is larger than the threshold count value width B1, ON. By making the determination, it is possible to make a determination in consideration of the environmental conditions, and as a result, it is possible to appropriately perform on / off detection without being influenced by changes in the environmental conditions.

  Similarly, the processes in steps S301 to S304 are executed for the switch 2 (step S305), the switch 3 (step S306), and the switch 4 (step S307). As a result, the ON / OFF determination is also performed for all the switches 2 to 4.

(Fourth embodiment)
FIG. 10 is a diagram showing a storage state of the RAM included in the control circuit 98 according to the fourth embodiment of the present invention. As shown, the RAM stores the following values for the switch 1.
Switch 1 OFF state count value Z1
Switch 1 ON state count value W1
Switch 1 Count value change width A1
Switch 1 threshold count width B1
Switch 1 detection count value X1
Switch 1 change rate C1
Here, the count value Z1 in the OFF state is a count value when the switch is in the OFF state, and the count value W1 in the ON state is a count value when the switch is in the ON state. The count value change width A1 is the difference between the count value Z1 in the OFF state and the count value W1 in the ON state, Z1−W1 = A1, and the threshold count value width B1 is 80% of the count value change width A1. A1 × 0.8 = B1. The detection count value X1 is the count value of the switch 1 detected this time. As shown in FIG. 11, the change ratio C1 is the ratio of the change width (Z1-X1), which is the difference between the count value Z1 in the OFF state and the detected count value X1, to the threshold count value width B1, that is, (Z1-X1). / B1 = C1.
As shown in FIG. 10, these values are stored in the RAM for each of the switches 1 to 4, and comparison flags F1 to F4 corresponding to the switches 1 to 4 are stored.

  FIG. 12 is a flowchart showing a processing procedure of the control circuit 98 in the present embodiment. The control circuit 98 first detects the count value X1 of the switch 1 a plurality of times in order to detect the count values of the switches 1 to 4 in a time division manner (step S401). Next, it is determined whether or not the difference between the detected current count value X1 and the count value Z1 in the off state is equal to or greater than the threshold count value width B1, that is, “Z1−X1> B1”. (Step S402). If it is determined that Z1-X1> B1 is not satisfied, that is, if the change amount (Z1-X1) is not equal to or greater than B1, the process proceeds to the switch 2 process (step S405) without performing the processes of steps S403 and S404. If the change amount (Z1-X1) is equal to or greater than B1, the change rate C1 is calculated from (Z1-X1) / B1 = C1 (step S403), and the comparison flag F1 is set (step S404). .

  Similarly, the processes in steps S401 to S404 are executed for the switch 2 (step S405), the switch 3 (step S406), and the switch 4 (step S407). Thereafter, it is determined whether or not any of the comparison flags F1 to F1 is set (step S409). If it is set, the change rate is calculated and stored as shown in step S403. Therefore, the stored change ratios are compared (step S409). Then, the switch with the largest change rate is determined to be ON (step S410).

  In other words, in this embodiment, the actual oscillation frequency values of the CR oscillation circuits 91 to 94 (the count value Z1 in the OFF state, the count value W1 in the ON state) in the OFF state and the ON state of the switches 1 to 4. Are detected in advance, and a threshold count value width B1 that is a reference change amount is calculated. Therefore, since the threshold count value width B1 (reference change amount) is calculated based on the oscillation frequency value detected under a certain environmental condition, the calculated reference change amount is considered in consideration of the environmental condition. Become. Thereafter, when the oscillation frequencies of the CR oscillation circuits 91 to 94 change, the ratio (Z−X) / B = the detected change amount (Z−X) based on the detected oscillation frequency value (X) to the threshold count value width B C is calculated, and it is determined that the switch having the largest calculated ratio has been changed to the ON determination ON state. As a result, it is possible to make a determination in consideration of the environmental conditions, and as a result, it is possible to appropriately perform on / off detection without being influenced by changes in the environmental conditions.

  In the embodiment, the case where the present invention is applied to a wristwatch has been described. However, the present invention is not limited to this, and may be applied to various electronic devices including a switch.

1 is a vertical sectional view of a wristwatch to which an embodiment of the present invention is applied. It is an AA arrow directional cross-sectional view of FIG. It is a block diagram which shows the structure of the detection circuit which concerns on one embodiment of this invention. It is a flowchart which shows the process sequence in 1st Embodiment. It is a figure which shows the memory | storage data in the same embodiment. It is a flowchart which shows the process sequence in the 2nd Embodiment of this invention. It is a figure which shows the memory | storage data in the same embodiment. It is a figure which shows the memory | storage data in the 2nd Embodiment of this invention. It is a flowchart which shows the process sequence in the embodiment. It is a figure which shows the memory | storage data in the 2nd Embodiment of this invention. It is explanatory drawing which shows the relationship of memory | storage data. It is a flowchart which shows the process sequence in the embodiment.

Explanation of symbols

4 Back cover 5 Upper housing 6 Lower housing 7 Circuit board 8 LSI
DESCRIPTION OF SYMBOLS 9 Detection circuit 10 Liquid crystal display panel 12-15 Electrode part 18 Touch part 91-94 CR oscillation circuit 95 OR gate 96 Counter 97 Timer 98 Control circuit c Key input signal

Claims (3)

A plurality of electrodes with which the human body is contacted or approached;
A reference value storage means for storing a reference value corresponding to each of the plurality of electrodes,
Detecting means for detecting an oscillation frequency value of each electrode, having an oscillation circuit whose oscillation frequency is changed by a capacitance coupled to the electrode;
Based on the oscillation frequency value of each electrode detected by the detection means and the corresponding reference value stored in the reference value storage means, for each electrode, the amount of change in oscillation frequency due to the capacitance coupled to the electrode is calculated. A calculating means for calculating;
A discriminating means for discriminating for each electrode whether or not the change amount of the oscillation frequency of the electrode calculated by the calculating means is larger than a predetermined value;
When all of the change amounts of the plurality of electrodes are determined to be larger than a predetermined value by the determination unit, all the reference values corresponding to the plurality of electrodes stored in the reference value storage unit are detected. Reference value changing means for changing based on each oscillation frequency value detected by the means;
When it is determined by the determining means that there is an oscillation frequency change amount smaller than a predetermined value among the plurality of electrodes, the human body is in contact with or close to an electrode whose oscillation frequency change amount is greater than a predetermined value. An electrostatic capacity detection type switching device comprising: a determination means for determining. A wristwatch comprising the capacitance detection type switch device according to claim 1. The wristwatch according to claim 2, wherein the plurality of electrodes are embedded in an inner surface of a wristwatch case made of synthetic resin.

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