Electrostatic input device

Abstract

Provided is an electrostatic input device which is capable of activating an electrostatic capacitance detection unit before contact is determined so that false detection is suppressed.　The electrostatic input device includes: an electrostatic capacitance detection unit that is arranged in an operation unit which is operated by a living body and that detects electrostatic capacitance; and a control unit that switches the electrostatic capacitance detection unit to an activated state when the electrostatic capacitance detection unit is in a standby state and contact with the living body has not been detected, and if an increase of electrostatic capacitance detected by the electrostatic capacitance detection unit reaches or exceeds a first prescribed value a prescribed number of times within a prescribed period.

Description

Technical Field

[0001] The present invention relates to an electrostatic input device.

Background Art

[0002] Conventionally, there has been a driving method for input means in which a capacitance detection unit is provided in an operation unit, and the capacitance detection unit is set to a standby state when there is no contact with the operation unit for power saving, and the capacitance detection unit is set to an activated state when there is contact with the operation unit (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the conventional driving method for input means is for reaching a determination threshold value for determining that there is contact in a short time, but there is still room for improvement because it may not be fast enough. In addition, in order to take countermeasures, it is conceivable to lower the determination threshold value for determining that there is contact with the operation unit, but in that case, there is a possibility of activation due to instantaneous noise or the like accompanying the movement of the user, and there is a risk of an increase in false detection.

[0005] Therefore, an object of the present invention is to provide an electrostatic input device capable of activating a capacitance detection unit from a state before determining contact and suppressing false detection.

Means for Solving the Problems

[0006] The electrostatic input device according to an embodiment of the present invention is disposed in an operation unit operated by a living body, and includes a capacitance detection unit that detects capacitance, and when the capacitance detection unit is in a standby state and contact by the living body has not been detected, if the increase amount of the capacitance detected by the capacitance detection unit is equal to or greater than a first predetermined value a predetermined number of times or more within a predetermined period, a control unit that sets the capacitance detection unit to an activated state.

Advantages of the Invention

[0007] It is possible to provide an electrostatic input device that can activate the capacitance detection unit from a state before determining contact and suppress false detection.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Figure 7

Figure 8

Figure 9

Figure 10

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Figure 12

Figure 13

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments to which the electrostatic input device of the present invention is applied will be described.

[0010] <Embodiment> FIG. 1 is a diagram showing a door handle 10 attached to a vehicle 1. The door handle 10 is attached to a door 2 of the vehicle 1. The door handle 10 has an elongated shape so as to be easily grasped by a human finger or the like. An electrostatic sensor 110 is provided inside the door handle 10. In FIG. 1, the longitudinal direction of the door handle 10 is the lateral direction in which the door handle 10 extends longitudinally.

[0011] FIG. 2 is a diagram showing the electrostatic sensor 110. The electrostatic sensor 110 includes a substrate 110A and sensors 111, 112, and 113. The sensors 111, 112, and 113 are arranged along the longitudinal direction of the door handle 10 as an example. The electrostatic sensor 110 is an example of a capacitance detection unit.

[0012] FIG. 3 is a diagram showing the electrostatic input device 100 of the embodiment. The electrostatic input device 100 includes an electrostatic sensor 110 and an integrated circuit 120.

[0013] The integrated circuit 120 includes a switch 121, a switch 122, an amplifier 123, an ADC (Analog-to-digital converter) 124, an arithmetic unit 125, and a control unit 126. The control unit 126 incorporates a storage unit 126A.

[0014] As shown in FIG. 3, switches 121 of the integrated circuit 120 are connected to sensors 111, 112, and 113 of the electrostatic sensor 110.

[0015] The switch 121 is provided between the sensors 111, 112, 113 and the inverting input terminal of the amplifier 123, and the connection destination is switched by the control unit 126, so that the inverting input terminal of the amplifier 123 is connected to any one of the sensors 111, 112, 113. A power supply Vdd is connected to a line branching from between the switch 121 and the inverting input terminal of the amplifier 123 via a switch 122.

[0016] The switch 122 is provided to apply a pulsed voltage (voltage value is Vdd) to the sensors 111, 112, 113 in order by being intermittently turned on / off by the control unit 126 when the switch 121 is connected to each of the sensors 111, 112, 113.

[0017] In this way, while the connection destination of the switch 121 is switched by the control unit 126 and the on / off of the switch 122 is switched, a pulsed voltage is applied to the sensors 111, 112, 113 in order. In this way, applying a pulsed voltage to the sensors 111, 112, 113 is to scan the sensors 111, 112, 113.

[0018] By scanning the sensors 111, 112, 113 in this way, the potentials detected by each of the sensors 111, 112, 113 are amplified by the amplifier 123 and converted from an analog signal to a digital signal by the ADC 124. Based on the digital signal thus converted, the capacitance between the sensors 111, 112, 113 and the finger 200 can be calculated in the arithmetic unit 125. The information on the calculated capacitance is stored in the storage unit 126A of the control unit 126. The control unit 126 detects (determines) the approach of the user to the door handle 10 based on the information on the capacitance calculated by the arithmetic unit 125.

[0019] FIG. 4 is a diagram showing the scan intervals in the normal mode and the power-saving mode. Here, the normal mode is a mode in which the electrostatic sensor 110 is activated at short time intervals to detect contact or proximity of a living body. Here, when the electrostatic sensor 110 is in the normal mode, it is in the activated state.

[0020] The power-saving mode is a mode in which the electrostatic sensor 110 is in a standby state. In the standby state, the activation of the electrostatic sensor 110 is restricted, and for example, the scan interval is lengthened or the number of measurement pulses is reduced so that the power consumption in the electrostatic sensor 110 and the integrated circuit 120 is reduced. The power-saving mode is released when a predetermined condition is satisfied and transitions to the normal mode, and the electrostatic sensor 110 changes from the standby state to the activated state.

[0021] In the normal mode, the sensors 111, 112, and 113 are scanned at intervals of, for example, 5 ms, and pulse voltages are applied in order at intervals of 5 ms. The period for performing one scan is, as shown in FIG. 4, the period during which a pulse voltage is applied to each of the sensors 111, 112, and 113 once.

[0022] Further, the pulse voltage applied every 5 ms specifically includes, for example, eight pulses as shown in the enlarged view on the right side. The pulse voltages applied to the sensors 111, 112, and 113 every 5 ms are out of phase with each other in time series.

[0023] The capacitance calculated by the arithmetic unit 125 in one scan is the average value of the eight capacitances obtained when each of the eight enlarged pulses is applied, that is, the number of measurements in one scan is eight. Here, for the sake of simplicity of explanation, the number of measurements is set to eight for convenience, but in actual measurement, for example, a larger number of measurements such as 128 times or 256 times may be set to obtain an average value, or the number of measurements may be less than eight such as once.

[0024] In the power-saving mode, for sensors 111, 112, and 113, as an example, scanning is performed at intervals of 20 ms, and pulse voltages are applied in order at intervals of 20 ms. The pulse voltage applied every 20 ms, more specifically, as shown in the enlarged view on the right, includes, for example, eight pulses. The pulse voltages applied to sensors 111, 112, and 113 every 20 ms are out of timing with each other in time series.

[0025] The period for performing one scan is, as in the normal mode, the period during which a pulse voltage is applied to each of sensors 111, 112, and 113 once, and the capacitance calculated by the arithmetic unit 125 in one scan is the average value of the eight capacitances obtained when each of the eight enlarged pulses is applied.

[0026] In this way, in the power-saving mode, since the number of times the pulse voltage is applied to sensors 111, 112, and 113 is reduced compared to the normal mode, the power consumption of the integrated circuit 120 is also reduced, and the power consumption of the entire electrostatic input device 100 can be reduced.

[0027] By the way, in order to quickly activate the electrostatic sensor 110 at an early stage before determining approach from the power-saving mode, for example, it is conceivable that the control unit 126 sets a low threshold for detecting (determining) the user's approach to the door handle 10 based on the outputs of sensors 111, 112, and 113, and activates the electrostatic sensor 110 at the detected time.

[0028] However, before the user's hand touches the door handle 10, the outputs of sensors 111, 112, and 113 may include noise due to changes in the relative position between the user and the door handle 10, external disturbance noise, etc. Even if the control unit 126 performs filter processing, it is difficult to accurately detect (determine) the user's approach to the door handle 10.

[0029] FIG. 5 is a diagram showing the outputs of sensors 111, 112, and 113. In FIG. 5(A), for comparison, the relationship between the outputs of sensors 111, 112, and 113 and a threshold value when detecting (determining) the approach of a user to the door handle 10 using one threshold value for the outputs of sensors 111, 112, and 113 is shown. FIG. 5(A) is a characteristic diagram shown schematically and represents the output of any one of sensors 111, 112, and 113. The average value of the outputs of sensors 111, 112, and 113 also shows similar characteristics.

[0030] Here, the outputs of sensors 111, 112, and 113 are signals in which the signals representing the potentials detected by sensors 111, 112, and 113 are converted into one signal as the output of switch 121, amplified by amplifier 123, then converted into digital signals by ADC 124, the capacitance is obtained by arithmetic unit 125, and input to control unit 126. That is, the outputs of sensors 111, 112, and 113 are signals representing the capacitance input to control unit 126.

[0031] As shown in FIG. 5(A), when control unit 126 detects (determines) the approach of a user to door handle 10 based on the outputs of sensors 111, 112, and 113 using one threshold value set low to detect the approach of the user to door handle 10, the capacitance may exceed the threshold value just by fluctuating greatly once due to the influence of noise or an unintended operation of the user, and it may be detected as the approach of the user to door handle 10. This may lead to false detection.

[0032] Also, if the threshold value is increased to avoid false detection, there is a possibility that when the user approaches door handle 10, the electrostatic sensor 110 cannot be activated at just the right timing so that the user does not feel a delay in response.

[0033] Therefore, in the electrostatic input device 100 of the embodiment, when the increase amount of the capacitance detected by the electrostatic sensor 110 is equal to or greater than a predetermined value Ca (an example of a first predetermined value) a predetermined number of times or more within a predetermined period, the electrostatic sensor 110 is activated.

[0034] Figure 5(B) is an example showing the waveform obtained when scanning is actually performed in the normal mode or the power-saving mode by the method shown in FIG. 4, and shows the capacitance variations measured by the sensors 111, 112, and 113 by three scans. Note that the capacitance measured by each sensor 111, 112, 113 for each scan represents the average value of the eight capacitances obtained when the eight pulses are applied as described above. Also, in this graph, the scan result immediately before is the capacitance data at the far left. Here, for the sake of easy understanding, assuming a state where the user is not approaching the door handle 10 (no-operation state), the capacitance values measured by the sensors 111, 112, 113 are simply described as the same value C0.

[0035] In each scan, three capacitances are measured by the three sensors 111, 112, and 113. Here, the increase amounts ΔC1, ΔC2, and ΔC3 of the capacitance obtained from any of the sensors 111, 112, and 113 in the first to third scans are described in a form where the value is obtained by subtracting the capacitance measured in the previous scan by the sensor (any one of 111, 112, and 113) that obtained the maximum value from the maximum value among the capacitances measured by the sensors 111, 112, and 113 in the current scan.

[0036] As an example, for calculating the increase amount, the maximum value of the increase amount of the capacitance for each sensor between each scan may be used as the representative value of the increase amount between the scans. Alternatively, the increase amount between each scan may be calculated using the average value or the total value of the capacitances of the plurality of sensors measured in each scan. Also, the maximum value among the capacitances of each sensor in each scan may be used as the representative value in that scan, and the increase amount between the scans may be calculated using it. Alternatively, the average value or the total value of the increase amounts of the plurality of sensors between the scans may be used as the increase amount between the scans. The method for calculating the representative value of the capacitance and the increase amount for each scan can be appropriately determined according to the system.

[0037] As an example, assume that in the first scan, the capacitance measured by sensor 111 is the largest, in the second scan, the capacitance measured by sensor 112 is the largest, and in the third scan, the capacitance measured by sensor 113 is the largest. This assumes, for example, a case where a human hand or finger approaches obliquely from above sensor 111 towards sensor 113.

[0038] In this case, ΔC1 is the value obtained by subtracting the capacitance C0 in the immediately preceding scan (no-operation state) from the capacitance measured by sensor 111, which is the maximum value in the first scan. Also, ΔC2 is the value obtained by subtracting the capacitance measured by sensor 112 in the first scan from the capacitance measured by sensor 112, which is the maximum value in the second scan. Similarly, ΔC3 is the value obtained by subtracting the capacitance measured by sensor 112 in the second scan from the capacitance measured by sensor 113, which is the maximum value in the third scan.

[0039] As shown in FIG. 5(B), when the capacitance detected by the electrostatic sensor 110 increases three or more times within the period TP1 and ΔC1, ΔC2, and ΔC3 in each scan of the increase amount of the capacitance measured in three or more scans are equal to or greater than a predetermined value Ca, the transition is made from the power-saving mode to the normal mode and the electrostatic sensor 110 is activated. ΔC1 > Ca, ΔC2 > Ca, and ΔC3 > Ca.

[0040] That is, in an example shown in FIG. 5(B), the predetermined period is period TP1, the predetermined number of times is three times, and the amounts of increase in capacitance used for determination are ΔC1, ΔC2, and ΔC3. Here, for simplicity of explanation, an example where scans with an amount of increase in capacitance equal to or greater than a predetermined value Ca are continuous will be described. However, scans where the amount of increase does not exceed the predetermined value Ca or the capacitance decreases during the scans as described above may be included. As long as there are a predetermined number or more of scans with an amount of increase equal to or greater than the predetermined value Ca within the predetermined period even with a discontinuous increase, it is acceptable. Also, in FIG. 5(B), period TP1 is shown as being approximately the same period as the period for three scans. However, if it is a period in which more scans than the predetermined number are possible, the predetermined period may be set to a longer period. Further, in an example shown in FIG. 5(B), period TP1 is shown when counting starts from the first scan where the amount of increase in capacitance exceeds Ca. However, when period TP1 ends, the count of period TP1 may be restarted when the amount of increase in capacitance exceeds Ca again. Also, as an example, when the amount of increase in capacitance exceeds Ca again before the count of period TP1 started in the first scan ends (for example, the second or third scan in FIG. 5(B)), the count of the predetermined period is started from that point, and the count of the predetermined period is performed in parallel with the count of period TP1 started in the first scan, and the number of adjacent times is counted for each predetermined period. At this time, when the number of adjacent times becomes equal to or greater than the predetermined number during the count of any of the predetermined periods, a transition is made from the power-saving mode to the normal mode. Also, as an example, the start point of period TP1 may be when a parameter other than the amount of increase in capacitance exceeds a predetermined value set in advance. Also, it may be set so that period TP1 is counted at predetermined time intervals regardless of the predetermined value.

[0041] Further, the control unit 126 has a proximity count counter that counts the number of proximities. The proximity count counter is an example of a counter. When the capacitance detected by the electrostatic sensor 110 in the current scan increases by a predetermined value Ca or more compared to the capacitance detected in the previous scan, the control unit 126 increments the proximity count counter. When the proximity count counter reaches 3 or more within a predetermined period (period TP1), the control unit 126 activates the electrostatic sensor 110.

[0042] Also, hereinafter, in the power saving mode, when the increase amounts ΔC1, ΔC2, ΔC3 of the capacitance detected by the electrostatic sensor 110 are equal to or greater than a predetermined value Ca three or more times within the period TP1, it is said that the activation condition is satisfied. When the activation condition is satisfied, the control unit 126 activates the electrostatic sensor 110.

[0043] In the electrostatic input device 100 of the embodiment, when the electrostatic sensor 110 is in the standby state, the approach of the user to the door handle 10 is detected (determined) using the determination method as shown in FIG. 5(B).

[0044] Further, when the activation condition is satisfied and the electrostatic sensor 110 is activated, if the output of any one of the sensors 111, 112, 113 exceeds a threshold value for determining that contact with the vehicle 1 (see FIG. 1) has occurred in the normal mode, it is determined that contact with the door handle has occurred, and a signal permitting the release of the door lock is transmitted to the ECU (Electronic Control Unit) that controls the door lock of the vehicle 1. As a result, the door lock is released.

[0045] FIG. 6 is a flowchart showing the processing executed by the control unit 126 during the power saving mode. The control unit 126 repeatedly executes the flowchart shown in FIG. 6 at a predetermined control cycle corresponding to one scan operation shown in FIG. 4. Here, the capacitance calculated by the arithmetic unit 125 is converted from an analog value to a digital value. For example, 10 pF becomes 1 count in the digital value.

[0046] When the process starts, the control unit 126 controls the connection of the switches 121 and 122 in the power saving mode to execute the scanning of the sensors 111, 112, and 113 (step S1).

[0047] The control unit 126 determines whether the capacitance calculated by the arithmetic unit 125 is equal to or greater than a predetermined value Cwake that permits the transition to the normal mode (step S2). Note that the capacitance calculated at this time represents the average value of the eight capacitances obtained when the eight pulses are applied as described above. Also, the predetermined value Cwake is set to a sufficiently large capacitance so that an increase in capacitance due to the user's approach to the door handle 10 can be accurately discriminated without false detection by a single determination using one threshold value.

[0048] When the control unit 126 determines that it is equal to or greater than the predetermined value Cwake (S2: YES), it transitions to the normal mode (step S3). Here, as an example, the form in which the transition condition to step S3 is equal to or greater than the predetermined value Cwake representing the user's approach to the door handle 10 is described. However, if it is possible to determine that the user has surely approached the sensors 111, 112, and 113, such a condition may be used as the normal mode transition condition.

[0049] The control unit 126 clears the proximity count counter stored in the memory to 0 (step S4).

[0050] When the control unit 126 finishes the process of step S4, it ends the process in the control cycle corresponding to the current scan timing (END).

[0051] When the control unit 126 determines in step S2 that it is not equal to or greater than the predetermined value Cwake (S2: NO), it determines whether the increase amount with respect to the capacitance obtained in the previous scan is equal to or greater than a predetermined value Ca (step S5).

[0052] The determination in step S5 corresponds to the operation for the example shown in FIG. 5(B), and is a process of determining whether the maximum value among the three capacitances obtained by sensors 111, 112, and 113 in the current scan has increased by a predetermined value Ca or more with respect to the capacitance of the corresponding sensor (any one of 111, 112, and 113) in the previous scan.

[0053] When the control unit 126 determines that it has increased by a predetermined value Ca or more (S5: YES), it increments the proximity count counter, that is, adds 1 to the count value stored in the memory and overwrites it (step S6).

[0054] The control unit 126 determines whether the proximity count counter is 3 or more (step S7).

[0055] When the control unit 126 determines that the proximity count counter is 3 or more (S7: YES), it advances the flow to step S3 in order to transition to the normal mode.

[0056] When the control unit 126 determines in step S5 that it has not increased by a predetermined value Ca or more (S5: NO), it determines whether the time from the start of counting, that is, the duration, is equal to or longer than a period TP1 (step S8).

[0057] When the control unit 126 determines that the duration is equal to or longer than the period TP1 (S8: YES), it clears the proximity count counter stored in the memory to 0 (step S9).

[0058] Note that when the control unit 126 determines in step S7 that the proximity count counter is not 3 or more (S7: NO), it ends the process in the current control cycle (END). Then, it repeats the operations from step S1 in the control cycle corresponding to the next scan timing.

[0059] Further, in step S8, when the control unit 126 determines that the continuous time is not longer than the period TP1 (S8: NO), it ends the processing in the control cycle corresponding to the current scan timing (END).

[0060] In the above operation, in the power saving mode, when the capacitance detected by the electrostatic sensor 110 increases due to the user approaching the door handle 10, and when the increase amount of the capacitance with respect to the previous scan is not less than a predetermined value Ca three or more times within the period TP1, the mode is switched to the normal mode.

[0061] Therefore, false detection due to noise or unintended operations of the user can be suppressed, and the mode can be quickly switched from the power saving mode to the normal mode as the user's hand or finger approaches the electrostatic sensor.

[0062] Accordingly, it is possible to quickly activate the electrostatic sensor 110 from the standby state and provide the electrostatic input device 100 that suppresses false detection.

[0063] In the above description, the form in which the electrostatic sensor 110 includes three sensors 111, 112, and 113 has been described. However, the number of sensors may be two or four or more. The control process by the control unit 126 in these cases is the same as when the electrostatic sensor 110 has three sensors 111, 112, and 113.

[0064] Further, the electrostatic sensor 110 may be in a form including one sensor (for example, sensor 111). In this case, when the capacitance obtained by the sensor 111 increases by not less than a predetermined value Ca three or more times within the period TP1 compared to the capacitance at the previous scan, the mode may be switched from the power saving mode to the normal mode.

[0065] Also, in step S5, when the value of the capacitance increases by a predetermined value Ca or more compared to the previous scan, the proximity count counter is incremented. However, the proximity count counter may also be incremented when the increase amount of the capacitance increases with the passage of time. Specifically, as shown in FIG. 5(B), when the increase amount of the capacitance obtained in the first scan within the period TP1 is ΔC1, the increase amount of the capacitance obtained in the second scan is ΔC2, and the increase amount of the capacitance obtained in the third scan is ΔC3, in step S5, in the first scan, if ΔC1 is equal to or greater than the predetermined value Ca, in the second scan, if ΔC1 < ΔC2, and in the third scan, if ΔC2 < ΔC3, the proximity count counter may be incremented respectively. In that case, scans that do not exceed the predetermined value Ca or in which the capacitance decreases may be included during the period TP1. As a method for confirming this, the capacitance value in each scan is stored in the memory, and the increase amounts of the scans with an increase amount equal to or greater than the predetermined value Ca are sequentially set as ΔC1, ΔC2, ΔC3. It is determined whether the relationship ΔC1 < ΔC2 < ΔC3 holds within the period TP1. If it holds, the transition to the normal mode may be made. The same applies to ΔC1, ΔC2, and ΔC3 hereafter.

[0066] Also, in the above description, the case where the increase amount increases in the first, second, and third scans has been described. However, the predetermined values for comparison may be sequentially increased and compared. Specifically, when Ca < ΔC1, Cb < ΔC2, Cc < ΔC3, and Ca < Cb < Cc hold, the transition to the normal mode may be made.

[0067] Also, a threshold may be set for the difference in the increase amount of the capacitance obtained within the period TP1. Specifically, as shown in FIG. 5(B), when the increase amounts of the capacitance ΔC1, ΔC2, and ΔC3 obtained three times within the period TP1 increase by a predetermined value Ca or more with the passage of time, the transition to the normal mode may be made. This means that ΔC2 - ΔC1 > Ca and ΔC3 - ΔC2 > Ca hold.

[0068] Further, when the difference in the increase amount of the capacitance is Ca or more and increases with the passage of time such that ΔC3 - ΔC2 > ΔC2 - ΔC1 > Ca holds, the transition to the normal mode may be made.

[0069] In other words, when the difference in the increase amount of the capacitance increases with the passage of time such that ΔC2 - ΔC1 > Ca, ΔC3 - ΔC2 > Cb, and Cb > Ca hold, and the difference increases stepwise to Ca and Cb (>Ca), the transition to the normal mode may be made.

[0070] Also, in step S8, the form of clearing the proximity count counter when the period TP1 has passed was described. However, for example, when a very large increase amount is obtained, such as when the increase amount with respect to the capacitance obtained in the previous scan is twice or more the predetermined value Ca, and the value in this scan is smaller than the predetermined value and the period TP1 has passed, the count value may not be cleared but may be decremented by 1 or not changed without clearing the proximity count counter. This is to enable a quicker transition to the normal mode (activation of the electrostatic sensor 110) in the next determination because there are individual differences in the way of approaching the vehicle 1. Note that the value twice that of Ca is an example of the third predetermined value, and the decremented count value 1 or the unchanged count value is an example of the second predetermined count value.

[0071] FIG. 7 is a flowchart showing the processing executed by the control unit 126 in the first modification of the embodiment. The flowchart shown in FIG. 7 is obtained by adding a transition operation from the normal mode to the power saving mode schematically and adding the processing of steps S11 to S15 to the flowchart shown in FIG. 6. Therefore, only the differences from FIG. 6 will be described.

[0072] When the process starts, the control unit 126 determines whether the power saving mode is set (step S11).

[0073] When the control unit 126 determines that the power saving mode is not set (S11: NO), it executes scanning in the normal mode (step S12). That is, as shown in FIG. 4, scanning is performed at a cycle of 5 ms.

[0074] The control unit 126 determines whether or not the transition condition to the power saving mode is satisfied (step S13). The transition condition to the power saving mode is that the capacitance obtained by the sensors 111, 112, and 113 over the past 30 seconds is equal to or less than a predetermined value indicating that there is no contact with the door handle 10. 30 seconds is an example of the predetermined time included in the transition condition to the power saving mode.

[0075] When the control unit 126 determines that the transition condition to the power saving mode is satisfied (S13: YES), it transitions to the power saving mode (step S14).

[0076] The control unit 126 clears the proximity count counter (step S15). When the control unit 126 finishes the process of step S15, it ends the flow (END).

[0077] Also, when the control unit 126 determines in step S13 that the transition condition to the power saving mode is not satisfied (S13: NO), it ends the flow (END).

[0078] Also, when the control unit 126 determines in step S11 that the power saving mode is set (S11: YES), it advances the flow to step S1. After that, the process proceeds in the same manner as the flowchart shown in FIG. 6.

[0079] As described above, as shown in FIG. 7, in the form of first determining whether or not the power saving mode is set, when it is determined that the power saving mode is not set (S11: NO), scanning in the normal mode is performed.

[0080] FIG. 8 is a diagram showing pulse waveforms used in scanning in the normal mode and the power saving mode in the second modification of the embodiment.

[0081] In the normal mode, as shown in FIG. 4, for sensors 111, 112, and 113, as an example, scanning is performed at intervals of 5 ms, and the pulse voltage applied every 5 ms includes, as an example, 8 pulses as shown in the enlarged view on the right side. The capacitance calculated by the arithmetic unit 125 in one scan is the average value of the 8 capacitances obtained when each of the 8 enlarged pulses is applied.

[0082] On the other hand, in the power saving mode, for sensors 111, 112, and 113, as an example, scanning is performed at intervals of 20 ms, but the pulse voltage applied every 20 ms includes, as an example, 4 pulses as shown in the enlarged view on the right side. The capacitance calculated by the arithmetic unit 125 in one scan is the average value of the 4 capacitances obtained when each of the 4 enlarged pulses is applied. That is, the number of measurements in one scan is 4 times.

[0083] In this way, by reducing the number of measurements in one scan, further power consumption can be reduced in the power saving mode.

[0084] FIG. 9 is a flowchart showing the processing executed by the control unit 126 in the second modification of the embodiment. The flowchart shown in FIG. 9 is a modification of the processing in steps S3 and S14 in the flowchart shown in FIG. 7. Therefore, only the differences from FIG. 7 will be described.

[0085] When the control unit 126 determines that the transition condition to the power saving mode is satisfied (S13: YES), it transitions to the power saving mode (step S14A). In step S14A, as shown in the enlarged view of the power saving mode in FIG. 8, the number of measurements in one scan is reduced to 4 times.

[0086] Also, when the control unit 126 determines in step S2 that it is equal to or greater than the predetermined value Cwake (S2: YES), it transitions to the normal mode (step S3A). In step S3A, the number of measurements in one scan is changed to 8 times in the normal mode.

[0087] As described above, in the power saving mode, the number of measurements in one scan may be reduced compared to the normal mode. Although the form of reducing it to four times has been described here, any number may be used as long as it is less than the number of measurements in the normal mode.

[0088] FIG. 10 is a diagram showing pulse waveforms used in scans in the normal mode and the power saving mode in the third modification of the embodiment.

[0089] In the power saving mode, since the capacitance is measured while the user is approaching the door handle 10, it may be affected by external disturbance noise or the like. In such a case, the frequency at which pulses for performing a plurality of measurements in one scan are output may be changed to a frequency less affected by noise. Here, so-called frequency hopping is used to change the frequency.

[0090] To select a frequency less affected by noise, it is necessary to detect a frequency less affected by noise. The amount of noise can be estimated by continuously measuring capacitance values of the same frequency in a very short period and looking at the difference in those values. In the third modification, as shown in the enlarged view of FIG. 10, in the normal mode, after outputting the measurement pulses shown by the solid line eight times, the frequency is changed to output the pulses shown by the broken line six times in order to detect a frequency less affected by noise. Here, measuring the capacitance with the pulses shown by the broken line is referred to as noise scan.

[0091] When such a noise scan is performed, the smaller the capacitance calculated by the arithmetic unit 125, the less affected by noise the frequency is. The six pulses shown by the broken line consist of three types of frequencies, and pulses of the same frequency are output continuously twice.

[0092] Measurements may be performed with the six pulses for noise scan, and the frequency of the pulse with the lowest capacitance may be set as the frequency of the eight pulses for measurement in the next scan.

[0093] When using such frequency hopping, in the power-saving mode, after outputting the measurement pulses indicated by the solid line 8 times, the frequency is changed and the noise scan pulses indicated by the broken line are output 4 times. That is, the number of pulses indicated by the broken line for noise scan is 2 less than that in the normal mode.

[0094] As described above, in the power-saving mode, by reducing the number of pulses for noise scan, the power consumption can be reduced. Note that since the number of types of frequencies and the number of pulses described in FIG. 10 are examples, they can be changed as appropriate.

[0095] FIG. 11 is a flowchart showing the processing executed by the control unit 126 in the third modification of the embodiment. The flowchart shown in FIG. 11 adds step S21 to the flowchart shown in FIG. 9 and changes the processing of steps S3 and S14. Therefore, only the differences from FIG. 9 will be described.

[0096] When the process starts, the control unit 126 sets the frequency of the measurement pulses from the result of the noise scan (step S21). When performing the process of step S21 for the first time, since there is no result of the noise scan, the frequency of the noise scan pulses may be set to a predetermined initial value. After finishing the process of step S21, the control unit 126 advances the flow to step S11.

[0097] Also, in step S14B, when transitioning to the power-saving mode, the control unit 126 reduces the number of noise scan pulses to 4 (step S14B).

[0098] Also, in step S3B, when transitioning to the normal mode, the control unit 126 increases the number of noise scan pulses to 6 (step S3B).

[0099] As described above, when performing noise scan using frequency hopping, in the power-saving mode, the power consumption may be reduced by reducing the number of noise scan pulses.

[0100] FIG. 12 is a diagram showing the outputs of sensors 111, 112, and 113 in the fourth modification of the embodiment. In the fourth modification, as shown in FIG. 5(B), when the increases in capacitance ΔC1, ΔC2, and ΔC3 over three or more times increase by a predetermined value Ca or more with the passage of time, instead of transitioning to the normal mode, a determination is made as to whether to transition using the integrated value of the differences in the increases.

[0101] As shown in FIG. 12, when the sensors 111, 112, and 113 perform four scans, it is assumed that the increases in capacitance obtained by the sensors 111, 112, and 113 in the first scan are ΔC11, ΔC12, and ΔC13. Similarly, it is assumed that the increases in capacitance obtained by the sensors 111, 112, and 113 in the second scan are ΔC21, ΔC22, and ΔC23, and the increases in capacitance obtained by the sensors 111, 112, and 113 in the third scan are ΔC31, ΔC32, and ΔC33. Also, it is assumed that the increases in capacitance obtained by the sensors 111, 112, and 113 in the fourth scan are ΔC41, ΔC42, and ΔC43.

[0102] In this case, if the integrated value of the differences between the increases in capacitance obtained with the passage of time within a predetermined period (period TP1) and the increases in capacitance in the previous scan is equal to or greater than a predetermined value Cb for a predetermined number of times or more, the transition to the normal mode is made. In the example shown in FIG. 5(B), the period TP1 starts from the scan where the increase in capacitance exceeds Ca, whereas in the fourth modification of the present embodiment, as an example, the case where the scan where the increase in capacitance exceeds a predetermined value is taken as the starting point (in FIG. 12, it is assumed that the increase exceeds the predetermined value in the first scan) is shown. This is not limited to this, and the starting point of the period TP1 may be the integrated value of the differences in the increases, or the time when the capacitance exceeds a predetermined value. Also, as the starting point of the period TP1, in addition to the case where the increase in capacitance or the integrated value of the differences in the increases exceeds a predetermined value as described above, it may be set at a predetermined time interval.

[0103] Note that the integrated value referred to in the present invention may be the integrated value of a target numerical value (the difference in the increase in capacitance in the fourth modification of the above-described embodiment) during a preset scan period or the number of scans. Also, the scan period and the number of scans for integration are set to appropriate periods or numbers according to the detection level of capacitance, scan conditions, etc. For example, the scan period for obtaining the integrated value may be the same as the above-described predetermined period (period TP1), or may be shorter than that. Also, an integrated value that starts integration from a period before the above-described predetermined period (period TP1) may be set. Note that the integrated value is cleared when the scan period and the number of scans for integration are completed.

[0104] When the electrostatic sensor 110 has three sensors 111, 112, and 113, the difference from the increase in capacitance in the previous scan may be obtained by taking the difference between the average value of the increase in capacitance in the previous scan and the average value of the increase in capacitance in the current scan.

[0105] And the integrated value is obtained as follows. For example, when performing four scans, a difference Cα1 is obtained by subtracting the average value of the increases ΔC11, ΔC12, ΔC13 obtained in the first scan from the average value of the increases ΔC21, ΔC22, ΔC23 obtained in the second scan.

[0106] Similarly, a difference Cα2 is obtained by subtracting the average value of the increases ΔC21, ΔC22, ΔC23 obtained in the second scan from the average value of the increases ΔC31, ΔC32, ΔC33 obtained in the third scan.

[0107] Similarly, a difference Cα3 is obtained by subtracting the average value of the increases ΔC31, ΔC32, ΔC33 obtained in the third scan from the average value of the increases ΔC41, ΔC42, ΔC43 obtained in the fourth scan.

[0108] Then, the total integrated value of the differences Cα1, Cα2, and Cα3 is obtained. If this integrated value is equal to or greater than a predetermined value Cb (an example of the second predetermined value), a transition to the normal mode is made. The predetermined value here is a value indicating that the user has approached the door handle 10.

[0109] Note that instead of the average value of the increase amounts obtained in each scan, the maximum value or the total value of the increase amounts of the three sensors obtained in each scan may be used. The representative value of the capacitance of each scan and the calculation method of the increase amount are appropriately determined according to the system.

[0110] FIG. 13 is a flowchart showing the processing executed by the control unit 126 in the fourth modification of the embodiment. The flowchart shown in FIG. 13 is a modification of the processing of steps S5 and S8 in the flowchart shown in FIG. 9. Therefore, only the differences from FIG. 9 will be described.

[0111] In step S5A, the control unit 126 determines whether the integrated value of the difference between the average value of the capacitance increase amount obtained in the previous scan and the average value of the capacitance increase amount obtained in the current scan is equal to or greater than the predetermined value Cb (step S5A).

[0112] In step S8A, if the control unit 126 determines in step S5A that the integrated value is not equal to or greater than the predetermined value Cb (S5A: NO), it determines whether the continuous time is equal to or greater than the period TP1 (step S8A).

[0113] In the flowchart shown in FIG. 13, by repeating the scan in step S1, when the integrated value of the difference becomes equal to or greater than the predetermined value Cb three or more times within the period TP1, it is determined as YES in step S7, and a transition to the normal mode is made in step S3, and the electrostatic sensor 110 is activated. Note that the number of times of determining YES in STEP7 can be set as appropriate. For example, the electrostatic sensor 110 may be activated as long as the integrated value exceeds the predetermined value Cb once.

[0114] Also, here, a form in which the integrated value of the difference between the increase in capacitance in the previous scan and the increase in capacitance is used has been described. However, the same process may be performed using the increase in capacitance instead of the difference. For example, when the integrated value of the increases in capacitance ΔC1, ΔC2, and ΔC3 becomes equal to or greater than a predetermined value Cb for a predetermined number of times, a transition to the normal mode is made. At this time, the predetermined value Cb of the integrated value may be set to increase step by step.

[0115] At this time, only the increases in capacitance ΔC1, ΔC2, and ΔC3 when the increase in capacitance is equal to or greater than a predetermined value Ca may be used, and when the integrated value thereof becomes equal to or greater than a predetermined value Cb, a transition to the normal mode may be made.

[0116] Also, when the increase in capacitance ΔC1 is equal to or greater than a predetermined value Ca and ΔC1 < ΔC2 < ΔC3 holds, the integrated value of ΔC1, ΔC2, and ΔC3 may be calculated and used for determination.

[0117] Also, in this case, when Ca < ΔC1, Cb < ΔC2, Cc < ΔC3, and Ca < Cb < Cc hold, the integrated value of ΔC1, ΔC2, and ΔC3 may be calculated and used for determination.

[0118] As described above, the capacitive input device according to the exemplary embodiments of the present invention has been described. However, the present invention may be a combination of the specifically disclosed embodiments.

[0119] Also, the present invention is not limited to the specifically disclosed embodiments, and various modifications and changes can be made without departing from the scope of the claims.

[0120] This international application claims priority based on Japanese Patent Application No. 2022-000281 filed on January 4, 2022, and the entire content thereof is incorporated herein by reference.

Explanation of Reference Numerals

[0121] 10 Door handle 100 Capacitive input device 110, 110M electrostatic sensors 111, 112, 113, 111M, 112M sensors 120 integrated circuit 126 control unit

Claims

1. A capacitance detection unit that is disposed in an operation unit operated by a living body and repeatedly detects capacitance; When the capacitance detection unit is in a standby state and no contact of the living body is detected, when an increase amount of capacitance equal to or greater than a first predetermined value is detected a plurality of times within a predetermined period by the capacitance detection unit, a control unit that activates the capacitance detection unit comprising; The increase amount of the capacitance is a difference between the capacitance detected last time and the capacitance detected this time among the capacitances repeatedly detected by the capacitance detection unit, and is a value obtained by subtracting the capacitance detected last time from the capacitance detected this time, an electrostatic input device.

2. The control unit has a counter that increments a value when the increase amount of the capacitance is equal to or greater than the first predetermined value, and when the count value of the counter reaches a predetermined count value corresponding to the plurality of times within the predetermined period, activates the capacitance detection unit, the electrostatic input device according to Claim 1.

3. The control unit activates the capacitance detection unit when the increase amount of the capacitance that becomes equal to or greater than the first predetermined value increases with the passage of time, the electrostatic input device according to Claim 1.

4. The control unit gradually increases the first predetermined value within the predetermined period, the electrostatic input device according to Claim 1.

5. A capacitance detection unit that is disposed in an operation unit operated by a living body and repeatedly detects capacitance; When the capacitance detection unit is in a standby state and no contact of the living body is detected, for the difference in the increase amount of capacitance continuously detected by the capacitance detection unit, when the difference equal to or greater than a first predetermined value is detected a plurality of times within a predetermined period, a control unit that activates the capacitance detection unit comprising; The increase amount of the capacitance is a difference between the capacitance detected last time and the capacitance detected this time among the capacitances repeatedly detected by the capacitance detection unit, and is a value obtained by subtracting the capacitance detected last time from the capacitance detected this time, The difference in the increase amount of the capacitance is a value obtained by subtracting the increase amount of the capacitance obtained last time from the increase amount of the capacitance obtained this time, an electrostatic input device.

6. The control unit has a counter that increments a value when the difference is greater than or equal to the first predetermined value, and activates the capacitance detection unit when the count value of the counter reaches a predetermined count value corresponding to the plurality of times within the predetermined period. The electrostatic input device according to claim 5.

7. The control unit activates the capacitance detection unit when the difference is greater than or equal to the first predetermined value and the difference that becomes greater than or equal to the first predetermined value increases with the passage of time. The electrostatic input device according to claim 5.

8. The control unit gradually increases the first predetermined value within the predetermined period. The electrostatic input device according to claim 5.

9. The electrostatic input device according to any one of claims 1 to 7, further including the operation unit.

10. The control unit sets the capacitance detection unit to the standby state when there is no contact of the living body with the operation unit, and sets the capacitance detection unit to the activated state when there is contact of the living body with the operation unit. The electrostatic input device according to any one of claims 1 to 7.

11. The capacitance detection unit has a plurality of sensors, The control unit uses, as the capacitance, the maximum value, average value, or total value of the plurality of capacitances detected by the plurality of sensors over the plurality of times within the predetermined period, and activates the capacitance detection unit. The electrostatic input device according to any one of claims 1 to 7.

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