JP5605205B2 - Capacitance detection device and contact detection sensor - Google Patents

Description

  The present invention uses a capacitance detection device and a capacitance detection device that determine the approach of a detection object by detecting a change in the capacitance value of a capacitance formed through free space. The present invention relates to a contact detection sensor.

  A smart key system has been put to practical use that receives a radio signal from a portable device owned by a driver on the vehicle side and automatically unlocks and locks the door of the vehicle. In recent smart key systems, in addition to ID authentication of wireless signals from portable devices, the driver's intention is confirmed by detecting the driver's contact with the door handle, and more accurate unlocking and locking operations are performed. To do. As a method of detecting a driver's contact, it is common to detect a change in the capacitance value of the capacitance formed by an electrode built in the door handle. In this type of capacitance-type contact detection sensor, a technique for reliably discriminating the influence of rainwater or the like that changes the capacitance value from the driver's contact is important, and Patent Examples 1 to 3 disclose technical examples. ing.

  The capacitance-type contact detection device of Patent Document 1 includes a capacitance sensor configured by a sensor electrode provided on a door handle, and a detection unit that detects a user's contact based on a change in capacitance. The capacitance sensor is characterized in that the contact detection sensitivity in a portion near the door panel is lower than that in a portion far from the door panel. Furthermore, in order to realize the characteristics of the contact detection sensitivity, there are disclosed an aspect in which a notch is formed in the sensor electrode, an aspect in which a portion having a different dielectric constant is provided, and an aspect in which a plurality of capacitance sensors are provided. Thereby, it is supposed that it is possible to prevent erroneous detection that the user has contacted when rainwater has accumulated at the boundary between the upper surface of the door handle and the door panel.

  The capacitance type door touch sensor of Patent Document 2 is a conversion circuit that installs two or more sensor electrodes in or near the door handle and converts the capacitance change of each sensor electrode into a voltage or frequency parameter. And a determination circuit for detecting a parameter, wherein a detection output is generated by an output from two or more sensor electrodes. That is, the presence or absence of contact is determined by the logical product of outputs from two or more sensor electrodes. As a result, a detection output is not generated in a contact where the willingness of touching just passing is not recognized, and there is no inconvenience that the door is unlocked at an unexpected time due to a malfunction.

  In addition, the capacitive touch sensor of Patent Document 3 includes first and second electrodes, an oscillation unit, and a detection unit. The first and second electrodes form a capacitance with the ground based on a touch operation, and parasitic capacitance is generated between the electrodes due to adhesion of water droplets. In addition, the output voltage of the detection unit decreases in the touch operation, and the output voltage of the detection unit increases in the case of water droplet adhesion. Therefore, the presence or absence of the touch operation can be determined with high accuracy.

JP 2009-133777 A JP 2006-344554 A JP 2009-218876 A

  By the way, in patent document 1, although the effect will be produced if the amount of rainwater is small and adheres as water droplets, the risk of erroneous detection when the amount of water increases is not eliminated. For example, when the amount of precipitation is high outdoors or when a water injection car is being washed, a large amount of water falls on the door handle and the entire top surface of the door handle is covered with water. The increase in capacitance at this time is similar to that when a human hand touches the upper surface of the door handle, so the possibility of erroneous detection is not eliminated.

  Also, in Patent Document 2, the logical product of outputs from two or more sensor electrodes is used to prevent malfunction due to accidental contact by a passing person, but the effect of preventing malfunction due to rainwater cannot be expected. . This is because rainwater exerts an influence on all of two or more sensor electrodes even if there is a difference in degree, and increases capacitance, so that it is difficult to discriminate it as a driver's contact. On the other hand, the driver cannot detect that all the sensor electrodes are not in contact with each other at the same time, and the usability is inferior as compared with the method using only one sensor electrode.

  Further, in Patent Document 3, as in Patent Document 1, when the amount of water applied to the door handle increases, not only the parasitic capacitance between the electrodes but also the capacitance with the ground increases. Therefore, the equivalent circuit and circuit constants when the water exposure increases are similar when a person touches, and the output voltage of the detection unit is considered to change in a similar manner, making it difficult to discriminate by increasing or decreasing the output voltage. The risk of misdetecting the effects of rainwater as human contact is not resolved.

  The present invention has been made in view of the above problems of the background art, and even when the amount of water on the door handle is large, the increase in the capacitance value is detected and the approach of the human hand is approached without being affected by this. It is an object to be solved to provide a capacitance detection device and a contact detection sensor that can be reliably determined. Considering further generalization, an event other than a person's hand that is a detection object touching or approaching the door handle can be regarded as a noise event. Therefore, it is possible to provide a capacitance detection device that can detect the increase in the capacitance value and reliably determine the approach of the detection target without being affected by noise events other than the approach of the detection target. It should be a challenge.

  According to a first aspect of the present invention, there is provided a first electrostatic capacity detecting device formed through a free space between a first electrode built in a non-conductive member and a conductive substrate. A capacitance, a second capacitance formed through a free space between the second electrode built in the non-conductive member and the conductive substrate, and a capacitance value of the first capacitance , And a detection unit that measures a capacitance value of the second capacitance at a predetermined time interval, a first change capacitance that is a time change amount of the capacitance value of the first capacitance, and the first A calculation unit that calculates a second change capacity that is a time change amount of a capacitance value of two capacitances, and when the first change capacity is equal to or greater than a first threshold and the second change capacity is less than a second threshold. A first determination process for determining that an object to be detected has approached the first electrode; and the second change capacity is equal to or greater than a fourth threshold value. A determination unit that performs at least one determination process of a second determination process that determines that the detection object has approached the second electrode when the first change capacity is less than a third threshold. Features.

  The invention according to claim 2 is characterized in that, in claim 1, the determination unit performs both the first determination process and the second determination process.

  According to a third aspect of the present invention, in the first aspect, the determination unit determines that the detection object has approached the first electrode when the first change capacitance is equal to or greater than the first threshold. 4th determination process and 1st determination which perform a process and the said 2nd determination process, or determine that the said detection target approached to the said 2nd electrode when the said 2nd change capacity is more than the said 4th threshold value It is characterized by performing processing.

The invention according to a fourth aspect relates to the time constant when the first capacitance and the second capacitance are charged or discharged in the first electrostatic capacitance according to any one of the first to third aspects. A switched-capacitor-type detection unit that measures an index, wherein one of the first capacitance and the second capacitance is charged and the other discharge is performed in synchronization.
The invention according to claim 5 relates to the time constant according to any one of claims 1 to 4, wherein the detection unit is a time constant when the first capacitance and the second capacitance are charged or discharged. A switched-capacitor-type detection unit that measures an index, and has a plurality of charge / discharge repetition frequencies, and measures each capacitance value of the first and second capacitances at each repetition frequency; The calculation unit calculates the first and second change capacities at each repetition frequency, and the determination unit performs the first and second changes in at least one determination process of the first to fourth determination processes. The approach of the detection object is determined with reference to the frequency dependence of the capacity with respect to each repetition frequency.

  The invention according to claim 6 is the electronic device according to any one of claims 1 to 5, wherein the conductive base is a door panel, the non-conductive member is a door handle, and the detection target is a human hand. It is characterized by being.

  According to a seventh aspect of the present invention, in the sixth aspect, the door panel constitutes a door of a vehicle, the first electrode is built in the back side of the door handle near the door panel, and the second electrode is the door handle. It is built in the surface side away from the said door panel, and is displaced to the longitudinal direction of the said door handle with respect to the said 1st electrode.

  The invention according to claim 8 is the invention according to claim 7, wherein the vehicle includes a smart key system that includes a vehicle-side wireless device and a portable device-side wireless device, and automatically locks and unlocks the door, At least one of the first electrode and the second electrode also serves as a radio communication antenna of the vehicle-side radio apparatus.

  The invention of a contact detection sensor according to claim 9 is to detect contact of a human hand to the non-conductive member using the capacitance detection device according to any one of claims 1 to 8. Features.

  In the capacitance detecting device according to the first aspect, the first and second capacitances are provided between the first and second electrodes built in the non-conductive member and the conductive base via a free space. Each capacitance value is detected, and first and second change capacitances corresponding to the time change are calculated. Then, the determination unit applies to the first or second electrode of the detection object on the condition that when one of the first and second change capacities increases to a predetermined threshold value or more, the increase in the other is not remarkable. Determine approach. Therefore, when a noise event occurs in free space and affects both the first and second capacitances, such as rain due to rain, both the first and second change capacities increase, and thus detection is performed. There is no misjudgment that the object is approaching. On the other hand, when the detection object selectively approaches one of the first and second electrodes, only one of the change capacities increases, so that the approach of the detection object can be reliably determined. That is, it is possible to reliably determine the approach of the detection object by detecting an increase in the capacitance value without being affected by a noise event other than the approach of the detection object.

  In the invention according to claim 2, the determination unit performs both the first determination process and the second determination process, and when one of the first and second change capacities increases to a predetermined threshold value or more, the other increase The approach of the detection target is determined on the condition that it is not noticeable. Therefore, it is possible to reliably determine whether the detection target object approaches either the first electrode or the second electrode without being affected by the noise event.

  In the invention according to claim 3, the determination unit requires that when one of the first and second change capacities increases beyond a predetermined threshold, the increase in the other is not significant, but the other is a predetermined threshold. When it increases above, it does not refer to one increase. When the degree of influence from the noise event differs between the first and second capacitances, the approach of the detection target may be determined using only the other change capacitance for the other capacitance that is not easily affected. . Thereby, the determination process is simplified.

  In the invention which concerns on Claim 4, a detection part is a switched capacitor type | mold detection part which measures the parameter | index regarding the time constant when a 1st electrostatic capacitance and a 2nd electrostatic capacitance charge or discharge an electric charge, and One charge and the other discharge of the first capacitance and the second capacitance are performed in synchronization. In general, when a charge is charged or discharged, the voltage of the capacitive element fluctuates rapidly, and line noise and electromagnetic wave noise may occur. In this aspect, by performing one charge and the other discharge in synchronization, the generated noises have different polarities and cancel each other, so that the influence of noise on the other can be reduced.

  In the invention which concerns on Claim 5, the 1st and 2nd change capacity | capacitance in a some repetition frequency is each calculated, The frequency dependence of the 1st and 2nd change capacity | capacitance by at least 1 determination process of the 1st-4th determination process The approach of the detection object is determined with reference to the sex. That is, in addition to the detection of the increase in the change capacity, the determination is performed by using also the frequency dependency effective for the determination from the noise event. As a result, the fact that the detection object has approached both the first and second electrodes can be determined as a noise event, and the determination accuracy is further improved.

  In the invention according to claim 6, the conductive substrate is a door panel, the non-conductive member is a door handle, and the detection target is a human hand. INDUSTRIAL APPLICABILITY The present invention can be incorporated in doors such as entrances and exits of buildings and is effective for detecting approach when a person enters and exits and detecting contact with a door handle.

  In the invention according to claim 7, the door panel constitutes a door of the vehicle, the first electrode is built in the back side of the door handle near the door panel, and the second electrode is built in the surface side of the door handle away from the door panel. Further, the first electrode is displaced in the longitudinal direction of the door handle. INDUSTRIAL APPLICABILITY The present invention can be incorporated into a vehicle door, and is effective in that contact with a human hand's door handle can be discriminated as being wet by rain. Further, when the positions where the first and second electrodes are built in the door handle as described above are determined, the human hand is prevented from approaching the first and second electrodes at the same time. The approach to one electrode can be determined, and the approach to the second electrode of a human hand can be determined when getting off. Therefore, the present invention is suitable for a smart key system that needs to discriminate between getting on and getting off.

  In the invention according to claim 8, the vehicle includes a smart key system having a vehicle-side wireless device and a portable device-side wireless device, and at least one of the first electrode and the second electrode has a wireless communication antenna of the vehicle-side wireless device. Also serves as. Thereby, since the number of members is reduced and the structure is simplified, it is possible to contribute to the cost reduction of the vehicle.

  In the invention which concerns on Claim 9, a capacitance detection apparatus can be used and the contact detection sensor which detects the contact of a human hand to a nonelectroconductive member can be comprised. The present invention can be implemented as a contact detection sensor, and the effect is the same as in claims 1-8.

It is a perspective view explaining the state which mounted the electrostatic capacitance detection apparatus of 1st Embodiment in the door of the vehicle. It is a figure explaining arrangement | positioning of the sensor electrode for unlocking, and is AA sectional drawing in FIG. It is a figure explaining arrangement | positioning of the sensor electrode for a lock | rock, a detection part, and an electronic control part, and is BB sectional drawing in FIG. It is a figure explaining the functional structure of the electrostatic capacitance detection apparatus of 1st Embodiment. It is a figure explaining the structural example of a switched capacitor system detection part. It is a figure explaining the timing which detects each electrostatic capacitance value of the 1st and 2nd electrostatic capacitance in a detection part, (1) shows synchronous detection and (2) has shown asynchronous detection. It is a figure explaining the determination processing flow which an electronic control part performs with the electrostatic capacitance detection apparatus of 1st Embodiment. It is a figure explaining the determination processing flow which an electronic control part performs with the electrostatic capacitance detection apparatus of 2nd Embodiment. It is a figure explaining the timing which detects each electrostatic capacitance value of the 1st and 2nd electrostatic capacitance in a detection part in 3rd and 4th embodiment, (1) is synchronous detection, (2) is asynchronous detection. Show. It is a figure explaining the determination processing flow which an electronic control part performs with the electrostatic capacitance detection apparatus of 3rd Embodiment. It is a figure explaining the determination processing flow which an electronic control part performs with the electrostatic capacitance detection apparatus of 4th Embodiment.

  A capacitance detection apparatus according to a first embodiment of the present invention will be described with reference to FIGS. The capacitance detection device according to the first embodiment is used as a contact detection sensor that is incorporated in a vehicle door and detects contact of a human hand with a door handle, and is a part of a smart key system. FIG. 1 is a perspective view illustrating a state where the capacitance detection device 1 of the first embodiment is mounted on a door 2 of a vehicle. In the figure, the upper right side is the front side of the vehicle and the lower left side is the rear side of the vehicle, and the door panel 21 and the door handle 25 constituting the door 2 are shown.

  The door 2 is pivotally supported by the vehicle body so as to be opened and closed, and can be locked and unlocked by a smart key system. The door panel 21 is a member formed by press molding of a metal plate and corresponds to the conductive substrate of the present invention. The door handle 25 is provided on the outside of the door panel 21, extends in the front-rear direction of the vehicle, and is attached to the door panel 21 at two front and rear positions. The door handle 25 is formed in a hollow shape having an internal space 26 by resin molding, and corresponds to the non-conductive member of the present invention in which the first and second electrodes are built. A recess 22 is formed inside the door handle 25 of the door panel 21 so that a human hand can easily grasp the vicinity of the center of the door handle 25.

  The door handle 25 includes an unlocking sensor electrode 3, a locking sensor electrode 4, a detection unit 5, and an electronic control unit 6. FIG. 2 is a view for explaining the arrangement of the unlocking sensor electrode 3, and is a cross-sectional view taken along the line AA in FIG. The unlocking sensor electrode 3 corresponds to a first electrode, and is a metal strip-shaped plate material as shown in FIGS. 1 and 2. The unlocking sensor electrode 3 is built in the back surface 27 close to the door panel 21 in the internal space 26 of the door handle 25, and extends in the front-rear direction near the center of the internal space 26 in the front-rear direction. The unlocking sensor electrode 3 constitutes a contact detection sensor that detects the unlocking timing by the smart key system, that is, an unlocking sensor. When a person enters the dent 22 and grips the door handle 25 (that is, touches) when getting on, the sensor electrode 3 for unlocking approaches and does not touch directly.

  FIG. 3 is a view for explaining the arrangement of the locking sensor electrode 4, the detection unit 5, and the electronic control unit 6, and is a cross-sectional view taken along the line BB in FIG. The locking sensor electrode 4 corresponds to a second electrode, and is a metal strip plate material smaller than the unlocking sensor electrode 3 as shown in FIGS. The locking sensor electrode 4 is built in the surface side 28 away from the door panel 21 in the internal space 26 of the door handle 25, is displaced forward with respect to the unlocking sensor electrode 3, and extends forward and backward. ing. The locking sensor electrode 4 constitutes a contact detection sensor that detects the timing of locking by the smart key system, that is, a locking sensor. Even if a human hand enters the depression 22 and grips the door handle 25, it does not approach the locking sensor electrode 4. Instead, when the finger of the hand is brought into contact with the vicinity of the front portion of the door handle 25 when getting off, the sensor electrode 4 for locking is approached.

  The detection unit 5 is a switched capacitor type detection unit 5 described later, and is formed of an electronic circuit board. As shown in FIGS. 1 and 3, the detection unit 5 is disposed on the back side 29 close to the locking sensor electrode 4 in the internal space 26 of the door handle 25. The electronic control unit 6 is disposed on the back side 29 close to the locking sensor electrode 4 in the internal space 26 of the door handle 25 in the same manner as the detection unit 5 (for convenience, the detection unit 5 and the electronic control unit 6 are connected). (Displayed in gray in the figure).

  FIG. 4 is a diagram illustrating a functional configuration of the capacitance detection device 1 according to the first embodiment. As shown in the figure, the unlocking sensor electrode 3 and the door panel 21 are connected to the detection unit 5, and a first capacitance 31 is formed between the both 3 and 21 via a free space. Similarly, the unlocking sensor electrode 4 is also connected to the detection unit 5, and a second capacitance 41 is formed between the door panel 21 and the door panel 21 through a free space.

  The electronic control unit 6 includes a CPU (not shown), operates with software, and doubles as a calculation unit and a determination unit of the present invention. The electronic control unit 6 controls the detection operation of the detection unit 5 through the control line, and the capacitance values of the first and second capacitances 31 and 41 detected by the detection unit 5 through the signal line. Signals related to C1 and C2 are acquired. Further, the electronic control unit 6 obtains the respective capacitance values C1 and C2 from the acquired signals, stores them as time series data, and performs a sequential update process so as to leave a predetermined number of latest data. The functions of the electronic control unit 6 as the calculation unit and determination unit after obtaining the capacitance values C1 and C2 will be described in detail later in the determination processing flow.

  FIG. 5 is a diagram illustrating a configuration example of the switched capacitor type detection unit 5. The detection unit 5 has the same detection circuit configuration with respect to the first and second capacitances 31 and 41, and the first capacitance 31 will be described as a representative. As shown in the figure, a known reference capacitor Cs1 and a first switch S1 are connected in parallel between a first terminal T1 and a second terminal T2 on one side V1 of the power supply line, and the second terminal T2 and the second terminal T2 are connected in parallel. A second switch S2 is connected between the three terminals T3. Further, the first capacitance 31 (capacitance value C1) and the third switch S3 are connected in parallel between the third terminal T3 and the fourth terminal T4 on the other side V2 of the power supply line. Further, the comparator Cmp is provided, the second terminal T2 is connected to the negative input terminal −, and the reference voltage Vref1 is input to the positive input terminal +. Then, the electronic control unit 6 is configured to control the opening and closing of the first to third switches S <b> 1 to S <b> 3 and take in the signal of the output terminal Vout of the comparator Cmp to the electronic control unit 6.

  In the detection unit 5 described above, first, the first switch S1 and the second switch S2 are closed, the third switch S3 is opened, and the first capacitance 31 is charged with the power supply voltage. Next, the first switch is opened, and the second switch S2 and the third switch S3 are repeatedly opened and closed alternately at a short time pitch, whereby the charge of the first capacitance 31 is charged and discharged. Then, the voltage at the second terminal T2 gradually decreases while moving up and down, and the signal at the output terminal Vout is turned on when the voltage becomes lower than the reference voltage Vref1. With this configuration, the speed at which the voltage at the second terminal T2 decreases depends on the charge / discharge time constant, and the time constant depends on the capacitance value C1 of the first capacitance 31. Therefore, the number of times the second and third switches S2 and S3 are opened and closed until the output terminal Vout is turned on is an index relating to the time constant, and the electronic control unit 6 counts this to detect the capacitance value C1. it can.

  The detection circuit configuration of the detection unit 5 with respect to the second capacitance 41 is such that the first to third switches are replaced with the fourth to sixth switches, respectively, and the capacitance value C2 of the second capacitance 41 is matched. The difference is that the reference capacitor Cs2 and the reference voltage Vref2 are set, and the other configuration is the same as the detection circuit configuration for the first capacitance 31.

  Here, the electronic control unit 6 performs the charging of one of the first capacitance 31 and the second capacitance 41 and the discharging of the other in synchronization. That is, the first capacitance 31 is charged by the closing operation of the second switch S2 in the open state of the third switch S3, and the second capacitance 41 is set by the closing operation of the sixth switch S6 in the open state of the fifth switch S5. This is performed in synchronization with the discharge. Further, the first capacitance 31 is discharged by the closing operation of the third switch in the opened state of the second switch S2, and the second capacitance 41 is charged by the closing operation of the fifth switch in the opened state of the sixth switch S6. Synchronize with. As a result, noise generated in the first capacitance 31 and the second capacitance 41 has different polarities and cancels each other, so that the influence of noise on other on-vehicle devices can be reduced.

  FIGS. 6A and 6B are diagrams illustrating timings for detecting the capacitance values C1 and C2 of the first and second capacitances 31 and 41 in the detection unit 5. FIG. 6 illustrates synchronization detection and FIG. Indicates asynchronous detection. The horizontal axis in the figure is a common time axis, and the time zone in which the capacitance values C1 and C2 are detected is indicated by a gray rectangle. As described above, when the electronic control unit 6 controls opening and closing the first to third switches S1 to S3 and the fourth to sixth switches S4 to S6 in parallel, the same time as shown in (1). The capacitance values C1 and C2 of the first and second capacitances 31 and 41 are detected in the band. Further, in another method shown in (2), the first to third switches S1 to S3 are first controlled to detect the capacitance value C1 of the first capacitance 31, and then the fourth to sixth switches. The capacitance value C2 of the second capacitance 41 may be detected by controlling the opening and closing of S4 to S6. In any case, the electronic control unit 6 performs control so that the detection time intervals t1 of the capacitance values C1 and C2 are constant.

  Next, functions of the electronic control unit 6 as a calculation unit and a determination unit will be described with reference to a determination processing flow. FIG. 7 is a diagram illustrating a determination processing flow performed by the electronic control unit 6 in the capacitance detection device 1 of the first embodiment. In the figure, the unlocking sensor determination process and the locking sensor determination process are described on the right and left, but it does not mean that the determination process is performed in parallel by two CPUs, but one CPU. For convenience, the two determination processes are alternately performed and the calculation results are mutually used as indicated by the broken-line arrows.

  In step S11 of the unlocking sensor determination process in FIG. 7, the electronic control unit 6 first acquires the latest data C1new of the capacitance value C1 of the unlocking sensor electrode 3 and updates the time series data. Next, the first change capacity ΔC1 is calculated by subtracting a predetermined number of previous old data C1old from the latest data C1new (ΔC1 = C1new−C1old). The predetermined number can be appropriately determined with reference to the detection time interval t1 of the capacitance values C1 and C2 and the speed at which a human hand approaches and contacts the door handle 25. The function of step S11 corresponds to the function of the calculation unit of the present invention.

  In the next step S12, it is compared whether or not the first change capacity ΔC1 is greater than or equal to the first threshold value A1, and if the condition is not satisfied, the unlocking sensor determination process is terminated. That is, when the increase in the capacitance value C1 is not recognized, it is determined that the human hand is not in contact with the unlocking sensor electrode 3 of the door handle 25. When the condition of step S12 is satisfied, the process proceeds to step S13, and the latest value of the second change capacity ΔC2 of the locking sensor electrode 4 is used. Then, in step S14, it is compared whether or not the second change capacity ΔC2 is less than the second threshold value A2. If the condition is not satisfied, the unlocking sensor determination process is terminated. That is, when an increase in the capacitance value C1 is recognized and an increase in the capacitance value C2 is also recognized, it affects both the unlocking sensor electrode 3 and the locking sensor electrode 4, for example, water exposure due to rain, etc. It is determined that the noise event has occurred.

  When the condition of step S14 is satisfied, an increase in the capacitance value C1 is recognized and an increase in the capacitance value C2 is not recognized. At this time, since it can be determined that a human hand has come into contact with the unlocking sensor electrode 3 of the door handle 25, the process proceeds to step S15 to output an unlocking sensor signal. As a result, the smart key system unlocks the door 2. The determination process from step S12 to step S14 corresponds to the first determination process of the determination unit of the present invention.

  Steps S21 to S25 of the locking sensor determination process in FIG. 7 are substantially the same as steps S11 to S15 of the unlocking sensor determination process. That is, in step S21, the electronic control unit 6 first acquires the latest data C2new of the capacitance value C2 of the locking sensor electrode 4 and updates the time series data. Next, the second change capacity ΔC2 is calculated by subtracting the past old data C2old from the latest data C2new by the same number as the predetermined number in the unlocking sensor determination process (ΔC2 = C2new−C2old). The function of step S21 corresponds to the function of the calculation unit of the present invention.

  In the next step S22, it is compared whether or not the second change capacity ΔC2 is greater than or equal to the fourth threshold value A4. If the condition is not satisfied, the locking sensor determination process is terminated. That is, when an increase in the capacitance value C2 is not recognized, it is determined that a human hand is not in contact with the position of the door handle 25 close to the locking sensor electrode 4. When the condition of step S22 is satisfied, the process proceeds to step S23, and the latest value of the first change capacity Δ1 of the unlocking sensor electrode 3 is used. Then, in step S24, it is compared whether or not the first change capacity ΔC1 is less than the third threshold value A3. If the condition is not satisfied, the locking sensor determination process is terminated. That is, when an increase in the capacitance value C2 is recognized and an increase in the capacitance value C1 is also recognized, it is determined that a noise event has occurred.

  When the condition of step S24 is satisfied, an increase in the capacitance value C2 is recognized and an increase in the capacitance value C1 is not recognized. At this time, since it can be determined that a human hand has come in contact with the position of the door handle 25 close to the locking sensor electrode 4, the process proceeds to step S25, and a locking sensor signal is output. Thereby, the smart key system locks the door 2. The determination process from step S22 to step S24 corresponds to the second determination process of the determination unit of the present invention. In the first embodiment, the electronic control unit 6 performs both the first determination process and the second determination process.

  The appropriate values of the first to fourth threshold values A1 to A4 for determining the increase in the capacitance values C1 and C2 are the shapes and materials of the door panel 21 and the door handle 25, the unlocking sensor electrode 3, and the locking sensor. It varies depending on the size and arrangement of the electrode 4. Therefore, it is preferable to set the first to fourth threshold values A1 to A4 by a technique such as a simulation using a computer or a prototype experiment.

  In the first embodiment, the first and second change capacities are generated when a noise event occurs in free space and affects both the first and second capacitances 31 and 41, for example, water exposure due to rain. Since ΔC1 and ΔC2 both increase, it is not erroneously determined that the object to be detected, that is, the approach of a human hand is approaching. On the other hand, the positions of the unlocking sensor electrode 3 and the locking sensor electrode 4 are separated into the back side 27 and the front side 28 of the door handle 25 and are displaced in the vehicle front-rear direction. Selectively approach one (3 or 4). For this reason, only one change capacity (ΔC1 or ΔC2) is increased, and the electronic control unit 6 can reliably determine the approach of a human hand. Further, since the unlocking sensor electrode 3 and the locking sensor electrode 4 can distinguish between getting on and getting off, it is suitable for a smart key system.

  Next, a capacitance detection device according to a second embodiment in which the determination process of the unlocking sensor is simplified will be described with reference to FIG. The capacitance detection device of the second embodiment is the same as the device configuration of the first embodiment described with reference to FIGS. 1 to 6, and the determination processing flow of the electronic control unit 6 is replaced with FIGS. 7 to 8. FIG. 8 is a diagram illustrating a determination processing flow performed by the electronic control unit 6 in the capacitance detection device of the second embodiment. As is clear when FIG. 8 is compared with FIG. 7, Step S13 and Step S14 are omitted in the second embodiment. The determination process in step S12 of FIG. 8 corresponds to the third determination process of the determination unit of the present invention. That is, in the second embodiment, the electronic control unit 6 performs the third determination process and the second determination process.

  The reason for performing the determination based only on the first change capacity ΔC1 in the third determination process and using the first change capacity ΔC1 in addition to the second change capacity ΔC2 in the second determination process is that the influence from the flooded water This depends on the degree of difference between the unlocking sensor electrode 3 and the locking sensor electrode 4. That is, in the unlocking sensor electrode 3, if the surface of the door handle 25 on the back surface facing the door panel 21 is flooded, the first change capacity ΔC1 can be increased, but it is hardly generated actually. Therefore, when the first change capacity ΔC1 increases, there is little risk of error even if it is immediately determined that the human hand is approaching.

  On the other hand, in the sensor electrode 4 for locking, since the second change capacity ΔC2 can increase even if the upper surface of the door handle 25 is flooded as well as the surface facing the outside of the door handle 25, it occurs relatively frequently. It is thought to get. Therefore, there is a risk of erroneous determination that it is determined that the human hand is approaching only by increasing the second change capacity ΔC2, and the determination reliability can be improved by making it a necessary condition that the increase in the first change capacity ΔC1 is not recognized. . Further, as described above, in the second embodiment, the determination process can be simplified as compared with the first embodiment.

  When the degree of influence from a noise event such as flooding is opposite to the above, the direction in which the calculation result is diverted is reversed. That is, step S23 and step S24 are omitted from the determination processing flow shown in FIG. 7 of the first embodiment. In this application mode, the electronic control unit 6 determines the fourth determination process based on only the second change capacity ΔC2, and the first determination process that uses the second change capacity ΔC2 in addition to the first change capacity ΔC1 for determination. I do.

  Next, the capacitance detection devices of the third and fourth embodiments in which the switched capacitor type detection unit 5 has a plurality of charge / discharge repetition frequencies will be described with reference to FIGS. 9 to 11. The capacitance detection devices of the third and fourth embodiments are the same as the device configuration of the first embodiment described with reference to FIGS. 1 to 6, and the operation of the switched capacitor type detection unit 5 shown in FIG. Different. Further, the determination processing flow of the electronic control unit 6 is replaced with FIG. 10 in the third embodiment and FIG. 11 in the fourth embodiment. This will be described in detail below.

  In the third and fourth embodiments, when the detection unit 5 repeatedly opens and closes the second switch S2 and the third switch S3 with a short pitch with respect to the first capacitance 31, two types of repetition frequencies f1, Use f2. The repetition frequencies f1 and f2 can be realized by appropriately opening and closing the second and third switches S2 and S3 from the electronic control unit 6, and the capacitance values C11 (f1) and C12 (f2) are respectively obtained. It can be detected. Similarly, regarding the second capacitance 41, the fifth and sixth switches S5 and S6 are repeatedly controlled to open and close at the frequencies f1 and f2, thereby allowing two types of capacitance values C21 (f1) and C22 (f2). ) Can be detected. These four capacitance values can be detected at the detection timing shown in FIG. FIG. 9 is a diagram for explaining the timing for detecting the capacitance values C1 and C2 of the first and second capacitances 31 and 41 in the detection unit 5 in the third and fourth embodiments. Indicates synchronous detection, and (2) indicates asynchronous detection. Similar to the first embodiment, the two capacitance values C1 and C2 may be detected simultaneously in parallel, or may be detected while being shifted in time.

  In the third embodiment, the electronic control unit 6 performs the determination processing flow shown in FIG. 10 using the detected four capacitance values. The unlocking sensor determination process and the locking sensor determination process in the figure are performed alternately. In step S51 of the unlocking sensor determination process in FIG. 10, the electronic control unit 6 acquires the latest data of the capacitance value C11 at the repetition frequency f1 for the unlocking sensor electrode 3 and updates the time series data. To do. Next, a predetermined number of old data is subtracted from the latest data to calculate the first change capacity ΔC11 at the repetition frequency f1. Similarly, in step S52, the first change capacity ΔC12 at the repetition frequency f2 is calculated.

  Next, in step S53, it is compared whether or not the first change capacity ΔC11 is greater than or equal to the threshold value A11 and / or the first change capacity ΔC12 is greater than or equal to the threshold value A12. If the condition is not satisfied, the unlocking sensor determination process is terminated. To do. That is, when the increase in the capacitance value C11 or C12 is not recognized, it is determined that the human hand is not in contact with the unlocking sensor electrode 3 of the door handle 25. When the condition of step S53 is satisfied, the process proceeds to step S54, and it is compared whether the two first change capacitors ΔC11 and ΔC12 have the same frequency dependency. For example, it is compared whether or not each increase amount or each increase rate of the two first change capacities ΔC11 and ΔC12 is substantially the same. It has already been found that this frequency dependence does not coincide with water, but coincides with the approach of a human hand. Therefore, when the condition is not satisfied, the unlocking sensor determination process is terminated, and when the condition is satisfied, the process proceeds to step S55.

  In step S55, the latest values of the two second change capacities ΔC21 and ΔC22 of the locking sensor electrode 4 are used. In step S56, when the second change capacitance ΔC21 is less than the threshold value A21 and / or the second change capacitance ΔC22 is less than the threshold value A22, it can be determined that the human hand has come into contact with the position close to the unlocking sensor electrode 4. Therefore, it progresses to step S58. In step S56, if the second change capacitance ΔC21 is greater than or equal to the threshold A21 and / or the second change capacitance ΔC22 is greater than or equal to the threshold A22, for example, rain that affects both the unlocking sensor electrode 3 and the locking sensor electrode 4 It is determined that a noise event such as wetting has occurred or that a human hand has come into contact with the locking sensor electrode 4, and the process proceeds to step S57. In step S57, it is compared whether or not the two second change capacitors ΔC21 and ΔC22 have the same frequency dependency. When the condition is not satisfied, the unlocking sensor determination process is terminated, and when the condition is satisfied, that is, when it is determined that the human hand touches the locking sensor electrode 4, the process proceeds to step S58. In step S58, an unlocking sensor signal is output. The determination process from step S53 to step S57 corresponds to a first determination process using a determination based on frequency dependence.

  Further, steps S61 to S68 in the locking sensor determination process in FIG. 10 are substantially the same as the steps S51 to S58 of the unlocking sensor determination process described above, and thus description thereof is omitted. The determination process from step S63 to step S67 corresponds to a second determination process in which determination based on frequency dependency is used together.

  Of course, appropriate values are set for the thresholds A11 to A42. In the above-described third embodiment, the determination is performed by using the frequency dependency effective for the discrimination from the noise event in addition to the change capacity increasing at the two repetition frequencies f1 and f2. Therefore, it is possible to determine the approach to both the unlocking sensor electrode 3 and the locking sensor electrode 4 of the human hand.

  Moreover, in 4th Embodiment, the electronic control part 6 performs the determination processing flow shown by FIG. 11 using the detected 4 electrostatic capacitance value. As is clear from comparing FIG. 11 with FIG. 10, steps S55 to S57 are omitted in the fourth embodiment. The determination processes in step S53 and step S54 in FIG. 11 correspond to a third determination process in which determination based on frequency dependency is used together. As in the second embodiment, the fourth embodiment is effective for a configuration in which the degree of influence received from water is different between the unlocking sensor electrode 3 and the locking sensor electrode 4, and the determination processing is performed more than in the third embodiment. It can be simplified.

  When the degree of influence from a noise event such as flooding is reversed, the direction in which the calculation result is diverted is reversed. That is, steps S65 to S67 are omitted from the determination processing flow shown in FIG. 10 of the third embodiment. In this applied form, the electronic control unit 6 performs the fourth determination process for determining based on the two second change capacitors ΔC21 and ΔC22, and the two second change capacitors ΔC21 and ΔC12 in addition to the two second change capacitors ΔC21 and ΔC12. The first determination process that also uses ΔC22 for determination is performed while using determination based on frequency dependence.

  In each embodiment, at least one of the unlocking sensor electrode 3 and the locking sensor electrode 4 may also serve as the vehicle-side wireless communication antenna of the smart key system. Thereby, since the number of members is reduced and the structure is simplified, it is possible to contribute to the cost reduction of the vehicle. In addition, the present invention can be implemented for uses other than the smart key system, and various modifications and applications are possible.

1: Capacitance detection device 2: Door 21: Door panel (conductive base) 22: Recess
25: Door handle (non-conductive member) 26: Interior space 27: Back side 28: Front side 29: Back side 3: Unlocking sensor electrode (first electrode) 31: First capacitance 4: Locking sensor Electrode (second electrode) 41: Second capacitance 5: Detection unit 6: Electronic control unit (calculation unit and determination unit)
C1, C11, C12: capacitance values of the first capacitance ΔC1, ΔC11, ΔC12: first change capacitance C2, C21, C22: capacitance values of the second capacitance ΔC2, ΔC21, ΔC22: second Change capacities A1 to A4: first to fourth threshold values A11 to A42: threshold values

Claims (9)

A first capacitance formed through a free space between the first electrode incorporated in the non-conductive member and the conductive substrate;
A second capacitance formed through a free space between the second electrode incorporated in the non-conductive member and the conductive base;
A detection unit that detects a capacitance value of the first capacitance and a capacitance value of the second capacitance at a predetermined time interval;
A calculation unit that calculates a first change capacitance that is a time change amount of the capacitance value of the first capacitance and a second change capacitance that is a time change amount of the capacitance value of the second capacitance; ,
A first determination process for determining that a detection object has approached the first electrode when the first change capacity is equal to or greater than a first threshold and the second change capacity is less than a second threshold; and the second change capacity A determination unit that performs at least one determination process of a second determination process in which it is determined that the detection target has approached the second electrode when the first change capacity is less than a third threshold when the first change capacity is less than a fourth threshold When,
An electrostatic capacity detection device comprising:   The capacitance detection device according to claim 1, wherein the determination unit performs both the first determination process and the second determination process.   In Claim 1, The said determination part performs the 3rd determination process and a said 2nd determination process which determine with the said detection target approaching to the said 1st electrode when the said 1st change capacity is more than a said 1st threshold value. Or performing a fourth determination process and a first determination process for determining that the detection object has approached the second electrode when the second change capacity is equal to or greater than the fourth threshold value. Capacitance detection device.   4. The switched capacitor method according to claim 1, wherein the detection unit measures an index related to a time constant when the first capacitance and the second capacitance are charged or discharged. 5. A capacitance detection device that is a detection unit and that performs charging of one of the first capacitance and the second capacitance in synchronization with the other discharge. In any one of Claims 1-4,
The detection unit is a switched capacitor type detection unit that measures an index related to a time constant when the first capacitance and the second capacitance are charged or discharged, and a charge / discharge repetition frequency And measuring each capacitance value of the first and second capacitances at each repetition frequency,
The calculation unit calculates the first and second change capacities at each repetition frequency,
The determination unit determines the approach of the detection target with reference to the frequency dependence of the first and second change capacities with respect to each repetition frequency in at least one determination process of the first to fourth determination processes. A capacitance detection device characterized by:   6. The electrostatic device according to claim 1, wherein the conductive base is a door panel, the non-conductive member is a door handle, and the detection target is a human hand. Capacity detection device.   7. The door panel according to claim 6, wherein the door panel constitutes a door of the vehicle, the first electrode is built in a back surface side of the door handle near the door panel, and the second electrode is a surface side of the door handle away from the door panel. And a displacement detecting device that is displaced in a longitudinal direction of the door handle with respect to the first electrode. The vehicle according to claim 7, comprising a smart key system that includes a vehicle-side wireless device and a portable device-side wireless device, and that automatically locks and unlocks the door,
At least one of the first electrode and the second electrode also serves as a wireless communication antenna of the vehicle-side wireless device.   A contact detection sensor using the capacitance detection apparatus according to claim 1 to detect contact of a human hand with the non-conductive member.

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