Touch detection device

Abstract

To measure electrostatic capacitance without range-over even if an output value of an electrostatic capacitance type sensor is considerably fluctuated by a temperature change.SOLUTION: A touch detection device 1 includes an electrostatic capacitance type sensor 2, a phase component calculation section 10 and a touch detection section. The touch detection section includes: a temperature detection section 5; a storage section 11 storing a reference range used for touch detection in a medium temperature zone, a first offset value for changing the reference range corresponding to a high temperature zone, and a second offset value for changing the reference range corresponding to a low temperature zone; a range change section 12 for estimating a temperature zone based on an environmental temperature detected by the temperature detection section 5 and changing the reference range just by the first or second offset value in a case where the temperature zone is estimated as the high temperature zone or the low temperature zone; and a touch determination section 13 for determining the presence / absence of touch of a hand based on a change amount of an orthogonal phase component from a predetermined reference value and a predetermined threshold.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a contact detection device that detects contact with a conductor, including a person, by using a capacitance sensor. [Background technology]

[0002] Vehicles and other devices are equipped with devices that use a contact detection device that detects contact with a human finger using a capacitance sensor. The capacitance sensor changes its capacitance when a finger touches or approaches the sensor, and an ECU (Electronic Control Unit) determines the presence or absence of contact based on this change in capacitance (output) and controls the device. However, since the accuracy of a capacitance sensor is significantly affected by the ambient temperature, measures must be taken into consideration of temperature changes in order to maintain detection accuracy.Therefore, for example, Patent Document 1 discloses an invention of a vehicle operation input device that employs a capacitance touch sensor in an operation input device such as a car navigation system, stores a correction table that defines the relationship between the elapsed operation time of an in-vehicle device and the temperature of the touch sensor, estimates the temperature of the touch sensor from the current elapsed operation time, obtains a correction coefficient for the estimated temperature, and corrects the sensitivity of the touch sensor based on the correction coefficient. Patent document 2 discloses an invention for a contact determination processing device in which a contact sensor that detects a contact state is provided on the handle, and when the output of the contact sensor is equal to or greater than a predetermined threshold, it is determined that a contact state exists, and when the output of the contact sensor is less than the threshold, it is determined that a non-contact state exists. The device also detects the ambient temperature using a temperature detection unit, and changes the threshold value depending on the detected ambient temperature. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-48290 A [Patent Document 2] JP 2017-87883 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a capacitance type sensor is used, the presence or absence of contact is determined by monitoring a change in the output value within a predetermined measurement range. However, if the output value fluctuates significantly due to changes in the environmental temperature, it may exceed the measurement range. In this case, even if the sensitivity or threshold is changed, there is a risk of measurement becoming impossible or erroneous detection.

[0005] Therefore, the present disclosure aims to provide a contact detection device that is capable of measuring capacitance without going over range, even if the output value of the capacitance sensor fluctuates greatly due to temperature changes, thereby enabling highly accurate contact detection. [Means for solving the problem]

[0006] In order to achieve the above object, the present disclosure provides a contact detection device, comprising: a capacitance type sensor that detects contact of a conductor; a phase component calculation unit that calculates a phase component based on an output value of the capacitance type sensor; a contact detection unit that detects contact of a conductor based on a phase component, The contact detection unit is A temperature detection unit for detecting an environmental temperature; a storage unit that stores a reference range that defines an upper and lower limit range of a phase component and is used for contact detection in a first temperature range that is a predetermined reference environmental temperature range, and a first offset value that is an amount of change for changing the reference range in response to a predetermined second temperature range different from the first temperature range; The temperature range is estimated based on the environmental temperature detected by the temperature detection unit, and when the temperature range is estimated to be the second temperature range, the range change unit changes the reference range by the first offset value. Another aspect of the present disclosure is a temperature sensor comprising: a temperature detector configured to detect a temperature of a first temperature range; and a second capacitor configured to detect a temperature of a second temperature range. the storage unit stores at least one of a first temperature table that predefines a correspondence relationship between a temperature in a first temperature region and a capacitance value of the first capacitor, and a second temperature table that predefines a correspondence relationship between a temperature in a second temperature region and a capacitance value of the second capacitor; The range change unit estimates the temperature range based on at least one of the capacitance value of the first capacitor and the first temperature table and the capacitance value of the second capacitor and the second temperature table. Another aspect of the present disclosure is a temperature detection unit configured with both the first capacitor and the second capacitor in the above configuration, The storage unit stores both the first temperature table and the second temperature table, The range change unit estimates the temperature range based on both the capacitance value of the first capacitor and the first temperature table, and the capacitance value of the second capacitor and the second temperature table. In another aspect of the present disclosure, in the above configuration, the temperature detection unit further includes a third capacitor provided in correspondence with a predetermined third temperature range different from the first temperature range and the second temperature range; the storage unit stores a second offset value which is a change amount for changing the range in accordance with the third temperature region, and a third temperature table which predetermines a correspondence relationship between the temperature in the third temperature region and the capacitance value of the third capacitor; The range change unit estimates the temperature range based on at least the capacitance value of the third capacitor and the third table, and when it estimates that the temperature range is the third temperature range, changes the reference range by the second offset value. Another aspect of the present disclosure is characterized in that, in the above configuration, the range change unit estimates the temperature range based on the capacitance value of the first capacitor and the first temperature table, the capacitance value of the second capacitor and the second temperature table, and the capacitance value of the third capacitor and the third temperature table. Another aspect of the present disclosure is characterized in that, in the above configuration, the phase component is a quadrature phase component. Another aspect of the present disclosure is characterized in that, in the above configuration, the contact detection unit further includes a contact determination unit that determines whether or not the conductor is in contact based on the amount of change in the phase component from a predetermined reference value and a predetermined threshold value. Effect of the Invention

[0007] According to the present disclosure, a temperature range is estimated based on the environmental temperature detected by a temperature detection unit, and when it is estimated that the temperature range is a second temperature range different from a first temperature range that can be monitored in the reference range, a range change unit changes the reference range by the first offset value. Therefore, even if the output value of the capacitance type sensor fluctuates greatly due to temperature changes, it is possible to measure capacitance without going over the range, and highly accurate contact detection is possible. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a functional block diagram of the contact detection device. [Diagram 2] 1 is a graph showing temperature characteristics of a capacitor. [Diagram 3] 1 is a graph showing the relationship between an output value of a capacitance type sensor and a reference range. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. 1 is a functional block diagram showing an example of a contact detection device. The contact detection device 1 here is provided to detect contact (grasping) of a conductive human hand with a steering wheel in a vehicle, and plays a part of a driving assistance function. The contact detection device 1 includes a capacitance type sensor 2 and a measurement ECU 3. The measurement ECU 3 includes a capacitance IC 4, a temperature detection unit 5, a phase component calculation unit 10, a storage unit 11, a range change unit 12, and a contact determination unit 13. In this embodiment, the temperature detection unit 5, the storage unit 11, the range change unit 12, and the contact determination unit 13 configure the contact detection unit of the present disclosure. The capacitance type sensor 2 is provided on the handle, and when an AC power of a predetermined frequency is applied from an AC power source (not shown), the capacitance changes in response to contact (grasping) with a human hand. The capacitance IC 4 outputs an output value (voltage value or current value) according to the capacitance of the capacitance type sensor 2 to the measurement ECU 3. The temperature detection unit 5 is composed of three capacitors C1 to C3 connected to a capacitance IC4. The capacitors C1 to C3 output capacitance values ​​to the capacitance IC4. The capacitance IC4 outputs an output value (voltage value or current value) according to the capacitance value.

[0010] However, the capacitors C1 to C3 are in different temperature ranges. Fig. 2 shows quadrature components (to be described later) calculated from the capacitance values ​​of the capacitors C1 to C3 in a temperature range including temperatures t1 to t3. 2, the temperature range in which changes can be measured for the central capacitor C1 is the mid-temperature region that includes temperatures t1 to t3. Capacitor C1 is an example of the first capacitor of the present disclosure, and the mid-temperature region is an example of the first temperature region of the present disclosure. For the capacitor C2 on the right side, the temperature range in which changes can be measured is a high temperature region from temperature t2 to temperature t3 inclusive, which is higher than temperature t3. Capacitor C2 is an example of the second capacitor of the present disclosure, and the high temperature region is an example of the second temperature region of the present disclosure. In the capacitor C3 on the left side, the temperature range in which the change can be measured is a low temperature region that is lower than temperature t1, including temperature t2 to temperature t1. Capacitor C3 is an example of a third capacitor of the present disclosure, and the low temperature region is an example of a third temperature region of the present disclosure.

[0011] The measurement ECU 3 has a CPU and a non-transitory computer-readable storage medium including a memory connected to the CPU, and detects a touch of a person's hand on the steering wheel based on a program stored in the storage medium. The measurement ECU 3 includes, in addition to the capacitance IC 4 and the temperature detection unit 5, a phase component calculation unit 10, a storage unit 11, a range change unit 12, and a contact determination unit 13 as functional units. In the measurement ECU 3, a phase component calculation unit 10 calculates quadrature phase components from the output value of the capacitance type sensor 2 input from the capacitance IC 4 and the output values ​​of the capacitors C1 to C3. The quadrature phase components are an example of phase components in the present disclosure.

[0012] The storage unit 11 pre-stores changes in the capacitance values ​​of the capacitors C1 to C3 shown in Fig. 2 as temperature tables T1 to T3, respectively. The temperature table T1 is an example of a first temperature table of the present disclosure, the temperature table T2 is an example of a second temperature table of the present disclosure, and the temperature table T3 is an example of a third temperature table of the present disclosure. The storage unit 11 also stores a reference range R that defines the upper and lower limit ranges for contact detection based on the output value V of the quadrature phase component calculated by the phase component calculation unit 10, as shown in FIG. However, since the output value V tends to be larger as the environmental temperature decreases and smaller as the environmental temperature increases, there is a risk that with a fixed reference range R, contact cannot be detected depending on the temperature region.

[0013] Therefore, the range change unit 12 estimates whether the environmental temperature is in the low temperature region, the medium temperature region, or the high temperature region based on the quadrature phase components calculated from the capacitance values ​​of the capacitors C1 to C3, and if the estimated temperature region is a temperature region that cannot be measured with the reference range R, the reference range R is offset to match the estimated temperature region. Therefore, the storage unit 11 pre-stores an offset value O1 that offsets the reference range R to match the high temperature region, and an offset value O2 that offsets the reference range R to match the low temperature region. The offset value O1 is an example of a first offset value of the present disclosure. The offset value O2 is an example of a second offset value of the present disclosure. 2, when the quadrature phase component Q1 calculated from the capacitance value of the capacitor C1 is measured, the range change unit 12 estimates that the current temperature is t2 and that the environmental temperature is in the medium temperature range. When the quadrature phase component Q2 calculated from the capacitance value of the capacitor C2 is measured, the range change unit 12 estimates that the current temperature is t3 and that the environmental temperature is in the high temperature range. When the quadrature phase component Q3 calculated from the capacitance value of the capacitor C3 is measured, the range change unit 12 estimates that the current temperature is t1 and that the environmental temperature is in the low temperature range.

[0014] Since the reference range R is initially set to correspond to the medium temperature region, when the environmental temperature is estimated to be in the high temperature region, the range change unit 12 offsets the reference range R to the lower side of the output value (quadrature phase component) by the offset value O1. In other words, the change amount V1 of the output value (quadrature phase component) V in the high temperature region higher than the temperature t3 is shifted to the higher side. On the other hand, when the environmental temperature is estimated to be in the low temperature range, the range change unit 12 offsets the reference range R toward the higher side of the measurement value by the offset value O2. In other words, the change amount V2 of the output value (quadrature phase component) V in the low temperature range lower than the temperature t2 is shifted toward the lower side.

[0015] When the estimated temperature region is a medium temperature region, the contact determination unit 13 compares the amount of change in the output value (quadrature phase component) V from a predetermined reference value within the reference range R with a threshold value T previously stored in the storage unit 11 to determine the presence or absence of contact. That is, if the amount of change in the output value (quadrature phase component) V from a predetermined reference value exceeds the threshold value T, it is determined that the contact is caused by a hand. When the estimated temperature region is a high temperature region, the contact determination unit 13 compares the amount of change in the output value (quadrature phase component) V from a predetermined reference value within the reference range R offset by the offset value O1 with the threshold value T to similarly determine the presence or absence of contact. When the estimated temperature region is a low temperature region, the contact determination unit 13 compares the amount of change in the output value (quadrature phase component) V from a predetermined reference value within the reference range R offset by the offset value O2 with the threshold value T to similarly determine the presence or absence of contact. Thus, the contact determination unit 13 can compare the output value (quadrature phase component) V with one threshold value T over the entire temperature region to determine the presence or absence of contact.

[0016] Thus, the contact detection device 1 of the above embodiment includes a capacitance sensor 2 that detects contact with a human hand, a phase component calculation unit 10 that calculates an orthogonal phase component based on the output value of the capacitance sensor 2, and a contact detection unit that detects contact with the hand based on the orthogonal phase component. The contact detection unit includes a temperature detection unit 5 that detects the ambient temperature, a memory unit 11 that stores a reference range R, which is a range that defines the upper and lower limit range of the orthogonal phase component and is used for contact detection in a medium temperature region that is a predetermined reference ambient temperature region, an offset value O1 that is a change amount for changing the reference range R to correspond to a predetermined high temperature region different from the medium temperature region, and an offset value O2 that is a change amount for changing the reference range R to correspond to a predetermined low temperature region different from the medium temperature region and the high temperature region, a range change unit 12 that estimates the temperature region based on the ambient temperature detected by the temperature detection unit 5, and changes the reference range R by the offset value O1 or O2 when it estimates that the temperature region is the high temperature region or the low temperature region, and a contact determination unit 13 that determines the presence or absence of hand contact based on the amount of change from a predetermined reference value of the orthogonal phase component and a pre-stored threshold value T. According to this configuration, even if the output value V of the capacitance type sensor 2 varies greatly due to temperature changes, it is possible to measure the capacitance without going over the range, and highly accurate contact detection is possible.

[0017] In particular, the temperature detection unit 5 includes a capacitor C1 provided corresponding to the medium temperature region, a capacitor C2 provided corresponding to the high temperature region, and a capacitor C3 provided corresponding to the low temperature region, and the memory unit 11 stores a temperature table T1 that predefines the correspondence between the temperature in the medium temperature region and the capacitance value of capacitor C1, a temperature table T2 that predefines the correspondence between the temperature in the high temperature region and the capacitance value of capacitor C2, and a temperature table T3 that predefines the correspondence between the temperature in the low temperature region and the capacitance value of capacitor C3, and the range change unit 12 estimates the temperature region based on the capacitance value and temperature table T1 of capacitor C1, the capacitance value and temperature table T2 of capacitor C2, and the capacitance value and temperature table T3 of capacitor C3. Therefore, the environmental temperature can be detected by utilizing the temperature characteristics of the capacitors C1 to C3, and an appropriate temperature range can be estimated.

[0018] Modifications of the present disclosure will be described below. The temperature regions of each capacitor may be changed as appropriate, and may partially overlap or may be separate. In the above embodiment, the temperature range is estimated using three capacitors, but the number of capacitors may be increased or decreased as appropriate. For example, even if there is one capacitor, if the capacitor has characteristics corresponding to either the first temperature range or the second temperature range, it is possible to distinguish between a temperature range that can be estimated using the capacitance value of the capacitor and the temperature table and a temperature range that cannot be estimated. In this case, the one capacitor is an example of the first capacitor or the second capacitor of the present disclosure, and the temperature table is an example of the first temperature table or the second temperature table of the present disclosure. The temperature range may also be estimated using the capacitance value of the capacitor. Even if there are two capacitors, it is possible to estimate the temperature range by setting one of the capacitors to have characteristics corresponding to a first temperature range and the other to have characteristics corresponding to a second temperature range. Even when there are three capacitors, it is not limited to estimating three temperature ranges based on the capacitance value of each capacitor and each temperature table as in the above embodiment, but it is also possible to distinguish between a temperature range that can be estimated using the capacitance value of the third capacitor and the third temperature table and a temperature range that cannot be estimated. The number of temperature regions and capacitors may be four or more. The temperature table may be a calculation formula.

[0019] The number of capacitance sensors is not limited to one, and multiple capacitance sensors may be provided. In this case, contact determination may be performed based on the average output value of each capacitance sensor, or the maximum or minimum output value. In the above embodiment, one threshold is used to determine whether or not there is contact, but two thresholds may be used to distinguish between contact and gripping. The thresholds may also be changed depending on the estimated temperature region. In the above embodiment, the quadrature phase component is calculated by the phase component calculation section, but an in-phase component may be calculated as the phase component, and contact determination may be performed based on the output value of the in-phase component. The present disclosure is not limited to touch detection of a steering wheel, but may also be applied to a touch panel or the like provided in an operation input device such as a car navigation system of a vehicle. [Explanation of symbols]

[0020] 1··Contact detection device, 2··Capacitive sensor, 3··Measurement ECU, 4··Capacitive IC, 5··Temperature detection section, 10··Phase component calculation section, 11··Memory section, 12··Range change section, 13··Contact determination section, C1 to C3··Capacitors, T1 to T3··Temperature table, R··Reference range, T··Threshold value, V··Output value of quadrature phase component.

Claims

1. a capacitance type sensor that detects contact of a conductor; a phase component calculation unit that calculates a phase component based on an output value of the capacitance type sensor; a contact detection unit that detects a contact of a conductor based on the phase component, The contact detection unit is A temperature detection unit for detecting an environmental temperature; a storage unit that stores a reference range that defines an upper and lower limit range of the phase component and is used for contact detection in a first temperature range that is a predetermined reference environmental temperature range, and a first offset value that is an amount of change for changing the reference range in response to a predetermined second temperature range different from the first temperature range; a range change unit that estimates a temperature range based on an environmental temperature detected by the temperature detection unit, and when it is estimated that the temperature range is the second temperature range, changes the reference range by the first offset value.

2. the temperature detection unit is configured with at least one of a first capacitor provided corresponding to the first temperature region and a second capacitor provided corresponding to the second temperature region, the storage unit stores at least one of a first temperature table that predefines a correspondence relationship between a temperature in the first temperature region and a capacitance value of the first capacitor, and a second temperature table that predefines a correspondence relationship between a temperature in the second temperature region and a capacitance value of the second capacitor, The contact detection device according to claim 1 , wherein the range change unit estimates the temperature range based on at least one of a capacitance value of the first capacitor and the first temperature table, and a capacitance value of the second capacitor and the second temperature table.

3. the temperature detection unit is configured by both the first capacitor and the second capacitor, the storage unit stores both the first temperature table and the second temperature table, The contact detection device according to claim 2 , wherein the range change unit estimates the temperature range based on both the capacitance value of the first capacitor and the first temperature table, and the capacitance value of the second capacitor and the second temperature table.

4. the temperature detection unit further includes a third capacitor provided in correspondence with a predetermined third temperature range different from the first temperature range and the second temperature range, the storage unit stores a second offset value which is a change amount for changing the range in accordance with the third temperature region, and a third temperature table which predetermines a correspondence relationship between a temperature in the third temperature region and a capacitance value of the third capacitor; 4. The contact detection device according to claim 3, wherein the range change unit estimates the temperature range based on at least a capacitance value of the third capacitor and the third temperature table, and when it estimates that the temperature range is the third temperature range, changes the reference range by the amount of the second offset value.

5. The contact detection device according to claim 4 , wherein the range change unit estimates the temperature range based on a capacitance value of the first capacitor and the first temperature table, a capacitance value of the second capacitor and the second temperature table, and a capacitance value of the third capacitor and the third temperature table.

6. 6. The contact detection device according to claim 1, wherein the phase component is a quadrature phase component.

7. 6. The contact detection device according to claim 1, wherein the contact detection unit further comprises a contact determination unit that determines whether or not the conductor is in contact based on an amount of change in the phase component from a predetermined reference value and a predetermined threshold value.

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