Contact detection device

Abstract

[Problem] To enable capacitance measurement without causing a range overflow, even when an output value of a capacitance type sensor fluctuates significantly due to temperature change. [Solution] A contact detection device 1 includes: a capacitance type sensor 2 to which an AC voltage is applied by means of a voltage application unit 7; a phase component calculation unit 10; and a contact detection unit. The contact detection unit comprises: a temperature detection section 5; and a storage unit 11 that stores a reference range and a standard quadrature phase table which defines a relationship between a quadrature phase component in a state of no hand contact and the ambient temperature. The contact detection unit comprises: a reference phase component calculation unit 12 for calculating a reference quadrature phase component corresponding to an initial temperature, on the basis of the initial temperature and the standard quadrature phase table; a range change unit 13 for changing the reference range on the basis of a difference value between an initial quadrature phase component and the reference quadrature phase component in a state of no hand contact in the initial stage; and a contact determination unit 14 for determining the presence or absence of a hand contact on the basis of a threshold value and a change amount from a prescribed reference value of the quadrature phase component.

Description

Contact detection device

[0001] The present disclosure relates to a contact detection device that uses a capacitance sensor to detect contact with a conductor, including a person.

[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 device. An electronic control unit (ECU) determines whether a touch has occurred based on this change in capacitance (output), and controls the device accordingly. However, since the accuracy of capacitance sensors is significantly affected by ambient temperature, measures must be taken to account for temperature changes in order to maintain detection accuracy. Patent Document 1, for example, 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 defining the relationship between the elapsed operation time of the 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. Furthermore, Patent Document 2 discloses a contact determination processing device in which a contact sensor is provided on the steering wheel to detect a contact state, and when the output of the contact sensor is equal to or greater than a predetermined threshold, a contact state is determined, and when the output of the contact sensor is less than the threshold, a non-contact state is determined, and a temperature detection unit detects the ambient temperature and changes the threshold value depending on the detected ambient temperature.Furthermore, Patent Document 3 discloses an invention in which, in a contact determination device that also uses a contact sensor, a deterioration detector is provided to detect deterioration of the contact sensor, and when the deterioration detector detects deterioration of the contact sensor, the contact determination threshold value is changed.

[0003] JP 2012-48290 A JP 2017-87883 A JP 2017-177920 A

[0004] When using a capacitance sensor, the presence or absence of contact is determined by monitoring changes in the output value within a specified measurement range. However, if the output value fluctuates significantly due to changes in 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 false detection.

[0005] Therefore, the present disclosure aims to provide a contact detection device that can measure capacitance without going over the range, even if the output value of the capacitance sensor fluctuates significantly due to temperature changes.

[0006] In order to achieve the above object, the present disclosure provides a contact detection device including a capacitance sensor that detects contact of a conductor, a voltage application unit that applies an AC voltage of a predetermined frequency to the capacitance sensor, a phase component calculation unit that calculates a phase component based on an output value of the capacitance sensor when the AC voltage is applied by the voltage application unit, and a contact detection unit that detects contact of the conductor based on the phase component, wherein the contact detection unit includes: a temperature detection unit that detects an ambient temperature, a storage unit that stores a standard phase table that defines the relationship between a phase component calculated in advance in a predetermined ambient temperature range and the ambient temperature when the conductor is not in contact, and a phase component range that is an input range of the phase component output from the phase component calculation unit and that defines an upper and lower limit range of the phase component used for contact detection of the conductor, and a reference phase component calculation unit that calculates a reference phase component corresponding to an initial temperature based on an initial temperature obtained from the temperature detected by the temperature detection unit at a predetermined initial stage and the standard phase table, and a phase component range change unit that changes the phase component range based on an initial phase component calculated by the phase component calculation unit when the conductors are not in contact at an initial stage and a value equivalent to a difference between the initial phase component and a reference phase component. Another aspect of the present disclosure is the above-mentioned configuration, wherein the temperature detection unit has at least a first capacitor and a second capacitor, the phase component calculation unit calculates the first capacitor phase component and the second capacitor phase component based on output values ​​of the first capacitor and the second capacitor when an AC voltage is applied by the voltage application unit, and calculates a value equivalent to a difference between the first capacitor phase component and the second capacitor phase component as a capacitor difference equivalent value, the storage unit stores a temperature table that defines a correspondence relationship between an ambient temperature and a value equivalent to a difference between the first capacitor phase component and the second capacitor phase component calculated in advance within the ambient temperature range, and the reference phase component calculation unit calculates the initial temperature based on the capacitor difference equivalent value and the temperature table. Another aspect of the present disclosure is the above-mentioned configuration, wherein the phase component is a quadrature phase component. Another aspect of the present disclosure is characterized in that, in the above configuration, the phase component is an in-phase component.According to another aspect of the present disclosure, in the above configuration, the contact detection unit further includes a contact determination unit that determines whether or not a conductor is in contact based on an amount of change in the phase component from a predetermined reference value and a predetermined threshold. According to another aspect of the present disclosure, in the above configuration, the contact detection unit further includes: a reference resistor having a predetermined resistance value; a resistance phase component calculation unit that calculates, in an initial stage, a resistance phase component based on an output value when an AC voltage is applied to the reference resistor by the voltage application unit using a phase component range changed by the phase component range change unit; and a degradation detection unit that detects degradation of the capacitance-type sensor based on the resistance phase component and the initial phase component calculated by the phase component calculation unit using the phase component range changed by the phase component range change unit. Another aspect of the present disclosure is characterized in that, in the above configuration, in a predetermined operation stage after the initial stage, the resistance phase component calculation unit calculates a resistance phase component of the operation stage based on an output value when an AC voltage is applied to the reference resistor by the voltage application unit, while the phase component calculation unit calculates a phase component of the operation stage based on an output value of the capacitance sensor when the AC voltage is applied by the voltage application unit, and the degradation detection unit detects degradation of the capacitance sensor based on the resistance phase component of the operation stage and the phase component of the operation stage. Another aspect of the present disclosure is characterized in that, in the above configuration, each phase component used by the degradation detection unit when detecting degradation of the capacitance sensor is an in-phase phase component.

[0007] According to the present disclosure, the range change unit changes the phase component range based on a value corresponding to the difference between the initial phase component and the reference phase component, thereby enabling capacitance measurement without over-range even when the output value of the capacitance sensor fluctuates significantly due to temperature changes. According to another aspect of the present disclosure, the contact detection unit further includes a degradation detection unit that detects degradation of the capacitance sensor based on the initial phase component calculated by the phase component calculation unit and the resistance phase component calculated by the resistance phase component calculation unit. Therefore, in addition to the above-mentioned effect, degradation of the capacitance sensor in the early stage can be detected with a simple configuration that adds a reference resistor. According to another aspect of the present disclosure, the degradation detection unit detects degradation of the capacitance sensor based on the resistance phase component in the operating stage and the phase component in the operating stage. Therefore, in addition to the above-mentioned effect, degradation of the capacitance sensor in the operating stage can also be detected.

[0008] 6A is a functional block diagram of a contact detection device; FIG. 6B is a graph showing the I values ​​of the capacitance sensor and the reference resistor in a disconnected state after offsetting them; FIG. 6C is a graph showing the temperature characteristics of a capacitor; FIG. 6D is a graph showing the relationship between the difference in capacitor output values ​​and temperature; FIG. 6E is a graph showing the relationship between the output value of the quadrature phase component and temperature; and FIG. 6F is a graph showing the change in the output value of the capacitance sensor from the initial value in a normal state to the disconnected value as deterioration progresses.

[0009] An embodiment of the present disclosure will be described below with reference to the drawings. FIG. 1 is a functional block diagram illustrating an example of a contact detection device. The contact detection device 1 is provided to detect contact (grasping) of a conductive human hand with a steering wheel in a vehicle and performs part of a driving assistance function. The contact detection device 1 includes a capacitance sensor 2 and a measurement ECU 3. The measurement ECU 3 includes a capacitance IC 4, a temperature detection unit 5, a reference resistor 6, a voltage application unit 7, a phase component calculation unit 10, a memory unit 11, a reference phase component calculation unit 12, a range change unit 13, a contact determination unit 14, and a deterioration detection unit 15. In this embodiment, the temperature detection unit 5, the reference resistor 6, the voltage application unit 7, the memory unit 11, the reference phase component calculation unit 12, the range change unit 13, the contact determination unit 14, and the deterioration detection unit 15 constitute the contact detection unit of the present disclosure. The capacitance sensor 2 is mounted on the handle, and changes its capacitance in response to contact (grasping) with a human hand when an AC power supply of a predetermined frequency is applied from the voltage application unit 7. The capacitance IC 4 outputs an output value (voltage value or current value) corresponding to the capacitance of the capacitance sensor 2 when AC voltage is applied.

[0010] The temperature detection unit 5 consists of three capacitors C1 to C3 connected to a capacitance IC 4. When an AC voltage is applied to the capacitors C1 to C3 from the voltage application unit 7, the capacitors C1 to C3 output capacitance values ​​to the capacitance IC 4. The capacitance IC 4 outputs an output value (voltage value or current value) corresponding to the capacitance value. When an AC voltage is applied to the reference resistor 6 from the voltage application unit 7, the reference resistor 6 outputs capacitance values ​​to the capacitance IC 4. The capacitance IC 4 outputs an output value (voltage value or current value) corresponding to the capacitance value. The measurement ECU 3 has a non-transitory computer-readable storage medium including a CPU and a memory connected to the CPU, and detects contact of a human hand with the steering wheel based on a program stored in the storage medium. The voltage application unit 7 is configured within the capacitance IC 4 and applies AC voltage to the capacitance sensor 2, the temperature detection unit 5, and the reference resistor 6 at predetermined timings during the initial and operational stages described below based on the program.

[0011] In addition to the capacitance IC 4, temperature detection unit 5, reference resistor 6, and voltage application unit 7, the measurement ECU 3 includes, as functional units, a phase component calculation unit 10, a memory unit 11, a reference phase component calculation unit 12, a range change unit 13, a contact determination unit 14, and a deterioration detection unit 15. In the measurement ECU 3, the phase component calculation unit 10 calculates quadrature phase components from the output value of the capacitance sensor 2 input from the capacitance IC 4 and the output values ​​of the capacitors C1 to C3 when an AC voltage is applied. The quadrature phase component of the output value of the capacitance sensor 2 is an example of a phase component of the present disclosure. The phase component calculation unit 10 also calculates a resistance in-phase component based on the output value when an AC voltage is applied to the reference resistor 6. The phase component calculation unit 10 also functions as a resistance phase component calculation unit of the present disclosure. However, when the reference range R described later is shifted, the phase component calculation unit 10 offsets the in-phase component of the output value of the capacitance sensor 2 and the resistance in-phase component of the reference resistor 6 according to the amount of shift.

[0012] Capacitors C1 to C3 correspond to different temperature ranges. Fig. 2 shows the temperature-dependent changes in phase components (quadrature phase components) P1 to P3 calculated from the output values ​​of capacitors C1 to C3, respectively. Across the entire temperature range, the phase component P1 of capacitor C1 is the highest, followed by the phase component P2 of capacitor C2 and the phase component P3 of capacitor C3. From the phase components P1 to P3 of capacitors C1 to C3 shown in Fig. 2, the storage unit 11 calculates the environmental temperature and the difference value D between the phase component P1 of capacitor C1 and the phase component P2 of capacitor C2, as shown in Fig. 3. Ｐ The relationship between the phase component P1 and the phase component P2 is stored in advance as a temperature table T. The capacitor C1 is an example of a first capacitor of the present disclosure, and the phase component P1 is an example of a first capacitor phase component of the present disclosure. The capacitor C2 is an example of a second capacitor of the present disclosure, and the phase component P2 is an example of a second capacitor phase component of the present disclosure. The difference value D between the phase component P1 and the phase component P2 is Ｐ is an example of a value equivalent to the difference between the first capacitor phase component and the second capacitor phase component (capacitor difference equivalent value) of the present disclosure.

[0013] 4, the storage unit 11 stores the correspondence relationship between the output value V of the quadrature phase component of the capacitance sensor 2 calculated in advance by the phase component calculation unit 10 in a predetermined environmental temperature range when the hand is not in contact with the steering wheel and the temperature t in a standard quadrature table T. Ｓ The standard quadrature phase table T Ｓ is an example of a standard phase table of the present disclosure. Furthermore, the storage unit 11 stores a reference range R that defines the upper and lower limit ranges of the quadrature phase component for contact detection based on the output value V of the quadrature phase component. The reference range R is an example of a phase component range of the present disclosure. However, because the output value V of the quadrature phase component due to contact changes depending on the environmental temperature, a fixed reference range R may make it impossible to detect a change in the output value V within the reference range R.

[0014] Therefore, in a predetermined initial stage, the reference phase component calculation unit 12 obtains the phase components P1 and P2 of the capacitors C1 and C2, and calculates the difference D Ｐ Based on the temperature table T in FIG. 3, the initial temperature t ０ Then, the reference phase component calculation unit 12 estimates the estimated initial temperature t ０ and the standard quadrature phase table T Ｓ 4 is calculated based on the above. The reference quadrature phase component Q1 is an example of a reference phase component of the present disclosure. If there is a difference between the initial quadrature phase component Q2 calculated by the phase component calculation unit 10 and the reference quadrature phase component Q1 calculated by the reference phase component calculation unit 12 in the initial stage, the range change unit 13 calculates the difference value D Ｑ The reference range R is shifted by the amount indicated by the two-dot chain line. That is, the deviation between the reference quadrature phase component Q1 and the initial quadrature phase component Q2 due to the ambient temperature is compensated for by the shift of the reference range R. The range change unit 13 is an example of a phase component range change unit of the present disclosure. The initial quadrature phase component Q2 is an example of an initial phase component of the present disclosure. The difference value D Ｑis an example of a value corresponding to the difference between the initial phase component and the reference phase component in the present disclosure. The contact determination unit 14 determines whether or not contact has occurred by comparing the amount of change from a predetermined reference value of the output value V of the quadrature phase component calculated by the phase component calculation unit 10 with a threshold value previously stored in the storage unit 11. In other words, if the amount of change from the predetermined reference value of the output value V exceeds the threshold value, it is determined that a hand has contacted the object.

[0015] In the initial stage, when the reference range R is shifted by the range changing unit 13, the deterioration detection unit 15 detects deterioration of the capacitance sensor 2 based on the initial resistance in-phase phase component I1 of the reference resistor 6 and the initial in-phase phase component I2 of the capacitance sensor 2, which are calculated by the phase component calculation unit 10 when an AC voltage is applied to the reference resistor 6 from the voltage application unit 7. The initial resistance in-phase phase component I1 is an example of a resistance phase component used for deterioration detection in the initial stage of the present disclosure. The initial in-phase phase component I2 is an example of an initial phase component used for deterioration detection in the initial stage of the present disclosure. Furthermore, even in the operation stage after not detecting deterioration in the initial stage, the deterioration detection unit 15 detects deterioration of the capacitance sensor 2 based on the resistance in-phase phase component I1' calculated by the phase component calculation unit 10 when an AC voltage is applied to the reference resistor 6 from the voltage application unit 7 and the in-phase phase component I2' calculated by the phase component calculation unit 10 when an AC voltage is applied to the capacitance sensor 2 from the voltage application unit 7. The resistive in-phase component I1' is an example of a resistive phase component in the operational stage of the present disclosure. The in-phase component I2' is an example of a phase component in the operational stage of the present disclosure.

[0016] In the contact detection device 1 configured as above, the contact detection control by the measurement ECU 3 will be described with reference to the flowchart of Fig. 5. First, when the contact detection device 1 is activated, the temperature detection unit 5 detects the ambient temperature in S1. Next, in S2, the reference phase component calculation unit 12 calculates the initial temperature t from the output value of the temperature detection unit 5 based on the temperature table T in Fig. 3. ０ and the estimated initial temperature t ０ and the standard quadrature table T ＳNext, in S3, the phase component calculation unit 10 calculates an initial quadrature phase component Q2 from the output value V of the capacitance sensor 2. Next, in S4, the range change unit 13 compares the reference quadrature phase component Q1 with the initial quadrature phase component Q2 to obtain a difference value D between Q1 and Q2. Ｑ Here, it is determined whether or not there is a difference value D Ｑ If there is a difference value D Ｑ If there is no difference, the reference range R is not shifted and the process proceeds to S9.

[0017] After the reference range R is shifted in S5, the phase component calculation unit 10 calculates the initial resistance in-phase phase component I1 and the initial in-phase phase component I2 using the offset reference range R in S6. Next, in S7, the degradation detection unit 15 determines whether the initial in-phase phase component I2 is greater than the initial resistance in-phase phase component I1. The offset initial resistance in-phase phase component I1 and the initial in-phase phase component I2 are calculated for the following reason. FIG. 6A shows the trend of change in the output value of the capacitance sensor 2 from a normal initial value v0 to an open circuit value vd as degradation progresses. The vertical axis represents the quadrature phase component (Q value), and the horizontal axis represents the in-phase phase component (I value). In this case, the I value of the output value decreases initially as degradation progresses, and then begins to increase. FIG. 6A shows an example of a reference range R offset from the initial value v0 when the initial value v0 is normal. In this embodiment, as shown in FIG. 6A , the reference resistor 6 is set so that the initial resistance in-phase component I1 is between the initial value v0 and the open circuit value vd. This allows for detection of a normal state in the initial stage based on the magnitude relationship (I2 < I1) between the initial in-phase component I2 (initial value v0) and the initial resistance in-phase component I1. On the other hand, if the initial value v0 is abnormal, for example, if an open circuit state is detected in the initial stage, the reference range R is offset based on the open circuit value vd. In this case, as shown in FIG. 6B , the open circuit value vd is offset to become the initial in-phase component I2 in accordance with the offset amount of the reference range R, and the initial resistance in-phase component I1 is also offset in the same manner. In this case, the magnitude relationship between the initial in-phase component I2 (vd) and the initial resistance in-phase component I1 is reversed from that in the normal state (I2 > I1), allowing for detection of an abnormal state in the initial stage. Therefore, if the judgment in S7 determines that the initial in-phase phase component I2 is greater than the initial resistance in-phase phase component I1, the deterioration detection unit 15 determines that deterioration (here, a break) has occurred in the capacitance sensor 2, terminates the contact judgment operation, and notifies of the abnormality by an alarm or the like in S8.

[0018] On the other hand, if the determination in S7 indicates that the initial in-phase phase component I2 is smaller than the initial resistance in-phase phase component I1, it is determined that no disconnection has occurred, and the process proceeds to the operation stage. In S9, the phase component calculation unit 10 calculates the resistance in-phase phase component I1' and the in-phase phase component I2'. If the reference range R is shifted in S5, the offset resistance in-phase phase component I1' and the in-phase phase component I2' are calculated. If the reference range R is not shifted in S5, the non-offset resistance in-phase phase component I1' and the in-phase phase component I2' are calculated. Next, in S10, it is determined whether the in-phase phase component I2' is greater than the resistance in-phase phase component I1'. If the in-phase phase component I2' is greater than the resistance in-phase phase component I1', the deterioration detection unit 15 determines that deterioration (here, a disconnection) has occurred in the capacitance sensor 2, terminates the contact determination operation, and notifies the user of an abnormality in S8.

[0019] If no break is detected during operation in S10, the contact determination unit 14 compares the amount of change from a predetermined reference value of the quadrature phase component output value V calculated by the phase component calculation unit 10 with a threshold in S11. If the amount of change exceeds the threshold, a hand contact is determined in S12, and determination information is output to an external device such as a driving assistance ECU. Next, the process returns to S9, in which the degradation detection unit 15 detects deterioration of the capacitance sensor 2 during operation. If no break is detected in S10, monitoring continues in S11. If the amount of change does not exceed the threshold in S11, a hand contact is not determined, and the degradation detection unit 15 detects deterioration of the capacitance sensor 2 during operation in S9. If no break is detected in S10, monitoring continues in S11. Thus, even if the output value V fluctuates due to environmental temperature, the reference range R is shifted in the initial stage to match the fluctuation, preventing the output value V acquired during operation from significantly deviating from the reference range R.

[0020] Thus, the contact detection device 1 of the above embodiment includes a capacitance sensor 2 that detects contact with a human hand, a voltage application unit 7 that applies an AC voltage of a predetermined frequency to the capacitance sensor 2, a phase component calculation unit 10 that calculates a quadrature component based on the output value of the capacitance sensor 2 when the AC voltage is applied by the voltage application unit 7, and a contact detection unit that detects contact with a hand based on the quadrature component. The contact detection unit includes a temperature detection unit 5 that detects an ambient temperature, and a standard quadrature table T that defines the relationship between the ambient temperature and the quadrature component calculated in advance when no hand is in contact within a predetermined ambient temperature range. Ｓ and a reference range R, which is an input range of the quadrature phase component output from the phase component calculation unit 10 and defines the upper and lower limit ranges of the quadrature phase component used for detecting contact with a hand. ０ and the standard quadrature table T Ｓ Based on this, the initial temperature t ０ and a difference value D between the reference quadrature phase component Q1 and the initial quadrature phase component Q2 calculated by the phase component calculation unit 10 in an initial state where the hand is not in contact with the object. Ｑ and a contact determination unit 14 that determines whether or not a hand is in contact based on the amount of change from a predetermined reference value of the quadrature phase component and a threshold value. Ｑ Since the range change unit 13 changes the reference range R based on the above, even if the output value V of the capacitance type sensor 2 fluctuates greatly due to temperature changes, it is possible to measure the capacitance without going over the range.

[0021] In particular, the temperature detection unit 5 has a capacitor C1 and a capacitor C2, and the phase component calculation unit 10 calculates a phase component P1 and a phase component P2 based on the output values ​​of the capacitors C1 and C2, respectively, and calculates a difference value D between the phase components P1 and P2. ＰThe storage unit 11 calculates the difference value D between the phase component P1 and the phase component P2 calculated in advance within the environmental temperature range. Ｐ The reference phase component calculation unit 12 stores a temperature table T that defines the correspondence relationship between the difference value D Ｐ and the temperature table T. Therefore, the ambient temperature can be detected by utilizing the temperature characteristics of the capacitors C1 and C2, and an appropriate initial temperature can be calculated.

[0022] The contact detection unit further includes a reference resistor 6 having a predetermined resistance value, a phase component calculation unit 10 that calculates an initial resistance in-phase component I1 based on an output value when an AC voltage is applied to the reference resistor 6 by the voltage application unit 7 using a reference range R changed by the range change unit 13 in an initial stage, and a deterioration detection unit 15 that detects deterioration of the capacitance sensor 2 based on the initial resistance in-phase component I1 and the initial resistance in-phase component I2 calculated by the phase component calculation unit 10 using the reference range R changed by the range change unit 13. Thus, with the simple configuration of adding the reference resistor 6, it is possible to detect a disconnection in an early stage. Furthermore, in a predetermined operation stage after the initial stage, the phase component calculation unit 10 calculates a resistance in-phase phase component I1' in the operation stage based on the output value when an AC voltage is applied to the reference resistor 6 by the voltage application unit 7, while the phase component calculation unit 10 calculates an in-phase phase component I2' in the operation stage based on the output value of the capacitance sensor 2 when an AC voltage is applied by the voltage application unit 7, and the deterioration detection unit 15 detects deterioration of the capacitance sensor 2 based on the resistance in-phase phase component I1' in the operation stage and the in-phase phase component I2' in the operation stage. Thus, it is possible to detect disconnections even in the operation stage.

[0023] Modified examples of the present disclosure will be described below. In the above embodiment, the temperature table is set based on the relationship between the temperature and the difference value of the phase components of C1 and C2 out of the three capacitors. However, other combinations of capacitors may be used to obtain the difference value. The number of capacitors may also be two, four, or more. The difference value between the two capacitors may be calculated by a functional unit separate from the phase component calculation unit. However, the detection of the environmental temperature is not limited to using a capacitor. The environmental temperature may also be detected using a temperature sensor such as a thermistor. The temperature table and the standard quadrature phase table may be calculated by formulas. The number of capacitance sensors is not limited to one, and multiple capacitance sensors may also be provided. In this case, contact determination may be performed based on the average value of the output values ​​of each capacitance sensor, or based on the maximum or minimum value.

[0024] In the above embodiment, the difference value itself is calculated as the value equivalent to the difference between the initial phase component and the reference phase component, but the value equivalent to the difference value is not limited to this. For example, the value equivalent to the difference value may also be the ratio of the two values, such as difference / initial phase component (or reference phase component). This change also applies to the value equivalent to the difference between the first phase component and the second phase component of two capacitors. In the above embodiment, the phase component calculation unit calculates the quadrature phase component when changing the phase component range. However, it is also possible to calculate the in-phase phase component as the phase component and shift the phase component range or perform contact detection based on the output value of the in-phase phase component. In the above embodiment, a disconnection is detected as the deterioration detection, but deterioration may also be detected before the disconnection by using resistors with different resistance values. In this case, the reference resistor may be provided with multiple resistors with different resistance values ​​or may be a variable resistor. In this way, deterioration at any stage before the disconnection can be detected in advance. In the above embodiment, the resistance phase component calculated during the operation phase is used for deterioration detection during the operation phase, but the phase component calculated during the initial phase may also be used. In the above embodiment, the phase component calculation unit also functions as the resistance phase component calculation unit, but each calculation unit may be provided separately. The present disclosure is not limited to steering wheel contact detection. For example, the present disclosure can be applied to a touch panel or the like provided in an operation input device such as a car navigation system of a vehicle.

[0025] 1. Contact detection device, 2. Capacitive sensor, 3. Measurement ECU, 4. Capacitive IC, 5. Temperature detection unit, 6. Reference resistor, 7. Voltage application unit, 10. Phase component calculation unit, 11. Storage unit, 12. Reference phase component calculation unit, 13. Range change unit, 14. Contact determination unit, 15. Deterioration detection unit, C1 to C3. Capacitors, T. Temperature table, R. Reference range, T Ｓ ..standard quadrature phase table, Q1..reference quadrature phase component, Q2..initial quadrature phase component, D Ｐ , D Ｑ .Differential value.

Claims

a temperature detection unit that detects an ambient temperature; a standard phase table that defines a relationship between the phase component calculated in advance in a predetermined ambient temperature range and the ambient temperature when the conductor is not in contact with the ambient temperature; and a phase component range that is an input range of the phase component output from the phase component calculation unit and defines an upper and lower limit range of the phase component used for detecting the contact of the conductor; and a reference phase component calculation unit that calculates a reference phase component corresponding to the initial temperature based on an initial temperature obtained from the temperature detected by the temperature detection unit at a predetermined initial stage and the standard phase table. a phase component range change unit that changes the phase component range based on a value equivalent to the difference between an initial phase component calculated by the phase component calculation unit when no conductor is in contact at the initial stage and the reference phase component.

2. The contact detection device of claim 1, wherein the temperature detection unit has at least a first capacitor and a second capacitor, the phase component calculation unit calculates a first capacitor phase component and a second capacitor phase component based on output values ​​of the first capacitor and the second capacitor when the AC voltage is applied by the voltage application unit, and calculates a value equivalent to the difference between the first capacitor phase component and the second capacitor phase component as a capacitor difference equivalent value, the memory unit stores a temperature table that specifies the correspondence between the environmental temperature and a value equivalent to the difference between the first capacitor phase component and the second capacitor phase component that is calculated in advance within the environmental temperature range, and the reference phase component calculation unit calculates the initial temperature based on the capacitor difference equivalent value and the temperature table.

3. A contact detection device according to claim 1 or 2, wherein the phase component is a quadrature phase component.

4. A contact detection device according to claim 1 or 2, wherein the phase components are in-phase components.

5. A contact detection device as described in claim 1 or 2, wherein the contact detection unit further comprises a contact determination unit that determines whether or not a conductor is in contact based on the amount of change in the phase component from a predetermined reference value and a predetermined threshold value.

6. The contact detection device of claim 1 or 2, further comprising: a reference resistor having a predetermined resistance value; a resistance phase component calculation unit that calculates a resistance phase component based on an output value when the AC voltage is applied to the reference resistor by the voltage application unit using the phase component range changed by the phase component range change unit in the initial stage; and a deterioration detection unit that detects deterioration of the capacitance type sensor based on the initial phase component calculated by the phase component calculation unit using the phase component range changed by the phase component range change unit and the resistance phase component.

7. A contact detection device as described in claim 6, wherein, in a predetermined operation stage after the initial stage, the resistance phase component calculation unit calculates the resistance phase component of the operation stage based on an output value when the AC voltage is applied to the reference resistor by the voltage application unit, while the phase component calculation unit calculates the phase component of the operation stage based on an output value of the capacitance type sensor when the AC voltage is applied by the voltage application unit, and the deterioration detection unit detects deterioration of the capacitance type sensor based on the resistance phase component of the operation stage and the phase component of the operation stage.

8. The contact detection device according to claim 6, wherein the phase components used by the deterioration detection section when detecting deterioration of the capacitance sensor are in-phase components.

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