JP2011069784A - Angle detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an angle detector having a simpler structure than before. <P>SOLUTION: The angle detector 2 includes an annular resistor 10, first and second fixed electrodes A1 and A2 and movable electrode B provided to the annular resistor 10, a capacitor 15 connected between the movable electrode B and a ground node GND, a voltage application part 40, and a detection part 49A. The voltage application part 40 applies a pulse voltage to the first and second fixed electrodes A1 and A2 at timings different from each other. The detection part 49A detects a first delay time counted before a voltage of the movable electrode B exceeds a threshold voltage when pulse voltage is impressed on the first fixed electrode A1, and a second delay time counted before the voltage of movable electrode B exceeds a threshold voltage when the pulse voltage is impressed on the second fixed electrode A2. The detection part 49A detects a rotational angle around the central axis of the movable electrode B based on the detected first and second delay times. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an angle detection device that detects rotation angles of wheels, a pan head, a jog dial, and the like.

  As a method for detecting a rotation angle that continuously changes from 0 ° to 360 °, an annular resistance disclosed in Japanese Patent Laid-Open No. 6-180205 (Patent Document 1) and Japanese Patent Laid-Open No. 11-108609 (Patent Document 2). A method using a body has been conventionally used.

  The first prior art described in JP-A-6-180205 (Patent Document 1) uses two annular resistors. In the first annular resistor, the first and second fixed electrodes are provided at intervals of 180 degrees. The annular second resistor is provided with third and fourth fixed electrodes spaced apart from each other by 180 degrees. An angle difference of 90 degrees is provided between the first and second fixed electrodes and the third and fourth fixed electrodes. First and second movable electrodes that contact the first and second resistors, respectively, are provided, and these movable electrodes rotate in synchronization. Angular position data is created by a triangular wave obtained when the first movable electrode is rotated. Since the same value is obtained from the first movable electrode in the 0-180 degree range and in the 180-360 degree range, the value of the second movable electrode is used to distinguish this.

  The second prior art described in Japanese Patent Laid-Open No. 11-108609 (Patent Document 2) uses one annular resistor. This conventional angle detecting device includes one annular resistor, first to fourth electrodes, switching means, one slider, and potential detecting means. The first to fourth electrodes are provided in a state of being conducted to the annular resistor. The second electrode is disposed at a position 180 degrees from the first electrode. The third electrode is disposed between the first electrode and the second electrode. The fourth electrode is disposed at a position of 180 degrees from the third electrode. When the voltage is applied between the first electrode and the second electrode, the switching means opens the third and fourth electrodes, and conversely applies the voltage between the third electrode and the fourth electrode. When this occurs, the first and second electrodes are opened. The slider is brought into contact with the annular resistor. The potential detection means detects the potential of the slider.

JP-A-6-180205 JP-A-11-108609

  The first prior art is more complicated in structure than the second prior art because it uses two annular resistors. The second prior art has a simpler structure than the first prior art in that the number of annular resistors is one, but four fixed electrodes fixed to the annular resistor, It is necessary to provide a switch (switching means) for switching the supply of voltage to the fixed electrode.

  An object of the present invention is to provide an angle detection device having a simpler structure than conventional ones.

  In summary, the present invention is an angle detection device, and includes an annular resistor, first and second fixed electrodes provided on the annular resistor, a movable electrode, a passive element, a voltage application unit, and a detection unit. With. The second fixed electrode is provided on the annular resistor so that the angle around the central axis of the annular resistor is an angle other than 180 degrees with the first fixed electrode. The movable electrode is provided on the annular resistor, and the angle around the central axis is variable. The passive element is connected between the movable electrode and the ground node. The voltage application unit applies a voltage to the first and second fixed electrodes at different timings. Based on the voltage of the movable electrode when the voltage is applied to the first fixed electrode and the voltage of the movable electrode when the voltage is applied to the second fixed electrode, the detection unit is arranged around the central axis of the movable electrode. Detect the angle.

  In a preferred embodiment, the passive element is a capacitor. In this case, the detection unit includes a delay time detection unit and a data processing unit. The delay time detection unit includes a first delay time from when the voltage is applied to the first fixed electrode until the voltage of the movable electrode exceeds a threshold value, and the voltage of the movable electrode after the voltage is applied to the second fixed electrode. The second delay time until the voltage exceeds the threshold is detected. The data processing unit obtains an angle value around the central axis of the movable electrode based on the first and second delay times.

  In the above embodiment, more preferably, the detection unit further includes a storage unit that stores a plurality of first and second delay times measured in advance with respect to a plurality of angles around the central axis of the movable electrode. . In this case, the data processing unit compares the plurality of first delay times stored in the storage unit with the first delay time detected by the delay time detection unit, thereby detecting the detected first delay time. A candidate value of an angle around the central axis of the movable electrode corresponding to is obtained. The data processing unit further compares the plurality of second delay times stored in the storage unit with the second delay times detected by the delay time detection unit, thereby detecting the movable electrode at the time of detection from the angle candidate. Specify the angle around the center axis of.

  In another preferred embodiment, the passive element is a resistive element. In this case, the detection unit includes a voltage detection unit and a data processing unit. The voltage detection unit detects a first voltage value of the movable electrode when a voltage is applied to the first fixed electrode and a second voltage value of the movable electrode when a voltage is applied to the second fixed electrode. To do. The data processing unit obtains an angle value around the central axis of the movable electrode based on the first and second voltage values.

  In another embodiment of the present invention, more preferably, the data processing unit uses the first voltage value and the resistance value of the resistance element to calculate the first resistance value between the first fixed electrode and the movable electrode. The candidate value of the angle around the central axis of the movable electrode corresponding to the first resistance value is calculated. The data processing unit further calculates a second resistance value between the second fixed electrode and the movable electrode by using the second resistance value and the resistance value of the resistance element, and the second of the angle candidates. The angle corresponding to the resistance value of is specified.

  According to the present invention, it is possible to detect the rotation angle more easily than in the past using two fixed electrodes and one movable electrode provided on one annular resistor.

It is a block diagram of the angle detection apparatus 1 by Embodiment 1 of this invention. It is a functional block diagram of the angle detection apparatus 1 of FIG. It is a graph which shows the characteristic of the cyclic resistor 10 of FIG. It is a figure for demonstrating the detection principle of the rotation angle by the angle detection apparatus 1 of FIG. It is a flowchart which shows the detection procedure of the rotation angle by the angle detection apparatus 1 of FIG. It is a figure which shows an example of the waveform of the output voltage of the microcomputer 20 of FIG. 2, and an input voltage. It is a block diagram of the angle detection apparatus 2 by Embodiment 2 of this invention. It is a functional block diagram of the angle detection apparatus 2 of FIG. It is a flowchart which shows the detection procedure of the rotation angle by the angle detection apparatus 2 of FIG. It is a figure which shows an example of the waveform of the output voltage and input voltage of the microcomputer 20A of FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

<Embodiment 1>
[Configuration of angle detector]
FIG. 1 is a configuration diagram of an angle detection apparatus 1 according to Embodiment 1 of the present invention. Referring to FIG. 1, an angle detection device 1 includes an annular resistor 10, fixed electrodes A <b> 1 and A <b> 2 provided on the annular resistor 10, a movable electrode B provided on the annular resistor 10, and a passive element 13. The resistance element 14 and the microcomputer 20 are included.

  The fixed electrodes A1 and A2 are provided at positions where the angular difference around the central axis 12 of the annular resistor 10 does not become 180 °. The fixed electrode A1 is connected to the signal output terminal 31 of the microcomputer 20. The fixed electrode A <b> 2 is connected to the signal output terminal 32 of the microcomputer 20.

  The movable electrode B is provided at the other end of the rod-like conductor 11 whose one end is pivotally supported at the position of the central axis 12 and slides on the annular resistor 10. As the movable electrode B slides, the angle around the central axis 12 from the reference position (for example, the fixed electrode A1) on the annular resistor 10 to the movable electrode B (that is, the rotation angle) changes. The movable electrode B is connected to the signal input terminal 33 of the microcomputer 20 through the rod-shaped conductor 11.

  The resistance element 14 is connected between the end of the rod-shaped conductor 11 on the side close to the central axis 12 and the ground node GND. That is, the resistance element 14 is provided between the movable electrode B and the ground GND.

  The microcomputer 20 includes a central processing unit 21 (CPU: Central Processing Unit), a storage device 22 having a ROM (Read Only Memory) and a RAM (Random Access Memory), a peripheral circuit 23, and these elements 21 to 23. And a bus 28 to be connected. The peripheral circuit 23 includes a clock oscillator and a timer.

  The microcomputer 20 is further connected to an input / output control circuit 24 connected to the bus 28, three-state buffers 25 and 26 as output gates, and output nodes of the three-state buffers 25 and 26, respectively. Signal output terminals 31 and 32. These components 24 to 26, 31, and 32 schematically show general-purpose digital output ports provided in the microcomputer 20.

  The input / output control circuit 24 switches the control electrode of the three-state buffer 25 (or 26) to a high (H) level or a low (L) level in accordance with a command from the CPU 21. When the control electrode is set to the H level, the three-state buffer 25 (or 26) can output the voltage signal OUT1 (OUT2) via the corresponding signal output terminal 31 (32). Conversely, the three-state buffer 25 (or 26) places the output node in a high impedance state when the control electrode is set to the L level.

  The microcomputer 20 further includes an analog / digital converter (ADC) 27 connected to the bus 28 and a signal input terminal 33. These components schematically show analog input ports provided in the microcomputer 20. The ADC 27 converts the analog voltage signal IN received via the signal input terminal 33 into a digital signal. The digitally converted input signal IN is output to the CPU 21 and the like via the bus 28.

  FIG. 2 is a functional block diagram of the angle detection device 1 of FIG. As shown in FIG. 2, the microcomputer 20 of FIG. 1 includes a voltage application unit 40, a voltage detection unit 41, and a data processing unit 42 when viewed functionally. The voltage detection unit 41 and the data processing unit 42 constitute a detection unit 49 that detects the rotation angle of the movable electrode B.

  The voltage application unit 40 applies voltages to the fixed electrodes A1 and A2 at different timings via the signal output terminals 31 and 32, respectively. At this time, in practice, a pulsed voltage is repeatedly applied to the fixed electrodes A1 and A2. Since the rotation angle of the movable electrode B needs to be equal between when the voltage is applied to the fixed electrode A1 and when the voltage is applied to the fixed electrode A2, the period of the output pulse voltage is the period of change in the rotation angle. Is set sufficiently short.

  The voltage application unit 40 corresponds to the CPU 21, the input / output control circuit 24, and the three-state buffers 25 and 26 in FIG. The function of the voltage application unit 40 is realized by controlling the input / output control circuit 24 based on a command from the CPU 21. When the voltage Vin is applied to the fixed electrode A1 via the signal output terminal 31, the input / output control circuit 24 controls the three-state buffer 26 of FIG. 1 so that the signal output terminal 32 is in a high impedance state. To do. Conversely, the input / output control circuit 24 applies the voltage Vin to the fixed electrode A2 via the signal output terminal 32 so that the signal output terminal 31 is in a high impedance state so that the three-state buffer 25 of FIG. To control.

  The voltage detector 41 detects the voltage of the movable electrode B input via the signal input terminal 33. The voltage detection unit 41 corresponds to the ADC 27 in FIG. The voltage of the movable electrode B is input to the ADC 27 as an analog voltage signal IN, and is converted into digital voltage data by the ADC 27. The converted voltage data is output to the data processing unit 42.

  The data processing unit 42 corresponds to the CPU 21 in FIG. Based on the voltage value of the movable electrode B when a voltage is applied to the fixed electrode A1 and the voltage value of the movable electrode B when a voltage is applied to the fixed electrode A2, the data processing unit 42 Find the angle around the center axis. Hereinafter, the detection principle of the rotation angle by the data processing unit 42 will be described.

[Rotation angle detection principle]
When the voltage Vin is applied to the fixed electrode A1, the voltage detection unit 41 of the angle detection device 1 uses the resistance value R1 between the fixed electrode A1 and the movable electrode B and the resistance value Rd of the resistance element 14 to determine the fixed electrode. A voltage V1 obtained by dividing the voltage Vin applied to A1 is detected. That is, the detection voltage V1 is
V1 = Vin × Rd / (R1 + Rd) (1)
It is expressed as Similarly, when the voltage Vin is applied to the fixed electrode A2, the voltage detection unit 41 applies the resistance value R2 between the fixed electrode A2 and the movable electrode B and the resistance value Rd of the resistance element 14 to the fixed electrode A2. A voltage V2 obtained by dividing the applied voltage Vin is detected. That is, the detection voltage V2 is
V2 = Vin × Rd / (R2 + Rd) (2)
It is expressed as

  Since the resistance values R1 and R2 change corresponding to the rotation angle of the movable electrode B, the resistance values R1 and R2 can be calculated by calculating the resistance values R1 and R2 from the detection voltages V1 and V2 according to the above equations (1) and (2), respectively. The rotation angle of the electrode B can be detected.

  FIG. 3 is a graph showing characteristics of the annular resistor 10 of FIG. 2 and 3, the horizontal axis of FIG. 3 shows the rotation angle θ1 from the fixed electrode A1 to the movable electrode B as a reference point. A clockwise direction is positive and a counterclockwise direction is negative. 3 represents the resistance value R1 between the fixed electrode A1 and the movable electrode B of the annular resistor 10. Let R be the resistance value of 1/4 turn of the annular resistor 10.

  The resistance value R1 between the fixed electrode A1 and the movable electrode B is the resistance value of the arc portion when the fixed electrode A1 reaches the movable electrode B in the clockwise direction and the counterclockwise direction from the fixed electrode A1 to the movable electrode B. It becomes a parallel combined resistance with the resistance value of the arc portion when reaching. In this case, when the movable electrode B is in a mirror symmetrical position with respect to the plane including the fixed electrode A1 and the central axis 12, the resistance values R1 at both positions are equal to each other.

Specifically, using an equation, if the angle from the fixed electrode A1 to the movable electrode B is θ1 (clockwise direction is positive) and the absolute value is | θ1 |, the resistance value R1 is
R1 = R × | θ1 | × (360 ° − | θ1 |) / (90 ° × 360 °) (3)
It is expressed as In the above equation (3), R represents a resistance value corresponding to 1/4 of the annular resistor 10. A graph of the above equation (3) is shown in FIG.

  As shown in FIG. 3, the positive rotation angle θ1 and the negative rotation angle −θ1 correspond to the resistance value between the fixed electrode A1 and the movable electrode B. Therefore, the rotation angle of the movable electrode B cannot be specified only by applying the voltage Vin to one of the fixed electrodes A1 and A2. The rotation angle of the movable electrode B can be specified by using both the voltage values of the movable electrode B detected when the voltage Vin is applied to each of the fixed electrodes A1 and A2. This will be described in more detail with reference to FIG.

  FIG. 4 is a diagram for explaining the principle of detection of the rotation angle by the angle detection device 1 of FIG. Referring to FIG. 4, the current position of the movable electrode is represented by B, and the case where the movable electrode is at a position symmetrical to the current position with respect to the plane passing through fixed electrode A1 and central axis 12 is represented by B1. A case where the movable electrode is located at a position symmetrical to the current position with respect to the plane passing through the fixed electrode A2 and the central axis 12 is represented by B2.

  In FIG. 4, the resistance value between A1 and B is equal to the resistance value between A1 and B1. Therefore, when the voltage Vin is applied to the fixed electrode A1, it cannot be distinguished from B or B1 in FIG. 4 from the detected voltage of the movable electrode. Similarly, the resistance value between A2 and B is equal to the resistance value between A2 and B2. Therefore, when the voltage Vin is applied to the fixed electrode A2, it cannot be distinguished from B or B2 in FIG. 4 from the detected voltage of the movable electrode.

  Therefore, in order to specify the position of the movable electrode, the detection result of the voltage value of the movable electrode when the voltage Vin is applied to the fixed electrode A1, and the voltage value of the movable electrode when the voltage Vin is applied to the fixed electrode A2 It is necessary to combine with the detection result.

[Rotation angle detection procedure]
FIG. 5 is a flowchart showing a procedure for detecting the rotation angle by the angle detection device 1 of FIG. With reference to FIG. 2 and FIG. 5, the detection procedure of the rotation angle by the angle detection apparatus 1 is as follows.

  In step S <b> 1, the voltage application unit 40 applies the voltage Vin to the fixed electrode A <b> 1 provided on the annular resistor 10.

  In the next step S2, the voltage detector 41 detects the voltage V1 applied to the resistance element 14 provided between the movable electrode B and the ground node GND when the voltage Vin is applied to the fixed electrode A1.

  In the next step S3, the data processing unit 42 calculates a resistance value R1 between the fixed electrode A1 and the movable electrode B from the voltage V1 detected in step S2 using the relationship of the above-described equation (1).

  In the next step S4, the data processing unit 42 obtains the angle candidates θ1 and −θ1 of the movable electrode B from the resistance value R1 calculated in step S3 using the relationship of the above-described equation (3). Here, the angle of the movable electrode B is positive in the clockwise direction with respect to the position of the fixed electrode A1.

  In the next step S <b> 5, the voltage application unit 40 applies the voltage Vin to the fixed electrode A <b> 2 provided on the annular resistor 10.

  In the next step S6, the voltage detector 41 detects the voltage V2 applied to the resistance element 14 between the movable electrode B and the ground node GND when the voltage Vin is applied to the fixed electrode A2.

  In the next step S7, the data processing unit 42 calculates the resistance value R2 between the fixed electrode A2 and the movable electrode B using the relationship of the above-described equation (2) from the voltage V2 detected in step S6.

  In the next step S8, the data processing unit 42 determines the angle θ1 of the movable electrode B at the current position among the angle candidates θ1 and −θ1 obtained in step S4 based on the resistance value R2 calculated in step S7. Identify.

Specifically, if the angle from the fixed electrode A2 to the movable electrode B is θ2 (the clockwise direction is positive) and the absolute value is | θ2 |, the resistance value R2 detected in step S7 is
R2 = R × | θ2 | × (360 ° − | θ2 |) / (90 ° × 360 °) (4)
It is expressed as R in the above equation (4) is a resistance value corresponding to 1/4 turn of the annular resistor 10. From this relational expression (4), angles θ2 and −θ2 corresponding to the resistance value R2 are obtained. Here, the angle from the fixed electrode A1 to the fixed electrode A2 is Θ12 (the clockwise direction is positive). The angle from the fixed electrode A2 to the movable electrode B can be converted into the angle from the fixed electrode A1 to the movable electrode B by subtracting the angles θ2 and −θ2 obtained by the equation (4) from Θ12. For example, in the case of FIG. 4, since Θ12 = θ1 + θ2, the angles θ2, −θ2 obtained according to the equation (4) are converted into θ1 and (θ1 + 2 × θ2). By comparing this converted angle with the angle candidates θ1, −θ1 obtained in step S4, the actual movable electrode angle θ1 can be specified.

  In the rotation angle detection procedure, the voltage Vin may be applied first to the fixed electrode A2 and then to the fixed electrode A1.

  FIG. 6 is a diagram showing an example of the output voltage and input voltage waveforms of the microcomputer 20 of FIG. The horizontal axis in FIG. 6 represents time, and the vertical axis in FIG. 6 represents the voltage signal OUT1 output from the signal output terminal 31, the voltage signal OUT2 output from the signal output terminal 32, and the signal input terminal 33 in order from the top. The voltage signal IN detected via the is shown.

  2 and 6, voltage Vin is applied to fixed electrode A1 provided on annular resistor 10 through signal output terminal 31 in the time period from time t1 to time t2 (step S1 in FIG. 5). ). At this time, the voltage V1 of the movable electrode B is detected via the signal input terminal 33 (step S2 in FIG. 5). Based on the detected voltage V1, the data processing unit 42 calculates a resistance value R1 between the fixed electrode A1 and the movable electrode B (step S3 in FIG. 5), and the movable electrode based on the calculated resistance value R1. A candidate value for the angle B is obtained (step S4 in FIG. 5).

  Next, the voltage Vin is applied to the fixed electrode A2 provided in the annular resistor 10 through the signal output terminal 32 in the time period from time t3 to t4 (step S5 in FIG. 5). At this time, the voltage V2 of the movable electrode B is detected via the signal input terminal 33 (step S6 in FIG. 5). Based on the detected voltage V2, the data processing unit 42 calculates a resistance value R2 between the fixed electrode A2 and the movable electrode B (step S7 in FIG. 5), and the movable electrode based on the calculated resistance value R2. The angle B is specified (step S8 in FIG. 5).

[Summary of Embodiment 1]
As described above, according to the first embodiment, the angle detection device 1 includes the first and second fixed electrodes A1 and A2, the movable electrode B, the movable electrode B, and the ground provided on the annular resistor 10. The rotation angle around the central axis 12 of the movable electrode B is detected using the resistance element 14 provided between the node GND. Specifically, the angle detection device 1 applies the voltage Vin to the fixed electrodes A1 and A2 at different timings, and applies the voltage Vin to the fixed electrode A1 and the voltage value V1 of the movable electrode B to the fixed electrode A2. The voltage value V2 of the movable electrode B when the voltage Vin is applied is detected. The angle detection device 1 obtains the rotation angle of the movable electrode B based on the detected voltage values V1 and V2. As a result, the rotation angle can be detected with a simpler configuration than in the prior art.

<Embodiment 2>
[Configuration of angle detector]
FIG. 7 is a configuration diagram of an angle detection device 2 according to Embodiment 2 of the present invention. The angle detection device 2 in FIG. 7 differs from the angle detection device 1 in FIG. 1 in that a capacitor 15 is included instead of the resistance element 14 as the passive element 13. Further, the microcomputer 20A constituting the angle detection device 2 is different from the microcomputer 20 of FIG. 1 in that it includes an AND circuit 29 as an input gate instead of the ADC 27. Since the other points of FIG. 7 are the same as those of the angle detection apparatus 1 of FIG.

  The signal input terminal 33, the AND circuit 29, and the input / output control circuit 24 schematically show general-purpose digital input ports provided in the microcomputer 20A. The input / output control circuit 24 switches one input node of the AND circuit 29 as an input gate to H level or L level in accordance with a command from the CPU 11. The AND circuit 29 is in a state in which the voltage signal IN can be input via the signal input terminal 33 when one of the input nodes is set to the H level. Conversely, when it is set to L level, signal input becomes impossible. During detection of the rotation angle, the AND circuit 29 sets the voltage signal IN to a state where it can be input.

  In the angle detection device 2 of FIG. 7, the voltage change of the movable electrode B becomes gentler than the voltage change of the pulse voltage applied to the fixed electrode A1 or A2 by providing the capacitor 15. The voltage change of the movable electrode B is detected by the microcomputer 20A via the AND circuit 29 as an input gate. The AND circuit 29 switches to the on state when the input voltage IN exceeds the threshold voltage VTH, and switches to the off state when the input voltage IN becomes equal to or lower than the threshold voltage VTH. Therefore, the pulse voltage detected through the AND circuit 29 is delayed compared to the pulse voltage output to the fixed electrode A1 or A2. The delay time of the pulse voltage depends on a time constant determined by the resistance values R1, R2 between the fixed electrodes A1, A2 and the movable electrode B and the capacitance value of the capacitor 15. In this case, since the resistance values R1 and R2 change according to the rotation angle of the movable electrode B, the rotation angle of the movable electrode B can be detected by detecting the delay time.

  FIG. 8 is a functional block diagram of the angle detection device 2 of FIG. As shown in FIG. 8, the microcomputer 20A of FIG. 7 includes a voltage application unit 40, a delay time detection unit 43, a data processing unit 42A, and a storage unit 44 in terms of function. The delay time detection unit 43, the data processing unit 42A, and the storage unit 44 constitute a detection unit 49A that detects the rotation angle of the movable electrode B.

  The voltage application unit 40 applies a pulse voltage having a voltage intensity Vin to the fixed electrodes A1 and A2 via the signal output terminals 31 and 32 at different timings. At this time, in practice, a pulsed voltage is repeatedly applied to the fixed electrodes A1 and A2. Since the rotation angle of the movable electrode B needs to be equal between when the pulse voltage is applied to the fixed electrode A1 and when the pulse voltage is applied to the fixed electrode A2, the cycle of the output pulse voltage is a change in the rotation angle. It is set sufficiently shorter than the period.

  The voltage application unit 40 corresponds to the CPU 21, the input / output control circuit 24, and the three-state buffers 25 and 26 in FIG. The function of the voltage application unit 40 is realized by controlling the input / output control circuit 24 based on a command from the CPU 21. When the pulse voltage is applied to the fixed electrode A1 via the signal output terminal 31, the input / output control circuit 24 controls the three-state buffer 26 so that the signal output terminal 32 is in a high impedance state. When the pulse voltage is applied to the fixed electrode A2 via the signal output terminal 32, the input / output control circuit 24 controls the three-state buffer 25 so that the signal output terminal 31 is in a high impedance state. A voltage change occurs in the movable electrode B by applying a pulse voltage from the voltage application unit 40 to the fixed electrodes A1 and A2. This change in voltage is such that the rising edge and the falling edge are dull compared to the pulse voltage applied to the fixed electrodes A1 and A2.

  The delay time detection unit 43 corresponds to the built-in timers of the AND circuit 29, the input / output control circuit 24, the CPU 21, and the peripheral circuit 23 of FIG. The delay time detection unit 43 detects the delay time based on the time difference between the rising edge timing of the pulse voltage output from the voltage application unit 40 and the rising edge timing of the output of the AND circuit 29 as an input gate. This time difference can be detected by a timer built in the microcomputer 20A. For detecting the delay time, the falling edge of the pulse voltage may be used.

  The storage unit 44 corresponds to the storage device 22 of FIG. 7 and stores a delay time measured in advance for each rotation angle of the movable electrode B as a data table. The data table is created in advance for both the case where the pulse voltage is applied to the fixed electrode A1 and the case where the pulse voltage is applied to the fixed electrode A2. In any case, the rotation angle of the movable electrode B is changed from 0 ° to 360 °, and the delay time and the rotation angle detected at this time are associated with each other and stored in the storage unit 44 in advance.

  The data processing unit 42A corresponds to the CPU 21 in FIG. The data processing unit 42A compares the detected delay time with the delay time stored in the storage unit 44 when a pulse voltage is applied to the fixed electrode A1. As a result, the data processing unit 42A obtains the rotation angle of the movable electrode B when the detected delay time substantially matches the delay time stored in the storage unit 44. As described with reference to FIG. 4, as the rotation angle of the movable electrode B, two values of θ1 and −θ1 corresponding to the resistance value R1 between the fixed electrode A1 and the movable electrode B are obtained. Therefore, two candidates are also obtained for the rotation angle corresponding to the delay time determined by the resistance value R1 and the capacitance value of the capacitor 15.

  Next, the data processing unit 42A compares the data of the detected delay time and the delay time stored in the storage unit 44 when the pulse voltage is applied to the fixed electrode A2. As a result, the data processing unit 42A specifies the rotation angle at the time of detection from among the rotation angle candidates of the movable electrode B previously obtained.

[Rotation angle detection procedure]
FIG. 9 is a flowchart showing a procedure for detecting the rotation angle by the angle detection device 2 of FIG. With reference to FIG. 8 and FIG. 9, the detection procedure of the rotation angle by the angle detection device 2 is as follows.

  In step S <b> 11, the voltage application unit 40 applies a pulse voltage to the fixed electrode A <b> 1 provided on the annular resistor 10. At this time, the voltage of the movable electrode B changes according to the input pulse voltage.

  In the next step S12, the delay time detector 43 detects the voltage change of the movable electrode B as a binary pulse voltage of H level or L level by detecting the voltage change of the movable electrode B through the input gate. To do. The delay time detector 43 obtains a time difference (delay time) between the rising edge of the detected pulse voltage and the rising edge of the pulse voltage output in step S11.

  In the next step S13, the data processing unit 42A compares the delay time detected in step S12 with the delay time stored in advance in the storage unit 44, and determines the rotation angle corresponding to the delay time when both are substantially the same. Ask. Thus, two rotation angle candidates are obtained.

  In next step S <b> 14, the voltage application unit 40 applies a pulse voltage to the fixed electrode A <b> 2 provided in the annular resistor 10. At this time, the voltage of the movable electrode B changes according to the input pulse voltage.

  In the next step S15, the delay time detector 43 detects a voltage change of the movable electrode B as a binary pulse voltage via the input gate. The delay time detector 43 obtains a time difference (delay time) between the rising edge of the detected pulse voltage and the rising edge of the pulse voltage output in step S14.

  In the next step S16, the data processing unit 42A compares the delay time detected in step S16 with the delay time stored in advance in the storage unit 44, and determines the rotation angle corresponding to the delay time when both are substantially the same. Ask. The data processing unit 42A identifies the final rotation angle of the movable electrode B by comparing the obtained rotation angle with the rotation angle candidate obtained in step S13.

  FIG. 10 is a diagram showing an example of waveforms of the output voltage and the input voltage of the microcomputer 20A of FIG. The horizontal axis of FIG. 10 is time, and the vertical axis of FIG. 10 is, in order from the top, the voltage signal OUT1 output from the signal output terminal 31, the voltage signal OUT2 output from the signal output terminal 32, and the signal input terminal 33. The output voltage signal IN and the output voltage of the AND circuit 29 as an input gate are shown.

  With reference to FIGS. 8 and 10, a pulse voltage is applied to fixed electrode A <b> 1 provided in annular resistor 10 during a time period from time t <b> 1 to t <b> 3 (step S <b> 11 in FIG. 9). At this time, the rising edge and falling edge of the voltage signal IN input to the signal input terminal 33 are gentler than the rising edge and falling edge of the pulse voltage applied to the fixed electrode A1. In FIG. 10, the exponential voltage change is approximated by a straight line.

  At time t2, since the voltage signal IN input to the signal input terminal 33 exceeds the threshold voltage VTH of the input gate (AND circuit 29), the output voltage of the input gate is switched from L level to H level. In response to this, the delay time detector 43 detects the difference between the rise time t1 of the voltage signal OUT1 applied to the fixed electrode A1 and the rise time t2 of the pulse voltage detected via the input gate as the delay time TD1. (Step S12 in FIG. 9). The data processing unit 42A compares the detected delay time TD1 with the delay time stored in advance in the storage unit 44 to obtain a candidate for the rotation angle of the movable electrode B (step S13 in FIG. 9).

  At time t4, since the voltage signal IN input to the signal input terminal 33 becomes equal to or lower than the threshold voltage VTH, the output voltage of the input gate is switched from the H level to the L level.

  Next, a pulse voltage is applied to the fixed electrode A2 provided in the annular resistor 10 during the time period from time t5 to time t7 (step S14 in FIG. 9). At this time, the rising edge and falling edge of the voltage signal IN input to the signal input terminal 33 are gentler than the rising edge and falling edge of the pulse voltage applied to the fixed electrode A2.

  At time t6, since the voltage signal IN input to the signal input terminal 33 exceeds the threshold voltage VTH of the AND circuit 29, the output voltage of the input gate is switched from L level to H level. In response to this, the delay time detector 43 detects the difference between the rise time t5 of the voltage signal OUT2 applied to the fixed electrode A2 and the rise time t6 of the pulse voltage detected through the input gate as the delay time TD2. (Step S15 in FIG. 9). The data processing unit 42A finally identifies the rotation angle of the movable electrode B by comparing the detected delay time TD2 with the delay time stored in advance in the storage unit 44 (step S16 in FIG. 9).

  At time t8, since the voltage signal IN input to the signal input terminal 33 becomes equal to or lower than the threshold voltage VTH, the output voltage of the input gate is switched from the H level to the L level.

[Summary of Embodiment 2]
As described above, according to the second embodiment, the angle detection device 2 includes the first and second fixed electrodes A1 and A2, the movable electrode B, the movable electrode B, and the ground provided on the annular resistor 10. The rotation angle around the central axis 12 of the movable electrode B is detected using the capacitor 15 provided between the node GND. Specifically, the angle detection device 1 applies a pulse voltage to the fixed electrodes A1 and A2 at different timings, and delays the pulse voltage corresponding to the voltage change of the movable electrode B when the pulse voltage is applied to each fixed electrode. Detect time. The angle detection device 2 detects the rotation angle of the movable electrode B based on the detected delay time of the pulse voltage. As a result, the rotation angle can be detected with a simpler configuration than in the prior art.

  In particular, in the case of the angle detection device 2 according to the second embodiment, the rotation angle of the movable electrode B is detected based on the delay time of the pulse voltage. Therefore, the magnitude of the analog voltage is changed as in the angle detection device 1 according to the first embodiment. The ADC 27 for detection is not required. There is an advantage that the rotation angle of the movable electrode B can be detected by using a general-purpose input / output port provided in the microcomputer.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1, 2 angle detector, 10 annular resistor, 12 central axis, 13 passive element, 14 resistive element, 15 capacitor, 20, 20A microcomputer, 40 voltage applying unit, 41 voltage detecting unit, 42, 42A data processing unit, 43 delay time detection unit, 44 storage unit, 49, 49A detection unit, A1, A2 fixed electrode, B movable electrode.

Claims (5)

An annular resistor;
A first fixed electrode provided on the annular resistor;
A second fixed electrode provided on the annular resistor so that an angle around the central axis of the annular resistor is an angle other than 180 degrees with the first fixed electrode;
A movable electrode provided on the annular resistor and having a variable angle about the central axis;
A passive element connected between the movable electrode and a ground node;
A voltage applying unit that applies voltages to the first and second fixed electrodes at different timings;
The central axis of the movable electrode based on the voltage of the movable electrode when a voltage is applied to the first fixed electrode and the voltage of the movable electrode when a voltage is applied to the second fixed electrode An angle detection apparatus comprising: a detection unit that detects a turning angle. The passive element is a capacitor;
The detector is
The first delay time from when the voltage is applied to the first fixed electrode until the voltage of the movable electrode exceeds a threshold, and the voltage of the movable electrode after the voltage is applied to the second fixed electrode A delay time detector that detects a second delay time until the threshold is exceeded;
The angle detection device according to claim 1, further comprising: a data processing unit that obtains an angle value around the central axis of the movable electrode based on the first and second delay times. The detection unit further includes a storage unit that stores a plurality of the first and second delay times measured in advance with respect to a plurality of angles around the central axis of the movable electrode,
The data processing unit compares the plurality of first delay times stored in the storage unit with the first delay times detected by the delay time detection unit to detect the first delay time detected. A candidate value of an angle around the central axis of the movable electrode corresponding to the delay time of the movable electrode, and the data processing unit includes a plurality of the second delay time and the delay time detection unit stored in the storage unit The angle detection device according to claim 2, wherein an angle around the central axis of the movable electrode at the time of detection is specified from the angle candidates by comparing the second delay time detected by the step. The passive element is a resistive element;
The detector is
A first voltage value of the movable electrode when a voltage is applied to the first fixed electrode and a second voltage value of the movable electrode when a voltage is applied to the second fixed electrode are detected. A voltage detector;
The angle detection device according to claim 1, further comprising: a data processing unit that obtains a value of an angle around the central axis of the movable electrode based on the first and second voltage values.   The data processing unit calculates a first resistance value between the first fixed electrode and the movable electrode by using the first voltage value and the resistance value of the resistance element, and A candidate value of an angle around the central axis of the movable electrode corresponding to a resistance value is obtained, and the data processing unit uses the second resistance value and the resistance value of the resistance element to determine the second fixed value. The angle detection device according to claim 4, wherein a second resistance value between an electrode and the movable electrode is calculated, and an angle corresponding to the second resistance value is specified among the angle candidates.

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