Gyro sensor

Abstract

A control unit of this gyro sensor has a first injection unit, a sense circuit unit, and a first determination unit. The first injection unit generates a first addition signal obtained by adding a first test signal to a first signal and a second addition signal obtained by adding a second test signal to a second signal. The first determination unit determines whether the gyro sensor has failed on the basis of at least one among the first addition signal and the second addition signal. The first test signal is in phase with the second test signal.

Description

Gyro sensor

[0001] The present disclosure relates generally to gyro sensors, and more particularly to a gyro sensor that performs fault determination.

[0002] The gyro sensor described in Patent Document 1 includes a gyro element and a control unit electrically connected to the gyro element. An analog processing unit of the control unit selectively outputs a detection component and a quadrature component included in a detection signal to an AD conversion unit. A checker unit of the control unit performs fault diagnosis (fault determination) of the control unit based on a first output signal output from the AD conversion unit to which the quadrature component has been input, or a second output signal output from the digital calculation unit to which the first output signal has been input.

[0003] International Publication No. 2023 / 149171

[0004] A gyro sensor according to one aspect of the present disclosure includes a vibrator, multiple electrodes, multiple connection wires, and a control unit. The multiple electrodes are arranged to face the vibrator and form a capacitance between the vibrator and the multiple electrodes. The control unit is connected to the multiple electrodes via the multiple connection wires. The multiple electrodes include a drive electrode that induces drive vibration of the vibrator, a first detection electrode that outputs a first signal, and a second detection electrode that outputs a second signal. The first signal is a signal generated by applying an angular velocity to the vibrator. The second signal is a signal generated by applying an angular velocity to the vibrator and has an opposite phase to the first signal. The control unit includes an injection unit, a sense circuit unit, and a determination unit. The injection unit generates a first summed signal by adding a first test signal to the first signal and a second summed signal by adding a second test signal to the second signal. The sense circuit unit generates a detection signal corresponding to the angular velocity applied to the vibrator based on a differential signal between the first summed signal and the second summed signal. The determination unit determines whether the gyro sensor has a fault based on at least one of the first summed signal and the second summed signal. The first test signal is a signal in phase with the second test signal.

[0005] The present disclosure has an advantage in that it is possible to suppress a decrease in the detection accuracy of angular velocity in a gyro sensor while enabling a failure determination.

[0006] Fig. 1 is a block diagram of a gyro sensor according to one embodiment. Fig. 2 is a plan view of a main part of the gyro sensor. Fig. 3 is a block diagram of a gyro sensor according to a first modified example. Fig. 4 is a block diagram of a gyro sensor according to a second modified example.

[0007] (Embodiments) A gyro sensor 1 according to an embodiment will be described below with reference to the drawings. However, the following embodiment is merely one of various embodiments of the present disclosure. The following embodiment can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Furthermore, each figure described in the following embodiments is a schematic diagram, and the ratios of the sizes and thicknesses of the components in the figures do not necessarily reflect the actual dimensional ratios.

[0008] In this disclosure, "applying a voltage" to an object means applying a voltage between the object and a structure maintained at a reference potential (eg, ground).

[0009] The term "terminal" as used herein may be any component that can be electrically connected to another component. The term "terminal" may be a component such as a connector for connecting an electric wire, or may be a part of a conductor such as a wire, a printed wiring, or a metal wiring in a semiconductor.

[0010] (Overview) As shown in FIG. 1 , a gyro sensor 1 of this embodiment includes a vibrator 10, a plurality of electrodes 2, a plurality of connection wires 3, and a control unit 4. The plurality of electrodes 2 are arranged to face the vibrator 10 and form a capacitance between them. The control unit 4 is connected to the plurality of electrodes 2 via the plurality of connection wires 3. The plurality of electrodes 2 include drive electrodes (first drive electrode 21 a and second drive electrode 21 b) that induce drive vibration of the vibrator 10, a first detection electrode 22 a that outputs a first signal 91 a, and a second detection electrode 22 b that outputs a second signal 91 b. The first signal 91 a is a signal generated by applying an angular velocity to the vibrator 10. The second signal 91 b is a signal generated by applying an angular velocity to the vibrator 10 and has an opposite phase to the first signal 91 a. The control unit 4 includes an injection unit (first injection unit 51), a sense circuit unit 81, and a judgment unit (first judgment unit 71). The injection unit (first injection unit 51) generates a first summed signal 93a by adding a first test signal 92a to a first signal 91a, and a second summed signal 93b by adding a second test signal 92b to a second signal 91b. The sense circuit unit 81 generates detection signals (first detection signal 94a and second detection signal 94b) corresponding to the angular velocity applied to the vibrator 10 based on the differential signal between the first summed signal 93a and the second summed signal 93b. The judgment unit (first judgment unit 71) judges whether the gyro sensor 1 has a fault based on at least one of the first summed signal 93a and the second summed signal 93b. The first test signal 92a is a signal in phase with the second test signal 92b.

[0011] According to the above configuration, the judgment unit (first judgment unit 71) can judge whether there is a fault in the first detection electrode 22a, the second detection electrode 22b, and the electrical circuits connected thereto. Here, since the first test signal 92a is in phase with the second test signal 92b, when the sense circuit unit 81 generates a differential signal between the first summed signal 93a including the first test signal 92a and the second summed signal 93b including the second test signal 92b, the first test signal 92a and the second test signal 92b cancel each other out, resulting in a small amplitude. Preferably, the differential signal between the first summed signal 93a and the second summed signal 93b does not include the first test signal 92a or the second test signal 92b. Thus, the amplitudes of the first test signal 92a and the second test signal 92b included in the differential signal between the first summed signal 93a and the second summed signal 93b are relatively small. This reduces the degree to which the first test signal 92 a and the second test signal 92 b affect the detection signal generated by the sense circuit unit 81 based on the differential signal. That is, it reduces the degree to which the first test signal 92 a and the second test signal 92 b affect angular velocity detection as noise. This makes it possible to suppress a decrease in angular velocity detection accuracy while enabling fault determination based on at least one of the first test signal 92 a and the second test signal 92 b.

[0012] (Details) The gyro sensor 1 of this embodiment will be described in more detail below.

[0013] (1) Overall Configuration As shown in Figures 1 and 2, the gyro sensor 1 includes a vibrator 10, a plurality of electrodes 2 (six in Figures 1 and 2), a plurality of connecting wires 3 (six in Figure 1), and a control unit 4.

[0014] The plurality of electrodes 2 include a first drive electrode 21a, a second drive electrode 21b, a first detection electrode 22a, a second detection electrode 22b, a first sense feedback electrode 23a, and a second sense feedback electrode 23b.

[0015] The plurality of connection wires 3 include connection wires 31a, 31b, 32a, 32b, 33a, and 33b.

[0016] The control unit 4 includes a first series circuit SC1, a second series circuit SC2, a third series circuit SC3, and a fourth series circuit SC4. The control unit 4 also includes a first injection unit 51, a second injection unit 52, a transimpedance amplifier 61, a differential buffer 62, a first determination unit 71, a second determination unit 72, a sense circuit unit 81, a sense feedback circuit unit 82, a VI converter 83, an AD converter 84, a detection processing circuit 85, a drive circuit 86, a switching control unit 87, and an output unit 88. The control unit 4 also includes wirings L1a, L1b, L2a, L2b, L3a, and L3b. The control unit 4 also includes terminals 41a, 41b, 42a, 42b, 43a, and 43b.

[0017] (2) Vibrator and Multiple Electrodes The vibrator 10 is formed of a material containing, for example, single crystal silicon or polycrystalline silicon, etc. The shape of the vibrator 10 is, for example, a disk shape.

[0018] The plurality of electrodes 2 are arranged around the vibrator 10 at intervals between them. Each of the plurality of electrodes 2 has a facing surface facing the vibrator 10.

[0019] The plurality of electrodes 2 preferably correspond to each other in pairs. In this embodiment, the plurality of electrodes 2 include a first driving electrode 21 a and a second driving electrode 21 b that correspond to each other, a first detecting electrode 22 a and a second detecting electrode 22 b that correspond to each other, and a first sense feedback electrode 23 a and a second sense feedback electrode 23 b that correspond to each other.

[0020] 1, in order to simply show the connection relationship between the plurality of electrodes 2 and the control unit 4, two corresponding electrodes 2 are shown as being adjacent to each other. However, in reality, as shown in FIG. 2, the two corresponding electrodes 2 are arranged on opposite sides of the center 101 of the vibrator 10. In other words, the vibrator 10 is arranged between the two corresponding electrodes 2.

[0021] More specifically, the vibrator 10 is disposed between the first drive electrode 21 a and the second drive electrode 21 b. The vibrator 10 is disposed between the first sense feedback electrode 23 a and the second sense feedback electrode 23 b.

[0022] Furthermore, the vibrator 10 is disposed between the first detection electrode 22 a and the second detection electrode 22 b. Due to this arrangement, the first signal 91 a output from the first detection electrode 22 a and the second signal 91 b output from the second detection electrode 22 b are in opposite phase to each other.

[0023] 2, the axis along which the first drive electrode 21a and the second drive electrode 21b are arranged is defined as the X-axis. An axis perpendicular to the X-axis is defined as the Y-axis. In FIG. 2, the arrows representing the X-axis and the Y-axis are merely shown for the purpose of explanation and do not have any substance.

[0024] The first detection electrode 22a and the second detection electrode 22b are aligned in the Y-axis direction.

[0025] Around the periphery of vibrator 10, first sense feedback electrode 23a is disposed between first drive electrode 21a and first detection electrode 22a. Around the periphery of vibrator 10, second sense feedback electrode 23b is disposed between second drive electrode 21b and second detection electrode 22b.

[0026] (3) Multiple Connection Wires Each of the multiple connection wires 3 includes, for example, at least one of a bonding wire and a printed wiring.

[0027] The plurality of electrodes 2 are electrically connected to corresponding terminals among terminals 41a, 41b, 42a, 42b, 43a, and 43b via corresponding connection wirings 3. More specifically, the first drive electrode 21a, the second drive electrode 21b, the first detection electrode 22a, the second detection electrode 22b, the first sense feedback electrode 23a, and the second sense feedback electrode 23b are electrically connected to terminals 41a, 41b, 42a, 42b, 43a, and 43b via connection wirings 31a, 31b, 32a, 32b, 33a, and 33b, respectively.

[0028] (4) Drive Circuit The drive circuit 86 is connected to the first drive electrode 21a and the second drive electrode 21b via the connection wiring 31a, 31b and the terminals 41a, 41b, respectively. The drive circuit 86 outputs (applies) a drive signal D1 to each of the first drive electrode 21a and the second drive electrode 21b. The drive signal D1 is a voltage signal. As an example, the waveform of the drive signal D1 is a rectangular wave. Note that the waveform of the drive signal D1 may also be a sine wave. The drive signal D1 output to the first drive electrode 21a is in the opposite phase to the drive signal D1 output to the second drive electrode 21b.

[0029] When a drive signal D1 is output to at least one of the first drive electrode 21 a and the second drive electrode 21 b, the electrostatic force between the vibrator 10 and the at least one drive electrode causes the vibrator 10 to periodically vibrate (expand and contract). This vibration is referred to as drive vibration in the present disclosure.

[0030] The frequency of the drive signal D1 is, for example, 1 MHz or more and 10 MHz or less.

[0031] (5) First Signal and Second Signal When the vibrator 10 rotates, the Coriolis force causes the vibrator 10 to resonate. Then, the distance between the vibrator 10 and the first detection electrode 22a and the second detection electrode 22b changes depending on the angular velocity of the vibrator 10, and the capacitance between the vibrator 10 and the first detection electrode 22a and the second detection electrode 22b also changes. A first signal 91a corresponding to the magnitude of the capacitance between the vibrator 10 and the first detection electrode 22a is output from the first detection electrode 22a. A second signal 91b corresponding to the magnitude of the capacitance between the vibrator 10 and the second detection electrode 22b is output from the second detection electrode 22b. The first signal 91a and the second signal 91b are signals corresponding to the magnitude of the angular velocity of the vibrator 10.

[0032] The first signal 91a and the second signal 91b are signals of opposite phase to each other. In the present disclosure, "two signals of opposite phase to each other" means that when one signal has a positive sign, the other signal has a negative sign. The two signals of opposite phase to each other may have different amplitudes.

[0033] The amplitude of the first signal 91 a is preferably equal to the amplitude of the second signal 91 b. In this disclosure, "equal" does not necessarily mean that the two values ​​are completely equal, but also includes that the two values ​​are substantially equal. For example, the two values ​​may be considered equal if the difference between the two values ​​is 10% or less of the larger of the two values.

[0034] 1, the transimpedance amplifier 61 has a first input terminal 61 a, a second input terminal 61 b, a first output terminal 61 c, and a second output terminal 61 d. The transimpedance amplifier 61 converts signals input to the first input terminal 61 a and the second input terminal 61 b ​​from current signals to voltage signals, and outputs the voltage signals from the first output terminal 61 c and the second output terminal 61 d.

[0035] The first input terminal 61a is electrically connected to the terminal 42a via the wiring L1a, and therefore is electrically connected to the first detection electrode 22a.

[0036] The second input terminal 61b is electrically connected to the terminal 42b via the wiring L1b, and therefore to the second detection electrode 22b.

[0037] The first output terminal 61c is electrically connected to the sense circuit unit 81 via a line L2a. The second output terminal 61d is electrically connected to the sense circuit unit 81 via a line L2b.

[0038] (7) First Series Circuit and Second Series Circuit The first series circuit SC1 includes a first capacitor C1 and a first switch S1. The first series circuit SC1 is a circuit in which the first capacitor C1 and the first switch S1 are connected in series with each other.

[0039] A first end of the first series circuit SC1 is electrically connected to the wiring L1a. A second end of the first series circuit SC1 is electrically connected to ground. A first capacitor C1 and a first switch S1 are inserted between the first and second ends of the first series circuit SC1.

[0040] Therefore, as shown in FIG. 1, the first series circuit SC1 is inserted between the first detection electrode 22a and the ground.

[0041] The second series circuit SC2 includes a second capacitor C2 and a second switch S2, and is a circuit in which the second capacitor C2 and the second switch S2 are connected in series with each other.

[0042] A first end of the second series circuit SC2 is electrically connected to the line L1b. A second end of the second series circuit SC2 is electrically connected to ground. A second capacitor C2 and a second switch S2 are inserted between the first and second ends of the second series circuit SC2.

[0043] Therefore, as shown in FIG. 1, the second series circuit SC2 is inserted between the second detection electrode 22b and the ground.

[0044] The switching control unit 87 controls the on / off of the first switch S1 and the second switch S2. The switching control unit 87 includes, for example, a computer system having one or more processors and a memory. At least some of the functions of the switching control unit 87 are realized by the processor of the computer system executing a program recorded in the memory of the computer system. The program may be recorded in the memory, or may be provided via a telecommunications line such as the Internet, or may be provided by being recorded on a non-transitory recording medium (such as a memory card) readable by the computer system.

[0045] (8) First Injection Unit The first injection unit 51 generates a first test signal 92a and a second test signal 92b. The first test signal 92a is a signal in phase with the second test signal 92b. In the present disclosure, two signals being in phase with each other means that when one signal has a positive sign, the other signal has a positive sign, and when one signal has a negative sign, the other signal has a negative sign. Two signals that are in phase with each other may have different amplitudes.

[0046] In this embodiment, the first test signal 92a is the same as the second test signal 92b. That is, the first test signal 92a is completely identical to the second test signal 92b. The amplitude of the first test signal 92a is equal to the amplitude of the second test signal 92b.

[0047] The frequency of the first test signal 92a and the second test signal 92b is, for example, not less than 1 MHz and not more than 10 MHz.

[0048] As an example, the waveforms of the first test signal 92a and the second test signal 92b are square waves, but the waveforms of the first test signal 92a and the second test signal 92b may also be sine waves.

[0049] The first injection part 51 is electrically connected to the lines L1a and L1b at a stage subsequent to the first series circuit SC1 and the second series circuit SC2.

[0050] The first injection unit 51 is electrically connected to the line L1a. The first injection unit 51 outputs a first test signal 92a to the line L1a. As a result, a first summed signal 93a is generated by adding the first test signal 92a to the first signal 91a. The first summed signal 93a is input to a first input terminal 61a of the transimpedance amplifier 61.

[0051] The first injection unit 51 is electrically connected to the line L1b. The first injection unit 51 outputs a second test signal 92b to the line L1b. As a result, a second sum signal 93b is generated by adding the second test signal 92b to the second signal 91b. The second sum signal 93b is input to the second input terminal 61b of the transimpedance amplifier 61.

[0052] Resistors may be provided between the wiring L1a and the branch points of the first injection part 51 to the wirings L1a and L1b, and between the wiring L1a and L1b. These resistors can prevent electrical short circuits between the wirings L1a and L1b.

[0053] The connection between the first injection unit 51 and the wirings L1a and L1b can be simplified in configuration because the wirings L1a and L1b are connected to the transimpedance amplifier 61. Specifically, the first signal 91a and the first test signal 92a can be added, and the second signal 91b and the second test signal 92b can be added, simply by connecting the first injection unit 51 to the wirings L1a and L1b without using an adder.

[0054] (9) First Determination Unit The first determination unit 71 is electrically connected to the wirings L2a and L2b. The first determination unit 71 receives the first summed signal 93a and the second summed signal 93b via the wirings L2a and L2b. The first determination unit 71 may receive only one of the first summed signal 93a and the second summed signal 93b.

[0055] The first summed signal 93a and the second summed signal 93b acquired by the first determination unit 71 are voltage signals.

[0056] The first determination unit 71 determines whether or not there is a failure in the gyro sensor 1 based on at least one of the first sum signal 93 a and the second sum signal 93 b. The first determination unit 71 determines whether or not there is a failure in the gyro sensor 1 when the control unit 4 is connected to the plurality of electrodes 2 via the plurality of connection wires 3 and when the control unit 4 is not connected to the plurality of electrodes 2.

[0057] Hereinafter, the state in which the control unit 4 is connected to the first detection electrode 22a and the second detection electrode 22b via the connection wirings 32a and 32b will be referred to as a "detection connection state."

[0058] As an example, the first determination unit 71 compares the peak value of at least one of the first summed signal 93a and the second summed signal 93b with a corresponding threshold value to determine whether there is a fault in the gyro sensor 1. More specifically, the first determination unit 71 compares the peak value of at least one of the first summed signal 93a and the second summed signal 93b with a plurality of corresponding threshold values ​​to narrow down the location of the fault in the gyro sensor 1.

[0059] (9.1) When the first switch and the second switch are off Let us assume a case where the detection connection state is established and the first switch S1 and the second switch S2 are off (the first detection electrode 22a and the second detection electrode 22b are not grounded via the first capacitor C1 and the second capacitor C2).

[0060] The multiple thresholds corresponding to the first summed signal 93a include a first threshold, a second threshold, a third threshold, and a fourth threshold. The first threshold is greater than the second threshold. The second threshold is greater than the third threshold. The third threshold is greater than the fourth threshold.

[0061] If the peak value of the first summed signal 93a is greater than the first threshold, the first determination unit 71 determines that a fault has occurred in the first detection electrode 22a. If the peak value of the first summed signal 93a is smaller than the second threshold and greater than the third threshold, the first determination unit 71 determines that a fault has occurred in the first detection electrode 22a. If the peak value of the first summed signal 93a is smaller than the fourth threshold, the first determination unit 71 determines that a fault has occurred in the connecting wiring 32a.

[0062] A state in which a foreign object is present between the vibrator 10 and the first detection electrode 22a is an example of a fault state of the gyro sensor 1. In this case, the capacitance between the vibrator 10 and the first detection electrode 22a becomes larger or smaller than in a normal state (when there is no fault).

[0063] The state in which the peak value of the first summed signal 93a is greater than the first threshold value corresponds to a state in which the capacitance between the vibrator 10 and the first detection electrode 22a is greater than normal.

[0064] The state in which the peak value of the first summed signal 93a is smaller than the second threshold value and larger than the third threshold value corresponds to a state in which the capacitance between the vibrator 10 and the first detection electrode 22a is smaller than normal.

[0065] The state in which the peak value of the first sum signal 93a is smaller than the fourth threshold corresponds to, for example, a state in which the connection wiring 32a is broken.

[0066] Furthermore, the multiple thresholds corresponding to the second sum signal 93b include a fifth threshold, a sixth threshold, a seventh threshold, and an eighth threshold. The fifth threshold is greater than the sixth threshold. The sixth threshold is greater than the seventh threshold. The seventh threshold is greater than the eighth threshold.

[0067] If the peak value of the second summed signal 93b is greater than the fifth threshold, the first determination unit 71 determines that a fault has occurred in the second detection electrode 22b. If the peak value of the second summed signal 93b is less than the sixth threshold and greater than the seventh threshold, the first determination unit 71 determines that a fault has occurred in the second detection electrode 22b. If the peak value of the second summed signal 93b is less than the eighth threshold, the first determination unit 71 determines that a fault has occurred in the connecting wiring 32b.

[0068] A state in which a foreign object is present between the vibrator 10 and the second detection electrode 22b is an example of a fault state of the gyro sensor 1. In this case, the capacitance between the vibrator 10 and the second detection electrode 22b becomes larger or smaller than in a normal state (when there is no fault).

[0069] The state in which the peak value of the second summed signal 93b is greater than the fifth threshold corresponds to a state in which the capacitance between the vibrator 10 and the second detection electrode 22b is greater than normal.

[0070] The state in which the peak value of the second summed signal 93b is smaller than the sixth threshold and larger than the seventh threshold corresponds to a state in which the capacitance between the vibrator 10 and the second detection electrode 22b is smaller than normal.

[0071] The state in which the peak value of the second sum signal 93b is smaller than the eighth threshold corresponds to, for example, a state in which the connection wiring 32b is broken.

[0072] (9.2) When the first switch and the second switch are on Next, assume that the first switch S1 and the second switch S2 are on (the first detection electrode 22a and the second detection electrode 22b are grounded via the first capacitor C1 and the second capacitor C2).

[0073] The plurality of thresholds corresponding to the first sum signal 93a include a ninth threshold and a tenth threshold, which are values ​​set according to the capacitance of the first capacitor C1.

[0074] When the detection connection state is not established, the peak value of the first summed signal 93a corresponds to the capacitance of the first capacitor C1. When the detection connection state is not established and the peak value of the first summed signal 93a is smaller than the ninth threshold, the first determination unit 71 determines that a fault, such as a break, has occurred in the electrical path from the first series circuit SC1 to the first determination unit 71 (e.g., the wiring L1a and wiring L2a). In this way, by turning on the first switch S1 when the detection connection state is not established, a fault in the control unit 4 can be determined separately from a fault in the vibrator 10, the plurality of electrodes 2, and the plurality of connecting wirings 3. In other words, the location of the fault can be narrowed down.

[0075] The peak value of the first summed signal 93a in the detection connection state corresponds to the combined capacitance of the capacitance of the first capacitor C1 and the capacitance between the first detection electrode 22a and the vibrator 10. In other words, by turning on the first switch S1, the apparent capacitance between the first detection electrode 22a and the vibrator 10 increases by the capacitance of the first capacitor C1. In this way, by turning on the first switch S1, it is possible to intentionally create a state in which the capacitance between the first detection electrode 22a and the vibrator 10 is abnormal.

[0076] When the peak value of the first summed signal 93a is smaller than the tenth threshold in the detection connection state, the first determination unit 71 determines that a fault has occurred in at least one of the first determination unit 71 and the first injection unit 51. That is, if the first determination unit 71 and the first injection unit 51 are normal, the peak value of the first summed signal 93a corresponding to the combined capacitance will be relatively large. More specifically, if the first determination unit 71 and the first injection unit 51 are normal, the peak value of the first summed signal 93a corresponding to the combined capacitance will be approximately the same as the peak value when the first determination unit 71 determines that a fault has occurred when the first switch S1 is off. Conversely, if the peak value of the first summed signal 93a corresponding to the combined capacitance is relatively small and smaller than the tenth threshold, it can be determined that a fault has occurred in at least one of the first determination unit 71 and the first injection unit 51.

[0077] If a failure occurs in at least one of the first determination unit 71 and the first injection unit 51, there is a possibility that the first determination unit 71 will not be able to detect the failure in the gyro sensor 1. In other words, the failure in at least one of the first determination unit 71 and the first injection unit 51 is a so-called latent failure.

[0078] Furthermore, the multiple thresholds corresponding to the second sum signal 93b include an eleventh threshold and a twelfth threshold, which are values ​​set according to the capacitance of the second capacitor C2.

[0079] When the detection connection state is not established, the peak value of the second summed signal 93b corresponds to the capacitance of the second capacitor C2. When the detection connection state is not established and the peak value of the second summed signal 93b is smaller than the eleventh threshold, the first determination unit 71 determines that a fault, such as a break, has occurred in the electrical path from the second series circuit SC2 to the first determination unit 71 (e.g., the wiring L1b and the wiring L2b). In this way, by turning on the second switch S2 when the detection connection state is not established, a fault in the control unit 4 can be determined separately from a fault in the vibrator 10, the plurality of electrodes 2, and the plurality of connecting wirings 3. In other words, the location of the fault can be narrowed down.

[0080] The peak value of the second summed signal 93b in the detection connection state corresponds to the combined capacitance of the capacitance of the second capacitor C2 and the capacitance between the second detection electrode 22b and the vibrator 10. In other words, by turning on the second switch S2, the apparent capacitance between the second detection electrode 22b and the vibrator 10 increases by the capacitance of the second capacitor C2. In this way, by turning on the second switch S2, it is possible to intentionally create a state in which the capacitance between the second detection electrode 22b and the vibrator 10 is abnormal.

[0081] In the detection connection state, if the peak value of the second summed signal 93b is smaller than the twelfth threshold, the first determination unit 71 determines that a fault has occurred in at least one of the first determination unit 71 and the first injection unit 51. That is, if the first determination unit 71 and the first injection unit 51 are normal, the peak value of the second summed signal 93b corresponding to the combined capacitance will be relatively large. More specifically, if the first determination unit 71 and the first injection unit 51 are normal, the peak value of the second summed signal 93b corresponding to the combined capacitance will be approximately the same as the peak value when the first determination unit 71 determines that a fault has occurred when the second switch S2 is off. Conversely, if the peak value of the second summed signal 93b corresponding to the combined capacitance is relatively small and smaller than the twelfth threshold, it can be determined that a fault has occurred in at least one of the first determination unit 71 and the first injection unit 51.

[0082] In this way, in the detection connection state, with the first switch S1 and the second switch S2 both on, the first determination unit 71 can determine whether there is a failure in the first determination unit 71 and the first injection unit 51. That is, in this case, the first determination unit 71 can determine whether there is a latent failure (a state in which the first determination unit 71 cannot detect a failure in the gyro sensor 1).

[0083] (10) Sense Circuit Unit The sense circuit unit 81 acquires the first summed signal 93a and the second summed signal 93b. The sense circuit unit 81 generates two detection signals based on the differential signal between the first summed signal 93a and the second summed signal 93b. The two detection signals are a first detection signal 94a and a second detection signal 94b.

[0084] The first summed signal 93a includes the first test signal 92a, and the second summed signal 93b includes the second test signal 92b, with the first test signal 92a being in phase with the second test signal 92b. Therefore, when the difference between the first summed signal 93a and the second summed signal 93b is calculated, the first test signal 92a and the second test signal 92b cancel each other out, resulting in a smaller amplitude. In other words, the amplitudes of the first test signal 92a and the second test signal 92b included in the differential signal are smaller than the first test signal 92a included in the first summed signal 93a and the second test signal 92b included in the second summed signal 93b. Preferably, the differential signal does not include the first test signal 92a and the second test signal 92b.

[0085] The sense circuit 81 demodulates the differential signal using the drive signal D1 to generate a first detection signal 94a and a second detection signal 94b. The first detection signal 94a is a signal having an opposite phase to the second detection signal 94b.

[0086] The first detection signal 94 a and the second detection signal 94 b each include a signal component corresponding to the magnitude of the angular velocity of the vibrator 10 .

[0087] The sense circuit section 81 outputs the first detection signal 94 a and the second detection signal 94 b to the detection processing circuit 85 via the VI converter 83 and the AD converter 84 .

[0088] (11) Detection of Angular Velocity The VI converter 83 converts the voltage signal into a current signal. The VI converter 83 includes, for example, a transconductance amplifier. The AD converter 84 converts the analog signal into a digital signal.

[0089] The VI converter 83 converts the first detection signal 94 a and the second detection signal 94 b, which are voltage signals, into current signals. The current signals output from the VI converter 83 are analog signals, which are converted into digital signals by the AD converter 84 and then input to the detection processing circuit 85.

[0090] The detection processing circuit 85 generates an angular velocity signal representing the angular velocity of the vibrator 10 based on the input first detection signal 94a and second detection signal 94b (digital signals). In other words, the detection processing circuit 85 detects the angular velocity of the vibrator 10.

[0091] As described above, the first test signal 92a and the second test signal 92b cancel each other out in the sense circuit unit 81, and then the first detection signal 94a and the second detection signal 94b are generated in the sense circuit unit 81. The detection processing circuit 85 generates an angular velocity signal based on the first detection signal 94a and the second detection signal 94b. Therefore, it is possible to reduce the influence (noise) of the first test signal 92a and the second test signal 92b on the angular velocity signal generated in the detection processing circuit 85.

[0092] At least one of the first detection signal 94 a and the second detection signal 94 b may be input to the detection processing circuit 85. The detection processing circuit 85 may generate an angular velocity signal representing the angular velocity of the vibrator 10 based on at least one of the first detection signal 94 a and the second detection signal 94 b.

[0093] The detection processing circuit 85 may generate an angular velocity signal based on the differential signal between the first detection signal 94a and the second detection signal 94b.

[0094] (12) Sense Feedback Circuit Unit The sense circuit unit 81 outputs a first detection signal 94 a and a second detection signal 94 b to the sense feedback circuit unit 82 .

[0095] The sense feedback circuit unit 82 generates a first control signal 95a and a second control signal 95b that is opposite in phase to the first control signal 95a based on the first detection signal 94a and the second detection signal 94b. More specifically, the sense feedback circuit unit 82 generates a first modulated signal by modulating the first detection signal 94a using the drive signal D1, and generates the first control signal 95a based on the first modulated signal. The sense feedback circuit unit 82 also generates a second modulated signal by modulating the second detection signal 94b using the drive signal D1, and generates the second control signal 95b based on the second modulated signal.

[0096] The sense feedback circuit unit 82 may generate the first control signal 95a and the second control signal 95b based on one of the first detection signal 94a and the second detection signal 94b. For example, the sense feedback circuit unit 82 may generate the first control signal 95a based on the first detection signal 94a, and generate the second control signal 95b by inverting the sign of the first control signal 95a.

[0097] The first control signal 95a and the second control signal 95b output from the sense feedback circuit 82 are input to the first sense feedback electrode 23a and the second sense feedback electrode 23b, respectively, via the differential buffer 62. More specifically, the first control signal 95a and the second control signal 95b are input as voltage signals to the first sense feedback electrode 23a and the second sense feedback electrode 23b, respectively. More specifically, as described below, a third test signal 96a is added to the first control signal 95a. A third sum signal 97a obtained by adding the first control signal 95a and the third test signal 96a is input to the first sense feedback electrode 23a. Furthermore, as described below, a fourth test signal 96b is added to the second control signal 95b. A fourth sum signal 97b obtained by adding the second control signal 95b and the fourth test signal 96b is input to the second sense feedback electrode 23b.

[0098] By applying voltages (third sum signal 97a and fourth sum signal 97b) to the first sense feedback electrode 23a and the second sense feedback electrode 23b, the amplitude of the resonant vibration of the vibrator 10 corresponding to the angular velocity of the vibrator 10 decreases. As a result, the amplitude of the angular velocity components of the first signal 91a and the second signal 91b decreases relative to the magnitude of the angular velocity of the vibrator 10. Therefore, the gyro sensor 1 can detect larger angular velocities. In other words, the dynamic range of the gyro sensor 1 is expanded.

[0099] In this way, each of the first control signal 95a and the second control signal 95b is a signal for controlling the change in capacitance between the vibrator 10 and each of the first detection electrode 22a and the second detection electrode 22b, which occurs when an angular velocity is applied to the vibrator 10.

[0100] (13) Differential Buffer The differential buffer 62 includes a first input terminal 62a, a second input terminal 62b, a first output terminal 62c, a second output terminal 62d, and a reference voltage terminal 62e.

[0101] The first output terminal 62c outputs a voltage (third sum signal 97a in FIG. 1) corresponding to the differential voltage between the reference voltage input to the reference voltage terminal 62e and the first voltage (first control signal 95a in FIG. 1) input to the first input terminal 62a.

[0102] The second output terminal 62d outputs a voltage (fourth sum signal 97b in FIG. 1) corresponding to the differential voltage between the reference voltage input to the reference voltage terminal 62e and the second voltage (second control signal 95b in FIG. 1) input to the second input terminal 62b.

[0103] The first output terminal 62c is electrically connected to the terminal 43a via a wiring L3a, and the terminal 43a is electrically connected to the first sense feedback electrode 23a via a connection wiring 33a.

[0104] The second output terminal 62d is electrically connected to the terminal 43b via a wiring L3b, and the terminal 43b is electrically connected to the second sense feedback electrode 23b via a connection wiring 33b.

[0105] (14) Second Injection Unit The second injection unit 52 generates a third test signal 96a. The third test signal 96a is a signal in phase with the fourth test signal 96b.

[0106] In this embodiment, the third test signal 96a is the same as the fourth test signal 96b. That is, the third test signal 96a is completely identical to the fourth test signal 96b. The amplitude of the third test signal 96a is equal to the amplitude of the fourth test signal 96b.

[0107] The frequency of the third test signal 96a and the fourth test signal 96b is, for example, not less than 1 MHz and not more than 10 MHz.

[0108] As an example, the waveforms of the third test signal 96a and the fourth test signal 96b are square waves, but the waveforms of the third test signal 96a and the fourth test signal 96b may also be sine waves.

[0109] The second injection unit 52 is electrically connected to the reference voltage terminal 62e of the differential buffer 62. The second injection unit 52 inputs a third test signal 96a (or a fourth test signal 96b) to the reference voltage terminal 62e. In other words, the second injection unit 52 applies the third test signal 96a (or a fourth test signal 96b) to the reference voltage terminal 62e as a reference voltage. More specifically, the second injection unit 52 applies a signal obtained by adding a DC voltage and the third test signal 96a (or a fourth test signal 96b) to the reference voltage terminal 62e.

[0110] As a result, the first output terminal 62c of the differential buffer 62 outputs a third summed signal 97a corresponding to the differential voltage between the third test signal 96a and the first voltage (first control signal 95a) input to the first input terminal 62a. Also, the second output terminal 62d of the differential buffer 62 outputs a third summed signal 97a corresponding to the differential voltage between the fourth test signal 96b and the second voltage (second control signal 95b) input to the second input terminal 62b.

[0111] As a result, the second injection unit 52 generates a third summed signal 97a by adding the third test signal 96a to the first control signal 95a, and a fourth summed signal 97b by adding the fourth test signal 96b to the second control signal 95b. More specifically, the third test signal 96a included in the third summed signal 97a is an inverse phase signal (phase-shifted signal) of the third test signal 96a output from the second injection unit 52. Similarly, the fourth test signal 96b included in the fourth summed signal 97b is an inverse phase signal (phase-shifted signal) of the fourth test signal 96b output from the second injection unit 52.

[0112] The third summed signal 97a is applied to the first sense feedback electrode 23a, and the fourth summed signal 97b is applied to the second sense feedback electrode 23b. Here, the vibrator 10 is disposed between the first sense feedback electrode 23a and the second sense feedback electrode 23b (see FIG. 2), and the third test signal 96a is a signal in phase with the fourth test signal 96b. Therefore, the third test signal 96a and the fourth test signal 96b cancel each other out in the vibrator 10, reducing the effect on the operation of the vibrator 10.

[0113] More specifically, third test signal 96a is completely identical to fourth test signal 96b. Therefore, the degree to which third test signal 96a and fourth test signal 96b affect the operation of vibrator 10 is reduced. In other words, the operation of vibrator 10 is similar to that in the case where first control signal 95a, rather than third sum signal 97a, is applied to first sense feedback electrode 23a, and second control signal 95b, rather than fourth sum signal 97b, is applied to second sense feedback electrode 23b.

[0114] As described above, the second injection unit 52 applies the third test signal 96a (or the fourth test signal 96b) to the reference voltage terminal 62e of the differential buffer 62. Therefore, compared to when the control unit 4 does not include the differential buffer 62, the circuit for injecting (outputting) the third test signal 96a and the fourth test signal 96b can be configured on a smaller scale. For example, the circuit for injecting (outputting) the third test signal 96a and the fourth test signal 96b can be configured without using an adder. Furthermore, the number of branch wirings in the electrical path between the sense feedback circuit unit 82 and the first and second sense feedback electrodes 23a and 23b can be reduced, thereby reducing noise generated in this electrical path. Therefore, the effect of noise on the operation of the gyro sensor 1 can be reduced.

[0115] (15) Third Series Circuit and Fourth Series Circuit The third series circuit SC3 includes a third capacitor C3 and a third switch S3. The third series circuit SC3 is a circuit in which the third capacitor C3 and the third switch S3 are connected in series with each other.

[0116] A first end of the third series circuit SC3 is electrically connected to the line L3a. A second end of the third series circuit SC3 is electrically connected to ground. A third capacitor C3 and a third switch S3 are inserted between the first and second ends of the third series circuit SC3.

[0117] Therefore, as shown in FIG. 1, the third series circuit SC3 is inserted between the first sense feedback electrode 23a and the ground.

[0118] The fourth series circuit SC4 includes a fourth capacitor C4 and a fourth switch S4, and is a circuit in which the fourth capacitor C4 and the fourth switch S4 are connected in series to each other.

[0119] A first end of the fourth series circuit SC4 is electrically connected to the line L3b. A second end of the fourth series circuit SC4 is electrically connected to ground. A fourth capacitor C4 and a fourth switch S4 are inserted between the first and second ends of the fourth series circuit SC4.

[0120] Therefore, as shown in FIG. 1, the fourth series circuit SC4 is inserted between the second sense feedback electrode 23b and ground.

[0121] The open / close control unit 87 controls the on / off of the third switch S3 and the fourth switch S4.

[0122] (16) Second Determination Unit The second determination unit 72 is electrically connected to the lines L3a and L3b at a stage preceding the third series circuit SC3 and the fourth series circuit SC4.

[0123] The second determination unit 72 receives the third summed signal 97a and the fourth summed signal 97b via the lines L3a and L3b. The second determination unit 72 may receive only one of the third summed signal 97a and the fourth summed signal 97b.

[0124] The third summed signal 97a and the fourth summed signal 97b acquired by the second determination unit 72 are, for example, voltage signals.

[0125] The second determination unit 72 determines whether or not there is a failure in the gyro sensor 1 based on at least one of the third sum signal 97 a and the fourth sum signal 97 b. The second determination unit 72 determines whether or not there is a failure in the gyro sensor 1 when the control unit 4 is connected to the plurality of electrodes 2 via the plurality of connection wires 3 and when the control unit 4 is not connected to the plurality of electrodes 2.

[0126] Hereinafter, the state in which the control unit 4 is connected to the first sense feedback electrode 23a and the second sense feedback electrode 23b via the connection wirings 33a and 33b will be referred to as a "feedback connection state."

[0127] As an example, the second determination unit 72 compares the peak value of at least one of the third sum signal 97a and the fourth sum signal 97b with a corresponding threshold value to determine whether there is a fault in the gyro sensor 1. More specifically, the second determination unit 72 compares the peak value of at least one of the third sum signal 97a and the fourth sum signal 97b with a plurality of corresponding threshold values ​​to narrow down the location of the fault in the gyro sensor 1.

[0128] (16.1) Case where the third switch and the fourth switch are off Let us assume a case where the feedback connection state is established and the third switch S3 and the fourth switch S4 are off (the first sense feedback electrode 23 a and the second sense feedback electrode 23 b are not grounded via the third capacitor C3 and the fourth capacitor C4).

[0129] The multiple thresholds corresponding to the third sum signal 97a include a 13th threshold, a 14th threshold, a 15th threshold, and a 16th threshold. The 13th threshold is greater than the 14th threshold. The 14th threshold is greater than the 15th threshold. The 15th threshold is greater than the 16th threshold.

[0130] If the peak value of the third sum signal 97a is greater than the thirteenth threshold, the second determination unit 72 determines that a fault has occurred in the first sense feedback electrode 23a. If the peak value of the third sum signal 97a is smaller than the fourteenth threshold and greater than the fifteenth threshold, the second determination unit 72 determines that a fault has occurred in the first sense feedback electrode 23a. If the peak value of the third sum signal 97a is smaller than the sixteenth threshold, the second determination unit 72 determines that a fault has occurred in the connecting wiring 33a.

[0131] A state in which a foreign object is present between the vibrator 10 and the first sense feedback electrode 23a is an example of a fault state of the gyro sensor 1. In this case, the capacitance between the vibrator 10 and the first sense feedback electrode 23a becomes larger or smaller than in normal times (when there is no fault).

[0132] The state in which the peak value of the third sum signal 97a is greater than the thirteenth threshold corresponds to a state in which the capacitance between the vibrator 10 and the first sense feedback electrode 23a is greater than normal.

[0133] The state in which the peak value of the third sum signal 97a is smaller than the fourteenth threshold and larger than the fifteenth threshold corresponds to a state in which the capacitance between the vibrator 10 and the first sense feedback electrode 23a is smaller than normal.

[0134] The state in which the peak value of the third sum signal 97a is smaller than the sixteenth threshold corresponds to, for example, a state in which the connection wiring 33a is broken.

[0135] Furthermore, the multiple thresholds corresponding to the fourth sum signal 97b include a 17th threshold, an 18th threshold, a 19th threshold, and a 20th threshold. The 17th threshold is greater than the 18th threshold. The 18th threshold is greater than the 19th threshold. The 19th threshold is greater than the 20th threshold.

[0136] If the peak value of the fourth sum signal 97b is greater than the 17th threshold, the second determination unit 72 determines that a fault has occurred in the second sense feedback electrode 23b. If the peak value of the fourth sum signal 97b is less than the 18th threshold and greater than the 19th threshold, the second determination unit 72 determines that a fault has occurred in the second sense feedback electrode 23b. If the peak value of the fourth sum signal 97b is less than the 20th threshold, the second determination unit 72 determines that a fault has occurred in the connecting wiring 33b.

[0137] A state in which a foreign object is present between the vibrator 10 and the second sense feedback electrode 23b is an example of a fault state of the gyro sensor 1. In this case, the capacitance between the vibrator 10 and the second sense feedback electrode 23b becomes larger or smaller than in normal times (when there is no fault).

[0138] The state in which the peak value of the fourth sum signal 97b is greater than the seventeenth threshold corresponds to a state in which the capacitance between the vibrator 10 and the second sense feedback electrode 23b is greater than normal.

[0139] The state in which the peak value of the fourth sum signal 97b is smaller than the 18th threshold and larger than the 19th threshold corresponds to a state in which the capacitance between the vibrator 10 and the second sense feedback electrode 23b is smaller than normal.

[0140] The state in which the peak value of the fourth sum signal 97b is smaller than the twentieth threshold corresponds to, for example, a state in which the connection wiring 33b is broken.

[0141] (16.2) Case where the third switch S3 and the fourth switch S4 are on Next, assume a case where the third switch S3 and the fourth switch S4 are on (a case where the first sense feedback electrode 23a and the second sense feedback electrode 23b are grounded via the third capacitor C3 and the fourth capacitor C4).

[0142] The plurality of thresholds corresponding to the third sum signal 97a include a 21st threshold and a 22nd threshold, which are values ​​set in accordance with the capacitance of the third capacitor C3.

[0143] When the feedback connection state is not established, the peak value of the third sum signal 97a corresponds to the capacitance of the third capacitor C3. When the feedback connection state is not established and the peak value of the third sum signal 97a is smaller than the 21st threshold, the second determination unit 72 determines that a fault, such as a break, has occurred in the electrical path (e.g., the wiring L3a) from the third series circuit SC3 to the second determination unit 72. In this way, by turning on the third switch S3 when the feedback connection state is not established, a fault in the control unit 4 can be determined separately from a fault in the vibrator 10, the plurality of electrodes 2, or the plurality of connecting wirings 3. In other words, the location of the fault can be narrowed down.

[0144] The peak value of the third sum signal 97a in the feedback connection state corresponds to the combined capacitance of the capacitance of the third capacitor C3 and the capacitance between the first sense feedback electrode 23a and the vibrator 10. In other words, by turning on the third switch S3, the apparent capacitance between the first sense feedback electrode 23a and the vibrator 10 increases by the capacitance of the third capacitor C3. In this way, by turning on the third switch S3, it is possible to intentionally create a state in which the capacitance between the first sense feedback electrode 23a and the vibrator 10 is abnormal.

[0145] In the feedback connection state, if the peak value of the third sum signal 97a is smaller than the 22nd threshold, the second determination unit 72 determines that a fault has occurred in at least one of the second determination unit 72 and the second injection unit 52. That is, if the second determination unit 72 and the second injection unit 52 are normal, the peak value of the third sum signal 97a corresponding to the combined capacitance will be relatively large. More specifically, if the second determination unit 72 and the second injection unit 52 are normal, the peak value of the third sum signal 97a corresponding to the combined capacitance will be approximately the same as the peak value when the second determination unit 72 determines that a fault has occurred when the third switch S3 is off. Conversely, if the peak value of the third sum signal 97a corresponding to the combined capacitance is relatively small and smaller than the 22nd threshold, it can be determined that a fault has occurred in at least one of the second determination unit 72 and the second injection unit 52.

[0146] If a failure occurs in at least one of the second determination unit 72 and the second injection unit 52, there is a possibility that the second determination unit 72 will not be able to detect the failure in the gyro sensor 1. In other words, the failure in at least one of the second determination unit 72 and the second injection unit 52 is a so-called latent failure.

[0147] Furthermore, the plurality of thresholds corresponding to the fourth sum signal 97b include a 23rd threshold and a 24th threshold, which are values ​​set according to the capacitance of the fourth capacitor C4.

[0148] When the feedback connection state is not established, the peak value of the fourth sum signal 97b corresponds to the capacitance of the fourth capacitor C4. When the feedback connection state is not established and the peak value of the fourth sum signal 97b is smaller than the 23rd threshold, the second determination unit 72 determines that a fault, such as a break, has occurred in the electrical path (e.g., wiring L3b) from the fourth series circuit SC4 to the second determination unit 72. In this way, by turning on the fourth switch S4 when the feedback connection state is not established, a fault in the control unit 4 can be determined separately from a fault in the vibrator 10, the plurality of electrodes 2, or the plurality of connecting wirings 3. In other words, the location of the fault can be narrowed down.

[0149] The peak value of the fourth sum signal 97b in the feedback connection state corresponds to the combined capacitance of the capacitance of the fourth capacitor C4 and the capacitance between the second sense feedback electrode 23b and the vibrator 10. In other words, by turning on the fourth switch S4, the apparent capacitance between the second sense feedback electrode 23b and the vibrator 10 increases by the capacitance of the fourth capacitor C4. In this way, by turning on the fourth switch S4, it is possible to intentionally create a state in which the capacitance between the second sense feedback electrode 23b and the vibrator 10 is abnormal.

[0150] In the feedback connection state, if the peak value of the fourth sum signal 97b is smaller than the 24th threshold, the second determination unit 72 determines that a fault has occurred in at least one of the second determination unit 72 and the second injection unit 52. That is, if the second determination unit 72 and the second injection unit 52 are normal, the peak value of the fourth sum signal 97b corresponding to the combined capacitance will be relatively large. More specifically, if the second determination unit 72 and the second injection unit 52 are normal, the peak value of the fourth sum signal 97b corresponding to the combined capacitance will be approximately the same as the peak value when the second determination unit 72 determines that a fault has occurred when the fourth switch S4 is off. Conversely, if the peak value of the fourth sum signal 97b corresponding to the combined capacitance is relatively small and smaller than the 24th threshold, it can be determined that a fault has occurred in at least one of the second determination unit 72 and the second injection unit 52.

[0151] In this way, in the feedback connection state, and with the third switch S3 and the fourth switch S4 both on, the second determination unit 72 can determine whether there is a failure in the second determination unit 72 and the second injection unit 52. That is, in this case, the second determination unit 72 can determine whether there is a latent failure (a state in which the second determination unit 72 cannot detect a failure in the gyro sensor 1).

[0152] (17) Output Unit The output unit 88 outputs the determination results of the first determination unit 71 and the second determination unit 72. The output unit 88 may include, for example, a display device and display the determination results on the display device. The output unit 88 may also include, for example, an acoustic device such as a speaker and output the determination results as sound (which may include voice) from the acoustic device. The output unit 88 may also include, for example, a communication module and transmit the determination results from the communication module to an external device.

[0153] (Modifications) Modifications of the embodiment are listed below. The following modifications may be implemented in appropriate combination. Hereinafter, the configuration of the above-described embodiment will be referred to as the basic example. Configurations similar to those of the basic example will be assigned the same reference numerals and descriptions thereof will be omitted.

[0154] (Modification 1) A gyro sensor 1A according to Modification 1 will be described below with reference to FIG.

[0155] The gyro sensor 1A of this modified example differs from the gyro sensor 1 of the basic example in that the control unit 4 further includes a current buffer 63 .

[0156] The current buffer 63 is inserted between the terminals 42a, 42b and the transimpedance amplifier 61. The current buffer 63 amplifies the first signal 91a output from the first detection electrode 22a and the second signal 91b output from the second detection electrode 22b, and outputs the amplified signals to the sense circuit unit 81 via the transimpedance amplifier 61. Therefore, the signal components corresponding to the magnitude of the angular velocity of the vibrator 10, which are included in the first signal 91a and the second signal 91b, are amplified by the current buffer 63. This allows the detection accuracy of the angular velocity in the detection processing circuit 85 to be improved.

[0157] The current buffer 63 is electrically connected to the terminals 42a and 42b via wiring lines L1a and L1b. A first end of the first series circuit SC1 is electrically connected to the wiring line L1a. That is, the first end of the first series circuit SC1 is electrically connected to the electrical path (wiring line L1a) between the first detection electrode 22a and the current buffer 63. A first end of the second series circuit SC2 is electrically connected to the wiring line L1b. That is, the first end of the second series circuit SC2 is electrically connected to the electrical path (wiring line L1b) between the second detection electrode 22b and the current buffer 63.

[0158] The first injection unit 51 is electrically connected to the wirings L1a and L1b. The first injection unit 51 is electrically connected to the wirings L1a and L1b at a stage subsequent to the first series circuit SC1 and the second series circuit SC2. The first injection unit 51 injects (outputs) a first test signal 92a and a second test signal 92b into the wirings L1a and L1b. That is, the first injection unit 51 injects the first test signal 92a into the electrical path (wiring L1a) between the first detection electrode 22a and the current buffer 63, and injects the second test signal 92b into the electrical path (wiring L1b) between the second detection electrode 22b and the current buffer 63.

[0159] Resistors may be provided between the wiring L1a and the branch points of the first injection part 51 to the wirings L1a and L1b, and between the wiring L1a and L1b. These resistors can prevent electrical short circuits between the wirings L1a and L1b.

[0160] The current buffer 63 is electrically connected to the transimpedance amplifier 61 via lines L4a and L4b.

[0161] The first determination unit 71 acquires the first summed signal 93a and the second summed signal 93b via the wirings L4a and L4b. That is, the first determination unit 71 acquires the first summed signal 93a and the second summed signal 93b from the electrical path (the wirings L4a and L4b) between the current buffer 63 and the transimpedance amplifier 61.

[0162] The first determination unit 71 may obtain only one of the first summed signal 93a and the second summed signal 93b.

[0163] The transimpedance amplifier 61 is electrically connected to the sense circuit unit 81 via the wirings L2a and L2b. That is, the transimpedance amplifier 61 is inserted between the current buffer 63 and the sense circuit unit 81.

[0164] The first test signal 92a and the second test signal 92b, which are in phase, cancel each other out in the transimpedance amplifier 61. The first determination unit 71 can acquire at least one of the first summed signal 93a and the second summed signal 93b from an electrical path upstream of the transimpedance amplifier 61. In other words, the first determination unit 71 can acquire the first summed signal 93a and the second summed signal 93b before the first test signal 92a and the second test signal 92b are subtracted in the transimpedance amplifier 61. This reduces the possibility that the transimpedance amplifier 61 will interfere with the first determination unit 71's determination of a fault in the gyro sensor 1A.

[0165] (Modification 2) A gyro sensor 1B according to Modification 2 will be described below with reference to FIG.

[0166] The gyro sensor 1B of this modified example differs from the gyro sensor 1 of the basic example in that the control unit 4 further includes resistors R1 and R2.

[0167] The resistor R1 is inserted between the differential buffer 62 and the first sense feedback electrode 23a, and the resistor R2 is inserted between the differential buffer 62 and the second sense feedback electrode 23b.

[0168] The third series circuit SC3 is electrically connected to the electrical path between the resistor R1 and the first sense feedback electrode 23a, and the fourth series circuit SC4 is electrically connected to the electrical path between the resistor R2 and the second sense feedback electrode 23b.

[0169] The second determination unit 72 detects the first voltage signal applied across the resistor R1 and acquires the first voltage signal obtained by converting a current generated when the third sum signal 97a is injected into capacitances (the capacitance between the vibrator 10 and the first sense feedback electrode 23a and the capacitance of the third capacitor C3) into a voltage.

[0170] The second determination unit 72 detects a second voltage signal applied across the resistor R2 and acquires a second voltage signal obtained by converting a current generated when the fourth sum signal 97b is injected into capacitances (the capacitance between the vibrator 10 and the second sense feedback electrode 23b and the capacitance of the fourth capacitor C4) into a voltage.

[0171] Even with this configuration, the second determination unit 72 can determine whether the gyro sensor 1 has a malfunction.

[0172] (Modification 3) A gyro sensor 1 according to Modification 3 will be described below.

[0173] In the basic example, the first determination unit 71 determines whether the gyro sensor 1 has a malfunction by comparing the peak value of the first sum signal 93a and the peak value of the second sum signal 93b with the corresponding threshold values.

[0174] In contrast, in this modified example, the first determination unit 71 compares the difference between the peak value of the first summed signal 93a and the peak value of the second summed signal 93b with a threshold value to determine whether or not there is a failure in the gyro sensor 1. More specifically, if the absolute value of the difference between the peak value of the first summed signal 93a and the peak value of the second summed signal 93b is greater than the threshold value, the first determination unit 71 determines that a failure has occurred in at least one of the first detection electrode 22a and the second detection electrode 22b.

[0175] A state in which a foreign object exists between the vibrator 10 and the first detection electrode 22 a is an example of a fault state in the first detection electrode 22 a. A state in which a foreign object exists between the vibrator 10 and the second detection electrode 22 b is an example of a fault state in the second detection electrode 22 b.

[0176] (Modification 4) A gyro sensor 1 according to Modification 4 will be described below.

[0177] In the basic example, the second determination unit 72 determines whether the gyro sensor 1 has a malfunction by comparing the peak value of the third sum signal 97a and the peak value of the fourth sum signal 97b with the corresponding threshold values.

[0178] In contrast, in this modification, the second determination unit 72 compares the difference between the peak value of the third sum signal 97a and the peak value of the fourth sum signal 97b with a threshold value to determine whether or not there is a failure in the gyro sensor 1. More specifically, if the absolute value of the difference between the peak value of the third sum signal 97a and the peak value of the fourth sum signal 97b is greater than the threshold value, the second determination unit 72 determines that a failure has occurred in at least one of the first sense feedback electrode 23a and the second sense feedback electrode 23b.

[0179] A state in which a foreign object exists between the vibrator 10 and the first sense feedback electrode 23 a is an example of a fault state in the first sense feedback electrode 23 a. A state in which a foreign object exists between the vibrator 10 and the second sense feedback electrode 23 b is an example of a fault state in the second sense feedback electrode 23 b.

[0180] (Other Modifications) Other modifications of the embodiment are listed below. The following modifications may be realized in appropriate combination. Furthermore, the following modifications may be realized in appropriate combination with the above-described modifications.

[0181] The fault determination process by the first determination unit 71 and the second determination unit 72 shown in the basic example is merely an example. For example, the first determination unit 71 and the second determination unit 72 may perform fault determination using a threshold value different from the above-described threshold value.

[0182] The first determination unit 71 may determine whether the gyro sensor 1 has a malfunction based on only one of the first sum signal 93a and the second sum signal 93b.

[0183] The second determination unit 72 may determine whether the gyro sensor 1 has a malfunction based on only one of the third sum signal 97a and the fourth sum signal 97b.

[0184] The sense circuit section 81 may generate only one of the first detection signal 94a and the second detection signal 94b.

[0185] The control unit 4 may have one or more of the first series circuit SC1, the second series circuit SC2, the third series circuit SC3, and the fourth series circuit SC4, or may have none of them.

[0186] The control unit 4 may include an adder that adds the first test signal 92 a and the second test signal 92 b output from the first injection unit 51 to the first signal 91 a and the second signal 91 b, respectively. In this case, the control unit 4 does not need to include the transimpedance amplifier 61.

[0187] The control unit 4 may include an adder that adds the third test signal 96 a and the fourth test signal 96 b output from the second injection unit 52 to the first control signal 95 a and the second control signal 95 b, respectively. In this case, the control unit 4 does not need to include the differential buffer 62.

[0188] The gyro sensor 1 does not necessarily have to include the sense feedback circuit unit 82, the first sense feedback electrode 23a, the second sense feedback electrode 23b, and the components between the sense feedback circuit unit 82 and the first sense feedback electrode 23a and the second sense feedback electrode 23b (the differential buffer 62, the second injection unit 52, the second judgment unit 72, the third series circuit SC3, the fourth series circuit SC4, etc.).

[0189] The first test signal 92a, the second test signal 92b, the third test signal 96a, and the fourth test signal 96b may be the same signal.

[0190] (Summary) The above-described embodiments and the like disclose the following aspects.

[0191] A gyro sensor (1; 1A; 1B) according to a first aspect includes a vibrator (10), a plurality of electrodes (2), a plurality of connection wirings (3), and a control unit (4). The plurality of electrodes (2) are arranged to face the vibrator (10) and form a capacitance between the vibrator (10). The control unit (4) is connected to the plurality of electrodes (2) via the plurality of connection wirings (3). The plurality of electrodes (2) include drive electrodes (first drive electrode 21a, second drive electrode 21b) that induce drive vibration of the vibrator (10), a first detection electrode (22a) that outputs a first signal (91a), and a second detection electrode (22b) that outputs a second signal (91b). The first signal (91a) is a signal generated when an angular velocity is applied to the vibrator (10). The second signal (91b) is a signal generated by applying an angular velocity to the vibrator (10) and is a signal of opposite phase to the first signal (91a). The control unit (4) has a first injection unit (51), a sense circuit unit (81), and a first determination unit (71). The first injection unit generates a first summed signal (93a) by adding a first test signal (92a) to the first signal (91a) and a second summed signal (93b) by adding a second test signal (92b) to the second signal (91b). The sense circuit unit (81) generates detection signals (first detection signal 94a and second detection signal 94b) corresponding to the angular velocity applied to the vibrator (10) based on the differential signal between the first summed signal (93a) and the second summed signal (93b). The first determination unit determines whether the gyro sensor (1; 1A; 1B) has a fault based on at least one of the first summed signal (93a) and the second summed signal (93b). The first test signal (92a) is a signal in phase with the second test signal (92b).

[0192] According to the above configuration, it is possible to suppress a decrease in the accuracy of detecting angular velocity while making it possible to determine a failure based on at least one of the first test signal (92a) and the second test signal (92b).

[0193] In the gyro sensor (1; 1A; 1B) according to the second aspect, in the first aspect, the control unit (4) further includes a first series circuit (SC1) including a first capacitor (C1) and a first switch (S1), and a second series circuit (SC2) including a second capacitor (C2) and a second switch (S2). The first series circuit (SC1) is inserted between the first detection electrode (22a) and ground. The second series circuit (SC2) is inserted between the second detection electrode (22b) and ground.

[0194] According to the above configuration, when the control unit (4) is not connected to the first detection electrode (22 a) and the second detection electrode (22 b), the first determination unit (71) can determine whether or not there is a failure (e.g., a disconnection failure) in the control unit (4) by turning on the first switch (S1) and the second switch (S2). Also, when the control unit (4) is connected to the first detection electrode (22 a) and the second detection electrode (22 b), the first determination unit can determine whether or not there is a failure in the first determination unit and the first injection unit (51) by turning on the first switch (S1) and the second switch (S2).

[0195] In a gyro sensor (1A) according to a third aspect, in the first or second aspect, the control unit (4) further includes a current buffer (63) and a transimpedance amplifier (61). The transimpedance amplifier (61) is inserted between the current buffer (63) and the sense circuit unit (81). The first injection unit (51) injects a first test signal (92a) into an electrical path between the first detection electrode (22a) and the current buffer (63), and injects a second test signal (92b) into an electrical path between the second detection electrode (22b) and the current buffer (63). The first determination unit (71) acquires at least one of a first summed signal (93a) and a second summed signal (93b) from the electrical path between the current buffer (63) and the transimpedance amplifier (61).

[0196] According to the above configuration, it is possible to reduce the possibility that the transimpedance amplifier (61) will interfere with the determination of a failure in the gyro sensor (1A) by the determination unit.

[0197] Furthermore, in a gyro sensor (1; 1A; 1B) according to a fourth aspect, in any one of the first to third aspects, the control unit (4) further includes a sense feedback circuit unit (82), a second injection unit (52), and a second determination unit (72). The sense feedback circuit unit (82) generates a first control signal (95a) and a second control signal (95b) that is in opposite phase to the first control signal (95a) based on the detection signals (first detection signal 94a and second detection signal 94b). The second injection unit (52) generates a third summed signal (97a) by adding a third test signal (96a) to the first control signal (95a), and a fourth summed signal (97b) by adding a fourth test signal (96b) to the second control signal (95b). The second determination unit (72) determines a fault in the gyro sensor (1; 1A; 1B) based on at least one of the third summed signal (97a) and the fourth summed signal (97b). The plurality of electrodes (2) further includes a first sense feedback electrode (23a) to which a first control signal (95a) is applied and a second sense feedback electrode (23b) to which a second control signal (95b) is applied. The vibrator (10) is disposed between the first sense feedback electrode (23a) and the second sense feedback electrode (23b). The first control signal (95a) and the second control signal (95b) are signals for controlling changes in capacitance between the vibrator (10) and each of the first detection electrode (22a) and the second detection electrode (22b), which occur when an angular velocity is applied to the vibrator (10). The third test signal (96a) is a signal in phase with the fourth test signal (96b).

[0198] According to the above configuration, the second determination unit (72) can determine whether there is a fault in the first sense feedback electrode (23a), the second sense feedback electrode (23b), and the electrical circuits connected thereto. Here, since the third test signal (96a) and the fourth test signal (96b) are in phase with each other, they cancel each other out in the vibrator (10), reducing their effect on the operation of the vibrator (10). Preferably, the third test signal (96a) and the fourth test signal (96b) completely cancel each other out in the vibrator (10). In this way, the degree to which the third test signal (96a) and the fourth test signal (96b) affect the operation of the vibrator (10) can be reduced.

[0199] In the gyro sensor (1; 1A; 1B) according to the fifth aspect, in the fourth aspect, the control unit (4) further includes a third series circuit (SC3) including a third capacitor (C3) and a third switch (S3), and a fourth series circuit (SC4) including a fourth capacitor (C4) and a fourth switch (S4). The third series circuit (SC3) is inserted between the first sense feedback electrode (23 a) and ground. The fourth series circuit (SC4) is inserted between the second sense feedback electrode (23 b) and ground.

[0200] According to the above configuration, when the control unit (4) is not connected to the first sense feedback electrode (23 a) and the second sense feedback electrode (23 b), the second determination unit (72) can determine whether or not there is a fault (e.g., a disconnection fault) in the control unit (4) by turning on the third switch (S3) and the fourth switch (S4). Also, when the control unit (4) is connected to the first sense feedback electrode (23 a) and the second sense feedback electrode (23 b), the second determination unit (72) can determine whether or not there is a fault in the second determination unit (72) and the second injection unit (52) by turning on the third switch (S3) and the fourth switch (S4).

[0201] In addition, in a gyro sensor (1; 1A; 1B) according to a sixth aspect, in the fourth or fifth aspect, the control unit (4) has a differential buffer (62). The differential buffer (62) includes a reference voltage terminal (62e), a first input terminal (62a), a second input terminal (62b), a first output terminal (62c), and a second output terminal (62d). The first output terminal (62c) outputs a voltage corresponding to a differential voltage between a reference voltage input to the reference voltage terminal (62e) and a first voltage input to the first input terminal (62a). The second output terminal (62d) outputs a voltage corresponding to a differential voltage between the reference voltage and a second voltage input to the second input terminal (62b). The third test signal (96a) is the same signal as the fourth test signal (96b). The second injection section (52) applies a third test signal (96a) as a reference voltage to the reference voltage terminal (62e) of the differential buffer (62).

[0202] According to the above configuration, noise on the electrical path downstream of the sense feedback circuit unit (82) can be reduced compared to when the second injection unit (52) is connected to the electrical path downstream of the sense feedback circuit unit (82) without going through the differential buffer (62).

[0203] In addition, in the gyro sensor (1; 1A; 1B) according to the seventh aspect, in any one of the first to sixth aspects, the first judgment unit (71) compares the peak value of at least one of the first summed signal (93a) and the second summed signal (93b) with a corresponding threshold value to make a fault judgment of the gyro sensor (1; 1A; 1B).

[0204] According to the above configuration, a fault can be determined by a relatively simple process.

[0205] In addition, in the gyro sensor (1; 1A; 1B) according to the eighth aspect, in any one of the first to seventh aspects, the first judgment unit (71) narrows down the location of a fault in the gyro sensor (1; 1A; 1B) by comparing the peak value of at least one of the first summed signal (93a) and the second summed signal (93b) with a corresponding plurality of threshold values.

[0206] According to the above configuration, the location of the failure can be narrowed down.

[0207] In addition, in the gyro sensor (1; 1A; 1B) according to the ninth aspect, in any one of the first to eighth aspects, the first judgment unit (71) judges whether the gyro sensor (1; 1A; 1B) has a fault by comparing the difference between the peak value of the first sum signal (93a) and the peak value of the second sum signal (93b) with a threshold value.

[0208] According to the above configuration, a fault can be determined by a relatively simple process.

[0209] In addition, in the gyro sensor (1; 1A; 1B) according to the tenth aspect, in any one of the first to ninth aspects, the amplitude of the first test signal (92a) is equal to the amplitude of the second test signal (92b).

[0210] According to the above configuration, the effect of the first test signal (92a) and the second test signal (92b) canceling each other out is enhanced.

[0211] The configurations other than the first aspect are not essential for the gyro sensor (1; 1A; 1B) and can be omitted as appropriate.

[0212] 1, 1A, 1B Gyro sensor 2 Electrode 3 Connection wiring 4 Control unit 10 Vibrator 21a First drive electrode (drive electrode) 21b Second drive electrode (drive electrode) 22a First detection electrode 22b Second detection electrode 23a First sense feedback electrode 23b Second sense feedback electrode 51 First injection unit (injection unit) 52 Second injection unit 61 Transimpedance amplifier 62 Differential buffer 62a First input terminal 62b Second input terminal 62c First output terminal 62d Second output terminal 62e Reference voltage terminal 63 Current buffer 71 First judgment unit (judgment unit) 72 Second judgment unit 81 Sense circuit unit 82 Sense feedback circuit unit 91a First signal 91b Second signal 92a First test signal 92b Second test signal 93a First summed signal 93b Second summed signal 94a First detection signal (detection signal) 94b Second detection signal (detection signal) 95a First control signal 95b Second control signal 96a Third test signal 96b Fourth test signal 97a Third summed signal 97b Fourth summed signal C1 First capacitor C2 Second capacitor C3 Third capacitor C4 Fourth capacitor S1 First switch S2 Second switch S3 Third switch S4 Fourth switch SC1 First series circuit SC2 Second series circuit SC3 Third series circuit SC4 Fourth series circuit

Claims

1. A gyro sensor comprising: a vibrator; a plurality of electrodes arranged to face the vibrator and forming a capacitance between the vibrator and the vibrator; a plurality of connection wires; and a control unit connected to the plurality of electrodes via the plurality of connection wires, wherein the plurality of electrodes include: a drive electrode that induces drive vibration of the vibrator; a first detection electrode that outputs a first signal generated by application of an angular velocity to the vibrator; and a second detection electrode that outputs a second signal that is generated by application of an angular velocity to the vibrator and has an opposite phase to the first signal; the control unit has: a first injection unit that generates a first summed signal by adding a first test signal to the first signal and a second summed signal by adding a second test signal to the second signal; a sense circuit unit that generates a detection signal according to the angular velocity applied to the vibrator based on a differential signal between the first summed signal and the second summed signal; and a first judgment unit that judges a failure of the gyro sensor based on at least one of the first summed signal and the second summed signal. The gyro sensor, wherein the first test signal is a signal in phase with the second test signal.

2. The gyro sensor of claim 1, wherein the control unit further has: a first series circuit of a first capacitor and a first switch inserted between the first detection electrode and ground; and a second series circuit of a second capacitor and a second switch inserted between the second detection electrode and ground.

3. The gyro sensor of claim 1, wherein the control unit further comprises: a current buffer; and a transimpedance amplifier inserted between the current buffer and the sense circuit unit; the first injection unit injects the first test signal into an electrical path between the first detection electrode and the current buffer, and injects the second test signal into an electrical path between the second detection electrode and the current buffer; and the first determination unit acquires at least one of the first sum signal and the second sum signal from the electrical path between the current buffer and the transimpedance amplifier.

4. The gyro sensor according to claim 1, wherein the control unit further comprises: a sense feedback circuit unit that generates a first control signal and a second control signal having an opposite phase to the first control signal based on the detection signal; a second injection unit that generates a third sum signal by adding a third test signal to the first control signal and a fourth sum signal by adding a fourth test signal to the second control signal; and a second judgment unit that performs a fault judgment of the gyro sensor based on at least one of the third sum signal and the fourth sum signal; the plurality of electrodes further include a first sense feedback electrode to which the first control signal is applied and a second sense feedback electrode to which the second control signal is applied; the vibrator is disposed between the first sense feedback electrode and the second sense feedback electrode; each of the first control signal and the second control signal is a signal for controlling a change in electrostatic capacitance between the vibrator and each of the first detection electrode and the second detection electrode generated by application of the angular velocity to the vibrator; and the third test signal is a signal in phase with the fourth test signal.

5. The gyro sensor according to claim 4, wherein the control unit further has: a third series circuit of a third capacitor and a third switch inserted between the first sense feedback electrode and ground; and a fourth series circuit of a fourth capacitor and a fourth switch inserted between the second sense feedback electrode and ground.

6. The gyro sensor of claim 4, wherein the control unit has a differential buffer including a reference voltage terminal, a first input terminal, a second input terminal, a first output terminal for outputting a voltage corresponding to a differential voltage between a reference voltage input to the reference voltage terminal and a first voltage input to the first input terminal, and a second output terminal for outputting a voltage corresponding to a differential voltage between the reference voltage and a second voltage input to the second input terminal, the third test signal is the same signal as the fourth test signal, and the second injection unit applies the third test signal as the reference voltage to the reference voltage terminal of the differential buffer.

7. The gyro sensor according to claim 1, wherein the first determination unit performs the fault determination for the gyro sensor by comparing the peak value of at least one of the first sum signal and the second sum signal with a corresponding threshold value.

8. The gyro sensor according to claim 1, wherein the first determination unit narrows down the location of a fault in the gyro sensor by comparing the peak value of at least one of the first sum signal and the second sum signal with a corresponding number of threshold values.

9. The gyro sensor according to claim 1, wherein the first determination unit performs the failure determination for the gyro sensor by comparing a difference between a peak value of the first sum signal and a peak value of the second sum signal with a threshold value.

10. The gyro sensor according to claim 1, wherein the amplitude of the first test signal is equal to the amplitude of the second test signal.

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