JP2010122231A - Physical quantity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To confirm with a simple structure whether a physical quantity sensor is operated normally. <P>SOLUTION: The physical quantity sensor 1 includes: a vibration element 10 with drive arms 11A and 11B and a detection arm 12; a drive circuit 231 for generating drive signals for driving the drive arms 11A and 11B through a first drive line D1 and second drive line D2; and a detection circuit 232 for detecting detection signals from the detection arm 12 through a first detection line S1 and second detection line S2. In the sensor, at least one of the first drive line D1 and second drive line D2 is wired so as to generate electrostatic coupling to the first detection line S1 and second detection line S2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a physical quantity sensor that outputs a signal corresponding to an angular velocity or acceleration applied to a device.

  As a physical quantity sensor that outputs a signal according to the angular velocity and acceleration applied to the device, an angular velocity sensor for detecting the angular velocity applied to the device, an acceleration sensor for detecting acceleration such as a falling velocity, an angular velocity (rate gyro) and an angle ( A gyro sensor or the like for measuring a posture gyro) is known. When these physical quantity sensors are mounted on an automobile or the like and used as a sensor at the time of a collision, it is fatal that the collision cannot be detected due to a failure of the sensor itself.

  In order to solve this problem, for example, in Patent Document 1, in a rotational speed sensor having a detection arm that vibrates according to rotation, a test electrode capacitively coupled to the detection arm is attached, and the test is performed before starting. A method is described in which a detection arm is vibrated on a test basis by supplying a test signal from an electrode.

Japanese Patent No. 2935810

  However, in the conventional method, the sensitivity as a rotation speed sensor is sacrificed because the test electrode is attached to the detection arm, and the number of electrical contacts increases because the number of test electrodes is increased in addition to the normal electrode, thereby impairing reliability. There is a problem.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
A vibration element having a drive arm portion and a detection arm portion; a drive circuit for generating a drive signal for driving the drive arm portion via the first drive line and the second drive line; and the detection arm portion. A physical quantity sensor including a detection circuit that detects a detection signal via a first detection line and a second detection line, wherein at least one of the first drive line and the second drive line is the first detection line. And a physical quantity sensor wired so as to generate electrostatic coupling to the second detection line.

  According to this configuration, when a drive signal is generated from the drive circuit while the physical quantity sensor is stationary, the drive signal is transmitted to the first detection line and the second detection line by electrostatic coupling, and a pseudo detection signal is generated. Therefore, it can be confirmed whether or not the detection circuit operates normally.

[Application Example 2]
In the physical quantity sensor described above, one of the first drive line and the second drive line is wired so as to generate different electrostatic coupling with respect to the first detection line and the second detection line. A physical quantity sensor.

  According to this configuration, when a drive signal is generated from the drive circuit while the physical quantity sensor is stationary, the drive signal is transmitted to the first detection line and the second detection line by electrostatic coupling, and a pseudo detection signal is generated. Therefore, it can be confirmed whether or not the detection circuit operates normally.

[Application Example 3]
In the physical quantity sensor described above, a first inverter and a second inverter are connected in series to one of the first drive line or the second drive line, and a wiring connecting the drive circuit and the first inverter; A physical quantity sensor, wherein wiring for connecting the first inverter and the second inverter is wired so as to generate electrostatic coupling to the first detection line and the second detection line.

  According to this configuration, when a drive signal is generated from the drive circuit while the physical quantity sensor is stationary, the drive signal is transmitted to the first detection line and the second detection line by electrostatic coupling, and a pseudo detection signal is generated. Therefore, it can be confirmed whether or not the detection circuit operates normally.

[Application Example 4]
In the physical quantity sensor described above, at least one wiring path of the first drive line and the second drive line is switched so that the electrostatic coupling does not occur during normal operation.

  According to this configuration, since the electrostatic coupling does not occur during normal operation, the detection sensitivity of the physical quantity sensor can be improved.

The top view and sectional drawing which show the structure of a gyro sensor. The circuit diagram and timing diagram which show the structure of the gyro sensor which concerns on 1st Embodiment. The circuit diagram and timing diagram which show the structure of the gyro sensor which concerns on the modification 1. FIG. The circuit diagram and timing diagram which show the structure of the gyro sensor which concerns on the modification 2. FIG. FIG. 9 is a circuit diagram showing a configuration of a gyro sensor according to Modification 3.

  Hereinafter, embodiments of the physical quantity sensor will be described with reference to the drawings.

(First embodiment)
<Configuration of gyro sensor>
First, the configuration of a gyro sensor that is a physical quantity sensor according to the first embodiment will be described with reference to FIG. FIG. 1A is a plan view showing the configuration of the gyro sensor according to the first embodiment, and FIG. 1B is a cross-sectional view taken along the line AA ′ in FIG.

  As shown in FIGS. 1A and 1B, the gyro sensor 1 includes a gyro element 10 that is a vibration element formed of a piezoelectric material such as quartz, and extends in the rod-shaped Y-axis direction. Drive arm portions 11A and 11B and detection arm portion 12 are provided. The drive arm portions 11A and 11B face each other with the detection arm portion 12 interposed therebetween, and are connected to the detection arm portion 12 by an arm support portion 13 extending in the X-axis direction at a substantially central portion of each arm. A support portion 14 for supporting the gyro element 10 is formed at the center of the detection arm portion 12.

An electrode (not shown) is formed on the gyro element 10 and is configured to be operable in a conventionally known drive mode and detection mode. In the drive mode, the drive arm portions 11A and 11B are configured to bend and vibrate in the X-axis direction in opposite phases to each other.
If rotation about the Z axis occurs during vibration of the drive arm portions 11A and 11B, Coriolis force is generated in the drive arm portions 11A and 11B, and this Coriolis force passes through the arm support portion 13 to detect the arm portion. 12 is propagated. In response to the Coriolis force, the detection arm unit 12 vibrates in the X-axis direction corresponding to the magnitude of the Coriolis force. Then, it is possible to recognize the magnitude and direction of the angular velocity by detecting the distortion generated by the vibration of the detection arm 12 as an electrical signal.

  A connection electrode 27 is provided on one surface of the gyro element 10, and the connection electrode 27 and the lead pieces 15A, 15B, 16A, and 16B are connected by a conductive adhesive. The lead pieces 15A, 15B, 16A, 16B are bent in the Z-axis direction by conductive band-like members, and hold the gyro element 10 so as to lift it up.

  The lead pieces 15A, 15B, 16A, and 16B are fixed to the support substrate 22, and the lead pieces 15A, 15B, 16A, and 16B and the package bottom 21 are thermocompression bonded via Au bumps. Electrical wiring (not shown) is formed on the package bottom portion 21, and electrical conduction is achieved from the gyro element 10 to the package bottom portion 21 via the lead pieces 15 </ b> A, 15 </ b> B, 16 </ b> A, 16 </ b> B. The support substrate 22 is a substrate in which an insulating layer such as polyimide resin is provided on the surface of a conductive material such as copper, and is configured to prevent a short circuit between the lead pieces.

  A circuit element 23 is provided on the package bottom 21 located below the gyro element 10, and is connected to electrical wiring formed on the package bottom 21 by wire bonding.

  Output terminals 24 and 25 are provided on the bottom of the outside of the ceramic package 20 and are electrically connected to electrical wiring formed on the package bottom 21. In this manner, the angular velocity signal can be output from the output terminal 24 to the outside. These output terminals 24 can be set at any location of the ceramic package 20.

  And the gyro sensor 1 is comprised by hold | maintaining the inside of the ceramic package 20 in a vacuum atmosphere, and sealing with the cover body 19. FIG. The gyro element is not limited to a piezoelectric material such as quartz, but may be composed of a constant elastic material such as an elimber material.

<Circuit configuration of gyro sensor>
Next, the circuit configuration of the gyro sensor will be described with reference to FIG. FIG. 2A is a circuit diagram illustrating a circuit configuration of the gyro sensor, and FIG. 2B is a timing diagram illustrating an operation of the gyro sensor.

  As shown in FIG. 2A, the circuit element 23 shown in FIG. 1 is output from the drive circuit 231 that generates a drive signal for driving the drive arm portions 11A and 11B and the detection arm portion 12. And a detection circuit 232 that converts the detection signal into an angular velocity signal Vout and outputs it from the output terminal 24.

  The electrodes formed on the drive arm portions 11A and 11B of the gyro element 10 are connected to the drive circuit 231 via the first drive line D1 and the second drive line D2. The drive signal amplified and phase-adjusted by the drive circuit 231 is applied to the electrodes formed on the drive arm portions 11A and 11B, and the drive arm portions 11A and 11B perform bending vibration.

  On the other hand, the electrode formed on the detection arm 12 of the gyro element 10 is connected to the detection circuit 232 via the first detection line S1 and the second detection line S2. The detection circuit 232 includes a differential amplifier circuit, a synchronous detection circuit, a smoothing circuit, a processing circuit, and the like (not shown), and the differential amplifier circuit is detected via the first detection line S1 and the second detection line S2. The signal is differentially amplified, and the synchronous detection circuit detects the output signal of the differential amplifier circuit in synchronization with the signal of the drive circuit 231. The output signal of the synchronous detection circuit is smoothed by the smoothing circuit, and the angular velocity signal is processed by the processing circuit. Converted to Vout.

  As shown in FIG. 2A, the first drive line D1 is routed around the first detection line S1 so as to generate electrostatic coupling with a width W. Further, the second drive line D2 is routed around the second detection line S2 so as to generate electrostatic coupling with a length of width W.

  FIG. 2B is a timing chart showing an operation for confirming whether or not the detection circuit 232 operates normally while the gyro sensor 1 is stationary. As shown in FIG. 2B, the drive circuit 231 outputs a drive signal waveform for driving the drive arm portions 11A and 11B of the gyro element 10 via the first drive line D1. The drive signal waveform of the first drive line D1 is transmitted to the first detection line S1 by electrostatic coupling with the width W between the first drive line D1 and the first detection line S1. In the second drive line D2, a waveform having a phase opposite to that of the first detection line S1 is generated from the drive signal waveform of the first drive line D1. The waveform of the second drive line D2 is transmitted to the second detection line S2 by electrostatic coupling having a width W between the second drive line D2 and the second detection line S2.

  To the detection circuit 232, the first detection line S1 and the second detection line S2 are input as pseudo detection signals, and an angular velocity signal Vout is output from the output terminal 24. When the detection circuit 232 is not operating normally, the angular velocity signal Vout does not become a desired voltage, so that it can be determined that a failure has occurred.

  According to the present embodiment described above, the following effects can be obtained.

  In this embodiment, when a drive signal is output from the drive circuit 231 while the gyro sensor 1 is stationary, the drive signal waveform is transmitted to the first detection line S1 and the second detection line S2 by electrostatic coupling, and a pseudo detection signal Therefore, it can be confirmed whether or not the detection circuit 232 operates normally.

  While the embodiments of the gyro sensor have been described above, the present invention is not limited to these embodiments, and can be implemented in various forms without departing from the spirit of the invention. Hereinafter, a modification will be described.

  (Modification 1) Modification 1 of the gyro sensor will be described. In the first embodiment, the electrostatic coupling with the width W between the first drive line D1 and the first detection line S1 and the electrostatic coupling with the width W between the second drive line D2 and the second detection line S2. The method of confirming the operation of the detection circuit 232 in a state where the gyro sensor 1 is stationary using the coupling has been described. However, as shown in FIG. 3A, the width W1 ≠ W2, and the first drive line D1 The electrostatic coupling with the width W1 between the first detection line S1 and the electrostatic coupling with the width W2 between the first drive line D1 and the second detection line S2 may be used. By making electrostatic coupling with different widths W1 ≠ W2 in this way, as shown in FIG. 3B, electrostatic coupling occurs even when the timing of signals generated on the first detection line S1 and the second detection line S2 is the same. The amplitude can be varied depending on the difference between the two. By inputting the amplitude difference between the first detection line S1 and the second detection line S2 to the detection circuit 232, the angular velocity signal Vout is output from the output terminal 24. When the detection circuit 232 is not operating normally, the angular velocity signal Vout does not become a desired voltage, so that it can be determined that a failure has occurred.

  (Modification 2) Modification 2 of the gyro sensor will be described. In the first modification, the width W1 is not equal to W2, and the electrostatic coupling of the width W1 between the first drive line D1 and the first detection line S1 and between the first drive line D1 and the second detection line S2 are performed. The method of using the electrostatic coupling with the width W2 has been described. As shown in FIG. 4A, two inverters IN1 and IN2 are inserted into the first drive line D1, and the inverters IN1 and IN2 are connected. The wiring D3 utilizes electrostatic coupling with a width W between the first drive line D1 and the first detection line S1 and electrostatic coupling with a width W between the wiring D3 and the second detection line S2. May be. As shown in FIG. 4B, the angular velocity signal Vout is output from the output terminal 24 by inputting the amplitude difference between the first detection line S1 and the second detection line S2 to the detection circuit 232. When the detection circuit 232 is not operating normally, the angular velocity signal Vout does not become a desired voltage, so that it can be determined that a failure has occurred.

  (Modification 3) Modification 3 of the gyro sensor will be described. In the second modification, two inverters IN1 and IN2 are inserted into the first drive line D1, and the width W between the first drive line D1 and the first detection line S1 is determined by the wiring D3 between the inverters IN1 and IN2. The method using the electrostatic coupling and the electrostatic coupling having the width W between the wiring D3 and the second detection line S2 has been described. However, the inverters IN1 and IN2 are unnecessary during normal operation. In order to avoid this problem, as shown in FIG. 5, the switch elements SW1 to SW7 are inserted, the switch elements SW1 to SW3 are connected and the switch elements SW4 to SW7 are disconnected during normal operation, and the detection circuit is activated at startup. When checking the operation of H.232, the switch elements SW1 to SW3 may be disconnected and the switch elements SW4 to SW7 may be connected.

  DESCRIPTION OF SYMBOLS 1 ... Gyro sensor, 10 ... Gyro element, 11A, 11B ... Drive arm part, 12 ... Detection arm part, 13 ... Arm support part, 14 ... Support part, 15A, 15B, 16A, 16B ... Lead piece, 19 ... Cover 20 ... ceramic package, 21 ... package bottom, 22 ... support substrate, 23 ... circuit element, 24,25 ... output terminal, 27 ... connection electrode, 231 ... drive circuit, 232 ... detection circuit.

Claims (4)

A vibration element including a drive arm and a detection arm;
A drive circuit for generating a drive signal for driving the drive arm portion via the first drive line and the second drive line;
A detection circuit for detecting a detection signal from the detection arm via a first detection line and a second detection line;
A physical quantity sensor including
At least one of the first drive line and the second drive line is wired to generate electrostatic coupling with the first detection line and the second detection line,
A physical quantity sensor characterized by that.   2. The physical quantity sensor according to claim 1, wherein one of the first drive line and the second drive line is wired so as to generate different electrostatic couplings with the first detection line and the second detection line. A physical quantity sensor characterized by   2. The physical quantity sensor according to claim 1, wherein a first inverter and a second inverter are connected in series to one of the first drive line or the second drive line, and the drive circuit and the first inverter are connected. A physical quantity characterized in that a wiring and a wiring connecting the first inverter and the second inverter are wired so as to generate electrostatic coupling with respect to the first detection line and the second detection line. Sensor.   4. The physical quantity sensor according to claim 1, wherein at least one wiring path between the first drive line and the second drive line is switched so that the electrostatic coupling does not occur during normal operation. A physical quantity sensor characterized by that.

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