ANGULAR VELOCITY DETECTOR CIRCUIT

Abstract: An angular velocity detector comprises a quartz crystal having driving electrodes and electrodes for detecting an electric field occurring in the quartz crystal due to a Corioli's force when the quartz crystal is rotated; an oscillator circuit including an inventing amplifier connected between the driving electrodes; a differential amplifier circuit connected at its input terminals with the detecting electrodes; a detector circuit that receives the output from the differential amplifier circuit and detects the output from the oscillator circuit; and an output amplifier circuit that receives the output from the detector circuit.

Description: Filed of the Invention The present invention relates to a circuit for detecting a rotation angular velocity using an angular velocity sensor comprising an oscillator, and, more particularly, to a circuit for detecting a rotation angular velocity which can provide highly accurate measurements and is adapted to mass production. Background Technology Mechanical rotation-type gyroscopes have been conventionally used as an instrument for inertia navigation of airplanes and ships. Although these gyroscopes exhibit stable performances, they are large and expensive. It is difficult to fabricate them into small-type equipment. The use of oscillator-type angular velocity sensors which detect Corioli's force from a detecting element on a vibrating object is being developed in recent years. In these sensors the mass of a gyroscope is vibrated at a specific frequency. When a rotation force is applied to the mass, a Corioli's force at the same frequency is created to the direction perpendicular to the vibration of the mass. The principle of the oscillator-type angular velocity sensor consists of measuring the mass vibration of this force for the determination of the angular velocity. A circuit for detecting an angular velocity using an angular velocity sensor based on this principle is disclosed, for example, in Japanese Patent Application Laid-open (kokai) 172711/1991. The oscillator disclosed in this patent application is a coupling oscillator of a tuning-fork structure which comprises vibrator units, each consisting of a driving section and a detection section joined perpendicularly to each other, and coupling blocks connecting these vibrator units. Conventionally, elastic-invariable metals, such as Elinvar, or PZT-type piezoelectric ceramics have been used as oscillators. In the case of oscillators using an elastic-invariable metal, electrodes are formed on the metal surface, a thin piezoelectric element is adhered to the electrodes, then electrodes are again formed on the piezoelectric element. An oscillator circuit for vibrating an oscillator principally consists of an amplifier and a feedback circuit. The following formulas (1) and (2) apply to the vibration conditions of the circuit, |α| • |β| > 1 1 + 2 = 360° wherein α is the amplification factor of the amplifier, 1 is the transmission rate of the feedback circuit, β is the transmission rate of the feedback circuit, and 2 is a phase lag. In order to satisfy the condition of the formula (2) conventional vibrator circuits for angular velocity circuits take a system of acquiring the phase lag of 360° for one loop by a phase lag of 180° at the amplifier, a phase lag of 90° by a phase circuit comprising a combination of resistors and capacities, and another phase lag of 90° by a resistor and the capacity of the piezoelectric element itself. Conventional angular velocity detector circuits thus not only require a phase circuit, but also they must create a phase shift by a resistor and the capacity of the piezoelectric element itself. Because of this, the transmission rate β of the feedback circuit and the phase lag 2 may vary due to changes in the constant of the phase circuit which is caused by temperature changes, resulting in instability of the vibration. In addition, when a rotation force is applied, vibration produced by a Corioli's force in the oscillator is rendered unstable. This results in production of drift in the detector circuit output, leading to inaccuracy in the determination. Furthermore, a decrease in the transmission rate β in the feedback circuit caused by the resistance of the phase circuit requires an increased amplification factor α for the amplifier or provision of two or more amplifiers. Further, in order to stabilize the vibration by maintaining the transmission rate β of the feedback circuit constant, a standard voltage generation circuit must be provided. This makes the detector circuit complicated. The present invention has been achieved in order to solve these problems, and has an object of providing a circuit for detecting a rotation angular velocity, which is equipped with an oscillator circuit having a simple structure and capable of creating vibrations in a highly stable manner, and which provides high accuracy measurements and is adapted to mass production. European patent application number EP 0503807 discloses a single ended tuning fork inertial sensor. The sensor has a housing and a single ended tuning fork of a quartz-like material of a predetermined thickness. The tuning fork has first and second tines lying in a plane and having an axis of symmetry and a body form integral with the first and second tines. The body is rigidly secured to the housing. The tines have a rectangular cross section and have a width which is different from the thickness. The body has a stem form therein which has a width less than that of the body. Drive electrodes are secured to the tines. An oscillatory frequency is supplied to the above drive electrodes to excite the tines in a drive mode and in the presence of an axial angular rate to cause the tines to operate in a pick-up mode which is substantially separated in frequency from the drive mode. Disclosure of the Invention In a first aspect, the present invention provides an angular velocity detector circuit comprising: a quartz crystal oscillator which is provided with two branches having a square cross section on the upper part of the base, and first and second electrodes, characterised in that, the first electrodes for driving the oscillator is installed along the entire length of at least one plane out of the two parallel planes in the two branches of the quartz crystal oscillator, the second electrodes for taking out the electric field generated by rotation of the quartz crystal oscillator is installed along the entire lengths of the same and/or different plane(s) as the plane in one of the two branches of quartz crystal oscillator on which the first electrode is installed, further including an oscillator circuit having an inverting amplifier with the input terminal connected to one of the first electrodes and the output terminal connected to one of the second electrodes of the quartz crystal oscillator, a differential amplifier circuit with the input terminal connected to the second electrode of the quartz crystal oscillator, a detector circuit which receives the output from the differential amplifier circuit and using the output from the oscillator circuit as detection signals, and an output amplifier circuit which receives the output from the detector circuit. In one embodiment, the circuit for detection of angular velocity according to the present invention comprises a quartz crystal oscillator which is provided with a first electrode for driving the oscillator and a second electrode installed perpendicularly to the first electrode for taking out an electric field generated by rotation of the oscillator; an oscillator circuit having an inverting amplifier with the input terminal connected to the first electrode and the output terminal connected to the second electrode of the quartz crystal oscillator; a differential amplifier circuit with the input terminal connected to the second electrode of the quartz crystal oscillator; a detector circuit which receives the output from the differential amplifier circuit and using the output from the oscillator circuit as detection signals; and an output amplifier circuit which receives the output from the detector circuit. In another embodiment of the present invention, the circuit for detection of angular velocity comprises a quartz crystal oscillator which is provided with a first electrode installed on two parallel planes of the oscillator for driving the oscillator and a second electrode installed perpendicularly to the first electrode for taking out an electric field generated by rotation of the oscillator; an oscillator circuit having an inverting amplifier with the input terminal connected to a portion of the first electrode and the output terminal connected to the other portion of the first electrode of the quartz crystal oscillator; a differential amplifier circuit with the input terminal connected to the second electrode of the quartz crystal oscillator; a detector circuit which receives the output from the differential amplifier circuit and using the output from the oscillator circuit as detection signals; and an output amplifier circuit which receives the output from the detector circuit. In a further embodiment of the present invention, the circuit for detection of angular velocity comprises a quartz crystal oscillator which is provided with a first electrode and a second electrode installed perpendicularly to the first electrode for driving the oscillator; a third electrode installed on the same plane as the oscillator as a part of the second electrode for taking out an electric field generated by rotation the oscillator; an oscillator circuit having an inverting amplifier with the input terminal connected to the first electrode and the output terminal connected to the second electrode of the quartz crystal oscillator; a differential amplifier circuit with the input terminal connected to the third electrode of the quartz crystal oscillator; a detector circuit which receives the output from the differential amplifier circuit and using the output from the oscillator circuit as detection signals; and an output amplifier circuit which receives the output from the detector circuit. In a still further embodiment of the present invention, the circuit for detection of angular velocity comprises a quartz crystal oscillator which is provided with a first electrode and a second electrode installed perpendicularly to the first electrode for driving the oscillator; a third electrode connected to the second electrode, a fourth electrode installed on the opposite plane of the third electrode, a fifth electrode installed on the same plane as the oscillator as the third electrode, and a sixth electrode installed on the same plane as the oscillator as the fourth electrode, for taking out an electric field generated by rotation the oscillator; an oscillator circuit having an inverting amplifier with the input terminal connected to the first electrode and the output terminal connected to the second electrode of the quartz crystal oscillator; a differential amplifier circuit having the input terminal connected to the fifth and sixth electrode of the quartz crystal oscillator; a detector circuit which receives the output from the differential amplifier circuit and using the output from the oscillator circuit as detection signals; and an output amplifier circuit which receives the output from the detector circuit. Further, a circuit for detection of angular velocity is provided according to the present invention, which comprises a quartz crystal oscillator which is provided with a first electrode and a second electrode installed perpendicularly to the first electrode for driving the oscillator; a third electrode connected to the second electrode, and a fourth electrode and a fifth electrode installed on the opposite plane of the third electrode, for taking out an electric field generated by rotation the oscillator; an oscillator circuit having an inverting amplifier with the input terminal connected to the first electrode and the output terminal connected to the second electrode of the quartz crystal oscillator; a differential amplifier circuit having the input terminal connected to the fourth and fifth electrodes of the crystal oscillator; a detector circuit which receives the output from the differential amplifier circuit and using the output from the oscillator circuit as detection signals; and an output amplifier circuit which receives the output from the detector circuit. Still further, a circuit for detection of angular velocity is provided according to the present invention, which comprises a quartz crystal oscillator which is provided with a first electrode and a second electrode installed perpendicularly to the first electrode for driving the oscillator; a third electrode connected to the second electrode, a fourth electrode installed perpendicularly to the third electrode, and a fifth electrode installed on the opposite plane of the fourth electrode, for taking out an electric field generated by rotation the oscillator, an oscillator circuit having an inverted amplifier with the input terminal connected to the first electrode and the output terminal connected to the second electrode of the quartz crystal oscillator; a differential amplifier circuit having the input terminal connected to the fourth and fifth electrodes of the quartz crystal oscillator; a detector circuit which receives the output from the differential amplifier circuit and using the output from the oscillator circuit as detection signals; and an output amplifier circuit which receives the output from the detector circuit. Because the oscillator circuit of the present invention has the above-mentioned construction with the quartz crystal oscillator and the inverting amplifier, in the case of the quartz crystal oscillator vibrating at a frequency in the neighborhood of 32 KHz, the return circuit has an amplification factor |β| of about 0.2-0.9 and a phase lag 2 of about 180°. The similar conditions can be achieved by the suitable selection of frequency even from a high frequency range. On the other hand, because of the fact that the amplification factor of an inverting amplifier is generally 20-30 db or higher and further that a phase rotation of a typical inverting amplifier is almost 180° at a frequency of about 30 KHz, the vibration conditions of formulas (1) and (2) can be satisfied. Therefore, the circuit for detection of angular velocity of the present invention requires no phase circuit for the return section of the oscillator circuit and can thus perform highly stable vibrations without reduction in the transmission rate and variations in the phase lag due to characteristic changes in a phase circuit. Further, detection output is superimposed to the vibration output to stabilize the operation of the differential amplifier circuit. This prevents drift from being generated in the detector circuit output, thus remarkably increasing the measurement accuracy. The circuit construction is simplified and adaptable to mass production. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a drawing showing the detector circuit for the first embodiment of the present invention. Figure 2 is a perspective view of the quartz crystal oscillator in the first embodiment of the present invention. Figure 3 is a cross-sectional view of the electrode for the quartz crystal oscillator in the first embodiment of the present invention. Figure 4 is a drawing showing the detector circuit for the second embodiment of the present invention. Figure 5 is a perspective view of the quartz crystal oscillator in the second embodiment of the present invention. Figure 6 is a cross-sectional view of the electrode for the quartz crystal oscillator in the second embodiment of the present invention. Figure 7 is a drawing showing the detector circuit for the third embodiment of the present invention. Figure 8 is a perspective view of the quartz crystal oscillator in the third embodiment of the present invention. Figure 9 is a cross-sectional view of the electrode for the quartz crystal oscillator in the third embodiment of the present invention. Figure 10 is a cross-sectional view of the electrode for the quartz crystal oscillator in the fourth embodiment of the present invention. Figure 11 is a cross-sectional view of the electrode for the quartz crystal oscillator in the fifth embodiment of the present invention. Figure 12 is a front elevation of the quartz crystal oscillator in the fifth embodiment of the present invention. Figure 13 is a rear elevation of the quartz crystal oscillator in the fifth embodiment of the present invention. Figure 14 is a cross-sectional view of the electrode for the quartz crystal oscillator in the sixth embodiment of the present invention. Figure 15 is a front elevation of the quartz crystal oscillator in the sixth embodiment of the present invention. Figure 16 is a rear elevation of the quartz crystal oscillator in the sixth embodiment of the present invention. Figure 17 is a cross-sectional view of the electrode for the quartz crystal oscillator in the seventh embodiment of the present invention. Figure 18 is a front elevation of the quartz crystal oscillator in the seventh embodiment of the present invention. Figure 19 is a side elevation of the quartz crystal oscillator in the seventh embodiment of the present invention. Figure 20 is a rear elevation of the quartz crystal oscillator in the seventh embodiment of the present invention. Figure 21 is a cross-sectional view of the electrode for the quartz crystal oscillator in the eighth embodiment of the present invention. Figure 22 is a front elevation of the quartz crystal oscillator in the eighth embodiment of the present invention. Figure 23 is a rear elevation of the quartz crystal oscillator in the eighth embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be illustrated by reference to the drawings. Figure 1 is a drawing showing the detector circuit for the first embodiment of the present invention, Figure 2 is a perspective view of the quartz crystal oscillator in the first embodiment, and Figure 3 is a cross-sectional view showing the arrangement and mutual connection among electrodes for the oscillator. The quartz crystal oscillator shown in Figure 2 is a so-called X-cut quartz crystal oscillator, in which the quartz crystal is cut at XY' plane having Y axis (mechanical axis ) Y' axis produced by rotating XY plane by 0-10° with respect to X axis (electric axis ), so as to arrange electrodes such that expansion to the direction of the Y' axis is allowed to occur at both sides of the neutral plane 81 (Figure 3) of vibration. Here, the Z' axis is a Z axis (optical axis ) crossing the Y' axis at right angle. The quartz crystal oscillator is of a tuning-fork-type consisting of branch sections 19, 20 and a base section 21. These are integrally formed from one quartz plate by a photoengraving and etching process or by a wire-saw technique. As shown in Figure 3, electrode 1 is provided on one of the planes parallel to the Y'Z' plane of one of the branches (19) of the tuning fork, and electrode 2 is provided on the opposite plane. Further, electrode 7 is provided on one of the planes parallel to the Y'Z' plane of the other branch 20 of the tuning fork, and electrode 8 is provided on the opposite plane. Electrodes 1 and 2, and electrodes 7 and 8 are connected to each other within the quartz crystal oscillator, and terminals 16 and 15 are provided, respectively. Electrodes 3 and 4 are provided on one of the planes parallel to the XY' plane of branch 19, and electrodes 5 and 6 are provided on the opposite plane. Electrodes 9 and 10 are provided on one of the planes parallel to the XY' plane of branch 20, and electrodes 11 and 12 are provided on the opposite plane. Then, electrodes 3 and 6, electrodes 4 and 5, electrodes 9 and 12, and electrodes 10 and 11 are connected to each other within the quartz crystal oscillator, and terminals 17, 18, 13 and 14 are provided, respectively. These electrodes 1-12 are formed by vacuum deposition of a metal film, such as chromium and gold. As shown in Figure 1, terminals 13 to 18 of the quartz crystal oscillator 30 are connected to oscillator circuit 40. Specifically, terminals 13 and 14 are connected to output of invertor 46, which is an inverting amplifier constructed by a CMOS transistor (complementary field effect transistor), via resistors 44 and 43 of oscillator circuit 40, and terminals 15 is connected to the input of invertor 46. Terminals 16 is connected to the output of invertor 46. Further, terminals 17 and 18 are connected to the input of invertor 46 via resistors 41 and 42. These resistors 41 and 42 may be provided as thin film resistors, for example, on the base 21 of the quartz crystal oscillator shown Figure 2. Although an invertor consisting of a CMOS transistor is given here as an example of the inverting amplifier, any amplifiers with a high input resistance can be used. Resistor 45 is a feedback resistor (Rf), and condensers 47 and 48 are respectively an input capacity (Cin) and an output capacity (Cout). These form a feedback circuit together with the quartz crystal oscillator 30. This construction satisfies the above-described conditions of formulas (1) and (2), so that when voltage is applied an electric field is created to the direction of the arrow shown by a solid line in Figure 3, and the oscillator circuit begins to vibrate and immediately reaches a steady state. Self-oscillation then occurs at a specific resonance frequency to the X axis direction of Figure 2. When a rotation force at an angular velocity of is applied around the Y' axis of the quartz crystal oscillator, Corioli's force Fc is created on the both branch sections 19 and 20 of tuning fork to the directions opposite to each other in a plane parallel to the Y'Z' plane. The Corioli's force Fc applied to one of the branches is expressed by the following formula (4), Fc = 2mωv = 2mω•a•sinω o 1 wherein v = a•sinω o t a is a velocity amplitude of vibration, ω o is an angular frequency of vibration, and m is the mass of the vibrating portion. The Corioli's force created by angular velocity ω deforms the branched section of the oscillator, and an electric field is generated to the direction of the arrow shown in a broken line in Figure 3. This creates a detection output at terminals 13 and 14, which is then applied to the input of differential amplifier circuit 50, superimposing to the output of oscillator circuit 40 in Figure 1. The output of oscillation circuit 40 is deducted from the output of the differential amplifier circuit 50, and the value thus obtained entirely depends on the field generated by angular velocity ω. The phase of the output voltage of differential amplifier circuit 50 and that of oscillator circuit 40 must be the same. In the detector circuit of this embodiment, the differential amplifier circuit 50 also acts as a phase circuit, so that the phase of the output voltage of differential amplifier circuit 50 and that of oscillator circuit 40 are identical. If necessary, a phase circuit may be provided after the differential amplifier circuit 50 or the oscillator circuit 40. Because the output voltage of the oscillator circuit applied to the input terminal of differential amplifier circuit 50, superimposing to the detection output, is large enough for differential amplifier circuit 50 to be actuated stably, drift created in the output is very small. The output of differential amplifier circuit 50 is connected to the input terminal of detector circuit 60, and detection is performed as the output of oscillator circuit 40 as detection signals. The output of oscillator circuit 60 is connected to the input terminal of output amplifier circuit 70 which contains a smoothing circuit. The rotation angular velocity of the amplifier circuit 70 is d.c. voltage, based on which value the rotation angular velocity can be known, and thus the system can act as an angular velocity detector (a gyroscope). An embodiment of the second invention will be illustrated by reference to the drawings. Figure 4 is a drawing showing the detector circuit for the second embodiment, Figure 5 is a perspective view of the quartz crystal oscillator in the second embodiment, and Figure 6 is a cross-sectional view showing the arrangement and mutual connection among electrodes for the oscillator. The quartz crystal oscillator shown in Figure 5 is an X-cut quartz crystal oscillator, the same as in the first embodiment, and consists of branched sections 19, 20 and base 21. The branched sections 19, 20 form electrodes. As shown in Figure 6, electrode 1 is provided on one of the planes parallel to the Y'Z' plane of one of the branches (19) of the tuning fork, and electrode 2 is provided on the opposite plane. Further, electrode 26 is provided on one of the planes parallel to the XY' plane and electrode 27 is provided on the opposite plane. On another branch 20 electrodes 7, 8, 9, 10, 11 and 12 are provided in the same manner as in the first embodiment, shown in Figure 3. Electrodes 1 and 2, electrodes 26 and 27, and electrodes 7 and 8 are connected to each other within the quartz crystal oscillator, and terminals 16 and 25 are provided, respectively. Further, in the same manner as the in first embodiment, terminal 13 connected to electrodes 9 and 12, and terminal 13 connected to electrodes 10 and 11 are provided. As shown in Figure 4, terminals 13, 14, 16 and 25 of the quartz crystal oscillator 30 are connected to oscillator circuit 40. Specifically, terminals 13 and 14 are connected to the output of invertor 46 via resistors 43 and 44 of oscillator circuit 40, and terminals 25 is connected to the input of invertor 46. This construction enables a driving voltage created by oscillator circuit 40 to be applied solely to the branch section 19 of the quartz crystal oscillator in Figure 5, thus ensuring high vibration stability. Further, in Figure 4, terminals 13 and 14 of quartz crystal oscillator 30 are connected to differential amplifier circuit 50. The construction and operation of the differential amplifier circuit 50, detector circuit 60, and output amplifier circuit 70 are the same as discussed for the first embodiment. An embodiment of the third invention will be illustrated by reference to the drawings. Figure 7 is a drawing showing the detector circuit for the third embodiment, Figure 8 is a perspective view of the oscillator in the third embodiment, and Figure 9 is a cross-sectional view showing the arrangement and mutual connection among electrodes for the oscillator. The quartz crystal oscillator shown in Figure 8 is a so-called NT-cut quartz crystal oscillator, in which the quartz crystal is cut on the Z'Y' plane at X' axis , Y' axis , and Z' axis , each corresponding respectively to X axis (electric axis ), Y axis , and Z axis , and produced by rotating the XY plane by 2-10° and the YZ plane by 50-60°, with respect to the X axis , so as to arrange electrodes such that expansion to the direction of the Z' axis is allowed to occur on the neutral plane of vibration 81. The quartz crystal oscillator consists of branch sections 19, 20 and base section 21. Electrodes are formed on these branched sections 19 and 20. As shown in Figure 9, electrode 1 is provided on one of the planes parallel to the X'Y' plane of one of the branches (19) of the tuning fork, and electrode 2 is provided on the opposite plane. Further, electrode 7 is provided on one of the planes parallel to the X'Y' plane of branch 20 of the tuning fork, and electrode 8 is provided on the opposite plane. Electrodes 1 and 2, and electrodes 7 and 8 are connected to each other within the quartz crystal oscillator, and terminals 16 and 15 are provided, respectively. Electrodes 3 and 4 are provided on one of the planes parallel to Z'Y' plane of branch 19, and electrodes 5 and 6 are provided on the opposite plane. Electrodes 9 and 10 are provided on one of the planes parallel to the Z'Y' plane of branch 20, and electrodes 11 and 12 are provided on the opposite plane. Then, electrodes 3 and 6, electrodes 10 and 11, electrodes 4 and 5, and electrodes 12 and 9 are connected to each other within the quartz crystal oscillator, and terminals 13 and 14 are provided, respectively. As shown in Figure 7, terminals 13 and 14 of the quartz crystal oscillator 30 are connected to oscillator circuit 40. Specifically, terminal 13 is connected to the output of invertor 46, and terminal 14 is connected to the input of invertor 46. Further, terminals 1, 5, and 16 are connected to the input of differential amplifier circuit 50. When a rotation force with angular velocity ω is applied to around the Y' axis of the quartz crystal oscillator, a Corioli's force is created, which in turn produces an electric field shown by a broken line arrow in Figure 9. Output 15 and output 16 thus produced are applied to the input terminal of differential amplifier circuit 50 shown in Figure 7, superimposing to the output of oscillator circuit 40. The output of oscillator circuit 40 is subtracted by output of the differential amplifier circuit 50, and the value thus obtained entirely depends on the field generated by angular velocity ω. The construction and operation of the differential amplifier circuit 50, detector circuit 60, and output amplifier circuit 70 are the same as discussed for the previous embodiment. An embodiment of the fourth invention will be illustrated by reference to the drawings. Figure 10 is a cross-sectional view of the arrangement and mutual connections of the electrode for the quartz crystal oscillator in the fourth embodiment of the present invention. The quartz crystal oscillator in this embodiment is an NT-cut quartz crystal oscillator, the same as that of the third embodiment. As shown in Figure 10, electrode 1 is provided on one of the planes parallel to X'Y' plane of one of the branches (19) of the tuning fork, and electrode 2 is provided on the opposite plane. Further, electrodes 7 is provided on one of the planes parallel to the X'Y' plane of branch 20 of the tuning fork, and electrode 8 is provided on the opposite plane. Electrodes 1 and 2, and electrodes 7 and 8 are connected to each other within the quartz crystal oscillator, and terminals 16 and 15 are provided, respectively. Further, electrodes 3 and 4 are provided on one of the planes parallel to the Z'Y' plane of the branch 19, and electrode 27 is provided on the opposite plane. Electrodes 9 and 10 are provided on one of the planes parallel to the Z'Y' plane of the branch 20, and electrode 24 is provided on the opposite plane. Electrodes 3 and 10, and electrodes 4 and 9 are connected to each other within the quartz crystal oscillator, and terminals 14 and 13 are provided, respectively. Electrodes 24 and 27 are connected to each other. As shown in Figure 7, terminals 13 and 14 of the quartz crystal oscillator 30 are connected to oscillator circuit 40. Specifically, terminals 13 is connected to the output of invertor 46, and terminals 14 is connected to the input of invertor 46. Further, terminals 15 and 16 are connected to the input of differential amplifier circuit 50. The construction and operation of the differential amplifier circuit 50, detector circuit 60, and output amplifier circuit 70 are the same as discussed for the previous embodiment. An embodiment of the fifth invention will be illustrated by reference to the drawings. Figure 11 is a cross-sectional view showing arrangement and mutual connection of the electrodes for the quartz crystal oscillator in the fifth embodiment, Figure 12 and Figure 13 are plan views showing arrangement of the electrodes for the quartz crystal oscillator, wherein Figure 12 is a front elevation and Figure 13 is a rear elevation of the quartz crystal oscillator. The quartz crystal oscillator of this embodiment is an X-cut quartz crystal oscillator. As shown in Figure 12, the quartz crystal oscillator consists of branched sections 19, 20 and base 21. The end of the base 21 is fixed by a member 22. The branched sections 19, 20, and the base 21 form electrodes as shown in Figures 12 and 13. As shown in Figure 11, electrode 1 is provided on one of the planes parallel to the Y'Z' plane of one of the branches (19) of the tuning fork, electrode 3 is provided on one of the planes parallel to the XY' plane, and electrode 5 is provided on the opposite plane. Further, electrode 8 is provided on the plane parallel to the Y'Z' of the other branch 20, electrodes 9 and 10 is provided on one of the planes parallel to the XY' plane, and electrodes 11 and 12 are provided on the opposite plane. Electrodes 1, 10 and 12, and electrodes 3, 5 and 8 are connected to each other within the quartz crystal oscillator, and terminals 13 and 14 are provided, respectively. These electrodes 1, 3, 5, 8, 10 and 12 are the electrodes driving the quartz crystal oscillator. Further, terminal 16 is provided to electrode 9, and terminal 15 is provided to electrode 11. These are electrodes for taking out the generated electric field. As shown in Figure 7, terminals 13 and 14 of the quartz crystal oscillator 30 are connected to oscillator circuit 40. Specifically, terminal 13 is connected to the output of invertor 46, and terminals 14 is connected to the input of invertor 46. Further, terminals 15 and 16 are connected to the input of differential amplifier circuit 50. When a rotation force with angular velocity ω is applied to around the Y' axis of the quartz crystal oscillator, a Corioli's force is created, which in turn produces an electric field in branches 19 and 20 of the tuning fork shown by a broken line arrow in Figure 11. Detection outputs are then created at terminals 15 and 16, superimposed to the output of oscillator circuit 30, and applied to the input terminal of differential amplifier circuit 50 of Figure 7. Because the output of oscillator circuit 40 is subtracted by the output of the differential amplifier circuit 50, the value thus obtained entirely depends on the field generated by the angular velocity ω. The construction and operation of the differential amplifier circuit 50, detector circuit 60, and output amplifier circuit 70 are the same as discussed for previous embodiments. An embodiment of the sixth invention will be illustrated by reference to the drawings. Figure 14 is a cross-sectional view of the arrangement and mutual connections of the electrodes for the quartz crystal oscillator in the sixth embodiment of the present invention, Figure 15 and Figure 16 are plan views showing arrangement of the electrodes for the quartz crystal oscillator, wherein Figure 15 is a front elevation and Figure 16 is a rear elevation of the quartz crystal oscillator. The quartz crystal oscillator of this embodiment is an X-cut quartz crystal oscillator. As shown in Figure 15, the quartz crystal oscillator consists of branched sections 19, 20 and base 21. The end of the base 21 forms a fixed member 23, which forms a terminal for external connection. Electrodes are formed at branched sections 19, 20, and base 21 as shown in Figures 15 and 16. As shown in Figure 14, electrode 1 is provided on one of the planes parallel to the Y'Z' plane of one of the branches (19) of the tuning fork, and electrode 2 is provided on the opposite plane. Further, electrode 26 is provided on one of the planes parallel to the XY' plane, and electrode 27 is provided on the opposite plane. Electrodes 9 and 10 are provided on the plane parallel to the XY' plane of the other branch 20, and electrodes 11 and 12 are provided on the opposite plane. Electrodes 1 and 2, and electrodes 26 and 27 are connected to each other within the quartz crystal oscillator, and terminals 13 and 14 are provided, respectively. These electrodes 1, 2, 26 and 27 are the electrodes for driving the quartz crystal oscillator. Further, electrodes 9, 11, and 2 are connected to each other within the quartz crystal oscillator. As discussed below, terminal 13 connected to these electrodes 2, 9 and 11 are connected to the output of oscillator circuit in Figure 7. Electrode 9 and electrode 11 therefore have the same potential as the output voltage of the oscillator circuit. Terminal 15 is provided to electrode 10, and terminal 16 is provided to electrode 12. These electrodes 10 and 12 are electrodes for taking out the electric field generated by rotation of the oscillator. Because electrodes 9 and 11 are of the same potential as the output of oscillator circuit 40, the output at electrodes 15 and 16 are the output of oscillator circuit 40, superimposed by the generated field. Arrangements obtained by rotating the electrodes on branched section 19 either right or left by 90° in Figure 14 are also part of this embodiment. As shown in Figure 7, terminals 13 and 14 of the quartz crystal oscillator 30 are connected to oscillator circuit 40. Specifically, terminal 13 is connected to the output of invertor 46, and terminal 14 is connected to the input of invertor 46. Further, terminals 15 and 16 are connected to the input of differential amplifier circuit 50. When a voltage is applied, an electric field is created to the direction of the arrow shown by a solid line in Figure 14, and the oscillator circuit begins to vibrate and immediately reaches a steady state. Self-oscillation then occurs at a specific resonance frequency to the X axis direction of Figure 15. When a rotation force with an angular velocity ω is applied to around the Y' axis of the quartz crystal oscillator, a Corioli's force is created, which in turn produces a field in tuning fork sections 19 and 20 as shown by a broken line arrow in Figure 14. The detection output thus produced is applied to the input terminal of the differential amplifier circuit 50 shown in Figure 7, superimposing to the output of oscillator circuit 40. Because the output of differential amplifier circuit 50 is subtracted by the output of oscillator circuit 40, this value is entirely dependent on the field generated by angular velocity ω. The construction and operation of the differential amplifier circuit 50, detector circuit 60, and output amplifier circuit 70 are the same as discussed for previous embodiments. An embodiment of the seventh invention will be illustrated by reference to the drawings. Figure 17 is a cross-sectional view of the arrangement and mutual connections of the electrodes for the quartz crystal oscillator in the seventh embodiment of the present invention, Figure 18 and Figure 19 are plan views showing arrangement of the electrodes for the quartz crystal oscillator, wherein Figure 18 is a front elevation and Figure 19 is a rear elevation of the quartz crystal oscillator. The quartz crystal oscillator of this embodiment is an X-cut quartz crystal oscillator. As shown in Figure 18, the quartz crystal oscillator consists of branched sections 19, 20, a base 21, and a fixed member 23. Electrodes are formed on the branched sections 19, 20, and the base 21, as shown in Figures 18, 19 and 20. As shown in Figure 17, electrode 1 is provided on one of the planes parallel to the Y'Z' plane of one of the branches (19) of the tuning fork, and electrode 2 is provided on the opposite plane. Further, electrode 26 is provided on one of the planes parallel to the XY' plane, and electrode 27 is provided on the opposite plane. Electrode 7 is provided on the plane parallel to the Y'Z' plane of the other branch 20, and electrodes 28 and 29 are provided on the opposite plane. Electrodes 1 and 2, and electrodes 26 and 27 are connected to each other within the quartz crystal oscillator, and terminals 13 and 14 are provided, respectively. These electrodes 1, 2, 26 and 27 are the electrodes for driving the quartz crystal oscillator. Further, electrode 7 is connected to electrodes 26 and 27. As discussed below, terminal 13 connected to these electrodes 26, 27 and 7 is connected to the output of oscillator circuit 40 in Figure 7. Electrode 7 therefore has the same potential as the output voltage of the oscillator circuit 40. Terminal 15 is provided to electrode 28, and terminal 16 is provided to electrode 29. These electrodes 28 and 29 are electrodes for taking out the electric field generated by rotation. Because electrode 7 is of the same potential as the output of oscillator circuit 40, output at terminals 15 and 16 is the output of oscillator circuit 30, superimposed by the generated field. Arrangements obtained by rotating the electrodes on branched section 19 either right or left by 90° in Figure 17 are also part of this embodiment. As shown in Figure 7, terminals 13 and 14 of the quartz crystal oscillator 30 are connected to oscillator circuit 40. Specifically, terminal 13 is connected to the output of invertor 46, and terminal 14 is connected to the input of invertor 46. Further, terminals 15 and 16 are connected to the input of differential amplifier circuit 50. The construction and operation of the differential amplifier circuit 50, detector circuit 60, and output amplifier circuit 70 are the same as discussed for the previous embodiments. An embodiment of the eighth invention will be illustrated by reference to the drawings. Figure 21 is a cross-sectional view of the arrangement and mutual connections of the electrodes for the quartz crystal oscillator in the eighth embodiment, Figures 22 and 23 are plan views showing an arrangement of the electrodes for the quartz crystal oscillator, wherein Figure 22 is a front elevation and Figure 23 is a rear elevation of the quartz crystal oscillator. The quartz crystal oscillator of this embodiment is an X-cut quartz crystal oscillator. As shown in Figure 22, the quartz crystal oscillator consists of branched sections 19, 20, a base 21, and a fixed member 23. Electrodes are formed on the branched sections 19, 20, and the base 21, as shown in Figures 22 and 23. As shown in Figure 21, electrode 1 is provided on one of the planes parallel the to Y'Z' plane of one of the branches (19) of the tuning fork, and electrode 2 is provided on the opposite plane. Further, electrode 26 is provided on one of the planes parallel to XY' plane, and electrode 27 is provided on the opposite plane. Electrode 10 is provided on the plane parallel to the Y'Z' plane of the other branch 20, electrode 12 is provided on the opposite plane, and electrode 7 is further provided on the plane parallel to the Y'Z' plane. Electrodes 1 and 2, and electrodes 26 and 27 are connected to each other within the quartz crystal oscillator, and terminals 14 and 13 are provided, respectively. These electrodes 1, 2, 26 and 27 are the electrodes driving quartz crystal oscillator. Further, electrode 7 is connected to electrodes 26 and 27. As discussed later, terminal 13 connected to these electrodes 26, 27 and 7 is connected to the output of oscillator circuit 40 in Figure 7. Electrode 7 therefore has the same potential as the output voltage of the oscillator circuit 40. Terminal 15 is provided to electrode 10, and terminal 16 is provided to electrode 12. These electrodes 10 and 12 are electrodes for taking out the electric field generated by rotation of the oscillator. Because electrode 7 is of the same potential as the output of oscillator circuit 40, the output at terminals 15 and 16 is the output of oscillator circuit 40, superimposed by the generated field. Arrangements obtained by rotating the electrodes on branched section 19 either right or left by 90° in Figure 21 are also part of this embodiment. As shown in Figure 7, terminals 13 and 14 of the quartz crystal oscillator 30 are connected to oscillator circuit 40. Specifically, terminal 13 is connected to the output of invertor 46, and terminal 14 is connected to the input of invertor 46. Further, terminals 15 and 16 are connected to the input of differential amplifier circuit 50. The construction and operation of the differential amplifier circuit 50, detector circuit 60, and output amplifier circuit 70 are the same as discussed for the previous embodiments. Although embodiments comprising invertors consisting of CMOS transistors as inverting amplifiers are shown in the above-described examples, it is possible to use CMOS transistors for all other circuits. Further, although quartz crystal oscillators with a vibration frequency about 32 KHz were given in the above embodiments, oscillators having a frequency of a higher range can also be used for these oscillator circuits with the same construction, if the frequency is suitably selected. Although oscillators using quartz for substrates are given in the above embodiments, it is possible to use other materials possessing piezoelectric characteristics, such as lithium tantalate single crystals, lithium niobate single crystals, and lithium borate single crystals. The oscillators can be also produced by adhering or coating materials having piezoelectric characteristics to silicon substrate. Further, although tuning-fork-type oscillators were exemplified in the above descriptions, other tuning instruments which can produce bending vibration are also applicable to the present invention. For the convenience of better understanding of the present invention, relationships between various embodiments given above and the subject matters in the claims are summarized as follows. The first and second embodiments are embodiments of claim 1; the third and fourth embodiments are those of claim 2; the fifth embodiment represents claim 3; the sixth embodiment, claim 4; the seventh embodiment, claim 5; and the eighth embodiment, claim 6. It should be understood that all embodiments are given for the purpose of illustration of the present invention and are not intended to be limiting thereof. INDUSTRIAL APPLICABILITY OF THE INVENTION As illustrated above, the circuits for detection of angular velocity of the present invention can be suitably used for inertia navigation of airplanes and ships. They are also suitable for use in small-type equipments, such as head-mount displays of virtual-reality-type, mouse for personal computers, hand-toutch equipments of video cameras, and small-type robots.

Claims: An angular velocity detector circuit comprising: a quartz crystal oscillator which is provided with two branches (19,20) having a square cross section on the upper part of the base, and first and second electrodes, characterised in that, the first electrodes for driving the oscillator is installed along the entire length of at least one plane out of the two parallel planes in the two branches of the quartz crystal oscillator, the second electrodes for taking out the electric field generated by rotation of the quartz crystal oscillator is installed along the entire lengths of the same and/or different plane(s) as the plane in one of the two branches of quartz crystal oscillator on which the first electrode is installed, further including an oscillator circuit (40) having an inverting amplifier (46) with the input terminal connected to one of the first electrodes and the output terminal connected to one of the second electrodes of the quartz crystal oscillator, a differential amplifier circuit (50) with the input terminal connected to the second electrode of the quartz crystal oscillator, a detector circuit (60) which receives the output from the differential amplifier circuit and using the output from the oscillator circuit as detection signals, and an output amplifier circuit (70) which receives the output from the detector circuit. The angular velocity detector according to claim 1, provided with two second electrodes for oscillating the oscillator and taking out the electric field generated by rotation of the quartz crystal oscillator in each plane of the two parallel planes. A detector according to claim 1 wherein the second electrode is installed along the entire lengths of two parallel planes which are perpendicularly crossing said plane in at least one branch out of the two branches of the quartz crystal oscillator on which the first electrode is installed. The angular velocity detector according to claim 1 wherein the electrodes for oscillating the quartz crystal oscillator are provided along the entire lengths of the same plane wherein said electrode for taking out the electric field generated by rotation of one branch out of said two branches is provided, one plane perpendicularly crossing said same plane, two parallel planes on the other branch out of said two branches, and one plane perpendicularly crossing these two parallel planes. The angular velocity detector according to claim 1, wherein the electrodes for oscillating the quartz crystal oscillator are provided in the entire lengths of the same plane wherein said electrode for taking out the electric field generated by rotation of one branch out of said two branches is provided, the two parallel planes on the other branch out of said two branches, and two planes which are perpendicularly crossing these two parallel planes. The angular velocity detector according to claim 1, wherein the electrodes for oscillating the quartz crystal oscillator are provided in the entire lengths of the plane opposing to the plane wherein said electrode for taking out the electric field generated by rotation of one branch out of said two branches is provided, the two parallel planes on the other branch out of said two branches, and two planes which are perpendicularly crossing these two parallel planes. The angular velocity detector according to claim 1, wherein the electrodes for oscillating the quartz crystal oscillator are provided in the entire lengths of one plane perpendicularly crossing the plane wherein said electrode for taking out the electric field generated by rotation of one branch out of said two branches is provided, the two parallel planes on the other branch out of said two branches, and two parallel planes which are perpendicularly crossing these two parallel planes. The angular velocity detector according to any one of the above claims, wherein the electrodes for oscillating the oscillator are connected in the quartz crystal oscillator and each electrode is charged with an electric voltage by one oscillator circuit. An angular velocity detector circuit according to claim 1 in which the second electrode is installed along a plane parallel to the plane in one of the two branches of the quartz crystal oscillator on which the first electrode is installed. An angular velocity detector circuit according to claim 1 wherein the second electrode is also usable for driving the oscillator.

Inventors: NAKAJIMA FUMIO, NAKAJIMA, FUMIO
Applicants: CITIZEN WATCH CO LTD, CITIZEN WATCH CO. LTD.
Application year: 1993
Main classification: G01C19
IPC codes: G01C19