Patent Description:
Vibrating-type gyroscope elements have been known as gyroscope elements for use in an angular velocity sensor. For example, electromagnetic gyroscope elements have been well-known, which have such a structure that is provided with a plurality of electrodes on a surface of a ring-shaped resonator and configured to apply a magnetic field in a direction crossing surfaces of the electrodes (see, e.g., Patent Documents <NUM> and <NUM>).

The electromagnetic gyroscope elements are so configured that, under the magnetic field application, the resonator is vibrated by resonance vibration (which may be also referred to as first order vibration hereinafter) caused by a current of a frequency equivalent to a resonance frequency of the resonator applied via some of the electrodes (hereinafter referred to as primary driving electrodes). If an angular velocity occurs when the resonator receives a Coriolis force, a voltage generated at other electrodes (hereinafter referred to as a secondary pickoff electrode) is detected as a signal for calculating an angular velocity. Gyroscope elements are typically configured with electrodes (hereinafter referred to as primary pickoff electrodes) for detecting the first order vibration for stabilization of the amplitude and frequency of the first order vibration, and with electrodes (hereinafter referred to as secondary driving electrodes) for driving the resonator on the basis of the signal detected by the secondary pickoff electrodes such that second order vibration is canceled.

On the other hand, in an angular velocity sensor having a vibrating-type gyroscope element, an output signal would be superimposed with a bias component sometimes. The bias component is also called, for example, a zero-point output or an offset, and is caused due to, e.g., angular offset among the plurality of electrodes provided in the vibrating-type gyroscope element or uneven magnetic field application in the case of the electromagnetic gyroscope element.

In order to remove such a bias component, for example, Patent Document <NUM> discloses such a configuration that drive control is performed such that a primary driving electrode and a primary pickoff electrode (hereinafter, such a pair will be sometimes referred to as a primary pair) are periodically switched over with a secondary driving electrode and a secondary pickoff electrode (hereinafter, such a pair will be sometimes referred to as a secondary pair). In this case, a difference between output signals before and after the switching-over is eliminated so that the bias component is canceled out.

Patent document <CIT> discloses a vibration gyro using a piezoelectric film, and more specifically a vibration gyro capable of measuring a change in angular velocity of one axis and a vibration gyro capable of measuring a change in angular velocity of a maximum of three axes.

Patent document <CIT> discloses an angular velocity sensor and an electronic device including the angular velocity sensor.

However, the above-described angular offset is mainly caused due to, e.g., mask misalignment or resist pattern distortion at gyroscope element production, and generally, is not symmetrical among the plurality of electrodes.

Thus, the bias component which cannot be canceled even by use of the method disclosed in Patent Document <NUM> remains in the output signal, leading to an error in an angular velocity detection value. Particularly, such a remaining bias component leads to a problem in a case where a highly accurate detection of the angular velocity is required.

The present disclosure has been made in view of the foregoing, and it is an object of the present disclosure to provide a vibrating-type gyroscope element capable of reducing a bias component included in an output signal and an angular velocity sensor including the vibrating-type gyroscope element.

The solution is provided by the subject-matter of the independent claims. Variations are as defined by the dependent claims.

In order to accomplish the above-described object, a vibrating-type gyroscope element according to the present disclosure includes at least a fixed part, a resonator, a plurality of support parts connecting the resonator to the fixed part and vibratably supporting the resonator, and a plurality of electrodes formed in the plane of the resonator, the resonator having a cos Nθ (N is a natural number of two or more) mode of vibration, the plurality of electrodes being arranged in such 4N orientations that the axes of the plurality of electrodes are arranged at equiangular intervals in an outer circumferential direction of the resonator, the plurality of electrodes including: a primary driving electrode that excites first order vibration of the resonator in the cos Nθ mode; a primary pickoff electrode that detects the first order vibration; a secondary pickoff electrode that detects second order vibration of the resonator; and a secondary driving electrode that drives the resonator such that the second order vibration is canceled, the primary pickoff electrode being arranged in an orientation identical to that of the primary driving electrode, and the secondary driving electrode being arranged in an orientation identical to that of the secondary pickoff electrode.

An angular velocity sensor according to the present disclosure includes at least the vibrating-type gyroscope element, a primary AC power supply that applies an AC power with a predetermined frequency to the primary driving electrode, a primary detector that detects a voltage signal generated at the primary pickoff electrode, a secondary AC power supply that applies an AC power to the secondary driving electrode, a secondary detector that detects a voltage signal generated at the secondary pickoff electrode, and a computing unit that calculates an angular velocity based on an output signal from the secondary AC power supply.

According to the vibrating-type gyroscope element of the present disclosure, the bias component included in the output signal can be reduced. According to the angular velocity sensor of the present disclosure, the bias component included in the output signal from the vibrating-type gyroscope element can be reduced, and the accuracy of detection of the angular velocity can be enhanced.

Embodiments of the present disclosure will be described below with reference to the drawings. Note that description of the preferred embodiments below is merely illustrative in nature and is not intended to limit the scope, application, and use of the present disclosure.

<FIG> shows a plan view of a vibrating-type gyroscope element according to a first embodiment, <FIG> shows a cross-sectional view taken along line II-II in <FIG>, and <FIG> shows an enlarged view of a portion surrounded by the broken line in <FIG>.

For the sake of convenience in description, a magnetic field applier <NUM> is not shown in <FIG> and <FIG>. Also, it should be noted that <FIG> schematically show the structure of a vibrating-type gyroscope element <NUM> and do not precisely show an actual dimensional relationship among members.

Note that in description below, a radius direction of a resonator <NUM> will be sometimes referred to as a radial direction, an outer circumferential direction of the resonator <NUM> will be sometimes referred to as a circumferential direction, and a direction crossing the radial direction and the circumferential direction will be sometimes referred to as an axial direction. Moreover, in the radial direction, the direction toward the center of the resonator <NUM> will be sometimes referred to as inner, inward, or inside, and the direction toward the outer circumference of the resonator <NUM> will be sometimes referred to as outer, outward, or outside. In the axial direction, the direction toward where an upper yoke <NUM> (see <FIG>) is provided will be sometimes referred to as upper, upward, or upside, and the direction toward where a lower yoke <NUM> (see <FIG>) is provided will be sometimes referred to as lower, downward, or downside. Note that an upper surface of each member described below will be sometimes referred to as a front surface and a lower surface will be sometimes referred to as a back surface.

Moreover, one or more primary driving electrodes will be sometimes collectively referred to as a primary driving electrode PD, and one or more primary pickoff electrodes will be sometimes collectively referred to as a primary pickoff electrode PPO. In addition, one or more secondary driving electrodes will be sometimes collectively referred to as a secondary driving electrode SD, and one or more secondary pickoff electrodes will be sometimes collectively referred to as a secondary pickoff electrode SPO.

As shown in <FIG> and <FIG>, the vibrating-type gyroscope element <NUM> has a fixed part <NUM>, the resonator <NUM>, a plurality of support parts <NUM>, a plurality of electrodes 40a to 40p, and the magnetic field applier <NUM>.

As shown in <FIG>, the fixed part <NUM> has an opening 10a at the center thereof, and the resonator <NUM>, the plurality of support parts <NUM>, the plurality of electrodes 40a to 40p, and the magnetic field applier <NUM> are arranged inside the opening 10a. As shown in <FIG>, the fixed part <NUM> is a member having a lamination structure in which a first silicon layer <NUM>, a silicon oxide layer (insulating layer) <NUM>, and a second silicon layer <NUM> are laminated in this order. Further, a silicon oxide film <NUM> is provided on the front surface of the second silicon layer <NUM>.

The resonator <NUM> is a circular ring-shaped member obtained by fabricating the second silicon layer <NUM>, and has a vibration mode of cos <NUM>θ.

The support parts <NUM> are members obtained by fabricating the second silicon layer <NUM>, and are formed integrally with the resonator <NUM>. Moreover, the support parts <NUM> connect the resonator <NUM> to the fixed part <NUM>. The support parts <NUM> support the resonator <NUM> in a cantilever manner, from another point of view, vibratably support the resonator <NUM>.

As illustrated in <FIG>, each of the plurality of support parts <NUM> has a first leg <NUM> and a second leg <NUM>. Each of the first leg <NUM> and the second leg <NUM> has a first end portion 30a and a second end portion 30b. The first end portions 30a are each connected to different locations of the resonator <NUM> at first intervals. The second end portions 30b are each connected to different locations of the fixed part <NUM> at second intervals narrower than the first interval.

The first leg <NUM> has a first portion 31a extending from the first end portion 30a outward in the radial direction of the resonator <NUM> and a second portion 31c bent at a first bent portion 31b at one end of the first portion 31a and extending in parallel with the outer circumference of the resonator <NUM>. Further, the first leg <NUM> has a third portion 31e bent at a second bent portion 31d at one end of the second portion 31c and extending outward to the second end portion 30b in the radial direction of the resonator <NUM>.

Similarly, the second leg <NUM> has a first portion 32a extending from the first end portion 30a outward in the radial direction of the resonator <NUM> and a second portion 32c bent at a first bent portion 32b at one end of the first portion 32a and extending in parallel with the outer circumference of the resonator <NUM>. Further, the second leg <NUM> has a third portion 32e bent at a second bent portion 32d at one end of the second portion 32c and extending outward to the second end portion 30b in the radial direction of the resonator <NUM>.

The second portion 31c of the first leg <NUM> and the second portion 32c of the second leg <NUM> extend to the second bent portions 31d, 32d so as to approach each other. The third portion 31e of the first leg <NUM> and the third portion 32e of the second leg <NUM> extend in parallel with each other from the second bent portions 31d, 32d to the second end portions 30b with a predetermined space kept therebetween. The first leg <NUM> and the second leg <NUM> are arranged symmetrically with respect to a virtual line passing through the center of the resonator <NUM> and extending between the third portions 31e, 32e.

The electrodes 40a to 40p are conductive members arranged circumferentially in the plane of the resonator <NUM>. Moreover, each of the electrodes 40a to 40p is formed so as to extend from the fixed part <NUM> on the front surface of the support part <NUM>. For example, as shown in <FIG>, the electrode 40d extends from the second end portion 30b of the first leg <NUM> to the second end portion 30b of the second leg <NUM> along the resonator <NUM> between the first leg <NUM> and the first end portions 30a, and the second leg <NUM>. Moreover, the electrode 40d is formed on the front surface of the silicon oxide film <NUM>. Note that in description below, the electrodes 40a to 40p will be sometimes collectively referred to as an electrode <NUM> in the case of not particularly focusing on an arrangement orientation at which the electrode is arranged or what function the electrode has. Note that some or all of the electrodes <NUM> different in the arrangement orientations but identical in their function are connected with wiring (not shown) provided in the fixed part <NUM>. Note that the "orientation" in the present Description corresponds to a "region" where the electrode <NUM> is arranged and the orientations are continuous in a case where these regions are adjacent to each other. Moreover, the electrode <NUM> may be arranged across one orientation. In addition, the size of the electrode <NUM> may be smaller than the size of one orientation (region). A plurality of electrodes <NUM> may be arranged in an orientation.

As shown in <FIG> and <FIG>, two electrodes <NUM> are provided in such a way that, in the plane of the support part <NUM> and the resonator <NUM>, the two electrodes <NUM> extend in parallel with each other with a space kept therebetween. As such, two electrodes 40e, <NUM> are provided in such a way that, in the plane of the support part <NUM> and the resonator <NUM>, the two electrodes 40e, <NUM> extend in parallel with each other with a space kept therebetween. Note that in the present Description, "parallel" includes not only a case where two members are arranged in parallel with each other, but also a case where two members are arranged in contact with each other or arranged and oriented with a space kept therebetween to such an extent that these members do not cross each other.

In the illustration of <FIG>, of two electrodes 40d, <NUM> provided on the front surface of one support part <NUM> and arranged in parallel with each other circumferentially, the electrode 40d arranged outside is the primary driving electrode PD, and the electrode <NUM> arranged inside is the primary pickoff electrode PPO. Of two electrodes 40e, <NUM> provided on the front surface of the other support part <NUM> and arranged in parallel with each other circumferentially, the electrode 40e arranged outside is the secondary driving electrode SD, and the electrode <NUM> arranged inside is the secondary pickoff electrode SPO. That is, the primary pickoff electrode PPO is arranged in the same orientation as that of the primary driving electrode PD, and the secondary driving electrode SD is arranged in the same orientation as that of the secondary pickoff electrode SPO.

As illustrated in <FIG>, the pairs of the primary driving electrode PD and the primary pickoff electrode PPO and the pairs of the secondary driving electrode SD and the secondary pickoff electrode SPO are alternately arranged in the circumferential direction. Moreover, the number of pairs of the primary driving electrode PD and the primary pickoff electrode PPO and the number of pairs of the secondary driving electrode SD and the secondary pickoff electrode SPO are the same as each other.

A certain pair of the primary driving electrode PD and the primary pickoff electrode PPO and another pair, which is the closest to the certain pair, of the primary driving electrode PD and the primary pickoff electrode PPO are arranged at locations apart from each other by <NUM> degrees. A certain pair of the secondary driving electrode SD and the secondary pickoff electrode SPO and another pair, which is the closest to the certain pair, of the secondary driving electrode SD and the secondary pickoff electrode SPO are arranged at locations apart from each other by <NUM> degrees. A certain pair of the primary driving electrode PD and the primary pickoff electrode PPO and another pair, which is the closest to the certain pair, of the secondary driving electrode SD and the secondary pickoff electrode SPO are arranged at locations apart from each other by <NUM> degrees.

Note that each of the plurality of electrodes 40a to 40p is provided with electrode pads (not shown) at both end portions. Four primary pickoff electrodes PPO are connected in series through the electrode pads. Similarly, four secondary pickoff electrodes SPO are connected in series through the electrode pads.

As shown in <FIG>, the magnetic field applier <NUM> has the upper yoke <NUM>, a magnet <NUM>, and the lower yoke <NUM>. Each of the upper yoke <NUM> and the lower yoke <NUM> is a bottomed tubular member made of a magnetic material such as iron. The upper yoke <NUM> and the lower yoke <NUM> are arranged such that a tubular portion of the upper yoke <NUM> and a tubular portion of the lower yoke <NUM> face each other with a space kept therebetween in the axial direction. The resonator <NUM> is arranged between the tubular portion of the upper yoke <NUM> and the tubular portion of the lower yoke <NUM>. The resonator <NUM> is arranged between the tubular portion of the upper yoke <NUM> and the tubular portion of the lower yoke <NUM> with a space kept between the resonator <NUM> and each tubular portion in the axial direction.

One of upper or lower portions of the magnet <NUM> is the N-pole, and the other one of the upper or lower portions is the S-pole. The magnet <NUM> is held by the upper yoke <NUM>, the lower yoke <NUM>, or both thereof, and is arranged in a fixed manner inside the resonator <NUM>.

A magnetic flux flowing from one magnetic pole of the magnet <NUM> passes through one of the upper yoke <NUM> or the lower yoke <NUM>, and reaches the resonator <NUM> and the electrodes 40a to 40p provided on the front surface of the resonator <NUM>. Further, the magnetic flux passes through the resonator <NUM> and the electrodes 40a to 40p, and flows into the other magnetic pole of the magnet <NUM> through the other one of the upper yoke <NUM> or the lower yoke <NUM>.

As described above, the magnetic field applier <NUM> applies a magnetic field to the plurality of electrodes 40a to 40p in a direction crossing the front surface of the resonator <NUM>, which is the axial direction in this case. The magnetic field applier <NUM> is supported by a support substrate (not illustrated) so as to keep the positional relationship thereof with the resonator <NUM> in the radial direction and the axial direction.

The vibrating-type gyroscope element <NUM> excluding the magnetic field applier <NUM> is, for example, a micro electro mechanical systems (MEMS) element obtained in such a manner that a well-known silicon on insulator (SOI) substrate is fabricated using a micromachining technique to which a semiconductor micromachining technique is applied.

The MEMS element is manufactured as follows, for example. An SOI substrate having a first silicon layer <NUM>, a silicon oxide layer <NUM>, and a second silicon layer <NUM> is thermally oxidized, and in this manner, a silicon oxide film <NUM> is formed on the front surface of the second silicon layer <NUM>.

Next, a plurality of electrodes 40a to 40p is formed on the front surface of the silicon oxide film <NUM> by use of a mask pattern (not shown). For example, the plurality of electrodes 40a to 40p is formed in such a manner that a metal film is applied to the front surface of the silicon oxide film <NUM> via the mask pattern.

The silicon oxide film <NUM> and the second silicon layer <NUM> are etched away via another mask pattern (not shown), until the silicon oxide layer <NUM> is exposed. The basic shapes of support parts <NUM> and a resonator <NUM> are formed through these steps.

Next, in a state in which the front surfaces of the electrodes 40a to 40p, the support parts <NUM>, and the resonator <NUM> are protected with, e.g., wax, the first silicon layer <NUM> located below the support parts <NUM> and the resonator <NUM> is etched away via a mask pattern (not shown) corresponding to an opening 10a of a fixed part <NUM>. Further, the silicon oxide layer <NUM> is etched away via the same mask pattern, thereby obtaining the above-described MEMS element.

The etching of the first silicon layer <NUM> and the silicon oxide layer <NUM> may be dry etching or wet etching. In either case, etchant having a high etch selectivity for a layer as a base layer of an etching layer may be used preferably.

<FIG> shows a schematic configuration diagram of a circuit block of an angular velocity sensor. Note that for the sake of convenience in description, only the primary driving electrode PD, the primary pickoff electrode PPO, the secondary driving electrode SD, and the secondary pickoff electrode SPO of the vibrating-type gyroscope element <NUM> are schematically illustrated in <FIG>.

As shown in <FIG>, an angular velocity sensor <NUM> includes the vibrating-type gyroscope element <NUM>, a primary AC power supply <NUM>, a primary detector <NUM>, a secondary AC power supply <NUM>, a secondary detector <NUM>, a computing unit <NUM>, a switcher <NUM>, and a plurality of switches <NUM>.

The primary AC power supply <NUM> is connected to four primary driving electrodes PD. The primary detector <NUM> is connected to four primary pickoff electrodes PPO connected in series. The secondary AC power supply <NUM> is connected to four secondary driving electrodes SD. The secondary detector <NUM> is connected to four secondary pickoff electrodes SPO connected in series. The computing unit <NUM> is connected to the secondary AC power supply <NUM>.

Operation of the angular velocity sensor <NUM> will be described below.

When an AC current Ip is supplied from the primary AC power supply <NUM> to the primary driving electrodes PD, Lorentz force is applied to the primary driving electrodes PD in a direction crossing both of the direction of the magnetic field applied from the magnetic field applier <NUM> and the direction of the flow of the AC current Ip. That is, the Lorentz force acts in a direction parallel with the front surface of the resonator <NUM>. The resonator <NUM> provided with the primary driving electrodes PD is deformed by the Lorentz force. The direction of the Lorentz force is reversed periodically according to the frequency of the AC current Ip, and therefore, the resonator <NUM> vibrates with the same frequency. In this case, the resonator <NUM> vibrates in the direction parallel with the front surface thereof.

By setting the frequency of the AC current Ip according to the resonance frequency of the resonator <NUM>, first order vibration of the resonator <NUM> in a cos <NUM>θ mode is excited.

It is necessary to apply the AC current Ip to each of four primary driving electrodes PD in such a way that such first order vibration of the resonator <NUM> is generated. More specifically, the AC current Ip is set in such a way that two primary driving electrodes PD at the locations apart from each other by <NUM> degrees receive the AC current Ip flowing in opposite directions, that is, in the clockwise direction and the counterclockwise direction as viewed from above. A relationship of connection among four primary driving electrodes PD and the primary AC power supply <NUM> may only be required to satisfy the above-described setting, and four primary driving electrodes PD may be connected in series with or in parallel with the primary AC power supply <NUM>.

The primary pickoff electrode PPO detects the first order vibration and generates a voltage signal whose level corresponds to the amplitude of the first order vibration, and such a voltage signal is fed back to the primary detector <NUM>. The primary detector <NUM> outputs an output signal to the primary AC power supply <NUM> based on the voltage signal generated by the primary pickoff electrode PPO. Based on the output signal from the primary detector <NUM>, the primary AC power supply <NUM> is controlled, specifically in terms of the amplitude and frequency of the AC current Ip, such that the vibrational frequency and amplitude of the resonator <NUM> are constant.

<FIG> schematically illustrates a first order vibration state of the resonator, and <FIG> schematically illustrates a second order vibration state of the resonator.

As shown in <FIG>, the first order vibration of the circular ring-shaped resonator <NUM> is generated to deform the resonator <NUM> periodically into ellipse shapes having main axes perpendicular to each other. In a case where an angular velocity is generated about the axial direction due to application of Coriolis force to the resonator <NUM>, the directions of the above-described main axes of the ellipse shapes change. In the case of the vibrating-type gyroscope element <NUM> of the present embodiment shown in <FIG>, the main axes of the ellipses rotate <NUM> degrees from where the main axes are in the case of the first order vibration, thereby bringing the resonator <NUM> into the second order vibration state, as shown in <FIG>.

The magnetic field is also applied to the secondary pickoff electrodes SPO in a direction crossing the front surfaces thereof. Meanwhile, in response to the vibration of the resonator <NUM>, the secondary pickoff electrodes SPO also vibrate in a direction parallel with the front surfaces thereof. Accordingly, a sinusoidal wave-shaped AC voltage is generated at the secondary pickoff electrodes SPO according to the intensity of the magnetic field and the moving velocity at which the secondary pickoff electrodes SPO vibrate. The moving velocity of the secondary pickoff electrodes SPO is different between the case of the resonator <NUM> in the first order vibration state and the case of the resonator <NUM> in the second order vibration state, and therefore, the generated voltage is also different between these states.

The secondary detector <NUM> detects the voltage generated at the secondary pickoff electrode SPO, and outputs to the secondary AC power supply <NUM> a signal corresponding to the level of such a voltage.

The output signal from the secondary detector <NUM> is input to the secondary AC power supply <NUM>. Based on such an output signal, the secondary AC power supply <NUM> drives the resonator <NUM> by supplying such a current to the secondary driving electrodes SD that the resonator <NUM> is driven in such a way that the second order vibration generated at the resonator <NUM> is canceled. Further, the secondary AC power supply <NUM> inputs an output signal based on the output current to the computing unit <NUM>.

The computing unit <NUM> determines, based on the output signal from the secondary AC power supply <NUM>, whether the resonator <NUM> is in the first order vibration state or the second order vibration state. In a case where it is determined that the resonator <NUM> is in the second order vibration state, the computing unit <NUM> calculates the angular velocity based on the output signal from the secondary AC power supply <NUM>.

The angular velocity sensor <NUM> switches over primary pairs and secondary pairs at a predetermined timing, acquires an output signal from the vibrating-type gyroscope element <NUM>, and calculates out the angular velocity based on the output signal. For example, the angular velocity is calculated based on a difference between the output signals before and after the switching-over. Such switching-over operation is performed by switching over internal wire connection by the switches <NUM> and the switcher <NUM> illustrated in <FIG>. The "predetermined timing" may be a timing at which the vibrating-type gyroscope element <NUM> is in a stop state or a timing at which the vibrating-type gyroscope element <NUM> is in a uniform motion state, for example.

<FIG> shows electrode arrangement before switching-over of the primary pairs and the secondary pairs, and <FIG> shows electrode arrangement after switching-over of the primary pairs and the secondary pairs.

The electrode arrangement illustrated in <FIG> is similar to that illustrated in <FIG>. Thus, the electrodes 40b, 40d, 40f, <NUM> function as the primary driving electrodes PD, and the electrodes 40j, <NUM>, 40n, 40p function as the primary pickoff electrodes PPO. Moreover, the electrodes 40a, 40c, 40e, <NUM> function as the secondary driving electrodes SD, and the electrodes 40i, <NUM>, <NUM>, 40o function as the secondary pickoff electrodes SPO.

A control signal is sent to four switches <NUM> from the switcher <NUM> so as to switch over wire connection inside the angular velocity sensor <NUM> at the predetermined timing. As a result, the electrodes 40b, 40d, 40f, <NUM> are connected to the secondary AC power supply <NUM>, and function as the secondary driving electrodes SD as shown in <FIG>. Similarly, the electrodes 40j, <NUM>, 40n, 40p are connected to the secondary detector <NUM>, and function as the secondary pickoff electrodes SPO. The electrodes 40a, 40c, 40e, <NUM> are connected to the primary AC power supply <NUM>, and function as the primary driving electrodes PD. The electrodes 40i, <NUM>, <NUM>, 40o are connected to the primary detector <NUM>, and function as the primary pickoff electrodes PPO.

Note that the vibrating-type gyroscope element <NUM>, the primary AC power supply <NUM>, the primary detector <NUM>, the secondary AC power supply <NUM>, the secondary detector <NUM>, and the computing unit <NUM> may be mounted on different substrates or on the same substrate. The vibrating-type gyroscope element <NUM>, the primary AC power supply <NUM>, the primary detector <NUM>, the secondary AC power supply <NUM>, the secondary detector <NUM>, and the computing unit <NUM> may be housed in different packages (not shown). The vibrating-type gyroscope element <NUM> and other components may be mounted on different substrates, or may be housed in different packages. In this case, the primary AC power supply <NUM> and the secondary AC power supply <NUM> may be mounted on a substrate other than these substrates, or may be housed in a package other than these packages.

<FIG> schematically shows displacements of the secondary pickoff electrode over time during operation, and <FIG> schematically shows the vibration angle dependence of an actual output signal from the secondary pickoff electrode and various signals included therein.

The secondary pickoff electrode SPO illustrated in (a) of <FIG> and the secondary pickoff electrode SPO illustrated in (b) of <FIG> are at locations apart from each other by <NUM> degrees in the circumferential direction. That is, these two secondary pickoff electrodes SPO are at locations perpendicular to each other. The white arrow mark illustrated in each of (a) and (b) of <FIG> indicates the direction of electromotive force of the voltage generated at the secondary pickoff electrode SPO.

The vibration angle illustrated in <FIG> is equivalent to the product of the time and the frequency of the AC voltage generated at the secondary pickoff electrode SPO. Moreover, <FIG> illustrates, for each of an SPO(L) and an SPO(R) as described later, an actual output signal and various signals included therein.

As described above, when the AC current Ip is applied, the Lorentz force acts on the primary driving electrodes PD due to the magnetic field and the AC current Ip. The Lorentz force is also applied to the resonator <NUM>, and accordingly, the resonator <NUM> periodically deforms and vibrates.

Although not shown in the figure, the direction of the AC current Ip flowing in the primary driving electrode PD is alternately reversed in four primary driving electrodes PD in order to excite the first order vibration of the resonator <NUM> in the cos <NUM>θ mode. That is, the primary driving electrodes PD in which the AC current Ip flows in the clockwise direction and the primary driving electrodes PD in which the AC current Ip flows in the counterclockwise direction are alternately arranged.

Thus, forces in the opposite directions in the radial direction act on both ends of a portion, which is formed in the plane of the reasoner <NUM>, of the secondary pickoff electrode SPO sandwiched between the primary driving electrodes PD. The direction of action of the force periodically changes.

The secondary pickoff electrode SPO adjacent to the pair of the primary driving electrode PD and the primary pickoff electrode PPO is at a location apart from the electrodes PD, PPO by <NUM> degrees in the circumferential direction.

Thus, as shown in each of (a) and (b) of <FIG>, the portion of the secondary pickoff electrode SPO formed in the plane of the resonator <NUM> deforms, in a plane parallel with the front surface of the resonator <NUM>, symmetrically with respect to a virtual center axis which is an axis passing through the center, centered in the circumferential direction, of the portion of the secondary pickoff electrode SPO and extending in the radial direction. That is, in a case where one end portion is displaced inward in the radial direction from a location before operation, the other end portion is displaced outward in the radial direction. In a case where one end portion is displaced outward in the radial direction from the location before operation, the other end portion is displaced inward in the radial direction. Needless to say, such deformation is repeated in a predetermined cycle.

Note that in description below, a portion of the secondary pickoff electrode SPO on the left side of the plane of paper with respect to the center axis will be sometimes referred to as an SPO(L) and a portion on the right side of the plane of paper will be sometimes referred to as an SPO(R).

The secondary pickoff electrode SPO illustrated in (a) of <FIG> is displaced symmetrically to the secondary pickoff electrode SPO illustrated in (b) in terms of time. That is, in the example shown in (a), as time advances from a time point t0 before operation to a time point t1, the SPO(L) is displaced outward in the radial direction, and the SPO(R) displaces inward in the radial direction. On the other hand, in the example shown in (b), the SPO(L) is displaced inward in the radial direction, and the SPO(R) is displaced outward in the radial direction. At a time point t2, the SPO returns to the same location as that at the time point t0 in both cases shown in (a) and (b). As time advances to a time point t3, the SPO(L) is displaced inward in the radial direction and the SPO(R) is displaced outward in the radial direction in the example shown in (a). On the other hand, in the example shown in (b), the SPO(L) is displaced outward in the radial direction, and the SPO(R) is displaced inward in the radial direction. As time further advances to a time point t4, the SPO returns to the same location as that at the time point t0 in both cases shown in (a) and (b).

Each of the secondary pickoff electrode SPO illustrated in (a) and (b) of <FIG> and the resonator <NUM> located immediately therebelow periodically repeatedly deform as described above. At the resonator <NUM> immediately below the secondary pickoff electrode SPO, the moving velocity is the maximum or minimum at a location where a deformation amount is zero, and therefore, the amplitude of the voltage generated at the secondary pickoff electrode SPO is also the maximum or minimum. The moving velocity is zero at a location where the deformation amount is the maximum or minimum, and therefore, the amplitude of the voltage generated at the secondary pickoff electrode SPO is also zero.

As described above, deformation of the secondary pickoff electrode SPO is such that there is a slight difference in the deformation amount between the deformation outward and the deformation inward in the radial direction, and accordingly, the voltage generated at the secondary pickoff electrode SPO has a distortion component superimposed on a fundamental sinusoidal wave (hereinafter sometimes referred to as a fundamental wave signal). This distortion component is equivalent to a difference (hereinafter, a differential signal) between the actual output signal from the secondary pickoff electrode SPO and the fundamental wave signal.

<FIG> illustrates the actual output signal from the secondary pickoff electrode SPO and the fundamental wave signal and the differential signal included therein. Moreover, t0 to t4 illustrated in <FIG> correspond to the time points t0 to t4 described with reference to <FIG>.

Focusing on one secondary pickoff electrode SPO, it is assumed that the direction of the fundamental wave is opposite between the SPO(L) and the SPO(R), i.e., when one of the SPO(L) or the SPO(R) has a positive value, the other one of the SPO(L) or the SPO(R) has a negative value. In the case of an ideal output signal with a differential signal of zero, one SPO signal, which is a combination of the SPO(L) and SPO(R) signals, is zero. However, due to the above-described superimposed distortion component, the direction of the differential signal with respect to the fundamental wave is the same direction between the SPO(L) and SPO(R), and therefore, the positive and negative values with respect to the fundamental wave change with a double frequency. Taking this fact into consideration, it can be said that a signal having a frequency twice as high as the frequency of the fundamental wave signal, i.e., the frequency of the AC current Ip, is generated at one secondary pickoff electrode SPO. Hereinafter, such a signal will be sometimes referred to as a second harmonic component.

The second harmonic component is an error component in the output signal from the secondary pickoff electrode SPO, and therefore, may be a bias component for an angular velocity detection value. This leads to a problem in a case where the angular velocity needs to be obtained with a high accuracy.

The second harmonic component is, as shown in <FIG>, formed such that the differential signals generated at the SPO(L) and the SPO(R) and having the same phase are superimposed on each other, and therefore, the amplitude thereof is also approximately doubled. This provides a greater influence on the angular velocity detection value.

Two secondary pickoff electrodes SPO at locations apart from each other by <NUM> degrees in the circumferential direction displace symmetrically in terms of time, as shown in <FIG>. The second harmonic components included in the output signals from the secondary pickoff electrodes SPO have the opposite phases. Thus, the output signals from two secondary pickoff electrodes SPO are added up so that the second harmonic components can be canceled out to almost zero.

In the vibrating-type gyroscope element <NUM> described in the present embodiment, four secondary pickoff electrodes SPO are arranged at locations apart from each other by <NUM> degrees in the circumferential direction, as shown in <FIG>. The voltages generated at four secondary pickoff electrodes SPO are added up and are output as the output signal, and therefore, the output signal eventually input to the secondary detector <NUM> from the secondary pickoff electrodes SPO has almost no second harmonic component and the error component is reduced.

As described above, the vibrating-type gyroscope element <NUM> according to the present embodiment includes at least the fixed part <NUM>, the resonator <NUM>, the support parts <NUM> connecting the resonator <NUM> to the fixed part <NUM> and vibratably supporting the resonator <NUM>, and the electrodes 40a to 40p provided circumferentially in the plane of the resonator <NUM>.

When the resonator <NUM> has a cos <NUM>θ mode of vibration, the electrodes 40a to 40p are arranged at equiangular intervals in the outer circumferential direction of the resonator <NUM>, which are intervals of <NUM> degrees for the eight orientations in this case.

These <NUM> electrodes 40a to 40p include the primary driving electrodes PD that excite the first order vibration of the resonator <NUM> in the cos <NUM>θ mode and the primary pickoff electrodes PPO that detect the first order vibration. Further, the electrodes 40a to 40p include the secondary pickoff electrodes SPO that detect the second order vibration generated when the angular velocity is provided to the resonator <NUM> and the secondary driving electrodes SD that drive the resonator <NUM> in such a way as to cancel the second order vibration.

The primary pickoff electrode PPO is arranged in the same orientation as that of the primary driving electrode PD, and the secondary driving electrode SD is arranged in the same orientation as that of the secondary pickoff electrode SPO. The pairs of the primary driving electrode PD and the primary pickoff electrode PPO and the pairs of the secondary driving electrode SD and the secondary pickoff electrode SPO are alternately arranged at eight orientations.

The vibrating-type gyroscope element <NUM> further includes the magnetic field applier <NUM> that applies the magnetic field to <NUM> electrodes 40a to 40p in the direction crossing the front surface of the resonator <NUM>, which is the axial direction in this case.

With this configuration of the vibrating-type gyroscope element <NUM>, it becomes possible that the bias component included in the output signal from the vibrating-type gyroscope element <NUM> can be reduced in a case where the angular velocity sensor <NUM> is so configured that an operation of switching over the primary pairs and the secondary pairs is performed therein. This will be further described with reference to the drawings.

<FIG> shows arrangement of electrodes <NUM> for comparison. A vibrating-type gyroscope element <NUM> shown in <FIG> has, for example, a configuration similar to that disclosed in Patent Document <NUM>.

In the vibrating-type gyroscope element <NUM> shown in <FIG>, electrodes 40a to <NUM> are each arranged on eight support parts <NUM>. Primary driving electrodes PD, secondary driving electrodes SD, primary pickoff electrodes PPO, and secondary pickoff electrodes SPO are arranged at eight orientations in this order in the clockwise direction in the circumferential direction. The electrodes PD, SD, PPO, SPO are provided two each, and the electrodes of the same type are arranged at locations apart from each other by <NUM> degrees in the circumferential direction.

In the vibrating-type gyroscope elements <NUM>, <NUM>, force acts on each of the electrodes 40a to 40p during operation, and a mechanical motion axis is virtually assumed accordingly. Assuming that the axis for the primary driving electrode PD is, for example, a PD axis, a predetermined angular relationship is unambiguously set, according to a relationship of arrangement of the electrodes, among the PD axis and an SD axis, a PPO axis, and a SPO axis which are motion axes for the secondary driving electrode SD, the primary pickoff electrode PPO, and the secondary pickoff electrode SPO.

The resonator <NUM> also has virtual motion axes for the first order vibration and the second order vibration. Ideally, the motion axis for the first order vibration and the PD axis overlap with each other. In this case, the motion axis for the second order vibration and the SD axis also overlap with each other.

However, as described above, usually in the vibrating-type gyroscope element <NUM>, e.g., angular offset among the electrodes 40a to 40p or uneven magnetic field application is caused. Due to these factors, angular offset is caused between the motion axis for the first order vibration and the PD axis. Further, the angular offset among the electrodes 40a to 40p also leads to angular offset between the PD axis and the SD axis. Similarly, the angular offset among the electrodes 40a to 40p also leads to angular offset between each of the PPO axis and the SPO axis and the PD axis. The above-described bias component is generated due to such angular offset.

The inventors of the present application have found that a noise component due to the angular offset between the PD axis and the motion axes for the electrodes SD, PPO, SPO other than the PD axis is superimposed on the bias component and is not canceled out even by, as disclosed in Patent Document <NUM>, operating the angular velocity sensor <NUM> with the primary pairs and secondary pairs thereof switched over to eliminate a difference in an output signal.

Thus, the inventors of the present application have noted an importance of the relationship of arrangement of the electrodes PD, SD, PPO, SPO, thereby finding that the angular offset between the PD axis and each of the SD axis, the PPO axis, and the SPO axis which are the motion axes other than the PD axis can be reduced by arranging the electrodes PD, SD, PPO, SPO at the locations as shown in <FIG>. With this configuration, the elimination of the difference in the output signal by an operation of switching over the primary pairs and the secondary pairs can substantially cancel out the entire bias component.

Two electrodes <NUM> are provided from a support part <NUM> to the resonator <NUM> in such a way as to extend in parallel with each other with the space kept therebetween. One electrode <NUM> provided on one support part <NUM> is the primary driving electrode PD, and the other electrode <NUM> provided thereon is the primary pickoff electrode PPO. One electrode <NUM> provided on the other support part <NUM> is the secondary driving electrode SD, and the other electrode <NUM> provided thereon is the secondary pickoff electrode SPO.

The electrodes 40a to 40p are arranged respectively on eight support parts <NUM> as described above so that the primary pickoff electrode PPO and the primary driving electrode PD can be easily arranged in the same orientation. In addition, the secondary driving electrode SD and the secondary pickoff electrode SPO can be easily arranged in the same orientation. With this configuration, the angular offset between the PD axis and each of the SD axis, the PPO axis, and the SPO axis which are the motion axes other than the PD axis can be reduced, and therefore, the bias component included in the output signal from the vibrating-type gyroscope element <NUM> can be significantly reduced. Moreover, this configuration can suppress an unnecessary increase in the size of the vibrating-type gyroscope element <NUM>.

In view of the above-described point, it can be said that the mechanical motion axis is virtually assumed for each of the electrodes 40a to 40p. Thus, the arrangement orientations of the electrodes 40a to 40p can be also said to be such orientations that the virtual motion axes (hereinafter sometimes referred to as the axis of the electrode <NUM>) are arranged at equiangular intervals in the outer circumferential direction of the resonator <NUM>.

Four secondary pickoff electrodes SPO may be preferably connected in series.

With this configuration, a greater voltage signal can be taken for detecting the second order vibration. Accordingly, a high S/N ratio of the output signal from the secondary detector <NUM> can be obtained, thereby making it possible to enhance the accuracy of detection of the angular velocity calculated by the computing unit <NUM>.

For a similar reason, four primary pickoff electrodes PPO may be connected in series, preferably.

Four secondary pickoff electrodes SPO may be arranged at the locations apart from each other by <NUM> degrees in the circumferential direction, preferably. With this configuration, the second harmonic component, which is the error component included in the output signal from the secondary pickoff electrode SPO can be reduced.

It is preferable that the support part <NUM> on which the electrode <NUM> is arranged include the first leg <NUM> having the first to third portions 31a, 31c, 31e and the second leg <NUM> having the first to third portions 32a, 32c, 32e. It is more preferable that the first leg <NUM> and the second leg <NUM> be arranged symmetrically with respect to the virtual line passing through the center of the resonator <NUM> and extending between the third portions 31e, 32e.

This configuration of the support part <NUM> makes it possible that, when the first order vibration of the resonator <NUM> is generated, the resonator <NUM> can be supported with no great influence on the vibration. The support parts <NUM> are provided at equiangular intervals in the circumferential direction and the first leg <NUM> and the second leg <NUM> are provided symmetrically with respect to the above-described virtual line, and therefore, the resonator <NUM> can be connected to the fixed part <NUM> with equal balance. Thus, the first order vibration of the resonator <NUM> can be stably generated.

According to the vibrating-type gyroscope element <NUM> of the present embodiment, a crosstalk voltage included in the voltage generated at the secondary pickoff electrode SPO can be reduced. This will be further described herein.

In a case where the primary driving electrode PD and the secondary pickoff electrode SPO are close to each other, mutual induction is caused at the secondary pickoff electrode SPO due to the AC current flowing in the primary driving electrode PD, and as a result, the crosstalk voltage is induced. Such a crosstalk voltage is also superimposed on the vibrating-type gyroscope element <NUM>, thereby being an error component.

On the other hand, in the vibrating-type gyroscope element <NUM> of the present embodiment, a pair of the primary driving electrode PD and the primary pickoff electrode PPO is arranged on each side of a pair of the secondary driving electrode SD and the secondary pickoff electrode SPO, as shown in <FIG>.

As described above, in order to excite the first order vibration of the resonator <NUM> in the cos <NUM>θ mode, the primary driving electrodes PD in which the AC current Ip flows in the clockwise direction and the primary driving electrodes PD in which the AC current Ip flows in the counterclockwise direction are alternately arranged.

In this case, crosstalk voltages being of the same level but different from each other in the direction of the electromotive force are induced between respective ones of primary driving electrodes PD and the secondary pickoff electrode SPO arranged therebetween, and as a result, are canceled out to almost zero. Since the crosstalk voltage is reduced as described above, the accuracy of detection of the angular velocity is enhanced.

As shown in <FIG>, the location where the secondary driving electrode SD is arranged between the primary driving electrode PD and the secondary pickoff electrode SPO is at a portion where the primary driving electrode PD and the secondary pickoff electrode SPO are the closest to each other, i.e., the first portions 31a, 32a of the support parts <NUM>. With this configuration, a mutual inductance between the primary driving electrode PD and the secondary pickoff electrode SPO can be decreased, and the level of the crosstalk voltage can be reduced.

Note that also in configurations described later in second to fourth modifications, the crosstalk voltage included in the voltage generated at the secondary pickoff electrode SPO can be further reduced as compared to the configuration shown in <FIG> and the accuracy of detection of the angular velocity can be more enhanced accordingly.

Note that depending on the arrangement orientation of the primary driving electrode PD and the number of primary driving electrodes PD, the resonator <NUM> may have a cos Nθ (N is a natural number of two or more) mode of vibration. In this case, the arrangement orientations of the axes of the electrodes <NUM> are 4N orientations.

That is, in the vibrating-type gyroscope element <NUM> of the present embodiment, the support parts <NUM> and the electrodes <NUM> are arranged in such 4N orientations that the axes of the electrodes <NUM> are arranged at equiangular intervals in the outer circumferential direction of the resonator <NUM> in a case where the resonator <NUM> has a cos Nθ mode of vibration.

One support part <NUM> is arranged at a location apart from another support part <NUM> by (<NUM>/4N) degrees. That is, a certain pair of the primary driving electrode PD and the primary pickoff electrode PPO and a pair, which is adjacent to the certain pair, of the secondary driving electrode SD and the secondary pickoff electrode SPO are arranged at locations apart from each other by (<NUM>/4N) degrees.

In a preferred embodiment, the plurality of secondary pickoff electrodes SPO included in the vibrating-type gyroscope element <NUM> are arranged at locations apart from each other by (<NUM>/2N + <NUM> × (M/N)) degrees in the circumferential direction. Here, M is an integer, and satisfies a relationship of <NUM> ≤ M ≤ N - <NUM>. With this configuration, the second harmonic component, which is the error component included in the output signal from the secondary pickoff electrode SPO can be reduced.

The angular velocity sensor <NUM> of the present embodiment includes at least the vibrating-type gyroscope element <NUM>, the primary AC power supply <NUM> that applies the AC current with the predetermined frequency to the primary driving electrodes PD, the primary detector <NUM> that detects the voltage signals generated at the primary pickoff electrodes PPO, the secondary AC power supply <NUM> that applies the AC current to the secondary driving electrodes SD, the secondary detector <NUM> that detects the voltage signals generated at the secondary pickoff electrodes SPO, and the computing unit <NUM> that calculates the angular velocity based on the output signal from the secondary AC power supply <NUM>.

The angular velocity sensor <NUM> further includes the switcher <NUM> that switches over the pairs of the primary driving electrode PD and the primary pickoff electrode PPO with the pairs of the secondary driving electrode SD and the secondary pickoff electrode SPO at the predetermined timing, so as to exchange their operations. The computing unit <NUM> calculates the angular velocity based on the output signals from the secondary AC power supply <NUM> before and after the switching-over operation.

According to the angular velocity sensor <NUM> of the present embodiment, the bias component included in the output signal from the vibrating-type gyroscope element <NUM> can be reduced, and the accuracy of detection of the angular velocity can be enhanced.

According to the present embodiment, the voltage generated at the primary pickoff electrode PPO is detected by the primary detector <NUM>, and the output signal from the primary detector <NUM> is fed back to the primary AC power supply <NUM>. With this configuration, the first order vibration generated at the resonator <NUM> can be stabilized.

The voltage generated at the secondary pickoff electrode SPO is detected by the secondary detector <NUM>, and based on the output signal from the secondary detector <NUM>, the output of the secondary AC power supply <NUM> is controlled such that the second order vibration generated at the resonator <NUM> is canceled. With this configuration, the vibration state of the resonator <NUM> can be stabilized. Also, with this configuration, the noise component included in the output signal from the secondary AC power supply <NUM> can be reduced, and the accuracy of detection of the angular velocity can be enhanced.

Note that in description above, when the angular velocity sensor <NUM> is operated, the primary driving electrode PD and the secondary driving electrode SD are switched over at the predetermined timing so as to exchange their operations, and the primary pickoff electrode PPO and the secondary pickoff electrode SPO are switched over at the predetermined timing so as to exchange their operations. However, the combination of the electrodes <NUM> to be switched over is not limited to the above. When the angular velocity sensor <NUM> is operated, the primary driving electrode PD and the secondary pickoff electrode SPO may be switched over at the predetermined timing so as to exchange their operations, and the primary pickoff electrode PPO and the secondary driving electrode SD may be switched over at the predetermined timing so as to exchange their operations.

<FIG> is a plan view showing electrode arrangement according to the present modification. Note that in <FIG> and each figure thereafter, the like reference numerals are used to represent like elements similar to those of the first embodiment and detailed description thereof will not be repeated.

The configuration shown in <FIG> is different from the configuration shown in the first embodiment in that three pairs of the primary driving electrode PD and the primary pickoff electrode PPO and three pairs of the secondary driving electrode SD and the secondary pickoff electrode SPO are provided.

In the configuration shown in <FIG>, the pairs of the primary driving electrode PD and the primary pickoff electrode PPO and the pairs of the secondary driving electrode SD and the secondary pickoff electrode SPO are sequentially and alternately arranged in the circumferential direction.

Note that regarding the electrodes 40a, <NUM>, 40i, 40p, the type of electrode <NUM>, e.g., whether the electrode <NUM> is the primary driving electrode PD or the secondary pickoff electrode SPO, is not clearly described. The electrodes <NUM> whose type is not clearly described as described above are so-called dummy electrodes provided for equalizing the balance of the mass of the resonator <NUM>, and do not contribute to detection of the first order vibration and the second order vibration of the resonator <NUM>. Similarly, in each figure hereinafter, the electrodes <NUM> whose type is not clearly described are dummy electrodes.

The vibrating-type gyroscope element <NUM> described in the present modification provides advantages similar to those of the configuration described in the first embodiment. That is, this configuration makes it possible that the bias component included in the output signal from the vibrating-type gyroscope element <NUM> can be reduced in a case where an operation of switching over the primary pairs and the secondary pairs is performed in the angular velocity sensor <NUM>.

According to the angular velocity sensor <NUM> on which the vibrating-type gyroscope element <NUM> of the present modification is mounted, the accuracy of detection of the angular velocity is enhanced as in the first embodiment.

<FIG> shows a plan view of electrode arrangement according to the present modification, and is different from the configuration shown in the first embodiment in that two pairs of the primary driving electrode PD and the primary pickoff electrode PPO and two pairs of the secondary driving electrode SD and the secondary pickoff electrode SPO are provided.

In the configuration shown in <FIG>, one pair of the primary driving electrode PD and the primary pickoff electrode PPO and one pair of the secondary driving electrode SD and the secondary pickoff electrode SPO are arranged at locations apart from each other by (<NUM>/4N) degrees in the circumferential direction, which are locations apart from each other by <NUM> degrees in this case. Further, two pairs of the primary driving electrode PD and the primary pickoff electrode PPO are arranged at locations apart from each other by (<NUM>/N) degrees in the circumferential direction, which are locations apart from each other by <NUM> degrees in this case. Similarly, two pairs of the secondary driving electrode SD and the secondary pickoff electrode SPO are arranged at locations apart from each other by <NUM> degrees in the circumferential direction.

In the configuration shown in <FIG>, one pair of the primary driving electrode PD and the primary pickoff electrode PPO and one pair of the secondary driving electrode SD and the secondary pickoff electrode SPO are arranged at locations apart from each other by (<NUM>/4N) degrees in the circumferential direction, which are locations apart from each other by <NUM> degrees in this case. Further, two pairs of the primary driving electrode PD and the primary pickoff electrode PPO are arranged at locations apart from each other by (<NUM>/2N + <NUM> × (M/N)) degrees in the circumferential direction. In this case, M = <NUM> and N = <NUM>, and two pairs of the primary driving electrode PD and the primary pickoff electrode PPO are arranged at locations apart from each other by <NUM> degrees in the circumferential direction. Similarly, two pairs of the secondary driving electrode SD and the secondary pickoff electrode SPO are arranged at locations apart from each other by <NUM> degrees in the circumferential direction.

In the present modification, two secondary pickoff electrodes SPO are arranged at locations apart from each other by <NUM> degrees in the circumferential direction, i.e., locations perpendicular to each other. Thus, as described in the first embodiment, the second harmonic component, which is the error component included in the output signal from the secondary pickoff electrode SPO can be reduced.

<FIG> shows a plan view of electrode arrangement according to the present modification, and is different from the configuration shown in the first embodiment in that one pair of the primary driving electrode PD and the primary pickoff electrode PPO and one pair of the secondary driving electrode SD and the secondary pickoff electrode SPO are provided.

In the configuration shown in <FIG>, one pair of the primary driving electrode PD and the primary pickoff electrode PPO and one pair of the secondary driving electrode SD and the secondary pickoff electrode SPO are arranged at locations apart from each other by (<NUM>/4N) degrees in the circumferential direction, which are locations apart from each other by <NUM> degrees in this case.

<FIG> shows a schematic configuration diagram of an angular velocity sensor according to the present embodiment, and this angular velocity sensor <NUM> includes a pair of angular velocity sensors <NUM>, <NUM> and a computing unit <NUM>.

The pair of angular velocity sensors <NUM>, <NUM> has vibrating-type gyroscope elements <NUM> having the same configuration and size. The vibrating-type gyroscope element <NUM> has the same structure as that described in the first embodiment. Further, the configuration of a unit that processes an electric signal is similar to that shown in <FIG>, and two angular velocity sensors <NUM>, <NUM> have the same structure and properties of each unit. Two angular velocity sensors <NUM>, <NUM>, particularly the vibrating-type gyroscope elements <NUM> provided therein, are provided at locations close to each other, such as locations on the same substrate. Alternatively, two angular velocity sensors <NUM>, <NUM> are arranged in the same package or the same case even in a case where these sensors <NUM>, <NUM> are provided on different substrates.

On the other hand, the pair of angular velocity sensors <NUM>, <NUM> is different from each other in an operation method. The angular velocity sensor <NUM> is operated in such a way that primary pairs and secondary pairs are switched over in a predetermined cycle. That is, the angular velocity sensor <NUM> operates in a manner similar to that of the angular velocity sensor <NUM> described in the first embodiment. Note that in the angular velocity sensor <NUM>, the cycle of the switching-over operation is constant.

On the other hand, the angular velocity sensor <NUM> is operated with primary pairs and secondary pairs fixed. That is, an operation of switching over the primary pairs and the secondary pairs is not performed therein. Thus, a switcher <NUM> and switches <NUM> shown in <FIG> may be omitted in the angular velocity sensor <NUM>.

An output signal from the angular velocity sensor <NUM> and an output signal from the angular velocity sensor <NUM> are input to the computing unit <NUM>.

The computing unit <NUM> corrects the output signal from the angular velocity sensor <NUM> based on the output signal from the angular velocity sensor <NUM>, and calculates an angular velocity based on the corrected signal. More specifically, a bias component may be extracted from the output signal from the angular velocity sensor <NUM>, and the extracted bias component may be subtracted from the output signal from the angular velocity sensor <NUM>. The bias component may be obtained from a value obtained by addition of the output signal from the angular velocity sensor <NUM> in an operation of switching over the primary pairs and the secondary pairs. As an alternative, the bias component included in the output signal from the angular velocity sensor <NUM> may be calculated by comparison between the output signal from the angular velocity sensor <NUM>, for which the bias component has been canceled in advance as described in the first embodiment, and the output signal from the angular velocity sensor <NUM>, thereby performing a correction of subtracting such a bias component.

In a case where the angular velocity sensor <NUM> is mounted on a moving object, a timing of switching over the primary pairs and the secondary pairs would not be properly settable in the angular velocity sensor <NUM> described in the first embodiment in some cases. Depending on an operating state of a device on which the angular velocity sensor <NUM> is mounted, the angular velocity sensor <NUM> would need to constantly output the angular velocity in some cases. In these cases, there is a probability that the bias component cannot be properly canceled and the accuracy of detection of the angular velocity is degraded.

On the other hand, according to the present embodiment, the output signal from the angular velocity sensor <NUM> in which the switching-over operation is not performed is corrected using the output signal from the angular velocity sensor <NUM> in which an operation of switching over the primary pairs and the secondary pairs is performed in a certain cycle.

With this configuration, the bias component included in the output signal from the angular velocity sensor <NUM> can be grasped regardless of a mounting status of the angular velocity sensor <NUM> and an operating status of the device, and the bias component can be properly reliably reduced. In addition, this can enhance the accuracy of detection of the angular velocity.

Note that <FIG> shows the example where the computing unit <NUM> is provided outside two angular velocity sensors <NUM>, <NUM>, but the function of the computing unit <NUM> may be incorporated into a computing unit <NUM> provided inside the angular velocity sensor <NUM>. With this configuration, the configuration of the angular velocity sensor <NUM> is simplified. Further, this allows cost reductions for the angular velocity sensor <NUM>.

Note that in description above, when the angular velocity sensor <NUM> is operated, the primary driving electrode PD and the secondary driving electrode SD are switched over in the predetermined cycle so as to exchange their operations, and the primary pickoff electrode PPO and the secondary pickoff electrode SPO are switched over in the predetermined cycle to exchange their operations. However, the combination of the electrodes <NUM> to be switched over is not limited to the above. When the angular velocity sensor <NUM> is operated, the primary driving electrode PD and the secondary pickoff electrode SPO may be switched over in the predetermined cycle so as to exchange their operations, and the primary pickoff electrode PPO and the secondary driving electrode SD may be switched over in the predetermined cycle so as to exchange their operations.

The components described in the first and second embodiments and each modification may be combined to create a new embodiment. For example, in the angular velocity sensors <NUM>, <NUM> described in the second embodiment, the vibrating-type gyroscope element <NUM> mounted thereon may be the vibrating-type gyroscope element <NUM> described in any of the first to fourth modifications. However, even in this case, two vibrating-type gyroscope elements <NUM> have the same structure and size in a preferred embodiment.

In the first and second embodiments and each modification, the electromagnetic vibrating-type gyroscope element <NUM> has been described as an example, but the present disclosure is not limited to above and the structure of the present disclosure is also applicable to, e.g., a piezoelectric vibrating-type gyroscope element.

<FIG> shows a plan view of the piezoelectric vibrating-type gyroscope element, and <FIG> shows a cross-sectional view taken along line XVI-XVI in <FIG>.

The vibrating-type gyroscope element <NUM> shown in <FIG> is similar to the vibrating-type gyroscope element <NUM> described in the first embodiment in the configurations and arrangement relationship of the fixed part <NUM>, the resonator <NUM>, and the support parts <NUM>. A relationship of arrangement of the primary driving electrodes PD, the primary pickoff electrodes PPO, the secondary driving electrodes SD, and the secondary pickoff electrodes SPO is also similar to that of the first embodiment.

On the other hand, the vibrating-type gyroscope element <NUM> shown in <FIG> and <FIG> is different from the vibrating-type gyroscope element <NUM> described in the first embodiment in that the magnetic field applier <NUM> is omitted and each of a plurality of electrodes 70a to 70p is a piezoelectric structure <NUM> in which a lower electrode layer <NUM>, a piezoelectric body layer <NUM>, and an upper electrode layer <NUM> are laminated on each other in this order.

The vibrating-type gyroscope element <NUM> shown in <FIG> operates as follows. First, when an AC voltage is applied to between the upper electrode layer <NUM> and the lower electrode layer <NUM> in the primary driving electrode PD, the piezoelectric body layer <NUM> periodically extends and contracts. The resonator <NUM> vibrates according to such extension and contraction. As in the first embodiment, the frequency of the AC voltage is adjusted to the resonance frequency of the resonator <NUM>, and accordingly, the first order vibration of the resonator <NUM> in the cos <NUM>θ mode is excited. Also, as in the first embodiment, the output signal from the primary detector <NUM> is fed back to the primary AC power supply <NUM>, and the first order vibration is stabilized accordingly.

The secondary pickoff electrodes SPO and the piezoelectric body layers <NUM> included therein extend and contract according to vibration of the resonator <NUM>. In response to such extension and contraction, an AC voltage is generated between the upper electrode layer <NUM> and the lower electrode layer <NUM> in the secondary pickoff electrode SPO.

When the angular velocity is generated at the resonator <NUM> and the second order vibration is generated accordingly, the voltage signal generated at the secondary pickoff electrode SPO is input to the secondary detector <NUM>, and based on the output signal from the secondary detector <NUM>, the output of the secondary AC power supply <NUM> is controlled such that the second order vibration is canceled. As in the first embodiment, the angular velocity is calculated by the computing unit <NUM> based on the output signal from the secondary AC power supply <NUM>.

As in the first embodiment, it can be clearly understood that the bias component included in the voltage generated at the secondary pickoff electrode SPO can also be reduced in the vibrating-type gyroscope element <NUM> shown in <FIG>. As in the first embodiment, the accuracy of detection of the angular velocity can also be enhanced in the angular velocity sensor <NUM> on which the vibrating-type gyroscope element <NUM> is mounted.

Taking the example shown in <FIG> into consideration as well, it can be said that the primary AC power supply <NUM> described in the present Description applies the AC power with the predetermined frequency to the primary driving electrodes PD. The secondary AC power supply <NUM> applies the AC power to the secondary driving electrodes SD.

Note that the resonator <NUM> may only be required to be in such a shape that the first order vibration is excitable with the shape and the vibration state of the shape changes when the angular velocity is generated, and therefore the resonator <NUM> is not limited particularly to the circular ring shape. For example, the resonator <NUM> may be in a regular polygonal ring shape or a discoid shape. The resonator <NUM> may also be in a hemispherical shape.

The support part <NUM> may only be required to connect the resonator <NUM> to the fixed part <NUM> without interference with vibration of the resonator <NUM>, and the shape thereof is not limited to that shown in <FIG> and <FIG>.

The first and second embodiments and each modification discuss the examples where the primary driving electrode PD and the primary pickoff electrode PPO are arranged in parallel with each other on the front surfaces of the resonator <NUM> and the support part <NUM>. However, the present disclosure is not limited to these, and, for example, the primary driving electrode PD and the primary pickoff electrode PPO may be arranged in parallel with each other with a space kept therebetween in a thickness direction of the resonator <NUM> and the support part <NUM>. More specifically, one of the primary driving electrode PD or the primary pickoff electrode PPO may be provided on the front surfaces of the resonator <NUM> and the support part <NUM>, and the other one of the primary driving electrode PD or the primary pickoff electrode PPO may be provided on the back surfaces of the resonator <NUM> and the support part <NUM>. Similarly, the secondary driving electrode SD and the secondary pickoff electrode SPO may be arranged in parallel with each other with a space kept therebetween in the thickness direction of the resonator <NUM> and the support part <NUM>. That is, one of the secondary driving electrode SD or the secondary pickoff electrode SPO may be provided on the front surfaces of the resonator <NUM> and the support part <NUM>, and the other one of the secondary driving electrode SD or the secondary pickoff electrode SPO may be provided on the back surfaces of the resonator <NUM> and the support part <NUM>. In addition, these electrodes may be arranged inside the resonator <NUM> and the support part <NUM>.

Claim 1:
A vibrating-type gyroscope element (<NUM>), comprising at least:
- a fixed part (<NUM>);
a resonator (<NUM>);
- a plurality of supports (<NUM>) connecting the resonator (<NUM>) to the fixed part and vibratably supporting the resonator (<NUM>); and
- a plurality of electrodes (40a-40p) formed in the plane of the resonator (<NUM>),
the resonator (<NUM>) having a cos Nθ (where N is a natural number of two or more) mode of vibration,
the plurality of electrodes (40a-40p) being arranged in such 4N orientations that the axes of the plurality of electrodes (40a-40p) are arranged at equiangular intervals in an outer circumferential direction of the resonator (<NUM>),
the plurality of electrodes (40a-40p) including:
- a primary driving electrode (PD) that excites first order vibration of the resonator (<NUM>) in the cos Nθ mode;
- a primary pickoff electrode (PPO) that detects the first order vibration;
- a secondary pickoff electrode (SPO) that detects second order vibration of the resonator (<NUM>); and
- a secondary driving electrode (SD) that drives the resonator (<NUM>) such that the second order - vibration is canceled,
- the primary pickoff electrode (SPO) being arranged in an orientation identical to that of the primary driving electrode (PD), and
- the secondary driving electrode (SD) being arranged in an orientation identical to that of the secondary pickoff electrode (SPO), wherein
the plurality of electrodes (40a-40p) includes, in equal numbers, pairs of the primary driving electrode (PD) and the primary pickoff electrode (PPO) and pairs of the secondary driving electrode (SD) and the secondary pickoff electrode (SPO), wherein the plurality of electrodes (40a-40p) is provided in such a way that
two electrodes (40d, <NUM>) extend in parallel with each other from a corresponding one of the support parts (<NUM>) to the resonator (<NUM>) with a space kept there between,
wherein one (40d) of electrodes (40d, <NUM>) provided on one support part (<NUM>) is the primary driving electrode (PD), and the other one (<NUM>) of the electrodes (40d, <NUM>) is the primary pickoff electrode (PPO), and
wherein one (40e) of electrodes (40e, <NUM>) provided on another support part (<NUM>) is the secondary driving electrode (SD), and the other one (<NUM>) of the electrodes (40e, <NUM>) is the secondary pickoff electrode (SPO).