Gyro sensor and electronic device including the same

A gyro sensor includes: a driving mass; a detection mass connected with the driving mass; a driving connection one end and the other end of which are connected with the driving mass and an anchor, respectively; an island connected with the anchor, and disposed with a clearance left between the island and the driving mass in such a manner as to be electrically connected with the driving mass; and a projection provided at least either on the surface of the driving mass opposed to the island, or on the surface of the island opposed to the driving mass. The driving unit includes a movable electrode unit connected with the driving mass, and a fixed electrode unit. The minimum distance between the driving mass and the island is longer than the driving amplitude of the driving mass and shorter than the maximum amplitude of the movable electrode unit.

BACKGROUND

1. Technical Field

The present invention relates to a gyro sensor and an electronic device including this gyro sensor, and more particularly to a gyro sensor capable of preventing damage to and adhesion of a drive system of the gyro sensor and to an electronic device including this gyro sensor.

2. Related Art

As known in the art, a gyro sensor is equipped on electronic devices such as digital cameras, video cameras, cellular phones, and automotive navigation systems to detect an angular velocity of the devices for position control or the like. An MEMS (micro electro mechanical system) capacitance gyro sensor includes a driving system and a detecting system, and determines an angular velocity based on a Coriolis force generated in the detecting system when an angular velocity is applied to the driving system oscillating at a constant oscillation frequency and to the detecting system interlocked with the driving system, regarding this force as a change of the capacitances of the detecting system (movable electrode) and a fixed electrode. According to this structure, the driving system is often disposed in such a position as to surround the outside of the detecting system. Also, there are often provided two units arranged side by side each including the driving system and the detecting system so as to cancel the acceleration components and detect only the angular velocity. In this case, the two driving systems are driven in the opposite phases and oscillate in the opposite directions. Therefore, when a physical amount such as an excessive voltage is applied to the driving electrode of the gyro sensor or when the gyro sensor drops, collision between the driving system and the element disposed outside or between the two driving systems may occur, producing risk of damage to the gyro sensor. Moreover, particularly in the case of a gyro sensor including silicon, charges generated on the surfaces of the electrodes are attracted to each other, in which condition the electrodes adhere to each other and are difficult to be separated therefrom in some cases.

There is disclosed in JP-A-2002-228680, a capacitance mechanical sensor provided with a movable electrode which shifts in accordance with a physical amount, and a fixed electrode which faces to the movable electrode with a small clearance left therebetween. According to this sensor, a projection is formed on at least one of the movable electrode and the fixed electrode to produce a height difference from the one electrode provided with the projection to the other electrode, so that adherence between the movable electrode and the fixed electrode can decrease. This projection is provided for the purpose of preventing adhesion between the electrodes or between a fixed portion and a weight portion.

According to the capacitance mechanical sensor disclosed in JP-A-2002-228680, however, it is required to increase the distance between the electrodes by the length corresponding to the projection disposed on the side of the fixed electrode opposed to the movable electrode. In this case, size reduction of the elements becomes difficult.

SUMMARY

An advantage of some aspects of the invention is to provide a gyro sensor capable of preventing adhesion of elements caused by collision, and to provide an electronic device including this gyro sensor. Another advantage of some aspects of the invention is to provide a gyro sensor capable of avoiding contact between a fixed electrode and a movable electrode caused by shock without the necessity for forming a projection between the fixed electrode and the movable electrode, and to provide an electronic device including this gyro sensor. A further advantage of some aspects of the invention is to provide a gyro sensor capable of preventing damage to the elements caused by collision, and to provide an electronic device including this gyro sensor.

The invention can be implemented as the following modes or application examples.

APPLICATION EXAMPLE 1

This application example of the invention is directed to a gyro sensor which includes: a driving mass driven in a first direction by a driving unit; a detection mass connected with the driving mass; a driving connection one end and the other end of which are connected with the driving mass and a first anchor, respectively; a first island connected with the first anchor, and disposed with a clearance left between the first island and the driving mass in such a manner as to be electrically connected with the driving mass; and a projection provided at least either on the surface of the driving mass opposed to the first island, or on the surface of the first island opposed to the driving mass. The driving unit includes a movable electrode unit connected with the driving mass, and a fixed electrode unit disposed opposed to the movable electrode unit. The minimum distance between the driving mass and the first island is longer than the driving amplitude of the driving mass and shorter than the maximum amplitude of the movable electrode unit.

According to this application example of the invention, damage to the driving mass can be avoided by forming the projection which collides with the driving mass and reduces shock caused when the driving mass greatly oscillates. Moreover, the contact area at the collision with the projection is small, and the driving mass, the projection, and the first island are electrically connected with each other to have the same potential, in which condition adhesion between the projection and the first island or the driving mass does not occur. Furthermore, the driving mass can be oscillated with the designed driving amplitude, while avoiding contact between the fixed electrode unit and the movable electrode unit without the necessity for forming a projection between the fixed electrode unit and the movable electrode unit.

APPLICATION EXAMPLE 2

This application example of the invention is directed to the gyro sensor according to the application example 1, wherein the first island has a first distance regulating portion extended to a position facing to the driving mass to regulate the distance between the driving mass and the first island; and the projection is provided at least either on the surface of the driving mass opposed to the first distance regulating portion, or on the surface of the first distance regulating portion opposed to the driving mass.

According to this application example of the invention, the distance between the provided projection and the element (projection, driving mass, or first distance regulating portion) opposed to the provided projection can be controlled by the first distance regulating portion.

APPLICATION EXAMPLE 3

This application example of the invention is directed to the gyro sensor according to the application example 1 or 2, wherein the two driving masses are arranged in the first direction; and the gyro sensor further includes an intermediate connection which connects the two driving masses, the intermediate portion of the intermediate connection being fixed via a second anchor, a second island disposed between the two driving masses and connected with the second anchor, and projections provided at least either on the surfaces of the driving masses opposed to the second island or on the surfaces of the second island opposed to the driving masses.

According to this application example of the invention, there are provided the two driving masses, and the second island and the projections are disposed between the two driving masses. In this case, the projections can reduce shock caused when the respective driving masses greatly oscillate in the direction approaching each other. Thus, damage to the driving masses can be avoided.

APPLICATION EXAMPLE 4

This application example of the invention is directed to the gyro sensor according to the application example 3, wherein the second island has a second distance regulating portion extended to positions facing to the respective driving masses to regulate the distances between the driving masses and the second island; and the projections are provided at least either on the surfaces of the driving masses opposed to the second distance regulating portion, or on the surfaces of the second distance regulating portion opposed to the driving masses.

According to this application example of the invention, the distance between the provided projection and the element (projection, driving mass, or second distance regulating portion) opposed to the provided projection can be controlled by the second distance regulating portion.

APPLICATION EXAMPLE 5

This application example of the invention is directed to the gyro sensor according to any of the application examples 1 through 4, wherein at least a pair of the first islands are arranged in a direction crossing the first direction.

According to this application example of the invention, at least a pair of the first islands and the driving mass have the same potential and repulsively move from each other. Accordingly, distortion produced in the oscillation of the driving mass, if any, can be corrected.

APPLICATION EXAMPLE 6

This application example of the invention is directed to the gyro sensor according to any of the application examples 1 through 5, wherein the detection mass is connected with the driving mass via a detection connection; and a projection is provided at least either on the detection mass or on the detection connection.

According to this application example of the invention, the contact area of the projection produced when the driving mass and the detection mass shift in the direction approaching each other is small. Thus, adhesion between the driving mass and the detection mass can be avoided.

APPLICATION EXAMPLE 7

This application example of the invention is directed to the gyro sensor according to any of the application examples 1 through 6, wherein: the anchor is fixed to a substrate; and a projection is provided on the substrate at a position overlapping at least either with the driving mass or with the detection mass in the plan view.

According to this application example of the invention, adhesion of the driving mass or the detection mass to the substrate can be prevented when the driving mass and the detection mass shift in the direction of approaching the substrate.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

An embodiment according to the invention is hereinafter described with reference to the drawings.

FIG. 1is a partial plan view schematically illustrating the main part of a gyro sensor1.FIG. 2is a plan view schematically illustrating the gyro sensor1according to the embodiment of the invention.FIG. 3is a cross-sectional view of the gyro sensor1shown inFIG. 2, taken along a line A-A inFIG. 2.

As illustrated in these figures, the gyro sensor1includes a substrate60on which two gyro sensor units10are arranged in the direction of an x axis, assuming that the plate surface of the substrate60corresponds to an x-y plane in the rectangular coordinates (seeFIG. 2), with a clearance left between the substrate60and the gyro sensor units10. The two gyro sensor units10are covered by a cap70for closure of the units10.

The substrate60is made of glass, for example. On the other hand, each of the gyro sensor units10is made of silicon, for example, and has an overall external appearance formed by etching.

Main constituents constituting each of the two gyro sensor units10, as will be described below, are disposed linearly symmetric with respect to the Y axis.

For each of the gyro sensor units10, a frame-shaped driving mass20is equipped at the center of the unit10. A frame-shaped detection mass30is disposed inside the driving mass20and connected therewith. The detection mass30may be positioned outside the driving mass20instead of inside the driving mass20. Besides, the shapes of the driving mass20and the detection mass30are not limited to the frame shapes but may be other shapes as long as they form mass bodies. For example, the driving mass20and the detection mass30may be U-shaped.

Each of the pair of the driving masses20is supported at its four corners on the substrate60via intermediate connections12and driving connections14in such a manner as to make planar movement in parallel with the upper surface of the substrate60. The expanding and contracting directions of the respective connections12and14are so designed as to allow reciprocating oscillation of the driving masses20particularly in the direction of their arrangement direction (x axis direction, corresponding to a “first direction”). The opposed two corners of the two driving masses20are connected via the intermediate connection12in such a manner as to generate elastic forces in the direction of moving close to and away from each other (x axis direction). Each of the intermediate connections12is supported on the substrate60via an anchor (corresponding to a “second anchor”)76provided in the middle portion of the intermediate connection12. The two corners of each of the driving masses20on the side opposite to the opposed sides of the respective driving masses20are connected with the driving connections14. Each of the driving connections14operates in a manner similar to the operation of the intermediate connections12with the fixing support point between the driving connection14and the substrate60located at an anchor (corresponding to a “first anchor”)72, and elastically supports the driving mass20in such a condition as to allow shift of the driving mass20in the direction of the x axis. The spring constants of the respective connections12and14disposed at the four corners of the respective driving masses20are equalized. The driving masses20are allowed to make independent planar oscillation in the direction of the x axis.

Moreover, each of the driving masses20is provided with two driving units22connected to each of the two sides of the corresponding driving mass20crossing the side thereof opposed to the side of the other driving mass20at right angles. The driving mass20is driven by the driving units22to oscillate in the direction of the x axis. Each of the driving units22includes a movable electrode unit24connected to the driving mass20, and a fixed electrode unit26disposed opposed to the corresponding movable electrode unit24and fixed to the substrate60. Each of the movable electrode unit24and the fixed electrode unit26has a comb-like electrode fingers. The electrode fingers of the movable electrode unit24and the fixed electrode unit26are alternately disposed with constant clearances therebetween.

When alternating voltage is applied to the driving units22, the movable electrode unit24oscillates in the direction of the x axis by electrostatic attraction generated between the movable electrode unit24and the fixed electrode unit26. As a result, the driving mass20connected with the corresponding movable electrode unit24similarly oscillates in the direction of the x axis. The two driving masses20oscillate in the opposite directions by applying alternating voltages in the opposite phases to the driving units22of the two gyro sensor units10.

The two sides of each of the driving masses20extending in the direction of the x axis are connected with the two sides of the corresponding detection mass30extending in the direction of the x axis via two detection connections16capable of expanding and contracting in the direction of the y axis. This structure allows the detection mass30interlocked with the driving mass20to oscillate in the direction of the x axis. When an angular velocity around the z axis is applied to the two detection masses30with the two driving masses20oscillating in the opposite directions along the x axis, the two detection masses30receive Coriolis forces and thus oscillate in the opposite directions along the y axis.

Each of the detection masses30contains a detection electrode32. The detection electrode32has a plurality of (two in this embodiment) movable electrodes34provided on the detection mass30and arranged in the shape of lateral crosspieces, and fixed electrodes36fixed to the substrate60and disposed in parallel with each other in such a manner that the movable electrodes34can be sandwiched between the fixed electrodes36.

When the detection mass30rotates around the Z axis, the distance between the movable electrodes34connected to the detection mass30and the fixed electrodes36changes, thereby producing a change of the capacitance. The angular velocity around the Z axis is determined based on this change of the capacitance.

As illustrated inFIGS. 1 and 2, each of the driving connections14connected with the outside corners of the driving mass20is formed by a plurality of spring pieces arranged in the direction of the y axis and connected in a zigzag line in such a manner as to expand and contract in the direction of the x axis. The driving connection14is connected such that one end thereof is joined with the driving mass20, while the other end is joined with an island (corresponding to a “first island”)40via the anchor72. The island40is formed integrally with the anchor72. The bottom surface of the island40is fixed to the substrate60. The island40is a rectangular flat plate leveled with the plane of the driving mass20, the detection mass30, or the driving connection14. The island40, the anchor72, the driving mass20, and the driving connection14are electrically connected to one another, and thus electrically have the same potential. In this embodiment, the anchor72and the island40are given different reference numbers. However, in the structure where the anchor72and the island40are formed integrally with each other and fixed to the substrate60as noted above, the function of the anchor is provided both by the anchor72and the island40.

The islands40are provided on each of the pair of the driving masses20with clearances left between the islands40and the driving mass20. According to this embodiment, the islands40are disposed opposed to the outer periphery of each of the driving masses20in the oscillation direction, and positioned adjacent to a pair of the upper and lower corners of the driving mass20as illustrated inFIG. 2. Accordingly, a pair of the islands40are provided with the y axis center line interposed therebetween, and another pair of the islands are provided with the x axis center line interposed therebetween, that is, there are formed the four islands40in total. The islands40of each pair are symmetrically disposed. Each of the islands40has a distance regulating portion (corresponding to a “first distance regulating portion”)42which is a part of the flat plate of the island40opposed to the driving mass20and expanded toward the driving mass20to regulate the separation distance between the island40and the driving mass20in the oscillation direction. The distance regulating portion42forms a rectangular area, and the edge of the expanded portion of the distance regulating portion42extends in parallel with the outside periphery of the driving mass20. A plurality of projections44are provided on the surface of the distance regulating portion42opposed to the driving mass20. The heights of the respective projections44are not required to be uniform. The number of the projections44provided on the surface may be single rather than plural.

According to this structure, the projections44thus provided collide with the driving mass20by a small contact area when the driving mass20greatly shifts in the direction of the x axis by an excessively large physical amount applied thereto or shock given from the outside. Accordingly, excessive displacement of the driving mass20does not occur, causing no damage to the driving mass20. The island40and the driving mass20are connected with the driving connection14and the anchor72, and therefore have the same potential on the whole. In this case, the island40and the driving mass20are not attracted to each other but only come into contact with each other. This structure thus prevents sticking between the island40and the driving mass20.

Moreover, a pair of the islands40are provided in the direction of the y axis in such positions as to be opposed to the driving mass20. The two islands40and the driving mass20have the same potential. According to this structure, distortion produced by a component included in the oscillation of the driving mass20and oscillating in the direction of the y axis, if any, can be corrected. The number of the islands40is not limited to one pair but may be three or more.

As illustrated inFIG. 1, it is preferable that a distance D between the projections44and the driving mass20is controlled by the distance regulating portion42in such a manner as to have a length larger than the driving amplitude of the driving mass20established beforehand at the time of design, and smaller than a maximum amplitude d in the possible oscillation range of the movable electrode unit24regulated by the fixed electrode unit26of the driving unit22and oscillating in the direction of the x axis from the neutral position.

This structure can prevent the problem that the driving mass20contacting the projections44is unable to oscillate with a driving amplitude designed beforehand. Moreover, since the driving mass20contacts the projections44before contact between the movable electrode unit24of the driving unit22and the fixed electrode unit26, damage caused by collision between the movable electrode unit24and the fixed electrode unit26can be avoided in the event of application of an excessive voltage or for other reasons.

The projections44may be provided on the driving mass20opposed to the distance regulating portion42as well as on the distance regulating portion42, or may be provided only on the driving mass20. When the projections44are formed on the driving mass20opposed to the distance regulating portion42as well as on the distance regulating portion42, the distance D corresponds to the distance between the projections44on the driving mass20and the projections44on the distance regulating portion42. When the projections44are formed only on the driving mass20, the distance D corresponds to the projections44disposed on the driving mass20and the surface of the distance regulating portion42opposed to the driving mass20.

In other words, when the projections44are provided at least on either the surface of the driving mass20opposed to the island40or on the surface of the island40opposed to the driving mass20, the distance D corresponds to the minimum distance between the driving mass20and the island40, that is, the remaining length of the distance between the surface of the driving mass20opposed to the distance regulating portion42of the island40and the surface of the distance regulating portion42opposed to the driving mass20, after subtraction of the height of the provided projections44(length in the direction of the x axis in the figure) from the distance.

As illustrated inFIG. 2, an island (corresponding to a “second island”)50extending in the direction of the y axis is provided between the two driving masses20. The island50is formed integrally with the anchors76, and the bottom surface of the island50is fixed to the substrate60. The island50has distance regulating portions (corresponding to a “second distance regulating portion”)52disposed opposed to the two driving masses20to regulate the respective distances between the island50and the opposed driving masses20. Each of the distance regulating portions52is expanded in a rectangular shape toward the driving masses20positioned on both sides, and the edge of the distance regulating portion52on the expanded side is formed in parallel with the inner periphery of the driving mass20. A plurality of projections54are provided on the surface of the distance regulating portion52opposed to the driving mass20. The island50is electrically connected with the anchors76, the intermediate connections12, the distance regulating portions52, and the driving masses20, and thus electrically has the same potential as the potentials of these components. In this embodiment, the anchor76and the island50are given different reference numbers. However, in the structure where the anchor76and the island50are formed integrally with each other and fixed to the substrate60as noted above, the function of the anchor is provided both by the anchor76and the island50.

The projections54prevent collision between the driving masses20when the driving masses20oscillate in the direction of approaching each other. This collision between the projections54and the driving masses20decreases excessive displacement, while avoiding adhesion between the projections54and the driving masses20by the considerably small contact area therebetween. Advantages similar to those referred to above can be offered when the distance between the projections54and the surface of the driving mass20opposed to the projections54is set longer than the preset driving amplitude of the driving mass20and shorter than the maximum amplitude d of the movable electrode unit24similarly to the distance between the projections44and the surface of the driving mass20opposed to the projections44. Moreover, advantages similar to those produced when the two islands40are provided opposed to the driving mass20as referred to above can be offered when the two or more distance regulating portions52provided with the projections54are formed opposed to the driving mass20.

The projections54may be provided on the surface of the driving mass20opposed to the distance regulating portion52as well as on the distance regulating portion52, or may be provided only on the driving mass20.

Projections56are further provided on the outside surfaces of the detection mass30on the sides extending in the direction of the x axis, and on the folded portions of the detection connections16connecting the driving mass20and the detection mass30. The projections56contribute to prevention of damage by reducing excessive displacement caused when the driving mass20and the detection mass30greatly shift in the direction of the y axis. In addition, adhesion is avoided by reducing the contact area produced at the time of collision with the projections56and equalizing the potential at the contact positions. The projections56may be provided on the inner side surface of the detection mass30extending in the direction of the x axis, or may be provided on the inner side surface or outer side surface of the driving mass20in the direction of the x axis. Alternatively, the projections56may be formed only on the detection connection16or only on the detection mass30.

As illustrated inFIG. 3, projections62are provided on the substrate60at positions overlapping with the driving mass20in the plan view. The projections62can be formed simultaneously with etching of the external shapes of the anchors72and76and others on the substrate60. The projections62reduce excessive displacement and damage by collision between the projections62and the driving mass20when the driving mass20greatly shifts in the direction of the z axis. Moreover, the contact portions are not attracted to each other due to the decreased contact area at the time of collision, in which condition adhesion does not occur. The projections62may be provided on the substrate60at the positions overlapping with the detection mass30in the plan view as well as on the substrate60at the positions overlapping with the driving mass20in the plan view, or may be provided only on the substrate60at the positions overlapping with the detection mass30in the plan view.

Accordingly, when the driving mass20greatly shifts and collides with the projections44,54,56, and62by shock such as an application of excessive physical amount and drop, this shock decreases by the presence of the projections44,54,56, and62. Thus, damage to the driving mass20is prevented. Moreover, the driving mass20is not attracted to the projections44,54,56, and62by reduction of the contact area between the driving mass20and the projections44,54,56, and62at the time of collision therebetween. Therefore, adhesion between the contact portions is avoided.

Furthermore, the distance between the driving mass20and the projections44and54is controlled by adjustment of the length in the direction of the x axis using the distance regulating portions42and52. According to this structure, the driving amplitude of the driving mass20designed beforehand can be securely maintained, and the movable electrode unit24can be designed to avoid collision with the fixed electrode unit26without the necessity for forming projections between the fixed electrode unit26and the movable electrode unit24of the driving unit22.

According to this embodiment, there are provided the two gyro sensor units10on the gyro sensor1. However, only the one gyro sensor unit10may be equipped on the gyro sensor1.

An electronic device according to an embodiment of the invention is hereinafter described.

FIG. 4is a perspective view illustrating the structure of a portable (or notebook) personal computer incorporating the electronic device according to the embodiment of the invention.

As can be seen from the figure, a personal computer1100includes a main body1104provided with a keyboard1102, and a display unit1106. The display unit1106is supported via a hinge structure in such a manner as to be rotatable with respect to the main body1104.

The personal computer1100having this structure contains the gyro sensor1.

FIG. 5is a perspective view illustrating the structure of a cellular phone (including PHS) incorporating the electronic device according to the embodiment of the invention.

As illustrated in this figure, a cellular phone1200includes an antenna (not shown), a plurality of operation buttons1202, a receiver1204, and a transmitter1206. A display unit is disposed between the operation buttons1202and the receiver1204.

The cellular phone1200having this structure contains the gyro sensor1.

FIG. 6illustrates the structure of a digital still camera incorporating the electronic device according to the embodiment of the invention. This figure schematically shows a connection with an external device as well.

While an ordinary camera causes exposure of a silver halide photo film by receiving a light image of a subject, a digital still camera1300carries out photo-electric transformation of a light image of a subject by using an imaging element such as a CCD (charge coupled device) and produces an imaging signal (image signal).

A display unit is provided on the back surface of a case (body)1302of the digital still camera1300for display in accordance with the imaging signal produced by the CCD. The display has the function of a viewfinder which displays the subject as an electronic image.

A light receiving unit1304including an optical lens (imaging system), the CCD and other components is further provided on the front side (rear surface side of the figure) of the case1302.

When a person taking an image identifies an image of the subject displayed on the display unit and presses down a shutter button1306, an imaging signal generated by the CCD at that time is transmitted to and stored in a memory1308.

According to the digital still camera1300, there are provided a video signal output terminal1312and a data communication input/output terminal1314disposed on the side surface of the case1302. As illustrated in the figure, a TV monitor1430connects with the video signal output terminal1312, and a personal computer1440connects with the data communication input/output terminal1314, when these connections are necessary. The imaging signal stored in the memory1308is outputted to the TV monitor1430or the personal computer1440in accordance with predetermined operation.

The digital still camera1300having this structure contains the gyro sensor1.

The respective electronic devices shown herein include the gyro sensor1having excellent sensitivity and shock resistance, and therefore can offer preferable reliability.

The electronic device according to the embodiment of the invention is not limited to the personal computer (portable personal computer) shown inFIG. 4, the cellular phone shown inFIG. 5, and the digital still camera shown inFIG. 6, but may be applied to ink jet ejectors (such as ink jet printers), laptop personal computers, televisions, video cameras, video tape recorders, automotive navigation systems, pagers, electronic organizers (including ones provided with communication function), electronic dictionaries, electronic calculators, electronic game machines, word processors, workstations, video phones, surveillance TV monitors, electronic binoculars, POS terminals, medical equipment (such as electronic clinical thermometers, sphygmomanometers, blood glucose meters, electrocardiographs, ultrasonic diagnostic equipment, and electronic endoscopies), fish finders, various types of measuring apparatuses, instruments (such as instruments for vehicles, airplanes, and vessels), flight simulators, and others.

The invention is not limited to the gyro sensor and the electronic device described and depicted in the embodiment herein, but may be practiced otherwise in various manners within the scope of the technical spirit of the invention as specified in the appended claims.

The entire disclosure of Japanese Patent Application No. 2012-084617, filed Apr. 3, 2012 is expressly incorporated by reference herein.