|Publication number||USRE42359 E1|
|Application number||US 12/381,534|
|Publication date||May 17, 2011|
|Filing date||Mar 12, 2009|
|Priority date||Oct 13, 1992|
|Also published as||US5734105, US6128953, US6470747|
|Publication number||12381534, 381534, US RE42359 E1, US RE42359E1, US-E1-RE42359, USRE42359 E1, USRE42359E1|
|Original Assignee||Denso Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (58), Non-Patent Citations (5), Referenced by (1), Classifications (7), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This is a continuation application Ser. No. 09/035,018, filed Mar. 5, 1998 now U.S. Pat. No. 6,128,953 the entire contents of which is hereby incorporated by reference which is a Divisional of application Ser. No. 08/578,371 filed Dec. 26, 1995 now U.S. Pat. No. 5,734,105, which is a File Wrapper Continuation of 08/135,498 filed Oct. 13, 1993 now ABN.
1. Field of the Invention
This invention relates to a dynamical quantity sensor for detecting a dynamical quantity such as an angular velocity, acceleration, or the like.
2. Description of the Related Art
A tuning fork type device or a tuning plate type device using a piezoelectric device has been known in the past as a device for detecting a yaw rate by utilizing the Coriolis force.
However, such a device requires machining of a complicated shape and bonding of a piezoelectric device, and is not therefore free from the problems that the reduction of size and cost of production and accomplishment of higher precision are difficult. A yaw rate sensor according to the prior art comprises piezoelectric ceramics, for example, and detects the yaw rate by utilizing the Coriolis force, but has been difficult to reduce size and the cost of production. To solve these problems, the inventors of the present invention have already proposed a yaw rate sensor having the construction which is shown in
On the other hand, the sensor device 1 must be vibrated in the vibrating direction 10 of the weight and the detecting direction 4 of the Coriolis force. Therefore, the sensor device 1 (that is, the weight) is constituted in such a manner that a supporting direction (the direction of the arrangement of a support member 2) coincides with a direction of the axis of rotation 7. In this construction, an electrode 6 for detecting the vibration must be disposed on a plane below the sensor device 1 opposing the first plane 8 of the sensor device. Accordingly, there remain the problems yet to be solved that the construction is complicated and the production is difficult.
It may be conceivable to form the second surface 9 of the sensor device 1 on the upper surface thereof but in such a case, the support member 2 must be disposed at a lower portion. In view of the production of the sensor device by micro-machining, however, it is quite impossible to accomplish the production method of such a sensor device.
It is therefore an object of the present invention to provide a dynamical quantity sensor having a novel structure which can be easily produced by micro-machining owing to its simple shape, and makes it possible to reduce size and the cost of production, and to accomplish higher precision.
To accomplish the object described above, the present invention provides a dynamical quantity sensor fundamentally comprising a weight, anchor portions, connecting portions for connecting the weight and the anchor portions, and peripheral members encompassing the members described above, wherein the members other than the peripheral members are integrally shaped by the same semiconductor material. The upper main planes of these members are mutually disposed on the same plane, the anchor portions and the peripheral members are fixed to a substrate, and the weight can move in a first direction and in a second direction orthogonally crossing the first direction inside a plane in parallel with the plane described above.
More specifically, the first embodiment of the present invention provides a dynamical quantity sensor wherein a weight is supported by L-shaped beams, a plane defined by these L-shaped beams is used as a moving plane of the weight, and the movement of the weight due to the function of a dynamical quantity is detected.
The second embodiment of the present invention provides a dynamical quantity sensor wherein first beams are extended from anchor portions, a movable intermediate support member is disposed on the first beams, second beams extending in a direction crossing substantially orthogonally the first beams are disposed on the intermediate support member, a weight is disposed on the second beams, and the movement of the weight resulting from a dynamical quantity is detected.
In the present invention, the weight is allowed to move with deformation of the L-shaped beams. The movement of the weight resulting from the action of a dynamical quantity is detected, and the dynamical quantity is detected.
The weight is allowed to move due to deformation of the first beams or the second beams. The movement of the weight with the dynamical quantity is detected, and the dynamical quantity is detected.
Hereinafter, preferred embodiments of dynamical quantity sensors according to the present invention will be explained with reference to the accompanying drawings.
In other words,
The construction of the dynamical quantity sensor according to the present invention will be explained in further detail. In
Five rod-like electrodes 11 are so disposed on the left side surface of the weight 10 as to extend in a transverse direction in
A pair of rod-like electrodes 15 are disposed between a pair of electrodes 11, respectively, and one of the ends of each rod-like electrode 15 is fixed to the upper surface of the substrate 1. The electrodes 11 and the electrodes 15 constitute opposed electrodes, respectively. A pair of rod-like electrodes 16 are disposed between a pair of electrodes 12, and one of the ends of each rod-like electrode 16 is fixed to the upper surface of the substrate 1. The electrodes 12 and the electrodes 16 constitute the opposed electrodes, respectively. Similarly, a pair of rod-like electrodes 17 are disposed between a pair of electrodes 13, and one of the ends of each rod-like electrode 17 is fixed to the upper surface of the substrate 1. The electrodes 13 and the electrodes 17 constitute the opposed electrodes, respectively. A pair of rod-like electrodes 18 are disposed between a pair of electrodes 14, and one of the ends of each rod-like electrode 18 is fixed to the upper surface of the substrate 1. The electrodes 14 and the electrodes 18 constitute the opposed electrodes, respectively. The spaces between the fixed electrodes 15 to 18 and the movable electrodes 11 to 14 serve as electrode gaps, respectively.
In other words, in the embodiment of the invention shown in
Here, the beams 6 to 9 corresponding to the connecting portions, the weight 10 including the electrodes 11 to 14, and the electrodes 15 to 18, are so arranged as to define a gap (space) of 1 to 2 μm with the upper surface of the substrate 1. In other words, the beams 6 to 9 and the weight 10 are supported by the anchor portions 2 to 5 in a floating state. These anchor portions function as extension terminals of movable electrodes. Moreover, according to the present invention, at least these portions other than the peripheral portions are preferably made of the same semiconductor material and their upper main plane exists on the same plane.
As will be described elsewhere, the anchor portions 2 to 5, the beams 6 to 9, the weight 10 including the electrode 11 to 14, and the electrodes 15 to 18, are formed by a micromachining technique of the surface of the substrate 1 using sacrifice layer etching.
Incidentally, the weight 10 is a rectangular parallelopiped (100 μm square, about 2 μm-thick) and is symmetrical with respect to the X axis (axis of excitation) and the Y axis (vibration axis due to the Coriolis force). Each of the L-shaped beams 6, 7, 8, and 9 has a thickness of about 2 μm, a width of about 1 μm and a length of about 100 μm. If the width is smaller than the thickness, the weight 10 can move more easily in the planar direction of the substrate (in the horizontal direction) but can move with more difficultly in the depth-wise direction (in the vertical direction) of the substrate 1. Further, each of the electrodes 11 to 18 has a thickness of about 2 μm, a width of about 1 μm and a length of about 100 μm.
Next, the production process of the angular velocity sensor will be explained with reference to
First of all, a silicon nitride (SiN) film 20 is formed on the surface of a single crystal silicon substrate 19 to a thickness of about 1 μm by plasma CVD or thermal CVD as shown in
Subsequently, as shown in
Further, a poly-silicon film 24 is deposited to a thickness of about 2 μm on the SiO2 film 22 inclusive of the inside of the openings 23 by thermal CVD as shown in
Next, as shown in
Further, as shown in
The angular velocity sensor thus produced operates in the following way.
The opposed electrodes 13, 17 and 14, 18 are excitation electrodes (capacitors), and when an A.C. voltage is applied to these electrodes, the weight 10 is vibrated (excited) in the X-axis direction due to the electrostatic attraction. At this time, since the linear portions of the L-shaped beams 6 to 9, which are in parallel with the Y axis (the portion 6a in the case of the beam 6 shown in
The opposed electrodes 11, 15 and 12, 16 are electrodes (capacitors) for detecting the Coriolis force. When an angular velocity Ω occurs round the axis orthogonally crossing the sheet of the drawing in
In this way, the weight 10 undergoes displacement in the Y-axis direction due to the Coriolis force, and this displacement (vibration) is detected as the capacitance change by the opposed electrodes 11, 15 and 12, 16. The rotary angular velocity Ω is detected on the basis of this capacitance change. In other words, since the amplitude in the Y-axis direction is proportional to the Coriolis force 2 mvΩ and since m and v are known, the rotary angular velocity Ω can be determined from the amplitude in the Y-axis direction.
As described above, this embodiment employs the construction wherein the weight 10 is supported by the L-shaped beams 6 to 9, the plane defined by the L-shaped beams 6 to 9 is used as the movable plane of the weight 10 and the motion of the weight 10 resulting from the application of the rotary angular velocity Ω is detected. In this way, this embodiment provides an angular velocity sensor having a novel structure having a beam structure which has a weight capable of two-dimensional displacement in the planar state which can be subjected to micro-machining.
However, the present invention is not particularly limited to the embodiment described above. For example, though the opposed electrodes (capacitors) have the comb-tooth shape so as to reduce the area in the embodiment described above, the electrode area can also be reduced in the depth-wise direction of the substrate 1, as shown in
Namely, four beams 26 to 29 corresponding to the L-shaped connecting portions are extended on the substrate 25, and the weight 30 is supported by the other end of each of these beams 26 to 29. Electrodes 31 to 34 on the side of the weight 30 and electrodes 35 to 38 on the fixed electrode side are formed in the X- and Y-axis directions orthogonally crossing each other on the surface of the substrate 25.
In this embodiment, the peripheral members 100 are formed with a predetermined height, and substantially encompass the weight 30. The electrodes 35 to 38 opposing the electrodes 31 to 34, which are disposed around the weight 30, are disposed on the opposed surface on the side of the peripheral members 100 which oppose the weight 30 in the proximity of the latter.
The production method of the sensor shown in
As another application example, the arrangement shown in
Besides the angular velocity sensor, a two dimensional acceleration sensor may also be produced. In other words, in
As described above, the present invention can provide a dynamical quantity sensor having a novel structure.
Hereinafter, another embodiment of the present invention, which embodies the dynamical quantity sensor as an angular velocity sensor will he explained with reference to
The substrate 101 consists of a single crystal silicon substrate which is several millimeters square and about 200 to 500 μm thick. A rectangular recess portion 102 is formed at the center of this substrate 101. First beams 103 to 106 are so formed on the side walls inside this recess portion 102 as to extend in the vertical direction in
A rectangular frame-like intermediate support member 107 is disposed inside the recess portion 102 and is connected to the other end of each of the first beams 103 to 106. Second beams 108 to 111 are so formed on the inner walls of the rectangular frame-like intermediate support member 107 as to extend in the transverse direction in
As shown in
Incidentally, each of the first and second beams 103 to 106, and 108 to 111 has a width of several millimeters and a thickness of 10 to 50 μm. The intermediate support member 107 has a width of dozens of millimeters, and has a frame-like shape and a thickness of 10 to 50 μm. The weight 112 comprises a rectangular parallelopiped having a dimension of hundreds of millimeters in both transverse and longitudinal directions and a thickness of 10 to 50 μm.
Electrodes 113 and 114 are formed on the right and left side walls on the external surface of the intermediate support member 107 shown in
Electrodes 117 and 118 are formed on the upper and lower internal walls of the intermediate support member 107 shown in
The first and second beams 103 to 106 and 108 to 111, the intermediate support member 107 and the weight 112 are formed by a surface micromachining technique of the substrate 101 using sacrifice layer etching, as will be described later.
Next, the production process of the angular velocity sensor will be explained with reference to
First of all, a single crystal silicon substrate 121 is prepared as shown in
In the embodiment described above, the opposed electrodes are not disposed at the portions where the peripheral members oppose the weight 112, but the electrodes are disposed on at least a part of each opposed surface of the weight 112 and the intermediate support member 107. Further, the rest of the electrode pairs are disposed on at least a part of each of the opposed surfaces between the inner walls of the recess portion 102 corresponding to the peripheral member 100 and the intermediate support member 107.
As shown in
The angular velocity sensor thus produced operates in the following way.
First, an A.C. voltage is applied to the opposed electrodes 117, 119 and 118, 120 shown in
When the rotary angular velocity (yaw rate: Ω) acts on the axis orthogonally crossing the drawing of
Though the weight 112 cannot undergo displacement in the X-axis direction with respect to the intermediate support to member 107, the Coriolis force is transmitted to the intermediate support member 107 through the second beams 108 to 111. The intermediate support member 107 can undergo displacement in the X-axis direction due to the deflection of the first beams 103 to 106. This displacement quantity of the intermediate support member 107 is substantially proportional to the Coriolis force. The displacement of the weight 112 due to this Coriolis force is detected as the capacitance change by the opposed electrodes 113, 115 and the opposed electrodes 114, 116. The rotary angular velocity (yaw rate: Ω) is detected on the basis of this capacitance change.
Another method of measuring the displacement quantity of the weight 112 comprises conducting servo control so that the capacitance change of capacitors (the opposed electrodes 113, 115 and the opposed electrodes 114, 116) becomes zero or in other words, controlling the voltage to be applied to the capacitors so that the displacement of the intermediate support member 107 becomes zero, and determining the Coriolis force from the impressed voltage.
As described above, the present invention employs the construction wherein the first beams 103 to 106 are so disposed as to extend from the substrate 101 (fixed portion), the movable intermediate support member 107 is disposed on these first beams 103 to 106, the second beams 108 to 111 are so disposed on this intermediate support member 107 as to extend in the direction substantially orthogonally crossing the first beams 103 to 106, the weight 112 is disposed on these second beams 108 to 111, the opposing electrodes 117, 119 and the opposing electrodes 118, 120 are used as the electrodes for excitation (capacitors for excitation), and the opposing electrodes 113, 115 and the opposing electrodes 114, 116 are used as the electrodes for detecting the angular velocity (capacitors for detection) so as to detect the movement of the weight with the application of the angular velocity. Since this embodiment uses the beam structure having the weight 112 capable of undergoing two-dimensional displacement under the planar state where micro-machining is possible, this embodiment provides an angular velocity sensor having a novel structure.
Incidentally, the present invention is not particularly limited to the embodiment described above. For example, though the weight 112 is of the center beam type in the embodiment described above, it may also be of a cantilever beam type as shown in
Though the intermediate support member has the frame-like shape in the foregoing embodiments, it is not particularly limited to the frame-like shape. In other words, it may have a rectangular shape as shown in
Besides the angular velocity sensor, the present invention may also be applied to a two-dimensional acceleration sensor. In other words, in
As described above in detail, the present invention provides a dynamical quantity sensor having a novel structure.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
|US9164119||Dec 5, 2012||Oct 20, 2015||Panasonic Intellectual Property Management Co., Ltd.||Angular velocity detection device and angular velocity sensor including the same|
|International Classification||G01C19/5719, G01P3/02, B81C1/00, B81B3/00|
|Jun 6, 2014||REMI||Maintenance fee reminder mailed|
|Oct 29, 2014||LAPS||Lapse for failure to pay maintenance fees|