Angular velocity sensor

Abstract: A multiple-axis gas flow type angular velocity sensor (1) which can accurately and stably detect the magnitude and direction of angular velocities acting in two or more directions is comprised of a plurality of semiconductor substrates (2-5) on which are formed thermosensitive resistor elements (H W-R , H W-L ; H W-U , H W-D ) and gas passage portions (7,9,11,13) by performing precision processing using a photo-engraving process from the semiconductor production field. The semiconductor substrates (2-5) are laminated together to provide a sensor having a plurality of pairs of resistor elements (H W-R , H W-L ; H W-U , H W-D ) in a gas passage (7,9,11,13).

Description: The present invention relates to a multiple-axis gas flow type angular velocity sensor which detects angular velocity in a plurality of directions such as a yaw direction and a pitch direction, and in particular relates to a multiple-axis gas flow type angular velocity sensor which is constructed using a semiconductor production process. Known conventional multiple-axis gas flow type angular velocity sensors include those in which thermosensitive resistor elements are constructed from thin platinum or tungsten wires, a plurality of thermosensitive resistor elements are attached in pairs to supports provided in a case and are located such that angular velocity in the desired directions is detected. (Refer to JP S61-180147) Conventional multiple-axis gas rate sensors have a construction in which discrete component thermosensitive resistor elements, consisting of thin platinum or tungsten wires, are attached to supports, and there are therefore problems relating to positional accuracy involving the location of the paired thermosensitive resistor elements, for example the distance to the central axis of the gas flow and the direction (perpendicular) with respect to the central axis, and there are also problems due to the time required for adjustment operations in order to maintain positional accuracy. Further, in conventional multiple-axis gas flow type angular velocity sensors, the thermosensitive resistor elements, the supports and the case are constructed from discrete components, and there are problems in that it is necessary to select components to unify the pairing properties and characteristics of individual thermosensitive resistor elements (resistance and temperature characteristics). US-A-4 254 659 discloses a gas flow type angular velocity sensor allowing measurements in three directions. Two orthogonal resistor pairs are provided orthogonally with respect to a first gas flow and/or an additional pair of resistors are provided orthogonally with respect to a second gas flow. EP-A-405452 teaches a single-axis sensor with a pair of thermosensitive resistor elements arranged on an axis perpendicular to the intended axis of a gas flow in a gas passage. According to one aspect, there is provided a multiple-axis gas flow type angular velocity sensor which is provided with a plurality of pairs of opposed thermosensitive resistor elements, each pair being arranged to lie on an axis substantially perpendicular to a respective direction of gas flow, wherein the sensor comprises a plurality of semiconductor substrates laminated together, the substrates having one or more of said thermosensitive resistor elements and/or a part of a gas passage formed thereon by means of a semiconductor production process; wherein two of the substrates are each formed with a single central thermosensitive resistor element thereon, and a substrate laminated between these two substrates is formed with two spaced apart thermosensitive resistor elements thereon, the two single resistor elements forming one of said pairs of resistor elements, and the two spaced apart resistor elements forming a second said resistor pair. According to another aspect, there is provided a method of forming a multiple-axis gas flow type angular velocity sensor, comprising the steps of forming one or more thermosensitive resistor elements and/or a part of a gas passage on each of a plurality of semiconductor substrates using a semiconductor production process, and laminating together the substrates to form a sensor having a plurality of pairs of opposed thermosensitive resistor elements, each pair being arranged along an axis substantially perpendicular to the direction of intended gas flow; wherein two of the substrates are each formed with a single central thermosensitive resistor element thereon, and a substrate laminated between these two substrates is formed with two spaced apart thermosensitive resistor elements thereon, the two single resistor elements forming one of said pairs of resistor elements, and the two spaced apart resistor elements forming a second said resistor pair. By laminating a plurality of these semiconductor substrates, a sensor case which has a sealed space which forms a gas passage is formed, and a multiple-axis gas flow type angular velocity sensor is provided, in which a plurality of pairs of thermosensitive resistor elements are mutually perpendicular, by the thermosensitive resistor elements being located mutually perpendicular to and symmetrical about the central axis of the gas flow. In the multiple-axis gas flow type angular velocity sensor according to the present invention, constructed as described above, thermosensitive resistor elements are formed on semiconductor substrates such as silicon using a photo-engraving process, which is a process for producing semiconductors, and thermosensitive resistor elements with good pairing properties are located accurately in desired positions, and it is therefore possible to detect angular velocity acting in any direction accurately and stably. Further, in the multiple-axis gas flow type angular velocity sensor according to the present invention it is possible to construct a sensor including a gas passage and a case by laminating a plurality of semiconductor substrates formed by micro-scale processes, and miniaturization and cost-effectiveness of the sensor can therefore be planned. Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a diagram showing the appearance of a multiple-axis gas flow type angular velocity sensor according to a first embodiment of the present invention. Figure 2 is a structural diagram of a multiple-axis gas flow type angular velocity sensor according to the first embodiment. Figure 3 is a circuit diagram showing components for detecting angular velocity in the yaw direction corresponding to Figure 1. Figure 4 is a circuit diagram showing components for detecting angular velocity in the pitch direction corresponding to Figure 1. Figure 5 is a conceptual diagram of a multiple-axis gas flow type angular velocity sensor with three axes, according to a second embodiment of the present invention. Figure 1 is an external view of a multiple-axis gas flow type angular velocity sensor according to the present invention, and Figure 2 is a structural drawing of this multiple-axis gas flow type angular velocity sensor. In Figure 1, the multiple-axis gas flow type angular velocity sensor 1 indicates an embodiment of a double-axis gas flow type angular velocity sensor, in which thermosensitive resistor elements H W-L , H W-R , H W-U , and H W-D , a gas flow inlet 6 through which gas G S is input, a gas passage through which a gas jet F R flows, and upper and lower cases, for example, are formed as semiconductor components, using a semiconductor production process such as a photo-engraving process, on a plurality of semiconductor substrates such as silicon, after which the sensor is constructed by laminating the plurality of semiconductor components using batch processing. One pair of thermosensitive resistor elements H W-L and H W-R are located facing each other in a direction (X axis) perpendicular to the central axis of the gas flow (Y axis), and detect the angular velocity acting on the multiple-axis gas flow type angular velocity sensor 1 with the Z axis as the axis of rotation. Further, a pair of thermosensitive resistor elements H W-U and H W-D are located facing each other in a direction (Z axis) which is perpendicular to both the central axis of the gas flow (Y axis) and the perpendicular direction (X axis), and detect the angular velocity acting on the multiple-axis gas flow type angular velocity sensor 1 with the X axis as the axis of rotation. Considering a situation in which the multiple-axis gas flow type angular velocity sensor 1 is mounted on a moving body (for example a vehicle), running in the Y-axis direction, the thermosensitive resistor elements H W-L and H W-R detect angular velocity in the horizontal (yaw) direction, while the thermosensitive resistor elements H W-U and H W-D detect angular velocity in the direction in which the front and rear of the moving body (for example a vehicle) rise and fall (pitch). The gas jet F Y flows in the form of a parabolic body of rotation with the Y axis of the gas passage of the multiple-axis gas flow type angular velocity sensor 1 as the axis of symmetry, and therefore the gas flow acts simultaneously on the thermosensitive resistor elements H W-L and H W-R , and the thermosensitive resistor elements H W-U and H W-D , and therefore angular velocity in the yaw direction and the pitch direction are detected simultaneously. For example, if an angular velocity acts in the yaw direction, then the Coriolis force acts and the gas flow is deflected, the balance of the amount of gas coming into contact with the thermosensitive resistor elements H W-L and H W-R is disturbed, the resistances of the thermosensitive resistor elements H W-L and H W-R change, and it is possible to detect the magnitude and direction of the angular velocity in the yaw direction. However, if an angular velocity acts in the yaw direction, the amounts of gas coming into contact with the thermosensitive resistor elements H W-U and H W-D are maintained, and no angular velocity in the pitch direction is detected. Further, if an angular velocity acts in the pitch direction, the Coriolis force acts on the gas flow in the pitch direction, causing the gas flow to be deflected, the balance of the amounts of gas coming into contact with the thermosensitive resistor elements H W-U and H W-D is disturbed, the resistances of the thermosensitive resistor elements H W-U and H W-D change, and it is possible to detect the magnitude and direction of angular velocity in the pitch direction, but no angular velocity in the yaw direction is detected. In this way it is possible to construct a double-axis rate sensor in which the yaw direction and pitch direction are independent from each other. It should be noted that if an angular velocity acts simultaneously in the yaw direction and the pitch direction, the gas flows in the yaw direction and the pitch direction are deflected simultaneously, and it is therefore possible to detect the magnitude and direction of the angular velocity in the yaw direction and the pitch direction simultaneously. The construction of a multiple-axis (double-axis) gas flow type angular velocity sensor will now be described. Figure 2 is a structural drawing of a multiple-axis gas flow type angular velocity sensor according to the present invention. In Figure 2, the multiple-axis gas flow type angular velocity sensor 1 consists of semiconductor substrates 2 to 5. The semiconductor substrate 2 is formed, using a semiconductor production process such as a photo-engraving process, with a gas flow inlet in the up/down direction of the substrate and a cover indentation 7 which has a space which is a specified width from the lower surface of the substrate. It constitutes an upper cover of the multiple-axis gas flow type angular velocity sensor 1. A bridge 8 is formed in the semiconductor substrate 3 using a semiconductor production process in which vacuum evaporation and a plurality of etching processes are repeated, and the semiconductor substrate 3 is provided with a thermosensitive resistor element H W-U and leads and external connection pads, which are formed by etching and patterning after platinum or tungsten has been vacuum evaporated onto a prescribed position on the bridge 8. For example, a photoengraving process for making substrate 3, 4 or 5 may comprise the steps of: depositing an insulator coating such as SiN on a silicon substrate; depositing platinum or another suitable metal on the SiN; etching the metal to form resistor element patterns, as well as leads and connection pads; possibly depositing a further insulator coating such as SiN again over the metal patterns; and etching the silicon substrate beneath the insulator coating and metal to make a through passage or indentation with a bridge thereacross of the insulator coating with the metal etched patterns thereon. The substrates may be laminated together by being placed in an oven and joined with thermosetting resin. It should be noted that the thermosensitive resistor element H W-U and a thermosensitive resistor element H W-D , which is formed on the semiconductor substrate 5, constitute a pair of sensors, and these are positioned accurately in advance using a photo-etching mask such that they detect angular velocity in the pitch direction. Further, a space underneath the bridge, and a through-passage 9, constituting part of the gas passage, are formed in the semiconductor substrate 3 by etching. The semiconductor substrate 4 is formed with a space underneath the bridge, and with a through-passage 11 using the same processes as for the semiconductor substrate 3, except that a pair of thermosensitive elements H W-L and H W-R are formed in prescribed positions on the bridge 10. It should be noted that the pair of thermosensitive resistor elements H W-L and H W-R are positioned accurately in advance using a photo-etching mask such that they detect angular velocity in the yaw direction, in the same way as with the thermosensitive resistor element H W-U formed on the semiconducor substrate 3. The semiconductor substrate 5 is formed with a bridge 12 and the thermosensitive resistor element H W-D , in exactly the same way as the semiconductor substrate 3. Further, a space enclosed by a gas passage floor 13 is formed by etching, thereby constructing the lower cover of the multiple-axis (double-axis) gas flow type angular velocity sensor 1. After the semiconductor substrates 2 to 5 have been formed by means of a semiconductor production process, the semiconductor substrates 2 through 5 are laminated in one direction to form the multiple-axis (double-axis) gas flow type angular velocity sensor 1. In this way it is possible to construct the multiple-axis (double-axis) gas flow type angular velocity sensor 1 with good positional accuracy by accurately setting the positions of the thermosensitive resistor elements H W-L , H W-R , H W-U and H W-D using production masks, and forming them using a semiconductor production process such as vacuum evaporation and etching. Further, it is possible to form the pair of thermosensitive resistor elements H W-L and H W-R , and the pair of thermosensitive resistor elements H W-U and H W-D with highly accurate respective resistance ratios. Figure 3 shows a circuit diagram for detecting angular velocity in the yaw direction and Figure 4 shows a circuit diagram for detecting angular velocity in the pitch direction, for use with the sensor of Figure 1. The circuit in Figure 3 has a construction in which thermosensitive resistor elements H W-L (resistor R L ) and H W-R (resistor R R ), and reference resistors R F1 and R F2 constitute a resistor bridge circuit 15, and after obtaining direct current voltage outputs V Z1 and V Z2 by driving the resistor bridge circuit using a supply 14 (constant current supply I 0 ), a detected angular velocity output V 01 , corresponding to the difference (V Z1 -V Z2 ) is obtained by feeding the outputs V Z1 and V Z2 to a comparator such as a differential amplifier 16. If the reference resistors R F1 and R F2 are set to the same value, then the detected angular velocity output V 01 which is obtained is proportional to the resistance difference (R R -R L ), and it is possible to detect angular velocity acting in the yaw direction. It should be noted that the magnitude of the angular velocity is obtained from the level of the detected output V 01 , and the direction of the angular velocity is obtained from the sign of the detected output V 01 . In the same way, in Figure 4, a resistor bridge circuit 18 is constituted by thermosensitive resistor elements H W-U (resistor R U ) and H W-D (resistor R D ), and reference resistors R F3 and R F4 (R F3 =R F4 ), and is supplied by a constant current source 17. Therefore, a detected angular velocity output V 02 corresponding to the difference between the direct current voltage outputs (V X1 -V X2 ) (corresponding to the resistance difference R U -R D ) is obtained from the differential amplifier 19, and it is possible to detect angular velocity acting in the pitch direction. Figure 5 shows a conceptual diagram of a multiple-axis gas flow type angular velocity sensor with three axes, according to a second embodiment of the present invention. In Figure 5, a gas passage 34 in the X-axis direction is provided on a semiconductor substrate 31 in a multiple-axis gas flow type angular velocity sensor 30, in addition to the gas passage 33 in the Y-axis direction, which has already been described. In the gas passage 33 in the Y-axis direction there are provided, as described in Figure 1, a pair of thermosensitive resistor elements Y 1 and Y 2 for detecting angular velocity in the yaw direction, and a pair of thermosensitive resistor elements P 1 and P 2 for detecting angular velocity in the pitch direction, and in the gas passage 34 in the X-axis direction there is provided a pair of thermosensitive resistor elements R 01 and R 02 , facing each other in the Z-axis direction, for detecting angular velocity in the roll direction. By arranging that gas jets F Y and F X are supplied simultaneously from a gas flow inlet 32 to the gas passage 33 in the Y-axis direction and the gas passage 34 in the X-axis direction it is possible to detect simultaneously and independently angular velocities acting in the yaw direction, the pitch direction and the roll direction. In the present invention, as described above in detail with reference to the embodiments, thermosensitive resistor elements are formed on semiconductor substrates such as silicon using a photo-engraving process, which is a process for producing semiconductors, and thermosensitive resistor elements with good pairing properties are located accurately in desired positions, and it is therefore possible to provide a multiple-axis gas flow type angular velocity sensor which accurately and stably detects angular velocity acting in any direction. Further, since the present invention can be constructed as a sensor including gas passages and a case by laminating a plurality of semiconductor substrates which are formed using a photo engraving process, it is possible to provide a multiple-axis gas flow type angular velocity sensor in which size-reduction and cost effectiveness of the sensor are achieved.

Claims: A multiple-axis gas flow type angular velocity sensor which is provided with a plurality of pairs of opposed thermosensitive resistor elements, each pair being arranged to lie on an axis substantially perpendicular to a respective direction of gas flow, wherein the sensor comprises a plurality of semiconductor substrates laminated together, the substrates having one or more of said thermosensitive resistor elements and/or a part of a gas passage formed thereon by means of a semiconductor production process; wherein two of the substrates are each formed with a single central thermosensitive resistor element thereon, and a substrate laminated between these two substrates is formed with two spaced apart thermosensitive resistor elements thereon, the two single resistor elements forming one of said pairs of resistor elements, and the two spaced apart resistor elements forming a second said resistor pair. The sensor of claim 1, wherein a said pair of resistor elements is located in each of two perpendicular directions to detect yaw and pitch angular velocities. The sensor of claim 1, wherein a said pair of resistor elements is located in each of three mutually perpendicular directions to detect yaw, pitch and roll angular velocities. The sensor of any preceding claim, wherein the sensor provides a gas flow in two substantially orthogonal directions, two resistor pairs being mounted in one gas flow to determine angular velocity in two directions, and at least one pair of elements being provided in the other gas flow to detect angular velocity in a third direction. The sensor of claim 4, wherein both gas flows originate from the same inlet before passing into substantially orthogonal passages. The sensor of any preceding claim, including resistor bridge circuits each comprising a said velocity detecting pair of thermosensitive resistor elements and a pair of reference resistors, the output from the circuits providing signals indicative of the absolute value and direction of the angular velocity acting on the sensor. A method of forming a multiple-axis gas flow type angular velocity sensor, comprising the steps of forming one or more thermosensitive resistor elements and/or a part of a gas passage on each of a plurality of semiconductor substrates using a semiconductor production process, and laminating together the substrates to form a sensor having a plurality of pairs of opposed thermosensitive resistor elements, each pair being arranged along an axis substantially perpendicular to the direction of intended gas flow; wherein two of the substrates are each formed with a single central thermosensitive resistor element thereon, and a substrate laminated between these two substrates is formed with two spaced apart thermosensitive resistor elements thereon, the two single resistor elements forming one of said pairs of resistor elements, and the two spaced apart resistor elements forming a second said resistor pair.

Inventors: FUEKI NOBUHIRO, KURIYAMA NARIAKI, NISHIO TOMOYUKI, FUEKI, NOBUHIRO, KURIYAMA, NARIAKI, NISHIO, TOMOYUKI, Fueki, Nobuhiro, c/o Honda R&amp;D Co., Ltd., Kuriyama, Nariaki, c/o Honda R&amp;D Co., Ltd., Nishio, Tomoyuki, c/o Honda R&amp;D Co., Ltd.
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1995
Main classification: G01P9
IPC codes: G01P9