JP5151935B2 - Vacuum gauge - Google Patents
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- JP5151935B2 JP5151935B2 JP2008303397A JP2008303397A JP5151935B2 JP 5151935 B2 JP5151935 B2 JP 5151935B2 JP 2008303397 A JP2008303397 A JP 2008303397A JP 2008303397 A JP2008303397 A JP 2008303397A JP 5151935 B2 JP5151935 B2 JP 5151935B2
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Description
本発明は、振動体を利用した真空計に関し、特に、前記振動体を測定可能な圧力範囲が異なる２方向に振動させるようにした真空計に関する。 The present invention relates to a vacuum gauge using a vibrating body, and more particularly to a vacuum gauge configured to vibrate the vibrating body in two directions having different measurable pressure ranges.
従来、振動方向によって測定することができる気体の圧力範囲が異なる振動体を利用した真空計が、たとえば下記特許文献１に開示されている。
真空計において振動体を利用する場合、一般に、板状振動子のQ値は、気体の圧力Pに反比例する。したがい、板状振動子のQ値は、気体の圧力Pとの関係において、振動体の形状に依る係数をCとすると、以下の式（１）のように表すことができる。 When a vibrating body is used in a vacuum gauge, generally, the Q value of a plate-like vibrator is inversely proportional to the gas pressure P. Accordingly, the Q value of the plate-like vibrator can be expressed as the following formula (1), where C is a coefficient depending on the shape of the vibrator in relation to the gas pressure P.
また上述の特許文献１における真空計は、高圧測定用の第１の振動方向と、低圧測定用の第２の振動方向を使い分けることで測定することができる気体の圧力範囲を広げている。しかし、振動方向を切り替えるときに気体の圧力を測定することができない時間が発生するという課題がある。また、振動方向を切り替える回路が必要であり、回路が複雑となるという課題もある。 Moreover, the vacuum gauge in the above-mentioned Patent Document 1 expands the pressure range of gas that can be measured by properly using the first vibration direction for high pressure measurement and the second vibration direction for low pressure measurement. However, there is a problem that a time during which the gas pressure cannot be measured when switching the vibration direction occurs. In addition, a circuit for switching the vibration direction is necessary, and there is a problem that the circuit becomes complicated.
上記した課題を解決するために本発明は、高圧測定用の第１の振動方向と低圧測定用の第２の振動方向とを使い分けることで測定可能な圧力範囲を広げている真空計において、測定する気体の圧力によって振動方向を切り替える際の測定不能な時間の発生を無くすとともに、振動方向を切り替える回路が必要ないようにした真空計を提供することを目的とする。 In order to solve the above-described problems, the present invention provides a vacuum gauge that expands the measurable pressure range by properly using the first vibration direction for high pressure measurement and the second vibration direction for low pressure measurement. An object of the present invention is to provide a vacuum gauge that eliminates the generation of unmeasurable time when the vibration direction is switched by the pressure of the gas to be used and eliminates the need for a circuit for switching the vibration direction.
上記課題を解決するために、本発明の真空計は、第１の振動方向と該第１の振動方向に直交する第２の振動方向とに振動することができるように形成された振動体と、該振動体を静電力により駆動する加振電極部と、前記振動体の振動を検出する振動検出部と、該振動検出部の検出信号に基づき、この検出信号の位相を変えて増幅することにより前記振動体を加振する駆動信号を生成する駆動信号生成部とを有し、前記駆動信号を前記加振電極部に印加して前記振動体を共振状態に保持して、前記振動体の振動特性から雰囲気の圧力を測定する真空計であって、前記加振電極部として、前記振動体を第１および第２の振動方向にそれぞれ振動させるための第１および第２の加振電極部を備え、前記振動検出部として、前記振動体の第１および第２の振動方向の振動をそれぞれ検出する第１および第２の振動検出部を備え、第１の振動検出部の検出信号に基づく駆動信号を第１の加振電極部に印加することにより、前記振動体を第１の振動方向に振動させて圧力を測定する第１の圧力測定部と、第２の振動検出部の検出信号に基づく駆動信号を第２の加振電極部に印加することにより、前記振動体を第２の振動方向に振動させて圧力を測定する第２の圧力測定部とを備え、前記第１および第２の圧力測定部により前記振動体を第１および第２の振動方向に同時に振動させて各振動方向での各圧力測定を同時に行うようにしたことを特徴とする（請求項１の発明）。 In order to solve the above-described problem, a vacuum gauge according to the present invention includes a vibrating body formed so as to vibrate in a first vibration direction and a second vibration direction orthogonal to the first vibration direction. A vibrating electrode unit for driving the vibrating body by electrostatic force, a vibration detecting unit for detecting the vibration of the vibrating body, and amplifying the detection signal by changing the phase based on the detection signal of the vibration detecting unit. A drive signal generating unit that generates a drive signal for exciting the vibrating body by applying the drive signal to the excitation electrode unit to hold the vibrating body in a resonance state, A vacuum gauge for measuring atmospheric pressure from vibration characteristics, wherein the first and second exciting electrode portions for vibrating the vibrating body in first and second vibration directions, respectively, as the exciting electrode portion The vibration detecting unit includes first and second vibrating bodies. The first and second vibration detection units for detecting vibrations in the two vibration directions, respectively, and applying a drive signal based on the detection signal of the first vibration detection unit to the first excitation electrode unit, By applying a drive signal based on the detection signal of the first vibration measurement unit and the second vibration detection unit that vibrates the vibrating body in the first vibration direction to the second vibration electrode unit. A second pressure measuring unit that measures the pressure by vibrating the vibrating body in a second vibration direction, and the first and second pressure measuring units cause the vibrating body to move to the first and second vibrations. The pressure is simultaneously measured in each vibration direction by simultaneously vibrating in the directions (invention of claim 1).
上記請求項１の発明によれば、振動体を測定可能な圧力範囲が異なる第１および第２の振動方向の両方で振動させて圧力を測定するようにすることにより、測定可能な圧力範囲を広げることが可能である。 According to the first aspect of the present invention, by measuring the pressure by vibrating the vibrating body in both the first and second vibration directions having different measurable pressure ranges, the measurable pressure range is reduced. It is possible to spread.
また、上記請求項１の発明によれば、振動体を第１および第２の振動方向に同時に振動させて各振動方向での各圧力測定を同時に行うことにより、気体の圧力によって振動方向を切り替える場合におけるような切り替えの際の測定不能な時間の発生を無くすことが可能となり、広範囲の圧力を連続的に測定することができるようになる。 According to the first aspect of the present invention, the vibration body is vibrated simultaneously in the first and second vibration directions, and each pressure measurement in each vibration direction is performed simultaneously, whereby the vibration direction is switched depending on the gas pressure. As a result, it is possible to eliminate the generation of unmeasurable time during switching, and it is possible to continuously measure a wide range of pressures.
また、上記請求項１の発明によれば、振動体の振動方向を切り替える回路が必要ないため、回路を簡略化することが可能である。
上記請求項１に記載の真空計において、前記第１の振動方向と前記第２の振動方向とで測定することができる圧力範囲が異なるようにするとよい（請求項２の発明）。
Further, according to the first aspect of the present invention, since a circuit for switching the vibration direction of the vibrating body is not necessary, the circuit can be simplified.
In the vacuum gauge according to claim 1, it is preferable that pressure ranges that can be measured differ between the first vibration direction and the second vibration direction (invention of claim 2).
上記請求項１または２に記載の真空計において、前記第１の加振電極部として、前記振動体の両側に第１の振動方向に沿って設置された第１および第２の加振電極から成る１組の加振電極を備えるとともに、前記第２の加振電極部として、前記振動体の両側に第２の振動方向に沿って設置された第３および第４の加振電極から成る１組の加振電極を備え、前記駆動信号生成部は、前記第１および第２の振動検出部の各検出信号の位相をそれぞれ変化させる第１および第２の位相シフト回路と、該第１および第２の位相シフト回路の各出力信号をそれぞれ増幅する第１および第２の増幅器と、該第１および第２の増幅器の各出力信号の位相をそれぞれ反転させる第１および第２の反転回路と、を有し、第１の振動検出部の検出信号に基づく逆相の駆動信号として、前記第１の反転回路および前記第１の増幅器の各出力信号を前記第１および第２の加振電極にそれぞれ印加することで、前記振動体の第１の振動方向における共振状態を保持するとともに、第２の振動検出部の検出信号に基づく逆相の駆動信号として、前記第２の反転回路および前記第２の増幅器の各出力信号を前記第３および第４の加振電極にそれぞれ印加することで、前記振動体の第２の振動方向における共振状態を保持するようにするとよい（請求項３の発明）。 3. The vacuum gauge according to claim 1, wherein the first excitation electrode unit includes first and second excitation electrodes disposed along a first vibration direction on both sides of the vibrating body. 1 which consists of the 3rd and 4th excitation electrode which is provided along the 2nd vibration direction as said 2nd excitation electrode part as said 2nd excitation electrode part. A pair of excitation electrodes, wherein the drive signal generator includes first and second phase shift circuits that change the phases of the detection signals of the first and second vibration detectors, and First and second amplifiers for amplifying the respective output signals of the second phase shift circuit, and first and second inversion circuits for inverting the phases of the respective output signals of the first and second amplifiers, respectively And having a reverse phase based on the detection signal of the first vibration detection unit By applying the output signals of the first inverting circuit and the first amplifier to the first and second excitation electrodes as drive signals, respectively, the resonance state in the first vibration direction of the vibrator And the output signals of the second inverting circuit and the second amplifier as the driving signals of opposite phase based on the detection signal of the second vibration detection unit, the third and fourth excitation electrodes It is good to keep the resonance state in the 2nd vibration direction of the said vibrating body by applying to each (invention of Claim 3).
上記請求項１ないし３のいずれか１項に記載の真空計において、前記駆動信号生成部は、前記駆動信号の電圧が一定となるように、前記振動検出部の検出信号の位相を変えた信号に対する増幅のゲインを調整するものであり、前記第１，第２の圧力測定部は、前記振動検出部の検出信号の大きさに基づいて圧力を測定するようにするとよい（請求項４の発明）。 4. The vacuum gauge according to claim 1, wherein the drive signal generation unit changes the phase of the detection signal of the vibration detection unit so that the voltage of the drive signal is constant. 5. The first and second pressure measurement units may measure the pressure based on the magnitude of the detection signal of the vibration detection unit (Invention of Claim 4). ).
上記請求項１ないし３のいずれか１項に記載の真空計において、前記駆動信号生成部は、前記振動検出部の検出信号の大きさが一定となるように、前記振動検出部の検出信号の位相を変えた信号に対する増幅のゲインを調整するものであり、前記第１，第２の圧力測定部は、前記駆動信号の電圧に基づいて圧力を測定するようにしてもよい（請求項５の発明）。 The vacuum gauge according to any one of claims 1 to 3, wherein the drive signal generation unit detects the detection signal of the vibration detection unit so that the magnitude of the detection signal of the vibration detection unit is constant. The gain of the amplification with respect to the signal whose phase is changed may be adjusted, and the first and second pressure measuring units may measure the pressure based on the voltage of the driving signal. invention).
上記請求項１ないし５のいずれか１項に記載の真空計において、前記振動体の固有周波数に対応した周波数の初期励振信号を出力する初期励振用信号源を備え、振動体の初期駆動時には、振動検出部の検出信号に基づく駆動信号の代わりに、前記初期励振信号に基づく初期駆動信号を前記加振電極部に印加するようにするとよい（請求項６の発明）。 The vacuum gauge according to any one of claims 1 to 5, further comprising an initial excitation signal source that outputs an initial excitation signal having a frequency corresponding to a natural frequency of the vibrating body, and at the time of initial driving of the vibrating body, Instead of the drive signal based on the detection signal of the vibration detection unit, an initial drive signal based on the initial excitation signal may be applied to the excitation electrode unit (invention of claim 6).
上記請求項１ないし６のいずれか１項に記載の真空計において、前記振動検出部は、前記振動体と検出電極との間の静電容量を検知することにより前記振動体の振動を検出するものであるようにするとよい（請求項７の発明）。 The vacuum gauge according to any one of claims 1 to 6, wherein the vibration detection unit detects vibration of the vibrating body by detecting a capacitance between the vibrating body and a detection electrode. It is good to make it (thing of invention of Claim 7).
本発明によれば、振動体を測定可能な圧力範囲が異なる第1の振動方向と第2の振動方向の両方で圧力を測定することで、評価可能な圧力範囲を広げることが可能である。また、第1の振動方向と第2の振動方向を同時に振動させ各圧力を同時に測定することで、広範囲の圧力を連続的に測定することが可能である。また、振動方向を切り替える回路が必要ないため、回路を簡略化することが可能である。 According to the present invention, it is possible to widen the evaluable pressure range by measuring the pressure in both the first vibration direction and the second vibration direction in which the pressure range in which the vibrator can be measured is different. In addition, by simultaneously vibrating the first vibration direction and the second vibration direction and measuring each pressure simultaneously, it is possible to continuously measure a wide range of pressures. In addition, since a circuit for switching the vibration direction is not necessary, the circuit can be simplified.
以下、発明を実施するための最良の形態を、図面を参照しながら説明する。
図１は、本発明の実施形態に係る真空計の機構部分を成す構造体の平面図であり、図２は、図１に示す構造体の側面図である。図１および図２において真空計の機構部分を成す構造体は、錘1、梁2および振動体固定部3からなる振動体4、振動体4を第1の振動方向に加振する加振電極5および6、振動体4を第2の振動方向に加振する加振電極7および8、振動体4の第1の振動方向の振動を検出するための振動検出電極9および10、振動体4の第2の振動方向の振動を検出するための振動検出電極11および12から構成される。
The best mode for carrying out the invention will be described below with reference to the drawings.
FIG. 1 is a plan view of a structure constituting a mechanical part of a vacuum gauge according to an embodiment of the present invention, and FIG. 2 is a side view of the structure shown in FIG. In FIG. 1 and FIG. 2, the structure constituting the mechanism of the vacuum gauge includes a vibrating body 4 comprising a weight 1, a beam 2 and a vibrating body fixing portion 3, and an excitation electrode for exciting the vibrating body 4 in the first vibration direction. 5 and 6, vibration electrodes 7 and 8 for vibrating the vibrating body 4 in the second vibration direction, vibration detection electrodes 9 and 10 for detecting vibration in the first vibration direction of the vibrating body 4, and the vibrating body 4 The vibration detection electrodes 11 and 12 for detecting vibrations in the second vibration direction.
次に、振動体4の形状、振動体4のQ値および気体の圧力Pとの関係について説明する。振動体4は気体分子の衝突により、抵抗力を受ける。分子流領域においては、気体分子による抵抗力は気体の圧力Pに正比例する。気体の圧力が低くなるに従い、振動体4が気体分子から受ける抵抗力が低下するため、振動体のQ値（共振の鋭さ）は高くなる。ただし、振動体4は固有のQ値QEを持っており、固有のQ値QE以上になることはない。すなわち、振動体4が測定することが可能な気体の圧力の下限は、固有のQ値QEによって制限されることを意味する。 Next, the relationship between the shape of the vibrating body 4, the Q value of the vibrating body 4, and the gas pressure P will be described. The vibrating body 4 receives a resistance force due to collision of gas molecules. In the molecular flow region, the resistance force by the gas molecules is directly proportional to the gas pressure P. As the gas pressure decreases, the resistance force that the vibrating body 4 receives from the gas molecules decreases, so the Q value (resonance sharpness) of the vibrating body increases. However, the vibrating body 4 has a specific Q value Q E and never exceeds the specific Q value Q E. That is, the lower limit of the pressure of the gas that can vibrator 4 is measured, meant to be limited by the specific Q value Q E.
振動体4のQ値と気体の圧力Pは、frを振動体4の固有周波数、mを錘の質量、Sを気体の抵抗力を受ける面積、Rを気体定数、Tを温度、Mを気体分子1molあたりの質量とすると、 The Q value of the vibrating body 4 and the gas pressure P are expressed as follows: fr is the natural frequency of the vibrating body 4, m is the mass of the weight, S is the area that receives the gas resistance, R is the gas constant, T is the temperature, and M is Assuming mass per 1 mol of gas molecule,
図３は、本発明の実施形態に係る振動体の設計値の一例を示す図であり、図４は、図３に示した振動体の設計値におけるQ値と気体の圧力Pとの関係を示す図である。図４に示すように、第1の振動方向に振動させた場合に測定することができる気体の圧力は約10Paから約10000Pa、第2の振動方向に振動させた場合に測定することができる気体の圧力は約0.1Paから約100Paである。すなわち、振動方向によって測定することができる気体の圧力を変えることができる。なお、図３に示される振動体の第１および第２の振動方向における各固有周波数は、例えば、振動体の材質をシリコンとした場合、それぞれ、約1680Hzおよび約560Hzとなる。
FIG. 3 is a diagram showing an example of the design value of the vibrating body according to the embodiment of the present invention. FIG. 4 shows the relationship between the Q value and the gas pressure P in the design value of the vibrating body shown in FIG. FIG. As shown in FIG. 4, the gas pressure that can be measured when vibrating in the first vibration direction is about 10 Pa to about 10,000 Pa, and the gas that can be measured when vibrating in the second vibration direction. The pressure is about 0.1 Pa to about 100 Pa. That is, the gas pressure that can be measured according to the vibration direction can be changed. Note that the natural frequencies in the first and second vibration directions of the vibrator shown in FIG. 3 are about 1680 Hz and about 560 Hz, respectively, when the vibrator is made of silicon, for example.
次に、本発明の実施形態に係る真空計の回路構成について説明する。図５は、本発明の実施形態に係る真空計の回路構成を示すブロック図であり、振動体4と振動検出電極9、10、11および12の静電容量の変化に応じた電圧を出力する容量電圧変換回路20、21、22および23、容量電圧変換回路20と21との出力の差分を出力する差分回路24、容量電圧変換回路22と23との出力の差分を出力する差分回路25、差分回路24の出力の位相を変化させる位相シフト回路26、位相シフト回路26の出力を増幅する増幅器28、入力された信号の位相を180度反転させる反転回路30、振動体4を第1の振動方向に初期加振するための初期加振用信号源32、加振電極5および6に印加される信号を選択するスイッチ回路34、差分回路25の出力の位相を変化させる位相シフト回路27、位相シフト回路27の出力を増幅する増幅器29、入力された信号の位相を180度反転させる反転回路31、振動体4を第2の振動方向に初期加振するための初期加振用信号源33、加振電極7および8に印加される信号を選択するスイッチ回路35から構成される。 Next, the circuit configuration of the vacuum gauge according to the embodiment of the present invention will be described. FIG. 5 is a block diagram showing a circuit configuration of the vacuum gauge according to the embodiment of the present invention, and outputs a voltage corresponding to a change in capacitance of the vibrating body 4 and the vibration detecting electrodes 9, 10, 11 and 12. Capacitance voltage conversion circuits 20, 21, 22, and 23, a difference circuit 24 that outputs a difference between outputs of the capacitance voltage conversion circuits 20 and 21, a difference circuit 25 that outputs a difference between outputs of the capacitance voltage conversion circuits 22 and 23, The phase shift circuit 26 that changes the phase of the output of the difference circuit 24, the amplifier 28 that amplifies the output of the phase shift circuit 26, the inversion circuit 30 that inverts the phase of the input signal by 180 degrees, and the vibrating body 4 as the first vibration Initial excitation signal source 32 for initial excitation in the direction, switch circuit 34 for selecting a signal applied to the excitation electrodes 5 and 6, phase shift circuit 27 for changing the phase of the output of the difference circuit 25, phase Amplifier 29 that amplifies the output of shift circuit 27, phase of input signal is inverted 180 degrees An inversion circuit 31 to be applied, an initial excitation signal source 33 for initial excitation of the vibrating body 4 in the second vibration direction, and a switch circuit 35 for selecting a signal applied to the excitation electrodes 7 and 8 .
次に、図３に示した振動体を利用した本発明の実施形態に係る真空計の動作について説明する。図５において、振動体4が初期加振される場合、スイッチ回路34および35はそれぞれAとB、DとEが接続された状態である。初期駆動用信号源32から振動体4の第1の振動方向の固有振動数に対応した周波数の信号が出力され、反転回路30を経て加振電極5に印加されるとともに加振電極6にも印加される。一方、初期駆動用信号源33から振動体4の第2の振動方向の固有振動数に対応した周波数の信号が出力され、反転回路31を経て加振電極7に印加されるとともに加振電極8にも印加される。初期加振用信号源32および33は初期駆動するときのみ使用され、振動体4が振動し始めた後はスイッチ回路34および35が切り替えられ、それぞれAとC、DとFが接続された状態となる。なお、スイッチ回路34および35の切替制御は、例えば、振動体4の振幅、すなわち、振動体4の変位に応じて出力される差分回路24および25の出力信号の各大きさが予め設定した値に到達したことを図示されないスイッチ回路用制御部で検出し、その検出タイミングで前記スイッチ回路用制御部からスイッチ回路34および35にB側からC側への切替信号およびE側からF側への切替信号をそれぞれ与えることにより行うことができる。 Next, the operation of the vacuum gauge according to the embodiment of the present invention using the vibrating body shown in FIG. 3 will be described. In FIG. 5, when the vibrating body 4 is initially vibrated, the switch circuits 34 and 35 are in a state where A and B and D and E are connected, respectively. A signal having a frequency corresponding to the natural frequency in the first vibration direction of the vibrating body 4 is output from the initial drive signal source 32 and applied to the excitation electrode 5 through the inversion circuit 30 and also to the excitation electrode 6. Applied. On the other hand, a signal having a frequency corresponding to the natural frequency in the second vibration direction of the vibrating body 4 is output from the initial drive signal source 33 and applied to the excitation electrode 7 via the inversion circuit 31 and the excitation electrode 8. Is also applied. The initial excitation signal sources 32 and 33 are used only during initial driving. After the vibrating body 4 starts to vibrate, the switch circuits 34 and 35 are switched, and A and C, and D and F are connected, respectively. It becomes. Note that the switching control of the switch circuits 34 and 35 is, for example, a value in which the amplitude of the vibrating body 4, that is, the magnitudes of the output signals of the difference circuits 24 and 25 output according to the displacement of the vibrating body 4 are set in advance. The switch circuit control unit (not shown) detects that the switch circuit has reached the switch circuit 34 and 35 from the switch circuit control unit to the switch circuits 34 and 35 at the detection timing, and from the E side to the F side. This can be done by giving each switching signal.
そして、スイッチ回路34および35でAとCとが接続されるとともにDとFとが接続された状態において、差分回路24の出力信号の位相を位相シフト回路26でシフトし、増幅器28で増幅し、さらに増幅器28の出力の位相を反転回路30で反転させる。反転回路30の出力および増幅器28の出力が加振電極5および加振電極6にそれぞれ印加され、振動体4の第1の振動方向の共振状態を保持する。一方、差分回路25の出力信号の位相を位相シフト回路27でシフトし、増幅器29で増幅し、さらに増幅器29の出力の位相を反転回路31で反転させる。反転回路31の出力および増幅器29の出力が加振電極7および加振電極8にそれぞれ印加され、振動体4の第2の振動方向の共振状態を保持する。 Then, in a state where A and C are connected and D and F are connected in the switch circuits 34 and 35, the phase of the output signal of the difference circuit 24 is shifted by the phase shift circuit 26 and amplified by the amplifier 28. Further, the phase of the output of the amplifier 28 is inverted by the inversion circuit 30. The output of the inverting circuit 30 and the output of the amplifier 28 are applied to the excitation electrode 5 and the excitation electrode 6, respectively, and the resonance state of the vibrating body 4 in the first vibration direction is maintained. On the other hand, the phase of the output signal of the difference circuit 25 is shifted by the phase shift circuit 27, amplified by the amplifier 29, and further the phase of the output of the amplifier 29 is inverted by the inverting circuit 31. The output of the inverting circuit 31 and the output of the amplifier 29 are applied to the excitation electrode 7 and the excitation electrode 8, respectively, and the resonance state of the vibrating body 4 in the second vibration direction is maintained.
加振電極5および6に印加する駆動信号の電圧が一定となるように増幅器28のゲインを、また加振電極7および8に印加する駆動信号の電圧が一定となるように増幅器29のゲインをそれぞれ調節する構成とした場合、振動体4の第１および第２の振動方向における各Q値に対応して振動体4の第１および第２の振動方向における各振幅、すなわち、振動体の変位量に応じて差分回路24および25から出力される信号の大きさが変化する。したがって、差分回路24および25の出力信号の大きさを第１および第２の振動方向における各Q値に変換し、さらにそれぞれ気体の圧力Pに変換することで、気体の圧力を測定することが可能である。また、差分回路24および25の各出力信号（振動体の振幅）から各圧力P値への変換は、Q値を介さないで直接的に変換するようにしてもよい。 The gain of the amplifier 28 is set so that the voltage of the drive signal applied to the excitation electrodes 5 and 6 is constant, and the gain of the amplifier 29 is set so that the voltage of the drive signal applied to the excitation electrodes 7 and 8 is constant. In the case of a configuration in which the vibration body 4 is adjusted, each amplitude in the first and second vibration directions of the vibration body 4 corresponding to each Q value in the first and second vibration directions of the vibration body 4, that is, displacement of the vibration body The magnitude of the signal output from the difference circuits 24 and 25 changes according to the amount. Therefore, it is possible to measure the gas pressure by converting the magnitudes of the output signals of the difference circuits 24 and 25 into the respective Q values in the first and second vibration directions and further converting them into the gas pressure P, respectively. Is possible. Further, the conversion from each output signal (the amplitude of the vibrating body) of the difference circuits 24 and 25 to each pressure P value may be performed directly without passing through the Q value.
ここで、図３に示される設計値であって材質がシリコンである振動体の場合、例えば第１の振動方向においては、加振電極5および6に印加する駆動信号の電圧が一定となるように増幅器28のゲインを調整するときの、差分回路24の出力信号の大きさ（振動体の振幅）と圧力P値との関係は、図６に示されるような、（約10Pa程度以上の）高圧領域では振幅が圧力にほぼ反比例するとともに低圧側では振幅がその最大限界値に向かって飽和していく特性となる。 Here, in the case of the vibrator having the design values shown in FIG. 3 and made of silicon, the voltage of the drive signal applied to the excitation electrodes 5 and 6 is constant in the first vibration direction, for example. Further, when adjusting the gain of the amplifier 28, the relationship between the magnitude of the output signal of the difference circuit 24 (amplitude of the vibrating body) and the pressure P value is as shown in FIG. 6 (about 10 Pa or more). In the high pressure region, the amplitude is almost inversely proportional to the pressure, and on the low pressure side, the amplitude is saturated toward its maximum limit value.
そして、例えば、差分回路24および25の各出力信号の大きさ（振動体の振幅）と各圧力P値との関係の特性データを取得し、この特性データのデータテーブルを格納した記憶部を備えた変換手段により、実測定時における上記各出力信号（振動体の振幅）から各圧力P値への変換を行う構成としてもよく、また、上記特性データの曲線から近似的に求められた関係式を格納した記憶部を備えた変換手段により、実測定時における上記各出力信号（振動体の振幅）から各圧力P値への変換を行う構成としてもよい。 Then, for example, characteristic data on the relationship between the magnitude of each output signal (vibration body amplitude) of each of the difference circuits 24 and 25 and each pressure P value is obtained, and a storage unit is provided that stores a data table of the characteristic data. The conversion means may convert each output signal (vibration body amplitude) at the actual measurement into each pressure P value, and a relational expression approximately obtained from the characteristic data curve may be obtained. It is good also as a structure which converts each said output signal (amplitude of a vibrating body) at the time of an actual measurement into each pressure P value by the conversion means provided with the memory | storage part stored.
また、振動体4の振幅、すなわち、振動体4の変位に応じて出力される差分回路24および25の出力信号の大きさが一定となるように増幅器28および29のゲインをそれぞれ調整する構成とすることもできる。この場合、振動体4の第１および第２の振動方向における各Q値に対応して増幅器28および29から加振電極5，6および7，8側に印加される各駆動信号の電圧が変化するので、各駆動信号を第１および第２の振動方向における各Q値に変換し、さらにそれぞれ気体の圧力Pに変換することで、気体の圧力を測定することが可能である。また、各駆動信号から各圧力P値への変換は、Q値を介さないで直接的に変換するようにしてもよい。 Further, the configuration is such that the gains of the amplifiers 28 and 29 are adjusted so that the amplitude of the vibrating body 4, that is, the magnitude of the output signals of the difference circuits 24 and 25 output according to the displacement of the vibrating body 4 is constant. You can also In this case, the voltages of the drive signals applied from the amplifiers 28 and 29 to the excitation electrodes 5, 6, 7 and 8 are changed corresponding to the Q values in the first and second vibration directions of the vibrating body 4. Therefore, it is possible to measure the gas pressure by converting each drive signal into each Q value in the first and second vibration directions, and further converting each drive signal into the gas pressure P. Further, the conversion from each drive signal to each pressure P value may be performed directly without passing through the Q value.
ここで、図３に示される設計値であって材質がシリコンである振動体の場合、例えば第１の振動方向においては、差分回路24の出力信号の大きさ（振動体の振幅）が一定となるように増幅器28のゲインを調整するときの、駆動信号の大きさ（駆動電圧）と圧力P値との関係は、図７に示されるような、（約10Pa程度以上の）高圧領域では駆動電圧が圧力にほぼ比例するとともに低圧側では駆動電圧がその最小限界値に向かって飽和するように減少していく特性となる。 Here, in the case of the vibrator having the design value shown in FIG. 3 and the material being silicon, for example, in the first vibration direction, the magnitude of the output signal of the difference circuit 24 (the amplitude of the vibrator) is constant. The relationship between the magnitude of the drive signal (drive voltage) and the pressure P value when the gain of the amplifier 28 is adjusted is as follows in the high pressure region (about 10 Pa or more) as shown in FIG. The voltage is approximately proportional to the pressure, and on the low pressure side, the drive voltage decreases so as to saturate toward the minimum limit value.
そして、例えば、各駆動信号の大きさと各圧力P値との関係の特性データを取得し、この特性データのデータテーブルを格納した記憶部を備えた変換手段により、実測定時における各駆動信号から各圧力P値への変換を行う構成としてもよく、また、上記特性データの曲線から近似的に求められた関係式を格納した記憶部を備えた変換手段により、実測定時における各駆動信号から各圧力P値への変換を行う構成としてもよい。 And, for example, the characteristic data of the relationship between the magnitude of each drive signal and each pressure P value is acquired, and each conversion signal provided with a storage unit storing a data table of this characteristic data is used for each drive signal at the time of actual measurement. The pressure P value may be converted into a configuration, and each pressure signal from each drive signal at the time of actual measurement is converted by a conversion means having a storage unit storing a relational expression approximately obtained from the curve of the characteristic data. It is good also as a structure which converts into P value.
また、振動体4を第1の振動方向と第2の振動方向に同時に振動させ、それぞれの振動方向で気体の圧力を測定するため、振動方向を切り替える場合と異なり連続的に気体の圧力を測定することが可能である。また、気体の圧力によって振動方向を切り替える必要がないため、制御回路などが簡単になる。 Also, since the vibrating body 4 is vibrated simultaneously in the first vibration direction and the second vibration direction and the gas pressure is measured in each vibration direction, the gas pressure is continuously measured unlike when the vibration direction is switched. Is possible. Further, since it is not necessary to switch the vibration direction depending on the gas pressure, the control circuit and the like are simplified.
なお、本発明では、第１および第２の振動方向における各Q値に対応して２つの圧力P値が求められるが、その測定時における気体の圧力レベルが高圧領域（例えば約10Pa以上）あるいは低圧領域（例えば約10Pa未満）のいずれにあるかに応じて、第１あるいは第２の振動方向におけるいずれかのQ値に対応する圧力P値を選択して出力する、図示されない出力信号選択回路を設けることにより、真空計から常に適正な圧力測定信号を出力することができるようになる。 In the present invention, two pressure P values are obtained corresponding to each Q value in the first and second vibration directions, and the pressure level of the gas at the time of measurement is in a high pressure region (for example, about 10 Pa or more) or An output signal selection circuit (not shown) that selects and outputs a pressure P value corresponding to either the Q value in the first or second vibration direction depending on whether it is in a low pressure region (for example, less than about 10 Pa). By providing this, it becomes possible to always output an appropriate pressure measurement signal from the vacuum gauge.
１ 錘
２ 梁
３ 振動体固定部
４ 振動体
５〜８ 加振電極
９〜12 振動検出電極
20〜23 容量電圧変換回路
24，25 差分回路
26，27 位相シフト回路
28，29 増幅器
30，31 反転回路
32，33 初期駆動用信号源
34，35 スイッチ回路
DESCRIPTION OF SYMBOLS 1 Weight 2 Beam 3 Vibrating body fixing | fixed part 4 Vibrating body 5-8 Excitation electrode 9-12 Vibration detection electrode
20-23 capacity voltage conversion circuit
24, 25 Difference circuit
26, 27 Phase shift circuit
28, 29 Amplifier
30, 31 Inversion circuit
32, 33 Initial drive signal source
34, 35 switch circuit
Claims (7)
前記加振電極部として、前記振動体を第１および第２の振動方向にそれぞれ振動させるための第１および第２の加振電極部を備え、
前記振動検出部として、前記振動体の第１および第２の振動方向の振動をそれぞれ検出する第１および第２の振動検出部を備え、
第１の振動検出部の検出信号に基づく駆動信号を第１の加振電極部に印加することにより、前記振動体を第１の振動方向に振動させて圧力を測定する第１の圧力測定部と、
第２の振動検出部の検出信号に基づく駆動信号を第２の加振電極部に印加することにより、前記振動体を第２の振動方向に振動させて圧力を測定する第２の圧力測定部とを備え、
前記第１および第２の圧力測定部により前記振動体を第１および第２の振動方向に同時に振動させて各振動方向での各圧力測定を同時に行うようにした
ことを特徴とする真空計。 A vibrator configured to vibrate in a first vibration direction and a second vibration direction orthogonal to the first vibration direction, and an excitation electrode unit that drives the vibration body by electrostatic force; A vibration detection unit that detects the vibration of the vibration body, and a drive signal that generates a drive signal for exciting the vibration body by changing the phase of the detection signal based on the detection signal of the vibration detection unit A vacuum gauge that measures the pressure of the atmosphere from the vibration characteristics of the vibrating body by holding the vibrating body in a resonance state by applying the drive signal to the excitation electrode unit,
As the excitation electrode unit, provided with first and second excitation electrode units for causing the vibrating body to vibrate in first and second vibration directions, respectively.
The vibration detection unit includes first and second vibration detection units that detect vibrations in the first and second vibration directions of the vibrating body, respectively.
A first pressure measurement unit that measures a pressure by vibrating the vibrating body in a first vibration direction by applying a drive signal based on a detection signal of the first vibration detection unit to the first excitation electrode unit. When,
A second pressure measurement unit that measures a pressure by vibrating the vibrating body in a second vibration direction by applying a drive signal based on the detection signal of the second vibration detection unit to the second excitation electrode unit. And
The vacuum gauge according to claim 1, wherein the first and second pressure measuring units simultaneously vibrate the vibrating body in first and second vibration directions to simultaneously measure each pressure in each vibration direction.
前記第１の加振電極部として、前記振動体の両側に第１の振動方向に沿って設置された第１および第２の加振電極から成る１組の加振電極を備えるとともに、前記第２の加振電極部として、前記振動体の両側に第２の振動方向に沿って設置された第３および第４の加振電極から成る１組の加振電極を備え、
前記駆動信号生成部は、前記第１および第２の振動検出部の各検出信号の位相をそれぞれ変化させる第１および第２の位相シフト回路と、該第１および第２の位相シフト回路の各出力信号をそれぞれ増幅する第１および第２の増幅器と、該第１および第２の増幅器の各出力信号の位相をそれぞれ反転させる第１および第２の反転回路と、を有し、
第１の振動検出部の検出信号に基づく逆相の駆動信号として、前記第１の反転回路および前記第１の増幅器の各出力信号を前記第１および第２の加振電極にそれぞれ印加することで、前記振動体の第１の振動方向における共振状態を保持するとともに、
第２の振動検出部の検出信号に基づく逆相の駆動信号として、前記第２の反転回路および前記第２の増幅器の各出力信号を前記第３および第４の加振電極にそれぞれ印加することで、前記振動体の第２の振動方向における共振状態を保持することを特徴とする真空計。 The vacuum gauge according to claim 1 or 2,
The first excitation electrode unit includes a pair of excitation electrodes including first and second excitation electrodes disposed along the first vibration direction on both sides of the vibrating body. As two excitation electrode portions, a set of excitation electrodes composed of third and fourth excitation electrodes installed along the second vibration direction on both sides of the vibrating body,
The drive signal generation unit includes first and second phase shift circuits that change phases of detection signals of the first and second vibration detection units, and each of the first and second phase shift circuits. First and second amplifiers for respectively amplifying output signals; and first and second inversion circuits for inverting the phases of the output signals of the first and second amplifiers, respectively.
Applying output signals of the first inversion circuit and the first amplifier to the first and second excitation electrodes, respectively, as drive signals having opposite phases based on the detection signal of the first vibration detection unit And maintaining the resonance state in the first vibration direction of the vibrator,
Applying the output signals of the second inversion circuit and the second amplifier to the third and fourth excitation electrodes, respectively, as drive signals having opposite phases based on the detection signal of the second vibration detection unit The vacuum gauge is characterized in that the resonance state in the second vibration direction of the vibrating body is maintained.
前記駆動信号生成部は、前記駆動信号の電圧が一定となるように、前記振動検出部の検出信号の位相を変えた信号に対する増幅のゲインを調整するものであり、
前記第１，第２の圧力測定部は、前記振動検出部の検出信号の大きさに基づいて圧力を測定することを特徴とする真空計。 The vacuum gauge according to any one of claims 1 to 3,
The drive signal generation unit adjusts an amplification gain for a signal obtained by changing the phase of the detection signal of the vibration detection unit so that the voltage of the drive signal is constant,
The vacuum gauge according to claim 1, wherein the first and second pressure measuring units measure pressure based on a magnitude of a detection signal of the vibration detecting unit.
前記駆動信号生成部は、前記振動検出部の検出信号の大きさが一定となるように、前記振動検出部の検出信号の位相を変えた信号に対する増幅のゲインを調整するものであり、
前記第１，第２の圧力測定部は、前記駆動信号の電圧に基づいて圧力を測定することを特徴とする真空計。 The vacuum gauge according to any one of claims 1 to 3,
The drive signal generation unit adjusts an amplification gain for a signal obtained by changing the phase of the detection signal of the vibration detection unit so that the magnitude of the detection signal of the vibration detection unit is constant.
The vacuum gauge, wherein the first and second pressure measuring units measure pressure based on the voltage of the drive signal.
前記振動体の固有周波数に対応した周波数の初期励振信号を出力する初期励振用信号源を備え、
振動体の初期駆動時には、振動検出部の検出信号に基づく駆動信号の代わりに、前記初期励振信号に基づく初期駆動信号を前記加振電極部に印加することを特徴とする真空計。 The vacuum gauge according to any one of claims 1 to 5,
An initial excitation signal source for outputting an initial excitation signal having a frequency corresponding to the natural frequency of the vibrator;
A vacuum gauge, wherein an initial drive signal based on the initial excitation signal is applied to the excitation electrode unit instead of a drive signal based on a detection signal of a vibration detection unit when the vibrating body is initially driven.
前記振動検出部は、前記振動体と検出電極との間の静電容量を検知することにより前記振動体の振動を検出するものであることを特徴とする真空計。 The vacuum gauge according to any one of claims 1 to 6,
The said vibration detection part detects the vibration of the said vibrating body by detecting the electrostatic capacitance between the said vibrating body and a detection electrode, The vacuum gauge characterized by the above-mentioned.
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