JP2008164540A - Quartz type gas pressure gage, and vacuum unit using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quartz type GAS pressure gage capable of eliminating collection man-hours and a computing circuit for a correlation characteristic data between a natural resonance resistance and a temperature of a quartz oscillator to reduce a cost, by controlling the temperature of the quartz oscillator to be kept constant, free from an influence onto a gas to be measured, and capable of facilitating maintenance, and a vacuum unit using the same. <P>SOLUTION: A heater 70 is arranged in an atmospheric air side while contacting with an outer wall of a metal cylindrical body 54, and heat is transferred using the metal cylindrical body 54 and a filter member 60 as heat transfer members, to heat the quartz oscillator 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a quartz gas pressure gauge and a vacuum apparatus using the same.

  2. Description of the Related Art Conventionally, there is known a method of measuring mainly a pressure below atmospheric pressure using a crystal resonator (hereinafter also referred to as a resonator) (Patent Document 1). This is because the resonance resistance of the vibrator increases in proportion to the pressure in the molecular flow region and increases in proportion to the 1/2 power of the pressure in the viscous flow region. Is.

Since it is possible to measure in a wide pressure range from atmospheric pressure to 10 ⁻² to 10 ⁻³ Torr, it is recognized as an effective pressure measuring means.

In this measurement method using a vibrator, the vibrator is arranged in a space where pressure is to be measured, the vibrator is vibrated through an oscillation circuit, and the resonance resistance Z is obtained. The gas pressure is measured from the difference ΔZ (= Z−Z ₀ ) between the measured resonance resistance Z and the natural resonance resistance Z ₀ (value in high vacuum).

  In this measuring method, since the temperature of the vibrator during measurement is generally indefinite, there is a problem that a measurement error becomes large on the low pressure side and accurate pressure measurement cannot be performed.

The intrinsic resonance resistance Z ₀ changes only a few kΩ over a wide temperature range (−20 to + 60 ° C.). On the other hand, the difference ΔZ is about several kΩ in the region of 10 ⁻¹ to 10 ⁻² Torr, and about several tens of Ω in the region of 10 ⁻² to 10 ⁻³ Torr, and the difference ΔZ decreases as the pressure decreases. In other words, the change in the natural resonance resistance Z ₀ of the oscillator varies with the temperature can not be ignored. This is the measurement limit of the pressure range when measuring pressure using a vibrator.

The applicant of the present application measures the resonance frequency f of the crystal resonator, obtains the temperature T of the crystal resonator from the resonance frequency f, and the difference ΔZ = the natural resonance frequency (Z ₀ + Zt) at the temperature T and the resonance resistance Z = A method for measuring the pressure of gas from Z- (Z ₀ + Zt) is proposed and patented (Patent Document 2).
Japanese Utility Model Publication No. 64-38547 Japanese Patent Publication No. 7-97060

  The above method has an effect of eliminating an error based on the temperature of the vibrator during measurement and measuring an accurate pressure.

However, since the pressure is calculated based on the correlation data between the resonance frequency f and the temperature T and the correlation between the temperature T and the natural resonance frequency (Z ₀ + Zt), data collection of correlation data for each crystal resonator is performed. There was a problem of increasing the cost by the number of man-hours and the arithmetic circuit.

In order to prevent the natural resonance resistance Z ₀ of the vibrator varies with temperature, the vibrator, the heater and temperature sensor embedded in the aluminum block, has also been proposed to maintain the transducer at a constant temperature by a heater .

  The technique of Patent Document 2 can accurately measure the gas pressure regardless of the ambient temperature without arranging a heater adjacent to the crystal unit in a vacuum system and controlling the crystal unit at a constant temperature. Is excellent.

  Here, if a heater is provided adjacent to the quartz crystal resonator in a vacuum system, there is a restriction on the gas to be measured, for example, it cannot be used for pressure measurement of combustible gas. Further, if the heater is disconnected, the measuring unit is removed from the vacuum gauge and replaced, and maintenance becomes complicated.

  In particular, the quartz resonator is extremely small and consumes no heat because it consumes power of the order of about 10 μW. Therefore, the advantage is not offset, but the advantage is offset. .

  The object of the present invention is to control the temperature of the crystal unit to be constant, to reduce the cost by eliminating the data collection man-hours and the arithmetic circuit, and to maintain the gas easily without affecting the gas to be measured. To provide a quartz gas pressure gauge and a vacuum apparatus using the same.

One embodiment of the present invention provides:
In a quartz gas pressure gauge that measures the gas pressure from the difference between the natural resonance resistance of the quartz crystal resonator and the measured resonance resistance,
A metal case body forming a chamber communicating with the gas atmosphere;
An electrode connected to the crystal unit;
A first seal body formed of an insulator for hermetically sealing and holding the electrode;
A cylindrical body made of metal, which is inserted into the case main body, and supports the first seal body in an airtight manner;
A second sealing body for hermetically sealing the metal cylinder and the case body;
A metal filter member that is held by the metal cylinder, surrounds the electrode and the crystal resonator connected thereto, forms a measurement chamber, and communicates with the measurement chamber and the gas atmosphere;
A heater that is disposed on the atmosphere side in contact with the outer wall of the cylindrical body, heats the cylindrical body and the filter member as a heat transfer member, and heats the crystal unit;
It is characterized by having.

  According to an aspect of the present invention, the quartz vibrator is heated by transferring heat using the cylinder and the filter member as a heat transfer member by the heater disposed on the atmosphere side in contact with the outer wall of the metal cylinder. be able to. Therefore, even if the ambient temperature changes, the crystal resonator can be controlled to a substantially constant temperature, and the resonance resistance value of the crystal resonator having temperature dependency can be made substantially constant. Therefore, the resonance resistance value is detected. It is not necessary to calibrate the gas pressure from the atmosphere to a high vacuum. Therefore, the device can be manufactured at a low cost. In addition, since the heater is arranged on the atmosphere side, the heater does not directly contact the gas to be measured, and the gas to be measured such as that the combustible gas is removed is not limited. Even if the heater breaks or the like, maintenance can be performed on the atmosphere side, and the heater can be quickly restored.

  In one embodiment of the present invention, the cylindrical body for disposing the crystal resonator in the measurement chamber and the filter member for forming the measurement chamber are both formed of metal, so that the heater-crystal resonator There is also an effect that can be used as a heat transfer path.

  In one aspect of the present invention, the case main body and the cylindrical body are grounded, and the case main body and the cylindrical body can be electrically insulated by the second seal body.

  In a vacuum apparatus that generates plasma by supplying RF power in a chamber in which the case body is mounted, there is a possibility that the quartz crystal unit is adversely affected by RF noise. When the case main body and the cylinder electrically insulated by the second seal body are grounded, the filter member is also grounded. Therefore, even if RF noise is superimposed on the case main body, the RF noise is not generated in the cylinder and the filter member. Is not superimposed, the adverse effect of RF noise can be prevented.

  In one aspect of the present invention, the crystal resonator has a resonance resistance that varies with temperature, and the heater is set to a temperature in a positive temperature characteristic region in which the resonance resistance increases as the temperature increases, A negative temperature characteristic resistor whose resistance value decreases as the temperature rises can be connected in series to the crystal resonator.

  In this case, the combined resistance value of the resonance resistance value of the crystal resonator and the resistance value of the resistor has a temperature characteristic that takes a minimum value at a predetermined temperature. If the crystal resonator is temperature controlled at a predetermined temperature at which this combined resistance value is minimized, the fluctuation of the resonance resistance value depending on the temperature is minimized, and the accuracy of the measured pressure value is reduced even if the accuracy of temperature control by the heater is poor. Can ensure.

  In one aspect of the present invention, the resistor can be composed of a first thermistor having a negative temperature characteristic in which a resistance value decreases with an increase in temperature, and a resistor connected in parallel thereto. In this case, the crystal resonator, the first thermistor, and the resistor constitute a pressure measurement unit, and the combined resistance value of the pressure measurement unit has a temperature characteristic that takes a minimum value at a predetermined temperature, The temperature of the crystal resonator controlled by the heater can be substantially set to the predetermined temperature.

In one aspect of the present invention, a current-voltage converter that is connected to one end of the pressure measurement unit and converts a current flowing through the crystal resonator into a voltage;
An attenuator connected to the other end of the pressure measuring unit;
A first full-wave rectifier that rectifies current from the attenuator;
A comparator that compares a voltage from the first full-wave rectifier with a reference voltage;
A voltage controlled attenuator that further attenuates the output of the attenuator based on the output voltage of the comparator;
A second full-wave rectifier that rectifies the summed output of the voltage controlled attenuator and the current-voltage converter;
Can further be included.

Then, if the resonance resistance of the crystal resonator is Z, (1 / Z) is output as the output of the second full-wave rectifier, and the known resonance resistance Z ₀ of the crystal resonator and the measured resonance The pressure of the gas can be measured from the difference ΔZ (= Z−Z ₀ ) of the resistance Z.

  In one aspect of the present invention, the heater can be a PTC (Positive Temperature Coefficien) heating element whose resistance value increases rapidly due to a temperature rise exceeding the Curie temperature.

  In this way, as long as the power supply is connected to the heater, the heating element with a positive temperature characteristic has a resistance value that suddenly increases due to a rise in temperature exceeding the Curie temperature, the current decreases, and the heating value decreases. As the resistance decreases, the resistance value decreases, the current increases, and the amount of heat generation also increases, so that the crystal resonator can be self-controlled at a substantially constant temperature.

  In one aspect of the present invention, the apparatus may further include a thermocouple that measures the temperature of the heater, and a heater power control circuit that controls the heater to a constant temperature based on an output from the thermocouple. In this case, the crystal resonator is controlled to a substantially constant temperature based on the temperature measured by the thermocouple.

  In one aspect of the present invention, the apparatus may further include a second thermistor that measures the temperature of the heater, and a heater power control circuit that controls the heater to a constant temperature based on an output from the second thermistor. . In this case, the temperature of the crystal resonator can be controlled to be substantially constant by using the second thermistor as a temperature sensor.

  In one aspect of the present invention, the crystal resonator is a temperature-sensitive resonator in which an oscillation frequency changes linearly with respect to temperature, and the crystal type gas pressure gauge includes frequency measuring means for measuring the oscillation frequency; And a heater power control circuit for controlling the heater to a constant temperature based on an output from the frequency measuring means.

  In the temperature sensitive oscillator, the oscillation frequency changes linearly with respect to the temperature. Therefore, if the oscillation frequency of the crystal oscillator is measured by the frequency measuring means, the temperature of the crystal oscillator can be measured. Based on the measured temperature, the temperature of the crystal unit can be controlled to be substantially constant.

  Another aspect of the present invention defines a vacuum apparatus in which the above-described quartz gas pressure gauge measures the pressure in a region where the atmosphere-vacuum is set.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are indispensable as means for solving the present invention. Not always.

1. First Embodiment FIG. 1 is a cross-sectional view of a crystal type gas pressure gauge according to a first embodiment of the present invention. In FIG. 1, the pressure gauge 1 has a case body 20 that forms a chamber 12 that communicates with a vacuum chamber 10. A crystal resonator, for example, a tuning fork crystal resonator 30 is connected to the electrode 40. The electrode 40 is hermetically sealed and held, and the quartz crystal resonator 30 connected to the electrode 40 is disposed in the chamber 12 to provide an airtight seal structure 50 that is hermetically sealed and supported with respect to the case body 20. It has been. Furthermore, a filter member 60 that is held by the hermetic seal structure 50 and surrounds the crystal resonator 30 connected to the electrode 40 to form the measurement chamber 62 and that allows the measurement chamber 62 and the vacuum chamber 10 to communicate with each other is provided. ing. A heater 70 is provided that is disposed on the atmosphere side of the hermetic seal body 50 and heats the crystal unit 30.

  The case body 20 is formed in a cylindrical shape, and the lower end flange 22 is fixed to the wall portion 14 of the vacuum chamber 10.

  The hermetic seal structure 50 is divided into, for example, a first seal body 52, a metal cylinder 54, and a second seal body 58. The first seal body 52 functions as an insulator that hermetically seals and holds the electrode 40 and electrically insulates the electrode 40. The cylindrical body 54 holds the first seal body 52 as an airtight seal therein. A threaded portion 56 is formed at the lower end of the cylindrical body 54 and is screwed into the filter member 60. The second seal body 58 is formed in a ring shape, and the cylinder is hermetically sealed in the case body 20 and held. The second seal body 58 also functions as an insulator that electrically insulates the case main body 20 and the cylindrical body 54 from each other when they are grounded.

  When RF plasma is generated in the vacuum chamber 10, the case body 20 and the cylinder body 54 are grounded, and the case body 20 and the cylinder body 54 are electrically connected using the second seal body 58 as an insulator. It is preferable to insulate. As a result, the filter member 60 is also grounded. This is because even if the RF noise is superimposed on the case body 20, it is possible to prevent the RF noise from being superimposed on the cylindrical body 54 and the filter member 60 that are electrically insulated from the case body 20. Thereby, the crystal unit 30 can be shielded from RF noise.

  Further, the metallic cylinder 54 and the filter member 60 are also used as a solid heat conduction path between the heater 70 and the crystal unit 30.

  Here, from the relationship of the hermetic seal, the thermal expansion coefficients of the case body 20 and the cylindrical body 54 that are metals and the thermal expansion coefficients of the first and second seal bodies 52 and 58 that are insulators are substantially equal. Is preferred. This is because the hermetic seal can be prevented from being damaged due to the difference in thermal expansion. In the present embodiment, the case main body 20 and the cylindrical body 54 are formed of Kovar metal, and the first and second seal bodies 52 and 58 are formed of Kovar glass (borosilicate glass), so that members that are in contact with each other are formed. The coefficient of thermal expansion of is made the same level. The lower flange 22 of the case body 20 can be formed of a different material, for example, a highly reliable stainless steel as a flange.

  The filter member 60 is formed of, for example, a SUS (stainless steel) sintered body in order to communicate the chamber 12 and the measurement chamber 62 and to protect the crystal unit 30.

  The heater 70 heats the crystal unit 40 to a predetermined temperature, for example, 45 ° C. higher than normal temperature (25 ° C.). The heater 70 is formed in a ring shape in contact with the cylindrical body 54 on the atmosphere side of the cylindrical body 54 and the third seal body 58. The heat transfer path from the heater 70 to the crystal unit 40 is the route of the cylindrical body 54 → the filter member 70 → the measurement chamber 72 → the crystal unit 30.

  According to the structure of FIG. 1, the temperature of the crystal unit 30 can be efficiently controlled even if the heater 30 is provided on the atmosphere side. Therefore, since it is not necessary to provide a heater in the vacuum atmosphere together with the crystal resonator, there is no limitation on the gas to be measured, such as elimination of combustible gas. Further, even if the heater 70 is disconnected, maintenance is easy because only the heater 70 can be easily replaced on the atmosphere side.

  An example of a drive circuit for the heater 70 is shown in FIGS. In FIG. 2A, the temperature of the heater 70 is measured by the thermocouple 80. The output of the thermocouple 80 is fed back to the heater power control circuit 84 via the cold junction temperature compensation circuit 82, and the temperature of the heater 70 is controlled to a constant temperature. The thermoelectromotive force in the thermocouple is generated according to the temperature difference between the measurement point (hot junction) of the heater 70 and the cold junction, and in order to compensate for the thermoelectromotive force due to the temperature change at the cold junction, A temperature compensation circuit 82 is provided.

  2B, the temperature of the heater 70 is measured by an NTC (Negative Temperature Coefficien) thermistor (second thermistor) 86 that functions as a temperature sensor. If the output of the NTC thermistor 86 is amplified by the amplifier 87 and fed back to the heater power control circuit 84, the heater 70 can be controlled to a constant temperature.

  Here, the resonance resistance Z of the crystal unit 30 varies with the temperature T as shown in FIG. At this time, in the temperature region where the change in the resonance resistance Z is small, the temperature Ts corresponding to the minimum value of the resonance resistance Z is considerably lower than room temperature, for example, 15 ° C.

In the present embodiment, the heater 70 is set to a temperature T _P in the positive temperature characteristic region where the resonance resistance increases as the temperature rises, for example, T _P = 45 ° C.

Thus, by controlling the heater 70 at a different temperature T _P of the temperature Ts and the corresponding minimum value of the resonance resistance Z, so that the crystal oscillator 30 is also temperature controlled to a temperature T _P. In this case, in crystal oscillator 30 is near the temperature T _P is the inclination of the positive temperature characteristic is steep, only the temperature of the crystal resonator 30 is slightly changed, the resonance resistance Z is changed relatively significantly. This degrades the measurement accuracy of the gas pressure.

In order to prevent this, as shown by the broken line in FIG. 3, the minimum value R _P of the combined resistance of the pressure measuring unit including the crystal unit 30 is minimized at the control temperature T _P of the heater 70. to correct. For this purpose, as shown by the alternate long and short dash line in FIG. 3, a resistor 90 having a negative temperature characteristic whose resistance value decreases as the temperature rises may be connected in series to the crystal unit 30 as shown in FIG. As shown in FIG. 4, the pressure measuring unit 100 is formed by the crystal resonator 30 and the resistor 90 connected in series thereto. The combined resistance in the pressure measuring portion 100, has a minimum value at a temperature T _P, as shown in FIG. Such a resistor 90 can be configured by connecting a resistor 94 in parallel to an NTC (negative temperature characteristic) thermistor (first thermistor) 92. Incidentally, the resistor 94 is an adjustment resistor for controlling the temperature T _P. The resistor 90 is not necessarily arranged in a vacuum, and can be connected to the crystal unit 30 on the atmosphere side.

  In this embodiment, as the NTC thermistor 92, one or a plurality of small and highly reliable bead thermistors in which bead elements are glass-sealed are used in series. The resistance value of the resistor 94 connected in parallel with this may be about several kΩ.

When T _P = 25 ° C. is set and the crystal resonator 30 is not temperature-controlled, when the atmospheric temperature changes at 25 ° C. ± 10 ° C., the resonance resistance Z of the crystal resonator 30 changes from −250Ω to + 250Ω. This change in the resonance resistance Z becomes a large error corresponding to a maximum of 5 × 10 ⁻³ Torr in terms of pressure.

On the other hand, when T _P = 45 ° C. is set using the pressure measuring unit 100 shown in FIG. 4 and the heater 70 is controlled to 45 ° C. ± 1 ° C., the resonance resistance Z of the crystal unit 30 is ± 40Ω or less. The change in the resonance resistance Z was an error as small as ± 6 × 10 ⁻⁶ Torr in terms of pressure.

  FIG. 5 is a block diagram of a quartz-type gas pressure gauge 200 using the pressure measuring unit 100 shown in FIG. In FIG. 5, a current / voltage converter 210 connected to one end of the pressure measuring unit 100 and converting a current flowing through the crystal resonator 30 into a voltage, and an attenuator connected to the other end of the pressure measuring unit 100, for example, 1/10. The attenuator 220, the first full-wave rectifier 230 that rectifies the current from the 1/10 attenuator 220, the voltage from the first full-wave rectifier 230, and the reference voltage from the reference voltage source 240 are compared. Comparator 250, voltage-controlled attenuator 260 that further attenuates the output of 1/10 attenuator 220 based on the output voltage of comparator 250, and the summed output of voltage-controlled attenuator 260 and current-voltage converter 210 are rectified. A second full-wave rectifier 270. In FIG. 5, in order to digitally display the pressure, an analog / digital (A / D) converter 280 connected to the second full-wave rectifier 270, and a CPU 290 that controls display of the display unit 300 based on the output thereof. Have

  In FIG. 6, an analog meter 310 is connected to the second full-wave rectifier 270 in order to output the pressure in an analog manner. The other members shown in FIG. 6 are the same as the members given the reference numerals shown in FIG.

5 and 6, the temperature of the crystal unit 30 is set to the minimum value T _{P of the} combined resistance shown in FIG. 3 by the heater 70 that is feedback-controlled by the method of FIG. 2A or 2B. To control. As a result, a value (1 / Z) reflecting the resonance resistance Z of the crystal resonator 30 is obtained as the output of the second full-wave rectifier 270 without any temperature correction. The difference ΔZ (= Z−Z ₀ ) between the measured resonance resistance Z of the crystal unit 30 and the intrinsic shared resistance Z ₀ of the crystal unit 30 corresponds to the gas pressure depending on the gas viscosity (concentration). To do. Here, the natural resonance frequency Z ₀ is substantially constant over a wide temperature range (−20 to + 60 ° C.). Therefore, the gas pressure can be output from the display unit 290 of FIG. 5 or the meter 310 of FIG.

In the configuration of FIG. 5, the arithmetic circuit, frequency counter, and D / A converter shown in FIGS. 3 and 4 of Patent Document 2 can be deleted. In the configuration of FIG. 6, the temperature correction calculation performed by the CPU of Patent Document 2 can be deleted. 5 and FIG. 6, the members added in comparison with FIGS. 3 and 5 of Patent Document 2 are the heater 70 shown in FIG. 1 and the heater power control system shown in FIG. 2A or 2B. In addition, only the resistor 90 (NTC thermistor 92 + resistor 92) shown in FIG. In addition, it is not necessary to collect correlation characteristic data between the specific resonance resistance (Z ₀ ) and temperature (T) of each vibrator. Therefore, the cost can be significantly reduced as compared with the configuration of Patent Document 2. In addition, the addition of the configuration of FIG. 4 can reduce the error of the resonance resistance Z of the crystal resonator 30 to be measured even if the temperature (T _P ) control accuracy of the heater 70 is poor. rare.

  The pressure gauge 1 according to the present embodiment can be combined with sensors having different pressure detection principles to form a combined vacuum gauge with an expanded measurement pressure range. Examples of other vacuum gauges combined with the quartz gas pressure gauge 1 include an ionization vacuum gauge and a Penning vacuum gauge using Penning discharge.

  For example, in an ionization vacuum gauge, a filament for emitting electrons becomes hot. On the other hand, in the Penning vacuum gauge, self-heating occurs in a high pressure region. Further, in any vacuum gauge, the temperature of the crystal unit 30 reaches 40 to 50 ° C. due to the heat generation described above.

When the crystal resonator 30 is used in combination with other sensors as described above, the resistor 90 is set so that the control temperature T _P = 45 ° C. corresponding to the minimum combined resistance value R _P shown in FIG. And the crystal unit 30 may be controlled to 45 ° C. by the heater 70.

  Here, as shown in FIG. 7, for example, a Peltier element 88 is arranged around the case body 20, and the temperature of the crystal unit 30 when various environmental temperatures are set by the Peltier element 88 was measured. The result is shown in FIG.

  8A and 8B, the temperature of the Peltier element 88 is changed in seven stages of 15 ° C., 20 ° C., 25 ° C., 30 ° C., 35 ° C., 40 ° C., and 45 ° C., and FIG. 2A and FIG. The result of having measured the temperature of the crystal oscillator 30 when the heater 70 is controlled to 45 degreeC by both control of these is shown. 2A and 2B, the crystal resonator 30 could be controlled to approximately 45 ° C. ± 1 ° C.

2. Second Embodiment FIG. 9 shows frequency measuring means for measuring the oscillation frequency of the crystal resonator 30 without adopting the method shown in FIG. 2A or FIG. 2B for the heater power control of FIG. For example, a frequency counter 320 is provided.

  Here, the relationship between the oscillation frequency of the crystal unit 30 and the temperature is as shown in FIG. 10, and the oscillation frequency f of the crystal unit 30 has a linear correlation with the actual temperature T. In this way, the crystal resonator 30 whose oscillation frequency changes linearly with respect to temperature is referred to as a temperature-sensitive resonator. Such a temperature sensitive oscillator can be formed depending on the cut angle of the crystal.

  The output of the 1/10 attenuator 220 in FIG. 9 is a rectangular wave output correlated with the oscillation frequency f of the crystal resonator 30. Therefore, the frequency counter 320 can detect the oscillation frequency f of the crystal unit 30 by counting the output frequency of the 1/10 attenuator 220. If the crystal unit 30 is a temperature-sensitive unit having the characteristics shown in FIG. 7, the temperature T of the crystal unit 30 can be obtained from the detected oscillation frequency f.

Heater power control circuit 330 shown in FIG. 9, based on the characteristic shown in FIG. 10, in accordance with the output of the frequency counter 320, the measured temperature T is less power supplied is higher than the control temperature T _P, the temperature T There was a lot of supply power is higher than the control temperature T _P, is controlled to be the heater 70 to control temperature T _P. In this way, pressure measurement can be performed while keeping the temperature of the crystal unit 30 constant.

  Thus, also in 2nd Embodiment of this invention, there can exist an effect equivalent to 1st Embodiment.

3. Third Embodiment FIG. 11 is a sectional view of a crystal type pressure gauge according to a third embodiment of the present invention, and FIG. 12 is a plan view. In the pressure gauge 400 shown in FIG. 11, members having the same functions as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

  The pressure gauge 400 shown in FIGS. 11 and 12 is different from the pressure gauge 1 shown in FIG. 1 in that a PTC (formed by a heating element whose resistance value increases as the temperature rises, instead of the heater 70 shown in FIG. (Positive temperature characteristic) This is the point that a heating element 410 is provided.

  In order to attach the PTC heating element 410, a heat transfer block 420 made of, for example, Al, which has a ring shape that is closely inserted between the case body 20 and the second seal body 54 and is screwed to the case body 20 is provided. Is provided.

  The PTC heating element 410 is in close contact with the upper surface of the heat transfer block 420 and extends from both ends of the ring-shaped sheet heating element 412 having both ends in the circumferential direction and the sheet heating element 422 and is drawn outward in the radial direction. Two terminals 414 and 416 are provided (see FIG. 12).

  And unlike these FIG.2 (A), FIG.2 (B), and FIG. 9, the power supply 440 is connected to these two terminals 414,416 as shown in FIG. That is, it is not necessary to control the temperature of the PTC heating element 410 from the outside. This is because, due to self-control of the PTC heating element 410 itself, when the temperature rises, the sheet resistance value of the sheet heating element 422 increases and the current is suppressed, so the heating temperature decreases. On the other hand, when the temperature drops, the sheet resistance value of the sheet heating element 412 decreases, the current increases, and the heating temperature increases.

  The heat transfer path from the PTC heating element 410 to the crystal unit 30 is different only in that a heat transfer block 420 having a high heat transfer effect is made of metal, and the heat transfer path after the heat transfer block 420 is the first embodiment. Is the same. Therefore, it is possible to control the temperature of the crystal unit 30 with characteristics more than the uniform temperature control shown in FIG. Moreover, since the PTC heating element 410 can be formed in a sheet shape, the pressure gauge 400 can be kept small.

  FIG. 13 shows a pressure gauge 500 further different from the pressure gauge 400 shown in FIG. The pressure gauge 500 shown in FIG. 13 is different from the pressure gauge 400 shown in FIG. 11 in the shape of the PTC heating element 510. The PTC heating element 510 has electrodes 514 and 516 protruding at both ends of a belt-like heating sheet 512 as shown in a development view in FIG.

  The PTC heating element 510 is wound in a ring shape and sandwiched between a ring-shaped heat transfer block 520 screwed to the second seal body 54 and the case body 20. Screwed. Note that a power source 440 is connected to the two electrodes of the PTC heating element 510 thus fixed in the same manner as in FIG.

  In the pressure gauge 500 of FIG. 13, the temperature adjustment effect of the crystal unit 30 is enhanced by the amount of ensuring a large surface area of the PTC heating element 510.

  In addition, although embodiment of this invention was described, it can be easily understood by those skilled in the art that many modified examples which do not deviate substantially from the invention specific matter and effect of this invention are possible. Accordingly, all such modifications are included in the scope of the present invention. For example, a different term described at least once together with a broader or synonymous term in this specification or the drawings can be replaced with the broader or synonymous term in any part of the present specification or the drawings.

Since the pressure gauge of the present invention can hold the crystal resonator at a constant temperature with a heater, measurement in a wide pressure range from atmospheric pressure to 10 ⁻² to 10 ⁻³ Torr is possible. It can be used for pressure measurement in a gas path that changes in For this reason, it is most suitable as a pressure gauge of a vacuum apparatus provided with a chamber whose pressure changes in the atmosphere-vacuum. In addition, for example, it can be used as a sensor that determines the opening / closing timing of a gate valve that is opened in the atmosphere and closed in a vacuum, or as a sensor that determines the control timing of a cryopump. At the time of use, as described above, it may be configured as a composite sensor with another sensor that does not use a crystal resonator.

  Further, the crystal resonator used in the present invention may be not only a temperature-sensitive resonator having the characteristics of FIG. 10 but also a non-temperature-sensitive resonator, except for the embodiment of FIG. A non-temperature-sensitive vibrator is a type in which the change in oscillation frequency with respect to temperature is not a straight line but a curve, and the temperature cannot be uniquely determined by the oscillation frequency. In the embodiment of FIG. 9, since the temperature is obtained from the oscillation frequency of the crystal resonator, only the temperature sensitive resonator is used. In other embodiments, since the temperature is not obtained from the oscillation frequency of the crystal resonator, both a temperature-sensitive resonator and a non-temperature-sensitive resonator can be used.

It is sectional drawing of the crystal-type gas pressure gauge which concerns on 1st Embodiment of this invention. 2A shows a heater power control unit using a thermocouple, and FIG. 2B shows a heater power control unit using an NTC (negative temperature characteristic) thermistor. FIG. 6 is a characteristic diagram of a combined resistance having a minimum value at room temperature, in which a resonance resistance of a crystal resonator and a resistance value of a resistor having negative temperature characteristics are combined. It is a figure which shows the structural example of the pressure measurement part which has the characteristic of FIG. 1 is an overall block diagram of a pressure gauge according to a first embodiment of the present invention. FIG. 6 is an overall block diagram of a pressure gauge having an analog output form different from that of FIG. 5. It is a figure which shows the pressure gauge which has arrange | positioned the Peltier device for experiment for temperature measurement. It is a figure which shows the actual temperature of the quartz oscillator measured by changing environmental temperature variously using the pressure gauge shown in FIG. It is a whole block diagram of the pressure gauge which concerns on 2nd Embodiment of this invention. It is a figure which shows the temperature-oscillation frequency characteristic of the thermosensitive oscillator used for 2nd Embodiment of this invention. It is sectional drawing of a pressure gauge by using the PTC heat generating body which concerns on 3rd Embodiment of this invention as a heater. It is a top view of the pressure gauge shown in FIG. It is sectional drawing of the pressure gauge further different from FIG. It is an expanded view of the PTC heat generating body used for the pressure gauge of FIG.

Explanation of symbols

  1,200,400,500 Pressure gauge, 10 Vacuum chamber, 12 rooms, 14 Wall, 20 Case body, 22 Flange, 30 Quartz vibrator, 40 Electrode, 50 Airtight seal body, 52 First seal body, 54 Cylindrical body , 56 screw part, 58 second seal body, 60 filter member, 70 heater, 80 thermocouple, 82 cold junction temperature compensation circuit, 84, 330 heater power control circuit, 86 second thermistor, 87 amplifier, 88 Peltier element, 90 first C thermistor, 92 resistor, 100 pressure measurement unit, 210 current voltage converter, 220 attenuator (1/10 attenuator), 230 first full wave rectifier, 240 reference voltage source, 250 comparator, 260 voltage controlled attenuator, 270 second full wave rectifier, 280 analog / digital (A / D) converter, 290 CPU, 300 Radical 113, 310 analog meter, 320 frequency counter, 410, 510 PTC heating elements, 412,512 sheet heating element, 412,414,512,514 electrodes, 420 and 520 heat transfer block, 440 power supply

Claims (10)

In a quartz gas pressure gauge that measures the gas pressure from the difference between the natural resonance resistance of the quartz crystal resonator and the measured resonance resistance,
A metal case body forming a chamber communicating with the gas atmosphere;
An electrode connected to the crystal unit;
A first seal body formed of an insulator for hermetically sealing and holding the electrode;
A cylindrical body made of metal, which is inserted into the case main body, and supports the first seal body in an airtight manner;
A second seal body that hermetically seals the metal cylinder and the case body;
A metal filter member that is held by the metal cylinder, surrounds the electrode and the quartz crystal resonator connected thereto, forms a measurement chamber, and communicates with the measurement chamber and the gas atmosphere;
A heater that is disposed on the atmosphere side in contact with the outer wall of the cylindrical body, heats the cylindrical body and the filter member as a heat transfer member, and heats the crystal unit;
A quartz-type gas pressure gauge characterized by comprising: In claim 1,
The case main body and the cylinder are grounded, and the case main body and the cylinder are electrically insulated by a second sealing body. In claim 1 or 2,
In the crystal resonator, the resonance resistance changes with temperature,
The heater is set to a temperature in a positive temperature characteristic region where the resonance resistance increases as the temperature rises,
A quartz-type gas pressure gauge, wherein a negative temperature characteristic resistor whose resistance value decreases as the temperature rises is connected in series to the crystal resonator. In claim 3,
The resistor is composed of a first thermistor having a negative temperature characteristic in which a resistance value decreases as the temperature rises, and a resistor connected in parallel thereto, and the crystal resonator, the first thermistor, and the resistor The pressure measurement unit is configured with
The combined resistance value of the pressure measuring unit has a temperature characteristic that takes a minimum value at a predetermined temperature,
A quartz-type gas pressure gauge, wherein the temperature of the crystal resonator controlled by the heater is substantially set to the predetermined temperature. In claim 4,
A current-voltage converter that is connected to one end of the pressure measuring unit and converts a current flowing through the crystal resonator into a voltage;
An attenuator connected to the other end of the pressure measuring unit;
A first full-wave rectifier that rectifies current from the attenuator;
A comparator that compares a voltage from the first full-wave rectifier with a reference voltage;
A voltage controlled attenuator that further attenuates the output of the attenuator based on the output voltage of the comparator;
A second full-wave rectifier that rectifies the summed output of the voltage controlled attenuator and the current-voltage converter;
A crystal type gas pressure gauge further comprising: In any of claims 1 to 5,
The quartz-type gas pressure gauge, wherein the heater is a PTC (positive temperature characteristic) heating element whose resistance value suddenly increases with a temperature rise exceeding the Curie temperature. In any one of Claims 1 thru | or 5,
A thermocouple for measuring the temperature of the heater;
A heater power control circuit for controlling the heater to a constant temperature based on an output from the thermocouple;
A crystal type gas pressure gauge further comprising: In any one of Claims 1 thru | or 5,
A second thermistor for measuring the temperature of the heater;
A heater power control circuit for controlling the heater to a constant temperature based on an output from the second thermistor;
A crystal type gas pressure gauge further comprising: In any one of Claims 1 thru | or 5,
The crystal resonator is a temperature-sensitive resonator whose oscillation frequency changes linearly with respect to temperature,
Frequency measuring means for measuring the oscillation frequency;
A heater power control circuit for controlling the heater to a constant temperature based on an output from the frequency measuring means;
A crystal type gas pressure gauge further comprising:   10. A vacuum apparatus, wherein the quartz gas pressure gauge according to claim 1 measures a pressure in a region set to atmosphere-vacuum.

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