Abstract:
In a thermomechanical measuring device and a thermogravimetry device, partition walls are provided in two sections such that two kinds of atmospheric gasses, which have passed a sample chamber and a detector chamber, respectively, do not flow back, and a thermally insulated gas mixing chamber is manufactured anew in the middle of the sample chamber and the detector chamber to make it possible to dilute a reactive gas and a water vapor gas having a high partial pressure. Consequently, it is possible to prevent moisture concentration to reduce an influence of water drops even in a high temperature and high humidity state at the time of humidity control and measurement.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a thermal analyzer including a sample chamber and a detector chamber that houses a detector for detecting a physical change due to temperature of a sample stored in the sample chamber as a displacement. 
   In the thermal analyzer including the sample chamber and the detector chamber that houses the detector for detecting a physical change due to temperature of a sample stored in the sample chamber as a displacement, when a gas is fed, different kinds of gasses are used as an atmospheric gas in the sample chamber and am atmospheric gas in the detector chamber that is provided to be connected to the sample chamber via a tubular member. In particular, when an atmospheric gas around a sample contains water vapor, a purge gas for protecting this water moisture from condensing on the detector is introduced into the detector. 
   In such a case, in the conventional thermal analyzer, an exhaust port is provided in the middle between the sample chamber and the detector chamber such that the atmospheric gases and the purge gas join to be discharged out of the thermal analyzer (see, for example, Japanese Patent No. 3084472, FIG. 2 and JP-A-2002-148230, FIG. 1). 
   In the conventional thermal analyzer, although the two kinds of atmospheric gasses having passed the sample chamber and the detector chamber, respectively, join to be discharged, since the sample chamber and the detector chamber communicate with each other, there is a problem in that it is likely that a part of the gasses flow back to the sample chamber and the detector chamber to damage gas purge performance. As the atmospheric gas fed to the sample chamber, an inert gas or an atmospheric gas, which has interaction with a sample and affects a change in a physical amount of the sample, is often selected. A highly reactive gas or water vapor may be often contained in the atmospheric gas. In addition, a cracker gas generated from the sample may be contained in the atmospheric gas. Thus, in general, it is desirable that the thermal analyzer has a structure in which the atmospheric gas does not flow back to the detector chamber. 
   In the case in which the air having an adjusted water vapor pressure is fed into the sample chamber to measure a change in physical properties of the sample in an atmosphere subjected to humidity control, when the sample chamber comes into a high-temperature and high-humidity state with temperature of 80° C. and relative humidity of 60% to temperature of 90° C. and relative humidity of 90%, in the structure of the thermal analyzer for performing thermomechanical measurement (TMA) shown in FIG. 2 of Japanese Patent No. 3084472, water vapor of a high partial pressure flows to a position near an entrance on the detector side crossing the middle between sample chamber and the detector chamber. Consequently, it is likely that the water vapor is liquefied and water drops are generated on a wall surface in the middle or a surface of a sample tube or a bar probe that is closer to the detector chamber and has temperature close to a room temperature. There are problems in that, for example, a weight of the water drops adhering to the bar probe causes an error in measurement of a weight of the sample, a load applied to the sample changes to cause an error in measurement of a physical amount of the sample, and, since the thermal analyzer is constituted vertically in FIG. 2 of Japanese Patent No. 3084472, the water drops drop to a sample part below the thermal analyzer to make the relative humidity unstable. 
   It is an object of the invention to solve the problems and provide a thermal analyzer that prevents back-flow of atmospheric gases to a sample chamber or a detector chamber by clearly distinguishing a location where the atmospheric gasses are mixed in a process in which the atmospheric gasses join to be discharged, prevents generation of water drops by clarifying a mixing location such that a part of water vapor does not flow into the detector chamber side even in the case in which the inside of the sample chamber is subjected to humidity control to be brought into a high-temperature and high-humidity state, and makes it possible to also mix the water vapor and a dry gas on the detector chamber side to lower a concentration of a highly reactive gas or lower a partial pressure of the water vapor to make it less likely that water drops are generated. 
   SUMMARY OF THE INVENTION 
   In order to solve the problems, in a thermal analyzer of the invention, partition walls are provided in two sections on a sample chamber side and a detector side such that two kinds of atmospheric gasses having passed a sample chamber and a detector chamber, which communicates with the sample chamber, respectively, do not flow back, and a gas mixing chamber serving as a partition chamber is disposed between the sample chamber and the detector chamber. A bar member extending from the sample chamber to the detector chamber through the gas mixing chamber is a balance beam in the case of a thermogravimetry device (TG) or a detection bar, which transmits a change in a sample length and a signal of a load, in the case of a thermomechanical measuring device (TMA). Therefore, the bar member cannot measure a change in a physical amount of a sample accurately when the bar member mechanically comes into contact with the partition walls. Thus, holes for gas flow larger in diameter than a diameter of the bar member are pierced near the center of the partition walls to prevent the bar member from coming into contact with the partition walls. 
   When it is difficult to alter the structure to provide a gas mixing chamber anew in the existing thermal analyzer, it is possible to provide partition members, which are made of a flexible material and have holes in the center thereof, and fit the partition members in the thermal analyzer to form the partition walls. A space between the partition members functions as the gas mixing chamber, whereby the same structure as described above is obtained. 
   In the thermal analyzer constituted as described above, since the sample chamber, the detector chamber, and the gas mixing chamber are separated from one other by the partition walls, gasses passing through the sample chamber and the detector chamber are fed independently from the sample chamber and the detector chamber, respectively. Thus, the gasses are never mixed. In the gas mixing chamber, the two kinds of gasses are mixed and diluted and then discharged to the outside. Since the bar member is inserted through gaps provided in the respective gas-flow holes of the partition walls, the bar member is not in contact with wall surfaces of the holes of the partition walls. Thus, it is possible to perform measurement of a physical amount accurately. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
       FIG. 1  is a longitudinal sectional view of a thermomechanical measuring device (TMA) to which the invention is applied; 
       FIG. 2  is a perspective view of the thermomechanical measuring device (TMA) to which the invention is applied; 
       FIG. 3  is a longitudinal sectional view of a vertical-type thermogravimetry device (TG) to which the invention is applied; 
       FIG. 4  is a longitudinal sectional view of a horizontal-type thermogravimetry device (TG) to which the invention is applied; and 
       FIG. 5  is a longitudinal sectional view of a thermal analyzer of a conventional example. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An embodiment of the invention will be explained with reference to the accompanying drawings.  FIG. 1  is a longitudinal sectional view of a thermal analyzer according to the invention. A type of the thermal analyzer is a thermomechanical measuring device (TMA). This is an example of a device that is capable of performing measurement as a humidity control type TMA assuming the air having an adjusted water vapor partial pressure as an atmospheric gas around a sample. 
   In  FIG. 1 , in an entire structure of the thermal analyzer, a sample chamber  2  is provided in a lower part, a detector chamber  3  is provided in an upper part, and a gas mixing chamber  4  is provided in the center to be placed between the sample chamber  2  and the detector chamber  3 . A gas containing a water vapor gas indicated by a solid line arrow is fed to the sample chamber  2 . On the other hand, a dry gas indicated by a dotted line arrow is fed to the detector chamber  3 . The two kinds of gasses are mixed in the gas mixing chamber  4  and discharged to the outside. The sample chamber  2  and the gas mixing chamber  4  are provided in the inside of a hot water furnace  14 , which is devised to have uniform temperature, to prevent moisture concentration. 
   Details of  FIG. 1  will be explained. As a representative example, it is assumed that a sample  1  is a film-like sample. The sample has a size of an effective length of 20 rom, an effective width of 3 rom, and an effective thickness of about several tens μm. The sample  1  is disposed in the sample chamber  2 , and the detector chamber  3 , which is connected to the sample chamber  2  via a bellows  18  formed as a tubular member, is disposed above the sample chamber  2 . The gas mixing chamber  4  is provided in the middle between the sample chamber  2  and the detector chamber  3 . An upper end of the sample  1  is fixed to a bar member  5  made of quartz glass with a diameter of 3.5 mm by a sample chuck  25   a  made of metal. A lower end of the sample  1  is fixed to a cylindrical sample tube  6  made of quartz glass by a sample chuck  25   b  made of metal. 
   As indicated by a dotted line in the figure, on a side of the sample tube  6 , a window for replacement of the sample  1  is opened and a vertical slit for replacement of the bar member  5  is opened extending from a sample portion to the gas mixing chamber  4 . Thus, an atmospheric gas can be exchanged easily between the inside and the outside of the sample tube  6 . 
   An atmospheric gas to be fed to the sample chamber  2  is introduced from a sample chamber gas inlet  7  provided below the sample chamber  2 . An atmospheric gas to be fed to the detector chamber  3  is introduced from a detector chamber gas inlet  8  provided on a side of the detector chamber  3 . A gas mixing chamber gas outlet  9  is provided in the gas mixing chamber  4 . The respective atmospheric gasses are fed through a not-shown tube of resin with an outer diameter of 6 mm and an inner diameter of 4 mm. The inlets  7  and  8  and the outlet  9  for the respective gasses are made in a pipe shape and have substantially the same diameter as the tube of resin. 
   The sample chamber  2  and the gas mixing chamber  4  are partitioned by a disc-like ring  10  made of silicon rubber and a gap ring  11  made of foamed resin. In other words, the disc-like ring  10  and the gap ring  11  form a partition wall. Taking into account a case in which the thermal analyzer is used as a usual TNA, the partitioning portion is made of flexible resin and constituted to be easily removable. The disc-like ring  10  is fixed to an inner wall of the sample chamber  2  to cover the inner wall of the sample chamber  2  and an outer periphery of the sample tube  6  without a gap. An outer periphery of the gap ring  11  adheres to an inner periphery of the sample tube  6 . However, an inner diameter of the gap ring  11  is set larger than a diameter of the bar member  5  by about 2 to 3 mm to form a gas outlet of the sample chamber  2  and provide a gap to thereby allow the bar member  5  to be inserted through the gap ring  11 . The detector chamber  3  and the gas mixing chamber  4  are partitioned by a partition wall comprised of a disc-like ring  12  made of silicon rubber and a gap ring  13  made of foamed resin in the same manner. The disc-like ring  12  adheres to the outer periphery of the sample tube  6  and the gap ring  13  forms a gas outlet of the detector chamber  3  and provides a gap to allow the bar member  5  to be inserted through the gap ring  13 . 
   It is also possible to provide the gas outlet of the sample chamber  2  and the gas outlet of the detector chamber  3  in plural places rather than one place. When it is assumed that the gas outlet, through which the bar member  5  is inserted, is a first outlet, if the first outlet having a very narrow gap between the outer periphery of the bar member  5  and the first outlet itself can be formed, the same effect is obtained when a large second outlet is provided in another place of the partition wall. The following explanation is about a case in which a sectional area obtained by cutting the second outlet with a partition wall surface around the second outlet is larger than a sectional area obtained by cutting the gap between the first outlet and the bar member  5  with a partition wall surface around the gap. Since the sectional area of the first outlet is small, an amount of a gas passing through the first outlet is small and is almost negligible in an extreme case. Thus, most of the gas passes through the second outlet with the large sectional area. When a gas flow rate is large, such a structure is effective. It is possible to form the second outlet in an appropriate size, for example, in the disc-like ring  10  or the disc-like ring  12  according to a gas flow rate. 
   The sample chamber  2  and the gas mixing chamber  4  form an inner space of a double cylinder type hot water furnace  14  made of stainless steel alloy. The middle of the double cylinder type hot water furnace  14  is welded and sealed. A hot water inlet  15  and a hot water outlet  16  for hot water circulation are attached to an outer wall of the double cylinder type hot water furnace  14 . This makes it possible to circulate a liquid subjected to temperature adjustment in a not-shown circulation thermostatic bath or the like such that the inside of the double cylinder type hot water furnace  14  is maintained at uniform temperature. Usually, since water is circulated, a temperature range is about 2° C. to 90° C. However, when silicon oil or the like is used, it is possible to expand the temperature range. When a water vapor partial pressure is low and there is no fear of moisture concentration, an electric heater heating system using a heating wire may be adopted instead of the hot water circulation system. This system is a simple heating method, but a temperature distribution tends to occur and moisture concentration tends to occur in a part of low temperature. However, when a water vapor partial pressure is low, that is, a dew point is low, moisture concentration is less likely to occur. Thus, the electric heater heating system using the heating wire may be adopted only when the water vapor partial pressure is low. 
   An upper part of the double cylinder type hot water furnace  14  is opened. There is a base  17  at an upper end of the double cylinder type hot water furnace  14 , and the disc-like ring  12  is placed on the base  17 . When the sample  1  is attached, the double cylinder type hot water furnace  14  is lowered by a not-shown hot water furnace vertical movement mechanism to expose a lower part of the sample tube  6 . At this point, since the disc-like ring  10  is fixed to an inner wall of the double cylinder type hot water furnace  14 , the disc-like ring  10  falls together with the double cylinder type hot water furnace  14  while sliding on the outer periphery of the sample tube  6 . When the sample  1  has been set, the double cylinder type hot water furnace  14  is lifted to return the disc-like ring  10  to an original position and the disc-like ring  12  is nipped by the base  17  to be pressed against the bellows  18 . Then, sealing performance is given to the double cylinder type hot water furnace  14  by a spring restoring force of the bellows  18  to prevent the external air from entering the double cylinder type hot water furnace  14 . 
   The detector chamber  3  is surrounded by a box of metal to prevent the external air from entering the detector chamber  3 . In the inside of the detector chamber  3 , there are a sample tube holding mechanism  19 , cantilever leaf springs  20   a  and  20   b  made of metal for holding the bar member  5  so as to be movable up and down, a differential transformer core  21  for sample displacement detection  24  attached to the bar member  5 , a differential transformer coil  22 , an electromagnetic load generating coil  23  fixed to an upper end of the bar member  5 , and a combination  24  of a permanent magnet and a yoke material fixed to the detector chamber  3 . 
   A temperature and humidity sensor  26  for temperature and relative humidity detection is inserted in the sample chamber  2 . A signal cable of the temperature and humidity sensor  26  is pierced through the portions of the disc-like ring  10  and the base  17  in an air tight state to be connected to the outside. 
     FIG. 2  is a perspective view of the thermomechanical measuring device (TMA) shown in  FIG. 1 . 
     FIG. 3  is a longitudinal sectional view of an example in which the invention is applied to a vertical type thermogravimetry device (TG). The vertical type thermogravimetry device (TG) is a device to which the thermomechanical measuring device (TMA) in  FIG. 1  is applied. A sample  27  is placed on a sample tray  28 , and the sample tray  28  is hung at a lower end of the bar probe  5  serving as a yoke by a sample tray wire  29 . A sample tube  30  has a shape obtained by cutting off about lower ⅓ of the sample tube  6  and is opened at a bottom thereof. As a mechanism for performing TG measurement, when feedback control is applied to the electromagnetic load generating coil  23  to hold a displacement signal (TMA signal) at zero, it is possible to measure a change in a load corresponding to a change in a sample weight. 
     FIG. 4  is a longitudinal sectional view of an example in which the invention is applied to a horizontal type thermogravimetry device (TG). A sample  31  is placed on a sample tray  32  held by a thermocouple  33 . The thermocouple  33  is inserted through a hole of a balance beam  34 , which serves as a yoke, from a tip of the balance beam  34  to measure temperature of the sample  31 . In the case of a differential TG device in which a balance beam for reference is also set, the thermocouple  33  is also used for obtaining a differential thermal signal (DTA signal). A gap ring holding cylinder  35  is fixed by a bellows base  36  of a disc ring shape. The gap ring holding cylinder  35  has a cylindrical shape with a vertical slit and holds the gap rings  11  and  13  made of foamed resin on an inner side thereof. 
   The sample chamber  2  and the gas mixing chamber  4  are partitioned by the disc-like ring  10 , which is fixed to the inner wall of the double cylinder hot water furnace  14 , and the gap ring  11 . The detector chamber  3  and the gas mixing chamber  4  are partitioned by the bellows base  35  and the gap ring  13 . 
   The thermomechanical measuring device and the thermogravimetry device are explained as examples of the invention. The invention effectively acts in these devices but is not limited to these devices. 
   The invention realizes effects to be described below. 
   Since the sample chamber and the detector chamber are separated, gasses passing through the sample chamber and the detector chamber are never mixed in the sample chamber and the detector chamber, and it is possible to feed only a target type of gas. Thus, there is an effect that gas purge effect is not damaged. 
   Since the gas mixing chamber is provided, the two kinds of gasses are mixed and diluted in the inside of the gas mixing chamber. In particular, when a gas containing a high-pressure water vapor gas is fed to the sample chamber side, if a dry gas is fed to the detector side, the gas containing the high-pressure water vapor gas and the dry gas are mixed in the gas mixing chamber. The water vapor gas does not enter the detector chamber, and a water vapor partial pressure in the gas mixing chamber falls due to the mixing of the two kinds of gasses. Consequently, in the detector chamber and the gas mixing chamber, dew points fall and an amount of generation of water drops is reduced when moisture concentration is less likely to occur. Moreover, if a thermal insulation measure is taken, it is possible to substantially eliminate generation of water drops. An error in measurement of a physical amount due to water drops does not occur, and phenomena such as wetting of a sample and unstable relative temperature due to dropping of water drops never occur.