Patent Publication Number: US-2004040847-A1

Title: Gas sensor element and method of manufacturing same

Description:
BACKGROUND OF THE INVENTION  
       [0001] The present invention relates to a gas sensor or gas sensor element (herein, called “gas sensor element”) for detecting concentration of a gas such as NOx contained in a gas to be measured and also relates to a method of manufacturing a such gas sensor element.  
       [0002] A gas sensor element is a kind of detector for detecting a gas concentration such as NOx contained in a gas, such as exhaust gas, to be measured by a plurality of electrochemical cells formed by providing a pair of electrodes to a solid electrolytic sheet. More specifically, between the solid electrolytic sheet and another (opposing) sheet disposed so as to oppose thereto, there is arranged a spacer by which a gas measurement chamber, into which a gas to be measured (measurement gas) is introduced, or a reference gas chamber, into which atmosphere as a reference gas for measurement is introduced. After oxygen concentration of the measurement gas introduced into the gas measurement chamber is adjusted or regulated, the concentration of NOx or like contained therein is obtained.  
       [0003] A gas sensor element utilized for the purpose mentioned above is, for instance, shown in FIG. 30.  
       [0004] With reference to FIG. 30, a gas sensor element  9  of a conventional structure comprises a porous sheet  931 , a shield sheet  932 , a spacer  933 , a solid electrolytic sheet  94  constituting a monitor cell  3  and a sensor cell  4 , a spacer  95 , a solid electrolytic sheet  96  constituting a pump cell  2 , a spacer  97 , a cover (coat) heater sheet  996  and a heater sheet  995  (both heater sheets may be called merely “heater sheet  99 ”). These sheets are laminated in a predetermined order as shown in FIG. 30, and this laminated structure is pressed in the laminated direction and then sintered in a state that the respective sheets  931 ,  932 ,  94 ,  96  and  99  ( 995 ,  996 ) and the respective spacers  933 ,  95 , and  97  are laminated in the order.  
       [0005] On the other hand, in the gas sensor element of the structure mentioned above, gas chambers  91 ,  92 ,  921  and  922  formed between the adjacent sheets and inside the respective spacers  933 ,  95  and  97  have hollow structures, and for this reason, when the pressure is applied to the laminated structure, the shield sheet  932  disposed most outside, upper side as viewed, of the gas sensor element  9  may be flexed towards the gas chamber  921 . In such case, as shown in FIGS. 31 and 32, crack(s)  901  may be caused along the longitudinal direction of the gas sensor element  9  at a substantially central portion in the width direction of the shield sheet  932 . This problem of crack generation may be also caused to the other sheets  931 ,  94 ,  96  and  99  in the laminated state.  
       [0006] Incidentally, electrodes  31  and  32  of the monitor cell  3  and electrodes  41  and  42  of the sensor cell  4  are formed by screen-printing a metal paste on a surface of the solid electrolytic sheet  94 , and also, electrodes  21  and  22  of the pump cell  2  are formed by screen-printing a metal paste on a surface of the solid electrolytic sheet  96 . In addition, a heating element  991  of the heater sheet  99  is also formed through the screen printing process on the surface of the heater sheet  995 .  
       [0007] As shown in FIGS. 33 and 34, however, in the gas sensor element  9 , the heating element  991  which is subjected to the screen printing has a protruded surface, i.e., circular surface having front end portion  992  as shown in FIG. 34. For this reason, when the laminated structure of the gas sensor element  9  is provided, the protruded front end  992  will abut linearly against the cover heat sheet  996  towards the longitudinal direction L of the gas sensor element  9 .  
       [0008] Therefore, when the respective sheets  931 ,  932 ,  94 ,  96 ,  996 ,  995  and the respective spacers  933 ,  95 ,  97  are laminated and then pressed in the laminated state, crack(s)  901  may be caused at a portion corresponding to the protruded front end forming portion  992 .  
       SUMMARY OF THE INVENTION  
       [0009] The present invention was conceived to substantially eliminate defects or drawbacks encountered in the prior art mentioned above, and one primary object of the present invention is to provide a gas sensor element having an improved structure capable of effectively prevent cracks from causing to sheets forming the sensor element at a time of manufacturing the gas sensor element.  
       [0010] Another object of the present invention is to provide a method of manufacturing a gas sensor element capable of effectively preventing cracks from causing at a time of the manufacture thereof.  
       [0011] The above and other objects can be achieved according to the present invention by providing, in one aspect, a gas sensor element comprising:  
       [0012] a solid electrolytic sheet provided with a pair of electrodes so as to constitute an electrochemical cell;  
       [0013] another sheet disposed so as to oppose to the solid electrolytic sheet so as to define a gas chamber therebetween in which gas contacts the electrodes;  
       [0014] a spacer disposed in the gas chamber between these sheets; and  
       [0015] a support member disposed in the gas chamber so as to support a pressing force applied in a direction of lamination of the solid electrolytic sheet and the another sheet.  
       [0016] In this aspect, it may be preferred that the gas chamber has a long scale extending along a longitudinal direction thereof and the support member is disposed at a position for supporting substantially a central portion of the gas chamber in a width direction thereof normal to the longitudinal direction thereof.  
       [0017] The support member may have a sectional area taken along the line normal to the longitudinal direction of the gas chamber, the sectional area occupies 5 to 95% of a sectional area of the gas chamber in the longitudinal direction thereof.  
       [0018] In a more specific embodiment, there is provided a gas sensor element comprising:  
       [0019] a shield sheet;  
       [0020] a first solid electrolytic sheet constituting a monitor cell and a sensor cell;  
       [0021] a first spacer disposed between the shield sheet and the first solid electrolytic sheet so as to form a first reference gas chamber therebetween;  
       [0022] a second solid electrolytic sheet constituting a pump cell;  
       [0023] a second spacer disposed between the first and second solid electrolytic sheets so as to form a gas measurement chamber therebetween;  
       [0024] a heater sheet provided with a heating element;  
       [0025] a third spacer disposed between the second solid electrolytic sheet and the heater sheet so as to form a second reference gas chamber, the shield sheet, the first and second solid electrolytic sheets and the heater sheet being laminated in a predetermined order; and  
       [0026] support members disposed respectively in the first and second reference gas chambers and the gas measurement chamber.  
       [0027] There may be also provided a gas sensor element comprising:  
       [0028] a first solid electrolytic sheet constituting a first pump cell;  
       [0029] a second solid electrolytic sheet constituting a second pump cell, a monitor cell and a sensor cell;  
       [0030] a first spacer disposed between the first and second solid electrolytic sheets so as to form a gas measurement chamber therebetween;  
       [0031] a heater sheet provided with a heating element;  
       [0032] a second spacer disposed between the second solid electrolytic sheet and the heater sheet so as to form a reference gas chamber therebetween, the first and second solid electrolytic sheets and the heater sheet being laminated in a predetermined order; and  
       [0033] support members disposed respectively in said reference gas chamber and said gas measurement chamber.  
       [0034] According to the gas sensor element of the structures and characters mentioned above, even if any pressing force is applied, in the lamination direction, to the solid electrolytic sheet and the other sheet opposing to the solid electrolytic sheet, this pressing force can be supported (held) by the support member disposed in the gas measurement chamber formed between the above-mentioned sheets, thus providing a strength to the gas sensor element.  
       [0035] More in detail, in the manufacture of the gas sensor element, the solid electrolytic sheet, the opposing sheet and the spacer disposed therebetween are pressurized in their laminated state. In such case, this pressing force can be supported by the support member disposed in the gas measurement chamber defined between the above-mentioned sheets, thus preventing the bending or flexing of the solid electrolytic sheet and/or the opposing sheet towards the gas measurement chamber and also preventing cracks from causing to the solid electrolytic sheet and the opposing sheet.  
       [0036] After the pressurizing process, a sintering treatment is carried out. In this process, if the opposing sheet and/or the spacer are made of materials different from a material of the solid electrolytic sheet, there is a fear that the solid electrolytic sheet or opposing sheet may be flexed towards the gas measurement chamber due to difference in thermal expansion coefficient of the opposing sheet or spacer and the solid electrolytic sheet. In such case, according to the present invention, the bending or flexing of the solid electrolytic sheet and/or the opposing sheet towards the gas measurement chamber can be prevented, and the generation of cracks to the solid electrolytic sheet and the opposing sheet can be also prevented.  
       [0037] Furthermore, in the embodiments in which a plurality of sheets such as including the shield sheet, first and second solid electrolytic sheets, and the heater sheets are arranged in the laminated state and the spacers disposed between the respective sheets so as to define the gas measurement chamber and the reference gas chamber therebetween, the support members may be disposed in the respective gas chambers so as to prevent the sheets from being flexed or bent and to prevent cracks from causing thereto.  
       [0038] In another aspect of the present invention, there is provided a method of manufacturing a gas sensor element comprising the steps of:  
       [0039] preparing a non-sintered substrate;  
       [0040] forming a conductive layer on a surface of the non-sintered substrate and forming a flat portion on the surface of the conductive layer during the conductive layer forming step so that the flat portion has a width more than 3% of a width of the conductive layer;  
       [0041] laminating a non-sintered lamination sheet on the surface of the conductive layer on the non-sintered substrate so as to provide an intermediate product; and  
       [0042] sintering the thus laminated intermediate product.  
       [0043] According to this method, the flat portion is formed to the protruded front end portion of the conductive layer, and this flat portion abuts against the non-sintered lamination sheet at the time of manufacturing the intermediate product, which can prevent the excessive local load from being applied to the non-sintered substrate and the non-sintered lamination sheet, thus preventing cracks from causing to the non-sintered substrate and the non-sintered lamination sheet.  
       [0044] In a case of less than 3% in the width ratio of the flat portion with respect to the conductive layer, the width of the flat portion is too small, so that only less crack generation preventing effect is obtainable. It may be preferred that this width ratio is as much as large, but it will be difficult to be made to 100% in consideration of the conductive layer formation by a printing method mentioned later.  
       [0045] In a further aspect of the manufacturing method of the present invention, there may be also provided a method of manufacturing a gas sensor element comprising the steps of:  
       [0046] preparing a non-sintered substrate;  
       [0047] printing a metal past on a surface of the non-sintered substrate so as to form a conductive layer thereon, the metal paste having a viscosity of 200±50 [Pa·s] at a temperature of 20° C.;  
       [0048] forming a flat portion on a surface of the conductive layer formed of the metal paste;  
       [0049] laminating a non-sintered lamination sheet on the surface of the conductive layer on the non-sintered substrate so as to provide an intermediate product; and  
       [0050] sintering the thus laminated intermediate product.  
       [0051] According to this method, the flat portion is also formed to the protruded front end portion of the conductive layer by applying the metal paste, and this flat portion abuts against the non-sintered lamination sheet at the time of manufacturing the intermediate product, which can prevent the excessive local load from being applied to the non-sintered substrate and the non-sintered lamination sheet, thus preventing cracks from causing to the non-sintered substrate and the non-sintered lamination sheet.  
       [0052] In a case of the metal paste being less than 200±50 [Pa·s] at a temperature of 20° C., there is a fear of no formation of the aimed conductive layer because of too small viscosity, and on the other than, in a case of the metal paste being more than 200±50 [Pa·s] at a temperature of 20° C., there is a fear that the flat portion formed may have too small width and, hence, the desired crack generation preventing effect is not obtainable.  
       [0053] In a still further aspect, there may be also provided a method of manufacturing a gas sensor element comprising the steps of:  
       [0054] preparing a non-sintered substrate;  
       [0055] printing a metal paste on a surface of the non-sintered substrate for a conductive layer;  
       [0056] drying the metal paste so as to form the conductive layer;  
       [0057] forming a flat portion by pressurizing the conductive layer so that the flat portion has a width more than 3% of a width of the conductive layer;  
       [0058] laminating a non-sintered lamination sheet on the surface of the conductive layer on the non-sintered substrate so as to provide an intermediate product; and  
       [0059] sintering the thus laminated intermediate product.  
       [0060] According to this method, the flat portion having a predetermined width ratio is also formed to the protruded front end portion of the conductive layer by applying the metal paste, and this flat portion abuts against the non-sintered lamination sheet at the time of manufacturing the intermediate product, which can prevent the excessive local load from being applied to the non-sintered substrate and the non-sintered lamination sheet, thus preventing cracks from causing to the non-sintered substrate and the non-sintered lamination sheet.  
       [0061] In these manufacturing method, the conductive layer may comprise a heat generation portion and a lead portion for connecting the heat generation portion to an external element of the gas sensor element, and-the substrate may comprise a heater sheet provided with a conductive layer.  
       [0062] The conductive layer may comprise an electrode and a lead portion for connecting the heat generation portion to an external element of the gas sensor element, and the substrate may comprise a solid electrolytic sheet provided with a pair of conductive layers so as to constitute an electrochemical cell.  
       [0063] In the above embodiments of the manufacturing method of the gas sensor element, the non-sintered substrate and the non-sintered lamination sheet are substrate and sheet before the sintering process, and the width of the flat portion is formed in a direction normal to the longitudinal direction of the substrate in which the conductive layer extends. Furthermore, the conductive layer is a layer formed of a metal layer capable of being electrically conductive. The metal paste may be formed from more than one kind of noble metal such as Au, Pt, Pd and Rh, a resin and a solvent, which are mixed with each other. The conductive layer may be formed by drying the solvent in the metal paste.  
       [0064] Further, it is to be noted that the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0065] In the accompanying drawings:  
     [0066]FIG. 1 is a sectional view of a gas sensor element according to a first embodiment of the present invention;  
     [0067]FIG. 2 is a developed perspective view of the gas sensor element of FIG. 1;  
     [0068]FIG. 3 is a sectional view taken along the line III-III in FIG. 1, in which a support member covers electrodes;  
     [0069]FIG. 4 is a view similar to FIG. 3, in which the support member, however, does not cover the electrodes;  
     [0070]FIG. 5 is a view similar to FIG. 3, in which a plurality of rectangular support members are disposed;  
     [0071]FIG. 6 is a view similar to FIG. 3, in which a plurality of elliptical support members are disposed;  
     [0072]FIG. 7 is a view similar to FIG. 3, in which a plurality of circular support members are disposed;  
     [0073]FIG. 8 is a view similar to FIG. 3, in which a plurality of support members are disposed in zigzag form;  
     [0074]FIG. 9 is a partial sectional view taken along the line I—I in FIG. 1 showing a ratio in sectional area of the support member and a gas measurement chamber;  
     [0075]FIG. 10 is a graph showing a relationship between a time and a NOx concentration;  
     [0076]FIG. 11 is a sectional view, corresponding to FIG. 1, representing a second embodiment of a gas sensor element of the present invention;  
     [0077]FIG. 12 is a sectional view taken along the line XII—XII in FIG. 11 and illustrates a state of forming a support member according to the second embodiment;  
     [0078]FIG. 13 is a sectional view, corresponding to FIG. 1, representing a third embodiment of a gas sensor element of the present invention;  
     [0079]FIG. 14 is a sectional view taken along the line XIV—XIV in FIG. 13 and illustrates a state of forming a support member according to the third embodiment;  
     [0080]FIG. 15 is a sectional view of a gas sensor element manufactured in accordance with an embodiment (first) of a gas sensor element manufacturing method of the present invention;  
     [0081]FIG. 16 is a developed perspective view of the gas sensor element of FIG. 15 before a sintering treatment;  
     [0082]FIG. 17 is a plan view illustrating a state that a conductive layer is formed on a surface of a non-sintered heat sheet of the gas sensor element of FIG. 15 ( 16 );  
     [0083]FIG. 18 is a sectional view taken along the line XVIII—XVIII in FIG. 17, showing the conductive layer as a heating section in an enlarged scale;  
     [0084]FIG. 19 is a sectional view showing the conductive layer of FIG. 15( 16 ) as a lead section in an enlarged scale;  
     [0085]FIG. 20 is an illustrated sectional view showing a state that a binder agent is applied to the surface of a conductive layer formed on a non-sintered heater sheet of the embodiment shown in FIG. 15( 16 );  
     [0086]FIG. 21 is an illustrated sectional view showing a state that a binder agent is applied to the surface of a conductive layer formed on a non-sintered solid electrolytic sheet of the embodiment shown in FIG. 15( 16 );  
     [0087]FIG. 22 is an illustrated sectional view showing a state that a non-sintered cover sheet is laminated on the surface of a conductive layer formed on a non-sintered heater sheet of the embodiment shown in FIG. 15( 16 );  
     [0088]FIG. 23 is an illustrated sectional view showing a state that non-sintered spacers are applied to both the surfaces of a conductive layer formed on a non-sintered solid electrolytic sheet of the embodiment shown in FIG. 15( 16 );  
     [0089]FIG. 24 is an illustrated sectional view showing a state that a metal paste is screen-printed on a surface of a non-sintered heater sheet and then dried to thereby form a conductive layer having a circular section, according to another embodiment of the gas sensor element manufacturing method of the present invention;  
     [0090]FIG. 25 is an illustrated sectional view showing a state that a metal paste is screen-printed on a surface of a non-sintered solid electrolytic sheet and then dried to thereby form a conductive layer having a circular section, according to another embodiment of the gas sensor element manufacturing method of the present invention;  
     [0091]FIG. 26 is an illustrated sectional view showing a state that a metal paste is screen-printed on a surface of a non-sintered solid electrolytic sheet and then dried to thereby form a conductive layer having a circular section, according to another embodiment of the gas.-sensor element manufacturing method of the present invention;  
     [0092]FIG. 27 is an illustrated sectional view showing a state that a conductive layer of the non-sintered solid electrolytic sheet is pressurized by means of press according to another embodiment of the gas sensor element manufacturing method of the present invention;  
     [0093]FIG. 28 is a sectional view of a gas sensor element manufactured in accordance with another (second) embodiment of a gas sensor element manufacturing method of the present invention;  
     [0094]FIG. 29 is a sectional view of a gas sensor element manufactured in accordance with a further (third) embodiment of a gas sensor element manufacturing method of the present invention;  
     [0095]FIG. 30 is a sectional view, similar to FIG. 1, showing a conventional gas sensor element;  
     [0096]FIG. 31 is a plan view of the gas sensor element of FIG. 30;  
     [0097]FIG. 32 is a sectional of the gas sensor element of FIG. 30 taken along the line XXX—XXX;  
     [0098]FIG. 33 is a plan view showing a heater section, of the gas sensor element of FIG. 30, to which cracks are generated; and  
     [0099]FIG. 34 is a sectional view taken along the line XXXIV—XXXIV in FIG. 33. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0100] Preferred embodiments of the gas sensor element of the present invention will be described hereunder with reference to the accompanying drawings.  
     First Embodiment  
     [0101] A first embodiment of a gas sensor element will be first described hereunder with reference to FIGS.  1  to  10 .  
     [0102] In this embodiment, a gas sensor element (or merely gas sensor)  1  is a sensor for detecting NOx concentration in an exhaust gas, as a gas to be measured, from an engine of a vehicle.  
     [0103] The gas sensor element  1  is provided with, as shown in FIGS. 1 and 2, gas measurement chambers  11  and  12 , a pump cell  2 , a monitor cell  3 , a sensor cell  4  and a heater  19 . The gas measurement chambers  11  and  12  each has a structure in which the gas to be measured (which may be called merely measurement gas for the sake of easy understanding) can be introduced under a predetermined diffusion resistance.  
     [0104] The pump cell  2  comprises an oxygen ion conductive solid electrolytic sheet  16  and a pair of electrodes  21  and  22  formed on the surface of the sheet  16 . One electrode  21  is disposed in the gas measurement chamber  11  and the other one electrode  22  is disposed in a reference gas chamber  121 .  
     [0105] Inside the gas measurement chamber  11 , an exhaust gas from an engine is introduced through a porous sheet  131  and a gas inducing port  101 . The pump cell  2  acts to regulate or control oxygen concentration in the exhaust gas in the gas introduced in the gas measurement chamber  11  by applying voltage to the paired electrodes  21  and  22 . The exhaust gas subjected to the oxygen concentration control is thereafter introduced from the gas measurement chamber  11  into the other gas measurement chamber  12  through a diffusion resisting passage  102 .  
     [0106] On the other hand, the monitor cell  3  comprises an oxygen ion conductive solid electrolytic sheet  14  and a pair of electrodes  31  and  32  formed on the surface of the sheet  14 . One electrode  31  is disposed inside a reference gas chamber  122  into which atmosphere is introduced and the other electrode  32  is disposed inside the gas measurement chamber  12 .  
     [0107] The monitor cell  3  acts to measure an oxygen ion current passing through the paired electrode  31  and  32  on the basis of a difference in the oxygen concentrations in the gas measurement chamber  12  and the reference gas chamber  122  and then detect the oxygen concentration in the gas measurement chamber  12 . Then, in accordance with the detected oxygen ion current, the voltage to be applied to the pump cell  2  is regulated.  
     [0108] The sensor cell  4  comprises the oxygen ion conductive solid electrolytic sheet  14  and a pair of electrodes  41  and  42  formed on the surface of the sheet  14 . One electrode  41  is disposed inside the reference gas chamber  122  into which atmosphere is introduced and the other electrode  42  is disposed inside the gas measurement chamber  12 .  
     [0109] The sensor cell  4  acts to-decompose the NOx in the exhaust gas by the electrode  42  and then measure a change of the oxygen concentration generated in accordance with the decomposed amount of the NOx as an oxygen ion current passing through the paired electrodes  41  and  42 , thus obtaining the NOx concentration.  
     [0110] Further, the heater  19  acts to heat the pump cell  2 , the monitor cell  3  and the sensor cell  4  to their predetermined activation temperatures and comprises an insulating heater sheet  195 , an insulating coat heater sheet  196  and a heating element  191  disposed between these heater sheets. The heating element  191  generates heat through the current conduction between the heater sheets  195  and  196 .  
     [0111] The gas sensor element  1  of this embodiment comprises a porous sheet  131 , a shield sheet  132 , a spacer  132  constituting the reference gas chamber  122 , the solid electrolytic sheet  14  constituting the monitor cell  3  and the sensor cell  4 , a spacer  15  constituting the gas measurement chambers  11  and  12 , the solid electrolytic sheet  16  constituting the pump cell  2 , a spacer  17  constituting the other reference gas chamber  121 , and the heater sheet  195  on which the coat heater sheet  196  and the heating element  191  are disposed. The gas sensor element  1  is formed by laminating these sheets and elements in the illustrated or predetermined order.  
     [0112] Furthermore, as shown in FIGS. 1 and 2, the spacer  133  is formed between the solid electrolytic sheet  14  constituting the monitor cell  3  and the sensor cell  4  and the shield sheet  132  opposing to the solid electrolytic sheet  14 , and this spacer  133  forms the reference gas chamber  122  in which the atmosphere contacts the electrodes  41  and  42 . The shield sheet  132  and the spacer  133  are formed on the side on which the electrodes  31  and  32  of the solid electrolytic sheet  14  are formed.  
     [0113] Next, with reference to FIG. 3, a support member for supporting (bearing) pressing force in the lamination direction of the solid electrolytic sheet  14  and the shield sheet  132  is disposed in the reference gas chamber  122 .  
     [0114] The support member  51  support a portion between the solid electrolytic sheet  14  and the shield sheet  132  and between the electrodes  31 ,  41  and the shield sheet  132  so as to prevent these portions (i.e., spaces) from being reduced in size.  
     [0115] The reference gas chamber  122  has a long scale in its longitudinal direction shown in FIG. 9, and the support member  51  is supported, at its central portion in a width direction W of the reference gas chamber  122  normal to the longitudinal direction L thereof. Accordingly, a portion, which is most likely to be flexed, of the shield sheet  132 , i.e., the central portion in the width direction, can be supported by the support member  51 .  
     [0116] The gas sensor element  1  is itself formed to have a long scale and the longitudinal direction of the reference gas chamber  122  accords with the longitudinal direction of the gas sensor element  1 .  
     [0117] With further reference to FIG. 9, in this embodiment, the sectional area A (thickened broken line area) of the support member in a section normal to the longitudinal direction L is of about 35% of the sectional area B (thickened solid line area) of the reference gas chamber  122  in the section normal to the longitudinal direction L. According to such structure, it becomes possible to prevent the sectional area of the atmosphere inducing passage of the reference gas chamber  122  from being reduced in size, and the deterioration of responsibility at the time of the detection of the NOx concentration in the measurement of the gas sensor element  1 .  
     [0118] This deterioration in the responsibility will appear as a delay in detection and an error of a detected concentration. FIG. 10 is a graph showing a relationship between the actual NOx concentration and the detected NOx concentration, in which the axis of abscissa represents a time and the axis of ordinate represents the NOx concentration.  
     [0119] In the delay in the detection, as shown in FIG. 10, the change of the detected concentration appears in a delayed manner with respect to the change of the actual NOx concentration, and accordingly, the delay in the detection deteriorates the responsibility. On the other hand, the error in the detected concentration will appear as over-shoot X 1  or under-shoot X 2 , in which, at the time when the actual NOx concentration changes, the over-shoot X 1  shows a case that the detected NOx concentration shows a value higher than the actual NOx concentration and the under-shoot X 2  shows a case that the detected NOx concentration shows a value lower than the actual NOx concentration. Thus, the responsibility becomes worse.  
     [0120] Furthermore, as shown in FIG. 3, the support member  51  in the described embodiment is also disposed between the electrodes  31 ,  41  and the shield sheet  132  so as to cover the electrodes  31 ,  41 .  
     [0121] The support member  51 , on the other hand, maybe disposed between the solid electrolytic sheet  14  and the shield  132 .  
     [0122] Furthermore, the support member  51  may be divided into a plurality of portions so as to have various sectional shapes such as rectangular shape, elliptical shape and circular shape as shown in FIGS.  5  to  7 , respectively. Further, it is desired that the thus divided support portions  51  at their central portions in the width direction W.  
     [0123] On the other hand, as shown in FIG. 8, the divided support portions may be arranged in a zigzag form. In this example, as shown in FIG. 10, it is desired to be supported at their central portions in the width direction W.  
     [0124] Referring back to FIG. 1, the spacer  15  forming the gas measurement chamber  12 , in which the exhaust gas, after regulating the oxygen concentration, contacts the electrodes  32  and  42 , is formed between the solid electrolytic sheet  14  constituting the monitor cell  3  and the sensor cell  4  and the solid electrolytic sheet  16  disposed at a position opposing to the shield sheet  132  with respect to the sheet  14 . In this gas measurement chamber  12 , another support member  52  for supporting (bearing) pressing force in the lamination direction of the solid electrolytic sheets  14  and  16 .  
     [0125] This support member  52  supports a portion between the solid electrolytic sheets  14  and  16  and a portion between the electrodes  32 ,  42  and the solid electrolytic sheet  16  to thereby prevent the solid electrolytic sheets  14  and  16  from being reduced in size or distance therebetween.  
     [0126] Furthermore, as shown in FIG. 1, the gas measurement chamber  11  is formed, for rendering the exhaust gas to contact the electrode  21 , by the spacer  15 , between the solid electrolytic sheets  14  and  16 , and a further support member  53  is disposed in this gas measurement chamber  11  so as to support a portion between the solid electrolytic sheets  14  and  16  and a portion between the electrode  21  and the solid electrolytic sheet  14 .  
     [0127] As mentioned above, according to the structure of this embodiment, the solid electrolytic sheets  14  and  16  are also prevented from being reduced in size therebetween also by this support member  53 .  
     [0128] Furthermore, the spacer  17  forming the reference gas chamber  121 , in which the atmosphere contacts the electrode  22 , is formed between the solid electrolytic sheet  16  constituting the pump cell  2  and the cover heater sheet  196  disposed at a position opposing to the solid electrolytic sheet  14  with respect to the sheet  16 . In this reference gas chamber  121 , a further support member  54 -for supporting pressing force in the lamination direction of the solid electrolytic sheet  16  and the cover heater sheet  196 .  
     [0129] This support member  54  supports a portion between the solid electrolytic sheet  16  and the cover heater sheet  196  and a portion between the electrode  22  and the cover heater sheet  196 .  
     [0130] Further, it is to be noted that the above support members  52 ,  53  and  54  have substantially the same as or identical to the support member  51  in size, shape, sectional area, arrangement and so on, and the support members  51  to  54  of this embedment will be preferably made from an insulating material such as alumina.  
     [0131] Incidentally, the paired electrodes  21 ,  22  of the pump cell  2 , the paired electrodes  31 ,  32  of the monitor cell and the electrode  41  of the sensor cell  4  have substantially no decomposing activity with respect to the NOx. More specifically, these electrodes  21 ,  22 ,  31 ,  32  and  41  are composed of porous cermet electrodes containing, as main components, Pt and Au.  
     [0132] On the other hand, the electrode  42  of the sensor cell  4  has the decomposing activity with respect to the NOx. More specifically, this electrode  42  is composed of the porous cermet electrode containing, as main components, Pt and Rh.  
     [0133] The respective solid electrolytic sheets  14  and  16  are composed of solid electrolytic substance, such as zirconia or ceria, having oxygen ion conductive property. Further, the shield sheet  132  and the respective spacers  133 ,  15 ,  17 , the heater sheet  195  and the coat heater sheet  196  are formed of insulating material such as alumina.  
     [0134] According to the gas sensor element  1  of the embodiment described above, the support members  51  to  54  are disposed in the respective gas chambers  122 ,  12 ,  11 ,  121  for supporting or bearing the pressing force in the lamination direction of the respective sheets  131 ,  132 ,  14 ,  16 ,  195 ,  196  and the spacers  133 ,  15 ,  17 . Because of the arrangement of the support members  51  to  54 , even if the pressing force is applied in the lamination direction of the gas sensor element  1 , the respective sheets  132 ,  14 ,  16 ,  196  can be prevented from being flexed or bent towards the respective gas chambers  122 ,  12 ,  11 ,  121 , thus providing the improved strength to the gas sensor element.  
     [0135] Moreover, at a time of manufacturing the gas sensor element  1  of the structure mentioned above, the respective sheets  131 ,  132 ,  14 ,  16 ,  195 ,  196  and the spacers  133 ,  15 ,  17  are pressurized in the laminated state, and at this time, the pressing force is applied between the respective sheets  132 ,  14 ,  16 ,  196 . In such case, this pressing force can be supported by these support members  51  to  54  disposed in the respective gas chambers  122 ,  12 ,  11 ,  121  and the flexing of the respective sheets  132 ,  14 ,  16 ,  196  towards the gas chambers  122 ,  12 ,  11 ,  121  can be effectively suppressed, thus preventing cracks from causing to these sheets.  
     [0136] In addition, after the pressurizing process mentioned above, the sintering process is performed to thereby manufacture the gas sensor element  1 . In the present embodiment, since the respective sheets  131 ,  132 ,  14 ,  16 ,  195 ,  196  and the respective spacers  133 ,  15 ,  17  are formed from different materials or substances, there may cause a fear that the respective sheets  132 ,  14 ,  16 ,  196  will be flexed towards the gas chambers  122 ,  12 ,  11 ,  121  because of differences in thermal shrinkage percentage (coefficient of contraction) at the time of sintering.  
     [0137] Even in such case, however, according to the structure of the present embodiment, the flexing of the sheet can be suppressed from causing by the support members  51  to  54 , thus effectively preventing cracks from being generated to the respective sheets  132 ,  14 ,  16 ,  196 .  
     [0138] Furthermore, in an alternation, the spacers  133 ,  15 ,  17  may be formed by coating a binding agent or like for forming the spacer on the surfaces of the respective sheets  196 ,  16 ,  14 . Further, the respective support members  51  to  54  may be also formed by coating the bonding agent or like for forming the support member on the surfaces of the respective sheets  196 ,  16 ,  14 . In such alternation, as the bonding agents for forming the spacers and for forming the support members, there is used an alumina paste obtained by kneading fine alumina powders and a solvent in which a binder is dissolved. There may be used, as the binder, for example, polyvinyl-alcohol, and as the solvent, terpineol.  
     [0139] Furthermore, in an alternation, there may be used the spacers  133 ,  15 ,  17  formed with the gas chambers  122 ,  12 ,  11 ,  121  by preliminarily cutting the spacers  133 ,  15   17  in forms of the respective gas chambers. There may be also used the support members  51  to  54  which are preliminarily formed so as to provide their shapes. In the case mentioned above, the respective sheets  131 ,  132 ,  14 ,  16 ,  195 ,  196  and spacers  133 ,  15 ,  17  would be joined together by means of bonding agent or like.  
     [0140] In such alternation, as the bonding agents for forming the spacers and for forming the support members, there is also used an alumina paste obtained by kneading fine alumina powder and a solvent in which a binder is dissolved. There may be used, as the binder, for example, polyvinyl-alcohol, and as the solvent, terpineol.  
     [0141] In the above case, the respective sheets  131 ,  132 ,  14 ,  16 ,  195 ,  196  and the spacers  133 ,  15 ,  17  may be bonded through the sintering process without using any binding agent.  
     Second Embodiment  
     [0142] The second embodiment of the gas sensor element according to the present invention will be described hereunder with reference to FIGS. 11 and 12.  
     [0143] This second embodiment differs from the first embodiment mainly in the arrangement of support members  71  to  74 .  
     [0144] The gas sensor element  10  of this second embodiment is provided with, as shown in FIGS. 11 and 12, gas measurement chambers  61 ,  610  and  62 , a first pump cell  2  and a second pump cell  200 , a monitor cell  3 , a sensor cell  4  and a heater  19 .  
     [0145] The gas sensor element  10  of this embodiment is constructed by laminating a solid electrolytic sheet . 64  constituting the first pump cell  2 , a spacer  65  constituting the gas measurement chambers  61 ,  610 ,  62 , a solid electrolytic sheet  66  constituting the second pump cell  200 , the monitor cell  3  and the sensor cell  4 , a spacer  67  constituting a reference gas chamber  63 , and a heater portion  19  including a cover heater sheet  196  and a heater sheet  195 .  
     [0146] The first pump cell  2  comprises an oxygen ion conductive solid electrolytic sheet  64  and a pair of electrodes  21  and  22  formed on the surface of the sheet  64 . One electrode  21  is exposed to the atmosphere and the other one electrode  22  is disposed inside a reference gas chamber  61 .  
     [0147] Inside the gas measurement chamber  61 , an exhaust gas from an engine is introduced through a gas introducing passage  611 . The first pump cell  2  acts to regulate or control oxygen concentration in the exhaust gas in the gas introduced in the gas measurement chamber  61  by applying voltage to the paired electrodes  21  and  22 . The exhaust gas subjected to the oxygen concentration control is thereafter introduced from the gas measurement chamber  61  into the other gas measurement chamber  610  through a diffusion resisting passage  612 .  
     [0148] On the other hand, the monitor cell  3  of this second embodiment comprises an oxygen ion conductive solid electrolytic sheet  66  and a pair of electrodes  31  and  32  formed on the surface of the sheet  14 . One electrode  31  is disposed in the a gas measurement chamber  61  and the other electrode  32  is disposed in the a reference gas chamber  63  into which the atmosphere is introduced.  
     [0149] The monitor cell  3  acts to measure an electromotive force generated between the paired electrodes  31  and  32  on the basis of a difference in the oxygen concentrations in the gas measurement chamber  61  and the reference gas chamber  63  and then detect the oxygen concentration in the gas measurement chamber  61 . Then, in accordance with the detected electromotive force, the voltage to be applied to the pump cell  2  is regulated.  
     [0150] The second pump cell  200  is composed of an oxygen ion conductive solid electrolytic sheet  66  and a pair of electrodes  251  and  252  formed on the surface of the sheet  66 . One electrode  251  is disposed in a gas measurement chamber  610  and the other one electrode  252  is disposed in a reference gas chamber  63 .  
     [0151] The first pump cell  200  of this embodiment acts to regulate or control oxygen concentration in the exhaust gas in the gas introduced in the gas measurement chamber  610  by applying voltage to the paired electrodes  251  and  252 . The exhaust gas subjected to the oxygen concentration control is thereafter introduced from the gas measurement chamber  610  into the other gas measurement chamber  62  through a diffusion resisting passage  613 .  
     [0152] The sensor cell  4  of this embodiment comprises the oxygen ion conductive solid electrolytic sheet  66  and a pair of electrodes  41  and  42  formed on-the surface of the sheet  14 . One electrode  41  is disposed in the gas measurement chamber  62  and the other electrode  42  is disposed in the reference gas chamber  63  into which the atmosphere is introduced.  
     [0153] The sensor cell  4  acts to decompose the NOx in the exhaust gas by the electrode  41  and then measure a change of the oxygen concentration generated in accordance with the decomposed amount of the NOx as an oxygen ion current passing through the paired electrodes  41  and  42 , thus obtaining the NOx concentration.  
     [0154] The heater  19  is identical to that of the first embodiment.  
     [0155] In the gas measurement chambers  61 ,  610 ,  62 , there are arranged support members  71  to  73  for supporting portions between the respective solid electrolytic sheets  64  and  66 . According to the location of these support members  71  to  73 , the respective solid electrolytic sheets  64  and  66  can be prevented from being flexed towards the gas measurement chambers  61 ,  610  and  62 , respectively, and hence, the generation of cracks to the respective sheets  64  and  66  can be effectively prevented.  
     [0156] In addition, a further support member  74  may be disposed in the reference gas chamber  63  so as to support a portion between the solid electrolytic sheet  66  and the cover heater sheet  196 . According to the arrangement of this support member  74 , the respective solid electrolytic sheets  66  and  196  can be prevented from being flexed towards the reference gas chamber  63 , and hence, the generation of cracks to the respective sheets  66  and  196  can be effectively prevented.  
     [0157] Other structures or arrangement of this second embodiment and advantageous effects attained thereby are substantially the same as or identical to those of the first embodiment.  
     Third Embodiment 3  
     [0158] The third embodiment of the gas sensor element of according to the present invention will be described hereunder with reference to FIGS. 13 and 14.  
     [0159] This third embodiment differs from the first embodiment mainly in the arrangement of support members  75  to  77 .  
     [0160] The gas sensor element  100  of this third embodiment is provided with, as shown in FIGS. 13 and 14, gas measurement chambers  81  and  82 , a first pump cell  2  and a second pump cell  200 , a monitor cell  3 , a sensor cell  4  and a heater  19 .  
     [0161] The gas sensor element  100  of this embodiment is constructed by laminating a solid electrolytic sheet  84  constituting the first pump cell  2 , a spacer  85  constituting the gas measurement chambers  81 ,  82 , a solid electrolytic sheet  86  constituting the second pump cell  200 , the monitor cell  3  and the sensor cell  4 , a spacer  87  constituting a reference gas chamber  83 , and a heater portion  19  including a cover heater sheet  196  and a heater sheet  195 .  
     [0162] The first pump cell  2  of this embodiment comprises the oxygen ion conductive solid electrolytic sheet  84  and a pair of electrodes  21  and  22  formed on the surface of the sheet  84 . One electrode  21  is exposed to the atmosphere and the other one electrode  22  is disposed in the gas measurement chamber  81 .  
     [0163] Inside the gas measurement chamber  81 , an exhaust gas from an engine is introduced through a gas introducing passage  811 . The first pump cell  2  acts to regulate or control oxygen concentration in the exhaust gas in the gas introduced in the gas measurement chamber  81  by applying voltage to the paired electrodes  21  and  22 . The exhaust gas subjected to the oxygen concentration control is thereafter introduced from the gas measurement chamber  81  into the other gas measurement chamber  82  through a diffusion resisting passage  812 .  
     [0164] On the other hand, the monitor cell  3  of this third embodiment comprises an oxygen ion conductive solid electrolytic sheet  86  and a pair of electrodes  31  and  32  formed on the surface of the sheet  86 . One electrode  31  is disposed in the gas measurement chamber  81  and the other electrode  32  is disposed in the reference gas chamber  83  into which the atmosphere is introduced. The electrode  32  is utilized as an electrode for the second pump cell  200  and the sensor cell  4  as mentioned hereinafter.  
     [0165] The monitor cell  3  of this embodiment acts to measure an electromotive force generated between the paired electrodes  31  and  32  on the basis of a difference in the oxygen concentrations in the gas measurement chamber  81  and the reference gas chamber  83  and then detect the oxygen concentration in the gas measurement chamber  81 . Then, in accordance with the detected electromotive force, the voltage to be applied to the pump cell  2  is regulated.  
     [0166] The second pump cell  200  is composed of an electrode  251  disposed on the surface of the oxygen ion conductive solid electrolytic sheet  84 , a spacer  85  having an oxygen ion conductivity, the solid electrolytic sheet  86 , an electrode  253  disposed on the surface of the sheet  86 , and the electrode  32 . These electrodes  251  and  253  are disposed inside the measurement gas chamber  81 .  
     [0167] The second pump cell  200  further regulates the oxygen concentration in the exhaust gas introduced in the gas measurement chamber  82  by applying a voltage to the paired electrodes  251  and  32 .  
     [0168] The sensor cell  4  of this embodiment comprises the oxygen ion conductive solid electrolytic sheet  86  and a pair of electrodes  41  and  32  formed on the surface of the sheet  86 . One electrode  41  is disposed in the gas measurement chamber  82 .  
     [0169] The sensor cell  4  of this embodiment acts to decompose the NOx in the exhaust gas by the electrode  41  and then measure a change of the oxygen concentration generated in accordance with the decomposed amount of the NOx as an oxygen ion current passing through the paired electrodes  41  and  32 , thus obtaining the NOx concentration.  
     [0170] The heater  19  is identical to that of the first embodiment.  
     [0171] In the gas measurement chambers  81 ,  82 , there are arranged support members  75  and  76  for supporting portions between the respective solid electrolytic sheets  84  and  86 . According to the location of these support members  75  and  76 , the respective solid electrolytic sheets  84  and  86  can be prevented from being flexed towards the gas measurement chambers  81  and  82 , respectively, and hence, the generation of cracks to the respective sheets  84  and  86  can be effectively prevented.  
     [0172] In addition, a further support member  77  may be disposed in the reference gas chamber  83  so as to support a portion between the solid electrolytic sheet  86  and the cover heater sheet  196 . According to the arrangement of the support member, the respective solid electrolytic sheets  86  and  196  can be prevented from being flexed towards the reference gas chamber  83 , and hence, the generation of cracks to the respective sheets  86  and  196  can be effectively prevented.  
     [0173] Other structures or arrangement of this third embodiment and advantageous effects attained thereby are substantially the same as or identical to those of the first or second embodiment.  
     [0174] In the followings, a method of manufacturing a gas sensor element or gas sensor of the structure mentioned above will be described with reference to a gas sensor element  1 A of FIGS. 15 and 16, which may be similar to that shown in FIGS. 1 and 2. Accordingly, same reference numerals of FIGS. 1 and 2 are added to the same or corresponding members or portions of FIGS. 15 and 16, and overlapped explanations thereof are herein omitted.  
     [0175] With reference to FIGS. 15 and 16, the pump cell  2  is formed by printing conductive layers  20  on both surfaces of the solid electrolytic sheet  16 . The conductive layer  20  is composed of a pair of electrodes  21 ,  22  as electrode section, a pair of terminals  212 ,  222  as terminal section for connecting the electrodes  21  and  22  to external elements of the gas sensor element  1 A, and a pair of leads  211 ,  221 , as lead section, for connecting these electrode section and the terminal section to each other.  
     [0176] The monitor cell  3  is formed by printing conductive layers  30  on both surfaces of the solid electrolytic sheet  14 . The conductive layer  30  is composed of a pair of electrodes  31 ,  32 , as electrode section, and a pair of leads  311 ,  321 , as lead section, for connecting the electrode section to an external element of the gas sensor element  1 A.  
     [0177] The sensor cell  4  is formed by printing conductive layers  40  on both surfaces of the solid electrolytic sheet  14 . The conductive layer  40  is composed of a pair of electrodes  41 ,  32 , as electrode section, and a pair of leads  411 ,  421 , as lead section, for connecting the electrode section to an external element of the gas sensor element  1 A.  
     [0178] A conductive layer  190  is formed, through a printing process, on a surface of the heater sheet  195 , and the conductive layer  190  is composed of a heating section  192  corresponding to the heating element  191  and a lead section  193  for connecting the heating section  192  to an external element of the gas sensor element  1 A. Further, the heating section  192  (heating element  191 ) generates heat by designing its sectional area to be smaller than the sectional area of the lead section  193 .  
     [0179] In the foregoing descriptions, the conductive layer may include a terminal section as a junction point in the connection of the lead section to the external element of the gas sensor element  1 A. More concretely, in a non-sintered solid electrolytic sheet  140  in FIG. 16, the conductive layers  30  and  40  include terminals  310  and  410  for connecting the leads  321  and  421  to the external elements of the gas sensor element  1 A.  
     [0180] Further, the paired electrodes  21 ,  22  of the pump cell  2 , the paired electrodes  31 ,  32  of the monitor cell and the electrode  41  of the sensor cell  4  have substantially no decomposing activity with respect to the NOx. More specifically, these electrodes  21 ,  22 ,  31 ,  32  and  41  are composed of porous cermet electrodes containing, as main components, Pt and Au.  
     [0181] On the other hand, the electrode  42  of the sensor cell  4  has the decomposing activity with respect to the NOx. More specifically, this electrode  42  is composed of the porous cermet electrode containing, as main components, Pt and Rh.  
     [0182] The respective solid electrolytic sheets  14  and  16  are composed of solid electrolytic substance, such as zirconia or ceria, having oxygen ion conductive property. Further, the shield sheet  132  and the respective spacers  133 ,  15 ,  17 , the heater sheet  195  and the cover (coat) heater sheet  196  are formed of insulating material such as alumina.  
     [0183] A gas sensor element manufacturing method according to the present invention will be specifically described hereunder through following preferred embodiments.  
     Embodiment 1  
     [0184] In this embodiment, through experiment, of the gas sensor element manufacturing method, a conductive layer is formed by a printing step and a flat portion forming step.  
     [0185] That is, as shown in FIG. 17, in the printing step and the flat portion forming step, the conductive layer  190  is formed by a screen printing on a surface of a heater sheet  195  before the sintering process, which is denoted as non-sintered heater sheet  1950 . In this screen printing, a metal paste is utilized for forming the conductive layer  190 , and it is desirable to use, as this metal paste, a paste having viscosity of 200±50 [Pa·s] at a temperature of 20° C.  
     [0186] As such metal paste, there will be listed up: Pt, organic binder, a paste prepared by kneading alumina powder and terpineol as solvent. Zirconia powder may be substituted for the alumina powder, or Pt may be substituted with a paste including Pt and Rh or including Pt and Au.  
     [0187] When the screen printing is carried out by using the paste of the type mentioned above, the metal paste is spread flatly on the surface of the non-sintered heater sheet  1950  because of low viscosity of the metal paste. The metal paste is thereafter dried to thereby form the conductive layer  190 . In this process, a flat portion  199  is formed on the conductive layer  190  as shown in FIG. 18.:  
     [0188] With reference to FIG. 18, which is an enlarged sectional view taken along the line XVIII—XVIII in FIG. 17, showing a conductive layer forming portion in the width direction normal to the longitudinal direction L of the non-sintered heater sheet  1950 . In the embodiment of the gas sensor element manufacturing method, there is adopted a metal paste having viscosity of  190 [Pa ·s] at a temperature of 20° C., and accordingly, the width of the flat portion  199  of the conductive layer  190  is about 65% of the width B of the conductive layer  190  (A/B×100=65 (%)). Further, the width B of the conductive layer  190  means the width of the conductive layer  190  in a direction normal to the extending direction of the conductive layer on the non-sintered heater sheet  1950 . In this embodiment, the conductive layer  190  is formed so as to extend in the longitudinal direction L of the non-sintered heater sheet  1950 .  
     [0189] Furthermore, in the screen printing step and the flat portion forming step mentioned above with reference to the conductive layer  190 , conductive layers  30  and  40  are formed on both the surfaces of a non-sintered solid electrolytic sheet  140 , which is a sheet before the sintering step to the solid electrolytic sheet  14 . Thereafter, flat portions  301  and  401  are formed to these conductive layers  30  and  40 . In substantially the same process, the conductive layers  20  are formed on both the surfaces of a non-sintered solid electrolytic sheet  160 , which is a sheet before the sintering step to the solid electrolytic sheet  16 . Thereafter, flat portions  201  are formed to the conductive layers  20 .  
     [0190] The above steps will be made clear with reference to FIG. 19, which is an enlarged sectional view, showing a conductive layer forming portion in the width direction normal to the longitudinal direction L of the non-sintered solid electrolytic sheets  140  and  160 . In this embodiment, the width Of each of the flat portions  201 ,  301 , and  401  of the conductive layers  20 ,  30  and  40  is about  50 % of the width B of the conductive layers (A/B×100=50 (%)).  
     [0191] As mentioned above, the conductive layer  190  is formed on the non-sintered heater sheet  1950  and the conductive layers  30 ,  40 ,  20  are also formed on the non-sintered solid electrolytic sheets  140  and  160  through the screen printing step. Thereafter, in a laminating step, as shown in FIG. 16, a non-sintered cover (coat) heater sheet  1960 , which is a sheet before the sintering process to the cover heater sheet  196 , is laminated on the conductive layer  190  of the non-sintered heater sheet  1960 . Then, a non-sintered spacer  170 , which is a spacer before the sintering step to the spacer  17 , is laminated on the surface of the non-sintered heater sheet  1960 , and a non-sintered solid electrolytic sheet  160  as a non-sintered substrate is then laminated on the non-sintered spacer  170 .  
     [0192] Furthermore, as shown in FIG. 16, a non-sintered spacer  150  as non-sintered lamination layer is laminated on the surface of the non-sintered solid electrolytic sheet  160 , and the non-sintered solid electrolytic sheet  140  as non-sintered substrate is then overlapped on the surface of this non-sintered spacer  150 . Furthermore, a non-sintered porous sheet  1310  and a non-sintered spacer  1330  as non-sintered lamination sheets are laminated on the surface of the non-sintered electrolytic sheet  140 , and a non-sintered shield sheet  1320  is overlapped on the surface of the non-sintered spacer  1330 .  
     [0193] As understood from the above, the non-sintered spacers  1310 ,  150  and  170  are spacers before the sintering treatment to the spacers  131 ,  15  and  17 . The non-sintered porous sheet  1310  and the non-sintered shield sheet  1320  are also sheets before the sintering treatment to the porous sheet  131  and the shield sheet  132 .  
     [0194] Further, as shown in FIGS. 20 and 21, bonding agent  5  is applied, at the overlapping process mentioned above, between the respective non-sintered sheets  310 ,  1320 ,  140 ,  160 ,  1950  and  1960 , and the non-sintered spacers  1330 ,  150  and  170 , respectively. As this bonding agent  5 , there will be provided one obtained by kneading alumina, preferably having fine particle size, organic type binder and solvent. As the binding agent  5 , there will be also provided one obtained by kneading zirconia, organic binder and solvent. In each binding agent, terpineol may be utilized as the solvent.  
     [0195] In this embodiment, as shown in FIG. 20, the binding agent  5  is coated on the surface of the non-sintered heater sheet  1950  on the side of the conductive layer  190  so as to be substantially flush with the flat portion  199  of the conductive layer  190 . Further, as shown in FIG. 21, the binding agent  5  is coated on the surfaces of the non-sintered solid electrolytic sheets  140  and  160  on both the sides of the conductive layers  30  and  40  so as to be substantially flush with the flat portions  301 ,  401  and  201  of the conductive layers  30 ,  40  and  20 .  
     [0196] Thereafter, as shown in FIGS. 22 and 23, the respective non-sintered sheets  1310 ,  1320 ,  140 ,  160 ,  1950  and  1960  and the respective non-sintered spacers  1330 ,  150 ,  170  are pressurized in the stacked state to thereby provide a lamination layer structure and hence provide an intermediate product of the gas sensor element  1 A. In this process, as shown in FIG. 20, the non-sintered cover heater sheet  1960  abuts against the flat surface portion  199  of the conductive layer  20  and the bonding agent  5 , which are flatly formed on the surface of the non-sintered heater sheet  1950 .  
     [0197] As shown in FIG. 23, the non-sintered spacers  1330  and  150  also abuts against the flat surface portions  301  and  401  of the lead portions  311 ,  321 ,  411  and  421 , and the bonding agent  5  which are flatly formed on both side surfaces of the non-sintered solid electrolytic sheet  140 . Further, since the electrodes  31 ,  32 ,  41  and  42  of the non-sintered solid electrolytic sheet  140  are arranged inside the gas measurement chambers  11  and  12 , these electrodes do not abut against the non-sintered spacer  1330 .  
     [0198] On the other hand, the non-sintered spacers  150  and  170  abuts against the flat surface portion  201  of the lead portions  211  and  221 , flatly formed, and the bonding agent  5 , on both side surfaces of the non-sintered solid electrolytic sheet  160 . Further, since the electrodes  21  and  22  of the non-sintered solid electrolytic sheet  160  are arranged inside the reference gas chamber  121 , these electrodes do not abut against the non-sintered spacers  150  and  170 .  
     [0199] According to the reason mentioned above, it becomes possible to prevent the application of the local load between the respective non-sintered sheets  140 ,  160 ,  1950  and  1960  and the respective non-sintered spacers  1330 ,  150  and  170 , whereby it is possible to prevent the cracks from causing to these non-sintered sheets  140 ,  160 ,  1950  and  1960  and the non-sintered spacers  1330 ,  150  and  170 .  
     [0200] Thereafter, in the sintering process, the intermediate product as the laminated structure is sintered to thereby manufacture the gas sensor element  1 A in which the respective sheets and the spacers mentioned above are laminated in the prescribed order.  
     [0201] Further, in an alternation, the non-sintered spacer  1330  maybe formed by applying a bonding agent, for forming the spacer, on the surface of the non-sintered shield sheet  1320  or non-sintered solid electrolytic sheet  140 . The non-sintered spacer  150  may be formed also by-applying a bonding agent, for forming the spacer, on the surface of the non-sintered solid electrolytic sheet  140  or. 160 . Furthermore, the non-sintered spacer  170  may be formed also by applying a bonding agent, for forming the spacer, on the surface of the non-sintered solid electrolytic sheet  160  or non-sintered cover heater sheet  1960 . In such alternation, a bonding agent having composition or component identical to that of the bonding agent  5  may be also utilized for the bonding agents for the spacer, or it may be applicable to the support member mentioned hereinbefore with reference to the embodiment of the gas sensor element.  
     Embodiment 2  
     [0202] Hereunder, the second embodiment, through experiment, of the manufacturing method of the gas sensor element  1 A of the present invention will be described. In this embodiment, a measurement was performed as to the relationship between the viscosity [Pa·s] at the temperature of 20°C. of the metal paste shown in the above embodiment 1 and A/B×100 (%) (ratio the width A of the flat portion  199 ,  201 ,  301 ,  401  to the width B of the conductive layer  190 ,  20 ,  30 ,  40 ).  
     [0203] That is, by changing the viscosity of the metal paste at the temperature of 20° C. to the viscosity of 120 to 280 [Pa ·s], the screen printing was effected to the surfaces of the non-sintered heater sheet  1950  or non-sintered solid electrolytic sheets  140 ,  160  and, then, the ration A/B (%) was measured.  
     [0204] As a result of such measurement, in a case where the viscosity of the metal paste at the temperature of 20° C. was 150 to 250 [Pa·s] , the ratio A/B×100 (%) became more than 3%, which revealed the effect of preventing the cracks from being generated. On the other hand, in a case where the viscosity of the metal paste at the temperature of 20° C. was less than 150 [Pa·s], it was found to be impossible to form the conductive layers  190 ,  20 ,  30 ,  40  having desired shapes because of too low viscosity. Furthermore, in a case where the viscosity of the metal paste at the temperature of 20° C. was more than 250 [Pa·s], the crack generation preventing effect could not be effectively achieved because of too small thickness of the widths of the flat portions  199 ,  201 ,  301 ,  401  formed on the conductive layers.  
     Embodiment 3  
     [0205] This embodiment, through experiment, represents a method in which the flat portions  199 ,  201 ,  301 , and  401  were not formed by using a metal paste having low viscosity and were formed by pressurizing the conductive layers  190 ,  20 ,  30  and  40  which are formed through the printing process by using the metal paste.  
     [0206] That is, in this embodiment, the conductive layer formation process includes a printing step, a drying step and a flat portion forming step. In the printing step, the metal paste for forming the conductive layer  190  is printed on the surface of the non-sintered heater sheet  1950 . Likely, the metal pastes for forming the conductive layers  20 ,  30 ,  40  are also printed on the surfaces of the non-sintered solid electrolytic sheets  140 ,  160 .  
     [0207] In the drying step, the above respective metal pastes are dried to thereby form the conductive layers  190 ,  20 ,  30  and  40 . As shown in FIGS. 24 and 25, the thus formed conductive layers  190 ,  20 ,  30  and  40  each has a circular or circular-arc sectional shape in its width direction.  
     [0208] Then, in the flat portion forming step, as shown in FIG. 26, the conductive layer  190  is pressurized by snapping the non-sintered heater sheet  1950  between a pair of pressing members P 1  and P 2  of a press. In this step, the protruded front end portion  198  of the circular-arc shaped conductive layer  190  is pressurized and then crushed to thereby provide the flat end portion  199 . This flat portion  199  has a width A of more than 3% with respect to the width B of the conductive layer  190  (A/B×100=3 (%)). In this embodiment, the pressure was applied till the ratio A/B became about 70 (%).  
     [0209] Furthermore, as shown in FIG. 27, in the flat portion forming step, the conductive layers  30 ,  40  and  20  are pressurized by snapping the non-sintered solid electrolytic sheets  140  and  160  between a pair of pressing members P 1  and P 2  of a press. In this step, the protruded front end portions  202 ,  302  and  402  of the circular-arc shaped conductive layers  20 ,  30  and  40  are pressurized and then crushed to thereby provide the flat end portions  201 ,  301  and  401 , respectively. In this embodiment, the pressure was applied till the ratio A/B became about 80 (%) Thereafter, as like as the first method embodiment, the lamination step and sintering step were performed to thereby manufacture the gas sensor element  1 A in which the respective sheets  131 ,  132 ,  14 ,  16 ,  195  and  196  (after the sintering step) and the spacers  133 ,  15  and  17  (after the sintering step) were laminated.  
     [0210] In this embodiment, the other steps were substantially the same as or identical to those in the first embodiment and substantially the same advantageous effects could be achieved.  
     [0211] Furthermore, it is to be noted that although the manufacturing methods of the above embodiments of manufacturing the gas sensor element  1 A are described specifically described with reference to FIGS. 15 and 16, these methods may be applicable to the gas sensor elements  10 A and  100 A of FIGS. 28 and 29, which may basically correspond to the gas sensor element  10  and  100  of FIGS. 11 and 13, respectively.  
     [0212] The gas sensor element  10 A of FIG. 14 includes the pump cell  2  formed to the solid electrolytic sheet  14 , and the monitor cell  3  and the sensor cell  4  are formed to the solid electrolytic sheet  16 . A secondary pump cell  7  including a pair of electrodes  171  and  172  is further disposed so as to regulate the oxygen concentration.  
     [0213] The gas sensor element  100 A of FIG. 29 includes the pump cell  2  formed to the solid electrolytic sheet  14 , and the monitor cell  3  and the sensor cell  4  are formed to the solid electrolytic sheet  16 . Secondary pump cells  7 , each including a pair of electrodes  171  and  172 , are further disposed so as to regulate the oxygen concentration.  
     [0214] It is to be noted that the present invention is not limited to the specifically described embodiments mentioned above and many other changes and modifications or alternations may be made without departing from the scopes of the appended claims.