JP2003517146A - Gas sensor design and how to use it - Google Patents

Abstract

A gas sensor is a reference gas channel that allows simultaneous or sequential pumping of oxygen and detection of exhaust gas (eg, to determine whether the exhaust gas is rich or lean). Is used. The method includes using a gas sensor having a first electrode and a reference electrode in ion communication with each other and a reference gas channel in fluid communication with the reference electrode and the exterior of the sensor. Introducing a voltage to one electrode, applying a voltage to the reference electrode, ionizing oxygen at the first electrode, transferring ionized oxygen to the reference electrode through the electrolyte, and removing molecular oxygen at the reference electrode. Forming, ionizing molecular oxygen on the reference electrode, transferring the ionized oxygen through the electrolyte to the first electrode to generate a voltage, and measuring the voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION       [0001] Cross-reference of related applications   This application filed a provisional application, US Provisional Patent Application No. 60/1, filed October 15, 1999.
Claims the filing date benefit of 59,837, which is incorporated by reference in its entirety.
.       [0002] Technical field   The present invention relates to gas sensors, and more particularly to oxygen sensors.       [0003] Background of the Invention   Oxygen sensors are used in various applications where qualitative and quantitative analysis of gas is required.
ing. In automotive applications, the oxygen concentration in the exhaust gas and the fuel supplied to the engine
The oxygen sensor has a direct relationship with the air-to-fuel ratio of the
By performing concentration measurement, it is possible to determine optimal combustion conditions, maximize fuel efficiency, and reduce exhaust gas emissions.
Can manage.       [0004]   Conventional stoichiometric oxygen sensors are generally used for ion-conducting solid electrolyte materials and exhaust gases.
A porous electrode having a porous protective overcoat on the exposed outer surface of the electrolyte;
An electrode on the sensor inner surface is exposed to a known oxygen partial pressure. In the field of automotive applications
The type of sensor used is an electrification based on yttria-stabilized zirconia.
Galvanic cells and platinum electrodes. It operates in the potential difference mode.
To detect the relative amount of oxygen present in the exhaust gas of the car engine. this
When opposing surfaces of a galvanic cell are exposed to different oxygen partial pressures,
Occurs between electrodes on opposing faces of the konia wall. This is given by the following Nernst equation:
Based.       [0005] (Equation 5)      [0006] However,   E = electromotive force   R = gas constant   F = Faraday constant   T = absolute temperature of gas   P^ref _O2= Oxygen partial pressure of reference gas   P_O2= Oxygen partial pressure of exhaust gas       [0007]   High oxygen partial pressure between fuel-rich and fuel-lean exhaust conditions
The difference causes the electromotive force to change sharply at the stoichiometric point, a characteristic switch for these sensors.
Triggering operation. Therefore, these stoichiometric oxygen sensors are
Qualitatively indicates whether it is operating fuel-rich or fuel-lean,
Do not quantify the air to fuel ratio.       [0008]   For example, an oxygen sensor based on a solid oxide electrolyte, such as zirconia,
The difference in oxygen activity between the unknown gas and the known reference gas is measured. Usually a known gas
Is atmospheric air, and the unknown gas contains oxygen at the equilibrium level to be determined.
You. Typically, sensors have the structure of an air channel, which surrounds a reference electrode.
Contact air. To avoid contamination of the reference electrode by unknown gases
, The sensor usually provides a sufficient gas seal between the reference air and the unknown gas
Requires expensive sensor packages with complex features. Historically, this
Gas-sealed sensor packages such as
It is clear. The problem is to use electrochemical oxygen pumping in situ.
That can be avoided. In this method, the air reference electrode chamber is
Is replaced with a cooled reference electrode and oxygen is electrochemically pumped from the exhaust gas.
You. While this solution eliminates the problem of exhaust gas pollution, its inherent disadvantages are:
Occurs. That is, expensive electronic circuits are required for electrochemical oxygen pumping.
It is important to note that the excess oxygen gas pressure
May break ceramic body.       [0009]   What is needed in the art is to use electrochemical pumping of oxygen
It is a simple gas sensor.       [0010] BRIEF SUMMARY OF THE INVENTION   Gas sensors and how to use them. One embodiment of a gas sensor has an electrolyte
And a first electrode and a reference electrode in ionic communication with each other, and the reference electrode and the reference electrode.
And a reference gas channel in fluid communication with the outside of the sensor.
Have a diffusion limiter.       [0011]   One embodiment of the method comprises the steps of placing an electrolyte therebetween and in ionic communication with each other.
One electrode and a reference electrode and a reference gas in fluid communication with the reference electrode and the outside of the sensor
Using a gas sensor with a channel and exhaust gas to a first electrode.
Introducing, applying a voltage to the reference electrode, and ionizing oxygen at the first electrode.
And transferring the ionized oxygen to the reference electrode through the electrolyte
Forming molecular oxygen at the step and the reference electrode;
Ionizing and transferring the ionized oxygen through the electrolyte to the first electrode
And generating a voltage, and measuring the voltage.       [0012]   For the above and other features and advantages of the present invention, those skilled in the art will perceive the following details.
From the detailed description, drawings, and appended claims.
U.       [0013] Detailed description of the invention   The apparatus and method will be described by way of example with reference to the accompanying drawings. Drawing
Is illustrative and not limiting.       [0014]   The gas sensor comprises one or more electrochemical cells (ie, exhaust gas side electrodes).
And an electrolyte disposed between the two reference electrodes), disposed adjacent to the external electrode
Porous protective layer, reference gas chamber in fluid communication with reference electrode, electrochemical
A heater in thermal communication with the cell. The reference gas chamber also
Fluid communication between the atmosphere surrounding the sensor (ie, air and exhaust gas).
It is not necessary to hermetically seal the reference chamber from the exhaust gas. With this gas sensor
Pumps oxygen into the reference electrode to create a reference gas chamber.
The need to hermetically seal the bus is avoided. Therefore, the reference chamber
A pressure gradient is created in the chamber. Optionally, one or more gas diffusion restrictors
May be used in the reference chamber.       [0015]   Referring to FIG. 1, the Nernst oxygen sensor has the following basic features (components:
). Exhaust gas side electrode 1, reference electrode 2, heater leads 3 and 4,
Porous protective layer 5, solid electrolyte layer 6, insulating alumina layers 7 and 8, air channel
9 and heater 12. In FIG. 1, an exhaust gas electrode 1 passes through a porous protective layer 5.
Exposed to exhaust gases. The reference electrode 2 is separated from the exhaust gas electrode 1 by a high-density solid-state electrode.
The channel 9 (opened to the surrounding atmosphere) is separated by the
(Opens at the tail 13). Heater leads 3 and 4 are
The positive electrode and the negative electrode of the data electrode 14 are respectively connected. Optionally, sensors
The positive heater lead 3 is connected to the reference electrode lead 17 via a resistor R.
The negative heater lead 4 can be connected to the exhaust gas side lead 19.
In this embodiment, there is a resistor R located between leads 3 and 17.
Connection and resistors, optionally inside the sensor ceramic body
Can be arranged.       [0016]   During use, the exhaust gas passes through the protective coating layer 5 and moves to the electrode 1 to generate an electromotive force.
A force is generated between the exhaust gas electrode 1 and the reference electrode 2. The reference electrode 2 has a constant oxygen activity
To maintain the volume, the oxygen flux is pumped into the electrode 2. this is,
By maintaining the reference electrode 2 at a positive polarity, the power supplied from the heater lead 3
Done. Oxygen generated at the reference electrode 2 flows from the reference gas channel 9 to the open end 13.
And diffuses into the surrounding atmosphere (eg, exhaust gas or air).       [0017]   The rate of diffusion out of the reference gas chamber 9/9 '(see FIGS. 1 and 4)
Between the quasi-electrode (about 1 atm or more) and the ambient atmosphere (atm.) (About 0.21 atm or less)
It is linearly proportional to the oxygen pressure difference. In this embodiment, a gas diffusion limiting process is used entirely.
The oxygen pressure in the reference gas channel is lower than the ceramic sensor body
It will never increase to a level that could damage the device. On the other hand, air
And / or the rate of diffusion of the exhaust gas into the reference gas chamber is determined by the reference electrode (
Fuel concentration is maintained at zero by oxygen generated by pump current) and ambient
It is linearly proportional to the difference in fuel concentration between atmospheres (typically less than about 21%). Fuel concentration
The exhaust flux is limited because the difference does not exceed 21%. Exhaust flux is
It can be represented by the following formula (I).       [0018] (Equation 6)         F_exh= DCA / L (1) Where F_exhIs the exhaust gas flux (ie the exhaust gas passing through the channel
Travel speed)   D is the diffusion constant of the exhaust gas constant   C is the ambient atmosphere exhaust gas concentration at the open end of the reference gas channel   A is the average cross section of the gas channel   L is the length of the gas channel       [0019]   To keep the fuel concentration near zero at the reference electrode, the oxygen flux
Must be greater than the fuel's critical flux. The amount of oxygen flux
, Can be adjusted by the resistance value of R in FIG. 1 and the heater voltage. Fuel limit flash
The amount of gas is determined by the cross-sectional area and length of the gas channel.       [0020]   The components of the gas sensor are: the protective layer 5, the electrodes 1, 2, 3, 4 (and
(Lead), heater 12, dielectric layers 7 and 8, and heater power supply 14. Also
In addition to these conventional components, additional conventional components may be used. example
(But not limited to) additional protective coatings (eg, spinel,
Alumina, magnesium aluminate and the like, and at least one of the above-mentioned coats.
Combinations including contacting, lead gettering layers, ground planes, support layers, additional
Such as a chemochemical cell.       [0021]   Dielectric layers 7 and 8 and any support layers typically prohibit electrical communication
Includes alumina or similar materials that can be stopped to provide physical protection. Like
Alternatively, the layers 7, 8 and the additional support layer can effectively be used in various parts of the gas sensor.
Can protect the minute, give structural integrity, separate the various components, heater
12 is electrically insulated from the sensor circuit, and the reference electrode 2, the heater 12, and / or
May cover the leads, provide physical protection against wear, and / or
Preferably, the components of the sensor are electrically insulated from the package. Preferably
The various materials used in the manufacture of gas sensors have substantially similar coefficients of thermal expansion and yield.
By providing shrink properties and chemical compatibility, delamination and other processing issues
Minimize, if not eliminate, the problem.       [0022]   Each of the dielectric layer and the support layer may be less than about 200 μm thick,
Preferably, the thickness is from about 50 microns to about 200 microns. These layers are
Mick tape casting method or other methods, such as plasma scanning
Play deposition technology, screen printing, stencils, and the art
Can be formed using other materials conventionally used.       [0023]   Between two of the layers, for example 7 and 8, a heater 12 is arranged and
A surface (not shown) is optionally arranged between two support layers (not shown)
. The heater 12 heats the sensor end (that is, the end opposite to the opening end 13) to a sufficient temperature.
Can maintain and promote various electrochemical reactions there.
It may be a heater. Heater 12 (Platinum, alumina, palladium, etc.
Mixtures and alloys containing at least one of the foregoing metals), or
Any other conventional heater typically has about 5 microns to about 50 microns on the substrate.
Screen printed to thickness.       [0024]   Leads 17 and 19 are located on either side of the various dielectric layers and provide gas sensing.
The external wiring of the electrode is electrically connected to the electrodes 1 and 2. The lead is typically
Are formed on the same layer as the electrodes with which they are in electrical communication.
Terminal end. At the terminal end, the leads are connected to the corresponding vias (not shown).
Not). The heater 12 also has a lead in electrical communication with the via.
3 and 4.       [0025]   Electrically in communication with the leads are electrodes that are in ionic connection with the electrolyte.
You. The electrolyte layers 6, 6 ', 6 "preferably constitute all or part of the layers
(See FIG. 1, and 5 to 7), and the electrolyte layer is provided with an exhaust gas.
Enables electrochemical transfer of oxygen ions while prohibiting physical passage of gas
Any material having an ion / total conductivity ratio of about 1 and a gas
Any material (eg, up to about 1000 ° C.) in which the material is used. Also,
This electrolyte can be formed by many conventional processes. For example (this
But not limited to) die press, roll compaction, stencil and screen
Printing and tape casting technology. Potential solid electrolysis
The quality material may include any material conventionally used as a sensor electrolyte.
For example (but not limited to) zirconia, which is optionally
Calcium, barium, yttrium, magnesium, aluminum, lanthanum
, Cesium, gadolinium, etc., and combinations comprising at least one of the foregoing materials
May be stabilized. For example, the electrolyte is alumina and yttrium stabilized
It can be zirconia. Typically, solid electrolytes have a thickness of about 500 microns.
And is preferably about 25 microns to about 500 microns thick, especially
Preferably, it is about 50 microns to about 200 microns thick.       [0026]   Note that in some embodiments, a porous electrolyte may be used. Porous
The electrolyte can allow physical movement of the exhaust gas and electrochemical movement of oxygen ions.
Must be compatible with the environment in which the gas sensor is used.
Must-have. Typically, the porous electrolyte has a porosity of up to about 20%
The central pore size is about 0.5 microns, or alternatively, one or more
Exhaust gas physics by including solid electrolyte with holes, slits and openings
To allow the target to pass. US Pat. No. 5,762,73 assigned to the assignee of the present invention.
No. 7 (Bloink et al.), Incorporated herein by reference in its entirety.
Describes further porous electrolytes that may be useful in the present application.
Possible porous electrolytes include those already listed for solid electrolytes.
No.       [0027]   The electrolytes 6, 6 ', 6 "and the protective material 5 constitute all or any part of the layer.
can do. For example, the electrolyte and the protective material may form a layer,
May be attached to the layer (protective material / electrolyte next to the dielectric material) or
The parts may be arranged in layers (the protective material / electrolyte can be an insert). Last arrangement
Eliminates excessive use of electrolytes and protective materials and eliminates layers
Reduces the size of the gas sensor. Electrolyte and protective material in any shape
Can be used for the fee. Various inserts and therefore corresponding opening sizes
And the geometry depends on the desired size and geometry of the adjacent electrodes. Open
The mouth, insert, and electrodes are preferably of substantially similar geometry.       [0028]   A plurality of electrodes 1, 2, 10, 11 are provided with electrolytes 6, 6 ', 6 "(see FIGS. 1 and 5).
7) and a porous electrolyte in contact with these electrodes.
Any catalyst capable of ionizing oxygen can be included. For example (limited to these
Metal) such as platinum, palladium, osmium, rhodium, iri
Didium, gold, ruthenium; metal oxides such as zirconia, yttria, ceria
, Calcia, alumina, etc .; other materials such as silicon; at least one
Mixtures and alloys containing the above mentioned catalysts are included.       [0029]   The electrodes 1, 2, 10, 11 are made by conventional techniques such as sputtering, chemical vapor deposition
It can be formed using a method, screen printing, or a stencil. Among them, electrodes
Screen printing on a suitable tape is preferred because of its simplicity,
This is because it depends on cost and compatibility with the subsequent firing process. For example, reference electrode 2
Can be screen printed on the dielectric layer 7 or on the solid electrolyte 6,
The gas electrode 1 can be screen-printed on the solid electrolyte 6 or the protective layer 5
You. Vias and / or electrolyte layers (not shown) in the electrode leads and dielectric
Typically, it is formed simultaneously with the electrodes.       [0030]   Arranged in fluid communication with the reference electrode 2 is a reference gas channel 9,
9 '. These are carbon-based materials, i.e. non-rigid materials
For example, carbon black is deposited between the reference electrode 2 and the layer 7,
Bones are formed by burning out the voids (see FIGS. 1 and 4).
See). As can be seen from FIG. 4, the geometry of the reference chamber is adapted to the specific application
Can be changed to In this particular embodiment, the reference gas cylinder
The channel 9 'comprises two diffusion paths 21 and 23, two chambers 23 and
25. The various compartments (21, 2) of the reference gas channel 9 '
3, 25, and 27) are given by the above equation (I) and the exhaust gas flow rate.
Determined based on the lux. In this embodiment, two chambers and two
By using two diffusion paths, it is possible to respond to the periodic repetition of the heater voltage
. Basically, if no voltage is applied to the heater, the reference gas channel
No voltage that induces pumping is applied to the electrodes. Ambient atmosphere becomes reference electrode
A multistage spreading channel is used to prohibit approaching. Used for pumping
If the voltage is not periodic, a single chamber and channel may be used.
it can. Here, the channels and chambers have the same size but different sizes.
And may be based on Equation I and the voltage to be used.       [0031]   Oxygen pump current moves oxygen through electrolyte into reference gas channel
Therefore, it must be larger than the fuel limit current. But the current is too large
And a new polarization due to the current is caused by the electrolyte (ohmic drop) and the electrode (electrode polarization)
And the error signal for the electromotive force measurement is
Can occur in between. As a result, about 30 milliamps of exhaust gas electrode area
A / square centimeter (mA / cm^Two) The following pump currents can be used
, Preferably about 20 mA / cm^TwoOr less, particularly preferably about 20 mA / cm^TwoBelow
is there. This requirement includes, for example, the correct resistance value of R (see FIG. 1),
It can be realized by making a selection depending on the application voltage. Resistor can be carbon or metal acid
Resistor or a thick film type (sensor, ceramic,
Can be screen-printed). AC to heater (ac)
If a power supply is used, a diode can optionally be added to the circuit (
In series with R. See FIG. 1).       [0032]   Due to the fuel limit current, the physical dimensions of the reference gas channel are
About 30 milliamps / square centimeter of electrode area
mA / cm^Two) Or less, preferably about 20 mA / cm^TwoBelow, particularly preferably about 10
mA / cm^TwoThe following must be obtained: Various parameters interact
Can vary, depending on the specific design of the sensor.
Wear. The design must be based on a combination of upper formula I and lower formula II.       [0033] (Equation 7)         I_p= (V_hV_emf) / R (II) Where I_pIs the pump current   V_hIs the heater voltage   V_emfIs the sensor electromotive force   R is the resistance of the resistor       [0034]   In general, for voltages from about 10 to about 21 volts (V), the channel length (L)
Is about 35 mm to about 65 mm, width (W) is about 0.50 mm or less, and height (H) is about
0.05 mm or less, preferably about 35 mm to about 50 mm in length and about 0.3 mm in width
0 mm or less, height of about 0.025 mm or less, particularly preferably about 40 mm in length.
From about 48 mm, less than about 0.13 mm in width and less than about 0.015 mm in height
You. Note that the lower limit for the cross-sectional area (ie, width x height) is based on the desired diffusion rate.
I want to be reminded. The lower limit for both width and height is about 0.005 mm, but
The practical lower limit is substantially higher due to the limitations of manufacturing equipment. For example, the nominal V _h Is about 13.5 volts, R is about 2 megaohms (MQ), I_pIs about 7 microamps
In the case of a (μA), the dimension of the channel is about 43 m (L) × 0.2 mm (W) × 0
. 02 mm (H).       [0035]   The production of the reference gas channel is performed by mechanical notch duck, temporary
Screen printing of materials (eg, carbon that can burn out at high temperatures), controlled porosity
Can be performed by forming a coated coating layer, laser drilling of holes, etc.
it can. For example, the channel is the tip of the gas sensor for the surrounding exhaust gas.
(Reference numeral 13 in FIG. 1), the channel dimension is about 10 millimeters (m
m) Length (L) x width of 0.007 mm (W) x height of 0.01 mm (H)
You can.       [0036]   A heater or any other power device can provide power for oxygen pumping.
You can. If the heater is a power supply and is operating in periodic mode, the oxygen pump
There is a time zone in which no logging occurs. If these hours last for a very long time,
Oxygen may be depleted at the reference electrode. Buffer channel in gas channel
In addition to within the Zain, such obstacles can be avoided (see FIGS. 4 to 6)
. In these figures, the reference electrode is located adjacent to the small chamber 25 and
The buffer 27 functions as a buffer zone, and the short diffusion limiting path 21
A long diffusion path 23 connects to the tail of the gas sensor. Pong
The oxygen introduced by the ping is stored in the buffer zone and
Is maintained during times when no oxygen is supplied. Such gas channels
, Temporary materials (such as graphite or carbon, which can burn out during the sintering process)
) Can be produced by screen printing. And oxygen storage materials
Optionally, all or part of the reference gas channel (eg, the entire channel,
To one or more diffusion paths, to one or more chambers, or to these channels.
Increase the effectiveness of the function in addition to any combination of channel parts)
You can also. Such materials include metals such as platinum, rhodium, and palladium.
, Ruthenium, iridium, osmium, etc .; metal oxides such as seridium oxide
And other conventional oxygen storage materials, and
Mixtures and alloys containing at least one of the aforementioned materials are included. Assignment of the present invention
Patent application assigned to another person, agent reference number DP300023, US patent application No. 0
No. 9 / 476,834 (Detwiller, filed on January 3, 2000)
Incorporated in its entirety in the text), the acids that may be useful in the present application
Element storage materials are further described.       [0037]   In an alternative embodiment, the electrical insulation between the heater and the electromotive member is
This can be done by using an additional insulated set of electrodes for pumping.
it can. A possible way to do so is shown in FIGS. Figure 5 shows a symmetric design
In The sensors have two identical sensor layouts. This
These are similar to those shown in FIG. 1, but provided on the opposite side of the ceramic heater.
Have been. One of these sensors has an open reference gas channel and
Sensor leads 3 and 4 are connected to the heater. The other sensor is a heater
Having a gas channel through the ceramic, one of its electrodes (2)
Exposure to oxygen generated by electrodes 10 and 11 causes an electromotive force to be applied to electrodes 1 and 2
Measured by Electrodes 1 and 2 are electrically insulated from electrodes 10 and 11
Therefore, this sensor design has the characteristic of signal ground isolation. In addition, electrode 1
And 2 are separated from electrodes 10 and 11, so that the maximum oxygen pump current is
30mA / cm^TwoNot limited to The hole passing through the ceramic heater is green
Machine piercing of green tapes prior to thermal lamination
, By making a hole.       [0038]   FIG. 6 shows another possible design that can achieve the same signal isolation. now
The electromotive force detection electrodes 1 and 2 and the oxygen pump electrodes 10 and 11
On the same side of the data. Electrical insulation layer (eg dielectric layer) eg aluminum
An electrode is provided between the two solid electrolytes coated between the electrodes. Insulated
The two electrolytes can be in the form of a button or a strip. Reference gas to open
The channels connect both electrodes 2 and 4. Two sets of electrodes
And may be alternated.       [0039]   There are still other ways to improve signal noise separation. Contact between electrodes 1 and 4
Disconnect from the sensor member position (see FIG. 1) and reconnect at the control panel position
(Shown in FIG. 7). The addition of resistor R2 provides a substantial ground isolation feature. Figure
This method is simpler than the method shown in FIGS. 4 (a) and 4 (b).       [0040]   In use, pumping by exhaust gas electrode 1, electrolyte 6, and reference electrode 2
-Both cells and reference cells are formed. Both can work even at the same time
You. Oxygen in the exhaust gas passes through the protective layer 5 and enters the pumping cell. Pong
In the ping cell, the voltage applied to electrodes 1 and 2 causes the oxygen on electrode 1
Are ionized and pumped to the reference electrode 2. Thus, at the exhaust gas electrode
If the exhaust gas is fuel rich (A / F is less than about 14.7 for a gas engine)
Or fuel-lean (A / F exceeds about 14.7 for a gas engine)
Oxygen can be used to supply the reference gas to determine if any.       [0041]   The following examples are merely to further illustrate embodiments of the present invention,
It does not limit the scope of the invention in any way.       [0042]   An example   Zirconia doped with alumina and yttria, a binder, a plasticizer,
After mixing with a solvent, the mixture was roll-kneaded in the same manner as in the prior art to form a slurry. Next
Ri was put into a mold and taped. This is Doctor Blade Tape Casty
This was performed using the aging method.       [0043]   Screen printing of platinum ink and carbon ink on tape
1 (electrodes 1 and 4 are platinum and reference gas channel 9 is
Bonn). The printed material of the carbon channel 9 has a basic physical dimension of 49.
mm L x 0.86 mm W x 0.015 mm H. W is shown here
13%, 20%, 25%, 50%, and 100% of the calculated values. Reference
The schannel had an opening in the tail of the gas sensor.       [0044]   The tape is laminated by heat, cut, and baked at 1500 ° C for several hours.
Then packaged for final testing. The sensor is new and hermetically sealed
Therefore, leak holes of various sizes are created in the sensor package to
Can leak into the tail of the sensor.       [0045]   The sensor is then moved to a hot rich engine operating condition (eg, 5.7 liters).
(L), 2700 revolutions / minute (rpm) with an 8-valve (V8) engine, 70 kPa
Skull (kPa) exhaust gas pipe back pressure, stoichiometric point (that is, A / F is about 13.
2) 10% rich, and the exhaust gas temperature was 850 ° C.). Based on current
The critical exhaust gas flux measured by the
(Measured with a vacuum pump at).       [0046]   Fig. 2 shows the diffusion limiting effect on the exhaust gas and flux of the air channel.
The results are shown below. In FIG. 2, the fuel limiting current is measured by the logarithmic leakage of the sensor package.
Rate (cubic centimeter / second (cm^Three/ Sec))
You. The flat portion of the observed limiting current is 5 microamps (mA). This
This is because the exhaust gas flux that diffuses into the reference gas channel
This indicates that the gas has a limit value regardless of the amount of polluting exhaust gas.       [0047]   Oxygen was pumped into the reference chamber (ie up to 1.5 volts (V))
(Directly applied between the exhaust gas electrode and the reference electrode).
Does not destroy. In other words, in contrast to a sealed reference gas channel,
The current reference gas channel has a voltage of about 1.5V or less and even higher.
Excessive increase in internal oxygen pressure, able to withstand pumped up oxygen
Do not cause rupture. This allows the reference gas channel to be
It can be seen that it has the characteristic of restricting gas diffusion in the opposite direction. As a result, exhaust gas
Oxygen pressure is applied to the reference
And increases to the rupture point.       [0048]   Next, the fuel limit flux was measured as a function of the reference channel width. In FIG.
Plot the result. In FIG. 3, the limit exhaust gas flux is shown in the reference channel.
Plotted against percent change in width. As seen in this figure
, The critical exhaust gas flux is linearly proportional to the linear dimension of the reference gas channel.
You.       [0049]   Depending on the design of the gas sensor and especially the reference gas channel, exhaust gas
Alternatively, the diffusion of the contaminated air toward the reference electrode is suppressed. This means that
Requirements for hermetically sealed sensor packages in conjunction with a dynamic pumping method
Eliminates the problem of increased oxygen pressure and eliminates expensive power supplies and circuits
. A further advantage of this sensor is that when using the firing embodiment, the reference gas channel
Manufacturing can be simplified because temporary materials can be used when forming the
.       [0050]   While the preferred embodiment has been shown and described, various changes and substitutions may be made in the present invention.
Without departing from the spirit and scope of the invention. For example, in this specification
Use of the taught geometry in other conventional sensors. I
Accordingly, the devices and methods have been described by way of illustration only and are not disclosed herein.
Such examples and embodiments described are to be interpreted as limiting the scope of the claims.
Please understand that you must not deny. [Brief description of the drawings]     FIG. 1 is an enlarged view of a gas sensor design.     Fig. 2 Gas diffusion limiting effect on sensor package leak rate.
It is a figure showing exhaust gas flux measured from an arc channel. Data
The flat part indicates the limit value of the exhaust gas flux.     Fig. 3 Limit discharge for air channel width distribution (percent (%))
It is a figure which shows a gas-gas flux value.     FIG. 4 shows oxygen related to the periodic operation of the heater (on / off operation of the heater).
Gas buffering (storage) with gas restrictors to overcome pump problems
Kura) Single air channel design with space. Angled top view.
is there.     FIG. 5 is a view showing a gas having electric insulation (ground insulation between a heater and a sensor electromotive force).
FIG. 4 is an enlarged view of an alternative design of the sensor, showing the electromotive force element and the oxygen pump element.
Is on the opposite side of the heater.     FIG. 6 shows a gas having electrical insulation (ground insulation between a heater and a sensor electromotive force).
Enlarged view of an alternative design of the sensor, with an electromotive force sensor and an oxygen pump
The sensor is on the same side of the heater.     FIG. 7 is an enlarged view of an alternative gas sensor design, showing an electromotive electrode
To further address the issue of insulation between the leads and heater leads,
The connection to the heater lead is outside the sensor member location.

────────────────────────────────────────────────── ─── Continuation of front page    (72) Kikuchi, Paul Cathay             Gran, 48430, Michigan, United States             De Blank, Clyde Road 12824 (72) Inventors Goodwin, William Russell             48439, Gran, Michigan, United States             De Blanc, Georgetown 5169 (72) Inventor Ron-Uren F             48309, Roche, Michigan, United States             Star Hills, Silvervale de             Live 380 (72) Inventor Detweiler, Eric Jay             Davi, 48423, Michigan, United States             Son, Colleen Lane 1518 (72) Inventors Kennard, Frederick Lincoln,             The Third             Holly, 48442, Michigan, USA             East Holly Road 5499 (72) Inventor Kore, Jeffrey Tee             48507, Flynn, Michigan, United States             G, Maple Park Drive 5483

Claims (1)

Claims: 1. A reference gas channel having an electrolyte disposed between electrodes and in ionic communication with each other, a first electrode and a reference electrode, and in fluid communication with the reference electrode and the exterior of the sensor, the reference gas channel having a diffusion limiter. And a gas sensor comprising: 2. The reference gas channel has a reference electrode area of about 30 mA / c.
The gas sensor according to claim 1, wherein the gas sensor has a critical exhaust flux that is less than or equal to m ² . 3. The reference gas channel has a reference electrode area of about 20 mA / c.
^3. The gas sensor according to claim 2, wherein the gas sensor has a critical exhaust flux that is less than or equal to m2. 4. The reference gas channel has a reference electrode area of about 10 mA / c.
m ² has a at which limit exhaust flux less, the gas sensor according to claim 3. 5. The reference gas channel has a size determined by the formula (I): F _exh = (DCA) / L (I), where F _exh is the exhaust gas flux (ie, channel , D is the diffusion constant of the exhaust gas, C is the ambient atmospheric fuel concentration at the open end of the reference gas channel, A is the average cross-sectional area of the gas channel, and L is the length of the gas channel. The gas sensor according to claim 3. 6. The design of the reference gas channel is further based on the formula (II): I _p = (V _h V _emf ) / R (II), where I _p is the pump current and V _h is The gas sensor according to claim 5, wherein the heater voltage, V _emf is the sensor electromotive force, and R is the resistance of the resistor. 7. The reference gas channel has a length of about 35 mm to about 65 mm.
The gas sensor according to claim 1, wherein the gas sensor has a width of about 0.50 mm or less and a height of about 0.05 mm or less. 8. The length is about 35 mm to about 50 mm, and the width is about 0.30.
The gas sensor according to claim 7, wherein the height is less than or equal to about 0.025 mm. 9. The length is about 40 mm to about 48 mm, and the width is about 0.13.
9. The gas sensor according to claim 8, wherein the height is no greater than about 0.015 mm. 10. The reference gas channel further includes an oxygen storage material.
The gas sensor according to claim 1. 11. The oxygen storage material is platinum, rhodium, palladium,
11. The gas sensor according to claim 10, wherein the gas sensor is selected from the group consisting of ruthenium, iridium, osmium, cerium oxide, bismuth oxide, and alloys and mixtures containing at least one of the above materials. 12. The reference gas channel further comprises a first chamber adjacent to a reference electrode, wherein a cross-sectional area of the first chamber is larger than a cross-sectional area of the diffusion restrictor.
The gas sensor according to claim 1. 13. The reference gas channel further includes a second chamber and a second diffusion path, wherein the second chamber is disposed in fluid communication with the first chamber, wherein the first diffusion path is in communication with the second chamber. A second diffusion path disposed in fluid communication with the first diffusion path, the second chamber being disposed in fluid communication with the first diffusion path;
13. The cross-sectional area of the second chamber is greater than the cross-sectional area of the first chamber and the cross-sectional area of the second diffusion path is smaller than the cross-sectional area of the first chamber.
A gas sensor according to claim 1. 14. The gas sensor according to claim 1, wherein the sensor further comprises a heater and a resistor, wherein the resistor is connected to a positive lead of the heater and a reference electrode. 15. The gas sensor according to claim 1, further comprising firing the sensor. 16. Using a gas sensor having an electrolyte disposed between the electrodes and having a first electrode and a reference electrode in ionic communication with each other, and a reference gas channel in fluid communication with the reference electrode and the exterior of the sensor. Introducing a gas to the first electrode; applying a voltage to the reference electrode; ionizing oxygen at the first electrode; transferring oxygen to the reference electrode through the ionized electrolyte; Forming molecular oxygen; ionizing molecular oxygen on a reference electrode; transferring ionized oxygen to a first electrode through an electrolyte to generate a voltage; and measuring the voltage. A method for operating a gas sensor, comprising: 17. The method for operating a gas sensor according to claim 16, wherein the reference gas channel further comprises a diffusion limiter. 18. The reference gas channel has a reference electrode area of about 30 mA / cm ^2.
17. The method for operating a gas sensor according to claim 16, having a limiting exhaust gas flux that is: 19. The reference gas channel has a reference electrode area of about 20 mA / cm ^2.
19. The method for operating a gas sensor according to claim 18, wherein the method has a critical exhaust gas flux that is: 20. The reference gas channel has a reference electrode area of about 10 mA / cm ^2.
20. A method for operating a gas sensor according to claim 19, having a limiting exhaust gas flux that is: 21. The reference gas channel has a size determined by the formula (I): F _exh = (DCA) / L (I), where F _exh is the exhaust gas flux (ie, channel , D is the diffusion constant of the exhaust gas, C is the ambient atmospheric fuel concentration at the open end of the reference gas channel, A is the average cross-sectional area of the gas channel, and L is the length of the gas channel. 17. A method for operating a gas sensor according to claim 16. 22. The design of the reference gas channel is further based on the formula (II): I _p = (V _h V _emf ) / R (II), where I _p is the pump current and V _h is the heater 22. The method for operating a gas sensor according to claim 21, wherein the voltage, V _emf is the sensor electromotive force, and R is the resistance of the resistor. 23. The reference gas channel has a length of about 35mm to about 65mm.
23. The method for operating a gas sensor according to claim 22, wherein the width is about 0.50 mm or less and the height is about 0.05 mm or less. 24. The length is about 35 mm to about 50 mm, and the width is about 0.3 mm.
24. The method for operating a gas sensor according to claim 23, wherein the height is 0 mm or less, and the height is about 0.025 mm or less. 25. The length is between about 40 mm and about 48 mm, and the width is about 0.1 mm.
25. The method for operating a gas sensor according to claim 24, wherein the height is 3 mm or less, and the height is about 0.015 mm or less. 26. The reference gas channel further comprises an oxygen storage material.
A method for operating a gas sensor according to claim 16. 27. The oxygen storage material is platinum, rhodium, palladium,
27. The method for operating a gas sensor according to claim 26, wherein the method is selected from the group consisting of ruthenium, iridium, osmium, cerium oxide, bismuth oxide, and alloys and mixtures containing at least one of the above materials. 28. The gas sensor of claim 16, wherein the reference gas channel further comprises a first chamber adjacent to a reference electrode, wherein a cross-sectional area of the first chamber is greater than a cross-sectional area of the diffusion limiter. Way to let. 29. The reference gas channel further comprises a second chamber and a second diffusion path, wherein the second chamber is disposed in fluid communication with the first chamber, wherein the first diffusion path is connected to the second chamber and the first diffusion path. A second diffusion path is disposed between the chambers, the second diffusion path is disposed in fluid communication with the first diffusion path, a second chamber is disposed between the second diffusion path and the first diffusion path, and a cross-sectional area of the second chamber is the first diffusion path. 30. The method for operating a gas sensor according to claim 29, wherein the cross-sectional area of the second diffusion path is larger than the cross-sectional area of the first chamber, the cross-sectional area being larger than one of the chambers. 30. The apparatus further comprising a heater electrically connected to the reference electrode,
30. The method for operating a gas sensor according to claim 29, wherein the voltage is applied to the heater periodically. 32. The operation of ionizing oxygen at the first electrode, moving the ionized oxygen through an electrolyte to a reference electrode, and forming molecular oxygen at the reference electrode, comprises ionizing molecular oxygen on the reference electrode. 17. The method for operating a gas sensor of claim 16, wherein the operation occurs substantially simultaneously with the operation of transferring ionized oxygen through the electrolyte to the first electrode to generate a voltage. 33. The method for operating a gas sensor according to claim 16, wherein the gas sensor further comprises a heater, wherein the sensor is fired.