JP4781950B2 - Composite sensor element - Google Patents

Description

  The present invention relates to a composite gas sensor element capable of detecting a plurality of types of specific gas concentrations in a gas to be measured.

  A gas sensor configured to measure oxygen concentration, NOx concentration, engine combustion chamber air-fuel ratio, and the like may be installed in an exhaust system of an automobile engine. At that time, a composite gas sensor element capable of measuring a plurality of types of specific gas concentrations or the like may be used for the gas sensor for the purpose of saving installation space and reducing the failure probability. The composite sensor element includes an electrochemical cell corresponding to each specific gas concentration detection, and is provided with a terminal for outputting an output to each electrochemical cell and a terminal for performing an input for operating each electrochemical cell.

The output current and voltage, input current and voltage of each electrochemical cell vary greatly depending on the cell type. Therefore, a leakage current generated between the terminals may be a problem.
The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a composite sensor element capable of ensuring insulation between terminals and detecting gas concentration more accurately.

According to a first aspect of the present invention, there are provided a surface of a composite sensor element and a surface of the surface of the composite sensor element, each of which is electrically connected to a plurality of electrochemical cells and takes out an output of each electrochemical cell and a terminal for inputting electric power to the electrochemical cell. in more with integrated sensor elements a pair of terminals opposing comprising in the width direction of the opposite surface on each side of the surface and the opposite surface of, all of the pair of adjacent terminals on each side, the width direction and the longitudinal direction of each plane The composite sensor element is arranged so as to be shifted from each other (claim 1). The second invention is a terminal for taking out the output of each electrochemical cell, a terminal for inputting electric power to the electrochemical cell, and a terminal for applying electric power to the heating element, which are electrically connected to a plurality of electrochemical cells, respectively. In a composite sensor element having a plurality of terminals on each surface of the surface and the opposite surface, a pair of terminals adjacent to each other in the width direction of the surface of the composite sensor element and the opposite surface of the surface. is the integrated sensor device characterized by being staggered in the width direction and the longitudinal direction of each surface (claim 2).

  In the composite sensor element according to the first and second inventions, adjacent terminals (including the terminal of the heating element) are arranged shifted in the longitudinal direction on the same plane of the composite sensor element. Therefore, sufficient insulation between the terminals can be ensured, leakage current generated between the terminals can be prevented, and accurate gas concentration detection can be realized.

  As described above, according to the present invention, it is possible to provide a composite sensor element that can ensure insulation between terminals and perform more accurate gas concentration detection.

  The electrochemical cell described in the first and second inventions comprises a solid electrolyte body and a pair of electrodes provided on the solid electrolyte body. Each cell functions as a gray electromotive force type or limit current type detection cell. For example, for an electrochemical cell that can measure the oxygen concentration in the gas to be measured, an electrochemical cell that can measure the concentration of various gases such as HC, CO, and NOx in the gas to be measured, a gas chamber to be measured provided inside the device, etc. An electrochemical cell or the like capable of gas pumping (gas in / out) is a specific example of the electrochemical cell in the first and second inventions.

  In particular, a composite sensor element used in an exhaust system of an internal combustion engine may have an electrochemical cell capable of measuring the air-fuel ratio in the combustion chamber of the internal combustion engine. Furthermore, an electrochemical cell that monitors the state of the gas to be measured in order to control the operation of the electrochemical cell can be given as the specific example. Each electrochemical cell may be generally called a sensor cell, a monitor cell, or a pump cell.

  The solid electrolyte body can use various materials generally used as an electrolyte. Moreover, what consists of various electrically-conductive materials generally utilized as an electrode can be used for the said electrode. In the examples described later, oxygen ion conductive zirconia ceramics and noble metal electrodes are used, but known materials can be used without being limited thereto. In addition, each electrochemical cell and a terminal corresponding to each electrochemical cell are electrically connected by a conductive lead portion, a conductive through hole, or the like.

  The composite sensor element according to the second aspect of the invention includes a heating element, and this heating element functions as a heater. Since some electrochemical cells do not operate normally unless heated to an activation temperature or higher, a configuration in which the electrochemical cell is forcibly heated with a heater may be employed when used in a low temperature environment. In this case, a terminal for applying electric power to the heating element is required, and the terminal described in the second invention is a terminal for energization. This terminal also secures a distance between terminals of 0.5 mm or more like the terminal of the electrochemical cell.

  In particular, the voltage and current applied to the heating element are often larger than the voltage and current input and output to and from the electrochemical cell. Is preferred.

  When the distance between each terminal is less than 0.5 mm, the following problem occurs. Between adjacent terminals, one terminal (tentatively referred to as terminal x) is held at a high potential, a large current flows, the other terminal (tentatively referred to as terminal y) is held at a low potential, and a minute current flows , A leakage current is generated from the terminal x toward the terminal y. For this reason, the potential of the terminal y becomes higher than that in the case where the terminal x does not exist, and a larger current flows.

  In addition, when the potential or current of one terminal (assumed to be terminal u) greatly fluctuates in time and the potential or current of the other terminal (tentatively assumed to be terminal v) is in a steady state, the voltage at terminal u The time variation of the current affects the terminal v through the leak current, and the voltage and current on the terminal v side cause the time variation. Therefore, the measurement by the electrochemical cell that is in electrical conduction with the terminal y and the terminal v becomes inaccurate.

  In addition, when the distance between the terminals is particularly 1 mm or more, the insulation between the terminals can be more reliably ensured and accurate detection can be performed.

  In addition, since the output from the terminal is taken out of the element, misalignment or the like may occur due to manufacturing variations in the connector to be contacted for inputting to the terminal from the outside. Preventing short circuit caused by this misalignment can do. The upper limit of the distance between terminals is preferably 10 mm in the element short side direction and 20 mm in the element long side direction in order to prevent an increase in the size of the element.

  The distance between terminals is defined in consideration of the path length through which the current flows. When the terminals are simply arranged adjacent to each other on the same plane of the element as shown in Example 1 described later, the distance is the shortest distance between the terminals. However, for example, when a terminal is provided on the side surface of an element as in Example 4 described later, as shown in FIG. 7, the length of a path from one terminal tracing the surface of the element to a different terminal is expressed as the distance between terminals. And

  In addition, it is preferable that adjacent terminals are shifted in the longitudinal direction of the composite sensor element. Even in the case of an element with a small width and a small physique, by disposing adjacent terminals in the longitudinal direction, the two terminals can be sufficiently insulated by separating the distance between the adjacent terminals.

  Moreover, it is preferable to provide a groove part between adjacent terminals. (Claim 4). Leakage current generated between the terminals flows through the element surface, so providing a groove can increase the path length between the terminals and ensure insulation between the terminals without increasing the size of the element. can do. The groove is preferably formed by processing the element surface between the terminals into a recess. Alternatively, it is possible to provide a convex portion where a terminal is to be formed on the surface of the element so that a gap is formed between the convex portions (see FIGS. 5A and 5B).

  In addition, it is preferable that the groove part has a groove width of 0.5 mm or more and a groove part depth of 0.1 mm or more. As a result, it is possible to achieve insulation and reduce the size of the element. If the groove width or the groove depth is smaller than the above range, the insulating property may be lowered.

  In addition, it is preferable that the detection side of the composite sensor element is narrow. In the composite sensor element, the detection side can be made narrower than the other parts, so that the vicinity of the detection side can be reduced in size, and the input power to the heating element can be reduced to obtain a low-power element. Can do. Note that the detection side in the composite gas sensor element refers to a location where an electrochemical cell is provided, and particularly a location where an electrode constituting the electrochemical cell is provided. Usually, as shown in FIG. 3 and FIG.

The element width of the composite sensor element is preferably 4 mm or more. In this case, the air-fuel ratio sensor, the O ₂ sensor, the A / F sensor, etc., in which the composite sensor element according to the present invention is installed, are already put into practical use, such as the air-fuel ratio sensor, the O ₂ sensor, the A / F sensor, etc. The assembly structure can be made similar, and many parts can be shared with these sensors. Further, the composite sensor element according to the present invention can be installed as it is in an air-fuel ratio sensor, an O ₂ sensor, an A / F sensor or the like that has already been put into practical use. In addition, the strength of the element can be increased. When the element width is less than 4 mm, the composite sensor element is thin, the strength is weak, and the durability may be reduced.

  The upper limit of the element width is preferably 10 mm. If the element becomes larger than this, the physique of the element becomes large, and the physique of the sensor or the like to which the element is assembled also becomes large, which may deteriorate the vehicle mountability. In addition, as the element becomes larger, the heat capacity of the element also increases, and there is a possibility that the element cannot be sufficiently heated unless the power of the heater is increased.

Further, it is preferable that the width of the terminal is not less than 0.5 mm (claim 7). Since the output from the terminal can be taken out of the element or the contact resistance between the terminal and the connector to be contacted for inputting to the terminal from the outside can be reduced, the poor conduction between the two is less likely to occur.

  The terminal width is the length of the terminal along a direction parallel to the width direction perpendicular to the longitudinal direction of the element. If the width of the terminal is less than 0.5 mm, the output from the terminal is taken out of the element, and it is likely to cause poor conduction between the terminal and the connector to be contacted for external input. There is a risk that the electrical resistance at the terminal increases. Further, the upper limit of the width of the element is preferably 2 mm in order to prevent an increase in the size of the element.

Further, it is preferable that the length of the terminal is not less than 1 mm (claim 8). Since the output from the terminal can be taken out of the element or the contact resistance between the terminal and the connector to be contacted for inputting from the outside can be reduced, poor conduction between the two is less likely to occur. The length of the terminal is the length of the terminal along the direction parallel to the longitudinal direction of the element.

  If the length of the terminal is less than 1 mm, the output from the terminal is taken out of the element, so it is likely to cause poor continuity with the connector that is in contact with the terminal for input from the outside. There is a risk that the electrical resistance at the end increases. Further, the upper limit of the terminal length is preferably 10 mm in order to prevent the device from becoming large.

Further, it is preferable that the surface of the farthest integrated sensor element than the heater surface including the surface of the heating element is provided over four said terminal (claim 9). Since many terminals are provided at remote positions that are not easily affected by the leakage current from the heating element, a composite sensor element capable of more accurate detection can be obtained. If the number is less than 4, the number of terminals affected by the leakage current increases, and the detection accuracy of the composite sensor element may be reduced.

  Embodiments of the present invention will be described below with reference to the drawings.

Example 1
The composite sensor element according to the present invention will be described with reference to FIGS. As shown in FIGS. 1 to 3, the gas sensor element 1 of this example includes a plurality of electrochemical cells, has a terminal for taking out the output of the electrochemical cell, a terminal for applying electric power to the electrochemical cell, and , A heating element and a terminal for applying electric power to the heating element, and the distance between the terminals is 0.5 mm or more.

  This will be described in detail below. The composite sensor element of this example is an element that is attached to the exhaust system of an automobile engine and combines the measurement of NOx concentration, which is an air pollutant in the exhaust gas, and the detection of the λ characteristic and the air-fuel ratio in the engine.

  As shown in FIG. 1, the composite sensor element 1 includes a heater 15, a spacer 56, a second solid electrolyte plate 55, a spacer 54, a first solid electrolyte plate 53, a porous plate 51, and a spacer 52. Each of the spacers 52, 54 and 56 is made of an alumina ceramic plate, and the first and second solid electrolyte plates 53 and 55 are made of oxygen ion conductive zirconia ceramic. The heater 15 is a ceramic heater in which a heating element 150 is built between a heater substrate 151 made of insulating alumina ceramic and a cover plate 152. The heater surface 159 on the surface of the heating element 150 is located approximately near the boundary between the heater substrate 151 and the cover plate 152.

  The first solid electrolyte plate 53 is provided with a through hole that becomes the first diffusion resistance passage 110, and the porous plate 51 is provided so as to cover the diffusion passage 110. A spacer 52 is provided adjacent to the porous plate 51, and the first reference gas chamber 13 is formed by the spacer 52 and the first solid electrolyte plate 53.

  The first measured gas chamber 11 and the second measured gas chamber 12 are formed of a space surrounded by the first solid electrolyte plate 53, the spacer 54, and the second solid electrolyte plate 55. The second reference gas chamber 14 is a space surrounded by the second solid electrolyte plate 55 and the spacer 56. As shown in FIGS. 1 and 2, the first measured gas chamber 11 and the second measured gas chamber 12 communicate with each other through a thin second diffusion resistance passage 120.

  The third electrochemical cell 4 of this example functions as an oxygen concentration electromotive force type battery. The measured gas side oxygen sensor electrode 41 constituting the third electrochemical cell 4 is disposed between the first solid electrolyte plate 53 and the porous plate 51, and the reference oxygen sensor electrode 42 faces the first reference gas chamber 13. Provide. The third electrochemical cell 4 is connected to an oxygen sensor circuit 45 having a voltmeter 451. The voltmeter 451 measures an electromotive force between the electrodes 41 and 42 (this electromotive force is generated by oxygen concentration in the gas atmosphere to be measured outside the composite sensor element and the first reference gas chamber atmosphere). This electromotive force is the output of the third electrochemical cell 4.

  The first electrochemical cell 2 of this example functions as a pump cell. A voltage is applied from a power source 252 that is feedback-controlled by the current value of the ammeter 651 of the fourth electrochemical cell 6, and oxygen corresponding to this applied voltage is supplied to the first measured gas chamber 11 and the second reference gas chamber 14. It functions to move in and out. Further, feedback control may be performed from a map set in advance according to the pump current.

  The first electrochemical cell 2 is provided on the second solid electrolyte plate 55 and includes a measured gas side pump electrode 21 facing the first measured gas chamber 11 and a reference pump electrode 22 facing the second reference gas chamber 14. A pump circuit 25 to which an ammeter 251 and a power source 252 are connected is provided between the electrodes 21 and 22. A feedback circuit 655 is provided between an ammeter 651 and a power source 252 described later.

  The pump current corresponds to the oxygen concentration in the first gas chamber 11 to be measured, and the power supply 252 is controlled using the feedback circuit 655 so that the current in the fourth electrochemical cell 6 always takes a constant value. With this control, the first electrochemical cell 2 can maintain a constant oxygen concentration in the first measured gas chamber 11, and hence in the second measured gas chamber 12 communicating with the first measured gas chamber 11. The measured gas side pump electrode 21 is an electrode that does not decompose NOx and is inert to NOx.

  A constant voltage (which does not vary with time) is applied to the second electrochemical cell 3 of this example, and the NOx concentration is measured using an oxygen ion current generated by the constant voltage. The second electrochemical cell 3 includes a measurement gas side sensor electrode 31 provided on the first solid electrolyte plate 53 and facing the second measurement gas chamber 12 and a reference sensor electrode 32 facing the first reference gas chamber 13. To do. A sensor circuit 35 having an ammeter 351 and a power source 352 is provided between the electrodes 31 and 32. The reference sensor electrode 32 is provided integrally with reference oxygen sensor electrodes 42 and 62 described later.

  The measured gas side sensor electrode 31 is an active electrode capable of decomposing NOx into nitrogen and oxygen. By applying a voltage to the second electrochemical cell 3, oxygen ions are generated on the surface of the measured gas side sensor electrode 31, and the oxygen ions flow through the first solid electrolyte plate 53 as an ionic current. An ammeter 351 measures the ion current. This ionic current is proportional to the NOx concentration in the measured gas unless the measured gas side pump electrode 21 of the first electrochemical cell 3 decomposes the NOx, so the value readable from the ammeter 351 becomes the NOx concentration.

  Although oxygen in the measurement gas is also decomposed on the measurement gas side sensor electrode 31, the oxygen concentration in the measurement gas is kept substantially constant by the first electrochemical cell 2, so that the NOx concentration is preliminarily maintained. By measuring the value of the ammeter 351 at 0, the magnitude of the ion current derived from NOx can be measured correctly. Alternatively, it can be measured correctly by subtracting the current value of the fourth electrochemical cell 6, that is, the correction of the residual oxygen concentration in the chamber 12.

  The fourth electrochemical cell 6 of this example functions as an oxygen pump cell, and measures the oxygen concentration in the second measured gas chamber 12. The fourth electrochemical cell 6 is provided on the first solid electrolyte plate 53, and includes a measured gas side sensor electrode 61 facing the second measured gas chamber 12 and a reference sensor electrode 62 facing the first reference gas chamber 13. A sensor circuit 65 to which an ammeter 651 and a power source 652 are connected is provided between the electrodes 61 and 62. A feedback circuit 655 is provided between the ammeter 651 and the power source 252 described above.

  The measured gas side sensor electrode 61 is an inert electrode for NOx. In the fourth electrochemical cell 6, a current corresponding to the oxygen concentration in the second gas chamber 12 to be measured is generated, and this current is detected by the ammeter 651, whereby the feedback circuit 655 is used and the first electrochemical cell 2 Control pumping.

  Terminals applied to the first to fourth electrochemical cells 2, 3, 4 and 6 of the composite sensor element 1 configured in this way are the surface 109 of the composite sensor element 1 and the terminals as shown in FIGS. An exposed surface 108 is formed opposite to the surface 109.

  In particular, the terminals 711 to 714 for the second and third electrochemical cells 3 and 4 are provided on the surface 109 of the composite sensor element 1 in the positional relationship as shown in FIG. As shown in FIG. 4, terminals 721 to 726 electrically connected to the other cells 2 and 6 and the heating element 150 of the heater 15 are provided on the opposite surface 108 of the surface 109.

  That is, as shown in FIGS. 3A and 3B, the terminals 711 and 712 are provided at the end of the composite sensor element 1 on the take-out side, and the terminals 713 and 712 are spaced apart from the terminals 711 and 712 in the longitudinal direction of the element. , 714 are provided.

  As shown in FIG. 3A, the width of the element at the end on the extraction side where the terminals 711 and 712 are provided is A. The distance between the terminals 712 and 714 along the longitudinal direction of the element, that is, the distance between the ends of both terminals is B. A distance along the width direction between the terminal 713 and the terminal 714 is C. The same dimensional relationship is established for the terminals 721 to 726 provided on the opposite surface 108 (see FIG. 4).

  The composite sensor element 1 according to this example is configured to have A = 4.8 mm, B = 3.6 mm, and C = 3.6 mm. Each of the terminals 711 to 714 and 721 to 726 has the same shape, a width E = 1.2 mm, and a length D = 3.2 mm. The surface 109 provided with the terminals 711 to 714 is a surface farthest from the heater surface 159.

  The effect of this example will be described. In the composite sensor element 1 of this example, the distance between the terminals 711 to 714 and 721 to 726 conducting to the first to fourth electrochemical cells 2, 3, 4, 6 and the heating element 150 is 0.5 mm. Release more. Therefore, sufficient insulation between the terminals can be ensured, leakage current generated between the terminals can be prevented, and accurate gas concentration detection can be realized.

  As described above, according to this example, it is possible to provide a composite sensor element capable of ensuring insulation between terminals and detecting gas concentration more accurately.

  Further, in this example, the terminals are shifted in the longitudinal direction of the composite sensor element 1 such as the terminals 711 and 713, the terminals 712 and 714, etc., so that a sufficient distance between the terminals is ensured and the terminals are high. Insulation can be ensured.

  In addition, since the element width A is 4 mm or more in this example, the strength of the element can be increased. In addition, since the width E of each terminal is 0.5 mm or more and the length D of each terminal is 1 mm or more, it is possible to take out an output from each terminal or to contact a connector to input to each terminal. It is possible to reduce the contact resistance between them and ensure stable conduction with the connector.

(Example 2)
As shown in FIG. 5, a groove 75 is provided between the terminals 711 and 712 in the composite sensor element 1 of this example. As shown in FIG. 5A, a recess is provided on the surface 109 of the composite gas sensor element 1 between the terminals 711 and 712. This recess becomes the groove 75. Alternatively, as shown in FIG. 5B, a convex portion 710 for forming terminals 711 and 712 is provided on the surface 109 of the composite gas sensor element 1. Since the terminals 711 and 712 are formed thereon, a groove 75 is formed between the terminals 711 and 712. Other details are the same as those in the first embodiment.

  In the composite sensor element 1 according to this example, a groove 75 is provided between the terminals 711 and 712. As indicated by the arrow R, the leakage current generated between the terminals 711 and 712 flows through the element surface, so that the path length between the terminals can be made longer by providing the groove 75. In addition, insulation between terminals can be ensured without increasing the size of the element. Other details have the same effects as those of the first embodiment.

(Example 3)
The composite sensor element 1 of this example is a composite sensor element having the same configuration as that of the first embodiment. However, as shown in FIG. 6, the detection side provided with the first to fourth electrochemical cells (not shown) is configured to be narrow. The element width M on the extraction side of the composite sensor element 1 according to the figure is 4.8 mm, and the element width N on the detection side is 4 mm.

  The composite sensor element 1 can reduce the input power to the heater. Therefore, it is possible to reduce the electric power supplied to the heating element built in the heater, and to further reduce the leakage current from the terminal connected to the heating element. Other details have the same effects as those of the first embodiment.

( Reference example )
As shown in FIG. 7, the composite sensor element of this reference example is provided with terminals 764 and 768 on the side surface 107 in addition to the element surfaces 109 and 108. The composite sensor element 1 has eight terminals 761-768 in total, the One not a three to surface 109 terminal 761～763,765～767, providing terminals 764,768 One not a one to the side surface 107. By enlarging the location where the terminals are formed up to the side surface 107, more terminals can be arranged with a predetermined interval .

FIG. 3 is a cross-sectional explanatory view of the vicinity of the detection side of the composite sensor element in the first embodiment. The top view of the 1st to-be-measured gas chamber and the 2nd to-be-measured gas chamber in a composite sensor element in Example 1. FIG. In Example 1, (a) The top view of the detection side vicinity of the surface of a composite sensor element, (b) The perspective view of a composite sensor element. The top view of the detection side vicinity of the surface on the opposite side to FIG. 3 in Example 1. FIG. FIG. 6 is an explanatory diagram of a composite sensor element in which a groove is provided between adjacent terminals in the second embodiment. The top view of the composite sensor element in which the detection side became narrow in Example 3. FIG. Explanatory drawing of the composite sensor element in which the terminal was provided also to the side surface in a reference example .

Explanation of symbols

1. . . Composite sensor elements,
109,108. . . surface,
150. . . Heating element,
2,3,4,6. . . First to fourth electrochemical cells,
711-714. . . Terminal,

Claims (11)

The width of the surface of the composite sensor element and the opposite surface of the surface are a terminal for extracting the output of each electrochemical cell and a terminal for inputting electric power to the electrochemical cell, which are electrically connected to a plurality of electrochemical cells, respectively. In the composite sensor element having a plurality of terminals facing each other in the direction on each of the surface and the opposite surface ,
All of the pair of terminals adjacent to each other in the respective surfaces are arranged so as to be shifted in the width direction and the longitudinal direction of the respective surfaces . A composite sensor element comprising: a terminal for taking out an output of each electrochemical cell, a terminal for inputting electric power to the electrochemical cell, and a terminal for applying electric power to the heating element, each electrically connected to a plurality of electrochemical cells In a composite sensor element having a plurality of terminals on each surface of the surface and the opposite surface, a plurality of terminals facing each other in the width direction of the surface and the opposite surface of the surface ,
All of the pair of terminals adjacent to each other in the respective surfaces are arranged so as to be shifted in the width direction and the longitudinal direction of the respective surfaces . 3. The composite sensor element according to claim 1, wherein the distance between the terminals is 0.5 mm or more. 4. The composite sensor element according to claim 1, wherein a groove is provided between adjacent terminals. 5. The composite sensor element according to claim 1, wherein the detection side of the composite sensor element is narrowly configured. 6. The composite sensor element according to claim 1, wherein an element width of the composite sensor element is 4 mm or more. 7. The composite sensor element according to claim 1, wherein the terminal has a width of 0.5 mm or more . 8. The composite sensor element according to claim 1, wherein the terminal has a length of 1 mm or more . 9. The composite sensor element according to claim 2 , wherein four or more terminals are provided on the surface of the composite sensor element farthest from the heater surface including the surface of the heating element. 10. The composite sensor element according to claim 2, wherein the terminal of the electrochemical cell is provided on a surface opposite to the terminal of the heating element. The terminal of the electrochemical cell according to any one of claims 1 to 10, including a pump cell capable of pumping a gas with respect to a gas chamber to be measured provided in the element, and a terminal of the electrochemical cell other than the pump cell is A composite sensor element provided on a surface opposite to the terminal of the pump cell .

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