TW201447294A - Sensor for detecting a gas content - Google Patents

Abstract

The invention relates to a sensor (S) for detecting a gas content in the environment of the sensor (S). The sensor (S) comprises a sensor body (SK), an electrode chamber (EK), which is formed in the sensor body (SK), a heating element, which is embedded in the sensor body (SK), a longitudinal axis (L), an end face (SF) of the sensor body (SK) extending substantially perpendicularly to the longitudinal axis (L), an inlet channel (EAK), which is coupled to the electrode chamber (EK) and has an inlet (EA) at the surface of the sensor body (SK), and a thermal insulation sleeve (IH) on the sensor body (SK), which thermal insulation sleeve extends at least axially in the direction of the longitudinal axis (L) over the region of the electrode chamber (EK).

Description

Sensor for detecting gas content

The present invention relates to a sensor for detecting gas content in the environment of a sensor.

Gas sensors (especially oxygen sensors) are used in the intake flank or exhaust flank of an internal combustion engine (eg, an Otto motor or a Diesel motor). Such an oxygen sensor is, for example, a linear Lambda sensor. Such sensors are of course sensitive to thermal shock. For example, if a water droplet touches a sensitive part of the sensor, the part will be damaged in most cases.

It is an object of the present invention to provide a sensor that has good thermal shock safety.

The above objects are achieved by the features of the independent patent application scope. Advantageous configurations are shown in the dependents of the scope of the patent application.

A feature of the invention is a sensor for detecting gas content in the environment of a sensor. Such a sensor includes a sensor body. The sensor further includes an electrode chamber formed in the sensor body. The sensor includes a heating element embedded in the sensor body whereby the predetermined area around the electrode chamber is heated to a predetermined operating temperature. The feeling The detector includes a longitudinal axis and a front surface of one of the sensor bodies extending substantially perpendicular to the longitudinal axis. Additionally, the sensor includes an inlet channel coupled to the electrode chamber and having an inlet on a surface of the sensor body. Furthermore, the sensor comprises a thermal isolating sleeve on the body of the sensor which extends at least in the axial direction in the direction of the longitudinal axis over the region of the electrode chamber.

The inlet is formed in particular on the front side. Alternatively, the inlet may be formed on a face adjacent to the front side.

By thermal isolation in the region of the electrode chamber, the sensor achieves a good thermal shock durability without thereby changing the measurement rate. In addition, most of the heat transfer is not required to be performed by convection due to the isolation. Thus, more flow can be received on the sensor, which can result in improved response rates for the sensor.

A preset operating temperature is, for example, a temperature between 600 ° C and 850 ° C.

According to an advantageous form, the front side is not provided with the separating sleeve and the separating sleeve is previously spaced apart from the front side.

The front faces, for example, must be spaced apart in advance so that the sensor can easily protrude from the isolating sleeve. In this manner, if the inlet is formed on the front side of the sensor body, the entry of gas will be unrelated to the isolation sleeve.

According to another advantageous form, the isolating sleeve has ceramic fibers and/or metal fibers.

These fibers have high temperature durability and thus make thermal conductivity as small as possible. The spacer sleeve is for example composed of ceramic fiber strands approximately 2 mm thick.

According to another advantageous form, the ceramic fibers and/or metal fibers are arranged in a metal sleeve.

The metal sleeve is for example fixedly welded to the sensor, so that a spacer sleeve which is as stable as possible is achieved.

According to another advantageous form, the ceramic fibers and/or metal fibers are separated from the metal sleeve by an air gap.

Thus, another isolation can be achieved by the air gap.

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

S‧‧‧ sensor

SK‧‧‧Sensor body

EK‧‧‧electrode room

BB‧‧‧Preset area

H‧‧‧Support

K‧‧‧Contact layer

L‧‧‧ vertical axis

SF‧‧ positive

DB‧‧‧Diffusion

EA‧‧ entrance

EAK‧‧ Entrance Channel

IH‧‧‧Isolation sleeve

P-‧‧‧first electrode

P+‧‧‧second electrode

YSZ‧‧‧钇-stabilized zirconia

Figure 1 is a sensor for detecting gas content.

Figure 2 is a sensor for detecting the gas content.

Embodiments of the present invention will be described in detail below with reference to the drawings. Elements of the same construction or function are denoted by the same reference numerals throughout the drawings.

Figure 1 is a sensor S for detecting the gas content in the environment of the sensor S. The sensor S is in particular formed as an oxygen sensor, which determines the oxygen content in the environment of the sensor S. The sensor S includes a sensor body SK. The sensor body SK includes, for example, a substrate composed of yttrium-stabilized zirconia YSZ. An electrode chamber EK is formed in the sensor body SK. Furthermore, a heating element is embedded in the sensor body SK, whereby a predetermined area BB around the electrode chamber EK can be heated to a predetermined operating temperature. This preset operating temperature is, for example, between 600 ° C and 850 ° C or approximately 700 ° C.

Furthermore, the sensor S has a longitudinal axis L and a front surface SF of one of the sensor bodies SK extending substantially perpendicular to the longitudinal axis L.

Further, the sensor body SK has an inlet passage EAK coupled to the electrode chamber EK and having an inlet EA in the surface of the sensor body SK, the inlet EA being formed in the sensor body SK On the front SF.

A diffusion barrier DB is formed between the inlet EA and the electrode chamber EK, through which oxygen can diffuse into the electrode chamber EK.

Furthermore, the sensor S has a thermal isolating sleeve IH which is formed on the sensor body SK and extends at least in the axial direction in the direction of the longitudinal axis L over the region of the electrode chamber EK.

Figure 2 shows a second view of the sensor S. Figure 2 illustrates the construction of the layer form of the sensor S. The first electrode P-system is connected to the electrode compartment EK and may also be referred to as a cathode. A solid electrolyte layer is formed between the first electrode P- and a second electrode P+, which may also be referred to as an anode, which is formed, for example, by ytterbium-stabilized zirconia YSZ.

The sensor S further has a plurality of contact layers K (see Fig. 1), which are used, for example, to control the various heating elements and to apply a voltage to operate the sensor S.

In addition, the sensor S has a piece H (see Fig. 1) which can also be used to dissipate heat. This support H is thus formed, for example, of aluminum and is fixed to the sensor body SK by an adhesive.

The mode of operation of the sensor S will be described below.

In order to detect the gas content around the sensor S, a kind of, for example, 0.8 volt (V) must be applied between the first electrode P- and the second electrode P+. The voltage difference. When the oxygen content under the cathode is adjusted to 0 and the sensor S is installed in an oxygen-containing environment, the oxygen atoms pass through the diffusion due to the concentration difference or partial pressure difference between the environment and the lower region of the cathode (where almost no oxygen is present). The barrier DB and the cathode diffuse into the substrate of the sensor body SK. The oxygen atoms diffuse into the substrate of the sensor body SK to become double negatively charged ions, wherein the electrons required for ionization of the oxygen atoms are provided by the conductive cathode. A differential diffusion limiting current is measured in the voltage applied between the electrodes. This current is related to the oxygen partial pressure in the oxygen-containing measuring gas. The oxygen ions are again converted to oxygen atoms on the anode and diffused again into the oxygen-containing environment via the anode. In terms of sufficient ionic conductivity, the sensor body SK requires an increased temperature. Therefore, the sensor body SK is heated by the heating element in the heatable region BB of the electrode chamber EK to a predetermined operating temperature, for example, the operating temperature is between 600 ° C and 850 ° C.

In order to achieve a protective effect against thermal shock, the sensor S has the above-described isolating sleeve IH. By thermal isolation in the region of the electrode chamber EK, the sensor S achieves good thermal shock durability and thus does not change the measurement rate. In addition, most of the heat transfer is not required to be performed by convection due to the isolation. Thus, more flow can be received on the sensor S, which can result in an improved reaction rate of the sensor S.

The isolating sleeve IH has, for example, ceramic fibers and/or metal fibers. The ceramic fibers and/or metal fibers are for example arranged in a metal sleeve. Alternatively, the ceramic fibers and/or metal fibers are separated from the metal sleeve by an air gap. For example, the spacer sleeve IH has a thickness of approximately 2 mm.

For example, the front side SF of the sensor S is not provided with the isolating sleeve IH and the isolating sleeve IH is previously spaced apart from the front side SF. The front side SF, for example, must be spaced apart in advance so that the sensor S can easily protrude from the isolating sleeve IH. Thus, the inlet EA is not associated with the isolating sleeve IH, so that the measurement is not affected.

S‧‧‧ sensor

SK‧‧‧Sensor body

EK‧‧‧electrode room

BB‧‧‧Preset area

H‧‧‧Support

K‧‧‧Contact layer

L‧‧‧ vertical axis

SF‧‧ positive

DB‧‧‧Diffusion

EA‧‧ entrance

EAK‧‧ Entrance Channel

IH‧‧‧Isolation sleeve

Claims (5)

A sensor (S) for detecting a gas content in a sensor (S) environment, comprising: a sensor body (SK), an electrode chamber (EK) formed on the sensor body ( In SK), a heating element embedded in the sensor body (SK), whereby a predetermined area (BB) around the electrode chamber (EK) is heated to a predetermined operating temperature, a front side (SF) extending from a longitudinal axis (L) and one of the sensor body (SK) substantially perpendicular to the longitudinal axis (L), an inlet channel (EAK), which is associated with the electrode chamber (EK) Coupling and having an inlet (EA) on the surface of the sensor body (SK), and a thermal isolation sleeve (IH) on the sensor body (SK), at least in the axial direction The direction of the longitudinal axis (L) extends over the area of the electrode chamber (EK). The sensor (S) of claim 1, wherein the front side (SF) is not provided with the isolating sleeve (IH) and the isolating sleeve (IH) is previously spaced apart from the front side (SF). A sensor (S) according to claim 1 or 2, wherein the isolating sleeve (IH) has ceramic fibers and/or metal fibers. The sensor (S) of claim 3, wherein the ceramic fibers and/or metal fibers are disposed in a metal sleeve. The sensor (S) of claim 4, wherein the ceramic fibers and/or metal fibers are separated from the metal sleeve by an air gap.