Multi-channel temperature measuring device

Abstract

Multi-channel temperature measuring device (MS), comprising: a main body part (50) with a plurality of sensor connection parts (521a to 521d); and a plurality of temperature sensors (TS1 to TS4) connected to the plurality of sensor connection parts (521a to 521d) in a one-to-one relationship, each of which comprises a temperature-sensitive part (12a to 12d) and a metal tube (10a to 10d) that temperature-sensitive part (12a to 12d), wherein, of the metal tubes (10a to 10d) of the plurality of temperature sensors (TS1 to TS4), the metal tube (10a) of at least one temperature sensor (TS1) has a part (11a) covering at least the temperature-sensitive part (12a) and is formed from a material that is different from a material used to form respective parts of the metal tubes (10b to 10d) of the remaining temperature sensors (TS2 to TS4), the respective parts covering at least the respective temperature-sensitive parts (12b to 12d), the at least one temperature sensor (TS1) using a different measuring scheme than the remaining temperature sensors (TS2 to TS4).

Description

The present invention relates to a temperature measuring device, and more particularly, it relates to a multi-channel temperature measuring device used for an internal combustion engine.As a multi-channel temperature measuring device used for an internal combustion engine, a pair type temperature sensor including a pair of temperature sensors disposed on, for example, an exhaust pipe so as to measure the temperature of exhaust gas flowing out of an internal combustion engine is known (see, for example, Patent Document 1).Patent Document 2 discloses a temperature sensor arrangement having two alloy temperature sensors 600 facing in different directions. Patent Document 3 discloses a paired temperature sensor having two different temperature sensors whose electrical characteristics are the same.Patent Document 1: JP 2014-134 495 APatent Document 2: DE 20 2008 018 148 U1Patent Document 3: DE 10 2014 200 292 A1However, the conventional multi-channel temperature measurement devices do not sufficiently consider that the temperature sensors of the multi-channel temperature measurement device are exposed to different temperatures. Namely, in all the temperature sensors, metal pipes for accommodating respective temperature sensitive elements are formed of a common material (e.g., alloy 600; see Patent Document 2) selected for the temperature sensor which is exposed to the highest temperature.Accordingly, for some temperature sensors, metal pipes whose heat resistances to the temperatures to which they are exposed are excessively large can be used. Metal pipes formed of a material having high heat resistance have a problem of high cost. Since all the temperature sensors have metal pipes made of the same material, there is a problem that it is not easy to distinguish the temperature sensors from each other.Accordingly, it is desired that each temperature sensor in such a multi-channel temperature measuring device comprises a metal tube formed of a material appropriately selected in accordance with a location where the temperature sensor is disposed.[Means for Solving the Problem]The present invention has been designed to solve the above problem and can be carried out in the following modes.A multi-channel temperature measuring device according to a first mode of the present invention includes a main body part having a plurality of sensor connection parts, and a plurality of temperature sensors connected to the plurality of sensor connection parts in a one-to-one relationship and each of which includes a temperature sensitive part and a metal pipe including the temperature sensitive part, wherein of the metal pipes of the plurality of temperature sensors, the metal pipe of at least one temperature sensor has a part covering at least the temperature sensitive part and is formed of a material different from a material used to form respective parts of the metal pipes of the remaining temperature sensors, the parts covering at least the respective temperature sensitive parts.In the multi-channel temperature measuring device according to the first mode, a part of the metal pipe of at least one temperature sensor of the plurality of temperature sensors, the part covering at least the temperature sensitive part, is formed of a material different from a material used to form respective parts of the metal pipes of the remaining temperature sensors, the parts covering at least the respective temperature sensitive parts. Therefore, each temperature sensor may comprise a metal tube formed of a material suitably selected according to the location at which the temperature sensor is disposed.In the multi-channel temperature measuring device according to the first mode, the plurality of temperature sensors may have distinguishing features at least for distinguishing the at least one temperature sensor from the remaining temperature sensors. In this case, it becomes easier to distinguish the at least one temperature sensor from the other temperature sensors.In the multi-channel temperature measuring device according to the first mode, each of the distinguishing features may be at least one of the emissivity of the metal tube, the length of the metal tube, the shape of the metal tube, or a mark attached to the temperature sensor. In this case, the distinguishing characteristics of the temperature sensors can be easily distinguished.In the multi-channel temperature measuring device according to the first mode, the at least one temperature sensor may employ a different measurement scheme than the remaining temperature sensors. In this case, the measurement schemes of the temperature sensors can be distinguished.In the multi-channel temperature measuring device according to the first mode, only the at least one temperature sensor may be detachably connected to the corresponding sensor connection part. In this case, the at least one temperature sensor may be replaced, and erroneous connection with other sensor connection parts may be prevented.Exemplary embodiments of the invention are explained below with reference to figures. The following shows: FIG. 1 is an explanatory view showing the configuration of a multi-channel temperature measuring device according to a first embodiment; FIG. 2 is an explanatory view schematically showing the internal structure of a temperature sensor of the multi-channel temperature measuring device according to the first embodiment; FIG. 3 is a block diagram showing the internal functional configuration of a main body part of the multi-channel temperature measuring device; FIG. 4 is an explanatory view showing only temperature sensors of a multi-channel temperature measuring device according to a second embodiment; FIG. 5 is an explanatory view showing only temperature sensors of a multi-channel temperature measuring device according to a third embodiment.First Embodiment:A mode of the multi-channel temperature measuring device according to the present invention will be described while considering a multi-channel temperature measuring device to which four temperature sensors are connected as an example. FIG. 1 is an explanatory view showing the configuration of a multi-channel temperature measurement device according to a first embodiment. Namely, the number of temperature sensors may be two, three, five or more.The multi-channel temperature measuring device MS includes first, second, third and fourth temperature sensors TS 1, TS 2, TS 3 and TS 4 and a main body part 50. the temperature sensors TS 1 to TS 4 are connected to the main body part 50 through lead wires 30 a, 30 b, 30 cand 30 din a one-to-one relationship. The lead wires 30 ato 30 dare each composed of, for example, a pair of lead wires, and have respective connectors 35 a, 35 b, 35 c, and 35 dthat can be detachably attached to connection parts of the main body part 50. Therefore, the replacement of the temperature sensors TS 1 to TS 4 is easy. The main body part 50 is connected to an external output part thereof by an external connection cable 60, for example, an engine control unit (ECU) that controls the operation state of an unillustrated internal combustion engine, and transmits signals output from the temperature sensors TS 1 to TS 4 for ECU measurement. The external connection cable 60 includes an ECU-side connector 61, a main body-side connector 62, and two digital signal lines 63.The structure of each temperature sensor will be briefly described with reference to FIGS. 1 and 2. FIG. 2 is an explanatory view schematically showing the internal structure of a temperature sensor of the multi-channel temperature measurement device according to the first embodiment. The first temperature sensor TS 1 includes a metal pipe 10 a, a fixing part 21 a, a screw part 22 a, and a hexagonal nut part 23 a. The second temperature sensor TS 2 includes a metal pipe 10 b, a fixing part 21 b, a screw part 22 b, and a hexagonal nut part 23 b. The third temperature sensor TS 3 includes a metal pipe 10 c, a fixing part 21 c, a screw part 22 c, and a hexagonal nut part 23 c. The fourth temperature sensor TS 4 includes a metal pipe 10 d, a fixing part 21 d, a screw part 22 d, and a hexagonal nut part 23 d.Hereinafter, the first temperature sensor TS 1 will be described as a representative example, and the description of the second to fourth temperature sensors TS 2 to TS 4 will be omitted. Namely, the second to fourth temperature sensors TS2 to TS4 have the same structure as the first temperature sensor TS1, except that they do not have a part 11a of other material.The metal tube 10a is in the form of a bottomed tube having a hemispherical closed distal end and an open proximal end. The metal pipe 10 aincludes a temperature measurement connection point 12 a( 12 b, 12 c, 12 d) provided at the distal end and serving as a temperature sensitive part, and a pair of thermocouple wires 131 aand 132 a, the ends (distal ends) of which are joined together at the temperature measurement connection point 12 a. An inorganic insulating powder such as magnesium oxide is filled in the space between the thermocouple wires 131a and 132a and the metal pipe 10a. Therefore, in the first embodiment, the first temperature sensor TS 1 is a sheath thermocouple of the non-grounding type, and the metal tube 10 ais also called a "sheath tube". The junction of thermocouple wires 131 aand 132 amay be the junction of thermocouple wires of a B thermocouple, an R thermocouple, an S thermocouple, an N thermocouple, a K thermocouple, an E thermocouple, a J thermocouple, or a T thermocouple. The fastening part 21 a, the screw part 22 a, and the hexagonal nut part 23 ahave a through hole 20 a. Inside the through hole 20a, the thermocouple wires 131a and 132a are connected to the lead wire 30a through compensation contact points. A connector or a connection block may be used for connection between the thermocouple wires 131 aand 132 aand the lead wire 30 a. In the case where a thermocouple is used for temperature measurement, compensating conductors are used for the lead wire 30a. The compensating conductors are conductors formed of the same materials as the thermocouple (thermocouple wires 131a and 132a) or have thermal voltage characteristics very similar to the thermocouple.The metal pipe 10a may be formed of any of Fe-based alloys including stainless steels such as SUS303, SUS304, SUS310S, SUS316, SUSXM7, and SUS430, an alloy containing an alloy based on Fe and Al in an amount of w i= 0,1 % or more including Fe-Cr-Al alloy (product name Kanthal, HCF), Ni-based alloys such as NCF600, NCF601, NCF617, NCF625, NCF718, and NCFX750, and Cr-based alloys such as Cr-W-Ti alloy (product name Kurimax). The Fe-based alloys have a heat resistance of below 1000° C. The alloy containing an Fe and Al (w i= 0,1 % or more) based alloy, the Ni based alloys, and the Cr based alloys have a heat resistance of 1000° C. or higher. In the present embodiment, the metal pipe 10 ais formed of stainless steel, and the other material part 11 ais formed of any one of the Ni-based alloys, the Cr-based alloys, and the alloy containing an alloy based on Fe and Al (w i= 0,1 % or more). Generally, a part of the temperature sensor exposed to a high temperature is a part located in the middle of a flow of a fluid, i.e., the temperature sensitive part. In view of this, in the present embodiment, the metal pipe 10 ais used which has a part 11 aof other material formed of an alloy having high heat resistance and which covers the temperature measurement connection point 12 aserving as the temperature sensitive part. In the present embodiment, the temperature measurement connection point 12 ais located near the distal end (i.e., the semi-spherical sealing part) of the metal pipe 10 a, and the other material part 11 ais disposed on the distal end side of the metal pipe 10 a. More specifically, the other material part 11 ais also in the form of a tube having a hemispherical bottom, and is joined to the metal tube 10 ain place of a distal end part of the metal tube 10 aby welding or the like. Namely, the metal pipe 10a also functions as a protective pipe to protect the temperature measurement connection point 12a and the thermocouple wires 131a and 132a.The metal pipes 10 bto 10 dof the second to fourth temperature sensors TS 2 to TS 4 are formed of stainless steel.The first temperature sensor TS 1 is disposed, for example, on at least one of the inlet or outlet sides of a compressor (exhaust turbine type compressor) where the temperature of the exhaust gas to be measured becomes high. Each of the second to fourth temperature sensors TS2 to TS4 is disposed, for example, on at least one of the inlet and outlet sides of a device such as an exhaust catalyst unit, an EGR cooler or a DPF disposed in an exhaust pipe and where the exhaust gas temperature does not become as high as compared with the inlet and outlet sides of the compressor. Namely, the high temperature in the present embodiment refers to a temperature equal to or higher than 1000° C.The internal functional configuration of the main body part will be described with reference to FIG. 3. FIG. 3 is a block diagram showing the internal functional configuration of a main body part of the multi-channel temperature measuring device. The main body part 50 includes a control circuit 51, first, second, third, and fourth signal input circuits 52 a, 52 b, 52 c, and 52 d, an input-output interface 53, and a power supply circuit 54.The signal input circuits 52 a, 52 b, 52 c, and 52 dreceptor the thermal voltages (voltages) output from the temperature sensors TS 1, TS 2, TS 3, and TS 4, convert them into temperature signals, and output the temperature signals to the control circuit 51. The first, second, third, and fourth signal input circuits 52 a, 52 b, 52 c, and 52 dhave first, second, third, and fourth connection terminals 521 a, 521 b, 521 c, and 521 d, respectively, serving as sensor connection parts. As shown in FIG. 1, the connector 35 aof the first temperature sensor TS 1 is connected to the first connection terminal 521 aof the first signal input circuit 52 a. The connector 35 bof the second temperature sensor TS 2 is connected to the second connection terminal 521 bof the second signal input circuit 52 b. The connector 35 cof the third temperature sensor TS 3 is connected to the third connection terminal 521 cof the third signal input circuit 52 c. The connector 35 dof the fourth temperature sensor TS 4 is connected to the fourth connection terminal 521 dof the fourth signal input circuit 52 d.The control circuit 51 includes an unillustrated CPU (main processor), unillustrated memories, and an unillustrated input-output interface connected to each other so as to be capable of communicating with each other. The control circuit 51 converts the temperature signals received from the first to fourth signal input circuits 52 ato 52 dinto digital signals, and outputs the digital signals to the input-output interface 53. Further, the control circuit 51 selectively outputs a temperature signal from a measurement point (temperature sensor) designated by the ECU to the input-output interface. Namely, the control circuit 51 may perform frame generation in accordance with a communication protocol required for communications with the ECU not illustrated.The input-output interface 53 includes a communication connection terminal 531. As shown in FIG. 1, the connector 62 on the main body side of the outside connection cable 60 is connected to the communication connection terminal 531.The power supply circuit 54 receives DC electric power from an external power source and transforms the voltage of the DC electric power downward into a voltage suitable for operation of the control circuit 51. The power supply circuit 54 includes a power connection terminal 541 and is connected to the external power source through a power supply cable not illustrated.In the above-described multi-channel temperature measuring device MS according to the first embodiment, the other material part 11 aof which heat resistance is high is provided on the metal pipe 10 aof the first temperature sensor TS 1 disposed on the exhaust pipe at a location where the temperature of the exhaust gas is higher than other locations, and the other material part 11 aof which heat resistance is high is not provided on the metal pipes 10 bto 10 dof the second to fourth temperature sensors TS 2 to TS 4 disposed on the exhaust pipe at locations where the temperature of the exhaust gas is lower than the location where the first temperature sensor TS 1 is disposed. Therefore, each temperature sensor may comprise a metal tube formed of a material suitably selected according to the location at which the temperature sensor is disposed. As a result, in the multi-channel temperature measuring device, it is not necessary that the metal pipe formed of a material having high heat resistance selected for high exhaust gas temperature is used for all the temperature sensors. Therefore, reduction in cost increase caused by using a material having high heat resistance and required performance can be realized simultaneously.In the above-described multi-channel temperature measuring device MS according to the first embodiment, the first temperature sensor TS 1 includes the part 11 aof material other than a part of the metal pipe 10 a. Namely, a material having high heat resistance, which is expensive, is used only for a part of the metal pipe 10a whose part must have higher heat resistance or a part of the metal pipe 10a whose part must have the highest heat resistance. Therefore, reduction in cost of the multi-channel temperature measuring device and required performance can be realized simultaneously.Since the metal pipe 10a of the first temperature sensor TS1 disposed on the exhaust pipe at a position where the temperature of the exhaust gas is higher than other positions has the part 11a of other material, the metal pipe 10a of the temperature sensor TS1 can be easily distinguished from the metal pipes 10b to 10d of the second to fourth temperature sensors TS2 to TS4 on the basis of their external appearance, for example, their colors and / or the degree of their luster. Accordingly, when the multi-channel temperature measuring device MS is implemented, it is possible to avoid occurrence of a situation in which, due to confusion of the first temperature sensor TS 1 with the second to fourth temperature sensors TS 2 to TS 4, the second to fourth temperature sensors TS 2 to TS 4 are disposed at the location where high heat resistance is required.Second Embodiment:A multi-channel temperature measuring device MS 2 according to a second embodiment will be described with reference to FIG. 4. FIG. 4 is an explanatory view showing only the temperature sensors of the multi-channel temperature measuring device according to the second embodiment. The multi-channel temperature measuring device MS 2 according to the second embodiment is different from the multi-channel temperature measuring device MS according to the first embodiment in that the length (tube length) of the metal tube 10 xof the first temperature sensor TS 1 xis smaller than the tube lengths of the metal tubes 10 bto 10 dof the second to fourth temperature sensors TS 2 to TS 4, and in that the metal tube 10 xincludes a part 11 xof other material treated with an emissivity increasing treatment. Since the remaining structure of the first temperature sensor TS 1 xand the structures of the second to fourth temperature sensors TS 2 to TS 4 are the same as those in the multi-channel temperature measuring device MS according to the first embodiment, their constituent elements are denoted by reference numerals identical to those used in the first embodiment, and their descriptions are not repeated.Namely, in the multi-channel temperature measuring device MS2 according to the second embodiment, in order to allow the first temperature sensor TS1x to be distinguished from the second to fourth temperature sensors TS2 to TS4, the first sensor TS1x has a distinguishing feature: the tube length of the metal tube 10x of the first temperature sensor TS1x is shorter than the tube lengths of the metal tubes 10b to 10d of the second to fourth temperature sensors TS2 to TS4.Also, the other material part 11 xof the metal pipe 10 xof the first temperature sensor TS 1 xis treated with an emissivity enhancing treatment. This is another distinguishing feature of the first temperature sensor TS1x. The emissivity enhancing treatment may be performed, for example, by coating the other material part 11 xwith black ceramic. The imparted emissivity is, for example, 0.43 or more, preferably 0.58 or more, and more preferably 0.66 or more. As a result of the emissivity enhancing treatment, the color (hue) of the material surface changes to a dark color or black. Accordingly, the part treated with the emissivity increasing treatment may function as a distinctive feature that allows the first temperature sensor TS 1 xcomprising the part 11 xmade of another material treated with the emissivity increasing treatment to be distinguished from the second to fourth temperature sensors TS 2 to TS 4. The black ceramic coating can be performed by any of various methods such as a thermal spraying method, a spraying method, and a dip coating method. Namely, the emissivity enhancing treatment may be performed by heat treating the other material part 11 x. The heat treatment may be performed by any method known to those skilled in the art.In the multi-channel temperature measuring device MS 2 according to the second embodiment, even in the case where the other material part 11 xhas a color approximately the same as the colors of the metal pipes 10 xand 10 bto 10 d, the first temperature sensor TS 1 xcan be easily distinguished from the second to fourth temperature sensors TS 2 to TS 4 on the basis of its pipe length or the emissivity increasing treatment. Also, in the multi-channel temperature measuring device MS 2 according to the second embodiment, even in the case where the other material part 11 xhas a color different from the colors of the metal pipes 10 xand 10 bto 10 d, the first temperature sensor TS 1 xcan be more easily distinguished from the second to fourth temperature sensors TS 2 to TS 4 on the basis of its pipe length or the emissivity increasing treatment.In the multi-channel temperature measuring device MS 2 according to the second embodiment, since the other material part 11 xhas been treated with the emissivity increasing treatment, a change in emissivity due to the use over a long period of time can be suppressed or prevented. Particularly, in the case where the other material part 11 xhas not been treated with the emissivity increasing treatment, when the temperature sensor TS 1 xis used in a high temperature environment, for example, used for measuring the temperature of a supercharger, the other material part 11 xis subjected to a treatment similar to the emissivity increasing treatment caused by heat treatment, and as a result, the emissivity of the other material part 11 xincreases. As a result, the heat absorption ratio of the temperature sensor increases from an initial value, whereby temperature drift occurs. On the other hand, in the multi-channel temperature measuring device MS 2 according to the second embodiment, temperature drift due to the use over a long period of time can be suppressed or prevented because the emissivity increasing treatment is performed from the beginning. Specifically, a thermocouple-type temperature sensor is less affected by a reducing atmosphere than a thermistor element-type temperature sensor. Therefore, in many cases, an oxide film forming treatment is not performed for a distal end portion of the metal pipe. Accordingly, there arises a problem that, as described above, the emissivity increases and temperature drift occurs due to use in a high temperature environment.Namely, in the second embodiment, the pipe length of the metal pipe 10 xof the first temperature sensor TS 1 xmay be larger than the pipe length of the metal pipes 10 bto 10 dof the second to fourth temperature sensors TS 2 to TS 4. Also, not only the pipe length of the metal pipe 10 xof the first temperature sensor TS 1 xbut also the pipe length of, for example, the metal pipe 10 bof the second temperature sensor TS 2 may be smaller than or larger than the pipe length of the metal pipes 10 cand 10 dof the third and fourth temperature sensors TS 3 and TS 4. Namely, in the plurality of temperature sensors provided in the multi-channel temperature measuring device MS 2 according to the second embodiment, the lengths of the metal pipes of two or more temperature sensors may be different from the lengths of the metal pipes of the remaining temperature sensors. Namely, the difference in pipe length between the metal pipe 10 xand the metal pipes 10 bto 10 dmay be considered as a shape difference. In the case where the metal pipe 10 xdiffers from the metal pipes 10 bto 10 din shape-bound feature other than length, the shape-bound feature can be used as a distinguishing feature.Third Embodiment:A multi-channel temperature measuring device MS 3 according to a third embodiment will be described with reference to FIG. 5. FIG. 5 is an explanatory view showing only the temperature sensors of the multi-channel temperature measuring device according to the third embodiment. The multi-channel temperature measuring device MS 3 according to the third embodiment is different from the multi-channel temperature measuring device MS according to the first embodiment in that the entirety of a metal pipe 10 aof the first temperature sensor TS 1 is formed of another material, i.e., a part 11 aof another material extends over the entire length of the metal pipe 10 a, and in that marks 24 a, 24 b, 24 c, and 24 dfor distinguishing the first to fourth temperature sensors TS 1, TS 2, TS 3, and TS 4 from each other are provided on the hexagonal nut parts 23 a, 23 b, 23 c, and 23 dof the first to fourth temperature sensors TS 1, TS 2, TS 3, and TS 4. Since the remaining structure of the multi-channel temperature measuring device MS 3 according to the third embodiment is the same as the multi-channel temperature measuring device MS according to the first embodiment, constituent elements thereof are denoted by reference numerals identical to those used in the first embodiment, and descriptions thereof are not repeated.In the multi-channel temperature measuring device MS3 according to the third embodiment, the temperature sensors TS1 to TS4 have the marks 24a, 24b, 24c and 24d provided on the hexagonal nut parts 23a, 23b, 23c and 23d as a distinguishing feature for distinguishing the temperature sensors TS1 to TS4 from each other, namely, as a distinguishing feature also functioning as a distinguishing feature for distinguishing the first temperature sensor TS1 from the second to fourth temperature sensors TS2 to TS4.In the multi-channel temperature measuring device MS3 according to the third embodiment, even in the case where the other material part 11a has a color approximately the same as the colors of the metal pipes 10b to 10d, the first temperature sensor TS1 can be easily distinguished from the second to fourth temperature sensors TS2 to TS4 on the basis of the marks 24a to 24d, and further, the first to fourth temperature sensors TS1 to TS4 can be easily distinguished from each other. Also, in the multi-channel temperature measuring device MS 3 according to the third embodiment, even in the case where the other material part 11 ahas a color different from the colors of the metal pipes 10 bto 10 d, the first temperature sensor TS 1 can be more easily distinguished from the second to fourth temperature sensors TS 2 to TS 4 on the basis of the marks 24 ato 24 d, and further, the first to fourth temperature sensors TS 1 to TS 4 can be more easily distinguished from each other.In the multi-channel temperature measuring device MS 3 according to the third embodiment, the marks 24 ato 24 dmay be numerals, letters, patterns, or colors. In the example shown in FIG. 5, the marks 24 ato 24 dare provided on the side surfaces of the hexagonal nut parts 23 ato 23 dfor easy recognition. However, the marks 24 ato 24 dmay be provided on the end surfaces of the hexagonal nut parts 23 ato 23 d, or may be provided on the metal pipes 10 ato 10 dor the fastening parts 21 ato 21 d, which are not visible after the fastening. The markers 24 ato 24 dmay be provided on any parts of the temperature sensors TS 1 to TS 4 as long as the markers can prevent erroneous attachment of the temperature sensors TS 1 to TS 4 at the respective attachment locations. The attachment of the marks 24 ato 24 dthat serve as distinguishing features, i.e., the marking, can be performed by any of various methods, such as scribing, laser marking, applying punches, and painting. Namely, marks corresponding to these marks 24 ato 24 dmay be further provided on the main body part 50.Modifications:(1) In the above-described embodiments, the first to fourth temperature sensors TS 1 to TS 4 employ the same temperature measurement scheme, and each of the temperature sensitive parts 12 ato 12 dis a non-contact type sheath thermocouple whose temperature measurement connection point is not in contact with the metal pipe. However, each of the temperature sensitive parts 12 ato 12 dmay be a grounded-type sheath thermocouple in which the distal ends of the thermocouple wires are welded and directly joined to the metal tube, thereby forming the temperature measurement connection point, or an exposed-type sheath thermocouple in which the temperature measurement connection point protrudes from the distal end of the metal tube and is exposed to the outside. Namely, in the case where the sheath thermocouple of the grounded type is used, its performance characteristic may deteriorate as a result of heat treatment. Thus, sufficient heat treatment cannot be performed for the metal pipe. Therefore, the emissivity enhancing treatment is performed by black ceramic coating. In the case where a thermocouple is used as a temperature sensitive part, the thermocouple may be a sheath-type thermocouple in which thermocouple wires are covered with an insulating tube. Further, a thermistor element or a temperature sensing resistor may be provided as a temperature sensitive part. Further, the temperature sensitive parts 12 ato 12 dof the temperature sensors TS 1 to TS 4 may be different from each other, and at least the first temperature sensor TS 1 may be different from the second to fourth temperature sensors TS 2 to TS 4 in the temperature measurement scheme.(2) In the above-described embodiments, the metal pipes 10 ato 10 dare bottomed pipes whose openings have the same diameter. However, each of the metal pipes 10 ato 10 dmay be a hollow pipe whose distal end is closed by a hemispherical cap member, a hollow pipe whose distal end is an open end (has an opening), or a generally triangular pyramid-shaped pipe whose diameter decreases from its open proximal end to its distal end. The metal pipes 10a to 10d may be formed by cutting or drawing.(3) In the above-described embodiments, the lead wires 30 ato 30 dhave the connectors 35 a, 35 b, 35 c, and 35 dthat can be detachably attached to the connection terminals (connection parts) 521 ato 521 dof the main body part 50. However, the connectors 35 a, 35 b, 35 c, and 35 dmay be fixedly attached to the connection terminals 521 ato 521 d. In this case, it is possible to prevent occurrence of a faulty connection between the connectors 35 ato 35 dand the connection terminals 521 ato 521 d. Alternatively, the connector 35 aof the first temperature sensor TS 1 (TSx) may be detachably attached to the connection terminals 521 a, and the connectors 35 bto 35 dof the remaining temperature sensors (i.e., the second to fourth temperature sensors TS 2 to TS 4) may be fixedly attached to the connection terminals 521 bto 521 d. In this case, the first temperature sensor TS 1 (TSx) exposed to the high-temperature exhaust gas can be easily replaced, and erroneous connection with the remaining connection ports 521 bto 521 dmay be prevented.(4) In the above-described embodiments, the control circuit 51 converts the temperature signals input from the first to fourth signal input circuits 52 ato 52 dinto digital signals, and outputs the digital signals to the input-output interface 53. However, in the case where analog signal lines are provided instead of the digital signal lines 63, the control circuit 51 may output the analog signals to the input-output interface without performing analog-to-digital conversion. In this case, the control circuit 51 functions to selectively output, to the input-output interface, the temperature signal from a measurement point (temperature sensor) designated by the ECU.The present invention has been described on the basis of embodiments and modifications. However, the above-described embodiments of the present invention are provided to facilitate understanding of the present invention and do not limit the present invention. The present invention can be modified or improved without departing from the spirit and scope of the invention, and the present invention encompasses its equivalents. For example, in order to partially or completely solve the above-mentioned problem or partially or completely achieve the above-mentioned effects, the technical features of the embodiments and modifications corresponding to the technical features of the modes described in the section "Summary of the Invention" may be replaced or combined as appropriate. Also, the technical feature(s) may be excluded as appropriate unless the present specification mentions that the technical feature(s) is obligatory.In summary, it is an object of the present invention to provide a multi-channel temperature measuring apparatus in which each of the temperature sensors includes a metal tube formed of a material appropriately selected in accordance with a location where the temperature sensor is disposed. To this end, a multi-channel temperature measuring device includes a main body part having a plurality of sensor connection parts and a plurality of temperature sensors connected to the plurality of sensor connection parts and including metal pipes including a temperature sensitive part. Of the metal pipes of the plurality of temperature sensors, the metal pipe of at least one temperature sensor has a part covering at least the temperature sensitive part and formed of a material different from a material used to form respective parts of the metal pipes of the remaining temperature sensors, the parts covering at least the respective temperature sensitive parts.Description of Reference Numerals and Symbols10 a, 10 b, 10 c, 10 d, 10 xmetal pipe 11 a, 11 xpart made of other material 12 atemperature-sensitive part (temperature measurement connection point) 12 b, 12 c, 12 dtemperature-sensitive part 20 athrough hole 21 a, 21 b, 21 c, 21 dmounting part 22 a, 22 b, 22 c, 22 dscrew part 23 a, 23 b, 23 c, 23 dhexagonal nut part 24 a, 24 b, 24 c, 24 dmark 30 a, 30 b, 30 c, 30 dconnection wire 35 a, 35 b, 35 c, 35d connector 50 main body part 51 control circuit 52a first signal input circuit 52b second signal input circuit 52c third signal input circuit 52d fourth signal input circuit 53 input-output interface 54 power supply circuit 60 external connection cable 61 ECU-side connector 62 main body side connector 63 digital signal line 131a, 132a thermocouple wire 521a first connection terminal 521b second connection terminal 521c third connection terminal 521d fourth connection terminal 531 communication connection terminal 541 power connection terminal MS multi-channel temperature measuring device MS2 multi-channel temperature measuring device MS3 multi-channel temperature measuring device TS1, TS1x first temperature sensor TS2 second temperature sensor TS3 third temperature sensor TS4 fourth temperature sensor

Claims

A multi-channel temperature measuring device (MS) comprising: a main body part (50) having a plurality of sensor connection parts (521a to 521d); and a plurality of temperature sensors (TS1 to TS4) connected to the plurality of sensor connection parts (521a to 521d) in a one-to-one relationship and each of which comprises a temperature sensitive part (12a to 12d) and a metal pipe (10a to 10d) including the temperature sensitive part (12a to 12d), wherein, of the metal pipes (10a to 10d) of the plurality of temperature sensors (TS1 to TS4), the metal pipe (10a) of at least one temperature sensor (TS1) has a part (11a) covering at least the temperature sensitive part (12a) and formed of a material, different from a material used to form respective parts of the metal pipes (10b to 10d) of the remaining temperature sensors (TS2 to TS4), the respective parts covering at least the respective temperature sensitive parts (12b to 12d), the at least one temperature sensor (TS1) employing a different measurement scheme than the remaining temperature sensors (TS2 to TS4).The multi-channel temperature measuring device (MS) according to claim 1, wherein the plurality of temperature sensors (TS1 to TS4) have distinguishing features (10a to 10d, 10x, 11x, 24a to 24d) at least for distinguishing the at least one temperature sensor (TS1) from the remaining temperature sensors (TS2 to TS4).The multi-channel temperature measuring device (MS) according to claim 2, wherein each of the distinguishing features (10a to 10d, 24a to 24d) is at least one of the group comprising the emissivity of the metal tube, the length of the metal tube, the shape of the metal tube, and a mark (24a to 24d) attached to the temperature sensor.The multi-channel temperature measuring device (MS) according to any one of claims 1 to 3, wherein only the at least one temperature sensor (TS1, TSx) is detachably connected to the corresponding sensor connection part (521a).

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