Method for manufacturing a sensor of a thermal, flow measuring device for measuring mass flow of a medium in a measuring tube

Abstract

The present disclosure relates to a method for manufacturing a sensor for a thermal, flow measuring device. The method includes, in such case, manufacturing a metal jacketing for a sensor core, introducing the sensor core into the metal jacketing and sintering the metal jacketing with introduced sensor core.

Claims

1. A method for manufacturing a sensor of a thermal, flow measuring device for measuring mass flow of a medium in a measuring tube, the method comprising: manufacturing a metal jacketing using a metal powder injection molding method, wherein the jacketing has a first blind hole, an open first end, and a closed second end; introducing a sensor core into the first blind hole of the jacketing through the open first end, wherein the jacketing completely encloses the sensor core; and sintering the jacketing such that, after sintering, a releasing of the sensor core from the jacketing requires a tensile force of at least 1 Newton, wherein the sensor core includes: a ceramic core having a lateral surface; a metal wire wound around the lateral surface of the ceramic core; and an electrically insulating layer adapted to insulate the metal wire electrically from the jacketing.

2. The method as claimed in claim 1, wherein the jacketing shrinks during the sintering, wherein a cross section of the first blind hole before sintering of the jacketing is greater than a cross section of the sensor core, wherein after sintering of the jacketing the cross section of the first blind hole equals the cross section of the sensor core, and wherein the jacketing after sintering of completely encloses the sensor core and establishes a thermal contact with the sensor core.

3. The method as claimed in claim 1, wherein the metal powder injection molding method uses a metal powder having a grain size less than 6 micrometers.

4. The method as claimed in claim 2, wherein the volume of the jacketing decreases by less than 40% from the sintering after insertion of the sensor core.

5. The method as claimed in claim 1, wherein the ceramic core has a hollow-cylindrical structure having an open third end and an open fourth end, wherein the metal wire is led through the fourth end to the third end, and wherein the third end of the ceramic core faces toward the open first end of the jacketing and the fourth end of the ceramic core faces toward the closed second end of the jacketing.

6. The method as claimed in claim 1, wherein the ceramic core has a hollow-cylindrical structure having an open third end and a fifth end, wherein the ceramic core has in the region of the fifth end a radial bore, wherein the metal wire is led through the radial bore to the third end, and wherein the third end of the ceramic core faces toward the open first end of the jacketing and the fifth end of the ceramic core faces toward the closed second end of the jacketing.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) In the following, the invention will now be explained based on examples of embodiments and the appended drawing, the figures of which show as follows:

(2) FIG. 1 shows a schematic process flow diagram for manufacturing a temperature sensor of the invention.

(3) FIG. 2 shows a schematic cross section of a metal jacketing of the invention with sensor core before and after sintering.

(4) FIG. 3a shows a schematic cross section of a sensor core of the invention according to a first form of embodiment.

(5) FIG. 3b shows a schematic cross section of a sensor core of the invention according to a second form of embodiment.

DETAILED DESCRIPTION

(6) FIG. 1 shows a form of embodiment of the process flow 100 for manufacturing a temperature sensor of the invention. In a first step 101, in such case, a metal jacketing 10 for a sensor core 50, 51 of a sensor 60 for a thermal, flow measuring device is manufactured by means of a metal powder injection molding method. In a second step 102, the sensor core 50, 51 is introduced into the metal jacketing 10. By sintering the metal jacketing 10 in a third step 103 with introduced sensor core 50, 51, the metal jacketing 10 shrinks until it tightly holds the sensor core 50, 51 and assures a good thermal contact. The sensor core can, in such case, only be released from the metal jacketing 10 by tensile forces of at least 1 N.

(7) FIG. 2 shows a form of embodiment of the sensor 60 before and after sintering. FIG. 2a shows the sensor 60 before the sintering, wherein the metal jacketing 10 completely encloses but does not grasp the sensor core 50, 51. A wire 30 is, in such case, led through an open first end 12 of the metal jacketing 10, which forms a blind hole 11, and to an operating electronics, which is adapted to operate the sensor 60. Ideally, the sensor core 50, 51 is in contact with a closed second end 13 of the metal jacketing 10 at the beginning of the sintering. The sintering shrinks the metal jacketing 10, until the inner diameter of the metal jacketing assumes the size of the outer diameter of the sensor core 60; see FIG. 2b.

(8) FIG. 3 shows schematically two forms of embodiment of the sensor core 50, 51 for the invention. FIG. 3a shows a sensor core 50 having a ceramic core 40 having a lateral surface 47. Ceramic core 40 has a hollow-cylindrical structure with an open third end 42 and with an open fourth end 43, wherein the metal wire 30 is led from the lateral surface 47 through the fourth end 43 to the third end 42. FIG. 3b shows a sensor core 51, whose ceramic core 40 in contrast to the form of embodiment shown in FIG. 3a has in the region of the fifth end 44 a radial bore 45, through which the wire 30 is led from the lateral surface to the open third end 42. The fifth end 44 can, in such case, be, instead, a closed end. The winding of the wire 30 around the lateral surface 47 of the ceramic core 50, 51 is concentrated, in such case, in both forms of embodiment in a limited region, in order to bring about a resistance concentration within the region. The sensor 60 can be operated in a number of ways. On the one hand, it can be used for heating a medium flowing around it. On the other hand, it can be used for measuring the temperature of the medium and/or of the sensor. In all cases, a resistance concentration to a limited region is advantageous. Sensor core 50, 51 includes an electrically insulating layer 20, which electrically insulates the wire 30 from the metal jacketing 10, wherein the electrically insulating layer 20 is a ceramic powder or a ceramic paste.