Pressure measuring glow plug

Abstract

Described is a pressure measuring glow plug with a housing, a glow pin, which projects out of the housing and can be displaced in its longitudinal direction relative to the housing against a restoring force. A sensor acquires the position of the glow pin or a pressure acting on the glow pin, and a center pole is arranged in the housing and electrically connected to the glow pin via a contact spring. This disclosure provides that the contact spring is a U-shaped, bent metal strip, which in a middle section has a reduced width, and broadens from the middle section toward its two ends.

Claims

1. A pressure measuring glow plug, comprising: a housing; a glow pin projecting from the housing and displaceable in a longitudinal direction relative to the housing; a sensor for measuring the position of the glow pin relative to the housing or for measuring pressure acting on the glow pin; and a center pole arranged in the housing and electrically connected to the glow pin via a contact spring; wherein the contact spring is a U-shaped, bent metal strip, the bent metal strip defining a length, a width and a thickness, the length of the bent metal strip extending between two ends with a middle section between the two ends, the width extending perpendicular to the length, and the thickness extending perpendicular to both the length and the width with the thickness being smaller than the width, and wherein the middle section of the bent metal strip has a reduced width, and the width of the bent metal strip broadens from the middle section toward its two ends.

2. The pressure measuring glow plug according to claim 1, wherein the metal strip broadens continuously from the middle section towards its ends.

3. The pressure measuring glow plug according to claim 1, wherein the middle section of the metal strip has an incision or an indentation on both sides.

4. The pressure measuring glow plug according to claim 1, wherein the width of the metal strip in the middle section measures less than of the maximal width of the metal strip.

5. The pressure measuring glow plug according to claim 1, wherein the metal strip has its smallest width in the middle of its U-shaped bend.

6. The pressure measuring glow plug according claim 1, wherein the metal strip is made of sheet metal.

7. The pressure measuring glow plug according to claim 1, wherein the middle section of the metal strip has a minimal width that is at least twice as large as its thickness.

8. The pressure measuring glow plug according to claim 1, wherein the metal strip has two legs, whose end sections face away from the U-shaped bend and are outwardly bent.

9. The pressure measuring glow plug according to claim 8, wherein the outwardly bent end sections taper toward the middle section.

10. The pressure measuring glow plug according to claim 9, wherein the middle section has a constant width.

11. The pressure measuring glow plug according to claim 10, wherein the middle section has a length greater than its width.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 is a schematic view of a pressure measuring glow plug;

(3) FIG. 2 is an embodiment of a contact spring, which electrically connects the glow pin to the center pole of the glow plug;

(4) FIG. 3 is the contact spring shown on FIG. 2 with a radial orientation of the glow plug;

(5) FIG. 4 is an embodiment of a contact spring, which electrically connects the glow pin to the center pole of the glow plug; and

(6) FIG. 5 is a sectional view of a pressure measuring glow plug with the contact spring shown on FIG. 4.

DESCRIPTION

(7) The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.

(8) The glow plug schematically shown on FIGS. 1 and 5 comprises a glow pin 1, which is held in a housing 2 and can move relative to the latter in an axial direction against a restoring force. One end of the glow pin 1 here projects out of the housing 2, while its other end is electrically connected to a center pole 4 arranged in the housing 2 by means of a contact spring 3. The position of the glow pin 1 relative to the housing 2 or the pressure acting on the glow pin 1 is measured by a sensor 5, for example a piezoelectric sensor or a strain gauge.

(9) In a detailed view of the glow plug, FIG. 2 schematically depicts the contact spring 3 with an end section of the center pole 4 and an end section of the glow pin 1. The contact spring 3 is a U-shaped, bent metal strip, which has a reduced width in a middle section 3a and expands from the middle section 3a toward its two ends. In this way, the metal strip forms a spring having two legs, which are moved toward each other by pressure. The legs are connected with each other by the bent middle section 3a of the metal strip, and have outwardly bent end sections 3b.

(10) The metal strip can broaden from the middle section 3a toward its two ends, either continuously or in steps, for example. The metal strip can here broaden in the bend, with which the end sections 3b are outwardly bent.

(11) For example, the metal strip consists of sheet metal, and has its smallest width in the middle section 3a. The metal strip preferably has its minimal width in a bent section that is longer than the minimal width. The minimal width of the metal strip should not be too small, so as to prevent the electrical resistance of the contact spring from becoming so large that resistive heating leads to problems. The middle section of the metal strip preferably has a minimal width that is at least double, preferably at least triple, its thickness. As a rule, it is favorable for the metal strip to have a width measuring less than three fourths, for example less than two thirds, of its maximal width.

(12) FIG. 3 shows the contact spring 3 together with a marking on the glow plug, relative to which the contact spring 3 is mounted with a defined orientation. In the example shown, the marking is designed as a flat surface of an otherwise circular component, wherein a narrow side of the U-shaped, bent metal strip is oriented toward this marking.

(13) FIG. 4 shows another embodiment of a contact spring 3, which only differs from the embodiment shown on FIG. 2 in that the width is additionally reduced in the middle section 3a by bilateral incisions or indentations.

(14) While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

REFERENCE LIST

(15) 1 Glow pin 2 Housing 3 Contact spring 3a Middle section 3b End section 3c Indentation 4 Center pole 5 Sensor 6 Marking