DE102018105182A1 - Chamber candle with piezo pressure sensor - Google Patents

Abstract

The invention relates to a chamber candle 1 for an internal combustion engine, comprising a clamping sleeve 2 with a central axis M, wherein the clamping sleeve 2 has a bottom 21 and a side wall 22, wherein the bottom 21 and the side wall 22 define an inner space 24 of the clamping sleeve 2, an at least partially conductive base body 4 for fixing the chamber candle 1 to a combustion chamber of the internal combustion engine, wherein on the base body 4, a ground electrode 6 is provided which projects into the combustion chamber, wherein the base body 4 is fixed to the clamping sleeve 2, an insulator 3 with a Center electrode 7, which is placed in the inner space 24 and at least indirectly abuts on the base body 4 via a first abutment surface 31 of the insulator 3 projecting in the radial direction to the central axis M and via a second abutment surface 32 of the insulator 3 on the bottom 21 projecting in the radial direction of the central axis M. at least indirectly applied, wherein the insulator 3 in axial Richtu ng the center axis M is mounted between the base body 4 and the clamping sleeve 2, wherein the center electrode 7 is guided through the insulator 3 to the ground electrode 6 and both together form an air link, wherein the insulator 3 is movably mounted in the axial direction and that between the Insulator 3 and the clamping sleeve 2 and / or between the insulator 3 and the base body 4 acting in the axial direction of the central axis M piezoelectric element 5 is provided, wherein an explosion pressure in the combustion chamber via the insulator 3 on the piezoelectric element 5 is transferable and measurable.

Description

The invention relates to a chamber candle for an internal combustion engine, comprising a clamping sleeve with a central axis M wherein the clamping sleeve has a bottom and a side wall, wherein the bottom and the side wall define an interior of the clamping sleeve, an at least partially conductive base body for fixing the chamber candle to a combustion chamber of the internal combustion engine, wherein on the base body a ground electrode is provided which in the Combustion chamber protrudes, wherein the base body is fixed to the clamping sleeve, an insulator having a center electrode, which is placed in the interior and a radial direction to the central axis M projecting first contact surface of the insulator at least indirectly abuts the base body and via a in the radial direction of the central axis M protruding second contact surface of the insulator at the bottom at least indirectly, wherein the insulator in the axial direction of the central axis M is mounted between the base body and the clamping sleeve, wherein the center electrode is guided through the insulator to the ground electrode and together form an air radio link.

To evaluate the combustion pressure of an internal combustion engine, the cylinder head is often drilled. This hole is structurally very complicated, since often quasi cooling water space and oil space must be crossed. Furthermore, separate components are needed. Another option for evaluating the combustion pressure is the preparation of the chamber candle itself.

From the DE 10 2013 109 278 A1 is already known a chamber candle for a gas-powered internal combustion engine. The chamber candle has a ceramic insulator, through which a center electrode is guided, which opens into a pre-chamber formed by a cap and a base body and forms there an air radio link with a ground electrode, which is provided on the base body. For measuring the combustion pressure of the internal combustion engine, a pressure sensor is provided in the prechamber, which is connected via a connecting line, which is guided in the longitudinal direction between a sleeve and the insulator into the prechamber.

Such chamber candles find in normal operation of the internal combustion engine, therefore outside the engine dynamometer no application. The chamber candles on the engine tester thus do not correspond to the chamber candles that are used in normal operation of the internal combustion engine.

The invention has for its object to form a chamber candle and arrange so that a structurally simple and inexpensive design is guaranteed.

The object is achieved according to the invention in that the insulator is mounted movably in the axial direction and that between the insulator and the clamping sleeve and / or between the insulator and the base body in the axial direction of the central axis M acting piezoelectric element is provided, wherein an explosion pressure in the combustion chamber via the insulator on the piezoelectric element can be transmitted and measured. The insulator is movable in the sense that the generated by the combustion pressure axial force of the insulator can be at least partially absorbed by the piezoelectric element. In the fixed state of the base body and clamping sleeve in particular a relative axial movement between the base body and the clamping sleeve is not possible. The piezo element is placed between the ferrule and the insulator and slightly biased. As the combustion pressure increases, the axial force to be absorbed by the piezoelectric element increases, so that the combustion pressure is determined. On a storage of the piezoelectric element under bias could be dispensed with in relation to this pressure measurement. In particular, however, if the piezoelectric element is arranged between the insulator and the main body, the piezoelectric element must be under axially acting bias, so that the cylinder pressure, thus the combustion pressure on the decrease of the pressure resulting from the bias is detected.

The piezoelectric pressure sensor can also be used in the sense of a vibration sensor. Thus, it is possible to use the piezo element for knock detection. The evaluation of the pressure sensor data differs from the combustion pressure measurement in that a Fast Hartley transformation with adapted frequency filter is to be performed.

The fixing between the body and the clamping sleeve can be solvable. A releasable connection according to the invention is not a material connection such as welding or gluing. Rather, releasable connections in the context of the invention are positive connections, as they are achieved in particular by screwing or non-positive connections, in particular by clamping.

Due to the optional detachable connection, the piezoelectric element can be easily replaced by a cheaper dummyring, which is used in normal operation of the chamber candle. In this way costs are saved. The wiring that is needed to connect the piezoelectric element, in particular be led out of the clamping sleeve along the insulator.

Furthermore, it may be advantageous if the base body is connected to the clamping sleeve at an end region of the side wall of the clamping sleeve opposite the bottom. With such a simple design, the chamber candle is correspondingly compact and easy to install, especially with regard to the assembly of the piezoelectric element.

It may also be advantageous for this purpose if the main body has a cap which together with the base body for forming an antechamber, wherein the cap has at least one opening through which the mixture to be ignited between the prechamber and the combustion chamber outside the antechamber is interchangeable wherein the ground electrode and the center electrode protrude into the prechamber. The chamber optimizes the ignition process to the effect that it prevents an output of the mixture to be ignited due to the gas movement in the cylinder and thus comparable conditions exist for each ignition.

• 1 eine Schnittdarstellung der Kammerkerze mit Piezoelement;
• 2 eine Schnittdarstellung der Kammerkerze mit Piezoelement an alternativer Position.

It shows:

• 1 a sectional view of the chamber candle with piezoelectric element;
• 2 a sectional view of the chamber candle with piezoelectric element in alternative position.

To 1 has a chamber candle 1 a clamping sleeve 2 with a central axis M , an insulator 3 and a metallic base body 4 on. The clamping sleeve 2 is formed from a soil 21 with a bottom opening 23 and a side wall 22 , The floor 21 and the side wall 22 form an interior 24 ,

In the interior 24 is the insulator 3 placed. The insulator 3 is substantially cylindrical and has an upper portion 33 , a middle area 34 and a lower area 35 on. The upper area 33 is through the bottom opening 23 led, whereby the middle range 34 from the side wall 22 is surrounded and the lower area 35 into the main body 4 is guided. The diameter of the middle area 34 is larger than the diameter of the upper area 33 and the lower part 35 , whereby a lower shoulder 31 or an upper shoulder 32 are formed. This results in the formation of an axial direction to the central axis M extending first contact surface 31 and a correspondingly extending second contact surface 32 , In addition, a piezoelectric element 5 provided that between the shoulder 32 and the floor 21 is placed. The clamping sleeve 2 is at the body 4 set. The first contact surface 31 or shoulder 31 of the insulator 3 lies on the body 4 on. The second contact surface 32 or shoulder 32 lies directly on a piezoelectric element 5 and indirectly via the piezoelectric element 5 on the ground 21 the clamping sleeve 2 on. This is the insulator 3 in the axial direction to the central axis M axially tensioned. Inside the clamping sleeve 2 is the insulator 3 movably mounted, so that one on the insulator 3 acting axial force on the piezo element 5 is derivable.

At the base body 4 is a cap 8th provided, together with the main body 4 an antechamber 82 limited. This cap 8th has openings 81 on, through which a mixture to be ignited in the antechamber 82 arrives. Furthermore, the main body 4 a ground electrode 6 on that in the antechamber 82 is placed. This ground electrode 6 forms with a center electrode 7 , which also in the antechamber 82 opens, an air radio link.

The embodiment according to 2 is essentially the same 1 , However, here is the piezo element 5 between the first contact surface 31 or the lower shoulder 31 and the body 4 intended. The insulator 3 as well as the piezo element 5 are under pretension between the clamping sleeve 2 and the main body 4 clamped. The bias of the piezoelectric element 5 decreases in proportion to the axial force due to increasing combustion pressure.

LIST OF REFERENCE NUMBERS

1

chamber candle

2

collet

21

ground

22

Side wall

23

bottom opening

24

inner space

25

end

3

insulator

31

first contact surface, lower shoulder

32

second contact surface, upper shoulder

33

upper area

34

middle area

35

lower area

4

body

5

piezo element

6

ground electrode

7

center electrode

8th

cap

81

openings

82

antechamber

M

central axis

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102013109278 A1 [0003]

Claims (3)

A chamber candle (1) for an internal combustion engine, comprising - a clamping sleeve (2) with a central axis M, wherein the clamping sleeve (2) has a bottom (21) and a side wall (22), wherein the bottom (21) and the side wall (22 ) an inner space (24) of the clamping sleeve (2) limit, - an at least partially conductive base body (4) for fixing the chamber candle (1) to a combustion chamber of the internal combustion engine, wherein on the base body (4) a ground electrode (6) is provided, which protrudes into the combustion chamber, wherein the base body (4) on the clamping sleeve (2) is fixed, - an insulator (3) having a center electrode (7), which is placed in the interior (24) and via a radial direction to the central axis M projecting first contact surface (31) of the insulator (3) on the base body (4) at least indirectly and abuts a radially extending in the middle axis M projecting second contact surface (32) of the insulator (3) on the bottom (21) at least indirectly, wherein the insulator ( 3) in the axial direction of the central axis M between the base body (4) and the clamping sleeve (2) is mounted, wherein the center electrode (7) through the insulator (3) to the ground electrode (6) is guided and together form an air radio link, characterized in that the insulator (3) is movably mounted in the axial direction and that between the insulator (3) and the clamping sleeve (2) and / or between the insulator (3) and the base body (4) in the axial direction of the central axis M acting piezoelectric element (5) is provided, wherein an explosion pressure in the combustion chamber via the insulator (3) on the piezoelectric element (5) can be transmitted and measured. Device after Claim 1 , characterized in that the base body (4) at a bottom (21) opposite end portion (25) of the side wall (22) of the clamping sleeve (2) with the clamping sleeve (2) is connected. Device after Claim 1 or 2 , characterized in that the base body (4) has a cap (8) which serves together with the base body (4) for forming an antechamber (82), wherein the cap (8) has at least one opening (81) over which the mixture to be ignited is interchangeable between the prechamber (82) and the combustion chamber area outside the prechamber (82), the ground electrode (6) and the center electrode (7) projecting into the prechamber (82).

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