DE102018105182B4 - Chamber candle with piezo pressure sensor - Google Patents

Abstract

Chamber candle (1) for an internal combustion engine, comprising a clamping sleeve (2) with a central axis M, the clamping sleeve (2) having a base (21) and a side wall (22), the base (21) and the side wall (22) ) delimit an interior (24) of the clamping sleeve (2), - an at least partially conductive base body (4) for fixing the chamber plug (1) to a combustion chamber of the internal combustion engine, a ground electrode (6) being provided on the base body (4), which protrudes into the combustion chamber, the base body (4) being fixed to the clamping sleeve (2), - an insulator (3) with a central electrode (7), which is placed in the interior (24) and has a radial direction to the central axis M protruding first contact surface (31) of the insulator (3) rests at least indirectly on the base body (4) and at least indirectly rests on the base (21) via a second contact surface (32) of the insulator (3) protruding in the radial direction of the central axis M, wherein the insulator (3) in axial direction respect of the central axis M is mounted between the base body (4) and the clamping sleeve (2), the central electrode (7) being guided through the insulator (3) to the ground electrode (6) and both together forming an air radio path, the insulator ( 3) is mounted movably in the axial direction and that a piezo element (5) acting in the axial direction of the central axis M is provided between the insulator (3) and the clamping sleeve (2) and / or between the insulator (3) and the base body (4) is, wherein an explosion pressure in the combustion chamber can be transmitted and measured via the insulator (3) to the piezo element (5), characterized in that the attachment between the base body (4) and the clamping sleeve (2) is releasable.

Description

The invention relates to a chamber plug for an internal combustion engine, comprising a clamping sleeve with a central axis M, the clamping sleeve having a bottom and a side wall, the bottom and the side wall delimiting an interior of the clamping sleeve, an at least partially conductive base body for fixing the chamber plug on a combustion chamber of the internal combustion engine, wherein a ground electrode is provided on the base body, which protrudes into the combustion chamber, the base body is fixed to the clamping sleeve, an insulator with a center electrode that is placed in the interior and one in the radial direction to the center axis M. protruding first contact surface of the insulator rests at least indirectly on the base body and at least indirectly rests on the ground via a second contact surface of the insulator projecting in the radial direction of the central axis M, the insulator being mounted in the axial direction of the central axis M between the base body and the clamping sleeve t, wherein the center electrode is led through the insulator to the ground electrode and both together form an air radio link, the insulator being mounted movably in the axial direction and that between the insulator and the clamping sleeve and / or between the insulator and the base body an in axial direction Piezo element acting in the direction of the central axis M is provided, an explosion pressure in the combustion chamber being transferable and measurable to the piezo element via the insulator. Such a chamber candle is off, for example DE 102 27 371 A1 known.

The cylinder head is often drilled to evaluate the combustion pressure of an internal combustion engine. This borehole is structurally very complicated, since the cooling water space and the oil space often have to be traversed at the same time. Separate components are also required. Another option for evaluating the combustion pressure is to prepare the chamber candle itself.

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

The DE 31 30 238 A1 and the EP 0 718 612 A2 each disclose a spark plug having a one-piece housing, the insulator and a piezoelectric pressure sensor being provided in the housing.

The DE 102 27 371 A1 discloses a spark plug which is provided with a piezoelectric pressure sensor which is provided together with an insulator in a two-part housing, the housing halves not being detachably connected to one another by notching or welding.

Such chamber plugs are not used in normal operation of the internal combustion engine, therefore outside of the engine test bench. The chamber candles on the engine test bench therefore do not correspond to the chamber candles that are used in normal operation of the internal combustion engine.

The invention is based on the object of designing and arranging a chamber candle in such a way that a structurally simple and inexpensive design is ensured.

The object is achieved according to the invention in that the fixation between the base body and the clamping sleeve can be released. The isolator is movable in the sense that the axial force of the isolator generated by the combustion pressure can be at least partially absorbed by the piezo element. In the fixed state of the base body and the 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 clamping sleeve and the insulator and is slightly preloaded. As the combustion pressure increases, the axial force to be absorbed by the piezo element increases, so that the combustion pressure is determined. With regard to this pressure measurement, it would be possible to dispense with mounting the piezo element under preload. In particular, if the piezo element is arranged between the insulator and the base body, the piezo element must be under axially acting prestress so that the cylinder pressure, and therefore the combustion pressure, can be detected via the decrease in pressure resulting from the prestress.

The piezo pressure sensor can also be used in the sense of a vibration sensor. It is thus possible to use the piezo element for knock detection as well. The evaluation of the pressure sensor data differs from the combustion pressure measurement in that a Fast Hartley transformation must be carried out with an adapted frequency filter.

The fixation between the base body and the clamping sleeve is releasable. A releasable connection within the meaning of the invention is not a material connection such as welding or gluing. Rather, releasable connections within the meaning of the invention are form-fitting connections, as are achieved in particular by screw connections or force-fitting connections, in particular by clamping.

Due to the detachable connection, the piezo element can be easily installed and replaced by a more cost-effective dummy ring that is used in normal operation of the chamber candle. This saves costs. The cabling that is required for connecting the piezo element can in particular be led out of the clamping sleeve along the insulator.

Furthermore, it can be advantageous if the base body is connected to the clamping sleeve at an end region of the side wall of the clamping sleeve which is opposite the bottom. With such a simple design, the chamber candle is correspondingly compact and easy to assemble, in particular with a view to assembling the piezo element.

It can also be advantageous here if the base body has a cap which, together with the base body, serves to form an antechamber, the cap having at least one opening through which the mixture to be ignited can be exchanged between the antechamber and the combustion chamber area outside the antechamber , wherein the ground electrode and the center electrode protrude into the antechamber. The chamber optimizes the ignition process in such a way that it prevents the mixture to be ignited from being driven down 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 piezo element;
• 2 a sectional view of the chamber candle with piezo element in an alternative position.

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

In the interior 24 is the isolator 3 placed. The isolator 3 is essentially cylindrical and has an upper area 33 , a middle area 34 and a lower area 35 on. The upper area 33 is through the bottom opening 23 led, with the middle area 34 from the side wall 22nd is surrounded and the lower area 35 in the main body 4th is led. The diameter of the middle area 34 is larger than the diameter of the top area 33 and the lower area 35 , bringing a lower shoulder 31 or an upper shoulder 32 are trained. This results in the formation of a central axis in the axial direction M. running first contact surface 31 and a correspondingly extending second contact surface 32 . There is also a piezo element 5 provided that between the shoulder 32 and the ground 21 is placed. The clamping sleeve 2 is on the main body 4th fixed. The first contact surface 31 or shoulder 31 of the isolator 3 lies on the main body 4th at. The second contact surface 32 or shoulder 32 lies directly on a piezo element 5 and indirectly via the piezo element 5 on the floor 21 the clamping sleeve 2 at. That’s the isolator 3 in the axial direction to the central axis M. axially clamped. Inside the clamping sleeve 2 is the isolator 3 movably mounted so that one on the isolator 3 acting axial force on the piezo element 5 can be derived.

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

The embodiment according to 2 essentially corresponds to the after 1 . However, here is the piezo element 5 between the first contact surface 31 or the lower shoulder 31 and the main body 4th intended. The isolator 3 as well as the piezo element 5 are under tension between the clamping sleeve 2 and the main body 4th clamped. The bias of the piezo element 5 decreases proportionally to the axial force due to increasing combustion pressure.

List of reference symbols

1

Chamber candle

2

Clamping sleeve

21

ground

22nd

Side wall

23

Bottom opening

24

inner space

25th

End area

3

insulator

31

first contact surface, lower shoulder

32

second contact surface, upper shoulder

33

upper area

34

middle area

35

lower area

4th

Base body

5

Piezo element

6th

Ground electrode

7th

Center electrode

8th

cap

81

openings

82

Antechamber

M.

Central axis

Claims (3)

Chamber candle (1) for an internal combustion engine, comprising - a clamping sleeve (2) with a central axis M, the clamping sleeve (2) having a base (21) and a side wall (22), the base (21) and the side wall (22) ) delimit an interior (24) of the clamping sleeve (2), - an at least partially conductive base body (4) for fixing the chamber plug (1) to a combustion chamber of the internal combustion engine, a ground electrode (6) being provided on the base body (4), which protrudes into the combustion chamber, the base body (4) being fixed to the clamping sleeve (2), - an insulator (3) with a central electrode (7) which is placed in the interior (24) and has a radial direction to the central axis M protruding first contact surface (31) of the insulator (3) rests at least indirectly on the base body (4) and at least indirectly rests on the base (21) via a second contact surface (32) of the insulator (3) protruding in the radial direction of the central axis M, wherein the isolator (3) in an axial direction Direction of the central axis M between the base body (4) and the clamping sleeve (2), the central electrode (7) being guided through the insulator (3) to the ground electrode (6) and both together forming an air radio path, the insulator ( 3) is mounted movably in the axial direction and that a piezo element (5) acting in the axial direction of the central axis M is provided between the insulator (3) and the clamping sleeve (2) and / or between the insulator (3) and the base body (4) wherein an explosion pressure in the combustion chamber can be transmitted and measured to the piezo element (5) via the insulator (3), characterized in that the attachment between the base body (4) and the clamping sleeve (2) is releasable. Chamber candle (1) Claim 1 , characterized in that the base body (4) is connected to the clamping sleeve (2) at an end region (25) of the side wall (22) of the clamping sleeve (2) opposite the bottom (21). Chamber candle (1) Claim 1 or 2 , characterized in that the base body (4) has a cap (8) which, together with the base body (4), serves to form an antechamber (82), the cap (8) having at least one opening (81) through which the mixture to be ignited is exchangeable between the antechamber (82) and the combustion chamber area outside the antechamber (82), the ground electrode (6) and the center electrode (7) protruding into the antechamber (82).

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