EP3391484B1

EP3391484B1 - Spark plug

Info

Publication number: EP3391484B1
Application number: EP16806127.3A
Authority: EP
Inventors: Friedrich Schaefer
Original assignee: Caterpillar Energy Solutions GmbH
Current assignee: Caterpillar Energy Solutions GmbH
Priority date: 2015-12-18
Filing date: 2016-12-06
Publication date: 2020-08-05
Anticipated expiration: 2036-12-06
Also published as: WO2017102465A1; ES2825849T3; GB201522418D0; GB2545656A; EP3391484A1

Description

Technical Field

The present disclosure is directed to a spark plug, a cylinder head, a spark plug cylinder head assembly and an internal combustion engine.

Background

In internal combustion engines, spark plugs are used to ignite a fuel air mixture in a combustion chamber. The combustion chamber may be a main combustion chamber defined by a cylinder or a cylinder liner, by a piston arranged reciprocally in the cylinder or in the cylinder liner and a cylinder head. Alternatively or additionally, the combustion chamber may be a pre-combustion chamber with walls extending into the main combustion chamber. The walls may include one or more openings, which allow the fuel air mixture from the main combustion chamber entering the pre-combustion chamber and an ignited fuel air mixture from the pre-combustion chamber to enter the main combustion chamber.
The cylinder head includes a receptacle to hold the spark plug. The receptacle extends from an outer side of the cylinder head to a side of the cylinder head, which faces the combustion chamber. The spark plug is detachably arranged in the receptacle to position an ignition end of the spark plug in the combustion chamber and to seal the receptacle to prevent any fuel, air, exhaust and/or pressure to escape from the combustion chamber.
JP 2006 059588 A refers to a type of spark plug having an exposed single electrode and capable of making it difficult that foreign matters such as combustion gas, soot, and the like invade into a gap between an engine head and a main fitting when the engine head is engaged with the spark plug, at least when an internal combustion engine is operating. As a solution a taper locking part formed on the periphery of the main fitting abuts on a stage portion formed on the inside perimeter of the mounting hole of the engine head. The spark plug is positioned in the mounting hole. A taper locking part formed on the further tip side than the above-mentioned locking part abuts on a stage portion formed in the mounting hole at least when the engine is operating. Although a screw part is not formed on the periphery on the further tip side of the locking part of the main fitting and a gap exists between the periphery and the inside perimeter of the mounting hole of the engine head, the gap is sealed because the locking part abuts on the stage portion.
WO 97/02417 A1 also refers to a spark plug of the type having an exposed single electrode and mounted in a cylinder head in such a manner that its electrode end at least partially protrudes into a combustion chamber. The spark plug is screwed into a sleeve, which functions as a valve means. The sleeve might be in a first position, in which a sealing element, disposed at the sleeve and located closest to the combustion chamber, with a contact surface abuts against a seat in the cylinder head. This provides a seal between the combustion chamber and a chamber, which is formed in the cylinder head and through which the sleeve extends in the above-mentioned position. The sleeve can be arranged in a second position, in which the sealing element abuts with a second contact surface against a second seat in the cylinder head at the end of the chamber remote from the combustion chamber. This means that the chamber has in this position free communication with the combustion chamber and in practice is a part thereof. By moving the sleeve between the first position and the second position, it is therefore possible to provide two different compression ratios in the engine to adapt the engine to different operating conditions.
US 2014/102404 A1 discloses generally spark plugs of the type having a pre-combustion chamber including one or more induction ports in a configuration which achieves flow fields and flow field forces inside the pre-combustion chamber which act to direct flame growth away quenching surface of the pre-combustion chamber.
US20150068489A1 discloses a turbulent jet ignition pre-chamber combustion system for spark ignition engines. The pre-chamber combustion system has a housing to position the pre-chamber in respect to the spark plug and in respect to the cylinder head. The spark plug seals the receptacle by a sealing seat and is connected to the housing by a thread, which is next to the combustion chamber. Such thread may be polluted by soot and combustion residuals due to the combustion in the combustion chamber. This may result in difficulties to remove and/or replace the spark plug.

Summary of the Disclosure

According to one aspect of the present disclosure, a spark plug includes an ignition end and a first protrusion to form a sealing seat between the spark plug and a cylinder head. A sealing lip is arranged between the protrusion and the ignition end. A thread connects the spark plug with a cylinder head. The thread is arranged on the spark plug in the order: thread, protrusion, sealing lip. The spark plug forms a pre-combustion chamber.
According to a second aspect of the present disclosure, a cylinder head includes a receptacle to hold a spark plug as disclosed herein. The cylinder head has a surface inclined to the main axis of the receptacle to form a sealing seat intended to abut to the protrusion of the spark plug.
According to a third aspect of the present disclosure, a cylinder head spark plug assembly comprises a spark plug as disclosed herein and a cylinder head as disclosed herein. The thread of the spark plug meshes with the thread in the receptacle of the cylinder head. The protrusion of the spark plug abuts the inclined surface of the cylinder head. The sealing lip of the spark plug abuts the sealing lip of the cylinder head.
According to a forth aspect of the present disclosure, a combustion engine comprises a cylinder head spark plug assembly as disclosed herein.

Brief Description of the Drawings

The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate exemplary embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. In the drawings:

FIG. 1 is a schematic cross-sectional view of a combustion engine comprising a conventional spark plug;
FIG. 2 is a cross sectional view of a cylinder head - spark plug assembly.

Detailed Description

The following is a detailed description of exemplary embodiments of the present disclosure. The exemplary embodiments described therein and illustrated in the drawings are intended to teach the principles of the present disclosure, enabling those of ordinary skill in the art to implement and use the present disclosure in many different environments and for many different applications. Therefore, the exemplary embodiments are not intended to be, and should not be considered as, a limiting description of the scope of patent protection. Rather, the scope of patent protection shall be defined by the appended claims.
FIG. 1 shows schematically a combustion engine 1 with an engine block 2, a cylinder 3 positioned in the engine block 2 and cylinder head 4. A cylinder liner 5 may be positioned in the cylinder 3 and may define with a top 7 of a piston 8 and the cylinder head 4 a combustion chamber 6. The piston 8 is positioned reciprocating in the cylinder liner 5. The top 7 of the piston 8 is facing the cylinder head 4. At the opposite side 9 of the piston 8, the piston 8 is connected to a piston rod 10. The piston rod 10 extends from the piston 8 to a crank pin 11 connected to a crankshaft 12 of the engine 1.
The cylinder head 4 contains a receptacle 13 to hold a spark plug 14. Starting from an inner side 15 of the cylinder head 4 facing the combustion chamber 6, the receptacle 13 has a round opening 16 facing the combustion chamber 6. Next to the opening 16, a first section of the receptacle 13 forms a sealing lip 17. This sealing lip 17 may have a circular cross-section and may be cylindrical. Alternatively, the sealing lip 17 may have a decreasing diameter in direction of the inner side 15 of the cylinder head 4 resulting in a basic shape of a truncated cone. Adjacent to the sealing lip 17 in the direction towards an outer side 18 of the cylinder head 4 opposite to the inner side 15 is a second section 19 of the receptacle 13. The second section 19 may form a recess and may have a cylindrical shape with a diameter larger than the diameter of the sealing lip 17.
Between the sealing lip 17 and the second section 19 a transitional section 20 may be arranged, where the diameter of the receptacle 13 decreases from the size of the diameter of the sealing lip 17 to the diameter of the second section 19.
Neighboring to the second section 19 of the receptacle 13 is a third section 21, which is defined by a protrusion 22. The third section 21 may have a round cross section and a decreasing diameter in the direction from the outer side 18 of the cylinder head 4 towards the inner side 15 of the cylinder head 4 resulting in a truncated cone like basic shape of the third section 21. The protrusion 22 defining the third section 21 forms a sealing seat 33, to seal the receptacle 13. Sidewalls 23 of the protrusion 22 are inclined in respect to the main axis 24 of the receptacle 13. The sidewalls 23 may define with the main axis an angle α, which may be between 10 and 90 °, especially between 30 and 60°.
A forth section 25 of the receptacle 13 may have a cylindrical shape and a diameter equal to the largest diameter of the third section 21. A thread 36 positioned at the forth section may correspond to a thread 35 at the spark plug 14.
The receptacle 13 may end at the outer side 18 of the cylinder head 4 forming an outer opening 16. The main axis 24 of the receptacle 13 may be normal to the outer side 18 and/or the inner side 15 of the cylinder head 4. The main axis 24 of the receptacle 13 may be parallel to or identical with a main axis 29 of the cylinder 3.
The spark plug 14 has an ignition end 26, which may extend into the combustion chamber 6 and a connection end 30 opposite to the ignition end 26. The spark plug 14 may include at the ignition end 26 at least a phase electrode 27 and a ground electrode 28 for igniting a fuel air mixture in the combustion chamber 6. Additionally or alternatively, the spark plug 14 may include several electrodes, a laser or similar means for igniting the fuel air mixture.
The spark plug 14 has near the ignition end 26 a sealing lip 31 which may have a round cross section and an outer diameter corresponding to the inner diameter of the sealing lip 17 of the receptacle 13. Such sealing lip 31 of the spark plug 14 may have a constant diameter and a cylindrical shape or may have a diameter, which decreases in direction to the ignition end 26.
The spark plug 14 may be provided with a recess 32 adjacent to the sealing lip 31 of the spark plug 14 in direction to the connection end 30 of the spark plug 14. The recess 32 of the spark plug may be cylindrical and have a smaller outer diameter as the sealing lip 31. The diameter of the spark plug 14 at the recess 32 may be also smaller than the diameter of the corresponding section 19 of the receptacle 13. Between the sealing lip 31 of the spark plug 14 and the recess 32 of the spark plug 14 a transition section 51 may be arranged, where the outer diameter of the spark plug 14 increases from the diameter of the recess 32 to the diameter of the sealing lip 31.
Next to the recess 32 may be a protrusion 50 of the spark plug 14 with a round cross-section. At such protrusion 50, the spark plug diameter increases steadily from the diameter of the recess 32 to a diameter of an end section, which is next to the connection end 30. The end section may include a thread 35 which correspond to the thread 36 at the receptacle 13.
FIG. 2 discloses a cylinder head- spark plug assembly 54 with the cylinder head 4 and the spark plug 14. The spark plug 14 is detachably positioned in the cylinder head 4. The spark plug 14 includes at the ignition end 26 a pre-combustion chamber 37. The pre-combustion chamber 37 extends to the main combustion chamber 6. Transfer bores 38 at a first end 39 of the pre-combustion chamber 37 may allow to push a fuel air mixture from the main combustion chamber 6 into the pre-combustion chamber 37 and to expel ignited fuel and/or air from the pre-combustion chamber 37 into the main combustion chamber 6.
At another end 40 of the pre-combustion chamber 37 may be a phase electrode 27 and a ground electrode 28 to produce an igniting spark to ignite the fuel air mixture in the pre-combustion chamber 37.
The spark plug 14 has a sealing lip 31 arranged concentric around a main axis 41 of the spark plug 14. A lower side 42 of the sealing lip 31 facing the combustion chamber 6 may be aligned with the inner side 15 of the cylinder head 4. The outer surface 43 of the sealing lip may be aligned with an inner surface 53 of the receptacle 13. The flat outer surface 43 at the sealing lip 31 may be parallel to the main axis 41 of the spark plug 14 or may be inclined to the main axis 41 of the spark plug 14. The sealing lip 31 may have a diameter larger at a first end 44 at the inner side 15 of the cylinder head 4 as at a second end 45 of the sealing lip 31 opposite to the first end 44. At least partly, the diameter 55 of the receptacle 13 is almost equal or slightly larger as the diameter 56 of the spark plug 14 at the sealing lip 31.
Attached to the sealing lip 31 is the transitional section 51 located between the sealing lip 31 and the recess 32. The transitional section 51 may have a rotational symmetric shape in respect to the main axis of the 41 of the spark plug 14. At the transitional section 51 of the spark plug 14 the diameter of the spark plug 14 decreases beginning from the sealing lip 31 in direction towards the recess 32.
The length of the recess 32 of the spark plug 14 may correspond to the length of the recess 19 of the receptacle 13, if the spark plug 14 is mounted in the receptacle 13.
Attached to the recess 32 the sealing seat 33 of the spark plug 14 may be arranged. The sealing seat 33 may consist of first surface 46 normal to the main axis of the spark plug 14 and the second surface 47 which is inclined to the first surface 46 and intended to abut to the sealing seat 33 of the cylinder head 4.
Next to the second surface 47 of the sealing seat 33 of the spark plug 14 third surface 48 is arranged, which may be parallel to the main axis 41 of the spark plug 14. The third surface 48 defines with the walls of the receptacle 13 a second volume 49. Next to this second volume 49, a thread 35 may be arranged to mesh with a thread 36 at the walls 23 of the receptacle 13.

Industrial Applicability

In the following, mounting and dismounting of the spark plug 14 is disclosed. To mount the spark plug 14 in the receptacle 13 the spark plug 14 may be introduced into the receptacle 13 through an opening 52 of the receptacle 13 at the outer side 18 of the cylinder head 4 with the ignition end 26 of the spark plug 14 pointing to in the combustion chamber 6. When the thread 35 of the spark plug 14 meshes with the thread 36 of the receptacle 13, the spark plug 14 is turned until the spark plug 14 is in the intended position and the receptacle 13 is sealed by the sealing lip 17 of the receptacle 13 and the sealing lip 31 of the spark plug 14 and a sealing seat 33 is defined by the spark plug 14 and the receptacle 13. Additionally, the spark plug 14 may be connected to a spark plug control and supply device by connecting a spark plug connector to the upper end of the spark plug 14.
To disassemble the spark plug 14 from the receptacle 13 the steps described above may be executed in the opposite direction.

Claims

A spark plug (14) comprising:
- an ignition end (26);

- a protrusion (50) to form a sealing seat (33) between the spark plug (14) and a cylinder head (4);

- a sealing lip (31) arranged between the protrusion (50) and the ignition end (26);

- a thread (35) to connect the spark plug (14) with the cylinder head (4), where the thread (35) is arranged on the spark plug (14) in the order: thread (35), protrusion (50), sealing lip (31); and
wherein the spark plug (14) forms a pre-combustion chamber (37).
The spark plug (14) of claim 1,
wherein the thread (35) is arranged around the main axis (41) of the spark plug (14).
The spark plug (14) of one of the preceding claims,
wherein the protrusion (50) is arranged around the main axis (41) of the spark plug (14).
The spark plug (14) of one of the preceding claims,
wherein the protrusion (50) has a lower surface (47) which defines with the main axis (41) an angle smaller than 90°.
The spark plug (14) of one of the preceding claims,
wherein a recess (32) is arranged between the protrusion (50) and the sealing lip (31).
The spark plug (14) of the preceding claim 5,
wherein the recess (32) is rotationally symmetric.
The spark plug (14) of one of the preceding claims,
wherein the protrusion (50) is rotationally symmetric.
A cylinder head (4) comprising a receptacle (13) to hold a spark plug (14) of any one of the claims 1-7, wherein the cylinder head (4) has a surface (23) inclined to the main axis (24) of the receptacle (13) to form a sealing seat (33) intended to abut to the protrusion (50) of the spark plug (14).
The cylinder head (4) of the preceding claim 8,
wherein the receptacle (13) comprises a sealing lip (17).
The cylinder head of one of the preceding claims 8 and 9,
wherein the receptacle (13) has an opening (16) open to a combustion chamber (6), where a thread (36) is arranged in the receptacle (13) in the order: thread (35), inclined surface (23), sealing lip (17), opening (16).
A cylinder head spark plug assembly (54) comprising:
- a spark plug (14) of any one of the claims 1 to 7; and

- a cylinder head (4) of any one of claims 8 to 10;
wherein:
the thread (35) of the spark plug (14) meshes with the thread (36) in the receptacle (13) of the cylinder head (4);

the protrusion (50) of the spark plug (14) abuts the inclined surface (23) of the cylinder head (4); and

the sealing lip (31) of the spark plug (14) abuts the sealing lip (17) of the cylinder head (4).
A combustion engine (1) comprising a cylinder head spark plug assembly (54) of claim 11.