GB2632010A

GB2632010A - Water cooled spark plug and spark plug sleeve

Info

Publication number: GB2632010A
Application number: GB2311235.2A
Authority: GB
Inventors: Guisasola Inigo
Original assignee: Caterpillar Energy Solutions GmbH
Current assignee: Caterpillar Energy Solutions GmbH
Priority date: 2023-07-21
Filing date: 2023-07-21
Publication date: 2025-01-22
Also published as: WO2025021311A1; GB202311235D0

Abstract

An insert 22 for a water cooled spark plug sleeve 12 of a combustion engine comprises a longitudinal body having an outer wall 28. The outer wall defines an inner cavity to removably accommodate a spark plug 10. The longitudinal body is movably arranged within the spark plug sleeve between a first position sealing a radial opening 38 of the spark plug sleeve and a second position providing a fluid communication between the radial opening and an end portion 16 of the spark plug. The radial opening may be sealed by a portion of the outer wall in the first position, and the outer wall may comprises a radial through-hole aligned with the radial opening in the second position, where the radial through-hole provides a fluid communication between the radial opening and the inner cavity. The longitudinal body may transition between the first position and the second position by rotation or by longitudinal translation. The longitudinal body may comprise an inner wall 30 connected to the outer wall via a bottom portion of the longitudinal body, the inner wall radially and longitudinally delimiting the inner cavity forming a reservoir 32, where the bottom portion comprises a selectively closable bore 34.

Description

Water cooled spark plug and spark plug sleeve

Technical Field

100011 The present invention pertains to inserts for a spark plug sleeve of a combustion engine as well as a spark plug sleeve comprising such insert. In particular, inserts are suggested to improve a cooling of a spark plug mounted in a spark plug sleeve.

Technological Background

100021 In combustion engines, cooling of the spark plugs is required to avoid overheating. Such cooling is typically enabled by the provision of a coolant, wherein the coolant ensures that generated heat may be dissipated. The coolant, however, is typically not in direct contact with the spark plug to ensure that the spark plug may be removed during overhaul or maintenance for replacement without requiring that the coolant to be removed.

100031 Such indirect cooling is provided by means of a spark plug sleeve, which is mounted in the cylinder head and which is configured to accommodate a spark plug therein. The spark plug sleeve hence provides a liquid barrier for the coolant, but enables that the coolant may surround the spark plug sleeve for the required heat dissipation. Upon removal of the spark plug, it the spark plug sleeve furthermore ensures that the coolant does not inadvertently enter the combustion area.

100041 While the spark plug sleeve hence enables that the spark plug can be replaced without removing the cooling water of the engine, the mounted spark plug does not have a direct contact with the cooling water. The cooling of the spark plug is therefore indirect, for example, through a metal contact to the spark plug sleeve and/or the cylinder head. A disadvantage of this design is that the contact between the spark plug and the spark plug sleeve or the contact between the spark plug and the cylinder head often represents a bottleneck through small contact surfaces, such that the heat transmission or heat flow is not very efficient.

100051 Accordingly, a need exists to further improve the cooling of a spark plug mounted in a spark plug sleeve.

Summary of the invention

100061 Starting from the prior art, it is an objective to provide a new and inventive means to improve the cooling of a spark plug mounted in a spark plug sleeve. In particular, it may be an objective to provide such means without requiring the removal of a coolant prior to a removal of the spark plug.

100071 This objective is solved by means of an insert for a spark plug sleeve of a combustion engine with the features of claim 1. Preferred embodiments are set forth in the present specification, the Figures as well as the dependent claims.

100081 Accordingly, an insert for a spark plug sleeve of a combustion engine is suggested, comprising a longitudinal body having an outer wall, said outer wall defining an inner cavity being configured to removably accommodate a spark plug therein in the mounted state of the insert, wherein the longitudinal body is configured to be movably arranged within the spark plug sleeve between a first position sealing a radial opening of the spark plug sleeve and a second position providing a fluid communication between the radial opening and an end portion of the spark plug in the mounted state of the insert.

100091 Furthermore, a spark plug sleeve for a combustion engine is suggested, which is configured to radially seal a coolant cavity of a cylinder head and comprises a radial opening for providing a fluid communication with the coolant cavity, wherein the spark plug sleeve comprises a corresponding insert according to the invention.

100101 Furthermore, a spark plug system for a combustion engine is suggested, comprising a spark plug sleeve according to the invention and a spark plug which is configured for being removably accommodated within the spark plug sleeve.

[0011] Furthermore, a spark plug for a combustion engine is suggested, having an interface comprising a sliding surface configured for enabling rotational or translational sliding of an insert according to the invention relative to the spark plug.

Brief description of the drawings

[0012] The present disclosure will be more readily appreciated by reference to the following detailed description when being considered in connection with the accompanying drawings in which: [0013] Figure 1 shows a prior art configuration of a spark plug sleeve and an accommodated spark plug; [0014] Figure 2 shows an insert according to the invention having a rotatable configuration; [0015] Figure 3 shows an insert according to the invention having a configuration for longitudinal translation; [0016] Figure 4 shows the reservoir and selective closing of the reservoir of the insert according to Figure 3 in further detail; [0017] Figure 5 shows an insert according to the invention having a configuration for longitudinal translation with a biasing element; and [0018] Figure 6 shows further details of the biasing element and the securing of the insert according to Figure 5.

Detailed description of preferred embodiments

[0019] In the following, the invention will be explained in more detail with reference to the accompanying figures. In the Figures, like elements are denoted by identical reference numerals and repeated description thereof may be omitted in order to avoid redundancies.

[0020] In Figure 1 a prior art configuration of a spark plug sleeve 12 and an accommodated spark plug 10 is shown in a sectional view. At an upper end of the spark plug sleeve 12, an outer thread 14 is provided, which facilitates mounting of the spark plug sleeve 12 within a bore of a cylinder head 18. Details of the cylinder head 18 have been omitted to provide an improved overview of the various components. Furthermore, at a bottom surface of the cylinder head 18 a bore is provided having a thread for providing a threaded engagement with the spark plug 10. Accordingly, in the mounted state of the spark plug sleeve 12 and the spark plug 10, an end portion 16 of the spark plug 10 is brought into proximity of an adjacent combustion area delimited by the cylinder head 18.

[0021] As shown in Figure 1, the spark plug 10 is received within an inner cavity of the spark plug sleeve 12, such that a wall of the spark plug sleeve 12 fully surrounds the spark plug 10. The end portion 16 of the spark plug 10 is hence enclosed by the spark plug sleeve 12 in the mounted state.

[0022] A portion of the spark plug sleeve 12 corresponding to the end portion 16 of the spark plug 10 as well as a portion of the cylinder head 18 being adjacent to the end portion 16 of the spark plug 10 defines a contacting surface 20 for a coolant within an adjacent coolant cavity. Accordingly, the coolant of a coolant system may provide an indirect cooling of the spark plug 10 being accommodated within the spark plug sleeve 12. Due to the continuous structure of the spark plug sleeve 12, the spark plug 10 may be removed and replaced without requiring the coolant from the adjacent coolant cavity to be removed.

[0023] As described above, a disadvantage of the prior art configuration is that only small contacting surfaces are provided, which allow an indirect heat dissipation from the spark plug 10 to the spark plug sleeve 12 and the cylinder head 18 to the adjacent coolant system.

[0024] Therefore, exemplary inserts 22 according to the invention, which may abrogate this disadvantage, are shown in the embodiments depicted in Figures 2 to 6.

[0025] Accordingly, Figure 2 shows an insert 22 in two different states, wherein the insert 22 is accommodated within the spark plug sleeve 12 and continuously interfaces with an inner wall surface of the spark plug sleeve 12 in the circumferential and longitudinal direction. The insert 22 comprises a longitudinal body which is essentially formed by an outer wall defining an inner cavity. Within said inner cavity, the spark plug 10 is accommodated, wherein the spark plug 10 is mounted to the cylinder head 18 via a corresponding bore.

100261 The longitudinal body of the insert 22 extends along the entire height of the spark plug sleeve 12 in a longitudinal direction and is in rotatable engagement with the inner wall surface of the spark plug sleeve 12, such that the entire insert 22 may be rotated along its longitudinal axis within the spark plug sleeve 12. As shown, a portion of the wall of the longitudinal body comprises a radial through-hole 24. In the arrangement depicted in the left, the insert 22 and its longitudinal body are in a first position, wherein the radial through-hole 24 is aligned with a continuous wall portion of the spark plug sleeve 12, such that the inner cavity defined by the wall of the longitudinal body is fluidically sealed.

[0027] Upon rotation of the longitudinal body of the insert 22, the radial through-hole 24 may be brought into alignment with a radial opening of the spark plug sleeve 12, as depicted in the right arrangement. Accordingly, the spark plug sleeve 12 comprises a radial opening towards an adjacent coolant cavity, such that, upon alignment with the radial through-hole 24 of the longitudinal body, a fluid communication between the end portion 16 of the spark plug 10 and the adjacent coolant cavity is provided.

[0028] In the aligned state of the radial through-hole 24, i.e. in the second position of the longitudinal body of the insert 22, the coolant may hence enter the inner cavity and be brought in direct contact with the end portion 16 of the spark plug 10. The coolant is retained in the bottom portion or along the end portion 16 of the spark plug 10 by means of a plurality of sealing rings 26. In addition, the spark plug 10 according to the present non-limiting example comprises a radial extension 52 at the level of the end portion 16 facilitating fluidic sealing, wherein said radial extension also comprises a sealing ring 26 to effectively avoid any coolant from flowing beyond the end portion 16 of the spark plug 10 in the longitudinal direction.

[0029] Specifically, the radial extension 52 provides for an interface comprising a sliding surface 50 configured for enabling rotational sliding of the insert 22 relative to the spark plug 10.

[0030] In Figure 3 another embodiment of an insert 22 is shown having a configuration for longitudinal translation of the longitudinal body. In this embodiment, the longitudinal body comprises no radial through-hole. Instead, the longitudinal body may be translated or displaced in the longitudinal direction, e.g. by means of a sliding engagement with the inner wall surface of the spark plug sleeve 12. Accordingly, when transitioning the insert 22 or longitudinal body thereof from a first position, as depicted in the left arrangement, to a second position, as depicted in the right arrangement, wherein the longitudinal body is moved in an upward direction away from the end portion 16 of the spark plug 10 and the adjacent combustion area, the radial opening 38 of the spark plug sleeve 12 is exposed. Thereby, a fluid communication is provided between the adjacent coolant cavity and the end portion 16 of the spark plug 10.

[0031] As shown, the coolant within the spark plug sleeve 12 is only enclosed by the inner wall surface of the spark plug sleeve 12 in the radial direction, such that the coolant volume may be advantageously increased.

[0032] Furthermore, the longitudinal body is shown in Figure 3 to be formed by an outer wall 28 and an inner wall 30, which are each continuous in the longitudinal direction and circumferential direction and which are radially spaced apart to form a double walled structure defining a reservoir 32. The reservoir 32 is delimited by a bottom portion connecting the inner wall 30 and outer wall, so as to form a fluid tight enclosure that is only open at a top end, i.e. an end facing away from the combustion area.

[0033] Specifically, the spark plug 10 has an interface comprising a sliding surface 50 configured for enabling translational sliding of the insert 22 relative to the spark plug 10. Accordingly, the sliding surface 50 may substantially correspond to the inner wall 30. Hence, the sliding surface 50 may be continuous in the longitudinal direction and circumferential direction.

100341 As shown in the left arrangement of Figure 3, the longitudinal body effectively closes and fluidically seals the radial opening 38 of the spark plug sleeve 12 while the radial opening 38 is exposed and forms a fluid communication, when translating the longitudinal body beyond the radial opening 38 in the longitudinal direction. The longitudinal body is then adjacent to the radial opening 38 or arranged with a longitudinal offset to the end portion 16 of the spark plug 10 and/or the radial opening 38.

100351 In order to enable replacement of the spark plug, the insert 22 needs to be transitioned back into the first position from the second position. To ensure that no residual coolant is present upon removal of the spark plug 10, the bottom portion of the longitudinal body comprises a bore 34, which in the present non-limiting example is selectively closed by a screw 36, as depicted in further detail in Figure 4. Advantageously, said screw 36 may be removed or loosened prior to transitioning the longitudinal body back into the first position. Thereby, by pressing the longitudinal body downward, residual coolant may enter the reservoir 32 via said bore 34, such that the reservoir 32 receives any residual coolant previously being present around the end portion 16 beneath the bottom portion of the longitudinal body.

100361 After replacement of the spark plug 10, the screw 36 may be mounted again so as to close the bore 34 before transitioning the longitudinal body into the second position to ensure proper cooling of the end portion 16 of the spark plug 10 during operation of the combustion engine.

100371 Figure 5 shows an insert 22 being similar to the insert depicted in Figure 3. In this exemplary embodiment, a biasing element 40 has been provided, which is arranged at a predefined position having a longitudinal offset to the end portion 16 of the spark plug 10. The outer wall 28 of the longitudinal body extends along the entire height of the spark plug sleeve 12 and extends along an outer surface of the biasing element 40 while the inner wall 30 is accommodated within a radially inner recess 42 defined by the biasing element 40.

[0038] When transitioning the longitudinal body from the first position, as depicted in the left arrangement, to the second position, depicted in the right arrangement, the biasing element 40 is received within the reservoir 32 and fills the reservoir 32. Thereby, the coolant entering the spark plug sleeve 12 at the level of the end portion 16 of the spark plug 10 may not enter the reservoir 32 via the bore 34, since said bore is closed by the biasing element 40.

[0039] When transitioning the longitudinal body from the second position back into the first position, e.g. to enable replacement of the spark plug 10, the coolant that has entered the spark plug sleeve 12 during operation of the combustion engine enters the reservoir 32 via the bore 34, such that no residual coolant is present upon replacement of the spark plug 10.

[0040] After replacement of the spark plug 10, the longitudinal body is again transitioned into the second position, wherein the biasing element 40 presses the coolant contained within the reservoir 32 out of the reservoir 32 via the bore, such that the coolant may surround the end portion 16 of the spark plug 10 during operation. Accordingly, such configuration may omit a selective closing means of the bore, e.g. a screw or actuatable valve, since the biasing element 40 may provide such function.

[0041] Also shown in the right arrangement of Figure 5, wherein the longitudinal body is arranged in the second position, is that the longitudinal body extends beyond the spark plug sleeve 12 and covers an upper portion of the spark plug 10, as shown in further detail in Figure 6.

[0042] Accordingly, a hexagonal head 44 or other suitable geometry configured for facilitating mounting and removal of the spark plug 10 may be enclosed by the longitudinal body, such that said geometry is not accessible in the second position of the longitudinal body. Thereby, it may be avoided that the hexagonal head 44 is inadvertently actuated while the longitudinal body is arranged in a position, wherein a fluid communication between an adjacent coolant cavity and the end portion 16 of the spark plug 10 is provided. Hence, due to the extension of the longitudinal body, flow of the coolant into the bore of the cylinder head 18 may be effectively avoided.

[0043] Also shown in further detail in Figure 6 are the optional inner thread 46 of the biasing element 40 and the optional outer thread 48 of the longitudinal body, which respectively provide a securing means of the biasing element 40 to the spark plug 10 and of the longitudinal body to the spark plug sleeve 12 in the mounted state.

[0044] It will be obvious for a person skilled in the art that these embodiments and items only depict examples of a plurality of possibilities. Hence, the embodiments shown here should not be understood to form a limitation of these features and configurations. Any possible combination and configuration of the described features can be chosen according to the scope of the invention.

[0045] This is in particular the case with respect to the following optional features which may be combined with some or all embodiments, items and/or features mentioned before in any technically feasible combination.

[0046] An insert for a spark plug sleeve of a combustion engine is provided.

[0047] The insert comprises a longitudinal body having an outer wall, wherein said outer wall defines an inner cavity being configured to removably accommodate a spark plug therein in the mounted state of the insert. The longitudinal body is configured to be movably arranged within the spark plug sleeve between a first position sealing a radial opening of the spark plug sleeve and a second position providing a fluid communication between the radial opening and an end portion of the spark plug in the mounted state of the insert.

[0048] By means of the sleeve, a spark plug mounted therein, e.g. via a threaded engagement with the cylinder head, may hence be effectively cooled. This is because a coolant from an adjacent cavity of the cylinder head may enter the inner cavity in the second position via the radial opening or bore and the provided fluid communication. By directly surrounding the spark plug heat may be effectively removed from the end portion of the spark plug being adjacent to the combustion area and being most susceptible to potential overheating.

[0049] The insert hence provides a locking mechanism for the fluid communication between the first position and the second position and allows the spark plug to come in contact with cooling water system during engine operation. Thereby, the insert can be used for maximizing cooling of the spark plug. At the same time, as will be explained in further detail below, the configuration of the insert may minimize the amount of coolant, e.g. water, being left inside the spark plug sleeve during its replacement.

[0050] The improved cooling of the spark plug provided by the insert advantageously increases the lifetime and proper functioning of the spark plug. Furthermore, the insert may also be advantageously implemented for combustion engines using hydrogen or hydrogen-based fuels, which may require an optimized cooling e.g. to avoid hot spots in the combustion chamber, which may potentially cause a pre-combustion.

[0051] To facilitate heat dissipation, the insert may be formed of a corresponding metal or metal alloy. This also provides a level of material flexibility upon mounting the insert into the spark plug sleeve. Alternatively, the insert may also be formed of a ceramic material exhibiting a similar heat transfer coefficient.

[0052] The outer wall may be configured to contact and/or interface with an inner wall surface of the spark plug sleeve adapted to enclose or surround a spark plug in the mounted state of the insert, wherein the outer wall has an essentially circular cross-section.

[0053] The outer wall may hence be configured to be fitted within a corresponding cavity of the spark plug sleeve while the inner cavity of the insert is configured such that a spark plug may be mounted therein, e.g. via a bottom thread of the cylinder head being exposed and accessible within the inner cavity.

[0054] By means of the provided contact and/or interface, a sealing of the radial opening of the spark plug sleeve may be achieved in the first position, such 1_0 that no fluid communication between an adjacent coolant cavity and the inner cavity of the insert is present. Such sealing may also be provided or be facilitated by means of radial bearings or one or more circumferential sealing rings provided at the outer wall and engaging the inner wall surface of the spark plug sleeve.

[0055] Preferably, a continuous contact is provided in the circumferential and longitudinal direction. Such continuous contact may furthermore reduce the risk of inadvertent tilting of the insert, in particular upon transitioning the insert between the first position and the second position and/or during mounting of the insert into the spark plug sleeve.

[0056] According to an embodiment, the outer wall may be configured to seal the radial opening by a portion of the outer wall in the first position, wherein the outer wall comprises a radial through-hole being arranged to be aligned with the radial opening in the second position.

[0057] The provision of the radial through-hole in the outer wall hence enables that a fluid communication with the radial opening of the spark plug sleeve is provided in the second position, such that a coolant from an adjacent coolant cavity may enter the radial through-hole, if the radial through-hole and the radial opening are aligned.

[0058] The radial through-hole may be advantageously configured to provide a fluid communication between the radial opening and the inner cavity in the second position.

[0059] Hence, a direct cooling of the end portion of the spark plug may be provided, wherein the coolant entering the inner cavity via the radial opening of the spark plug sleeve and the radial through-hole of the outer wall is enclosed by the end portion of the spark plug accommodated within the inner cavity in the mounted state and the outer wall.

[0060] For structural integrity of the insert it may be advantageous to have a single radial through-hole. However, it may also be provided that the outer wall comprises more than one radial through-hole, wherein the radial through-holes are spaced apart from each other in the circumferential direction. Such configuration may e.g. be advantageous, if the adjacent spark plug sleeve also comprises more than one radial opening, wherein the number of and the circumferential spacing between the radial through-holes and the radial openings is preferably approximately identical.

[0061] In this manner, an improved flow of the coolant through the inner cavity may be provided. Depending on the requirements and e.g. the thickness of the outer wall, the radial through-holes may optionally be dimensioned smaller when compared with a single radial through-hole. Such smaller dimensioning still provide a sufficient cooling capacity due to the provision of multiple through-holes and radial openings and the corresponding improved exchange of coolant.

[0062] To facilitate the alignment of the radial through-hole with the radial opening, the longitudinal body may be configured to transition between the first position and the second position by rotation. The longitudinal body may hence be rotated along its longitudinal or central axis, such that a continuous outer wall portion is aligned with the radial opening in the first position and the radial through-hole of the insert is aligned with the radial opening of the spark plug sleeve in the second position.

[0063] In case multiple radial through-holes and radial openings are present, the circumferential extension of the continuous wall portion between adjacent through-holes at least corresponds to the circumferential extension or diameter of the respective through-holes to ensure that the continuous wall portion sufficiently seals the respective radial opening in the first position.

[0064] Hence a rotatable locking mechanism is suggested, which is configured to directly fluidically connect the end portion of the spark plug with the coolant system upon rotation into the second position. Furthermore, it enables a closing of the coolant supply, i.e. an uncoupling of the spark plug to the coolant system, by means of rotation back into the first position for removal and replacement of the spark plug.

[0065] To facilitate removal of the coolant from the inner cavity upon rotating the insert from the second position into the first position, the radial openings in the spark plug sleeve for the connection to the coolant system may be optimized to maximize the cooling of the spark plug and at the same time minimize the amount of water left inside the spark plug sleeve during the replacement of the spark plug. Such configuration may be based e.g. on the positioning of the cylinder heads, typically forming a V-Angle of the engine, wherein the relative angle in the gravitational field and the shape and direction of the radial openings may facilitate that no or at least no significant amount of coolant enters the cylinder head or combustion area during the replacement of the spark plug.

[0066] According to another embodiment the longitudinal body may be configured to transition between the first position and the second position by longitudinal translation.

[0067] The longitudinal body may hence be moved in an up-down manner, i.e. in the direction of its longitudinal axis. The longitudinal body preferably slidably engages an inner wall surface of the spark plug sleeve in the mounted state to provide the longitudinal displacement. Alternatively, a threaded engagement may be provided, e.g. via an outer thread of the outer wall engaging a corresponding thread at the inner wall surface of the spark plug sleeve, wherein a rotational movement of the longitudinal body around its longitudinal axis is translated into a longitudinal displacement corresponding to the threaded engagement.

[0068] To facilitate a fluid communication between the radial opening of the spark plug sleeve and the end portion of the spark plug, the longitudinal body may be configured to be arranged with a longitudinal offset to or adjacent to the end portion of the spark plug in the second position.

[0069] Accordingly, the outer wall of the longitudinal body may be moved upwards in a longitudinal direction, such that the outer wall does not cover the radial opening of the spark plug sleeve. The coolant may hence be enclosed by an inner wall surface of the spark plug sleeve and the spark plug, but not by the outer wall of the longitudinal body. Thereby, a larger volume of coolant may directly surround the end portion of the spark plug in the mounted state and in the second position of the longitudinal body.

100701 By the same token, a wall portion of the outer wall of the longitudinal body may cover the radial opening in the first position to provide a sealing and avoid a fluid communication. In other words, in the first position, a longitudinal offset of at least a portion of the outer wall of the longitudinal body to the radial opening of the spark plug sleeve is not present.

100711 Similar to the above-described rotation, the longitudinal translation of the longitudinal body hence provides an uncoupling and coupling of the spark plug to the coolant system when transitioning between the first position and the second position.

100721 To avoid that the coolant passes beyond the longitudinal body, the coolant may be delimited by a bottom wall portion extending from the outer wall. Accordingly, the bottom wall portion forms a barrier, preventing the coolant from moving in a longitudinal direction beyond the longitudinal body in the second position.

100731 In order to facilitate the removal of the coolant surrounding the end portion of the spark plug when transitioning from the second position to the first position, the longitudinal body may comprise an inner wall connected to the outer wall via a bottom portion of the longitudinal body, wherein the inner wall radially and longitudinally delimits the inner cavity so as to form a reservoir, wherein the bottom portion comprises a bore being selectively closable.

100741 The provision of the reservoir, i.e. the inner cavity being delimited by the outer wall, the bottom portion, and the inner wall, removal of the coolant may be facilitated. In particular, the reservoir may be configured to selectively enable a coolant being in direct contact with the end portion of the spark plug to flow into the reservoir, when the longitudinal body is transitioned from the second position to the first position, i.e. translated from an upper position to a bottom position. To enable fluid entering the reservoir, the bore in the bottom portion may be selectively opened, e.g. when operation of the combustion engine has been terminated and the spark plug is to be removed and/or replaced.

[0075] In the open state of the bore, the fluid below the bottom portion is biased into the reservoir by means of compression, when moving the longitudinal body into the first position. Accordingly, the coolant is retained within the reservoir and the radial opening of the spark plug sleeve is sealed in the first position, such that the spark plug may be removed without fluid entering combustion area.

100761 After replacement of the spark plug, the bore may again be closed, such that the longitudinal body again forms an effective upper barrier for a coolant entering the spark plug sleeve, when the longitudinal body is again translated into the second position. The residual coolant within the reservoir may then e.g. evaporate due to residual heat or heat dissipating towards the spark plug sleeve upon operation of the combustion engine.

100771 The outer wan and inner wall are preferably spaced apart from each other in a radial direction, thereby forming a double wall structure of the reservoir. Furthermore, the outer wall and inner wall each preferably form a continuous surface in the circumferential and longitudinal direction to facilitate the provision of a selectively closeable fluid tight reservoir covering the interior of the spark plug sleeve. Sealing means may be present at the inner wall surface facing the spark plug in the mounted state to facilitate the fluidic sealing in the longitudinal direction in the second position. In this regard, the inner wall may be configured to be in slidable engagement with an outer surface of an adjacent spark plug in the mounted state to facilitate the fluidic sealing.

100781 To facilitate the selective closing and selective opening of the bore the insert may comprise an actuatable valve or screw selectively closing the bore.

[0079] The bore or through-hole may e.g. be closed by means of a one-way valve or check-valve, such that a coolant may e.g. only pass the valve, when the longitudinal body is translated from the second position into the first position and a coolant present beneath the bottom portion is pressed into the reservoir via the valve.

[0080] Alternatively, a screw may be provided, wherein the screw may be removed to enable a coolant entering the reservoir. Such screw may also have a radial through-hole, such that the screw may be in partial engagement with the bore to enable a coolant entering the reservoir without the need to fully remove the screw.

[0081] The reservoir may be open at an end portion of the reservoir longitudinally opposing the bottom portion. Accordingly, an upper or top side of the reservoir may be at least partially open, which may be advantageous to enable manual actuation of the valve or screw by a technician to facilitate the removal of the coolant around the end portion of the spark plug or to avoid coolant from passing beyond the longitudinal body. Furthermore, the opening may facilitate evaporation of residual coolant in the reservoir, when the longitudinal body is arranged in the second position.

[0082] The upper side of the reservoir may also selectively opened, e.g. by the provision of a removable cover and/or mesh. This may be advantageous e.g. to prevent dirt or contaminations entering the reservoir. Although a fluid pathway from the reservoir to the portion beneath the bottom portion is preferably avoided, avoiding any contaminations within the reservoir may e.g. facilitate the long-term translation of the longitudinal body and/or the actuation of the selective closing means of the bore.

[0083] To facilitate the removal of the coolant from the reservoir, the insert may also comprise a biasing element securable to the spark plug and/or secured to the longitudinal body at a position with a predefined longitudinal offset from the end portion of the spark plug, wherein the biasing element is configured to be received by and fill out the reservoir in the second position.

[0084] The biasing element is hence to be understood as a body formed e.g. as a plug or fitting, which is fully accommodated within the reservoir and essentially fills the reservoir in the second position. For example, the biasing element may be dimensioned so as to form a slidable engagement with the inner surface of the reservoir, i.e. the inner surface of the outer wall and the inner wall.

[0085] Accordingly, any coolant that has entered the reservoir upon transitioning the longitudinal body from the second position into the first position is pressed out of the reservoir via the bore by means of the biasing element, when the longitudinal body is again translated from the first position to the second position, i.e. to resume operation of the combustion engine. The residual coolant is then again brought into contact with the end portion of the spark plug and may e.g. be exchanged with fresh coolant due to the provided fluid communication with the coolant cavity in the second position.

[0086] Furthermore, the biasing element prevents coolant from passing beyond the biasing element in the longitudinal direction away from the bottom portion by effectively sealing the bore. Accordingly, the selective closing and opening of the bore may be provided by the biasing element, such that further sealing means, e.g. a valve or screw, may be optionally present or be omitted.

[0087] The longitudinal offset of the biasing element to the end portion of the spark plug, which may still be directly adjacent, also provides a predefined positional restriction of the longitudinal body. Thereby, the position of the biasing element may define a predefined volume for the coolant surrounding the end portion of the spark plug in the mounted state. Said position may be adjustable, such that the volume of coolant surrounding the end portion of the spark plug may be adapted to the respective requirements.

[0088] The biasing element may comprise a radially inner recess configured to accommodate the inner wall of the longitudinal body, when the longitudinal body is transitioned to the second position.

[0089] The radial inner recess may provide that the inner wall of the longitudinal body is in slidable engagement with the biasing element. This may facilitate that the biasing element is fully accommodated within the reservoir in the second position and fills-out the reservoir, thereby facilitating a complete emptying of the reservoir in view of the coolant. Furthermore, the radial inner recess may prevent any tilting of the longitudinal body relative to the biasing element upon translation. In this regard, the inner wall may be at least partially positioned within the radial inner recess in the first position, such that an improved guiding of the inner wall along the biasing element may be provided.

[0090] As described above, the inner wall of the longitudinal body may slidably engage the outer surface of the end portion of the spark plug in the mounted state, e.g. to facilitate proper fluidic sealing. By the same token, the outer wall may extend beyond and along the outer surface of the biasing element in longitudinal direction. Such configuration also facilitates proper alignment of the longitudinal body relative to the biasing element and/or fluidic sealing.

[0091] The biasing element may be secured by means of a respective threaded engagement. The position and extension of the thread may e.g. define a predefined position of the biasing element in view of the spark plug in the mounted state and a predefined longitudinal offset to the reservoir in the first position. For example, the biasing element may comprise an inner thread enabling a threaded engagement with a spark plug to be mounted. Such inner thread may e.g. be present on a portion of the biasing element adjacent to a radial inner recess and being in contact with the spark plug in the mounted state. When the spark plug needs to be replaced, the longitudinal body is arranged in the first position, wherein removal of the spark plug advantageously does not result in a longitudinal displacement of the biasing element. For example, the biasing element may be dimensioned to provide an interference fit with the longitudinal body, e.g. with the inner wall and outer wall defining the reservoir.

[0092] In the mounted state of the spark plug and upon translating the longitudinal body from the first position to the second position, the screwing engagement between the biasing element and the mounted spark plug prevents a longitudinal displacement of the biasing element, which may otherwise occur e.g. due to frictional forces exerted by the inner wall and the outer wall of the longitudinal body.

[0093] The outer wan of the longitudinal body may be dimensioned so as to provide a press-fit or interference fit within the spark plug sleeve. Alternatively, or in addition, an outer thread may be provided at the outer wall, e.g. to engage a corresponding inner thread of the spark plug sleeve, for example at a top portion away from the combustion area. Such configuration may provide a more robust securing of the insert within the spark plug sleeve while simultaneously enabling longitudinal translation by means of rotation and the screwing engagement.

[0094] The outer wall may extend in a longitudinal direction beyond the radial opening towards an end portion of the spark plug sleeve longitudinally opposing an end portion adjacent a combustion area. Such further extension may facilitate actuation of the longitudinal body, e.g. facilitating a rotation or longitudinal translation by rendering the longitudinal body more accessible for a technician.

[0095] Preferably, the outer wall extends beyond the end portion of the spark plug sleeve longitudinally opposing the end portion adjacent a combustion area in the second position of the longitudinal body. IN other words, the outer wall may extend beyond a top surface of the spark plug sleeve and/or cylinder head. Such extension may provide a better hold or grip for actuating the longitudinal body. Furthermore, such extension, in particular in case of a longitudinal translation of the longitudinal body, may cover a portion of the spark plug intended for facilitating mounting and demounting of the spark plug into the cylinder head. For example, the extension in the second position may be such that the outer wall covers a portion of the spark plug having a hexagonal geometry or hexagonal head intended for enabling engagement with a key to facilitate mounting of the spark plug. In this manner inadvertent removal of the spark plug while the longitudinal body is in the second position may be effectively avoided, such that coolant does not inadvertently enter the cylinder head or corresponding combustion area.

[0096] To ensure that the longitudinal body is arranged in a predefined position, the longitudinal body may comprise a mechanical stop configured to l9 engage a protrusion arranged at the spark plug sleeve in the second position. Thereby, it may be ensured that the radial opening of the spark plug sleeve is no longer covered by the outer wall of the longitudinal body, such that a fluid communication with the end portion of the spark plug is present and proper cooling is ensured. In other words, it may be ensured that a proper alignment and/or position of the longitudinal body relative to the radial opening is provided.

[0097] Alternatively, the longitudinal body may comprise a positional indicator indicating a position of an outer wall portion relative to the spark plug sleeve, in particular relative to the radial opening thereof [00981 According to a further aspect, a spark plug sleeve for a combustion engine is provided, which is configured to radially seal a coolant cavity of a cylinder head and comprises a radial opening for providing a fluid communication with the coolant cavity, wherein the spark plug sleeve comprises an insert according to the invention as described above.

[0099] The spark plug sleeve may hence be essentially formed as a typical spark plug sleeve, e.g. formed as an essentially hollow cylinder, and may accordingly comprise an outer thread for mounting the spark plug sleeve in to a bore of the cylinder head. When mounted, the spark plug sleeve defines an inner cavity configured for receiving a spark plug, such that a spark plug may be mounted to the cylinder head via the spark plug sleeve. For example, the spark plug sleeve may comprise a bore so as to provide an opening towards an adjacent combustion area. Said bore may e.g. expose a thread of the cylinder head to provide a threaded engagement with a corresponding thread of the spark plug. [00100] In the mounted state, the spark plug sleeve is surrounded by a coolant from a coolant system of the cylinder head. In accordance with the present invention a radial opening is present in the spark plug sleeve enabling a fluid communication with an end portion of a spark plug mounted therein. As described above, the insert ensures that said fluid communication is avoided in the first position of the longitudinal body, facilitating replacement of the spark plug without removing the coolant, while enabling said fluid communication in the second position of the longitudinal body to provide an improved cooling of the end portion of the spark plug during operation of the combustion engine.

1001011 The features and advantages discussed with respect to the insert also apply to the spark plug sleeve and vice versa.

Industrial Applicability

[00102] With reference to the Figures, an insert for a spark plug sleeve of a combustion engine as well as a corresponding spark plug sleeve with such insert are suggested. The suggested insert is applicable in a variety of combustion engines and cylinder heads, wherein excessive heat is generated and insufficient cooling of the spark plug is provided. The provision of the insert is particularly advantageous, since it provides an improved and direct cooling of the end portion of the spark plug while at the same time providing a mechanism to avoid removal of the coolant upon replacement of the spark plug. The lifetime of the spark plug may be significantly extended due to the improved cooling while at the same time replacement of the spark plug is facilitated by provision of the moveable longitudinal body of the insert. The disclosed insert may be mounted into existing spark plug sleeves or may be mounted together with a modified spark plug sleeve upon or prior to overhaul or prior to initial use of the combustion engine.

List of reference numerals Spark plug 12 Spark plug sleeve 14 Outer thread 16 End portion 18 Cylinder head Coolant contacting surface 22 Insert 24 Radial through-hole 26 Sealing ring 28 Outer wall Inner wall 32 Reservoir 34 Bore 36 Screw 38 Radial opening Biasing element 42 Radially inner recess 44 Hexagonal head 46 Inner thread 48 Outer thread Sliding surface 52 Radial extension

Claims

Claims What is claimed is: 1. An insert (22) for a spark plug sleeve (12) of a combustion engine, comprising a longitudinal body having an outer wall (28), said outer wall (28) defining an inner cavity being configured to removably accommodate a spark plug (10) therein in the mounted state of the insert (22), wherein the longitudinal body is configured to be movably arranged within the spark plug sleeve (12) between a first position sealing a radial opening (38) of the spark plug sleeve (12) and a second position providing a fluid communication between the radial opening (38) and an end portion (16) of the spark plug (10) in the mounted state of the insert (22).
2. The insert (22) according to claim 1, wherein the outer wall (28) is configured to contact and/or interface with an inner wall surface of the spark plug sleeve (12) adapted to enclose or surround a spark plug (10) in the mounted state of the insert (22), the outer wall (28) having an essentially circular cross-section.
3. The insert (22) according to claim 1 or 2, wherein the outer wall (28) is configured to seal the radial opening (38) by a portion of the outer wall (28) in the first position and wherein the outer wall (28) comprises a radial through-hole (24) being arranged to be aligned with the radial opening (38) in the second position.
4. The insert (22) according to claim 3, wherein the radial through-hole (24) is configured to provide a fluid communication between the radial opening (38) and the inner cavity in the second position.
5. The insert (22) according to claim 3 or 4, wherein the longitudinal body is configured to transition between the first position and the second position by rotation.
6. The insert (22) according to claim 1 or 2, wherein the longitudinal body is configured to transition between the first position and the second position by longitudinal translation.
7. The insert (22) according to claim 6, wherein the longitudinal body is configured to be arranged with a longitudinal offset to or adjacent to the end portion (16) of the spark plug (10) in the second position.
8. The insert (22) according to claim 6 or 7, wherein the longitudinal body comprises an inner wall (30) connected to the outer wall (28) via a bottom portion of the longitudinal body, the inner wall (30) radially and longitudinally delimiting the inner cavity forming a reservoir (32), wherein the bottom portion comprises a bore (34) being selectively closable.
9. The insert (22) according to claim 8, wherein the insert (22) comprises an actuatable valve or screw (36) selectively closing the bore (34).
10. The insert (22) according to claim 8 or 9, wherein the reservoir (32) is open at an end portion of the reservoir (32) longitudinally opposing the bottom portion.
11. The insert (22) according to any of claims 8 to 10, comprising a biasing element (40) securable to the spark plug (10) and/or secured to the longitudinal body at a position with a predefined longitudinal offset from the end portion (16) of the spark plug (10), wherein the biasing element (40) is configured to be received by and fill out the reservoir (32) in the second position.
12. The insert (22) according to claim 11, wherein the biasing element (40) comprises a radially inner recess (42) configured to accommodate the inner wall (30) of the longitudinal body, when the longitudinal body is transitioned to the second position.
13. The insert (22) according to claim 11 or 12, wherein the biasing element (40) is secured by means of a respective threaded engagement.
14. The insert (22) according to any of the preceding claims, wherein the outer wall (28) extends in a longitudinal direction beyond the radial opening (38) towards an end portion of the spark plug sleeve (12) longitudinally opposing an end portion adjacent a combustion area.
15. The insert (22) according to claim 14, wherein the outer wall (28) extends beyond the end portion of the spark plug sleeve (12) longitudinally opposing the end portion adjacent a combustion area in the second position of the longitudinal body.
16. The insert (22) according to any of the preceding claims, wherein the longitudinal body comprises a mechanical stop configured to engage a protrusion arranged at the spark plug sleeve (12) in the second position.
17. A spark plug sleeve (12) for a combustion engine, configured to retain a coolant in an adjacent cavity of a cylinder head (18) in the mounted state of the spark plug sleeve (12) and comprising a radial opening (38) for providing a fluid communication with the coolant cavity, wherein the spark plug sleeve (12) comprises an insert (22) according to any of the preceding claims.
18. A spark plug system for a combustion engine, comprising a spark plug sleeve (12) according to claim 17 and a spark plug (10) which is configured for being removably accommodated within the spark plug sleeve (12).
19. A spark plug (10) for a combustion engine, having an interface comprising a sliding surface (50) configured for enabling rotational or translational sliding of an insert (22) according to any of claims 1-16 relative to the spark plug (10).
20. The spark plug (10) according to claim 19, wherein the interface comprises a radial extension (52) at the level of an end portion (16) of the spark plug (10) having a sealing element, in particular a sealing ring (26) and/or a sealing ring notch, for preventing a coolant from flowing beyond the end portion 16 in a longitudinal direction opposite to the end portion 16.