Pre-chamber spark plug

Abstract

The pre-chamber spark plug includes: a housing that extends along a longitudinal axis and includes an inner surface. The pre-chamber spark plug further includes: an insulator that includes an outer surface. The pre-chamber spark plug further includes: a pre-chamber cover that is connected to the housing. The pre-chamber cover and the housing together form a pre-chamber. The pre-chamber spark plug further includes: an annular reservoir defined between the outer surface of the insulator and the inner surface of the housing. The annular reservoir is spaced from the pre-chamber relative to the longitudinal axis. The pre-chamber spark plug further includes: a plurality of protrusions that are disposed between the annular reservoir and the pre-chamber relative to the longitudinal axis. The plurality of protrusions at least partially define a plurality of flow channels therebetween.

Description

Technical Field

[0001] The present disclosure generally relates to pre-chamber spark plugs, and more particularly to pre-chamber spark plugs for internal combustion engines. Background Art

[0002] Pre-chamber (i.e., pre-combustion chamber) spark plugs are typically used to increase the lean flammability limit in lean burn engines. Generally, for passive pre-chamber spark plugs, there are no active components or devices to actively introduce or remove fresh air, fuel, or residual gas, other than being in communication with the main combustion chamber via an opening in the pre-chamber cover. Additionally, in passive pre-chamber spark plugs, there is no active mechanism to affect or regulate the flow field of fresh air and residual gas in the pre-chamber.

[0003] During the compression stroke of the engine, the fuel-air mixture must enter the pre-chamber of the pre-chamber spark plug in such a way that a combustible mixture is present at the spark gap. Due to subsequent combustion and the resulting pressure increase, the flame jet escapes through the opening in the pre-chamber cover and ignites the fuel-air mixture in the main combustion chamber of the engine. However, in some cases, some of the residual gas between the pre-chamber and the spark plug electrodes is not completely exhausted and may remain in the pre-chamber during the exhaust and intake strokes. The pressure differential between the main combustion chamber and the pre-chamber can be increased to force the fresh charge to enter the pre-chamber through the opening. Pressurizing the fresh charge into the pre-chamber can compress the residual gas towards the spark plug. Residual gas remaining in the pre-chamber can cause pre-ignition, engine misfire, and / or abnormal combustion, especially when the engine is operating in a richer λ (air-fuel ratio) range. In other words, the residual burned fuel-air mixture can cause the fuel-air mixture entering the pre-chamber during subsequent engine cycles to auto-ignite. In most cases, the residual gas accumulates in the pre-chamber volume and in the gap between the insulator and the metal housing of the pre-chamber spark plug.

[0004] In addition, when the spark plug overheats, uncontrolled ignition may occur in the main combustion chamber before the ignition point. This may increase the risk of engine damage. Premature ignition in the pre-chamber of the spark plug not only increases the temperature of various spark plug components such as the ground electrode, center electrode, insulator body, or pre-chamber cover, but may also cause premature ignition in the main combustion chamber. One way to prevent spontaneous ignition and / or premature ignition in the pre-chamber is to increase the volume of the pre-chamber. However, the volume of the pre-chamber cannot be increased by simply increasing the diameter of the pre-chamber because the pre-chamber is limited by the specific engine geometry. Additionally, the increased volume of the pre-chamber may result in an unbalanced ratio of the lower chamber volume (the volume of the pre-chamber below the spark gap and towards the combustion chamber) to the upper chamber volume (the volume of the pre-chamber above the spark gap) within the pre-chamber spark plug. This may lead to a reduced movement of the fresh charge into the spark gap region within the pre-chamber. This may again result in poor combustion in the pre-chamber and a narrow operating range of the engine.

[0005] Conventional methods for preventing spontaneous ignition and / or premature ignition in the pre-chamber include providing an auxiliary pre-chamber insert in addition to the conventional spark plug. The geometry of the auxiliary pre-chamber insert is selected such that an additional upper chamber volume can be formed externally and a balanced ratio of the lower chamber volume to the upper chamber volume can be achieved within the pre-chamber spark plug. However, introducing the auxiliary pre-chamber insert may result in space limitations and increase the total manufacturing cost and complexity of the engine. Another conventional technique for preventing spontaneous ignition and / or premature ignition in the pre-chamber involves adjusting the pre-chamber spark plug to provide optimal combustion performance within a narrow operating range and adding a completely independent auxiliary spark plug in the combustion chamber. The auxiliary spark plug provides ignition in the combustion chamber when ignition in the pre-chamber spark plug is ineffective. However, introducing the auxiliary spark plug may again result in space limitations and increase the total manufacturing cost and complexity of the engine. Summary of the Invention

[0006] According to one aspect, a pre-chamber spark plug is provided. The pre-chamber spark plug includes a housing extending along a longitudinal axis. The housing includes an inner surface. The pre-chamber spark plug further includes an insulator that includes an outer surface and is at least partially disposed within the housing. The outer surface of the insulator faces the inner surface of the housing. The pre-chamber spark plug further includes a pre-chamber cover connected to the housing. The pre-chamber cover and the housing together form a pre-chamber. The pre-chamber cover includes one or more openings that allow gas exchange between the pre-chamber and a space external to the pre-chamber. The pre-chamber spark plug further includes: an annular reservoir defined between the outer surface of the insulator and the inner surface of the housing. The annular reservoir is spaced apart from the pre-chamber relative to the longitudinal axis. The pre-chamber spark plug further includes: a plurality of protrusions angularly separated from each other relative to the longitudinal axis. The plurality of protrusions are disposed between the annular reservoir and the pre-chamber relative to the longitudinal axis, and at least partially define a plurality of flow channels between the plurality of protrusions. Each flow channel extends at least partially parallel to the longitudinal axis. Each flow channel fluidly extends between the annular reservoir and the pre-chamber such that the annular reservoir is in fluid communication with the pre-chamber.

[0007] From the detailed description provided below, other applicable fields of the present disclosure will become apparent. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present disclosure, are for illustrative purposes only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a partial cross-sectional view of an internal combustion engine having a pre-chamber spark plug according to an embodiment of the present disclosure;

[0009] Figure 2 is according to an embodiment of the present disclosure Figure 1 cross-sectional view of the pre-chamber spark plug;

[0010] Figure 3 is Figure 2 cross-sectional perspective view of the pre-chamber spark plug;

[0011] Figure 4 is according to an embodiment of the present disclosure Figure 2 magnified cross-sectional view of a portion of the pre-chamber spark plug;

[0012] Figure 5 is according to an embodiment of the present disclosure through Figure 2 cross-sectional view of the pre-chamber spark plug taken along section A-A';

[0013] Figure 6 is according to an embodiment of the present disclosure Figure 2 cross-sectional perspective view of the housing of the pre-chamber spark plug; and

[0014] Figure 7is a cross-sectional view of a pre-chamber spark plug through section B-B' according to another embodiment of the present disclosure Figure 2 of the pre-chamber spark plug Detailed Description

[0015] The following description is merely exemplary in nature and is not intended to limit the invention, its application, or uses. Now referring to the drawings, in several views, like reference numerals denote like or corresponding parts. Referring to Figure 1 , a cross-sectional view of an internal combustion engine 100 is shown. The internal combustion engine 100 includes: a cylinder head 104 and an engine block 102 that define a combustion chamber 106 therein. The internal combustion engine 100 further includes a plurality of cylinders 108, and one of the cylinders is partially depicted in Figure 1 . The cylinder 108 has a piston 110 that is movable within the engine block 102. The engine block 102, the cylinder head 104, and the piston 110 define the combustion chamber 106, the volume of which changes as the piston 110 moves. The piston displacement of the cylinder 108 can range from 300 cm 3 to 500 cm 3 . The combustion chamber 106 is supplied by a duct 112, which can be an intake duct or an exhaust duct. The duct 112 can be closed by a valve 114

[0016] The internal combustion engine 100 further includes: a pre-chamber spark plug 200 that extends at least partially through the cylinder head 104 and is at least partially received within the cylinder head 104. The pre-chamber spark plug 200 extends at least partially into the combustion chamber 106 through the cylinder head 104. Generally, the pre-chamber spark plug 200 is screwed into the cylinder head 104 with its external threads (not shown).

[0017] Figure 2 is a cross-sectional view of the pre-chamber spark plug 200 according to an embodiment of the present disclosure Figure 3 is a cross-sectional view of the pre-chamber spark plug 200 seen from another angle Figure 4 is an enlarged view of a part of the pre-chamber spark plug 200. The pre-chamber spark plug 200 includes: a housing 202 that extends along a longitudinal axis LA. Referring to Figure 3 , the housing 202 includes: an inner surface 204 and an outer surface 206 that faces the external environment of the pre-chamber spark plug 200. The housing 202 has a metal body. The inner surface 204 can correspond to the radially inner surface of the housing 202, while the outer surface 206 can correspond to the radially outer surface of the housing 202

[0018] Referring to Figures 2 to 4, the pre-chamber spark plug 200 further includes: a spark plug seat 208 disposed between the housing 202 and the cylinder head 104. The spark plug seat 208 limits how far the pre-chamber spark plug 200 can be screwed into the internal combustion engine 100. The spark plug seat 208 is an external sealing seat adapted to seal the combustion chamber 106. The spark plug seat 208 is thermally connected to each of the housing 202 and the cylinder head 104. The spark plug seat 208 may be disposed between the annular extension 203 of the housing 202 and the cylinder head 104. The spark plug seat 208 may engage each of the annular extension 203 and the cylinder head 104.

[0019] The pre-chamber spark plug 200 further includes an insulator 210 that extends along a longitudinal axis LA and is at least partially disposed within the housing 202. The insulator 210 includes: an outer surface 212 (as Figure 3 shown), which faces the inner surface 204 of the housing 202. The outer surface 212 of the insulator 210 may correspond to the radially outer surface of the insulator 210. The insulator 210 sits in the channel of the housing 202. The insulator 210 may be made of a ceramic material, including any suitable spark plug insulator material. In some embodiments, the insulator 210 further includes: a tapered portion 214 that is at an end 216 of the insulator 210 and is disposed within the housing 202.

[0020] The pre-chamber spark plug 200 further includes: a pre-chamber cover 218 connected to the housing 202. The pre-chamber cover 218 is connected to the housing 202 such that the pre-chamber cover 218 and the housing 202 together form a pre-chamber 220. In some cases, the pre-chamber cover 218 may be connected to an end of the housing 202 by a weldment. The tapered portion 214 of the insulator 210 faces the pre-chamber cover 218. Specifically, the pre-chamber 220 is disposed between the tapered portion 214 of the insulator 210 and the pre-chamber cover 218 with respect to the longitudinal axis LA.

[0021] In addition, the pre-chamber cover 218 includes one or more openings 222 that allow gas exchange between the pre-chamber 220 and the space outside the pre-chamber 220. Specifically, the one or more openings 222 enable fluid communication between the pre-chamber 220 and the combustion chamber 106. In particular, a fuel-air mixture may be introduced from the combustion chamber 106 into the pre-chamber 220 via the one or more openings 222 and then may be combusted in the pre-chamber 220. In some embodiments, the pre-chamber cover 218 includes: two openings 222 spaced 180°. In other embodiments, the pre-chamber cover 218 includes: four openings 222 spaced 90°. In other embodiments, the pre-chamber cover 218 includes: six openings 222 spaced 60°, or eight openings 222 spaced 45°.

[0022] The pre-chamber spark plug 200 further includes: a center electrode 224 extending from the insulator 210 into the pre-chamber 220. The center electrode 224 extends from the tapered portion 214 of the insulator 210. The center electrode 224 includes a center electrode body 226 and a center electrode tip 228, and in the illustrated embodiment, the shape of the center electrode tip is a cylindrical post. The center electrode body 226 can be made of Inconel TM 600 or other suitable center electrode materials, and the center electrode tip 228 can be made of a nickel alloy or a noble metal (e.g., platinum, iridium) or an alloy thereof. The center electrode body 226 is disposed within the central hole of the insulator 210 and projects from the insulator 210.

[0023] The pre-chamber spark plug 200 further includes at least one ground electrode 230, which is electrically coupled to the housing 202 and forms a spark gap 232 with the center electrode 224. Specifically, the spark gap 232 is formed between at least one ground electrode 230 and the center electrode tip 228 of the center electrode 224. In some embodiments, at least one ground electrode 230 can be connected to the housing by resistance welding. In some embodiments, at least one ground electrode 230 can be connected to the housing by a laser beam that is laterally oriented with respect to the longitudinal axis LA. In Figures 2 to 4 the illustrated embodiment, at least one ground electrode 230 includes two ground electrodes 230 in total. Each ground electrode 230 forms a spark gap 232 with the center electrode 224. Each ground electrode 230 extends laterally with respect to the longitudinal axis LA. Thus, each ground electrode 230 can extend radially with respect to the longitudinal axis LA. The spark gap 232 is a radial spark gap, which includes: a gap portion between the center electrode tip 228 and at least one ground electrode 230. An electric spark is generated in the spark gap 232, and through the electric spark, combustion of the fuel-air mixture (received from the combustion chamber 106 via one or more openings 222) occurs in the pre-chamber 220. The combustion can propagate from the spark gap 232 to the combustion chamber 106 via one or more openings 222, so as to ignite the fuel-air mixture in the combustion chamber 106.

[0024] In some embodiments, each ground electrode 230 includes two parts (a support member 234 and a reinforcement member 236 (as Figure 4As shown). The strengthening member 236 forms the burnout surface of the spark gap 232. The strengthening member 236 may be composed of a noble metal alloy (especially a platinum and / or iridium alloy). The support member 234 may be composed of a nickel-based alloy or a noble metal. In some cases, the support member 234 may be composed of a nickel-based copper core member that can conduct high-voltage ignition pulses electrically and can conduct heat away from the spark surface. In some cases, the support member 234 may be composed of a solid nickel-based alloy to have good heat flow and good corrosion resistance at the operating temperature. In some cases, each of the support member 234 and the strengthening member 236 is implemented in the form of a cylinder and made of wire.

[0025] In addition, as Figure 2 shown, the pre-chamber 220 defines: a lower chamber C1, which is below the spark gap 232 and towards the combustion chamber 106; and an upper chamber C2, which is above the spark gap 232.

[0026] The pre-chamber spark plug 200 further includes: an internal seal 240, which is arranged between the inner surface 204 of the housing 202 and the outer surface 212 of the insulator 210. The internal seal 240 is spaced apart from the pre-chamber 220 with respect to the longitudinal axis LA. In some embodiments, the internal seal 240 is thermally coupled to the cylinder head 104 via the housing 202 and the spark plug seat 208. Therefore, the internal seal 240 can exchange heat with the radiator (i.e., the cylinder head 104) through the housing 202 and the spark plug seat 208.

[0027] The pre-chamber spark plug 200 further includes: an annular reservoir 242, which is defined between the outer surface 212 of the insulator 210 and the inner surface 204 of the housing 202. The annular reservoir 242 is an internal annular space formed between the outer surface 212 of the insulator 210 and the inner surface 204 of the housing 202. The annular reservoir 242 is spaced apart from the pre-chamber 220 with respect to the longitudinal axis LA.

[0028] Figure 5 is a cross-sectional view of the pre-chamber spark plug 200 through Figure 2 section A-A' according to an embodiment of the present disclosure. Figure 6 is a cross-sectional view of the housing 202 according to an embodiment of the present disclosure.

[0029] See Figures 2 to 6 , the pre-chamber spark plug 200 further includes: a plurality of protrusions 244, which are angularly separated from each other with respect to the longitudinal axis LA. In addition, the plurality of protrusions 244 are arranged between the annular reservoir 242 and the pre-chamber 220 with respect to the longitudinal axis LA. In some embodiments, the tapered portion 214 of the insulator 210 is arranged between the plurality of protrusions 244 and at least one ground electrode 230 with respect to the longitudinal axis LA.

[0030] In some embodiments, at least one of the plurality of protrusions 244 is configured to engage at least partially with one of the outer surface 212 of the insulator 210 and the inner surface 204 of the housing 202. In some embodiments, each of the plurality of protrusions 244 engages at least partially with one of the outer surface 212 of the insulator 210 and the inner surface 204 of the housing 202. Since at least one of the plurality of protrusions 244 engages at least partially with one of the outer surface 212 of the insulator 210 and the inner surface 204 of the housing 202, the insulator 210 is disposed at least partially and centrally within the housing 202. Accordingly, the plurality of protrusions 244 can serve as centering elements that limit lateral movement of the insulator 210 relative to the housing 202.

[0031] In some embodiments, each protrusion 244 is an annular segment that extends radially between the inner surface 204 of the housing 202 and the outer surface 212 of the insulator 210. In some embodiments, each protrusion 244 is a separate component from each of the housing 202 and the insulator 210 and is also inserted between the housing 202 and the insulator 210. Each protrusion 244 can also be attached to one of the housing 202 and the insulator 210. Specifically, each protrusion 244 can also be attached to one of the inner surface 204 of the housing 202 and the outer surface 212 of the insulator 210. In some embodiments, each protrusion 244 can be attached to one of the inner surface 204 of the housing 202 and the outer surface 212 of the insulator 210 by welding. In some embodiments, each protrusion 244 is part of the inner surface 204 of the housing 202 or the outer surface 212 of the insulator 210. In other words, each protrusion 244 can be integral with one of the inner surface 204 of the housing 202 and the outer surface 212 of the insulator 210. In Figures 2 to 6 the illustrated embodiment, each protrusion 244 is part of the inner surface 204 of the housing 202.

[0032] A plurality of protrusions 244 at least partially define a plurality of flow channels 246 therebetween. Specifically, each flow channel 246 is circumferentially defined between a corresponding pair of adjacent protrusions 244 among the plurality of protrusions 244. Each flow channel 246 extends at least partially parallel to the longitudinal axis LA. Additionally, each flow channel 246 is at least partially formed between the inner surface 204 of the housing 202 and the outer surface 212 of the insulator 210. Each flow channel 246 extends between the annular reservoir 242 and the prechamber 220 such that the annular reservoir 242 is in fluid communication with the prechamber 220. In some embodiments, each flow channel 246 extends from the prechamber 220 to near the tapered portion 214 of the insulator 210. Thus, each flow channel 246 is in direct fluid communication with the upper chamber C2 of the prechamber 220. Additionally, each flow channel 246 is formed or defined by the protrusion 244, the inner surface 204 of the housing 202, and the outer surface 212 of the insulator 210.

[0033] In some embodiments, the plurality of protrusions 244 includes a total of four protrusions 244 (as Figure 5 shown), such that the plurality of flow channels 246 includes a total of four flow channels 246 (as Figure 5 shown). Each of the four flow channels 246 is circumferentially defined between a corresponding pair of adjacent protrusions 244 among the four protrusions 244. In some embodiments, each protrusion 244 is angularly spaced 90 degrees from an adjacent protrusion 244 relative to the longitudinal axis LA. In some embodiments, the plurality of protrusions 244 may include a total of three protrusions 244, or more than four protrusions 244. In some embodiments, the plurality of protrusions 244 are equally spaced from each other. In other embodiments, the plurality of protrusions 244 are not equally spaced from each other.

[0034] The annular reservoir 242 is disposed between the inner seal 240 and the plurality of flow channels 246 relative to the longitudinal axis LA. The inner seal 240 may prevent or significantly reduce leakage of fluid from the annular reservoir 242. It should be noted that the inner seal 240 is axially spaced from the tapered portion 214 of the insulator 210. Additionally, when the annular reservoir 242 is in fluid communication with the prechamber 220 via the plurality of flow channels 246 and the inner seal 240 is thermally coupled to the cylinder head 104, the inner seal 240 allows heat exchange between the gas disposed in the annular reservoir 242 and the cylinder head 104. In other words, the inner seal 240 allows heat exchange between the cylinder head 104 and the gas present in the prechamber 220.

[0035] In some embodiments, the housing 202 has no openings between the inner surface 204 and the outer surface 206 of the housing 202 such that the housing 202 is configured to fluidly isolate the annular reservoir 242 and the plurality of flow channels 246 from the external environment. In other words, there is no passage through which the annular reservoir 242 can be fluidly connected to the external environment between the inner surface 204 and the outer surface 206 of the housing 202. Thus, the annular reservoir 242 can be in fluid communication with only the pre-chamber 220 via the plurality of flow channels 246 and is otherwise sealed from the external environment.

[0036] During operation of the internal combustion engine 100, hot residual gases are typically released from the combustion of the fuel-air mixture in the pre-chamber 220. In some cases, residual gases from a previous ignition cycle can be trapped within the pre-chamber 220. In the disclosed pre-chamber spark plug 200, when the annular reservoir 242 is in fluid communication with the pre-chamber 220, the residual gases can flow out of the pre-chamber 220 and into the annular reservoir 242 via the plurality of flow channels 246 formed at least in part by the plurality of protrusions 244. When the annular reservoir 242 is disposed between the inner seal 240 and the plurality of flow channels 246 and the inner seal 240 is thermally coupled to the cylinder head 104 via the housing 202 and the spark plug seat 208, the residual gases in the annular reservoir 242 can exchange heat with the cylinder head 104. Thus, due to the heat exchange between the inner seal 240 and the cylinder head 104, the temperature of the hot residual gases can be reduced, which otherwise could cause pre-ignition, engine misfire, and / or abnormal combustion during a subsequent ignition cycle. In other words, the pre-chamber spark plug 200 including the annular reservoir 242, the inner seal 240, and the plurality of protrusions 244 defining the plurality of flow channels 246 can provide a thermal path for the residual gases to exchange heat with the housing 202 and ultimately with the radiator (i.e., the cylinder head 104). In this way, pre-ignition and auto-ignition of the fuel-air mixture during a subsequent ignition cycle can be prevented.

[0037] In addition, the axial distance between the internal seal 240 and the spark plug seat 208 is relatively smaller than the axial distance between the internal seal and the spark plug seat in a conventional pre-chamber spark plug. In the present disclosure, the internal seal 240 is disposed in the larger diameter portion of the housing 202, and the internal seal in a conventional pre-chamber spark plug is typically disposed in the threaded portion of the housing. By providing the internal seal 240 in the larger diameter portion of the housing 202, the surface area of the internal seal is relatively increased. In this way, the internal seal 240 has a relatively larger surface contact area with the housing 202. Additionally, the temperature of the housing 202 in the larger diameter portion is lower than the temperature of the housing 202 in the threaded portion. Therefore, when the internal seal 240 is disposed in the larger diameter portion of the housing 202, more heat can be exchanged with the housing 202 and ultimately more heat can be exchanged with the radiator. This can also maintain the desired temperature of the center electrode tip 228. This position of the internal seal 240 can enable a high-power engine to operate with an acceptable center electrode temperature and an effective heat flow path.

[0038] When the insulator 210 is at least partially and centrally disposed within the housing 202, the residual gas can flow through the plurality of flow channels 246 in a uniform manner. Thus, this can maintain a continuous and balanced fluid communication between the pre-chamber 220 and the annular reservoir 242. In other words, the plurality of protrusions 244 can provide an effective and consistent flow path (through the plurality of flow channels 246) for the gas between the pre-chamber 220 and the annular reservoir 242.

[0039] Including the annular reservoir 242, the internal seal 240, and the plurality of protrusions 244 that at least partially define the plurality of flow channels 246 in the pre-chamber spark plug 200 can prevent uncontrolled ignition in the combustion chamber 106 before the ignition point. Therefore, the reduction of the residual gas temperature can prevent the risk of damaging the internal combustion engine 100.

[0040] When compared with the heat transfer between the pre-chamber and the radiator through various insulator components in a conventional pre-chamber spark plug, the pre-chamber spark plug 200 can provide effective heat transfer from the pre-chamber 220 to the cylinder head  104 through the internal seal 240 and the spark plug seat 208. In other words, the pre-chamber spark plug 200 can provide: an effective heat path that transfers relatively less heat from the pre-chamber 220 to the radiator (i.e., the cylinder head 104). The relatively less heat transfer from the pre-chamber 220 to the cylinder head 104 can increase the overall thermal efficiency of the pre-chamber spark plug 200 and the combustion chamber 106. Therefore, the disclosed pre-chamber spark plug 200 can provide more energy to the combustion chamber 106 to convert it into useful mechanical work, and less thermal energy is lost by the cooling system. This can further improve the fuel economy of the internal combustion engine 100 including the pre-chamber spark plug 200.

[0041] When residual gases are trapped in the pre - combustion chamber 220 from a previous ignition cycle, the residual gases can flow out into the annular reservoir 242 via a plurality of flow channels 246 defined at least in part by a plurality of protrusions 244. The flow of the residual gases from the pre - combustion chamber 220 to the annular reservoir 242 via the plurality of flow channels 246 can allow a fresh charge of the fuel - air mixture to enter the pre - combustion chamber 220 and the spark - gap region at a desired moment in the next ignition cycle. The intake of the fresh charge of the fuel - air mixture can prevent engine misfires and poor combustion performance, which are noted in conventional pre - combustion chamber spark plugs in which residual gases have been trapped in their pre - combustion chambers.

[0042] Including the plurality of flow channels 246 and the annular reservoir 242 can provide additional space for the upper - chamber volume of the pre - combustion chamber 220 (the volume defined by the upper chamber C2 shown in Figure 2 ). In other words, the pre - combustion chamber spark plug 200 including the plurality of flow channels 246 and the annular reservoir 242 has an increased upper - chamber volume compared to a conventional pre - combustion chamber spark plug. Due to the increased upper - chamber volume, the pre - combustion chamber spark plug 200 has a relatively reduced ratio of the lower - chamber volume (the volume defined by the lower chamber C1 shown in Figure 2 ) to the upper - chamber volume. The reduced ratio of the lower - chamber volume to the upper - chamber volume can result in improved movement of the fresh charge into the spark - gap region within the pre - combustion chamber 220. Additionally, the reduced ratio of the lower - chamber volume to the upper - chamber volume can prevent poor combustion in the pre - combustion chamber 220 and optimize the wide - range performance of the internal combustion engine 100.

[0043] The ratio of the lower - chamber volume to the upper - chamber volume can be selected and adjusted according to desired application attributes. Thus, for the pre - combustion chamber 220 with an increased upper - chamber volume, it may not be necessary to follow the conventional method of increasing the upper - chamber volume by installing an external auxiliary pre - combustion chamber insert or a completely separate auxiliary spark plug within the combustion chamber 106. Thus, even with improved combustion performance, the pre - combustion chamber spark plug 200 including the annular reservoir 242 and the plurality of flow channels 246 can reduce the total manufacturing cost and complexity of the internal combustion engine 100 compared to a conventional pre - combustion chamber spark plug. Additionally, due to the presence of the plurality of flow channels 246 and the annular reservoir 242 within the housing 202, the pre - combustion chamber spark plug 200 does not form any space limitations when the upper - chamber volume is increased.

[0044] Accordingly, when the annular reservoir 242 and the plurality of channels 246 are fully disposed within the pre-chamber spark plug 200, the pre-chamber spark plug 200 can increase the upper chamber volume without the need for any external inserts or components. Thus, the pre-chamber spark plug 200 can have a compact design while providing improved combustion performance. Additionally, no additional channels are required within the housing 202 for fluid communication between the pre-chamber 220 and any external chambers, thereby maintaining the structural integrity of the housing 202 and preventing any additional leakage of fluid through the housing 202. Further, no additional components (e.g., one or more valves) may be required to regulate the flow between the pre-chamber 220 and any external chambers.

[0045] Moreover, when the pre-chamber spark plug 200 does not require any auxiliary pre-chamber inserts to increase the upper chamber volume, the maximum area of the pre-chamber spark plug 200 can be used to obtain an increased dielectric strength of the insulator 210. In other words, the maximum area of the pre-chamber spark plug 200 can be optimized to provide the required housing strength and maximize the insulator dielectric strength.

[0046] See Figure 4 and Figure 5 , the axial length of each flow channel 246 is substantially equal to the axial length of each protrusion 244. Additionally, the annular reservoir 242 has a maximum reservoir width W1 perpendicular to the longitudinal axis LA (as Figure 4 shown). The maximum reservoir width W1 can correspond to the maximum radial width of the annular reservoir 242. Each flow channel 246 has a maximum channel width W2 between the inner surface 204 of the housing 202 and the outer surface 212 of the insulator 210 (as Figure 5 shown). In some embodiments, the maximum reservoir width W1 of the annular reservoir 242 perpendicular to the longitudinal axis LA is greater than the maximum channel width W2 of each flow channel 246. In some embodiments, the maximum reservoir width W1 is at least twice as large as the maximum channel width W2. In some embodiments, the total reservoir volume of the annular reservoir 242 is larger than the total volume of the plurality of flow channels 246. In some embodiments, the total reservoir volume of the annular reservoir 242 is at least 2 times, 3 times, or 5 times larger than the total volume of the plurality of flow channels 246.

[0047] Figure 7 is a cross-sectional view of the pre-chamber spark plug 200 taken along section B-B' according to another embodiment of the present disclosure. In Figure 2 the Figure 7In the illustrated embodiment, the pre-chamber spark plug 200 includes at least one ground electrode 230' (instead of at least one ground electrode 230). The at least one ground electrode 230' includes: a total of two ground electrodes 230', which are bent in such a way that each of the two ground electrodes 230' forms a spark gap 232 with the center electrode 224. The two ground electrodes 230' are in electrical contact with the housing 202. In some embodiments, the at least one ground electrode 230' is inclined with respect to the radial direction "R" defined by the relative longitudinal axis LA. As Figure 7 shown, each of the two ground electrodes 230' is inclined with respect to the radial direction "R" defined by the relative longitudinal axis LA.

[0048] Although aspects of the present disclosure have been particularly shown and described with reference to the above embodiments, those skilled in the art will understand that various additional embodiments may be contemplated by modifying the disclosed machines, systems, and methods without departing from the spirit and scope of the disclosed subject matter. These embodiments should be understood to fall within the scope of the present disclosure as determined based on the claims and any equivalents thereof.

Claims

1. A pre-chamber spark plug, comprising: A housing extending along a longitudinal axis, the housing including an inner surface; An insulator, the insulator including an outer surface and being at least partially disposed within the housing such that the outer surface of the insulator faces the inner surface of the housing; A pre-chamber cover connected to the housing, the pre-chamber cover and the housing together forming a pre-chamber, the pre-chamber cover including one or more openings that permit gas exchange between the pre-chamber and a space external to the pre-chamber; An annular reservoir defined between the outer surface of the insulator and the inner surface of the housing, wherein the annular reservoir is spaced from the pre-chamber relative to the longitudinal axis; and A plurality of protrusions angularly separated from each other relative to the longitudinal axis, characterized in that the plurality of protrusions are disposed between the annular reservoir and the pre-chamber relative to the longitudinal axis, and at least partially define a plurality of flow channels between the plurality of protrusions, and each flow channel fluidly extends between the annular reservoir and the pre-chamber such that the annular reservoir is in fluid communication with the pre-chamber.

2. The pre-chamber spark plug according to claim 1 further includes an internal seal disposed between an inner surface of the housing and an outer surface of the insulator, and wherein, The annular reservoir is disposed between the inner seal and the plurality of flow channels relative to the longitudinal axis.

3. The prechamber spark plug according to claim 2, wherein, The inner seal is thermally coupled to the cylinder head via the housing such that the inner seal permits heat exchange between the gas disposed within the annular reservoir and the cylinder head.

4. The pre-chamber spark plug according to any one of claims 1 to 3, wherein, At least one of the plurality of protrusions is configured to at least partially engage one of the outer surface of the insulator and the inner surface of the housing such that the insulator is at least partially and centrally disposed within the housing.

5. The pre-chamber spark plug according to claim 4, wherein, The plurality of protrusions includes a total of four protrusions such that the plurality of flow channels includes a total of four flow channels, and wherein each of the four flow channels is defined between a corresponding pair of adjacent ones of the four protrusions.

6. The pre-chamber spark plug according to claim 1, wherein Each protrusion is an annular segment radially extending between the inner surface of the housing and the outer surface of the insulator.

7. The pre-chamber spark plug according to claim 1, wherein, Each protrusion is a part of the inner surface of the housing or the outer surface of the insulator.

8. The pre-chamber spark plug according to claim 1, wherein, The maximum reservoir width of the annular reservoir perpendicular to the longitudinal axis is greater than the maximum channel width of each flow channel between the inner surface of the housing and the outer surface of the insulator.

9. The pre-chamber spark plug according to claim 8, wherein, The maximum reservoir width is at least twice greater than the maximum channel width.

10. The pre-chamber spark plug according to claim 1, wherein, The total reservoir volume of the annular reservoir is greater than the total volume of the plurality of flow channels.

11. The pre-chamber spark plug according to claim 1, wherein, The housing further includes an outer surface facing the external environment of the pre-chamber spark plug, wherein the housing has no openings between the inner surface and the outer surface of the housing such that the housing is configured to fluidly isolate the annular reservoir and the plurality of flow channels from the external environment.

12. The pre-chamber spark plug according to claim 1, further comprising: A center electrode extending from the insulator into the pre-chamber; And At least one ground electrode, the at least one ground electrode being electrically coupled to the housing and forming a spark gap with the center electrode.

13. The pre-chamber spark plug according to claim 12, wherein, The insulator further includes a tapered portion at an end of the insulator and disposed within the housing, wherein the tapered portion faces the pre-chamber cover such that the pre-chamber is disposed between the tapered portion and the pre-chamber cover relative to the longitudinal axis, and wherein the center electrode extends from the tapered portion.

14. The pre-chamber spark plug according to claim 13, wherein, Each flow passage extends from the pre-chamber to near the tapered portion.

15. The pre-chamber spark plug according to claim 13 or 14, wherein, The tapered portion is disposed between the plurality of protrusions and the at least one ground electrode relative to the longitudinal axis.

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