PRECOMBUSTION-CHAMBER ENGINE

Abstract

A precombustion-chamber engine includes a cylinder, a cylinder head disposed on a top of the cylinder, and a piston reciprocably disposed within the cylinder. A main combustion chamber is defined between the piston and the cylinder head. The cylinder head includes a precombustion-chamber forming part which defines a precombustion chamber communicating with the main combustion chamber through a nozzle. The precombustion chamber includes a cylindrical first passage part extending upwardly from the nozzle, a second passage part extending upwardly from the first passage part and having an upwardly-increasing cross-sectional area, and a cylindrical space part which extends upwardly from the second passage part and in which a spark plug is disposed. Center O of a cross-section, orthogonal to straight line L, of the second passage part is eccentric with respect to straight line L composed of an axis of the first passage part and an extended line of the axis.

Claims

1. A precombustion-chamber engine, comprising: a cylinder; a cylinder head disposed on a top of the cylinder; and a piston reciprocably disposed within the cylinder, the piston and the cylinder head defining a main combustion chamber therebetween, the cylinder head including a precombustion-chamber forming part which defines a precombustion chamber communicating with the main combustion chamber through a nozzle, the precombustion chamber including: a cylindrical first passage part extending upwardly from the nozzle; a second passage part extending upwardly from the first passage part and having an upwardly-increasing cross-sectional area; and a cylindrical space part which extends upwardly from the second passage part and in which a spark plug is disposed, wherein a center O is eccentric with respect to a straight line L, where the straight line L is composed of an axis of the first passage part and an extended line of the axis, and the center O is a center of a cross-section, orthogonal to the straight line L, of the second passage part.

2. The precombustion-chamber engine according to claim 1, wherein a second-passage-part forming surface which defines the second passage part is smoothly connected with a first-passage-part forming surface which defines the first passage part and with a space-part forming surface which defines the space part.

3. The precombustion-chamber engine according to claim 1, wherein, provided that a direction A is a direction in which the center O of the cross-section is eccentric with respect to the straight line L, a cross-section S is a cross-section of the precombustion chamber, including the straight line L and the direction A, a first line is a part of a second-passage-part forming surface which defines the second passage part on a direction A side across the straight line L in the cross-section S, a second line is a part of the second-passage-part forming surface on an opposite side to the direction A across the straight line L in the cross-section S, 1 is an angle between the straight line L and a straight line connecting an upper end and a lower end of the first line, and 2 is an angle between the straight line L and a straight line connecting an upper end and a lower end of the second line, the second-passage-part forming surface is configured to satisfy 1>2.

4. The precombustion-chamber engine according to claim 3, wherein the second-passage-part-forming surface is configured to satisfy 30<1<45.

5. The precombustion-chamber engine according to claim 3, wherein the first line extends upwardly with increasing a distance from the straight line L, and wherein the second line includes: an extended line part extending, from a first-passage wall surface which defines the first passage part, in a direction of extending the first-passage wall surface; and a tapered line part connecting the extended line part with a space wall surface which defines the space part and extending upwardly with increasing a distance from the straight line L.

6. The precombustion-chamber engine according to claim 1, further comprising an ignition-fuel-gas supply channel for supplying an ignition fuel gas to the precombustion chamber, wherein the second passage part is symmetric across the cross-section S, and wherein the ignition-fuel-gas supply channel has a supply port disposed on a space-part forming surface which defines the space part, the supply port being situated away from the cross-section S.

7. The precombustion-chamber engine according to claim 1, further comprising an ignition-fuel-gas supply channel for supplying an ignition fuel gas to the precombustion chamber, wherein the ignition-fuel-gas supply channel has a supply port disposed on a space-part forming surface which defines the space part, the supply port being situated on an opposite side to the direction A across the straight line L, and wherein the ignition-fuel-gas supply channel is configured to inject the ignition fuel gas through the supply port toward a direction A side.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0027] FIG. 1 is a schematic view showing a schematic configuration of a precombustion-chamber gas engine according to an embodiment of the present invention.

[0028] FIG. 2 is a perspective view showing a schematic shape of a precombustion chamber 20 according to an embodiment.

[0029] FIG. 3 is a plan view showing an example of the shape and the arrangement of a cross-section S1 of a first passage part 32, a cross-section S2 of a second passage part 34, and a cross-section S3 of a space part 36 along a straight line L.

[0030] FIG. 4 is a diagram showing an example of a cross-section S4 of the precombustion chamber 20 in FIG. 2 and FIG. 3.

[0031] FIG. 5 is a diagram showing an example of a cross-section S4 of the precombustion chamber 20 in FIG. 2 and FIG. 3.

[0032] FIG. 6 is a diagram showing another example of a cross-section S4 of the precombustion chamber 20.

[0033] FIG. 7 is a diagram showing another example of a cross-section S4 of the precombustion chamber 20.

[0034] FIG. 8 is a diagram showing, in case where ignition fuel gas g is injected toward the direction A side, an angle 3 between a straight line M and a direction of injecting the ignition fuel gas g, viewing from a direction orthogonal to a cross-section S4.

[0035] FIG. 9 is a diagram showing, in case where ignition fuel gas g is injected opposite to the direction A side, an angle 4 between a straight line M and a direction of injecting the ignition fuel gas g, viewing from a direction orthogonal to a cross-section S4.

DETAILED DESCRIPTION

[0036] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It is intended, however, that unless particularly identified, dimensions, materials, shapes, relative positions and the like of components described in the embodiments shall be interpreted as illustrative only and not intended to limit the scope of the present invention.

[0037] For instance, an expression of relative or absolute arrangement such as in a direction, along a direction, parallel, orthogonal, centered, concentric and coaxial shall not be construed as indicating only the arrangement in a strict literal sense, but also includes a state where the arrangement is relatively displaced by a tolerance, or by an angle or a distance whereby it is possible to achieve the same function.

[0038] On the other hand, an expression such as comprise, include, have, contain and constitute are not intended to be exclusive of other components.

[0039] FIG. 1 is a schematic view showing a schematic configuration of a precombustion-chamber gas engine according to an embodiment of the present invention.

[0040] The precombustion-chamber gas engine 100 includes a cylinder (liner) 2, a cylinder head 4 disposed on a top of the cylinder 2, a piston 8 reciprocably disposed within the cylinder 2, in which a main combustion chamber (main chamber) 6 is defined between the piston 8 and the cylinder head 4. The precombustion-chamber gas engine 100 also includes an intake valve 12 for opening or closing an intake port 10 disposed at the cylinder head 4, and an exhaust valve 16 for opening or closing an exhaust port 14 disposed at the cylinder head 4.

[0041] A precombustion chamber 20 communicating with the main combustion chamber 6 through nozzles 18 is formed inside the cylinder head 4. Further, the precombustion-chamber gas engine 100 includes an ignition-fuel-gas supply channel 24 for supplying ignition fuel gas to the precombustion chamber 20 without interposing the main combustion chamber 6 and an ignition plug 26 for igniting air-fuel mixture containing the ignition fuel gas introduced into the precombustion chamber 20.

[0042] The cylinder head 4 includes a cylinder head body 28, a cylindrical precombustion-chamber cap 30 accommodated in the cylinder head body 28 with the nozzles 18 formed on the bottom, and a plug holder 31 holding the ignition plug 26. In the illustrated exemplary embodiment, the precombustion chamber 20 is defined by an inner peripheral surface of the precombustion-chamber cap 30, a lower surface of the ignition plug 26, and a lower surface of the plug holder 31. That is, the precombustion-chamber cap 30, the ignition plug 26, and the plug holder 31 constitute a precombustion-chamber forming part 22 which defines the precombustion chamber 20. The ignition-fuel-gas supply channel 24 is formed inside the plug holder 31.

[0043] Combustion gas generated in the precombustion chamber 20 is, as shown by dotted lines in the vicinity of the nozzles 18 in FIG. 1, injected as a torch through the nozzles 18 of the precombustion chamber 20 to combust the mixed gas in the main combustion chamber 6. This makes it possible to combust the lean mixed gas in the main combustion chamber 6, thus enabling low fuel consumption. Further, since the combustion of the lean mixed gas in the main combustion chamber 6 is performed at a relatively low temperature, the generation of NO.sub.X or the like is reduced, and low pollution is achieved.

[0044] FIG. 2 is a perspective view showing a schematic shape of the precombustion chamber 20 according to an embodiment. As shown in FIG. 2, the precombustion chamber 20 includes a first passage part 32 (throat part), a second passage part 34, and a space part 36.

[0045] The first passage part 32 is a cylindrical passage part extending upwardly from the nozzles 18. The cross-sectional area of the first passage part 32 (i.e. surface area of a cross-section S1 orthogonal to a straight line L composed of an axis of the first passage part 32 and an extended line thereof) is constant regardless of the height-directional position.

[0046] The second passage part 34 extends upwardly from the first passage part 32 and has an upwardly-increasing cross-sectional area (i.e. surface area of a cross-section S2 orthogonal to the straight line L).

[0047] The space part 36 is a cylindrical space part which extends upwardly from the second passage part 34 and in which the ignition plug 26 (see FIG. 1) is disposed. The cross-sectional area of the space part 36 (i.e. surface area of a cross-section S3 orthogonal to the straight line L) is constant regardless of the height-directional position.

[0048] In an embodiment, for instance as shown in FIG. 1, a second-passage-part forming surface 40 which defines the second passage part 34 is smoothly (without angled corners) connected with a first-passage-part forming surface 38 which defines the first passage part 32 and with a space-part forming surface 42 which defines the space part 36. This prevents an unburnt region (to be afterburned) from remaining in the precombustion chamber 20 and enables efficient combustion in the precombustion chamber 20. In the illustrated exemplary embodiment, the first-passage-part forming surface 38 and the second-passage-part forming surface 40 each form a part of the inner peripheral surface of the precombustion-chamber cap 30. Additionally, the space-part forming surface 42 is composed of a part of the inner peripheral surface of the precombustion-chamber cap 30, a lower surface of the plug holder 31, and a lower surface of the ignition plug 26.

[0049] FIG. 3 is a diagram showing an example of the shape and the arrangement of a cross-section S1 orthogonal to the straight line L in the first passage part 32, a cross-section S2 orthogonal to the straight line L in the second passage part 34, and a cross-section S3 orthogonal to the straight line L in the space part 36, in the precombustion chamber 20 shown in FIG. 2. FIGS. 4 and 5 are diagrams showing an example of a cross-section S4 of the precombustion chamber 20 in FIGS. 2 and 3. The cross-section S4 is a cross-section including the straight line L and a later-described direction A (i.e. a cross-section including the straight line L and a straight line intersecting with the straight line L and parallel to the direction A) in the precombustion chamber 20.

[0050] As shown in FIG. 3, the center O (centroid) of the cross-section S2 of the second passage part 34 is eccentric with respect to the straight line L. Additionally, as shown in FIG. 3, the center P (centroid) of the cross-section S3, orthogonal to the straight line L, of the space part 36 is eccentric with respect to the straight line L in the direction A in which the center O of the cross-section S2 of the second passage part 34 is eccentric with respect to the straight line L.

[0051] With this configuration, the center O of the cross-section S2 of the second passage part 34 is eccentric with respect to the straight line L; thus, as shown by the arrow B in FIG. 5, lean premixed gas which enters from the main combustion chamber 6 through the nozzles 18 into the first passage part 32 moves upwardly through the first passage part 32; then moves upwardly along a surface 44, on an opposite side to the direction A across the straight line L, of the second-passage-part forming surface 40; flows along a top surface 46 of the space-part forming surface 42 toward the direction A side; and moves downwardly along a surface 45, on the direction A side across the straight line L, of the second-passage-part forming surface 40. That is, a flow direction of the lean premixed gas which enters the precombustion chamber 20 from the nozzles 18 can be stabilized in a direction shown by the arrow B.

[0052] Thus, it is possible to facilitate mixing of the lean premixed gas which enters from the main combustion chamber 6 through the nozzles 18 with the ignition fuel gas which enters from the ignition-fuel-gas supply channel 24, in the precombustion chamber 20, and thereby an improved mixture state is stably achieved. As a result, it is possible to stably obtain a torch from the nozzles 18 and thus reduce combustion fluctuation in the main chamber 6.

[0053] In an embodiment, for instance as shown in FIG. 4, the second-passage-part forming surface 40 is configured to satisfy 1>2, where 1 is an angle between the straight line L and a straight line M passing through an upper end 52 of a first line 48 and a lower end 54 of the first line 48; 2 is an angle between the straight line L and a straight line N passing through an upper end 56 of a second line 50 and a lower end 58 of the second line 50, where the first line 48 is a part of the second-passage-part forming surface 40, on the direction A side across the straight line L, in the cross-section S4; the second line 50 is a part of the second-passage-part forming surface 40, on the opposite side to the direction A across the straight line L, in the cross-section S4.

[0054] When 1>2 is satisfied, the lean premixed gas can flow smoothly in the precombustion chamber 20 in accordance with the arrow B in FIG. 5. Thus, it is possible to efficiently facilitate mixing of the lean premixed gas which enters from the nozzles 18 with the ignition fuel gas which enters from the ignition-fuel-gas supply channel 24.

[0055] In an embodiment, the second-passage-part forming surface 40 is configured to satisfy 30<1<45. This enables the lean premixed gas to flow more smoothly in accordance with the arrow B in FIG. 5, resulting in an improved mixture state.

[0056] In an embodiment, as shown in FIG. 4, in the cross-section S4, the first line 48 extends upwardly with increasing a distance d1 from the straight line L. Additionally, in the cross-section S4, the second line 50 includes an extended line part 60 extending from the first-passage-part forming surface 38 in a direction of extending the first-passage-part forming surface 38 (i.e. a direction parallel to the straight line L) and a tapered line part 62 connecting the extended line part 60 and the space-part forming surface 42 and extending upwardly with increasing a distance d2 from the straight line L.

[0057] This makes it easy that the gas which flows downwardly along the first line 48 is introduced under a junction Q of the extended line part 60 and the tapered line part 62, as shown by the arrow B in FIG. 5. This enables the lean premixed gas to flow more smoothly in accordance with the arrow B in FIG. 5, resulting in an improved mixture state.

[0058] In an embodiment, in FIG. 2, the second passage part 34 is symmetric across the cross-section S4. Additionally, as shown in FIGS. 2 and 3, a supply port 64 of the ignition-fuel-gas supply channel 24 is situated away from the cross-section S4.

[0059] With this configuration, the supply port 64 is situated away from the cross-section S4, which is the center of symmetry of the second passage part 34. Thus, a flow direction of the ignition fuel gas g supplied from the supply port 64 can be easily stabilized in the precombustion chamber 20, which makes it possible to facilitate mixing of the ignition fuel gas with the lean premixed gas which enters through the nozzles 18.

[0060] In an embodiment, as shown in at least one of FIGS. 2 and 3, the supply port 64 disposed on the top surface 46 of the space-part forming surface 42 is situated on the opposite side to the direction A across the straight line L. Additionally, the ignition-fuel-gas supply channel 24 is configured to inject the ignition fuel gas g, through the supply port 64, obliquely downward on the direction A side.

[0061] With this configuration, the ignition-fuel-gas supply channel 24 injects the ignition fuel gas g, through the supply port 64, to a relatively large space on the direction A side (i.e. the eccentric direction side of the second passage part 34). Thus, it is possible to facilitate mixing of the ignition fuel gas g supplied through the supply port 64 with the lean premixed gas which enters through the nozzles 18.

[0062] Additionally, since the ignition-fuel-gas supply channel 24 injects the ignition fuel gas g, through the supply port 64, to a relatively large space on the direction A side (i.e. the eccentric direction side of the second passage part 34) when viewing from a direction orthogonal to the cross-section S4, an angle 3 (see FIG. 8) between the straight line M and a direction in which the ignition fuel gas g is injected (i.e. a direction in which the axis of the ignition-fuel-gas supply channel 24 extends from the support port 64) is made larger than an angle 4 (see FIG. 9) between the straight line N and a direction in which the ignition fuel gas g would be injected if the ignition fuel gas g was injected opposite to the direction A side. Thus, a flow of the ignition fuel gas g supplied toward the nozzles 18 is reduced compared with the case shown in FIG. 9, and thereby the amount of the ignition fuel gas g held in the precombustion chamber 20 is increased. Therefore, it is possible to ensure a necessary amount of the ignition fuel gas g in the precombustion chamber 20, with a low supply amount of the ignition fuel gas g.

[0063] Embodiments of the present invention were described in detail above, but the present invention is not limited thereto, and various amendments and modifications may be implemented.

[0064] For instance, the embodiments depicted in FIGS. 4 and 5 showed the case where the second line 50 includes, in the cross-section S4, the extended line part 60 extending from the first-passage-part forming surface 38 in a direction of extending the first-passage-part forming surface 38 (i.e. a direction parallel to the straight line L) and a tapered line part 62 connecting the extended line part 60 with the space-part forming surface 42 and extending upwardly with increasing the distance d2 from the straight line L.

[0065] However, the present invention is not limited to this embodiment. The second line 50 may be wholly inclined in the cross-section S4 so that the distance d2 from the straight line L upwardly increases, for instance as shown in FIG. 6. Alternatively, the second line 50 may be a straight line parallel to the straight line L in the cross-section S4, for instance as shown in FIG. 7.

REFERENCE SIGNS LIST

[0066] 2 Cylinder [0067] 4 Cylinder head [0068] 6 Main combustion chamber [0069] 8 Piston [0070] 10 Intake port [0071] 12 Intake valve [0072] 14 Exhaust port [0073] 16 Exhaust valve [0074] 18 Nozzle [0075] 20 Precombustion chamber [0076] 22 Precombustion-chamber-forming part [0077] 24 Ignition-fuel-gas supply channel [0078] 26 Ignition plug [0079] 28 Cylinder head body [0080] 30 Precombustion-chamber cap [0081] 31 Plug holder [0082] 32 First passage part [0083] 34 Second passage part [0084] 36 Space part [0085] 38 First-passage-part forming surface [0086] 40 Second-passage-part forming surface [0087] 42 Space-part forming surface [0088] 44 Surface [0089] 45 Surface [0090] 46 Top surface [0091] 48 First line [0092] 50 Second line [0093] 52 Upper end [0094] 54 Lower end [0095] 56 Upper end [0096] 58 Lower end [0097] 60 Extended line part [0098] 62 Tapered line part [0099] 64 Supply port [0100] 100 Precombustion-chamber gas engine