Internal combustion engine with auxiliary combustion chamber

Abstract

This internal combustion engine with an auxiliary combustion chamber has: a main combustion chamber 41 that is formed from a cylinder head, a cylinder block and a piston; and an auxiliary combustion chamber 43 that is provided to the cylinder head and is partitioned off from the main combustion chamber 41 by a partitioning wall 42, with a first communication passage 44a and a second communication passage 44b, which are provided in the partitioning wall 42 and communicate the auxiliary combustion chamber 43 and the main combustion chamber 41, being provided side by side in the circumferential direction, wherein a main combustion chamber 41-side opening of the first communication passage 44a is circular, and the circumferential direction-side width of a main combustion chamber 41-side opening of the second communication passage 44b is formed longer than the axial direction-side width of the cylinder block 36.

Description

Internal combustion engine with auxiliary combustion chamber

[0001] The present invention relates to an internal combustion engine having a sub-combustion chamber within a main combustion chamber.

[0002] Many internal combustion engines, such as gasoline engines used in automobiles, have an injector (fuel injection device) that injects fuel into the intake passage or combustion chamber, and an ignition device (spark plug) that is arranged facing the combustion chamber inside the cylinder.

[0003] Furthermore, Patent Document 1 discloses an internal combustion engine equipped with an auxiliary combustion chamber within a combustion chamber (main combustion chamber). In the internal combustion engine described in Patent Document 1, a mixture with a relatively high fuel concentration is supplied into the auxiliary combustion chamber, and the mixture in the auxiliary combustion chamber is ignited by an ignition device, causing a flame to be injected (ejected) from the auxiliary combustion chamber into the main combustion chamber and combust the mixture in the main combustion chamber. This makes it possible to improve the ignition ability of the mixture in the main combustion chamber and increase the output of the internal combustion engine, or to reduce the fuel concentration in the main combustion chamber and improve fuel efficiency.

[0004] Furthermore, Patent Document 1 discloses an internal combustion engine that has a plurality of nozzle holes that inject flames from a secondary combustion chamber to promote combustion in the main combustion chamber, and is configured so that the flames are injected radially toward the cylinder wall surface.

[0005] Japanese Patent Application Laid-Open No. 2019-31961

[0006] Direct-injection internal combustion engines are known in which fuel is directly injected into a main combustion chamber from an injector mounted on a cylinder head. Even in such direct-injection internal combustion engines, there are cases where a configuration including a pre-combustion chamber is required, as in Patent Document 1. In direct-injection internal combustion engines with a pre-combustion chamber, it is necessary not only to promote combustion in the main combustion chamber as in Patent Document 1, but also to efficiently introduce fuel from the injector into the pre-combustion chamber to improve combustibility in the pre-combustion chamber.

[0007] The present invention has been made to solve these problems, and its object is to provide an internal combustion engine with a pre-combustion chamber that efficiently introduces fuel into the pre-combustion chamber and promotes combustion in the main combustion chamber by the flame injected from the pre-combustion chamber.

[0008] In order to achieve the above object, the internal combustion engine with an auxiliary combustion chamber of the present invention comprises a main combustion chamber formed by a cylinder head, a cylinder block, and a piston, an auxiliary combustion chamber provided in the cylinder head and separated from the main combustion chamber by a partition wall, a fuel injection device that injects fuel into the main combustion chamber, an ignition device that ignites fuel in the auxiliary combustion chamber, and a plurality of communication passages provided in the partition wall that communicate the auxiliary combustion chamber with the main combustion chamber and are arranged side by side in the circumferential direction of the partition wall, wherein the communication passages have a first communication passage located in the injection area of ​​the fuel injection device and a plurality of second communication passages other than the first communication passage, and are formed to extend toward the central axis of the auxiliary combustion chamber, the opening of the first communication passage on the main combustion chamber side being circular, and the opening of the second communication passage on the main combustion chamber side being formed so that the circumferential width of the opening is longer than the axial width of the cylinder block.

[0009] As a result, fuel injected from the fuel injection device toward the auxiliary combustion chamber within the main combustion chamber is taken into the auxiliary combustion chamber mainly through the first communication passage, and the flame generated by ignition in the auxiliary combustion chamber is injected into the main combustion chamber through the first and second communication passages.

[0010] The flame is widely injected into the main combustion chamber through a plurality of second communication passages that are arranged in a row around the circumferential direction of the partition wall and have an elongated hole-shaped opening on the main combustion chamber side that is long in the circumferential direction, thereby increasing the surface area of ​​the flame within the main combustion chamber and promoting combustion.

[0011] Furthermore, because the opening of the first communication passage on the main combustion chamber side is circular, even if the fuel injected from the fuel injection device moves in the axial direction of the cylinder block relative to the opening of the first communication passage due to, for example, changes in the intake tumble flow within the main combustion chamber, the fuel can still flow efficiently into the first communication passage, improving combustibility within the auxiliary combustion chamber.

[0012] Preferably, the opening areas of all the first and second communication passages on the main combustion chamber side are the same, which allows the same amount of flame to be injected into the main combustion chamber from each of the second and first communication passages, thereby allowing the air-fuel mixture to be combusted approximately evenly around the auxiliary combustion chamber in the main combustion chamber.

[0013] Preferably, the fuel injection device is disposed on the intake side of the cylinder head, and the first communication passage is disposed on the intake side of the partition wall, so that fuel injected from the fuel injection device toward the first communication passage can efficiently reach the first communication passage along the flow of intake air that flows from the intake side to the exhaust side above the main combustion chamber.

[0014] Preferably, the plurality of second communication passages are formed so that their circumferential lengths increase as their installation positions in the partition wall approach the intake side or the exhaust side. This allows the flame to be injected with a long circumferential width toward the intake side or the exhaust side of the main combustion chamber, where fuel is likely to stagnate due to tumble flow, and the flame to be injected with a short circumferential width between the intake side and the exhaust side, allowing fuel to be injected far away without being obstructed by the cylinder head, thereby improving combustibility over a wide area around the auxiliary combustion chamber.

[0015] Preferably, all of the communication passages have the same inclination angle with respect to the direction perpendicular to the central axis of the cylinder block and extend toward the same position on the central axis of the partition wall. This allows flames generated by ignition in the auxiliary combustion chamber to be injected radially evenly from the first and second communication passages into the main combustion chamber, improving combustibility in the main combustion chamber.

[0016] In the internal combustion engine with a pre-combustion chamber of the present invention, fuel injected from the fuel injection device can be efficiently introduced into the pre-combustion chamber mainly through the first communication passage, increasing the fuel concentration in the pre-combustion chamber and improving combustibility. Therefore, when ignition occurs in the pre-combustion chamber, a strong flame can be injected from the pre-combustion chamber.

[0017] Furthermore, the flame generated in the auxiliary combustion chamber is injected through the first and second communication passages so as to spread around the partition wall, and the flame is particularly injected from the second communication passage so as to spread widely, thereby improving combustibility in the main combustion chamber. This improves the output of the internal combustion engine, or reduces fuel consumption by reducing the amount of fuel injected.

[0018] Fig. 1 is a configuration diagram of an intake and exhaust system of an internal combustion engine according to one embodiment of the present invention; Fig. 2 is a top view of a cylinder in the internal combustion engine according to this embodiment; Fig. 3 is a front view showing the shape of a partition wall; Fig. 4 is a side view seen from the intake side showing the shape of the partition wall; Fig. 5 is a longitudinal sectional view showing the detailed shape of the partition wall; Fig. 6 is a longitudinal sectional view inside the cylinder showing the fuel injection state; Fig. 7 is a longitudinal sectional view inside the cylinder showing the injection state of flame from the auxiliary combustion chamber; Fig. 8 is an explanatory view showing the shape of a communication passage in a partition wall according to another embodiment;

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a diagram showing the configuration of an intake and exhaust system of an internal combustion engine 1 (an internal combustion engine with a pre-combustion chamber) according to one embodiment of the present invention.

[0020] As shown in Figure 1, the internal combustion engine 1 of this embodiment is a direct injection gasoline engine having an injector 3 (fuel injection device) that injects gasoline as fuel into the combustion chamber. An intake passage 5 of the internal combustion engine 1 of this embodiment is provided with an air cleaner 6, an intercooler 7, and a throttle valve 8 upstream of the intake port 2 along the flow of intake air. An exhaust passage 11 of the internal combustion engine 1 is provided with an upstream exhaust purification catalyst 12 and a downstream exhaust purification catalyst 13 along the flow of exhaust gas from the exhaust port 31.

[0021] The internal combustion engine 1 is also equipped with a turbocharger 15 and an EGR system 16. The EGR system 16 includes an EGR passage 20 that connects the exhaust passage 11 of the internal combustion engine 1 with the intake passage 5, an EGR valve 21 that changes the flow path area of ​​the EGR passage 20, and an EGR cooler 22 that cools the exhaust gas passing through the EGR passage 20. The EGR passage 20 connects the exhaust passage 11 between the upstream side exhaust purification catalyst 12 and the downstream side exhaust purification catalyst 13 with the intake passage 5 between the air cleaner 6 and the compressor of the turbocharger 15.

[0022] Fig. 2 is a top view of the inside of the cylinder 30 in the internal combustion engine 1 of this embodiment. Fig. 3 is a front view showing the structure of the partition wall 42 that defines the auxiliary combustion chamber 43 therein. Fig. 4 is a side view of the partition wall 42 as seen from the intake side.

[0023] 2, the internal combustion engine 1 is provided with two intake ports 2 and two exhaust ports 31 for each cylinder 30. Furthermore, each of the two intake ports 2 is provided with an intake valve 32, and each of the two exhaust ports 31 is provided with an exhaust valve 33. In the upper part (cylinder head 34) of the cylinder 30 of the internal combustion engine 1, the two intake ports 2 are arranged side by side on one side of the center, and the two exhaust ports 31 are arranged side by side on the other side.

[0024] One injector 3 is provided for each cylinder in the cylinder head 34, and is located circumferentially between two intake ports 2. The injector 3 is positioned so as to inject fuel toward the upper center of the combustion chamber, more specifically, the main combustion chamber 41 described below. A spark plug 35 (ignition device) is provided in the center of the cylinder head 34. The bottom surface of the cylinder head 34 facing the main combustion chamber 41 is pent-roof shaped, sloping downward (toward the piston 37) from the center in the intake / exhaust direction toward both the intake side and the exhaust side.

[0025] Within the cylinder 30, there is provided a main combustion chamber 41, which is a substantially cylindrical space surrounded by the cylinder block 36, cylinder head 34, and piston 37. Furthermore, an auxiliary combustion chamber 43 is provided at the upper center of the main combustion chamber 41. Specifically, the cylinder head 34 is provided with a partition wall 42 that surrounds the center electrode of the ignition plug 35, and the portion of the main combustion chamber 41 surrounded by the partition wall 42 forms the auxiliary combustion chamber 43. The main combustion chamber 41 has a substantially circular cross section taken along a plane perpendicular to the movement direction of the piston 37. The partition wall 42 is also substantially hemispherical, protruding downward (toward the piston 37), and has a substantially cylindrical cross section taken along a plane perpendicular to the movement direction of the piston 37. The partition wall 42 is provided with a plurality of communication passages 44a, 44b, which communicate between the main combustion chamber 41 and the auxiliary combustion chamber 43.

[0026] The operation of the internal combustion engine 1 is controlled by a control unit 50 (controller). The control unit 50 is composed of an output device, a storage device (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), etc. The control unit 50 acquires the crank angle, intake air amount, exhaust temperature, EGR gas amount, etc., and controls the operation of the injector 3, the spark plug 35, the throttle valve 8, the EGR valve 21, etc.

[0027] 2 to 4, in this embodiment, eight communicating passages 44a, 44b are arranged at approximately equal intervals around the circumferential direction of the partition wall 42. The communicating passages 44a, 44b are provided near the radially outermost portion (near the upper end of the approximately hemispherical portion protruding downward) in a cross section of the partition wall 42 taken along a plane perpendicular to the direction of movement of the piston 37.

[0028] Of the eight communication passages 44a, 44b, the first communication passage 44a, which is located directly opposite the fuel injection port 3a of the injector 3, has a circular opening on the main combustion chamber 41 side. Fuel injected from the injector 3 is directed toward the first communication passage 44a, and a large amount of fuel flows into the communication passage 44a due to the penetration force of the fuel injection. In other words, the first communication passage 44a is located in the injection area of ​​the fuel injected from the injector 3.

[0029] Of the eight communication passages 44a, 44b, the seven second communication passages 44b other than the first communication passage 44a are elongated holes that are long in the circumferential direction of the partition wall 42. The major axis of the second communication passages 44b is longer than the diameter of the first communication passage 44a, and the minor axis (diameter in the vertical direction) of the second communication passages 44b is shorter than the diameter of the first communication passage 44a.

[0030] Furthermore, the opening area of ​​the first communication passage 44a on the main combustion chamber 41 side is set to be the same as the opening area of ​​each second communication passage 44b on the main combustion chamber 41 side. As shown in FIG. 5 , the first communication passage 44a and the second communication passage 44b extend at an angle relative to a plane perpendicular to the axis CL of the partition wall 42 (the axis of the cylinder block 36), and are inclined upward (toward the spark plug 35) from the main combustion chamber 41 toward the auxiliary combustion chamber 43. The axes of all of the communication passages 44a, 44b are set to intersect at the same intersection point P1 on the axis CL of the partition wall 42. In this embodiment, the partition wall 42 is located at the center of the cylinder block 36, and the intersection point P1 of the axes of the first communication passage 44a and the second communication passage 44b is located on the central axis of the cylinder block 36.

[0031] As described above, the internal combustion engine 1 of this embodiment is provided with the auxiliary combustion chamber 43, which is partitioned by the partition wall 42, at the upper center of the main combustion chamber 41. The partition wall 42 is provided with communication passages 44a, 44b that connect the main combustion chamber 41 and the auxiliary combustion chamber 43.

[0032] As shown in Figure 6, this embodiment uses a direct-injection injector 3, which first injects fuel to supply it into the main combustion chamber 41. Then, another injection is performed to supply fuel to the auxiliary combustion chamber 43. The injector 3 is positioned to inject fuel toward the auxiliary combustion chamber 43. As the piston 37 moves in the compression direction while injecting fuel, some of the fuel that has reached the periphery of the partition wall 42 flows into the auxiliary combustion chamber 43 through the communication passages 44a, 44b. The remaining fuel that does not flow into the auxiliary combustion chamber 43 is mixed with the intake air in the main combustion chamber 41, just like the initially injected fuel. Note that a tumble flow, in which the intake air swirls vertically, is generated in the main combustion chamber 41.

[0033] The air-fuel mixture in the auxiliary combustion chamber 43 is then ignited by the spark plug 35. As a result, as shown in Figure 7, the flame generated by ignition in the auxiliary combustion chamber 43 passes through the communication passages 44a and 44b and is injected into the main combustion chamber 41, causing the air-fuel mixture in the main combustion chamber 41 to combust.

[0034] The communicating passages 44a, 44b are arranged in a row at approximately equal intervals in the circumferential direction in the partition wall 42 of the auxiliary combustion chamber 43, which is located approximately in the center of the main combustion chamber 41, so that flames are injected from the auxiliary combustion chamber 43 radially outward of the main combustion chamber 41 around the entire circumference.

[0035] In this embodiment, the second communication passage 44b is an elongated hole extending in the circumferential direction of the partition wall 42, so that the flame injected from the second communication passage 44b is injected so as to spread in the circumferential direction from near the center of the main combustion chamber 41. Therefore, the surface area of ​​the flame injected from the second communication passage 44b can be increased, and combustion in the main combustion chamber 41 can be promoted.

[0036] Furthermore, in the main combustion chamber 41, tumble flow is generated by the intake air, and its strength varies in correlation with the intake air volume. Therefore, the fuel injected from the injector 3 toward the first communication passage 44a may be affected by the tumble flow in the main combustion chamber 41 and reach a different position relative to the first communication passage 44a in the axial direction of the cylinder block 36 (the axial direction of the cylinder 30: the up-down direction). However, because the opening of the first communication passage 44a directly facing the fuel injection port 3a of the injector 3 is circular, even if the fuel injected from the injector 3 moves vertically and horizontally in the main combustion chamber 41 due to the tumble flow, it easily flows into the first communication passage 44a. This increases the fuel concentration in the auxiliary combustion chamber 43 and improves combustibility. Therefore, a stronger flame can be injected from the auxiliary combustion chamber 43 to further promote combustion in the main combustion chamber 41, improving the power output of the internal combustion engine 1 or reducing the fuel injection amount and improving fuel economy. Furthermore, the outflow of unburned gas from the main combustion chamber 41 can be suppressed.

[0037] Furthermore, since the opening area of ​​the first communication passages 44a lined up in the circumferential direction of the partition wall 42 is set to be the same as the opening area of ​​each of the second communication passages 44b, the same amount of flame can be injected from each of the communication passages 44a, 44b from the auxiliary combustion chamber 43 to the main combustion chamber 41. Therefore, the air-fuel mixture can be combusted approximately uniformly and efficiently around the auxiliary combustion chamber 43 in the main combustion chamber 41.

[0038] Furthermore, since the injector 3 is disposed on the intake side (intake valve 32 side) of the cylinder head 34, the fuel injected from the injector 3 toward the first communication passage 44a can efficiently reach the first communication passage 44a along the tumble flow of intake air that flows from the intake side to the exhaust side at the top of the main combustion chamber 41.

[0039] Furthermore, all of the communicating passages 44a, 44b have the same inclination angle with respect to the central axis CL of the partition wall 42, i.e., the direction perpendicular to the central axis of the cylinder block 36, and extend toward the intersection point P1 at the same position on the central axis CL. Therefore, the flame generated by ignition in the auxiliary combustion chamber 43 can be sprayed radially from the first communicating passage 44a and the second communicating passage 44b into the main combustion chamber 41 at the same angle, thereby improving combustibility in the main combustion chamber 41.

[0040] The present invention is not limited to the above embodiment. For example, the circumferential lengths of the multiple second communication passages 44b provided in the partition wall 42 may vary depending on the installation position. As shown in Figure 8, the circumferential lengths of the second communication passages 44b (indicated by dashed arrows in Figure 8) may be shorter for the second communication passages 44b located to the sides in the intake / exhaust direction and longer as they approach the intake side or the exhaust side. Figure 8 also shows a cross-sectional view of the partition wall 42 and the shape of each second communication passage 44b as viewed from the front.

[0041] As a result, in the main combustion chamber 41, a flame is injected with a long circumferential width toward the intake side or exhaust side where fuel is likely to stagnate due to tumble flow, improving combustibility, and a flame is injected with a short circumferential width between the intake side and exhaust side, allowing fuel to be injected far outward in the circumferential direction without being obstructed by the wall surface of the pent roof type cylinder head 34, improving combustibility over a wide area around the auxiliary combustion chamber 43.

[0042] For example, in the above embodiment, a total of eight first communication passages 44a and second communication passages 44b are provided in the partition wall 42 and aligned in the circumferential direction, but the number may be more than eight or may be other numbers. Furthermore, the position and detailed shape of each communication passage 44a, 44b may be changed as appropriate. For example, the shape of the opening of the second communication passage 44b on the main combustion chamber 41 side may be a rectangle, a pentagon, a triangle, or the like that is elongated in the circumferential direction of the partition wall 42.

[0043] The present invention may also be applied to an internal combustion engine in which the central axis CL of the partition wall 42 is inclined with respect to the central axis of the cylinder block 36. In this case, it is preferable that all of the communication passages 44a, 44b are formed so that they have the same inclination angle with respect to the direction perpendicular to the central axis of the cylinder block 36 and extend toward the same position on the central axis of the partition wall 42.

[0044] In this embodiment, one cylinder is provided with two intake valves 32 and two exhaust valves 33, but the present invention can also be applied to an internal combustion engine with other numbers, such as one intake valve 32 and one exhaust valve 33. Furthermore, the internal combustion engine of the present invention can be applied to various internal combustion engines, such as those used to drive automobiles.

[0045] In this embodiment, the injector 3 that supplies fuel to the auxiliary combustion chamber 43 is used as a means for supplying fuel to the main combustion chamber 41, but a separate injector may also be provided, and the injector may be installed not only inside the cylinder but also in the intake port, thereby enabling application of intake port injection.

[0046] REFERENCE SIGNS LIST 1 Internal combustion engine (internal combustion engine with auxiliary combustion chamber) 3 Injector (fuel injection device) 3a Fuel injection hole 34 Cylinder head 35 Spark plug (ignition device) 36 Cylinder block 37 Piston 41 Main combustion chamber 43 Auxiliary combustion chamber 42 Partition wall 44a First communication passage (communication passage) 44b Second communication passage (communication passage)

Claims

1. an internal combustion engine with a pre-combustion chamber, comprising: a main combustion chamber formed by a cylinder head, a cylinder block, and a piston; an auxiliary combustion chamber provided in the cylinder head and partitioned from the main combustion chamber by a partition wall; a fuel injection device that injects fuel from the main combustion chamber toward the auxiliary combustion chamber; and an ignition device that ignites fuel in the auxiliary combustion chamber, wherein the partition wall is provided with a plurality of communication passages that communicate the auxiliary combustion chamber with the main combustion chamber and are arranged side by side in the circumferential direction of the partition wall, the communication passage is formed to extend from the main combustion chamber toward the central axis of the auxiliary combustion chamber, and includes a first communication passage facing the fuel injection device and located in an injection region, and a second communication passage other than the first communication passage, The opening of the first communication passage on the side of the main combustion chamber is circular, and the opening of the second communication passage on the side of the main combustion chamber is formed so that the width in the circumferential direction is longer than the width in the axial direction of the cylinder block. An internal combustion engine with a pre-combustion chamber.

2. The opening areas of all the first communication passages and the second communication passages on the main combustion chamber side are the same.

2. The internal combustion engine with a pre-combustion chamber according to claim 1.

3. the fuel injection device is disposed on the intake side of the cylinder head, The first communication passage is disposed on the intake side of the partition wall.

3. The internal combustion engine with a pre-combustion chamber according to claim 1 or 2.

4. The second communication passages are formed such that their circumferential lengths increase as their installation positions in the partition wall approach the intake side or the exhaust side.

4. An internal combustion engine with a combustion chamber according to claim 1.

5. All of the communication passages have the same inclination angle with respect to the direction perpendicular to the central axis of the cylinder block, and extend toward the same position on the central axis of the partition wall.

5. An internal combustion engine with a combustion chamber according to claim 1.