internal combustion engine

Abstract

To realize a ventilation system capable of reducing an installation space of a ventilation device and power required to operation the ventilation device so as to be low in cost.SOLUTION: An internal combustion engine which is capable of burning fuel including hydrogen gas comprises: a cylinder block which stores at least one cylinder and includes a crank case provided below the cylinder to store a crank shaft; a rocker cover which demarcates an upper space covering an upper section of a cylinder head provided above the cylinder block; a ventilation gas introduction port which is formed on the crank case; a gas passage forming section which forms a gas passage communicating a crank chamber of the crank case with the upper space of the rocker cover; and an exhaust gas exhaust port which is formed above the rocker cover.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to internal combustion engines. [Background technology]

[0002] Four-stroke engines (for example, gasoline engines and gas engines) perform a compression stroke, ignition / combustion stroke, expansion stroke, etc. to produce work, but it is known that gas containing a small amount of unburned gas (blow-by gas) leaks from the piston ring into the crankcase during the compression stroke.If blow-by gas leaks into the crankcase, the pressure inside the crankcase increases and there is a risk that the unburned gas that has leaked into the crankcase will ignite, so the crankcase is usually equipped with an air bleed valve called a breather.

[0003] When using fuel containing hydrogen gas, it is necessary to improve ventilation efficiency to prevent hydrogen gas from remaining inside the engine, as hydrogen gas has a wider flammable range and is more easily ignited than other fuels such as natural gas and gasoline.

[0004] Patent Document 1 discloses a ventilation device that prevents ignition of hydrogen gas accumulated inside a crankcase when using a fuel containing hydrogen gas. This device has an outside air inlet passage and a ventilation flow path equipped with a ventilation fan connected to the crankcase. The ventilation fan is driven to introduce outside air into the crankcase through the outside air inlet passage and forcibly exhaust gas in the crankcase through the ventilation flow path, thereby reducing the hydrogen gas concentration in the crankcase below the lower limit of the flammable range and preventing ignition of the hydrogen gas in the crankcase. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-127704 Summary of the Invention [Problem to be solved by the invention]

[0006] The ventilation device disclosed in Patent Document 1 requires a ventilation fan or the like to be provided in the crankcase, which increases costs and requires space for providing the ventilation fan and auxiliary power to drive the ventilation fan.

[0007] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to realize a low-cost ventilation system that can reduce the installation space for the ventilation device and the power required for the ventilation device. [Means for solving the problem]

[0008] In order to achieve the above object, one aspect of the internal combustion engine according to the present disclosure is an internal combustion engine capable of burning fuel containing hydrogen gas, and comprises: a cylinder block including a crankcase that houses at least one cylinder and a crankshaft provided below the cylinder; a rocker cover that defines an upper space that covers the upper part of a cylinder head provided above the cylinder block; a ventilation gas inlet port formed in the crankcase; a gas passage forming portion that forms a gas passage that connects the crank chamber of the crankcase and the upper space of the rocker cover; and an exhaust gas outlet port formed in the upper part of the rocker cover. [Effects of the Invention]

[0009] According to one aspect of the internal combustion engine of the present disclosure, when blow-by gas containing hydrogen gas that has accumulated in the crankcase of the engine is discharged to the outside to prevent ignition, etc., the ventilation efficiency of gas containing hydrogen gas can be improved, and the installation space and required power of the ventilation device can be reduced, resulting in cost reduction. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a vertical cross-sectional view of an internal combustion engine according to one embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing the shape of a rocker cover according to one embodiment. [Figure 3] FIG. 3 is a schematic plan view seen from the direction of arrow A in FIG. 2. [Figure 4] 1 is a perspective view of an internal combustion engine according to one embodiment; [Figure 5] 1 is a vertical cross-sectional view of an internal combustion engine according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in these embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention. For example, expressions expressing relative or absolute arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement exactly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. On the other hand, the expressions "comprises," "includes," "has," "includes," or "has" one element are not exclusive expressions that exclude the presence of other elements.

[0012] Fig. 1 is a longitudinal sectional view of an internal combustion engine according to one embodiment. In Fig. 1, an internal combustion engine 10A according to one embodiment is an internal combustion engine capable of burning fuel containing hydrogen gas, and is a four-stroke engine that can be applied to, for example, a gasoline engine, a gas engine, etc.

[0013] The cylinder block 12 of the internal combustion engine 10A comprises a cylinder housing portion 14 that houses at least one cylinder 18, and a crankcase 16 that is provided below the cylinder housing portion 14. A crankshaft 20 that is provided below the cylinder 18 is housed in the crankcase 16. A cylinder head 24 is provided above the cylinder 18, and a rocker cover 22 is provided above the cylinder head 24. The rocker cover 22 defines an upper space Sc between the cylinder block 12 and the rocker cover 22, which covers the upper part of the cylinder head 24. The cylinder head 24 is provided with an ignition plug 26, an intake valve 28, an exhaust valve 30, etc.

[0014] A cylinder chamber is formed inside the cylinder 18, and a piston 32 slides within the cylinder chamber. A crank chamber Cr is formed below the cylinder chamber. A main combustion chamber Rc is formed facing the top surface 32a of the piston 32. Combustion air is supplied from an intake pipe 34 to an intake port 36, and a fuel pipe 44 is connected to the intake pipe 34 or the main combustion chamber Rc, supplying fuel Gf directly to the intake pipe 34 or the main combustion chamber Rc. During the ignition and combustion stroke, the spark plug 26 ignites the gas mixture in the main combustion chamber Rc, propagating a flame f. During the expansion stroke, the piston 32 descends within the cylinder chamber. The reciprocating linear motion of the piston 32 is transmitted to the crankshaft 20 via a connecting rod 38, causing the crankshaft 20 to rotate in the direction of the arrow. During the exhaust stroke, exhaust gas e is discharged from an exhaust port 40 into an exhaust pipe 42 connected to the exhaust port 40. The exhaust gas Gv, which will be described later, refers to a gas including ventilation gas, blow-by gas Gb, which will be described later, and vapor gas, and is distinguished from the exhaust gas e.

[0015] In the embodiment shown in FIG. 1, the tip opening of the fuel pipe 44 is arranged to communicate with the main combustion chamber Rc so that the fuel Gf is directly supplied to the main combustion chamber Rc. In another embodiment, the fuel pipe 44 may be connected to the intake pipe 34 upstream of the intake port 36 so that the fuel Gf is supplied to the intake pipe 34 upstream of the intake port 36 .

[0016] Furthermore, a ventilation gas inlet 46 is formed in the partition wall of the crankcase 16, which defines the crank chamber Cr therein, so that ventilation gas can be introduced into the crank chamber Cr through the ventilation gas inlet 46. Also, a gas passage forming section 48 is provided which forms a gas passage Gp that communicates with the crank chamber Cr and the upper space Sc, and an exhaust gas outlet 50 is formed in the upper part of the rocker cover 22.

[0017] In this configuration, during operation of the internal combustion engine 10A, blow-by gas Gb leaks into the crank chamber Cr through the gap between the cylinder 18 and the piston 32. When the engine is operated using a fuel containing hydrogen gas, the hydrogen gas contained in the blow-by gas Gb gradually increases the hydrogen gas concentration in the crank chamber Cr. In this case, in this embodiment, ventilation gas is introduced through the ventilation gas inlet 46 to dilute the hydrogen gas concentration, thereby reducing the hydrogen gas concentration in the crank chamber Cr below the lower limit of the flammable range. When the pressure in the crank chamber Cr increases due to the introduction of ventilation gas into the crank chamber Cr, the gas in the crank chamber Cr flows into the upper space Sc through the gas passage Gp, which has a relatively low pressure. The gas that flows into the upper space Sc is discharged to the outside of the rocker cover 22 through the exhaust gas outlet 50.

[0018] Since hydrogen gas is lighter than other gases, hydrogen gas that accumulates in the crankcase Cr is more likely to accumulate in the upper part of the crankcase Cr than other gases. 1, the inlet opening Fi of the gas passage Gp, which opens into the crank chamber Cr, is formed at the top of the crank chamber Cr. Therefore, hydrogen gas flows more easily into the gas passage Gp than other gases. Furthermore, in the upper space Sc, hydrogen gas accumulates in the upper part of the upper space Sc, and is therefore efficiently discharged from the exhaust gas discharge port 50 formed at the top of the rocker cover 22.

[0019] As described above, according to this embodiment, hydrogen gas is lighter than other gases, and therefore when mixed with other gases, buoyancy occurs, causing the hydrogen gas to naturally move to the upper space Sc. This eliminates the need for a ventilation fan or other equipment, as well as the installation space and power required for such a fan, thereby reducing costs. Furthermore, in the upper space Sc, the buoyancy of hydrogen gas allows hydrogen gas to be discharged to the outside of the internal combustion engine 10A preferentially over other gases, thereby improving the ventilation efficiency of hydrogen gas compared to other gases.

[0020] When the valve train of the internal combustion engine 10A is of the overhead valve type, as will be described later, a casing for accommodating a power transmission device 82 (a device for transmitting the rotational movement of the crankshaft 20 to the valve drive device) that constitutes part of the valve train is provided across the crankcase 16 and the rocker cover 22. In this case, since the casing can be used as the gas passage forming portion 48, there is no need to provide a new gas passage forming portion 48, which further reduces costs.

[0021] Furthermore, in this embodiment, the fuel pipe 44 is disposed in the upper space Sc, and even if the fuel Gf leaks from the fuel pipe 44, the gasified fuel Gf can be discharged together with the exhaust gas Gv from the exhaust gas discharge port 50. Therefore, it is possible to prevent the leaked fuel Gf from igniting or burning.

[0022] 1, the central axis O of the crankshaft 20 extends in a direction perpendicular to the plane of the page. The internal combustion engine 10A may have only one cylinder 18 or may have multiple cylinders 18 arranged in a direction perpendicular to the plane of the page.

[0023] In one embodiment, as shown in FIG. 1 , the ventilation gas inlet 46 is formed on one side of the crankcase 16 with respect to a vertical plane V that passes through the central axis O of the crankshaft 20. The vertical plane V is a vertical plane that passes through the central axis O of the crankshaft 20. That is, in the embodiment shown in FIG. 1 , the ventilation gas inlet 46 is formed on the side in the direction of arrow b with respect to the vertical plane V. For example, the ventilation gas inlet 46 may be formed outside the cylinder 18. On the other hand, the gas passage forming portion 48 is used on the opposite side (the other side) of the crankcase 16 from the one side with respect to the vertical plane V. For example, the gas passage forming portion 48 may be provided outside the cylinder 18. That is, in the embodiment shown in FIG. 1 , the gas passage forming portion 48 is disposed on the side in the direction of arrow c with respect to the vertical plane V.

[0024] In the embodiment shown in FIG. 1, the vertical plane V is formed by a flat plane extending in a direction perpendicular to the plane of the paper on which FIG. 1 is drawn.

[0025] According to this embodiment, the ventilation gas inlet 46 and the gas passage forming portion 48 are disposed on one side and the other side of a vertical plane V passing through the central axis O of the crankshaft 20, and therefore the ventilation gas introduced from the ventilation gas inlet 46 flows across the interior of the crank chamber Cr from one side to the other side of the vertical plane V. Therefore, most of the gas accumulated in the crank chamber Cr can be ventilated efficiently, improving ventilation efficiency.

[0026] If the internal combustion engine 10A has multiple cylinders 18, the ventilation gas inlet 46 may be provided in the crankcase 16 for each cylinder, or one ventilation gas inlet 46 may be provided for each set of multiple cylinders. The gas passage forming portion 48 may form one gas passage Gp extending in the direction in which the cylinders are arranged so that one gas passage forming portion 48 is shared by multiple cylinders. That is, one gas passage forming portion 48 may be provided for multiple cylinders, or multiple gas passage forming portions 48 may be provided, each partitioned for each cylinder.

[0027] The installation height of the ventilation gas inlet 46 in the crankcase 16 and the height position of the inlet opening Fi of the gas passage forming portion 48 can be selected appropriately.

[0028] 1 , the exhaust gas discharge port 50 is formed on one side of the rocker cover 22 with respect to the vertical plane V. That is, the exhaust gas discharge port 50 is formed on the side in the direction of arrow b with respect to the vertical plane V. As a result, gas that flows out from the outlet opening Fo of the gas passage Gp formed in the gas passage formation portion 48 into the upper space Sc flows from the other side to one side, that is, across the upper space Sc in the direction of arrow b to the exhaust gas discharge port 50. Therefore, gas that has accumulated in the upper space Sc can be efficiently discharged from the exhaust gas discharge port 50, and the ventilation efficiency of the upper space Sc can be improved.

[0029] 1, the exhaust gas discharge port 50 is formed in the partition wall that forms the upper surface 23a of the rocker cover 22. Because hydrogen gas is lighter than other gases, it collects in the upper region of the upper space Sc within the rocker cover 22, that is, in the region that contacts the back surface of the partition wall that forms the upper surface 23a. Because this region is close to the installation position of the exhaust gas discharge port 50, hydrogen gas is discharged from the exhaust gas discharge port 50 in preference to other gases.

[0030] 1, the front and back surfaces of the partition wall that forms the upper surface 23a of the rocker cover 22a form flat surfaces that extend in a substantially horizontal direction. Therefore, when the exhaust gas Gv flows along the back surface of the partition wall in the direction of arrow b, the exhaust gas Gv is not hindered from flowing in the direction of arrow b because there are no protrusions or the like on the back surface of the partition wall, and the exhaust gas Gv can smoothly reach the exhaust gas discharge port 50.

[0031] 1, the rocker cover 22a has side surfaces 23b extending in the vertical direction, and both side surfaces 23b are inclined downward and outward. The exhaust gas discharge port 50 may be formed in an upper region of the side surfaces 23b in addition to the top surface 23a. For example, as shown in FIG. 1, if the height of the side surfaces 23b in the vertical direction is h, the exhaust gas discharge port 50 is formed in the side surfaces 23b in a range from the top surface 23a to a height of h / 3.

[0032] FIG. 2 is a schematic cross-sectional view showing another embodiment of the rocker cover 22, and FIG. 3 is a schematic plan view seen from the direction A in FIG. 2, the upper surface 23a of the rocker cover 22b includes inclined surfaces 23a1 and 23a2 that are inclined upward relative to the horizontal. The exhaust gas discharge port 50 is formed at the top where the inclined surfaces 23a1 and 23a2 intersect. Therefore, the hydrogen gas contained in the exhaust gas Gv discharged from the exhaust gas discharge port 50 collects in a region of the top that is in contact with the back surface of the partition wall that forms the top. Because the exhaust gas discharge port 50 is formed at the top, the hydrogen gas that has collected in a region near the top can be efficiently discharged from the exhaust gas discharge port 50.

[0033] 2 and 3, the inclined surface 23a1 is inclined upward at an angle θ1 with respect to the horizontal plane H, and the inclined surface 23a2 is inclined upward at an angle θ2 with respect to the horizontal plane H. Lr indicates the ridge line where the inclined surfaces 23a1 and 23a2 intersect. That is, the uppermost point of the rocker cover 22 is on the ridge line Lr, and point Pt indicates one of the uppermost points of the rocker cover 22 located on the ridge line Lr. As shown in FIG. 3, the uppermost point Pt is located inside the exhaust gas discharge port 50 in a plan view.

[0034] In another embodiment, side surface 23b and inclined surface 23a2 may form a continuous plane (i.e., the angle formed between side surface 23b and inclined surface 23a2 is 180°), or side surface 23b and inclined surface 23a1 may form a continuous plane. In yet another embodiment, the inclined surfaces 23a1 and 23a2 may not be strictly flat (straight in the cross section shown in FIG. 2), but may form curved surfaces.

[0035] 1 , a ventilation gas introduction passage 52 is connected to the ventilation gas inlet 46. The ventilation gas can be introduced from the ventilation gas introduction passage 52 through the ventilation gas inlet 46 into the crank chamber Cr. A valve device 54 is provided in the ventilation gas introduction passage 52, and the flow rate of the ventilation gas introduced from the ventilation gas introduction passage 52 into the crank chamber Cr can be adjusted by the valve device 54. According to this embodiment, by adjusting the flow rate of the ventilation gas introduced into the crank chamber Cr by the valve device 54, it is possible to prevent the internal pressure of the crank chamber Cr from becoming excessive and to prevent the hydrogen gas concentration in the crank chamber Cr from reaching a flammable range. The valve device 54 may be, for example, a flow rate adjusting valve.

[0036] In another embodiment, the ventilation gas introduction passage 52 may be connected to the intake pipe 34 so that the exhaust gas Gv discharged from the exhaust gas outlet 50 is introduced into the outside air a drawn into the intake port of the compressor 66 .

[0037] In one embodiment, as shown in FIG. 1 , the internal combustion engine 10A includes a compressor 66 that draws in outside air a and generates compressed air. The compressed air generated by the compressor 66 passes through the intake pipe 34 and is supplied from the intake port 36 to a main combustion chamber Rc formed inside the cylinder 18. A portion of the compressed air is used as ventilation gas and is supplied from the ventilation gas inlet port 46 to the crank chamber Cr via a ventilation gas inlet passage 52 branching from the intake pipe 34. A differential pressure valve or the like is provided in the ventilation gas inlet passage 52 as necessary, and the pressure of the ventilation gas flowing through the ventilation gas inlet passage 52 is adjusted by the differential pressure valve.

[0038] The pressure in the crank chamber Cr fluctuates during each stroke, such as during full load, partial load, or during the compression stroke or expansion stroke of the piston 32. According to this embodiment, air compressed by the compressor 66 is introduced into the crank chamber Cr as ventilation gas, so that ventilation gas can be smoothly introduced into the crank chamber Cr even if pressure fluctuations occur in the crank chamber Cr.

[0039] In the embodiment shown in FIG. 1 , the internal combustion engine 10A includes a turbocharger 60. The turbocharger 60 includes an exhaust turbine 64 provided on one end of a rotary shaft 62, and the exhaust turbine 64 includes a turbine wheel 68 attached to one end of the rotary shaft 62. The turbocharger 60 also includes a compressor 66 provided on the other end of the rotary shaft 62, and the compressor 66 includes a compressor wheel 70 attached to the other end of the rotary shaft 62. During the exhaust stroke, exhaust gas e discharged from the main combustion chamber Rc of the cylinder 18 is discharged from the exhaust port 40 into the exhaust pipe 42. The exhaust pipe 42 is connected to the exhaust turbine 64, and the exhaust gas e discharged into the exhaust pipe 42 is introduced into the exhaust turbine 64, causing the turbine wheel 68 to rotate. The rotation of the turbine wheel 68 rotates the rotary shaft 62 and the compressor wheel 70 attached to the other end of the rotary shaft 62. As the compressor wheel 70 rotates, outside air a is drawn into the compressor 66 and compressed to generate compressed air.

[0040] Compressed air generated by the compressor 66 is cooled in the air cooler 72, and the cooled compressed air is supplied to the main combustion chamber Rc of the cylinder 18 through the intake pipe 34. The ventilation gas introduction passage 52 branches off from the intake pipe 34 downstream of the air cooler 72, and a portion of the cooled compressed air is diverted to the ventilation gas introduction passage 52 to be used as ventilation gas.

[0041] According to this embodiment, compressed air generated by the compressor 66 constituting part of the turbocharger 60 is used as the ventilation gas, eliminating the need to install a new compressor and reducing costs. Furthermore, if the compressed air is used as the ventilation gas while it is still hot, the temperature of the cylinder block 12 may rise, causing the lubricant to deteriorate and resulting in poor lubrication. Therefore, by cooling the compressed air with the air cooler 72, the risk of poor lubrication due to a rise in the temperature of the engine body can be avoided.

[0042] 1 , an exhaust gas discharge path 74 is connected to the exhaust gas discharge port 50, and the exhaust gas Gv introduced into the upper space Sc of the rocker cover 22 via the gas passage Gp is ​​discharged to the exhaust gas discharge path 74. A hydrogen concentration sensor 76 is provided in the exhaust gas discharge path 74, and the hydrogen concentration sensor 76 detects the concentration of hydrogen gas contained in the exhaust gas Gv flowing through the exhaust gas discharge path 74.

[0043] According to this embodiment, by detecting the hydrogen gas concentration of the exhaust gas Gv discharged from the exhaust gas outlet 50 with the hydrogen concentration sensor 76, it is possible to determine whether the hydrogen gas concentration contained in the exhaust gas Gv has reached an abnormal range and is in a flammable range. Furthermore, if the internal combustion engine 10A is an internal combustion engine having a plurality of cylinders 18, by providing an exhaust gas discharge path 74 and a hydrogen concentration sensor 76 for each rocker cover 22 of each cylinder 18, it is possible to identify the cylinder in which the hydrogen gas concentration contained in the exhaust gas Gv has reached an abnormal state from the detection value of each hydrogen concentration sensor 76.

[0044] 1, a control unit 78 is provided to which the detected value of the hydrogen concentration sensor 76 is input. When the hydrogen concentration detected by the hydrogen concentration sensor 76 becomes equal to or greater than the lower limit of combustion, the control unit 78 adjusts the opening of the valve device 54 so that the hydrogen concentration becomes less than the lower limit of combustion. For example, the control unit 78 is configured by a processor incorporated in a computer or personal computer.

[0045] According to this embodiment, the control unit 78 can constantly keep the hydrogen gas concentration of the exhaust gas discharged from the exhaust gas outlet 50 below the lower flammable limit. This prevents combustion of the exhaust gas Gv accumulated inside the internal combustion engine 10A. Even if the exhaust gas Gv leaks from the upper space Sc to the outside, the hydrogen concentration of the exhaust gas Gv is below the lower flammable limit, so there is no risk of abnormal combustion of the leaked exhaust gas Gv.

[0046] 4 shows an embodiment in which the internal combustion engine has multiple cylinders. The internal combustion engine 10B according to this embodiment has an independent rocker cover 22 for each cylinder, and the upper surface 23a of the rocker cover 22 (22a) extends horizontally. An exhaust gas discharge port 50 is formed in the upper surface 23a of each rocker cover 22, and each exhaust gas discharge port 50 is connected to an exhaust gas discharge passage 74. A hydrogen concentration sensor 76 is provided in each exhaust gas discharge passage 74, and the detection values ​​of each hydrogen concentration sensor 76 are input to a control unit 78. The control unit 78 can determine which cylinder has an abnormal hydrogen concentration based on the detection values ​​input from each hydrogen concentration sensor 76.

[0047] The internal combustion engine 10B shown in FIG. 4 includes a cylinder block 12 shared by multiple rocker covers 22a. The cylinder block 12 includes a cylinder housing 14 consisting of a single casing and a crankcase 16 below the cylinder housing 14, which is shared by multiple cylinders. Although not shown in FIG. 4, the crankcase 16 is formed with one or more ventilation gas inlets 46, which are connected to ventilation gas inlet passages 52, and which are provided with valve devices 54. A control unit 78 adjusts the aperture of the valve device 54 for a cylinder whose detection value from the hydrogen concentration sensor 76 is equal to or greater than the lower combustion limit, thereby reducing the detection value below the lower combustion limit. This prevents combustion of exhaust gas Gv accumulated in the upper space Sc of the rocker cover 22 for that cylinder 18.

[0048] In one embodiment, a threshold value is set for the hydrogen concentration value detected by the hydrogen concentration sensor 76, and if the detected hydrogen concentration value exceeds the threshold value, an alarm is provided to sound an alarm, or an emergency stop signal is sent from the control unit 78.

[0049] 1, a valve drive device 80 is provided in the upper space Sc of the rocker cover 22. The valve drive device 80 drives the intake valve 28 and the exhaust valve 30. A power transmission device 82 that transmits the rotational motion of the crankshaft 20 to the valve drive device 80 is provided in the gas passage Gp formed in the gas passage formation portion 48. 1, the power transmission device 82 includes a camshaft 84 that rotates when the rotation of the crankshaft 20 is transmitted to it by a power transmission device such as gears, and a push rod 86 that converts the rotation of the camshaft 84 into reciprocating linear motion and transmits it to the valve drive device 80. The above-described valve train is known as an overhead valve type.

[0050] According to this embodiment, in an overhead valve internal combustion engine, a casing that is provided in advance to accommodate the power transmission device 82 can be used as the gas passage forming portion 48. Therefore, there is no need to form a new gas passage forming portion 48, which reduces costs.

[0051] The valve train of the internal combustion engine 10B shown in Fig. 4 is of the overhead valve type, similar to the valve train of the internal combustion engine 10A shown in Fig. 1. A flywheel 90 is provided on the crankshaft 20 outside the crankcase 16, and the rotation of the crankshaft 20 is transmitted to a camshaft 84 by a power transmission device such as a gear 88. Two push rods 86, one for the intake valves and one for the exhaust valves, are provided vertically above the camshaft 84, and the camshaft 84 reciprocates these two push rods 86 up and down.

[0052] FIG. 5 is a longitudinal cross-sectional view showing an internal combustion engine 10C according to yet another embodiment. In this embodiment, a camshaft 84 is provided in the upper space Sc within the rocker cover 22, and the engine is equipped with a valve drive device that drives the intake valves 28 and the exhaust valves 30 via the camshaft 84. A power transmission device that transmits the rotational motion of the crankshaft 20 to the camshaft 84 is formed by a cam chain or the like that is provided on the end side of the crankshaft 20 in the direction in which the center axis O extends. This valve train is known as an overhead cam type. In an overhead valve type internal combustion engine, the camshaft 84 is provided in the upper space Sc, so no casing for accommodating the power transmission device is provided on the side of the cylinder block 12. Therefore, a new gas passage formation portion 48b must be provided. In FIG. 5, the ventilation gas supply system is omitted.

[0053] 1 is an overhead valve type internal combustion engine, and the gas passage forming portion 48a has a casing for accommodating a power transmission device 82, which is provided on the side of the cylinder block 12 integrally with the cylinder block 12 and the rocker cover 22. Therefore, the casing can be used as the gas passage forming portion 48. On the other hand, in the overhead cam type internal combustion engine 10C shown in FIG. 5, the gas passage forming portion 48b has a casing formed separately from the cylinder block 12 and the rocker cover 22, and the casing is attached to the cylinder block 12 and the rocker cover 22.

[0054] When compressed air is cooled by the air cooler 72 as in the above embodiment, moisture contained in the compressed air condenses into droplets, which may contaminate the lubricating oil in the crankcase Cr or adhere to sliding parts, resulting in poor lubrication. These risks are particularly high when fuel contains hydrogen gas, since the amount of water vapor in the exhaust gas e is high. Therefore, in another embodiment, a drain separator (not shown) is provided in the intake flow path downstream of the air cooler 72 formed by the intake pipe 34, and moisture is removed from the compressed air cooled by the drain separator, thereby reducing these risks.

[0055] In one embodiment, as shown in FIG. 1, an exhaust gas return path 92 connected to the exhaust pipe 42 is provided. At least a portion of the exhaust gas e discharged from the exhaust gas return path 92 into the exhaust pipe 42 is returned to the ventilation gas inlet 46 and used as ventilation gas for the crankcase Cr. Because the exhaust gas e is in a low-oxygen state and is more inert than air, using it as ventilation gas reduces the risk of ignition in the crankcase Cr. In addition, the exhaust gas e obtained after burning fuel containing hydrogen gas is soot-free and does not cause contamination of lubricating oil. In addition, because the exhaust gas e discharged into the exhaust pipe 42 is in a pressurized state, no compressor is required to supply it to the crankcase Cr as ventilation gas.

[0056] 1, the exhaust gas e used as the ventilation gas may be the exhaust gas e extracted from the downstream side of the exhaust turbine 64 via an exhaust gas return path 92. In this case, it is possible to avoid a decrease in the efficiency of the turbocharger 60. In another embodiment, as shown in FIG. 1, the exhaust gas e extracted from the upstream side of the exhaust turbine 64 via an exhaust gas return path 94 can be used as the ventilation gas.

[0057] 1, in another embodiment, a heat exchanger 96 for cooling the exhaust gas e is provided in the exhaust gas return path 92. In this way, the exhaust gas e is cooled by the heat exchanger 96 before being used as ventilation gas, so that the volume of the exhaust gas e can be reduced and the volume of the heat exchanger 96 can also be reduced.

[0058] Furthermore, in one embodiment, as shown in Fig. 1, an exhaust gas boiler 102 is provided in the exhaust gas system (in Fig. 1, an exhaust passage 100 downstream of the exhaust turbine 64). In this embodiment, exhaust gas e whose temperature has been reduced in the exhaust gas boiler 102 is introduced into the crankcase Cr via exhaust passages 104, 92, the heat exchanger 96, and the ventilation gas introduction passage 52, and is used as ventilation gas. This makes it possible to reduce the capacity of the heat exchanger 96, and also improve the thermal efficiency of the entire plant by utilizing heat in the exhaust gas boiler 102.

[0059] 1, one embodiment further includes a cooling tower 98 for cooling the cooling water used as a cooling medium for cooling the exhaust gas e in the heat exchanger 96. The cooling water cooled in the cooling tower 98 has a temperature of around 40°C, which can improve the cooling efficiency of the ventilation gas.

[0060] Furthermore, it is preferable to set the temperature of the ventilation gas after being cooled by the heat exchanger 96 to 60 to 80°C. If the temperature of the ventilation gas is below this temperature range, oil mist in the exhaust gas e will adhere to the inner surfaces of the pipes that make up the ventilation gas inlet passage 52, impairing the flow of ventilation gas through these pipes and creating a risk of clogging the pipes. Conversely, if the temperature exceeds this range, cooling of the cylinder block 12 will be hindered, and combustion chamber components such as the piston 32 and cylinder liner will become too hot, potentially causing damage such as liner scuffs. Setting the temperature of the ventilation gas within this temperature range can solve the above problems.

[0061] In one embodiment, when the exhaust gas e is extracted from the exhaust gas return path 94 upstream of the exhaust turbine 64 and used as ventilation gas, a portion of the exhaust gas e extracted upstream of the heat exchanger 96 is discharged via the exhaust gas return path 92 into the exhaust pipe 42 downstream of the exhaust turbine 64. By doing this when the pressure in the crank chamber Cr becomes high, the flow rate of ventilation gas supplied to the crank chamber Cr can be reduced, and the pressure in the crank chamber Cr can be prevented from increasing.

[0062] 1 , an exhaust gas recirculation (EGR) system 106 is provided that returns a portion of the exhaust gas e discharged from the cylinders 18 to the exhaust pipe 42 to the intake line. The EGR system 106 includes an EGR passage 107 connected to the exhaust pipe 42 and the fresh air intake port, and an EGR cooler 108 provided in the EGR passage 107. The EGR passage 107 is connected to the ventilation gas introduction passage 52 downstream of the EGR cooler 108. A portion of the exhaust gas e cooled by the EGR cooler 108 is extracted and supplied to the crank chamber Cr as ventilation gas via the ventilation gas introduction passage 52. According to this embodiment, the exhaust gas e cooled by the EGR cooler 108 can be used to ventilate the crank chamber Cr without providing an additional heat exchanger.

[0063] In the embodiment shown in FIG. 1, the EGR path 107 is connected to the exhaust pipe 42 downstream of the exhaust turbine 64 and the fresh air intake port of the compressor 66, but it may also be connected to the exhaust pipe 42 upstream of the exhaust turbine 64 and the intake pipe 34 downstream of the compressor 66.

[0064] 1, a drain separator 110 is provided in the ventilation gas inlet passage 52 downstream of the heat exchanger 96. By removing drain water from the ventilation gas supplied to the crankcase Cr, the risk of damage to the internal combustion engine 10A due to poor lubrication or the like can be reduced.

[0065] The contents described in each of the above embodiments can be understood, for example, as follows.

[0066] 1) An internal combustion engine according to one embodiment is an internal combustion engine (10) capable of burning a fuel (Gf) containing hydrogen gas, and includes: a cylinder block (12) including a crankcase (16) that houses at least one cylinder (18) and a crankshaft (20) provided below the cylinder (18); a rocker cover (22) that defines an upper space (Sc) that covers the upper part of a cylinder head (24) provided above the cylinder block (12); a ventilation gas inlet (46) formed in the crankcase (16); a gas passage forming portion (48) that forms a gas passage (Gp) that connects a crank chamber (Cr) of the crankcase (16) and the upper space (Sc) of the rocker cover (22); and an exhaust gas outlet (50) formed in an upper part of the rocker cover (22).

[0067] With this configuration, the pressure in the crank chamber (Cr) increases due to the ventilation gas introduced into the crank chamber (Cr) through the ventilation gas inlet (46). Gas, including blow-by gas (Gb), accumulated in the crank chamber (Cr) flows into the gas passage (Gp) formed by the gas passage forming portion (48), rises, and then flows through the gas passage forming portion (48) into the upper space (Sc) defined within the rocker cover (22). The hydrogen gas contained in the gas flowing into the upper space (Sc) is lighter than other gases and therefore accumulates in the upper part of the upper space (Sc). Therefore, the hydrogen gas is efficiently discharged through the exhaust gas outlet (50) formed in the upper part of the rocker cover (22). This eliminates the need for a power-consuming ventilation device, such as a ventilation fan, thereby reducing the installation space and power required for the ventilation device and lowering costs. Furthermore, when the fuel pipe (44) for supplying the fuel (Gf) to the cylinder (18) is arranged in the upper space (Sc), even if a fuel leak occurs from the fuel pipe (44), the leaked fuel gas can be discharged from the exhaust gas discharge port (50) together with other exhaust gases, thereby preventing the fuel (Gf) from igniting in the upper space (Sc).

[0068] 2) In another aspect of the internal combustion engine, in the internal combustion engine described in 1), the ventilation gas inlet (46) is formed on one side of the crankcase (16) with respect to a vertical plane (V) passing through the central axis (O) of the crankshaft (20), and the gas passage forming portion (48) is provided on the opposite side of the vertical plane (V).

[0069] According to this configuration, the ventilation gas inlet (46) and the gas passage forming portion (48) are disposed on opposite sides of the vertical plane (V) passing through the central axis (O) of the crankshaft (20), so that the ventilation gas introduced through the ventilation gas inlet (46) inside the crankcase (16) flows across the interior of the crank chamber (Cr) from one side to the other side of the vertical plane (V). Therefore, gas accumulated in the crank chamber (Cr) can be efficiently ventilated, thereby improving ventilation efficiency.

[0070] 3) In an internal combustion engine according to yet another aspect, in the internal combustion engine according to 2), the exhaust gas discharge port (50) is formed on the one side of the rocker cover (22) with respect to the vertical plane (V).

[0071] With this configuration, the gas flowing from the gas passage forming portion (48) into the upper space (Sc) in the rocker cover (22) flows across the upper space (Sc) from one side to the other side of the vertical plane (V) passing through the central axis (O) of the crankshaft (20) to the exhaust gas discharge port (50). Therefore, the gas accumulated in the upper space (Sc) can be efficiently ventilated, thereby improving ventilation efficiency.

[0072] 4) In accordance with yet another aspect of the internal combustion engine, in the internal combustion engine according to any one of 1) to 3), the exhaust gas discharge port (50) is formed in an upper surface of the rocker cover (22).

[0073] According to this configuration, the exhaust gas discharge port (50) is formed on the upper surface of the rocker cover (22), so that the hydrogen gas accumulated in the upper part of the upper space (Sc) is efficiently discharged from the exhaust gas discharge port (50), thereby improving the ventilation efficiency of the hydrogen gas.

[0074] 5) In yet another aspect of the internal combustion engine, in the internal combustion engine described in 4), the upper surface (23a) of the rocker cover (22 (22b)) includes inclined surfaces (23a1, 23a2), and the exhaust gas discharge port (50) is formed at the uppermost part (Pt) of the inclined surfaces (23a1, 23a2).

[0075] With this configuration, hydrogen gas is lighter than other gases and therefore gathers at the tops (Pt) of the inclined surfaces (23a1, 23a2) along the inner surfaces of the partition walls that form the inclined surfaces (23a1, 23a2). As a result, the hydrogen gas can be efficiently discharged from the exhaust gas discharge port (50) at the tops (Pt).

[0076] 6) In yet another aspect, the internal combustion engine is an internal combustion engine described in any one of 1) to 5), further comprising: a ventilation gas inlet passage (52) connected to the ventilation gas inlet (46) and capable of introducing ventilation gas into the crank chamber (Cr) via the ventilation gas inlet (46); and a valve device (54) provided in the ventilation gas inlet passage (52) and capable of adjusting the flow rate of the ventilation gas.

[0077] According to this configuration, by adjusting the flow rate of the ventilation gas introduced into the crank chamber (Cr) by the valve device (54), it is possible to prevent the internal pressure of the crank chamber (Cr) from becoming excessive and to prevent the hydrogen gas concentration of the gas in the crank chamber (Cr) from reaching a flammable range.

[0078] 7) In yet another aspect, the internal combustion engine is the internal combustion engine described in 6), further comprising a compressor device (66) for generating compressed air to be supplied to the internal combustion engine (10), and is configured such that a portion of the compressed air generated by the compressor device (66) is introduced into the ventilation gas introduction passage (52) as the ventilation gas.

[0079] According to this configuration, part of the compressed air generated by the compressor device (66) is introduced as ventilation gas into the ventilation gas introduction passage (52), so that the ventilation gas can be smoothly introduced into the crankcase (Cr) even if the pressure in the crankcase (Cr) fluctuates to some extent. Furthermore, if the internal combustion engine (10) is equipped with a supercharger (60), the compressor device (66) constituting part of the supercharger (60) can be used as the compressor device. Therefore, there is no need to provide a new compressor device.

[0080] 8) In yet another aspect, the internal combustion engine is the internal combustion engine described in either 6) or 7), further comprising: an exhaust gas discharge passage (74) connected to the exhaust gas discharge port (50) and capable of discharging exhaust gas (Gv) containing the ventilation gas introduced into the upper space (Sc) of the rocker cover (22) via the gas passage (Gp); and a hydrogen concentration sensor (76) provided in the exhaust gas discharge passage (74) for detecting the concentration of hydrogen gas contained in the exhaust gas (Gv).

[0081] With this configuration, it is possible to determine whether the hydrogen gas concentration has reached the flammable range and is in an abnormal state by detecting the hydrogen gas concentration in the exhaust gas (Gv) discharged from the exhaust gas discharge port (50) with the hydrogen concentration sensor (76). In addition, in the case of an internal combustion engine (10) having a plurality of cylinders (18), it is possible to identify the cylinder (18) in which the abnormal state has occurred based on the hydrogen gas concentration in the exhaust gas (e) discharged from each cylinder (18).

[0082] 9) In yet another aspect, the internal combustion engine is the internal combustion engine described in 8), further including a control unit (78) that controls the opening of the valve device (54) so ​​that the detection value of the hydrogen concentration sensor becomes less than the lower combustion limit value.

[0083] According to this configuration, the control unit (78) adjusts the opening of the valve device (54) to control the flow rate of the ventilation gas introduced into the crankcase (Cr), thereby making it possible to suppress the hydrogen gas concentration in the exhaust gas (Gv) discharged from the exhaust gas outlet (50) below the lower flammable limit, thereby preventing the hydrogen gas concentration from reaching the flammable range inside the internal combustion engine (10), thereby preventing ignition, combustion, or the like.

[0084] 10) According to yet another aspect, the internal combustion engine is the internal combustion engine described in any one of 1) to 9), further comprising: a valve drive device (80) provided in the upper space (Sc) of the rocker cover (22) and driving an intake valve (28) and an exhaust valve (30); and a power transmission device (82) provided in the gas passage (Gp) and transmitting the rotational motion of the crankshaft (20) to the valve drive device (80).

[0085] According to this configuration, a casing that is provided in advance to accommodate the power transmission device (82) can be used as the gas passage forming portion (48), which eliminates the need to form a new gas passage forming portion (48), thereby reducing costs.

[0086] 11) In yet another aspect, the internal combustion engine is the internal combustion engine described in 1), further comprising an exhaust passage (42) through which exhaust gas (e) is discharged from the internal combustion engine (10), and an exhaust gas return passage (92) connected to the exhaust passage (42) and supplying at least a portion of the exhaust gas (e) to the ventilation gas inlet (46).

[0087] With this configuration, the low-oxygen exhaust gas (e) is more inert than air, so using it as ventilation gas reduces the risk of ignition in the crankcase (Cr). Furthermore, the exhaust gas (e) obtained after burning fuel containing hydrogen gas is soot-free, so it does not contaminate lubricating oil. Furthermore, the exhaust gas (e) discharged into the exhaust passage (42) is pressurized, so a compressor is not required to supply it to the crankcase (Cr) as ventilation gas.

[0088] 12) An internal combustion engine according to yet another aspect is the internal combustion engine according to 11), further comprising a heat exchanger (96) for cooling the exhaust gas (e) flowing through the exhaust gas return passage (92).

[0089] According to this configuration, the exhaust gas (e) flowing through the exhaust gas return paths (92, 94) can be cooled by the heat exchanger (96) and then used as ventilation gas, thereby reducing the volume of the exhaust gas (e) and the volume of the heat exchanger (96).

[0090] 13) According to yet another aspect, the internal combustion engine is the internal combustion engine described in 12), further comprising a cooling tower (98) for cooling cooling water used as a cooling medium for cooling the exhaust gas (e) in the heat exchanger (96), and the exhaust gas (e) is cooled to a temperature of 60°C or more and 80°C or less by the cooling water in the heat exchanger (96).

[0091] According to this configuration, the cooling water cooled in the cooling tower (98) has a temperature of approximately 40°C, thereby improving the cooling efficiency of the ventilation gas. Furthermore, if the temperature of the ventilation gas is below the above-mentioned temperature range, oil mist in the exhaust gas (e) adheres to the inner surfaces of the piping constituting the ventilation gas inlet passage (52), impairing the flow of the ventilation gas through the piping and potentially causing clogging within the piping. Conversely, if the temperature exceeds the above-mentioned temperature range, cooling of the cylinder block (12) is hindered, and combustion chamber components such as the piston (32) and cylinder liner become too hot, potentially causing damage such as liner scuffs.

[0092] 14) In yet another aspect, the internal combustion engine is the internal combustion engine described in 1), further comprising an exhaust turbine (64) driven by exhaust gas (e) discharged from the internal combustion engine (10), and at least a portion of the exhaust gas (e) discharged from the exhaust turbine (64) is introduced into the ventilation gas inlet (46).

[0093] According to this configuration, the flow rate of the exhaust gas (e) flowing into the exhaust turbine (64) can be ensured, and therefore, deterioration in the efficiency of the turbocharger (60) including the exhaust turbine (64) can be avoided.

[0094] 15) In yet another aspect, the internal combustion engine is the internal combustion engine described in 7), further comprising an intake passage (34) that supplies the compressed air from the compressor device (66) to the internal combustion engine (10), an air cooler (72) provided in the intake passage (34), and a drain separator provided in the intake passage (34) downstream of the air cooler (72).

[0095] When the compressed air is cooled by the air cooler (72), moisture contained in the compressed air condenses into droplets, which may contaminate the lubricating oil in the crankcase (Cr) or cause poor lubrication due to the moisture adhering to sliding parts. These risks are particularly high when the fuel contains hydrogen gas, since the amount of water vapor in the exhaust gas (e) is large. Therefore, according to the above-described embodiment, these risks can be reduced by providing a drain separator downstream of the air cooler (72) and removing moisture from the compressed air cooled by the drain separator. [Explanation of symbols]

[0096] 10(10A, 10B, 10C) Internal combustion engine 12 Cylinder block 14 Cylinder housing 16 Crankcase 18 cylinders 20 crankshaft 22(22a, 22b) Rocker cover 23a Top surface 23a1, 23a2 Slope 23b Side 24 Cylinder head 26 Spark plug 28 Intake valve 30 Exhaust valve 32 piston 32a top surface 34 Intake pipe 36 Air intake 38 Connecting rod 40 exhaust port 42 Exhaust pipe 44 Fuel pipe 46 Ventilation gas inlet 48 (48a, 48b) Gas passage forming portion 50 Exhaust gas outlet 52 Ventilation gas inlet 54 Valve gear 60 Supercharger 62 Rotation axis 64 Exhaust Turbine 66 Compressor 68 Turbine Wheel 70 Compressor Wheel 72 Air cooler 74 Exhaust gas discharge channel 76 Hydrogen concentration sensor 78 Control Unit 80 Valve drive unit 82 Power Transmission Device 84 Camshaft 86 push rod 88 Gears 90 flywheel 92, 94 Exhaust gas return passage 96 Heat exchanger 98 Cooling Tower 100, 104 exhaust passage 102 Exhaust gas boiler 106 EGR system 107 EGR road 108 EGR cooler 110 Drain separator Cr crankcase Fi inlet opening Fo outlet opening Gb blow-by gas Gf fuel Gp gas passage Gv exhaust gas H horizontal plane Lr ridgeline O center axis Pt highest point Rc Main combustion chamber Sc upper space V vertical plane a. Outside air e Exhaust gas

Claims

1. An internal combustion engine capable of burning fuel containing hydrogen gas, a cylinder block including a crankcase in which at least one cylinder is housed and a crankshaft provided below the cylinder is housed; a rocker cover that defines an upper space covering an upper portion of a cylinder head provided above the cylinder block; a ventilation gas inlet formed in the crankcase; a gas passage forming portion that forms a gas passage that connects a crank chamber of the crankcase and the upper space of the rocker cover; an exhaust gas outlet formed in an upper portion of the rocker cover, a ventilation gas inlet passage connected to the ventilation gas inlet and capable of introducing ventilation gas into the crank chamber through the ventilation gas inlet; a valve device provided in the ventilation gas introduction path and capable of adjusting the flow rate of the ventilation gas; a compressor device for generating compressed air to be supplied to the internal combustion engine; The ventilation gas introduction path is configured so that a portion of the compressed air generated by the compressor device is introduced as the ventilation gas. Internal combustion engine.

2. the ventilation gas inlet is formed on one side of the crankcase with respect to a vertical plane passing through a central axis of the crankshaft, the gas passage forming portion is provided on the opposite side to the one side with respect to the vertical plane; 2. The internal combustion engine according to claim 1.

3. the exhaust gas outlet is formed on the one side of the rocker cover with respect to the vertical plane; 3. The internal combustion engine according to claim 2.

4. The exhaust gas outlet is formed on the upper surface of the rocker cover. An internal combustion engine according to any one of claims 1 to 3.

5. the top surface of the rocker cover includes an inclined surface; The exhaust gas outlet is formed at the top of the inclined surface.

5. The internal combustion engine according to claim 4.

6. an exhaust gas discharge passage connected to the exhaust gas discharge port and capable of discharging exhaust gas including the ventilation gas introduced into the upper space of the rocker cover via the gas passage; a hydrogen concentration sensor provided in the exhaust gas discharge path to detect the concentration of hydrogen gas contained in the exhaust gas, 2. The internal combustion engine according to claim 1.

7. a control unit that controls the opening of the valve device so that the detected value of the hydrogen concentration sensor is less than a lower limit of combustion; 7. The internal combustion engine according to claim 6.

8. a valve drive device provided in the upper space of the rocker cover and configured to drive an intake valve and an exhaust valve; a power transmission device provided in the gas passage and configured to transmit the rotational motion of the crankshaft to the valve drive device. An internal combustion engine according to any one of claims 1 to 7.

9. an intake passage that supplies the compressed air from the compressor device to the internal combustion engine; an air cooler provided in the intake passage; a drain separator provided in the intake passage downstream of the air cooler; 2. The internal combustion engine according to claim 1.

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