Internal combustion engine

Abstract

To provide an internal combustion engine capable of reducing cooling loss by using steam generated due to combustion.SOLUTION: An internal combustion engine comprises: a piston 4 that reciprocates in conjunction with rotation of a crankshaft 1; a combustion chamber C that is formed between the piston 4 and a cylinder head 3, and in which hydrogen gas is burned; and a cooling unit D that is arranged on a side wall defining the combustion chamber C, and cools the combustion chamber C. The cooling unit D comprises a high-temperature cooling area D1 that is arranged on a top dead center side in an operating direction of the piston 4, and a low-temperature cooling area D2 that is at a lower temperature than the high-temperature cooling area D1 and is arranged on a bottom dead center side with respect to the high-temperature cooling area D1 in the operating direction of the piston 4.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an internal combustion engine. [Background technology]

[0002] Patent Document 1 describes an internal combustion engine having a spark ignition engine that burns an air-fuel mixture with an excess air ratio λ of 1.7 or more, the engine having a water injection device that injects water into the combustion chamber.

[0003] In the spark ignition engine described in Patent Document 1, water is injected so that water vapor is distributed only on the top surface of the piston, and not in the main combustion region. This maintains combustion in the main combustion region while lowering the gas temperature only near the piston wall, thereby suppressing wall heat transfer and knocking.

[0004] Furthermore, Patent Document 1 describes that by applying stratified steam heat insulation to ultra-lean combustion, it is possible to improve thermal efficiency by suppressing knock, thereby advancing the ignition angle and reducing cooling losses. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-169630 A Summary of the Invention [Problem to be solved by the invention]

[0006] In internal combustion engines, which obtain their driving force by burning hydrogen gas in a combustion chamber, the flame propagates quickly during combustion, which tends to increase cooling loss and reduce thermal efficiency.

[0007] For these reasons, in order to reduce cooling loss, it is conceivable to configure the engine so that water injection is possible as described in Patent Document 1. However, in order to perform water injection as described in Patent Document 1, an injector dedicated to water is required, which leads to an increase in the number of parts and thus to an increase in costs.

[0008] One possible solution is to use the water generated by the combustion of hydrogen gas; however, because the inside of the cylinder is exposed to high temperatures and pressures during combustion, it is not possible to expect any vaporization effect of liquid water.

[0009] For these reasons, there is a demand for an internal combustion engine that can reduce cooling losses by utilizing the water vapor generated by combustion. [Means for solving the problem]

[0010] The internal combustion engine according to the present invention has a characteristic configuration comprising a piston that reciprocates in conjunction with the rotation of a crankshaft, a combustion chamber formed between the piston and a cylinder head for burning hydrogen gas, and a cooling section that is disposed on a side wall that defines the combustion chamber and cools the combustion chamber, the cooling section having a high-temperature cooling region that is disposed on the top dead center side in the operating direction of the piston, and a low-temperature cooling region that is cooler than the high-temperature cooling region and is disposed on the bottom dead center side of the high-temperature cooling region in the operating direction.

[0011] According to this configuration, in the combustion stroke, the top surface of the piston is in the high-temperature cooling region, so that the cooling loss during combustion is reduced. In addition, in this combustion stroke, the water present in the combustion chamber is vaporized by heat, and a layer of water vapor is formed along the outer periphery of the combustion chamber, so that the water vapor layer prevents the combustion gas from contacting the side wall of the combustion chamber, suppressing the inconvenience of temperature drop. In addition, when the top surface of the piston moves from the high-temperature cooling region to the bottom dead center side in the combustion stroke, the low-temperature cooling region condenses the water vapor contained in the combustion gas, reducing the internal pressure of the combustion chamber and making it possible to reduce the load when the piston operates in the next exhaust stroke. In this way, by configuring the cooling section surrounding the combustion chamber with a high-temperature cooling region on the top dead center side and a low-temperature cooling region on the bottom dead center side of the high-temperature cooling region, the cooling loss is reduced even when the flame propagation during combustion is fast. Therefore, an engine that makes it possible to reduce cooling loss by utilizing the water vapor generated by combustion has been configured. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a vertical sectional view of an internal combustion engine. [Diagram 2] FIG. 2 is a block diagram showing a configuration of a cooling unit. [Diagram 3] 1 is a vertical cross-sectional view of an internal combustion engine during an intake stroke. [Figure 4] FIG. 1 is a vertical cross-sectional view of an internal combustion engine during a compression stroke. [Diagram 5] FIG. 2 is a vertical cross-sectional view of an internal combustion engine immediately after ignition at a spark plug. [Figure 6] FIG. 1 is a vertical cross-sectional view of an internal combustion engine in which a piston is near bottom dead center during an expansion stroke. [Figure 7] FIG. 2 is a vertical sectional view of an internal combustion engine when the exhaust stroke is started. [Figure 8] FIG. 4 is a PV diagram of the internal combustion engine of this configuration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of an internal combustion engine according to the present invention will be described with reference to the drawings. In this embodiment, as an example of an internal combustion engine, a configuration in which a water jacket constituting a cooling part is divided into upper and lower parts will be described. However, the present invention is not limited to the following embodiment, and various modifications can be made to the structure of the combustion chamber C and the configuration of the cooling part D without departing from the gist of the invention.

[0014] [Basic configuration] 1 shows an internal combustion engine E that is installed in a vehicle such as a passenger car. This internal combustion engine E has a cylinder head 3 on top of a cylinder block 2 that supports a crankshaft 1, pistons 4 are housed in the cylinder bores of the cylinder block 2 so as to be capable of reciprocating freely, and the pistons 4 are connected to the crankshaft 1 by connecting rods 5, making it a four-stroke engine. This internal combustion engine E uses hydrogen gas as fuel.

[0015] 1, in an internal combustion engine E, a combustion chamber C is formed in a region surrounded by a top surface 4T of a piston 4, the lower surface of a cylinder head 3 at a position opposite to the top surface 4T of the piston 4, and an upper side wall of a cylinder block 2. In the cylinder head 3, an intake passage 15 that draws air into the combustion chamber C, and an exhaust passage 16 that exhausts combustion gas from the combustion chamber C are formed.

[0016] The cylinder head 3 is equipped with an intake valve Va that opens and closes the intake passage 15, and an exhaust valve Vb that opens and closes the exhaust passage 16. The internal combustion engine E is equipped with an intake camshaft 7 that controls the intake valve Va, and an exhaust camshaft 8 that controls the exhaust valve Vb, located at an upper position of the cylinder head 3.

[0017] The internal combustion engine E includes an intake timing control device VTa coaxially arranged with an intake camshaft 7, and an exhaust timing control device VTb coaxially arranged with an exhaust camshaft 8.

[0018] The intake timing control device VTa has an intake side drive case 21, and an intake side pulley portion 21P is formed on the outer periphery of this intake side drive case 21. The intake timing control device VTa controls the relative rotation phase between the intake camshaft 7 and the intake side drive case 21 by the driving force of an electric actuator (which may be a hydraulic actuator), and controls the opening and closing timing of the intake valve Va.

[0019] Similarly, the exhaust timing control device VTb has an exhaust side drive case 22, and an exhaust side pulley portion 22P is formed on the outer periphery of this exhaust side drive case 22. This exhaust timing control device VTb controls the relative rotation phase between the exhaust camshaft 8 and the exhaust side drive case 22 by the driving force of an electric actuator (which may be a hydraulic actuator), and controls the opening and closing timing of the exhaust valve Vb.

[0020] In the internal combustion engine E, a timing belt 6 (which may be a timing chain) is wound around an output pulley portion 1P that rotates integrally with the crankshaft 1, an intake side pulley portion 21P, and an exhaust side pulley portion 22P.

[0021] With this configuration, the intake camshaft 7 and exhaust camshaft 8 rotate synchronously with the crankshaft 1, and the intake valve Va and exhaust valve Vb are opened and closed. Furthermore, the opening and closing timing of the intake valve Va and exhaust valve Vb is controlled (to the advance side or retard side) by the control of the intake timing control device VTa or the exhaust timing control device VTb.

[0022] The cylinder head 3 is equipped with an in-cylinder injector 9 that injects fuel (hydrogen gas) into the combustion chamber C, and an ignition plug 10 that ignites the air-fuel mixture in the combustion chamber C. Furthermore, the cylinder head 3 is connected to an intake manifold 11 that supplies air to the combustion chamber C via an intake valve Va, and an exhaust manifold 12 that sends out the combustion gas from the combustion chamber C via an exhaust valve Vb.

[0023] The intake manifold 11 is equipped with a throttle valve 13 that controls the amount of intake air. The exhaust manifold 12 sends out exhaust gas to a catalytic converter 14 that purifies the exhaust gas with a catalyst.

[0024] [Cooling section] 1 and 2, an internal combustion engine E has a first cooling section D1 and a second cooling section D2 formed in a side wall of a combustion chamber C as a cooling section D for cooling a combustion chamber C. The side wall defines the combustion chamber C in an upper portion of a cylinder block 2, and a water jacket divided into two in the operating direction of a piston 4 is disposed inside the side wall.

[0025] The cooling section D includes a water jacket divided into two parts, a first cooling section D1 arranged on the top dead center side in the operating direction of the piston 4, and a second cooling section D2 arranged on the bottom dead center side in the operating direction of the piston 4. The first cooling section D1 and the second cooling section D2 are arranged side by side in the operating direction of the piston 4. In the cooling section D, the first cooling section D1 functions as a high-temperature cooling region, and the second cooling section D2 functions as a low-temperature cooling region.

[0026] The first cooling part D1 is maintained at a temperature within a range of, for example, 70° C. to 90° C., and the second cooling part D2 is maintained at a temperature within a range of, for example, 15° C. to 25° C. As a result, the temperature of the first cooling part D1 acts on the combustion chamber C when the top surface 4T of the piston 4 is on the top dead center (TDC) side of the boundary Ds between the first cooling part D1 and the second cooling part D2 (hereinafter, this may be referred to as a high-temperature cooling state).

[0027] In contrast, when the top surface 4T of the piston 4 is located on the bottom dead center (BDC) side of the boundary Ds between the first cooling section D1 (high temperature cooling area) and the second cooling section D2 (low temperature cooling area), the temperature of the second cooling section D2 is applied to the area of ​​the combustion chamber C close to the top surface 4T of the piston 4 (hereinafter sometimes referred to as the low temperature cooling state).

[0028] As shown in FIG. 2, in the combustion chamber C, the position of the top surface 4T of the piston 4 when the piston 4 is at top dead center is indicated as “TDC”, and the position of the top surface 4T of the piston 4 when the piston 4 is at bottom dead center is indicated as “BDC”.

[0029] 2, the distance between "TDC" and "BDC" in the operating direction of the piston 4 is the stroke X of the piston 4, and the low-temperature cooling region length Y in the operating direction of the piston 4 (the dimension in the operating direction of the piston 4 of the region of the second cooling part D2) is set to less than half (e.g., 40% or less, preferably 20% or less) 20% or less of the stroke X. As a result, the dimension in the operating direction of the piston 4 of the low-temperature cooling region is smaller than the dimension in the operating direction of the piston 4 of the high-temperature cooling region.

[0030] [Cooling section: 1st cooling section] 2, the first cooling section D1 is connected to a first cooling water passage 25 that circulates the cooling water. The first cooling water passage 25 includes a first water pump P1 that circulates the cooling water in the passage, a first radiator 26 that dissipates heat from the cooling water, and a first water temperature sensor S1 that detects the water temperature of the first cooling section D1.

[0031] The first radiator 26 is equipped with a radiator fan 26a whose air volume can be adjusted. As the cooling water, a long-life coolant (LLC) containing ethylene glycol, propylene glycol, or the like is used, but insulating oil or the like may also be used.

[0032] As a result, while the internal combustion engine E is operating, the amount of coolant circulated per unit time by the first water pump P1 and the amount of air blown by the radiator fan 26a are controlled in a manner that feeds back the water temperature detected by the first water temperature sensor S1. This control maintains the water temperature of the first cooling section D1 in the range of 70°C to 90°C.

[0033] [Cooling section: 2nd cooling section] 2, the second cooling section D2 is connected to a second cooling water passage 28 that circulates cooling water. The second cooling water passage 28 includes a second water pump P2, a chiller 29, and a second water temperature sensor S2 that detects the water temperature of the second cooling section D2.

[0034] Furthermore, the chiller 29 removes heat from the water flowing in the second cooling water passage 28 by using the refrigerant supplied from the cooling unit F. The refrigerant used in the cooling unit F is hydrofluorocarbon (HFC), hydrofluoroolefin (HFO), or the like.

[0035] The cooling unit F uses a refrigeration cycle including a compressor 31, a condenser 32, a receiver 33, an expansion valve 34, and an accumulator 35, which are arranged in a refrigerant flow path 30 through which the refrigerant circulates. Note that the cooling unit F may use a radiator or a heater to adjust the temperature of the cooling water instead of using the refrigeration cycle to adjust the temperature.

[0036] As a result, while the internal combustion engine E is operating, the amount of cooling water circulated per unit time by the second water pump P2 and the amount of refrigerant circulated by the compressor 31 are controlled by feeding back the water temperature detected by the second water temperature sensor S2. Through this control, the water temperature of the second cooling section D2 is maintained in the range of 15°C to 25°C.

[0037] Although not shown in the drawings, the internal combustion engine E is equipped with a control device that sets a target temperature value (70°C to 90°C) for the first cooling section D1 and a target temperature value (15°C to 25°C) for the second cooling section D2 as control targets. This control device controls the temperature of the first cooling section D1 and the temperature of the second cooling section D2 separately in a form in which the detection signal of the first water temperature sensor S1 and the detection signal of the second water temperature sensor S2 are fed back.

[0038] [Internal combustion engine process] The relationship between the stroke of the piston 4 of the internal combustion engine E and the heat acting from the cooling section D (first cooling section D1, second cooling section D2) will be described with reference to Figs. 3 to 7.

[0039] As described above, when the top surface 4T of the piston 4 is on the top dead center (TDC) side of the boundary Ds, the internal combustion engine E is in a high-temperature cooling state in which the temperature of the first cooling portion D1 acts on the combustion chamber C. Also, when the top surface 4T of the piston 4 is on the bottom dead center (BDC) side of the boundary Ds, the internal combustion engine E is in a low-temperature cooling state in which the temperature of the second cooling portion D2 acts on the combustion chamber C.

[0040] For this reason, as shown in Fig. 3, when the top surface 4T of the piston 4 reaches the bottom dead center (BDC) side of the boundary Ds during the intake stroke, the internal combustion engine E enters a low-temperature cooling state in which heat is removed by the second cooling section D2. As a result, part of the combustion gas in the vicinity of the top surface 4T of the piston 4 condenses and turns into water (for example, in a mist state), reducing the gas density in the combustion chamber C and enabling an increase in the amount of fresh air taken in.

[0041] Furthermore, when the piston 4 begins to move from top dead center (TDC) to bottom dead center (BDC) at the beginning of the intake stroke (not shown), the internal combustion engine E is in a high-temperature cooling state in which the heat of the first cooling section D1 acts on the combustion chamber C, and fresh air is not taken in smoothly.

[0042] Next, as shown in FIG. 4, in the internal combustion engine E, when the top surface 4T of the piston 4 is located on the top dead center side of the boundary Ds during the compression stroke, water is vaporized by the action of heat from the first cooling section D1, and the water already present in the combustion chamber C is vaporized by the heat of the first cooling section D1 (high-temperature cooling region), and a portion of the water consumes thermal energy in the same manner as in an isothermal cycle (Carnot cycle).

[0043] That is, in the early stage of the compression stroke, the top surface 4T of the piston 4 is in the second cooling part D2, and the water vapor present in the combustion chamber C becomes water (in a state such as mist). After this, the top surface 4T of the piston 4 reaches the first cooling part D1, and the water vaporizes in the combustion chamber C due to the heat of the first cooling part D1, consuming thermal energy as described above.

[0044] In particular, in the internal combustion engine E, when the piston 4 approaches top dead center during the compression stroke, the water already present in the combustion chamber C is vaporized by the heat of the first cooling section D1, and a layered vapor layer region M is formed along the outer periphery of the combustion chamber C, as shown in Figure 5.

[0045] Furthermore, during this compression stroke, the temperature of the combustion chamber C increases with compression, which makes it possible to reduce cooling losses. In particular, the internal combustion engine E lowers the temperature of the combustion chamber C by injecting hydrogen gas into the combustion chamber C using the injector 9 during the compression stroke, thereby making it possible to reduce the energy required to operate the piston 4 in the compression direction.

[0046] 5, when ignition is performed by the spark plug 10 in the combustion process of the internal combustion engine E, the combustion ends in a short time due to the nature of hydrogen gas combustion. During the combustion of hydrogen gas, the piston 4 is in a high-temperature cooling state where the heat of the first cooling portion D1 acts on it, so that cooling loss is reduced.

[0047] Furthermore, the internal combustion engine E is in a state where a layered steam layer region M has already been formed along the outer periphery of the combustion chamber C. Therefore, the combustion gas is prevented from contacting the side wall of the combustion chamber C by the steam layer region M, and the cooling loss that causes a decrease in the temperature of the combustion gas is reduced.

[0048] In this combustion stroke, when the top surface 4T of the piston 4 reaches the bottom dead center (BDC) side of the boundary Ds as shown in FIG. 6, a state in which the cooling loss increases temporarily occurs due to the effect of heat from the second cooling portion D2.

[0049] 7, in the internal combustion engine E, during the exhaust stroke, the top surface 4T of the piston 4 exceeds the boundary Ds and reaches the second cooling section D2 (low-temperature cooling region), increasing the cooling loss, but part of the water vapor contained in the combustion gas condenses into water (for example, in a mist state), lowering the gas density and reducing the load acting on the piston 4. Furthermore, the water vapor contained in the combustion gas forms a water vapor layer on the top surface 4T of the piston 4, making it possible to reduce the cooling loss.

[0050] [PV diagram] Fig. 8 shows a cycle line in which the horizontal axis represents the "volume" of the combustion chamber C, which changes due to the operation of the piston 4, and the vertical axis represents the pressure of the combustion chamber C. Fig. 8 is also called a PV diagram.

[0051] In the same figure, the cycle line in an internal combustion engine E having a first cooling section D1 (high-temperature cooling area) and a second cooling section D2 (low-temperature cooling area) as the cooling section D is shown by a solid line (hereinafter sometimes simply referred to as the cycle line), and the cycle line in an internal combustion engine E having a general (undivided configuration) cooling section D (hereinafter sometimes referred to as the conventional line) is shown by a dashed line.

[0052] FIG. 8 shows that the compression process line L1, which indicates the compression process, is performed at a lower pressure than in the conventional line.

[0053] That is, as explained above with reference to Fig. 3, in the intake stroke, water is produced from the water vapor contained in the combustion gas in the combustion chamber C. In the subsequent compression stroke, as explained above with reference to Fig. 4, the water present in the combustion chamber C is vaporized, consuming the thermal energy of the combustion chamber C. This suppresses the pressure rise in the combustion chamber C, and achieves the compression stroke with less energy than before.

[0054] The ignition timing Pf shown on this cycle line indicates the timing at which ignition is performed by the spark plug 10. The cycle line in Fig. 8 indicates that after ignition, the pressure value at the maximum pressure point Pt of the combustion chamber C due to the combustion of hydrogen gas is higher than the maximum pressure point on the conventional line.

[0055] The reason why the pressure at the maximum pressure point Pt is higher than the maximum pressure in the conventional line is that the combustion of hydrogen gas ends in a short time, and as explained above with reference to Figure 5, the vapor layer region M formed in a layer along the outer periphery of the combustion chamber C suppresses cooling loss when the combustion gas comes into contact with the inner surface of the combustion chamber C, and the influence of the added pressure value (air pressure + water vapor pressure) of the air pressure that enters the combustion chamber C due to water condensation during the intake stroke and the water vapor pressure that evaporates during the compression stroke.

[0056] In addition, because cooling loss during combustion is suppressed, the pressure indicated by the combustion process line L2 of the cycle line is maintained at a higher value than the pressure of the conventional line. As a result, when the piston 4 moves to bottom dead center (BDC), the pressure of the combustion chamber C is continuously applied to the piston 4, efficiently extracting the energy of combustion and obtaining a high torque output.

[0057] Furthermore, since the exhaust process line L3 is at a lower pressure than the conventional line, it is possible to reduce the energy consumed in the exhaust process.

[0058] In other words, as explained above with reference to FIG. 7, a portion of the water vapor contained in the combustion gas is condensed, thereby reducing the gas density and the load acting on the piston 4 when it moves, thereby realizing a reduction in energy consumption.

[0059] [Effects of the embodiment] Thus, in the internal combustion engine E, when the top surface 4T of the piston 4 is on the bottom dead center (BDC) side of the boundary Ds during the intake stroke, the second cooling section D2 is in a low-temperature cooling state in which heat is removed from the combustion chamber C. As a result, part of the combustion gas near the top surface 4T of the piston 4 is condensed and turned into water, reducing the gas density in the combustion chamber C and enabling an increase in the amount of fresh air taken in.

[0060] In addition, in the internal combustion engine E, the water present in the combustion chamber C is vaporized during the compression stroke, thereby consuming the thermal energy of the combustion chamber C and reducing the force acting on the piston 4 in the direction against compression. This suppresses the pressure rise in the combustion chamber C and achieves the compression stroke with less energy than before.

[0061] In particular, the internal combustion engine E reduces the temperature of the combustion chamber C by injecting hydrogen gas into the combustion chamber C using the injector 9 during the compression stroke, and condenses the water vapor into condensed water, thereby making it possible to reduce the load when the piston 4 is operated in the compression direction.

[0062] In the internal combustion engine E, when ignition is performed by the spark plug 10 in the combustion process, the combustion ends in a short time due to the combustion properties of hydrogen gas. Also, in the compression process immediately before the transition to the combustion process, water is already present in the combustion chamber C, and this water is vaporized by the heat of the first cooling section D1 in the combustion process, forming a layered vapor layer region M along the outer periphery of the combustion chamber C as shown in Fig. 5. Therefore, in the internal combustion engine E, the vapor layer region M suppresses the phenomenon in which the combustion gas comes into contact with the inner surface of the combustion chamber C, and the cooling loss that causes a drop in the temperature of the combustion gas is reduced.

[0063] As a result, as shown by the maximum pressure point Pt of the cycle line in FIG. 8, the maximum pressure in the combustion stroke is increased, and the output of the internal combustion engine E is increased.

[0064] Furthermore, in this internal combustion engine E, since cooling loss during combustion is suppressed, the pressure indicated by the combustion process line L2 of the cycle line is maintained at a higher value than the pressure of the conventional line, and when the piston 4 moves to bottom dead center (BDC), the pressure of the combustion chamber C is continuously applied to the piston 4, making it possible to efficiently extract the energy of combustion.

[0065] In this way, the internal combustion engine E achieves the effects described above by arranging the cooling section D into the first cooling section D1 (high temperature cooling area) and the second cooling section D2 (low temperature cooling area) along the operating direction of the piston 4.

[0066] [Another embodiment] The present invention may be configured as follows other than the above-described embodiment (common numbers and symbols as in the embodiment are used to designate components having the same functions as in the embodiment).

[0067] (a) By controlling the intake timing by the intake timing control device VTa and the exhaust timing by the exhaust timing control device VTb described in the embodiment, an internal EGR is configured to set an overlap period during which the intake valve Va is open while the exhaust valve Vb is open. The internal combustion engine E can control the intake of a portion of the exhaust gas into the combustion chamber C by this internal EGR.

[0068] By controlling in this manner to take in a portion of the exhaust gas into the combustion chamber C, it becomes possible to supply water vapor contained in the exhaust gas to the combustion chamber C, and condensed water is produced from the water vapor in the low-temperature cooling state of the second cooling section D2 (low-temperature cooling region), making it possible to effectively utilize the insulating effect.

[0069] As a modified example of the EGR previously described in this alternative embodiment (a), it is also possible to provide the internal combustion engine E with a configuration in which a portion of the combustion gas flowing in the exhaust passage 16 is returned to the intake passage 15 via a return passage.

[0070] (b) The cooling section D is arranged in three or three or more cooling regions with different temperatures in the operating direction of the piston 4. In this configuration, for example, when three regions are set, it is possible to arrange a region with an intermediate cooling temperature between the first cooling section D1 (high temperature cooling region) of the embodiment and the second cooling section D2 (low temperature cooling region) of the embodiment in the operating direction of the piston 4.

[0071] In accordance with the configuration of this alternative embodiment (b), the temperatures of the first cooling section D1 (high temperature cooling region) and the second cooling section D2 (low temperature cooling region) are changed based on the temperature of the exhaust gas of the internal combustion engine E and the environmental temperature. With such a configuration and temperature settings, it is possible to operate the internal combustion engine E efficiently.

[0072] (c) In the internal combustion engine E having a piston jet that supplies lubricating oil to the inner surface of the cylinder from inside the cylinder block 2, the temperature of the lubricating oil supplied to the piston jet can be lowered by a chiller or the like to form a second cooling section D2 (low-temperature cooling region) of the cooling section D described in the embodiment.

[0073] As described in the embodiment, this piston jet can also be provided as an auxiliary to an internal combustion engine E equipped with a first cooling section D1 (high temperature cooling area) and a second cooling section D2 (low temperature cooling area).By providing it as such an auxiliary, it is also possible to suppress the temperature rise of the second cooling section D2.

[0074] (d) In an internal combustion engine E that uses hydrogen gas as fuel, the internal combustion engine E does not use an ignition plug 10, and instead starts combustion of the air-fuel mixture by a static spark discharge instead of ignition by the ignition plug 10. The internal combustion engine E is provided with a cooling section D having a high-temperature cooling region and a low-temperature cooling region as described in the embodiment.

[0075] In this way, even in the case of an internal combustion engine E that uses static electricity to ignite hydrogen gas, by forming a high-temperature cooling region and a low-temperature cooling region in the cooling section D, it is possible to improve the performance of the internal combustion engine E.

[0076] In addition, when spark discharge is caused by static electricity, static electricity is charged to the inner surface of the cylinder head 3 when fuel is injected, and a spark discharge is caused between the cylinder head 3 and the piston 4 when the piston 4 approaches the cylinder head 3.

[0077] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, provided that no contradiction arises. Furthermore, the embodiments disclosed in this specification are merely examples, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope that does not deviate from the purpose of the present invention.

[0078] In the above-described embodiment, the following configurations are envisaged. (1) An internal combustion engine E comprising: a piston 4 which reciprocates in conjunction with the rotation of a crankshaft 1; a combustion chamber C which is formed between the piston 4 and a cylinder head 3 and which burns hydrogen gas; and a cooling section D which is arranged on a side wall which defines the combustion chamber C and which cools the combustion chamber C, wherein the cooling section D has a high-temperature cooling area (first cooling section D1) which is arranged on the top dead center side in the operating direction, and a low-temperature cooling area (second cooling section D2) which has a lower temperature than the high-temperature cooling area (first cooling section D1) and is arranged on the bottom dead center side of the high-temperature cooling area (first cooling section D1) in the operating direction of the piston 4.

[0079] According to this configuration, in the combustion stroke, the top surface 4T of the piston 4 is in a high temperature region, so that the cooling loss during combustion is reduced. Also, in this combustion stroke, the water present in the combustion chamber C is vaporized by heat, and a layer of water vapor is formed along the outer periphery of the combustion chamber C. The water vapor layer prevents the combustion gas from contacting the side wall of the combustion chamber C, suppressing the inconvenience of temperature drop. Also, when the top surface 4T of the piston 4 moves to the bottom dead center side in the combustion stroke, the low-temperature cooling region (second cooling section D2) condenses the water vapor contained in the combustion gas, making it possible to reduce the load when the piston 4 operates in the next exhaust stroke. In this way, by configuring the cooling section D surrounding the combustion chamber C with a high-temperature cooling region (first cooling section D1) on the top dead center side and a low-temperature cooling region (second cooling section D2) on the bottom dead center side, the cooling loss is reduced even when the flame propagation during combustion is fast.

[0080] (2)(1) The internal combustion engine E preferably has a high-temperature cooling area (first cooling section D1) and a low-temperature cooling area (second cooling section D2) arranged side by side in the operating direction, and the dimension of the high-temperature cooling area (first cooling section D1) in the operating direction is larger than the dimension of the low-temperature cooling area (second cooling section D2) in the operating direction.

[0081] According to this, when the piston 4 starts to operate due to combustion in the combustion chamber C, the heat of the high-temperature cooling area (first cooling section D1) having a large volume acts on the combustion chamber C, so that in the early stage of operation, the piston 4 can be operated at the high pressure of the combustion chamber C without causing a drop in the temperature of the combustion gas. Furthermore, when the operation of the piston 4 progresses and the heat of the low-temperature cooling area (second cooling section D2) acts on the combustion chamber C, the water vapor contained in the combustion gas condenses and turns into water (for example, in a mist state). This makes it possible to reduce the load for operating the piston 4 in the next compression stroke.

[0082] (3) The internal combustion engine E of (1) or (2) preferably includes an in-cylinder injector 9 that injects hydrogen gas into the combustion chamber C.

[0083] According to this, when hydrogen gas is injected into the combustion chamber C by the injector 9 during the compression stroke, it is possible to lower the temperature of the mixture in the combustion chamber C, and it is possible to reduce the driving load of the piston 4 in the compression direction.

[0084] (4) The internal combustion engine E of (1) is provided with an intake valve Va that draws in outside air into the combustion chamber C by opening during the intake stroke, and an exhaust valve Vb that exhausts combustion from the combustion chamber C by opening during the exhaust stroke, and it is preferable that an overlap period during which the intake valve Va is open while the exhaust valve Vb is open is set in the time domain from the exhaust stroke to the intake stroke.

[0085] This allows the combustion gas to be drawn into the combustion chamber C during the overlap period, making it possible to take in water vapor into the combustion chamber C. The water vapor contained in the combustion gas condenses into water when the top surface 4T of the piston 4 reaches the area of ​​the second cooling part D2, not only allowing the pressure in the combustion chamber C to decrease, but also creating a layer of water vapor in the combustion chamber C by the heat acting from the first cooling part D1, making it possible to suppress cooling loss. [Industrial Applicability]

[0086] The present invention can be used in an internal combustion engine. [Explanation of symbols]

[0087] 1: crankshaft, 3: cylinder head, 4: piston, 9: injector, C: combustion chamber, D: cooling section, D1: first cooling section (high temperature cooling area), D2: second cooling section (low temperature cooling area), Va: intake valve, Vb: exhaust valve

Claims

1. A piston that reciprocates in conjunction with the rotation of the crankshaft; a combustion chamber formed between the piston and a cylinder head for burning hydrogen gas; a cooling portion that is disposed on a side wall that defines the combustion chamber and that cools the combustion chamber; An internal combustion engine, wherein the cooling section has a high-temperature cooling area that is arranged on the top dead center side in the operating direction of the piston, and a low-temperature cooling area that is cooler than the high-temperature cooling area and is arranged on the bottom dead center side of the high-temperature cooling area in the operating direction.

2. 2. The internal combustion engine of claim 1, wherein the high temperature cooling region and the low temperature cooling region are arranged side by side in the operating direction, and a dimension of the high temperature cooling region in the operating direction is greater than a dimension of the low temperature cooling region in the operating direction.

3. 3. The internal combustion engine according to claim 1, further comprising an in-cylinder injector that injects the hydrogen gas into the combustion chamber.

4. an intake valve that draws outside air into the combustion chamber by opening during an intake stroke, and an exhaust valve that exhausts combustion gas from the combustion chamber by opening during an exhaust stroke; 2. The internal combustion engine according to claim 1, wherein an overlap period during which the intake valve is open while the exhaust valve is open is set in a time region spanning from the exhaust stroke to the intake stroke.

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