Internal combustion engine

Abstract

Provided is an internal combustion engine including: an asynchronous injection valve configured to inject water into an intake port during closing of one or more intake valves; and a synchronous injection valve configured to inject water into the intake port during opening of the one or more intake valves. The asynchronous injection valve and the synchronous injection valve are configured to have mutually different injection characteristics.

Description

Technical Field

[0001] The present invention relates to an internal combustion engine that performs water injection into the air intake. Background Art

[0002] Japanese Patent Application Laid-Open No. 2009-138661 discloses an internal combustion engine that uses water injection. This internal combustion engine is used, for example, as an internal combustion engine for racing. In this internal combustion engine, the injected water vaporizes to cool the intake air. Summary of the Invention

[0003] Problems to be solved by the invention

[0004] In internal combustion engines using water injection as described above, some of the injected water may adhere to the intake port or cylinder walls. The amount of water adhering to the walls reduces the effectiveness of vaporization cooling. Furthermore, if a large amount of water adheres to the intake port or cylinder walls, it can mix with the engine oil. This water can cause the oil to become cloudy or evaporate within the crankcase, increasing the crankcase's internal pressure.

[0005] Technical solutions to problems

[0006] An internal combustion engine according to one embodiment of the present disclosure includes: a cylinder; an intake port connected to the cylinder; one or more intake valves configured to selectively allow and block communication between the intake port and the cylinder; an asynchronous injection valve configured to inject water into the intake port while the one or more intake valves are closed; and a synchronous injection valve configured to inject water into the intake port while the one or more intake valves are open. The asynchronous injection valve and the synchronous injection valve are configured to have different injection characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a diagram schematically showing the structure of the cylinder and its surroundings of an internal combustion engine according to one embodiment.

[0008] Figure 2 Yes Figure 1 Diagram of the planar configuration of an air intake of an internal combustion engine.

[0009] Figure 3 yes Figure 1 A cross-sectional view of a nozzle tip portion of an asynchronous injection valve included in an internal combustion engine.

[0010] Figure 4 yes Figure 1 A cross-sectional view of a nozzle tip portion of a synchronous injection valve included in an internal combustion engine. DETAILED DESCRIPTION

[0011] Below, refer to Figures 1 to 4 An embodiment of an internal combustion engine will be described in detail. The internal combustion engine 10 of this embodiment is a hydrogen engine that uses hydrogen as fuel.

[0012] <Structure of Internal Combustion Engine 10>

[0013] like Figure 1 As shown, the internal combustion engine 10 has one or more cylinders 11. A piston 12 is provided in the cylinder 11 so as to be reciprocating. Inside the cylinder 11, a combustion chamber 13 for combustion of a mixture is defined by the piston 12. An intake port 14 is connected to the cylinder 11 via one or more intake valves 15, serving as an inlet path for introducing intake air into the cylinder 11. The intake valve 15 selectively allows and blocks the connection between the intake port 14 and the cylinder 11. In addition, an exhaust port 16 is connected to the cylinder 11 via one or more exhaust valves 17, serving as an exhaust path for exhausting exhaust gas from the cylinder 11. The exhaust valve 17 selectively allows and blocks the connection between the exhaust port 16 and the cylinder 11. The cylinder 11 is provided with a hydrogen injection valve 18 for injecting hydrogen into the cylinder 11 and an ignition plug 19 for igniting the mixture of hydrogen and intake air by spark discharge. In the following description, regarding the air intake port 14, the direction corresponding to the movement direction of the piston 12 in the cylinder 11 is described as the height direction H of the air intake port 14. In the following description, in the height direction H of the air intake port 14, the side where the distance from the cylinder 11 increases is described as the upper side of the air intake port 14, and the side where the distance from the cylinder 11 decreases is described as the lower side of the air intake port 14.

[0014] like Figure 2 As shown, the downstream portion of the intake port 14 in the direction of intake air flow branches into two. The intake port 14 is connected to the cylinder 11 via two intake valves 15 corresponding to the two branching portions. In the following description, the direction corresponding to the arrangement direction of the two intake valves 15 is referred to as the width direction W of the intake port 14.

[0015] In the internal combustion engine 10, two water injection valves, an asynchronous injection valve 20 and a synchronous injection valve 21, are provided for each cylinder 11. The asynchronous injection valve 20 is an asynchronous water injection valve for injecting water into the intake port 14 while the intake valve 15 is closed. The synchronous injection valve 21 is a synchronous water injection valve for injecting water into the intake port 14 while the intake valve 15 is open. Figure 2 The figure shows a spray of water SP1 injected by the asynchronous injection valve 20 and a spray of water SP2 injected by the synchronous injection valve 21. The asynchronous injection valve 20 and the synchronous injection valve 21 are arranged side by side in the height direction H at the center of the width direction W of the intake port 14. In the internal combustion engine 10 of the present embodiment, both the asynchronous injection valve 20 and the synchronous injection valve 21 are arranged in the upper portion of the intake port 14.

[0016] Figure 3 The cross-sectional structure of the nozzle front end portion of the asynchronous injection valve 20 is shown. Figure 4 The cross-sectional structure of the nozzle tip of the synchronous injection valve 21 is shown. The asynchronous injection valve 20 has two nozzles 20A. The synchronous injection valve 21 has two nozzles 21A. The angle θ1 between the two nozzles 20A of the asynchronous injection valve 20 is larger than the angle θ2 between the two nozzles 21A of the synchronous injection valve 21. The asynchronous injection valve 20 and the synchronous injection valve 21 are each arranged in the internal combustion engine 10 so that the spray of water ejected from the two nozzles 20A and 21A is directed toward the two branching portions of the intake port 14. The asynchronous injection valve 20 is configured to inject water at a wider angle in the width direction W of the intake port 14 than the synchronous injection valve 21.

[0017] On the other hand, the nozzle 20A of the asynchronous injection valve 20 has a smaller diameter than the nozzle 21A of the synchronous injection valve 21. In other words, the asynchronous injection valve 20 has a smaller nozzle 20A than the nozzle 21A of the synchronous injection valve 21. Furthermore, the injection pressure of water from the asynchronous injection valve 20 and the synchronous injection valve 21 is the same. Therefore, the asynchronous injection valve 20 is configured to inject water at a lower injection rate than the synchronous injection valve 21. "Injection rate" refers to the amount of water injected per unit time. The smaller the nozzle, the more easily the water spray ejected from the nozzle is atomized.

[0018] <Effects of Implementation Methods>

[0019] In the internal combustion engine 10, water is injected into the intake port 14 using an asynchronous injection valve 20 and a synchronous injection valve 21 depending on the operating conditions. Furthermore, during water injection, the internal combustion engine 10 switches between asynchronous and synchronous injection depending on the operating conditions of the internal combustion engine 10 and the amount of water to be injected. Asynchronous injection is performed while the intake valve 15 is closed. Synchronous injection is performed while the intake valve 15 is open. In the internal combustion engine 10, asynchronous injection is performed by the asynchronous injection valve 20, and synchronous injection is performed by the synchronous injection valve 21.

[0020] Furthermore, when water is injected into the intake port 14, some of the water may not vaporize and may adhere to the wall surface of the intake port 14 or the surface of the intake valve 15. In the following description, the amount of water adhering to the wall surface of the intake port 14 or the surface of the intake valve 15 is referred to as the intake port wetting amount. Furthermore, during simultaneous injection, the injected water may flow into the cylinder 11 along with the intake air and adhere to the wall surface of the cylinder 11. In the following description, the amount of water adhering to the wall surface of the cylinder 11 is referred to as the cylinder liner wetting amount.

[0021] Furthermore, during asynchronous injection, the intake valve 15 is closed, causing the flow of intake air in the intake port 14 to stagnate. In contrast, during synchronous injection, the intake valve 15 is open, allowing intake air to flow through the intake port 14 toward the cylinder 11. Furthermore, when water is injected at a low injection rate, the spray is more likely to be atomized and diffused than when injected at a high injection rate. Therefore, even with asynchronous injection, where the flow of intake air in the intake port 14 is stagnant, injecting water at a low injection rate can suppress an increase in the amount of intake port wetting. Furthermore, since the period during which the intake valve 15 is open is shorter than the period during which it is closed, the time during which water can be injected is shorter with synchronous injection than with asynchronous injection. Therefore, when synchronous injection is performed at a low injection rate, the amount of water that can be injected may be limited. On the other hand, with synchronous injection, where intake air flows through the intake port 14, even with a high injection rate, the spray is atomized by the airflow, thus suppressing an increase in the amount of intake port wetting. Therefore, it is preferable that the asynchronous injection be performed at a low injection rate and the synchronous injection be performed at a high injection rate.

[0022] When the intake valve 15 is open, the flow of intake air is stronger in the widthwise outer portions of the intake port 14 than in the widthwise central portion. During synchronous injection, if water is injected toward the widthwise outer portions of the intake port 14, the injected water flows into the cylinder 11 along with the strong airflow, thereby increasing the amount of cylinder liner wetting. Therefore, synchronous injection preferably involves injecting water at a narrow angle in the width direction W to minimize the amount of spray reaching the widthwise outer portions of the intake port 14. On the other hand, during asynchronous injection while the intake valve 15 is closed, it is preferable to inject water at a wide angle to diffuse the spray over a wide area, thereby minimizing any increase in intake port wetting.

[0023] The asynchronous injection valve 20 in the internal combustion engine 10 of this embodiment is configured to inject water at a lower injection rate than the synchronous injection valve 21. Furthermore, the asynchronous injection valve 20 is configured to inject water over a wider angle in the width direction W of the intake port 14 than the synchronous injection valve 21. Therefore, increases in both the intake port wetting amount and the cylinder liner wetting amount can be suppressed.

[0024] According to the internal combustion engine 10 of the present embodiment described above, the following effects can be achieved.

[0025] (1) The state of the airflow in the intake port 14 differs between the period when the intake valve 15 is closed and the period when the intake valve 15 is open. Therefore, when synchronous injection is performed with injection characteristics for asynchronous injection set to suppress an increase in intake port wetting, the cylinder liner wetting amount may increase. The internal combustion engine 10 of this embodiment includes two water injection valves with different injection characteristics for each cylinder 11, namely, an asynchronous injection valve 20 for performing asynchronous injection of water into the intake port 14 and a synchronous injection valve 21 for performing synchronous injection of water into the intake port 14. Therefore, both asynchronous injection and synchronous injection can be performed with injection characteristics suitable for suppressing intake port wetting and cylinder liner wetting, respectively.

[0026] (2) The asynchronous injection valve 20 is configured to inject water at a lower injection rate than the synchronous injection valve 21. By performing asynchronous injection at a low injection rate, the atomization and diffusion of the spray can be promoted. Therefore, even in the case of asynchronous injection in which the flow of the intake air in the intake port 14 is stagnant, the increase in the intake port wetting amount can be suppressed. On the other hand, by performing synchronous injection at a high injection rate, which cannot ensure a long injection time compared to asynchronous injection, it is easy to ensure the water injection amount. In addition, in synchronous injection, since the spray is atomized by the airflow in the intake port 14, the intake port wetting amount is not likely to increase even if water is injected at a high injection rate. Therefore, while easing the limitation of the water injection amount in synchronous injection, the increase in the intake port wetting amount in both asynchronous injection and synchronous injection can be suppressed.

[0027] (3) The asynchronous injection valve 20 is configured to have a nozzle opening 20A that is smaller than the nozzle opening 21A of the synchronous injection valve 21. Therefore, even if the injection pressures of the water of the asynchronous injection valve 20 and the synchronous injection valve 21 are not changed, the asynchronous injection valve 20 can be configured to inject water at a lower injection rate than the synchronous injection valve 21.

[0028] (4) During synchronous injection, since the airflow in the portion outside the width direction of the intake port 14 is enhanced, injecting water at a narrow angle can better suppress the increase in the cylinder liner wetting amount. On the other hand, during asynchronous injection, where the flow of intake air in the intake port 14 is stagnant, injecting water at a wide angle to diffuse the spray can better suppress the intake port wetting amount. In this regard, in the internal combustion engine 10 of this embodiment, the asynchronous injection valve 20 is configured to inject water at a wider angle in the width direction W of the intake port 14 than the synchronous injection valve 21. Therefore, it is possible to simultaneously suppress the increase in the intake port wetting amount during asynchronous injection and the increase in the cylinder liner wetting amount during synchronous injection.

[0029] (5) By suppressing the amount of intake port wetting and cylinder liner wetting, it is possible to suppress the incorporation of water into the engine oil. As a result, it is possible to suppress the engine oil from becoming cloudy and the evaporation of water in the engine oil in the crankcase, which in turn increases the internal pressure of the crankcase.

[0030] (6) In order to evenly inject water into the two branched portions of the intake port 14, it is preferable to provide a water injection valve at the center of the width direction W of the intake port 14. In this regard, in the internal combustion engine 10 of this embodiment, the asynchronous injection valve 20 and the synchronous injection valve 21 are arranged side by side in the height direction H of the intake port 14. Therefore, both the asynchronous injection valve 20 and the synchronous injection valve 21 can be provided at the center of the width direction W of the intake port 14. As a result, water can be evenly injected into the two branched portions of the intake port 14 regardless of whether asynchronous injection or synchronous injection is used.

[0031] This embodiment can be implemented by modifying the following aspects: This embodiment and the following modifications can be implemented in combination with each other within the scope of no technical contradiction.

[0032] One or both of the asynchronous injection valve 20 and the synchronous injection valve 21 may be arranged at a portion below the intake port 14 .

[0033] The asynchronous injection valve 20 and the synchronous injection valve 21 may be arranged side by side in the width direction W of the intake port 14 .

[0034] The injection rate of the asynchronous injection valve 20 can also be lowered compared to the synchronous injection valve 21 by setting the injection pressure of water of the asynchronous injection valve 20 lower than that of the synchronous injection valve 21. In this case, the injection rate of the asynchronous injection valve 20 can be lowered compared to that of the synchronous injection valve 21 without making the nozzle 20A of the asynchronous injection valve 20 smaller than the nozzle 21A of the synchronous injection valve 21.

[0035] The number of nozzles of each of the asynchronous injection valve 20 and the synchronous injection valve 21 may be one or three or more. In addition, the number of nozzles 20A of the asynchronous injection valve 20 may be different from the number of nozzles 21A of the synchronous injection valve 21 .

[0036] The asynchronous injection valve 20 of the above embodiment is configured to (A) inject water at a lower injection rate than the synchronous injection valve 21, and (B) inject water over a wider angle in the width direction W of the air intake port 14 than the synchronous injection valve 21. Alternatively, the asynchronous injection valve 20 may be configured to meet only one of (A) and (B). In such a case, either the effect described in (2) or (4) above can be achieved.

[0037] The water injection system in the internal combustion engine 10 of the above-described embodiment can also be applied to internal combustion engines other than hydrogen engines.

Claims

1. An internal combustion engine comprising: cylinder; an air inlet connected to the cylinder; one or more intake valves configured to selectively allow and cut off communication between the intake port and the cylinder; an asynchronous injection valve configured to inject water into the intake port during a period in which the one or more intake valves are closed; and a synchronous injection valve configured to inject water into the intake port while the one or more intake valves are open; The asynchronous injection valve and the synchronous injection valve are configured to have injection characteristics different from each other. The more than one intake valve is two intake valves, The intake port is connected to the cylinder via the two intake valves. The air intake has a width direction corresponding to the arrangement direction of the two air intake valves. The asynchronous injection valve is configured to inject water at a wider angle in the width direction of the air intake port than the synchronous injection valve.

2. The internal combustion engine according to claim 1, wherein The air inlet has a height direction corresponding to the movement direction of the piston in the cylinder, The asynchronous injection valve and the synchronous injection valve are arranged side by side in the height direction of the air intake.

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