Internal combustion engine

Abstract

To inhibit wear of a seat surface of an injector for jetting a gaseous fuel.SOLUTION: An internal combustion engine 10 includes an injector 11 for injecting a gaseous fuel which has an injection port 14 configured to inject the gaseous fuel, a nozzle valve 15 configured to open or close the injection port 14, and a seat surface 16 on which the nozzle valve 15 is seated. Providing an introduction passage 18 for introducing a blow-by gas in a crank case 17 into the injection port 14 of the injector 11 causes oil contained in the blow-by gas to be supplied to the seat surface 16 of the injector 11.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an internal combustion engine including an injector for injecting gaseous fuel.

Background Art

[0002] In the case of an injector for injecting gaseous fuel such as hydrogen gas, the contact between the nozzle valve and the seat surface on which the nozzle valve seats becomes dry contact. Therefore, the injector for injecting gaseous fuel is more likely to experience wear of the nozzle seat than the injector for injecting liquid fuel. In contrast, Patent Document 1 describes an injector for gaseous fuel injection provided with a seat portion that has been subjected to a soft nitriding treatment to improve wear resistance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] If a soft nitriding treatment is performed, the manufacturing cost of the injector increases. Also, if the contact remains dry, wear of the seat surface may not be sufficiently suppressed even when a soft nitriding treatment is performed.

Means for Solving the Problems

[0005] The internal combustion engine that solves the above problems includes an injector for gaseous fuel injection having a nozzle for injecting gaseous fuel, a nozzle valve for opening and closing the nozzle, and a seat surface on which the nozzle valve seats. Further, the internal combustion engine includes an introduction passage for introducing blow-by gas in the crankcase to the nozzle.

[0006] In the internal combustion engine described above, blow-by gas containing oil is introduced into the injector nozzle. A portion of the introduced blow-by gas flows into the injector through the nozzle. This supplies the oil from the blow-by gas to the seat surface. The supplied oil then lubricates the seat surface. Therefore, the above-described internal combustion engine has the effect of suppressing wear on the seat surface of the injector used for gaseous fuel injection. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram schematically shows the configuration of one embodiment of an internal combustion engine. [Figure 2] This is a flowchart of the processes performed by the control unit of the internal combustion engine. [Figure 3] This diagram schematically shows the configuration of another embodiment of an internal combustion engine. [Figure 4] This diagram shows the configuration of the fuel system of an internal combustion engine, which has a lubrication function for the injector seat. [Modes for carrying out the invention]

[0008] Below, one embodiment of an internal combustion engine will be described in detail with reference to Figures 1 to 3. <Configuration of an internal combustion engine> First, the configuration of the internal combustion engine 10 of this embodiment will be described with reference to Figure 1. The internal combustion engine 10 is equipped with an injector 11 for gaseous fuel injection. In the case of the internal combustion engine 10 in Figure 1, hydrogen gas is used as the gaseous fuel. Note that the gaseous fuel may also be CNG or LPG. The injector 11 is installed in the cylinder head 12 of the internal combustion engine 10. In the case of the internal combustion engine 10 in Figure 1, the injector 11 is an in-cylinder injection type injector that injects gaseous fuel into the combustion chamber 13.

[0009] The injector 11 has a nozzle 14, which is the injection port for gaseous fuel. Inside the injector 11, there is a nozzle valve 15 and a seat surface 16 on which the nozzle valve 15 sits. The nozzle 14 is closed when the nozzle valve 15 sits on the seat surface 16. The nozzle 14 is opened when the nozzle valve 15 moves away from the seat surface 16. The injector 11 injects gaseous fuel when the nozzle 14 is open. The injector 11 stops injecting gaseous fuel when the nozzle 14 is closed.

[0010] The internal combustion engine 10 has an intake passage 18 that introduces blow-by gas from the crankcase 17 to the nozzle 14 of the injector 11. The downstream portion of the intake passage 18 is formed inside the cylinder head 12. The intake passage 18 opens to the area around the nozzle 14 of the injector 11 in the cylinder head 12. A control valve 19 is installed in the intake passage 18. The control valve 19 is a valve that opens and closes by external control. In the case of the internal combustion engine 10 in Figure 1, the control valve 19 is a normally closed solenoid valve. In the case of the internal combustion engine 10 in Figure 1, the pressure inside the crankcase 17 is approximately equal to atmospheric pressure.

[0011] The internal combustion engine 10 is equipped with a control unit 21. The control unit 21 is an electronic control unit comprising a processor 22 and a memory 23. In the case of the internal combustion engine 10 shown in Figure 1, the control unit 21 is configured to perform overall control of the internal combustion engine 10. The memory 23 of the control unit 21 pre-stores programs and data for controlling the opening and closing of the control valve 19. The control unit 21 controls the internal combustion engine 10 by having the processor 22 read and execute the program from the memory 23. In addition, as part of the control of the internal combustion engine 10, the control unit 21 controls the opening and closing of the control valve 19.

[0012] The control unit 21 is connected to various sensors installed in different parts of the internal combustion engine 10. The control unit 21 then determines state variables indicating the operating state of the internal combustion engine 10 based on the detection signals from these sensors. These state variables include the rotational speed of the internal combustion engine 10, the load factor, the water temperature, and the pressure and temperature of the gaseous fuel injected by the injector 11.

[0013] <Lubrication control of seat surface 16> The control unit 21 performs lubrication control to supply lubricant to the seat surface 16 of the injector 11 through the opening and closing control of the control valve 19. The following describes this lubrication control of the seat surface 16.

[0014] Figure 2 shows a flowchart of the lubrication control routine executed by the control unit 21 for lubrication control of the seat surface 16. The control unit 21 repeatedly executes this routine at predetermined control cycles while the internal combustion engine 10 is in operation.

[0015] When this routine is started, the control unit 21 first calculates the evaporation rate ΔW of the oil from the seat surface 16 in step S100. Specifically, the control unit 21 calculates the value of "ΔW" that satisfies the relationship between equations (1) and (3) as the value of the evaporation rate ΔW. "Hg" represents the heat transfer coefficient of the gaseous fuel that passes around the seat surface 16 when fuel is injected by the injector 11. "Cp" represents the specific heat of the gaseous fuel, "Pg" represents the pressure of the gaseous fuel, and "Wgas" represents the molecular weight of the gaseous fuel. Furthermore, "Pls" represents the saturated vapor pressure of the oil, "Pls0" represents the saturated vapor pressure of the oil at the reference pressure, "Wls" represents the molecular weight of the oil, "Ts" represents the surface temperature of the oil, and "Tbs" represents the boiling point of the oil. Finally, "ΔHev" represents the heat of vaporization of the oil at the boiling point Tbs.

[0016]

number

[0017] Among the state quantities in formulas (1) to (3), Hg, Pg, and Ts are variables, and the others are constants. The control unit 21 calculates the evaporation rate ΔW by obtaining the heat transfer coefficient Hg, the pressure Pg, and the temperature Ts in the following manner.

[0018] The control unit 21 obtains the pressure Pg of the gaseous fuel from the detection result of the sensor. Further, the heat transfer coefficient Hg of the gaseous fuel is obtained as a function of the flow velocity Vg of the gaseous fuel. The flow velocity Vg of the gaseous fuel passing around the seat surface 16 during fuel injection is the speed of sound. The speed of sound in the gaseous fuel is obtained from the temperature and the pressure Pg of the same gaseous fuel. Therefore, the control unit 21 calculates the heat transfer coefficient Hg based on the temperature and the pressure Pg of the gaseous fuel injected by the injector 11. Furthermore, the temperature Ts of the oil is approximately equal to the tip temperature of the injector 11. The control unit 21 estimates the tip temperature of the injector 11 based on the rotational speed, the load factor, the water temperature, etc. of the internal combustion engine 10. Then, the control unit 21 uses the estimated tip temperature of the injector 11 as the value of the oil temperature Ts.

[0019] Subsequently, in step S110, the control unit 21 updates the value of the evaporation amount Wt based on the evaporation rate ΔW. Specifically, the control unit 21 updates the value of the evaporation amount Wt such that the sum of the value before the update and the value of the evaporation rate ΔW is the value after the update.

[0020] Next, in step S120, the control unit 21 determines whether the evaporation amount Wt is equal to or greater than a predetermined threshold value X. If the evaporation amount Wt is less than the threshold value X (NO), the control unit 21 ends the processing of this routine in the current control cycle as it is. On the other hand, if the evaporation amount Wt is equal to or greater than the threshold value X (YES), the control unit 21 proceeds to step S130.

[0021] In step S130, the control unit 21 introduces blow-by gas to the nozzle 14 of the injector 11 through the introduction passage 18. Specifically, the control unit 21 repeatedly opens the control valve 19, limited to the intake stroke when the combustion chamber 13 is under negative pressure, for a predetermined period of time. After that, the control unit 21 resets the value of the evaporation amount Wt to ​​"0" and then terminates the processing of this routine for the current control cycle.

[0022] In this lubrication control routine, the value of the evaporation amount Wt is increased by the calculated value of the evaporation rate ΔW each time the routine is executed. On the other hand, each time blow-by gas is introduced in this routine, the value of the evaporation amount Wt is reset to "0". This value of evaporation amount Wt represents the total amount of oil that has evaporated from the seat surface 16 since the last blow-by gas introduction.

[0023] <Effects of the Embodiment> The internal combustion engine 10 of this embodiment has an introduction passage 18 for introducing blow-by gas from the crankcase 17 into the nozzle 14 of the injector 11. The internal combustion engine 10 also has a control valve 19 for opening and closing the introduction passage 18.

[0024] When the control valve 19 opens during the intake stroke, when the combustion chamber 13 is under negative pressure, blow-by gas containing oil is introduced to the nozzle 14 of the injector 11 through the introduction passage 18. Then, a portion of the introduced blow-by gas flows into the inside of the injector 11, supplying the oil in the blow-by gas to the seat surface 16.

[0025] The control unit 21 calculates the amount of oil evaporation Wt from the seat surface 16. When the evaporation amount Wt exceeds a threshold X, the control unit 21 controls the control valve 19 to introduce blow-by gas for a predetermined period. The threshold X is set as the assumed amount of oil supplied to the seat surface 16 during this blow-by gas introduction period. Therefore, in the internal combustion engine 10 of this embodiment, oil is replenished to the seat surface 16 at a time before oil depletion occurs.

[0026] The internal combustion engine 10 of this embodiment can achieve the following effects. (1) The internal combustion engine 10 is equipped with a gaseous fuel injection injector 11 having a nozzle 14 for injecting gaseous fuel, a nozzle valve 15 for opening and closing the nozzle 14, and a seat surface 16 on which the nozzle valve 15 sits. Furthermore, the internal combustion engine 10 is equipped with an introduction passage 18 for introducing blow-by gas from the crankcase 17 to the nozzle 14 of the injector 11. In such an internal combustion engine 10, blow-by gas containing oil is introduced near the nozzle 14 of the injector 11. A portion of the introduced blow-by gas flows into the injector 11 from the nozzle 14. As a result, the oil in the blow-by gas is supplied to the seat surface 16. The supplied oil then lubricates the seat surface 16. Therefore, the internal combustion engine 10 of this embodiment has the effect of suppressing wear on the seat surface 16 of the gaseous fuel injection injector 11.

[0027] (2) Furthermore, the internal combustion engine 10 includes a control valve 19 that opens and closes the introduction passage 18, and a control unit 21 that controls the opening and closing of the control valve 19. The control unit 21 calculates the amount of oil evaporated from the seat surface 16 Wt, and when the evaporation amount Wt becomes equal to or greater than a threshold X, it opens the control valve 19 to introduce blow-by gas. As a result, oil can be replenished to the seat surface 16 at an appropriate time to prevent oil depletion.

[0028] (Other examples) <Example of change 1> As shown in Figure 3, the internal combustion engine 100 of modification example 1, like the internal combustion engine 10 in Figure 1, is equipped with an injector 11 for gaseous fuel injection and an introduction passage 18 for introducing blow-by gas from the crankcase 17 into the nozzle 14 of the injector 11. However, the introduction passage 18 of the internal combustion engine 100 is equipped with a check valve 20 instead of a control valve 19. The check valve 20 is a differential pressure valve that opens when the internal pressure of the crankcase 17 is higher than the internal pressure of the combustion chamber 13, and closes when the internal pressure of the crankcase 17 is lower than the internal pressure of the combustion chamber 13.

[0029] In this type of internal combustion engine 100, when the combustion chamber 13 becomes negative pressure during the intake stroke, the check valve 20 opens, and blow-by gas is introduced into the nozzle 14 of the injector 11. Then, oil in the blow-by gas is supplied to the seat surface 16. Therefore, this type of internal combustion engine 100 also has the effect of suppressing wear on the seat surface 16 of the injector 11 for gaseous fuel injection. On the other hand, when the combustion chamber 13 becomes positive pressure during the compression stroke or combustion stroke, the check valve 20 closes, preventing the backflow of gas from the combustion chamber 13 to the crankcase 17.

[0030] A control unit is provided to control the throttle opening of the internal combustion engine 100 in Figure 3, and the amount of oil supplied to the seat surface 16 may be controlled by adjusting the throttle opening. When the throttle opening of the internal combustion engine 100 is reduced, the negative pressure in the combustion chamber 13 during the intake stroke increases. When the negative pressure in the combustion chamber 13 increases, the amount of blow-by gas introduced near the nozzle 14 of the injector 11 through the introduction passage 18 increases. Therefore, in the internal combustion engine 100 in Figure 3, the amount of oil supplied to the seat surface 16 can be increased by reducing the throttle opening. Furthermore, the reduction of the throttle opening to increase the amount of oil supplied may be performed based on the amount of oil evaporated from the seat surface 16 Wt. That is, the lubrication control routine in Figure 2, in which step S130 is replaced with a process to reduce the throttle opening, may be implemented in the internal combustion engine 100 in Figure 3.

[0031] <Example of change 2> Figure 4 shows the configuration of the fuel system of an internal combustion engine that has a lubrication function for the seat portion of the injector 11. As shown in Figure 4, the fuel system of this internal combustion engine is equipped with a fuel tank 30 for storing gaseous fuel. The fuel tank 30 is connected to a delivery pipe 32 through a fuel passage 31. The injectors 11 of each cylinder are connected to the delivery pipe 32. A pressure control valve 33, a pressure regulator 34, and a gate valve 35 are installed in the fuel passage 31. The pressure control valve 33 is a valve that adjusts the pressure of the gaseous fuel supplied to the delivery pipe 32. The pressure regulator 34 is a valve that relieves gaseous fuel from the fuel passage 31 when the internal pressure of the fuel passage 31 exceeds a certain level. The gate valve 35 is a valve that is open when the internal combustion engine is running and closed when it is stopped.

[0032] Furthermore, the fuel system is equipped with an oil tank 36 for storing oil. The oil tank 36 is connected to the portion of the fuel passage 31 downstream of the gate valve 35 via an oil passage 37. An oil pump 38 is installed in the oil passage 37 to pump oil from the oil tank 36 and send it towards the fuel passage 31.

[0033] The operation of the oil pump 38 is controlled by the control unit 21, similar to the case in Figure 1. The control unit 21 calculates the amount of oil evaporated from the seat surface 16, Wt, in the same way as in the case of the internal combustion engine 10 in Figure 1. The control unit 21 then operates the oil pump 38 when the evaporation amount Wt exceeds a threshold X. In other words, the control unit 21 performs lubrication control by replacing step S130 in Figure 2 with the process of operating the oil pump 38.

[0034] In such an internal combustion engine, when the control unit 21 operates the oil pump 38, oil is added to the gaseous fuel supplied to the delivery pipe 32. Then, the oil-containing gaseous fuel is supplied from the delivery pipe 32 to the injectors 11 of each cylinder. As a result, the oil in the gaseous fuel is supplied to the seat surface 16 of the injector 11. Therefore, even in an internal combustion engine equipped with such a fuel system, there is an effect of suppressing wear on the seat surface 16 of the injector 11 for gaseous fuel injection.

[0035] <Other examples of changes> The above embodiments and modified examples 1 and 2 can be implemented with the following modifications. Furthermore, the following modifications can be combined with each other to the extent that they do not contradict each other technically and applied to the above embodiments and modified examples 1 and 2.

[0036] The internal combustion engine 10 in Figure 1 may also be configured such that a check valve 20, as shown in Figure 3, is installed in the intake passage 18 along with the control valve 19. In this case, regardless of whether the combustion chamber 13 is under positive or negative pressure, blow-by gas can be introduced near the nozzle 14 by maintaining the control valve 19 in an open state. Therefore, the control of the control valve 19 in lubrication control becomes simpler.

[0037] The control unit 21 calculated the amount of oil evaporation Wt from the seat surface 16 during lubrication control. When the evaporation amount Wt exceeded a threshold X, the control unit 21 supplied oil to the seat surface 16 by introducing blow-by gas or adding oil to the gaseous fuel. The content of this lubrication control may be changed as appropriate. For example, oil supply to the seat surface 16 may be performed at predetermined intervals.

[0038] The injector 11 may inject gaseous fuel into the intake port of the internal combustion engine. (Additional notes) [Note 1] An internal combustion engine comprising: an injector having a nozzle for injecting gaseous fuel, a nozzle valve for opening and closing the nozzle, and a seat surface on which the nozzle valve sits; a supply device for supplying oil to the seat surface; and a control unit for controlling the supply device, wherein the control unit calculates the total amount of oil evaporated from the seat surface after the oil supply from the supply device is stopped, and controls the supply device to perform the oil supply when the total amount exceeds a threshold.

[0039] [Note 2] The internal combustion engine according to Note 1, wherein the supply device is configured to supply oil by introducing blow-by gas from the crankcase to the nozzle. [Note 3] The internal combustion engine according to Note 1, wherein the supply device is configured to supply the oil by adding the oil to the gaseous fuel supplied to the injector. [Explanation of Symbols]

[0040] 10,100…Internal combustion engine, 11…Injector, 12…Cylinder head, 13…Combustion chamber, 14…Nozzle, 15…Nozzle valve, 16…Seat surface, 17…Crankcase, 18…Inlet passage, 19…Control valve, 20…Check valve, 21…Control unit, 22…Processor, 23…Memory, 30…Fuel tank, 31…Fuel passage, 32…Delivery pipe, 33…Pressure control valve, 34…Pressure regulator, 35…Gate valve, 36…Oil tank, 37…Oil passage, 38…Oil pump

Claims

1. An internal combustion engine comprising a nozzle for injecting gaseous fuel, a nozzle valve for opening and closing the nozzle, and an injector for injecting gaseous fuel having a seat surface on which the nozzle valve sits, It is equipped with an introduction passage for introducing blow-by gas from the crankcase to the nozzle, The internal combustion engine comprises a control valve that opens and closes the intake passage, and a control unit that controls the opening and closing of the control valve. The control unit calculates the amount of oil evaporated from the seat surface, and when the amount of evaporation exceeds a threshold, it opens the control valve to introduce the blow-by gas. Internal combustion engine.

2. An internal combustion engine comprising a nozzle for injecting gaseous fuel, a nozzle valve for opening and closing the nozzle, and an injector for injecting gaseous fuel having a seat surface on which the nozzle valve sits, It is equipped with an introduction passage for introducing blow-by gas from the crankcase to the nozzle, The injector is equipped with a check valve that opens the intake passage when the intake pressure is negative and closes the intake passage when the intake pressure is positive. Internal combustion engine.

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