JP6830455B2 - Internal combustion engine - Google Patents

Description

The present invention relates to an internal combustion engine that uses gas as fuel. More specifically, the present invention relates to a configuration for heating a vaporizer for vaporizing a liquefied fuel gas and cooling the EGR gas.

Conventionally, an internal combustion engine such as a gas engine in which a liquefied fuel gas is vaporized by using a vaporizer and supplied for combustion has been known. Patent Document 1 discloses this type of liquefied gas engine.

In the liquefied gas engine of Patent Document 1, a part of the cooling water of the engine is supplied as a heating medium to a heating device of a vaporizer (vaporizer) that vaporizes the liquefied gas, and then cooled to an EGR cooler that cools the EGR gas. The cooling water is recirculated to the heater of the vaporizer and the EGR cooler so as to be supplied as a medium.

Japanese Unexamined Patent Publication No. 2001-173520

In the configuration of Patent Document 1, the cooling water whose temperature has been raised as the EGR gas is cooled is combined with the cooling water cooled by the radiator. Therefore, the temperature of the cooling water supplied to the cylinder head rises, which causes a decrease in the cooling effect of the cylinder head. Further, in the configuration of Patent Document 1, it is necessary to provide a branch path for supplying cooling water to the heating device of the vaporizer and the EGR cooler, which causes the configuration of the engine to be complicated. Further, if the temperature of the cooling water is not sufficiently raised at the time of starting the engine, the warming effect on the vaporizer cannot be expected with the configuration of Patent Document 1.

The present invention has been made in view of the above circumstances, and an object thereof is an internal combustion engine capable of heating the vaporizer and cooling the EGR gas with a simple structure and quickly heating the vaporizer even at the time of starting. To provide an institution.

Means and effects to solve problems

The problem to be solved by the present invention is as described above, and next, the means for solving this problem and its effect will be described.

According to the viewpoint of the present invention, an internal combustion engine having the following configuration is provided. That is, this internal combustion engine includes a vaporizer, an exhaust bypass passage, an exhaust return passage, a condensed water storage unit, a cooling avoidance passage, and an on-off valve . The vaporizer vaporizes the liquefied fuel gas. The exhaust bypass passage supplies a part of the exhaust gas obtained by burning the fuel gas for heating the vaporizer. The exhaust return passage returns the exhaust gas cooled by heating the vaporizer to the intake side. The condensed water storage unit stores the condensed water generated by the vaporizer. The cooling avoidance path guides the exhaust gas flowing through the exhaust bypass passage to the upstream side of the vaporizer without passing through the condensed water storage unit. The on-off valve opens and closes the cooling avoidance path.

As a result, it is not necessary to separately provide an EGR cooler for cooling the EGR gas, and it is possible to realize heating of the vaporizer and cooling of the EGR gas with a simple configuration. Since the exhaust gas is used for heating the vaporizer, a sufficient heating effect on the vaporizer can be obtained even when the internal combustion engine is started. Further, depending on the situation, it is possible to easily switch between a state in which the EGR gas is cooled by using the vaporizer and a state in which the EGR gas is cooled by both the condensed water storage unit and the vaporizer.

The internal combustion engine preferably has the following configuration. That is, in this internal combustion engine , the condensed water storage portion is arranged on the upstream side of the vaporizer in the direction in which the exhaust gas flows through the exhaust bypass passage. The exhaust gas flowing through the exhaust bypass passage is cooled by heat exchange with the condensed water stored in the condensed water storage unit.

As a result, a complex cooling structure of the EGR gas by the condensed water storage unit and the vaporizer can be realized with a simple configuration, and the EGR gas can be efficiently cooled. Further, since the exhaust gas is cooled before being supplied to the vaporizer, the heat load on the members included in the vaporizer can be reduced, and the durability of these members can be improved.

The internal combustion engine preferably has the following configuration. That is, this internal combustion engine includes an exhaust gas passage, an exhaust gas purification device, and a condensed water discharge passage. The exhaust gas passage discharges the exhaust gas. The exhaust gas purification device is provided in the exhaust gas passage on the downstream side of the exhaust bypass passage in the direction in which the exhaust gas flows. The condensed water discharge passage connects the condensed water storage unit and the exhaust gas passage on the downstream side of the exhaust gas purification device.

As a result, the heat of the exhaust gas can be used to evaporate and discharge the condensed water. Further, in the exhaust gas passage, even if the condensed water discharged from the condensed water discharge passage to the exhaust gas passage tries to return to the exhaust bypass passage, the return direction is opposite to the flow of the exhaust gas, and the exhaust gas is exhausted on the way back. The layout is such that it must pass through the gas purification device. Therefore, it is possible to prevent the condensed water discharged from the condensed water storage unit from returning to the intake side on the flow of the EGR gas.

In the internal combustion engine, it is preferable that the exhaust bypass passage passes in the vicinity of a cooling fan that blows air.

Thereby, the EGR gas flowing through the exhaust bypass passage can be suitably cooled by the flow of air created by the cooling fan.

The schematic diagram which shows the structure of the internal combustion engine which concerns on one Embodiment of this invention. The schematic diagram which shows the structure of the internal combustion engine of the 1st modification. The schematic diagram which shows the structure of the internal combustion engine of the 2nd modification.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of an internal combustion engine 100 according to an embodiment of the present invention.

The internal combustion engine 100 shown in FIG. 1 is a gas engine that uses gas as fuel, and is configured as an in-line 4-cylinder engine having a plurality of (four in this embodiment) cylinders. The gas used as the fuel of the internal combustion engine 100 is not particularly limited, and examples thereof include propane gas and the like.

The internal combustion engine 100 includes an intake unit 1, a cylinder (not shown), an exhaust unit 2, and a fuel gas supply unit 3 as main configurations.

The intake unit 1 sucks air from the outside. The intake unit 1 includes an intake pipe 11, a throttle valve 12, and an intake manifold 13. The intake pipe 11 constitutes an intake passage, and air sucked from the outside can flow into the inside.

The throttle valve 12 is arranged in the middle of the intake passage. The throttle valve 12 changes the cross-sectional area of the intake passage by changing its opening degree according to a control command from the control device (not shown). As a result, the amount of air supplied to the intake manifold 13 via the throttle valve 12 can be adjusted.

The intake manifold 13 is connected to the downstream end of the intake pipe 11 in the direction in which the intake air flows. The intake manifold 13 can distribute the air supplied through the intake pipe 11 according to the number of cylinders and supply the air to the combustion chamber 10 of each cylinder.

A combustion chamber 10 is formed in each of the cylinders. The gas fuel gas supplied from the fuel gas supply unit 3 is distributed and guided to the combustion chamber 10 of each cylinder. The details of the configuration of the fuel gas supply unit 3 will be described later.

In the combustion chamber 10, the mixed gas in which the gaseous fuel gas and the air supplied from the intake manifold 13 are mixed is compressed and ignited at an appropriate timing by an appropriate method (for example, ignition by a spark plug). To. A piston (not shown) is arranged in the cylinder, and this piston moves by the propulsive force obtained by the explosion in the combustion chamber 10. The power thus obtained is transmitted to an appropriate device on the downstream side of the power via a crankshaft or the like (not shown).

The exhaust unit 2 discharges the exhaust gas generated in the combustion chamber 10 to the outside. The exhaust unit 2 includes an exhaust pipe 21, an exhaust manifold 22, and an exhaust gas purification device 23. The exhaust pipe 21 constitutes an exhaust gas passage, and the exhaust gas discharged from the combustion chamber 10 can flow into the exhaust pipe 21.

The exhaust manifold 22 is connected to the upstream end of the exhaust pipe 21 in the direction in which the exhaust gas flows. The exhaust manifold 22 collectively guides the exhaust gas generated in each combustion chamber 10 to the exhaust pipe 21.

The exhaust gas purification device 23 is provided on the outlet side of the exhaust pipe 21. The exhaust gas purification device 23 purifies the exhaust gas by removing harmful components such as NOx (nitrogen oxides), CO (carbon monoxide), HC (hydrocarbons) and particulate matter contained in the exhaust gas. To do.

The fuel gas supply unit 3 includes a fuel gas supply pipe 31, a fuel gas tank 32, a vaporizer 33, and a fuel gas valve 34.

The fuel gas supply pipe 31 constitutes a fuel gas supply passage for supplying fuel gas from the fuel gas tank 32 to the combustion chamber 10. A vaporizer 33 and a fuel gas valve 34 are arranged in the middle of the fuel gas supply passage in order from the upstream side in the direction in which the fuel gas flows.

The fuel gas tank 32 stores the liquefied fuel gas. The fuel gas tank 32 is connected to the upstream end of the fuel gas supply pipe 31 in the direction in which the fuel gas flows. The liquefied fuel gas stored in the fuel gas tank 32 is supplied to the vaporizer 33 by a pump or the like (not shown).

The vaporizer 33 is configured as, for example, an air-temperature vaporizer, and vaporizes the liquefied fuel gas supplied from the fuel gas tank 32. Specifically, the liquefied fuel gas supplied to the vaporizer 33 is depressurized and heat exchanged with air. As a result, the fuel gas can be vaporized.

Generally, the vaporizer 33 cooled by vaporizing the liquefied fuel gas is heated by an electric heater, a hot water heater, or the like. In this respect, in the internal combustion engine 100 of the present embodiment, since the EGR reflux path 5 described later is formed so as to pass through the vaporizer 33, it is not necessary to separately provide a heater, and the vaporizer 33 is preferably used. Can be heated. The details of the configuration for this heating will be described later.

In the vaporizer 33, condensed water is generated by condensing water vapor in the exhaust gas. The internal combustion engine 100 of the present embodiment is provided with a condensed water storage tank (condensed water storage unit) 6 for storing the condensed water.

The condensed water storage tank 6 temporarily stores the condensed water generated by the vaporizer 33 or the like. The condensed water storage tank 6 is made of, for example, a metal having corrosion resistance.

The internal combustion engine 100 further includes a condensed water introduction pipe 61 and a condensed water discharge pipe (condensed water discharge passage) 62.

The condensed water introduction pipe 61 is provided so as to connect the vaporizer 33 and the condensed water storage tank 6 to each other. The condensed water introduction pipe 61 guides the condensed water generated by the vaporizer 33 to the condensed water storage tank 6.

As shown in FIG. 1, the condensed water discharge pipe 62 is provided so as to connect the condensed water storage tank 6 and the exhaust pipe 21 on the downstream side of the exhaust gas purification device 23 to each other. The condensed water discharge pipe 62 guides the condensed water stored in the condensed water storage tank 6 into the exhaust pipe 21. In this way, the condensed water discharge pipe 62 constitutes a condensed water discharge passage for discharging condensed water from the condensed water storage tank 6.

With this configuration, the condensed water guided into the exhaust pipe 21 evaporates due to the heat of the exhaust gas, and is discharged to the outside along with the flow of the exhaust gas. Therefore, it is possible to avoid discharging the acidic condensed water as a liquid. Further, in the direction in which the exhaust gas flows through the exhaust pipe 21, the portion where the EGR recirculation path 5 described later branches from the exhaust pipe 21 is located on the upstream side of the portion where the condensed water discharge pipe 62 joins the exhaust pipe 21. At the same time, an exhaust gas purification device 23 is arranged between the two locations. Therefore, it is possible to prevent the condensed water guided into the exhaust pipe 21 from being mixed with the EGR gas via the EGR recirculation path 5.

The internal combustion engine 100 of the present embodiment is formed with an EGR (Exhaust Gas Recirculation) recirculation path 5 for recirculating a part of the exhaust gas to the intake side. The EGR recirculation path 5 is composed of an exhaust bypass passage 51 and an exhaust recirculation passage 52. In the present embodiment, the exhaust gas passing through the EGR recirculation path 5 may be particularly referred to as EGR gas.

The exhaust bypass passage 51 is formed of, for example, a metal pipe such as copper having excellent thermal conductivity, and is formed so as to guide a part of the exhaust gas passing through the exhaust pipe 21 to the vaporizer 33 as EGR gas. The exhaust bypass passage 51 connects the exhaust pipe 21 and the vaporizer 33. The exhaust bypass passage 51 is arranged so as to branch from the exhaust pipe 21 on the upstream side of the exhaust gas purification device 23 in the direction in which the exhaust gas flows.

The exhaust bypass passage 51 includes an air cooling unit 51a and a tank cooling unit 51b.

As shown in FIG. 1, the air-cooled portion 51a is arranged so as to pass between the gear case 7 arranged at the side end portion of the internal combustion engine 100 and the cooling fan 8. The air cooling portion 51a is arranged near the cooling fan 8 and is located on the downstream side of the cooling fan 8 and on the upstream side of the gear case 7 in the direction in which air is sent by the cooling fan 8. As a result, the EGR gas flowing in the air-cooled portion 51a is suitably cooled by the flow of air generated by the cooling fan 8.

The tank cooling unit 51b is arranged so that the metal pipe passes through the condensed water storage space formed inside the condensed water storage tank 6. As a result, the EGR gas flowing in the tank cooling unit 51b is suitably cooled by the condensed water stored in the condensed water storage tank 6. In order to prevent corrosion due to condensed water, the above metal pipe may be subjected to appropriate corrosion prevention processing.

In this way, the exhaust bypass passage 51 that guides a part of the exhaust gas to the vaporizer 33 is supplied to the vaporizer 33 by arranging the exhaust bypass passage 51 so as to pass in the vicinity of the cooling fan 8 and the inside of the condensed water storage tank 6. A two-stage cooling structure (cooling structure by a cooling fan 8 and a condensed water storage tank 6) for the EGR gas can be configured. Therefore, since it is possible to prevent the EGR gas from being introduced into the vaporizer 33 at a high temperature, it is possible to prevent the members such as the diaphragm included in the vaporizer 33 from being deteriorated by heat.

The exhaust / return passage 52 is formed so as to connect the vaporizer 33 and the intake pipe 11 on the upstream side of the throttle valve 12. The EGR gas is cooled as the vaporizer 33 is heated, and then is returned to the intake side through the exhaust gas recirculation passage 52. A condensed water removing device 53 and an EGR gas valve 54 are provided in the middle of the exhaust gas recirculation passage 52.

The condensed water removing device 53 is arranged on the upstream side of the EGR gas valve 54 in the recirculation direction of the EGR gas. The condensed water removing device 53 includes, for example, a discharge valve, and opens and closes the discharge valve according to the detection result (for example, pressure, temperature, etc.) of an appropriate sensor in the figure. The condensed water removing device 53 is connected to the condensed water introduction pipe 61 or the condensed water storage tank 6 via a route (not shown), and transfers the condensed water generated by cooling the EGR gas to the condensed water storage tank 6. Discharge. As a result, it is possible to avoid corrosion of the EGR gas valve 54 due to the acidic condensed water in which the components in the EGR gas are dissolved.

The EGR gas valve 54 is arranged on the downstream side of the condensed water removing device 53 in the recirculation direction of the EGR gas, and is configured so that the recirculation amount of the EGR gas can be adjusted. The EGR gas valve 54 changes the cross-sectional area of the exhaust gas recirculation passage 52 by changing its opening degree according to a control command from the control device (not shown). Thereby, the recirculation amount of EGR gas can be adjusted.

In this way, by using the high-temperature EGR gas as the heat medium for heating the vaporizer 33, the vaporizer 33 can be quickly heated even when the internal combustion engine 100 is started. Further, since the vaporizer 33 functions as an EGR cooler for cooling the EGR gas, it is not necessary to separately provide an EGR cooler, and the configuration of the internal combustion engine 100 can be simplified.

Further, by arranging the exhaust bypass passage 51 that supplies the EGR gas to the vaporizer 33 as described above, a two-stage cooling structure (air cooling portion 51a and tank cooling portion 51b) that cools the EGR gas separately from the vaporizer 33 is provided. ) Is formed. Therefore, as a whole, a three-stage cooling structure is realized by the air cooling unit 51a, the tank cooling unit 51b, and the vaporizer 33 for the EGR gas recirculated to the intake side, and the EGR gas can be efficiently cooled.

As a result, the internal combustion engine 100 of the present embodiment can efficiently and effectively cool the EGR gas, and thus can increase the amount of air sucked on the intake side.

When viewed from the vaporizer 33 side, the EGR recirculation path 5 of the EGR gas passes through the vaporizer 33, so that it is not necessary to separately provide a heating device for heating the vaporizer 33, and the vaporizer 33 is suitably added. Can be warmed.

As described above, the internal combustion engine 100 of the present embodiment includes a vaporizer 33, an exhaust bypass passage 51, and an exhaust return passage 52. The vaporizer 33 vaporizes the liquefied fuel gas. The exhaust bypass passage 51 supplies a part of the exhaust gas for heating the vaporizer 33. The exhaust return passage 52 returns the cooled exhaust gas to the intake side by heating the vaporizer 33.

As a result, it is not necessary to separately provide an EGR cooler for cooling the EGR gas, and heating of the vaporizer 33 and cooling of the EGR gas can be realized with a simple configuration. Then, by using the exhaust gas for heating the vaporizer 33, a sufficient heating effect can be brought about even when the internal combustion engine 100 is started.

Further, the internal combustion engine 100 of the present embodiment includes a condensed water storage tank 6 for storing the condensed water generated by the vaporizer 33. The condensed water storage tank 6 is arranged on the upstream side of the vaporizer 33 in the direction in which the exhaust gas flows through the exhaust bypass passage 51. The exhaust gas flowing through the exhaust bypass passage 51 is cooled by heat exchange with the condensed water stored in the condensed water storage tank 6.

As a result, a complex cooling structure of the EGR gas by the condensed water storage tank 6 and the vaporizer 33 can be realized with a simple configuration, and the EGR gas can be efficiently cooled. Further, since the exhaust gas is cooled before being supplied to the vaporizer 33, the heat load on the members such as the diaphragm included in the vaporizer 33 can be reduced, and the durability of these members can be improved.

Further, the internal combustion engine 100 of the present embodiment includes an exhaust pipe 21, an exhaust gas purifying device 23, and a condensed water discharge pipe 62. The exhaust pipe 21 discharges the exhaust gas. The exhaust gas purification device 23 is provided in the exhaust pipe 21 on the downstream side of the exhaust bypass passage 51 in the direction in which the exhaust gas flows. The condensed water discharge pipe 62 connects the condensed water storage tank 6 and the exhaust pipe 21 on the downstream side of the exhaust gas purification device 23.

As a result, the heat of the exhaust gas can be used to evaporate and discharge the condensed water. Further, in the exhaust pipe 21, even if the condensed water discharged from the condensed water discharge pipe 62 to the exhaust pipe 21 tries to return to the exhaust bypass passage 51, the return direction is opposite to the flow of the exhaust gas, and the return is in progress. The layout is such that it must pass through the exhaust gas purification device 23. Therefore, it is possible to prevent the condensed water discharged from the condensed water storage tank 6 from returning to the intake side on the flow of the EGR gas.

Further, in the internal combustion engine 100 of the present embodiment, the air-cooled portion 51a provided in the exhaust bypass passage 51 passes in the vicinity of the cooling fan 8.

As a result, the EGR gas flowing through the exhaust bypass passage 51 can be suitably cooled by the flow of air created by the cooling fan 8.

Next, a first modification of the above embodiment will be described. FIG. 2 is a diagram showing the configuration of the internal combustion engine 100 of the first modification. In the description after this modification, the same reference numerals may be given to the drawings for the same or similar members as those in the above-described embodiment, and the description may be omitted.

In the internal combustion engine 100x of the present modification shown in FIG. 2, a cooling avoidance path 55 that bypasses the tank cooling unit 51b arranged in the condensed water storage tank 6 is further formed in the EGR recirculation path 5x.

The cooling avoidance path 55 is provided from the exhaust bypass passage 51 on the upstream side of the condensed water storage tank 6 (that is, the tank cooling unit 51b) and the condensed water storage tank 6 (that is, the tank cooling unit 51b) in the direction in which the EGR gas flows. It is connected to the exhaust bypass passage 51 on the downstream side and on the upstream side of the vaporizer 33. As a result, a first passage in which the EGR gas is cooled by the condensed water storage tank 6 and introduced into the vaporizer 33 and a second passage in which the EGR gas is directly introduced into the vaporizer 33 without being cooled by the condensed water storage tank 6 are formed. Will be done.

An on-off valve 56 is provided in the middle of the cooling avoidance path 55. The on-off valve 56 can switch the opening and closing of the cooling avoidance path 55 (the second passage) according to, for example, a control command from the control device.

As a result, for example, the control device detects the temperature of the EGR gas flowing in the exhaust gas recirculation passage 52 by a sensor or the like, and the entire EGR gas is cooled by the condensed water storage tank 6 according to the detection result. It is possible to switch whether only the part is cooled by the condensed water storage tank 6. In this first modification, an on-off valve for switching the opening and closing of the tank cooling unit 51b may be further provided.

Further, in this first modification, the cooling avoidance passage 55 is configured to connect the exhaust bypass passage 51 on the upstream side of the air cooling portion 51a and the exhaust bypass passage 51 on the downstream side of the tank cooling portion 51b. Is also good.

Next, a second modification of the above embodiment will be described. FIG. 3 is a diagram showing the configuration of the internal combustion engine 100 of the second modification.

In the internal combustion engine 100y of the present modification shown in FIG. 3, the EGR recirculation path 5y includes an exhaust bypass passage 51 on the upstream side of the tank cooling unit 51b and an exhaust recirculation passage 52 on the downstream side of the condensed water removing device 53. An EGR gas bypass passage 57 to be connected is further formed. A metering valve 58 is provided in the middle of the EGR gas bypass passage 57.

In this configuration, for example, the control device detects the temperature of the EGR gas flowing in the exhaust gas recirculation passage 52 by a sensor, and the valve opening amount of the metering valve 58 is controlled based on the detection result, so that the high temperature EGR A part of the gas can be directly returned to the exhaust gas recirculation passage 52. As a result, the temperature of the EGR gas recirculated to the intake side can be appropriately adjusted, and the temperature of the EGR gas can be prevented from dropping too much.

Although preferred embodiments and modifications of the present invention have been described above, the above configuration can be changed as follows, for example.

The internal combustion engine 100 may include a supercharger that compresses air by using exhaust gas and forcibly sucks air. Further, the internal combustion engine 100 may include a mixer that mixes intake air and fuel gas.

In the above embodiment and the like, the tank cooling unit 51b is configured such that the pipe passes through the inside of the condensed water storage tank 6. However, the tank cooling unit 51b can be configured by, for example, a hollow path formed inside the tank wall of the condensed water storage tank 6. Even in this case, the exhaust gas flowing through the tank cooling unit 51b is cooled by heat exchange with the condensed water inside the condensed water storage tank 6.

Either one of the air cooling unit 51a and the tank cooling unit 51b may be omitted. Alternatively, a path for directly connecting the tank cooling unit 51b and the exhaust pipe 21 and a switching valve are provided, and the EGR gas passes through both the air cooling unit 51a and the tank cooling unit 51b according to the EGR gas temperature. , The state in which only the tank cooling unit 51b passes through may be switched.

33 Vaporizer 51 Exhaust bypass passage 52 Exhaust return passage 100 Internal combustion engine

Claims (4)

A vaporizer that vaporizes liquefied fuel gas,
An exhaust bypass passage that supplies a part of the exhaust gas obtained by burning the fuel gas for heating the vaporizer, and
An exhaust gas recirculation passage that recirculates the exhaust gas cooled by heating the vaporizer as EGR gas to the intake side.
A condensed water storage unit that stores the condensed water generated by the vaporizer,
A cooling avoidance path that guides the exhaust gas flowing through the exhaust bypass passage to the upstream side of the vaporizer without passing through the condensed water storage portion.
An on-off valve that opens and closes the cooling avoidance path,
An internal combustion engine characterized by being equipped with. The internal combustion engine according to claim 1.
The condensed water storage unit is arranged on the upstream side of the vaporizer in the direction in which the exhaust gas flows through the exhaust bypass passage.
An internal combustion engine characterized in that the exhaust gas flowing through the exhaust bypass passage is cooled by heat exchange with the condensed water stored in the condensed water storage unit. The internal combustion engine according to claim 1 or 2.
The exhaust gas passage that discharges the exhaust gas and
An exhaust gas purification device provided in the exhaust gas passage on the downstream side of the exhaust bypass passage in the direction in which the exhaust gas flows.
A condensed water discharge passage connecting the condensed water storage unit and the exhaust gas passage on the downstream side of the exhaust gas purification device.
An internal combustion engine characterized by being equipped with. The internal combustion engine according to any one of claims 1 to 3 .
The exhaust bypass passage is an internal combustion engine characterized in that it passes in the vicinity of a cooling fan that blows air.

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