JP2020033916A - engine - Google Patents

Abstract

To inhibit deterioration of an outer surface caused by temperature rise in an engine comprising an exhaust passage including a double pipe structure formed by a cast.SOLUTION: An engine 1 includes: an engine body 10 having an output shaft 11 which utilizes energy generated by combustion to rotate; an exhaust passage (an exhaust manifold 50 etc.) in which exhaust gas generated by combustion in the engine body 10 flows; a decompression device (a vacuum pump 60, a vacuum pipeline 61, and a control valve 62); and a control device 200. The exhaust manifold 50 includes a double pipe structure. The double pipe structure has: an inner pipe 51 and an outer pipe 52 formed by casts; and an intermediate space Vs formed between the inner pipe 51 and the outer pipe 52. The control device 200 is configured so that the intermediate space Vs is decompressed by the decompression device in a case where a surface temperature of the outer pipe 52 exceeds an allowable temperature.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine, and more particularly to an engine having an exhaust passage including a double pipe structure.

  Japanese Patent Application Laid-Open No. 60-78925 (Patent Document 1) discloses an engine having an exhaust passage including a double pipe structure. The double pipe structure has an inner pipe, an outer pipe, and an intermediate space formed between the inner pipe and the outer pipe. Exhaust gas flows in the inner pipe. The surface (inner surface) of the inner tube is in contact with the exhaust gas, and the surface (outer surface) of the outer tube is in contact with the atmosphere. Hereinafter, the double pipe structure included in the exhaust passage is also referred to as “exhaust double pipe”.

JP-A-60-78925

  By the way, the exhaust double pipe is roughly classified into first and second exhaust double pipes described below according to a manufacturing method.

  The first exhaust double pipe presses two metal plates (for example, stainless steel plates) corresponding to the inner pipe and the outer pipe, and then welds the obtained two pressed products (TIG welding, MIG welding). Welding, laser welding, etc.). The exhaust double pipe described in Patent Document 1 is a first exhaust double pipe.

  On the other hand, the second exhaust double pipe is a casting manufactured by casting. According to the casting, an exhaust double pipe having a complicated structure can be easily manufactured. Further, it is also possible to integrally form the inner pipe and the outer pipe to make the exhaust double pipe a seamless structure (seamless structure).

  However, in the second exhaust double pipe (i.e., the exhaust double pipe formed of a casting), the outer pipe is heated by the high-temperature exhaust gas flowing in the inner pipe, and when the surface temperature of the outer pipe increases, the outer pipe increases. Surface is easily degraded.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an engine having an exhaust passage including a double-pipe structure formed of a casting in an engine having an outer pipe surface caused by a temperature rise. It is to suppress alteration.

  The engine according to the present invention includes an engine body having an output shaft that rotates using energy generated by combustion, an exhaust passage through which exhaust gas generated by combustion flows, a pressure reducing device, and a control device. The exhaust passage includes a double pipe structure. The double pipe structure has an inner pipe and an outer pipe formed of a casting, and an intermediate space formed between the inner pipe and the outer pipe. The decompression device is configured to decompress the intermediate space. The control device is configured to control the pressure reducing device. The control device is configured to reduce the pressure in the intermediate space by the pressure reducing device when it is determined that the surface temperature of the outer tube exceeds the allowable temperature.

  In the above-mentioned engine, when it is determined that the surface temperature of the outer tube exceeds the allowable temperature (that is, the outer tube surface may be degraded due to the temperature rise), the pressure in the intermediate space is reduced by the pressure reducing device. When the pressure in the intermediate space is reduced, the amount of gas existing in the intermediate space decreases. As a result, the thermal conductivity of the intermediate space (therefore, the thermal conductivity between the inner tube and the outer tube) is reduced. Therefore, when the intermediate space is depressurized, heat is hardly transmitted from the inner tube to the outer tube due to the heat insulating effect of the intermediate space, and the surface temperature of the outer tube increases even when high-temperature exhaust gas flows in the inner tube. It becomes difficult to do. Therefore, by decompressing the intermediate space by the decompression device, it is possible to suppress the deterioration of the outer tube surface due to the temperature rise.

  The above control device determines whether the surface temperature of the outer tube exceeds the allowable temperature by using at least one of the temperature of the predetermined portion in the outer tube, the temperature of the exhaust gas flowing in the inner tube, and the operating condition of the engine body. It may be configured to judge whether or not.

  By using the above parameters, the surface temperature of the outer tube can be easily measured or estimated with sufficient accuracy. In particular, when the surface temperature of the outer tube is estimated using the operating conditions of the engine body, the exhaust gas temperature (or the outer tube before the exhaust gas is generated by combustion (or almost simultaneously with the generation of the exhaust gas)). Surface temperature), it is possible to determine early whether the surface temperature of the outer tube exceeds the permissible temperature and execute the decompression process by the decompression device at an early stage.

  The above-described pressure reducing device may include a pump driven by using the rotational force of the output shaft, and a control valve whose opening is controlled by the control device. The above pump may be connected to the intermediate space via a control valve. Then, when it is determined that the surface temperature of the outer tube exceeds the allowable temperature, the control device opens the control valve and depressurizes the intermediate space by the pump, while the surface temperature of the outer tube decreases the allowable temperature. The control valve may be configured to be closed when it is determined not to exceed.

  In the above configuration, since the pump is driven by using the rotational force of the output shaft of the engine body, it is not necessary to separately provide a drive source for the pump. Further, the execution / non-execution of the pressure reduction processing of the intermediate space by the pressure reduction device can be easily switched by opening / closing the control valve.

  In the above control valve, “closed state” means a fully closed state, and “open state” means a state other than the fully closed state. Further, the above control valve may be an on / off valve (a valve whose valve opening degree can take only two positions of full open / full close) or a continuous control valve (continuous control between full close and full open). The valve may be a valve whose opening degree can be automatically adjusted.

  When the engine is mounted on a vehicle having a master back that assists the brake pedal force, the pump may generate a negative pressure for the master back.

  By performing the decompression process of the intermediate space using a pump used for another purpose in the vehicle, it is not necessary to separately provide a pump for performing the decompression process of the intermediate space. In particular, a pump (for example, a vacuum pump) used for a master bag has excellent suction performance, and is therefore suitable for depressurizing the intermediate space.

  The above-described pressure reducing device may include an electric pump connected to the intermediate space and controlled by the control device. When the controller determines that the surface temperature of the outer tube exceeds the allowable temperature, the controller reduces the pressure in the intermediate space by operating the electric pump, while the surface temperature of the outer tube exceeds the allowable temperature. When it is determined that there is no electric pump, the electric pump may be stopped.

  As described above, since the pressure reducing device is configured to perform the pressure reducing process using the electric pump, the electric pump can be driven independently of the state of the engine body. Further, the execution / non-execution of the pressure reduction processing of the intermediate space by the pressure reduction device can be easily switched by operating / stopping the electric pump.

  At least one of the exhaust manifold and the supercharger included in the exhaust passage of the engine may have the double pipe structure. For example, the exhaust passage may include an exhaust manifold connected to the engine body, and at least a part of the exhaust manifold may have a double pipe structure. The engine may further include a supercharger that supercharges intake air of the engine body using exhaust gas flowing through the exhaust passage, wherein at least a part of the double pipe structure included in the exhaust passage is supercharged. May be formed by the machine housing.

  Each of the exhaust manifold and the housing of the supercharger is often arranged near the engine body, and it is likely to require a complicated structure by casting from the viewpoint of exhaust fluidity and heat dissipation. However, in the exhaust passage formed by casting, as described above, the surface of the outer tube may be deteriorated due to a rise in temperature. With respect to such a problem, by using the above-described configuration of the engine, it is possible to suppress the deterioration of the outer tube surface due to the temperature rise by the decompression process of the intermediate space by the decompression device.

  In the double pipe structure, the inner pipe and the outer pipe may be formed of cast iron. The control device may be configured such that, when it is determined that the surface temperature of the outer tube exceeds the allowable temperature, the intermediate space is evacuated by a pressure reducing device.

  From the viewpoints of strength, heat resistance, workability, cost, etc., cast iron is suitable as a material for the exhaust passage. However, cast iron is easily oxidized. With respect to such a problem, by setting the intermediate space to a vacuum state by the decompression device, it becomes easy to secure sufficient heat insulating properties in the intermediate space, and it is easy to suppress oxidation of cast iron on the outer tube surface due to a temperature rise.

In the above-mentioned double pipe structure, the inner pipe and the outer pipe may be integrally formed.
As described above, since the inner tube and the outer tube are integrally formed, it is not necessary to join the inner tube and the outer tube by welding or the like, and it is easy to secure sufficient airtightness in the intermediate space.

  ADVANTAGE OF THE INVENTION According to this invention, in the engine provided with the exhaust passage including the double pipe structure formed of the casting, it becomes possible to suppress the deterioration of the outer pipe surface due to the temperature rise.

FIG. 1 is an overall configuration diagram of an engine according to an embodiment of the present invention. It is sectional drawing which expands and shows a part of exhaust manifold (double pipe structure) shown in FIG. It is a flowchart for demonstrating the temperature control of the outer tube surface performed by the control apparatus which concerns on embodiment of this invention. FIG. 4 is a diagram illustrating an example of a relationship among a fuel injection amount, an engine rotation speed, and an exhaust temperature. FIG. 4 is a diagram showing a control map used in opening / closing control of a control valve provided in a pressure reducing passage. It is a figure which shows the modification of a decompression device. It is a figure showing the modification of a double pipe structure. 8 is a flowchart for explaining temperature control of the outer tube surface performed by the control device shown in FIG. 7.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions have the same reference characters allotted, and description thereof will not be repeated.

  FIG. 1 is an overall configuration diagram of an engine 1 according to the present embodiment. Referring to FIG. 1, engine 1 is mounted on a vehicle (for example, a four-wheeled vehicle) as a power generation device for traveling, for example. The engine 1 shown in FIG. 1 is an in-line four-cylinder diesel engine. However, the type of engine is not limited to a diesel engine, and may be a gasoline engine. The configuration of the engine shown in FIG. 1 is an example, and can be changed as appropriate. For example, a cylinder layout other than in-line (for example, V type or horizontal type) may be adopted. Also, the number of banks and cylinders can be arbitrarily changed. Although only some of the sensors are shown in FIG. 1, various sensors (for example, an intake pressure sensor, an exhaust pressure sensor, and the like) that detect a state of the engine 1 and output the detected result to the control device 200 are further provided. You may. Further, the engine 1 may include an EGR (Exhaust Gas Recirculation) device.

  The engine 1 includes an engine body 10, an air cleaner 20, an intercooler 25, an intake throttle valve 26, an intake manifold 28, a supercharger 30, and an exhaust manifold 50. The engine 1 is controlled by the control device 200. Hereinafter, in the engine 1, one end on the upstream side is referred to as a “first end” and the other end on the downstream side is referred to as a “second end” with respect to a pipe functioning as a flow path.

  The engine main body 10 is an internal combustion engine including an output shaft 11, a plurality of cylinders 12, a common rail 14, and a plurality of injectors 16.

  The output shaft 11 is configured to rotate using energy generated by combustion. The output shaft 11 is, for example, a crankshaft. More specifically, a piston (not shown) is provided in each cylinder 12, and a combustion chamber (a space in which fuel burns) is formed by the inner wall of the cylinder 12 and the top of the piston. When fuel is burned in the combustion chamber, heat energy generated by the combustion is converted into kinetic energy, and the piston reciprocates. Further, the reciprocating motion of the piston is converted into a rotary motion by the crank mechanism of the output shaft 11. Thus, the output shaft 11 rotates in accordance with the reciprocating motion of the piston. Then, the rotational force of the output shaft 11 is transmitted to the drive wheels of the vehicle, so that the drive wheels are driven and the vehicle travels. The output shaft 11 is provided with a rotation speed sensor 108. The rotation speed sensor 108 detects the rotation speed of the output shaft 11 (engine rotation speed) and outputs a detection value NE to the control device 200.

  The injector 16 is configured to supply fuel to the combustion chamber. More specifically, an injector 16 is provided for each cylinder 12, and each injector 16 is connected to the common rail 14. Fuel stored in a fuel tank (not shown) is pressurized to a predetermined pressure by a supply pump (not shown) and supplied to the common rail 14. The fuel supplied to the common rail 14 is injected from each injector 16 into the combustion chamber at a predetermined timing. The fuel injected and supplied by the injector 16 burns in the combustion chamber, so that torque is generated on the output shaft 11. The output shaft 11 is configured to rotate with the torque thus generated. The injection timing and fuel injection amount of each injector 16 are controlled by the control device 200.

  The air cleaner 20 is provided in the middle of the first intake pipe 22, and is configured to remove foreign matter contained in air taken in from an intake port (not shown) provided at a first end of the first intake pipe 22. You. A second end of the first intake pipe 22 is connected to an intake inlet of a compressor 32 of the supercharger 30, and a first end of the second intake pipe 24 is connected to an intake outlet of the compressor 32. The first intake pipe 22 and the second intake pipe 24 are connected to each other via an intake passage (not shown) formed in a housing of the compressor 32.

  The intercooler 25 is provided in the middle of the second intake pipe 24, and is configured to cool the air flowing through the second intake pipe 24. The intercooler 25 is, for example, an air-cooled or water-cooled heat exchanger.

  A first end of the third intake pipe 27 is connected to the intercooler 25, and a second end of the third intake pipe 27 is connected to the intake manifold 28. An intake throttle valve 26 is provided in the middle of the third intake pipe 27. The intake throttle valve 26 includes a valve, a motor, an opening degree sensor (throttle position sensor), and the like. The flow rate of air supplied to the intake manifold 28 changes according to the degree of opening of the intake throttle valve 26. The opening degree of the intake throttle valve 26 is controlled by the control device 200.

  The intake manifold 28 is connected to an intake port (not shown) of each cylinder 12 of the engine body 10. In the combustion chamber of each cylinder 12, an air-fuel mixture is generated by intake gas supplied from the intake manifold 28 and fuel supplied from the injector 16, and exhaust gas is generated by burning the fuel. The exhaust gas generated by the combustion flows through the exhaust passage of the engine 1 and is discharged outside the vehicle. The exhaust passage of the engine 1 includes an exhaust manifold 50, a turbine 36, a first exhaust pipe 54, an exhaust purification device 56, and a second exhaust pipe 58.

  A first end of the exhaust manifold 50 is connected to an exhaust port (not shown) of each cylinder 12 of the engine body 10. A second end of the exhaust manifold 50 is connected to an exhaust inlet of the turbine 36 of the supercharger 30. Exhaust gas exhausted from the exhaust port of each cylinder 12 is supplied to the turbine 36 through the exhaust manifold 50.

  The exhaust manifold 50 includes a double tube structure. In this embodiment, the entire exhaust manifold 50 has a double pipe structure. The exhaust manifold 50 has an inner pipe 51, an outer pipe 52, and an intermediate space Vs. The intermediate space Vs is a space formed between the inner pipe 51 and the outer pipe 52. The exhaust gas flows inside the inner pipe 51. The surface (inner surface) of the inner tube 51 contacts the exhaust gas, and the surface (outer surface) of the outer tube 52 contacts the atmosphere.

  FIG. 2 is a cross-sectional view showing a part of the exhaust manifold 50 (double pipe structure) in an enlarged manner. Referring to FIG. 2, exhaust manifold 50 is a casting manufactured by casting. The exhaust manifold 50 further includes a flange 53 in addition to the inner pipe 51 and the outer pipe 52. FIG. 2 shows only one end of the exhaust manifold 50, but the flange portions 53 are formed at both ends of the exhaust manifold 50. The inner pipe 51 and the outer pipe 52 are connected to each other via a flange 53. The inner pipe 51, the outer pipe 52, and the flange 53 are formed of, for example, cast iron. The thickness of each of the inner pipe 51 and the outer pipe 52 is, for example, about 5 mm. The exhaust manifold 50 is a double-pipe structure having a seamless structure, and the inner pipe 51, the outer pipe 52, and the flange 53 are integrally formed by casting. Since there is no seam (weld portion or the like) that easily causes a decrease in airtightness, the intermediate space Vs has high airtightness. Thus, when the pressure in the intermediate space Vs is reduced, the pressure in the intermediate space Vs can be reduced to a desired pressure (for example, 100 Pa or less) at an early stage. Further, after the decompression process of the intermediate space Vs is stopped, it becomes easier to maintain the intermediate space Vs at the pressure at the time when the decompression is stopped.

  Referring to FIG. 1 again, engine 1 further includes a pressure reducing device for reducing the pressure in intermediate space Vs. The pressure reducing device includes a vacuum pump 60, a vacuum pipe 61, and a control valve 62. The vacuum pipe 61 connects the negative pressure generating part of the vacuum pump 60 and the intermediate space Vs of the exhaust manifold 50. The vacuum pipe 61 functions as a passage (decompression passage) for sucking a gas component from the object to be decompressed (in this embodiment, the intermediate space Vs) and depressurizing the object to be decompressed. A control valve 62 is provided in the middle of the vacuum pipe 61. In this embodiment, as the control valve 62, an on / off valve that is ON (open) / OFF (closed) controlled by the control device 200 is employed. The control valve 62 is, for example, an electromagnetic valve (solenoid valve). However, the control valve 62 is not limited to the above-described on / off valve, and may be a continuous control valve that can be adjusted to an intermediate opening.

  The vacuum pump 60 is driven by using the rotational force of the output shaft 11 (for example, a crankshaft). The vacuum pump 60 includes a drive unit (for example, a rotor) connected to the output shaft 11 so as to interlock with the output shaft 11, and the drive unit of the vacuum pump 60 is driven by the rotation of the output shaft 11, whereby the vacuum pump 60 is driven. A negative pressure (a pressure lower than the atmospheric pressure) is generated at a predetermined portion (negative pressure generating section) of the pump 60. The rotational force of the output shaft 11 is transmitted to a drive unit of the vacuum pump 60 via, for example, a drive gear (not shown). The drive gear is housed in a gear box (not shown) of the engine body 10 together with other gears that mesh with the output shaft 11.

  The vacuum pump 60 is, for example, a vane type vacuum pump. The control valve 62 is turned on (opened) when a pressure reduction process (for example, evacuation) by the vacuum pump 60 is performed. When the control valve 62 is opened during operation of the vacuum pump 60, gas components and the like existing in the intermediate space Vs are sucked into the vacuum pump 60 through the vacuum pipe 61, and the intermediate space Vs is depressurized. In order to control the pressure in the intermediate space Vs, a pressure sensor for detecting the pressure in the intermediate space Vs may be provided.

  The vehicle on which the engine 1 is mounted is provided with a master back 70 that assists a brake pedaling force (a stepping force on a brake pedal (not shown)). The master back 70 is a booster using negative pressure. The vacuum pump 60 is configured to generate a negative pressure for the master bag 70. For example, the master back 70 includes a negative pressure chamber (not shown) in which the internal pressure is maintained at a negative pressure, and a variable pressure chamber (not shown) in which the internal pressure changes according to the operation of the brake pedal. It is configured to increase the brake depression force applied to the brake pedal according to the difference between the internal pressures of the negative pressure chamber and the variable pressure chamber. The negative pressure chamber of the master bag 70 is connected to a negative pressure generator of the vacuum pump 60 via a control valve (not shown) (for example, a control valve that is opened and closed by the control device 200). In order to control the pressure in the negative pressure chamber, a pressure sensor for detecting the pressure in the negative pressure chamber may be provided.

  A first end of a first exhaust pipe 54 is connected to an exhaust outlet of the turbine 36. The exhaust manifold 50 and the first exhaust pipe 54 are connected to each other via an exhaust passage (not shown) formed in a housing of the turbine 36. Further, a second end of the first exhaust pipe 54 is connected to an exhaust gas inlet of the exhaust gas purification device 56.

  An exhaust gas temperature sensor 104 is provided at a predetermined portion of the first exhaust pipe 54 (for example, near the exhaust gas inlet of the exhaust gas purification device 56). The exhaust gas temperature sensor 104 detects the temperature of the exhaust gas flowing in the first exhaust pipe 54 and outputs the detected value Tc to the control device 200.

  Examples of the exhaust gas purification device 56 include a PM (particulate matter) removal filter, a NOx catalyst, and a DPNR (Diesel Particlulate-NOx Reduction). A first end of a second exhaust pipe 58 is connected to an exhaust outlet of the exhaust purification device 56. The exhaust gas purified by the exhaust gas purification device 56 passes through the second exhaust pipe 58 and is discharged outside the vehicle via a muffler and the like (not shown).

  In the engine 1, the compressor 32 and the turbine 36 form a supercharger 30 (for example, a variable nozzle turbo). A compressor wheel 34 is provided in an intake passage in a housing of the compressor 32, and a turbine wheel 38 is provided in an exhaust passage in a housing of the turbine 36. The compressor wheel 34 and the turbine wheel 38 are connected by a connection shaft 35 and rotate integrally. The compressor wheel 34 is driven to rotate together with the turbine wheel 38 by the exhaust gas flowing through the turbine 36, compresses air taken into the compressor 32 through the first intake pipe 22, and discharges the compressed air to the second intake pipe 24. Thereby, the intake air of the engine body 10 (that is, the air taken into the combustion chamber of each cylinder 12) is supercharged.

  The engine 1 further includes an air flow meter 102, an intake air temperature sensor 106, a water temperature sensor 110, an accelerator pedal position sensor 112, an atmospheric pressure sensor 114, and an outside air temperature sensor 116.

  Air flow meter 102 detects the amount of air (fresh air amount) taken in from outside through air cleaner 20 and supplied to engine body 10, and outputs the detected value FI to control device 200. Intake air temperature sensor 106 detects the temperature of intake gas (intake air temperature) in intake manifold 28 and outputs a detected value Tb to control device 200. Water temperature sensor 110 detects the temperature of the cooling water of engine body 10 (engine cooling water temperature) and outputs a detected value TE to control device 200. Accelerator pedal position sensor 112 detects a depression amount (accelerator opening) of an accelerator pedal (not shown) and outputs a detected value AP to control device 200. The atmospheric pressure sensor 114 detects the atmospheric pressure, and outputs the detected value Pa to the control device 200. The outside air temperature sensor 116 detects the outside air temperature and outputs the detected value Ta to the control device 200.

  The control device 200 includes a CPU (Central Processing Unit) as an arithmetic device, a storage device, and an input / output port for inputting and outputting various signals (neither is shown). The storage device includes a RAM (Random Access Memory) as a working memory and a storage (ROM (Read Only Memory), a rewritable nonvolatile memory, and the like). The control device 200 receives signals from various devices and various sensors connected to the input port, and controls various devices (such as the injector 16) connected to the output port based on the received signals. Various controls are executed by the CPU executing the programs stored in the storage device. However, various controls are not limited to processing by software, and processing by dedicated hardware (electronic circuit) is also possible.

  By the way, a stainless steel exhaust manifold and a cast iron exhaust manifold are known as exhaust manifolds for automobile engines. Among them, the surface of the exhaust manifold made of cast iron is easily oxidized due to a rise in temperature when high-temperature exhaust gas flows. For this reason, when employing a cast iron exhaust manifold, it is necessary to reduce the exhaust temperature by adjusting the combustion conditions (fuel injection amount and fuel injection timing, etc.) of the engine so that the surface of the exhaust manifold is not oxidized. Can be However, when determining the combustion conditions, if the above-described restrictions are imposed from the viewpoint of preventing the oxidation of the exhaust manifold, it becomes difficult to optimize the combustion conditions from the viewpoint of the engine output performance, fuel consumption performance, and the like. There is a possibility that the performance of the engine cannot be fully exhibited.

  Therefore, in the engine 1 according to the present embodiment, a double pipe structure (see FIG. 2) formed of a casting (for example, cast iron) is adopted as the exhaust manifold 50 connected to the engine main body 10. By performing the pressure reduction control as described, even if high-temperature exhaust gas flows in the exhaust manifold 50, it is possible to suppress the deterioration (for example, oxidation) of the surface of the outer pipe 52 of the exhaust manifold 50. ing.

  In engine 1, control device 200 determines whether or not the surface temperature of outer tube 52 exceeds an allowable temperature by using a parameter (hereinafter, also referred to as a “temperature parameter”) correlated with the surface temperature of outer tube 52, When it is determined that the surface temperature of the outer tube 52 exceeds the allowable temperature, the control valve 62 is opened, and the pressure in the intermediate space Vs is reduced by the vacuum pump 60. When the pressure in the intermediate space Vs is reduced, the amount of gas existing in the intermediate space Vs decreases. Thereby, the thermal conductivity of the intermediate space Vs (therefore, the thermal conductivity between the inner pipe 51 and the outer pipe 52) decreases. For this reason, when the intermediate space Vs is depressurized, heat is hardly transmitted from the inner pipe 51 to the outer pipe 52 due to the heat insulating action of the intermediate space Vs. The temperature of the tube 52 (and thus the surface temperature of the outer tube 52) does not easily rise. Therefore, by reducing the pressure in the intermediate space Vs, it is possible to suppress the deterioration of the surface of the outer tube 52 due to the temperature rise.

  When it is determined that the surface temperature of outer tube 52 does not exceed the allowable temperature, control device 200 does not reduce the pressure in intermediate space Vs by the pressure reducing device. More specifically, the control valve 62 is closed. By closing the control valve 62, the load on the vacuum pump 60 is reduced, and loss in the engine 1 (for example, engine friction) is reduced. As described above, by reducing the frequency of the decompression process by the decompression device, the amount of energy consumed to drive the vacuum pump 60 is reduced, so that the fuel efficiency (fuel consumption rate) of the engine 1 can be improved. .

  As the temperature parameter, for example, the operating condition of the engine body 10 can be adopted. The operating conditions of the engine main body 10 include a combustion condition in the combustion chamber during the operation of the engine main body 10 (hereinafter, also simply referred to as “combustion condition”) and a state of the engine main body 10 (hereinafter, also simply referred to as “engine operating state”). And Each of the combustion condition and the engine operating condition is a parameter correlated with the surface temperature of the outer tube 52. For example, as the amount of fuel supplied to the combustion chamber (fuel injection amount) increases, and as the temperature of the intake gas supplied to the combustion chamber (intake temperature) increases, the thermal energy generated by combustion increases, The temperature of the exhaust gas discharged to the exhaust manifold 50 tends to increase. Further, during combustion, the higher the engine rotation speed and the higher the engine cooling water temperature, the higher the temperature of the exhaust gas discharged to the exhaust manifold 50 by combustion. The surface temperature of the outer tube 52 tends to increase as the temperature of the exhaust gas discharged to the exhaust manifold 50 increases.

  As described above, in engine 1 according to the present embodiment, when it is determined that the surface temperature of outer tube 52 exceeds the allowable temperature, control device 200 performs a decompression process on intermediate space Vs. This suppresses an excessive rise in the surface temperature of the outer pipe 52 in the exhaust manifold 50. That is, in this embodiment, when the surface of the outer tube 52 is degraded due to a temperature rise, the pressure reduction process of the intermediate space Vs is performed, so that the surface temperature of the outer tube 52 is reduced so that the degeneration does not occur. Controlled. Hereinafter, the temperature control of the outer tube surface according to this embodiment will be described with reference to FIG.

  FIG. 3 is a flowchart for explaining the temperature control of the outer tube surface performed by control device 200. The processing shown in this flowchart is called from a main routine (not shown) and executed repeatedly at predetermined control cycles.

  Referring to FIG. 3, at step (hereinafter, step is referred to as “S”) 11, control device 200 changes operating conditions (more specifically, combustion conditions and engine operating state) of engine body 10. get. As the combustion condition, for example, a fuel injection amount is obtained. Further, as the engine operating state, for example, an engine rotation speed (a detection value NE of the rotation speed sensor 108) is obtained.

  The fuel injection amount is calculated by control device 200 based on a request from a user (for example, detection value AP of accelerator pedal position sensor 112), an engine operating state (for example, engine rotation speed), and the like. For example, optimal combustion conditions (fuel injection amount, fuel injection timing, etc.) are calculated from the viewpoint of the output performance and / or fuel efficiency of the engine 1. The calculated combustion conditions are used in the control of the injector 16 performed in parallel with the processing in FIG.

  In S12, control device 200 determines whether or not the surface temperature of outer tube 52 exceeds the allowable temperature using the fuel injection amount and the engine rotation speed (temperature parameter) acquired in S11. Hereinafter, the determination process in S12 will be described with reference to FIG.

  FIG. 4 is a diagram showing a relationship among a fuel injection amount, an engine rotation speed, and an exhaust gas temperature. The numerical values shown in FIG. 4 are exhaust gas temperatures in the exhaust manifold 50 measured in advance for each engine operating condition (more specifically, conditions defined by the fuel injection amount and the engine rotation speed) by experiments.

  As shown in FIG. 4, basically, the higher the fuel injection amount and the higher the engine speed, the higher the exhaust gas temperature. Since the surface temperature of the outer tube 52 increases as the exhaust temperature increases, in this embodiment, the surface temperature of the outer tube 52 is determined based on whether the exhaust temperature estimated from the engine operating conditions is equal to or higher than a predetermined temperature. Is higher than the allowable temperature. More specifically, when the exhaust temperature is 650 ° C. or higher, it is determined that the surface temperature of the outer tube 52 exceeds the allowable temperature, and when the exhaust temperature is lower than 650 ° C., It is determined that the temperature does not exceed the allowable temperature.

  Referring again to FIG. 3, when it is determined in S12 that the surface temperature of outer tube 52 exceeds the allowable temperature (YES in S12), control device 200 turns on (opens) control valve 62 in S13. State). When the control valve 62 is opened, the pressure in the intermediate space Vs is reduced by the vacuum pump 60, and the intermediate space Vs is evacuated. On the other hand, when it is determined in S12 that the surface temperature of the outer tube 52 does not exceed the allowable temperature (NO in S12), the control device 200 turns the control valve 62 to the OFF state (closed state) in S14. . When the control valve 62 is closed, communication between the vacuum pump 60 and the intermediate space Vs is stopped. Therefore, in a state where the control valve 62 is closed, the decompression process of the intermediate space Vs by the vacuum pump 60 is not performed.

  FIG. 5 is a diagram showing a control map used in the opening / closing control of the control valve 62 (S12 to S14 in FIG. 3). This control map is created in advance by an experiment or the like, for example, and stored in the storage device of the control device 200.

  Referring to FIG. 5 together with FIG. 4, in the control map shown in FIG. 5, the engine operating condition (see FIG. 4) in which the exhaust temperature becomes 650 ° C. or more is “ON”, and the engine in which the exhaust temperature becomes less than 650 ° C. “OFF” is defined as the operating condition (see FIG. 4). The control device 200 refers to such a control map and sets the control valve 62 to a state (ON / OFF) according to the engine operating conditions (more specifically, the conditions defined by the fuel injection amount and the engine rotation speed). I do. As a result, the control valve 62 is opened under engine operating conditions where the exhaust temperature is 650 ° C. or higher, and the control valve 62 is closed under engine operating conditions where the exhaust temperature is lower than 650 ° C.

  When the series of processes shown in FIG. 3 is repeatedly executed, when it is determined that the surface temperature of the outer pipe 52 exceeds the allowable temperature from the engine operating conditions (for example, when the exhaust gas temperature becomes 650 ° C. or more). Means that the control valve 62 is in the ON state (open state). Thereby, the intermediate space Vs is depressurized by the vacuum pump 60. When the pressure in the intermediate space Vs is reduced, the surface temperature of the outer tube 52 is less likely to increase even when high-temperature exhaust gas flows in the inner tube 51. For this reason, by decompressing the intermediate space Vs by the vacuum pump 60, it is possible to suppress the deterioration of the surface of the outer tube 52 (for example, oxidation of cast iron) due to the temperature rise. When it is determined from the engine operating conditions that the surface temperature of the outer pipe 52 does not exceed the allowable temperature (for example, when the exhaust gas temperature is lower than 650 ° C.), the control valve 62 is turned off (closed state). become. Accordingly, the amount of energy consumed to drive the vacuum pump 60 is reduced, and the fuel efficiency of the engine 1 can be improved. For example, when a warm-up operation (for example, an idling operation) is performed in the engine body 10, it is determined from the engine operation conditions that the surface temperature of the outer pipe 52 does not exceed the allowable temperature.

  Further, by setting the intermediate space Vs of the exhaust manifold 50 to a vacuum state (preferably, 1 Pa or less), sound radiation (combustion noise) from the exhaust manifold 50 is reduced. Thereby, the quietness of the engine 1 is improved.

  In the above embodiment, the combustion condition (more specifically, the fuel injection amount) and the engine operating state (more specifically, the engine speed) are adopted as the temperature parameters. The surface temperature of the outer tube can be estimated with high accuracy from the combustion conditions and the engine operating state. In addition, according to such an estimation method, the exhaust gas temperature (and, consequently, the surface temperature of the outer tube 52) can be predicted before the exhaust gas is generated by combustion, so that the surface temperature of the outer tube 52 exceeds the allowable temperature. It is possible to perform the determination as to whether or not it is early, and to execute the decompression process by the decompression device early. In addition to the fuel injection amount and the engine rotation speed, control device 200 takes into account the intake air temperature (detected value Tb of intake air temperature sensor 106), engine coolant temperature (detected value TE of water temperature sensor 110), and the like. It may be configured to determine whether the surface temperature of the tube 52 exceeds the allowable temperature.

  In the above embodiment, since the vacuum pump 60 is driven by using the rotational force of the output shaft 11 of the engine body 10, suction is always performed during operation of the engine body 10. However, the pump used in the decompression device is not limited to the pump using the engine main body 10 as a driving source, such as the vacuum pump 60, and may be an electric pump. FIG. 6 is a diagram showing a modified example of the pressure reducing device. Hereinafter, the pressure reducing device of the engine 1A shown in FIG. 6 will be described focusing on differences from the engine 1 shown in FIG.

  Referring to FIG. 6, engine 1A includes an electric pump 60A instead of vacuum pump 60 and control valve 62. The electric pump 60A can use, for example, a motor that receives supply of electric power from a vehicle-mounted battery as a drive source. The negative pressure generator of the electric pump 60 </ b> A is connected to the intermediate space Vs of the exhaust manifold 50 via the vacuum pipe 61. The engine 1A includes a control device 200A that executes the processing of FIG. However, if it is determined in S12 that the surface temperature of outer tube 52 exceeds the allowable temperature (YES in S12), control device 200A operates electric pump 60A in S13. By operating the electric pump 60A, the intermediate space Vs is depressurized by the electric pump 60A. On the other hand, when it is determined in S12 that the surface temperature of outer tube 52 does not exceed the allowable temperature (NO in S12), control device 200A stops electric pump 60A in S14. By stopping the electric pump 60A, the pressure reduction processing of the intermediate space Vs by the electric pump 60A is not performed.

  In the engine 1A shown in FIG. 6, since the pressure reducing device performs the pressure reducing process using the electric pump 60A, the electric pump 60A can be driven independently of the state of the engine body 10. Further, the execution / non-execution of the pressure reduction processing of the intermediate space Vs by the pressure reduction device can be easily switched by operating / stopping the electric pump 60A.

  When the electric pump 60A is stopped, air may be introduced into the intermediate space Vs by opening the intermediate space Vs. By injecting air into the intermediate space Vs (for example, by setting the pressure of the intermediate space Vs to the atmospheric pressure), the heat conductivity of the intermediate space Vs increases, so that the heat radiation of the inner tube 51 can be improved. When the thermal conductivity of the intermediate space Vs increases, the heat of the inner tube 51 is easily released to the outside through the intermediate space Vs and the outer tube 52.

  In the example of FIG. 6, the electric pump 60A is directly connected to the intermediate space Vs without passing through a valve. However, a vacuum valve whose opening degree is adjusted (for example, opening / closing control) by the control device 200A is connected to a vacuum pipe. The electric pump 60A may be provided in the middle of 61 and connected to the intermediate space Vs via a vacuum valve. Then, when the electric pump 60A is stopped, the intermediate space Vs may be maintained in a reduced pressure state (for example, a vacuum state) by closing the vacuum valve and sealing the intermediate space Vs.

  The material of the double pipe structure is not limited to cast iron, and can be arbitrarily changed as long as it is a casting. In addition, the member connecting the inner tube and the outer tube in the double tube structure is not limited to the flange portion. The range and position where the double pipe structure is applied in the exhaust passage can be arbitrarily changed. For example, only a part of the exhaust manifold 50 (for example, a part where the temperature is particularly likely to increase) may be formed of a double pipe structure. The portion of the exhaust manifold 50 formed by the double pipe structure may be a portion near the flange portion or a portion distant from the flange portion. Further, instead of or in addition to the exhaust manifold 50, the housing of the turbine 36 may have a double-pipe structure. If both the exhaust manifold 50 and the supercharger 30 have a double-pipe structure, it is formed by the double-pipe structure of the exhaust manifold 50 and the housing of the supercharger 30 (more specifically, the turbine 36). May be connected to each other, or may be separated from each other.

  In the above embodiment, the engine operating condition is adopted as the temperature parameter. However, the temperature parameter used for determining whether the surface temperature of the outer tube 52 exceeds the allowable temperature is not limited to the engine operating condition, Another parameter correlated with the surface temperature of the outer tube 52 may be used. The temperature parameter may be a temperature of a predetermined portion of the outer tube 52 (for example, a surface temperature of the outer tube 52), or a temperature of a portion that can exchange heat with the outer tube 52 (for example, exhaust gas flowing through the inner tube 51). Gas temperature). For example, the temperature of the exhaust gas flowing through the inner pipe 51 can be estimated from the actual measured value of the exhaust temperature downstream of the inner pipe 51 (detected value Tc of the exhaust temperature sensor 104).

  FIG. 7 is a view showing a modified example of the double pipe structure. Referring to FIG. 7, the double pipe structure includes an inner pipe 51A, an outer pipe 52A, and a connecting portion 53A. The inner tube 51A and the outer tube 52A are connected to each other via a connecting portion 53A. The inner tube 51A, the outer tube 52A, and the connecting portion 53A are integrally formed by casting. That is, each of the inner tube 51A, the outer tube 52A, and the connecting portion 53A is formed of a casting.

  A temperature sensor 120 for detecting the surface temperature of the outer tube 52A is provided on the surface of the outer tube 52A. The value detected by temperature sensor 120 is output to control device 200B. Control device 200B determines whether or not the surface temperature of outer tube 52A exceeds the allowable temperature using the output of temperature sensor 120 (that is, the surface temperature of outer tube 52A detected by temperature sensor 120). Be composed.

  FIG. 8 is a flowchart for explaining the temperature control of the outer tube surface performed by control device 200B shown in FIG. Hereinafter, the processing illustrated in FIG. 8 will be described, focusing on differences from the processing illustrated in FIG.

  Referring to FIG. 8, in this process, S11A is executed instead of S11 in FIG. In S11A, control device 200B acquires the actual measured value of the surface temperature of outer tube 52A (the detected value of temperature sensor 120). Then, in S12, control device 200B determines whether or not the surface temperature of outer tube 52A exceeds the allowable temperature, using the actually measured value (temperature parameter) of the surface temperature of outer tube 52A acquired in S11A. . For example, when the surface temperature (actually measured value) of the outer tube 52A is equal to or higher than a predetermined value, it is determined that the surface temperature of the outer tube 52A exceeds the allowable temperature, and the surface temperature (actually measured value) of the outer tube 52A is increased to a predetermined value. If it is less than the predetermined temperature, it is determined that the surface temperature of the outer tube 52A does not exceed the allowable temperature. Control device 200B uses, for example, a control map (not shown) indicating the relationship between the surface temperature of outer tube 52A and the state (ON / OFF) of control valve 62, instead of the control map shown in FIG. , The opening and closing of the control valve 62 can be controlled.

  According to the processing of FIG. 8, when it is determined from the detection value of the temperature sensor 120 that the surface temperature of the outer tube 52A exceeds the allowable temperature, the control valve 62 is turned on (opened). Thereby, the deterioration of the surface of the outer tube 52A due to the temperature rise can be suppressed. When it is determined from the detection value of the temperature sensor 120 that the surface temperature of the outer tube 52A does not exceed the allowable temperature, the control valve 62 is turned off (closed state). Thereby, the fuel efficiency of the engine 1 can be improved.

  In S11A, the control device 200B determines whether or not the surface temperature of the outer tube 52A exceeds the allowable temperature using the detection value of the temperature sensor 120. Whether the surface temperature of the outer pipe 52A exceeds the allowable temperature may be determined using the detection value Tc (FIG. 1) of the temperature sensor 104 and the detection value Ta (FIG. 1) of the outside temperature sensor 116.

  A target to which the engine of the present invention is applied is not limited to a vehicle, and is arbitrary. The application target may be, for example, another vehicle (ship, airplane, or the like).

The above-described modifications may be implemented by combining all or some of them.
The embodiments and examples disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1, 1A engine, 10 engine body, 11 output shaft, 12 cylinder, 14 common rail, 16 injector, 20 air cleaner, 22 first intake pipe, 24 second intake pipe, 25 intercooler, 26 valve, 27 third intake pipe, 28 intake manifold, 30 supercharger, 32 compressor, 34 compressor wheel, 35 connecting shaft, 36 turbine, 38 turbine wheel, 50 exhaust manifold, 51, 51A inner pipe, 52, 52A outer pipe, 53 flange part, 53A connection part , 54 first exhaust pipe, 56 exhaust purification device, 58 second exhaust pipe, 60 vacuum pump, 60A electric pump, 61 vacuum pipe, 62 control valve, 70 master bag, 102 air flow meter, 104 exhaust temperature sensor, 106 intake temperature Sensor, 108 rotation speed sensor, 10 the water temperature sensor, 112 an accelerator pedal position sensor, 114 atmospheric pressure sensor, 116 the outside air temperature sensor, 120 temperature sensor, 200, 200A, 200B controller, Vs intermediate space.

Claims (9)

An engine body having an output shaft that rotates by utilizing energy generated by combustion,
An exhaust passage through which exhaust gas generated by the combustion flows,
The exhaust passage includes a double-pipe structure having an inner pipe and an outer pipe formed of a casting, and an intermediate space formed between the inner pipe and the outer pipe,
The engine is
A decompression device for decompressing the intermediate space,
A control device for controlling the pressure reducing device,
The engine, wherein the control device reduces the pressure in the intermediate space by the pressure reducing device when it is determined that the surface temperature of the outer tube exceeds the allowable temperature.   The controller uses at least one of a temperature of a predetermined portion in the outer pipe, a temperature of exhaust gas flowing in the inner pipe, and an operating condition of the engine body to adjust the surface temperature of the outer pipe to The engine according to claim 1, wherein it is determined whether the temperature exceeds an allowable temperature. The pressure reducing device includes a pump driven by using the rotational force of the output shaft, and a control valve whose opening is controlled by the control device,
The pump is connected to the intermediate space via the control valve,
When it is determined that the surface temperature of the outer tube exceeds the allowable temperature, the control device opens the control valve and depressurizes the intermediate space by the pump, while the surface of the outer tube is reduced. 3. The engine according to claim 1, wherein the control valve is closed when it is determined that the temperature does not exceed the allowable temperature. Mounted on vehicles equipped with a master back that assists brake pedaling,
The engine according to claim 3, wherein the pump generates a negative pressure for the master bag. The pressure reducing device includes an electric pump connected to the intermediate space and controlled by the control device,
The control device, when it is determined that the surface temperature of the outer tube exceeds the allowable temperature, depressurizes the intermediate space by operating the electric pump, while the surface temperature of the outer tube is reduced. The engine according to claim 1, wherein when it is determined that the temperature does not exceed the allowable temperature, the electric pump is stopped. The exhaust passage includes an exhaust manifold connected to the engine body,
The engine according to any one of claims 1 to 5, wherein at least a part of the exhaust manifold has the double pipe structure. A supercharger that supercharges intake air of the engine body using exhaust gas flowing through the exhaust passage;
The engine according to any one of claims 1 to 6, wherein at least a part of the double pipe structure included in the exhaust passage is formed by a housing of the supercharger. The inner pipe and the outer pipe are formed of cast iron,
The controller according to any one of claims 1 to 7, wherein, when it is determined that the surface temperature of the outer tube exceeds the allowable temperature, the controller sets the intermediate space in a vacuum state by the pressure reducing device. Engine.   The engine according to any one of claims 1 to 8, wherein the inner pipe and the outer pipe are integrally formed.

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