JP2018193899A - Intake/exhaust structure of compressed natural gas engine - Google Patents

Abstract

To provide an intake/exhaust structure of a compressed natural gas engine which suppresses a rise of an exhaust temperature, and hardly affects the durability of the compressed natural gas engine adversely.SOLUTION: The problem can be solved by an intake/exhaust structure 100 of a compressed natural gas engine which comprises: a compressor 106 of a supercharger 105 installed in an intake passage 101; a first throttle valve 108 installed in the intake passage 101 at an intake downstream side of the compressor 106; a bypass intake passage 109 for making the intake passage 101 at an intake upstream side of the compressor 106 communicate with the intake passage 101 at an intake upstream side of the first throttle valve 108 being the intake downstream side of the compressor 106; and a second throttle valve 110 installed in the bypass intake passage 109.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an intake / exhaust structure of a compressed natural gas engine.

  In a compressed natural gas vehicle, a three-way catalyst is used to purify nitrogen oxides, hydrocarbons, and carbon monoxide in the exhaust (see, for example, Patent Document 1).

JP 2017-002865 A

  In order to purify nitrogen oxides, hydrocarbons, and carbon monoxide in exhaust using a three-way catalyst, it is necessary to operate a compressed natural gas engine in a stoichiometric combustion operation region.

  However, when the compressed natural gas engine is operated in the stoichiometric combustion operation region, the fuel consumption is deteriorated and the exhaust temperature becomes high, which may adversely affect the durability of the compressed natural gas engine.

  Especially in the high-load operation region, it is necessary to lower the exhaust temperature by using exhaust gas recirculation without using fuel enrichment that causes fuel consumption deterioration. However, in a compressed natural gas vehicle equipped with a supercharger, The exhaust pressure tends to be lower than the intake pressure, and it is difficult to increase the exhaust gas recirculation rate.

  In addition, unlike a diesel engine, a compressed natural gas engine requires a large amount of air to be supplied to the cylinder together with fuel in order to obtain a predetermined torque. Therefore, a compressed natural gas vehicle equipped with a supercharger has a small capacity. The transient response (starting response) is improved by using the prime mover.

  However, if a small-capacity prime mover equipped with a turbocharger is used, it will not be optimal in all areas, and a considerable amount of loss will occur, and the exhaust pressure will become high in the high-rotation and high-load operation area. There is a risk of rising.

  Therefore, the present invention provides a compressed natural gas engine intake / exhaust structure that suppresses an increase in exhaust temperature and does not adversely affect the durability of the compressed natural gas engine while reducing the loss of the supercharger and reducing fuel consumption deterioration. The purpose is to provide.

  The present invention provides a compressor of a supercharger installed in an intake passage, a first throttle valve installed in the intake passage on the intake downstream side of the compressor, and the intake air on the intake upstream side of the compressor An intake of a compressed natural gas engine, comprising: a bypass intake passage communicating with the intake passage between the compressor and the first throttle valve; and a second throttle valve installed in the bypass intake passage. Provide an exhaust structure.

  A supercharger prime mover installed in the exhaust passage, a bypass exhaust passage that connects the exhaust passage upstream of the prime mover to the exhaust passage downstream of the prime mover, and a bypass exhaust passage It is desirable to further include an exhaust relief valve.

  An intake manifold connected to an intake downstream end of the intake passage, an exhaust manifold connected to an exhaust upstream end of the exhaust passage, an exhaust recirculation passage communicating the exhaust manifold with the intake manifold, It is desirable to further include an exhaust gas recirculation valve installed in the exhaust gas recirculation passage.

  It is desirable to further include a control device that opens and closes the first throttle valve, the second throttle valve, the exhaust relief valve, and the exhaust recirculation valve.

  The control device opens the first throttle valve and the second throttle valve and closes the exhaust relief valve and the exhaust recirculation valve in a low rotation low load operation region, It is desirable to close the second throttle valve as the valve rises.

  It is desirable that the control device opens the first throttle valve and the exhaust gas recirculation valve and closes the second throttle valve and the exhaust relief valve in the low rotation and high load operation region.

  It is desirable that the control device opens the first throttle valve, the second throttle valve, and the exhaust gas recirculation valve and closes the exhaust relief valve in the middle and high rotation low load operation region.

  It is desirable that the control device opens the first throttle valve, the second throttle valve, the exhaust relief valve, and the exhaust recirculation valve in the low, medium, and high rotation middle load operation region.

  The control device opens the first throttle valve, the second throttle valve, and the exhaust recirculation valve and closes the exhaust relief valve in the middle / high rotation / high load operation region, thereby accelerating the intake pressure. When the target intake pressure according to the opening degree and the engine speed cannot be reached, it is desirable to open the exhaust relief valve so that the intake pressure reaches the target intake pressure.

  The control device opens the first throttle valve, the second throttle valve, and the exhaust relief valve and closes the exhaust recirculation valve in a medium / high rotation / high load operation region at low and high temperatures. Is desirable.

  It is desirable to further include an exhaust brake valve installed in the exhaust passage on the exhaust downstream side of the prime mover, and the control device also opens and closes the exhaust brake valve.

  In the exhaust braking operation operation region, the control device preferably opens the first throttle valve and the second throttle valve and closes the exhaust brake valve.

  According to the present invention, an intake / exhaust structure for a compressed natural gas engine is provided which suppresses an increase in exhaust temperature and hardly adversely affects the durability of the compressed natural gas engine while reducing supercharger loss and improving fuel efficiency. I can do it.

It is a figure explaining the intake / exhaust structure of the compression natural gas engine which concerns on embodiment of this invention. It is a figure explaining the input / output relationship of a control apparatus. It is a figure explaining a driving | operation area | region. It is a figure explaining operation | movement of the intake / exhaust structure in a low rotation low load operation area | region. It is the figure which summarized the control in the low rotation low load operation area | region, and the operation | movement of a compression natural gas engine. It is a figure explaining operation | movement of the intake / exhaust structure in a low rotation high load operation area | region. It is the figure which summarized the control in the low rotation high load operation area | region, and the operation | movement of a compression natural gas engine. It is a figure explaining operation | movement of the intake / exhaust structure in a medium-high rotation low load operation area | region. It is the figure which summarized the control in the middle and high rotation low load operation area | region, and the operation | movement of a compression natural gas engine. It is a figure explaining operation | movement of the intake / exhaust structure in a low middle high rotation middle load operation area | region. It is the figure which summarized the control in the low middle high rotation medium load operation area | region, and the motion of a compression natural gas engine. It is a figure explaining operation | movement of the intake / exhaust structure in a medium-high rotation high load operation area | region. It is the figure which summarized the control in the middle and high rotation high load operation area | region, and the operation | movement of a compression natural gas engine. It is a figure explaining operation | movement of the intake / exhaust structure in the medium / high rotation high load operation area | region at the time of low temperature. It is the figure which summarized the control in the middle and high rotation high load operation area | region at the time of low temperature, and a motion of a compression natural gas engine. It is a figure explaining operation | movement of the intake / exhaust structure in an exhaust-braking operation area | region. It is the figure which put together the control in the exhaust-braking operation operation area | region, and the operation | movement of a compression natural gas engine.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  As shown in FIGS. 1 and 2, an intake / exhaust structure 100 for a compressed natural gas engine according to an embodiment of the present invention includes an intake passage 101, an exhaust passage 102, an intake manifold 103, an exhaust manifold 104, Compressor 106 of supercharger 105, prime mover 107 of supercharger 105, first throttle valve 108, bypass intake passage 109, second throttle valve 110, bypass exhaust passage 111, and exhaust relief valve 112, an exhaust gas recirculation passage 113, an exhaust gas recirculation valve 114, an exhaust braking valve 115, and a control device 116.

  The intake passage 101 is a so-called intake pipe and supplies intake air to each of the plurality of cylinders 117. The exhaust passage 102 is a so-called exhaust pipe, and exhausts exhaust from each of the plurality of cylinders 117. The intake passage 101 and the exhaust passage 102 are routed along various routes according to the vehicle type.

  The intake manifold 103 is connected to the intake downstream end of the intake passage 101 and diverts the intake air supplied to the compressed natural gas engine through the intake passage 101 to each of the plurality of cylinders 117. The exhaust manifold 104 is connected to the exhaust upstream end of the exhaust passage 102 and joins exhaust exhausted from each of the plurality of cylinders 117 to the exhaust passage 102.

  A first pressure detector 118 is installed in the intake manifold 103. The first pressure detector 118 is a so-called MAP sensor, and is connected to the control device 116 to detect the absolute pressure of the intake manifold 103. In this specification, the absolute pressure of the intake manifold 103 detected by the first pressure detector 118 is defined as “intake manifold pressure”.

  The supercharger 105 includes a compressor 106, a prime mover 107, and a rotating shaft 119. The supercharger 105 is a so-called exhaust turbine supercharger, and the prime mover 107 is driven using the kinetic energy of the exhaust gas, and the compressor 106 is driven using the kinetic energy of the prime mover 107. The air is compressed (supercharged) and supplied to each of the plurality of cylinders 117. The compressor 106 is a so-called compressor and is installed in the intake passage 101. The prime mover 107 is a so-called turbine and is installed in the exhaust passage 102. The rotating shaft 119 connects the compressor 106 and the prime mover 107 rotatably on the same axis.

  A three-way catalyst 120 is installed in the exhaust passage 102 on the exhaust downstream side of the prime mover 107. The three-way catalyst 120 purifies nitrogen oxides, hydrocarbons, and carbon monoxide in the exhaust.

  The first throttle valve 108 is installed in the intake passage 101 on the intake downstream side of the compressor 106 and increases or decreases the intake air supplied to the intake manifold 103 through the intake passage 101 according to the opening.

  An intercooler 121 is installed in the intake passage 101 between the compressor 106 and the first throttle valve 108. The intercooler 121 is a so-called heat exchanger, and cools the air compressed and heated by the supercharger 105.

  A second pressure detector 122 is installed in the intake passage 101 between the first throttle valve 108 and the intercooler 121. The second pressure detector 122 is a so-called MAP sensor, and is connected to the control device 116 to detect the absolute pressure of the intake passage 101 between the first throttle valve 108 and the intercooler 121. In this specification, the absolute pressure of the intake passage 101 between the first throttle valve 108 and the intercooler 121 detected by the second pressure detector 122 is defined as “intake passage pressure”.

  The bypass intake passage 109 is a so-called bypass intake pipe, and the intake passage 101 on the intake upstream side of the compressor 106 is provided between the compressor 106 and the first throttle valve 108, more specifically, with the intercooler 121. While communicating with the intake passage 101 between the first throttle valve 108, the intake air supplied to the intake manifold 103 through the intake passage 101 is divided into two paths.

  The second throttle valve 110 is installed in the bypass intake passage 109 and increases or decreases the intake air supplied to the intake manifold 103 through the bypass intake passage 109 according to the opening degree. As a result, the second throttle valve 110 increases or decreases the intake air supplied to the compressor 106 through the intake passage 101 according to the opening degree.

  The bypass exhaust passage 111 is a so-called bypass exhaust pipe, and communicates the exhaust passage 102 on the exhaust upstream side of the prime mover 107 with the exhaust passage 102 on the exhaust downstream side of the prime mover 107, and the exhaust discharged through the exhaust passage 102. Shunt into the path.

  The exhaust relief valve 112 is installed in the bypass exhaust passage 111 and increases or decreases the amount of exhaust discharged through the bypass exhaust passage 111 according to the opening degree. The exhaust relief valve 112 increases or decreases the exhaust gas supplied to the prime mover 107 as a result according to the opening degree.

  The exhaust gas recirculation passage 113 is a so-called exhaust gas recirculation pipe that communicates the exhaust manifold 104 with the intake manifold 103 and circulates a part of the exhaust gas to the intake air. An exhaust gas recirculation cooler 123 is installed in the exhaust gas recirculation passage 113. The exhaust gas recirculation cooler 123 is a so-called heat exchanger, and cools the exhaust gas recirculated to the intake air through the exhaust gas recirculation passage 113.

  The exhaust gas recirculation valve 114 is installed in the exhaust gas recirculation passage 113 downstream of the exhaust gas recirculation cooler 123 and increases or decreases the amount of exhaust gas circulated to the intake air through the exhaust gas recirculation passage 113 according to the opening degree.

  The exhaust brake valve 115 is installed in the exhaust passage 102 on the exhaust downstream side of the prime mover 107, and shuts off the exhaust discharged through the exhaust passage 102 when the exhaust brake is operated to increase the braking force.

  The control device 116 is a so-called engine control unit, and opens and closes the first throttle valve 108, the second throttle valve 110, the exhaust relief valve 112, the exhaust recirculation valve 114, and the exhaust brake valve 115.

  Note that the accelerator opening and the engine speed are input to the control device 116. The accelerator opening is detected by an accelerator opening sensor 124. The engine speed is detected by an engine speed sensor 125.

  In the present specification, an operation region where the engine speed is low is defined as a “low rotation operation region”, and an operation region where the engine speed is high is defined as a “high rotation operation region”. An operation region between the “low rotation operation region” and the “high rotation operation region” is defined as a “medium rotation operation region”.

  Similarly, an operation region where the engine load is low is defined as a “low load operation region” and an operation region where the engine load is high is defined as a “high load operation region”. The operation region between the “low load operation region” and the “high load operation region” is defined as the “medium load operation region”.

  In addition, since the boundary which divides each operation area | region changes according to engine performance, the boundary which divides each operation area | region is not specified in this specification.

[Operation of Intake / Exhaust Structure 100 in Low Rotation and Low Load Operation Region]
As shown in FIG. 3, in the low rotation and low load operation region A, the control device 116 opens the first throttle valve 108 and the second throttle valve 110 as shown in FIGS. The exhaust relief valve 112 and the exhaust recirculation valve 114 are closed, and the second throttle valve 110 is closed as the supercharging pressure increases. The exhaust brake valve 115 is naturally closed.

  Specifically, when the driver depresses the accelerator, the controller 116 reduces the first throttle valve 108 so that the intake manifold pressure detected by the first pressure detector 118 matches the target intake manifold pressure. open.

  The target intake manifold pressure can be set according to the accelerator opening detected by the accelerator opening sensor 124 and the engine speed detected by the engine speed sensor 125.

  When the first throttle valve 108 is opened to a small extent, only a small amount of intake air is supplied to each of the plurality of cylinders 117 and burned as a mixture with fuel in each of the plurality of cylinders 117.

  The control device 116 determines the fuel injection pulse width and ignition timing according to the intake air amount calculated based on the intake manifold pressure detected by the first pressure detector 118 and the engine speed detected by the engine speed sensor 125. And fuel is injected by the injector according to the set pulse width, and ignited by the spark plug according to the set ignition timing.

  However, since the load is low and the exhaust does not have enough kinetic energy to drive the prime mover 107, the compressor 106 may become a throttle loss of the intake air.

  In the intake / exhaust structure 100, the control device 116 bypasses by opening the second throttle valve 110 in accordance with the accelerator opening detected by the accelerator opening sensor 124 and the engine speed detected by the engine speed sensor 125. Intake air can be supplied to each of the plurality of cylinders 117 while bypassing the compressor 106 through the intake passage 109.

  Since it is possible to suppress the compressor 106 from becoming a throttle loss of intake air, it is possible to quickly increase the torque and to provide kinetic energy sufficient to drive the prime mover 107 to exhaust.

  In addition, since the intake air is supplied to each of the plurality of cylinders 117 while bypassing the compressor 106 through the bypass intake passage 109, the compressor 106 is unlikely to become a driving resistance to the prime mover 107, and the prime mover 107 (and thus the compressor 106). ) And the supercharging pressure can be easily increased.

  Further, since the exhaust relief valve 112 and the exhaust recirculation valve 114 are closed, the exhaust loss is small, the exhaust pressure is easily increased, and the supercharging pressure is easily increased.

  Further, since the second throttle valve 110 is closed as the supercharging pressure rises, transient response (starting response) can be improved without using a small capacity prime mover 107.

  Therefore, in the intake / exhaust structure 100, the torque can be quickly started up while suppressing the deterioration of fuel consumption.

[Operation of Intake / Exhaust Structure 100 in Low Rotation and High Load Operation Area]
As shown in FIG. 3, in the low rotation and high load operation region B, the controller 116 opens the first throttle valve 108 and the exhaust gas recirculation valve 114 as shown in FIGS. The double throttle valve 110 and the exhaust relief valve 112 are closed.

  Specifically, when the driver greatly depresses the accelerator, the controller 116 completely opens the first throttle valve 108 so that the intake manifold pressure detected by the first pressure detector 118 matches the target intake manifold pressure. Open to. Further, the control device 116 completely closes the second throttle valve 110 so as to increase the torque together with the supercharging pressure.

  When the first throttle valve 108 is fully opened and the second throttle valve 110 is completely closed, the first throttle valve 108 does not become a throttle loss of the intake air, and the compressor 106 is driven to generate a large amount of intake air. In addition to being supplied to each of the cylinders 117 and being burned as an air-fuel mixture in each of the plurality of cylinders 117, the rotational speed of the prime mover 107 (and thus the compressor 106) is increased and the supercharging pressure is also increased. Is done.

  The control device 116 determines the fuel injection pulse width and ignition timing according to the intake air amount calculated based on the intake manifold pressure detected by the first pressure detector 118 and the engine speed detected by the engine speed sensor 125. And fuel is injected according to the set pulse width and ignited according to the set ignition timing.

  At the same time, since the control device 116 closes the exhaust relief valve 112, the difference between the intake pressure and the exhaust pressure is reduced by increasing the exhaust pressure, and calculation is performed based on the intake manifold pressure detected by the first pressure detector 118. Exhaust gas recirculation can be applied to the extent that knocking can be prevented by opening the exhaust gas recirculation valve 114 by the control device 116 in accordance with the intake air amount and the engine speed detected by the engine speed sensor 125.

  When exhaust gas recirculation is applied, the knocking control device does not make a knocking determination, so that the ignition timing is not delayed and the ignition timing can be set to an optimum value. Furthermore, exhaust temperature can be lowered by applying exhaust gas recirculation.

  Therefore, in the intake / exhaust structure 100, since there is no throttle loss of intake air and the ignition timing can be set to an optimum value, fuel consumption can be improved.

[Operation of the intake / exhaust structure 100 in the middle / high rotation / low load operation region]
As shown in FIG. 3, in the middle / high rotation / low load operation region (and a part of the low rotation / low load operation region) C, the controller 116 controls the first throttle valve as shown in FIGS. 108, the second throttle valve 110 and the exhaust gas recirculation valve 114 are opened, and the exhaust relief valve 112 is closed.

  Specifically, when the driver depresses the accelerator, the controller 116 reduces the first throttle valve 108 so that the intake manifold pressure detected by the first pressure detector 118 matches the target intake manifold pressure. open.

  When the first throttle valve 108 is opened to a small extent, only a small amount of intake air is supplied to each of the plurality of cylinders 117 and burned as a mixture with fuel in each of the plurality of cylinders 117.

  The control device 116 determines the fuel injection pulse width and ignition timing according to the intake air amount calculated based on the intake manifold pressure detected by the first pressure detector 118 and the engine speed detected by the engine speed sensor 125. And fuel is injected according to the set pulse width and ignited according to the set ignition timing.

  However, since the load is low and the exhaust does not have enough kinetic energy to drive the prime mover 107, the compressor 106 may become a throttle loss of the intake air.

  In the intake / exhaust structure 100, the control device 116 bypasses by opening the second throttle valve 110 in accordance with the accelerator opening detected by the accelerator opening sensor 124 and the engine speed detected by the engine speed sensor 125. Intake air can be supplied to each of the plurality of cylinders 117 while bypassing the compressor 106 through the intake passage 109.

  Since it is possible to suppress the compressor 106 from becoming a throttle loss of intake air, it is possible to quickly increase the torque and to provide kinetic energy sufficient to drive the prime mover 107 to exhaust.

  In addition, since the intake air is supplied to each of the plurality of cylinders 117 while bypassing the compressor 106 through the bypass intake passage 109, the compressor 106 is unlikely to become a driving resistance to the prime mover 107, and the prime mover 107 (and thus the compressor 106). ) And the supercharging pressure can be easily increased.

  At the same time, the controller 116 opens the exhaust gas recirculation valve 114 in accordance with the intake air amount calculated based on the intake manifold pressure detected by the first pressure detector 118 and the engine speed detected by the engine speed sensor 125. Since the opening of the throttle valve 108 is small and the intake pressure is low, the difference between the intake pressure and the exhaust pressure is large, and a large amount of exhaust gas is recirculated. A large amount of exhaust gas recirculation can reduce pumping loss and improve fuel efficiency.

  Further, since the exhaust relief valve 112 is closed, the exhaust loss is small, the exhaust pressure is easily increased, and the supercharging pressure is also easily increased.

  Therefore, in the intake / exhaust structure 100, the torque can be quickly started up while suppressing the deterioration of fuel consumption.

[Operation of Intake / Exhaust Structure 100 in Low, Medium and High Rotation Medium Load Operation Region]
As shown in FIG. 3, in the low, middle and high rotation middle load operation region D, the control device 116, as shown in FIGS. 10 and 11, the first throttle valve 108, the second throttle valve 110, and the exhaust relief. The valve 112 and the exhaust gas recirculation valve 114 are opened.

  Specifically, when the driver depresses the accelerator to a medium level (accelerator opening degree of about 50%), the control device is configured to make the intake manifold pressure detected by the first pressure detector 118 coincide with the target intake manifold pressure. 116 opens the first throttle valve 108 to a medium level (about 50% opening).

  Further, in order to obtain acceleration force, the control device 116 opens the second throttle valve 110 in a small manner according to the accelerator opening detected by the accelerator opening sensor 124 and the engine speed detected by the engine speed sensor 125.

  When the first throttle valve 108 is opened moderately and the second throttle valve 110 is opened small, the compressor 106 is driven to supply intake air to each of the plurality of cylinders 117 and to each of the plurality of cylinders 117. Since it is burned as a mixture with fuel, the rotational speed of the prime mover 107 (and thus the compressor 106) is increased and the supercharging pressure is also increased.

  The control device 116 determines the fuel injection pulse width and ignition timing according to the intake air amount calculated based on the intake manifold pressure detected by the first pressure detector 118 and the engine speed detected by the engine speed sensor 125. And fuel is injected according to the set pulse width and ignited according to the set ignition timing.

  At the same time, the control device 116 opens the exhaust gas recirculation valve 114 according to the intake air amount calculated based on the intake manifold pressure detected by the first pressure detector 118 and the engine speed detected by the engine speed sensor 125. Further, the exhaust relief valve 112 is opened according to the accelerator opening detected by the accelerator opening sensor 124.

  As the exhaust pressure rises, exhaust gas recirculation is applied. Even if the first throttle valve 108 is closed, the intake manifold pressure becomes close to positive pressure, and the pumping loss is reduced, so that fuel consumption can be improved. .

  Further, the control device 116 opens the intake manifold pressure detected by the first pressure detector 118 and the intake passage pressure detected by the second pressure detector 122 in order to open the first throttle valve 108 as much as possible (completely). In order to make them coincide, the opening degree of the second throttle valve 110 is adjusted.

  That is, when the intake air amount fed by the compressor 106 exceeds the required intake air amount of the compressed natural gas engine, the first throttle valve 108 is closed, so that an intake throttle loss occurs, but the intake throttle loss is reduced as much as possible. In order to eliminate the pressure, the opening of the second throttle valve 110 is adjusted so that the intake manifold pressure detected by the first pressure detector 118 and the intake passage pressure detected by the second pressure detector 122 coincide with each other. The resistance of the compressor 106 due to excessive increase in the pressure is reduced.

  Therefore, in the intake / exhaust structure 100, the first throttle valve 108 that controls the torque is unlikely to cause a throttle loss of the intake air, and the fuel efficiency can be improved.

[Operation of Intake / Exhaust Structure 100 in Medium / High Speed / High Load Operation Area]
As shown in FIG. 3, in the middle / high rotation / high load operation region E, as shown in FIGS. 12 and 13, the control device 116 performs the first throttle valve 108, the second throttle valve 110, and the exhaust gas recirculation. The valve 114 is opened and the exhaust relief valve 112 is closed, and the intake pressure (the intake manifold pressure detected by the first pressure detector 118) is detected by the accelerator position sensor 124 and the engine speed sensor 125. When it is impossible to reach the target intake pressure according to the engine speed, the exhaust relief valve 112 is opened so that the intake pressure reaches the target intake pressure.

  Specifically, when the driver depresses the accelerator largely (accelerator opening 70% or more), the controller 116 controls the intake manifold pressure detected by the first pressure detector 118 to coincide with the target intake manifold pressure. Opens the first throttle valve 108 completely.

  Further, in order to obtain acceleration force, the control device 116 opens the second throttle valve 110 in a small manner according to the accelerator opening detected by the accelerator opening sensor 124 and the engine speed detected by the engine speed sensor 125.

  When the first throttle valve 108 is fully opened and the second throttle valve 110 is opened small, the compressor 106 is driven to supply intake air to each of the plurality of cylinders 117 and to each of the plurality of cylinders 117. Since it is burned as an air-fuel mixture, the rotational speed of the prime mover 107 (and consequently the compressor 106) is increased and the supercharging pressure is also increased. Further, the control device 116 increases the exhaust pressure by closing the exhaust relief valve 112.

  The control device 116 determines the fuel injection pulse width and ignition timing according to the intake air amount calculated based on the intake manifold pressure detected by the first pressure detector 118 and the engine speed detected by the engine speed sensor 125. And fuel is injected according to the set pulse width and ignited according to the set ignition timing.

  At the same time, the control device 116 knocks by opening the exhaust gas recirculation valve 114 in accordance with the intake air amount calculated based on the intake manifold pressure detected by the first pressure detector 118 and the engine speed detected by the engine speed sensor 125. Exhaust gas recirculation can be applied to the extent that can be prevented.

  When exhaust gas recirculation is applied, the knocking control device does not make a knocking determination and does not retard. Further, since exhaust gas recirculation is applied and the combustion speed becomes slow, the advance angle can be made, and the exhaust gas temperature does not rise even if the fuel is not enriched. That is, fuel consumption can be suppressed.

  When the torque is excessively increased by completely opening the first throttle valve 108, the second throttle valve 110 is opened to release the pressure. Further, if the target torque does not reach even when the second throttle valve 110 is completely closed, the boost pressure is adjusted by adjusting the opening of the exhaust relief valve 112.

  As described above, in the middle / high rotation / high load operation region, the exhaust gas temperature becomes high, and it is necessary to increase the exhaust gas recirculation rate in order to lower the exhaust gas temperature. Therefore, the exhaust manifold pressure is increased by closing the exhaust relief valve 112.

  However, since the exhaust kinetic energy increases as the engine speed increases, the amount of intake air sent by the compressor 106 increases when the exhaust kinetic energy is large, the intake manifold pressure increases, and the exhaust gas recirculates. Therefore, the optimum state can be obtained by opening the second throttle valve 110 and releasing the pressure.

[Operation of Intake / Exhaust Structure 100 in Medium / High Speed / High Load Operation Region at Low Temperature]
In the middle / high rotation / high load operation region at the time of low temperature and high temperature, the control device 116 opens the first throttle valve 108, the second throttle valve 110, and the exhaust relief valve 112 as shown in FIGS. At the same time, the exhaust gas recirculation valve 114 is closed.

  More specifically, when the coolant temperature is low or abnormally high, the exhaust gas recirculation device is likely to break down, so the exhaust gas recirculation control is stopped and the exhaust gas recirculation valve 114 is completely closed. Therefore, when the driver depresses the accelerator largely (accelerator opening 70% or more), the controller 116 first throttles the intake manifold pressure detected by the first pressure detector 118 to coincide with the target intake manifold pressure. Open the air valve 108 completely.

  Further, in order to obtain an acceleration force, the intake manifold pressure detected by the first pressure detector 118 depends on the accelerator opening detected by the accelerator opening sensor 124 and the engine speed detected by the engine speed sensor 125. Further, the control device 116 opens the second throttle valve 110 small so as to coincide with the target intake manifold pressure for stopping exhaust gas recirculation.

  Further, when the intake manifold pressure detected by the first pressure detector 118 does not reach the target intake manifold pressure for stopping exhaust gas recirculation, the opening degree of the second throttle valve 110 is adjusted.

  When the first throttle valve 108 is fully opened and the second throttle valve 110 is opened small, the compressor 106 is driven to supply intake air to each of the plurality of cylinders 117 and to each of the plurality of cylinders 117. Since it is burned as an air-fuel mixture, the rotational speed of the prime mover 107 (and consequently the compressor 106) is increased and the supercharging pressure is also increased.

  The control device 116 is configured to stop fuel injection according to the intake air amount calculated based on the intake manifold pressure detected by the first pressure detector 118 and the engine speed detected by the engine speed sensor 125. A pulse width for exhaust gas and an ignition timing for exhaust gas recirculation stop are set, and fuel is injected according to the set pulse width for exhaust gas recirculation stop, and ignition is performed in accordance with the set ignition timing for exhaust gas recirculation stop. At this time, knocking does not occur because the boost pressure is lowered and the retarded ignition timing is used.

  Since exhaust gas recirculation is not applied and torque is excessively generated even when the exhaust relief valve 112 is fully opened, the second throttle valve 110 is opened, and the pressure is set so that the first throttle valve 108 does not cause intake throttle loss. Let it go. At this time, since there is no exhaust gas recirculation, retard is performed to avoid knocking. The amount of fuel is increased and the exhaust temperature is lowered so that the exhaust temperature does not rise too much due to the timing retard.

  As described above, exhaust gas recirculation cannot be applied due to the influence of coagulated water at low water temperature and reliability problems of the exhaust gas recirculation cooler 123 at high water temperature. When exhaust gas recirculation cannot be used, an output can be obtained with a small amount of intake air, and therefore the intake air amount is reduced by opening the exhaust relief valve 112 and the second throttle valve 110.

[Operation of Intake / Exhaust Structure 100 in Exhaust Braking Operation Operation Area]
As shown in FIG. 3, in the exhaust braking operation region F, the control device 116 opens the first throttle valve 108 and the second throttle valve 110 and exhausts as shown in FIGS. The brake valve 115 is closed.

  Specifically, when the driver turns on the exhaust brake switch and removes the accelerator, the control device 116 cuts the fuel and matches the intake manifold pressure detected by the first pressure detector 118 with the target intake manifold pressure. Opens the first throttle valve 108 and sends a small amount of intake air.

  Further, the control device 116 increases the exhaust pressure by closing the exhaust brake valve 115, and the accelerator opening detected by the accelerator opening sensor 124 and the engine speed sensor 125 are detected so as to bypass the compressor 106 that does not rotate. The control device 116 opens the second throttle valve 110 according to the engine speed. As a result, air is compressed and braking force is improved. When the temperature decreases and the pressure decreases, the braking force decreases, so the first throttle valve 108 is opened while observing the pressure.

  When exhaust braking is no longer necessary, the exhaust brake valve 115 is opened to return to normal control. That is, when the engine speed is less than the fuel return speed, the exhaust brake valve 115 is opened and fuel injection is resumed.

  As described above, when the exhaust braking operation is performed, the compressor 106 becomes a throttle loss of the intake air, and the intake air does not enter and the exhaust braking force becomes small. However, in the intake and exhaust structure 100, the second throttle valve 110 is opened. The intake air can be sent and the exhaust braking force can be increased.

  As described above, according to the present invention, the compressed natural gas that reduces the loss of the turbocharger and reduces the deterioration of fuel consumption, suppresses the rise of the exhaust temperature and hardly adversely affects the durability of the compressed natural gas engine. An engine intake / exhaust structure 100 can be provided.

100 Intake / Exhaust Structure 101 Intake Passage 102 Exhaust Passage 103 Intake Manifold 104 Exhaust Manifold 105 Supercharger 106 Compressor 107 Primer 108 First Throttle Valve 109 Detour Intake Path 110 Second Throttle Valve 111 Bypass Exhaust Path 112 Valve 113 Exhaust gas recirculation passage 114 Exhaust gas recirculation valve 115 Exhaust brake valve 116 Controller 117 Cylinder 118 First pressure detector 119 Rotating shaft 120 Three-way catalyst 121 Intercooler 122 Second pressure detector 123 Exhaust gas recirculation cooler 124 Accelerator opening Sensor 125 Engine speed sensor A Low rotation / low load operation region B Low rotation / high load operation region C Medium / high rotation / low load operation region D Low / high / high rotation / medium load operation region E Medium / high rotation / high load operation region F Exhaust braking operation region

Claims (12)

A turbocharger compressor installed in the intake passage;
A first throttle valve installed in the intake passage on the intake downstream side of the compressor;
A bypass intake passage communicating the intake passage on the intake upstream side of the compressor with the intake passage between the compressor and the first throttle valve;
A second throttle valve installed in the bypass intake passage;
A compressed natural gas engine intake and exhaust structure characterized by comprising A prime mover for the turbocharger installed in the exhaust passage;
A bypass exhaust passage communicating the exhaust passage on the exhaust upstream side of the prime mover with the exhaust passage on the exhaust downstream side of the prime mover;
An exhaust relief valve installed in the bypass exhaust passage;
The intake / exhaust structure for a compressed natural gas engine according to claim 1. An intake manifold connected to an intake downstream end of the intake passage;
An exhaust manifold connected to the exhaust upstream end of the exhaust passage;
An exhaust recirculation passage communicating the exhaust manifold with the intake manifold;
An exhaust gas recirculation valve installed in the exhaust gas recirculation passage;
The intake / exhaust structure for a compressed natural gas engine according to claim 2. The intake / exhaust structure of the compressed natural gas engine according to claim 3, further comprising a control device that opens and closes the first throttle valve, the second throttle valve, the exhaust relief valve, and the exhaust recirculation valve. The control device opens the first throttle valve and the second throttle valve and closes the exhaust relief valve and the exhaust recirculation valve in a low rotation low load operation region, The intake and exhaust structure of the compressed natural gas engine according to claim 4, wherein the second throttle valve is closed as the engine rises. The control device opens the first throttle valve and the exhaust recirculation valve and closes the second throttle valve and the exhaust relief valve in a low-rotation and high-load operation region. The intake / exhaust structure of the compressed natural gas engine according to claim 5. 7. The control device opens the first throttle valve, the second throttle valve, and the exhaust recirculation valve and closes the exhaust relief valve in a middle and high rotation low load operation region. The intake / exhaust structure of the compressed natural gas engine according to any one of the above. The control device opens the first throttle valve, the second throttle valve, the exhaust relief valve, and the exhaust recirculation valve in a low, medium, and high rotation middle load operation region. An intake / exhaust structure for a compressed natural gas engine according to any one of the preceding claims. The control device opens the first throttle valve, the second throttle valve, and the exhaust recirculation valve and closes the exhaust relief valve in the middle / high rotation / high load operation region, thereby accelerating the intake pressure. 9. The exhaust relief valve is opened to allow the intake pressure to reach the target intake pressure when the target intake pressure according to the opening degree and the engine speed cannot be reached. Compressed natural gas engine intake and exhaust structure. The control device opens the first throttle valve, the second throttle valve, and the exhaust relief valve and closes the exhaust recirculation valve in a medium / high rotation / high load operation region at low and high temperatures. Item 10. The intake / exhaust structure of a compressed natural gas engine according to any one of Items 4 to 9. An exhaust brake valve installed in the exhaust passage on the exhaust downstream side of the prime mover;
The intake / exhaust structure of a compressed natural gas engine according to any one of claims 4 to 10, wherein the control device also opens and closes the exhaust brake valve. 12. The compressed natural gas engine intake according to claim 11, wherein the control device opens the first throttle valve and the second throttle valve and closes the exhaust brake valve in an exhaust brake operation region. Exhaust structure.

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