JP5999123B2 - Exhaust gas purification system for gas heat pump engine - Google Patents

Description

  The present invention relates to an exhaust gas purification system for a gas heat pump engine.

  In recent years, gas heat pump systems having high energy efficiency and excellent energy saving have been widely used as air conditioners. In a gas heat pump system, a compressor is driven using the power of a gas heat pump engine that uses natural gas, LPG, city gas, or the like as fuel. The gas heat pump engine is usually driven in a lean operation in which the air is excessive with respect to the stoichiometric air-fuel ratio in order to further reduce fuel consumption.

  As a device for purifying the exhaust gas of the gas heat pump engine, for example, a three-way catalyst used in a gasoline automobile can be used. The three-way catalyst can detoxify carbon monoxide (CO), total hydrocarbons (THC), and nitrogen oxides (NOx), which are harmful components contained in the exhaust gas. However, in order to detoxify the three harmful components of carbon monoxide (CO), total hydrocarbon (THC), and nitrogen oxide (NOx) with a three-way catalyst, the air-fuel ratio, which is the ratio of air to fuel, is set. It must be within a predetermined range near the theoretical air-fuel ratio. When the above-described lean operation is performed, the three-way catalyst can detoxify carbon monoxide (CO) and total hydrocarbons (THC), but it is difficult to detoxify nitrogen oxides (NOx). is there.

  Therefore, in Patent Document 1, NOx is occluded in the exhaust path of the gas heat pump engine during lean operation (excess air with respect to fuel) and during rich operation (excess fuel with respect to air). Discloses an internal combustion engine equipped with a nitrogen oxide storage reduction catalyst for reducing and purifying stored NOx. The internal combustion engine uses gas as fuel, and an air-fuel mixture in which intake air and fuel gas are mixed by a mixer is supplied to the internal combustion engine. When the lean operation is normally performed and it is determined that the accumulated amount of NOx to the nitrogen oxide storage reduction catalyst has reached a predetermined amount, the rich operation is performed for about 4 to 6 seconds, and the nitrogen oxide storage reduction is performed. The reduction and purification of NOx stored in the catalyst is repeated. In the rich operation, the stepping motor is operated to adjust the excess air ratio control valve of the mixer.

  Further, Patent Document 2 includes a NOx adsorption reduction catalyst that stores NOx during lean operation and reduces and purifies NOx stored during rich operation in the exhaust path of the gas heat pump engine. A gas heat pump exhaust gas purification device is described. The lean operation is usually performed, and when NOx adsorbed on the NOx adsorption reduction catalyst exceeds a certain value, the rich operation is performed by injecting the fuel into the engine cylinder for the second time in the expansion stroke or the exhaust process. The NOx adsorbed on the NOx adsorption reduction catalyst is reduced and purified.

JP 2000-045752 A JP 2006-037790 A

  In the invention described in Patent Document 1, when the lean operation is normally performed and the temporary rich operation is performed, the stepping motor is operated to operate the air excess ratio control valve of the mixer, and the air and fuel by the mixer are operated. Fuel is excessive in the generation of the air-fuel mixture. However, because the excess air ratio control valve is operated by the stepping motor and the distance from the mixer to each cylinder is relatively long, the responsiveness is poor and the transition from the lean operation state to the rich operation state is made. The response delay time until the operation is relatively long, and the response delay time until the transition from the rich operation state to the lean operation state is also relatively long. Therefore, the rich operation time becomes longer, the fuel consumption increases, and unpurified CO and THC are generated, which is not preferable. That is, it is more preferable that the responsiveness from the lean operation to the rich operation and from the rich operation to the lean operation is good because the fuel consumption is small and the unpurified CO and THC are suppressed.

  Further, in the invention described in Patent Document 2, when performing the rich operation temporarily, the rich operation is performed by injecting the fuel into the engine cylinder for the second time in the expansion stroke or exhaust process of the gas heat pump engine. The responsiveness to lean operation-> rich operation and rich operation-> lean operation is very good compared to Patent Document 1. However, in order to inject fuel directly into the engine cylinder, a device that raises the pressure of the fuel gas, a special injector that injects the high-pressure fuel gas, examination of the position and direction of the injector embedded in the cylinder, the expansion process of the engine Alternatively, detection means for detecting the exhaust process is required, and the system becomes complicated and expensive.

  The present invention was devised in view of the above points, and has a simple structure and a gas with good responsiveness from transition from lean operation to rich operation and from rich operation to lean operation. It is an object of the present invention to provide an exhaust purification system for a heat pump engine.

In order to solve the above problems, an exhaust gas purification system for a gas heat pump engine according to the present invention takes the following means. First, the first invention of the present invention is provided in the exhaust path of the gas heat pump engine, and stores NOx during lean operation in which the air is excessive with respect to the stoichiometric air-fuel ratio, and excessive fuel with respect to the stoichiometric air-fuel ratio. A NOx occlusion catalyst that reduces and purifies the occluded NOx during the rich operation is provided. An air-fuel ratio detecting means for detecting an air-fuel ratio provided in the exhaust path between the gas heat pump engine and the NOx storage catalyst; and an gas manifold provided in an intake manifold in the intake path of the gas heat pump engine. Fuel injection means capable of injecting fuel gas into the intake manifold so as to increase the amount of fuel gas supplied to the engine, and control means for controlling the fuel injection means based on a detection signal from the air-fuel ratio detection means; , Also. The control means controls the gas heat pump engine in the lean operation for a predetermined period, and when the predetermined period is reached, the fuel injection means is used to supply fuel gas to be supplied to the gas heat pump engine. The amount is temporarily increased and the control of the gas heat pump engine is temporarily repeated in the rich operation. The fuel gas supplied from the fuel injection means is the intake manifold by a differential pressure between the pressure of the fuel gas on the input side of the fuel injection means and the negative pressure in the intake manifold on the output side of the fuel injection means. Is injected into the inside. And a regulator for reducing the pressure of the input fuel gas to atmospheric pressure and outputting the pressure, and the fuel gas input to the fuel injection means is input to the fuel injection means from the output side of the regulator .

  In the first aspect of the invention, the fuel injection means is provided in the intake manifold, and the fuel injection is performed by the differential pressure between the pressure of the fuel gas on the input side of the fuel injection means and the negative pressure in the intake manifold on the output side of the fuel injection means. The fuel gas is injected from the means. For this reason, there is no need for a device or a special injector for increasing the pressure of the fuel gas, and it is possible to inject the fuel gas appropriately just by opening a general-purpose general-purpose injector. It can be configured. Further, since the fuel gas is injected into the intake manifold, it is possible to instantaneously change the air-fuel mixture immediately before being sucked by the gas heat pump engine from the lean state to the rich state, the transition from the lean operation to the rich operation, and The response from the rich operation to the lean operation is good.

The fuel gas supplied to the gas heat pump engine is natural gas or LPG from a gas cylinder, city gas supplied to a general household through a gas pipe, and the pressure of the gas may not be stable. If the pressure of the fuel gas input to the fuel injection means is not stable, the amount of fuel gas supplied is different even during the same valve opening time, which is not preferable. In the case of a naturally aspirated engine, the pressure in the intake manifold is a relatively stable negative pressure lower than the atmospheric pressure during steady operation of the engine. Therefore, in the first aspect of the invention, the amount of fuel gas injected for shifting to the rich operation is stabilized by inputting the fuel gas having a stable pressure (in this case, atmospheric pressure) using the regulator to the fuel injection means. It can be made.

Next, the invention described in the present embodiment is arranged upstream of the intake manifold in the intake path of the gas heat pump engine, and a regulator for reducing the pressure of the input fuel gas to atmospheric pressure and outputting it. And a fuel mixing means for mixing the inputted fuel gas and the intake air and capable of adjusting the mixing ratio by the control means. Fuel gas is input to the fuel mixing means from the output side of the regulator, and fuel gas input to the fuel injection means is input to the fuel injection means from the input side of the regulator.

In the invention described in the present embodiment, the fuel gas for the lean operation for a predetermined period is supplied from the fuel mixing means, and the increased amount of the fuel gas for the temporary rich operation is supplied from the fuel injection means. . Fuel gas to the fuel injection means is input from the input side of the regulator. With this configuration, a lean operation for a predetermined period and a temporary rich operation can be easily realized. Also, by inputting the fuel gas to the fuel injection means from the input side of the regulator, fuel gas having a pressure higher than the atmospheric pressure can be supplied to the fuel injection means, so that the responsiveness from lean operation to rich operation is further improved. Can be improved.

Next, the second invention of the present invention is an exhaust gas purification system for a gas heat pump engine according to the first aspect, is disposed upstream of the intake manifold in the intake path of the gas heat pump engine, is input And a fuel mixing means capable of mixing the fuel gas and the intake air and adjusting the mixing ratio by the control means . Fuel gas is input to the fuel mixing means from the output side of the regulator .

In the second aspect of the invention , the fuel gas for the lean operation for a predetermined period is supplied from the fuel mixing means, and the increased amount of the fuel gas for the temporary rich operation is supplied from the fuel injection means. Fuel gas to the fuel injection means is input from the output side of the regulator. With this configuration, a lean operation for a predetermined period and a temporary rich operation can be easily realized. Also, by inputting the fuel gas to the fuel injection means from the output side of the regulator, fuel gas at a stable pressure that has been reduced to atmospheric pressure can be supplied to the fuel injection means. It is possible to supply a stable amount of fuel.

It is a figure explaining the exhaust gas purification system of the gas heat pump engine in 1st Embodiment. It is a flowchart explaining the process sequence of 1st Embodiment. It is a flowchart explaining the process sequence of 1st Embodiment. It is a figure explaining the lean operation and temporary rich operation of a predetermined period in a 1st embodiment, and change of the storage state of NOx by the operation. It is a figure explaining the exhaust gas purification system of the gas heat pump engine in 2nd Embodiment. It is a figure explaining the exhaust gas purification system of the gas heat pump engine in 3rd Embodiment. It is a flowchart explaining the process sequence of 3rd Embodiment. It is a figure explaining the lean operation and temporary rich operation of a predetermined period in 3rd Embodiment, and the change of the occlusion state of NOx by the said operation. It is a figure explaining the exhaust gas purification system of the gas heat pump engine in 4th Embodiment. It is a figure explaining the exhaust gas purification system of the gas heat pump engine in 5th Embodiment. It is a flowchart explaining the process sequence of 6th Embodiment.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated using drawing. The exhaust gas purification system for a gas heat pump engine of the present invention is a system for purifying exhaust gas from a gas heat pump engine for air conditioning using natural gas, LPG, city gas, or the like as fuel. Hereinafter, first to sixth embodiments of an exhaust gas purification system for a gas heat pump engine will be described in order.

[Configuration of exhaust gas purification system 1A for the gas heat pump engine in the first embodiment (FIG. 1)]
As shown in FIG. 1, in the exhaust purification system 1A for a gas heat pump engine according to the first embodiment, an air cleaner 21, a mixer 22, a throttle 23, a throttle opening detection means 23A, An intake manifold 24, an injector 25, a pressure detection means 26, and the like are provided. Further, an exhaust manifold 31, a NOx storage catalyst 32, an exhaust gas heat exchanger 33, a silencer 34, an air-fuel ratio detection means 35, etc. are provided in the exhaust path 30 of the gas heat pump engine 10. In addition, description of the three-way catalyst in the exhaust path is omitted. An oxidation catalyst that oxidizes and burns CO and HC may be used instead of the three-way catalyst. Further, the exhaust gas purification system 1A for the gas heat pump engine includes a regulator 40, a control unit 50, a rotation detection unit 11, and the like. The rotational power of the gas heat pump engine 10 is transmitted to the compressor 80, and a cooling medium circulates in the medium pipe 82 between the compressor 80 and the compressor heat exchanger 81.

  The air cleaner 21 is provided at the most upstream position in the intake passage 20 and filters the air sucked into the intake passage 20. The air cleaner 21 may be omitted. The mixer 22 corresponds to fuel mixing means and is disposed upstream of the intake manifold 24 in the intake passage 20. Further, the mixer 22 mixes the fuel gas supplied via the pipe 41, the regulator 40, and the pipe 42 with the intake air in the intake passage 20 and supplies the mixture to the intake manifold 24. The mixer 22 has a mixing ratio adjusting means that can adjust the mixing ratio of the intake air and the fuel gas, and the mixing ratio (that is, the air-fuel ratio) is adjusted based on a control signal from the control means 50. The

  The throttle 23 is disposed between the mixer 22 and the intake manifold 24 in the intake passage 20, and has a throttle valve driven by a DC motor controlled based on a control signal from the control means 50, for example. Adjust the air volume. The throttle opening detection means 23A (for example, a throttle opening sensor) is provided in the throttle 23, and outputs a detection signal corresponding to the opening (rotation angle) of the throttle valve to the control means 50. The control means 50 can detect the opening degree of the throttle valve (that is, the load of the gas heat pump engine 10) based on the detection signal from the throttle opening degree detection means 23A. As in the above example, when the throttle 23 is driven by a DC motor, the throttle opening degree detecting means 23A is required. However, for example, when the throttle 23 is driven by a stepping motor, the throttle opening degree detecting means 23A can be omitted. The control means 50 can know the opening degree of the throttle valve from the step position of the stepping motor.

  The intake manifold 24 is provided at a position on the most downstream side of the intake passage 20 and distributes the air-fuel mixture evenly to each cylinder of the gas heat pump engine 10. The injector 25 corresponds to fuel injection means, and is provided upstream of the intake manifold 24. The injector 25 injects the fuel gas supplied through the pipe 41 and the pipe 41A into the intake manifold 24 based on the control signal from the control means 50, and the fuel gas supplied to the gas heat pump engine 10 is injected. It is possible to increase the amount (increase instantaneously with respect to the fuel gas supplied from the mixer 22). The piping 41A connected to the input side of the injector 25 is connected to the input side of the regulator 40, and relatively high-pressure fuel gas before being regulated to atmospheric pressure by the regulator 40 is supplied to the injector 25. Have been entered.

  When the gas heat pump engine 10 is driven at steady rotation, the pressure in the intake manifold 24 is stable at a predetermined negative pressure lower than atmospheric pressure. Accordingly, when the injector 25 is opened, the fuel gas is discharged from the injector 25 by the differential pressure between the pressure of the fuel gas on the input side of the regulator 40 (pressure higher than atmospheric pressure) and the negative pressure in the intake manifold 24. It is injected into the intake manifold 24. For this reason, it is not necessary to make the fuel gas input to the injector 25 at a particularly high pressure. The injector 25 is not particularly required to be a special injector for high pressure, and a general purpose one can be used.

  The pressure detection means 26 is, for example, a pressure sensor, is provided in the intake manifold 24, and outputs a detection signal corresponding to the pressure in the intake manifold 24 to the control means 50. The control means 50 can detect the pressure in the intake manifold 24 (that is, the load of the gas heat pump engine 10) based on the detection signal from the pressure detection means 26.

  The exhaust manifold 31 is disposed on the most upstream side of the exhaust path 30 and collects exhaust from each cylinder. The NOx storage catalyst 32 is disposed downstream of the exhaust manifold 31 in the exhaust passage 30, and is in a lean operation that is in an excess air state (λ> 1.0) with respect to the theoretical air-fuel ratio (λ = 1.0). Is stored, and NOx stored is reduced and purified when a rich operation in which the fuel is excessive (λ <1.0) with respect to the stoichiometric air-fuel ratio is performed. The air-fuel ratio detection means 35 is, for example, an A / F sensor and is disposed between the gas heat pump engine 10 and the NOx storage catalyst 32 in the exhaust path 30 and outputs a detection signal corresponding to the air-fuel ratio to the control means 50. The control means 50 can detect the air-fuel ratio of the air-fuel mixture supplied into the cylinder of the gas heat pump engine 10 based on the detection signal from the air-fuel ratio detection means 35.

  The exhaust gas heat exchanger 33 is provided on the downstream side of the NOx storage catalyst 32 in the exhaust passage 30 and absorbs the heat of the exhaust when heating is performed. The exhaust gas heat exchanger 33 may be omitted. The silencer 34 is disposed on the most downstream side in the exhaust path 30 and suppresses exhaust noise. The silencer 34 may be omitted.

  The regulator 40 is a pressure of fuel gas supplied through the pipe 41 (such as natural gas supplied from a gas cylinder or the like, city gas supplied from LPG or pipes, etc.). ) Is adjusted to approximately atmospheric pressure and output. Natural gas, LPG, city gas, and the like are set at a low pressure of about 2 [kPa] for safety reasons. And even if the pressure of the input fuel gas fluctuates, the regulator 40 adjusts the pressure to approximately atmospheric pressure and a stable pressure, and outputs it to the mixer 22 via the pipe 42. The rotation detection unit 11 is provided, for example, on the crankshaft of the gas heat pump engine 10, and outputs a detection signal corresponding to the rotation of the gas heat pump engine 10 to the control unit 50. The control means 50 can detect the rotational speed of the gas heat pump engine 10 based on the detection signal from the rotation detection means 11.

  The control means 50 is a control device called, for example, an engine control unit (ECU). The control means 50 includes detection from the pressure detection means 26, the throttle opening detection means 23A, the rotation detection means 11, and the air-fuel ratio detection means 35. The signal and the required load signal from the compressor 80 are input. The control means 50 outputs control signals to the mixing ratio adjusting means of the mixer 22, the throttle valve of the throttle 23, and the injector 25. The control means 50 performs the operation | movement shown to the process sequence demonstrated below using the above input / output.

[Processing procedure (FIGS. 2 and 3) and operation state (FIG. 4) of the control means 50 in the first embodiment]
The processing 10 shown in FIG. 2 is a processing procedure for controlling the throttle valve of the throttle 23 and the mixing ratio adjusting means of the mixer 22, for example, starting at a constant time interval (several ms to several 100 ms interval, etc.) or, for example, gas The heat pump engine 10 is started according to the rotation angle (every 180 ° rotation, every 360 ° rotation, etc.). In the processing procedure shown in FIG. 2, the lean operation is performed for a predetermined period. The predetermined period of the lean operation is calculated by a processing procedure of processing 30 shown in FIG. 3 described later.

  In step S10 of process 10, the control means 50 detects the load of the compressor based on the required load signal input from the compressor 80 (see FIG. 1), and proceeds to step S12. The compressor 80 outputs a load corresponding to the temperature commanded for air conditioning, the current temperature in the air-conditioned room, and the like to the control means 50. When the control unit 50 can calculate the load of the compressor by taking in the commanded temperature, the current temperature in the air-conditioning target room, etc., the input of the required load signal from the compressor 80 may be omitted.

  In step S12, the control means 50 calculates a target engine speed and a target lean air-fuel ratio (for example, about air-fuel ratio λ = 1.3) of the gas heat pump engine based on the detected or calculated compressor load, and then in step S14. move on. In step S14, the control means 50 feedback-controls the throttle valve of the throttle 23 based on the target engine speed and the engine speed detected by the detection signal from the rotation detecting means. Further, the control means 50 feedback-controls the mixing ratio adjusting means of the mixer 22 based on the target lean air-fuel ratio and the air-fuel ratio detected by the detection signal from the air-fuel ratio detecting means, and ends the processing.

  The process 20 shown in FIG. 2 is a process procedure for calculating a predetermined period during which the lean operation of the gas heat pump engine is performed. In step S20 of process 20, the control means 50 counts the lean operation time, and proceeds to step S22. The control means 50 clears, for example, a counter that measures the lean operation time when the rich injection (step S26) is performed, and counts every process 20 (every fixed time) in FIG. It is possible to measure a predetermined period during which the vehicle should be operated.

  In step S22, the control means 50 determines whether or not the predetermined period for performing the lean operation has ended based on the counted lean operation time. If it is determined that the control period has ended (Yes), the process proceeds to step S24. A process is complete | finished when it determines with not complete | finishing (No). For example, the predetermined period is about 60 seconds. When the process proceeds to step S24, the control means 50 opens the injector at a rich injection time, which will be described later with reference to FIG. 3, so that fuel gas is instantaneously injected from the injector into the intake manifold, and the fuel from the mixer In addition to supplying the gas, the fuel gas is instantaneously increased from the injector, and the process proceeds to step S26. The rich injection time from the injector is, for example, about 1 second. In step S26, after performing the rich injection in step S24, the control unit 50 schedules the process 30 so that the process 30 shown in FIG. 3 is started after a predetermined time, and proceeds to step S28. In step S28, the control means 50 clears the lean operation time (for example, clears the lean operation time measurement counter) and ends the process.

  The process 30 shown in FIG. 3 includes calculation of a rich injection time that is a time for injecting fuel gas from an injector that is to be temporarily rich after the end of the predetermined period for which lean operation is to be performed, and a predetermined period for which lean operation is to be performed. It is a processing procedure which calculates. The process 30 illustrated in FIG. 3 is activated after a predetermined time (for example, several tens to several hundreds of milliseconds) after execution of the rich injection by the scheduling performed in step 26 illustrated in the process 20 of FIG.

  In step S30 of the process 30, the control unit 50 detects the engine speed based on the detection signal from the rotation detection unit, detects the engine load based on the detection signal from the load detection unit, and proceeds to step S32. The engine load is, for example, at least one of the pressure in the intake manifold detected based on the detection signal from the pressure detection means, the throttle opening detected based on the detection signal from the throttle opening detection means, or It is detected by a physical quantity (for example, engine torque detected by the torque detection means) detected by the other detection means.

  In step S32, the control means 50 calculates a target rich air-fuel ratio by rich injection (for example, λ = 0.9 and the air-fuel ratio in the next rich operation) based on the detected engine speed and engine load. Then, the process proceeds to step S34. For example, the control means 50 stores a target rich air-fuel ratio map in which a target rich air-fuel ratio is set according to the engine speed and engine load. The control means 50 stores the target rich air-fuel ratio map, the engine speed, A target rich air-fuel ratio is calculated from the engine load. In step S34, the control means 50 calculates the base injection time of the rich injection (for example, about 1 second, the base injection time in the next rich operation) based on the detected engine speed and engine load. Proceed to step S36. For example, the control means 50 stores a base injection time map in which a base injection time corresponding to the engine speed and the engine load is set. The control means 50 stores the base injection time map, the engine speed, and the engine load. From this, the base injection time is calculated.

  In step S36, the control means 50 detects the current air-fuel ratio (the air-fuel ratio in the previous rich operation) based on the detection signal from the air-fuel ratio detection means, and proceeds to step S38. In step S38, the control means 50 makes a correction amount (for example, correction) for increasing or decreasing the base injection time based on the target rich air-fuel ratio calculated in step S32 and the current air-fuel ratio detected in step S36. Coefficient) is calculated, and the process proceeds to step S3A. For example, the control means 50 sets “current air / fuel ratio / target rich air / fuel ratio” as the correction amount. In step S3A, the control means 50 calculates the rich injection time, and proceeds to step S3C. For example, the control means 50 calculates “the base injection time calculated in step S34 * the correction amount calculated in step S38” as the rich injection time (the rich injection time in the next rich operation).

  In step S3C, the control means 50 calculates a predetermined period, which is a period during which lean operation should be performed, based on the detected engine speed and engine load, and ends the process. For example, the control unit 50 stores a lean period map in which a lean period corresponding to the engine speed and the engine load is set. The control unit 50 performs a lean operation based on the lean period map, the engine speed, and the engine load. A predetermined period (for example, a predetermined time) to be performed is calculated.

  The state of the air-fuel ratio according to the configuration of the first embodiment (FIG. 1) and the processing procedure (FIGS. 2 and 3) described above, the injection state of the injector, and the state of NOx stored in the NOx storage catalyst A time series change will be described with reference to FIG.

  As shown in FIG. 4, the air-fuel ratio detected by the air-fuel ratio detection means is maintained in a lean state for a predetermined period ΔTL (a period during which lean operation is to be performed). The air-fuel ratio maintained during the predetermined period ΔTL is the target lean air-fuel ratio calculated in step S12 in FIG. Further, after reaching the predetermined period, the fuel gas is injected from the injector, and the engine is in a rich state for a temporary rich period ΔTR. The air / fuel ratio at the most rich position in the rich period ΔTR is the target rich air / fuel ratio calculated in step S32 of FIG. 4 indicates the position of the stoichiometric air-fuel ratio (λ = 1.0). In the air-fuel ratio graph, the upper side of the stoichiometric air-fuel ratio indicates a lean state, and the lower side indicates a rich state. Show.

  In addition, the valve opening / closing graph of the injector in FIG. 4 shows the opening and closing states of the injector, and the energization waveform graph of the injector shows the voltage waveform and the current waveform applied to the injector. In the first embodiment, the injector is controlled to either a fully open state or a fully closed state. Further, as shown in the NOx occlusion amount graph, the NOx occlusion amount of the NOx occlusion catalyst gradually increases during the predetermined period ΔTL during the lean operation, and decreases during the rich period ΔTR due to NOx being reduced and purified. .

  As described above, in the first embodiment, the air-fuel mixture at the time of lean operation is supplied using the mixer, and the fuel is temporarily increased temporarily using the injector, so that the instantaneous rich operation is instantaneously performed. It is possible to instantaneously shift from rich operation to lean operation. The transition from lean operation to rich operation and from rich operation to lean operation is much more responsive than the invention described in Japanese Patent Application Laid-Open No. 2000-045752 using a stepping motor. It is possible to reduce and suppress unpurified components of CO and THC. Further, in contrast to the invention described in Japanese Patent Application Laid-Open No. 2006-037790 in which fuel is directly injected into the cylinder, a device for increasing the pressure of fuel gas, a special injector for high pressure, and the like are not required. Since injection is performed using differential pressure, a simpler system can be used. Further, by inputting the fuel gas from the input side of the regulator to the injector, the differential pressure can be further increased, and the responsiveness from the lean operation to the rich operation can be further improved. Even if the pressure of the fuel gas on the input side of the regulator is somewhat unstable and fluctuates, this pressure fluctuation can be absorbed by the correction amount calculated in step S38 shown in FIG.

[Configuration of exhaust gas purification system 1B of the gas heat pump engine in the second embodiment (FIG. 5)]
Next, the exhaust gas purification system 1B of the gas heat pump engine in the second embodiment will be described with reference to FIG. The overall configuration of the exhaust gas purification system 1B of the gas heat pump engine of the second embodiment shown in FIG. 5 is different from the overall configuration of the exhaust gas purification system 1A of the gas heat pump engine of the first embodiment shown in FIG. The fuel gas pipe 42B connected to the injector 25 is connected to the output-side pipe 42 of the regulator 40, and the processing content of the control means 50B is different. Hereinafter, this difference will be mainly described.

  Since the fuel gas piping 42B connected to the injector 25 is connected to the piping 42 on the output side of the regulator 40, the pressure of the fuel gas input to the injector 25 is lower than that of the first embodiment. Pressure (approximately atmospheric pressure). The processing procedure of the control means 50B is the same as the processing procedure of the first embodiment shown in FIGS. 2 and 3, but the pressure of the fuel gas input to the injector is low, so the steps shown in FIG. The difference is that the length of the base injection time in S34 is longer.

  In the configuration of the second embodiment, the pressure of the fuel gas input to the injector is lower than that of the first embodiment, but is a stable and almost atmospheric pressure (in the first embodiment, the fuel gas Pressure may fluctuate). Therefore, it is possible to make the amount of fuel gas injected from the injector more accurate, and when shifting from lean operation to rich operation, it is possible to shift more accurately to the target rich air-fuel ratio. However, since the pressure of the fuel gas is lower than that in the first embodiment, it is considered that the first embodiment is superior in responsiveness from lean operation to rich operation.

[[Configuration of Exhaust Purification System 1C for Gas Heat Pump Engine in Third Embodiment (FIGS. 6 to 8)]
Next, an exhaust purification system 1C for a gas heat pump engine according to a third embodiment will be described with reference to FIGS. The overall configuration of the exhaust gas purification system 1C of the gas heat pump engine of the third embodiment shown in FIG. 6 is different from the overall configuration of the exhaust gas purification system 1A of the gas heat pump engine of the first embodiment shown in FIG. The regulator 40, the pipe 42, and the mixer 22 are omitted, and the fuel gas pipe 41C connected to the injector 25 is connected to the pipe 41, and the processing content of the control means 50C is different. Hereinafter, this difference will be mainly described.

  Since the fuel gas piping 41C connected to the injector 25 is connected to the piping 41, the pressure of the fuel gas input to the injector 25 is the same as that of the first embodiment. Further, since the mixer 22 is omitted, it is necessary to supply the fuel gas for the lean operation supplied from the mixer 22 from the injector 25. Therefore, as shown in FIG. 8, the control means 50C sets the injector 25 to an intermediate opening degree as duty control for energizing the injector for the energization time TON during the period T during the lean operation of the predetermined period ΔTL. (Opening between fully open and fully closed). For this reason, the process of step S14 shown in FIG. 2 is changed to the process of step S14C shown in FIG. In step S14C, the control means 50C feedback-controls the throttle opening and the injector opening (duty ratio to the injector) so that the target engine speed and the target lean air-fuel ratio are obtained. In the above description, the example in which the injector 25 is controlled to an intermediate opening between the fully opened and fully closed state during the lean operation has been described. However, for example, the injector is intermittently fully opened for each intake process of each cylinder of the gas heat pump engine. Then, the fuel gas necessary for the lean operation may be supplied (in this case, cam angle detecting means for determining the intake process of each cylinder is necessary).

  In the configuration of the third embodiment, the regulator 40 and the mixer 22 can be omitted as compared with the first embodiment, so that an exhaust gas purification system for a gas heat pump engine can be realized with a simpler configuration. Can do. Moreover, since the pressure of the fuel gas input to the injector is a high pressure that may fluctuate, the responsiveness from the lean operation to the rich operation is good compared to the fourth embodiment described later.

[Configuration of exhaust gas purification system 1D for a gas heat pump engine in the fourth embodiment (FIG. 9)]
Next, an exhaust gas purification system 1D for a gas heat pump engine according to a fourth embodiment will be described with reference to FIG. The overall configuration of the exhaust gas purification system 1D of the gas heat pump engine of the fourth embodiment shown in FIG. 9 is different from the overall configuration of the exhaust gas purification system 1C of the gas heat pump engine of the third embodiment shown in FIG. The regulator 40 is added, and the fuel gas pipe 42D connected to the injector 25 is connected to the output side of the regulator 40, and the processing content of the control means 50D is different. Hereinafter, this difference will be mainly described.

  Since the fuel gas pipe 42D connected to the injector 25 is connected to the output side of the regulator 40, the pressure of the fuel gas input to the injector 25 is lower than that of the third embodiment (almost). Atmospheric pressure). Further, the processing procedure of the control means 50D is the same as the processing procedure of the third embodiment, but the pressure of the fuel gas input to the injector is low, so that it is shown in FIG. 3 as in the second embodiment. The difference is that the length of the base injection time in step S34 is longer.

  In the configuration of the fourth embodiment, the pressure of the fuel gas input to the injector is lower than that of the third embodiment, but the atmospheric pressure is stable and almost atmospheric (in the third embodiment, the fuel gas Pressure may fluctuate). Therefore, it is possible to make the amount of fuel gas injected from the injector more accurate, and when shifting from lean operation to rich operation, it is possible to shift more accurately to the target rich air-fuel ratio. However, since the pressure of the fuel gas is lower than that in the third embodiment, the response from the lean operation to the rich operation is considered to be superior to that in the third embodiment.

[Configuration of exhaust gas purification system for gas heat pump engine in the fifth embodiment (FIG. 10)]
Next, an exhaust purification system for a gas heat pump engine according to a fifth embodiment will be described with reference to FIG. The overall configuration of the exhaust gas purification system of the gas heat pump engine of the fifth embodiment shown in FIG. 10 is an injector compared to the overall configuration of the exhaust gas purification system of the gas heat pump engine of the first to fourth embodiments described above. The arrangement position of 25E, the number of injectors 25E, and the processing contents of the control means are different. Moreover, since it is necessary to detect the timing of the intake process of the gas heat pump engine 10, the cam angle detection means 12 is also added. It is also possible to omit the rotation detecting means and obtain the engine speed based on the detection signal from the cam angle detecting means. Hereinafter, this difference will be mainly described. FIG. 10 shows only the gas heat pump engine 10, the intake manifold 24, the exhaust manifold 31, and the detection means and injectors provided on them, and other descriptions are omitted. FIG. 10 shows the gas heat pump engine 10 as viewed from above.

  In the exhaust gas purification system of the gas heat pump engine according to the first to fourth embodiments described above, one injector 25 is provided at an upstream position before the intake air is distributed to each cylinder in the intake manifold 24. . However, in the fifth embodiment shown in FIG. 10, the injector 25 </ b> E is provided at each port portion after the intake air is distributed to each cylinder in the intake manifold 24. Therefore, in the fifth embodiment, the injector 25E is provided for each cylinder, and each injector 25E is provided at a position adjacent to each cylinder. In order to detect the intake process of each cylinder, a cam angle detecting means 12 is provided at a position adjacent to the cam shaft of the gas heat pump engine 10, and the cam angle detecting means 12 outputs a detection signal to the control means.

  When executing the rich injection in step S24 in the flowchart shown in the process 20 of FIG. 2, the control means determines whether or not the cylinder is in the intake process, and corresponds to the cylinder in the intake process. The rich injection is executed by the injector. The intake process for each cylinder can be performed based on a detection signal from the cam angle detection means and a detection signal from the rotation detection means.

  In the fifth embodiment, as compared with the first to fourth embodiments, fuel gas is injected from the injector from a position close to each cylinder at the timing of the intake process of the cylinder. Responsiveness to can be further improved.

[Exhaust gas purification system for a gas heat pump engine in the sixth embodiment (FIG. 11)]
Next, the processing procedure of the exhaust gas purification system for the gas heat pump engine in the sixth embodiment will be described with reference to FIG. The sixth embodiment differs from the first to fifth embodiments in the method of obtaining the predetermined period ΔTL for performing lean operation, the processing content of the control means is different, and the processing 20 shown in FIG. And the process 30 shown in FIG. 3 is different. Note that the processing 10 shown in FIG. 2 or the processing 10C shown in FIG. 7 is the same as that in the first to fifth embodiments, so the description of the processing 10 and the processing 10C will be omitted. In the first to fifth embodiments, the predetermined period ΔTL (predetermined time) for which the lean operation is to be performed is calculated based on the engine speed and the engine load in step S3C in the process 30 of FIG. In the process 20, it was determined whether or not a predetermined period ΔTL (predetermined time) was reached. On the other hand, the sixth embodiment is different in that the integrated amount of NOx stored in the NOx storage catalyst 32 is estimated, and the period until the NOx integrated amount reaches a predetermined amount is set as a predetermined period ΔTL. Hereinafter, this difference will be mainly described.

  In the sixth embodiment, the control unit executes the process 20F shown in FIG. 11 instead of the process 20 shown in FIG. 2, and executes the process 30F shown in FIG. 11 instead of the process 30 shown in FIG. Further, in the process 20F shown in FIG. 11, the changed part from the process 20 shown in FIG. 2 is indicated by a thick solid line, and in the process 30F shown in FIG. 11, the changed part from the process 30 shown in FIG. ing.

  The activation timing of the process 20F shown in FIG. 11 is the same as the process 20 shown in FIG. 2, and is activated, for example, at regular time intervals (several ms to several 100 ms). In step S20F, the control means detects the (current) air-fuel ratio based on the detection signal from the air-fuel ratio detection means, detects the engine speed based on the detection signal from the rotation detection means, and loads detection means. The engine load is detected based on the detection signal from and the process proceeds to step S21F. The engine load is at least one of the pressure in the intake manifold detected based on the detection signal from the pressure detection means, the throttle opening based on the detection signal from the throttle opening detection means, or other not shown Is detected by a physical quantity detected by the detecting means (for example, engine torque detected by the torque detecting means).

  In step S21F, the control means estimates the NOx generation amount based on the detected air-fuel ratio, engine speed, and engine load, adds the NOx generation amount calculated this time to the current NOx integration amount, and The amount of accumulated NOx is obtained, and the process proceeds to step S22F. The obtained NOx integrated amount is the amount of NOx stored in the NOx storage catalyst. Then, in step S22F, the control means determines whether or not the NOx integrated amount exceeds a predetermined amount. If it exceeds (Yes), the process proceeds to step S24, and if not (No), the process ends. . Note that the predetermined amount, which is the determination threshold, is appropriately set based on the storage allowable amount of the NOx storage catalyst. The processing in step S24 is the same as step S24 in processing 20 shown in FIG. In step S26F, the control unit schedules the process 30F. In step S28F, the control unit clears the NOx integrated amount, newly starts measurement of the NOx integrated amount, and ends the process. Further, the process 30F differs from the process 30 shown in FIG. 3 in that the activation timing is the same and step S3C is omitted.

  In the sixth embodiment, the rich injection is executed in the expected time by estimating the amount of NOx stored in the NOx storage catalyst and executing the rich injection before reaching the allowable storage amount of NOx. Compared with the first to fifth embodiments, the rich injection can be executed more accurately after storing a larger amount of NOx. For this reason, the predetermined period ΔTL in which the lean operation should be performed can be made longer, and the number of executions of rich injection can be reduced, so that the fuel consumption is higher than in the first to fifth embodiments. Can be further reduced, and unpurified components of HC and THC in the exhaust can be further suppressed.

The exhaust purification system of the gas heat pump engine of the present invention is not limited to the configuration, structure, operation, processing procedure, etc. described in the present embodiment, and various modifications, additions, and deletions are possible without departing from the scope of the present invention. Is possible.
In the description of the present embodiment, the pressure detection means and the accelerator opening detection means are described as examples of the detection means for the control means to detect the engine load. However, the control means is not limited to these. The engine load can be detected based on detection signals from various detection means.
Further, the above (≧), the following (≦), the greater (>), the less (<), etc. may or may not include an equal sign.
The numerical values used in the description of the present embodiment are examples, and are not limited to these numerical values.

1A-1D Exhaust gas purification system (for gas heat pump engine) 10 Gas heat pump engine 11 Rotation detection means 20 Intake path 21 Air cleaner 22 Mixer (fuel mixing means)
23 Throttle 23A Throttle opening detection means (load detection means)
24 Intake manifold 25, 25E Injector (fuel injection means)
26 Pressure detection means (load detection means)
DESCRIPTION OF SYMBOLS 30 Exhaust path 31 Exhaust manifold 32 NOx storage catalyst 33 Exhaust gas heat exchanger 34 Silencer 35 Air-fuel ratio detection means 40 Regulator 41, 42, 41A Piping 50, 50B-50D Control means 80 Compressor 81 Compressor heat exchanger

Claims (2)

Provided in the exhaust path of the gas heat pump engine, it stores NOx during lean operation when the air is excessive with respect to the stoichiometric air-fuel ratio, and stores it during rich operation when the fuel is excessive with respect to the stoichiometric air-fuel ratio. A NOx storage catalyst for reducing and purifying NOx;
An air-fuel ratio detecting means provided in the exhaust path between the gas heat pump engine and the NOx storage catalyst for detecting an air-fuel ratio;
A fuel injection means provided in an intake manifold in an intake path of the gas heat pump engine and capable of injecting fuel gas into the intake manifold so as to increase the amount of fuel gas supplied to the gas heat pump engine;
Control means for controlling the fuel injection means based on a detection signal from the air-fuel ratio detection means,
The control means controls the gas heat pump engine in the lean operation for a predetermined period, and temporarily uses the fuel injection means when the predetermined period is reached to supply fuel gas to be supplied to the gas heat pump engine. Repeatedly increasing and temporarily controlling the gas heat pump engine in the rich operation,
The fuel gas supplied from the fuel injection means is generated in the intake manifold by a differential pressure between the pressure of the fuel gas on the input side of the fuel injection means and the negative pressure in the intake manifold on the output side of the fuel injection means. Injected into
With a regulator that reduces the pressure of the input fuel gas to atmospheric pressure and outputs it,
The fuel gas input to the fuel injection means is input to the fuel injection means from the output side of the regulator.
Exhaust gas purification system for gas heat pump engines. An exhaust gas purification system for a gas heat pump engine according to claim 1 ,
A fuel mixing means disposed upstream of the intake manifold in the intake path of the gas heat pump engine, for mixing the input fuel gas and the intake air and capable of adjusting the mixing ratio by the control means ;
Fuel gas is input to the fuel mixing means from the output side of the regulator .
Exhaust gas purification system for gas heat pump engines.

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