JP2009185737A - Supercharger for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accelerate the speed of the warm-up of a catalyst in an exhaust emission control device 43 and improve an acceleration response as much as possible at a request for acceleration in a supercharger in an engine 1 including an exhaust turbo supercharger 61 and an exhaust emission control device 43. <P>SOLUTION: The engine 1 includes an exhaust temperature sensor 44 for detecting a temperature associated with the exhaust emission control device 43. If a temperature detected by the exhaust temperature sensor 44 is lower than a prescribed temperature, the opening degree of an intake air bypass valve 65 disposed in an intake air bypass passage 64 for bypassing a compressor 61a of the exhaust turbo supercharger 61 is made larger than an opening degree of the intake air bypass valve set according to an operating state of the engine 1. Furthermore, an opening degree of a regulating valve 68 disposed in a first exhaust bypass passage 67 for bypassing a turbine 61b of the exhaust turbo supercharger 61 is made equal to or smaller than an opening degree of the regulating valve set according to an operating state of the engine 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention belongs to a technical field related to an engine turbocharger including an exhaust turbocharger and an exhaust gas purification device disposed downstream of a turbine of the exhaust turbocharger in an exhaust passage.

  In general, the catalyst in the exhaust purification device disposed in the exhaust passage of the engine is heated by the thermal energy of the exhaust gas passing through the exhaust purification device, and has an exhaust purification function when it reaches the activation temperature of the catalyst. Demonstrate.

  On the other hand, in the exhaust turbocharger, the turbine disposed in the exhaust passage is rotationally driven by the exhaust heat energy, thereby operating the compressor disposed in the intake passage to supercharge intake air. The turbine of the exhaust turbocharger is usually located upstream of the exhaust purification device, and therefore, the exhaust heat energy supplied to the exhaust purification device is reduced by the operation of the exhaust turbocharger. become. Therefore, if the exhaust turbocharger operates when the catalyst temperature is lower than the activation temperature, such as when the engine is started, the time until the catalyst temperature reaches the activation temperature becomes long.

Therefore, in Patent Document 1, for example, an exhaust turbocharger equipped with an electric motor capable of controlling the rotational speed of the turbine is used to control the rotational speed of the turbine until the catalyst temperature reaches the activation temperature. It is proposed to reduce the pressure difference between the exhaust inflow pressure and the exhaust outflow pressure within a predetermined range, thereby suppressing exhaust heat energy consumption by the turbine and prematurely warming up the catalyst. .
JP 2007-278252 A

  However, the exhaust turbocharger of the above proposed example is provided with an electric motor capable of controlling the rotational speed of the turbine, and cannot be adopted when such an electric motor is not provided.

  Therefore, if an exhaust bypass passage for bypassing the turbine is provided and the exhaust turbocharger is not operated by flowing the exhaust through the exhaust bypass passage until the catalyst temperature reaches the activation temperature, an electric motor is provided. Even if there is no exhaust turbocharger, the catalyst can be warmed up early.

  However, if the exhaust turbo-supercharger is not operated by flowing exhaust through the exhaust bypass passage, it takes time for the turbine speed to reach the specified level when an accelerating request is received from the passenger of the vehicle equipped with the engine. There is a problem of getting worse. Further, the same problem occurs even in the above-described proposed example that restricts the rotation of the turbine in the exhaust turbocharger including the electric motor.

  The present invention has been made in view of such a point, and an object of the present invention is to provide an exhaust turbocharger and a downstream side of the turbine of the exhaust turbocharger in the exhaust passage. In an engine supercharging device equipped with an exhaust gas purification device, an attempt is made to improve the acceleration response at the time of an acceleration request as much as possible while trying to warm up the catalyst of the exhaust gas purification device early.

  In order to achieve the above object, according to the present invention, an intake bypass valve disposed in an intake bypass passage that bypasses a compressor of an exhaust turbocharger when a temperature related to an exhaust purification device is lower than a predetermined temperature. The opening of the exhaust bypass valve disposed in the exhaust bypass passage that bypasses the turbine of the exhaust turbocharger and is larger than the intake bypass valve opening set according to the operating state of the engine Is made equal to or less than the exhaust bypass valve opening degree set according to the engine operating state.

  Specifically, according to the first aspect of the present invention, a first exhaust turbocharger having a compressor disposed in an intake passage of an engine and a turbine disposed in an exhaust passage targeting an engine supercharging device. An intake bypass passage that bypasses the compressor of the first exhaust turbocharger, an intake bypass valve disposed in the intake bypass passage, and a first exhaust that bypasses the turbine of the first exhaust turbocharger The opening of the bypass passage, the first exhaust bypass valve disposed in the first exhaust bypass passage, the intake bypass valve and the first exhaust bypass valve is set to an opening set according to the operating state of the engine. Bypass valve control means for controlling each, an exhaust purification device disposed downstream of the turbine in the exhaust passage, and a temperature associated with the exhaust purification device are detected. Degree detection means, and the bypass valve control means makes the opening degree of the intake bypass valve larger than the set intake bypass valve opening degree and the opening degree of the first exhaust bypass valve at the low temperature. It is assumed that it is configured to be equal to or less than the set first exhaust bypass valve opening.

  With the above configuration, supercharging is achieved by increasing the opening degree of the intake bypass valve when the temperature related to the exhaust purification device is lower than a predetermined temperature (a temperature corresponding to the catalyst activation temperature or a catalyst temperature close thereto). Efficiency decreases and engine torque decreases. For this reason, an occupant (driver) of a vehicle equipped with the engine depresses the accelerator pedal more in order to set the torque related to the exhaust gas purification device to the same torque as when the temperature is higher than the predetermined temperature. The fuel injection amount and the amount of air supplied to the engine (and hence the exhaust amount) increase, and as a result, the exhaust heat energy increases. Therefore, the opening of the first exhaust bypass valve is made equal to or less than the first exhaust bypass valve opening (the first exhaust bypass valve opening at a high temperature) set according to the operating state of the engine. Thus, even if the turbine is rotationally driven, sufficient exhaust heat energy can be supplied to the exhaust purification device, and the catalyst temperature of the exhaust purification device can be raised to the activation temperature at an early stage. Also, by setting the opening degree of the first exhaust bypass valve to be equal to or less than the opening degree of the first exhaust bypass valve at a high temperature, the turbine will continue to rotate, so that the passenger further depresses the accelerator pedal. When the acceleration request is made, since the turbine is already rotating, for example, by setting the opening degree of the intake bypass valve to the intake bypass valve opening degree at the time of high temperature, it is possible to immediately perform appropriate supercharging and high Acceleration response is obtained.

  According to a second aspect of the invention, in the first aspect of the invention, the compressor disposed upstream of the compressor of the first exhaust turbocharger in the intake passage, and the first exhaust turbo excess in the exhaust passage. A second exhaust turbocharger having a turbine of a feeder and a turbine disposed between the exhaust gas purification device, and the bypass valve control means, when the engine load is a low load below a predetermined load, At the time of the low temperature, the opening degree of the intake bypass valve is made larger than the set intake bypass valve opening degree, and the opening degree of the first exhaust bypass valve is equal to or less than the set first exhaust bypass valve opening degree. It shall be comprised so that it may become.

  When two exhaust turbochargers are used in this way, the supercharging performance can be improved. However, when the two exhaust turbochargers are operated, the exhaust heat energy supplied to the exhaust purification device is reduced. It will decrease even more. However, in the present invention, the opening degree of the intake bypass valve is set to be larger than the intake bypass valve opening degree (intake valve opening degree at high temperature) set according to the operating state of the engine, particularly at a low load with small exhaust heat energy. Since the opening of the first exhaust bypass valve is made larger than the first exhaust bypass valve opening (first exhaust bypass valve opening at a high temperature) set according to the operating state of the engine, As described above, the exhaust heat energy can be increased by depressing the accelerator pedal of the occupant. As a result, even if the turbines of the two exhaust turbochargers are driven to rotate, sufficient exhaust heat energy is supplied to the exhaust purification device. The catalyst temperature of the exhaust emission control device can be raised to the activation temperature early. Further, when the acceleration is requested, since the turbine of the first exhaust turbocharger has already been rotated, a high acceleration response can be obtained.

  The first exhaust turbocharger is normally operated at a high temperature at a low load so that an appropriate supercharging pressure can be obtained. For this reason, the intake bypass valve and the first exhaust bypass valve are in a state other than full open. On the other hand, the second exhaust turbocharger is operated almost fully at low temperatures and at high temperatures when the load is low (the second exhaust bypass valve according to claim 3 is fully closed or close to the opening degree). It is preferable to make it. In this way, a certain degree of supercharging pressure can be stably obtained at low load and low temperature, and at the time of acceleration request, the two exhaust turbocharger turbines are already rotating, so high acceleration is achieved. A response is obtained. In particular, the turbine of the second exhaust turbocharger is usually larger in size and has a larger inertia than the turbine of the first exhaust turbocharger. By always rotating at times, a high acceleration response can be reliably obtained.

  According to a third aspect of the invention, in the second aspect of the invention, a second exhaust bypass passage that bypasses the turbine of the second exhaust turbocharger, and a second exhaust bypass valve disposed in the second exhaust bypass passage. The bypass valve control means sets the opening of the second exhaust bypass valve in accordance with the operating state of the engine in addition to the opening of the intake bypass valve and the first exhaust bypass valve. When the engine load is higher than the predetermined load and the engine load is higher than the predetermined load, the opening of the second exhaust bypass valve is set to the second exhaust bypass valve opening at the low temperature. It shall be comprised so that it may become larger.

  That is, when the first exhaust turbocharger is operated at high load, the exhaust resistance is reversed. Therefore, the intake bypass valve and the first exhaust bypass valve are normally fully opened, and the second exhaust bypass valve is fully closed. Or an opening close to that (opening that can prevent over-rotation). For this reason, at the time of high load, the opening degree of the intake bypass valve cannot be made larger than the intake opening degree of the intake bypass valve at high temperature when the temperature is low as in the case of low load. Also, if the opening of the first exhaust bypass valve is smaller than the first exhaust bypass valve opening at high temperatures at low temperatures at high loads when acceleration response is not a major problem compared to low loads, exhaust resistance will result. It is preferable not to do so. Therefore, at the time of high load, the opening degree of the second exhaust bypass valve is set at the low temperature from the second exhaust bypass valve opening degree (second exhaust bypass valve opening degree at high temperature) set according to the operating state of the engine. Also make it bigger. On the other hand, the intake bypass valve and the first exhaust bypass valve maintain the same fully open state as when the temperature is high. Thereby, the exhaust heat energy can be suppressed from being reduced by the first and second exhaust turbochargers, and sufficient exhaust heat energy can be supplied to the exhaust purification device.

  According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, a portion of the intake passage downstream of the compressor of the first exhaust turbocharger and the first exhaust turbo excess in the exhaust passage. An exhaust gas recirculation passage connecting the upstream portion of the turbine of the feeder, an exhaust gas recirculation valve disposed in the exhaust gas recirculation passage, and an exhaust gas recirculation valve for controlling the opening degree of the exhaust gas recirculation valve Control means, and the exhaust gas recirculation valve control means, when the bypass valve control means makes the opening degree of the intake bypass valve larger than the set intake bypass valve opening degree at the low temperature, It is assumed that the opening degree of the reflux valve is corrected to the smaller side.

  That is, when the opening degree of the intake bypass valve is larger than the opening degree of the intake bypass valve at the high temperature when the bypass valve control means is at a low temperature, if the opening degree of the exhaust gas recirculation valve is left as it is, the boost pressure Exhaust gas recirculation amount becomes excessive by the amount of decrease. However, in the present invention, since the opening degree of the exhaust gas recirculation valve is corrected to a smaller side, it is possible to suppress the exhaust gas recirculation amount from becoming excessive, and appropriate exhaust gas can be achieved even at low temperatures as at high temperatures. The amount of gas reflux can be maintained.

  As described above, according to the engine supercharging device of the present invention, at low temperatures, the opening degree of the intake bypass valve is made larger than the intake bypass valve opening degree set according to the operating state of the engine and the exhaust bypass valve. Acceleration at the time of acceleration request is made possible while prematurely warming up the catalyst of the exhaust purification device by making the opening of the engine equal to or less than the exhaust bypass valve opening set according to the engine operating condition Response can be improved.

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

  FIG. 1 shows a schematic configuration of an engine 1 employing a supercharging device according to an embodiment of the present invention. The engine 1 is a diesel engine mounted on a vehicle, and includes a cylinder block 3 provided with a plurality of cylinders 2 (only one is shown), a cylinder head 4 disposed on the cylinder block 3, An oil pan 9 is provided below the cylinder block 3 and stores lubricating oil. In each cylinder 2 of the engine 1, pistons 5 are fitted so as to be able to reciprocate. A deep dish-shaped combustion chamber 6 is formed on the top surface of the piston 5. The piston 5 is connected to the crankshaft 8 via a connecting rod 7.

  In the cylinder head 4, an intake port 12 and an exhaust port 13 are formed for each cylinder 2, and an intake valve 14 and an exhaust valve that open and close the opening of the intake port 12 and the exhaust port 13 on the combustion chamber 6 side. 15 are arranged respectively.

  The cylinder head 4 is provided with an injector 20 for injecting fuel, and a glow plug 25 for warming intake air and improving fuel ignitability when the engine 1 is cold. The injector 20 is arranged so that its fuel injection port faces the combustion chamber 6 from the ceiling surface of the combustion chamber 6 so that fuel is directly injected and supplied to the combustion chamber 6 near the top dead center of the compression stroke. It has become. The injector 20 is connected to a common rail (not shown) via a fuel supply pipe 21 and is configured so that fuel is supplied from a fuel tank (not shown) via the fuel supply pipe 21 and the common rail. . Excess fuel is returned to the fuel tank through the return pipe 22.

  An intake passage 30 is connected to one side of the engine 1 so as to communicate with the intake port 12 of each cylinder 2. An air cleaner 31 that filters intake air is disposed at the upstream end of the intake passage 30, and the intake air filtered by the air cleaner 31 passes through the intake passage 30 and the intake port 12 and is a combustion chamber of each cylinder 2. 6 is supplied.

  An air flow sensor 32 for detecting the flow rate of intake air is disposed in the intake passage 30 near the downstream side of the air cleaner 31. A surge tank 33 is disposed near the downstream end of the intake passage 30. The intake passage 30 downstream of the surge tank 33 is an independent passage branched for each cylinder 2, and the downstream end of each independent passage is connected to the intake port 12 of each cylinder 2.

  Further, a compressor 61 a of the first exhaust turbocharger 61 and a compressor 62 a of the second exhaust turbocharger 62 are disposed between the air flow sensor 32 and the surge tank 33 in the intake passage 30. The compressor 61a of the first exhaust turbocharger 61 is located downstream of the compressor 62a of the second exhaust turbocharger 62. The intake air is supercharged by the operation of both the compressors 61a and 62a. The intake passage 30 is connected to an intake bypass passage 64 that bypasses the compressor 61a of the first exhaust turbocharger 61. The intake bypass passage 64 adjusts the amount of air flowing to the intake bypass passage 64. An intake bypass valve 65 is provided. In the present embodiment, a bypass passage that bypasses the compressor 62a of the second exhaust turbocharger 62 is not provided. However, such a bypass passage is provided, and the bypass passage is similar to the intake bypass valve 65. This valve may be provided.

  Furthermore, between the compressor 61a and the surge tank 33 of the first exhaust turbocharger 61 in the intake passage 30, an intercooler that cools the air compressed by the compressors 61a and 62a in order from the upstream side. 35, an intake pressure sensor 36 for detecting the pressure of the air compressed by the compressors 61a and 62a, and an intake throttle valve 37 for adjusting the amount of intake air into the combustion chamber 6 of each cylinder 2 are provided. Yes. The intake throttle valve 37 is basically fully opened, but when the filter 43b described later is regenerated or when NOx is reduced, the intake throttle valve 37 is changed from the fully opened state to the closing direction to have a predetermined opening. The intake throttle valve 37 is fully closed so that no shock occurs when the engine 1 is stopped.

  An exhaust passage 40 for discharging burned gas (exhaust gas) from the combustion chamber 6 of each cylinder 2 is connected to the other side of the engine 1. The upstream portion of the exhaust passage 40 is constituted by an exhaust manifold having an independent passage branched for each cylinder 2 and connected to the outer end of the exhaust port 13 and a collecting portion where the independent passages gather. Yes. A turbine 61b of the first exhaust turbocharger 61 and a turbine 62b of the second exhaust turbocharger 62 are disposed in the exhaust passage 40 on the downstream side of the exhaust manifold. The turbine 61b of the charger 61 is positioned upstream of the turbine 62b of the second exhaust turbocharger 62. The turbines 61b and 62b are rotated by the exhaust gas flow, and the compressors 61a and 62a connected to the turbines 61b and 62b are operated by the rotation of the turbines 61b and 62b, respectively.

  The exhaust passage 40 includes a first exhaust bypass passage 67 that bypasses the turbine 61 b of the first exhaust turbocharger 61 and a second exhaust bypass passage 69 that bypasses the turbine 62 b of the second exhaust turbocharger 62. And are connected. The first exhaust bypass passage 67 is provided with a regulating valve 68 (first exhaust bypass valve) for adjusting the amount of exhaust flowing to the first exhaust bypass passage 67, and the second exhaust bypass passage 69 includes A waste gate valve 70 (second exhaust bypass valve) for adjusting the amount of exhaust flowing to the second exhaust bypass passage 69 is provided.

  An exhaust gas purification device 43 that purifies harmful components in the exhaust gas is disposed downstream of the turbine 62b of the second exhaust turbocharger 62 in the exhaust passage 40. The exhaust purification device 43 includes an oxidation catalyst unit 43a, a diesel particulate filter (hereinafter referred to as a filter) 43b, and a lean NOx catalyst unit 43c, which are arranged in this order from the upstream side. The oxidation catalyst portion 43a and the filter 43b are accommodated in one case, and the lean NOx catalyst portion 43c is accommodated in a case different from the case that accommodates the oxidation catalyst portion 43a and the filter 43b. A silencer 48 is provided at the downstream end of the exhaust passage 40 (downstream of the lean NOx catalyst portion 43c).

The oxidation catalyst unit 43a has an oxidation catalyst supporting platinum or platinum added with palladium, etc., and performs a reaction in which CO and HC in the exhaust gas are oxidized to produce CO ₂ and H ₂ O. It is a thing to encourage. The filter 43b collects particulates such as soot contained in the exhaust gas of the engine 1. The filter 43b may be coated with an oxidation catalyst.

  The lean NOx catalyst unit 43c has a NOx occlusion reduction type catalyst that occludes NOx in exhaust gas to reduce and purify it. For example, an alkali metal such as potassium, magnesium, strontium, or lanthanum containing barium as a main component. And a NOx occlusion material in which an alkaline earth metal or rare earth and a noble metal having a chemical reaction catalytic action such as platinum are supported. The lean NOx catalyst unit 43c occludes NOx in the exhaust gas when the air-fuel ratio of the exhaust gas is leaner than the stoichiometric air-fuel ratio, while the NOx occluded in this way is enriched according to the enrichment of the air-fuel ratio. The NOx is released and subjected to an oxidation-reduction reaction with CO and HC in the exhaust gas to be decomposed into oxygen and nitrogen. Further, when the air-fuel ratio of the exhaust gas is in the vicinity of the stoichiometric air-fuel ratio, HC, CO and NOx are substantially completely purified.

  Since the engine 1 of this embodiment is a diesel engine, a lean operation is performed in which the air-fuel ratio is larger than the stoichiometric air-fuel ratio (λ> 1) in the entire operation region. If this lean operation is continued, the amount of NOx occluded in the lean NOx catalyst portion 43c increases, eventually becoming saturated, and the NOx purification capacity decreases. In order to prevent this, the air-fuel ratio is enriched so that the stored NOx is decomposed and released into oxygen and nitrogen to restore the NOx storage capacity. Specifically, the NOx amount occluded in the lean NOx catalyst unit 43c can be estimated from a NOx amount discharge map created in advance based on the operating state of the engine 1 such as the engine speed and engine load. When the estimated integrated value of NOx amount exceeds a preset set amount, the air-fuel ratio of the exhaust gas is made richer than the air-fuel ratio during lean operation (for example, the stoichiometric air-fuel ratio or more To be rich). This enrichment is performed by changing the opening degree of the intake throttle valve 37 from the fully opened state to the closing direction to reduce the amount of air supplied to the combustion chamber 6. Then, when the enrichment time has passed a predetermined time, the air-fuel ratio is returned to the original lean state. The predetermined time is set to a time during which all the stored NOx (the set amount) is reduced and released in relation to the degree of enrichment.

  An exhaust gas temperature sensor 44 is disposed between the oxidation catalyst unit 43a and the filter 43b in the exhaust gas purification device 43, and the exhaust gas flowing through the portion where the exhaust gas temperature sensor 44 is disposed by the exhaust gas temperature sensor 44. Temperature is detected. That is, the exhaust temperature sensor 44 constitutes a temperature detection means that detects the temperature associated with the exhaust purification device 43. The temperature related to the exhaust purification device 43 is not limited to the temperature of the exhaust gas flowing between the oxidation catalyst unit 43a and the filter 43b. For example, the temperature of the exhaust gas just before flowing into the oxidation catalyst unit 43a The temperature of the case etc. which covers the oxidation catalyst part 43a and the filter 43b may be sufficient.

  In the exhaust purification device 43, upstream and downstream pressure detectors 45 and 46 for detecting the pressure of the exhaust gas immediately before and after flowing into the filter 43b are provided on the upstream and downstream sides of the filter 43b, respectively. The upstream and downstream pressure detectors 45 and 46 are connected to a differential pressure sensor 47 that detects a differential pressure between the pressure detectors 45 and 46. This differential pressure corresponds to the amount of fine particles collected by the filter 43b (that is, the collected amount), and the larger the differential pressure, the larger the collected amount. When this amount of collection increases, the filter 43b becomes clogged. To prevent this, when the amount of collection exceeds a predetermined amount (for example, 70% of the maximum amount of collection), that is, When the differential pressure reaches a predetermined value corresponding to the predetermined amount, the filter 43b is regenerated by burning the fine particles. In order to regenerate the filter 43b, unburned fuel is supplied to the oxidation catalyst unit 43a of the exhaust purification device 43, and the temperature of the filter 43b is increased by the oxidation reaction heat of the unburned fuel, and is collected in the filter 43b. Burn off the fine particles. The unburned fuel is supplied to the oxidation catalyst unit 43a at a time (expansion stroke or exhaust stroke) delayed from the main injection for injecting fuel near the top dead center of the compression stroke, intended for combustion in the combustion chamber 6. This is done by post-injection. The post injection is preferably divided injection divided into a plurality of times. When performing the post injection, the opening degree of the intake throttle valve 37 is changed from the fully opened state to the closing direction in order to increase the pump loss of the engine 1 and increase the exhaust heat energy. Further, when performing the post injection, it is preferable that an exhaust gas recirculation valve 51 described later is fully closed so that fuel by the post injection does not flow into the intake passage 30.

  A portion of the intake passage 30 between the surge tank 33 and the intake throttle valve 37 (that is, a portion on the downstream side of the compressor 61a of the first exhaust turbocharger 61), the exhaust manifold and the first exhaust passage 40 in the exhaust passage 40. A portion between the first exhaust turbocharger 61 and the turbine 61b (that is, a portion upstream of the turbine 61b of the first exhaust turbocharger 61) is for returning a part of the exhaust gas to the intake passage 30. The exhaust gas recirculation passage 50 is connected. The exhaust gas recirculation passage 50 is provided with an exhaust gas recirculation valve 51 for adjusting the recirculation amount of the exhaust gas to the intake passage 30 and an EGR cooler 52 for cooling the exhaust gas with engine cooling water. ing.

  The first exhaust turbocharger 61 is small, and the second exhaust turbocharger 62 is large. That is, the inertia of the turbine 62 b of the second exhaust turbocharger 62 is larger than that of the turbine 61 b of the first exhaust turbocharger 61. Here, the T / C efficiency map of the first exhaust turbocharger 61 (showing how much the rotational energy of the turbine 61b can be converted into a pressure increase by the compressor 61a) is shown by a solid line in FIG. A T / C efficiency map of the exhaust turbocharger 62 is shown by a broken line in FIG. In FIG. 2, the “air flow rate” on the horizontal axis is the amount of air detected by the air flow sensor 32, and the “pressure ratio” on the vertical axis is the air pressure immediately after flowing out from the compressor with respect to the air pressure just before flowing into the compressor. Ratio. A plurality of annular lines drawn for each exhaust turbocharger are the efficiency obtained from the relationship between the air flow rate and the pressure ratio, and the efficiency increases as the center line increases. As can be seen from FIG. 2, the large second exhaust turbocharger 62 has a wider area of high efficiency.

  As shown in FIG. 3, signals detected by the air flow sensor 32, the intake pressure sensor 36, the exhaust temperature sensor 44, and the differential pressure sensor 47 are sent to an engine control unit (hereinafter referred to as ECU) 81 that controls the engine 1. Entered. In addition to these components, the ECU 81 includes an engine speed sensor 73 that detects the speed of the engine 1, a crank angle sensor 74 that detects the crank angle, a coolant temperature sensor 75 that detects the temperature of the engine coolant, and an accelerator. Signals of respective detection values such as an accelerator opening sensor 76 for detecting the opening are inputted, and based on these input signals, the injector 20, the intake throttle valve 37, the exhaust gas recirculation valve 51, the intake bypass valve 65, the regulating valve. 68 and the wastegate valve 70 are controlled. That is, the ECU 81 constitutes bypass valve control means for controlling the opening degree of the intake bypass valve 65, the regulating valve 68 and the waste gate valve 70, and the exhaust gas recirculation valve control for controlling the opening degree of the exhaust gas recirculation valve 51. Means.

  The ECU 81 controls the openings of the intake bypass valve 65, the regulator valve 68 and the waste gate valve 70 to the openings set according to the operating state of the engine 1. In the present embodiment, the low load and low rotation side region A (the engine load is smaller than the predetermined load (the smaller the engine rotation speed is larger)) in the map having the engine rotation speed and the engine load as parameters shown in FIG. In the region), both the first and second exhaust turbochargers 61 and 62 are operated, and in order to do so, the intake bypass valve 65 and the regulating valve 68 are set to openings other than fully open, and the wastegate valve 70 is a fully closed state. On the other hand, in the high load and high rotation side region B (region in which the engine load is larger than the predetermined load), the first exhaust turbocharger 61 becomes exhaust resistance, so that only the second exhaust turbocharger 62 is used. In order to operate and do this, the intake bypass valve 65 and the regulating valve 68 are fully opened, and the wastegate valve 70 is set to an opening close to the fully closed state. The waste gate valve 70 may be always fully closed (or the second exhaust bypass passage 69 and the waste gate valve 70 may be eliminated). However, in order to prevent over-rotation, the waste gate valve 70 is slightly opened in the region B. I'm offended.

  The opening degree of the intake bypass valve 65 in the region A is determined by the target intake pressure set by the operating state of the engine 1 and the accelerator opening degree. Further, as shown in FIG. 5, the regulating valve 68 gradually increases the opening as the load becomes high (high torque). In FIG. 5, the higher torque side of the line with the opening degree of 100% is an area corresponding to the area B, and the opening degree is 100% in this area. Furthermore, the opening degree of the waste gate valve 70 is as shown in FIG. In FIG. 6, the lower torque side of the line with the opening degree of 10% is an area corresponding to the area A, and the opening degree is 0% in this area. The solid line in FIGS. 5 and 6 is the maximum torque line generated in the engine 1.

  In the region including the line indicated by the broken line in FIG. 4 and the lower load and lower rotation side (including the region A), the exhaust gas recirculation valve 51 is opened, and a part of the exhaust gas enters the intake passage 30. It is designed to be refluxed. Hereinafter, this region is referred to as an EGR region. The opening degree of the exhaust gas recirculation valve 51 in this EGR region is set according to the operating state of the engine 1. On the other hand, the exhaust gas recirculation valve 51 is fully closed at a higher load and higher rotation side than the above line, and the recirculation of the exhaust gas to the intake passage 30 is not performed.

  The region A for operating both the first and second exhaust turbochargers 61 and 62, the region B for operating only the second exhaust turbocharger, and the EGR region are shown in FIG. The T / C efficiency map may be used for setting. That is, the area corresponding to the area A is an area surrounded by a thick line in FIG. 7A, the area corresponding to the area B is an area surrounded by a thick line in FIG. 7B, and the EGR area The corresponding area is an area surrounded by a thick line in FIG. Thereby, from the relationship between the amount of air detected by the air flow sensor 32 and the ratio of the air pressure immediately after flowing out of the compressor to the air pressure immediately before flowing into the compressor, the first and second exhaust turbochargers 61, It is determined whether or not both of 62 are operated, only the second exhaust turbocharger 62 is operated, or the exhaust gas is recirculated to the intake passage 30.

  Each opening degree of the intake bypass valve 65, the regulating valve 68 and the waste gate valve 70 described above is such that the temperature detected by the exhaust temperature sensor 44 is a predetermined temperature (the catalyst activation temperature of the exhaust purification device 43 or a catalyst temperature close thereto). (Temperature corresponding to about 250 ° C.)) or higher, and the ECU 81 performs the above setting as described below in order to warm up the catalyst at an early time when the temperature is lower than the predetermined temperature. Change the opening (opening at high temperature).

  That is, in the region A, at the low temperature, the opening degree of the intake bypass valve 65 is larger than the intake bypass valve opening degree set according to the operating state of the engine 1 (the intake bypass valve opening degree at the high temperature). In addition, the opening degree of the regulating valve 68 is set to be equal to or smaller than the regulating valve opening degree (the regulating valve opening degree at the time of high temperature) set according to the operating state of the engine 1. In addition, the waste gate valve 70 is in a fully closed state similar to that at the time of the high temperature.

  When the opening degree of the intake bypass valve 65 is made larger than the intake bypass valve opening degree at the high temperature in this way, the supercharging efficiency is reduced and the engine torque is reduced compared to the high temperature, so that the vehicle occupant (driver) In order to obtain the same torque as that at high temperature, the accelerator pedal is further depressed (accelerator opening is increased), whereby the fuel injection amount and the amount of air supplied to the combustion chamber 6 (and hence the exhaust amount) are reduced. This results in an increase in exhaust heat energy. Therefore, even if the opening degree of the regulating valve 68 is made equal to or less than that at a high temperature and the turbine 61b of the first exhaust turbocharger 61 is rotationally driven by the exhaust heat energy, sufficient exhaust heat is generated in the exhaust purification device 43. Energy can be supplied, and the catalyst temperature of the exhaust purification device 43 can be raised to the activation temperature at an early stage.

  Further, by making the opening degree of the regulating valve 68 equal to or less than the opening degree of the regulating valve at the high temperature, the turbine 61b of the first exhaust turbocharger 61 continues to rotate. When the occupant further depresses the accelerator pedal to make an acceleration request, that is, when the rate of change of the accelerator opening detected by the accelerator opening sensor 76 is greater than or equal to a predetermined value, the turbine 61b is already rotating. By setting the opening degree of the valve 65 to the intake bypass valve opening degree at the time of high temperature, appropriate supercharging can be performed immediately and a high acceleration response can be obtained.

  Sufficient exhaust heat energy can be supplied to the exhaust purification device 43 within a range where the opening degree of the regulating valve 68 at the low temperature is the same as or smaller than the opening degree of the regulating valve at the high temperature. Although it may be set appropriately from the viewpoint of obtaining a high acceleration response, it is preferable to set the opening so that the turbine 61b of the first exhaust turbocharger 61 rotates at a rotational speed equal to or higher than a predetermined rotational speed. For this reason, it is preferable that the opening degree of the regulating valve 68 at a low temperature is larger as the engine load is larger, like the regulating valve opening degree at a high temperature. In this embodiment, if the regulator valve 68 is in a fully closed state at a high temperature, the regulator valve 68 is also in a fully closed state at a low temperature. If the regulator valve 68 is not in a fully closed state at a high temperature, the regulator valve 68 is opened at a low temperature. Decreasing the degree by a certain percentage with respect to the regulating valve opening at high temperature.

  In the region B, as described above, the intake bypass valve 65 and the regulator valve 68 are fully opened at a high temperature and the first exhaust turbocharger 61 is not operated. You cannot change the direction to open. Further, in the region B where the acceleration response is not a big problem compared to the region A, if the opening degree of the regulating valve 68 is made smaller than the regulating valve opening degree at the high temperature, the exhaust resistance is caused. It is better not to do that. Accordingly, in the region B, the ECU 81 sets the opening of the waste gate valve 70 according to the operating state of the engine 1 at the low temperature (the waste gate valve opening at the high temperature). ). On the other hand, the opening degree of the intake bypass valve 65 and the regulating valve 68 at the time of low temperature in the region B is set to the fully opened state at the time of high temperature. By doing so, it is possible to suppress the reduction of the exhaust heat energy by the first and second exhaust turbochargers 61 and 62 and supply sufficient exhaust heat energy to the exhaust purification device 43.

  Further, the ECU 81 reduces the opening of the exhaust gas recirculation valve 51 to a smaller side when the opening of the intake bypass valve 65 is larger than the intake bypass valve opening at the high temperature as described above. to correct. That is, it is made smaller than the exhaust gas recirculation valve opening degree set according to the operating state of the engine 1. This suppresses the exhaust gas recirculation amount from becoming excessive due to the decrease in the supercharging pressure.

  Here, control operations of the exhaust gas recirculation valve 51, the intake bypass valve 65, the regulating valve 68, and the wastegate valve 70 in the ECU 81 will be described based on the flowchart of FIG.

  In the first step S1, input signals from various sensors are read. In the next step S2, the target intake pressure and the target opening of the exhaust gas recirculation valve 51, the intake bypass valve 65, the regulating valve 68 and the wastegate valve 70 ( Set the opening at the high temperature.

  In the next step S3, it is determined whether or not the operating state of the engine 1 is in the EGR region. If the determination in step S3 is YES, the process proceeds to step S4, and the exhaust gas recirculation valve 51 (in FIG. 8). The opening of the EGR valve is set to an opening corresponding to the operating state of the engine 1 (the set target opening), and then the process proceeds to step S6. On the other hand, when the determination in step S3 is NO, the process proceeds to step S5, the exhaust gas recirculation valve 51 is fully closed, and then the process proceeds to step S6.

  In step S6, it is determined whether or not the temperature detected by the exhaust temperature sensor 44 is a low temperature smaller than the predetermined temperature. If the determination in step S6 is NO, the process returns as it is, while step S6. When the determination is YES, the process proceeds to step S7.

  In step S7, it is determined whether or not the operating state of the engine 1 is in the region A. When the determination in step S7 is NO, that is, when the operating state of the engine 1 is in the region B, the process proceeds to step S8. Thus, the opening degree of the waste gate valve 70 is changed to a larger side (opening direction) with respect to the waste gate valve opening degree set in step S2, and then the process returns.

  On the other hand, when the determination in step S7 is YES, the process proceeds to step S9, and the opening of the intake bypass valve 65 is changed to a larger side (opening direction) than the intake bypass valve opening set in step S2. At the same time, the opening degree of the regulating valve 68 is changed to a side smaller than the regulating valve opening degree set in the above step S2 by a certain percentage (closed direction) (the regulating valve opening set in the step S2). When the degree is 0, it is set to 0 as it is). However, the target intake pressure is kept constant.

  In the next step S10 following step S9, the opening of the exhaust gas recirculation valve 51 is corrected to the smaller side (closed direction), and in the next step S11, the change in the accelerator opening detected by the accelerator opening sensor 76 is corrected. Whether the rate (the value obtained by subtracting the accelerator opening detected last time from the accelerator opening detected this time divided by the detection time interval) is greater than or equal to a predetermined value, that is, whether the passenger is requesting acceleration Determine.

  If the determination in step S11 is NO, the process returns as it is. If the determination in step S11 is YES, the process proceeds to step S12, and the opening of the intake bypass valve 65 is changed to the opening at the high temperature. In the next step S13, the closing direction correction of the exhaust gas recirculation valve 51 is stopped, and then the process returns.

  Therefore, in the present embodiment, when the engine load is a low load equal to or lower than the predetermined load, the opening degree of the intake bypass valve 65 is determined based on the operation of the engine 1 when the temperature detected by the exhaust gas temperature sensor 44 is low. The intake bypass valve opening set according to the state (the intake bypass valve opening at a high temperature at which the temperature detected by the exhaust temperature sensor 44 is equal to or higher than the predetermined temperature) and the opening of the regulating valve 68 are increased. The exhaust emission control device can be operated by depressing the accelerator pedal of the occupant by making it equal to or less than the regulated valve opening set according to the operating state of the engine 1 (regular valve opening at the high temperature). As a result, sufficient exhaust heat energy can be supplied to the exhaust gas 43, so that the catalyst of the exhaust gas purification device 43 can be warmed up early. Both by the turbine 61b of the first exhaust turbocharger 61 continues to rotate, it is possible to improve the acceleration response at the time of the acceleration request.

  Further, since the wastegate valve 70 is in a fully closed state at the low temperature at the time of the low load, even if the opening degree of the intake bypass valve 65 is increased, a certain level of supercharging pressure can be stably obtained. When acceleration is requested, the turbine 62b of the large second exhaust turbocharger 62 is already rotating, so that a high acceleration response can be obtained with certainty.

  Further, when the engine load is higher than the predetermined load, the opening of the waste gate valve 70 is set according to the operating state of the engine 1 at the low temperature. Since the exhaust heat energy is suppressed from decreasing by the second exhaust turbocharger 62, sufficient exhaust heat energy is supplied to the exhaust gas purification device 43. be able to.

  In the above embodiment, the intake air is supercharged (two-stage supercharging) by the two exhaust turbochargers 61 and 62, but the intake air is supercharged only by the first exhaust turbocharger 61. It is also possible to pay. In this case, the characteristics of the inertia and the like of the first exhaust turbocharger 61 are not necessarily the same as those of the first exhaust turbocharger 61 of the above embodiment, and the second exhaust turbocharger 62 of the above embodiment. It may be the same, and may be an intermediate characteristic between the first and second exhaust turbochargers 61 and 62 of the above embodiment. As in the above embodiment, when the engine is in an engine operating state in which the first exhaust turbocharger 61 is operated (the intake bypass valve opening and the regulating valve opening set according to the operating state of the engine 1 are When the temperature is low, the opening degree of the intake bypass valve 65 is set larger than the opening degree of the intake bypass valve set according to the operating state of the engine 1 and the opening degree of the regulating valve 68 is What is necessary is just to make it equivalent or less compared with the regulating valve opening set according to the driving | operation state of 1.

  Further, the present invention can be applied not only to a diesel engine but also to a gasoline engine.

  INDUSTRIAL APPLICABILITY The present invention is useful for an engine supercharging device including an exhaust turbocharger and an exhaust gas purification device disposed downstream of the exhaust turbocharger turbine in the exhaust passage. Useful for those with two exhaust turbochargers.

It is the schematic which shows the structure of the engine which employ | adopted the supercharging apparatus which concerns on embodiment of this invention. It is a T / C efficiency map of the 1st and 2nd exhaust turbocharger. It is a block diagram which shows schematic structure of a supercharging device. 3 is an operation map of first and second exhaust turbochargers and an exhaust gas recirculation valve. It is a map which shows the opening degree of a regulating valve. It is a map which shows the opening degree of a waste gate valve. FIG. 5 is an operation map different from FIG. 4 for the first and second exhaust turbochargers and the exhaust gas recirculation valve. It is a flowchart which shows control operation | movement of an exhaust-gas recirculation valve, an intake bypass valve, a regulating valve, and a wastegate valve in an engine control unit.

Explanation of symbols

1 Engine 30 Intake passage 40 Exhaust passage 43 Exhaust purification device 44 Exhaust temperature sensor (temperature detection means)
50 Exhaust gas recirculation passage 51 Exhaust gas recirculation valve 61 First exhaust turbocharger 61a Compressor 61b Turbine 62 Second exhaust turbocharger 62a Compressor 62b Turbine 64 Intake bypass passage 65 Intake bypass valve 67 First exhaust bypass passage 68 Reg Rate valve (first exhaust bypass valve)
69 Second exhaust bypass passage 70 Wastegate valve (second exhaust bypass valve)
81 Engine control unit (bypass valve control means)
(Exhaust gas recirculation valve control means)

Claims (4)

A first exhaust turbocharger having a compressor disposed in an intake passage of the engine and a turbine disposed in an exhaust passage;
An intake bypass passage for bypassing the compressor of the first exhaust turbocharger;
An intake bypass valve disposed in the intake bypass passage;
A first exhaust bypass passage for bypassing the turbine of the first exhaust turbocharger;
A first exhaust bypass valve disposed in the first exhaust bypass passage;
Bypass valve control means for controlling the opening degree of the intake bypass valve and the first exhaust bypass valve to an opening degree set according to the operating state of the engine;
An exhaust purification device disposed downstream of the turbine in the exhaust passage;
Temperature detecting means for detecting a temperature related to the exhaust purification device,
The bypass valve control means has a first exhaust bypass valve in which the opening degree of the intake bypass valve is larger than the set intake bypass valve opening degree and the opening degree of the first exhaust bypass valve is set at the low temperature at the low temperature. An engine supercharging device characterized by being configured to be equal to or less than an opening degree. The engine supercharging device according to claim 1,
The compressor is disposed upstream of the compressor of the first exhaust turbocharger in the intake passage, and between the turbine of the first exhaust turbocharger and the exhaust purification device in the exhaust passage. And a second exhaust turbocharger having a turbine.
The bypass valve control means is configured to make the opening degree of the intake bypass valve larger than the set intake bypass valve opening degree and to set the first exhaust bypass valve at the low temperature when the engine load is a low load equal to or lower than a predetermined load. A supercharging device for an engine, characterized in that the opening of the valve is configured to be equal to or less than the first exhaust bypass valve opening set above. The engine supercharging device according to claim 2,
A second exhaust bypass passage for bypassing the turbine of the second exhaust turbocharger;
A second exhaust bypass valve disposed in the second exhaust bypass passage,
The bypass valve control means controls the opening of the second exhaust bypass valve to an opening set according to the operating state of the engine, in addition to the opening of the intake bypass valve and the first exhaust bypass valve. When the engine load is higher than the predetermined load, the opening of the second exhaust bypass valve is made larger than the set second exhaust bypass valve opening at the low temperature. An engine supercharger characterized by being configured as follows. The engine supercharging device according to any one of claims 1 to 3,
An exhaust gas recirculation passage connecting the downstream portion of the intake passage with respect to the compressor of the first exhaust turbocharger and the upstream portion of the exhaust passage with respect to the turbine of the first exhaust turbocharger;
An exhaust gas recirculation valve disposed in the exhaust gas recirculation passage;
An exhaust gas recirculation valve control means for controlling the opening degree of the exhaust gas recirculation valve,
The exhaust gas recirculation valve control means reduces the opening of the exhaust gas recirculation valve when the bypass valve control means makes the opening of the intake bypass valve larger than the set intake bypass valve opening at the low temperature. A supercharging device for an engine characterized by being configured to correct to the side.

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