JP6558896B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine with an exhaust turbocharger.

  As an internal combustion engine for vehicles, a turbo engine provided with an exhaust turbocharger is known. The exhaust turbocharger is configured such that a drive turbine disposed on the exhaust passage side of the internal combustion engine and a compressor disposed on the intake passage side are coaxially connected and interlocked. The remaining energy of the exhaust is used to rotate the turbine, and thus the compressor impeller (compressor wheel), and pump the compressor so that the intake air is compressed (supercharged) and sent to the cylinder. Can do.

  Recently, a two-stage turbo (sequential turbo) engine using two exhaust turbochargers having different capacities has been developed (see, for example, the following patent document). In an in-line two-stage turbo system, a relatively large capacity exhaust turbocharger and a relatively small capacity exhaust turbocharger are connected in series, and the former is used in an operating region where the engine speed is high. In the operating region where the engine speed is low, the latter is used to supercharge the intake air.

International Publication WO2012 / 081062 Pamphlet

  In the above-described two-stage turbo engine, an intake bypass passage that bypasses the compressor of the low-speed exhaust turbocharger is usually provided in the intake passage. However, an intake bypass passage that bypasses the compressor of the high-speed exhaust turbocharger is not necessarily provided. That is, the intake air flowing through the intake passage always flows into the compressor of the high-speed turbocharger. On the other hand, the high-speed turbocharger does not perform the work of supercharging the intake air during a low load or low speed operation region with a small exhaust flow rate, or during idle operation. Therefore, the compressor of this high-speed turbocharger may cause intake air loss and reduce fuel consumption performance.

  The problem of deterioration in fuel consumption performance in the idle operation region, the low load operation region, or the low rotation operation region is not unique to the two-stage turbo engine. A similar problem can occur with an internal combustion engine having only one exhaust turbocharger.

  The present invention made by paying attention to the above problems is intended to further improve the fuel consumption performance of an internal combustion engine attached with an exhaust turbocharger.

In the present invention, an internal combustion engine having an exhaust turbocharger that uses the energy of exhaust gas flowing through an exhaust passage to rotate a turbine and drive a compressor to pressurize and compress intake air flowing through the intake passage and send it to a cylinder. It is equipped with two exhaust turbochargers, a high-speed turbocharger and a low-speed turbocharger. In the intake passage, the low-speed turbocharger is downstream of the compressor of the high-speed turbocharger. There is a first compressor that opens and closes a bypass passage that bypasses the compressor of the turbocharger for low speed, and there is a high speed downstream of the turbine of the turbocharger for low speed in the exhaust passage. A turbocharger turbine and a second valve that opens and closes a bypass passage that bypasses the high-speed turbocharger turbine. Feedback control is performed to operate the second valve so that the intake pressure on the downstream side of the compressor of the high-speed turbocharger becomes atmospheric pressure or a value in the vicinity thereof in a low-speed operation region where the rotational speed is equal to or less than a predetermined value. Further, the control device opens the first valve in an idling operation or low load operation region where the engine speed is a predetermined value or less and an accelerator opening is a predetermined value or less, An internal combustion engine is configured that closes the first valve in a low-speed operation region where the engine speed is equal to or less than a predetermined value and in which the accelerator opening is larger than the idle operation or low-load operation region .

  ADVANTAGE OF THE INVENTION According to this invention, the further improvement of the fuel consumption performance of the internal combustion engine attached with the exhaust turbo supercharger can be aimed at.

The figure which shows the structure of the internal combustion engine for vehicles of one Embodiment of this invention. The figure which shows the relationship between the driving | operation area | region of the internal combustion engine of the embodiment, and supercharging by an exhaust turbo supercharger.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine of the present embodiment is a compression ignition type four-stroke engine such as a diesel engine or a HCCI (homogeneous-charge compression ignition) engine, and a plurality of cylinders 1 (one of which is shown in FIG. 1). Are shown). An injector 11 that directly injects fuel into the combustion chamber of the cylinder 1 is installed on the ceiling of the combustion chamber of each cylinder 1. Further, a glow plug (residual heat plug) 12 and a swirl control valve 13 are provided in the vicinity of the intake port of each cylinder 1.

  The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, a compressor 51 of the exhaust turbocharger 5, a compressor 61 of the exhaust turbocharger 6, a water-cooled intercooler 35, an electronic throttle valve 32, a surge tank 33 and an intake manifold 34 are disposed upstream. Are arranged in this order.

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42, an exhaust turbine 62 of the exhaust turbocharger 6, an exhaust turbine 52 of the exhaust turbocharger 5, and an exhaust purification device 41 are disposed on the exhaust passage 4. The exhaust emission control device 41 includes a filter that removes particulate matter contained in the exhaust (Particulate Material) and a catalyst that promotes oxidation or reduction of harmful substances.

  The exhaust turbochargers 5 and 6 are configured such that the exhaust turbines 52 and 62 and the impellers of the compressors 51 and 61 are coaxially connected via a shaft and interlocked with each other. Then, the impellers of the turbines 52 and 62 and the compressors 51 and 61 are rotationally driven using the energy of the exhaust, and the compressor is pumped with the rotational force to compress and compress (supercharge) the intake air. Into cylinder 1.

  The internal combustion engine of the present embodiment is a so-called two-stage turbo (sequential turbo) engine including two exhaust turbochargers 5 and 6. The exhaust turbocharger 5 is a high-speed turbocharger that works in an operation region where the engine speed is relatively high. On the other hand, the exhaust turbocharger 6 is a low-speed turbocharger that works in an operation region where the engine speed is relatively low. The capacity of the low-speed turbocharger 6 is smaller than the capacity of the high-speed turbocharger 5.

  In the intake passage 3, an intake bypass passage 36 that bypasses the compressor 61 of the low-speed turbocharger 6 is provided, and a valve 37 that opens and closes the outlet of the intake bypass passage 36 is provided. The valve 37 controls the flow rate of intake air flowing through the intake bypass passage 36. There is no intake bypass passage that bypasses the compressor 51 of the high-speed turbocharger 5.

  Further, the exhaust passage 4 also includes an exhaust bypass passage 43 that bypasses the turbine 62 of the low-speed turbocharger 6, and an exhaust bypass passage 44 that bypasses the turbine 52 of the high-speed turbocharger 5, and Exhaust bypass valves 45 and 46 for opening and closing the respective inlets of the exhaust bypass passages 43 and 44 are provided. The valve 45 controls the flow rate of exhaust flowing through the exhaust bypass passage 43, and the valve 46 controls the flow rate of exhaust flowing through the exhaust bypass passage 44. The exhaust bypass valves 45 and 46 may be referred to as WGV (Waste Gate Valve).

  Valves 37 and 46 are VSV (Vaccum Switching Valve) using negative pressure actuators 371 and 461. The negative pressure actuators 371 and 461 are diaphragm actuators, and negative pressure and an elastic biasing force by a built-in spring are applied to one surface of the diaphragm, and atmospheric pressure is applied to the other surface. The negative pressure is supplied from the vacuum pump 91. The vacuum pump 91 generates a negative pressure having a certain magnitude. Electromagnetic solenoid valves 372 and 462 are installed on pipes connecting the diaphragm actuators 371 and 461 and the vacuum pump 91, respectively. The magnitude of the negative pressure that actually acts on one surface of the diaphragms of the diaphragm actuators 371 and 461 varies depending on the opening degree of the electromagnetic solenoid valves 372 and 462. The opening degrees of the valves 37 and 46 change according to the difference between the differential pressure between the negative pressure and the atmospheric pressure acting on both surfaces of the diaphragm and the elastic biasing force of the spring that elastically biases the diaphragm. That is, the opening degree of the valves 37 and 46 can be operated through the operation of the opening degree of the electromagnetic solenoid valves 372 and 462.

  On the other hand, the valve 45 is an EVRV (Electric Vacuum Regulating Valve) which is an electromagnetic valve.

  External EGR (Exhaust Gas Recirculation) devices 2 and 7 return a part of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3 to be mixed with the intake air. The internal combustion engine of this embodiment includes two EGR devices 2 and 7. The EGR device 2 realizes a so-called low pressure loop EGR, and communicates the downstream side of the exhaust purification device 41 in the exhaust passage 4 to the upstream side of the compressor 51 of the high-speed turbocharger 5 in the intake passage 3. 21 and an EGR valve 22 that opens and closes the EGR passage 21 are included as elements. The EGR valve 22 controls the flow rate of the low-pressure loop EGR gas that flows through the EGR passage 21.

  The EGR device 7 realizes a so-called high-pressure loop EGR, and an EGR passage 71 that communicates the upstream side of the turbine 62 of the low-speed turbocharger 6 in the exhaust passage 4 to the downstream side of the intercooler 35 in the intake passage 3. An EGR valve 72 that opens and closes the EGR passage 71 is included as an element. The EGR valve 72 controls the flow rate of the high-pressure loop EGR gas that flows through the EGR passage 71.

  In addition, an exhaust throttle valve 47 is installed in the exhaust passage 4 at a location downstream of the connection location of the low-pressure loop EGR passage 21. The pressure on the upstream side of the compressor 51 in the intake passage to which the low-pressure loop EGR passage 21 is connected varies depending on the degree of supercharging by the compressor 51. As a result, the flow rate of EGR gas flowing through the low pressure loop EGR passage 21 changes. The exhaust throttle valve 47, together with the EGR valve 22, functions to converge the flow rate of the low-pressure loop EGR gas, and thus the EGR rate, which is the ratio of EGR gas in the intake air charged in the cylinder 1, to the target value.

  An ECU (Electronic Control Unit) 0 serving as a control device for an internal combustion engine according to the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface of the ECU 0 includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects the rotation angle of the crankshaft and the engine speed, and an accelerator pedal. The accelerator opening signal c output from a sensor that detects the amount of depression of the engine or the opening of the throttle valve 32 as an accelerator opening (in other words, a required engine torque or load), and in the surge tank 33 of the intake passage 3 (that is, The intake air temperature / intake pressure signal d output from the intake air temperature / intake pressure sensor for detecting the temperature and pressure (supercharging pressure) of the intake air (flowing into the cylinder 1), and output from the atmospheric pressure sensor for detecting the atmospheric pressure. At the atmospheric pressure signal e, the most upstream of the intake passage 3, that is, downstream of the air cleaner 31 and upstream of the connection point of the low pressure loop EGR passage 21. An air flow meter for detecting the flow rate and temperature of fresh air, a fresh air flow rate / temperature signal f output from a fresh air temperature sensor, an intake pressure downstream of the compressor 51 and upstream of the compressor 61 in the intake passage 3 (high-speed turbocharger) An intake pressure signal g output from an intake pressure sensor that detects a supercharging pressure by the machine 5, a cooling water temperature signal h output from a water temperature sensor that detects a cooling water temperature that indicates the temperature of the internal combustion engine, and the like are input.

  From the output interface of the ECU 0, the fuel injection signal i for the injector 11, the opening operation signal j for the throttle valve 32, the opening operation signal k for the EGR valve 22, and the opening operation signal for the EGR valve 72. Opening operation signal m for the electromagnetic solenoid valve 372 that controls the opening / closing drive of the signal l, VSV 37, opening operation signal n for the EVRV 45, and opening operation signal o for the electromagnetic solenoid valve 462 that controls the opening / closing drive of the VSV 46. The opening operation signal p and the like are output to the exhaust throttle valve 47.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the fuel injection amount commensurate with the amount of intake air (fresh air). At the same time, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, required EGR rate (or EGR amount), and target supercharging of supercharging by the exhaust turbochargers 5 and 6 Various operating parameters such as pressure are determined. The ECU 0 applies various control signals i, j, k, l, m, n, o, and p corresponding to the operation parameters via the output interface.

  FIG. 2 shows the relationship between the operating range of the internal combustion engine of the present embodiment and the supercharging by the exhaust turbochargers 5 and 6. In FIG. 2, the horizontal axis represents the engine speed and the vertical axis represents the engine torque. Region A1 in which the accelerator opening is small and the engine torque output from the internal combustion engine is relatively small (the non-supercharging region A1 includes an idle operation state in which the accelerator opening is 0 or less than a threshold value close to 0. ), The flow rate of the exhaust gas flowing through the exhaust passage 4 is small, and the exhaust turbochargers 5 and 6 do little or no work. Accordingly, the ECU 0 opens the VSVs 37 and 46 and the EVRV 45, respectively, and opens the bypass passages 36, 43 and 44 to reduce the pumping loss of the internal combustion engine as much as possible. At this time, the ECU 0 feedback-controls the opening degree of the VSV 46 so that the intake pressure downstream of the compressor 51 and upstream of the compressor 61, which is known with reference to the intake pressure signal g, converges to the target intake pressure. The target intake pressure is preferably set to an atmospheric pressure obtained by referring to the atmospheric pressure signal e or a value in the vicinity thereof. Then, the loss due to the compressor 51 of the high-speed turbocharger 5 in the intake passage 3 is reduced, which can contribute to improvement in fuel efficiency.

In the region A2 where the accelerator opening is larger than a certain level and the engine torque is larger than a certain level, but the engine speed is relatively low, supercharging by the low-speed turbocharger 6 is performed. In the region A2, the ECU 0 fully closes the VSV 37 and closes the intake bypass passage 36, and causes all the intake air flowing through the intake passage 3 to flow into the compressor 61. At the same time, the EVRV 45 is fully closed or its opening degree is reduced, and the exhaust gas flowing through the exhaust passage 4 is sufficiently introduced into the turbine 62. At this time, the opening degree of the EVRV 45 may be feedback-controlled so that the intake pressure obtained by referring to the intake air temperature / intake pressure signal d follows the target boost pressure. In addition, ECU0 is be learned with reference to the intake pressure signal g, as the intake pressure of the upper stream of the lower flow and compressor 61 of the compressor 51 converges to the target intake pressure, the feedback control of the opening degree of VSV46 To do. The target intake pressure is preferably set to an atmospheric pressure obtained by referring to the atmospheric pressure signal e or a value in the vicinity thereof. Then, the inlet side of the compressor 61 of the low-speed turbocharger 6 does not become negative pressure, the supercharging of the intake air charged in the cylinder 1 becomes efficient, and the compressor 51 of the high-speed turbocharger 5 Loss is reduced, which can contribute to improved fuel efficiency.

  In the region A4 where the accelerator opening is larger than a certain level, the engine torque is larger than a certain level, and the engine speed is relatively high, supercharging by the high-speed turbocharger 5 is performed. In the area A4, the ECU 0 opens the VSV 37 and the EVRV 45 to open the bypass passages 36 and 43. Then, the VSV 46 is fully closed or its opening degree is reduced, and the exhaust gas flowing through the exhaust passage 4 is sufficiently introduced into the turbine 52. At this time, the intake pressure obtained by referring to the intake air temperature / intake pressure signal d and / or the intake pressure upstream of the compressor 51 and downstream of the compressor 61 obtained by referring to the intake pressure signal g are determined. The opening degree of the VSV 46 is feedback-controlled so as to follow the target boost pressure.

  In the region A4, supercharging by the low-speed turbocharger 6 is not performed, but the rotation of the compressor 61 and the turbine 62 needs to be maintained at a rotation speed that does not cause excessive rotation (for example, about 100,000 rpm). is there. This is based on the assumption that the bearing seal of the low-speed turbocharger 6 rotates the shaft, and if the rotation of the compressor 61 and the turbine 62 ceases or stops, lubricating oil leakage occurs (the intake bypass passage 36 is opened). And when the inlet side of the compressor 51 is in a negative pressure state, the lubricating oil is sucked). Therefore, the ECU 0 keeps the opening degree of the VSV 37 as large as possible, while maintaining the opening degree of the EVRV 45 so that the rotation speeds of the compressor 61 and the turbine 62 are maintained within the predetermined rotation speed range or in the vicinity thereof. Slightly squeeze.

  A region A3 where the accelerator opening is larger than a certain level, the engine torque is larger than a certain level, and the engine speed is medium is a transient region between the low-speed turbo region A2 and the high-speed turbo region A4. In the transition region A3, supercharging is performed by both the low-speed turbocharger 6 and the high-speed turbocharger 5. In the process of transition from the low-speed turbo region A2 to the high-speed turbo region A4, as the engine speed increases, the respective openings of the VSV 37 and the EVRV 45 gradually increase so as to go from substantially fully closed to substantially fully open. At this time, the ECU 0 feedback-controls the opening degree of the EVRV 45 so that the intake pressure obtained by referring to the intake air temperature / intake pressure signal d follows the target boost pressure. In turn, the opening of the VSV 46 gradually decreases as the engine speed increases. The ECU 0 feedback-controls the opening degree of the VSV 46 so that the intake pressure upstream of the compressor 51 and downstream of the compressor 61, which is known with reference to the intake pressure signal g, follows the target boost pressure.

  In the present embodiment, the exhaust turbocharger that compresses and compresses the intake air flowing through the intake passage 3 by rotating the turbine 52 by using the energy of the exhaust gas flowing through the exhaust passage 4 and driving the compressor 51 to send it to the cylinder 1. 5, a valve 46 that opens and closes a bypass passage 44 that bypasses the turbine 51 in the exhaust passage 4, an idle operation region or a low load operation region in which the accelerator opening is equal to or less than a predetermined value, or a low-speed operation in which an engine speed is equal to or less than a predetermined value In the regions (the non-supercharging region A1 and the low-speed turbo region A2), the intake pressure upstream of the compressor 51 (atmospheric pressure obtained by referring to the atmospheric pressure signal e) and the downstream intake pressure (intake pressure) An internal combustion engine comprising a control device 0 that performs control to operate the valve 46 so that the differential pressure with respect to the intake pressure obtained by referring to the signal g is equal to or less than a predetermined pressure is configured.

  According to the present embodiment, in the idle operation region, the low load operation region, or the low rotation operation region, the problem that the compressor 51 of the high-speed turbocharger 5 causes a loss of intake air and decreases fuel consumption performance is alleviated or eliminated. Can do.

  The present invention is not limited to the embodiment described in detail above. In particular, the application target of the present invention is not limited to a two-stage turbo engine. That is, the exhaust turbo supercharger provided in the internal combustion engine may be one. The structure of the internal combustion engine in that case is such that the exhaust turbocharger 6, the bypass passages 36 and 43 and the valves 37 and 45 are omitted from the internal combustion engine shown in FIG. In addition, in the idling operation region, the low load operation region, or the low rotation operation region, the ECU 0 serving as the control device is configured so that the differential pressure between the intake pressure on the upstream side and the intake pressure on the downstream side of the compressor 51 is equal to or less than a predetermined value. Control for operating the valve 46 is performed.

  The control for operating the valve 46 so that the differential pressure between the intake pressure on the upstream side and the intake pressure on the downstream side of the compressor 51 is equal to or less than a predetermined value is limited to the low load and low speed operation region during idle operation and close to idle operation. May be performed.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 3 ... Intake passage 4 ... Exhaust passage 44 ... Exhaust bypass passage 46 ... Valve (VSV)
5 ... High speed exhaust turbocharger 51 ... Compressor 52 ... Turbine 6 ... Low speed exhaust turbocharger 61 ... Compressor 62 ... Turbine

Claims (1)

An internal combustion engine comprising an exhaust turbocharger that uses the energy of exhaust gas flowing through an exhaust passage to rotate a turbine and drive a compressor to pressurize and compress intake air flowing through the intake passage and send it to a cylinder .
And an exhaust turbocharger of the two groups of high-speed turbo supercharger and the low-speed turbo supercharger,
In the intake passage, the low-speed turbocharger compressor exists downstream of the high-speed turbocharger compressor, and the first valve that opens and closes the bypass passage that bypasses the low-speed turbocharger compressor exists. And
In the exhaust passage, there is a high-speed turbocharger turbine downstream of the low-speed turbocharger turbine, and a second valve that opens and closes a bypass passage that bypasses the high-speed turbocharger turbine. And
The control device controls the second valve so that the intake pressure on the downstream side of the compressor of the high-speed turbocharger becomes atmospheric pressure or a value in the vicinity thereof in a low-speed operation region where the engine speed is a predetermined value or less. Feedback control to operate,
Furthermore, the control device opens the first valve in a low-speed operation region where the engine speed is less than a predetermined value and in an idle operation or low-load operation region where the accelerator opening is less than a predetermined value. An internal combustion engine that closes the first valve in the following low-speed operation region and in a region where the accelerator opening is larger than the idle operation or low-load operation region.

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