JP2009299506A - Intake air control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure a sufficient supercharging effect while avoiding surging of a compressor. <P>SOLUTION: In an engine system 10, a compressor 218 and an impulse valve 224 are provided in an intake pipe 204, and an engine 200 is configured to perform supercharging and inertia supercharging by exhaust gas. Supercharging control is performed by an ECU 100. In the control, whether the compressor surge is generated is determined based on intake air quantity Ga and a before and after intake air pressure ratio Rpin being a ratio of atmospheric pressure P0 to supercharging pressure Pin as pressures in before and after the compressor 218. When the intake air quantity Ga is less than a surge limit intake air quantity Gasg, the ECU 100 performs the inertia supercharging by driving the impulse valve 224 for opening/closing so that the supercharging pressure Pin becomes lower than a surge limit pressure Pinsg while appropriately performing supercharging pressure decreasing processing by a compressor bypass valve 227, for avoiding the compressor surge. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an internal combustion engine provided with a supercharger, and more particularly to a technical field of an intake control device for an internal combustion engine capable of avoiding a compressor surge.

  As this type of technical field, one having a variable diffuser has been proposed (see, for example, Patent Document 1). According to the turbocharger control device disclosed in Patent Document 1 (hereinafter referred to as “conventional technology”), by setting the target opening of the diffuser vane within a range that does not exceed the surge limit, the surge region is reduced. It is said that it is possible to use a region with high turbo efficiency while avoiding it.

  In addition, a technique of increasing the post-compressor supercharging pressure by reducing the nozzle opening of a VNT (Variable Nozzle Turbo) in order to increase the pulse supercharging effect in a low rotation range is also disclosed (for example, see Patent Document 2).

  Further, a technique for increasing the pulse supercharging effect in a low rotation range when combining turbo supercharging and pulse supercharging is also disclosed (for example, see Patent Document 3).

  Furthermore, when combining turbocharging and pulse supercharging, the pressure between the intake control valve and the intake valve before opening the intake valve is maintained high, and the internal EGR is exhausted and scavenged when the valve overlaps. Technology has also been proposed (see, for example, Patent Document 4).

JP 2007-132232 A JP 2007-327379 A JP 2007-2837 A JP 2006-283654 A

  In the prior art, the surge line is made variable by changing the opening of the diffuser vane. Therefore, the intake air pressure ratio itself before and after the compressor is substantially unchanged, and of course, even if the supercharging effect can be improved considerably by changing the surge line, the supercharging effect is basically limited to the surge limit. It will be. In other words, the conventional technique does not solve the technical problem that the supercharging effect is hindered by the compressor surge.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an intake control device for an internal combustion engine that can ensure a sufficient supercharging effect while avoiding a compressor surge.

  In order to solve the above-described problems, an intake control device for an internal combustion engine according to the present invention is provided in a vehicle, and includes a plurality of cylinders, an intake passage communicating with the plurality of cylinders, a supercharger having a compressor in the intake passage, and the An intake control device for an internal combustion engine comprising an intake control valve that is installed on the downstream side of the compressor in an intake passage and is configured to open and close to enable inertia supercharging utilizing intake air pulsation, Determining means for determining an opening / closing characteristic of the intake control valve so that a front-rear intake pressure ratio, which is a ratio of intake pressure between the upstream side and the downstream side of the compressor, is outside a predetermined compressor surge region due to inertia supercharging; And a control means for controlling the intake control valve based on the determined opening / closing characteristic.

  The "internal combustion engine" according to the present invention has a plurality of cylinders, and various fuels such as gasoline, light oil, various alcohols, or a mixed fuel of various alcohols and gasoline, or the like in each of the cylinders, or The force generated when an air-fuel mixture containing various fuels explodes or burns can be taken out as a driving force through a physical or mechanical transmission path such as a piston, a connecting rod and a crankshaft. It is a concept that encompasses various institutions. An “intake engine control device for an internal combustion engine” relating to this type of internal combustion engine includes intake air (ie, intake air as air sucked from the outside world) as a part of the concept, and the intake air itself. Or, for example, when an exhaust gas recirculation device such as an EGR device is provided, for example, a mixture of EGR gas (that is, a part of exhaust gas) and the intake air according to the open / close state of a flow rate adjusting means such as an EGR valve, etc. The device can control the supply of various forms of the above.

  The “intake passage” in the intake control apparatus for an internal combustion engine according to the present invention is the intake passage described above. As a preferred embodiment, for example, an air cleaner, an air flow meter, a throttle valve (ie, an intake throttle valve). The surge tank, the intake port, and the like can be connected or communicated with each other as appropriate, for example, in the form of a single or a plurality of tubular members.

  An internal combustion engine according to the present invention can adjust an intake air amount, which is an intake air amount, according to an open / close state that can be controlled, for example, in a binary, stepwise or continuous manner, for example, a valve body, or the like In addition to the valve body, an intake control valve is provided as means that can take various forms such as a valve operating mechanism or a valve operating apparatus that appropriately includes a drive device that drives the valve body. When the internal combustion engine is provided with a so-called intake throttle valve such as a throttle valve, the intake control valve is installed on the downstream side of the intake throttle valve as a preferred form.

  At this time, the installation mode of the intake control valve can be appropriately changed according to the structure of the intake passage and the like. For example, in the case where the intake passage has a configuration that appropriately branches in accordance with each cylinder or a group of cylinders such as a communication pipe in a section between the surge tank and each cylinder, for example, Alternatively, a single intake control valve may be provided on the upstream side so as to be shared by a plurality of cylinders (in this case, the intake system is a so-called one-valve type intake manifold-less intake system). In such a configuration of the intake passage, a plurality of intake passages corresponding to each cylinder (that is, downstream of the branch position) may be provided with a plurality of intake control valves for each cylinder (for example, Including multi-valve intake manifold intake system). Alternatively, when a part of the intake passage is a so-called intake manifold or the like, for example, an independent configuration for each cylinder on the downstream side of the surge tank, it is needless to say that intake control is performed on each (or part of) these independent pipes. A valve may be provided.

  The internal combustion engine according to the present invention includes a supercharger, such as a turbocharger, provided with a compressor in the intake passage. In this type of supercharger, as a preferred embodiment, when the turbine installed in the exhaust system rotates due to the exhaust pressure, the compressor rotates coaxially to perform supercharging.

  On the other hand, in this type of supercharger, the upstream side of the compressor (where “upstream” and “downstream” are one of the directional concepts based on the direction of intake air flow. In this case, the upstream side means the outside world. And the downstream side, that is, the cylinder side) (preferred form is an atmospheric pressure or a pressure equivalent thereto, hereinafter referred to as “compressor upstream pressure” as appropriate) and the intake air pressure on the downstream side of the compressor (As a preferred form, for example, so-called supercharging pressure, which will be referred to as “compressor downstream pressure” hereinafter), the intake air is temporarily transferred in the compressor due to the relative relationship between the front and rear intake pressure ratio and the intake air amount. In some cases, the compressor surge may be stagnant due to, for example, repeated entry into and exit from the compressor.

  Here, the compressor surge region in which this type of compressor surge occurs can be defined by, for example, the front / rear intake pressure ratio (or intake air amount) that is uniquely determined with respect to the intake air amount (or front / rear intake pressure ratio) (qualitative). Specifically, for example, the front-rear intake pressure ratio (or intake air amount) is higher (or lower) than the intake air amount (or front-rear intake pressure ratio). Accordingly, if the purpose is at least simply to avoid compressor surge, as a preferred embodiment, for example, the surge limit value defined for the intake air amount is a constant value defined for the compressor downstream pressure. The supercharging pressure of the supercharger may be adjusted so as not to exceed an indefinite surge limit pressure.

  However, when the supercharging operation of the supercharger is limited so that the compressor downstream pressure does not reach the surge limit pressure, the supercharging by the supercharger is limited by the surge limit pressure. Also, unless the compressor has a suction bypass path on the downstream side of the compressor, once the compressor downstream pressure exceeds the surge limit pressure, for example, the intake air amount naturally rises and the operating point of the supercharger becomes the compressor surge. No more waiting for departure from the area. Further, when this kind of intake bypass path (or compressor bypass path) is provided, the supercharged intake air is not provided at least for intake into the cylinder. That is, in any case, a decrease in the power performance of the internal combustion engine due to the compressor surge is a problem that is difficult to avoid in practice.

  Therefore, according to the intake air control apparatus for an internal combustion engine according to the present invention, during its operation, it is configured as various processing units such as an ECU (Electronic Control Unit), various controllers or various computer systems such as a microcomputer device, or the like. The determining means to determine the opening / closing characteristics of the intake control valve described above so that the front-rear intake pressure ratio that is the ratio of the intake pressure between the upstream side and the downstream side of the compressor is outside a predetermined compressor surge region due to inertia supercharging. At the same time, control means that can be configured as various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device controls the intake control valve based on the determined opening / closing characteristics.

  Here, the intake control valve described above is configured to be capable of inertial supercharging (also referred to as pulse supercharging or impulse charge) using intake air pulsation by opening and closing driving. Inertia supercharging is a preferred form, for example, the intake control valve is closed before or after the intake valve is opened, and for example, an appropriate time elapses after the intake valve is opened (defined as an angle concept based on the crank angle or the like). The intake control valve is opened (that is, the intake control valve is opened in a state where the downstream side of the intake control valve is negative pressure and the upstream side of the intake control valve is equal to or higher than atmospheric pressure). A pressure wave is generated and reflected as a negative pressure wave near the combustion chamber entrance of each cylinder, which can be regarded as an open end, and the negative pressure wave is arranged in series or in parallel with the intake passage, for example, a surge tank. When natural intake is performed using the pulsation of intake that can take the form of a secondary positive pressure wave or the like, which is reflected by the open end again at the opening of various volume means such as a resonator or a resonator (a suitable one) As a form, intake Regardless of the presence or absence of the intake control valve, it can be basically taken into the cylinder as a pulsating wave, but the pulsation caused by the opening and closing control applied to the intake control valve is stronger than this type of pulsation as a preferred form It means that a large amount of intake air is taken into the cylinder (that is, supercharged) in the intake stroke.

  The opening / closing characteristics determined to realize such inertia supercharging are, for example, the opening / closing timing, valve opening period or opening degree of the intake control valve (that is, the degree of valve opening, which uniquely defines the opening / closing state). ) Etc. The control means controls the intake control valve according to at least the determined opening / closing characteristics to achieve inertia supercharging. In addition to the opening / closing characteristics of this type of intake control valve, the control means controls the intake valve opening / closing characteristics. Control of the timing or valve opening period, or correction of the fuel injection amount according to the change of the intake amount accompanying the change of the charging efficiency of the intake air may be performed, for example, the intake valve (that is, combustion as a preferable form) The valve closing timing of the valve that controls the communication state between the chamber and the intake passage) is synchronized with the timing at which the peak of the intake pulsation wave (positive pressure wave) reaches the intake valve (it does not necessarily indicate that they coincide with each other) (The control subject according to the present invention may be the control means according to the present invention or other means).

  In particular, according to the inertia supercharging, it is possible to improve the charging efficiency of the intake air for each cylinder. The pressure can be reduced at least somewhat considerably. Therefore, by deviating the front / rear intake pressure ratio, which is the ratio of the intake pressure before and after the compressor, out of the compressor surge region, a sufficient supercharging effect is secured while avoiding the compressor surge. “To be outside the compressor surge region” does not necessarily mean that escape from the compressor surge region is achieved only by inertia supercharging. For example, a wastegate valve, compressor bypass When there is a supercharging pressure adjusting means such as a valve or VN, or when the supercharger itself has a configuration capable of assisting the rotation of a compressor or turbine such as a so-called MAT (Motor Assist Turbo), these drive controls For the purpose of assisting in avoiding the compressor surge due to the inertia supercharging, the supercharging pressure of the supercharger may be appropriately adjusted. With such assistance, the practical benefits related to avoiding compressor surge while maintaining the supercharging effect of inertial supercharging are not impaired at all.

  Supplementally, the present invention has been made in view of the fact that the reduction of the compressor downstream pressure can be realized as a phenomenon accompanying the intake air charging into the cylinder. In other words, the present invention is completely different from the technical idea of simply avoiding the compressor surge by reducing the compressor downstream pressure irrespective of the intake charging efficiency. According to the present invention, the intake control valve is used as a supercharger in at least a part of the operation region of the internal combustion engine in which the supercharging effect of the supercharger is limited by the compressor surge, so to say, for each supercharger. The operating area is shared, and the compressor surge can be avoided while maintaining or improving the supercharging effect at the desired time, whether it is after the compressor surge occurs or before the compressor surge occurs. In that respect, it provides a great benefit in practice.

  In addition, according to the present invention, it is possible to maintain or improve at least the supercharging effect and avoid compressor surge by reducing the downstream pressure of the compressor by inertial supercharging. The effect of increasing the amount can also be expected. When the intake air amount increases, the compressor flow rate increases, and the compressor downstream pressure (surge limit pressure) that defines the compressor surge limit increases. That is, according to the present invention, it is possible to simultaneously cause two different types of phenomena that act in the direction of avoiding the compressor surge, such as reduction of the compressor downstream pressure and increase of the intake air amount. In other words, supercharging by the supercharger and inertial supercharging act in a coordinated manner, so that it is possible to obtain a suitable intake characteristic over a wide operating range of the internal combustion engine.

  Note that this kind of inertia supercharging performed by the determining means and the control means in consideration of the compressor surge may be at least the same type as that of the inertia supercharging originally performed in the intake control valve. That is, if the original inertial supercharging realized by the intake control valve is executed as inertial supercharging control appropriately including, for example, the above-described opening / closing characteristics, intake valve opening / closing characteristics, and fuel injection amount correction, etc. The operation of the control means according to the invention is to control the execution subject of the inertial supercharging control so that the inertial supercharging control is executed (if the executing subject is the control means, “execute the inertial supercharging control”) It may be expressed) ”.

  By the way, this kind of inertial supercharging in the original meaning is, as a preferred form, a vehicle operating condition such as an internal combustion engine load (which may include various index values corresponding to the load), an engine speed, and the like. It is executed according to the necessity of inertia supercharging, which is appropriately determined based on the necessity. At this time, the driving condition of the vehicle and the necessity of execution of the inertia supercharging control may be associated with each other. For example, the engine speed is low (for example, the engine speed is the operation of the intake control valve). As a region where the speed can follow, or as a region excluding the high rotation region as a region where a significant difference in effect is unlikely to appear between the pulsation inherent in the intake air and the pulsation generated by the opening / closing control of the intake control valve This may be performed when the load belongs to a low load region) and the load belongs to a high load region excluding the low load region that originally does not require supercharging. Therefore, the inertial supercharging (inertial supercharging that avoids compressor surge by reducing the compressor downstream pressure without hindering the supercharging effect) performed by the control means according to the present invention is an inertia in this original meaning. Supercharging and some of its execution conditions may overlap.

  In one aspect of the intake control device for an internal combustion engine according to the present invention, the control device further includes a determination unit that determines whether or not the front / rear intake pressure ratio corresponds to the compressor surge region, and the control unit includes the front / rear intake pressure ratio. When it is determined that the compressor surge region falls, the intake control valve is controlled based on the determined opening / closing characteristic.

  According to this aspect, for example, only when it is determined that the front / rear intake pressure ratio corresponds to the compressor surge region by a determination unit that can be configured as various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device. In such a case, in order to avoid compressor surge due to inertia supercharging preferentially, or at least in such a case, the control means can efficiently consume the finite drive energy of the intake control valve. It is possible and useful in practice.

  Incidentally, the phrase “applicable to the compressor surge region” includes, of course, a case where the front-rear intake pressure ratio exists in the compressor surge region as a preferred form, but is not limited to this, for example, current operating conditions Or when the driving condition continues for a predetermined time, it can be determined that the front / rear intake pressure ratio will reach the compressor surge region in the near future (that is, the front / rear intake pressure ratio will enter the compressor surge region) The purpose is to include cases.

  In another aspect of the intake control apparatus for an internal combustion engine according to the present invention, the pressure on the downstream side of the compressor is an average intake pressure on the downstream side of the compressor.

  According to this aspect, since the compressor downstream pressure that defines the front-rear intake pressure ratio is the average intake pressure on the compressor downstream side, the compressor downstream can be maintained as high as possible, and the supercharging effect can be as much as possible. Highly maintainable. Further, according to the inertia supercharging, the average intake pressure downstream of the compressor is at least surely reduced, so that the control load is obviously reduced.

  In another aspect of the intake control apparatus for an internal combustion engine according to the present invention, the pressure on the downstream side of the compressor is a peak pressure of an intake pulsation wave that reaches the compressor on the downstream side of the compressor.

  According to this aspect, the compressor downstream pressure that defines the front and rear intake pressure is the peak pressure of the intake pulsation wave that reaches the compressor on the compressor supercharging side. Inertia supercharging is supercharging by pulsation of intake air as described above, and there is a possibility that a pulsation wave related to the compressor arrives in a reverse flow in the intake passage. Compressor surge occurs in the compressor. Even if the average intake pressure downstream of the compressor is less than the surge limit pressure, the peak pressure of the pulsating wave that reaches the compressor transiently or instantaneously is the surge limit. If the pressure is exceeded, the possibility of intermittent compressor surge cannot be denied. According to this aspect, the front-rear intake pressure ratio is prevented from existing in the compressor surge region even if instantaneously. That is, the compressor surge can be surely avoided, which is extremely useful in practice.

  In this aspect, the internal combustion engine may further include a peak pressure reducing unit that is capable of reducing at least a peak pressure of the intake pulsation wave and is different from the intake control valve.

  If this kind of peak pressure reducing means is provided, this kind of peak pressure reducing means can provide this kind of effect simply by being installed, even if it requires active control in reducing such peak pressure. Even if it plays, it is preferable because the peak pressure can be reduced relatively easily.

  Further, in this aspect, the peak pressure reducing means is a cooling means installed so as to cool intake air downstream of the compressor in the intake passage, an intake throttle valve installed downstream of the compressor in the intake passage, At least a part of a surge tank installed downstream of the compressor in the intake passage, a resonator installed downstream of the compressor in the intake passage, and a supercharging pressure adjusting means capable of adjusting the supercharging pressure of the supercharger. May be included.

  The configuration of the peak pressure reducing means can take various forms, but according to the supercharging pressure adjusting means such as the wastegate valve described above, the supercharging pressure can be controlled relatively finely. It is effective in reducing Further, various volume means (volume) such as a surge tank and a resonator are preferably interposed between the compressor and the intake control valve. At this time, if they have a sufficient volume, the intake air pulsation due to inertial supercharging occurs predominantly downstream of them, and the compressor surge between them and the compressor is at least due to the peak pressure. There is no pulsation large enough to define the presence or absence. That is, when these volume means are provided, it is possible to reduce the peak pressure of the pulsating wave that reaches the compressor without aggressive control, which is preferable. Further, for example, a cooling means such as an intercooler is preferable because it can be expected to have an effect equivalent to that of the previous volume means, and it is also possible to cool the pulsating wave and suppress the scale of the pulsation. Furthermore, for example, an intake throttle valve such as a throttle valve is far from the cylinder compared to an intake control valve, and does not necessarily effectively work for inertia supercharging, but restricts the arrival of intake pulsation to the compressor. This is preferable.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

<Embodiment of the Invention>
Various preferred embodiments of the present invention will be described below with reference to the drawings.
<First Embodiment>
<Configuration of Embodiment>
First, the configuration of the engine system 10 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram conceptually showing the configuration of the engine system 10.

  In FIG. 1, an engine system 10 is mounted on a vehicle (not shown) and includes an ECU 100 and an engine 200.

  The ECU 100 is an electronic control unit that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and is configured to be able to control the entire operation of the engine 200. 1 is an example of an “intake control device for an internal combustion engine”. The ECU 100 is configured to execute impulse valve drive control and supercharging control, which will be described later, according to a control program stored in the ROM.

  The ECU 100 is an integrated electronic control unit configured to function as an example of the “determination unit”, “determination unit”, and “control unit” according to the present invention. The ECU 100 is configured to be executed. However, the physical, mechanical, and electrical configurations of each of the units according to the present invention are not limited to this. For example, each of these units includes a plurality of ECUs, various processing units, various controllers, a microcomputer device, and the like. It may be configured as various computer systems.

  The engine 200 is an in-line four-cylinder diesel engine that is an example of an “internal combustion engine” according to the present invention that uses light oil as fuel. The outline of the engine 200 will be described. The engine 200 has a configuration in which four cylinders 202 are arranged in parallel in a cylinder block 201. Then, in the compression stroke in each cylinder, the air-fuel mixture containing the fuel is compressed, and the force generated when self-ignition is performed is converted into the rotational motion of a crankshaft (not shown) via a piston and a connecting rod (not shown), respectively. It is the composition which becomes. The rotation of the crankshaft is transmitted to drive wheels of a vehicle on which the engine system 10 is mounted, and the vehicle can travel. Below, the principal part structure of the engine 200 is demonstrated with a part of the operation | movement. Since the configurations of the individual cylinders 202 are equal to each other, only one cylinder 202 will be described here.

  In FIG. 1, the intake air, which is air guided from the outside, is guided to the intake pipe 204 via an air cleaner (not shown). The intake pipe 204 is provided with a throttle valve 205 capable of adjusting the amount of intake air guided to the intake pipe 204. The throttle valve 205 is a rotary valve that is configured to be rotatable by a driving force supplied from a throttle valve motor (not shown) that is electrically connected to the ECU 100 and controlled by the ECU 100 at the upper level. The rotational position is continuously controlled from a fully closed position where the upstream and downstream portions of the intake pipe 204 at the boundary are substantially blocked to a fully open position where the intake pipe 204 communicates almost entirely. As described above, in the engine 200, the throttle valve 205 and the throttle valve motor constitute a kind of electronically controlled throttle device.

  The intake pipe 204 is connected to the communication pipe 206 on the downstream side of the throttle valve 205 and is configured to communicate with the communication pipe 206 therein. The communication pipe 206 communicates with each intake port (not shown) of each cylinder 202, and the intake air guided to the intake pipe 204 is guided to the intake port corresponding to each cylinder via the communication pipe 206. It is configured to be written. Two intake ports are provided for each cylinder 202, and each intake port is configured to communicate with the inside of the cylinder 202. The intake pipe 204 and the communication pipe 206 constitute an example of the “intake passage” according to the present invention. The intake pipe 204, the communication pipe 206, and the intake port are examples of the “intake passage” according to the present invention.

  Here, the communication pipe 206 is provided with a supercharging pressure sensor 228 capable of detecting a supercharging pressure Pin that is the pressure of intake air inside the communication pipe 206. The supercharging pressure sensor 228 is electrically connected to the ECU 100, and the detected supercharging pressure Pin is a constant or indefinite period by the ECU 100 as an example of “an intake pressure downstream of the compressor” according to the present invention. It is the composition referred in. Although not shown, a pressure sensor capable of detecting the atmospheric pressure P0 is provided upstream of the compressor 218 in the intake pipe 204. This pressure sensor is electrically connected to the ECU 100, and the detected atmospheric pressure P0 is referred to by the ECU 100 at a constant or indefinite period as an example of the “intake pressure upstream of the compressor” according to the present invention. It has a configuration.

  The injection valve of the injector 203 is exposed inside the combustion chamber of each cylinder as part of an in-cylinder direct injection system such as a common rail system or a unit injector for directly injecting fuel into the high-temperature and high-pressure cylinder 202. Thus, the fuel oil can be injected into the combustion chamber. The injector drive system is electrically connected to the ECU 100 and is controlled by the ECU 100 to the upper level. That is, the operation of the injector is controlled by the ECU 100. The fuel injected through the injector is mixed with the intake air (which is a mixed gas of intake air and EGR gas, which will be described later) sucked in the intake stroke inside the cylinder, and becomes the above-described air-fuel mixture. The mixture is further promoted in the compression stroke following the intake stroke, and spontaneously ignites (ie, explodes) in the vicinity of the compression TDC.

  The engine 200 according to the present embodiment is a diesel engine having a compression ignition type combustion mode. However, as an internal combustion engine according to the present invention, a gasoline engine using gasoline as fuel or gasoline and alcohol are mixed. It is also possible to use a bi-fuel engine or the like that can use alcohol mixed fuel. When the internal combustion engine takes these forms, the fuel injection injector may be a so-called port injection type injector that can inject fuel into the intake port.

  The communication state between the intake port and the cylinder 202 is controlled by an intake valve 207 provided in each intake port. The intake valve 207 is fixed to the intake camshaft 208 that rotates in conjunction with the crankshaft. The cam profile of the intake cam 209 that has an elliptical cross section perpendicular to the extending direction of the intake camshaft 208 (in short, The opening / closing characteristics are defined according to the shape), and the intake port and the inside of the cylinder 202 can communicate with each other when the valve is opened.

  On the other hand, the burned mixture or the partially unburned mixture is led to the exhaust manifold 213 through the exhaust port (not shown) as exhaust when the exhaust valve 210 that opens and closes in conjunction with the opening and closing of the intake valve 207 is opened. It is configured to be written. The exhaust valve 210 is fixed to the exhaust camshaft 211 that rotates in conjunction with the crankshaft, and the cam profile of the exhaust cam 212 having an elliptical cross section perpendicular to the extending direction of the exhaust camshaft 211 (in short, The opening / closing characteristics are defined according to the shape), and the exhaust port and the cylinder 202 can be communicated with each other when the valve is opened. The exhaust gas collected in the exhaust manifold 213 is supplied to the exhaust pipe 214 communicating with the exhaust manifold 213.

  A turbine 216 is installed in the exhaust pipe 214 so as to be accommodated in the turbine housing 215. The turbine 216 is a ceramic impeller configured to be rotatable about a predetermined rotation axis by the pressure of exhaust gas (that is, exhaust pressure) guided to the exhaust pipe 214. The rotating shaft of the turbine 216 is shared with the compressor 218 installed in the intake pipe 204 so as to be accommodated in the compressor housing 217. When the turbine 216 is rotated by exhaust pressure, the compressor 218 is also centered on the rotating shaft. It is configured to rotate.

  The compressor 218 is configured to be able to supply the intake air sucked into the intake pipe 204 from the outside via an air cleaner to the downstream side by the pressure accompanying the rotation. The compressor 218 pumps the intake air. The effect is so-called supercharging. That is, in the engine 200, the turbine 216 and the compressor 218 constitute a kind of turbocharger. In the following description, the term “turbocharger” will be used as appropriate as a comprehensive concept including the turbine 216 and the compressor 217. The turbocharger is an example of the “supercharger” according to the present invention.

  In addition, a DPNR (Diesel Particulate NOx Reduction system) 219 is installed in the exhaust pipe 214. The DPNR 219 employs a configuration in which an oxidation catalyst and an NSR (NOx Storage Reduction) catalyst are arranged upstream and downstream of a wall flow type DPF (Diesel Particulate Filter) provided with a NOx storage layer, respectively, and CO, This exhaust gas purifying means can purify exhaust gas by continuously oxidizing and reducing HC, PM and NOx.

  A water temperature sensor 220 is disposed in the cylinder block 201 that houses the cylinder 202. Inside the cylinder block 201, a water jacket as a cooling water flow path for cooling the cylinder 202 is stretched. Inside the water jacket, LLC as cooling water is circulated and supplied by the action of a circulation system (not shown). ing. The water temperature sensor 220 has a configuration in which a part of the detection terminal is exposed inside the water jacket, and is configured to be able to detect the temperature of the cooling water. The water temperature sensor 220 is electrically connected to the ECU 100, and the detected cooling water temperature is referred to by the ECU 100 at a constant or indefinite period.

  On the upstream side of the compressor 218, a hot wire type air flow meter 221 capable of detecting an intake air amount Ga which is a mass flow rate of the intake air is installed. The air flow meter 221 is electrically connected to the ECU 100, and the detected intake air amount Ga is referred to by the ECU 100 at a constant or indefinite period. In the present embodiment, the detected intake air amount is uniquely related to the amount of intake air (ie, the intake air amount) sucked into the cylinder 202, and is an index that defines the actual load of the engine 200. Treated as a value.

  In the intake pipe 204, an intercooler 222 is installed on the downstream side of the compressor 218 and the upstream side of the throttle valve 205. The intercooler 222 has a heat exchange wall inside thereof, and when supercharged intake air passes (the same is true even in a low rotation region where the compressor 218 does not act substantially), It is an example of the “cooling means” according to the present invention configured to be able to cool intake air by heat exchange through such a heat exchange wall. The engine 200 can increase the density of the intake air by the cooling by the intercooler 222, so that the supercharging via the compressor 218 can be performed more efficiently.

  On the other hand, the intake pipe 204 is formed with a compressor bypass passage 226 that bypasses the compressor housing 217 by communicating the upstream and downstream of the compressor 218 without passing through the compressor 218. A compressor bypass valve 227 is installed in the compressor bypass passage 226. In the compressor bypass valve 227, the opening degree of the valve body is a fully opened opening degree that fully communicates the upstream and downstream sides of the compressor bypass valve 227 in the compressor bypass passage 226, and a fully closed opening degree that blocks the upstream and downstream communication. It is an electromagnetic opening-and-closing valve comprised so that it can change continuously between. The compressor bypass valve 227 is electrically connected to the ECU 100, and the opening degree of the compressor bypass valve 227 is controlled by the ECU 100. In a state where the compressor bypass valve 227 is considerably opened, a part of the intake air stored on the downstream side of the compressor 218 is released from the downstream side, so that the turbocharger supercharging pressure is reduced. That is, the compressor bypass valve 227 is configured to function as an example of the “supercharging pressure adjusting means” in the present invention.

  Here, a surge tank 223 is installed on the downstream side of the throttle valve 205 in the intake pipe 204. The surge tank 223 suppresses irregular pulsation of the intake air supplied while appropriately receiving the above-described turbocharger supercharging action, and stably supplies the intake air to the downstream side (that is, the cylinder 202 side). At the same time, during the execution of inertia supercharging control, which will be described later, the storage means is configured to be able to reverse the phase of the negative pressure wave (that is, to cause the pulsation of intake air). It is connected to the intake pipe 204 at a branch position (not shown) on the downstream side of the surge tank 223. However, since the intake air is basically supplied to the cylinder 202 while pulsating to a greater or lesser extent, the intake air passing through the surge tank 223 during the non-execution period of inertia supercharging is also a kind of pulsating wave.

  A single impulse valve 224 shared and shared by each cylinder is provided in the vicinity of a branch position to the communication pipe 206 on the downstream side of the surge tank 223 installed in the intake pipe 204. The impulse valve 224 has an opening degree defined by the position of the valve body, a fully-closed opening degree that blocks communication between the intake pipe 204 and the communication pipe 206, and almost complete communication between the intake pipe 204 and the communication pipe 206. It is a rotary valve which is an example of the “intake control valve” according to the present invention, which is configured to be able to continuously change between the fully opened opening.

  The impulse valve 224 is configured such that its opening degree is controlled by the driving force supplied from the actuator 225. The actuator 225 is electrically connected to the ECU 100, and the driving state is controlled by the ECU 100. That is, the opening degree of the impulse valve 224 is controlled by the ECU 100.

  In the engine 200, a so-called single valve type intake manifold in which the communication pipe 206 is aggregated on the upstream side of the portion corresponding to each cylinder 202 (more specifically, the intake port) and the impulse valve 224 is shared. However, the structure of the intake system is not limited to this, and a multi-valve type intake manifold in which an impulse valve 224 is provided for each cylinder individually at a position corresponding to each intake port in the communication pipe 206. For example, the intake manifold may be branched from the surge tank 223 to the individual cylinders 202. In this case, the impulse valve 224 may be installed in each intake manifold so as to be independently controllable.

  The required load of the engine 200 is determined according to an accelerator opening degree Ta which is an operation amount (that is, an operation amount by a driver) of an unillustrated accelerator pedal. The accelerator opening degree Ta is detected by the accelerator opening degree sensor 11 and is grasped at a constant or indefinite period by the ECU 100 electrically connected to the accelerator opening degree sensor 11. In general, the smaller the accelerator opening, the smaller the required load, and the larger the accelerator opening, the larger the required load. Since the magnitude of the required load correlates with the magnitude of the required output, in the engine system 10, the engine required output changes according to the accelerator opening degree Ta.

  Although not shown, the engine 200 is provided with an EGR (Exhaust Gas Recirculation) device that recirculates part of the exhaust gas from the exhaust manifold 213 to the intake pipe 204 as EGR gas. The EGR device includes an EGR passage that allows the exhaust manifold 213 and the intake pipe 204 to communicate with each other, an EGR valve that is provided on the EGR passage and can adjust the flow rate of the EGR gas, and an EGR cooler that can cool the EGR gas. The EGR device has a low correlation with the gist of the present invention, and is not shown for the purpose of preventing complication of the page.

<Operation of Embodiment>
Next, details of the impulse valve drive control executed by the ECU 100 will be described as operations of the present embodiment with reference to FIG. FIG. 2 is a flowchart of the impulse valve drive control.

  In FIG. 2, the ECU 100 acquires the driving conditions of the vehicle (step S101). In the present embodiment, the engine speed Ne and the accelerator opening degree Ta are acquired as the operating conditions. When the engine rotation speed Ne and the accelerator opening degree Ta are acquired, it is determined whether or not the acquired operating condition corresponds to the inertial supercharging region (step S102).

  Here, the inertia supercharging region will be described with reference to FIG. FIG. 3 is a schematic diagram of the inertia supercharging region.

  In FIG. 3, the inertia supercharging region is a region corresponding to the hatched region shown in the two-dimensional coordinate system in which the accelerator opening degree Ta and the engine rotational speed Ne are arranged on the vertical axis and the horizontal axis, respectively. More specifically, it is assumed that the range of engine rotation speeds that can be taken by the engine 200 is not less than the minimum rotation speed NeL (which is the minimum rotation speed at which self-rotation is possible) and not more than the maximum rotation speed NeH (which is a so-called rev limit). When the accelerator opening degree Ta changes from 0% (ie, fully closed) to 100% (ie, fully open), the inertial supercharging region is NeL ≦ Ne ≦ Neth (Neth <NeH) and Tath ≦ Ta ≦. Qualitatively speaking, it is a low rotation and high load region.

  The minimum rotation speed NeL is a value of about 800 rpm, for example, and Neth is a judgment reference value, which is a value of about 2000 rpm. Further, Tath is a reference value for the accelerator opening, and is a value that can be used to determine that inertial supercharging is necessary in terms of required load. In other words, in the low load region below the reference value Tath, it is not necessary to increase the intake charge amount from the beginning, so that it is not necessary to execute the inertia supercharging control from the viewpoint of the supercharging effect. .

  Returning to FIG. 2, when the acquired operating condition does not correspond to the inertial supercharging region (step S102: NO), the ECU 100 executes non-inertial supercharging control (step S104). Here, the non-inertial supercharging control refers to control for fixing the opening of the impulse valve 224 to a fully opened opening that is a default value. The driving mode of the impulse valve 224 when the impulse valve 224 is fixed to the fully open position is not particularly limited. For example, the opening degree of the impulse valve 224 when the actuator 225 is not energized is the fully open position of the impulse valve 224. , The impulse valve 224 may be fixed at the fully open position by simply stopping the energization of the actuator 225, or the opening of the impulse valve 224 when the actuator 225 is not energized may be fully opened. When the opening is different, the actuator 225 may be appropriately energized so that the impulse valve 224 is maintained and fixed at the fully opened opening.

  On the other hand, when the operating condition corresponds to the inertial supercharging region (step S102: YES), the ECU 100 executes inertial supercharging control (step S103).

  Here, the inertia supercharging control refers to a series of controls for generating intake air pulsation by opening and closing the impulse valve 224 and improving the charging efficiency of the intake air by inertia supercharging. The outline is roughly as follows. Become.

  That is, for one cylinder 202 (for example, the first cylinder), the impulse valve is used before the start of the intake stroke (that is, preferably at the end of the intake stroke of another cylinder (for example, the second cylinder)) or at the beginning of the intake stroke. When the valve 224 is closed, since the impulse valve 224 is closed, the pipe pressure of the communication pipe 206 becomes negative as the piston of the cylinder 202 descends, and is maintained at atmospheric pressure or higher by atmospheric pressure or supercharging. The pressure difference with the pipe internal pressure of the intake pipe 204 increases. When the impulse valve 224 is opened in a state where the negative pressure is sufficiently formed in the communication pipe 206 in this manner (that is, the valve is opened in a valve opening period after the valve opening timing of the intake valve 207), the intake pipe 204 is opened. And the inside of the corresponding cylinder 202 (that is, the first cylinder in this case) communicate with each other, and the intake air flows into the combustion chamber inside the cylinder 202 at once as the intake air via the impulse valve 224.

  On the other hand, the communication pipe 206 is a so-called open end at the communication part with the combustion chamber, and the positive pressure wave caused by the inflow of the intake air into the combustion chamber is reflected by the combustion chamber, so that the phase is inverted. It becomes a pressure wave. The negative pressure wave reaches the surge tank 223 sequentially through the communication pipe 206 and the impulse valve 224, and reaches the combustion chamber again as a positive pressure wave whose phase is inverted by reflection at the open end at the open hole. When the peak of the positive pressure wave reaches the combustion chamber (or to the intake valve 207) (not necessarily limited to that point in time, but includes that point as long as the charging efficiency of the intake can be improved to some extent) The valve opening timing of the impulse valve 224 may be such that the positive pressure wave reaches the combustion chamber by closing the intake valve 207 or at the timing when the intake valve 207 is closed. By controlling this, the pressure in the combustion chamber rises, and the charging efficiency of the intake air is improved. Inertia supercharging using the impulse valve 224 is executed in this way.

  When executing the inertia supercharging control according to step S107, the ECU 100 increases the intake charging efficiency as much as possible for each vehicle operating condition in advance experimentally, empirically, theoretically, or based on simulation or the like. The actuator 225 is controlled so that the impulse valve 224 opens and closes with an opening / closing characteristic determined to be able to be controlled. At this time, since the amount of intake air taken into the cylinder 202 changes, the fuel injection amount is corrected to maintain the air-fuel ratio at a predetermined value. When correcting the fuel injection amount, the fuel injection amount correction amount mapped in advance in association with the vehicle operating conditions and the opening / closing timing of the impulse valve 224 (related to the improvement in the charging efficiency of intake air by inertia supercharging) The reference fuel injection amount is appropriately increased and corrected. For this reason, when the inertia supercharging control is executed, the emission does not deteriorate.

  The ECU 100 executes supercharging control that controls supercharging by the turbocharger in parallel with the control of the impulse valve 224 described above. Here, the details of the supercharging control will be described with reference to FIG. FIG. 4 is a flowchart of the supercharging control. In the figure, the same reference numerals are given to the same portions as those in FIG. 2, and the description thereof is omitted as appropriate.

  In FIG. 4, the ECU 100 acquires an intake air amount Ga, a supercharging pressure Pin, and an atmospheric pressure P0 as vehicle operating conditions (step S201). Subsequently, the ECU 100 acquires the surge limit intake air amount Gasg (step S202), and determines whether or not the intake air amount Ga acquired in step S201 is less than the surge limit intake air amount Gasg (step S203).

  Here, the surge limit intake air amount Gasg will be described with reference to FIG. FIG. 5 is a schematic diagram of the surge limit line Sg1 that defines the surge limit intake air amount Gasg.

  In FIG. 5, the front and rear intake pressure ratio Rpin and the intake air amount Ga are shown on the vertical axis and the horizontal axis, respectively. Here, the front / rear intake pressure Rpin is a ratio of the supercharging pressure Pin to the atmospheric pressure P0 (that is, Rpin = Pin / P0), and “the intake pressure between the upstream side and the downstream side of the compressor” according to the present invention. This is an example of the “front-rear intake pressure ratio”. The compressor 218 is sufficiently charged by the compressor surge when the front-rear intake pressure ratio Rpin is in the illustrated surge region SG1 (that is, an example of the “compressor surge region” according to the present invention, the illustrated hatched region). It becomes difficult.

  Here, the surge limit line Sg1 is a line that defines the boundary between the surge region SG1 and the other region, and is higher than the surge limit line Sg1 (the side on which Rpin is higher) when compared with the same intake air amount Ga. However, if compared with the same front-rear intake pressure ratio Rpin, the left side (light load side) of the surge limit line Sg1 is the surge region SG1. In any case, the surge limit line Sg1 defines a value corresponding to the surge limit. The ECU 100 previously stores a surge limit map that can be referred to by numerically expressing the surge limit line Sg1 shown in FIG.

  Returning to FIG. 4, the ECU 100 determines, from the surge limit map, one intake air amount corresponding to the front / rear intake pressure ratio Rpin calculated from the boost pressure Pin and the atmospheric pressure P0 acquired in step S201 on the surge limit line Sg1. The value of Ga is selected and acquired as the surge limit intake air amount Gasg. Since the surge limit line Sg1 is a boundary line between the surge region SG1 and other regions, in step S202, instead of the surge limit intake air amount Gasg, the intake air amount Ga acquired in step S201 It is also possible to obtain the corresponding surge pressure ratio Rpinsg before and after the surge limit.

  When the intake air amount Ga is equal to or greater than the surge limit intake air amount Gasg (step S203: NO), the front-rear intake pressure ratio Rpin does not exist in the surge region SG1, and thus the ECU 100 returns the process to step S201. At this time, normal supercharging control is executed. In the normal supercharging control, a target supercharging pressure for setting the actual load of the engine 200 to follow a required load represented by the accelerator opening degree Ta or the like is set so that the supercharging pressure Pin becomes the target supercharging pressure. In addition, the compressor bypass valve 227 is appropriately controlled. When engine 200 includes a waste gate valve, VN, or the like instead of or in addition to compressor bypass valve 227, the supercharging pressure may be converged to the target supercharging pressure by cooperative control with these. . Alternatively, when the turbocharger adopts a kind of MAT configuration that can control the compressor rotation speed by motor assist or the like, the supercharging pressure control may be executed more finely.

  On the other hand, when the intake air amount Ga is less than the surge limit intake air amount Gasg (step S203: YES), the ECU 100 calculates an average supercharging pressure Pinave (step S204). Here, the average supercharging pressure Pinave is an average value of the pressure of the communication pipe 206 that decreases at least by executing the above-described inertia supercharging control, and “the average intake pressure on the downstream side of the compressor” according to the present invention. It is an example. In the inertia supercharging control, as described above, intake pulsation is generated, and the pulsation wave is synchronized with the closing timing of the intake valve to improve the intake charging efficiency. For this reason, the total amount of intake air in the communication pipe 206 and the intake pipe 204 communicating therewith decreases, and the intake pressure Pin decreases.

  The ECU 100 holds an average supercharging pressure map in which the engine speed Ne, the supercharging pressure Pin, and the average supercharging pressure Pinave are associated with each other in advance. The average supercharging pressure Pinave is calculated by selecting one value corresponding to the supercharging pressure Pin and the engine speed Ne (Note that “calculation” refers to a mode of selectively acquiring from the map in this way. Included). However, even if this type of map is not provided, the average supercharging pressure Pinave may be calculated as a result of an appropriately performed numerical calculation process when an appropriate algorithm or arithmetic expression is provided. .

  When the average boost pressure Pinave is calculated, the ECU 100 can derive from the average boost pressure Pinave, the surge limit boost pressure Pinsg corresponding to the intake air amount Ga and the atmospheric pressure P0 (that is, the surge limit line Sg1 described above). If the average boost pressure Pinave is larger, the compressor bypass valve 227 is controlled so that the boost pressure is reduced by an amount corresponding to the deviation, and the boost pressure Pin is set to Decrease (step S205). Further, in step S204, when the average boost pressure Pinave is equal to or less than the surge limit boost pressure Pinsg, the front / rear intake pressure ratio Rpin can be released out of the surge region SG1 only by the inertia boost, step S205 is Skipped.

  When the adjustment of the supercharging pressure Pin is completed, the ECU 100 executes the above-described inertia supercharging control (step S103). When the inertia supercharging control is executed, the process returns to step S201, and a series of processes is repeated. The supercharging control is executed in this way.

  In this case, the control according to step S103 is an example of the operation of “determining the opening / closing characteristics of the intake control valve”, but in this embodiment, the boost pressure adjustment by the compressor bypass valve 227 is possible. By adjusting the supercharging pressure, the supercharging pressure Pin after inertia supercharging can be maintained in the vicinity of the surge limit pressure Pinsg, so that the opening / closing drive of the impulse valve 224 specialized for avoiding the compressor surge is The structure is not made. Of course, an opening / closing characteristic of the impulse valve 224 specialized for avoiding this type of compressor surge may be set (that is, the inertia supercharging has different effects such as reduction of the supercharging pressure Pin and improvement of the charging efficiency of the intake air). However, the effect of the present invention is guaranteed as long as the effect is combined, regardless of the magnitude of the effect.If the main purpose is to avoid the compressor surge, the reduction effect of the supercharging pressure improves the charging efficiency of the intake air. In order to give priority to the effect (in the impulse valve drive control illustrated in FIG. 2, the inertial supercharging is the main purpose, which is the opposite), the switching characteristics can be separately defined).

  Here, the effect of the supercharging control will be described with reference to FIG. FIG. 6 is a schematic diagram for explaining the relationship between the intake air intake amount Ga and the front / rear intake pressure ratio Rpin in the process of supercharging control. In the figure, the same reference numerals are given to the same parts as those in FIG. 5, and the description thereof is omitted as appropriate.

  In FIG. 6, the operating point of the compressor 218 at a certain time (assuming that the operating point here is one coordinate point on the coordinate plane defined by the intake air amount Ga and the front / rear intake pressure ratio Rpin). The operating point m1 shown in the drawing (that is, the intake air amount Ga1 and the front / rear intake pressure ratio Rpin1). In this case, the operating point m1 is in the region of the surge region SG1. For this reason, the ECU 100 executes inertial supercharging control while appropriately reducing the supercharging pressure Pin (as described above, it may not always be necessary).

  By executing the inertia supercharging control, the intake air amount at least in the intake pipe 204 and the communication pipe 206 is reduced, and the supercharging pressure Pin is reduced. As a result, the front-rear intake pressure ratio Rpin decreases from the previous Rpin1 to Rpin2 (Rpin2 <Rpin1) and reaches outside the surge region SG1. On the other hand, as the intake air amount decreases, the intake air amount Ga increases and increases from the previous intake air amount Ga1 to the intake air amount Ga2 (Ga1 <Ga2). As a result, the operating point of the compressor 218 changes to the illustrated operating point m2 (front / rear intake pressure ratio Rpin2, intake air amount Ga2).

As described above, according to the supercharging control according to the present embodiment, when the operating point of the compressor 218 reaches the surge region, the inertial supercharging control with the opening / closing of the impulse valve 224 is performed and the supercharging pressure is appropriately set. By accompanying the decrease control, it is possible to quickly avoid the compressor surge. At this time, since the supercharging pressure Pin is lowered by pushing the intake air into the cylinder by inertia supercharging, the avoidance of the compressor surge is realized without sacrificing the supercharging effect or after improving the supercharging effect. can do. At this time, if the decrease in the supercharging pressure Pin is accompanied by an increase in the intake air amount Ga (see the operating point m2 in the drawing, it is possible to avoid the compressor surge sufficiently without the increase in the intake air amount Ga. In other words, both the decrease in the front-to-rear intake pressure ratio Rpin and the increase in the intake air amount Ga both change to the side where the compressor surge is avoided. .
Second Embodiment
Next, the supercharging control according to the second embodiment of the present invention will be described with reference to FIG. FIG. 7 is a flowchart of the supercharging control according to the second embodiment. In the figure, the same reference numerals are given to the same portions as those in FIG. 4, and the description thereof will be omitted as appropriate.

  In FIG. 7, when the intake air amount Ga is less than the surge limit intake air amount Gasg (step S203: YES), the ECU 100 calculates the maximum supercharging pressure Pinmax (step S301).

  Here, the maximum supercharging pressure Pinmax is the maximum value of the pressure of the communication pipe 206 which is at least lowered by executing the above-described inertia supercharging control, and according to the present invention “reach the compressor on the downstream side of the compressor”. It is an example of “peak pressure of intake pulsation wave”. In the inertia supercharging control, as described above, intake pulsation is generated, and the pulsation wave is synchronized with the closing timing of the intake valve to improve the intake charging efficiency. For this reason, the total amount of intake air in the communication pipe 206 and the intake pipe 204 communicating therewith decreases, and the intake pressure Pin decreases. At this time, since the intake air is a pulsating wave, the intake pressure Pin also has a maximum value and a minimum value.

  The ECU 100 holds in advance a maximum boost pressure map in which the engine speed Ne, the boost pressure Pin, and the maximum boost pressure Pinmax are associated with each other. In step S204, the ECU 100 determines the current value from the maximum boost pressure map. By selecting one value corresponding to the supercharging pressure Pin and the engine speed Ne, the maximum supercharging pressure Pinmax is calculated. However, even if this type of map is not provided, the maximum supercharging pressure Pinmax may be calculated as a result of an appropriately performed numerical calculation process when an appropriate algorithm or arithmetic expression is provided. .

  When the maximum boost pressure Pinmax is calculated, the ECU 100 can derive from the maximum boost pressure Pinmax and the surge limit boost pressure Pinsg corresponding to the intake air amount Ga and the atmospheric pressure P0 (that is, the surge limit line Sg1 described above). If the maximum boost pressure Pinmax is larger, the compressor bypass valve 227 is controlled so that the boost pressure is reduced by an amount corresponding to the deviation, and the boost pressure Pin is set to Decrease (step S205). In step S204, when the maximum boost pressure Pinmax is equal to or less than the surge limit boost pressure Pinsg, the front / rear intake pressure ratio Rpin can be released out of the surge region SG1 only by the inertia boost. Skipped.

  As described above, according to the second embodiment, in consideration of the fluctuation (that is, pulsation) of the supercharging pressure Pin, which is a particular problem when avoiding a compressor surge due to inertial supercharging, supercharging is performed by inertial supercharging. When the pressure Pin is lowered, the supercharging pressure Pin is adjusted so that the maximum supercharging pressure Pinmax, which is the peak pressure of the pulsation, does not exceed the surge limit pressure Pinsg. For this reason, the filtration supply pressure Pin does not exceed the surge limit pressure Pinmax instantaneously, and a compressor surge can be reliably avoided.

  The engine 200 is provided with a surge tank 223 and an intercooler 222. These hold a sufficient volume compared to the intake pipe 204, and in particular, the surge tank 223 is given a relatively large volume so that it can function as a phase inversion means during inertia supercharging. Yes. For this reason, even if these are simply provided, they can function as an example of the “peak pressure reducing means” according to the present invention. Remarkably, a situation in which the pulsation wave of the intake air generated in the communication pipe 206 reaches the compressor 218. Is unlikely to occur.

Therefore, when the physical shapes, volumes, and the like of the surge tank 223 and the intercooler 222 are determined in advance so that they can function as this kind of peak pressure reducing means, the first embodiment is preferably used. The compressor surge can be surely prevented by the supercharging control based on the average supercharging pressure as illustrated.
<Third Embodiment>
Next, the supercharging control according to the third embodiment of the present invention will be described with reference to FIG. FIG. 8 is a flowchart of the supercharging control according to the third embodiment. In the figure, the same reference numerals are given to the same portions as those in FIG. 4, and the description thereof will be omitted as appropriate.

  In FIG. 8, the ECU 100 obtains the engine rotational speed Ne and the target torque Ttag as the vehicle operating conditions (step S401). Here, the target torque Tetag is selectively acquired from the map based on the engine speed Ne and the accelerator opening degree Ta. When the target torque Tetag is acquired, the ECU 100 acquires the surge limit torque Tesg (step S402), and determines whether the target torque Ttag acquired in step S401 is larger than the surge limit torque Tesg (step S402). S403).

  Here, the surge limit torque Tesg will be described with reference to FIG. FIG. 9 is a schematic diagram of the surge limit line Sg2 that defines the surge limit torque Tesg. In the figure, the same reference numerals are given to the same parts as those in FIG. 5, and the description thereof is omitted as appropriate.

  In FIG. 9, the vertical axis and the horizontal axis represent the engine torque Te and the engine rotational speed Ne, respectively. Here, when the engine torque Te is in the illustrated surge region SG2 (that is, an example of the “compressor surge region” according to the present invention), the compressor 218 becomes difficult to be sufficiently charged by the compressor surge.

  Here, the surge limit line Sg2 is a line that defines the boundary between the surge region SG2 and other regions, and the upper side (high torque side) above the surge limit line Sg2 when compared with the same engine speed Ne. If compared with the same engine torque, the left side (low rotation side) of the surge limit line Sg2 is the surge region SG2. In any case, the surge limit line Sg2 defines a value corresponding to the surge limit. The ECU 100 previously stores a surge limit map that can be referred to by numerically expressing the surge limit line Sg2 shown in FIG.

  Returning to FIG. 8, the ECU 100 selects one engine torque Te value corresponding to the engine rotational speed Ne acquired in step S401 on the surge limit line Sg2 from the surge limit map, and sets it as the surge limit torque Tesg. get. Since the surge limit line Sg2 is a boundary line between the surge region SG2 and the other region, the surge corresponding to the target torque Ttag acquired in step S401 is substituted for the surge limit torque Tesg in step S402. It is also possible to acquire the limit engine speed Nesg.

  When the target torque Tetag is larger than the surge limit torque Tesg (step S403: YES), the ECU 100 executes avoidance of compressor surge with a supercharging effect by inertia supercharging control as in the first embodiment (ie, , Steps S204, S205 and S103). If the target torque Tetag is equal to or less than the surge limit torque Tesg (step S403: NO), the process returns to step S401.

  That is, in this embodiment, it is determined whether or not a compressor surge occurs based on the relationship between the engine torque Te and the engine rotational speed Ne instead of the relationship between the intake air amount Ga and the front / rear intake pressure ratio Rpin. Also in this case, since the physical characteristics of the engine 200 do not change, the opening / closing characteristics of the impulse valve 224 according to the present invention are determined such that the front / rear intake pressure ratio is outside a predetermined compressor surge region. There is no.

Here, in particular, according to the present embodiment, the target torque Tetag is used when determining whether or not a compressor surge occurs. The target torque Tetag is only a target value, and is a near-future engine torque value. Therefore, when the determination in step S403 branches to the “YES” side, there is a high possibility that the compressor surge has not yet occurred. That is, according to this embodiment, by predicting whether or not a compressor surge will occur in the near future, the compressor surge can be avoided without actually causing the compressor 218 to generate a compressor surge. Remarkably effective.
<Fourth embodiment>
Next, the supercharging control according to the fourth embodiment of the present invention will be described with reference to FIG. FIG. 10 is a flowchart of the supercharging control according to the fourth embodiment. In the figure, the same reference numerals are given to the same portions as those in FIG. 4, and the description thereof will be omitted as appropriate.

  In FIG. 10, the ECU 100 acquires the above-described average supercharging pressure Pinave and in-cycle supercharging pressure deviation ΔPin as the vehicle operating conditions (step S501). Here, the in-cycle supercharging pressure deviation ΔPin is a deviation between the maximum value and the minimum value of the supercharging pressure Pin in the intake stroke.

  Subsequently, the ECU 100 calculates the pressure fluctuation value DP (step S502). The pressure fluctuation value DP is obtained by dividing the in-cycle supercharging pressure deviation ΔPin acquired in step S501 by the average supercharging pressure Pinave. After calculating the pressure fluctuation value DP, the ECU 100 determines whether or not the calculated pressure fluctuation value DP is larger than the reference value DPth (step S503).

  When the pressure fluctuation value DP is larger than the reference value DPth (step S503: YES), the ECU 100 executes compressor surge avoidance control based on the determination that the compressor surge has occurred. When the pressure fluctuation value DP is equal to or less than the reference value DPth (step S503: NO), the ECU 100 returns the process to step S501.

When a compressor surge occurs, a pressure fluctuation peculiar to the compressor surge occurs (characteristics differ from the pressure fluctuation of inertia supercharging). Therefore, whether or not the compressor surge occurs based on the pressure fluctuation value DP in this way. Can be determined.
<Fifth Embodiment>
Next, with reference to FIG. 11, the supercharging control according to the fifth embodiment of the present invention will be described. FIG. 11 is a flowchart of the supercharging control according to the fifth embodiment. In the figure, the same reference numerals are given to the same portions as those in FIG. 8, and the description thereof will be omitted as appropriate.

  In FIG. 11, when the target torque Tetag is larger than the surge limit torque Tesg (step S403: YES), the ECU 100 determines the unit time of the engine speed Ne based on the value of the engine speed Ne acquired in step S401. A rotation change speed ΔNe representing the amount of change per win is calculated, and it is determined whether or not the rotation change speed ΔNe is less than a reference value ΔNeth (step S601). At this time, if the rotation change speed ΔNe is less than the reference value Neth (step S601: YES), compressor surge avoidance control is executed. If the rotation change speed ΔNe is equal to or higher than the reference value Neth (step S601: NO), the process returns to step S401.

  That is, according to this embodiment, when the change speed of the engine rotational speed Ne is high (for example, when accelerating at a low gear stage), the operating point of the compressor 218 deviates from the surge region at an early stage. Do not perform compressor surge avoidance control. For this reason, the compressor surge avoidance with the supercharging effect is executed only in the case where the deterioration of the power performance of the vehicle due to the compressor surge is not negligible, and the finite number for driving the impulse valve 224 is limited. It is possible to efficiently use the drive energy (here, the power resource supplied from the battery), which is useful in practice.

  In the various embodiments described above, the supercharging pressure Pin and the atmospheric pressure P0 are detected as examples of the “intake pressure on the downstream side of the compressor” and the “intake pressure on the upstream side of the compressor” according to the present invention, respectively. However, instead of or in addition to these, the longitudinal pressure of the compressor 218 closer to the compressor 218 may be detected. Since the compressor surge is a phenomenon that occurs in the compressor 218, it is possible to reliably avoid the compressor surge by executing various controls based on the front-rear pressure of the compressor 218 in this way.

  The present invention is not limited to the above-described embodiments, and can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification. The control device is also included in the technical scope of the present invention.

1 is a schematic configuration diagram conceptually showing a configuration of an engine system according to a first embodiment of the present invention. 2 is a flowchart of impulse valve drive control executed by an ECU in the engine system of FIG. 1. It is a schematic diagram of the inertial supercharging area | region referred in control of FIG. 2 is a flowchart of supercharging control executed by an ECU in the engine system of FIG. It is a schematic diagram of a surge limit line Sg1 that defines the surge limit intake air amount Gasg. FIG. 6 is a schematic diagram illustrating a relationship between an intake air intake amount Ga and a front / rear intake pressure ratio Rpin in the execution process of the supercharging control of FIG. 5. It is a flowchart of the supercharging control which concerns on 2nd Embodiment of this invention. It is a flowchart of the supercharging control which concerns on 3rd Embodiment of this invention. It is a schematic diagram of a surge limit line Sg2 that defines the surge limit torque Tesg. It is a flowchart of the supercharging control which concerns on 4th Embodiment of this invention. It is a flowchart of the supercharging control which concerns on 5th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine system, 100 ... ECU, 200 ... Engine, 202 ... Cylinder, 204 ... Intake pipe, 205 ... Throttle valve, 206 ... Communication pipe, 207 ... Intake valve, 216 ... Turbine, 218 ... Compressor, 222 ... Intercooler, 223 ... Surge tank, 224 ... Impulse valve, 225 ... Actuator, 226 ... Compressor bypass passage, 227 ... Compressor bypass valve, 228 ... Supercharging pressure sensor.

Claims (6)

A plurality of cylinders, an intake passage communicating with the plurality of cylinders, a supercharger having a compressor in the intake passage, and a downstream side of the compressor in the intake passage and driven to open and close by being opened and closed. An intake control device for an internal combustion engine comprising an intake control valve configured to enable inertial supercharging using
Determining means for determining an opening / closing characteristic of the intake control valve so that a front-rear intake pressure ratio, which is a ratio of intake pressure between the upstream side and the downstream side of the compressor, is outside a predetermined compressor surge region due to the inertia supercharging;
An intake control device for an internal combustion engine, comprising: a control unit that controls the intake control valve based on the determined opening / closing characteristic. Comprising a determining means for determining whether the front-rear intake pressure ratio corresponds to the compressor surge region;
The control unit controls the intake control valve based on the determined opening / closing characteristic when it is determined that the front / rear intake pressure ratio corresponds to the compressor surge region. Intake control device for internal combustion engine. The intake control device for an internal combustion engine according to claim 1 or 2, wherein the pressure on the downstream side of the compressor is an average intake pressure on the downstream side of the compressor. The intake control device for an internal combustion engine according to claim 1 or 2, wherein the pressure on the downstream side of the compressor is a peak pressure of an intake pulsation wave that reaches the compressor on the downstream side of the compressor. The intake control device for an internal combustion engine according to claim 4, wherein the internal combustion engine further includes a peak pressure reducing unit that is capable of reducing at least a peak pressure of the intake pulsation wave and is different from the intake control valve. . The peak pressure reducing means is a cooling means installed to cool intake air downstream of the compressor in the intake passage, an intake throttle valve installed downstream of the compressor in the intake passage, and the compressor in the intake passage. At least a part of a surge tank installed downstream of the compressor, a resonator installed downstream of the compressor in the intake passage, and a supercharging pressure adjusting means capable of adjusting the supercharging pressure of the supercharger. An intake control device for an internal combustion engine according to claim 5.

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