JP2011256743A - Device for control of supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably prevent a surge accompanied by a rapid accelerator-off operation from taking place in a supercharger having a compressor provided with a movable vane mechanism in a diffuser.SOLUTION: The supercharger control device (100) is provided for controlling the supercharger (300) provided with a compressor (340) in a suction passage (205) of an internal combustion engine (200) as a one of the driving sources of a vehicle (10), the compressor having movable vanes (343) capable of adjusting the airflow rate according to the opening angle thereof. The supercharger control device includes: a controller for controlling the opening angle so that the operation point of the supercharger falls within a certain operation permitted area which does not correspond to a surge area and an overspeed area; and a permitter for permitting, as the opening angle, an opening angle that allows the operation point to fall within the overspeed area when the vehicle in a rapid deceleration.

Description

  The present invention controls a supercharger that controls a supercharger having a compressor such as a VGC (Variable Geometry Compressor) having a movable vane capable of adjusting an air flow rate in accordance with an opening degree in a diffuser section. It relates to the technical field of equipment.

  As this type of supercharger, there is a supercharging device disclosed in Patent Document 1. According to the supercharging device disclosed in Patent Document 1, it is possible to improve the compressor efficiency by controlling the guide impeller provided in the diffuser portion so as to be able to protrude and retract according to the operating state of the engine. It is said that.

  Further, Patent Document 2 discloses a problem that the flow rate of air passing through the compressor decreases prior to a decrease in the pressure ratio of the compressor when the vehicle is decelerated due to a sudden accelerator off. Patent Document 2 discloses a technique for prohibiting the closing control in such a case in order to prevent a reduction in the passing air flow rate caused by the closing control of the movable vane on the turbine side in such a case. .

JP-A-8-254127 JP 2009-156197 A

  As described above, when the accelerator is turned off suddenly, the compressor air flow rate decreases before the pressure ratio decreases, so the operating point of the turbocharger exceeds the surge limit line as a transient phenomenon, and the surge region May rush into.

  On the other hand, if the vane opening of the movable vane mechanism provided in the diffuser section is changed to the closing side, the surge limit line changes to the low flow rate side. Thus, if the vane opening degree is sequentially shifted to the closing side, it is possible to prevent the compressor surge in such a surge region at first glance.

  However, in a transient phenomenon such as an abrupt accelerator-off operation, the amount of decrease in the air flow rate is large. Therefore, in the so-called follow-up vane opening control performed according to the transition of the operating point, the time for the compressor to operate in the surge region is set. There is concern that it will be too long to ignore. In other words, the technique disclosed in Patent Document 1 cannot sufficiently cope with this kind of transient phenomenon, and it is difficult to accurately prevent a surge of the compressor. Further, the technique disclosed in Patent Document 2 prevents a situation in which a decrease in the air flow rate is promoted by controlling the movable vane on the turbine side. It does not solve.

  Here, in order to avoid such a problem, it is possible to predictively shift the vane opening to the closing side according to detection of this kind of accelerator-off operation by a kind of feedforward control.

  However, when the vane opening degree is shifted to the closing side, the upper limit value of the rotational speed allowed for the supercharger is also lowered in synchronization with the change of the surge limit line described above. Even if the vane opening is changed predictably, the value that can be selected as the vane opening is a value within the operating range defined by the surge limit line and the upper limit of the rotation speed. For the accelerator-off operation that occurs at the opening, the upper limit value of the rotational speed naturally inevitably limits the change of the vane opening to the closing side, and it is not always possible to prevent the occurrence of compressor surge. .

  That is, in the category of conventional technical ideas including those disclosed in Patent Documents 1 and 2, there is a technical problem that it is difficult to sufficiently prevent the occurrence of a compressor surge against a sudden accelerator-off operation. is there.

  The present invention has been made in view of the above-described problems, and in a supercharger having a compressor having a movable vane mechanism in a diffuser portion, it is possible to reliably prevent the occurrence of a surge due to a sudden accelerator-off operation. It is an object of the present invention to provide a control device for a supercharger capable of performing the above.

  In order to solve the above-described problems, a control device for a supercharger according to the present invention provides an internal combustion engine having a compressor having a movable vane capable of adjusting an air flow rate according to an opening degree as a power source of a vehicle. A supercharger control device for controlling a supercharger provided in an intake passage, wherein the operating point of the supercharger is within a predetermined operation permission region not corresponding to a surge region and an overspeed region. Control means for controlling the opening, and permission means for permitting the opening at which the operating point becomes the over-rotation region as the opening when the vehicle is in a sudden deceleration state. .

  A supercharger according to the present invention includes a compressor in an intake passage of an internal combustion engine, and converts a part of kinetic energy of fluid (here, intake air compressed by a compressor impeller) into pressure energy in the compressor. A diffuser portion as a possible rectifying means is provided with a plurality of movable vanes (which are blade-like members) as commutators. Needless to say, the movable vane may be provided with various opening / closing mechanisms for opening / closing the movable vane and various driving devices for applying driving force to the various opening / closing mechanisms.

  Here, the movable vane is variable in a range in which the opening degree that defines the flow path area of the fluid in the diffuser portion is set in advance, and the air flow rate in the compressor can be changed according to the opening degree. The “opening degree” means the degree of opening and closing, and the reference value is free in the opening and closing range. However, in the present invention, for the purpose of avoiding confusion, the size of the opening corresponds to the size of the flow path area.

  The supercharger according to the present invention is preferably provided with exhaust heat recovery means such as a turbine for converting a part of the heat energy of the exhaust heat into kinetic energy in the exhaust passage of the internal combustion engine. The recovery means and the compressor are configured to be coaxially rotatable. That is, the supercharger according to the present invention is preferably a so-called turbocharger. Further, as a preferred form of the exhaust heat recovery means, the exhaust heat recovery means inlet side exhaust passage is changed in the flow passage area of the exhaust passage according to the opening degree in the same manner as the compressor side movable vane. What is called a VNT (Variable Nozzle Turbine) provided with the nozzle vane as a movable vane to obtain may be sufficient.

  The supercharger control device according to the present invention is a device for controlling such a supercharger, for example, one or a plurality of CPUs (Central Processing Units), MPUs (Micro Processing Units), various processors, or various types. Various processing such as a single or multiple ECUs (Electronic Controlled Units), which may appropriately include various storage means such as a controller or ROM (Read Only Memory), RAM (Random Access Memory), buffer memory or flash memory Various computer systems such as a unit, various controllers or a microcomputer device may be used.

  According to the present invention, the opening degree of the movable vane that can change the air flow rate of the compressor is controlled by the control means. Here, the opening degree of the movable vane defines the surge limit and rotation limit (substantially, that is, the choke limit) of the compressor or the operation efficiency of the compressor. The opening degree of the movable vane is controlled so that the operating point of the supercharger is within the operation permission region defined by the surge limit and the rotation limit.

  The “operation permission region” means a region that does not correspond to a surge region as a region where a surge occurs or an over-rotation region as a region where the rotational speed is higher than the allowable upper limit rotational speed. At this time, the opening degree of the movable vane may be controlled so that the operating point of the supercharger further increases the efficiency of the compressor as much as possible within this operation permission region, as a preferred embodiment. The “operating point of the supercharger” means one operating condition of the supercharger that is defined by a preset state quantity. As this kind of state quantity, for example, a value corresponding to the air flow rate of the compressor Further, a supercharging pressure equivalent value or the like is preferably used.

  By the way, when the vehicle is in a decelerating state, the air flow rate of the compressor decreases, and the operating point of the supercharger moves at least roughly to the surge limit side.

  Here, at the time of sudden deceleration, which can include, for example, a case where the reduction rate of the accelerator opening is equal to or greater than a predetermined value or the brake pedal depression amount is equal to or greater than a predetermined value, on the other hand, the air flow rate decreases The rate is large, and on the other hand, there is often no significant change in supercharging pressure. Therefore, in view of the relationship between the air flow equivalent value and the supercharging pressure equivalent value and the surge limit, the time delay until the operating point enters the surge region is not at least sufficiently large, and the supercharging that changes rapidly. Depending on the operating point of the vessel, it may be necessary to quickly and accurately change the opening of the movable vane.

  However, when there is a restriction on the opening degree setting related to the above-described operation permission region, there is a possibility that the optimum opening degree setting is hindered. In other words, whether the opening of the movable vane follows the change in the operating point, or the change in the opening follows the predictive operating point change, the opening of the movable vane is only the current operating point from the operation permission area. It must be set so that it does not deviate, and the current operating point will work for a truly effective movable vane opening (in other words, an opening that does not deviate from the surge limit to the surge limit). A situation may occur in which the permitted area deviates to the over-rotation area side. In other words, it is difficult to effectively follow the change in the opening to the operating point that changes suddenly in the change in the opening that occurs in such a limited range, and as a result, the opening control is a kind of follow-up control. Inevitably, the operating point of the supercharger often deviates to the surge region side.

  In particular, in the region on the high rotation / high load side, the maximum efficiency region of the compressor is close to the surge limit, and therefore this type of deviation of the operating point toward the surge region is more difficult to avoid. On the other hand, if an attempt is made to secure a positional margin of the operating point with respect to the surge limit in order to acquire a time delay until the operating point deviates to the surge region side, the efficient operation of the compressor is hindered from the beginning. Thus, if no countermeasure is taken, a compressor having this type of movable vane cannot eliminate the possibility of a surge occurring in the compressor when the vehicle is suddenly decelerated.

  In that regard, in the supercharger control device according to the present invention, a suitable solution to the problem is given by the action of the permission means. That is, the permitting unit permits the opening at which the operating point of the supercharger is in the over-rotation region as the opening of the movable vane when the vehicle is in a sudden deceleration state.

  When the restriction on the rotational speed side is removed in this way, the opening degree of the movable vane has only to be defined by the operating point of the supercharger and the surge limit of the compressor, so at least the surge continues for a long time that cannot be ignored. Is prevented. Ideally, the occurrence of a surge can be prevented.

  Here, if the opening degree of the movable vane whose operating point at that time is in the over-rotation region continues permanently, choke (flow path blockage) occurs in the supercharger, causing a sudden drop in the supercharging pressure. However, if the vehicle is in a sudden deceleration state, a sudden decrease in the air flow rate is already secured, and even if the operating point of the supercharger is temporarily located in this type of overspeed region, As time passes, the operating point converges within the operation permitted area. In other words, the sudden deceleration state is defined as a state in which a reduction rate of the air flow rate that is large enough to allow the operating point to stay in the over-rotation region in practical operation is obtained. .

  Thus, according to the supercharger control device of the present invention, on the other hand, the surge to the surge region side is not manifested while the demerit caused by the operating point of the supercharger staying in the overspeed region is not obvious. The effect of not deviating from the limit makes it possible to suitably prevent the surge of the compressor.

  That is, the present invention focuses on the point that the operating point of the supercharger tends to approach the surge limit and move away from the rotation limit when the vehicle is in a sudden deceleration state. A technical idea that gives priority to surge prevention and gives a greater degree of freedom compared to the prior art has achieved a practically beneficial effect of reliably preventing surges in the compressor.

  In one aspect of the supercharger control device according to the present invention, the operating point is defined by an air flow rate equivalent value of the compressor and a supercharging pressure equivalent value of the supercharger.

  According to this aspect, the operating point of the supercharger is defined by the air flow equivalent value of the compressor and the supercharging pressure equivalent value of the supercharger. These are suitable as state quantities that define the operating state of the supercharger.

  Here, the “air flow equivalent value” is a concept that includes physical amounts, control amounts, index values, etc. corresponding to the compressor air flow and one-to-one, one-to-many, many-to-one and many-to-many, preferably It means the air flow rate at the compressor inlet. In practice, the air flow rate at the compressor inlet may be an intake air amount detected by an air flow meter or the like. In addition, the “supercharging pressure equivalent value” is a concept that includes a physical quantity, a control amount, an index value, and the like corresponding to a supercharging pressure and one-to-one, one-to-many, many-to-one, and many-to-many. It means a pressure ratio or the like that is a ratio between the intake pressure on the compressor inlet side and the intake pressure on the outlet side. In practice, the intake pressure on the compressor inlet side may be the atmospheric pressure, and the intake pressure on the outlet side may be the pressure of the intake manifold (in manifold pressure).

  In another aspect of the supercharger control device according to the present invention, the supercharger control device further comprises prediction means for predicting a time transition of the operating point when the vehicle is in the sudden deceleration state, and the control means includes the prediction The opening degree is controlled based on the time transition.

  According to this aspect, since the time transition of the operating point is predicted by the predicting means, and the opening degree of the movable vane is controlled based on the predicted time transition, the opening degree of the movable vane is set to the actual operating point. Can be accurately followed. As a result, even when the high efficiency region of the compressor is located near the surge limit, it is possible to operate the compressor as efficiently as possible while preventing the occurrence of surge, which is extremely useful in practice. is there.

  Here, the prediction method of the time transition of the operating point according to the prediction means is not limited to a unique one, and may have various aspects. For example, the prediction means may predict the time transition based on the actual operating point change, the engine speed of the internal combustion engine, the throttle opening, or the like. Further, when the internal combustion engine is provided with EGR (Exhaust Gas Recirculation), the time transition may be predicted based on the EGR flow rate or the EGR valve opening degree.

  The “time transition of the operating point” may be more practically an operating point after a predetermined time has elapsed.

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

1 is a schematic configuration diagram conceptually illustrating a configuration of a vehicle according to an embodiment of the present invention. It is a schematic front view of the diffuser vane shown in FIG. 2 is a flowchart of VGC drive control executed by an ECU in the vehicle of FIG. It is a figure which illustrates the relationship between the air flow rate and pressure ratio in the turbocharger shown by FIG. FIG. 4 is a conceptual diagram of a VGC opening for sudden deceleration in the VGC drive control of FIG. 3. FIG. 4 is a diagram illustrating an hourly transition of the air flow rate at the time of sudden deceleration, related to the effect of the VGC drive control of FIG. 3. FIG. 4 is a diagram illustrating a one-hour transition of a rotational speed margin in relation to the effect of the VGC drive control of FIG. 3.

<Embodiment of the Invention>
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
<Configuration of Embodiment>
First, the configuration of the vehicle 10 according to an 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 vehicle 10.

  In FIG. 1, a vehicle 10 is an example of a “vehicle” according to the present invention, and includes an ECU 100, an engine 200, a turbocharger 300, and an EGR device 400.

  The ECU 100 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 operations of the engine 200, the turbocharger 300, and the EGR device 400. The unit is an example of the “supercharger control device” according to the present invention. The ECU 100 is configured to be able to execute VGC drive control to 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 “control means”, “permission means”, and “estimation means” 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 the units includes a plurality of CPUs, MPUs (Micro Processing Units), ECUs, various types. It may be configured as a processing unit, various controllers, various computer systems, or the like.

  The engine 200 is an in-line four-cylinder gasoline engine that is an example of an “internal combustion engine” according to the present invention that uses gasoline 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 with a cylinder block 201. The fuel gasoline is injected into the intake port, and is sucked into the cylinder as an air-fuel mixture mixed with air in the intake stroke. Inside this cylinder, the intake air is ignited by the ignition control of the ignition device in the compression stroke, and burns in the combustion chamber.

  Combustion energy accompanying this combustion is converted into kinetic energy by driving a crankshaft (not shown) through a piston and a connecting rod (not shown). The rotation of the crankshaft is transmitted to the drive wheels of the vehicle 10 so that the vehicle 10 can travel.

  In the present invention, the term “internal combustion engine” is a concept that encompasses an engine that can convert combustion energy of fuel into kinetic energy and take it out as power, for example, fuel type, fuel combustion mode, and number of cylinders. Practical aspects such as the cylinder arrangement, ignition mode, fuel supply mode, valve system configuration, intake / exhaust system configuration, etc. are not limited to those of the engine 200.

  Exhaust gas discharged from each cylinder in the exhaust stroke is collected in the exhaust manifold 203 and guided to an exhaust pipe 204 connected to the exhaust manifold 203. Here, the vehicle 10 includes a turbocharger 300, and the exhaust gas guided to the exhaust pipe 204 supplies thermal energy to a turbine blade 312 (to be described later) of the turbocharger 300, and then the downstream side. The structure is guided to a catalyst device (not shown). Details of the turbocharger 300 will be described later.

  On the other hand, air is sucked into the upstream intake pipe 205 from the outside through an air cleaner (not shown). This intake air is compressed by the rotation of a compressor impeller 342 (to be described later) that constitutes the turbocharger 300, and is supplied to the downstream intake pipe 206 installed on the downstream side of the compressor 340. Is supplied to an intercooler 207 installed in The intercooler 207 is a cooling device for improving the supercharging efficiency by cooling the compressed intake air.

  A throttle valve 208 is installed on the downstream side of the intercooler 207 in the downstream side intake pipe 206. The throttle valve 208 is a valve that adjusts intake air according to the open / close state, and is configured to be controlled by an actuator electrically connected to the ECU 100. That is, the throttle valve 208 forms a part of a so-called electronically controlled throttle device.

  The downstream side intake pipe 206 is connected to the intake manifold 209 on the downstream side of the throttle valve 208. The intake manifold 209 is connected to an intake port corresponding to each cylinder formed in the cylinder block 201. The intake air guided to the intake manifold 209 is mixed with the gasoline injected in a mist form at the intake port, and as described above, the intake air is sucked into the cylinder when the intake valve (not shown) in each cylinder is opened. The

  An air flow meter 210 is installed in the upstream side intake pipe 205. The air flow meter 210 is a sensor capable of detecting an air flow rate Qc that is an amount of intake air sucked from the outside. The air flow meter 210 is electrically connected to the ECU 100, and the detected air flow rate Qc is referred to by the ECU 100 at a constant or indefinite period.

  The air flow rate Qc is an example of a “compressor air flow rate equivalent value” according to the present invention.

  A first pressure sensor 211 is installed in the upstream side intake pipe 205. The first pressure sensor 211 is a sensor configured to be able to detect the pressure of the intake air in the upstream side intake pipe 205, that is, the compressor inlet pressure P0. The first pressure sensor 211 is electrically connected to the ECU 100, and the detected compressor inlet pressure P0 is appropriately referred to by the ECU 100. The compressor inlet pressure P0 is substantially equal to the atmospheric pressure.

  A second pressure sensor 212 is installed in the downstream side intake pipe 206. The second pressure sensor 212 is a sensor configured to be able to detect the pressure of intake air in the downstream side intake pipe 206, that is, the compressor outlet pressure P3. The second pressure sensor 212 is electrically connected to the ECU 100, and the detected compressor outlet pressure P3 is appropriately referred to by the ECU 100. The compressor outlet pressure P3 is substantially equal to the supercharging pressure.

  The vehicle 10 is configured such that a pressure ratio Rp (Rp = P3 / P0), which is a ratio between the compressor inlet pressure P0 and the compressor outlet pressure P3, is constantly calculated and grasped by the ECU 100.

  The turbocharger 300 recovers exhaust heat, rotationally drives the turbine blade 312, and supercharges the intake air to an atmospheric pressure or higher using the fluid compression action of the compressor impeller 342 that rotates integrally with the turbine blade 312. It is an example of a possible “supercharger” according to the present invention.

  The turbocharger 300 includes a VNT (Variable Nozzle Turbine: variable nozzle turbine) 310, a VNT actuator 320, a turbo rotating shaft 330, a VGC (variable geometry compressor) 340, and a VGC actuator 350.

  The VNT 310 includes a turbine housing 311, a turbine blade 312, and a nozzle vane 313.

  The turbine housing 311 is a housing that houses the turbine blade 312 and the nozzle vane 313.

  The turbine blade 312 is a rotary impeller configured to be rotatable around the turbo rotation shaft 330 by the pressure of exhaust gas (that is, exhaust pressure) guided to the exhaust pipe 204. As a material of the rotary impeller, for example, a metal such as ceramic or aluminum can be used. However, the material of the rotary impeller is not limited to these.

  The nozzle vanes 313 are blade-like members that are installed at equal intervals so as to surround the turbine blade 312 in the exhaust inlet portion corresponding to the exhaust inlet to the turbine blade 312 in the turbine housing 311. Each of these nozzle vanes 313 can be rotated at the same time within the exhaust inlet portion about a predetermined rotation axis by a link type rotation mechanism (not shown), and the exhaust pipe 204 and the turbine blade 312 are opened and closed according to the open / close state thereof. It is possible to change the communication area (the flow area of the exhaust flow path defined by the nozzle vanes). The communication area is minimum when the nozzle vane 313 is in a fully closed state, and is maximum when the nozzle vane 313 is in a fully open state.

  Here, since the flow velocity of the exhaust increases as the communication area decreases, the turbine blade 312 is efficiently driven by controlling the nozzle vane 313 to the closed side in a light load region where the displacement is relatively small. It becomes possible.

  The VNT actuator (VNTA) 320 is a hydraulic or electric type capable of applying a driving force for simultaneously rotating the nozzle vanes 313 to the links provided in the above-described link-type rotation mechanism for rotating the nozzle vanes 313. Actuator. The hydraulic control unit in the VNT actuator 320 is electrically connected to the ECU 100, and the open / close state of the nozzle vane 313 is controlled by the ECU 100 according to the operating conditions of the engine 200.

  In addition, the control aspect of the nozzle vane 313 may be a well-known thing, The detail is abbreviate | omitted here. However, qualitatively, the nozzle vane 313 is controlled to the closed side in the light load region as described above, and the exhaust gas regulating action by the nozzle vane 313 is not necessary in the high load region, so that an increase in engine back pressure is avoided. Therefore, the nozzle vane 313 is controlled to the opening side.

  The turbo rotating shaft 330 is a rotating shaft body that connects the turbine blade 312 and a compressor impeller 342 described later. The compressor impeller 342 and the turbine blade 312 rotate substantially integrally because they are configured to be connected to each other by the turbo rotating shaft 330.

  The VGC 340 includes a compressor housing 341, a compressor impeller 342, a diffuser vane 343, and a diffuser 344.

  The compressor housing 341 is a housing that houses the compressor impeller 342, the diffuser vane 343, and the diffuser 344.

  The compressor impeller 342 is configured so that air sucked into the upstream side intake pipe 205 from the outside through an air cleaner can be pumped and supplied to the downstream side intake pipe 206 by the pressure generated by the rotation accompanying the rotation of the turbine blade 312. The so-called supercharging is realized by the effect of pumping the intake air by the compressor impeller 342.

  A plurality of diffuser vanes 343 are installed at equal intervals so as to surround the compressor impeller 342 in a diffuser 344 that takes out pressure energy by adjusting the flow velocity of the intake air supplied via the compressor impeller 342 in the compressor housing 341. It is a blade-shaped member which is an example of the “movable vane” according to the invention.

  Each of the diffuser vanes 343 can be rotated at the same time in the diffuser 344 around a predetermined rotation axis by a link type rotation mechanism (not shown) (similar to the nozzle vanes of the VNT), and can be opened and closed. The flow area of the intake air in the diffuser 344 can be changed according to the state.

  The VGC actuator (VGCA) 350 is a known actuator that can apply a driving force that promotes the rotation of the diffuser vane 343 to each link of the link type rotation mechanism. The VGC actuator 350 is electrically connected to the ECU 100 and its operation is controlled by the ECU 100.

  Here, the configuration of the diffuser vane 343 will be described with reference to FIG. FIG. 2 is a schematic front view of the compressor impeller 342 viewed from the compressor impeller 342 toward the upstream intake passage 205. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

  In FIG. 2, a plurality of diffuser vanes 343 are disposed on the outer periphery of the compressor impeller 342. The diffuser vane 343 is configured to be rotatable within the diffuser 344.

  FIG. 2A shows the case where the diffuser vane 342 is at the reference position. The reference position is a position where the flow path area of the intake air defined by the diffuser vane 343 is minimized, and corresponds to a position where the VGC opening degree Avgc, which is the opening degree of the diffuser vane 342, becomes Avggc = 0.

  On the other hand, FIG. 2B shows a state in which the diffuser vane 343 is rotated at the rotation angle α (see the arrow) from the reference position (Avgc = 0). In a state of rotating with respect to the reference position, basically, the larger the rotation angle α, the larger the flow area of the intake air defined by the diffuser vane 361.

  If the communication area of the flow path is reduced, the flow rate of the intake air is increased. Therefore, in a light load region where the supercharging effect is relatively small, by controlling the diffuser vane 343 to the closed side (reference position side), the supercharging is performed. Efficiency can be improved. On the other hand, if supercharging is performed while the rotation angle of the diffuser vane 343 is kept constant, the air flow rate Qc reaches the choke flow rate, and there is a high possibility that choking will occur when the air flow rate further increases.

  Therefore, the diffuser vane 343 moves to the opening side in a stepwise manner, that is, the side where the rotation angle increases with the shift from the light load operation to the high load operation (generally, it is unambiguous with the rise of the compressor outlet pressure P3). Drive controlled. The rotation angle α of the diffuser vane 343 is detected by a rotation angle sensor (not shown) and can be referred to as appropriate by the ECU 100 electrically connected to the rotation angle sensor. Supplementally, the rotation angle α is expressed as a VGC opening degree Avgc that is normalized by setting the fully closed position corresponding to α = 0 to Avgc = 0 (%) and the fully open position corresponding to α = αmax to Avgc = 100 (%). Be grasped.

  The VGC opening degree Avgc is configured such that the ECU 100 that controls the operating state of the VGC 340 always recognizes the VGC opening degree Avgc in association with the control state of the VGCA 350.

  A choke flow rate determined in accordance with the pressure ratio Rp at that time defines a rotation limit line Nlim_i (i is an identifier), which will be described later, for one VGC opening Angc. The rotation limit line Nlim_i, that is, when the operating point shifts to the air flow rate increase side in the turbocharger 300, basically the operating point does not exceed the rotation limit line.

  Returning to FIG. 1, the EGR device 400 includes an EGR pipe 410, an EGR valve 420, and an EGR cooler 430.

  The EGR pipe 410 is a tubular member having one end connected to the exhaust pipe 204 and the other end connected to the downstream intake pipe 206.

  The EGR valve 420 is an electromagnetic opening / closing valve installed in the EGR pipe 410, and the opening degree of the EGR valve 420 is a fully closed opening degree that blocks communication between the exhaust pipe 204 and the downstream side intake pipe 206 via the EGR pipe 410. It is the structure controlled continuously between the full opening degree which communicates almost completely. The EGR valve 420 is electrically connected to the ECU 100, and the EGR valve opening degree is controlled by the ECU 100.

  The EGR cooler 430 is a cooling device that cools EGR gas (that is, exhaust gas) supplied to the EGR pipe 410.

  According to the EGR device 400, when the EGR valve 420 is opened and the intake valve is opened (that is, when negative pressure is formed), a part of the exhaust gas can be recirculated into the cylinder as EGR gas from the exhaust pipe 204. it can.

The vehicle 10 includes an accelerator pedal sensor and a brake pedal sensor (not shown). The accelerator pedal sensor is a sensor configured to be able to detect an accelerator opening degree Ta that is an operation amount of an accelerator pedal (not shown). The brake pedal sensor is a sensor configured to be able to detect a brake pedal depression amount Tb, which is an operation amount of a brake pedal (not shown). The accelerator opening degree Ta and the brake pedal depression amount Tb detected by each of these sensors are appropriately referred to by the ECU 100 electrically connected thereto.
<Operation of Embodiment>
Next, details of VGC drive control executed by the ECU 100 will be described as operations of the present embodiment.

  First, the flow of the VGC drive control process will be described with reference to FIG. FIG. 3 is a flowchart of the VGC drive control.

  In FIG. 3, the ECU 100 identifies the operating point of the turbocharger 300 (step S101). Here, in the present embodiment, the operating point of the turbocharger 300 is defined based on the air flow rate Qc and the pressure ratio Rp.

  Here, the operating point of the turbocharger 300 will be described with reference to FIG. FIG. 4 is a diagram conceptually illustrating the relationship between the air flow rate Qc and the pressure ratio Rp (Rp = P3 / P0) in the turbocharger 300.

  In FIG. 4, the horizontal axis represents the air flow rate Qc, and the vertical axis represents the pressure ratio Rp. The operating point of the turbocharger 300 corresponds to one coordinate point of this two-dimensional coordinate plane. That is, when the air flow rate Qc and the pressure ratio Rp are determined, the operating point is uniquely specified.

  On the other hand, FIG. 4 shows a surge limit line Sglim and a rotation limit line Nlim corresponding to two types of VGC opening of the diffuser vane 343 for convenience.

  That is, the surge limit line Sglim_L (see the broken line) and the rotation limit line Nlim_L (see the solid line) corresponding to the relatively small (ie, close side) VGC opening degree AvgcL and the relatively large (ie, open side) VGC They are a surge limit line Sglim_H (see the broken line) and a rotation limit line Nlim_H (see the solid line) corresponding to the opening degree AvgcH.

  Note that the diffuser vane 343 has a configuration in which the VGC opening degree Avgc can continuously change. In the coordinate space of FIG. 4, a large number of surge limit lines Sglim_i originally corresponding to a large number of VGC opening degrees Avgc. It goes without saying that the rotation limit line Nlim_i can also be defined.

  The surge limit line Sglim is a characteristic line that defines the surge limit of the VGC 340 constituting the turbocharger 300. The surge limit line Sglim is a region on the small air flow rate side (left side in the figure) or the high pressure ratio side ( It means that the upper region in the figure is a surge region. In the surge region, a surge as a resonance phenomenon occurs in the compressor impeller 342, and the turbocharging efficiency of the turbocharger 300 is extremely lowered. Further, when a surge occurs, a large physical load is applied to the turbocharger 300, which is not desirable.

  The rotation limit line Nlim is a characteristic line that defines the limit of the rotation speed allowed for the VGC 340. The rotation limit line Nlim is a characteristic line on the large air flow rate side (right side in the figure) and the high pressure ratio side (upper side in the figure). ) Means that the compressor impeller 342 falls into an overspeed state. In the process of changing the operating point from the light load side (left side in the figure) to the high load side (right side in the figure), when the VGC opening degree Avgc is constant, the operating point intersects the rotation limit line Nlim_i and beyond. When the load increases, choke is generated in the VGC 340, and the operating point drastically falls to the low pressure ratio side along the rotation limit line Nlim_i. Therefore, when the operating point changes in the direction in which the air flow rate is increased, the fact that the VGC 340 is in the over-rotation state and the generation of choke can be handled almost uniquely.

  As described above, for one VGC opening degree Avgc, an operation permission region sandwiched between the surge limit line Sglim and the rotation limit line Nlim is defined. The ROM of the ECU 100 holds a normal VGC opening map obtained by quantifying the surge limit line Sglim and the rotation limit line Nlim for each VGC opening Avgc illustrated in FIG. 4, and determines the VGC opening Avgc. In this case, the configuration is referred to as appropriate.

  Further, in this operation permission region, the operation efficiency of the VGC 340 is not constant, and so-called iso-efficiency lines (not shown) can be defined. In particular, the high efficiency region in one operation permission region is closer to the surge limit line Sglim than the rotation limit line Nlim. For example, if the current operating point of the turbocharger 300 is the illustrated operating point MH (see the black circle) corresponding to the air flow rate Qc1 and the pressure ratio Rp1, the VGC opening degree Avgc at which this operating point MH has the highest efficiency. As the VGC opening degree AvgcH is selected. Since an operating point that is too close to the surge limit line becomes a factor that destabilizes the operation of the VGC 340, the VGC opening degree Avgc is not necessarily determined so that the current operating point has the highest efficiency of the VGC 340. You don't have to. That is, between the surge limit line and the operating point, a so-called surge margin, for example, a margin of about 10% may be provided.

  Returning to FIG. 3, in step S101, the ECU 100 specifies the operating point of the turbocharger 300 based on the air flow rate Qc and the pressure ratio Rp, and sets the specified operating point based on the normal VGC opening degree map. On the other hand, an appropriate VGC opening degree Avgc is determined (step S102), and the VGC 340 is driven and controlled so that the determined VGC opening degree Avgc is obtained (step S103).

  The “appropriate VGC opening” according to the present embodiment is a VGC opening at which the operating point of the turbocharger 300 at that time is within the operation permission region, and the surge margin described above. This means the VGC opening that allows the VGC 340 to operate as efficiently as possible.

  Next, the ECU 100 determines whether or not the vehicle 10 is in a sudden deceleration state (step S104). Here, the sudden deceleration state is defined as a state in which the rate of decrease in the accelerator opening degree Ta is equal to or greater than a predetermined value, or the increase rate of the brake pedal depression amount Tb is equal to or greater than a predetermined value. When not in the sudden deceleration state (step S104: NO), the ECU 100 returns the process to step S101 and continues the appropriate VGC opening degree control according to the operating point of the turbocharger 300.

  On the other hand, when the vehicle 10 is in the rapid deceleration state (step S104: YES), the ECU 100 determines an operating point predicted value that means an operating point of the turbocharger 300 after a predetermined time has elapsed (step S105).

  Here, the predicted operating point is a reference value such as the time transition of the operating point so far, the engine speed of the engine 200, the throttle opening (detected by a throttle opening sensor not shown), and the EGR valve opening. Based on the above, a time transition of the operating point of the turbocharger 300 is predicted, and an operating point predicted value is determined as an operating point that is considered to arrive after a predetermined time. The operation according to step S105 is an example of the operation of the “prediction means” according to the present invention.

  When the predicted operating point is determined, the ECU 100 determines the VGC opening Avgcbrrk for rapid deceleration (step S106), and drives and controls the VGC 340 so that the VGC opening Avgc becomes the determined VGC opening Avgcbrk. (Step S107).

  Subsequently, the ECU 100 determines whether or not the sudden deceleration state has been resolved (step S108). If the sudden deceleration state has not been resolved (step S108: NO), the process returns to step S105 to predict the predicted operating point. If the rapid deceleration state is resolved (step S108: YES), the process returns to step S101 and the series of processes is repeated. The VGC drive control is executed as described above.

  Here, the VGC opening Avgcbrk for sudden deceleration will be described with reference to FIG. FIG. 5 is a diagram for explaining the concept of the sudden deceleration VGC opening degree Avgcbrk. 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. 5, in addition to the two sets of surge limit line Sglim and rotation limit line Nlim corresponding to the two types of VGC opening illustrated in FIG. 4, Avgc1 (AvgcL <Avgc1) corresponding to the opening between them. Two sets of surge and rotation limit lines are shown for <AvgcH) and Avgc2 (Avgc1 <Avgc2 <AvgcH). That is, the surge limit line Sglim_1 and the rotation limit line Nlim_1 corresponding to the VGC opening degree Avgc = Avgc1, and the surge limit line Sglim_2 and the rotation limit line Nlim_2 corresponding to the VGC opening degree Avgc = Avgc2.

  Here, it is assumed that the vehicle 10 suddenly decelerates in a situation where the operating point is the illustrated operating point MH. In the sudden deceleration state, the pressure ratio Rp is almost unchanged transiently, while the air flow rate Qc decreases rapidly, so that the predicted time transition of the operating point remains at Rp = Rp1, for example, as shown in the figure. The air flow rate changes as illustrated by a chain line in the order of QcH → Qc2 → Qc1 → QcL.

  In FIG. 5, for easy understanding, it is assumed that the optimum VGC opening corresponding to the operating point M1 and the operating point M2 is Avgc1 and Avgc2, respectively. That is, it is assumed that the VGC opening corresponding to the operating point M1 is Avgc1 and the VGC opening corresponding to the operating point M2 is Avgc2 on the normal VGC opening map described above.

  Here, if the operating point predicted in step S105 of FIG. 3, that is, the operating point after the elapse of a predetermined time, is the operating point M2, the VGC opening Avgcbrk for rapid deceleration is Avgc2, and the degree of rapid deceleration If the operating point after the elapse of a predetermined time is the operating point M1, the rapid deceleration VGC opening degree Avgcbrk becomes Avgc1. These are VGC opening degrees that can be accommodated in the operation permission region for the operation point MH that is the current operation point, and there is no practical problem.

  However, when an operating point change steeper than these is predicted, that is, when the predicted operating point after a predetermined time has elapsed is the operating point ML, AvgcL is set as the VGC opening according to the normal VGC opening map. Even if an attempt is made to select, the current operating point MH deviates from the rotation limit line Nlim_L defining the operation permission region corresponding to the VGC opening degree AvgcL to the over-rotation region side. For this reason, unless any countermeasure is taken, the interlock logic for preventing choke acts and this VGC opening degree AvgcL is excluded from the selection target.

  On the other hand, the “sudden deceleration VGC opening” according to the present embodiment foreseen that such a problem may occur, and the operation permission for the transient VGC opening control at the time of sudden deceleration. The restriction on the rotation limit line side related to the region is released (that is, an example of the operation of the “permission means” according to the present invention).

  In other words, at the time of sudden deceleration, it is obvious that the air flow rate Qc decreases after the start even if the VGC opening degree control is ahead. Therefore, regarding the temporary period that can occur transiently, assuming that the compressor impeller 342 falls into an overspeed state, the overspeed state naturally associated with the decrease in the air flow rate Qc is resolved without taking any special measures. It is. In other words, during such sudden deceleration, the over-rotation state, which is obvious to disappear naturally, is continued as long as the operating point is not placed on the higher load side than the surge limit line by the VGC opening degree control. There is no reasonable reason to prioritize surges or treat them equally.

  Due to the restriction release measure on the rotation limit side based on such a reason, in the present embodiment, for example, even when an extreme change in operating point from the operating point MH to the operating point ML is predicted, it is promptly performed. Thus, the VGC opening that can accommodate the operating point ML within the operation permission region can be selected as the VGC opening Avgcbrk for rapid deceleration. Therefore, even during sudden deceleration as a transition period, a good operation of the turbocharger 300 can be maintained without causing a surge in the VGC 340.

  Further, in view of the fact that the restriction on the rotation limit side is released as described above, the optimum VGC opening degree considering the operation efficiency of the compressor is selected for the predicted operation point without worrying about the occurrence of the surge. be able to. Therefore, the overall operating efficiency of the turbocharger 300 can be increased, which is practically beneficial from the viewpoint of fuel consumption.

  Next, the effect of this embodiment will be described visually with reference to FIG. Here, FIG. 6 is a diagram illustrating an hourly transition of the air flow rate Qc during rapid deceleration.

  In FIG. 6, the vertical axis and the horizontal axis represent the air flow rate Qc and the time, respectively.

  In FIG. 6, the solid line is the transition of the actual air flow rate Qc at the time of sudden deceleration, and the thin broken line is the transition of the surge limit flow rate corresponding to the VGC opening instruction value when the control according to the present embodiment is applied. The thin chain line is a transition of the surge limit flow rate corresponding to the VGC opening instruction value when the control according to the present embodiment is not applied as a comparative example.

  When the control according to the present embodiment is applied, it is not necessary to consider the limitation due to the rotation limit line. Therefore, at time T1 when it is determined that the vehicle is in the rapid deceleration state, the surge limit flow rate is changed from Qc1 to Qc2. If the actual air flow rate continues to decrease, the surge limit flow rate is further lowered from Qc2 to Qc3 at time T2 (see the white circle M4 in the drawing).

  As a result, the actual surge limit flow rate with respect to the VGC opening indication value when the control according to the present embodiment is applied (see the thick broken line in the figure) is constantly lower than the actual air flow rate (solid line), and during sudden deceleration In this case, the air flow rate Qc is prevented from deviating from the surge limit line to the surge region side. In other words, the turbocharger 300 can be stably operated.

  On the other hand, when the control according to the present embodiment is not applied, since there is a limitation due to the rotation limit line, it is necessary to control the VGC instruction value in small steps with a small step width (see white circles M5, M6, and M7 in the drawing). The actual surge limit flow rate with respect to the value (refer to the thick chain line in the figure) becomes slow with respect to time change. As a result, the actual air flow rate falls below the surge limit flow rate in most time regions during sudden deceleration as a transition period, and the turbocharger 300 is forced to move in the surge region almost constantly. As a result, undesired situations continue in terms of supercharging efficiency, durability, and fuel consumption.

  Finally, with reference to FIG. 7, the presence or absence of the restriction | limiting by a rotation limit line is demonstrated visually. FIG. 7 is a diagram illustrating a one-hour transition of the rotational speed margin during sudden deceleration. The rotation speed margin is the rotation speed defined by the rotation limit line and the allowable upper limit rotation speed corresponding to the operation point of the turbocharger 300 (the rotation speed at which the operation point is a component point of the rotation limit line). Deviation.

  In FIG. 7, the vertical axis and the horizontal axis represent the rotational speed margin Nmg and time, respectively.

  Here, when there is a limitation by the rotation limit line according to the present embodiment, the allowable upper limit rotation speed corresponding to the operating point does not exceed the rotation speed defined by the rotation limit line. Take a positive value (theoretically it can be zero, but in practice there is some margin).

  On the other hand, when the restriction release measure by the rotation limit line according to the present embodiment is taken, the allowable upper limit rotation speed corresponding to the operating point is temporarily allowed to exceed the rotation speed defined by the rotation limit line. For this reason, the rotational speed margin Nmg deviates to the negative region. However, at the time of sudden deceleration, the air flow rate Qc decreases, so the operating point naturally moves to the light load side, that is, the side that reduces the allowable upper limit rotational speed corresponding to the operating point, and eventually the rotational speed margin Nmg. The time domain in which takes a negative value is negligible in practice. Therefore, even if the limitation by the rotation limit line is released, the possibility of suffering a practical disadvantage is extremely low.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit or idea 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.

  The present invention can be applied to control of a supercharger including a compressor having a vane mechanism for adjusting an air flow rate on the intake side.

  DESCRIPTION OF SYMBOLS 10 ... Vehicle, 100 ... ECU, 200 ... Engine, 202 ... Cylinder, 204 ... Exhaust pipe, 205 ... Upstream intake pipe, 310 ... VNT, 340 ... VGC, 343 ... Diffuser vane, 344 ... Diffuser.

Claims (3)

A supercharger control device that controls a supercharger provided with a compressor having a movable vane capable of adjusting an air flow rate in accordance with an opening degree in a diffuser section in an intake passage of an internal combustion engine as a power source of a vehicle. And
Control means for controlling the opening so that the operating point of the supercharger is within a predetermined operation permission region not corresponding to the surge region and the over-rotation region;
A supercharger control device comprising: permission means for permitting an opening at which the operating point is in the over-rotation region as the opening when the vehicle is in a sudden deceleration state. 2. The supercharger control device according to claim 1, wherein the operating point is defined by an air flow rate equivalent value of the compressor and a supercharge pressure equivalent value of the supercharger. Further comprising prediction means for predicting a time transition of the operating point when the vehicle is in the sudden deceleration state;
The supercharger control device according to claim 1, wherein the control unit controls the opening degree based on the predicted time transition.

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