JP4412216B2 - Engine control apparatus and control method - Google Patents

Description

  The present invention relates to an engine control apparatus and control method, and more particularly to an engine control apparatus and control method capable of increasing the amount of air flowing into a cylinder by an intake control valve provided in an intake passage.

  An intake control valve that can close the intake passage and can be opened and closed in synchronization with the opening and closing of the intake valve is provided in the intake passage on the upstream side of the intake valve, and the intake control valve is opened instantly during the intake stroke. It is known that a larger amount of intake air is charged into a cylinder by utilizing the inertia supercharging effect or the pressure pulsation of the intake air (see, for example, Patent Document 1). Since the intake control valve can be opened and closed within one intake stroke, such supercharging can be started at the same time that the accelerator pedal is depressed, and is more responsive than turbocharging that waits for the start of the turbine. It is suitable for eliminating the acceleration delay. Further, since the intake air amount can be increased as compared with the case of natural intake, the maximum generated torque of the engine can be increased.

JP 2000-248946 A

  By the way, in the engine control, the amount of air flowing into the cylinder is estimated for each cylinder cycle, and the fuel injection amount, the fuel injection timing, the ignition timing, etc. may be set based on the estimated air amount. In this case, the air amount is estimated based on the detected value of the intake air flow rate detected by the air flow meter and the detected value of the intake pressure sensor.

  However, when the intake control valve as described above is employed, the amount of inflow air changes for each intake cycle in accordance with the operation timing of the intake control valve. Therefore, in the method using the detection value of the air flow meter or the intake pressure sensor, It is impossible to follow the change in the air amount for each cycle, and as a result, the air amount cannot be measured accurately. In other words, the method using the detection value of the air flow meter or the intake pressure sensor can only estimate the average amount of air flowing into the cylinder, and the fluctuation when there is a change in the air amount in units of the intake cycle is Cannot be estimated. Further, in the method using the detected value of the air flow meter or the intake pressure sensor, it is impossible to follow the change in the average flow rate when the intake control valve changes from the non-operating state to the operating state or vice versa.

  In a variable valve system that can arbitrarily set the opening / closing timing of the intake valve, the air amount can be estimated if the port pressure at the time when the intake valve of each cylinder is closed can be estimated. However, in the system using the intake control valve as described above, the port section becomes subsonic and the pressure change is rapid, and the intake air temperature changes. It is very difficult to estimate by the same, and even if it can be estimated, the air quantity obtained as a result must be inaccurate.

  Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide an engine control device and a control method capable of accurately estimating the amount of air flowing into the cylinder when the intake control valve is operated. There is to do.

  In order to achieve the above object, an engine control apparatus according to an aspect of the present invention is provided in an intake passage upstream of an intake valve, can close the intake passage, and is synchronized with opening and closing of the intake valve. An intake control valve that can be opened and closed, an intake control valve control means that opens the intake control valve during the intake stroke and then closes it, a valve opening timing of the intake control valve, and a valve closing of the intake control valve The amount of air that estimates the amount of air that flows into the cylinder after the intake control valve is opened based on the timing or valve opening period and the pressure on the downstream side of the intake control valve at the opening timing of the intake control valve And an estimation means.

  As a result of diligent research, the present inventors have determined that the intake control valve opening timing, the intake control valve closing timing or valve opening period, the intake control valve opening timing, and the downstream pressure of the intake control valve Thus, it has been found that the amount of air flowing into the cylinder when the intake control valve is opened can be estimated. In general, when trying to increase the amount of inflow air, the pressure on the downstream side of the intake control valve is lowered (the differential pressure on the upstream and downstream sides of the intake control valve increases and the flow velocity at the time of valve opening increases), and therefore the valve opening timing It is effective to delay the valve (for the same reason) or to take an appropriate valve opening period (close the valve immediately before the air flows backward). This embodiment of the present invention has been made based on the knowledge of the present inventors, and the amount of air flowing into the cylinder is accurately estimated by estimating the amount of air based on these three parameters. It becomes possible.

  Here, the air amount estimation means may determine the opening timing of the intake control valve and the closing timing or opening period of the intake control valve based on the operating state of the engine.

  Preferably, the air amount estimation means estimates the air amount according to a map using the valve opening timing, the valve opening period, and the pressure as parameters.

  Preferably, the apparatus further comprises pressure detection means for detecting a pressure downstream of the intake control valve, and the air amount estimation means is a pressure value detected by the pressure detection means at the opening timing of the intake control valve, or The pressure value estimated from the detected pressure value is defined as the pressure.

  Preferably, the apparatus further includes a control amount determining unit that determines a control amount based on the air amount estimated by the air amount estimating unit. This control amount is, for example, at least one of a fuel injection amount, a fuel injection timing, and an ignition timing.

  Preferably, the intake control valve control means includes an average pressure upstream of the intake control valve in the intake passage between the intake control valve and the intake valve from the end of the intake stroke to the next intake stroke. The intake control valve is closed so as to maintain different pressures or to maintain a pressure equivalent to the average pressure upstream of the intake control valve.

  According to this, when an overlap is set during the opening period of the intake valve and the exhaust valve, the retained pressure is used to reduce the backflow of the cylinder residual gas, or the cylinder residual gas Can be scavenged into the exhaust system, and the amount of air flowing into the cylinder can be increased.

  Further preferably, based on the held pressure and the pressure on the downstream side of the intake control valve after the intake valve is opened and at a predetermined timing before or after the intake control valve is opened, The apparatus further includes pre-valve air amount estimation means for estimating a pre-valve air amount that flows into the cylinder before the intake control valve is opened.

  The amount of air that flows into the cylinder from the intake passage on the downstream side of the intake control valve before opening the intake control valve is equal to the amount of air that has decreased from the downstream intake passage. Since the volume of the downstream intake passage is geometrically determined and is a known constant value, the change in the air density in the downstream intake passage from before the intake valve opens to before the intake control valve opens, The amount of air before opening can be estimated. The air density ratio before and after the change is correlated with the pressure ratio of the two pressures. Therefore, the air amount before valve opening can be estimated based on the two pressures.

  Preferably, the apparatus further comprises pressure detection means for detecting the pressure downstream of the intake control valve, and the pre-valve air amount estimation means is detected by the pressure detection means at a predetermined time before the intake valve is opened. The pressure value detected by the pressure detection means after the intake valve is opened and at a predetermined timing before or after the intake valve is opened is the downstream pressure value. Pressure. The holding pressure is not limited to the control for holding the pressure of the previous intake stroke.

  Preferably, the control amount is determined based on the sum of the air amount estimated by the air amount estimating means and the air amount before opening estimated by the pre-valve air amount estimating means.

  An engine control method according to another aspect of the present invention includes an intake control valve that can close an intake passage upstream of an intake valve and can be opened and closed in synchronization with the opening and closing of the intake valve. A step of opening the intake control valve in the middle of the intake stroke, and then closing the intake control valve; a timing for opening the intake control valve; a timing for closing or opening the intake control valve; And a step of estimating the amount of air flowing into the cylinder after the intake control valve is opened based on the downstream pressure of the intake control valve at the opening timing of the intake control valve. To do.

  Preferably, the step of closing the intake control valve includes an upstream side of the intake control valve in the intake passage between the intake control valve and the intake valve from the end of the intake stroke to the next intake stroke. Closing the intake control valve so as to maintain a pressure greater than an average pressure, and the held pressure and the opening timing of the intake control valve after opening the intake valve or The method further includes estimating a pre-valve air amount that flows into the cylinder before the intake control valve is opened based on a downstream pressure of the intake control valve at a previous predetermined time.

  Preferably, the method further includes a step of detecting a pressure downstream of the intake control valve.

  According to the present invention, an excellent effect that the amount of air flowing into the cylinder when the intake control valve is operated can be accurately estimated is exhibited.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 schematically shows a configuration of an engine control apparatus according to the present embodiment. In the present embodiment, the engine 1 is a vehicular multi-cylinder gasoline engine (only one cylinder is shown in the figure), and fuel made of gasoline is directly injected from the injector 10 into the combustion chamber 13 in the cylinder 12 and formed thereby. The air-fuel mixture is ignited by the spark plug 14 and exhaust gas is discharged through the exhaust passage 17.

  Thus, the engine is a so-called direct injection type, and can perform the following stratified combustion. That is, the fuel is injected from the injector 10 into the concave portion 40 provided on the top surface portion of the piston 24 while the piston 24 is raised, and the flow of the tumble fuel spray that rolls up along the inner surface of the concave portion 40. In the process of generating the fuel, air and fuel are mixed, and a relatively rich air-fuel mixture layer is formed in the vicinity of the spark plug 14, and a relatively lean air-fuel mixture layer is formed around the rich air-fuel mixture layer. Is done. Thus, the air-fuel mixture is stratified and stratified combustion is realized. According to the stratified combustion, while making the air-fuel ratio of the entire combustion chamber much leaner than the stoichiometric air-fuel ratio, reliable ignition combustion can be ensured and fuel efficiency can be greatly improved. The engine can also perform combustion other than lean combustion, such as stoichiometric combustion in which the air-fuel ratio of the entire combustion chamber is substantially the stoichiometric air-fuel ratio.

  As is known, the intake passage 11 is defined by an intake pipe 47, an intake manifold 43, and an intake port 15 connected in order from the upstream side. The intake manifold 43 has a surge tank 48 as a confluence portion common to each cylinder and a branch pipe 49 for each cylinder. The outlet of the intake port 15 is opened and closed by the intake valve 16. As is known, the exhaust passage 17 is defined by an exhaust port 19, an exhaust manifold 50, a catalyst 18, and an exhaust pipe 51 connected in order from the upstream side. The inlet of the exhaust port 19 is opened and closed by the exhaust valve 20. In the present embodiment, the intake valve 16 and the exhaust valve 20 are mechanically opened and closed at a constant cycle by a camshaft (not shown) that is rotationally driven by the crankshaft 26 at a cycle twice that of the crankshaft 26. The valve opening timing and the valve opening period may be controlled according to the engine operating state by a timing mechanism, an actuator, or the like. In this embodiment, the overlap is set between the valve opening periods of the intake valve 16 and the exhaust valve 20, but this may not be necessary. The catalyst 18 is provided in the middle of the exhaust pipe to remove harmful substances such as CO, HC, NOx in the exhaust gas.

  The intake passage 11 is provided with an air flow meter 21, an intake throttle valve 22, and an intake control valve 23 in order from the upstream side. The air flow meter 21 outputs a signal corresponding to the air flow rate passing through the air flow meter 21 to an electronic control unit (hereinafter referred to as ECU) 100 as a control means. Thus, in the present embodiment, the air flow meter 21 detects the air amount for all the cylinders of the engine. For example, this may be calculated based on the intake pressure detected by the intake pressure sensor 41. Good. The intake throttle valve 22 can be controlled. In this embodiment, the intake throttle valve 22 is electrically operated, and its opening degree is controlled by the ECU 100. The intake control valve 23 will be described in detail later. As described above, the intake control valve 23 is provided on the upstream side of the intake valve 16, and the intake throttle valve 22 is provided on the upstream side of the intake control valve 23. An injector 10 is provided on the downstream side of the intake control valve 23.

  A piston 24 is accommodated in the cylinder 12 so as to reciprocate. The piston 24 is connected to the crankshaft 26 via a connecting rod 25.

  The electrical configuration of the engine control apparatus will be described. In addition to the injector 10, spark plug 14, air flow meter 21, intake throttle valve 22, intake control valve 23, the ECU 100 includes a crank angle sensor 28, an oxygen concentration sensor 29, an accelerator opening sensor 30, a brake switch 31, an intake valve. An atmospheric pressure sensor 41, an intake air temperature sensor 42, and a pressure sensor 55 are connected.

  The injector 10 is opened and closed based on an on / off signal output from the ECU 100, thereby executing and stopping fuel injection. The spark plug 14 emits a spark based on an ignition signal output from the ECU 100. The intake throttle valve 22 is in the form of a butterfly valve, and detects the valve element 37 disposed in the intake passage 11, an electric actuator 38 such as a rotary solenoid that drives the valve element 37, and the opening degree of the valve element 37. Sensor 39. The accelerator opening sensor 30 outputs to the ECU 100 a signal corresponding to the operation amount (depression amount) of the accelerator pedal by the driver.

  The crank angle sensor 28 outputs a pulse signal to the ECU 100 at predetermined angular intervals of the crankshaft 26. Based on this pulse signal, ECU 100 detects the crank angle and calculates the engine rotation speed. The oxygen concentration sensor 29 outputs a signal corresponding to the oxygen concentration in the exhaust gas to the ECU 100. The brake switch 31 outputs to the ECU 100 an on / off signal corresponding to the operation of the brake pedal 44 by the driver. It is on when the brake is activated.

  The intake pressure sensor 41 is provided in the intake passage 11 at a position downstream of the intake throttle valve 22 and upstream of the intake control valve 23 (hereinafter referred to as an “intake manifold passage 11a”). Is referred to as “in-manifold pressure”). The intake air temperature sensor 42 outputs a signal corresponding to the intake air temperature to the ECU 100. The pressure sensor 55 is provided in the intake passage 11 (hereinafter referred to as “port passage 11b”) at a position downstream of the intake control valve 23 and upstream of the intake valve 16, and the pressure at the position (hereinafter referred to as “port passage 11b”). A signal corresponding to “port pressure” is output to the ECU 100. A pressure sensor 55 having a high response is used. In the present embodiment, one intake pressure sensor 41 and one intake temperature sensor 42 are provided in each surge tank 48, and a pressure sensor 55 is provided for each cylinder, more specifically, for each branch pipe 49 of each cylinder.

  The intake control valve 23 is provided for each branch pipe 49 of each cylinder at a position upstream of the pressure sensor 55. The intake control valve 23 includes a valve body 33 disposed in the intake passage 11 (more specifically, the branch pipe 49), and an electric actuator 34 such as a rotary solenoid that drives the valve body 33. A sensor for detecting the opening degree of the valve body 33 may be provided. The intake control valve 23 can close the inside of the intake passage 11. Unlike the intake throttle valve 22 in particular, the intake control valve 23 has a structure in which the intake passage 11 is hermetically closed when the valve is fully closed, and passage of intake air is blocked. On the other hand, the intake throttle valve 22 allows the intake air to pass only by restricting the intake passage 11 to the maximum when fully closed. Further, the electric actuator 34 of the intake control valve 23 can be operated at a much higher speed than the electric actuator 38 of the intake throttle valve 22 and has high responsiveness. Then, the engine can be opened and closed in the order of about 10 ° CA at 2000 rpm. Thereby, the intake control valve 23 can be opened and closed in synchronization with the opening and closing of the intake valve 16. In the present embodiment, the intake control valve 23 is in the form of a butterfly valve, but may be in another form such as a shutter valve.

  The opening degree of the intake control valve 23 is controlled from fully open to fully closed in accordance with an opening signal output from the ECU 100 to the electric actuator 34. The intake control valve 23 is provided for each cylinder. When each cylinder has a plurality of intake passages 11 (branch pipes 49), the intake control valve 23 is provided for each intake passage 11. The plurality of intake control valves 23 provided in this way can be individually controlled for each cylinder and for each intake passage 11.

  In the present embodiment, the intake control valve 23 is controlled in units of individual cylinders, and the opening degree is controlled only when the cylinders are fully opened or fully closed. In the present embodiment, when the intake control valve 23 is “open” or “closed”, it means “fully open” or “fully closed” of the intake control valve 23. Further, “full open” and “fully closed” do not necessarily mean mechanical full open and full close, but mean the degree of restriction to the passing air. For example, in the case of “full open”, mechanical full open Even if not, if there is no decrease in the flow rate of the passing air, it is in a fully open state. In the present embodiment, when the intake control valve 23 is “actuated”, it means that the intake control valve 23 is opened and closed during one cylinder cycle. When the intake control valve 23 is “non-actuated”, it is This means that the control valve 23 is held fully open.

  Next, estimation of the intake air amount that is characteristic in the present embodiment will be described. Each map described below is created in advance through experiments and analysis and stored in the ECU 100.

  First, the change in pressure and air flow rate in the intake stroke when the intake control valve 23 is operated so as to perform the above-described inertia supercharging will be described with reference to FIG. In the figure, the opening degree of the intake control valve 23 when the crank angle advances, the port pressure on the downstream side of the intake control valve, the average value of the intake manifold pressure on the upstream side of the intake control valve (average intake manifold pressure), The transition of the flow rate (g / s) of the inflowing air is shown. CA_Po, CA_Pc, and CA_Pw represent the opening timing, closing timing, and opening period of the intake control valve 23, respectively. These opening timing and closing timing are respectively determined by the ECU 100 to the intake control valve 23. Is expressed as the timing at which is output. These have the relationship CA_Pc = CA_Po + CA_Pw.

  As shown in the figure, before the intake control valve 23 is opened, the port pressure gradually decreases as the piston 24 descends. When the intake control valve 23 is instantaneously opened when the valve opening timing CA_Po is reached, air flows into the cylinder at once due to the differential pressure on the upstream and downstream sides of the intake control valve formed just before the intake control valve 23. Is executed (see part (Ga2)). At this time, the port pressure is higher than the average intake manifold pressure. When the intake control valve 23 and the intake valve 16 are closed in this state, the high pressure is held in the port passage 11b. When the intake valve 16 is opened in the next intake stroke, the air in the port passage 11b flows into the cylinder due to the high pressure and the negative pressure due to the lowering of the piston 24 (see the part (Ga1)). . When there is an overlap as in the present embodiment, this inflowing air scavenges exhaust gas (residual gas) remaining in the cylinder into the exhaust passage 17 and also partially blows out into the exhaust passage 17. Such an effect does not occur when there is no overlap.

  Among these, the intake air amount based on the main air inflow performed after the intake control valve opening in the latter half of the intake stroke is Ga2, and the intake air amount based on the air inflow performed before the intake control valve opening in the initial intake stroke is Ga1. It is. Hereinafter, these Ga2 and Ga1 are referred to as “the air amount after opening” and “the air amount before opening”, respectively. Late air inflow is due to inertial supercharging for increasing air volume, which is the original purpose. In addition, the air inflow is intended to scavenge the residual gas in the cylinder to the exhaust system using the port pressure maintained from the previous intake stroke and increase the amount of air into the cylinder. . Since this initial inflow reaches about 20% of the total, it is also important to accurately estimate this amount.

  Regarding the initial air inflow, the port pressure immediately before opening the intake valve is (i) the port pressure when the intake control valve and intake valve are closed in the latter half of the previous intake stroke, and (ii) immediately before the intake valve is opened from the previous intake stroke. (Iii) In-cylinder pressure when the intake valve is opened, etc. In (i) and (ii), measurement and estimation of changes over time are very difficult and cannot be measured with a normal sensor. Regarding (iii), the in-cylinder pressure when the intake valve is opened is strongly affected by exhaust pulsation while the exhaust valve is open, and there is an overlap where the intake valve and exhaust valve are opened in the same way The impact is even greater. For this reason, it is affected by the combustion state of other cylinders, and the fluctuation for each cycle is very large. Even if the average value in the steady state can be estimated, it is difficult to accurately estimate the in-cylinder pressure for each cycle. . The present embodiment also proposes a method that can accurately estimate the initial inflow air amount, which has been difficult to estimate in the past.

  Next, a main routine of engine control including estimation of the air amount will be described with reference to FIG. This main routine is executed by the ECU 100 for each cylinder and for each predetermined crank angle.

  First, in step S101, a target air amount Ga_trg, which is a target value of the air amount to be supplied to a certain cylinder, is calculated. Here, first, the engine rotational speed Ne and the accelerator opening degree Ac calculated and detected based on the output signals of the crank angle sensor 28 and the accelerator opening degree sensor 30 are acquired. Based on the accelerator opening degree Ac, a torque required for the engine, that is, a target torque Tt is determined. Naturally, the target torque Tt increases as the accelerator opening degree Ac increases. Next, based on the engine speed Ne and the target torque Tt, the target air amount Ga_trg is calculated using the target air amount map shown in FIG. The target air amount Ga_trg, the pre-valve air amount Ga1, the post-valve air amount Ga2, and the like are the air amount per intake stroke (g / cylinder) for one cylinder of the engine.

  Next, in step S102, it is determined whether or not the intake control valve 23 is in the operating range based on the target air amount Ga_trg and the engine rotational speed Ne that are parameters representing the engine operating state. This determination is made using an operating range map as shown in FIG. In this map, the entire area is divided into an operating area A and a non-operating area B. The operating area A exists on the low rotation side and the medium and high load side of the engine. When the engine operating state is in the operating range A, the intake control valve 23 is operated to increase the air amount. When the engine operating state is in the non-operating range B, the intake control valve 23 is deactivated. The boundary line between the operating area A and the non-operating area B is an area where the maximum air amount can be obtained when the intake control valve is not operating.

  When the values of the target air amount Ga_trg and the engine rotational speed Ne are in the operating range A, the process proceeds to step S103 and the operating flag is turned on. On the other hand, when it is not in the operation area A (that is, when it is in the non-operation area B), the process proceeds to step S104 and the operation flag is turned off. Thus, the presence or absence of the intake control valve operation request is determined based on the engine operating state.

  Next, it progresses to step S105 and it is determined whether an operation flag is ON. When the engine is off, the process proceeds to step S112, the air amount Ga flowing into the cylinder is estimated based on the detected value of the air flow meter 21, and then the process proceeds to step S113. On the other hand, when it is ON, the process proceeds to step S106, and the control valve 1 described later is executed to estimate the pre-valve air amount Ga1. Since this main routine is sequentially executed for each cylinder, at the start and end of the operation of the intake control valve 23, the air amount is estimated on the assumption that some cylinders are in an operating state (steps S106 to S111), and the remaining This is the air amount estimation (step S112) assuming that the cylinders in the non-operating state.

  After step S106, the process proceeds to step S107, and the target value Ga2_trg of the post-valve air amount is calculated by the formula: Ga2_trg = Ga_trg−Ga1.

  Next, proceeding to step S108, the valve opening timing CA_Po of the intake control valve 23 is determined with reference to the valve opening timing map of FIG. 6 based on the engine speed Ne and the post-valve target air amount target value Ga2_trg. .

  Next, in step S109, the closing timing CA_Pc of the intake control valve 23 is determined based on the engine speed Ne with reference to the closing timing map of FIG.

  In the next step S110, the control 2 described later is executed, and the intake control valve 23 is opened and closed at the timings of the valve opening timing CA_Po and the valve closing timing CA_Pc determined in steps S108 and S109, and the air amount after the valve opening. Ga2 is estimated.

  If the pre-valve air amount Ga1 and the post-valve air amount Ga2 are thus obtained by estimation, the process proceeds to step S111, and the air amount Ga as an estimated value is calculated by the formula: Ga = Ga1 + Ga2.

  Next, in step S113, based on the engine speed Ne and the target air amount Ga_trg, the basic ignition timing Tigb is determined with reference to the basic ignition timing map of FIG.

  In subsequent step S114, the ignition timing is corrected and the final ignition timing Tig is calculated. That is, based on the difference (= Ga−Ga_trg) between the estimated air amount Ga and the target air amount Ga_trg, the ignition timing correction amount ΔTig (BCA) is determined with reference to the ignition timing correction amount map of FIG. Then, this ignition timing correction amount ΔTig is added to the basic ignition timing Tigb, and the final ignition timing Tig is calculated. This routine is completed as described above. Here, when the estimated air amount is larger than the target air amount, the ignition timing is delayed and the torque is lowered. Conversely, when the estimated air amount is smaller than the target air amount, the ignition timing is advanced and the torque is lowered. Is suppressed. By doing so, torque fluctuations due to variations in the air amount between the cylinders are suppressed.

  To achieve the same purpose in the case of a diesel engine, for example, when the estimated air amount is larger than the target air amount, the fuel injection timing is delayed or the fuel injection amount is reduced.

  Here, only the case of the ignition timing has been described as an example of the control amount, but the fuel injection amount and the fuel injection timing, which are other control amounts, can be determined by the same logic. In this case, the target ignition timing is replaced with the target fuel injection amount and the target fuel injection timing, the ignition timing correction amount is replaced with the fuel injection correction amount and the fuel injection timing correction amount, and the final ignition timing is the final fuel injection amount and Replaced by fuel injection timing. When lean combustion is performed as in the present embodiment, the fuel injection amount may be determined based on the estimated air amount and the target air-fuel ratio. The ECU 100 controls the spark plug 14 and the injector 10 of each cylinder based on these control amounts.

  Next, the control A for estimating the pre-valve air amount Ga1 will be described with reference to FIG. In addition, since each timing etc. relevant to this control A are shown in FIG. 11, please refer suitably.

  First, in step S201, it is determined whether or not the actual crank angle detected by the crank angle sensor 28 is a predetermined angle CA_Iob. The predetermined angle CA_Iob is an angle immediately before the intake valve 16 is opened, in other words, an angle that is a predetermined angle before the valve opening timing CA_Io of the intake valve 16, for example, 5 ° CA before the valve opening timing of the intake valve 16. Is the angle.

  When the crank angle is the predetermined angle CA_Iob, in step S202, the port pressure at the predetermined angle CA_Iob is detected by the pressure sensor 55 and temporarily stored in the memory of the ECU 100 as the initial port pressure P0. The reason why such an initial port pressure P0 is detected and stored will be described later.

  After step S202, the process proceeds to step S203. On the other hand, if it is determined in step S201 that the crank angle is not the predetermined angle CA_Iob, step S202 is skipped and the process proceeds to step S203. In step S203, the temporary opening timing CA_Po0 of the intake control valve 23 is calculated. Here, in order to determine the timing for calculating the pre-valve air amount Ga1, the temporary opening timing CA_Po0 of the intake control valve 23 is determined based on the engine speed Ne and the air amount target value Ga_trg from the valve opening timing map of FIG. Is provisionally determined.

  Next, in step S204, it is determined whether or not the actual crank angle is a timing CA_P1 that is a predetermined angle ΔCA before the temporary opening timing CA_Po0 of the intake control valve 23. In the present embodiment, the predetermined angle ΔCA is set to 30 ° CA. When it is determined that the actual crank angle is the timing CA_P1 that is a predetermined angle ΔCA before the temporary valve opening timing CA_Po0, the process proceeds to step S205, the port pressure at the timing CA_P1 is detected by the pressure sensor 55, and the memory of the ECU 100 is stored as P1. Is temporarily stored. Then, the process proceeds to step S206. On the other hand, if it is determined that the actual crank angle is not the time CA_P1, the process skips step S205 and proceeds to step S206.

  In step S206, based on the initial port pressure P0 and the port pressure P1, a pre-valve air amount Ga1 ′ as a basic value is calculated by a method described later. Then, in step S207, correction is performed in consideration of blow-in of the intake air to the exhaust system during the overlap period, the final corrected pre-valve air amount Ga1 is calculated, and this routine ends. Here, the blow-through amount Ga_ex is calculated based on the basic value Ga1 ′ of the pre-valve air amount using the blow-off amount map of FIG. 12, and this blow-off amount Ga_ex is subtracted from the basic value Ga1 ′ of the pre-valve air amount. Thus, the final corrected air amount Ga1 before opening (= Ga1′−Ga_ex) is calculated. In the map, Ga1'max is the maximum value of the pre-valve air amount based on the cylinder volume at the time of overlap (this can be regarded as the intake top dead center). If there is no overlap, the intake air does not blow through, so this correction is omitted.

This control A will be described below. First, the outline of the control performed here is to detect the port pressures P0 and P1 at timings before and after the opening of the intake valve 16, respectively, and based on these port pressures, the air amount Ga1 ′ before opening as a basic value is obtained. It is to calculate.
Regarding the estimation of the pre-valve air amount Ga1 ′ in step S206, the amount of air that flows into the cylinder from the port passage 11b before the intake control valve 23 opens is equal to the amount of air that has decreased from the port passage 11b. Since the volume of the port passage 11b is determined geometrically and is a known constant value, the volume of the port passage 11b is opened from the change in the air density in the port passage 11b from just before the intake valve 16 is opened to just before the intake control valve 23 is opened. The pre-valve air amount Ga1 ′ can be estimated.

The decrease in port pressure when air flows into the cylinder from the port passage 11b can be regarded as an adiabatic change, and the change in density is determined from the pressure P0 before opening the intake valve and the pressure P1 before opening the intake control valve. Is obtained by the following equation.
ρ1 / ρ0 = (P0 / P1) ^ (− 1 / k) (1)
Here, ρ0 and ρ1 are air densities when P0 and P1 are detected, respectively. These are called the density before opening the intake valve and the density before opening the intake control valve. k is a predetermined constant. The symbol “記号” means power, and the right side: (P0 / P1) ＾ (− 1 / k) means (P0 / P1) to the power of (−1 / k) (the same applies hereinafter).

Therefore, the pre-valve air amount Ga1 ′ flowing into the cylinder is calculated by the following equation.
Ga1 ′ = V × (ρ0−ρ1) = V × ρ0 × (1- (P0 / P1) ^ (− 1 / k))
... (2)
Here, V is the volume of the port passage 11b.
The density ρ0 before opening the intake valve can be calculated from the intake air temperature and the intake manifold pressure. In the present embodiment, values detected by the intake air temperature sensor 42 and the intake pressure sensor 41 are used as the intake air temperature and the intake manifold pressure, respectively.

  Therefore, the air amount Ga1 ′ before opening can be calculated from the intake air temperature, the intake pressure, the pressure P0 before opening the intake valve and the pressure P1 before opening the intake control valve according to the equation (2). In the present embodiment, the ECU 100 performs such calculation to calculate the pre-valve air amount Ga1 ′.

Here, in order to increase the accuracy, it is desirable to consider the amount of heat received by the air from the intake system and the cylinder head. The amount C of increase in intake air temperature in consideration of the influence of this heat reception can be calculated by the following equation.
C = A × log ₁₀ Ne + B
Here, A and B are constant values obtained by experiments or the like.

  Next, regarding steps S204 and S205, the reason why the detection timing CA_P1 of the port pressure P1 is set to a predetermined angle ΔCA before the temporary opening timing CA_Po0 of the intake control valve 23 will be described.

When the air amount Ga1 before opening has a positive value (if there is a backflow from the exhaust system, it may have a negative value), Ga2_trg <Ga_trg, and the intake control valve assumed from the initial target air amount Ga_trg The intake control valve opening timing based on the post-opening air amount target value Ga2_trg is earlier than the valve opening timing. In consideration of the deviation of the intake control valve opening timing, in order to ensure that the detection timing of the port pressure P1 is earlier than the intake control valve opening timing, the detection timing of the port pressure P1 (that is, the air amount Ga1 before opening) Is calculated at a predetermined angle ΔCA before the temporary opening timing CA_Po0 of the intake control valve 23. That is,
CA_P1 <CA_Po <CA_Po0 (3)
The detection time CA_P1 of the port pressure P1 is set so as to satisfy this relationship.

  Here, the detection time CA_P1 (° ATDC) of the port pressure P1 may be determined based on the engine speed Ne and the target air amount Ga_trg using a detection time map as shown in FIG. FIG. 14 shows the relationship on the map when the engine speed Ne = N1.

  Next, regarding step S207, a method for improving the accuracy of the blow-by correction during the overlap will be described below.

  First, the measurement of the air amount Ga1 before opening is divided into two periods: (1) when the intake valve is opened to when the exhaust valve is closed, and (2) when the exhaust valve is closed to when the intake control valve is opened. To do. The calculation logic as in the routine is applied as it is to the air amount (Ga (1)) in (1). That is, the air amount Ga (1) ′ before the basic valve opening is corrected for blow-through to obtain Ga (1). On the other hand, for the air amount (Ga (2)) in (2), a logic obtained by removing the blow-by correction from the calculation logic as in the routine is applied. Finally, the sum of Ga (1) and Ga (2) is the final pre-valve air amount Ga1.

  Next, with regard to steps S204 and S205, correction for reducing the deviation between the detection timing of the port pressure P1 and the intake control valve opening timing, and before opening the valve using the port pressure P1 detected at the new detection timing. The calculation of the air amount Ga1 will be described.

  The port pressure P1 is detected when the intake valve is lifted above a certain level, the high-pressure air held in the port passage 11b sufficiently flows into the cylinder, and the differential pressure between the port pressure and the cylinder pressure becomes sufficiently small. Is desirable. Therefore, it is desirable that the detection timing of the port pressure P1 is as close as possible to the opening timing of the intake control valve 23, and the opening timing of the intake control valve 23, that is, the valve opening signal is sent from the ECU 100 to the intake control valve 23. Ideally, the control valve 23 itself is detected at a timing when it has not yet begun to open. However, in the above control 1, detection is performed at a timing earlier than the valve opening timing in order to reliably avoid detection of the port pressure P1 after the intake control valve 23 is opened.

Therefore, in order to reduce this deviation, it is more preferable to employ the following method. First, after calculating the target value Ga2_trg of the air amount after opening (step S107 in FIG. 3), the first method estimates the port pressure P1 at the valve opening timing CA_Po of the intake control valve 23 and again air before opening. This is a method of calculating the quantity Ga1. The port pressure P1 is obtained from a change in cylinder volume during the intake stroke and a change in port pressure with respect to this change. The cylinder volume is a function of the crank angle, and therefore the change in cylinder volume is obtained from the value detected by the crank angle sensor 28. More specifically, in a closed system, if the volume and pressure at a certain point in time are known, the pressure after the volume change can be calculated from the following equation.
p2 = p1 (v1 / v2) ^ k (4)
However, p is pressure, v is volume, k is a predetermined coefficient, subscript 1 is an initial state, and subscript 2 is after volume change.

  Therefore, by using this equation (4), the port pressure P1 at the valve opening timing CA_Po of the intake control valve 23 can be estimated. In other words, the port pressure P1 at the valve opening timing CA_Po can be estimated by detecting the pressures at the two previous times without directly detecting this.

  In the second method, the port pressure P1 at the valve opening timing CA_Po of the intake control valve 23 is directly detected by the pressure sensor 55, and the pre-valve air amount Ga1 is calculated based on the detected value.

Next, based on FIG. 15, the control B for estimating the post-valve air amount Ga2 will be described. In addition, since each timing etc. relevant to this control B are shown in FIG. 16, please refer suitably.
First, in step S301, it is determined whether or not the actual crank angle detected by the crank angle sensor 28 is the valve opening timing CA_Po of the intake control valve 23 obtained in step S108 of FIG.

  When the crank angle is the valve opening timing CA_Po, the intake control valve 23 is opened in step S302. That is, a valve opening signal is output from the ECU 100 to the intake control valve 23. At the same time, the port pressure at this time is detected by the pressure sensor 55, and is temporarily stored in the memory of the ECU 100 as the port pressure P2 during valve opening. Thus, the process proceeds to step S303. On the other hand, if it is determined in step S301 that the crank angle is not the valve opening timing CA_Po, step S302 is skipped and the process proceeds to step S303.

  In step S303, it is determined whether the actual crank angle detected by the crank angle sensor 28 is the closing timing CA_Pc of the intake control valve 23 obtained in step S109 of FIG.

When the crank angle is the valve closing timing CA_Pc, the intake control valve 23 is closed in step S304. That is, a valve closing signal is output from the ECU 100 to the intake control valve 23. Thus, the process proceeds to step S305. On the other hand, if it is determined in step S303 that the crank angle is not the valve closing timing CA_Pc, step S304 is skipped and the process proceeds to step S305.
In step S305, the valve opening period CA_Pw of the intake control valve 23 is calculated by the equation: CA_Pw = CA_Pc−CA_Po, and based on the valve opening port pressure P2, the valve opening timing CA_Po, and the valve opening period CA_Pw, the opening period of FIG. With reference to the post-valve air amount map, the post-valve air amount Ga2 ′ as a basic value is calculated. This point will be described in detail later.

Next, in step S306, the post-valve air amount is corrected based on the average intake manifold pressure, the final post-valve air amount Ga2 after correction is calculated, and this routine ends. This correction is performed by the following equation.
Ga2 = Ga2 ′ × (average intake manifold pressure) / (reference intake manifold pressure) (5)
Here, the pressure value detected by the intake pressure sensor 41 is used as the average intake manifold pressure.

  The reference intake manifold pressure is a constant value stored in advance in the ECU 100, and more specifically, the intake manifold pressure when the post-valve air amount map of FIG. 17 is created.

  The calculation of the post-valve air amount Ga2 ′ in step S305 will be described. The post-valve air amount map in FIG. 17 is based on the three parameters of the port-opening port pressure P2, the valve opening timing CA_Po, and the valve opening period CA_Pw. It is a three-dimensional map created so that after-valve air amount Ga2 'can be calculated. For example, when a map in a certain valve opening period CA_Pw_n is extracted, the map is as shown in FIG. TDC is an intake top dead center, and BDC is an intake bottom dead center. As can be seen, in the vicinity of the intake bottom dead center BDC, the post-valve air amount Ga2 ′ decreases as the valve opening timing CA_Po is delayed. This is the period from the opening of the intake control valve 23 to the closing of the intake valve 16. Is shortened and the amount of air entering the cylinder is reduced. This map assumes that the intake control valve 23 is closed and the intake valve 16 is closed at the same time. As a result, by using this post-valve air amount map, the post-valve air amount (more specifically, the basic value Ga2 ') can be obtained.

  As a result of earnest research, the present inventors have found that the amount of air flowing into the cylinder when the intake control valve 23 is opened can be estimated from these three parameters. In particular, the air flow rate after the intake control valve 23 is opened largely depends on the opening timing of the intake control valve 23 and the port pressure at that time. The post-valve air amount map is created through such processes as experiment and analysis based on such knowledge. In general, when trying to increase the intake air amount, the port pressure P2 at the time of valve opening is lowered (the differential pressure on the upstream and downstream sides of the intake control valve increases and the flow velocity at the time of valve opening increases), or the valve opening timing CA_Po is delayed. It is effective to take the valve opening period CA_Pw (close the valve immediately before the backflow of air occurs) or the like. However, the valve opening timing CA_Po has an optimum timing in relation to the valve opening port pressure P2, the cylinder volume, the valve opening period CA_Pw (or the intake valve closing timing) after the valve opening, and the like. In any case, by estimating the post-valve air amount based on these three parameters, it is possible to accurately estimate the air amount flowing into the cylinder when the intake control valve 23 is operated.

  Here, in this embodiment, the valve opening period CA_Pw is adopted as one of the parameters, but this may be replaced with the valve closing timing CA_Pc. This is because the relationship of CA_Pc = CA_Po + CA_P_w is such that if one is obtained, the other is obtained. Accordingly, the valve opening period CA_Pw can be replaced with the valve closing timing CA_Pc in step S305 of FIG. 15 and the post-valve air amount map of FIG.

  The present invention can be applied to any type of engine other than a gasoline engine. In the case of a gasoline engine, the present invention is not limited to the direct injection type or in-cylinder injection type as described above, but is also applied to an intake passage injection type engine or a so-called dual injection type engine capable of performing both intake passage injection and in-cylinder injection. it can. Moreover, it is applicable also to the engine using alternative fuels, such as a diesel engine and alcohol, liquefied natural gas. The present invention can also be applied to a supercharged engine. Particularly, in this case, since the intake manifold pressure is higher than that of natural intake air, the differential pressure on the upstream and downstream sides of the intake control valve can be increased, and the inertia supercharging effect is further promoted. Can do. The map as shown in the above embodiment can be replaced with an arithmetic expression.

  In the embodiment, the intake control valve control means, the air amount estimation means, the control amount determination means, and the pre-valve air amount estimation means referred to in the present invention are constituted by the ECU 100, and the pressure detection means is constituted by the pressure sensor 55.

  Embodiments of the present invention are not limited to the above-described embodiments, and all modifications, applications, and equivalents included in the spirit of the present invention defined by the claims are included in the present invention. Therefore, the present invention should not be construed as being limited, but can be applied to any other technique within the scope of the idea of the present invention.

1 is a system diagram schematically showing a configuration of an engine control device according to an embodiment of the present invention. It is a time chart which shows the mode of the change of the pressure at the time of an intake control valve action | operation, and an air flow rate. It is a flowchart of the main routine of the engine control which concerns on this embodiment. It is a target air amount map. It is a working area map of an intake control valve. It is a valve-opening time map of an intake control valve. It is a valve opening period map of an intake control valve. It is a basic ignition timing map. It is an ignition timing correction amount map. 3 is a flowchart of a control 1 routine. 4 is an auxiliary time chart regarding control 1; It is a blow-through amount map. It is a detection time map. The relationship on the detection time map when the engine speed Ne = N1 is shown. 7 is a flowchart of a control 2 routine. 10 is an auxiliary time chart regarding control 2; It is an air amount map after valve opening. It is an air amount map after valve opening in a certain valve opening period CA_Pw_n.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 10 Injector 11 Intake passage 11a Intake manifold passage 11b Port passage 12 Cylinder 13 Combustion chamber 14 Spark plug 15 Intake port 16 Intake valve 17 Exhaust passage 18 Catalyst 19 Exhaust port 20 Exhaust valve 22 Intake throttle valve 23 Intake control valve 33 Valve body 34 Actuator 41 Intake pressure sensor 42 Intake temperature sensor 55 Pressure sensor 100 Electronic control unit (ECU)
CA_Po Intake control valve opening timing
CA_Pc Inlet control valve closing timing
CA_Pw Opening period of the intake control valve Ga Air amount Ga1 Air amount before opening Ga2 Air amount after opening P0 Initial port pressure P1 Port pressure P2 Port pressure at the opening timing of the intake control valve

Claims (12)

An intake control valve provided in an intake passage on the upstream side of the intake valve, capable of closing the intake passage and opening and closing in synchronization with opening and closing of the intake valve;
An intake control valve control means for opening the intake control valve during the intake stroke and then closing the intake control valve;
Based on the opening timing of the intake control valve, the closing timing or opening period of the intake control valve, and the pressure on the downstream side of the intake control valve at the opening timing of the intake control valve, the intake control An engine control device comprising: an air amount estimating means for estimating an air amount flowing into the cylinder after the valve is opened.   2. The air amount estimating means determines a valve opening timing of the intake control valve and a valve closing timing or a valve opening period of the intake control valve based on an operating state of the engine. Engine control device.   The engine control device according to claim 1 or 2, wherein the air amount estimation means estimates the air amount according to a map using the valve opening timing, the valve opening period, and the pressure as parameters. Pressure detecting means for detecting the pressure downstream of the intake control valve;
The air amount estimation means uses the pressure value detected by the pressure detection means at the opening timing of the intake control valve or the pressure value estimated from the detected pressure value as the pressure. The engine control apparatus according to any one of 1 to 3.   5. The engine control device according to claim 1, further comprising a control amount determination unit that determines a control amount based on the air amount estimated by the air amount estimation unit.   The intake control valve control means is different from the average pressure upstream of the intake control valve in the intake passage between the intake control valve and the intake valve from the end of the intake stroke to the next intake stroke. The engine according to any one of claims 1 to 3, wherein the intake control valve is closed so that the pressure is maintained or a pressure equivalent to an average pressure upstream of the intake control valve is maintained. Control device.   The intake control valve is based on the held pressure and the downstream pressure of the intake control valve after the intake valve is opened and at a predetermined timing before or after the intake control valve is opened. 7. The engine control device according to claim 6, further comprising a pre-valve air amount estimating means for estimating a pre-valve air amount that flows into the cylinder before the valve is opened. Pressure detecting means for detecting the pressure downstream of the intake control valve;
The pre-valve air amount estimation means uses the pressure value detected by the pressure detection means at a predetermined time before the intake valve is opened as the holding pressure, and after the intake valve is opened and the intake control valve 8. The engine control device according to claim 7, wherein the pressure value detected by the pressure detecting means at the valve opening timing or the predetermined timing before the valve opening timing is set as the downstream pressure.   Control amount determination means for determining a control amount based on the sum of the air amount estimated by the air amount estimation means and the air amount before valve opening estimated by the pre-valve air amount estimation means is further provided. The engine control device according to any one of claims 6 to 8. Providing an intake control valve in the intake passage upstream of the intake valve that can close the intake passage and can be opened and closed in synchronization with the opening and closing of the intake valve;
Opening the intake control valve during the intake stroke, and then closing the valve;
Based on the opening timing of the intake control valve, the closing timing or opening period of the intake control valve, and the pressure on the downstream side of the intake control valve at the opening timing of the intake control valve, the intake control And a step of estimating an amount of air flowing into the cylinder after the valve is opened. The step of closing the intake control valve is based on an average pressure upstream of the intake control valve in the intake passage between the intake control valve and the intake valve from the end of the intake stroke to the next intake stroke. Closing the intake control valve to maintain a large pressure,
Based on the held pressure and the pressure on the downstream side of the intake control valve after the intake valve is opened and at a predetermined timing before or after the intake control valve is opened. The engine control method according to claim 10, further comprising a step of estimating a pre-valve air amount flowing into the cylinder before the valve is opened. The engine control method according to claim 10 or 11, further comprising a step of detecting a pressure downstream of the intake control valve.

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