JP2007255200A - Control device of variable valve train - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of a variable valve train capable of reducing an operation load by avoiding the heavy usage of a map, when controlling an operational characteristic (opening/closing timing and a lift characteristic) of an intake valve. <P>SOLUTION: A target intake valve opening timing setting part B13 stores an operation expression for arithmetically operating a spitting gas quantity Q<SB>IFB</SB>spitting to an intake port from the inside of a cylinder in a valve overlap period on the basis of an intake valve passing gas quantity in predetermined timing in a period and the valve overlap period up to the effective top dead center TDCR being timing for actually starting suction into the cylinder in the valve overlap period from the opening timing IVO of the intake valve, and calculates the target intake valve timing tIVO for obtaining a target spitting gas quantity tQ<SB>IFB</SB>on the basis of an inputted target spitting gas quantity (calculated from a target residual gas quantity)tQ<SB>IFB</SB>, the target effective top dead center tTDCR, the predetermined timing CA4 and a variation degree α of the intake valve passing gas quantity (spitting gas quantity). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for a variable valve mechanism that variably controls an operation characteristic of an intake valve of an engine, and more particularly to a technique for easily setting a target operation characteristic of an intake valve.

As the intake air amount control in the engine, the intake air amount that achieves the target torque by variably controlling the operating characteristics (opening / closing timing and lift amount (lift characteristic)) of the intake valve independently of the control of the throttle valve There is one that attempts to realize (cylinder intake air amount) (Patent Document 1).
JP 2002-256905 A

However, when the intake air amount is controlled by the operating characteristics of the intake valve as in the above-described conventional technology, the intake air amount varies greatly not only depending on the operating characteristics but also the operating conditions. Since precise adaptation is required, there is a problem that the map must be heavily used (including an increase in the number of dimensions), and the calculation load increases.
In the configuration in which the operation characteristic of the intake valve is variably controlled, the residual gas amount (internal EGR amount) in the combustion chamber is controlled by controlling the valve overlap period in which the intake valve open period and the exhaust valve open period overlap. Although it is possible to reduce the exhaust emission (NOx emission amount) by increasing the amount, it is desirable to achieve this. However, if the residual gas amount is excessively increased, the combustion becomes unstable. It is necessary to control the amount, that is, the valve overlap period (the operation characteristic of the intake valve) with high accuracy, and there is a possibility that the map may be further used and the calculation load may increase with respect to the operation characteristic control of the intake valve.

As described above, regarding the operation characteristic control of the intake valve, there has been a demand for a control method (such as a calculation method for target operation characteristics) that avoids heavy use of the map and has a small calculation load.
The present invention has been made in view of such circumstances, and provides a control device for a variable valve mechanism that can avoid the heavy use of a map and reduce the calculation load when controlling the operation characteristics of an intake valve. Objective.

  For this reason, the present invention is a control device for a variable valve mechanism that variably controls the operation characteristics of an intake valve of an engine. Target residual gas amount setting means for setting a certain target residual gas amount, and a target valve opening timing for setting the intake valve so as to achieve the target residual gas amount, and the variable valve mechanism based on the set target valve opening timing And a control means for controlling the control means, the control means from the opening timing of the intake valve to the effective top dead center which is the time when the intake into the cylinder is actually started during the valve overlap period And the amount of gas blown back from the inside of the cylinder to the intake port during the valve overlap period based on the amount of gas passing through the intake valve at a predetermined time during the valve overlap period. An arithmetic expression for calculating a gas amount is provided, and the target opening timing of the intake valve is calculated based on the target blowback gas amount calculated from the target residual gas amount and the arithmetic expression. .

  In the present invention, a model (calculation formula) for calculating the amount of blown back gas during the valve overlap period is constructed in accordance with the actual physical phenomenon of gas entering and exiting the cylinder (via the intake and exhaust valves). The target opening timing of the intake valve is set (calculated) using a model (calculation formula). As a result, in the opening timing control of the intake valve (setting of the target opening timing), there is no need for a map or the like set for each engine operating condition, and there is an effect that only a relatively simple calculation process is required. As the model (calculation formula), for example, the intake valve passing gas amount during the valve overlap period, the effective top dead center at which the intake into the cylinder is actually started, and the like are calculated, and then the intake valve opening is calculated. There is one that estimates the amount of blown-back gas using the period from the timing to the effective upper point and the intake valve passing gas amount at a predetermined time set in advance, and such a calculation formula and a target set according to the operating conditions The target opening timing of the intake valve is set based on the blowback gas amount (that is, the intake valve opening timing for realizing the target blowback gas amount is calculated (reverse calculation) from the arithmetic expression).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of an internal combustion engine (engine) 1 according to an embodiment of the present invention.
In FIG. 1, an electronically controlled throttle valve 102, a fuel injection valve 103, and an intake valve 104 are disposed in the intake passage 101 of the engine 1 from the intake upstream side. Here, a so-called MPI system in which the fuel injection valve 103 is provided in the intake port 101a of each cylinder is adopted, but a system in which fuel is directly injected into the cylinder (direct injection engine) may be used.

  The throttle valve 102 can control the intake air amount in accordance with its opening (throttle opening). However, in this embodiment, the intake air amount is controlled mainly by changing (controlling) the operating characteristics of the intake valve 104, and the throttle valve 102 is used as an auxiliary. The fuel injection valve 103 is driven to open by an input injection signal, and injects an amount of fuel necessary to achieve a predetermined equivalence ratio under the controlled intake air amount. When the intake valve 104 is driven to open, the mixture of intake air and fuel is introduced into the cylinder (inside the cylinder). The intake valve 104 is driven to open and close by a valve mechanism 105 provided thereabove.

As shown in FIG. 2, the valve mechanism 105 continuously changes the lift characteristics (lift amount) and the operating angle of the intake valve 104 and the central phase of the operating angle of the intake valve 104. And a VTC mechanism 105b that can be changed.
As shown in FIGS. 2 and 3, the VEL mechanism 105a rotates in conjunction with the rotation of the crankshaft and is attached to the drive shaft 151 extending in the cylinder row direction and the outer periphery of the drive shaft 151 so as to be relatively rotatable. A swing cam 152 that opens and closes the intake valve 104 via 141, an eccentric cam 153 that is fixed to the outer periphery of the drive shaft 151, a ring-shaped link 154 that is fitted on the eccentric cam 153 so as to be relatively rotatable, and a drive A control shaft 155 provided substantially parallel to the shaft 151, a control cam 156 that is eccentrically fixed to the outer periphery of the control shaft, and an external fitting that is relatively rotatable to the control cam 156, and a ring-shaped link 154 at one end thereof A rocker arm 157 linked (coupled) with the other end of the rocker arm 157 and a rod-shaped link 158 that links (links) the swing cam 152. It is. Then, when the control shaft 155 is rotated by the electromagnetic actuator 161 via the gear train 162, the rocking center of the rocker arm 157 is changed, and the lift characteristic and the operating angle of the intake valve 104 are continuously changed. .

  The VTC mechanism 105b changes the rotational phase of the drive shaft 151 with respect to the crankshaft, and a known so-called valve timing control mechanism can be used. Although a detailed description is omitted, here, a helical gear train is formed by interposing an intermediate gear between the cam sprocket 163 that rotates in synchronization with the crankshaft and the drive shaft 151, and the intermediate gear is moved in the front-rear direction (axis The rotational phase of the drive shaft 151 with respect to the cam sprocket 163 (crankshaft) is changed.

Returning to FIG. 1 again, the cylinder head H is provided with an ignition plug 106 facing the upper center of the combustion chamber 109, and the ignition plug 106 ignites the air-fuel mixture introduced into the cylinder. Done.
The combustion exhaust is discharged from the combustion chamber 109 to the exhaust passage 107 through the exhaust valve 108, purified by an exhaust purification catalyst (not shown) and the like, and then released into the atmosphere. The exhaust valve 108 is driven to open and close by a drive cam 111 provided on the exhaust side camshaft 110 with its operating angle (lift characteristic) and the central phase of the operating angle being constant. Of course, the same valve operating mechanism as that on the intake valve 104 side (may have a different configuration) may be provided so that the operating angle, lift, and / or the center phase of the operating angle can be changed.

  An engine controller (ECU) 201 incorporating a microcomputer includes an accelerator sensor 211 that detects an accelerator opening (accelerator operation amount) APO, a crank angle sensor 212 that detects a rotational position of a crankshaft, and a pressure ( Here, the intake pressure sensor 213 that detects the pressure in the intake collector and hereinafter referred to as “intake pressure”), the temperature in the intake passage 101 (that is, the air temperature upstream of the intake valve 104), An intake air temperature sensor 214 for detecting Tm (hereinafter referred to as “intake air temperature”), an exhaust pressure sensor 215 for detecting pressure in the exhaust passage 107 (hereinafter referred to as “exhaust pressure”) Pe, and a temperature in the exhaust passage 10 (hereinafter referred to as “exhaust gas”). Detection signals are input from various sensors such as an exhaust temperature sensor 216 that detects Te). . The engine rotation speed Ne is calculated based on the detection result of the crank angle sensor 212.

The ECU 201 executes various engine controls based on engine operating conditions such as the accelerator opening APO and the engine rotational speed Ne, and also controls the valve operating mechanism 105. The control of the valve operating mechanism 105 includes opening timing control of the intake valve 104 (hereinafter referred to as “open timing control”) and lift characteristics and operating angle control of the intake valve 104 (hereinafter simply referred to as “lift characteristics control”). Briefly described here, the opening timing control according to the present embodiment is based on the target residual gas amount (internal) in order to reduce NOx emissions and improve fuel efficiency. The EGR amount) tQ _RES is set, and the opening timing IVO of the intake valve 104 is controlled so that the target residual gas amount tQ _RES can be obtained (so as to achieve this). The control calculates a torque (target torque) tTE to be generated by the engine 1 based on the engine operating conditions, and a target fresh air amount (target new air equivalent to the target torque) required to achieve the target torque tTE. It calculates the amount) TQcyl, and controls the lift characteristics of the intake valve 104 (and the operating angle) on the basis of the target fresh air amount TQcyl.

Hereinafter, the opening timing control and the lift characteristic control in this embodiment will be described in order. Before that, particularly important values (effective top dead center TDCR, blown gas amount Q _IFB , effective IVC, IVC offset amount IVCOFS). Etc.).
FIG. 4 shows (a) operating characteristics of the intake valve 104 and the exhaust valve 108 (lift characteristics are denoted as VLIFTi and VLIFTe, respectively), and (b) cylinder inflow gas amount (cylinder intake air amount) DLTQ per unit crank angle. Is shown.

In the initial stage of valve overlap (a period from the intake valve opening timing IVO to the exhaust valve closing timing EVC), residual gas in the cylinder blows back to the intake port via the intake valve 104. The amount Q _IFB of the blown-back gas (hereinafter referred to as “blow-back gas”) is the amount of inflow into the cylinder per unit crank angle (also simply referred to as “cylinder intake air amount”) DLTQ during the period of “negative”. It is an integrated value (that is, it corresponds to a portion indicated by “A” in the figure). Thereafter, the blow-back from the inside of the cylinder to the intake port is completed, and air (gas) starts to be sucked into the cylinder. In the present embodiment, when switching from blowback to inflow (that is, the crank angle at which the cylinder intake air amount DLQ turns from “negative” to “positive”, which corresponds to the actual intake stroke start timing) The point is TDCR. This effective top dead center TDCR is also a point (time) at which the in-cylinder pressure Pc decreases and coincides with the intake pressure Pm.

After the effective top dead center TDCR, the blow-back gas is also sucked into the cylinder together with fresh air. For this reason, as shown in the figure, the in-cylinder inflow gas amount (cylinder intake air amount) Qcyl0 from the start of the intake stroke to the end of the intake stroke is equal to the blow-back gas amount Q _IFB and the cylinder intake fresh air amount Qvyl (“B Is equivalent to the part indicated by “)”. As is apparent from the drawing, the intake of air (gas) into the cylinder is actually completed before the intake valve closing timing IVC. When the intake of air (gas) into the cylinder is finished (in other words, the time when the compression of the intake air is substantially started in the cylinder) corresponds to the actual intake stroke end time. The timing is the effective closing time IVCR. The offset amount of the effective closing timing IVCR from the set intake valve closing timing IVC is set as “IVC offset amount IVCOFS”.

Here, in this embodiment, the calculation load is reduced by calculating the in-cylinder pressure Pc, the effective top dead center TDCR, and the blow-back gas amount Q _IFB as follows.
A. Calculation of Effective Top Dead Center TDCR (1) Approximation of In-Cylinder Pressure First, in the present embodiment, as shown in FIG. 5, the in-cylinder pressure Pc during the valve overlap period (IVO to EVC) From the opening timing IVO to the exhaust valve closing timing EVC, it is approximated as changing linearly from the exhaust pressure Pe to the intake pressure Pm. Thereby, the cylinder pressure Pc at each timing during the valve overlap period is easily calculated based on this approximation.

(2) Setting of approximate characteristic line L1 (corresponding to the first approximate characteristic line according to the present invention) Exhaust valve passing gas amount in the latter half of the valve overlap period (here, gas amount per unit crank angle, hereinafter). (Same) The approximate characteristic line L1 approximately representing the characteristic of DQex is set based on a plurality of times in the second half of the valve overlap period and the exhaust valve passage gas amount DQex in each of the plurality of times.

  In the present embodiment, as shown in FIG. 6, as the plurality of times related to the setting of the approximate characteristic line L1, the point A of the exhaust valve closing timing EVC and the period from the intake valve opening timing IVO to the exhaust valve closing timing EVC are approximately 3: Two points (time) of point B of time CA1 to be internally divided into 1 are adopted. The point A (exhaust valve closing timing EVC) is adopted because the calculation can be simplified because the exhaust valve passage gas amount DQexa is zero. On the other hand, about the point B, it determined by experiment etc. as a point (time) in the range in which the linearity with respect to the crank angle CA of the exhaust-gas passage gas amount is recognized. The exhaust valve passage gas amount DQex has a characteristic proportional to the opening area when the opening area of the exhaust valve 108 is small. Therefore, instead of the above-described experiment, the lift characteristic VLIFTe of the exhaust valve 108 is determined by the crank angle. An area that linearly changes (decreases) with respect to CA may be specified, and an arbitrary point in this area may be selected as point B (thus, only when the IVO to EVC is internally divided by 3: 1). Not possible). The exhaust valve passage gas amount DQexb at the point B is calculated by the following equation (1).

Here, Aev is the exhaust valve opening area at point B. Re is the gas constant of the exhaust gas and κe is the specific heat ratio of the exhaust gas. Both can be calculated based on the target equivalent ratio TFBYA. Δt is a value obtained by time-converting the predetermined crank angle Δθ, and is calculated by an arithmetic expression of Δt = Δθ / (6 · Ne) here. Then, a straight line passing through the point A (EVC, 0) and the point B (CA1, DQexb) is set as the approximate characteristic line L1.

(3) Setting of approximate characteristic line L2 (corresponding to the second approximate characteristic line according to the present invention) The approximate characteristic line L2 that approximately represents the characteristic of the change in the amount of gas in the cylinder during the valve overlap period It is set on the basis of a plurality of times during the lap period and the cylinder gas amount change DLTM in each of the plurality of times.
In the present embodiment, as shown in FIG. 7, as a plurality of times related to the setting of the approximate characteristic line L2, as shown in FIG. Two points (timing) of point C) (referred to as geometric dead center) and point D of intake valve opening timing IVO are employed. The in-cylinder gas amount change DLTM _{TDC at the} geometric dead center TDC is 0, and the DLTM _IVO at the intake valve opening timing IVO is calculated using the following equation (2). Here, the cylinder temperature is approximated by the exhaust temperature Te, and the exhaust gas constant Re is used as the gas constant. This is because the cylinder occupies the exhaust up to the geometric dead center TDC.

Here, Pc is the cylinder internal pressure at the intake valve opening timing IVO, which can be obtained from the above-described approximation (FIG. 5), and Vc is the cylinder internal volume Vc at the intake valve opening timing IVO, which is calculated geometrically. Is possible. Further, the rate of change dPc and dVc per hour of the cylinder internal pressure Pc and the cylinder internal volume Vc are obtained by multiplying the rate of change per crank angle by a coefficient corresponding to the engine rotational speed Ne. Then, a straight line passing through the point C (TDC, 0) and the point D (IVO, DLTM _IVO ) is set as the approximate characteristic line L2. When the two approximate characteristic lines L1 and L2 are set as described above, the intersection E is specified, and the time of the intersection E is calculated as the effective top dead center TDCR (see FIG. 7).

B. Calculation of blown back gas amount Q _IFB (4) Setting of approximate characteristic line L3 (corresponding to the third approximate characteristic line according to the present invention) Approximately represents the characteristic of intake valve passing gas amount DQin in the first half of the valve overlap period The approximate characteristic line L3 is set based on a plurality of times in the first half of the valve overlap period and the intake valve passage gas amount DQin at each of the plurality of times.

  In the present embodiment, as shown in FIG. 8, as the plurality of times related to the setting of the approximate characteristic line L3, the point F of the intake valve opening timing IVO and the interval from the intake valve opening timing IVO to the exhaust valve closing timing EVC are about 1: Two points (time) of point G of time CA2 to be internally divided into 1 are adopted. The reason why the point F (intake valve opening timing IVO) is adopted is that the calculation can be simplified because the intake valve passage gas amount DQint is zero. On the other hand, the point G is determined by an experiment or the like as a point (time) within a range where linearity of the intake valve passage gas amount with respect to the crank angle CA is recognized. As with the exhaust valve passage gas amount DQex, the intake valve passage gas amount DQin also has a characteristic proportional to the opening area when the opening area of the intake valve 104 is small. A region where the lift characteristic VLIFTe of the valve 104 changes (decreases) linearly with respect to the crank angle CA may be specified, and an arbitrary point in this region may be selected as the point G (IVO to EVC is 1: 1). It ’s not limited to when it ’s going to be divided. The intake valve passage gas amount DQing at point G is calculated by the following equation (3), with the intake valve opening area at this time being Aiv.

A straight line passing through the point F (IVO, 0) and the point G (CA2, DQing) is set as the approximate characteristic line L3. At this time, the angle α with respect to the horizontal axis (X axis) of the approximate characteristic line L3 is the degree of change in the intake valve passage gas amount (the degree of change in the intake valve passage gas amount in the first half of the valve overlap period). (The characteristic line L3 ′ in the figure indicates the intake valve passage gas amount (that is, the absolute value) that does not consider the direction of the intake valve passage gas).

(5) Setting of approximate characteristic line L4 (corresponding to the fourth approximate characteristic line according to the present invention) An approximate characteristic line L4 that approximately represents the characteristic of the exhaust valve passage gas amount DQex in the first half of the valve overlap period It is set based on a plurality of times in the first half of the overlap period and the exhaust valve passage gas amount DQex at each of the plurality of times.
In the present embodiment, as shown in FIG. 9, the plurality of times related to the setting of the approximate characteristic line L4 is the same time CA3 as the point D of the intake valve opening timing IVO and the intersection H of the approximate characteristic lines L2 and L3. Two points (time) of point I are adopted. The point D is adopted because the intake valve passage gas amount is zero at the intake valve opening timing IVO, and therefore the exhaust valve passage gas amount DQex becomes equal to the in-cylinder gas amount change DLTM. Also, the point I is adopted because the intersection H between the approximate characteristic lines L2 and L3 indicates the time when all of the in-cylinder gas amount change DLTM becomes the intake valve passage gas amount DQin. This is because the valve passing gas amount DQex becomes zero. A straight line passing through the point D (IVO, DLTM _IVO ) and the point I (CA3, 0) is set as the approximate characteristic line L4.

(6) Setting of approximate characteristic line L5 An approximate characteristic line L5 that approximately represents the characteristic of the intake valve passage gas amount DQin in the second half of the valve overlap period is represented by a plurality of periods and the plurality of periods in the second half of the valve overlap period. Is set based on the intake air passing gas amount DQin.
In the present embodiment, as a plurality of periods related to the setting of the approximate characteristic line L5, as shown in FIG. 10, a point K on the approximate characteristic line L3 at the same time CA4 as the intersection J of the approximate characteristic lines L1 and L4, and Two points (time) of the point M of the effective top dead center TDCR are adopted. Since the intersection J indicates the timing when the valve overlap period switches from the first half to the second half, the point K indicates the intake valve passing gas amount DQin at the start of the second half of the valve overlap period, and the effective top dead center. Since TDCR is the time at which actual intake into the cylinder is started, the intake valve passage gas amount DQin becomes 0 (switches from negative to positive). Then, the amount of gas passing through the intake valve in the second half of the valve overlap period is approximated to a linear change from the point K to the point M, and a straight line passing through the point K and the point M is set as the approximate characteristic line L5. .

(7) Calculation of blown back gas amount Q _IFB (approximate)
In the present embodiment, as shown in FIG. 11, the area of the region surrounded by the approximate characteristic lines L3, L5 and the horizontal axis (X axis: in-cylinder inflow gas amount = 0) (area of triangle FKM: region indicated by hatching) Is the blow back gas amount Q _IFB . Therefore, the blow back gas amount Q _IFB is calculated by the following equation (4). This formula (4) corresponds to the calculation formula (for calculating the blow-back gas amount) according to the present invention.

In Expression (4), DQin (CA4) is the intake valve passage gas amount at time CA4 (that is, the time when the valve overlap period is switched from the first half to the second half), and the intake valve passage gas at the predetermined time according to the present invention. It corresponds to the quantity (however, it is not limited to this).
FIG. 12 compares the blown-back gas amount (approximate) calculated as described above with the actual blown-back gas amount (a portion corresponding to part X in FIG. 4). Thus, although it is approximated using a relatively simple arithmetic expression (Expression (4)), it can be confirmed that it is very close to the actual behavior of the blown-back gas amount. That is, the blow-back gas amount Q _IFB , the effective top dead center TDCR, the intake valve opening timing IVO, and DQin (the intake valve passing gas amount in CA4) have the relationship of the above equation (4), and three values thereof Indicates that the remaining value can be obtained from the above equation (4).

C. Open timing control (setting of target intake valve opening timing tIVO)
Next, the opening timing control according to the present embodiment will be described.
In the opening timing control according to the present embodiment, the target residual gas amount tQ _RES is calculated from the target fresh air amount tQcyl0 and the target residual gas rate tREGR (%) set based on the engine operating conditions, and this target residual gas amount tQ. _The clearance volume portion gas amount Q _GAP is subtracted from _RES to obtain a target blow-back gas amount tQ _IFB . Then, based on the target blowback gas amount tQ _IFB and the above equation (4), the intake valve opening timing for realizing the target blowback gas amount tQ _IFB is calculated as the target opening timing tIVO. That is, the target intake valve opening timing tIVO is calculated by solving the arithmetic expression (4) with the blowback gas amount Q _IFB in the above equation (4) as the target blowback gas amount tQ _IFB . The target residual gas rate tREGR indicates a target ratio of the cylinder residual gas amount to the total gas amount in the cylinder at the end of the intake stroke.

FIG. 13 is a block diagram for calculating the target intake valve opening timing tIVO.
The multiplier B11 calculates the target residual gas amount tQ _RES by the following equation (5) based on the target fresh air amount tQcyl and the target residual gas rate tREGR set according to the engine operating conditions.

The residual gas amount Q _RES includes the blow back gas amount Q _IFB that is the amount of gas blown back from the cylinder to the intake port 101a during the valve overlap period, and the gap volume portion gas amount Q _GAP remaining in the gap volume portion in the cylinder. since is a combination of the bets, the target blown-back gas amount tQ _IFB is a target value of the gas amount Q _IFB blowback is subtracted the void volume portion gas quantity Q _gAP in a state where the target from the target residual gas amount tQ _RES . Therefore, the subtracting unit B12, calculates the target blown-back gas amount _{tQ IFB} from the target residual gas quantity _{tQ RES} by subtracting the target clearance volume gas quantity _{tQ GAP.} Note that the target clearance volumetric gas amount tQ _GAP in this embodiment is calculated as the amount of gas remaining in the cylinder at the target effective top dead center tTDCR as described later (that is, the cylinder at the target effective top dead center tTDCR). The internal volume VtTDCR is the clearance volume). As described above, this is based on the fact that the effective top dead center TDCR is the time when actual inhalation starts (blowback ends).

In the target intake valve opening timing calculation unit B13, the target blowback gas amount tQ _IFB , the target effective top dead center tTDCR, the intake valve passing gas amount (blowback gas amount) change rate (change ratio) α, the timing CA4 (valve overlap period is The intake valve opening timing at which the target blowback gas amount tQ _IFB is achieved is calculated as the target intake valve opening timing tIVO by using the timing of switching from the first half to the second half) and the arithmetic expression (4). Specifically, as shown in FIG. 14 and the following equation (6), a formula for the area of a triangle (with the third approximate characteristic line L3, the fifth approximate characteristic line L5, and the horizontal axis (X axis) as each side) The period (a + b) from the target intake valve opening timing tIVO to the target effective top dead center tTDCR is calculated, and this calculation result is subtracted from the target effective top dead center tTDCR to obtain the target intake valve opening timing tIVO. The calculation of the target effective top dead center tTDCR, the intake valve passage gas amount (blow-back gas amount) change rate (change rate) α, and the timing CA4 used here will be described later (see FIG. 15).

FIG. 15 is a block diagram for calculating the target clearance volumetric part gas amount tQ _GAP . Here, in addition to the target clearance volumetric gas amount tQ _GAP , the target effective top dead center tTDCR, the intake valve passing gas amount change rate α, and the timing at which the valve overlap period is switched from the first half to the second half as follows. CA4 is calculated.
The target intake pressure setting unit B21 sets the target intake pressure tPm based on engine operating conditions (Ne, APO, etc.).

The target exhaust pressure calculation unit B22 calculates (estimates) the target exhaust pressure tPe corresponding to the exhaust pressure Pe when the intake pressure Pm becomes the target intake pressure tPm. Such calculation (estimation) will be described later (see FIG. 16).
In the target effective top dead center calculation unit B23, based on the target intake pressure tPm, the target exhaust pressure tPe, the actual intake valve opening timing (current opening timing) IVO, and the actual intake valve operating angle (lift characteristic) θevent, The target effective top dead center tTDCR and the valve overlap period are switched from the first half to the second half in accordance with the processes in “A. Calculation of effective top dead center TDCR” and “B. Calculation of blown back gas amount Q _IFB ”. Timing CA4 and intake valve passage gas amount change degree α are calculated. That is, the current operating characteristics (opening / closing timing, lift characteristics) of the intake valve 104 are grasped from the current opening timing IVO (REIVO) and the current operating angle θevent (REVER) of the intake valve (the operating characteristics of the exhaust valve 108 are constant). Under the current operating characteristics of the intake valve 104, the cylinder pressure Pc during the valve overlap period is approximated to change linearly from the target exhaust pressure tPe to the target intake pressure tPm. A. above. Each calculation process in B is performed, and (target) effective top dead center tTDCR, timing CA4, and intake valve passage gas amount change rate α are calculated. Then, the target effective top dead center tTDCR calculated here is output to the clearance volume calculation unit B24, and the target effective top dead center tTDCR, the timing CA4, and the intake valve passage gas amount change rate α are set to the target intake valve opening in FIG. It outputs to time calculating part B13.

In the clearance volume calculation part B24, the cylinder internal volume VtTDCR at the target effective top dead center tTDCR is calculated, and this is set as the clearance volume. Such calculation is performed by searching a table as shown in the figure based on the target effective top dead center tTDCR.
In the clearance volume portion gas amount calculation unit B25, the clearance volume (that is, the cylinder internal volume at the target effective top dead center) VtTDCR is multiplied by the density (that is, the target density) tρ when the intake pressure becomes the target intake pressure. a target clearance volume gas quantity _{tQ gAP} with (= VtTDCR × tρ) to. Here, it is assumed that all gases (that is, residual gases) are also fresh air, and that the intake air temperature does not change, and the target (air) density tρ is expressed by the following equation (7). (Rρ: current density, rPm: current intake pressure).

The calculated target clearance volume portion gas amount tQ _GAP is output to the subtraction unit B12 in FIG.
FIG. 16 is a block diagram for calculating (estimating) the target exhaust pressure tPe, which is executed by the exhaust pressure calculation unit B22 of FIG.
First, in the target exhaust gas amount calculation unit B31, based on the engine speed Ne, the basic fuel injection pulse width Tp, and the target equivalent ratio TFBYA, the exhaust gas amount (target exhaust gas amount) in the target state by the following equation (8): MFEXG is calculated. This is based on the idea that exhaust gas amount (mass) = new air amount + fuel amount (mass). However, this is an example, and other calculation methods may be used. Note that CYLINDER is the number of cylinders.

The gas constant calculation unit B32 calculates an exhaust gas constant Re by searching a table as shown in the figure based on the target equivalent ratio TFBYA.
Based on the target exhaust gas amount MFEXG, the exhaust gas constant Re, the gas temperature during valve overlap (≈exhaust temperature Te) and the atmospheric pressure Patm, the target exhaust pressure calculation unit B33 calculates the target exhaust pressure by the following equation (7). tPe is calculated. This equation (7) is basically the sum (and atmospheric pressure) of the pressure loss in the laminar flow region (calculated by the Hagen-Poiseuille equation) and the pressure loss in the turbulent region (calculated by the Darcy-Weibach equation). Thus, the pressure loss of each part (catalyst, etc.) is obtained, and the exhaust pressure is approximately calculated by adding the pressure loss of each part and the atmospheric pressure, and the accuracy has been confirmed by experiments and the like.

  However, KTBF and KLMF are a turbulent flow coefficient and a laminar flow coefficient, respectively, and are (adapted) values determined by each model (catalyst, etc.) The target exhaust pressure tPe calculated in this way is output to the target effective top dead center calculator B23 in FIG. However, the above equation (9) is an example, and any method may be used as long as the exhaust pressure in the target state (when the target intake pressure tPm is reached) can be calculated (estimated) as the target exhaust pressure tPe. As a simpler example, the actual intake pressure rPm and the exhaust pressure rPe are detected, and the exhaust pressure (target exhaust pressure) tPe when the target intake pressure tPm is reached is calculated from the relationship between the detected two. It is also possible.

D. Lift characteristic control (setting of target intake valve operating angle (target lift characteristic) tθevent)
FIG. 17 is a block diagram for setting the target intake valve operating characteristic tθevent.
In addition section B101, as shown in the following equation (10), the target cylinder by adding the target blown-back gas amount tQ _IFB target fresh air amount TQcyl, corresponds to the amount of gas sucked into the cylinder during valve overlap period The intake air amount is tQcyl0.

Next, the division unit B102 is a target cylinder intake air quantity tQcyl0 divided by the maximum intake air quantity _{Q MAX,} the next conversion unit B 103, using a table as shown in FIG., The calculation result of the division section B102, namely converting (tQcyl0 _{/ Q MAX)} to (sonic intake air quantity _Q D _{/ Q MAX).}
Here, the relationship between (Q _D / Q _MAX ) and (Qcyl 0 / Q _MAX ) based on the cylinder intake air amount Qcyl 0, the sonic intake air amount Q _D and the maximum intake air amount Q _MAX will be described.

Sonic intake air quantity Q _D is the cylinder intake air amount when inhaled as a sonic flow with an opening area corresponding to the operating characteristic of intake valve 104 is calculated by the following equation (11).

However, (ΣA) is an integral value (total opening area) of the intake valve opening area detected (calculated) for each predetermined crank angle Δθ. Further, Δt is a value obtained by time-converting the predetermined crank angle Δθ as described above, and is calculated by an arithmetic expression of Δt = Δθ / (6 · Ne) here.
Here, when the intake air passing through the intake valve 104 is sonic, the front-rear pressure ratio (Pc / Pm) of the intake valve 104 is always the critical pressure ratio (= {2 / (κ + 1)} ^{(κ / κ−1} ). ⁾⁾ ), The fixed value (constant) q _SONIC . Therefore, the above equation (11) can be expressed by the following equation (12), which is used in the present embodiment.

Such sonic intake air quantity Q _D is specifically calculated by the block diagram shown in FIG. 18. In FIG. 18, the total opening area calculation unit B211 grasps the operating characteristics (opening / closing timing and lift characteristics) of the intake valve 104 from the current intake valve opening timing IVO and the intake valve closing timing IVC, and calculates the effective top dead center TDCR. In addition, (refer to “A. Calculation of effective top dead center” above), intake valve opening area A per unit crank angle (Δθ) during the intake valve 104 opening period from effective top dead center TDCR to intake valve closing timing IVC. Is calculated from the above-obtained operating characteristics, and the calculated values are integrated to obtain a total opening area (ΣA).

The multiplication unit B212 multiplies the intake air temperature Tm and the air gas constant Ra, and the conversion unit B213 searches a table as shown in the figure and obtains the calculation result (Ra · Tm) of the multiplication unit B212 by its square root {√ (Ra · Tm)}. Further, the division unit B214 divides the intake pressure Pm by the square root {√ (Ra · Tm)}, and the multiplication unit B215 multiplies the calculation result of the division unit B214 by a constant q _SONIC ({Pm · q _SONIC / (√ (Ra · Tm)}).

The multiplication unit B216 multiplies the calculation result (ΣA) of the total opening area calculation unit B211 by the calculation result of the multiplication unit B215 ({Pm · qSONIC / √ (Ra · Tm)}), and the multiplication unit B217 further integrates Multiplying by the interval time Δt {= Δθ / (6 · Ne)}, the sonic intake air amount Q _D shown in the above equation (12) is calculated.
On the other hand, the maximum intake air amount Q _MAX is the cylinder intake air amount when the cylinder stroke volume from the start to the end of the intake stroke is filled in the (intake) state upstream of the intake valve 104, and is calculated by the following equation (13). Is done.

  However, VIVC is the cylinder volume when the intake valve is closed, and VTDC is the cylinder volume at the top dead center. By the way, when viewed statically, as shown in the above equation (13), the value obtained by subtracting the cylinder volume at the top dead center from the cylinder volume at the intake valve closing timing is the (cylinder) stroke volume. Thus, in practice, the effective top dead center TDCR is the intake stroke start timing (point), and the effective close timing IVCR is the intake stroke end timing (point). Therefore, in the present embodiment, as shown in the following equation (14), the cylinder volume VIVCR at the effective closing timing IVCR is replaced with the top dead center cylinder volume VTDC instead of the intake valve closing cylinder volume VIVC in the above equation (13). Instead of this, the cylinder volume VTDCR at the effective top dead center TDCR is employed.

The maximum intake air amount Q _MAX is specifically calculated from the block diagram shown in FIG. In FIG. 19, the effective closing timing calculation unit B221 calculates an effective closing timing IVCR by subtracting the IVC offset amount IVCOFS from the intake valve closing timing IVC. Here, the IVC offset amount IVCOFS is calculated with reference to a map as shown in FIG. 20 based on the engine rotational speed Ne and the lift characteristic VLIFTi (for example, the maximum lift characteristic) of the intake valve 104. The IVC offset amount IVCOFS has a characteristic that it increases as the engine rotational speed Ne increases and the lift characteristic VLIFTi decreases.

  The effective closing timing cylinder volume calculation unit B222 calculates an effective closing timing cylinder volume VIVCR by searching a table as shown in the figure based on the calculated effective closing timing IVCR. Here, the effective closing timing IVCR is obtained by subtracting the IVC offset amount IVCOFS from the intake valve closing timing IVC (on the setting). However, this is an example, and the actual intake stroke end timing is calculated. If it can be obtained as the effective closing time IVCR, it may be obtained by another method.

On the other hand, the effective top dead center TDCR is calculated based on the above-mentioned “A. Calculation of effective top dead center TDCR”, and the effective top dead center cylinder volume calculation unit B223 is based on the effective top dead center IVCR as shown in FIG. To calculate the effective top dead center cylinder volume VTDCR. The method for calculating the effective top dead center TDCR is not limited to this.
Then, the effective stroke volume calculation unit B224 calculates an effective stroke volume (VIVCR-VTDCR) by subtracting the effective top dead center cylinder volume VTDCR from the effective closing timing cylinder volume VIVCR, and the multiplication unit B225 calculates the intake pressure Pm as air. The effective stroke volume (VIVCR-VTDCR) is multiplied by {Pm / (Ra · Tm)} divided by the product of the gas constant Ra and the intake air temperature Tm. Thereby, the maximum intake air amount Q _MAX shown in the above equation (13) is calculated.

Here, assuming that the actual cylinder intake air amount according to the operating characteristics of the intake valve 104 is Qcyl, (sonic intake air amount Q _D / maximum intake air amount Q _MAX ) and (cylinder intake air amount Qcyl 0 / maximum intake air amount) It is confirmed that there is a unique relationship with Q _MAX ), and if this relationship is stored in advance, based on one value (for example, Qcyl0 / Q _MAX ), the other corresponding to this (Q _D / Q _MAX ) can be immediately determined (ie, converted). Then, it shows such a relation is a table of the conversion unit B 103, which makes it calculates the result of the division section B102 a {(target) cylinder intake air quantity TQcyl0 / maximum intake air quantity _{Q MAX}} {( Target) Sonic intake air amount tQ _D / maximum intake air amount Q _MAX }.

Returning to FIG. 17 again, the multiplication unit B104 multiplies the output value (tQ _D / Q _MAX ) from the conversion unit B103 by the maximum intake air amount Q _MAX to obtain the target sonic intake air amount tQ _D.
Since the sonic intake air amount Q _D is expressed by the above equation (12), the division unit B105 divides the target sonic intake air amount tQ _D by {Pm · q _SONIC / √ (Ra · Tm)} Further, by dividing by Δt {= Δθ / (6 · Ne)} in the division unit B106, the target total opening area (tΣA) of the intake valve 104 can be obtained. The target total opening area (tΣA) corresponds to the opening area for obtaining the target sonic tQ _D.

In the target operating angle setting unit B107, the calculated target total opening area (tΣA) is converted into a crank angle unit, and a table as shown in the figure is searched to obtain the target intake valve operating angle tθevent (that is, the opening area is set as the opening area). Convert to working angle). The target intake valve operating angle tθevent is set to a larger value as the target total opening area tΣA is larger.
Then, the ECU 201 controls the valve mechanism 105 so that the actual intake timing and operating angle (lift characteristic) of the intake valve 104 become the target intake valve opening timing tIVO and the target intake valve operating angle tθevent. .

According to this embodiment, the following effects can be obtained.
That is, in the present embodiment, the valve overlap is based on the intake valve passing gas amount in the period from the intake valve opening timing IVO to the effective top dead center TDCR and in the timing CA when the valve overlap period switches from the first half to the second half. There is an arithmetic expression (expression (4)) for calculating the amount of blowback gas that blows back from the cylinder to the intake port during the period, and based on this calculation formula and the target blowback gas amount calculated from the target residual gas amount, The intake valve opening timing tIVO is set (calculated) (see formula (6)). For this reason, the target intake opening timing tIVO can be set relatively easily without causing heavy use of the map.

Furthermore, in this embodiment, the relationship between Q _D / Q _MAX and Qcyl0 / Q _MAX is created as a conversion table, and the target sonic intake air amount tQ _D is calculated from this conversion table and the target cylinder intake air amount tQcyl0. and was to set the target intake operation angle Tishitaevent (lift characteristic) based on the calculated target sonic intake air quantity tQ _D. For this reason, even when setting the target intake operation angle tθevent, the use of the map can be avoided by using the conversion table.

  As described above, it is possible to control the operation characteristics (opening / closing timing, lift characteristics) of the intake valve with a minimum calculation.

It is a figure showing the schematic structure of the engine concerning one embodiment of the present invention. It is a figure which shows the structure of the valve operating mechanism (VEL mechanism + VTC mechanism) of an intake valve same as the above. It is a figure which shows the structure of a VEL mechanism same as the above. It is a figure which shows the relationship between the valve operating characteristic VLIFT and the cylinder intake air amount DLTQ per unit crank angle. It is a figure which shows the approximate characteristic line of the pressure in a cylinder. It is a figure which shows the approximate characteristic line (1st approximate characteristic line) of the exhaust-valve passage gas amount in the second half of a valve overlap period. It is a figure which shows the approximate characteristic line (2nd approximate characteristic line) for the gas amount change in a cylinder during a valve overlap period. It is a figure which shows the approximate characteristic line (3rd approximate characteristic line) of the intake valve passage gas amount of the first half of a valve overlap period. It is a figure which shows the approximate characteristic line (4th approximate characteristic line) of the exhaust valve passage gas amount in the first half of the valve overlap period. It is a figure which shows the approximate characteristic line (5th approximate characteristic line) of the intake valve passage gas amount in the second half of the valve overlap period. It is a figure which shows the amount of blown-back gas (approximation). It is a figure which shows the relationship between actual blown-back gas amount and an approximate value. FIG. 6 is a block diagram for setting a target intake valve opening timing tIVO. It is a figure for demonstrating calculation of the target intake valve opening timing tIVO. It is a block diagram for calculating a target clearance volume gas quantity tQ _GAP. It is a block diagram which calculates target exhaust pressure tPe. It is a block diagram which sets the intake valve target operating angle tθevent. It is a block diagram which calculates sonic intake air amount QD. FIG. 6 is a block diagram for calculating a maximum intake air amount QMAX. It is a map for setting an IVC offset amount that is an offset amount from the intake valve closing timing IVC in setting the effective closing timing IVCR.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 101 ... Intake passage, 102 ... Throttle valve, 103 ... Injector, 104 ... Intake valve, 105 ... Valve mechanism, 105a ... VEL mechanism, 105b ... VTC mechanism, 106 ... Spark plug, 107 ... Exhaust passage, 108 ... Exhaust valve, 151 ... Drive shaft, 152 ... Oscillating cam, 153 ... Eccentric drive cam, 154 ... Ring link, 155 ... Control shaft, 156 ... Eccentric control cam, 157 ... Rocker arm, 158 ... Rod link, 161 ... Electromagnetic actuator 201 ... engine controller 211 ... accelerator sensor 212 ... crank angle sensor 213 ... intake pressure sensor 214 ... intake temperature sensor 215 ... exhaust pressure sensor 216 ... exhaust temperature sensor

Claims (16)

A control device for a variable valve mechanism that variably controls the operating characteristics of an intake valve of an engine,
A target residual gas amount setting means for setting a target residual gas amount, which is a target value of the residual gas amount remaining in the cylinder, based on engine operating conditions;
Control means for setting a target opening timing of the intake valve so as to achieve the target residual gas amount, and controlling the variable valve mechanism based on the set target opening timing;
Comprising
The control means includes a period from an opening timing of the intake valve to an effective top dead center that is a timing at which intake into the cylinder is actually started during a valve overlap period, and a predetermined period during a valve overlap period. Based on the amount of gas passing through the intake valve, an arithmetic expression for calculating the amount of blowback gas, which is the amount of gas blown back from the cylinder to the intake port during the valve overlap period,
A control device for a variable valve mechanism, wherein a target opening timing of the intake valve is calculated based on a target blowback gas amount calculated from the target residual gas amount and the arithmetic expression. The control means is an approximate characteristic line of the exhaust valve passage gas amount in the second half of the valve overlap period, based on a plurality of times in the second half of the valve overlap period and the exhaust valve passage gas amounts in each of the plurality of periods. While setting one approximate characteristic line,
A second approximate characteristic line, which is an approximate characteristic line for the change in the cylinder gas amount during the valve overlap period, based on the plurality of periods in the valve overlap period and the change in the cylinder gas amount at each of the plurality of periods. Set
2. The control device for a variable valve mechanism according to claim 1, wherein the timing of the intersection of the first and second approximate characteristic lines is calculated as the effective top dead center. The control means is an approximate characteristic line of the intake valve passage gas amount in the first half of the valve overlap period based on the plurality of times in the first half of the valve overlap period and the intake valve passage gas amounts in each of the plurality of periods. While setting 3 approximate characteristic lines,
Based on the plurality of periods in the first half of the valve overlap period and the exhaust valve passage gas amount in each of the plurality of periods, a fourth approximate characteristic line that is an approximate characteristic line of the exhaust valve passage gas quantity in the first half of the valve overlap period is Set,
2. The intake valve passing gas amount at the predetermined time is defined as a value on the third approximate characteristic line at the time of the intersection of the first approximate characteristic line and the fourth approximate characteristic line. Item 3. The control device for a variable valve mechanism according to Item 2.   4. The variable valve operating system according to claim 2, wherein when setting the first approximate characteristic line, the exhaust valve passage gas amount is calculated based on an exhaust valve opening area, an exhaust pressure, and a cylinder pressure. 5. Control device for the mechanism.   5. The variable motion according to claim 2, wherein when the first approximate characteristic line is set, the plurality of timings in the first half of the valve overlap period include an intake valve opening timing. Control device for valve mechanism.   6. The variable valve according to claim 2, wherein when the second approximate characteristic line is set, a change in the cylinder gas amount is calculated based on a cylinder pressure and a cylinder volume. Control device for the mechanism.   When setting the second approximate characteristic line, at least one of top dead center and intake valve opening timing is included in the plurality of times during the valve overlap period. The control apparatus of the variable valve mechanism as described in one.   8. The intake valve passing gas amount is calculated based on an intake valve opening area, an intake pressure, and a cylinder pressure when setting the third approximate characteristic line. Control device for variable valve mechanism.   9. The variable motion according to claim 3, wherein when setting the third approximate characteristic line, the plurality of timings in the first half of the valve overlap period include an intake valve opening timing. Control device for valve mechanism.   The exhaust valve passing gas amount at the time of the intersection of the second approximate characteristic line and the third approximate characteristic line is set to 0 when setting the fourth approximate characteristic line. The control apparatus of the variable valve mechanism as described in any one. Target intake pressure setting means for setting a target intake pressure based on engine operating conditions;
Further comprising target exhaust pressure calculating means for calculating the exhaust pressure when the target intake pressure is reached as the target exhaust pressure,
5. The cylinder internal pressure during the valve overlap period is approximated to a linear change from the target exhaust pressure to the target intake pressure from the intake valve opening timing to the exhaust valve closing timing. The control apparatus for a variable valve mechanism according to any one of claims 8 to 10.   The target residual gas amount is calculated based on the target fresh air amount and target residual gas rate set based on the engine operating conditions, and the clearance volume portion gas amount remaining in the clearance volume portion of the cylinder from the calculated target residual gas amount The control device for a variable valve mechanism according to any one of claims 1 to 11, wherein the target blow-back gas amount is obtained by subtracting.   The control device for a variable valve mechanism according to claim 12, wherein the clearance volume portion is a cylinder internal volume at the effective top dead center. The variable valve mechanism includes a variable lift mechanism capable of continuously changing a lift characteristic of the intake valve, and a variable center phase mechanism capable of continuously changing the central phase of the operating angle of the intake valve;
The control means sets a target lift characteristic of the intake valve based on a target fresh air amount set based on engine operating conditions,
The variable center mechanism according to any one of claims 1 to 13, wherein the center phase variable mechanism is controlled based on the target opening timing, and the variable lift mechanism is controlled based on the target lift characteristic. Control device for variable valve mechanism. The control means uses the sonic intake air amount Q _D as the cylinder intake air amount when suctioned as a sonic flow with the opening area corresponding to the lift amount of the intake valve, and the stroke volume from the start to the end of the intake stroke as the upstream side of the intake valve Between the maximum intake air amount Q _MAX when the cylinder is filled in the side state and the actual cylinder intake air amount is Qcyl, and between (Q _D / Q _MAX ) and (Qcyl / Q _MAX ) Based on the set relationship and the target fresh air amount, a target sonic intake air amount corresponding to the target fresh air amount is calculated,
The control device for a variable valve mechanism according to claim 14, wherein the target lift characteristic is set based on the calculated target sonic intake air amount.   16. The opening area for obtaining the target sonic intake air amount is calculated from the target sonic intake air amount, and the target lift characteristic is set based on the calculated opening area. The control apparatus of the variable valve mechanism as described.

Images