JP3680536B2 - Engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an engine control device provided in a vehicle provided with a traveling state control means for controlling the traveling state of the vehicle by adjusting the output of the engine.
[0002]
[Prior art]
  As vehicle running state control means to improve vehicle startability or acceleration
Therefore, a so-called traction control system that suppresses slippage of the drive wheels and a so-called stability control system (hereinafter referred to as SCS) that generates an appropriate yaw moment to the vehicle so that the turning traveling state of the vehicle becomes the target traveling state are known. It has been. In these running state control means, in addition to controlling the braking force on the wheels, the output of the engine is also controlled.
[0003]
  For example, in JP-A-7-127492, regarding traction control, a target value of drive torque (engine generated torque) to be applied to wheels is set in consideration of a road surface friction coefficient and a lateral acceleration of a vehicle, and driven by an electric motor. It is described that torque control is performed by adjusting the throttle opening by a throttle valve.
[0004]
  Japanese Laid-Open Patent Publication No. 7-301139 discloses an engine generated target torque based on an engine speed and an accelerator opening in a direct injection engine with a fuel injection valve that directly injects fuel into a combustion chamber. In addition, it is described that at least two parameters of fuel injection timing, air-fuel ratio, ignition timing, and air amount are controlled in accordance with the target torque. This control is aimed at improving fuel consumption and driving feeling. Further, this publication describes stratified combustion in which fuel mixture is unevenly distributed in a combustion chamber by performing fuel injection in a compression stroke.
[0005]
[Problems to be solved by the invention]
  By the way, the stratified combustion is performed at a lean air-fuel ratio. In that case, if exhaust gas recirculation is performed to return the exhaust gas to the intake system, NOx emission can be suppressed, and the effect becomes larger as the exhaust gas recirculation amount increases. Become. However, if the exhaust gas recirculation is performed as it is when the traveling state control means needs to reduce the output of the engine, misfire is likely to occur when the fuel injection amount is reduced. On the other hand, it is conceivable to adjust the exhaust gas recirculation amount by operating the exhaust gas recirculation valve in conjunction with the adjustment of the fuel injection amount, but from the operation of this valve until the exhaust gas recirculation amount actually decreases. Because there is a response delay, it is actually difficult to avoid misfire. On the other hand, it is conceivable to apply a delay process corresponding to the response delay to the adjustment of the fuel injection amount.NoTherefore, the engine control is required to have high responsiveness and cannot cope with this.
[0006]
  Therefore, the present invention is a cylinder direct injection engine that recirculates exhaust gas, and can control the engine output with good responsiveness when it is necessary to reduce the engine output in order to control the running state. It is.
[0007]
[Means for Solving the Problems]
  The present invention adopts an in-cylinder direct injection engine and requires a reduction in output from the running state control means.ButIn some cases, exhaust gas recirculationIn addition to prohibiting the engine, the engine operating range for stratified combustion is expanded to the high engine load side.By doing so, the above-mentioned problems are solved.
[0008]
  That is, the invention according to claim 1 of this application is a control of an engine provided in a vehicle provided with a traveling state control means for controlling the traveling state of the vehicle by adjusting the output of the engine by an output control means for controlling the output of the engine. A device,
  A fuel injection valve that directly injects fuel into the combustion chamber of the engine;
  An operating state detecting means for detecting the operating state of the engine;
  Combustion mode control means for adjusting the fuel injection timing of the fuel injection valve and executing stratified combustion when the engine is in a predetermined operating state;
  Exhaust recirculation control means for controlling the recirculation amount of exhaust gas recirculated to the intake system of the engine when the engine is at least in the predetermined operating state;With
  When the operating state of the engine is in the predetermined operating state and the traveling state control means needs to reduce the output, The exhaust gas recirculation by the exhaust gas recirculation control meansIn addition to prohibiting, expand the engine operating range for performing the stratified combustion to the high engine load sideIt is characterized by that.
[0009]
  In the stratified combustion method, by adjusting the fuel injection amount, the engine output can be adjusted with good responsiveness without greatly changing the intake air amount of the engine. However, since stable stratified combustion cannot be performed as the fuel injection amount increases, this stratified combustion is effective when the target torque to be generated by the engine is relatively low. Therefore, when the traveling state control means needs to reduce the engine output, the target torque decreases. Therefore, if the stratified combustion is performed, the engine output can be adjusted with good responsiveness to changes in the traveling state.
[0010]
  In the present invention, in the engine in which the exhaust gas is recirculated during the stratified combustion, when the running state control means needs to reduce the output, the exhaust gas is recirculated.BanTherefore, it can be avoided that the recirculated exhaust gas adversely affects the stability of the stratified combustion. That is, it is not necessary to change the exhaust gas recirculation amount in accordance with the increase or decrease of the fuel injection amount, and it is possible to prevent engine misfire due to a delay in response of the exhaust gas recirculation control. Therefore, in the stratified combustion region, it is possible to adjust the output with good responsiveness by increasing or decreasing the fuel injection amount according to the demand of the traveling state control means.
[0011]
  In this way, the misfire caused by the recirculated exhaust gas can be avoided when the output is adjusted according to the demand of the running state control means. In the steady operation, the exhaust gas is recirculated to the limit that does not cause the engine misfire. This is advantageous in reducing NOx.
[0012]
  Moreover, exhaust gas recirculation is prohibited.Accordingly, since the intake air amount increases, stratified combustion can be performed even when the fuel injection amount is larger than when the exhaust gas is recirculated. Therefore, in the present invention, when the exhaust gas recirculation is prohibited, the engine operating region in which stratified combustion is executed is expanded at least to the engine high load side. Therefore, this expansion makes it possible to shift from non-stratified combustion to stratified combustion in an operating region where the engine load is relatively high, and to quickly shift to stratified combustion in response to a request to reduce the output from the traveling state control means. be able to. Further, even when there is a request for an increase in engine output during stratified combustion, it becomes easy to respond to this.
[0013]
  Of this applicationClaim 2The invention according to claim 1 is the engine control apparatus according to claim 1,
  The traveling state control means obtains a deviation from the target traveling state of the current traveling state of the vehicle and requests a reduction in engine output when the deviation amount exceeds a first predetermined value;
  Means for outputting a control preliminary signal for a predetermined time when the deviation occurs and a second predetermined value smaller than the first predetermined value is first exceeded;
  The engine operating state is in the predetermined operating state,When receiving the above spare signalBy the exhaust gas recirculation control meansTo recirculate exhaust gasBanIt is characterized by doing.
[0014]
  That is, the control of the running state is executed based on the deviation between the current running state and the target running state, but when the deviation occurs, the output reduction control is not started immediately, but exceeds a predetermined threshold value. Sometimes that control begins. However, when the deviation occurs to some extent, it is highly possible that the output reduction control is executed. Therefore, in the present invention, a preliminary signal is output in such a case, and the exhaust gas recirculation is suppressed based on the preliminary signal. It is what you are doing. Therefore, if there is no subsequent output reduction request, it returns to the original exhaust gas recirculation state, but when there is a request, the exhaust gas recirculation has already been suppressed, so that it can be promptly performed without causing engine misfire. The engine output can be reduced by reducing the fuel injection amount.
[0015]
【The invention's effect】
  Therefore, according to the invention of this application, in the in-cylinder direct injection engine in which stratified combustion is performed when the engine is in a predetermined operating state and exhaust gas is recirculated,The engine operating state is in the predetermined operating state,When the running state control means needs to reduce the output, the exhaust gas recirculates.In addition to prohibiting, the engine operating range for performing stratified combustion is expanded to the high engine load sideTherefore, during steady operation in stratified combustion, the exhaust gas is introduced to the vicinity of the engine misfire limit to reduce NOx. Even if it is increased or decreased, the engine does not misfire due to the recirculated exhaust gas, and the engine output can be controlled with good responsiveness according to the running state of the vehicle.Moreover, the transition from non-stratified combustion to stratified combustion can be performed in an operating region where the engine load is relatively high,It is possible to quickly shift to stratified combustion in response to a request to reduce the output from the traveling state control means, and to respond to an increase or decrease in engine output in response to a request from the traveling state control means while maintaining stratified combustion. It becomes easy.
[0016]
  In addition, a control preliminary signal is output before the output reduction request of the traveling state control means, so that the exhaust gas is recirculated.BanAccording to this, when there is a subsequent output reduction request, the exhaust gas recirculation has already been performed.BanTherefore, the output can be quickly reduced without causing misfire of the engine, which is advantageous for the control of the driving state with good responsiveness.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
  (overall structure)
  FIG. 1 shows a vehicle with an SCS. In the figure, 1 is a vehicle body, 2, 2,... Are four hydraulic brakes (wheel cylinders) individually disposed on the four wheels 21FR, 21FL, 21RR, 21RL on the front, rear, left, and right. A pressurizing unit 4 for supplying pressurized fluid to 2, and a hydraulic unit 4 (Hudraulic Unit: hereinafter referred to as HU) for distributing and supplying the pressurized fluid from the pressurizing unit 3 to the brakes 2. Reference numeral 5 denotes a controller that controls each brake 2 through the pressurizing unit 3 and the HU 4 and controls engine output, 6 is a wheel speed sensor that detects the wheel speed of each wheel, and 7 is a vehicle lateral direction ( A lateral acceleration sensor for detecting the acceleration Y in the left-right direction, 8 a yaw rate sensor for detecting the yaw rate ψ ′ of the vehicle, 9 for a steering angle sensor for detecting the front wheel steering angle θH, and 10 for liquid according to the driver's brake operation A master cylinder for generating pressure, 11 is a multi-cylinder engine, and 12 is an automatic transmission (AT). An engine controller 13 controls the engine operating state by performing throttle valve opening control, fuel injection valve operation control, EGR valve operation control, and ignition timing control, which will be described later.
[0019]
  The engine 11 is an in-cylinder direct injection engine as shown in FIG. In the figure, 16 is a cylinder block, 17 is a cylinder head, 18 is a piston, 19 is a combustion chamber, 24 is an intake port, 25 is an exhaust port, 26 is an intake valve, and 27 is an exhaust valve. The cylinder head 17 is provided with an ignition plug 28 facing the center of the combustion chamber 19, and fuel is laterally applied to the combustion chamber side wall of the cylinder head 17 toward the lower side of the ignition plug 28 of the combustion chamber 19. A fuel injection valve 29 for injecting is provided. A cavity 30 is formed at the top of the piston 18, and the cavity 30 reflects the fuel injected from the fuel injection valve 29 to the vicinity of the spark plug 28. An exhaust purification catalyst 36 is provided in the exhaust passage 35 extending from the exhaust port 25. An intake passage 38 connected to the intake port 24 is provided with an electronically controlled throttle valve 37 that is mechanically disconnected from the accelerator pedal and driven by a motor based on the accelerator operation amount and the operating state.
[0020]
  An EGR passage 39 that recirculates the exhaust gas from the exhaust passage 35 to the intake system extends to the intake passage 38, and a diaphragm type EGR valve 40 that adjusts the recirculation amount of the exhaust gas is provided in the EGR passage 39.
[0021]
  As shown in FIG. 3, the brakes 2, 2 of the right front wheel 21FR and the left rear wheel 21RL are connected to the master cylinder 10 by the first hydraulic line 22a, and the brakes 2, 2 of the left front wheel 21FL and the right rear wheel 21RR are connected. Are connected to the master cylinder 10 by the second hydraulic pressure line 22b, so that two independent brake systems of the so-called X-pipe type are constructed, and braking force is applied to each wheel in response to the stepping operation of the brake pedal 14. It is to be granted.
[0022]
  The pressurizing unit 3 includes hydraulic pressure pumps 31a and 31b connected to the hydraulic pressure lines 22a and 22b, and hydraulic pressure lines 22a and 22b so that the hydraulic pressure pumps 31a and 31b and the master cylinder 10 can be intermittently connected. Are provided with cut valves 32a and 32b, and a hydraulic pressure sensor 33 for detecting the hydraulic pressure between the cut valves 32a and 32b and the master cylinder 10. Then, the cut valves 32a and 32b are closed in accordance with a signal from the controller 5, so that the hydraulic fluid discharged from the hydraulic pumps 31a and 31b is HU4 regardless of the brake operation by the driver. Is supplied to each brake 2 via
[0023]
  The HU 4 includes pressure valves 41, 41... For increasing the pressure by supplying the pressure fluid supplied from the pressure unit 3 to the brakes 2 via the first hydraulic pressure line 22a or the second hydraulic pressure line 22b. Each brake 2 is connected to a reservoir tank 42, and pressure reducing valves 43, 43. .. And the pressure reducing valves 43, 43,... Are controlled to increase or decrease independently according to the signal from the controller 5. The pressure is increased or decreased, and the braking force applied to each wheel 21FR, 21FL,.
[0024]
  The controller 5 uses a microcomputer and controls the SCS. As will be described in detail later, this SCS control is a slip control of each wheel (the friction between the road surface and the wheel) by adjusting the braking force applied to each wheel when the turning state of the vehicle collapses more than a predetermined value. Force control), the yaw moment is applied to the vehicle, and the engine output is controlled as necessary, so that the turning traveling state of the vehicle becomes the target traveling state. When the driver's brake operation is detected based on the input signal from the hydraulic pressure sensor 33, the controller 5 controls the operation of the pressurizing unit 3 and the HU 4 in response to the brake operation. ing.
[0025]
  (SCS control)
  The configuration of SCS control is shown in FIG.
[0026]
  -Detection system-
  As a detection system for detecting the state of the vehicle for defining the turning state of the vehicle, there are the wheel speed sensor 6, the lateral acceleration sensor 7, the yaw rate sensor 8, and the steering angle sensor 9. The hydraulic pressure sensor 33 also constitutes the detection system.
[0027]
  -Controlled system-
  As the adjusting system, there are provided braking force adjusting means for adjusting the braking force applied to the front, rear, left and right wheels of the vehicle, and output adjusting means for adjusting the output of the driving source for driving the vehicle. In this case, the pressurizing unit 3 and the hydraulic unit 4 constitute braking force adjusting means. Further, the engine output can be adjusted by the throttle valve opening control and the fuel injection valve operation control. Therefore, the throttle valve and the fuel injection valve constitute an output adjusting means.
[0028]
  -Control system-
  The control system includes a state quantity calculation unit 51 that calculates a current vehicle state quantity (a vehicle turning state quantity) based on input signal values from the detection systems 6 to 9, 33, and an input signal value from the detection system. Whether or not to enter SCS control based on a deviation between the vehicle state quantity and the target state quantity, and a target state quantity calculation unit 52 that computes and sets a state quantity (target turning travel state quantity) that is a control target based on And a control necessity determination unit 53 that determines whether or not. Further, as the control unit, a braking force control unit 54 for controlling the operation of the pressurizing unit 3 and the HU 4 to independently adjust the braking force applied to each of the four wheels and generating a yaw moment in the vehicle; There is an engine control unit 55 that reduces the output of the engine 11 by a predetermined amount in principle by the engine controller 13. The control includes β control and ψ ′ control described later.
[0029]
  -Engine controller-
  As shown in FIG. 5, the engine controller 13 includes a basic torque calculation unit 61 that calculates the basic torque Tb based on the operating state of the engine, a target torque calculation unit 62 that calculates the target torque Tr of the engine based on the running state of the vehicle, A combustion mode control unit 63 that selectively controls the combustion mode based on the operating state of the engine; and a combustion mode change unit 64 that causes the combustion mode control unit 63 to change the combustion mode based on the running state of the vehicle. Target air-fuel ratio setting unit 65, fuel injection amount calculation unit 66, throttle opening calculation unit 67, exhaust gas recirculation control unit 71 that controls recirculation of exhaust gas based on the operating state of the engine, exhaust gas based on the running state of the vehicle An exhaust gas recirculation suppression unit 72 that suppresses the recirculation of fuel and a fuel injection timing setting unit 73 are provided.
[0030]
  That is, basically, the basic torque Tb to be generated by the engine is set based on the accelerator amount (accelerator pedal depression amount) accel and the engine speed Ne, but the SCS is controlled based on the running state of the vehicle. When the control system needs to reduce the engine output, the target torque Tr to be generated by the engine is set accordingly, and the combustion method of the engine is changed.
[0031]
  The exhaust gas recirculation is basically controlled by calculating the lift amount of the EGR valve 40 based on the accelerator amount accel and the engine speed Ne, but the SCS control system is controlled based on the running state of the vehicle. When it is necessary to reduce the engine output, the exhaust gas recirculation control is suppressed.
[0032]
  Accordingly, the detection system for engine control includes an accelerator sensor 68 for detecting the accelerator amount accel from the amount of depression of the accelerator pedal, and a rotation sensor 69 for detecting the engine speed Ne, and also from the SCS control system. Input the signal.
[0033]
  -Details of control-
  FIG. 6 shows the overall operation for executing the travel control of the vehicle. First, when the ignition switch is turned on by the driver and the engine is started, the controller 5 is initialized in step S2, and the previous processing is performed. Clears the stored sensor detection signals and calculated values. In step S4, detection system signals such as the wheel speed signals v1 to v4, the steering angle signal θH, the yaw rate signal ψ ′, and the lateral acceleration signal Y are input. In step S6, a vehicle state quantity based on each detection signal described above is calculated. In step S8, the SCS control target value and control output value necessary for SCS control are calculated from the vehicle state quantity calculated in step S6, and the SCS is output in step S10.
[0034]
  -SCS processing-
  Next, details of the SCS calculation processing in step S8 will be described.
[0035]
  FIG. 7 shows a flow for executing the SCS calculation process. In step S30, the wheel speeds v1 to v4, the vehicle body speed (vehicle speed) V, the front wheel steering angle θ, the actual yaw rate (actual yaw rate) ψ′act, Enter the actual lateral acceleration Yact. The vehicle body speed V is calculated based on the wheel speed of the driven wheel, and the actual yaw rate ψ′act and the actual lateral acceleration Yact are obtained from the output signals of the yaw rate sensor 8 and the lateral acceleration sensor 7. In step S32, the vertical load generated in the vehicle is estimated and calculated by a well-known mathematical method based on the vehicle body speed V and the lateral acceleration Yact. In step S33, the actual side slip angle βact actually generated in the vehicle is calculated. The actual side slip angle βact is calculated by integrating the change rate Δβact, and the change rate Δβact is calculated by the following equation (1).
[0036]
    Δβact = ψact + Yact / V (1)
[0037]
  Next, in step S34, a reference value βref that is referred to in the calculation of the estimated skid angle βcont that is actually used for the SCS control is calculated. This reference value βref includes vehicle specifications and vehicle state quantities (body speed V, yaw rate ψ'act, actual lateral acceleration Yact, actual skid angle βact change rate Δβact, and yaw rate ψ'act change amount (differential value). Δψ′act), the estimated value D1 of the yaw moment generated by the brake, and the estimated value D2 of the lateral force decrease amount generated by the brake are calculated using the two-degree-of-freedom model. In short, the reference value βref calculates the side slip angle estimated based on the detected vehicle state quantity and the brake operation force. Thereafter, in step S35, an estimated side slip angle βcont actually used for the SCS control is calculated. The estimated side slip angle βcont is calculated by solving a differential equation derived from the following equations (2) and (3). That is,
[0038]
  Δβcont = Δβact + e + Cf (βref−βcont) (2)
  Δe = Cf (Δβref−Δβact−e) (3)
    E: Offset correction value of yaw rate sensor and lateral acceleration sensor
        Cf: Cut-off frequency
[0039]
  The cut-off frequency Cf is a correction speed for correcting the estimated side slip angle βcont to converge to the reference value βref according to the reliability of the reference value βref and resetting the integral error occurring in the estimated side slip angle βcont. This is a change factor, and is a coefficient that is corrected to be smaller as the reliability of the reference value βref is lower. In addition, the reliability of the reference value βref is lowered when a change occurs in the cornering power Cpf of the front wheels or the cornering power Cpr of the rear wheels.
[0040]
  In step S36, the wheel slip ratio and wheel slip angle of each wheel are calculated. The wheel slip ratio and the wheel slip angle are estimated and calculated by a well-known mathematical method from the wheel speeds v1 to v4, the vehicle body speed V, the estimated side slip angle βcont, and the front wheel steering angle θH of each wheel. In step S38, the load factor to each wheel is calculated. The wheel load factor is a ratio of the current grip force to the total grip force that can be exhibited by the tire 23 of each wheel, and is calculated from the wheel slip rate and wheel slip angle calculated in step S36 and the vertical load calculated in step S32. Estimated by a well-known mathematical method. In step S40, the friction coefficient μ of the running road surface is estimated and calculated by a well-known mathematical method from the actual lateral acceleration Yact and the wheel load factor calculated in step S38.
[0041]
  In step S42, a target yaw rate ψTR and a target side slip angle βTR, which are target values for converging the actual yaw rate ψ'act and the estimated side slip angle βcont, are calculated. The target yaw rate ψTR is estimated and calculated by a well-known mathematical method from the vehicle body speed V, the road surface friction coefficient μ calculated in step S40, and the front wheel steering angle θH. The target side slip angle βTR is calculated by solving a differential equation of Expression (6) derived from Expressions (4) and (5) below.
[0042]
  βx = 1 / (1 + A · V²) ・ {1- (M ・ Lf ・ V²)
          / (2L·Lr · Cpr)} · Lr · θH / L (4)
  A = M · (Cpr · Lr−Cpf · Lf) / 2L²・ Cpr ・ Cpf (5)
  ΔβTR = C · (βx−βTR) (6)
    V: Vehicle speed
        θH: Front wheel rudder angle
          M: Body mass
          I: Moment of inertia
          L: foil base
        Lf: Distance from the front wheel to the center of gravity of the vehicle
        Lr: Distance from the rear wheel to the center of gravity of the vehicle
        Cpf: Front wheel cornering power
        Cpr: Rear wheel cornering power
        C: Value corresponding to phase delay
[0043]
  Next, in step S44 shown in FIG. 8, it is determined whether or not the absolute value of a value obtained by subtracting the estimated side slip angle βcont from the target side slip angle βTR (hereinafter referred to as β deviation) is equal to or greater than the SCS control start threshold value A. When this determination is YES, the process proceeds to step S46, and the SCS control target value is set to the target skid angle βTR. On the other hand, when this determination is NO, the routine proceeds to step S52, where the absolute value of the value obtained by subtracting the actual yaw rate ψ'act from the target yaw rate ψ'TR (hereinafter referred to as ψ 'deviation) is equal to or greater than the SCS control start threshold B. It is determined whether or not. When this determination is YES, the process proceeds to step S54, and the SCS control target value is set to the target yaw rate ψ'TR. When this determination is NO, the process returns to step S30 to repeatedly execute the above-described processing.
[0044]
  Next, in step S50, the SCS control amount βamt actually used for the SCS control is calculated. In step S56, the SCS control amount ψ'amt actually used for the SCS control is calculated.
[0045]
  The SCS control amount ψ′amt is obtained by multiplying the absolute value of the ψ ′ deviation by the control gain G1.
[0046]
                  ψ′amt = G1 × | ψ′deviation |
  The SCS control amount βamt is obtained by multiplying the absolute value of β deviation by the control gain G2.
                  βamt = G2 × | β deviation |
[0047]
  That is, when the deviation of the vehicle from the target state in the turning state is not so large (step S44 = NO and step S45 = YES), the yaw rate ψ ′ converges to the target yaw rate ψ′TR corresponding to the driving operation. Ψ ′ control is performed in which a relatively small yaw moment proportional to the absolute value of the ψ ′ deviation is applied to the vehicle. On the other hand, when the deviation of the vehicle from the target state in turning is large (step S44 = YES), the vehicle side slip angle β is relatively proportional to the absolute value of the β deviation so that the vehicle body side slip angle β converges to the target side slip angle βTR. Β control for applying a large yaw moment to the vehicle is performed.
[0048]
  In the above-described ψ ′ control and β control, first, in steps S58 and S59, based on the SCS control amount ψ′amt or βamt, a wheel to which a braking force is applied for SCS control is selected from four wheels. This is done by calculating the amount of braking force applied to the selected wheel.
[0049]
  That is, when the yaw rate ψ ′ is increased clockwise in the ψ ′ control, and when the vehicle turning posture is to be corrected to the right side in the β control, the right front wheel 21FR or the right front and rear wheels 21FR, 21RR are compared. By applying a braking force according to the SCS control amount ψ′amt or βamt and adjusting the slip ratio of the wheel, that is, the frictional force between the wheel and the road surface, a clockwise yaw moment is applied to the vehicle. . On the other hand, when the yaw rate ψ ′ is increased counterclockwise, and when the vehicle turning posture is to be corrected to the left, the SCS control amount ψ is applied to the left front wheel 21FL or the left front and rear wheels 21FL, 21RL. By applying a braking force according to ′ amt or βamt and adjusting the frictional force between the wheel and the road surface, a counterclockwise yaw moment is applied to the vehicle. This brake control is executed by calculating the valve opening degree of each of the pressurizing valve 41 and the pressure reducing valve 43 of the HU 4 for applying a required braking force to the selected wheel (step S70).
[0050]
  When the β deviation or ψ ′ deviation is large, engine control is performed. The purpose of this engine control is to stabilize the turning state by deceleration of the vehicle. For this purpose, the engine torque-down amount Ts is calculated. The engine torque is reduced by the engine controller 13 by making the combustion of the engine stratified combustion and suppressing the recirculation of the exhaust gas to adjust the fuel injection amount. It is executed by making a cut. The fuel cut is to stop the fuel injection of all cylinders of the engine 11 instantaneously, and the cylinder cut is to stop the fuel injection of some cylinders.
[0051]
  That is, when the β deviation is equal to or greater than the predetermined value A1 or the ψ ′ deviation is equal to or greater than the predetermined value B1, a slip initial signal (engine control preliminary signal) is output for a predetermined time (steps S60 → S61 or S65 → S66). Further, when the β deviation is greater than or equal to the predetermined value A2 or the ψ ′ deviation is greater than or equal to the predetermined value B2, the torque reduction amount Ts is calculated (step S62 → S63 or S67 → S68), and the SCS flag Fscs is set to “1” (step S64, S69) Engine control is executed by the engine controller 13. When the β deviation is less than A and the ψ ′ deviation is less than B, Fscs is set to “0” (step S71). The torque down amount Ts is obtained by multiplying the β deviation or ψ ′ deviation by a predetermined control gain.
[0052]
  The slip initial signal is output when the deviation from the target value of the running state of the vehicle is increasing and there is a high possibility of entering into engine control. When the deviation further increases, the engine control is performed. Will enter. Therefore, A2> A1> A and B2> B1> B. The calculation of the torque-down amount Ts based on the β deviation or the ψ ′ deviation is performed with reference to a table (an optimal value obtained in advance through experiments and stored electronically; the same applies hereinafter). The characteristics of the table are as shown in FIGS. 9 and 10, and the torque down amount Ts increases as the β deviation or the ψ ′ deviation increases.
[0053]
  -Engine control-
  The control flow is shown in FIGS. In FIG. 11, signals of the engine speed Ne, the accelerator amount accel and the torque down amount Ts are taken in, and the basic torque calculator 61 obtains the basic torque Tb based on the engine speed Ne and the accelerator amount accel, and calculates the target torque. The unit 62 obtains the target torque Tr based on the basic torque Tb and the torque down amount Ts (steps S75 to S77). The basic torque Tb is calculated with reference to a table. The characteristics of the table are as shown in FIG. 13, and the basic torque Tb increases as the engine speed Ne decreases and as the accelerator amount accel increases. The characteristic line in the figure is an equal torque line.
[0054]
  Further, the exhaust gas recirculation control unit 71 refers to a map (the one in which an optimum value is obtained in advance by experiment and stored electronically based on the engine speed Ne and the target torque Tr. The same applies hereinafter). The lift amount of the valve 40 is obtained (step S78). The characteristics of this map are shown in FIG. 14. In the direct injection stratified combustion region (low to medium rotation and low load to medium load region), the higher the engine speed Ne, and the target torque Tr (engine load). As E becomes higher, the EGR valve lift amount increases (the exhaust gas recirculation amount increases). In the uniform lean combustion region (the region on the high rotation side and the high load side surrounding the direct injection stratified combustion region), the EGR valve lift amount is small, and the uniform λ = 1 further outside (the high load side) than this uniform lean combustion region. The lift amount becomes zero in the combustion region.
[0055]
  In the direct injection stratified combustion region, the lift amount increases on the high-rotation high-torque side because the rise in the combustion temperature is taken into account, and in the uniform lean combustion region, the lift amount decreases to reduce the combustion stability. This is because the lift amount is made zero in the uniform λ = 1 combustion region because NOx can be purified by the three-way catalyst and high output is secured.
[0056]
  The combustion system control unit 63 refers to the map based on the target torque Tr and the engine speed Ne when there is no initial slip signal from the SCS and there is no request for torque reduction (Fscs = 0). Is selected to set the injection mode of the fuel injection valve 29 (steps S79 to S85). The characteristics of the map are as shown in FIG.
[0057]
  In the stratified combustion, the target air-fuel ratio is set to an air-fuel ratio leaner than λ = 1, and fuel is injected only in the substantially second half of the compression stroke so that the air-fuel mixture is unevenly distributed around the spark plug 28. It is. In uniform lean combustion, the target air-fuel ratio is set to an air-fuel ratio leaner than λ = 1, and fuel is injected in its entirety at any time from the beginning of the intake stroke to the first half of the compression stroke, or divided into multiple times during this period. In this manner, the entire combustion chamber is ignited and burned with a substantially uniform lean air-fuel ratio. In the uniform λ = 1 combustion, the target air-fuel ratio is set to about λ = 1, and the fuel is injected in the whole amount at any time in the period from the beginning of the intake stroke to the first half of the compression stroke, or divided into multiple times in this period. In this way, the air-fuel ratio of the entire combustion chamber is set to approximately λ = 1 to cause ignition combustion. However, at the time of transition from stratified combustion to non-stratified combustion, and at the time of transition from non-stratified combustion to stratified combustion, fuel is divided and injected into an intake stroke and a compression stroke. Further, the split injection can be performed also in non-stratified combustion.
[0058]
  The combustion system changing unit 64 determines whether or not stratified combustion is necessary based on the presence or absence of the slip initial signal and the SCS flag Fscs. That is, if the slip initial signal is present or Fscs = 1 (torque down required), the direct injection stratified combustion mode is adopted as the combustion method to execute the stratified combustion in preference to the selection control of the combustion method control unit 63. (Steps S79, S80, S82).
[0059]
  The exhaust gas recirculation suppression unit 72 determines whether it is necessary to suppress exhaust gas recirculation based on the presence / absence of the slip initial signal and the SCS flag Fscs. That is, if the slip initial signal is present or Fscs = 1 (torque down is required), the lift amount of the EGR valve 40 is set to the minimum value (target torque) at the current engine speed Ne in preference to the control of the exhaust gas recirculation control unit 71. By setting the Tr to the lowest value), exhaust gas recirculation is suppressed (steps S79, S80, S86). As a result, the engine speed has a far greater delay than the EGR control delay, and even if the lift amount of the EGR amount is not fully closed, once the minimum value is set, the change in the engine speed is small, so it is urgent. EGR suppression effect can be exhibited.
[0060]
  The operation control of each cylinder for which the combustion method is determined as described above is performed according to FIG. First, the throttle opening is determined based on the target torque Tr and the engine speed Ne, and the throttle valve is driven (steps S89 and S90). That is, the target air-fuel ratio is obtained by referring to the map based on the target torque Tr and the engine speed Ne, and the throttle opening is obtained by referring to the map using the target air-fuel ratio. The characteristics of the change in the throttle opening with respect to the change in the target torque Tr and the engine speed Ne are shown in FIG. 15. In the direct injection stratified combustion mode, the change in the throttle opening with respect to the change in the target torque Tr is small. Further, the change becomes larger as the uniform λ = 1 mode is obtained.
[0061]
  Next, with respect to the target torque Tr, an annealing process (delay correction) is performed to reflect the previous value at a predetermined ratio in the current value, and Trd is obtained (step S91). A target air-fuel ratio A / F for fuel injection is set with reference to the map based on the corrected target Trd and engine speed Ne, and the target A / F, engine speed, and air flow rate upstream of the throttle valve are set. The fuel injection amount is obtained based on the output of the air flow sensor for detecting the fuel flow (steps S92 and S93). The characteristics of this A / F map are shown in FIG. 16, and the target A / F approaches λ = 1 from lean as the target torque Trd increases and the engine speed Ne increases.
[0062]
  Then, based on the target torque Tr and the engine speed Ne, the fuel injection split ratio (ratio of injection in the intake stroke) is set, and the first half injection (intake stroke injection) and the second half injection (compression stroke injection) are executed. (Steps S94 to S98).
[0063]
  Therefore, as shown in the time chart of control in FIG. 17, when the increase in torque reduction required by the SCS control side starts, the injection mode immediately becomes the direct injection stratified combustion mode, and the throttle opening is the opening suitable for stratified combustion. The fuel injection amount decreases as the torque down amount increases, and the fuel injection amount increases or decreases according to the increase or decrease of the torque down amount. In the direct injection stratified combustion mode, the throttle opening is maintained in a half-open state, and there is no substantial fluctuation. On the other hand, the lift amount of the EGR valve 40 decreases beyond the target value of the current operating condition (the lift amount determined by the engine speed Ne and the target torque Tr in FIG. 14).
[0064]
  As described above, when the SCS needs torque reduction, exhaust gas recirculation is suppressed and stratified combustion is executed. Therefore, it is possible to avoid the recirculated exhaust gas from adversely affecting the stability of stratified combustion. . That is, it is not necessary to change the exhaust gas recirculation amount in accordance with the increase or decrease of the fuel injection amount, and it is possible to prevent engine misfire due to a delay in response of the exhaust gas recirculation control. In the stratified combustion region, the torque can be controlled with good responsiveness only by adjusting the fuel injection amount without substantially changing the throttle opening, which is advantageous for stabilizing the running state. Further, since the ignition timing retard is not required, the problem of the exhaust gas temperature rise can be avoided. Moreover, since the exhaust gas recirculation itself continues at a minimum value, it is advantageous for suppressing the generation of NOx.
[0065]
  Further, even when there is an initial slip signal, exhaust gas recirculation is suppressed and stratified combustion is executed. When torque reduction is required after that, exhaust gas recirculation is already suppressed. The engine output can be reduced by quickly reducing the fuel injection amount without causing misfire of the engine.
[0066]
  Further, even when high responsiveness is required for torque control called SCS, this can be handled with good responsiveness.
[0067]
  (Other embodiments)
  FIG. 18 shows a control flow of another embodiment relating to suppression of exhaust gas recirculation and execution of stratified charge combustion. In this embodiment, the exhaust gas recirculation suppression means 72 employs a technique for prohibiting the recirculation as a means for suppressing the recirculation of the exhaust gas, and the stratified combustion region expansion means for expanding the direct injection stratified combustion region at that time is adopted. I have.
[0068]
  That is, if the slip initial signal is present or Fscs = 1 (torque down required), the lift amount of the EGR valve 40 is set to zero, and the combustion system control unit 63 refers to the map in which the direct injection stratified combustion region is expanded. Then, combustion type selection control is performed (steps S79, S80, S87, S88). In this case, as shown in FIG. 19, a map is used which is enlarged on the high rotation side and the high torque side than when the direct injection stratified combustion region and the uniform lean combustion region are not required to reduce the torque (shown by a broken line). However, the expansion width of the direct injection stratified combustion region is larger than the expansion width of the uniform lean combustion region.
[0069]
  The reason why such an area can be expanded is that the amount of intake air increases with the prohibition of recirculation of exhaust gas, and the combustibility increases. Also, the expansion width of the direct injection stratified combustion region is larger than the expansion width of the uniform lean combustion region because the direct injection stratified combustion region originally has a larger amount of exhaust gas recirculation. This is because the effect of improving stability is great.
[0070]
  Therefore, due to this expansion, when there is a request for torque reduction from the SCS side, stratified combustion is executed even when the target torque Tr is relatively high or the engine speed is relatively high. Thus, the increase / decrease control of the output can be performed with good responsiveness according to the change of the running state while maintaining the stratified combustion.
[0071]
  (Traction control)
  Next, traction control will be described with reference to the flowchart shown in FIG. 20. In step SD1, it is determined whether or not the throttle valve is open. If closed, the process proceeds to step SD2, and the accelerator operation by the driver is determined. The value of the accelerator flag Facc indicating presence / absence is set to Facc = 0 and the process returns. On the other hand, if the throttle valve is open, the process proceeds to step SD3, where the wheel slip ratio is calculated based on the road surface friction coefficient μTCS estimated from the wheel speeds v1 and v2 of the front wheels 21FR and 21FL, the vehicle body speed and the engine output. A target slip ratio STR, which is a control target value of S1, S2,..., And a traction control start threshold value SST are calculated.
[0072]
  In step SD5, the wheel slip rates S1 and S2 of the front wheels 21FR and 21FL are individually compared with the start threshold value SST. If the wheel slip rates S1 and S2 are both equal to or less than the start threshold value SST, the process proceeds to step SD6. If Facc = 1, the process proceeds to step SD8. If Facc = 0 and the accelerator is not being operated, the process returns. On the other hand, if either of the wheel slip ratios S1 and S2 is larger than the start threshold value SST, the process proceeds to step SD7, where the accelerator flag Facc = 1 is set, and the process proceeds to step SD8. That is, once this is started, the traction control is continued until the driver's accelerator operation is stopped, or until the wheel slip ratios S1, S2 of the front wheels 21FR, 21FL both reach the target slip ratio STR.
[0073]
  In step SD8, the base control amount Bbase of the brake control amount B of each of the front wheels 21FR, 21FL is calculated by subtracting the target slip ratio STR from the wheel slip ratios S1, S2 and the wheel slip ratios S1, S2,. Read from the map based on the amount of change. In this map, the wheel cylinder pressure increases as the slip ratio difference increases positively, decreases as the wheel slip ratio S1, S2,... Decreases, and increases as the wheel slip ratio S1, S2,. It is set to increase as the amount of change increases. In step SD9, the brake control amount B is calculated by multiplying the brake base control amount Bbase by preset control gains k1 and k2.
[0074]
  In step SD10, the engine torque increase / decrease amount Tud by the engine controller 13 is obtained from the map. The characteristics of this map are shown in FIG. 21, and the torque down amount increases as the slip ratio difference increases positively, and the torque up amount increases as the slip ratio difference decreases negatively.
[0075]
  In step SD11, as in the case of SCS, control output to the pressurizing unit 3 and HU4 is executed based on the calculated brake control amount B, and the pressurizing valve 41 attached to the left and right front wheels 21FR, 21FL is executed. 41 and pressure reducing valves 43 and 43 are respectively opened and closed to increase or decrease the wheel cylinder pressures of the brakes 2 and 2, thereby controlling the braking forces of the left and right front wheels 21FR and 21FL, respectively. At the same time, the engine controller 13 suppresses the exhaust gas recirculation, expands the direct injection stratified combustion region, and executes the stratified combustion of the engine based on the torque down amount Ts, thereby reducing the engine output torque. As described above, the driving force to the left and right front wheels 21FR and 21FL is controlled, and the front wheels 21FR and 21FL generate the maximum driving force.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of a vehicle according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing the structure of an in-cylinder direct injection engine.
FIG. 3 is a plan view showing a brake system of the vehicle.
FIG. 4 is a block diagram showing an SCS control system of the vehicle.
FIG. 5 is a block diagram showing a control system of an engine controller.
FIG. 6 is a flowchart showing the basic flow of SCS control.
FIG. 7 is a flowchart showing the flow of SCS calculation processing.
FIG. 8 is a flowchart showing the flow of SCS control using the calculation result.
FIG. 9 is a characteristic diagram showing the relationship between β deviation and torque down amount Ts.
FIG. 10 is a characteristic diagram showing a relationship between a ψ ′ deviation and a torque-down amount Ts.
FIG. 11 is a flowchart showing a flow of engine control.
FIG. 12 is a flowchart showing the continuation of the engine control flow.
FIG. 13 is a characteristic diagram showing the relationship between the engine speed Ne, the accelerator amount accel, and the target torque Tr.
FIG. 14 is a characteristic diagram showing the relationship between the engine speed Ne and the target torque Tr, the combustion mode region, and the EGR valve lift amount.
FIG. 15 is a characteristic diagram showing the relationship among the target torque Tr, the engine speed Ne, and the throttle opening.
FIG. 16 is a characteristic diagram showing the relationship among the target torque Tr, the engine speed Ne, and the target air-fuel ratio for fuel injection.
FIG. 17 is a diagram showing a control time chart when the SCS control side requires torque reduction.
FIG. 18 is a flowchart showing the flow of control according to another embodiment relating to suppression of exhaust gas recirculation and execution of stratified combustion.
FIG. 19 is an enlarged view of a direct injection stratified combustion region and a uniform lean combustion region in the same embodiment.
FIG. 20 is a flowchart showing the flow of traction control.
FIG. 21 is a characteristic diagram showing the relationship between the slip ratio difference and the torque increase / decrease amount.
[Explanation of symbols]
    5 Controller
  11 engine
  13 Engine controller
  19 Combustion chamber
  29 Fuel injection valve
  61 Basic torque calculator
  62 Target torque calculator
  63 Combustion system controller
  64 Combustion system change section
  66 Fuel injection amount calculation unit
  67 Throttle opening calculator
  71 Exhaust gas recirculation controller
  72 Exhaust gas recirculation suppression part

Claims (2)

An engine control device provided in a vehicle provided with a running state control means for controlling the running state of the vehicle by adjusting the output of the engine by an output control means for controlling the output of the engine,
A fuel injection valve that directly injects fuel into the combustion chamber of the engine;
Driving state detecting means for detecting the driving state of the engine;
Combustion mode control means for adjusting the fuel injection timing of the fuel injection valve and executing stratified combustion when the engine is in a predetermined operating state;
Exhaust recirculation control means for controlling a recirculation amount of exhaust gas recirculated to the intake system of the engine when the engine is at least in the predetermined operating state ;
When the operating state of the engine is in the predetermined operating state and the traveling state control unit needs to reduce the output , the exhaust gas recirculation control unit prohibits the exhaust gas recirculation and executes the stratified combustion. An engine control device that expands an engine operating range to a high engine load side . In the engine control device according to claim 1,
The traveling state control means obtains a deviation from the target traveling state of the current traveling state of the vehicle and requests a reduction in engine output when the deviation amount exceeds a first predetermined value;
Means for outputting a control preliminary signal for a predetermined time when the deviation occurs and a second predetermined value smaller than the first predetermined value is first exceeded;
An engine control device, wherein the exhaust gas recirculation is prohibited by the exhaust gas recirculation control means when the engine is in the predetermined operational state and receiving the preliminary signal.

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