JP3684814B2 - 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, a so-called traction control system that suppresses slippage of the drive wheels in order to improve the startability or acceleration of the vehicle, or a yaw suitable for the vehicle so that the turning running state of the vehicle becomes the target running state. A so-called stability control system (hereinafter referred to as SCS) that generates a moment is known. 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.
[0005]
[Problems to be solved by the invention]
However, in the method corresponding to this by reducing the throttle opening when the driving state control means needs to reduce the output of the engine, the electric throttle valve of the electric throttle valve is not affected until the influence of the change in the throttle opening appears in the engine output. Since a delay due to a drive delay or an intake delay occurs, it is not possible to expect a driving state control with good responsiveness. In addition, a method of reducing the engine output by retarding the ignition timing is generally known. However, unburned gas remains and is likely to burn afterwards, and the exhaust gas temperature becomes high and the catalyst of the exhaust system is provided. There is a problem that the temperature rises excessively.
[0006]
Therefore, the present invention enables the engine output to be controlled with good responsiveness while avoiding the problem of afterburning when it is necessary to reduce the engine output.
[0007]
[Means for Solving the Problems]
The present invention, by performing the forced stratified combustion when there is a request for output reduction adopted cylinder direct injection engine, which solves the above problems.
[0008]
That is, the invention according to claim 1 of this application is 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,
A fuel injection valve that directly injects fuel into the combustion chamber of the engine;
An injection amount setting means for setting the fuel injection amount based on at least the operating state of the engine according to the accelerator operation amount;
The target torque is set according to at least the accelerator operation amount, and when the driving state control means needs to reduce the output, the target torque is corrected and set by the output reduction value set by the driving state control means. Target torque setting means;
In a predetermined engine speed range, an engine operating state in which the target torque to be generated by the engine is equal to or less than a predetermined threshold is set as a first state, and an engine operating state in which the target torque is greater than the predetermined threshold is set as a second state. operating condition of the engine to adjust the fuel injection timing of the fuel injection valve performs a stratified charge combustion when in the first state based on the state, non-stratified combustion when the engine is in the second state Combustion method selection control means for executing
When output reduction is requested by the running state control means , if the engine operating state is in the second state because the corrected target torque is higher than the threshold value, the target torque is forcibly set to the threshold value. The combustion mode changing means for causing the combustion mode selection control means to execute stratified combustion with the operating state of the engine as the first state is set.
[0009]
In the stratified combustion system, by adjusting the fuel injection amount, it is possible to adjust the output with good responsiveness without causing misfire without significantly changing the intake air amount of the engine. No retard is required. Therefore, in the present invention, the stratified combustion method is adopted when there is a demand for output reduction. Further, when the output reduction is required, the target torque of the engine is low, so that it is easy to satisfy the target torque even in the stratified combustion with the air-fuel ratio lean. Thus, the present invention is characterized in that the output reduction request of the traveling state control means is combined with the stratified combustion in the direct injection engine. In particular, responsiveness is required for controlling the running state, which is satisfied by forcing the stratified combustion system in a direct injection engine.
[0010]
Thus, according to the present invention, when the target torque is still high in spite of a request to reduce the output by the traveling state control means, the target torque is forcibly lowered and stratified combustion is performed at the upper limit value of the stratified combustion region. It is something to make. As a result, it becomes possible to quickly respond to the subsequent reduction of the target torque, and the target torque has been reduced in advance, so avoid a torque shock when there is a large reduction request of the target torque. Can do.
[0011]
Invention, the traveling state of executing the output reduction control of the engine when the deviation amount calculated deviation from the target running state of the current running state of vehicles exceeds a first predetermined value according to claim 2 of this application An engine control device provided in a vehicle provided with a control means,
A fuel injection valve that directly injects fuel into the combustion chamber of the engine;
An injection amount setting means for setting the fuel injection amount based on at least the operating state of the engine according to the accelerator operation amount;
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 ;
In a predetermined engine speed range, a large engine operating conditions than the target torque target torque to be generated in the engine is an engine operating condition is below a predetermined threshold value as a first state a predetermined threshold value and the second state, the engine The fuel injection timing of the fuel injection valve is adjusted based on the operating state, and stratified combustion is executed when the engine operating state is in the first state, and non-stratified when the engine operating state is in the second state. Combustion mode selection control means for performing combustion;
When the engine operating state is in the second state because the target torque to be generated by the engine is higher than the threshold when receiving the preliminary signal, the target torque is forcibly set to the threshold. And a combustion mode changing means for causing the combustion mode selection control means to execute stratified combustion with the engine operating state as a first state.
[0012]
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 likely that the output reduction control is executed. Therefore, in the present invention, a preliminary signal is output in such a case, and stratified combustion is executed for a predetermined time based on the preliminary signal. It is what you are doing. Therefore, if there is no output reduction request after that, the combustion method returns to the original selection control, but when there is a request, the transition from non-stratified combustion to stratified combustion is no longer necessary, so the output is quickly reduced. Will be able to. In addition, the forced reduction of the target torque in this case is up to the upper limit value of the stratified combustion region and does not become an excessive reduction. Therefore, it is possible to avoid giving the driver a sense of incongruity. When a large deviation is occurring, this works on the safety side, which can be prevented in advance.
[0013]
Preferably, the engine is a multi-cylinder engine having a plurality of cylinders,
The combustion mode changing means causes stratified combustion to be executed in some cylinders in one cycle in which ignition performed in a predetermined cylinder order makes a round of all the cylinders when the traveling state control means needs to reduce output. In the remaining cylinders, the combustion state selection control means performs the combustion state selection control based on the engine operating state .
[0014]
That is, when the demand for output reduction is not strict, it is possible to control the output with high responsiveness so that the output becomes the target value only by performing stratified combustion in some cylinders. As a result, the remaining cylinders can be maintained in the non-stratified combustion system, and when there is a demand for increased output, the cylinders can respond immediately to the demand without switching from stratified combustion to non-stratified combustion. become.
[0015]
From the viewpoint of reducing the torque fluctuation of the engine, it is preferable to select a cylinder in which stratified combustion is to be performed from among a plurality of cylinders so that stratified combustion and non-stratified combustion are performed alternately. In such a case, the output torque of some cylinders adopting the stratified combustion system is reduced according to the degree of demand for output reduction, and the output torque is maintained for the remaining non-stratified combustion system cylinders. However, if the demand for output reduction becomes stronger, the number of cylinders used in the stratified charge combustion method should be increased.
[0016]
Preferably, during the stratified combustion, the intake air amount becomes a predetermined value or more according to the target torque to be generated by the engine (for example, A / F is 30 when the fuel injection amount of the fuel injection valve is minimum). That is, the throttle opening is determined, and the change in the throttle opening relative to the change in the target torque is smaller than that during non-stratified combustion .
[0017]
That is, since the intake air amount is generally large during stratified combustion, the throttle valve opening is relatively large, and the negative pressure downstream of the throttle valve is small (close to atmospheric pressure). Since it is difficult to control such a small negative pressure with high response according to the target torque, the A / F is controlled by adjusting the fuel injection amount rather than controlling the throttle valve. That is, during stratified combustion, the target air-fuel ratio is greatly changed with respect to the change of the target torque.
[0018]
The stratified combustion is performed by injecting fuel around the spark plug substantially in the second half of the compression stroke, and non-stratified combustion is performed by injecting the entire amount of fuel at any time from the beginning of the intake stroke to the first half of the compression stroke. Alternatively, it can be executed by dividing and injecting a plurality of times during this period .
[0019]
【The invention's effect】
Therefore, according to the invention according to claim 1 of this application, in the direct injection type engine, stratified combustion is executed when the target torque is in the first state equal to or lower than the predetermined threshold , and the target torque is larger than the predetermined threshold. The non-stratified combustion is executed when the second state is established , and the target torque is still higher than the predetermined threshold value even though there is a request for output reduction from the traveling state control means. Since the target torque is forcibly lowered and stratified combustion is executed at the upper limit of the stratified combustion region, it is advantageous for improving the response to the subsequent reduction of the target torque and avoiding the torque shock, and for the ignition timing. The engine output can be controlled with good responsiveness according to the running state of the vehicle without incurring an excessive rise in the exhaust gas temperature due to excessive retarding. It becomes profit.
[0020]
According to the invention of claim 2, in the direct injection type engine, the stratified combustion is executed when the target torque is in the first state equal to or less than the predetermined threshold, and the second state in which the target torque is larger than the predetermined threshold. together so as to perform a non-stratified combustion when in the state, as the control pre-signal is output before the output reduction request of the running state control means, it is so arranged to execute the stratified charge combustion predetermined time, After that, when there is a request to reduce the output, the output can be quickly reduced , and the engine output can be increased according to the running state of the vehicle without causing an excessive rise in the exhaust gas temperature due to an excessive ignition timing retard. It can be controlled with good responsiveness, which is advantageous for controlling the running state.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
(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, and ignition timing control, which will be described later.
[0023]
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 connected to the intake port 24 is provided with an electronically controlled throttle valve 37 that is mechanically separated from the accelerator pedal and driven by a motor based on the accelerator operation amount and the operating state.
[0024]
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.
[0025]
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
[0026]
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,.
[0027]
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.
[0028]
(SCS control)
The configuration of SCS control is shown in FIG.
[0029]
-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.
[0030]
-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 controlling the opening degree of the throttle valve and the operation control of the injector. Therefore, the throttle valve and the injector constitute output adjusting means.
[0031]
-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.
[0032]
-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 selection 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 selection control unit 63 to change the combustion mode based on the running state of the vehicle, Furthermore, a target air-fuel ratio setting unit 65, a fuel injection amount calculation unit 66, a throttle opening calculation unit 67, a fuel injection timing setting unit 71, and the like are provided.
[0033]
That is, the engine is basically controlled by setting the basic torque Tb to be generated by the engine based on the accelerator amount (accelerator pedal depression amount) accel and the engine speed Ne. Based on this, when the SCS 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. 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.
[0034]
-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.
[0035]
-SCS processing-
Next, details of the SCS calculation processing in step S8 will be described.
[0036]
FIG. 7 shows a flow for executing the SCS calculation process. In step S30, wheel speeds v1 to v4, vehicle body speed (vehicle speed) V, front wheel steering angle θ, 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 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).
[0037]
Δβact = ψact + Yact / V (1)
[0038]
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,
[0039]
Δβcont = Δβact + e + Cf (βref−βcont) (2)
Δe = Cf (Δβref−Δβact−e) (3)
However, e: Offset correction value of yaw rate sensor and lateral acceleration sensor Cf: Cut-off frequency
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.
[0041]
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.
[0042]
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. That is,
[0043]
.beta.x = 1 / (1 + A.V2). {1- (M.Lf.V2)
/ (2L·Lr · Cpr)} · Lr · θH / L (4)
A = M · (Cpr · Lr−Cpf · Lf) / 2L 2 · Cpr · Cpf (5)
ΔβTR = C · (βx−βTR) (6)
V: Vehicle speed θH: Front wheel rudder angle
M: Body mass
I: Moment of inertia
L: Wheel base Lf: Distance from front wheel to center of gravity of vehicle body Lr: Distance from rear wheel to center of gravity of vehicle body Cpf: Cornering power of front wheel Cpr: Cornering power of rear wheel C: Value corresponding to phase delay
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.
[0045]
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.
[0046]
The SCS control amount ψ′amt is obtained by multiplying the absolute value of the ψ ′ deviation by the control gain G1.
[0047]
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 |
[0048]
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.
[0049]
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.
[0050]
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).
[0051]
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. This torque reduction of the engine is performed by adjusting the fuel injection amount by stratified combustion of the engine by the engine controller 13, and further by performing fuel cut or cylinder cut as necessary. 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.
[0052]
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.
[0053]
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.
[0054]
-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 Tb is obtained based on the engine speed Ne and the accelerator amount accel (steps S75 and S76). This calculation is performed with reference to the 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.
[0055]
Next, the target torque Tr is obtained based on the basic torque Tb and the torque down amount Ts, and the setting of the cylinder (direct injection layer combustion cylinder) to perform the direct injection stratified combustion based on the torque down amount Ts and the fuel cut The cylinder to be performed is set (steps S77 and S78). That is, as shown in FIG. 14, if the torque reduction amount Ts is equal to or less than Ts1, some cylinders are direct injection stratified combustion cylinders, and the remaining cylinders are normal control holding cylinders (combustion system based on normal operating conditions). (That is, a cylinder that burns with uniform lean or uniform λ = 1). If the torque reduction amount Ts exceeds the threshold value Ts1 and is equal to or less than the threshold value Ts2, all the cylinders are set as the direct injection layer combustion cylinders. If the torque reduction amount Ts exceeds the value Ts2, some cylinders are set as the direct injection layer combustion cylinders. The remaining cylinders are designated as fuel cut cylinders. In this case, Ts1 <Ts2.
[0056]
However, when the increase amount of the torque down amount Ts is large (when the difference between the current torque down amount Ts (k) and the previous torque down amount Ts (K-1) is large), instead of the above Ts1, Also, a smaller threshold value Ts1s is adopted, and a smaller threshold value Ts2s is adopted instead of the above Ts2. This is because an even greater torque reduction is expected, so that it can be dealt with early.
[0057]
Here, in a four-cylinder engine in which the first to fourth cylinders are arranged in a line and ignition goes through all the cylinders in the order of first → third → fourth → second order, for example, the first and fourth cylinders Are set as a part of cylinders to be stratified combustion. In step S79, it is determined whether or not the cylinder is a predetermined cylinder (direct injection stratified combustion cylinder). If it is not the direct injection stratified combustion cylinder, the combustion system selection control unit 63 controls the combustion system to select the direct injection stratified combustion. If it is a cylinder, the combustion system change unit 64 determines whether or not the combustion system needs to be changed.
[0058]
The combustion system selection control unit 63 refers to a map (an optimal value obtained in advance through experiments and stored electronically based on the target torque Tr and the engine speed Ne. The same applies hereinafter). Is selected to set the injection mode of the fuel injection valve 29 (steps S80 to S84, S84A, S84B). That is, in the direct injection stratified combustion region, the direct injection stratified combustion mode, in the uniform lean region instead of the direct injection stratified combustion region, the uniform lean mode, not in the uniform lean mode, and uniform if not the fuel cut cylinder λ = 1 If the mode is a fuel cut cylinder, the fuel cut mode is set. The characteristics of the map are shown in FIG. The region of low rotation to medium rotation and low load to medium load is the direct injection stratified combustion (stratified combustion) region, and the other region is the non-direct injection stratified combustion region. In this embodiment, the high rotation side and high load side regions surrounding the direct injection stratified combustion region are the uniform lean combustion region, and the higher load side than this region is the uniform λ = 1 combustion region.
[0059]
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.
[0060]
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 F scs = 1 (torque down required), the target torque Tr is the upper limit value of the direct injection stratified combustion region (see FIG. 15), that is, the direct torque during normal direct injection stratified combustion operation. It is determined whether or not the torque of the upper limit value of the injection layer combustion operation is exceeded (steps S85 to S87). When the target torque Tr exceeds the upper limit value, the target torque Tr is set as the upper limit value (step S88), and the direct injection stratified combustion cylinder is used as the direct injection stratified combustion mode to execute stratified combustion. When the torque Tr does not exceed the upper limit value, stratified combustion is executed with the target torque Tr. If there is no slip initial signal and Fscs = 0, the injection mode is selected based on the operating state of the engine even in the direct injection stratified combustion cylinder (steps S80 to S84).
[0061]
Therefore, if all the cylinders are set to the direct injection stratified combustion cylinder in step S78 and the target torque Tr is set to the direct injection stratified combustion region upper limit value in step S88, the torque reduction amount will be further increased in the future. Prior to this, all the cylinders can be brought into a direct injection stratified combustion state in which torque control is easy, which is advantageous in ensuring the response to the subsequent torque down request and the necessary torque down amount. In addition, when some cylinders are set as direct injection stratified combustion cylinders in step S78 and the target torque Tr is set as the direct injection stratified combustion region upper limit value in step S88, a part of the torque amount of all cylinders is set. The direct injection stratified combustion cylinder can be finely adjusted, which is advantageous for improving the response and controlling the torque accurately.
[0062]
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. 16. 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.
[0063]
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 the engine speed Ne, and the target A / F, the engine speed, and the 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. 17, and the target A / F approaches λ = 1 from lean as the target torque Trd increases and as the engine speed Ne increases. If the cylinder is in the fuel cut mode, the process returns. If not, the process proceeds to step S94 (step S93A).
[0064]
That is, the fuel injection split ratio (ratio of injection in the intake stroke) is set based on the target torque Tr and the engine speed Ne, and the first-stage injection (intake stroke injection) and the second-stage injection (compression stroke injection) are executed. (Steps S94 to S98).
[0065]
Therefore, as shown in the control time chart in FIG. 18, when the torque reduction amount requested by the SCS control side begins to increase, the injection mode immediately becomes the direct injection stratified combustion mode, and the throttle opening is the opening suitable for stratified combustion. On the other hand, the fuel injection amount immediately decreases to a value corresponding to the upper limit value (region switching point) of the direct injection stratified combustion region due to the forced reduction of the target torque Tr described above. Thereafter, when the target Tr becomes less than or equal to the upper limit value of the direct injection stratified combustion region as the torque reduction amount increases, the fuel injection amount decreases accordingly, and the fuel injection amount increases or decreases according to the increase or decrease of the torque reduction amount. Will do. In the direct injection stratified combustion mode, the throttle opening is maintained in a half-open state, and there is no substantial fluctuation.
[0066]
As described above, since stratified combustion is executed when the SCS requires torque reduction, torque control with good responsiveness can be achieved simply by adjusting the fuel injection amount without changing the throttle opening. This is advantageous for stabilizing the running state. In addition, since the torque control is performed by the stratified combustion method, there is no risk of misfire, and since the ignition timing retard is not required, the problem of the exhaust gas temperature rise can be avoided.
[0067]
Further, when there is an initial slip signal, and when the target torque Tr is high even if there is a request for torque reduction, the target torque Tr is forcibly lowered to the upper limit value of the direct injection stratified combustion region so that stratified combustion is executed. Therefore, it is possible to promptly respond to the subsequent reduction of the target torque Tr, which is advantageous in quickly reestablishing the attitude of the vehicle, and torque when there is a large reduction request of the target torque Tr. Shock can be avoided.
[0068]
Also, when the amount of torque reduction is slightly small, not all the cylinders are subjected to direct injection stratified combustion as described above, but only a part of the cylinders are subjected to direct injection stratified combustion and the remaining cylinders are in the current combustion state ( By setting the uniform lean or uniform λ = 1), the overall torque can be finely adjusted, and when the torque down is released, the original torque can be quickly restored.
[0069]
(Traction control)
Next, traction control will be described with reference to the flowchart shown in FIG. 19. 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 rate 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 SST are calculated.
[0070]
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 and S2 of the front wheels 21FR and 21FL become the target slip ratio STR.
[0071]
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, and decreases as the wheel slip ratio S1, S2,... Increases, and 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.
[0072]
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. 20, 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.
[0073]
In step SD11, as in the case of SCS, the 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 and 21FL is executed. , 41 and the pressure reducing valves 43, 43 are respectively opened and closed to increase / decrease the wheel cylinder pressure of the brakes 2, 2, thereby controlling the braking force of the left and right front wheels 21FR, 21FL, respectively. At the same time, stratified combustion of the engine is executed by the engine controller 13 based on the torque reduction amount Ts to reduce 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.
[0074]
In this traction control, a region in which a part of the cylinders in FIG. 14 is a direct injection stratified combustion cylinder and the remaining cylinders are normal control holding cylinders is set to be enlarged to a large torque down amount side (threshold value). By increasing Ts1), it becomes easy to execute the shift to the acceleration operation after the traction control without delay.
[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 an engine speed Ne, an accelerator amount accel, and a target torque Tr.
FIG. 14 is a diagram showing threshold values for setting a direct injection stratified combustion cylinder and a fuel cut cylinder based on a torque-down amount.
FIG. 15 is a characteristic diagram showing the relationship between the engine speed Ne and the target torque Tr and the combustion method region;
FIG. 16 is a characteristic diagram showing the relationship among target torque Tr, engine speed Ne, and throttle opening.
FIG. 17 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. 18 is a diagram showing a control time chart when the SCS control side needs torque reduction.
FIG. 19 is a flowchart showing the flow of traction control.
FIG. 20 is a characteristic diagram showing the relationship between the slip ratio difference and the torque increase / decrease amount.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 5 Controller 11 Engine 13 Engine controller 19 Combustion chamber 29 Fuel injection valve 61 Basic torque calculating part 62 Target torque calculating part 63 Combustion system selection control part 64 Combustion system change part 66 Fuel injection amount calculating part 67 Throttle opening degree calculating part 71 Fuel injection Time setting section

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,
A fuel injection valve that directly injects fuel into the combustion chamber of the engine;
An injection amount setting means for setting the fuel injection amount based on at least the operating state of the engine according to the accelerator operation amount;
The target torque is set according to at least the accelerator operation amount, and when the driving state control means needs to reduce the output, the target torque is corrected and set by the output reduction value set by the driving state control means. Target torque setting means;
In a predetermined engine speed range, an engine operating state in which the target torque to be generated by the engine is equal to or less than a predetermined threshold is set as a first state, and an engine operating state in which the target torque is greater than the predetermined threshold is set as a second state. operating condition of the engine to adjust the fuel injection timing of the fuel injection valve performs a stratified charge combustion when in the first state based on the state, non-stratified combustion when the engine is in the second state Combustion method selection control means for executing
When output reduction is requested by the running state control means , if the engine operating state is in the second state because the corrected target torque is higher than the threshold value, the target torque is forcibly set to the threshold value. An engine control device comprising combustion mode change means for causing the combustion mode selection control means to execute stratified combustion with the engine operating state set to the first state by setting to Control of an engine provided in a vehicle provided with running state control means for obtaining a deviation of the current running state of the vehicle from the target running state and executing an engine output reduction control when the amount of deviation exceeds a first predetermined value A device,
A fuel injection valve that directly injects fuel into the combustion chamber of the engine;
An injection amount setting means for setting the fuel injection amount based on at least the operating state of the engine according to the accelerator operation amount;
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 ;
In a predetermined engine speed range, a large engine operating conditions than the target torque target torque to be generated in the engine is an engine operating condition is below a predetermined threshold value as a first state a predetermined threshold value and the second state, the engine The fuel injection timing of the fuel injection valve is adjusted based on the operating state, and stratified combustion is executed when the engine operating state is in the first state, and non-stratified when the engine operating state is in the second state. Combustion mode selection control means for performing combustion;
When the engine operating state is in the second state because the target torque to be generated by the engine is higher than the threshold when receiving the preliminary signal, the target torque is forcibly set to the threshold. And a combustion mode change means for causing the combustion mode selection control means to execute stratified combustion with the engine operating state as a first state.

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