JPH11129784A - Method and system for controlling vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a system for controlling a vehicle capable of minimizing the fuel consumption rate in the operation condition of the vehicle for every moment. SOLUTION: A control unit 100 to control an engine 10 of a vehicle and an automatic transmission 20, is provided with a target drive torque setting part 120 to set the target drive torque Td which is the target torque of a drive wheel from the accelerator step-in angle θac and a vehicle speed (v), and a target value setting part 140 to set the target air-fuel ratio tA/F to minimize the fuel consumption rate and the target transmission gear ratio tNin under the prescribed condition to realize the operation of the engine 10 and the transmission 20 while satisfying the target drive torque Td set by the target drive torque setting part to the present vehicle speed. A hydraulic circuit 28 of the transmission 20 is controlled by the target transmission gear ratio tNin and the engine 10 is controlled so as to realize the target air-fuel ratio tA/F.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vehicle control method and a vehicle control system, and more particularly to a vehicle control method and a vehicle control system for controlling an engine and an automatic transmission mounted on a vehicle to reduce a fuel consumption rate. About.

[0002]

2. Description of the Related Art As a conventional control method of an engine and a transmission for realizing low fuel consumption, for example, “Hideya Fujisawa,
Hisashinori Kobayashi, "Electronically Controlled Gasoline Injection" (July 5, 1987), Sankaido Publishing, p. As described in “164”, a method using a continuously variable transmission and a throttle drive actuator is known. In this method, a continuously variable transmission and a throttle drive actuator are used in accordance with an accelerator signal operated by a driver in order to operate the engine in an operation region where the fuel efficiency of the engine is the best and improve fuel efficiency. The throttle opening and the gear ratio are controlled in a complex manner. In this method, while operating such that the air-fuel ratio becomes a stoichiometric value of 14.7, the gear ratio is set to an optimum state to improve fuel efficiency.

On the other hand, as a method of improving fuel efficiency by controlling the engine alone, there are methods described in "Yasuo Nakajima, Shigeo Muranaka," Gasoline Engine for New Automobile "(April 30, 1994), Sankaido Shuppan, P.S. As described in “44”, lean burn control is known. According to this method, fuel having an air-fuel ratio of about 20 is burned in a lean state, thereby improving theoretical thermal efficiency and improving fuel efficiency.

[0004]

SUMMARY OF THE INVENTION The present inventors have studied to improve fuel economy by a method combining the above two methods. The method first calculates the target gear ratio and target torque from the accelerator signal operated by the driver using the fuel consumption rate table with the stoichiometric air-fuel ratio to minimize fuel consumption, and then achieves the target torque. Thus, the engine transmission is controlled by setting an air-fuel ratio with good fuel efficiency as much as possible. However,
It has been found that this method can improve the fuel efficiency but does not always operate the engine and the transmission at the optimum fuel efficiency point.

It is an object of the present invention to provide a vehicle control method and a vehicle control system capable of minimizing a fuel consumption rate in a running state of a vehicle every moment.

[0006]

[Means for Solving the Problems]

(1) In order to achieve the above object, the present invention provides a vehicle control method for controlling an engine and an automatic transmission of a vehicle, wherein a target drive torque which is a target torque of a drive wheel is calculated from an accelerator pedal depression angle and a vehicle speed, Calculate a target air-fuel ratio and a target gear ratio that minimize the fuel consumption rate under predetermined conditions that realize the operation of the engine and the transmission while satisfying the target drive torque with respect to the current vehicle speed. The engine and the transmission are controlled so as to achieve the target air-fuel ratio and the target gear ratio value. With this method, the engine and the transmission are controlled so as to realize the calculated target air-fuel ratio and target gear ratio value, so that the fuel consumption rate can be minimized in the instantaneous driving state of the vehicle. Become.

(2) In the above (1), preferably,
In the calculation of the target air-fuel ratio and the target gear ratio, a basic fuel consumption rate function represented by an engine generated torque obtained from the target drive torque and an engine speed obtained from the current vehicle speed was corrected by a combustion efficiency correction coefficient. The fuel consumption rate function is determined so as to be minimized. With this method, the target air-fuel ratio and the target gear ratio that minimize the fuel consumption rate function can be calculated.

(3) In the above (2), preferably,
The engine generated torque is calculated based on the change rates of the target drive torque and the vehicle speed and the change rate of the engine speed. With this method, the fuel consumption rate in the transient operation state of the engine can be optimized.

(4) In the above (1), preferably,
The calculation of the target air-fuel ratio and the target gear ratio uses a table in which the drive torque of the drive wheels and the vehicle speed are used as axis variables and data is obtained in advance so as to minimize the fuel consumption rate. . With this method, the calculation of the target air-fuel ratio and the target gear ratio can be easily performed.

(5) In the above (1), preferably,
Further, a target EGR rate that minimizes the fuel consumption rate is calculated, and the engine and the transmission are controlled so as to realize the target EGR rate. With this method, the target air-fuel ratio, the target gear ratio, and the target EGR rate that minimize the fuel consumption rate function can be calculated.

(6) In the above (1) or (5), preferably, the predetermined condition is a condition in which an air-fuel ratio can be taken,
This is a range in which the gear ratio can be taken or a range in which the EGR rate can be taken.

(7) In order to achieve the above object, the present invention provides a fuel supply system which satisfies a target driving torque for a current vehicle speed and realizes the operation of the engine and the transmission under predetermined conditions. A target air-fuel ratio and a target speed ratio that minimize the consumption rate are calculated, and the engine and the transmission are controlled so as to realize the target air-fuel ratio and the target speed ratio value. With this method, the engine and the transmission are controlled so as to realize the calculated target air-fuel ratio and target gear ratio value, so that the fuel consumption rate can be minimized in the instantaneous driving state of the vehicle. Become.

(8) In order to achieve the above object, the present invention relates to a vehicle control system having a control unit for controlling an engine and an automatic transmission of a vehicle, wherein the control unit determines a driving wheel based on an accelerator pedal depression angle and a vehicle speed. A target driving torque setting unit that sets a target driving torque that is a target torque of the engine and the transmission while satisfying the target driving torque set by the target driving torque setting unit with respect to the current vehicle speed. Under certain conditions to achieve,
A target value setting unit that sets a target air-fuel ratio and a target gear ratio so as to minimize the fuel consumption rate, and controls the engine and the transmission to realize the target air-fuel ratio and the target gear ratio value. It was done. With this configuration, the engine and the transmission are controlled so as to realize the calculated target air-fuel ratio and target gear ratio value, so that the fuel consumption rate can be minimized in the instantaneous driving state of the vehicle. Become.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle control method according to an embodiment of the present invention will be described below with reference to FIGS. First, a configuration of a vehicle control system to which a vehicle control method according to an embodiment of the present invention is applied will be described with reference to FIG.

The crankshaft 11 of the engine 10 is connected to a continuously variable transmission 20. A belt 26 is suspended between the input pulley 22 and the output pulley 24 of the continuously variable transmission 20, and rotation of the engine 10 is transmitted to the output pulley 24 via the belt 26. The rotation of the output pulley 24 is transmitted to the wheels via the axle. The diameter of the input pulley 22 and the output pulley 24 is
8 is variably controlled. Accordingly, by continuously changing the diameters of the input pulley 22 and the output pulley 24 by the hydraulic circuit 28, the speed ratio of the continuously variable transmission 20 can be continuously changed. The hydraulic circuit 28 is provided with an input pulley target rotation speed tN supplied from the control unit 100.
The speed ratio i of the continuously variable transmission 20 is controlled based on the in control signal. In the present embodiment, it is assumed that the speed ratio i of the continuously variable transmission 20 can be continuously changed in the range of 0.45 to 2.35.

A throttle valve 13 is rotatably supported on an intake pipe 12 of the engine 10. The opening of the throttle valve 13 is controlled by a throttle driving device 32. The throttle drive device 32 controls the opening of the throttle valve 13 based on a control signal of the target throttle opening tθth supplied from the control unit 100.

Each cylinder of the engine 10 has a fuel injector 34A, 34B, 34C, which injects fuel directly into the cylinder.
34D are provided. Here, the engine is illustrated as a four-cylinder engine, but the number of cylinders is not limited to this. The fuel injector 34 controls the fuel injection amount independently for each cylinder by the control signal of the fuel injection amount Gf supplied from the control unit 100. By using an in-cylinder direct injection type engine, combustion with a wide range of air-fuel ratios from stratified combustion to lean combustion is possible. In the present embodiment, the engine 10 can continuously change from a stoichiometric state where the air-fuel ratio A / F is 14.7 to a lean burn state where it is 40.0.

The exhaust pipe 14 and the intake pipe 12 of the engine 10 are connected by a bypass passage 15.
In the bypass passage 15, EGR (Exhaust Gas recirculation)
A valve 16 is provided to vary the flow rate of the exhaust gas recirculated from the exhaust pipe 14 to the intake pipe 12. The opening of the EGR valve 16 is controlled by a step motor 36. Step motor 3
Reference numeral 6 controls the amount of exhaust gas recirculation based on a pulse signal corresponding to the step motor target step number tStep supplied from the control unit 100.

An air amount sensor 40 attached to the intake pipe 12 detects an amount of air taken into the engine 10 from the intake pipe 12 and outputs a detection signal of an intake air amount Qa to the control unit 100. The accelerator angle sensor 42 detects the amount of depression of the accelerator pedal, and outputs a detection signal of the accelerator depression angle θac to the control unit 100. The rotation speed sensor 44 detects the rotation speed of the crankshaft of the engine, and outputs a detection signal of the engine rotation speed N to the control unit 100. The water temperature sensor 46 detects the temperature of the cooling water of the engine, and outputs a detection signal of the water temperature Temp to the control unit 100. The vehicle speed sensor 48 detects the rotation speed of the axle and outputs a detection signal of the vehicle speed v to the control unit 100.

The control unit 100 has an intake air amount Q
a, accelerator depression angle θac, engine speed N, water temperature Tem
Various detection signals such as p and vehicle speed v are input. The control unit 100 outputs various control signals such as an input pulley target rotation speed tNin, a target throttle opening degree tθth, a fuel injection amount Gf, and a step motor target step number tStep for exhaust gas recirculation based on these detection signals. Thus, the engine 10 and the continuously variable transmission 20 are controlled.

The control unit 100 includes a CPU 102, a ROM 104, and a RAM 10 connected to each other by a bus.
6, a timer 108 and an I / O LSI 110. The CPU 102 controls the engine 10 and the continuously variable transmission 20 based on a control program stored in the ROM 104. Various input signals are input to I / O LSI11
0 is input to the control unit 100 via the RAM 1
06 is temporarily stored. The CPU 102 has a RAM 1
A control signal is calculated based on the input signal indicating the state of the engine or the like stored in the control unit 06.
Output via the LSI 110. Timer 108
At a predetermined cycle, an interrupt request is issued to the CPU 102,
In response to this, the CPU 102 executes the control program stored in the ROM 104.

Next, the system configuration of the control unit 100 that executes the vehicle control method according to the present embodiment will be described with reference to FIG.

CPU of control unit 100 shown in FIG.
The control program of the vehicle control method executed in 102 includes:
As shown in FIG. 2, the control unit includes a target drive torque setting unit 120, a target value setting unit 140, and an engine operation amount calculation unit 160. Although the detailed configuration and operation of each part will be described in detail with reference to FIG. 3 and subsequent figures, the target drive torque setting unit 120 detects the driver's accelerator depression angle θac detected by the accelerator angle sensor 42 and the vehicle speed sensor 48 The target drive torque Td, which is the target torque of the drive shaft of the vehicle, is determined from the current vehicle speed v and the engine speed N detected by the speed sensor 44, and is output to the target value setting unit 140.

The target value setting section 140 satisfies the target driving torque Td obtained by the target driving torque setting section 120 and minimizes the fuel consumption rate Cf in accordance with the vehicle speed v. Value (target air-fuel ratio tA /
F, target EGR rate tRegr, target cylinder inflow air amount tQa
p, input pulley target rotation speed tNin, etc.). The input pulley target rotation speed tNin is supplied as a control signal to the hydraulic circuit 28 of the continuously variable transmission 20. Continuously variable transmission 20
In, information about the input pulley target rotation speed tNin, not the target speed ratio i, is input to the hydraulic circuit 28, and the input pulley rotation speed is controlled to control the speed ratio. The target air-fuel ratio tA / F, the target EGR rate tRegr, and the target cylinder inflow air amount tQap are input to the engine operation amount calculation unit 160.

The engine operation amount calculating section 160 operates the engine operation amount in response to the intake air amount Qa detected by the air amount sensor 40 and the step Step indicating the opening degree of the EGR valve 26 so as to realize the input target value. An amount (a target throttle opening tθth, a fuel injection amount Gf, a target step number tStep of a step motor) is obtained, and is output to the engine 10 as a control signal.

Next, the configuration of the target drive torque setting section 120 in this embodiment will be described with reference to FIG.

The target drive torque setting section 120 sets a target drive torque Td, and includes a target drive torque table 122, a target drive torque calculation section 124, and a time constant setting section 126. The target drive torque table 122 is a two-dimensional table including the accelerator pedal depression angle θac, the vehicle speed v, and the steady target drive torque Td0, and includes the driver's accelerator pedal depression angle θac detected by the accelerator angle sensor 42, the vehicle speed Based on the current vehicle speed v detected by the sensor 48, the steady target drive torque Td0 can be obtained. Here, the steady target drive torque Td0 is a target value of the drive torque generated by the vehicle when the current accelerator pedal depression angle θac and the vehicle speed v are maintained. The data of the target drive torque table 122 is
The current vehicle characteristics are simulated and set.

The target drive torque calculation section 124 is momentarily added to the steady target drive torque Td0 obtained from the target drive torque table 122, taking into account the delay caused by the time constant set by the time constant setting section 126. Is calculated.

The time constant setting section 126 is provided with the rotation speed sensor 44.
A time constant T (s) is calculated using the following equation (1) based on the engine speed N (rpm) detected by
Output to the target drive torque calculation unit 124.

[0030]

(Equation 1)

Here, Vm is the intake pipe volume (l),
Vd is the engine displacement (l), and η is the volumetric efficiency (here, set to a constant of about 0.8).

The target drive torque calculating section 124 calculates the time constant set by the time constant setting section 126 using the following equation (2) with respect to the steady target drive torque Td0 obtained from the target drive torque table 122. The target drive torque Td is calculated in consideration of the delay due to T.

[0033]

(Equation 2)

Here, Δt is a time step (here, 10 m
s), and j is time (here, one time corresponds to the time of Δt).

That is, the target drive torque calculating section 124 simulates a torque generation delay caused by a delay in the current air system of the engine. With this processing, a transient torque characteristic close to that of the current engine can be obtained.

Next, the configuration of the target value setting section 140 in the present embodiment will be described with reference to FIGS. First, the overall configuration of the target value setting unit 140 in the present embodiment will be described with reference to FIG.

The target value setting section 140 calculates various target values of the engine and the transmission that minimize the fuel consumption rate Cf while satisfying the target driving torque td obtained by the target driving torque setting section 120. , EGR rate table 14
2 and a target value calculation unit 144.

Here, the configuration of the EGR rate table 142 will be described with reference to FIG. EGR rate table 14
Reference numeral 2 denotes a two-dimensional table constituted by a target driving torque td obtained by the target driving torque setting unit 120, a current vehicle speed v detected by the vehicle speed sensor 48, and an equal target EGR rate curve. Based on td and the vehicle speed v, the momentary target EGR rate tRegr can be obtained.

The target value calculator 144 in FIG.
Target EGR rate t determined by R rate table 142
Based on Regr, the target driving force Td0 set by the target driving torque setting unit 120, and the detected vehicle speed v,
Engine 10 and transmission 20 for minimizing fuel consumption rate Cf
The various target values are determined by the optimal calculation.

The target value calculation section 144 has a fuel consumption rate function Cf given in advance by the following equation (3) modeled in an engine test.

[0041]

(Equation 3)

Here, f is the basic fuel consumption rate function obtained in the engine test, Te is the engine generated torque, N is the engine speed, and g is the combustion efficiency obtained in the engine test. A / F is an air-fuel ratio.

The engine generated torque Te is calculated by the following equation (4) based on the gear ratio i and the target drive torque Td.
Can be determined by:

[0044]

(Equation 4)

Here, k1 is a constant attributed to the characteristics of the engine and the transmission, and here, k1 is set to 0.2.

The engine speed N can be obtained from the following equation (5) based on the vehicle speed v and the speed ratio i.

[0047]

(Equation 5)

Here, k2 is a constant caused by the characteristics of the engine and the transmission, and here, k2 is set to 52.0.

Next, the characteristics of the basic fuel consumption rate function f will be described with reference to FIG. The basic fuel consumption rate function f is 2
It is stored as the dimension table 144A.

The basic fuel consumption rate function f is a two-dimensional table composed of an engine torque Te, a rotation speed N, and a fuel consumption rate curve, and can calculate the fuel consumption rate from the engine torque Te and the rotation speed N. it can. Here,
The fuel consumption rate data when the air-fuel ratio A / F is 30.0 is used as a representative. In addition, a third-dimensional axis (A / F) indicated by a wavy line in the drawing will be separately described later. In the present embodiment, the table 144A is a two-dimensional table of the engine torque Te and the rotation speed N.

Next, referring to FIG. 7, the combustion efficiency correction coefficient g
Will be described. The combustion efficiency correction coefficient g is stored as a one-dimensional table 144B.

The combustion efficiency correction coefficient g is a one-dimensional table including the air-fuel ratio A / F and the correction coefficient g, and the correction coefficient g can be obtained from the air-fuel ratio A / F. FIG.
The basic fuel consumption rate function f shown in FIG.
Since the fuel consumption rate data in the case of 0.0 is used as a representative, the correction coefficient g when the actual air-fuel ratio A / F is 30.0 is 1.0, and the actual air-fuel ratio A / F is 14.7
Is 0.75, and the actual air-fuel ratio A
The correction coefficient g when / F is 40.0 is 1.1. As the air-fuel ratio A / F becomes thinner, the correction coefficient g becomes larger, and the fuel efficiency is improved.

Next, the target value calculator 144 shown in FIG.
Performs minimization of the fuel consumption rate function Cf as follows. When the EGR rate tRegr, the target drive torque Td, and the vehicle speed v are known, the fuel consumption rate Cf is calculated according to the equations (3) to (5).
Is a function of the air-fuel ratio A / F and the gear ratio i. Therefore, for example, the downhill simplex method [Numerical Recipe
s in C (Technical Review) 295, the air-fuel ratio A / F and the speed ratio i at which the fuel consumption rate Cf is minimized.

The range that variables can take is limited by restrictions on combustion, exhaust performance, speed ratio, and the like. Therefore, in the present embodiment, in consideration of combustion, a range in which the air-fuel ratio A / F can be set is set by Expression (6), and a range in which the gear ratio i determined by the hardware constraint can be set is set by Expression (7). The fuel consumption rate function Cf is minimized within the range.

[0055]

(Equation 6)

[0056]

(Equation 7)

In addition to these restrictions, a pressure restriction may be provided from the viewpoint of securing the rotational speed and torque relating to the basic performance of the engine and securing a negative pressure for braking. When a pressure constraint is provided, it is necessary to model in advance the relationship between the pressure and other variables in the fuel consumption rate function.

Under the constraints of equations (6) and (7), the following fuel consumption rate function Cf0 with a penalty is used to minimize the fuel consumption rate function Cf.

[0059]

(Equation 8)

Here, Cf1 is represented by Expressions (9), (10), and (11) according to the value of the air-fuel ratio A / F.

[0061]

(Equation 9)

[0062]

(Equation 10)

[0063]

[Equation 11]

Further, Cf2 is determined according to the value of the speed ratio i.
It is represented by Expression (12), Expression (13), and Expression (14).

[0065]

(Equation 12)

[0066]

(Equation 13)

[0067]

[Equation 14]

By finding the air-fuel ratio A / F and the gear ratio i that minimize equation (8), the fuel consumption rate function Cf can be minimized under the constraints of equations (7) and (8). Become.
The downhill simplex method is used for minimizing equation (8). With the above method, the target air-fuel ratio tA / F and the target gear ratio ti that minimize the fuel consumption rate Cf can be obtained.

Further, the target value calculating section 144 converts the target speed ratio ti into the input pulley target rotational speed tNin based on the following equation (15).

[0070]

(Equation 15)

The input pulley target rotational speed tNin is sent to the hydraulic circuit 28 as a control signal as shown in FIG. 2, and controls the speed ratio i of the transmission 20.

Further, the target value calculation section 144 calculates the target value of the engine (the target engine torque tTe, the target fuel injection amount tGf, the target cylinder, based on the following equations (16), (17) and (18)). The inflow air amount tQap) is calculated.

[0073]

(Equation 16)

[0074]

[Equation 17]

[0075]

(Equation 18)

In the equation (17), k3 is a constant relating to the generated torque characteristic of the engine, which is obtained by an engine test.

The target value calculating section 144 calculates the target air-fuel ratio tA / F and the target EGR rate tReg among the calculated target values.
r, and outputs the value of the target cylinder inflow air amount tQap to the engine operation amount calculation unit 160.

Next, the configuration of the engine operation amount calculation unit 160 according to the present embodiment will be described with reference to FIGS. First, the overall configuration of the engine operation amount calculation unit 160 in the present embodiment will be described with reference to FIG.

The engine operation amount calculation unit 160 drives the fuel injection amount Gf, the target throttle opening tθth, and the EGR valve to achieve the target air-fuel ratio tA / F, the target EGR rate tRegr, and the target cylinder inflow air amount tQap. This is for calculating the target step number tStep of the step motor.
As shown in FIG. 8, the engine operation amount calculation unit 160 includes a cylinder inflow air amount calculation unit 161 and a fuel injection amount calculation unit 162.
A target throttle passing air amount calculation unit 163, an exhaust gas recirculation flow rate calculation unit 164, and an intake pipe internal pressure calculation unit 165.
, A throttle opening calculation unit 166, and a target step number calculation unit 167.

The cylinder inflow air amount calculation unit 161 and the fuel injection amount calculation unit 162 are processing units for calculating the fuel injection amount Gf from the target air-fuel ratio tA / F. Engine operation amount calculation unit 1
60 calculates the cylinder inflow air amount Qap from the measured air amount Qa detected by the air amount sensor 40 based on the following equation (19).

[0081]

[Equation 19]

Here, Δt is a time step (here, 10
ms), and j is the time (one time is Δt)
Where T is the time constant of the air system (equal to the variable T in equation (1)).

The fuel injection amount calculation unit 162 calculates the target air-fuel ratio tA / F obtained by the target value setting unit 140 and the cylinder inflow air amount Q obtained by the cylinder inflow air amount calculation unit 161.
ap, the fuel injection amount Gf is calculated based on the following equation (20).
Is calculated.

[0084]

(Equation 20)

Next, the target throttle passing air amount calculation unit 1
63, the exhaust gas recirculation flow rate calculation unit 164, the intake pipe internal pressure calculation unit 165, and the throttle opening calculation unit 166 calculate the target cylinder inflow air amount tQ calculated by the target value setting unit 140.
This is a processing unit that calculates a target throttle opening degree tθth from ap.

Target throttle passing air amount calculation section 163
Calculates the target throttle passing air amount tQat from the target cylinder inflow air amount tQap obtained by the target value setting unit 140 based on the following equation (21).

[0087]

(Equation 21)

Here, Δt is a time step (here, 10
ms), and j is the time (one time is Δt)
Where T is the time constant of the air system (equal to the variable T in equation (1)).

The exhaust gas recirculation flow rate calculating section 164 calculates an intake pipe internal pressure P estimated by an intake pipe internal pressure calculating section 165 described later.
m and the actual number of steps Step of the step motor 36 for driving the EGR valve 16 shown in FIG.
The exhaust gas recirculation flow rate Qegr passing through 6 is calculated.
The actual step number Step is determined by the target E in the control unit 100.
This is controlled so as to approach the target number of steps tStep for realizing the GR rate, and is always grasped in the control unit 100.

Here, referring to FIG. 9, the actual step number Ste
1 for calculating the opening area Aegr of the EGR valve from p
The dimension table 164A will be described. The one-dimensional table 164A includes the actual step number Step and the opening area Aegr of the EGR valve.
The opening area Aegr of the GR valve can be obtained.

Further, the exhaust gas recirculation flow rate calculation unit 164
Is the EGR calculated by the one-dimensional table 164A.
From the opening area Aegr of the valve, the following equations (22) and (2)
3) Based on (24), the amount of recirculated gas Qegr passing through the EGR valve is calculated.

[0092]

(Equation 22)

[0093]

(Equation 23)

[0094]

(Equation 24)

Here, Cd is a flow path coefficient (here, 0.
5), and Pexh is the exhaust pipe internal pressure (here, 1a
tm), and Tegr is the exhaust gas temperature (here, 5
Pm is an intake pipe internal pressure estimated by the intake pipe internal pressure calculation unit 165, and k is a specific heat ratio (here,
Mexh is the average molecular weight of the exhaust gas (here set at 29 g), and R is the gas constant.

The intake pipe internal pressure calculation unit 165 calculates the following based on the measured air amount Qa detected by the air amount sensor 40 and the recirculation gas amount Qegr passing through the EGR valve calculated by the exhaust gas recirculation flow rate calculation unit 164. Is calculated using the plurality of discrete equations (25) to (31).

[0097]

(Equation 25)

[0098]

(Equation 26)

[0099]

[Equation 27]

[0100]

[Equation 28]

[0101]

(Equation 29)

[0102]

[Equation 30]

[0103]

(Equation 31)

Here, Pair is the partial pressure of the air in the intake pipe, Pegr is the partial pressure of the recirculated gas in the intake pipe, and R
Is the gas constant, Tm is the gas temperature in the intake pipe (here, set to 300 K), Vm is the intake pipe volume, and Ma
ir is the average molecular weight of air, Mexh is the average molecular weight of the recirculated gas, Qap is the amount of air flowing into the cylinder, Qegro
Is the amount of recirculated gas flowing into the cylinder, Mavg is the average molecular weight of the gas in the intake pipe, Qallout is the total amount of gas flowing into the cylinder, j is time (one time corresponds to the time of Δt), Δt is a time step (here, a time of 10 ms).

The intake pipe internal pressure calculation unit 165 can estimate the instantaneous response of the intake pipe internal pressure Pm by repeating the calculations of the equations (25) to (31) in this order at a time period of Δt. it can. It should be noted that the cylinder inflow air amount Qap calculated by the cylinder inflow air amount calculation unit 161 may be used without calculating the Qap by equation (28).

The throttle opening calculating section 166 calculates the estimated intake pipe internal pressure Pm calculated by the intake pipe internal pressure calculating section 165 and the target throttle opening tQ calculated by the target value setting section 140.
From at, a target throttle opening tθth is calculated.

The throttle opening calculating section 166 obtains the throttle opening area A from the estimated intake pipe internal pressure Pm based on the following equation (32).

[0108]

(Equation 32)

Here, Cdo is a flow coefficient (here, 0.95
), And Ta is the intake air temperature (here, set to 293K)
Where Pa is the atmospheric pressure (here, set to 1 atm), Mair is the average molecular weight of air, and R is the gas constant.

Further, the throttle opening calculating section 166 calculates
Using the conversion table shown in FIG. 10, the opening area A is converted into a throttle opening θth to obtain a target throttle opening tθth.

Here, a one-dimensional table 1 for calculating the throttle opening θth from the opening area A using FIG.
65A will be described. The one-dimensional table 165A is
It is composed of the opening area A and the throttle opening θth, and the throttle opening θth can be obtained from the opening area A.

The control unit 100 sends a target value signal of the throttle opening θth to the throttle driving device 32 at a predetermined time period, and controls the opening of the throttle valve 13 so as to realize the target air amount.

Next, the target step number calculating section 167 calculates the target air amount tQap calculated by the target value setting section 140.
And a target step number tStep for the step motor 36 for driving the EGR valve 16 from the target EGR rate tRegr.

The target step number calculation section 167 calculates the target EGR flow rate tQegr from the target air amount tQap and the target EGR rate tRegr obtained by the target value setting section 140 using the following equation (33).

[0115]

[Equation 33]

Next, the target step number calculating section 167 calculates the intake pipe internal pressure Pm estimated by the intake pipe internal pressure calculating section 165,
From the calculated target EGR flow rate tQegr obtained by the equation (33), the target EGR valve opening area tAegr is obtained by using the following equation (34).

[0117]

(Equation 34)

Here, Cd is the flow path coefficient (here, 0.
5), and Pexh is the exhaust pipe internal pressure (here, 1a
tm), and Tegr is the exhaust gas temperature (here, 5
Pm is an intake pipe internal pressure estimated by the intake pipe internal pressure calculation unit 165, and k is a specific heat ratio (here,
Mexh is the average molecular weight of the exhaust gas (here set at 29 g), and R is the gas constant.

Further, the target step number calculating section 167
Target EGR valve opening area tA obtained by equation (34)
From egr, the target step number tStep is converted using the conversion table of FIG.

Here, a one-dimensional table 167A for calculating the target step number tStep from the target EGR valve opening area tAegr will be described with reference to FIG. 1
The dimension table 167A stores the target EGR valve opening area t.
Aegr and target step number tStep, and target E
From the GR valve opening area tAegr, the target number of steps tStep
Can be requested. The one-dimensional table 167A
Has the same characteristics as the one-dimensional table 164A shown in FIG.

The control unit 100 sets the target number of steps t
A pulse signal is sent to the step motor 36 so as to realize Step, and the opening area of the EGR valve 16 is controlled.

Next, referring to FIG.
The processing contents of the control program stored in the ROM 104 in the address 0 will be described.

The control program executed by the control unit 100 is executed at a period of 10 ms, and the target drive torque setting unit 120 and the target value setting unit 14 described above are executed.
0, the processing contents of the engine operation amount calculation unit 160 are provided.

In step 1201 of FIG. 12, the target drive torque setting section 120 searches the target drive torque table 122 shown in FIG.
Ask for.

Next, in step 1202, the target drive torque setting section 120 obtains a target drive torque Td which is a transient target value by the processing of the target drive torque calculation section 124 shown in FIG.

Next, in step 1203, the target value setting section 140 satisfies the target driving torque Td obtained by the target driving torque setting section 120 and minimizes the fuel consumption rate Cf according to the vehicle speed v. 10 and the target value of the transmission 20 (target air-fuel ratio tA / F, target EGR rate tR
egr, target cylinder inflow air amount tQap, input pulley target rotation speed tNin, etc.). Input pulley target rotation speed t
Nin is supplied to the hydraulic circuit 28 of the continuously variable transmission 20 as a control signal. In the continuously variable transmission 20, information on the input pulley target rotation speed tNin is input to the hydraulic circuit 28 instead of the target speed ratio i, and the input pulley rotation speed is controlled.
Control the gear ratio. The target air-fuel ratio tA / F, the target EGR rate tRegr, and the target cylinder inflow air amount tQap are input to the engine operation amount calculation unit 160.

Next, in step 1204, the engine operation amount calculation unit 160 indicates the intake air amount Qa detected by the air amount sensor 40 and the opening degree of the EGR valve 26 so as to realize the input target value. In accordance with Step, the engine operation amount (target throttle opening tθt)
h, fuel injection amount Gf, step motor target step number tS
tep), and outputs this to the engine 10 as a control signal.

Thereafter, the process waits until there is a next activation request.

In the above description, an in-cylinder fuel injection engine in which fuel is directly injected into a cylinder has been described as a fuel injection system of the engine. This embodiment is also applicable. However, in this case, the air-fuel ratio A / F
Cannot be controlled over a wide range such as 14.7 to 40.0, so the limitation range of the air-fuel ratio in equation (6) is set to 14.7 to 25.0, for example.

The transmission has also been described as a continuously variable transmission. For example, as in a 4-speed automatic transmission,
The present embodiment can be applied to a gear in which the gear ratio is limited to a plurality of stages. In this case, the possible value of the speed ratio is limited, but the fuel consumption rate can be minimized by selecting the optimum speed ratio within the limited range.

As described above, according to the present embodiment, the gear ratio i and the air-fuel ratio A / F are determined so as to satisfy the target drive torque Td and minimize the fuel consumption rate Cf. Of the input pulley tNin and the target air-fuel ratio tA such that the speed ratio i and the air-fuel ratio A / F are obtained.
/ F is controlled, so that the fuel consumption rate can be minimized in the instantaneous driving state of the vehicle.

Further, using the EGR rate as a parameter, the target EGR rate tReg is set so that the fuel consumption rate Cf is minimized.
Since r is also obtained and the step motor target step number tStep for controlling the EGR valve is controlled,
The fuel consumption rate can be minimized at every moment in the driving state of the vehicle.

Next, a vehicle control method according to a second embodiment of the present invention will be described with reference to FIG. The overall configuration of a vehicle control system to which the vehicle control method according to the present embodiment is applied is the same as that shown in FIG. The configuration of the control unit 100 is the same as that shown in FIG. 2, but the configuration of the target value setting unit 140 is the configuration of the target value setting unit 140A shown in FIG.

In the present embodiment, unlike the processing in the target value setting section 140 shown in FIG. 4, the fuel consumption rate function Cf
Is not performed on-line, and the target air-fuel ratio tA / F and the target EGR rate tReg for minimizing the fuel consumption rate Cf with respect to the driving torque Td and the vehicle speed v are not performed offline in advance.
r, the target gear ratio ti is obtained by the above-described method, and this is stored in the two-dimensional table.

In other words, in the present embodiment, as shown in FIG.
46, 147, a target air amount calculation unit 148, and a conversion processing unit 149. Two-dimensional table 142
As described with reference to FIG. 5, the target drive torque Td obtained by the target drive torque setting unit 120, the current vehicle speed v detected by the vehicle speed sensor 48, and the same target EG
This is a two-dimensional table constituted by an R rate curve, and a momentary target EGR rate tRegr can be obtained based on the target drive torque Td and the vehicle speed v.

The two-dimensional table 146 calculates a target air-fuel ratio tA / F from the target driving torque Td obtained by the target driving torque setting section 120 and the current vehicle speed v detected by the vehicle speed sensor 48. The target air-fuel ratio tA / F for minimizing the fuel consumption rate function Cf in the target value calculation unit 144 shown in FIG. The target air-fuel ratio tA / F can be determined from the target drive torque Td and the current vehicle speed v.

The two-dimensional table 147 stores the target driving torque Td obtained by the target driving torque setting section 120.
And a current vehicle speed v detected by the vehicle speed sensor 48 to obtain a target gear ratio ti. The target gear ratio ti for minimizing the fuel consumption rate function Cf in the target value calculator 144 shown in FIG. Are previously obtained offline and tabulated. The target gear ratio ti can be determined from the target drive torque Td and the current vehicle speed v.

The target air amount calculating section 148 calculates the equation (18),
Using the equations (17) and (16), the target driving torque Td obtained by the target driving torque setting unit 120, the current vehicle speed v detected by the vehicle speed sensor 48, and the two-dimensional table 146 are used. The target cylinder inflow air amount tQap can be obtained from the target air-fuel ratio tA / F and the target speed ratio ti obtained from the two-dimensional table 147.

The conversion processing unit 149 converts the target speed ratio ti into the input pulley target rotation speed tNin based on the equation (15).

In this embodiment, the target air-fuel ratio tA / F, which minimizes the fuel consumption rate Cf, is obtained by forming a two-dimensional table using the results obtained in advance off-line.
The processing for obtaining the target EGR rate tRegr and the target gear ratio ti can be speeded up, and the load on the CPU 101 of the control unit 100 can be reduced.

Next, a vehicle control method according to a third embodiment of the present invention will be described with reference to FIG. The overall configuration of a vehicle control system to which the vehicle control method according to the present embodiment is applied is the same as that shown in FIG. 1, and the configuration of the control unit 100 is the same as that shown in FIG.

In this embodiment, the basic fuel consumption rate function f used in the target value calculation section 144 shown in FIG.
6 is a three-dimensional table also shown by solid and wavy lines in FIG. 6 from the two-dimensional table shown by solid lines.
That is, in the present embodiment, the basic fuel consumption rate function f
Is the engine torque Te, the rotational speed N, and the air-fuel ratio A / F.
And a fuel consumption rate curve. The fuel consumption rate can be obtained from the engine torque Te, the rotation speed N, and the air-fuel ratio A / F.

In the first embodiment, a two-dimensional table is used, and data of the fuel consumption rate when the air-fuel ratio A / F is 30.0 is used as a representative. Holds the fuel consumption rate data for the air-fuel ratio in the range of 14.7 to 40.0. Therefore, in the first embodiment, it is necessary to perform correction using the correction coefficient g shown in FIG. 7, but such correction is not required.

The target value calculation section 144 has a function expressed by the following equation (35) instead of the function expressed by the equation (3) as the fuel consumption rate function Cf modeled in the engine test.

[0145]

(Equation 35)

However, when there is no EGR, tRegr = 0 in the equation (35).

As described above, the use of the three-dimensional table in which the air-fuel ratio A / F is also taken into account makes it possible to further reduce the fuel consumption rate. When a three-dimensional table is used, the storage capacity is increased. Therefore, in order to reduce the storage capacity, similarly, as shown by a broken line in FIG. 7,2
For each of the four points of 0.0, 30.0, and 40.0, the data of the fuel consumption rate is 14.7.
For the air-fuel ratio between 40.0 and 40.0, the fuel consumption rate may be obtained by interpolation.

Next, a vehicle control method according to a fourth embodiment of the present invention will be described. The overall configuration of a vehicle control system to which the vehicle control method according to the present embodiment is applied is shown in FIG.
And the configuration of the control unit 100 is the same as that shown in FIG. Note that, in the first embodiment, the target value setting
As shown in FIG.
Although the target value for minimizing the fuel consumption rate Cf has been obtained for obtaining the GR rate, the target EGR rate can also be included as a parameter for minimizing the fuel consumption rate. In this case, a restriction range regarding the target EGR rate, for example, a restriction range in which the target EGR rate is within 40 is provided, and the target air-fuel ratio, the target gear ratio, the target The EGR rate is determined by the simplex method. Further, if necessary, it is converted into another target value and used for calculating the operation amount of the control system.

Further, when the target EGR rate is also included as a parameter for minimizing the fuel consumption rate and is used for optimizing the fuel consumption rate in the engine transient operation state, the driving torque in the transient state is replaced with the equation (4). The following equation (36) representing the relationship between the torque and the engine torque is used.

[0150]

[Equation 36]

Here, k4 and k5 are constants determined from the moment of inertia of the engine and the transmission, the lowest gear ratio, and the transmission efficiency of torque. The differential value dN / dt of the rotational speed N and the differential value dv / dt of the vehicle speed v can be approximately obtained by the deviation of the time series data, and these are successively substituted into the expression (36) to obtain the expression (36). Use instead of 4). The other processes for obtaining the constraint and the target value other than minimizing the fuel consumption rate Cf are the same. (However, the target air-fuel ratio,
After the gear ratio is determined, equation (16) is not used and equation (3) is used.
The target engine torque tTe is determined based on 6). As described above, the target EGR rate can be included as a parameter for minimizing the fuel consumption rate to optimize the fuel consumption rate in the engine transient operation state.

[0152]

According to the present invention, in the vehicle control method and the vehicle control system, it is possible to minimize the fuel consumption rate in the running state of the vehicle every moment.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a vehicle control system to which a vehicle control method according to an embodiment of the present invention is applied.

FIG. 2 is a system configuration diagram of a control unit that executes a vehicle control method according to an embodiment of the present invention.

FIG. 3 is a system configuration diagram of a target drive torque setting unit in a control unit that executes the vehicle control method according to one embodiment of the present invention.

FIG. 4 is a system configuration diagram of a target value setting unit in a control unit that executes the vehicle control method according to one embodiment of the present invention.

FIG. 5 is a configuration diagram of an EGR rate table 142 used in a target value setting unit in a control unit that executes the vehicle control method according to one embodiment of the present invention.

FIG. 6 is a configuration diagram of a basic fuel consumption rate function f used in a target value setting unit in a control unit that executes the vehicle control method according to one embodiment of the present invention.

FIG. 7 is a configuration diagram of a combustion efficiency correction coefficient g used in a target value setting unit in a control unit that executes the vehicle control method according to one embodiment of the present invention.

FIG. 8 is a system configuration diagram of an engine operation amount calculation unit in a control unit that executes a vehicle control method according to an embodiment of the present invention.

FIG. 9 is a configuration diagram of a one-dimensional table for calculating an opening area Aegr of an EGR valve used in an engine operation amount calculation unit in a control unit that executes the vehicle control method according to one embodiment of the present invention.

FIG. 10 is a configuration diagram of a one-dimensional table for calculating a throttle opening θth used in an engine operation amount calculation unit in a control unit that executes the vehicle control method according to one embodiment of the present invention.

FIG. 11 is a configuration diagram of a one-dimensional table for calculating a target step number tStep used in an engine operation amount calculation unit in a control unit that executes a vehicle control method according to an embodiment of the present invention.

FIG. 12 is a flowchart showing processing contents of a control program executed by a control unit that executes the vehicle control method according to one embodiment of the present invention.

FIG. 13 is a system configuration diagram of a target value setting unit in a control unit that executes the vehicle control method according to the second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Engine 13 ... Throttle valve 16 ... EGR valve 20 ... Continuously variable transmission 28 ... Hydraulic circuit 32 ... Throttle drive 34A, 34B, 34C, 34D ... Fuel injector 36 ... Step motor 40 ... Air amount sensor 42 ... Accelerator angle Sensor 44: speed sensor 48: vehicle speed sensor 100: control unit 120: target drive torque setting unit 140: target value setting unit 160: engine operation amount calculation unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 45/00 364 F02D 45/00 364M F02M 25/07 550 F02M 25/07 550R

Claims (8)

[Claims] 1. A vehicle control method for controlling an engine and an automatic transmission of a vehicle, comprising: A) calculating a target drive torque which is a target torque of a drive wheel from an accelerator pedal depression angle and a vehicle speed; A) calculating a target air-fuel ratio and a target gear ratio that minimize the fuel consumption rate under predetermined conditions such that the operation of the engine and the transmission is realized while satisfying the target drive torque; A vehicle control method comprising controlling the engine and the transmission so as to achieve an air-fuel ratio and a target gear ratio value. 2. The vehicle control method according to claim 1, wherein the calculation of the target air-fuel ratio and the target gear ratio is expressed by an engine generated torque obtained from the target drive torque and an engine speed obtained from the current vehicle speed. A vehicle control method comprising: obtaining a basic fuel consumption rate function corrected by a combustion efficiency correction coefficient so as to minimize the fuel consumption rate function. 3. The vehicle control method according to claim 2, wherein the engine generated torque is calculated based on the target drive torque, the rate of change of the vehicle speed, and the rate of change of the engine speed. . 4. The vehicle control method according to claim 1, wherein the calculation of the target air-fuel ratio and the target gear ratio includes the drive torque of the drive wheels and the vehicle speed as shaft variables, and the fuel consumption rate is minimized in advance. A vehicle control method using a table for which data is obtained. 5. The vehicle control method according to claim 1, further comprising calculating a target EGR rate that minimizes a fuel consumption rate.
A vehicle control method comprising controlling the engine and the transmission so as to achieve the target EGR rate. 6. The vehicle control method according to claim 1, wherein the predetermined condition is a range where an air-fuel ratio can be taken, a range where a gear ratio can be taken, or a range where an EGR rate can be taken. A vehicle control method, characterized in that: 7. A vehicle control method for controlling an engine and an automatic transmission of a vehicle, wherein the operation of the engine and the transmission is realized under predetermined conditions while satisfying a target driving torque with respect to a current vehicle speed. Calculating a target air-fuel ratio and a target gear ratio so as to minimize a fuel consumption rate, and controlling the engine and the transmission so as to realize the target air-fuel ratio and the target gear ratio value. Method. 8. A vehicle control system having a control unit for controlling an engine and an automatic transmission of a vehicle, wherein the control unit sets a target drive torque which is a target torque of a drive wheel from an accelerator pedal depression angle and a vehicle speed. A torque setting unit, and a fuel consumption rate under a predetermined condition such that operation of the engine and the transmission is realized while satisfying the target driving torque set by the target driving torque setting unit with respect to a current vehicle speed. A target value setting unit that sets a target air-fuel ratio and a target gear ratio so as to minimize the engine speed and the engine and the transmission so as to realize the target air-fuel ratio and the target gear ratio value. Vehicle control system.