JPH03182650A - Control device of internal combustion engine for vehicle - Google Patents

Abstract

PURPOSE:To eliminate a traction system and to start without the occurrence of a slip during starting by calculating an engine limit based on the slip limit of each drive wheel and limiting a target value during control of an engine output. CONSTITUTION:Torque generated at each drive wheel is calculated by a wheel torque calculating means (a) based on generating torque of an engine, and a dynamic friction factor between each drive wheel and a road surface is calculated by a dynamic friction factor calculating means (e) based on the torque, a rotation angular acceleration (c) and a wheel load (d). Meanwhile, the slip ratio of each driven wheel is calculated by a slip ratio calculating means (g) based on a car body speed (f) and a wheel speed (b) of each drive wheel. The maximum dynamic friction factor of each drive wheel is calculated by a maximum dynamic friction factor calculating means (h) based on the dynamic friction factor (e) and the slip ratio (g), and based on the maximum dynamic friction factor, limit wheel torque, capable of being inputted, at which each drive wheel is moved without a slip is calculated by a limit wheel torque calculating means (i). From a total sum of limit wheel torque of each driven wheel or a value several times as large as that of each drive wheel having a minimum value of limit wheel torque of each drive wheel, limit torque is calculated by limit torque calculating means (j) and j', and by means of the limit torque being an upper limit value, a target value of an engine output is limited by an engine output limit means (k).

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a control device for appropriately changing the characteristics of a vehicle internal combustion engine in accordance with the driving condition of the vehicle to always obtain good driving performance.

<Prior Art> Conventionally, there are the following control devices for a vehicle internal combustion engine.

In order to make the output characteristics such as the generated torque of the engine in response to the accelerator operation favorable to the drivability of the vehicle, for example, as shown in Japanese Patent Application Laid-open No. 1984-1984, it is possible to , there is one that sets a throttle valve opening and drives the throttle valve to match the set opening.

Furthermore, the system disclosed in Japanese Utility Model Application No. 62-193151 is designed to control the governor of a diesel engine in a similar manner.

In addition, as an example in which the control mode of the engine output adjustment means is switched according to the driving condition of the vehicle so that the driver can obtain the desired drivability under various driving conditions, for example, Japanese Patent Application Laid-Open No. 1983-1999 There is one shown in Japanese Patent No. 25355.

<Invention tries to solve! Problem 1> However, in such a conventional control device for a vehicle internal combustion engine, when the accelerator opening is set as the target torque value, each wheel of a 4-wheel drive (4WD) vehicle etc. is Since the torque value is not determined while feeding back the torque limit that can actually be generated in the system, even though the generated torque is set as the control Il value for the entire system, this information cannot be used, and the torque value cannot be used on low μ roads etc. In this case, the demand from the accelerator becomes excessive, causing slippage in each wheel, and there is the unreasonable problem of having to go to the trouble of installing traction control separately to prevent this problem.

In view of such conventional problems, the present invention calculates the maximum torque that can be generated in consideration of the slip rate of each wheel, and responds to the driver's torque request while referring to this value. The purpose is to make it possible.

<Means for Solving the Problems> Therefore, as shown in FIG. 1, the present invention provides a vehicle internal combustion engine equipped with an engine output control means for controlling output such as engine torque or rotational speed to a target value. The control device is configured to include the following means (a) to (2).

(a) Wheel torque calculation means for calculating the torque generated at each drive wheel based on the torque generated by the engine. (C) Wheel speed detection means for detecting the wheel speed of each drive wheel. rotational angular acceleration calculation means (d) for calculating the rotational angular acceleration of each drive wheel based on the rotational angular acceleration of each drive wheel;
Wheel load detection means (e) for detecting the wheel load applied to each drive wheel; Dynamic friction coefficient calculation means for calculating the dynamic friction coefficient between each drive wheel and the road surface based on the torque, rotational angular acceleration, and wheel load of each drive wheel; (f) Vehicle speed detection means for detecting the vehicle speed (80) Slip rate calculation means for calculating the slip rate of each drive wheel based on the vehicle speed and the wheel speed of each of the drive wheels (b) Maximum dynamic friction coefficient calculation means for calculating the maximum dynamic friction coefficient of each drive wheel based on the dynamic friction coefficient and slip rate 0) Limit wheel torque that can be inputted so that each drive wheel can move without slipping based on the maximum dynamic friction coefficient of each drive wheel. Limit wheel torque calculation means 0) Limit torque calculation means that calculates the limit torque from the sum of the limit wheel torques of the respective drive wheels (G) The limit torque calculation means calculates the engine output in the engine output control means using the limit torque as an upper limit value. Output limiting means for limiting the target value Also, in place of the limit torque calculating means in 0) above, the following (
j) A limit torque calculation means can be provided.

(j) ゛Limit torque calculation means for calculating the limit torque from the value multiplied by the number of drive wheels of the minimum value among the limit wheel torques of each drive wheel (Operation) In the above configuration, each The torque generated in the drive wheels is calculated, and based on this, the rotational angular acceleration of each drive wheel, and the wheel load, the coefficient of dynamic friction between each drive wheel and the road surface is calculated.

On the other hand, the slip rate of each drive wheel is calculated based on the vehicle speed and the wheel speed of each drive wheel.

Then, based on the dynamic friction coefficient and slip rate of each drive wheel, the maximum dynamic friction coefficient of each drive wheel is calculated, and based on this, the limit wheel torque that can be inputted so that each drive wheel can move without slipping is calculated.

Then, the limit torque is calculated from the sum of the limit wheel torques of each drive wheel, or the value multiplied by the number of drive wheels of the minimum value among the limit wheel torques of each drive wheel, and the engine output is controlled using this limit torque as the upper limit. Limiting the target value of the output of the engine in the means.

<Example> The present invention will be explained in detail below.

First, the engine output control means will be explained. In this example, a target torque of the engine is calculated based on the accelerator operation amount, engine rotation speed, and external load, and the fuel supply amount to the engine ( The fuel injection amount) and intake air amount (throttle valve opening) are controlled.

In Fig. 2, a crank angle sensor 1 detects the crank angle of the engine, an accelerator opening sensor 2 detects the amount of accelerator operation (the amount of depression of the accelerator pedal) by the output voltage of the potentiometer, and a potentiometer detects the amount of sinking of the vehicle's ventilator. A stroke sensor 3 detects the output voltage based on the output voltage, and a gear position sensor 5 detects the gear position W (shift position f) of the transformer 4.
Input to U6A.

The CPU 6A calculates the target torque based on the detection signal, reads out the fuel injection amount necessary for outputting the target torque from the fuel injection amount table 6B on the ROM 6B, and generates the corresponding pulse. A fuel injection pulse having a width is output to an injector 7 provided in an intake passage of the engine to control the amount of fuel supplied. At the same time, the target throttle valve opening that provides the amount of intake air required to output the target torque is read from the throttle valve opening table 68t, and outputted to the servo drive circuit 8, through which the amount of intake air is controlled. I do.

Further, the CPU 6A simultaneously performs ignition control to output an ignition signal to the Ibnirasilane coil 13 based on the crank angle signal from the crank angle sensor 1.

The fuel injection amount table 6B is based on the fuel injection amount (basic injection pulse width) so that the fuel injection amount necessary to generate the target torque can be read by giving the target torque and engine rotational speed from time to time. The data is stored (see Fig. 5), and the throttle valve opening table 6B also shows the amount of intake air necessary to generate the target torque given the momentary target torque and engine rotational speed. Data on the throttle valve opening degree is stored so that the throttle valve opening degree corresponding to the throttle valve opening degree can be read out.

The servo drive circuit 8 operates based on the actual throttle valve opening θ detected by a throttle sensor 11 that detects the opening of a throttle valve IO installed in the intake passage 9 of the engine, and the target throttle input from the CPU 6A. Valve opening degree θ.

The servo motor 12 connected to the throttle valve 10 is driven in the forward and reverse directions according to the deviation from the target value, thereby causing the opening degree of the throttle valve lO to follow the target value.

Next, the control contents (target torque control) of the CPU 6A will be explained according to the flowcharts of FIGS. 3 and 4.

FIG. 3 shows a routine for calculating the target torque, fuel injection amount, and target throttle valve opening, and is executed at a constant cycle, for example, every 10 as.

At Pl, the accelerator opening (operation amount) a detected by the accelerator opening sensor 2 is read.

At Pl, the engine rotational speed N is calculated based on the crank angle signal from the crank angle sensor 1.

At P3, the target torque T0 is calculated according to the following equation.

To = k 1a k t ” No ””...
(1) Here, k+, kg are parameters that determine the characteristics of the engine output torque, k is the proportional coefficient of accelerator opening versus output torque, and k2 is the proportional coefficient of engine rotation speed versus output torque, which will be described later. The routine is set according to the external load applied to the engine's output shaft, which is detected based on the weight of the vehicle and the transmission gear ratio.

After this, in P3', it is determined whether or not the target torque change request flag F is set. If NO, proceed to P4 as it is; if YES, execute P3'' and then proceed to P4.
4, and P3°" will be explained later.

In P4, target torque T and engine rotation speed N.

Accordingly, the basic fuel injection pulse width Tp is read from the fuel injection amount table 6B. Here, the fuel injection amount table 6B is used to read data on the basic injection pulse width T from the target torque T0 and the engine rotational speed N, as shown in FIG. This data is determined from the performance of the engine.

At P5, various corrections are made to the basic injection pulse width T, which is determined according to the operating state of the engine, to obtain the fuel injection pulse width T,
Calculate. The corrections here include an increase in amount according to the cooling water temperature, an increase in amount at the time of starting, feedback correction of the air-fuel ratio, etc.

At P6, target torque T0 and engine rotation speed N.

Accordingly, the target throttle valve opening θ is determined from the throttle valve opening table 68g. Here, the throttle valve opening table 68g shows the target torque T as shown in FIG.
0 and the engine rotation speed N, the target throttle valve opening θ is obtained.

This data is determined from the performance of the engine installed in the vehicle.

In P7, the fuel injection pulse width T+ calculated in P5 is set to CP
Set it to the output port of U6A.

As a result, a fuel injection pulse having a pulse width of T1 is outputted to the injector 7 at a predetermined timing triggered by the crank angle signal from the crank angle sensor 1, and an amount of fuel corresponding to T1 is injected and supplied to the engine. Ru.

In P8, the target throttle valve opening θ calculated in P6. is output to the servo drive circuit 8. As a result, the throttle valve lO is driven by the servo motor 12 to reach the target throttle valve opening θ. feedback control to match.

Figure 4 shows a routine for setting the output torque characteristics of the engine used in the calculation of P3 in Figure 3.This routine is always at high speed like the fuel supply control and intake air amount control routines in Figure 3. There is no need for calculation, and it is executed every gear shift or in the background of the microcomputer, eliminating wasted calculation time.

For pH, the gear position of the transmitsilane 4 detected by the gear position sensor 5 is read.

In P12 to P13, the gear position (1st to 3rd gear) is determined and branched, and in P14 to P16, the 1st gear gear ratio data M1, the 2nd gear gear ratio data M, which are stored in the ROM 6B, are respectively stored. The gear ratio data M of the third speed is successively outputted, and the gear ratio of the current gear position is stored in the register m.

The PI3 reads the suspension depression If detected by the stroke sensor 3 (generated by the load of passengers and cargo), and calculates the vehicle type fiW according to the following equation.

W=W0-1-1/k (2) Here, Wo is the weight of only the vehicle body which is known in advance, and k is the spring constant of the suspension.

In PlB, a proportional coefficient of 1 is calculated from the vehicle weight W and the gear ratio m using the following equation, which sets the characteristic of the accelerator opening versus the output torque.

k+ = KI ・w/m −・− (3) In PI9, 2 is calculated from the vehicle type 1w and the gear ratio m as a proportionality coefficient that sets the characteristic of engine rotational speed versus output torque using the following equation.

k z = Kg HW/m”...-(4)
Here, K, , and are constants that have been determined in advance through experiments or the like and provide the best vehicle handling feeling.

Next, the operation of the target torque control of this embodiment will be explained based on FIG. 7 in comparison with the conventional example.

FIG. 7 shows a model of vehicle motion, and is the simplest representation, omitting the power loss of the engine and drive system. In this model, the relationship between the acceleration α of the vehicle body when the accelerator opening degree a is changed is shown by the following formula % formula % where D is running resistance, S is Laplace operator, and 61 to G
1 is the gain.

The first term on the right side of equation (5) indicates the responsiveness of the vehicle body acceleration α to the accelerator opening a, and the second term indicates the responsiveness of the vehicle body acceleration α to the running resistance. It determines the feeling.

The gains G1 to G are determined as follows.

G+ = k1・(m/R)・(g/W)
・”・=(6)Gy= =kz ・(m/R)”
・(g/W) =...(7) Gs=g/W
(8) In addition, R is the tire effective radius, and g is the gravitational acceleration.

As shown in the conventional example, when the ratio of the change in the actual throttle valve opening to the accelerator opening is changed, q in equation (6) changes, and for example, when q increases, the gain G increases and the accelerator opening changes. The change in acceleration α increases with respect to the change in degree a, resulting in a powerful steering feeling.

Furthermore, if Gt is large, a differential effect, that is, an effect that amplifies fluctuations, appears, and maneuverability deteriorates. Regarding G2 in equation (7), corresponds to the slope tan δ of the engine torque curve as shown in Fig. 7, and in the method of changing the throttle valve opening depending only on the accelerator opening, the engine It takes a characteristic value specific to , and cannot be changed arbitrarily.

Therefore, in this embodiment, the value of kt can be freely set by a method of calculating the target torque of the engine based on the accelerator opening degree and the engine rotational speed.

The gains G, , G, which determine the handling feeling of the vehicle, have values that can provide the best feeling, and can be experimentally matched to the engine characteristics using variable factors such as +, kg, and gear ratio m.

However, unless there is a means to change kI and kg according to the external load applied to the engine determined by the vehicle weight W and gear ratio m, as in the conventional example, even if matching is possible at a certain gear ratio, the gear change will not be possible. The best G when
+, the feeling deteriorates as it deviates from Gt0 For example, when in a low gear (m is large), G2 increases in proportion to the square of m as shown in equation (7), resulting in jerky and poor maneuverability. This is a phenomenon that often occurs. Similarly, the vehicle weight W also affects G,,G,.

Now, with gear ratio mo and vehicle weight W6, the best value of kI and kg is 1°, kg. Assuming that is obtained experimentally, the following relationship holds true.

G+ = ni+o・ (mo/R)' (g/We)
”-(9)G2 =kto・(me/R)2・(
g/We) -Qω When the gear ratio m and vehicle weight W change, in equations (6) and (7) 2, kI = +o. (me/wo) - W/m = +
−W/m ・−・・−(ll)kt =ni*o・
(mo”/Wo) ・(W/m”)-2 ・W/
If the kI and kgO values are set according to m and W, the gains G, , G, can always be set to the best value shown in equation (9), GO). can.

In this embodiment, the fuel supply amount and the intake air amount are always controlled collectively based on the target torque. This is to supply the necessary fuel and air without any delay between each other, control the target torque, and obtain good control performance suitable for use in achieving good vehicle maneuverability.

Furthermore, in this embodiment, the target throttle valve opening degree θ is used to control the intake air amount according to the target torque.

is output to the servo drive circuit 8, but other methods, for example, the target throttle valve opening θ. It is also possible to output suction negative pressure according to the target value as a target value and operate a servo mechanism so that the suction negative pressure reaches the target value.

Next, limit torque control according to the present invention will be explained.

Note that this example uses 4WD, so there are four driving wheels.

For such limit torque control, as shown in FIG. 2, a wheel speed sensor 14 as a wheel speed detection means, a wheel load sensor 15 as a wheel load detection means, and a vehicle speed sensor 16 as a vehicle speed detection means are provided. ing.

The wheel speed sensor 14 is, for example, a sensor mounted opposite to a toothed rotor.
It consists of an i-magnetic pickup and is installed on each drive wheel to detect wheel speeds VFII, VFL, Vlll, and VRL.

The wheel load sensor 15 is provided at each drive wheel and measures the wheel load W F I I W F t , W * * +
Detect W*t.

The vehicle speed sensor 16 detects the vehicle speed V using ultrasonic waves or the like.

From this information, control is performed according to the flowchart in FIG.

At P21, the wheel speed Vij (i=R, P j=R, L) detected by the wheel speed sensor 14, the wheel load Wij detected by the wheel load sensor 15, and the vehicle body detected by the vehicle body speed sensor 16. Read speed V.

In P22, the rotational angular acceleration Δωij of each drive wheel is calculated based on the wheel speed Vij of each drive wheel. This part corresponds to the rotational angular acceleration calculation means.

In P23, when starting or when the torque generated by the engine is sufficiently small, the distribution and combination of torque is calculated using a physical model from the engine to the wheel axle as shown in Figure 9, and the target torque T of the engine is calculated. Based on this, the torque Tij generated at each drive wheel is calculated. This part corresponds to the wheel torque calculation means.

In P24, the torque Tij and rotational angular acceleration Δ of each drive wheel are
Based on ωij and wheel load Wij, a dynamic friction coefficient μij between each drive wheel and the road surface is calculated. This part corresponds to the dynamic friction coefficient calculation means.

That is, if the ideal radius of the tire (assuming it does not sag) is r and the moment of inertia around the center of rotation is Iij, then 1ij・Δω1j=Tij−, czij−Wij−r
...a311 is possible.

From this relationship, μij= (Tij −1ij ・Δa+ij) /
(Wij-r)-04J, and the dynamic friction coefficient μij can be calculated from the torque Tij, the rotational angular acceleration Δωij, and the wheel load Wij.

In P25, the slip rate Sij of each drive wheel is calculated based on the vehicle body speed V and the wheel speed Vij of each drive wheel.

This part corresponds to the slip rate calculation means.

In P26, from the slip rate Sij of each drive wheel at this time, based on the relationship shown in FIG. 10 from the slip rate Sij and the dynamic friction coefficient μij, for example, when the slip rate is around 10%,
Assuming that it has a maximum dynamic friction coefficient μjjsA□, the maximum dynamic friction coefficient μlj,4ax of each wheel is estimated.

This part corresponds to the maximum dynamic friction coefficient calculation means.

In P27, T 1jxax is calculated using the C31 formula using the maximum dynamic friction coefficient μijwA of each drive wheel. Here, the generated torque at the slip limit for each drive wheel of each vehicle has been calculated. This part corresponds to the limit wheel torque calculation means.

In P2O, the total limit wheel torque for four wheels ΣT! L+
ax, and calculate this as engine limit torque TMAX=ΣT
Let ij, (A,

Alternatively, the minimum (l MIN (T iL + ax )) of the limit wheel torque Tij, 4B for four wheels is multiplied by the number of driven wheels (4), and this is calculated as the limit torque TMay=4・MIN
(T1L+ax). Such a method is effective when the estimation accuracy of the maximum dynamic friction coefficient μfjxax is not very accurate.

This part corresponds to the limit torque calculation means.

In P29, the current target torque T0 is read and compared with the limit torque T, □.

Here, if T0□, the process proceeds to P2O and the target torque change request flag F is reset. In this case, the target torque To calculated in P3 of the routine of FIG. 3 becomes the target torque as it is.

However, if To>7□8, the process proceeds to P31 and sets the target torque change request flag F.

When the target torque change request flag F is set in this way, the routine proceeds to P3' according to the determination at P3° in the routine of FIG. 3, and the limit torque TNAX is set as the target torque T0.

That is, ignoring the request for To due to the operation in P3,
Control is performed by reading □8 as target torque T0.

Therefore, P29 in FIG. P2O and P3 in Figure 3
The part 'P3' corresponds to the output limiting means.

<Effects of the Invention> As explained above, according to the present invention, the limit torque of the engine is calculated based on the slip limit of each drive wheel, and the target value is limited when controlling the output of the engine, so that the traction system etc., and it is possible to start without slipping when starting.

[Brief explanation of drawings]

Fig. 1 is a functional block diagram showing the configuration of the present invention, Fig. 2 is a system diagram showing an embodiment of the invention, Figs. 3 and 4 are flowcharts of target torque control, and Fig. 5 is a flowchart of the above control. 6 is a diagram showing the fuel injection amount table used, FIG. 6 is a diagram showing the throttle valve opening table used in the above control, FIG. 7 is a control block diagram in the same control, and FIG.
The figure is a diagram for calculating the driving friction coefficient. 2...Accelerator opening sensor 6A...CPU7.
...Injector 10...Throttle valve 12
... Servo motor 14 ... Wheel speed sensor 15 ... Wheel load sensor 6 ... Vehicle speed sensor

Claims (2)

[Claims] (1) A control device for a vehicle internal combustion engine comprising an engine output control means for controlling the output of the engine to a target value, comprising: a wheel torque calculation means for calculating the torque generated at each drive wheel based on the torque generated by the engine; wheel speed detection means for detecting the wheel speed of each drive wheel; rotational angular acceleration calculation means for calculating the rotational angular acceleration of each drive wheel based on the wheel speed of each drive wheel; wheel load detection means for detecting; dynamic friction coefficient calculation means for calculating a dynamic friction coefficient between each drive wheel and the road surface based on the torque, rotational angular acceleration, and wheel load of each drive wheel; and a vehicle body speed for detecting vehicle body speed. a detection means; a slip rate calculation means for calculating a slip rate of each drive wheel based on the vehicle body speed and a wheel speed of each drive wheel; Maximum dynamic friction coefficient calculation means for calculating the maximum dynamic friction coefficient of the wheels; Limit wheel torque calculation means for calculating the limit wheel torque that can be inputted so that each driving wheel can move without slipping based on the maximum dynamic friction coefficient of each driving wheel; limit torque calculation means for calculating a limit torque from the sum of limit wheel torques of each driving wheel; and output limiting means for limiting a target value of the engine output in the engine output control means using the limit torque as an upper limit value. A control device for a vehicle internal combustion engine, characterized in that: (2) A claim characterized in that, in place of the limit torque calculation means, limit torque calculation means is provided for calculating the limit torque from a value multiplied by the number of driving wheels of the minimum value among the limit wheel torques of each of the drive wheels. 2. The control device for a vehicle internal combustion engine according to item 1.