JP2001138776A - Driving force control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the transient characteristic of the driving force by restricting the overshoot of a target engine torque in the case where a driver quickly operates an acceleration pedal. SOLUTION: A joint controller 9 obtains the first target driving force tFdl on the basis of the acceleration operated quantity, and obtains a target change gear ratio tG of a continuously variable transmission 2 on the basis of the first target driving force tFd1 and the car speed VSP. The joint controller 9 determines the driving force control range to be realized in the transit driving so as to obtain the second target driving force tFd2 on the basis of the first target driving force tFd1, and divides the second target driving force tFd2 by a real change gear ratio G so as to obtain the target engine torque tTe. A CVT controller 8 controls the transmission 2 so that the real change gear ratio G coincides with the target change gear ratio tG, and an engine controller 7 controls an engine 1 so that the real engine torque Te coincides with the target engine torque tTe. With this structure, overshoot of the target engine torque can be restricted so as to stabilize the transient characteristic of the driving force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving force control device used for a vehicle having a continuously variable transmission.

[0002]

2. Description of the Related Art An engine capable of controlling engine torque independently of a driver's operation of an accelerator pedal and a continuously variable transmission (hereinafter referred to as CVT) capable of continuously changing a gear ratio. In a vehicle equipped with a control method, a target driving force is calculated based on an accelerator pedal operation amount and driving conditions, and the calculated target driving force is set as a predetermined engine torque to realize a CVT speed ratio.

In such a control system, if the CVT has a response delay, the target driving force cannot be obtained. However, in the driving force control device disclosed in Japanese Patent Application Laid-Open No. H11-78620. By calculating the target engine torque by dividing the target driving force by the actual gear ratio, the response delay of the CVT is compensated for by the engine torque so that the target driving force is realized.

According to this, for example, even when the driver suddenly depresses the accelerator pedal and the target driving force and the target gear ratio change stepwise, and the actual gear ratio increases with a delay, the actual The target engine torque is added until the gear ratio reaches the target gear ratio, and the engine torque is added, so that a shortage of driving force is suppressed.

[0005]

[Problems to be solved by the invention]
If the target engine torque exceeds the upper limit of the engine torque as a result of adding the target engine torque in this way (overshoot of the target engine torque), the engine torque does not reach the target engine torque and the target driving force Can not be obtained. Furthermore, at this time, since the driving force changes according to the limit performance of the engine,
There was a possibility that the driving force was not stabilized until the target driving force was reached.

The present invention has been made in view of such technical problems, and suppresses an overshoot of a target engine torque even when a driver depresses an accelerator pedal suddenly, thereby stabilizing a transient characteristic of a driving force. The purpose is to make it.

[0007]

According to a first aspect of the present invention, there is provided a vehicle driving force control apparatus for use in a vehicle in which the output of an engine is transmitted to driving wheels via a continuously variable transmission. Means for determining a first target driving force, means for determining a target gear ratio of the transmission based on the first target driving force or accelerator operation amount, and vehicle speed, and a driving force achievable under transient driving conditions. Means for determining a control range to determine a second target driving force from the first target driving force;
Means for obtaining a target engine torque based on the second target driving force and the actual gear ratio of the transmission; means for controlling the transmission such that the actual gear ratio becomes the target gear ratio; Means for controlling the engine so as to attain the target engine torque.

In a second aspect based on the first aspect, the means for calculating the target engine torque calculates the target engine torque in consideration of the influence of the inertia of the drive system on the driving force. It is.

In a third aspect based on the first or second aspect, the means for calculating the second target driving force comprises a second target driving force calculated from the first target driving force based on a response characteristic of the transmission. It is characterized by calculating a force.

According to a fourth aspect of the present invention, in the third aspect, the means for controlling the transmission performs a filtering process on the target speed ratio and controls the transmission according to the target speed ratio after the filtering process. The target gear ratio is a target gear ratio before a filter process is performed.

[0011]

Therefore, according to the first aspect of the present invention, the target engine torque is not the target driving force (first target driving force) set based on the accelerator operation amount, but the first engine torque.
Is determined based on a target driving force (second target driving force) set by determining a driving force control range that can be realized during transient operation (particularly during acceleration) from the target driving force.

As a result, even in the transient driving force control, the target driving force is set within the achievable driving force control range, and the target engine torque exceeds the upper limit of the engine torque. It can be prevented that the driving force changes according to the limit performance of the engine and the transient characteristics become unstable.

According to the second aspect of the present invention, the target engine torque is calculated in consideration of the influence of the inertia of the drive system, so that the target drive force can be obtained under the influence of the inertia of the drive system. Therefore, it is possible to prevent the driving force control performance from deteriorating.

According to the third and fourth aspects of the present invention, the second target driving force is calculated based on the response characteristic from the target speed ratio to the actual speed ratio, thereby causing a delay in the CVT response. Overshoot of the target engine torque can be reliably prevented, and the transient characteristics of the driving force can be further prevented from becoming unstable.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration of a vehicle provided with a driving force control device according to the present invention. The vehicle includes an engine 1 and a continuously variable transmission (CVT) 2, and the output of the engine 1 is transmitted to driving wheels 4 via a CVT 2, a final gear (not shown), and a drive shaft 3. ing.

The engine 1 is a gasoline engine provided with an electronically controlled throttle that can be controlled independently of a driver's accelerator operation. The engine 1 can adjust the engine torque by controlling the throttle opening of the electronically controlled throttle. The engine 1 may be a diesel engine. In this case, the engine torque can be adjusted by adjusting the fuel injection amount by the injector.

The CVT 2 is a so-called belt-type continuously variable transmission having a pair of pulleys 2a and 2b and a V-belt 2c stretched between the pulleys 2a and 2b, and by changing the groove width of the pulleys 2a and 2b. The gear ratio can be changed steplessly. The CVT 2 includes a torque converter with a lock-up mechanism, a forward / reverse switching mechanism for switching the transmission direction of engine rotation, and the like (not shown).

Further, the vehicle includes an accelerator operation amount sensor 1 as a means for detecting an accelerator operation amount by a driver.
0, vehicle speed sensor 11 as vehicle speed detecting means, input rotational speed sensor 1 as input rotational speed detecting means of CVT 2
2. Various sensors for detecting an operation state, such as an output rotation speed sensor 13 as output rotation speed detection means, are attached, and various signals detected by these sensors are input to the integrated controller 9. The vehicle speed VSP and CV
Since the T output rotational speed Nout can be obtained by calculation if one is obtained, the other may be provided with only one of the vehicle speed sensor 11 and the output rotational speed sensor 13.

The integrated controller 9 calculates a target driving force based on the driving conditions, and performs the driving force control that realizes the calculated target driving force as a predetermined engine torque at a CVT speed ratio.

Specifically, the integrated controller 9 determines the first target driving force tFd1 according to the accelerator operation amount APS and the vehicle speed VSP.
And a second target driving force tFd2 is set from the first target driving force tFd1 in consideration of the driving force realization performance at the time of transition.
The target engine torque t is obtained by dividing the second target driving force tFd2 by the actual gear ratio G so that the second target driving force tFd2 is realized.
Set Te. Also, the first target driving force tFd1 and the vehicle speed VSP
, The target speed ratio tG of CVT2 is calculated.

The target engine torque tTe and target gear ratio tG set as described above are output to the engine controller 7 and the CVT controller 8, respectively. The engine controller 7 controls the intake air amount (fuel injection amount in the case of a diesel engine) of the engine 1 so that the actual engine torque Te becomes the target engine torque tTe, and the CVT controller 8 adjusts the actual gear ratio G to the target gear ratio. Specific tG
Adjust the pulley groove width of CVT2 so that

The details of the driving force control performed by the integrated controller 9 will be described in more detail with reference to the block diagram shown in FIG.

As shown in FIG. 2, the integrated controller 9
Includes a first target driving force setting unit B1, a second target driving force calculation unit B2, a target engine torque calculation unit B3, and a target gear ratio setting unit B4.

The integrated controller 9 includes an accelerator operation amount APS detected by an accelerator operation amount sensor 10, a vehicle speed VSP detected by a vehicle speed sensor 11, a CVT input rotation speed Nin detected by an input rotation speed sensor 12, The CVT output rotation speed Nout detected by the output rotation speed sensor 13 is input.

Each element B1 to B4 of the integrated controller 9
The operation of will be described.

First, the first target driving force setting section B1 determines the vehicle speed.
The first target driving force tFd1 is set based on the VSP and the accelerator operation amount APS with reference to the map shown in FIG. The first target driving force tFd1 is set to a larger value as the accelerator operation amount APS increases, and when the accelerator operation amount is constant, the first target driving force tFd1 becomes maximum near the vehicle speed of 20 km / h.

Next, the second target driving force calculating section B2 determines a driving force control range that can be realized during the transient operation, and calculates a second target driving force tFd2 from the first target driving force tFd1.
Specifically, based on the first target driving force tFd1, which is the output of the first target driving force setting unit B1, the following expression:

[0029]

(Equation 1) Here, the second target driving force tFd2 is calculated by τ _a : time constant [sec] s: differential operator.

Equation (1) expresses the relationship between the first target driving force tFd1 and the second target driving force tFd2 using a transfer function in a continuous time system. Since the actual calculation is performed by discrete-time calculation, in the actual calculation, the second target driving force tFd2 is calculated by the following equation, which is equivalent to the equation (1):

[0031]

(Equation 2) Here, Δt: sampling time (constant) [sec] z: Calculated by z operator. Here the time constant tau _a is set to the second target driving force tFd2 is also feasible transient.
The time constant τa may be given as _a constant, or may be changed depending on the operation state.

Alternatively, the second target driving force tFd2 is CV
The calculation may be performed based on the response characteristic of T2 (= response characteristic from target gear ratio tG to actual gear ratio G). In this case, for example, the response characteristic from the target gear ratio tG to the actual gear ratio G is

[0033]

(Equation 3) Where ζ: damping coefficient ω: natural frequency t1: dead time Assuming that this is approximately expressed as the product of the dead time element and the secondary vibration element, the second target driving force tFd2 is also the same transfer function. Using the following equation:

[0034]

(Equation 4) Is calculated by However, also in this case, since the actual calculation is performed by a discrete-time calculation, in the actual calculation, the second target driving force tFd2 is expressed by the following equation equivalent to the equation (4):

[0035]

(Equation 5) Here, Δt: sampling time [sec] u: intermediate parameter Note that the intermediate parameter u
Is

[0036]

(Equation 6) It is represented by Further, the damping coefficient ζ, the natural frequency ω, and the dead time t1 may be constants or may be changed depending on the operation state.

In some cases, the target speed ratio tG is subjected to a filtering process in the control logic in a target speed ratio setting section B4, which will be described later. In this case, the target speed ratio tG before the filtering process is actually processed. It is assumed that the second target driving force tFd2 is calculated so as to match the response characteristic of the speed ratio G.

Further, the target engine torque calculating section B3 calculates
Based on a second target driving force tFd2, which is an output of the second target driving force calculation unit B2, and an actual speed ratio G of CVT2 obtained by dividing the input rotation speed Nin by the output rotation speed Nout,

[0039]

(Equation 7) However, the target engine torque tTe is calculated based on Rtire: effective radius of driving wheel [m] Gf: reduction ratio of final gear. This equation (7)
Is the relationship between the engine torque Te and the driving force Fd is approximately

[0040]

(Equation 8) Is assumed.

The target gear ratio setting section B4 sets the target gear ratio tG based on the first target driving force tFd1 and the vehicle speed VSP with reference to a map as shown in FIG. I do. The target gear ratio tG may be set based on the accelerator operation amount and the vehicle speed VSP (or the output rotation speed Nout).

Therefore, from the integrated controller 9,
The target engine torque tTe is sent to the engine controller 7,
The target gear ratio tG is output to the CVT controller 8, and the engine controller 7 outputs the target engine torque tT.
e, the throttle opening of the engine 1 is adjusted to control the intake air amount (fuel injection amount in the case of a diesel engine), and the CVT controller 8 sets the target gear ratio tG
Adjust the pulley groove width so that is achieved.

Next, the operation will be described.

Here, it is assumed that the driver suddenly depresses the accelerator pedal and the target driving force (first target driving force) changes stepwise.

FIG. 5 is a timing chart showing how the driving force, engine torque and gear ratio change when the present invention is not applied.

When the driver depresses the accelerator pedal rapidly at time T1 and the target driving force changes stepwise, the target speed ratio of the CVT 2 also changes stepwise as shown in FIG. The speed ratio follows the target speed ratio with a delay.

Here, the target engine torque is calculated by dividing the target driving force by the actual gear ratio, and is added as shown in FIG. 5 (c) in order to prevent the driving force from becoming insufficient due to the CVT response delay. . However, since the target engine torque exceeds the upper limit of the engine torque, the actual engine torque cannot reach the target engine torque, and the driving force also decreases as shown in FIG.
As shown in (b), the target driving force cannot be obtained.

Further, since the control according to the target driving force is not performed and the driving force changes according to the limit performance of the engine, there arises a problem that the transient characteristic of the driving force is not stabilized.

FIG. 6 is a timing chart showing changes in the driving force, the engine torque and the gear ratio when the present invention is applied.

According to this, when the driver suddenly depresses the accelerator pedal at time T1 and the first target driving force changes stepwise as shown in FIG.
The target gear ratio also changes stepwise as shown in FIG.
The actual gear ratio follows the target gear ratio with a delay.

However, the second target driving force is calculated from the first target driving force, for example, so as to match the response characteristic of the CVT 2 in consideration of the driving force realizing performance during transition.
The target engine torque is set such that the second target driving force is realized.

As a result, the target engine torque is kept below the upper limit of the engine torque even during the transition, the target engine torque exceeds the upper limit of the engine torque, the driving force changes according to the limit performance of the engine, and the transient response is reduced. Instability is prevented.

Next, a second embodiment of the present invention will be described.

The second embodiment is different from the first embodiment in the method of calculating the target engine torque tTe in the target engine torque calculator B3, and calculates the target engine torque tTe in consideration of the influence of the inertia of the drive system. The difference is that they do so. FIG. 7 is a block diagram corresponding to FIG. 2 of the previous embodiment. In addition to the second target driving force tFd2 and the actual gear ratio G, the vehicle speed VSP which is the output of the vehicle speed sensor 11 is stored in the target engine torque calculation unit B3. Is entered. The other configuration is the same as the previous embodiment.

The operation of the target engine torque calculator B3 will be described.
Calculates the target engine torque tTe by the following equation based on the second target driving force tFd2, the actual gear ratio G, and the vehicle speed VSP.

[0056]

(Equation 9) Where tTe2 and hTe are intermediate parameters,

[0057]

(Equation 10)

[0058]

[Equation 11] However, J1: Moment of inertia on the input side of the engine and CVT [N · m · s ² ] J2: Moment of inertia from the CVT output to the final gear input [N · m · s ² ] J3: From the final gear to the drive wheels Moment of inertia [N
・ M ・ s ² ] ω _w : Angular velocity of the wheel [rad / s] (Rtire, Gf, J1, J2 and J3 are constants).

Equations (9) to (11) show that the relationship between the engine torque and the driving force is approximately as follows:

[0060]

(Equation 12) Is assumed.

Here, the angular velocity ω _w of the wheel is obtained from the vehicle speed VSP and the effective radius of the driving wheel Rtire by the following equation:

[0062]

(Equation 13) Is calculated by Also, the actual gear ratio G and the wheel angular velocity ω _w
The time derivative of is

[0063]

[Equation 14]

[0064]

(Equation 15) Thus, it is approximately obtained as the amount of change per unit time.

[0065] It should be noted that the intermediate parameter hTe, in place of the equation (11), the following formula that ignores the differential value of the wheel of the angular velocity ω _w,

[0066]

(Equation 16) However, J1: the moment of inertia on the input side of the engine 1 and the CVT ² [N · m · s ² ] ω _w : the angular velocity of the wheel [rad / s] (Gf, J1 may be a constant). in this case,
The calculation becomes simpler than the formula (11), and the calculation of the formula (15) becomes unnecessary, and the calculation load is reduced.

Therefore, according to the second embodiment, similarly to the first embodiment, the overshoot of the target engine torque can be suppressed, and the transient characteristic of the driving force can be prevented from becoming unstable. By calculating the target engine torque in consideration of the influence of the inertia of the drive system, the second target drive force and the actual drive force can be matched, and the drive force control performance can be improved. .

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a vehicle including a vehicle driving force control device according to the present invention.

FIG. 2 is a block diagram showing details of driving force control performed by an integrated control unit.

FIG. 3 is an example of a first target driving force setting map.

FIG. 4 is an example of a target gear ratio setting map.

FIG. 5 is a timing chart showing changes in driving force, engine torque, and gear ratio when the accelerator pedal is rapidly depressed (not applied to the present invention).

FIG. 6 is a timing chart showing a driving force, an engine torque, and a gear ratio when an accelerator pedal is rapidly depressed (application of the present invention).

FIG. 7 is a block diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 engine 2 continuously variable transmission (CVT) 3 drive shaft 4 drive wheel 7 engine controller 8 CVT controller 9 integrated controller 10 accelerator operation amount sensor 11 vehicle speed sensor 12 input rotation speed sensor 13 output rotation speed sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // F16H 59:18 F16H 59:18 59:24 59:24 59:44 59:44 63:06 63: 06 F term (reference) 3D041 AA31 AC02 AC09 AC20 AD10 AD30 AD37 AD51 AE05 AE07 AE36 3G065 AA01 CA00 DA04 GA11 GA31 GA46 3G084 AA01 BA05 BA13 DA00 EA01 FA00 FA05 FA10 3G301 HA02 JA03 KA11 LA03 MA11 NB07Z01 PF07

Claims (4)

[Claims] An output of an engine which is transmitted to a drive wheel via a continuously variable transmission; means for obtaining a first target driving force based on an accelerator operation amount; and said first target driving force. A means for obtaining a target gear ratio of the transmission based on an accelerator operation amount and a vehicle speed; a driving force control range achievable under transient driving conditions; Means for obtaining a driving force; means for obtaining a target engine torque based on the second target driving force and an actual gear ratio of the transmission; means for controlling the transmission such that the actual gear ratio becomes the target gear ratio. And means for controlling the engine such that actual engine torque becomes the target engine torque. 2. The vehicle driving force according to claim 1, wherein the means for calculating the target engine torque calculates the target engine torque in consideration of the influence of the inertia of the driving system on the driving force. Control device. 3. The means for calculating the second target driving force includes:
3. The driving force control device according to claim 1, wherein a second target driving force is calculated from a first target driving force based on a response characteristic of the transmission. 4. When the means for controlling the transmission performs a filtering process on the target speed ratio and controls the transmission in accordance with the target speed ratio after the filtering process, the target speed ratio is determined by the filtering process. The driving force control device for a vehicle according to claim 3, wherein the target gear ratio is a target gear ratio before the operation is performed.