JPH0681683A - Driving force control device for vehicle - Google Patents

Abstract

PURPOSE:To make the realization of operability intended by a driver compatible with the guarantee of traveling stability at the time of the driver operating an accelerator by limiting the sudden increase of the slip reference value used for driving torque control. CONSTITUTION:The wheel rotating speed VFL, VFR, VRL, VRR of front and rear wheels and the accelerator operating quantity L are inputted into a CPU 11. The CPU 11 executes a specified control program and sets the slip reference value in such a way as to secure traveling stability and turning stability by limiting the increase of the slip reference value used for driving torque control at the time of the sudden accelerator depressing operation of a driver and the careless accelerator operation during turning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to vehicle driving force control capable of achieving both drivability intended by the driver and ensuring traveling stability when the driver operates the accelerator. It relates to the device.

[0002]

2. Description of the Related Art As a conventional example of a vehicle drive control device for performing drive torque control, which controls variablely the drive torque supplied to the drive wheel in accordance with the drive slip state when a drive slip occurs in the drive wheel, For example, JP-A-63-3183
There is one disclosed in Japanese Patent No. 0. In this conventional example, by using the accelerator operation amount (the throttle opening is substituted) as a parameter, the engine drive torque is variably controlled so that the drive slip state becomes the slip target value (reference value), The drive slip is eliminated. At this time, the slip target value is increased as the absolute value of the accelerator operation amount, which is a parameter indicating the driver's intention to accelerate, is increased to realize the drivability intended by the driver.

[0003]

However, in the above-described conventional vehicle driving force control device, the slip target value is simply increased as the accelerator operation amount is increased, and therefore the following problems occur. Invite. First
In addition, when the driver performs an abrupt accelerator depression operation, the target slip value suddenly increases and a large slip is allowed, so driving stability is ensured against accidental accelerator operation by the driver. The original function of the driving force control device is impaired.

Secondly, whether the vehicle is in a turning state or a straight traveling state is simply judged by the accelerator operation amount, and the fact that the accelerator operation amount is different depending on the road surface state, the vehicle speed, the turning radius, etc. is not taken into consideration. The target slip value changes with the same characteristics between the straight state and the straight state. For example, during a high G turn where the accelerator operation amount is originally large, the target slip value is large even when the vehicle is turning, even though the vehicle is turning. As a result, a large slip is allowed, so that the original function of the driving force control device to secure the turning stability is impaired.

According to the present invention, when the slip reference value is controlled according to the accelerator operation amount indicating the driver's intention of acceleration,
By limiting the slip reference value so that it does not increase suddenly, both the realization of the drivability intended by the driver and the securing of driving stability during the driver's accelerator operation are solved, thereby solving the above-mentioned problems. The purpose is to do.

[0006]

To this end, the structure of claim 1 of the vehicular driving force control device of the present invention is, as the concept is shown in FIG. 1, a driving slip for detecting a driving slip state of driving wheels. A vehicle comprising: detection means, slip reference value setting means for setting a slip reference value of the drive wheel, and drive torque control means for performing drive torque control based on the detected drive slip state and the set slip reference value. In the driving force control device for accelerator, the slip reference value is set in accordance with an accelerator operation detecting means for detecting an accelerator operation state and a control signal formed by multiplying an accelerator operation state signal output by the accelerator operation detecting means by at least a predetermined gain. And a slip reference value correcting means for correcting the accelerator operation state signal, a predetermined gain, and a slip reference when forming the control signal. Limiting at least one of,
A signal limiting means is provided.

According to a second aspect of the present invention, in addition to the structure of the first aspect, a straight-ahead turn determining means for determining whether the vehicle is in a straight-ahead state or a turning state is provided, and the vehicle is output according to an output signal of the straight-ahead turn-determining means. It is characterized in that the signal control means is operated when it is determined that the vehicle is in a turning state.

[0008]

According to the first aspect of the present invention, based on the drive slip state detected by the drive slip detection means and the slip reference value set by the slip reference value setting means,
When the drive torque control means performs the drive torque control, the slip reference value correction means corrects the slip reference value in accordance with a control signal formed by multiplying the accelerator operation state signal output by the accelerator operation detection means by at least a predetermined gain. However, the signal limiting means limits at least one of the accelerator operation state signal, the predetermined gain, and the slip reference value when forming the control signal. The increase of the slip reference value is restricted when the vehicle is depressed, and it is possible to prevent a problem that the traveling stability is impaired.

Further, according to the second aspect of the present invention, when the vehicle is judged to be in the turning state in response to the output signal of the straight ahead turning judgment means for judging whether the vehicle is in the straight ahead state or in the turning state during the control. Since the signal control means is operated only when the vehicle is turning, the increase of the slip reference value is restricted when the driver operates the accelerator inadvertently, and traveling stability during turning can be ensured.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 shows the first embodiment of the vehicle driving force control device of the present invention.
It is a figure which shows the structure of an Example, 1L, 1R shows a left front wheel, a right front wheel, 2L, 2R shows a left rear wheel, a right rear wheel, 3 shows an engine. This vehicle is a rear-wheel drive vehicle in which the engine 3 drives rear wheels 2L and 2R that are drive wheels.
Wheel rotation sensors 4, 5, 6 and 7 are provided near L, 1R, 2L and 2R, respectively (the vehicle may be an all-wheel drive vehicle).

The wheel rotation sensors 4 to 7 detect the rotation speed of each wheel as a pulse signal having a frequency corresponding to the rotation speed. The obtained rotation speeds VFL, VFR,
A pulse signal having a frequency corresponding to VRL and VRR is input to the F / V converter 9 of the driving force control unit 8. The driving force control section 8 comprises an F / V converter 9, an A / D converter 10 and a CPU 11, and the F / V converter 9
Converts the input signal from each of the wheel sensors 4 to 7 and inputs the voltage to the A / D converter 10. The A / D converter 10 digitally converts each input signal and inputs the digital signal to the CPU 11.
Note that the CPU 11 uses, for example, a microcomputer.

In this example, an accelerator opening sensor 14 is provided as an accelerator operation detecting means for detecting an accelerator operation state (accelerator operation amount), and an accelerator opening signal L which is an output signal thereof is input to the A / D converter 10. To do.

The CPU 11 executes the control programs of FIGS. 3 to 9 on the basis of the input wheel rotation speeds (wheel speeds) VFL, VFR, VRL, VRR and the accelerator opening (operation amount) L. The slip reference value used when performing the drive torque control is variably controlled according to the accelerator operation amount. The first embodiment is premised on the engine control system in which the torque applied to the drive wheels is adjusted by adjusting the drive torque itself of the engine, and the CPU 11 sends the fuel supply cut signal FC to the fuel supply control unit 12. Then, the injection pulse IP outputted from the fuel supply control unit 12 to each of the cylinders 13-1 to 13-6 of the engine is interrupted by this signal FC, and the fuel cut is executed.

The operation system (not shown) is repeatedly executed by a periodic interrupt every predetermined period.
In the control program, first, in step 101, the rotational speeds VFL and VFR of the left and right front wheels, which are driven wheels, and the rotational speeds VRL and VRR of the left and right rear wheels, which are driving wheels, are read from the corresponding wheel rotation sensors 4 to 7, respectively. In step 102, the average rotational speed VF of the front wheels (driven wheels) is VF = (VFL +
VFR) / 2, and in step 103, the average rotational speed VR of the rear wheels (driving wheels) is VR = (VRL + VRR) /
2 and the drive slip amount S is calculated in step 104 as
Calculated by S = VR-VF. In the control program of FIG. 3, the CPU 11 functions as a drive slip detecting means.

FIG. 4, performed after step 104,
In step 111 of the control program, the slip peak value Sp is read. In this reading,
In the first control, the slip S obtained in step 104 becomes the slip peak value Sp as it is, and in the second and subsequent control, the slip peak value is updated according to the determination in the next step 112. That is, when the current slip S exceeds the currently stored slip peak value Sp, such as when a drive slip occurs, the determination in the next step 112 is YES in S> Sp and step 113 is selected. In step 113, the slip peak value Sp is updated to the slip S. If S is less than or equal to Sp, step 113 is skipped and the slip peak value is not updated.

In the next step 114, the slip peak is judged depending on whether S <Sp-α. This slip peak determination is such that, while the slip S continues to increase when a drive slip occurs, the slip peak value Sp is continuously updated by executing steps 112-113 above, but after the slip S starts to decrease, Sp Since it is fixed without being updated, when the slip S at a certain point falls below the slip peak value Sp by a predetermined value α or more, it is determined that the slip has passed the peak, and if it is determined that the slip has passed the peak. In step 115, the peak determination flag PF is set (PF = 1). The state of PF = 1 of the peak determination flag obtained in this way indicates that the torque down control of the engine is performed due to the occurrence of the drive slip, and the slip is in the convergence direction. It should be noted that the predetermined value α is determined based on a safety factor that prevents erroneous peak determination due to noise or the like in the sensor signal.

FIG. 5, which is executed after step 115.
Control program determines whether or not to reset the peak determination flag. First, in step 121, the torque down instruction amount TD determined as described later is read. In the next step 122, it is determined whether or not the torque down instruction amount TD is 0. If the result of this determination is YES, that is, if the torque down instruction amount TD is 0 and drive torque reduction control is not being performed, it is determined that control has ended and the peak determination flag is reset in step 123 (PF = 0).

FIG. 6, which is executed after step 123.
In step 131 of the control program of
Front wheel average speed VF obtained in step 102
And the front left and right wheels rotate in step 132.
Number difference ΔVF_RLIs ΔVF_RL= | VFR-VFL |
calculate. In the next step 133, the reciprocal of the turning radius R
For a certain turning curvature ρ, ρ = (ΔVF _RL/ T_r) / By VF
Is calculated (however, T_rIs the front wheel tread),
In step 134, the turning curvature ρ is a predetermined value ρ₀ Greater than
Determine whether or not. In this determination, ρ> ρ₀ YE
If S, it is determined that the vehicle is turning and the control proceeds to step 135.
Then, the turning determination flag CFc is set (CF = 1), and ρ
≤ρ₀ If the answer is NO, it is judged that the vehicle is going straight and the control is stopped.
Proceed to page 136 to reset the turn determination flag CF (C
F = 0). In the control program of FIG. 6, CP
U11 functions as a straight turn determination means.

Steps 135 and 13 of the control program shown in FIG.
Steps of the control program of FIG. 7, executed after 6
At 141, the state of the peak determination flag PF is checked. Here, if YES, that is, if PF = 1 and it is determined that the slip has passed the peak and is heading toward convergence, the control proceeds to step 142 and subsequent steps to correct the slip reference value described later, and NO, that is, PF = When it is determined that the slip does not pass the peak at 0 or when the drive torque control is not performed, the control proceeds to step 143 to clear the slip reference value correction amount SL described later (SL = 0).

In step 142, the accelerator opening L read from the accelerator opening sensor is used to increase the accelerator opening (ΔA (n) = L (n)- It is calculated by L (n-1). Here, ΔL is an accelerator operation state signal indicating an accelerator operation state. In the next step 144, the turning determination flag CF is checked. Where CF = 1
If YES (when determining the turning state), ΔL = Min (ΔL, ΔL ₀ ) with respect to the increment ΔL of the accelerator opening in step 145.
The limiter is applied by the gain K in step 146.
If L is determined to be KL = KLc, and if CF = 0 is NO (when the vehicle is in a straight traveling state), the gain KL is changed to KL = KLs in step 147.
To decide. In the above, ΔL ₀ is the upper limit of the accelerator release speed allowed during turning, and the gain KLc
Is set to a value smaller than the gain KLs when going straight.

In step 148 following steps 146 and 147, the increment ΔSL of the slip reference value is set to ΔSL = KL.multidot..DELTA.L.
Calculate by Here, the increment ΔSL of the slip reference value
Is formed by multiplying the accelerator operation state signal .DELTA.L by at least the gain KL, and thus becomes a control signal used for the following slip reference value correction. In the next step 149, the slip reference value correction amount SL is calculated by SL (n) = SL (n-1) + ΔSL (n). Further, in the next step 170, the slip reference value correction amount SL is set to SL = so that the slip reference value correction amount SL always becomes a value of 0 or more (not to become negative).
Set by Max (SL, 0). In the control program of FIG. 7, the CPU 11 functions as accelerator operation detecting means and slip reference value correcting means, and
As will be described later, it also functions as a signal limiting unit.

In the control program of FIG. 8, which is executed after step 150 of the control program of FIG. 7, the front wheel average rotation speed VF is read in step 151. Next steps
In 152, the initial value S of the slip reference value is obtained by looking up the map of FIG. 10 based on this VF.
* Decide ₀ . In step 153, the previously calculated slip reference value correction amount SL is read, and in step 154, the slip reference value S * is calculated by S * = S * ₀ + SL. At that time, the characteristic of changing the slip reference value S * according to the accelerator opening degree changes according to the gain obtained in step 146 or step 147, in other words, according to the turning state / straight running state determination. In the control program of FIG. 8, the CPU 11 functions as slip reference value setting means.

In step 161 of the control program shown in FIG. 9, which is executed after step 154 of the control program shown in FIG. 8, the current drive slip amount S is read, and the step
In step 162, the slip reference value S * previously obtained is read, and in step 163 the two are compared. If S> S * is YES, the routine proceeds to step 164, where it is judged whether or not the torque down instruction amount TD is the maximum value TDmax. If S ≦ S * is NO, then the routine proceeds to step 165 and the torque down instruction amount TD is reached. Whether or not is 0 is determined.

The judgments at steps 164 and 165 become NO when TD takes a value between the upper limit value and the lower limit value, and in that case, at the next steps 166 and 167, respectively, T
The D is incremented (TD = TD + 1) and decremented (TD = TD-1). In the case of YES, since the upper limit value or the lower limit value has already been reached and incrementing and decrementing are impossible, respectively, step 16
Skip 6 and 167. Then, in step 168, the CPU 11 outputs the fuel supply cut signal FC corresponding to the torque down instruction amount TD to the fuel supply control unit 12. In the control program of FIG. 9, the CPU 11 functions as a drive torque control means.

By the way, in the first embodiment, the trade-off between the realization of the drivability intended by the driver and the securing of the traveling stability when the driver operates the accelerator is eliminated as follows. . That is, when entering a corner, as shown in FIG.
The turning curvature ρ obtained in step 133
Since the turning determination flag CF is set (CF = 1) in step 135 as the determination in step 134 becomes YES, if the determination in step 141 in FIG. 7 is YES, the control is YES-in step 141. 142-144 YES-145-146
Will proceed.

Therefore, when the slip reference value S * is increased by the gain KL in accordance with the accelerator opening increment ΔL as shown in FIG. 11 (a) by executing the control programs of FIGS. 7 and 8, The same figure (b)
As shown in Fig. 5, the increment ΔL of the accelerator opening is limited to a predetermined value ΔL ₀ or less, and by executing step 146, the gain KL is limited to a value of KLC smaller than the gain KLS for straight traveling as shown in Fig. 7C. Therefore, the CPU 11 functions as signal limiting means in steps 145 and 146. As a result, the increase of the slip reference value is restricted when the driver accidentally operates the accelerator while the vehicle is turning, and the traveling stability during turning is ensured.

On the other hand, when exiting a corner, the steps shown in FIG.
As the turning curvature ρ obtained in 133 decreases and the determination in step 134 becomes NO, the turning determination flag CF is reset (CF = 0) in step 135, so the determination in step 141 in FIG. 7 is YES. If so, control proceeds to step 141.
YES-142-144 NO-147
By executing the control programs shown in FIG. 7 and FIG.
As shown in (a), when the slip reference value S * is increased by the gain KL according to the increment ΔL of the accelerator opening, step 147 is executed to set the gain KL as shown in FIG.
Becomes KLS which is a value larger than the gain KLC during turning. As a result, when the vehicle exits the corner, the slip reference value increases as the accelerator operation amount increases, and the drivability intended by the driver is realized.

FIG. 12 is a flow chart showing the control program of the essential parts of the second embodiment of the vehicle driving force control apparatus of the present invention. The second embodiment has the same configuration as that of the first embodiment except that the control program of FIG. 12 is used instead of the control program of FIG. 7 of the first embodiment. 12 is executed after steps 135 and 136 of the control program of FIG.
The control program of step 14 is between step NO of step 144 and step 147 of the control program of FIG.
5a is inserted, and otherwise the configuration is exactly the same as in FIG.

In step 145a, the control advances when the straight traveling state is judged to be NO in step 144. In step 145a, similarly to step 145 described above, the limiter is set by ΔL = Min (ΔL, ΔL ₁ ) with respect to the accelerator opening increment ΔL. (Where ΔL ₁ is ΔL ₁ > ΔL ₀ , which is the upper limit value of the accelerator release speed that is allowed while going straight)
In 145, 146 and 145a, the CPU 11 functions as a signal limiting means.

In this second embodiment, the above steps
By adding 145a, regardless of whether the vehicle is in a straight traveling state or in a turning state, a limiter is applied to the increment ΔL of the accelerator opening (in the first embodiment, the limiter is applied only when the turning state is determined). Since the upper limit value ΔL ₀ of the accelerator release speed allowed for is set to be smaller than the upper limit value ΔL _{1 when} going straight, the limiter is applied more strongly when turning.
An increase in the slip reference value is restricted when the driver performs an inadvertent accelerator operation (for example, a sudden depression), and a problem in which traveling stability is impaired is prevented.

In each of the above embodiments, the signal limiting means has the characteristics shown in FIGS. 11 (b) and 11 (c), and the increment ΔL of the accelerator opening,
Although the gain KL is limited, the slip reference value S * (upper limit value) may be limited instead, as shown in FIG. In this case, the limit amount for turning shown by the dotted line is set to be smaller than the limit amount for turning straight indicated by the solid line. In each of the above embodiments, the front wheel average rotation speed VF, the left and right front wheel rotation speed difference ΔVF _RL, and the tread Tr are used to calculate the turning curvature of the vehicle, but a yaw rate may be used instead. Although the turning curvature ρ (turning radius R) is used as a parameter for determining whether the vehicle is turning or going straight, the yaw rate of the vehicle or the changing speed of each physical quantity may be used instead.

Further, in each of the above-mentioned embodiments, the drive torque control by cutting the fuel supply is adopted as the traction control, but the invention is not limited to this. For example, the throttle opening for electrically controlling the throttle valve of the engine is used. Control, engine ignition timing control, or brake control that directly applies pressure to the wheel cylinders may be used.

[0033]

As described above, the vehicle driving force control apparatus of the present invention, when controlling the slip reference value in accordance with the accelerator operation amount indicating the driver's intention of acceleration, rapidly increases the slip reference value. Since the restriction is made so as not to occur, the increase of the slip reference value is restricted when the driver performs an inadvertent accelerator operation (for example, a sudden depression), and it is possible to prevent a problem that the traveling stability is impaired. Further, by performing the above limitation only when it is determined that the vehicle is in a turning state, an increase in the slip reference value is limited when the driver accidentally operates the accelerator during turning of the vehicle. Driving stability can be secured.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of the present invention.

FIG. 2 is a diagram showing a configuration of a first embodiment of a vehicle driving force control device of the present invention.

FIG. 3 is a flowchart showing a control program for driving slip amount calculation in the same example.

FIG. 4 is a flowchart showing a control program for updating a slip peak value and setting a peak determination flag in the same example.

FIG. 5 is a flowchart showing a control program for resetting a peak determination flag in the same example.

FIG. 6 is a flow chart showing a control program for determining a straight traveling state / a turning state in the same example.

FIG. 7 is a flowchart showing a control program for setting a slip reference value correction amount in the same example.

FIG. 8 is a flowchart showing a control program for setting a slip reference value in the same example.

FIG. 9 is a flowchart showing a control program for drive torque control in the same example.

FIG. 10 is a diagram illustrating a map used for setting an initial value of a slip reference value in the same example.

FIG. 11A is a diagram for explaining the operation of the same example. (b) is a diagram for explaining the operation of the example. (c)
FIG. 8 is a diagram for explaining the operation of the same example. (d) is a figure for explaining the operation of the example.

FIG. 12 is a flowchart showing a control program of a main part of a second embodiment of the vehicle driving force control device of the invention.

[Explanation of symbols]

1L, 1R front wheel (driven wheel) 2L, 2R rear wheel (driving wheel) 3 engine 4-7 wheel rotation sensor 11 CPU (driving slip detecting means, slip reference value setting means, driving torque control means, slip reference value correcting means, Signal limiting means) 12 Fuel supply control unit 13-1 to 13-6 Cylinder 14 Accelerator opening sensor (accelerator operation detecting means)

Claims (2)

[Claims] 1. A drive slip detecting means for detecting a drive slip state of a drive wheel, a slip reference value setting means for setting a slip reference value of the drive wheel, and a detected drive slip state and a set slip reference value. In a vehicle driving force control device including drive torque control means for performing drive torque control, an accelerator operation detecting means for detecting an accelerator operation state and at least a predetermined accelerator operation state signal output by the accelerator operation detecting means. Compensating the slip reference value according to the control signal formed by multiplying the gain, slip reference value correction means, when forming the control signal, the accelerator operation state signal, a predetermined gain, among the slip reference value A driving force control device for a vehicle, comprising: a signal limiting means for limiting at least one. 2. A straight traveling turning determination means for determining whether the vehicle is in a straight traveling state or a turning state, and the signal control means is operated when the vehicle is determined to be in a turning state according to an output signal of the straight traveling turning determination means. The driving force control device for a vehicle according to claim 1, wherein