JPH03164333A - Drive control device for vehicle - Google Patents

Abstract

PURPOSE:To simplify a controller and improve the responsiveness of feedback control by forming a control system with a judging unit constituted of a running state judging means and a control target value setting means and the controller with a feedback control means. CONSTITUTION:Various running states of a vehicle are judged by a running state judging means based on the output of a drive state detecting means in a judging unit, and a control target value is set by a control target value setting means according to the judged running state. Vehicle drive is feedback-controlled in a controller so that the rotating speed difference between front and rear wheels determined from the detected value of a wheel speed detecting means becomes the above control target value. The feedback control by the controller is performed by a separate routine from those for judging the running state and setting the control target value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a drive control device for a vehicle, and more particularly, to a four-wheel drive system equipped with a center differential that performs differential operation between front wheels and rear wheels.
The present invention relates to a drive control device for a wheel drive vehicle.

(Prior Art) In a four-wheel drive system for an automobile, a center differential has been conventionally provided between the front wheels and the rear wheels. By providing the center differential in this manner, the tight corner braking phenomenon and the like can be avoided due to its differential operation, allowing stable four-wheel drive.

However, when a center differential is installed in a four-wheel drive system like this, when one of the wheels slips or spins when driving on rough roads, the total driving force is reduced due to the differential operation of the center differential. As a result, sufficient running performance cannot be obtained, so a differential limiting device consisting of, for example, a clutch means is installed to prevent slippage in which the difference between the rotational speed of the front wheels and the rotational speed of the rear wheels is greater than a predetermined value. When driving, this differential limiting device is activated to directly connect the front and rear wheels, and when driving other than that, the differential limiting device is deactivated to allow the center differential to operate differentially. This has traditionally been practiced. Conventionally, as a drive control device for a four-wheel drive vehicle equipped with a center differential and a differential limiting device that limits the differential operation of the center differential, for example, Japanese Patent Laid-Open No. 62-26
1. As stated in Publication No. 53, information such as wheel rotational speed and steering angle is input, and the target rotational speed difference between the front and rear wheels is determined from a map based on the steering angle, etc., and the actual rotational speed difference is determined. It has been proposed that the differential limiting device is feedback-controlled so that the rotational speed difference approaches the target rotational speed difference.

By the way, in a conventional drive control device that controls the operation of a differential limiting device, as in the one described in the above publication, there is a judgment section that inputs information and determines a target value using a map, and a feedback control section. The control device is configured such that the control section for executing the .

However, various driving conditions of the vehicle, such as the on/off status of the anti-lock brake system (abbreviated as ABS), tight corner braking when the steering angle is large. In order to obtain a wide variety of control characteristics in response to various conditions such as the occurrence of stacking, the conventional control device described above requires numerous maps and complex control units for each condition, and requires information processing. Since the processing from the input of the vehicle to the determination of the control target according to the driving state and the execution of the feedback control is performed in one routine, the problem arises that the processing time becomes long and the responsiveness of the feedback control deteriorates.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems.
In a drive control device for a vehicle such as a wheel drive type, it is an object of the present invention to simplify a control section and improve responsiveness of feedback control.

(Structure of the Invention) The present invention separates a determination unit that determines the driving state of a vehicle and sets a control target value according to the driving state, and a control unit that executes feedback control, so that each process can be performed in separate routines. The structure is as follows. That is, as shown in FIG. 1 (2L), the drive control device for a vehicle according to the present invention determines various running situations of the vehicle based on the output of a drive state detection means that detects the drive state of the vehicle. a determination means, a control target value setting means for setting a control target value of the vehicle drive system according to the driving situation determined by the driving situation determination means, and a rotation of the front and rear wheels determined from the detected value of the wheel speed detection means. In a vehicle drive control device comprising feedback control means for controlling a vehicle drive system so that a speed difference becomes a control target value set by the control target value setting means, the control system is configured to include the driving situation determining means and the control system. The present invention is characterized in that it is formed separately into a determination section comprising a target value setting means and a control section having the feedback control means.

Further, as shown in FIG. 1(b), the present invention has a drive system that includes:
A four-wheel drive device comprising a center differential that performs differential operation between front wheels and rear wheels, and differential limiting means that limits the differential operation of the center differential and brings the front and rear wheels closer to a direct connection state. The differential limiting means may be controlled by a feedback control means.

Further, as shown in FIG. 1(c), the present invention provides a control target value setting means for setting a target slip ratio between the front and rear wheels based on the driving condition determined by the driving condition determining means. It consists of a slip ratio setting means and a target value converting means for converting the set target slip ratio into a target value of the rotational speed difference between the front and rear wheels, and the control target value converted by the target value converting means is sent to the control section. It can be outputted.

Further, as shown in FIG. 1(d), the present invention further provides upper and lower limit setting means for setting the upper and lower limits of the control target value based on the driving condition determined by the driving condition determining means. The output of the upper limit/lower limit setting means may be output to the control section.

Furthermore, the present invention can be provided with a determining section changing means that allows the determining section to be changed as appropriate, as shown in FIG. 1 (6).

(Operation) In the determination section, various driving conditions of the vehicle are determined based on the output of the driving state detection means, and a control target value is set according to the determined driving condition. Further, in the control section, the vehicle drive system performs feedback control so that the rotational speed difference between the front and rear wheels determined from the detected value of the wheel speed detection means becomes the control target value. be done. In this case, the feedback control by the control unit can be performed by interruption in a routine that is separate from the determination of the driving situation and the setting of the control target value in the determination unit.

If the drive system is configured with a four-wheel drive device equipped with a center differential and a differential limiting means for limiting the differential operation thereof, the rotational speed difference between the front and rear wheels will be set to the above-mentioned control target value. A limited slip differential is controlled.

Furthermore, in the case where the control target value setting means is composed of a target slip ratio setting means and a target value converting means, the control target value is first set as the slip ratio, that is, the rotational speed difference between the front and rear wheels, and the rotational speed difference is is converted to

Further, in the case where the determination section includes upper and lower limit setting means, the upper and lower limits of the control target value are set depending on the driving situation, and these are output to the control section.

Furthermore, the present invention is capable of appropriately changing the conditions for determining the driving situation and the characteristics of the control target value depending on the characteristics of the vehicle and the destination by providing the determining section changing means.

(Example) Examples will be described below based on the drawings.

FIG. 2 is an overall system diagram showing an embodiment of the present invention applied to a four-wheel drive vehicle. In this embodiment, a power plant 1 consisting of an engine and a transmission is arranged vertically at the front of a vehicle, and its output shaft 2 extends rearward to the middle of the vehicle and is gear-coupled to a center differential 3. A front wheel drive shaft 4 and a rear wheel drive shaft 5 extend longitudinally from the two output parts of the center differential 3, and the front left and right wheels 8.9 and the left and right rear wheels 10 are connected to their tips via a front differential 6 and a rear differential 7, respectively. , 1l axle 12, 13
, 14, and 15 are connected, respectively.

The center differential 3 is provided with a hydraulic clutch l6 for limiting differential movement. A hydraulic control valve I9 whose duty is controlled by the controller 18 is provided in a hydraulic passage l7 that supplies engagement hydraulic pressure to the hydraulic clutch l6.

The vehicle includes rotational speed sensors 20a. 20b, 2Qc, 20
d are provided, and detection signals from these sensors 20a to 20d are input to the controller l8.

The controller 18 also receives a throttle opening signal from a throttle opening sensor attached to the throttle valve 21 of the engine, and a steering angle signal from a steering angle sensor that detects the operating angle (steering angle) of the steering wheel 22. An oil pressure signal from an oil pressure sensor 23 provided in the oil pressure passage 17 and an oil temperature signal from an oil temperature sensor 24 are respectively input. Furthermore, the controller 18 also receives an ABS signal from an ABS controller 25 that controls an anti-lock brake system (ABS). Gear position signals and the like from a FAT controller 26, which is a control device for an electronically controlled automatic transmission (FAT), are input.

FIG. 3(a) is an overall block diagram of the control system in the above control system. As shown in this figure, the control system is divided into a judgment section (A) and a control section (B).
) are input with the above-mentioned signals indicating the driving state of the vehicle.

And the judgment part (A)? As shown in FIG. 3(b), for example, the front wheel speed ω is calculated from the rotational speeds ωFR, ωFL of the left and right front wheels 8.9, and the rear wheel speed ω is calculated from the rotational speeds ωR8, ωIIL of the left and right rear wheels to, ti. A speed ωR is calculated.

In addition, the vehicle speed V is calculated based on the value of the smallest rotational speed among the rotational speeds of the four wheels 8 to l1, and the front and rear wheel speed ratio S and the front and rear wheel speed difference Δω are calculated from the front wheel speed ωf and the rear wheel speed ωR. be done. In addition, the judgment section judges the state of ABSh<'ON'', the driving situation such as anti-lock braking, stuck state, and start, based on each input signal and each calculated value above. A control target value is set according to the driving situation.This control target value is first set by the upper limit Δ of the slip rate ΔS, except for stack control, etc.
This is done in the form of setting S1.8 and a lower limit ΔS■. Here, the upper limit ΔS 111111 is a set value when the front wheel speed ω, is larger than the rear wheel speed ωB, and defines the upper limit of the dead zone described later. Further, the lower limit ΔS win is a set value when the rear wheel speed ω8 is greater than the front wheel speed ωt, and also defines the lower limit of the dead zone.

? These ΔS wax and ΔS aln are converted into the upper limit ΔωIIIK and lower limit Δω1o of the rotational speed difference by multiplying by the larger (or smaller depending on the driving condition) value of the front wheel speed ω and the rear wheel speed ωR. . In addition, in stack control etc., direct Δω■8
and Δω1 are set.

Further, FIG. 3(c) is a detailed block diagram of the control section (B), and FIG. 4 is a detailed diagram of control characteristics defined in this control section (B). The control unit (B) has an upper limit Δω of the rotational speed difference set by the determination unit (A). ．．
8 and the lower limit Δω1n are input. In the control section (B), the actual rotational speed difference Δω is the upper limit Δω. ．． or the lower limit Δω, 0, the clutch oil pressure target value T. ■(When the front wheel speed ω, is larger than the rear transport speed ω) or T■7 (When the rear wheel speed ω3 is the front wheel speed ω,
) is set to zero, allowing free differential operation of the center differential 3. Then, when Δω exceeds the upper limit Δω■8, or exceeds the lower limit Δω, 1, the value is reset according to the difference. A to T■8 and T +o
Change Ln. In other words, proportional control is performed in which the region defined by the upper limit Δω■8 and the lower limit Δω1n is a kind of dead zone. Then, if the difference between Δω and Δω■et or the difference between Δω and Δω1fi exceeds a certain limit,
Operate the limiter to reach maximum oil pressure. Next, the control section (
In B), these upper limit side and lower limit side target clutch oil pressure T. ．． By generating an addition signal of E and T min and multiplying the addition signal T by a gain K with a time lag, the control amount of the hydraulic control valve l9 is adjusted so that the actual maximum engagement oil pressure is achieved when T is maximum. Determine M. and,
The control amount M is corrected by a correction signal such as oil temperature, and outputted as a valve control signal.

By dividing the control system into the judgment section (A) and the control section (B) and having each process performed in a separate routine, the responsiveness of feedback control is improved.

In this case, the processing of the judgment section is made the main routine, and the processing of the control section is performed at short time intervals by interrupts.

Also, in the judgment department (A), what is the target slip rate? Since it is converted into a rotational speed difference and output to the control unit (B), it is easy to compare it with the actual driving state seen in the form of a rotational speed difference, which reduces the processing time in the control unit (B). be done.

Furthermore, although the slip ratio fluctuates and has large swings, a stable target value can be obtained by converting this into a rotational speed difference.

Also, depending on the driving situation, the upper limit Δω. ．． ．． X
and the lower limit Δω,. are set, and control is performed using the area defined by these as a dead zone, so that a variety of control characteristics can be easily obtained. At that time, the characteristics in the region exceeding the upper limit Δω■8 or the lower limit Δω1o can be changed to various shapes such as quadratic curves, and the lock region can be changed by taking the values of Δω■8 and Δω11. You can easily change the characteristics such as widening or expanding the free area.

Next, the control of the above embodiment will be explained in detail based on the flowcharts shown in FIGS. 5 and 6.

FIG. 5 shows a flowchart for executing the processing of the human resources section and the judgment section.

? First, the rotational speeds ωFR, ωFL, ω■ of the four wheels 8 to 1l are determined. ωRL is input, and then the steering angle θ. Oil temperature 0. T. , oil pressure 0. P. , ABS signal.
Input gear position G and throttle opening THO in sequence.

and) ωFR. ωFL. ωRR. Vehicle speed V is calculated based on the smallest value of ωRL. In addition, the left and right front wheels are 8.9
Calculate the front wheel speed ω1 from the rotational speeds ωFR and ωFL,
Rotational speed ωRR of left and right rear wheels 10.11. Calculate rear wheel speed ωR from ωRL. Then, the front and rear wheel speed ratio S is determined from the front wheel speed ω and the rear wheel speed ω, and then the front and rear wheel speed difference Δω is calculated.

Next, we move on to the step of determining each running state, first,
Check whether the BS is “ON” or not.

If YES, that is, ABS is "ON," the upper limit ΔS sag of the target slip ratio is set to 10, and the lower limit ΔS m l n is set to −10. ABS when free differential operation of center differential 3 is allowed.
As Il! Therefore, the slip rate has to be limited to some extent here.

? Then, ΔS 8 is converted to the upper limit Δω 8 of the rotational speed difference by multiplying ΔS wax by the larger value of front wheel speed ω and rear wheel speed ω 8, and similarly, ΔS 1111
Multiplying 1 by the larger of ω and ω■, ΔS f
fili is converted into the lower limit Δω1o of the rotational speed difference.

Furthermore, if the ABS is not "ON", the next step is to determine whether tight corner braking control is being performed. , if yes, then it is checked whether the vehicle speed V is smaller than km/h.

If V<IOkm/h, it is determined that the difference between the inner wheels is large and tight corner braking will occur.
Δω■8 to allow greater rotational speed on the front wheel side.
is set to 50, and Δω1n is set to zero.

If θ≦360° or V≧10 km/h, the next step is to determine stack control. Then, check whether V < 5 km/h, and
If < 5 km/h, the throttle opening THO is 2? %, and if it is smaller, then check whether the front and rear wheel speed ratio S is greater than 2. And ■<5kffl/hte, THO<20%
``i?'' and S>2, it is determined that a stack has occurred, and Δω. and Δω1n are set to zero to create a direct connection state.

If V≧5km/h, THO≧20%, or s≦2, and the situation is not such that a stuck condition occurs, the next step is to judge the start control situation.

First, it is checked whether V < 20 km/h, and if ■ < 20 km/h, then it is checked whether the gear position G is l speed.

■If it is fast, then check whether THO≧50%,
If yes, then check whether θ is 60°. And when V < 20 km/h, the gear position G! When THO≧50% and θ<60°, it is determined that the situation is start control, and in this case, ΔS 8 is set to 0.02 to approach the direct connection state, and ΔS sin
-〇． Let's be Ol. Then, let these ΔS sag and ΔS +mln be respectively the front wheel speed? By multiplying the smaller value of ωf and rear wheel speed ω3, the upper limit of the rotational speed difference Δω. 68 and the lower limit Δω·In.

Next, ■≦20 km/h or gear position G! l{1
If it is other than the speed, THO<50%, or θ≧60°, move on to the next situation judgment step.

Here, we first check whether the vehicle speed ■ exceeds 70 km/h, and when driving at a high speed exceeding 70 km/h, next we check whether the front and rear wheel speed ratio S is greater than 1.2. See if. And when V > 70 km/h, S
>1.2, it is determined that one of the wheels is in a slipping state and the internal circulation torque increases, which tends to worsen fuel efficiency, and ΔSmaK is 0.5, ΔS m
tn is set to a target value such as 10 or 5 that allows a certain degree of differential operation.

Then, by multiplying these ΔS llaK and ΔS m 1 n by the smaller value of the front wheel speed ω and the rear wheel speed ω3, the upper limit of the rotational speed difference Δω, .
, X and the lower limit Δω. ■Convert to 1.

And when the situation is not like the one above, what about other situations? The process moves on to the step of determining the line status, and control target values are set according to each status.

The target values Δω of the upper and lower limits set and converted in this way. ．． 8 and Δω+wln are output to the control section.

FIG. 6 is a flowchart for executing the processing of the control section.

Here, we start and first, Δωaax and Δω
■Enter.

Next, input the actual front and rear wheel speed difference Δω, then Δ
Check whether ω exceeds the upper limit Δωsag. Then, Δω does not exceed the upper limit Δωwax (Δω−Δ
ωnaK≦0), the upper limit T maX of the target clutch pressure is set to zero according to the characteristics shown in FIG. 4(a).

Also, Δω exceeded Δωn + ax (Δω - Δω, 48
〉0), next check whether the difference between Δω and Δω+uax is within a certain limit A, and set it within a certain limit A.
When it is within (Δω−Δω..a3≦A), T
Set maX in the form l/A·(Δω−Δωwax).

? On the other hand, the difference between Δω and Δω16 exceeded a certain limit A (
Δω−Δω−. ．． > A), use the limiter and set T. Limit ■ to l.

Similarly, Δω and Δω. ．． Based on the value of 1n, the fourth
The lower limit T s I n is set according to the characteristics shown in Figure (b).

Next, the target value T of the clutch oil pressure is determined by adding the two 'r'sa is applied to determine clutch oil pressure control IM.

Next, oil! (0.T.) and the final control amount M controls the hydraulic control valve l9.

In addition to the configuration of the above embodiment, the present invention also includes a plurality of determination units (+) and (II) and determination unit switching means (C) for selectively switching between them, as shown in FIG. It can be implemented in the following manner. According to this embodiment, it is possible to select the optimum control characteristic by switching the determining section according to the destination etc. In addition, other R
It is also possible to read the data stored in the OM according to the destination and the characteristics of the vehicle, or to make the ROM replaceable so that the determination section can be substantially changed.

(Effects of the Invention) Since the present invention is configured as described above, the control section of the vehicle drive control device can be configured simply, reliability is improved, and responsiveness is improved.

In particular, by converting the target slip rate into the front and rear wheel speed difference, control stability is improved, and by setting the control target value in the form of upper and lower limits depending on the driving condition, various control characteristics can be easily adjusted. It is possible to set it to .

Furthermore, by making the determination section changeable as appropriate, it becomes possible to select control characteristics that are appropriate for the destination or the characteristics of the vehicle.

[Brief explanation of the drawing]

FIGS. 1(a) to (e) are diagrams showing the overall configuration of the present invention, FIG. 2 is a diagram of the entire system of an embodiment of the present invention, and FIGS. 3(a) to (e)
c) is a block diagram showing the configuration of the control system in the same embodiment, FIG. 4 is a control characteristic diagram in the same embodiment, FIGS. 5 and 6 are flowcharts for executing control in the same embodiment, and FIG. FIG. 2 is a block diagram showing a control configuration of another embodiment of the present invention. l: Bow plant, 3. center differential,
8~l1 two wheels, l6: hydraulic clutch (differential limiting device)
, l8: Controller, l9: Hydraulic control valve, 20a-2
0d: Rotation speed sensor, 216 throttle valve, 22: Handle, 25: ABS controller, 26: EAT controller, (A) Nijuro, (B) Ni control section, (C):
Judgment section switching means.

Claims (5)

[Claims] (1) A driving condition determining means for determining various driving conditions of the vehicle based on the output of the driving condition detecting means for detecting the driving condition of the vehicle; Control target value setting means for setting a control target value, and vehicle drive so that the rotational speed difference between the front and rear wheels obtained from the detection value of the wheel speed detection means becomes the control target value set by the control target value setting means. In the drive control device for a vehicle, the control system includes a determination unit including the driving situation determination unit and the control target value setting unit, and a control unit including the feedback control unit. A vehicle drive control device characterized in that it is formed separately. (2) The drive system includes a center differential that operates differentially between the front wheels and the rear wheels, and a differential limiting means that limits the differential operation of the center differential and brings the front and rear wheels closer to a directly coupled state. 2. The drive control device for a vehicle according to claim 1, wherein the vehicle drive control device comprises a four-wheel drive device with a four-wheel drive device, and wherein the differential limiting device is controlled by a feedback control device. (3) The control target value setting means includes a target slip ratio setting means for setting a target slip ratio between the front and rear wheels based on the driving condition determined by the driving condition determining means; - The drive control for a vehicle according to claim 1 or 2, comprising a target value converting means for converting the rotational speed difference of the rear wheels into a target value, and the control target value converted by the target value converting means is output to the control section. Device. (4) The determination unit includes upper and lower limit setting means for setting upper and lower limits of the control target value based on the driving condition determined by the driving condition determination means, and outputs of the upper and lower limit setting means are sent to the control unit. The vehicle drive control device according to claim 1, 2 or 3, wherein the vehicle drive control device outputs an output. (5) The drive control device for a vehicle according to claim 1, further comprising a determining unit changing means that allows the determining unit to be changed as appropriate.