JPH0681908B2 - Sliding control method for vehicle driving wheels - Google Patents

Abstract

PURPOSE:To eliminate the excessive idle rotation of one driving wheel and prevent the deterioration in the accelerating property at the start of a vehicle by restricting the driving force of driving wheels even without detecting exces sive slip, when the difference in the rotating speed between right and left driving wheels is larger than a defined value. CONSTITUTION:The output signals of speed sensors 21-24 for detecting the speeds of right and left driving wheels 11, 12 and right and left driven wheels 13, 14 at the time of operating a vehicle are taken in an ECU35. In this ECU35 the excessive slip of the driving wheel with the lower rotating speed of the right and left driving wheels is detected at the time of a low sped operation and, when excessive slip is detected, a fuel injection valve 36 is controlled to restrict the slippage of the driving wheels 11, 12. In this case, when the difference in rotating speed between the right and left driving wheels 11, 12 is larger than a defined value, the driving force of the driving wheels 11, 12 is restricted even when excessive slip is not detected. Thereby, the excessive idle rotation of one driving wheel can be prevented, while preventing the deterioration of the accelerating property at the start of a vehicle.

Description

TECHNICAL FIELD The present invention relates to a drive wheel slip control method for a vehicle, and more particularly to a drive wheel slip control method for starting and accelerating the vehicle.

(Technical Background of the Invention and Problems Thereof) Generally, when the vehicle starts or accelerates, the driving force of the driving wheels is the frictional force between the tire and the road surface [friction coefficient between tires and road surface × load of vehicle weight on driving wheel]. (Wheel load)], the drive wheels slip, but the slip ratio λ representing the degree of this slip is Vw, which is the peripheral speed of the drive wheels, and V is the peripheral speed of the driven wheels. , Is calculated by the following equation (1).

λ = (Vw−V) / Vw (1) Due to this slip ratio λ, the frictional force between the tire and the road surface (that is, the limit value of the driving force of the driving wheels) changes as shown in FIG. This frictional force becomes maximum at λ ₀ . Also, the frictional force between the tire and the road surface is the longitudinal direction of the vehicle.
The frictional force in the lateral direction (lateral force) decreases as the slip ratio λ increases as indicated by the dotted line in the figure.

Based on this point, the longitudinal frictional force between the tire and the road surface is maximized to maximize the driving efficiency of the vehicle, and the lateral frictional force between the tire and the road surface is suppressed as much as possible to prevent lateral slippage of the vehicle. In order to prevent this, there is a method of detecting the slip ratio λ and controlling it to a value close to a predetermined value λ ₀ . More specifically, in this method, for example, a lower limit value λ ₁ and an upper limit value λ ₂ of a predetermined range including the predetermined value λ ₀ are set for the slip ratio λ and the drive wheel speed Vw is set. And vehicle speed V
The drive wheel torque control device controls the torque of the drive wheels in accordance with the value of the slip ratio λ obtained from the above to control the circumferential speed Vw of the drive wheels to set the slip ratio λ of the drive wheels to the predetermined range λ ₁ to Feedback control is performed within λ ₂ .

In such a conventional method, a high-select method in which one of the left and right driving wheel speeds that exhibits a higher value is selected and used as the driving wheel speed Vw for calculating the slip ratio λ based on the equation (1). Was adopted. According to this method, since excessive slip of one wheel is prevented, the difference between the driving forces of the left and right driving wheels does not increase. As a result, especially in a front-wheel drive vehicle, the driving forces of the left and right driving wheels are increased. There is no problem such as the steering wheel being removed due to the difference between the two, and the steering stability of the vehicle is improved.

By the way, when power is transmitted from the engine to the left and right drive wheels through a differential gear (hereinafter referred to as a differential), even if one of the drive wheels is excessively slipped, a certain friction is applied to the differential. Since the force exists, even if one wheel is excessively slipping, the driving force corresponding to the frictional force of the differential is transmitted to the other driving wheel that is not excessively slipping. Furthermore, when one excessively slipping drive wheel is accelerating the vehicle, the reaction force against the drive force required for acceleration by that drive wheel is also transmitted to the other drive wheel via the differential. To be done. However, when the high select system is adopted, these driving forces are not effectively utilized, and especially when the vehicle is traveling at a low speed, the driving force may be insufficient.

From the above circumstances, it is desirable to perform the slip control of the drive wheels by the low select method when the vehicle is running at a low speed. However, when one drive wheel is on a very slippery road surface and the other drive wheel hits a convex portion of the uneven road surface, etc., one drive wheel exceeds the excessive slip state and slips, There has been a problem that the starting acceleration of the vehicle deteriorates.

(Objects of the Invention) The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a drive wheel for a vehicle, which prevents one drive wheel from idling excessively and prevents deterioration of the starting acceleration of the vehicle. An object is to provide a slip control method.

(Structure of the Invention) In order to achieve the above object, in the present invention, during low speed operation of a vehicle, excessive slippage of a drive wheel on the side with a lower rotational speed among the left and right drive wheels is detected, and the excessive slip is detected. In a slip control method for a drive wheel of a vehicle, which sometimes limits the drive force of the drive wheel of the vehicle, when the difference in the rotational speeds of the left and right drive wheels is larger than a predetermined value, the vehicle slips even if the excessive slip is not detected. There is provided a slip control method for a drive wheel of a vehicle, which is characterized by limiting the drive force of the drive wheel.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a vehicle 1 to which the slip control method for a vehicle drive wheel according to the present invention is applied. The vehicle 1 is, for example, a front wheel drive type, and the front wheels 11 and 12 are drive wheels driven by an engine 31. The rear wheels 13 and 14 are driven wheels.
(In addition, as will be apparent from the following description, the present invention can be applied to a rear wheel drive type vehicle in exactly the same manner.) The drive wheel speed sensor is used for the drive wheels 11 and 12 and the driven wheels 13 and 14. 21, 22 and driven wheel speed sensors 23, 24 are provided respectively, the left and right driving wheel speeds ω _FL , ω _FR are detected by the driving wheel speed sensors 21, 22, and the driven wheel speed sensors 23, Left and right driven wheel speeds ω _RL and ω _RR are detected by 24, and these detection signals are input to ECU 35.
First, the average value of the driven wheel speeds ω _RL and ω _RR (ω _RL + ω _RR ) / 2
The vehicle speed V is calculated by The vehicle speed V is the predetermined speed V
When it is lower than _MIN (for example, 5km / h), the slip of the driving wheel with the lower speed is controlled (low select). That is, the lower one of the drive wheel speeds ω _FL and ω _FR is set as the ω _F value corresponding to the drive wheel speed Vw in the above equation (1).

When the vehicle speed V is higher than the predetermined speed V _MIN , the slip of the drive wheel having the higher speed is controlled (high select). That is, the higher one of the drive wheel speeds ω _FL and ω _FR is set as the ω _F value corresponding to the drive wheel speed Vw in the above equation (1).

In both the low-selection control and the high-selection control described above, the speed of the driven wheel on the same side as the control target drive wheel among the driven wheel speeds ω _RL and ω _RR is set to the vehicle speed in the above equation (1). Let ω _R value replace V. As a result, it is possible to reduce the apparent slip when the vehicle turns. Therefore, the slip ratio λ is obtained by the following equation (2).

Further, the ECU 35 obtains the change amount (differential value) of the slip ratio λ. In addition, in the digital control, the change amount is substituted by the difference for each operation processing cycle.

The clutch 15 and the transmission 16 that are interposed between the engine 31 and the drive wheels 11 and 12 are equipped with sensors (not shown), and the clutch signal and the transmission signal from these sensors are sent to the ECU 35. Is entered. When the ECU 35 determines that the clutch 15 is engaged based on the clutch signal, the ECU 35 controls the torque of the drive wheels 11 and 12 by controlling the engine 31 by a fuel supply control device described later to control the drive wheels 11 and 12.
The slip ratio λ (see the above equation (2)) is controlled. More specifically, the ECU 35 uses the predetermined value λ ₀ shown in FIG. 6 as a slip ratio control reference value that is determined according to the vehicle speed ω _R and the gear ratio detected by the transmission signal with respect to the slip ratio λ. A lower limit value λ ₁ and an upper limit value λ ₂ of a predetermined range including is set, and the device actually operates from the vehicle speed ω _R and the gear ratio with respect to the change amount of the slip ratio and an operation command to the fuel supply control device described later. The first and second slip ratio change amount control reference values ₁ and ₂ ( ₂ > ₁ ) are set according to the control delay until the start and the slip ratio control reference value, and the drive wheel speed ω _F ( ω _FL or ω _FR ) and a predetermined speed value V _R1 determined corresponding to the lower limit value λ ₁ and a predetermined speed value V _R2 determined corresponding to the upper limit value λ ₂ , and a change in slip ratio Control the fuel supply control device according to the difference between the amount and the first and second reference values ₁ and _2. To do. That is, the ECU 35 controls the fuel supply control device according to the following control rules (i) to (iii).

(I) If ω _F > V _R1 and> ₁ , control is performed so that λ decreases, for example, fuel cut (predictive control). (I
i) If ω _F > V _R2 , control is performed to reduce λ, for example, fuel cut (excessive slip ratio prevention). (Iii)>
If it is ₂ , control is performed in the direction of decreasing, for example, fuel cut (excessive slip ratio speed prevention).

In this case, the predetermined speed values V _R1 and V _R2 are calculated by the following equations (3) and (4), for example.

Further, as another example, V _R1 and V _R2 are calculated by the following equations (5) and (6) when the vehicle speed is high, and are set to constant values V _C1 and V _C2 when the vehicle speed is low. Good.

V _R1 = k ₁ · ω _R + C ₁ (5) V _R2 = k ₂ · ω _R + C ₂ (6) where k ₁ , k ₂ , C ₁ , C ₂ , D ₁ , D ₂ are _These are coefficients and constants for setting V _R1 and V _R2 to values corresponding to the lower limit value λ ₁ and the upper limit value λ ₂ , respectively.

Further, the reference values ₁ and ₂ for controlling the slip rate change amount are
Is calculated by the following equations (7) and (8). ₁ = r ₁ · ω _R + F ₁ (7) ₂ = r ₂ · ω _R + F ₂ (8) where r ₁ and r ₂ are ₁ values corresponding to the vehicle speed ω _R and
Is a coefficient for obtaining the _binary constants for correcting the value ₁ and ₂ value according to F _1, F ₂ is the gear ratio of each transmission or the like.

The slip ratio λ is used in addition to the slip ratio λ to control the slip ratio λ as in the control rules (i) and (iii) described above. Is within the predetermined range λ _{1 to} λ ₂ , the slip ratio λ is within the predetermined range λ ₁ when the slip ratio speed is high.
This is because the deviation from λ ₂ is predicted, and the prediction control corresponding to this is performed to improve the responsiveness of the control of the slip ratio λ.

FIG. 2 is an overall configuration diagram of the fuel supply control device. Reference numeral 31 indicates, for example, a four-cylinder internal combustion engine.
An intake pipe 32 is connected to. A throttle body 33 is provided in the middle of the intake pipe 32, and a throttle valve 33 ′ is provided inside.
Is provided. A throttle valve opening degree (θ _TH sensor 34 is connected to the throttle valve 33 ′ so that the valve opening degree of the throttle valve 33 ′ is converted into an electric signal and sent to an electronic control unit (hereinafter referred to as “ECU”) 35. Has been done.

Between the engine 31 and the throttle body 33 of the intake pipe 32, a fuel injection valve 36 is provided for each cylinder, slightly upstream of an intake valve (not shown) of each cylinder. The fuel injection valve 36 is connected to a fuel pump (not shown) and electrically connected to the ECU 35, and a signal from the ECU 35 controls the opening time of the fuel injection valve 36.

On the other hand, an absolute pressure (P _BA ) sensor 38 is provided downstream of the throttle valve 33 ′ of the throttle body 33 via a pipe 37. The absolute pressure signal converted into an electric signal by the absolute pressure sensor 38. Is sent to the ECU 35.

The engine cooling water temperature sensor (hereinafter referred to as "Tw
(Referred to as “sensor”) 39, and the Tw sensor 39 is composed of a thermistor or the like, is inserted into the engine cylinder peripheral wall filled with cooling water, and supplies the detected water temperature signal to the ECU 35. An engine speed sensor (hereinafter referred to as “Ne sensor”) 40 is mounted around a cam shaft or a crank shaft (not shown) of the engine, and the Ne sensor 40 is a crank shaft of the engine.
A crank angle position signal (hereinafter referred to as "TDC signal") at a predetermined crank angle position for each 180 ° rotation, that is, at a crank angle position that is a predetermined crank angle before the top dead center (TDC) at the start of the intake stroke of each cylinder. The TDC signal is sent to the ECU 35.

A three-way catalyst 42 is arranged in the exhaust pipe 41 of the engine 31 to purify HC, CO, and NOx components in the exhaust gas. This three-way catalyst 4
An O ₂ sensor 43 is inserted in the exhaust pipe 41 on the upstream side of ₂ , and this sensor 43 detects the oxygen concentration in the exhaust gas and outputs an O ₂ concentration signal to the EC.
Supply to U35.

Further, in the ECU 35, the drive wheel speed sensors 21, 22, the driven wheel speed sensors 23, 24, and other parameter sensor 44,
For example, a sensor that detects the engagement state of the clutch 15 or a transmission
A sensor for detecting the gear ratio of 16 is connected, and the other parameter sensor 44 supplies the detection value signal to the ECU 35.

The ECU 35 shapes the input signal waveforms from various sensors (including the drive wheel speed sensors 21 and 22, the driven wheel speed sensors 23 and 24, the clutch 15 sensor, and the transmission 16 sensor) to determine the voltage level. An input circuit 35a having a function of converting the analog signal value into a digital signal value by correcting it to a predetermined level, a central processing circuit (hereinafter referred to as "CPU") 35b, CP
The storage unit 35c stores various calculation programs and calculation results executed by the U35b, and an output circuit 35d that supplies a drive signal to the fuel injection valve 36.

The CPU 35b calculates the fuel injection time T _OUT of the fuel injection valve 36, which is given by the following equation, based on the engine parameter signals from the various sensors supplied through the input circuit 35a each time the TDC signal is input. .

T _OUT = Ti × K ₁ + K ₂ (9) where Ti is the reference value of the injection time of the fuel injection valve 36,
It is determined according to the engine speed Ne and the intake pipe absolute pressure P _BA .

K ₁ and K ₂ are calculated according to the engine parameter signals from the above-mentioned sensors so that various characteristics such as starting characteristics, exhaust gas characteristics, fuel consumption characteristics, acceleration characteristics, etc. will be optimized. The correction coefficient and the correction variable are calculated based on the formula.

The CPU 35b outputs a drive signal for opening the fuel injection valve 36 based on the fuel injection time T _OUT obtained as described above, to the output circuit 35.
Supply to the fuel injection valve 36 via d.

FIG. 3 is a flowchart of a vehicle drive wheel slip control program according to the present invention, which is executed by the CPU 35b at every predetermined timer cycle.

First, in step 1, the speeds ω _FL and ω _FR of the left and right driving wheels 11 and 12 and the speeds ω _RL and ω _RR of the left and right driven wheels 13 and 14 are read. Next, in step 2, the left and right driven wheel speeds ω _RL ,
calculates the vehicle speed _{V = (ω RL + ω RR} ) / 2 the average value of omega _RR.

In the next step 3, it is determined whether or not the vehicle speed V is lower than the lower limit value V _MIN, the answer if affirmative (Yes), since the vehicle is very certain low speed, set the slow flag F _L 1 pole Then (step 4), the process proceeds to the next step 5.

In step 5, the speed difference between the left and right driving wheels 11 and 12 | ω _FL −
It is determined whether or not ω _FR | is greater than a predetermined value Δω _G , and if the answer is affirmative (Yes), it means that only one drive wheel is idling excessively. Set the cut flag EC to 1 and terminate this program. This prevents deterioration of the vehicle start acceleration.

When the result of the determination in step 5 is negative (No), the fuel cut flag FC is reset to 0 (step 6), and the process proceeds to step 9 and later described later. Further, if the answer to the question of the step 3 is negative (No), it resets the slow flag F _L 0 poles (step 7), the process proceeds to step 9 below.

In step 9, it is determined which of the left and right drive wheel speeds ω _FL and ω _FR is larger (for example, whether ω _FR > ω _FL or not). The result of the determination in step 9 is stored in the drive wheel high flag F _F (step 10 or 11). The drive wheel high flag F _F is set to 1 when the right drive wheel speed ω _FR is higher, and is 0 when the left drive wheel speed ω _FL is higher.
Are set respectively.

In the next step 12, it is judged whether or not the extremely low speed flag _FL is set to 1, and if the answer is affirmative (Yes), one of the driving wheel speed which is lower and the driving speed which is lower. The speed of the driven wheel on the same side as the wheel is used to calculate the step ratio λ (low select), and thereby the torque of the driving wheel with the smaller slip is controlled (steps 13 to 17). That is, in step 13, it is determined whether or not the drive wheel high flag F _F is set to 1 (right),
If the answer is affirmative (Yes), the left driving wheel speed ω _FL and the left driven wheel speed ω _RL, which are opposite to the side indicated by the flag F _F, are set as the ω _F value and the ω _R value, respectively. Yes (steps 14 and 15). If the answer to step 13 is negative (No), the right drive wheel speed ω _FR and the right driven wheel speed ω _RR, which are opposite to the side indicated by the flag F _F as the ω _F value and the ω _R value, are obtained.
Are set respectively (steps 16 and 17).

On the other hand, if the determination result in step 12 is negative (No), the higher speed of the drive wheels and the speed of the driven wheels on the same side as the high speed drive wheel are used for the calculation of the slip ratio λ ( (High select), thereby controlling the torque of the drive wheel with the larger slip (steps 18 to 22). That is, in step 18, it is determined whether or not the driving wheel high flag F _F is set to 1 (right), and if the answer is affirmative (Yes), the flag F is set as the ω _F value and the ω _R value.
_The right drive wheel speed ω _FR and the right driven wheel speed ω _RR indicated by _F are set (steps 19 and 20). Also, step 1
If the answer to 8 is negative (No), the left driving wheel speed ω _FL and the left driven wheel speed ω _RL indicated by the flag F _F are set as the ω _F value and the ω _R value, respectively (steps 21 and 22). .

Then, in step 23, the slip ratio λn = (ω _F − at this loop is calculated from the ω _F value and the ω _R value set as described above.
Calculate ω _R ) / ω _F. Next, in step 24, the slip ratio differential value n is obtained from the difference between the slip ratio λn in the current loop and λn _{−1 in the} previous loop.

In steps 25, 26 and 27, the above-mentioned excessive step rate speed prevention control processing is performed. That is, it is determined whether or not the slip rate change amount n is larger than the reference value ₂ = r ₂ · ω _R + F ₂ (step 25), and if the answer is affirmative (Yes), the fuel cut flag FC is set to 1. Set it (step 26) and terminate this program. When the answer to step 25 is negative (No), the flag FC is reset to 0 (step 27),
Go to next step 28.

In steps 28, 29 and 30, the slip prediction control process described above is performed. That is, the slip rate change amount n is the reference value ₁ =
It is determined whether or not r ₁ · ω _R + F _{1 is} larger (step 2
8) If this answer is affirmative (Yes), the speed ω _{F of the} drive wheel that is the control target is the predetermined speed value V _R1 = k ₁ · ω _R + C
_It is determined whether or not it is larger than ₁ + D ₁ / ω _R (step 29),
If this answer is also affirmative (Yes), the fuel cut flag FC is set to 1 (step 30), and this program ends. The determination in step 29 is made in step 29 of FIG.
It may be replaced with the discrimination of 0, 291, 292 and 293. In this case, the predetermined speed value V _R1 = k ₁ · ω _R + C ₁ is the reference value V _c1 (for example,
5km / h) is determined (step 290), and if the answer is affirmative (Yes), the predetermined speed value is set as the ω _REF value.
Set V _R1 = k ₁ · ω _R + C ₁ (step 291) and negate (N
If it is o), the reference value V _{C1 is} set as the ω _REF value (step 292), and then it is determined whether or not the speed ω _{F of the} drive wheel that is the control target is larger than the ω _REF value (step 292). 293). If the determination result of either step 28 or 29 is negative (No), the process proceeds to the next step 31.

In steps 31, 32 and 33, the excessive slip ratio prevention control processing described above is performed. That is, it is determined whether or not the speed ω _{F of the} drive wheel to be controlled is larger than a predetermined speed value V _R2 = k ₂ · ω _R + C ₂ + D ₂ / ω _R (step 31). Is positive (Yes), the fuel cut flag FC is set to 1 (step 32), and this program ends.
The determination in step 31 is also made in steps 290, 291, 292 in FIG.
And 293 may be replaced by the same discrimination. In this case, it goes without saying that the constants of k ₁ , C ₁ and V _C1 are _{replaced with} the constants of k ₂ , C ₂ and V _C2 . If the answer to step 31 is negative (No), the flag FC is reset to 0 (step 33),
This program ends.

On the other hand, FIG. 4 is a flow chart of the fuel supply control program, which is executed by the CPU 35b every time the TDC signal is generated. This program is executed prior to the program of FIG. 3, that is, it is executed by interrupting the processing of the program of FIG.

First, at step 41, it is judged if the fuel cut flag FC set and reset by the program of FIG. 3 is set to 1. If the result of this determination is affirmative (Yes), it means that the fuel cut should be executed, so this program ends immediately. When the answer to step 41 is negative (No), the valve opening time T _OUT of the fuel injection valve is calculated (step 42), and the valve opening drive signal corresponding to the T _OUT value is output (step 43), This program ends.

(Effects of the Invention) As described in detail above, the slip control method for a drive wheel of a vehicle according to the present invention prevents excessive slippage of the drive wheel on the lower rotation speed side of the left and right drive wheels during low speed operation of the vehicle. In a slip control method for a vehicle drive wheel, which detects the excess slip and limits the drive force of the drive wheel of the vehicle when the excess slip is detected, when the rotational speed difference between the left and right drive wheels is larger than a predetermined value, the excess slip is detected. Since the driving force of the driving wheels of the vehicle is limited even when there is no detection, it is possible to prevent excessive idling of one driving wheel, thereby preventing deterioration of the vehicle start acceleration.

[Brief description of drawings]

FIG. 1 is a block diagram of a vehicle to which the slip control method for a drive wheel of a vehicle of the present invention is applied, FIG. 2 is a block diagram of a fuel supply control device which is a drive wheel torque control device, and FIG. 3 is executed in the ECU 35. Of the slip control program executed, FIG. 4 is a flowchart of the fuel supply control program, and FIG.
FIG. 6 is a flow chart showing another example of the determination of step 29 in FIG. 3, and FIG. 6 is a characteristic diagram with respect to the slip ratio of the frictional force between the tire and the road surface. 11,12 ... Drive wheels, 13,14 ... Drive wheels, 15 ... Clutch, 16 ... Transmission, 21,22 ... Drive wheel speed sensor, 23,24 ... Drive wheel speed sensor, 31 ... Engine, 35 ... ECU (drive) Wheel torque control device).

Claims (1)

[Claims] 1. When a vehicle is operating at a low speed, an excessive slip of one of the left and right drive wheels having a lower rotational speed is detected, and the drive force of the drive wheel of the vehicle is limited when the excessive slip is detected. In the slip control method for driving wheels, when the rotational speed difference between the left and right driving wheels is larger than a predetermined value, the driving force of the driving wheels of the vehicle is limited even when the excessive slip is not detected. A slip control method for driving wheels of a vehicle.