JP2580175B2 - Drive wheel slip control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a drive wheel slip control device for a vehicle, and more particularly to a control device that performs appropriate slip control when a drive wheel shifts to an excessive slip state. .

(Prior art and its problems) In general, when the vehicle starts or accelerates, the driving force of the driving wheel is determined by the frictional force between the tire and the road surface [the coefficient of friction between the tire and the road surface × the weight of the vehicle weight on the driving wheel (vehicle load). )], The drive wheel slips. The slip ratio λ representing the degree of the slip is obtained by the following equation (1), where Vw is the circumferential speed of the drive wheel and V is the speed of the vehicle.

λ = (Vw−V) / Vw (1) 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. At λ ₀ this frictional force is at a maximum. In addition, the frictional force between the tire and the road surface is determined by the traveling direction of the vehicle (vertical direction).
The frictional force in the lateral direction (lateral force) decreases as the slip ratio λ increases, as indicated by the dotted line in FIG.

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 decrease in the lateral frictional force between the tire and the road surface is minimized to reduce the vehicle's side slip. A slip prevention device for preventing the slip is disclosed, for example, in Japanese Patent Publication No. 52-35837.

However, in the conventional device, the control of the wheel speed to prevent the excessive slip of the driving wheel is performed by turning on the ignition device.
The switching is performed by changing the driving torque of the engine by switching off or switching between supplying and shutting off the fuel to the engine. After the combustion fuel is discharged, afterfire is easily generated in which the fuel is burned in the exhaust system, and when the exhaust system is provided with a three-way catalyst as an exhaust gas purification device, the temperature of the three-way catalyst increases. Therefore, there is a problem that the performance is deteriorated.

(Objects of the Invention) The present invention has been made to solve the above-mentioned problems of the prior art, and includes the occurrence of afterfire when the drive wheels shift to an excessive slip state and the temperature rise of the three-way catalyst in the exhaust system. It is an object of the present invention to provide a drive wheel slip control device capable of preventing performance degradation of a three-way catalyst caused by the above.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a fuel supply means for supplying fuel to an engine, an excessive slip detection means for detecting an excessive slip state of a drive wheel of a vehicle, A fuel supply stop means for stopping fuel supply from the fuel supply means when the slip detection means detects an excessive slip state, wherein the drive wheel has a slip state lower than the excessive slip state. A slip detecting means for detecting a slip state lower than an excessive slip state, a correction value setting means for setting a correction value for correcting an amount of fuel supplied from the fuel supply means in accordance with an operation state of the engine, Correction value invalidation for invalidating the correction value by the correction value setting means when the slip detection means detects the low slip state Means.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a vehicle 1 equipped with a drive wheel slip control device according to the present invention. The vehicle 1 is, for example, a front wheel drive type.
The front wheels 11, 12 are driving wheels driven by the internal combustion engine 31, and the rear wheels 13, 14 are driven wheels.
(Note that, 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 wheels 11, 12 and the driven wheels 13, 14 are provided with drive wheel speed sensors. Two
1 and 22, and driven wheel speed sensors 23 and 24, respectively, the left and right driving wheel speeds ω _FL and ω _FR are detected by the driving wheel speed sensors 21 and 22, respectively.
The left and right driven wheel speeds ω _RL and ω _RR are detected by the control units 3 and 24, and these detection signals are transmitted to an electronic control unit (hereinafter referred to as “EC
U ”).

In this embodiment, the ECU 35 constitutes excessive slip detecting means, slip detecting means, fuel supply stopping means, correction value setting means, and correction value invalid changing means.

The ECU 35 selects one of the left and right driving wheel speeds ω _FL and ω _FR as described later and sets it as the driving wheel speed Vw in the above equation (1), which is the same as the selected driving wheel speed ω _FL or ω _FR. The slip ratio λ is determined by the following equation (2), using the driven wheel speed ω _RL or ω _RR on the side as the vehicle speed V in the above equation (1).

Further, the ECU 35 obtains a change amount (differential value) of the slip ratio λ. In the digital control, the amount of change is used as a difference for each arithmetic processing cycle.

The transmission 16 interposed between the engine 31 and the driving wheels 11 and 12 is provided with a sensor (not shown), and a transmission signal from the sensor is input to the ECU 35. The ECU 35 controls the torque of the drive wheels 11 and 12 by controlling the output of the engine 31 by a fuel supply control device described later to control the slip state of the drive wheels 11 and 12.

FIG. 2 is an overall configuration diagram of the fuel supply control device,
The internal combustion engine 31 has, for example, six cylinders.
An intake pipe 32 is connected to 31. A throttle body 33 is provided in the middle of the intake pipe 32, and a throttle valve 3 is provided inside.
3 'is provided. A throttle valve opening (θ _TH ) sensor 34 is connected to the throttle valve 33 ′,
The 3 'valve opening is converted into an electric signal and sent to the ECU 35.

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 is also electrically connected to the ECU 35, and the opening time of the fuel injection valve 36 is controlled by a signal from the ECU 35.

On the other hand, on the downstream side of the throttle valve 33 ′ of the throttle body 33, an intake pipe absolute pressure (P _BA ) sensor 3 is connected 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.

An engine cooling water temperature sensor (hereinafter referred to as “Tw sensor”) 39 is provided on the engine 31 main body. The Tw sensor 39 is composed of a thermistor or the like, is inserted into an engine cylinder peripheral wall filled with cooling water, and detects a detected water temperature signal. Is supplied to the ECU 35. Engine speed sensor (hereinafter referred to as "Ne sensor")
The Ne sensor 40 is provided at a predetermined crank angle position every 120 ° rotation of the crankshaft of the engine, that is, the top dead point at the start of the intake stroke of each cylinder. A crank angle position signal pulse (hereinafter, referred to as a “TDC signal pulse”) is output at a crank angle position before a predetermined crank angle with respect to the point (TDC), and the TDC signal pulse is sent to the ECU 35.

A three-way catalyst 42 is disposed in an exhaust pipe 41 of the engine 31 and performs a purifying action of HC, CO, and NOx components in exhaust gas. Exhaust pipe 41
An O ₂ sensor 43 is inserted upstream of the three-way catalyst 42, and this sensor 43 detects the oxygen concentration in the exhaust gas and outputs an O ₂ concentration signal.
Supply to ECU35.

Further, the ECU 35 has the drive wheel speed sensors 21 and 22, the driven wheel speed sensors 23 and 24, and other parameter sensors 4.
4.For example, the sensors for detecting the gear ratio of the transmission 16 are connected.
Supply to U35.

The ECU 35 shapes input signal waveforms from various sensors (including the driving wheel speed sensors 21 and 22, the driven wheel speed sensors 23 and 24, and the sensor of the transmission 16), corrects the voltage level to a predetermined level, An input circuit 35a having a function of converting an analog signal value to a digital signal value, a central processing circuit (hereinafter referred to as a "CPU") 35b, and a storage means 35 for storing various operation programs executed by the CPU 35b and operation results.
c, an output circuit 35d for supplying a drive signal to the fuel injection valve 36, and the like.

The CPU 35b switches the input circuit 3 every time the TDC signal pulse is input.
The fuel injection time _TOUT of the fuel injection valve 36 is calculated based on the following equation according to the engine parameter signals from the various sensors supplied via 5a.

T _OUT = Ti × (K _TW · K _PA · K _STB · K _WOT · K _LS · K _AST · K _PB · K _O2 ) + (T _ACC + T _IDL ) ... (3) where Ti is the fuel injection valve 36 , Which is determined according to the engine speed Ne and the intake pipe absolute pressure _PBA .

K _TW is a water temperature increase coefficient applied for the purpose of ensuring an appropriate air-fuel ratio for early warm-up when the engine 31 is warmed up, and is determined according to the engine water temperature Tw. K _PA is an atmospheric pressure correction coefficient obtained according to the atmospheric pressure. K _STB is a slip control correction coefficient, which is determined according to the slip ratio λ, the slip ratio change amount, and the like, as described later.

K _WOT is the air-fuel mixture _enrichment coefficient when the throttle valve is fully open,
K _LS is the leaning coefficient of the mixture when the throttle valve is fully closed, K
_AST is a fuel increase coefficient after starting. K _PB is a predicted load correction coefficient determined according to the rate of change of the intake pipe absolute pressure _PBA , and K _O2 is an O ₂ feedback correction coefficient obtained according to the output of the O ₂ sensor 43.

T _ACC and T _IDL are correction coefficients. The former is an acceleration increasing variable applied when the engine 31 is accelerating, and the latter is an idle correction variable applied in an idle region of the engine 31.

The CPU 35b calculates the fuel injection time T _OUT obtained as described above.
A drive signal for opening the fuel injection valve 36 corresponding to the cylinder at which the intake stroke of the engine 31 starts based on
To the fuel injection valve 36 via

FIG. 3 is a logic circuit diagram showing a configuration of a main part of the CPU 35b in FIG. 2. The average vehicle speed calculating circuit 49 in FIG. 3 calculates an average value (ω _RL + ω _RR ) of the detected driven wheel speeds ω _RL and ω _RR. / 2, and an average vehicle speed discrimination circuit 50 outputs an output signal representing the average value (ω _RL + ω _RR ) / 2 and a discrimination value V _MIN (eg, 5 k
m / h), and when it is determined that the latter is greater, that is, when the average vehicle speed is lower than the determination value _VMIN , a high-level signal (hereinafter referred to as "H signal") is used. Outputs a low level signal (hereinafter referred to as “L signal”) to the drive wheel speed selection circuit 51.

The drive wheel speed selection circuit 51 detects the detected drive wheel speeds ω _FL , ω _FR
When the output signal from the average vehicle speed discrimination circuit 50 is an H signal, that is, when the vehicle speed is in an extremely low speed range, the smaller value, that is, the one indicating a lower wheel speed is selected (low select method). When the output signal is an L signal, that is, when the vehicle speed is not in the extremely low speed range, the larger value, that is, the one indicating the higher wheel speed is selected (high select method), and the selected detected drive wheel speed is selected. Let ω _FL or ω _{FR be} the drive wheel speed Vw in the above equation (1). The driven wheel speed selection circuit 52 selects one of the detected driven wheel speeds ω _RL and ω _RR on the same side as the detected drive wheel speed ω _FL or ω _FR selected by the drive wheel speed selection circuit 51. The selected detected driven wheel speed ω _RL or ω _RR is defined as the vehicle speed V in the above equation (1).

Based on the output signals from the selection circuits 51 and 52, the slip ratio calculation circuit 53 obtains the slip ratio λ based on the above equation (2). The differentiating circuit 54 obtains a differential value of the slip ratio based on the output signal from the slip ratio calculating circuit 53. In addition, the setting circuit 60 uses a signal representing a gear ratio output from a sensor provided in the transmission 16 to calculate a correction coefficient k ₁ according to the _first threshold value λ ₁ of the slip ratio based on the gear ratio. And a correction variable C ₁ , a correction coefficient k ₂ and a correction variable C ₂ corresponding to the _second threshold value λ ₂ of the slip rate, and a correction coefficient r ₁ and a correction variable for determining the _first slip rate change reference value _1. F _1, sets the correction coefficient r ₂ and correction variable F ₂ corresponding to the second slip ratio change amount reference value _2. The correction coefficients r ₁ , r ₂ and the correction variables F ₁ , F ₂ are set after being corrected according to a control delay from the time of an operation command to the fuel supply control device to the actual operation of the device. .

The first speed calculation circuit 61 includes an output signal representing the vehicle speed V from the driven wheel speed selection circuit 52 and a correction coefficient k ₁ and a correction variable C corresponding to the _first threshold value λ ₁ of the slip ratio from the setting circuit 60. ₁
The first predetermined speed value V _R1 is obtained based on the following equation (4) using the output signal representing

Relationship between _{V R1 = k 1 V + C} 1 ... (4) first threshold value lambda ₁ of the slip ratio at this time is _{λ 1 = (V R1 -V)} / V R1. Further, the first speed calculation circuit 61 compares the calculated first predetermined speed value V _R1 with the first speed lower limit value V _C1, and determines the larger one of the two values as the first slip rate. the first reference speed value corresponding to the threshold value lambda _1.

The second speed calculating circuit 62 outputs an output signal from the driven theory speed selecting circuit 52 similarly to the first speed calculating circuit 61,
A second predetermined speed value V _R2 is calculated based on the following equation (5) based on a correction coefficient k ₂ corresponding to the second threshold value λ ₂ of the slip ratio from the setting circuit 60 and an output signal representing the correction variable C _2. Of the second predetermined speed value V _CR2 and the second speed lower limit value V _C2 .
The second reference speed value corresponding large becomes value to the second threshold value lambda ₂ of the slip ratio.

V _R2 = k ₂ V + C ₂ (5) The first correction circuit 65 outputs the output signal from the driven theory speed selection circuit 52 and the first slip rate change speed reference value determined for each gear ratio from the setting circuit 60. the output signal representing the correction coefficients r ₁ and correction variable F ₁ corresponding to _1, based on the following equation (6),
The first slip rate change reference value ₁ is corrected according to the vehicle speed V. ₁ = r ₁ V + F ₁ (6) Similarly to the first correction circuit 65, the second correction circuit 66 also outputs an output signal from the driven wheel speed selection circuit 52 and a gear ratio from the setting circuit 60 for each gear ratio. the output signal representing the correction coefficient r ₂ and correction variable F ₂ corresponding to the second slip ratio change speed reference value ₂ stipulated in, based on the following equation (7), the second slip ratio change amount reference value ₂ is corrected according to the vehicle speed V. ₂ = r ₂ V + F ₂ (7) The first and second threshold values λ ₁ and λ ₂ of the slip rate and the first and second slip rate change reference values ₁ and _{2 described above} are set to any gear. The ratios are set so that the relationship of λ ₁ <λ ₂ and ₁ < ₂ is satisfied.

The excessive ₁ determination circuit 55 outputs the output signal from the differentiation circuit 54,
The differential value of the slip ratio is compared with the output signal representing the second reference value ₂ from the second correction circuit 66 to obtain the second reference value.
When it is determined to be larger than _2, an H signal is output via the OR circuit 56, and otherwise, an L signal is output.

The first predictive control determining circuit 58 compares the output signal from the differentiating circuit 54 with the output signal representing the first reference value ₁ from the first correcting circuit 66 to determine the differential value of the slip ratio as the first signal. When it is determined that the value is larger than the reference value ₁ , an H signal is output to the AND circuit 59, and otherwise, an L signal is output. The second predictive control determination circuit 63 compares the output signal from the drive wheel speed selection circuit 51 with the output signal from the first speed calculation circuit 61 and determines that the drive wheel speed Vw is the first threshold value of the slip ratio. when it is determined that greater than the first reference speed value corresponding to lambda _1, aN
An H signal is output to the D circuit 59, and an L signal is output in other cases. The AND circuit 59 includes the first and second predictive control determination circuits 5
When an H signal is input from both of the R and G, the H signal is output via the OR circuit 56.

The excessive λ determination circuit 64 compares the output signal from the drive wheel speed selection circuit 51 with the output signal from the second speed / speed calculation circuit 62, and determines that the drive wheel speed Vw is equal to the second threshold value λ of the slip ratio.
_When it is determined that the value is larger than the second reference speed value corresponding to No. 2, an H signal is output via the OR circuit 56.

As described above, one of (i)> ₂ (preventing excessive slip rate speed), (ii)> ₁ and λ> λ ₁ (predictive control) or (iii) λ> λ ₂ (preventing excessive slip rate) When the condition is satisfied, an H signal is output via the OR circuit 56, and in this case, a fuel cut (hereinafter referred to as "fuel cut") to be described later is executed, and the drive wheels 11 and 12 are driven.
, The slip ratio λ or the speed of change in the slip ratio is reduced, and the slip ratio λ is controlled to a desired value. Hereinafter, the H signal output from the OR circuit 56 is referred to as a fuel cut signal (FCM signal) ((b) (1) in FIG. 5), and the operating region of the vehicle 1 in which the fuel cut signal is turned on is a fuel. This is called a cut region ((c) (1) in FIG. 5).

The signals of the first and second prediction control determination circuits 58 and 63 are also output to an OR circuit 67, and the OR circuit 67 outputs at least one of the output signals of the first and second prediction control determination circuits 58 and 63. when a H signal, i.e.> one of the conditions of ₁ or lambda> lambda ₁ outputs an H signal when established. Hereinafter, the signal output from the OR circuit 67 is called a standby signal (STB signal) ((b) (2) in FIG. 5), and the standby signal is on and the fuel cut signal is off. The operation region of the vehicle 1 located in the vehicle 1 is referred to as a standby region ((c) (2) in FIG. 5), and the operation region of the vehicle 1 other than the standby region and the fuel cut region is referred to as an off standby region ((c) in FIG. 5). ) (3)).

The standby area has a setting condition (> ₁ or λ> λ ₁ ) and a fuel cut area setting condition (>
₁ and λ> λ ₁ ), immediately after the vehicle 1 shifts from the off-standby region, which is a normal operation region, to the fuel cut region in which the fuel cut should be performed, or immediately after the vehicle 1 shifts in the opposite direction. ((A), (c) in FIG. 5). The setting of such an operation region is based on the engine as described later in the region.
The three-way catalyst is controlled by appropriately controlling the amount of fuel supplied to the 31 and appropriately changing the air-fuel ratio of the air-fuel mixture and the driving force of the engine 31 when passing between the normal operation region and the fuel cut region. This is to prevent the rise in temperature and the occurrence of afterfire in 42 and to improve the drivability by preventing driving shock and the like.

The first vehicle speed discrimination circuit 68 receives an output signal indicating the vehicle speed V from the vehicle speed setting circuit 52 and a first predetermined value V ₁ (for example, 12 km
/ h), and outputs a _first vehicle speed discrimination signal (FCM ₁ signal) when the latter is greater than the former, ie, when V <V ₁ holds. Further, a second vehicle speed determination circuit 69
Likewise the first vehicle speed determination circuit 68 compares a signal representing the vehicle speed V, and the reference signal representing the first second a large consisting predetermined value V ₁ of the predetermined value V ₂ (e.g., 20 km / h) Then, when V <V ₂ is satisfied, a second vehicle speed determination signal (FCM ₂ signal) is output.

FIG. 4 is a control program for performing a slip control in accordance with the state of generation of the fuel cut signal and the standby signal output by the logic circuit of FIG. 3 and other operating parameters, and this program is a TDC signal. It is executed every time a pulse is generated.

First, in step 401, it is determined whether a standby signal has been input. If the answer is negative (No), that is, if the standby signal has not been input and therefore the vehicle 1 is in the off-standby area, step 402
Then, it is determined whether or not the second flag FLG _FCT2 is equal to 0. The second flag FLG _FCT2 is set when a standby signal is input, that is, when the vehicle 1 is in the standby area or the fuel cut area, a step 419 described later.
Is set to 1, and when the vehicle 1 is in the off standby area, it is set to 0 in step 416 described later.

If the answer to step 402 is negative (No), that is, if the second flag FLG _FCT2 is equal to 1, and therefore this loop is a loop immediately after shifting to the off standby area, the process proceeds to step 403. In step 403, a timer T.TRC composed of a down counter is set to a predetermined time t _TRC (for example, 2.0
Seconds), start this, then step
In 404, the engine speed Ne becomes a predetermined number of times Ne _TRC (for example, 2,30
0 rpm) is determined. This step 404
Is affirmative (Yes), that is, when Ne> Ne _TRC holds, the _routine proceeds to step 405, where the fifth control variable CU _FCT3 is _set to the fifth control variable CU _FCT3 .
Set a predetermined number of times N ₄ (for example, 2), and then
In 406, the slip control correction coefficient K _STB is set to a predetermined lean value X _STB2 (for example, 0.8) for the off standby area (section A in FIG. 5 (d) (3)). Next step
_Proceeding to 406a, after setting the water temperature increase coefficient K _TW to the predetermined value K _TW0 , proceed to step 411 described later.

Figure 7 is an illustration of an example of a K _TW0 table for setting the predetermined value K _TW0 according to the engine coolant temperature T _W. That is, according to the figure, the _{predetermined} value K _TW0 is equal to three boundary values T _{W1 to} T _W3 of the engine _coolant temperature T _W (for example, −10 ° C., + 20 ° C., and +50, respectively).
° C.) the relationship between, when the engine water temperature T _W is higher T _W1 or less than T _W3 to first predetermined value K _TW01 (e.g. 1.00), T _W1
If it is less than T _W2, the second predetermined value K _TW02 (for example, 0.9
0), when _TW2 or more and less than _TW3, the third predetermined value K
_{Set to TW03} (for example, 0.95).

When the answer to the step 404 is negative (No), that is, when the engine speed Ne ≦ the predetermined speed Ne _TRC is satisfied, the process proceeds to a step 407, where the third control variable CU _FCT3 is set to a value 0, and then a step 408. Then, the slip control correction variable K _STB is set to 1.0 (section B in (d) and (3) of FIG. 5), and the routine proceeds to step 411.

If the answer to step 402 is affirmative (Yes), that is, if the second flag FLG _FCT2 is equal to 0, and therefore both the previous loop and the current loop are in the off standby area, the process proceeds to step 409, where the third control variable It is determined whether or not CU _FCT3 is equal to 0. If the answer to this step 409 is negative (No), that is, if the third control variable CU _FCT3 is not equal to 0, then in step 410 the third count number C
The value 1 is subtracted from U _FCT3 , then step 406 is executed, and the process proceeds to step 411. When the answer to the step 409 is affirmative (Yes), that is, when the third control variable CU _FCT3 is equal to 0, the step 408 is executed, and the _routine proceeds to a step 411.

As described above, when the vehicle is greater the engine speed Ne immediately after transition to off standby region, a slip control correction coefficient K _STB after the transition to the region, equal to a predetermined number N ₄ of the fifth The value is set to a value smaller than the normal value thereafter several times for TDC (FIG. 5 (d) (1)). As a result, the air-fuel mixture supplied to the engine 31 in the early stage of canceling the fuel cut is made lean, and the output of the engine 31 is reduced as compared with the normal output in the region. Can be prevented. The reason why the lean operation is not performed when the engine speed Ne is small is to prevent engine stall.

Note that control for delaying the ignition timing may be performed instead of the lean operation. Since the output of the engine 31 is reduced due to the delay of the ignition timing, the same effect as the lean operation can be obtained in this case as well.

Next, the routine proceeds to step 411, where it is determined whether or not the count value T.TRC of the timer T.TRC set in step 403 is equal to zero. This answer is negative (No), that is, the count value T.TR
If C is not equal to 0, and thus the predetermined time t _TRC has not elapsed since the shift to the off standby area, the third flag FL is set in steps 412 and 413.
G _FCT3 and the fourth flag FLG _FCT4 are each set to 1,
The process proceeds to step 416 described below. When the answer to the step 411 is affirmative (Yes), that is, when the timer value T.TRC is equal to 0, and thus the predetermined time t _TRC has elapsed since the shift to the off standby area, the third step is performed in the steps 414 and 415. The flag FLG _FCT3 and the fourth flag FLG _FCT4 are set to 0, respectively, and then the _routine proceeds to step 416.

In step 416, the second flag FLG _FCT2 is set to 0. Then, in step 417, the first flag FCG _FCT1 is set to 0. Then, the process proceeds to step 418, where the slip control for the slip control set in step 406 or 408 is performed. Correction coefficient K
_The fuel injection time T _OUT is calculated by applying the _STB to the equation (3), fuel injection is performed based on the fuel injection time T _OUT , and the program ends.

When the answer to step 401 is affirmative (Yes), that is, when the standby signal is input, and therefore the vehicle is in either the standby area or the fuel cut area, the process proceeds to step 419 and the second flag FLG _FCT2
Is set to 1.

Next, proceeding to step 402, the predetermined value X _STB for the standby area, the predetermined value X _TRC for the fuel cut area, and the first and second predetermined times N ₀ and N ₁ are stored in the X _STB stored in the storage means 35c. Table, X _TRC table, N ₀ table and
From N ₁ table, selects according to the engine RPM Ne.

6 (a) to 6 (d) show examples of these tables. According to FIG.
Ne is divided into five regions, and X _STB ,
X _TRC , N ₀ and N ₁ are each set as a constant value. That is, Ne ₁ , Ne ₂ , Ne ₃ and Ne ₄ (for example, 2,30 respectively)
Set 0,2,800,3,300 and 4,800 rpm), less than the engine speed Ne Ne _1, less Ne ₁ or Ne _2, Ne ₂ or more _and less than Ne _3, N
e ₃ or more and less than Ne ₄ and the area of Ne ₄ or more
II, III, IV and V. Predetermined value X for standby area
_STBs correspond to _XSTB1 , _XSTB2 , _XSTB3 , _XSTB4 and _XSTB1 in order from the region I side, that is, from the low rotation speed region side, with respect to the regions I to _{V.
STB 5} (e.g., respectively 0.50,0.60,0.80,0.80 and 1.7
0) is set. Similarly, the predetermined value X _TRC for the fuel cut region and the first and second predetermined times N ₀ and N ₁ are also smaller than 1 for X _TRC for the regions I to V in order from the region I side. X _{TRC1 to} X _TRC5 (for example, 0.
35, 0.40, 0.40, 0.45 and 0), but for N ₀ N _{01 to} N
₀₅ (e.g., respectively 1, 2, 3, 4 and 255), N ₁₁ ~N ₁₅ (e.g., respectively 1,2,3,3 and 0) is set for N _1.

These tables are based on engine characteristics and three-way catalyst.
Various modes can be set according to the type of 42 and the like.

Next, the routine proceeds to step 421, where it is determined whether or not a fuel cut signal has been input. If this answer is negative (N
o), that is, no fuel cut signal is input,
Therefore, when the vehicle is in the standby area, the _routine proceeds to step 422, where it is determined whether or not the third flag FLG _FCT3 is equal to zero. If the answer in this step 422 is affirmative (Ye
s), that is, when the third flag FLG _FCT3 is equal to 0, the fourth flag FLG _FCT4 is set to 0 in step 423;
When the result is negative (No), that is, when the third flag FLG _FCT3 is equal to 1, the fourth flag FLG _FCT4 is set to 1 in step 424, and then the process proceeds to step 425.

In this step 425, among the correction coefficients applied to the equation (3), all the correction coefficients except the atmospheric pressure correction coefficient K _PA are set to 1.0, and all the correction variables are set to 0, These correction coefficients and correction variables are canceled. As a result, it is possible to eliminate the influence of the fluctuation of the correction coefficient and the correction variable on the fuel injection time _TOUT , so that the slip control correction coefficient _KSTB and the water temperature increase coefficient _KTW are set again in steps 426 and 427 described later. In combination with this, the air-fuel mixture supplied to the engine 31 can be set to an optimum desired air-fuel ratio. Therefore, the emission amount of unburned fuel is reduced, so that the generation of afterfire and the increase in the temperature of the three-way catalyst 42
Performance degradation can be prevented. Also, the atmospheric pressure correction coefficient K _PA is not canceled because the coefficient is multiplied by this coefficient to prevent the air-fuel ratio of the air-fuel mixture supplied to the engine 31 from changing with the change in the atmospheric pressure. This is because it is necessary to apply this coefficient also in the area as in the off-standby area.

Next, proceeding to step 426, the slip control correction coefficient K
_{The STB} is set to the predetermined value X _STB for the standby area set in the step 420 (section C of (d) (3) in FIG. 5). During a transition between an off-standby region, which is a normal operation region, and a fuel-cut region in which fuel cut is performed as described later, the air-fuel ratio of the air-fuel mixture supplied to the engine 31 tends to fluctuate.
Since the combustion characteristics of 31 become unstable and a large amount of unburned fuel is discharged, the temperature rise of the three-way catalyst 42 and afterfire are likely to occur. Further, the fuel characteristics of the engine 31 differ depending on the engine speed Ne. Further, in the low rotation speed region of the engine 31, a resonance phenomenon related to the suspension of the vehicle body occurs, so that the drivability tends to deteriorate. Therefore, as described above, by using the predetermined value X _STB of the standby region set according to the engine speed Ne as the slip control correction coefficient, the temperature rise of the three-way catalyst and the after- Fire can be prevented from occurring, and drivability can be improved.

The mixture is enriched by setting the predetermined value X _STB for the standby region to 1.0 or more on the high rotation side (region V in FIG. 6). This is because the cooling action of the three-way catalyst 42 is promoted by the heat of vaporization, and the temperature rise can be prevented.
Conversely, the air-fuel mixture may be made leaner by setting the predetermined value X _STB for the high-speed side standby region to a value less than 1.0 according to the type of the three-way catalyst 42 and the like.

Next, the _routine proceeds to step 427, where the water temperature increase coefficient K _TW canceled in step 425 is set to the above-mentioned predetermined value K _TW0 . As a result, the air-fuel mixture supplied to the engine 31 in the standby region can be made leaner, so that step 42
Coupled with canceling the correction coefficient and variable in 5,
The generation of afterfire and the deterioration of the performance of the three-way catalyst 42 due to the rise in the temperature of the three-way catalyst 42 can be prevented even when the temperature of the engine 31 is low.

Next, the steps 417 and 418 are executed, the fuel injection is performed by applying the slip control correction coefficient K _STB and the water temperature increase coefficient K _TW set in the steps 426 and 427, respectively, and the program ends.

When the answer to the step 421 is affirmative (Yes), that is, when the fuel cut signal has been input and the vehicle is in the fuel cut area, the process proceeds to a step 428 to determine whether or not the fourth flag FLG _FCT4 is equal to 0. Is determined. When the answer to this step 428 is affirmative (Yes), that is, when the fourth flag FLG _FCT4 is equal to 0, the third flag FLG _FCT3 is set to 1 in step 429, and then in step 430
Then, the first flag FLG _FCT1 is set to 1, and furthermore, step 431 is executed to perform fuel cut (section D of (d) (3) in FIG. 5), and this program is terminated.

The fourth flag FLG _FCT4 is set to the value 0 when the timer value T.TRC of the timer T.TRC is equal to 0, as is apparent from the aforementioned steps 411 and 415, that is, The vehicle is in the off standby area for a predetermined time t
_{If the vehicle} moves to the fuel cut area after staying for more than _TRC , the answer to step 428 is affirmative (Yes),
Fuel cut is continued. If the vehicle shifts to the fuel-cut area and if the vehicle stays in the off-standby area before that for a long time, it is estimated that the previous slip rate was 0 or an excessive slip during acceleration from an extremely low value close to 0. Therefore, it is predicted that the fluctuation width and the change speed of the slip ratio λ will increase, and by continuing the fuel cut as described above, the engine 31
Can be reliably reduced, and the slip ratio λ can quickly converge to a desired value.

It is also possible to set a condition different from the above as a condition for continuing the fuel cut. For example, when the throttle valve 33 'changes from the fully closed state to the open state or when the rate of change of the throttle valve opening degree θ _TH exceeds a predetermined value, the slip state of the drive wheels 11, 12 is excessive. When it is determined that the fuel cut has been performed, the fuel cut may be continued for a certain period, whereby the same effect as described above can be obtained.

When the answer to step 428 is negative (No), that is, when the fourth flag FLG _FCT4 is equal to 1, the process proceeds to step 432,
It is determined whether or not the first flag FLG _FCT1 is equal to 0. This first flag FLG _FCT1 is set to 1 at the time of executing the fuel cut in the fuel cut area, as is apparent from the steps 417 and 430,
In other areas, it is set to 0.

When the answer to the above step 432 is affirmative (Yes), that is, when the first flag FLG _FCT1 is equal to 0, and thus the current loop is a loop immediately after shifting to the fuel cut area, the process proceeds to step 433, where the FCM ₂ signal is input. Is determined, that is, whether the vehicle speed V of the vehicle is smaller than a _second predetermined value V2. If the answer in this step 433 is affirmative (Yes),
That is, when the FCM ₂ signal has been input and therefore V <V ₂ holds, the routine proceeds to step 434, where the second predetermined number N ₁ selected in step 420 is replaced by the fourth predetermined number N ₃
(For example, 1), and then the process proceeds to step 435.

Whether In step 435 FCM ₁ signal is input, i.e., vehicle speed V is determined whether or not the first or the predetermined value V ₁ is smaller than. If this answer is affirmative (Yes), that is, if the FCM ₁ signal has been input and therefore V <V ₁ holds, the process proceeds to step 436, where the first predetermined number of times N ₀ selected in the step 420 The predetermined number N ₂ (for example, 1) of 3 is subtracted, and the process proceeds to step 437.

The answer is negative at step 435 (No), i.e. not been FCM ₁ signal is input, so that when the V ≧ V ₁ is satisfied, and if the answer to the question of the step 433 is negative (No), i.e. FCM ₂
If no signal has been input, and therefore V ≧ V ₂ holds, the routine proceeds to step 437. That is, when V <V ₁ holds, the first predetermined number N ₀ of subtraction correction and the second
The additive correction of the predetermined number N ₁ is, only the second additive correction of a predetermined number N ₁ is performed respectively when the V ₁ ≦ V <V ₂ is satisfied, correction for both the predetermined number of times when the V ≧ V ₂ is satisfied Is not done.

In the step 437, the first control variable CU _FCT1 is set to the first predetermined number N ₀ selected in the step 420 or corrected in the step 436, and then the process proceeds to step 438.

If the answer to the above step 432 is negative (No), that is, the first flag FLG _FCT1 is equal to 1, and therefore the current loop is the second or subsequent loop after shifting to the fuel cut area, the process directly proceeds to the step 438. . That is, the above-described route of steps 432 to 437 is executed only once immediately after shifting to the fuel cut area.

In step 438, the first control variable CU _FCT1 is set to 0.
Is determined. The answer is no (No),
If CU _FCT1 is not 0, proceed to step 439,
Of the control variable CU _FCT2 of the second predetermined number N ₁ selected in step 420 or corrected in step 434.
Is set. Next, at step 440, the value 1 is subtracted from the first control variable CU _FCT1.
Perform the 0 and step 431, (section E ₁ of FIG. 5 (d) (3)) performs fuel cut, the program is finished.

When the answer to step 438 is affirmative (Yes), that is, when the first control variable CU _FCT1 is equal to 0, the process proceeds to step 441, and it is determined whether or not the second control variable CU _FCT2 is equal to 0. If the answer to this step 441 is negative (No), that is, if CU _FCT2 is not 0, the _routine proceeds to step 442, where the value 1 is subtracted from the second control variable CU _FCT2 . Next, the process proceeds to step 443, where all the correction coefficients and correction variables are canceled as in step 425. Next, a predetermined value X _TRC for the fuel cut area selected in step 420 is set as the slip control correction coefficient K _STB (section E ₂ of (d) (3) in FIG. 5), and in step 445 Set the water temperature increase coefficient K _TW to 1.0. Further, the step 418 is executed, the fuel injection is performed by applying the correction coefficient and the correction variable to the equation (3), and the program ends.

When the answer to step 441 is affirmative (Yes), that is, when the second control variable CU _FCT2 is equal to 0, the process proceeds to step 446, and the first control variable CU _{FCT1 is set} to the first predetermined number N as in step 437. Set ₀ , then step 44
Execute steps 0, 430, and 431, perform fuel cut, and end this program.

As described above, even when the vehicle is in the fuel cut area, when the fourth flag FLG _FCT4 is equal to 1,
Instead of continuing the fuel cut, the execution of the fuel cut of the TDC number equal to the first predetermined number N ₀ and the cancellation of the fuel cut of the TDC circuit equal to the second predetermined number N ₁ are alternately repeated ( Section (d) of FIG. 5 (section E). The fourth flag FLG _FCT4 is set to 1, as is apparent from steps 411 and 413, etc., as the time during which the vehicle _stays in the off-standby region before shifting to the fuel cut region is less than a predetermined time t _TRC. Or, as is apparent from Steps 429, 422 and 424, etc., after the vehicle shifts from the fuel cut area to the standby area, and then returns to the fuel cut area again without shifting to the off standby area. That is, the slip control is performed at a relatively short time interval. In such a case, since the variation width and the change speed of the slip ratio λ are small, the execution and release of the fuel cut are performed as described above. Are performed with a predetermined number of TDCs, respectively, thereby preventing a driving shock due to a sharp decrease in the driving torque of the engine 31 and improving drivability.

In this case, when the fuel cut is released, the engine
Since the air-fuel ratio of the air-fuel mixture supplied to 31 is set by the predetermined value X _TRC for the fuel cut region set in accordance with the engine speed Ne in step 420, the slip control correction coefficient K in the standby region. The predetermined value X _STB for the standby area set as _STB is set in accordance with the engine speed Ne in the same manner as the engine speed Ne.
Over the entire area of Ne, it is possible to prevent a rise in the temperature of the three-way catalyst 42 and the generation of afterfire, and to improve the operability.

Further, as described above, the first predetermined number N ₀ and the second predetermined number N ₁ for determining the TDC number ratio for performing and canceling the fuel cut are also set in accordance with the engine speed Ne, respectively. The standby area
The same effect as in the above-described case in which the X _STB and the predetermined value X _TRC for the fuel cut region are set according to the engine speed Ne can be obtained.

In the present embodiment, the first and second predetermined times N ₀ and N ₁ are set according to the engine speed Ne. However, the present invention is not limited to this, and the detected slip state of the vehicle, for example, It may be set according to the slip ratio λ or the slip ratio change amount. That is, the larger the slip ratio λ or the amount of change in the slip ratio, the more the drive torque of the engine 31 needs to be reduced. Therefore, the first predetermined number N ₀ according to the slip ratio λ or the amount of the change in the slip ratio. or by setting the second predetermined number N _1, it is possible to control the air-fuel ratio of the mixture by directly reflecting the slip state of the vehicle to an appropriate value. Accordingly, since the driving force of the engine 31 can be appropriately reduced, the slip ratio λ or the amount of change in the slip ratio can be quickly converged to a desired value.

Furthermore, instead of setting the predetermined value X _STB for the standby region, the predetermined value X _TRC for the fuel cut region, the first predetermined number N ₀ or the second predetermined number N _{1 according} to the engine speed Ne, or At the same time, it may be set according to the engine load, for example, the intake pipe absolute pressure _PBA or the throttle valve opening _θTH . That is, since the amount of decrease in the driving force of the engine 31 due to the slip control differs depending on the magnitude of the load on the engine 31, when the air-fuel ratio of the air-fuel mixture is set to match the high-load operation state, the low-load operation state In the case where the control is set to be suitable for the low load operation state, the control becomes insufficient in the high load operation state. Therefore, by setting the predetermined values X _STB , X _TRC and the predetermined number N ₀ or N ₁ according to the engine load, the air-fuel ratio control for the slip control can be appropriately performed over the entire load of the engine 31. , Good driving performance can be ensured. In this case, when setting the predetermined value X _STB or the like by both the engine speed Ne and the intake pipe absolute pressure P _BA is mapped from the predetermined value X the _STB such as the engine rotational speed Ne and the intake pipe absolute pressure P _BA Of course, it is possible.

In addition, the period for executing and canceling the fuel cut can be set in various modes, for example, the first predetermined number of times.
N ₀ and the second predetermined number N ₁ may be set according to the wheel speed on the driven wheel side. Further, instead of using the TDC number ratio as described above, the ratio of the period of execution and release of the fuel cut is set to a time ratio according to the operating state of the engine 31,
Alternatively, when the control device is simplified, a fixed value may be used.

(Effects of the Invention) As described in detail above, the present invention provides a drive wheel slip control device that supplies a slip detection unit that detects a slip state lower than an excessive slip state of a drive wheel and a fuel supply unit according to an engine operating state. Correction value setting means for setting a correction value for correcting the amount of fuel to be performed, and correction value invalidating means for invalidating the correction value by the correction value setting means when the slip detecting means detects the low slip state. Since the influence on the air-fuel ratio of the air-fuel mixture due to the invalidated correction value when the drive wheels shift to excessive slip is eliminated, the air-fuel mixture can be optimized to the desired air-fuel ratio. To reduce the amount of unburned fuel emitted, thus preventing the occurrence of afterfire and deterioration of the performance of the three-way catalyst in the exhaust system. Play a fruit.

[Brief description of the drawings]

FIG. 1 is a block diagram of a vehicle equipped with a drive wheel slip control device of the present invention, FIG. 2 is a block diagram of a fuel supply control device for controlling torque of drive wheels, and FIG. 3 is a logic circuit of a part of the ECU 35. FIG. 4 is a flowchart of a control program for performing the slip control. FIG. 5 is a diagram showing the relationship between the slip ratio or the amount of change in the slip ratio and the output signal from the logic circuit diagram of FIG. 3 and the slip control. 6 is a diagram showing a table of a predetermined value and a predetermined number of times applied to the control program of FIGS. 4 and 5, FIG. 7 is a diagram showing a table of a predetermined value K _TW0 of a water temperature increase coefficient K _TW , FIG. FIG. 4 is a characteristic diagram of a frictional force between a tire and a road surface with respect to a slip ratio. 1… vehicle, 11, 12… drive wheels, 21, 22… drive wheel speed sensors, 23, 24… driven wheel speed sensors, 31… engine, 35… electronic control unit (ECU), 36… …
Fuel injection valve.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-150034 (JP, A) JP-A-60-151158 (JP, A) JP-A-60-163755 (JP, A)

Claims (4)

(57) [Claims] 1. A fuel supply means for supplying fuel to an engine, an excessive slip detection means for detecting an excessive slip state of a driving wheel of a vehicle, and a fuel supply means for detecting the excessive slip state when the excessive slip detection means detects an excessive slip state. And a fuel supply stopping means for stopping fuel supply from the means, wherein the slip detecting means detects a slip state of the drive wheels lower than the excessive slip state, and Correction value setting means for setting a correction value for correcting the amount of fuel supplied from the fuel supply means, and invalidating the correction value by the correction value setting means when the slip detection means detects the low slip state. A drive wheel slip control device comprising: a correction value invalidating means. 2. The correction value set by the correction value setting means includes an acceleration increase correction value, a high load increase correction value, a post-start increase correction value,
The drive wheel slip control device according to claim 1, wherein the drive wheel slip control device is at least one of an idle correction value and a low load reduction correction value. 3. The excess slip detecting means according to at least one of a condition that a slip rate is larger than a first predetermined slip rate and a condition that a slip rate change is larger than a first predetermined slip rate change. The excessive slip state is detected, and the slip detecting means detects a condition that the slip rate is larger than a second predetermined slip rate that is smaller than the first predetermined slip rate and that the slip rate change amount is equal to the first predetermined slip rate. The slip state lower than the excessive slip state is detected by satisfying only one of the conditions larger than a second predetermined slip rate change amount smaller than the rate change amount. 3. The drive wheel slip control device according to claim 2. 4. The excess slip detecting means detects an excess slip condition when a condition that the slip rate is larger than the second predetermined slip rate and a condition that the slip rate change is larger than the second predetermined slip rate are satisfied. 4. The drive wheel slip control device according to claim 1, wherein a slip state is detected.