JPH0749785B2 - Vehicle drive force control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle drive force control device for preventing drive wheel slippage during low friction coefficient road traveling, starting, acceleration, and the like.

(Prior Art) Conventionally, as a driving force control device for a vehicle, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent No. 38347-, the drive wheel slip is detected from the difference between the average rotational speed of the left and right front wheels and the average rotational speed of the left and right rear wheels, and when the detected value indicates the drive wheel slip, the fuel cut ( There is known a device for preventing a drive wheel slip by stopping fuel supply).

Further, as shown in JP-A-58-202142, there is known a device for preventing slip by driving a brake when a drive wheel slip occurs, and further, JP-A-59-18.
As disclosed in Japanese Patent No. 251, there is known a device that prevents a slip by controlling a slot valve in a closing direction when a drive wheel slip occurs.

(Problems to be solved by the invention) However, in the conventional device disclosed in Japanese Patent Laid-Open No. 58-38347, which reduces the engine output by the fuel cut, the drive wheel slip ratio is the drive force control threshold value. When a drive wheel slip that exceeds a certain set slip ratio occurs, fuel cut is executed, and when the drive wheel slip ratio becomes less than the set slip ratio during engine output reduction control, fuel recovery (resumption of fuel supply) is executed. Therefore, the driving force control described below is performed.

When the drive wheel slip ratio becomes equal to or higher than the set slip ratio during traveling, the fuel cut is executed, and when the engine output suddenly decreases due to the fuel cut, the drive wheel slip falls below the set slip ratio and the fuel recovery is executed. Then, the fuel cut is executed again when the drive wheel slip ratio becomes equal to or higher than the set slip ratio by the fuel recovery, and the fuel recovery is executed again when the drive wheel slip is stopped by the fuel cut. Control hunting that repeats the operation occurs.

The cause of this control hunting is that the fuel cut has a higher control gain than other engine output controls (for example, throttle control and ignition timing control).

That is, when the fuel cut is started, the engine output decreases due to the steep gradient, and when the fuel recovery is started, the engine output increases due to the steep gradient, regardless of the occurrence of the drive wheel slip. However, when the drive wheel slip ratio is monitored, it is performed before and after the set slip ratio, which is the drive force control threshold, because the engine output increase range with a large head difference (all cylinder cut, 1/2 cylinder cut, etc.) is performed. To easily make a round trip.

Due to this control hunting, the engine speed fluctuates greatly while the drive wheel slip occurs, and a large increase and decrease in the engine output torque are repeated, so that the vehicle is vibrated violently back and forth, and the riding comfort is impaired.

Also, the engine output is reduced by a brake.
In the conventional device disclosed in Japanese Patent Laid-Open No. 58-202142, the braking force is required at times other than when the brake is operated, so a hydraulic power source capable of constantly generating hydraulic pressure is required, resulting in high device cost.

Further, in the conventional device disclosed in Japanese Patent Application Laid-Open No. 58-18251, in which the engine output is reduced by opening / closing the throttle, an actuator for opening / closing the throttle valve with high accuracy is required.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a low-cost device by fuel cut, but without causing control hunting and suppressing fluctuations in engine speed to a small value. It is an object to provide a vehicle driving force control device that achieves smooth slip prevention control.

(Means for Solving Problems) In order to achieve the above object, the vehicle driving force control device of the present invention has the following solving means.

The solution means of the present invention will be described with reference to the claim correspondence diagram of FIG. 1. A vehicle body speed detecting means a for detecting a vehicle body speed, a drive wheel speed detecting means b for detecting a drive wheel speed, and an engine speed are detected. An actual engine speed detecting means c, a slip ratio calculating means d for calculating a drive wheel slip ratio based on the vehicle speed and the drive wheel speed, and a set slip ratio in which the drive wheel slip ratio is a driving force control threshold value. Based on the actual engine speed, the vehicle body speed, and the drive wheel speed when the drive wheel slip state determination means e determines whether or not the above is the case, the optimum slip rate is a little larger than the set slip rate. Target engine speed calculating means f for calculating a target engine speed by converting the drive wheel speed into engine speed, and the actual engine speed detecting means c.
Excess engine speed calculation means g for calculating the difference between the actual engine speed detected in step 1 and the target engine speed calculated by the target engine speed calculation means f, and calculating the excess speed from the target engine speed. A fuel supply control means h for dividing the engine into a plurality of cylinder groups and increasing the stop time of the fuel supplied to the cylinder groups as the excess engine speed calculated by the excess engine speed calculation means g increases.
It is characterized by having.

(Operation) At the time of traveling, the slip ratio calculating means d is driven based on the vehicle speed from the vehicle speed detecting means a for detecting the vehicle speed and the driving wheel speed from the driving wheel speed detecting means b for detecting the driving wheel speed. The wheel slip ratio is calculated, and the driving wheel slip state judging means e judges whether the driving wheel slip ratio is equal to or higher than a set slip ratio which is a driving force control threshold value. That is, the drive wheel slip state is monitored by whether or not the drive wheel slip ratio is equal to or higher than the set slip ratio.

Then, when the drive wheel slip state determination means e determines the drive wheel slip state, the target engine speed calculation means f is based on the actual engine speed, the vehicle body speed, and the drive wheel speed, and is an optimum value that is slightly larger than the set slip ratio. The target engine speed is calculated by converting the drive wheel speed that is the slip ratio into the engine speed, and the excess engine speed calculation means g calculates the actual engine speed and the target engine speed detected by the actual engine speed detection means c. The difference from the target engine speed calculated by the calculating means f is calculated, and the excess speed from the target engine speed is calculated.

Then, the engine is divided into multiple cylinder groups to supply fuel.
In the fuel supply control means h for stopping, the control is performed to increase the stop time of the fuel supplied to the cylinder group as the excess engine speed calculated by the excess engine speed calculation means g increases.

That is, when the drive wheel slip ratio becomes equal to or higher than the set slip ratio, the engine output control is started, and during the engine output control, the drive wheel speed at which the optimum slip ratio is a little larger than the set slip ratio is converted into the engine speed. The fuel cut control is performed by feedback control that matches the target engine speed with the actual engine speed, divides the engine into a plurality of cylinder groups, and uses a precise control amount that changes the fuel stop time. .

Therefore, the rotational speed of the engine itself, which is the target of fuel cut, is feedback-controlled, so there is no delay element in the feedback control loop, and the engine speed control with good response greatly deviates from the target engine speed. Such a decrease or increase in engine speed can be suppressed.

For example, when the target drive wheel slip ratio is set instead of the target engine speed of the present invention and fuel cut control is performed to match the actual drive wheel slip with the target drive wheel slip ratio, the drive system from the engine to the drive wheels is set. Exists as a delay element in the feedback control loop, and there is a slight response delay due to the drive system. However, in the case of the fuel cut, the control gain is very high, and even if there is a slight response delay, a large decrease or increase in the engine speed due to overshoot is observed when the change situation of the engine speed is observed.

Further, since the engine is divided into a plurality of cylinder groups and the fuel cut control is performed by a precise control amount that changes the fuel stop time, when the excess engine speed is large at the beginning of the drive wheel slip start, etc. The control gain of fuel cut is adjusted by a precise control amount such that the control gain of fuel cut expressed by the change gradient is large and the control gain of fuel cut becomes small when the engine speed is low. Convergence with respect to the target engine speed of is increased.

Furthermore, since the optimum slip ratio, which is the basis for setting the target engine speed, is set to a value slightly larger than the set slip ratio, which is the driving force control threshold value, the actual engine speed during the engine speed control is the target engine speed. The driving force control itself will not be terminated even if it slightly falls below.

In this way, the fluctuation of the engine speed is suppressed small by the effect of suppressing the overshoot by adopting the engine speed control and the effect of highly converging the engine speed by finely controlling the fuel cut. Smooth anti-slip control is achieved, and by setting the optimum slip ratio, which is the base for setting the target engine speed, to a value slightly larger than the set slip ratio, the drive force control is repeatedly turned on and off. Prevention of hunting is achieved.

If the driver operates the accelerator pedal in the releasing direction or the road surface friction coefficient changes to a high friction coefficient road, and the drive wheel slip ratio falls below the set slip ratio, the driving force control by fuel cut ends.

(Example) Hereinafter, the Example of this invention is described based on drawing.

First, the configuration will be described.

In the overall system diagram of FIG. 2, 21 is an air flow meter, 22
Is a throttle valve, 23 is a fuel injection valve, 24 is an ignition coil, 25 is an engine, 26 is an engine speed sensor, 27 is a front wheel speed sensor, 28 is a rear wheel speed sensor, and is a rear-wheel drive vehicle (FR vehicle). In this case, the front wheels are non-driving wheels and the rear wheels are driving wheels.

Reference numeral 29 is a control device using a microcomputer, the basic performance of which is to obtain an appropriate fuel amount and ignition timing based on the output of the air flow meter 21, the engine speed sensor 26 and other information not shown, and to inject fuel. Valve 23, ignition coil 2
It gives commands to 4.

Further, the control device 29 has a driving force control performance, and the performance is the actual engine rotation speed Ne obtained by the input information from the engine rotation speed sensor 26, the front wheel wheel speed sensor 27, and the rear wheel wheel speed sensor 28, the front wheel. wheel speed V _F, as well as calculating a target engine rotational speed Ncut as the optimum slip ratio S ^* based on the rear wheel speed V _R, the front wheel speed V _F, the rear wheel speed V based on the _R driven wheel slip rate S is calculated and the drive wheel slip ratio S is calculated.
When a predetermined set slip ratio S ₀ indicating a drive wheel slip is exceeded, a part or all of the fuel supplied to the engine 25 is adjusted so that the actual engine speed Ne matches the target engine speed Ncut. A command to stop is given to the fuel injection valve 23.

Next, the operation will be described.

The flow of the driving force control operation will be described first with reference to the flowchart of the main routine shown in FIG.

First, at step 31, the engine speed Ne is read from the engine speed sensor 26 (corresponding to an actual engine speed detecting means). Next, in steps 32 and 33, the wheel speeds of the front and rear wheels are calculated and set as V _F and V _R , respectively (corresponding to vehicle body speed detecting means and drive wheel speed detecting means).

Next, in step 34, the slip ratio S is calculated by the following formula (corresponding to slip ratio calculating means).

This corresponds to the ratio of the difference between the wheel speeds of the front wheels (non-driving wheels) corresponding to the actual vehicle speed and the front and rear wheel speeds. Next, in step 35, it is compared whether or not the slip ratio S is larger than a predetermined set slip ratio S ₀ (for example, 0.15) (corresponding to a drive wheel slip state determination means). The flags FC1 and FC2 are set to 0 to prevent fuel cut, that is, normal operation is performed.

If the slip ratio S is larger than the predetermined set slip ratio S _{0, the} process proceeds to the slip 36 to suppress the slip, and the target engine speed Ncut of fuel cut (corresponding to the target engine speed calculation means) is obtained. For example, in the case of a manual transmission, (However, V _R = a × Ne, a is a gear ratio). That is, it corresponds to the engine speed when the slip ratio is 0.2.

Next, at step 37, fuel cut is executed.

The fuel cut method will be described in detail below.

FIG. 4 shows a fuel cut intermittent signal generation program for each cylinder group so as to alternately execute fuel cut for the cylinder groups, which is executed at a constant cycle in synchronization with rotation or time.

In steps 41 to 46, the counters TM1 and TM2, which are the reference for the time of the combustion cut intermittent signal, are counted.

In step 41, it is determined whether the value of the counter TM1 is φ, and φ
If so, the process proceeds to step 43, and if not φ, the process proceeds to step 42. In step 42, count each time this program is executed
Decrease TM1 by 1. Steps 43 and 44 count the counter TM2 in the same manner as steps 41 and 42. In step 45, it is determined whether the TM1 count value is 1/2 of the fuel cut intermittent cycle count number T. When the TM1 count value becomes 1/2 of T, in step 46 the counter TM2 intermittent cycle Set the count number T.

In the above steps, as shown in FIG. 6, the counter TM1 of the cycle T which is the reference of the intermittent fuel cut signal and 1 /
A counter TM2 having a 2-cycle phase difference is constructed.

In step 47, the difference between the actual engine speed Ne and the predetermined target engine speed Ncut is calculated, and the excess speed ΔNe from the target engine speed Ncut is calculated (corresponding to excess engine speed calculation means).

In steps 48 to 56, the fuel cut time ratio is set.

In step 48, TM1 is discriminated. If TM1 = φ is not satisfied, the process jumps to step 54 and steps 49 to 53 are not executed.

At step 49, ΔNe is determined, and if ΔNe ≦ φ, that is, if the engine speed Ne does not exceed the target engine speed Ncut, the routine jumps to step 57. At this time, the counter TM1 is not newly set and the state of φ continues.

When ΔNe> φ, the fuel cut execution time corresponding to ΔNe is assigned in steps 50 to 56.

If ΔNe ≦ N _{1 in} step 50, that is, φ <ΔNe ≦ N ₁ , in step 51 a predetermined cycle number T ₁ is set in the fuel recovery cycle number register TREC, and in step 53 the cycle count number T is set in the counter TM1. To do. If N ₁ <ΔNe, T ₂ is set in TREC in step 52, and T is set in TM ₁ in step 13.

In steps 54 to 56, ΔNe is a limit value larger than N < _1.
This is a routine for continuously performing fuel cut when N ₂ is exceeded.

Step 54 is always executed irrespective of the timing of TM1 = φ. When ΔNe> N ₂ , step 55 sets TM1 to a value one count larger than TM2, and step 56 sets TM2 to T / 2 from TM1.
Set a high value. By setting TM1 and TM2 in this way, it is possible to shift to the intermittent cycle of TREC = T ₂ when the engine speed decreases and ΔNe ≦ N ₂ .

The set values of the excessive rotation speeds N ₁ and N ₂ and the fuel recovery cycle numbers T ₁ and T ₂ are set as shown in FIGS. 8 and 9.

In steps 57 to 62, the cut state of the fuel cut / interruption signal and the recover state are switched for each cylinder group.

When the counter TM1 exceeds the set value of the fuel recovery cycle number register TREC in step 57, the fuel cut flag FC1 of the first cylinder group is set in step 58, and when TREC or less, FC1 is reset in step 59 (first (Fig. 7). Similarly, in steps 60 to 62, the fuel cut flag FC2 of the second cylinder group is set or reset by the counter TM2. As described above, since TM2 is set to be shifted by 1/2 cycle from TM1, FC1 and FC2 are intermittent signals with a 1/2 cycle phase shift.

FIG. 5 shows a program for executing the fuel cut, which is provided in the fuel injection pulse output program which is periodically executed.

At step 71, the fuel cut flag FC1 calculated by the fuel cut intermittent signal generation program is discriminated, and if “φ”, the fuel injection pulse is outputted to the fuel injection valve drive I / O of the first cylinder group at step 2. , Fuel injection of the first cylinder group is performed. If the flag FC1 is "1", the fuel injection pulse of the first cylinder group is not output and the fuel cut of the first cylinder group is executed.

Similarly, in steps 73 to 74, the fuel cut flag FC2 is determined. If "φ", the fuel injection of the second cylinder group is performed, and if "1", the fuel cut of the second cylinder group is executed. . The flowcharts of FIGS. 4 and 5 correspond to the fuel supply control means.

An explanatory diagram of the above operation is shown in FIG. 9, and the engine speed Ne
When exceeds a predetermined target engine speed Ncut, fuel cuts are regularly interrupted.

Although the time ratio for executing the fuel cut is changed in two steps according to the excess rotation speed ΔNe, it may be changed in one step or in multiple steps of three or more steps. Furthermore, the excess rotation speed Δ
When Ne further increases and exceeds N ₂ , continuous fuel cut occurs.

Next, FIG. 10 and FIG. 11 are time charts for explaining the operation of this embodiment.

When the vehicle accelerates rapidly at time t ₀ in FIG. 10 and slip occurs, V _R (solid line) rapidly rises with respect to V _F (broken line).
In a manual transmission, the engine speed Ne (solid line) also rises rapidly because it is connected via a specific gear ratio. Next, when the slip ratio S exceeds a predetermined set slip ratio S ₀ at time t ₁ , as shown in FIG.
The target engine speed Ncut is set according to V _F as shown by the broken line, and the fuel cut is performed as described above according to the setting, and the engine speed Ne is the target engine speed Ncut.
It smoothly rises while being controlled to the vicinity, so that the rear wheel speed V _R also rises smoothly after the descent due to the fuel cut so that the optimum slip ratio S ^* is obtained.

Although the embodiment has been described above with reference to the drawings, the specific configuration is not limited to this embodiment, and even if there is a design change or the like within the scope not departing from the gist of the invention, the invention is included in the invention. .

(Effects of the Invention) As described above, in the vehicle drive force control device of the present invention, the drive wheel that determines whether the drive wheel slip ratio is equal to or greater than the set slip ratio that is the drive force control threshold value. Based on the actual engine speed, the vehicle body speed, and the drive wheel speed when determining the slip condition of the drive wheel and the slip condition of the drive wheel, the drive wheel speed at which the optimum slip ratio is a little larger than the set slip ratio is converted into the engine speed. A target engine speed calculating means for calculating the target engine speed, and a difference between the actual engine speed detected by the actual engine speed detecting means and the target engine speed calculated by the target engine speed calculating means, Excess engine speed calculation means for calculating the excess speed from the target engine speed, and the engine is divided into a plurality of cylinder groups and calculated by the excess engine speed calculation means. Fuel supply control means for increasing the stop time of the fuel supplied to the cylinder group as the issued excess engine speed increases,
Since it is a device with a fuel cut, it provides a vehicle drive force control device that achieves smooth anti-slip control that does not cause control hunting and suppresses fluctuations in engine speed, even though it is a low-cost device by fuel cut. The effect of being able to do is obtained.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims showing a vehicle driving force control device of the present invention, FIG. 2 is an overall view of a system to which the vehicle driving force control device of the embodiment is applied, and FIG. 3 is a vehicle driving force of the embodiment. FIG. 4 is a flowchart showing a main routine of control, FIG. 4 is a fuel cut control flowchart showing a subroutine of driving force control for an embodiment vehicle, and FIG. 5 is a flowchart showing a fuel cutting program in the driving force control for an embodiment vehicle. FIG. 6 is a time chart diagram showing a counter of the cycle T which is the reference of the fuel cut intermittent signal, FIG. 7 is a time chart diagram for switching between the cut state of the fuel cut intermittent signal and the recovery state, and FIG. 8 is the fuel cut. FIG. 9 is a diagram for explaining the structure of the time ratio of the above in relation to the engine speed including the excess speed, and FIG. 9 is a time chart diagram for explaining the time structure of intermittent fuel cut. Wheel speed time chart when the drive wheel slip has occurred, FIG. 11 is an engine rotational speed-time chart when the driving wheel slip has occurred. a: vehicle speed detecting means b: driving wheel speed detecting means c: actual engine speed detecting means d: slip ratio calculating means e: driving wheel slip state judging means f: target engine speed calculating means g …… Excessive engine speed calculation means h …… Fuel supply control means

Claims (1)

[Claims] 1. A vehicle speed detecting means for detecting a vehicle speed, a driving wheel speed detecting means for detecting a driving wheel speed, an actual engine speed detecting means for detecting an engine speed, the vehicle speed and the driving wheel speed. A slip ratio calculating means for calculating a drive wheel slip ratio based on the drive wheel slip condition judging means for judging whether or not the drive wheel slip ratio is equal to or more than a set slip ratio which is a driving force control threshold value; At the time of state determination, a target engine speed is calculated based on the actual engine speed, the vehicle body speed, and the drive wheel speed by converting the drive wheel speed at which the optimum slip ratio is a little larger than the set slip ratio into the engine speed. Target engine speed calculating means, actual engine speed detected by the actual engine speed detecting means and target calculated by the target engine speed calculating means Engine speed calculation means for calculating the difference between the engine speed and the target engine speed, and an excess engine speed calculation means for dividing the engine into a plurality of cylinder groups and calculating the excess engine speed by the excess engine speed calculation means. A vehicle driving force control device comprising: a fuel supply control unit that increases a stop time of fuel supplied to the cylinder group as the engine speed increases.