JP2513248B2 - Acceleration slip prevention method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an acceleration slip prevention method capable of preventing slippage of a drive wheel during acceleration.

(Prior Art) When the vehicle is suddenly accelerated, the drive wheels spin idle, and the driving force of the engine is not properly transmitted to the road surface.

(Problems to be Solved by the Invention) A technique for preventing idling of the drive wheels when the vehicle is suddenly accelerated in this way is disclosed in Japanese Patent Laid-Open Nos. 61-046725 and 61-46725.
It is disclosed in JP-A-60-107429 and JP-A-60-107430.

However, in all of the above-mentioned publications, when restoring the torque reduced by slip detection, the torque change amount is set in consideration of the maximum torque that can be transmitted to the road surface. Not not. For this reason,
In the process of recovering the torque reduced by the slip detection, there is a problem that the drive torque cannot be quickly recovered to the maximum torque that can be transmitted to the road surface.

The present invention has been made in view of the above points, and an object of the present invention is to reduce torque when a vehicle is suddenly accelerated to prevent idling of drive wheels, and to quickly recover torque when recovering the torque. An object of the present invention is to provide a method for preventing accelerated slip that can be achieved.

[Configuration of Invention] (Means and Actions for Solving Problems) Preventing an acceleration slip of a vehicle by detecting an acceleration slip state of a drive wheel and reducing an output of an engine according to the degree of the slip state In the acceleration slip prevention method described above, when the driving wheel speed shows an increasing tendency and it is detected that the driving wheel speed is calculated based on the vehicle body speed and exceeds a reference speed higher than the vehicle body speed, the driving wheel speed shows a decelerating tendency. And, the first step of reducing the engine output based on the first output rate determined by a predetermined means until the speed becomes lower than the predetermined speed based on the reference speed, and the slip stops after the first step ends. Until it is determined that the second output rate required to obtain a drive torque that is greater than the first output rate and equal to the torque that can be transmitted from the drive wheels to the road surface. A second setting is performed based on the drive wheel rotation deceleration during deceleration of the drive wheels during execution of the first step, and the engine output reduced in the first step is recovered based on the second output rate. The acceleration slip prevention method is characterized in that the acceleration slip is prevented by the step of.

(Embodiment) An acceleration slip prevention method according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a traction control device for preventing idling during acceleration in a front-wheel drive vehicle. In FIG. 1, 11 is a drive wheel, that is, a drive wheel wheel speed sensor that detects the wheel speed Vfl of the left front wheel, and 12 is a drive wheel, that is, the wheel speed Vf of the right front wheel.
Drive wheel wheel speed sensor that detects r, 13 is a driven wheel, that is, a driven wheel wheel speed sensor that detects wheel speed Vrl of the left rear wheel, 14 is a driven wheel, that is, a driven wheel that detects wheel speed Vrr of the right rear wheel It is a wheel speed sensor. The wheel speeds Vfl and Vfr on the drive wheel side are averaged in the average circuit 15 to calculate the wheel speed VW on the drive wheel side. Further, the wheel speeds Vrl and Vrr on the driven wheel side are averaged in the average circuit 16 to calculate the vehicle speed VB. The wheel speed VW and the vehicle body speed VB are respectively E for traction control.
An output rate command A or B that is output to the CU (electronic control unit) 17 and reduces the output of the engine necessary for the control to prevent the slip of the drive wheels during acceleration is created. The output rate command A (B) is a command for reducing the output of the engine, is expressed as a ratio of the post-reduction output to the pre-reduction output, and is output to the engine ECU 18. The engine ECU 18 controls the engine as a whole and outputs fuel injection pulses that determine the fuel injection amount to the injectors I1 to I4. Further, based on the signal from the ECU 18 for the engine, the advance angle of the ignition timing of the engine is calculated by the ignition advance device 19. Further, 20 is an engine speed sensor for detecting the engine speed, 21 is an intake air amount sensor for detecting the intake air amount, and the intake air amount detected by the intake air amount sensor 21 is for the engine. Output to the ECU 18. ECU for this engine
Reference numeral 18 controls the engine output by reducing the fuel injection amount from the injectors I1 to I4 and delaying the ignition timing based on the output rate command A (B) output from the traction control ECU 17. Then, the intake air amount A / N per stroke is calculated in the engine ECU 18 based on the engine speed and the intake air amount.

Next, the operation of the embodiment of the present invention configured as above will be described. First, the wheel speeds Vfl and Vfr on the drive wheel side are averaged by the average circuit 15 to calculate the wheel speed VW on the drive wheel side. Further, the wheel speeds Vrl and Vrr on the driven wheel side are averaged in the average circuit 16 to calculate the vehicle speed VB. The wheel speed VW and the vehicle body speed VB are output to the traction control ECU (electronic control unit) 17, respectively. Then, in the ECU 17, the deviation DV = VW−Vth between the driving wheel speed Vw and the vehicle body speed,
That is, the slip of the drive wheels with respect to the reference speed is calculated, and the differential value D of the deviation DV is calculated.

Hereinafter, an acceleration slip prevention method in the traction control ECU 17 will be described with reference to the second flowchart. First, it is determined whether the deviation DV> 0 and its differential value D> 0. That is, time t1 in FIG.
As a result, the difference between the wheel speed VW and the vehicle body speed VB begins to open. This is because the drive wheels start to slip due to sudden acceleration. Then, after the time t2, the wheel speed VW exceeds the reference speed Vth, so that the deviation DV> 0. further,
Since the differential value D> 0 at time t2, it is determined to be "YES" in step S1, and the process of reducing the output of the engine and preventing the occurrence of slip is started as described later. First, the value of K1 is cleared and the time counter is cleared (step S2). Then, based on the intake air amount / engine speed (A / N), the output ratio K0 as the command A is determined by referring to the map in FIG. 7 (step S
3). Further, as shown in FIG. 7, the output rate K0 is changed so as to be inversely proportional to the intake air amount / engine speed (A / N). As shown in FIG. 5, when the intake air amount / engine speed (A / N) is constant, the output torque of the engine does not fluctuate with the change in the engine speed Ne, and the intake air amount / engine The rotation speed (A / N) can be regarded as a value representing the engine output. Therefore, by setting the output ratio K0 as shown in Fig. 7 in accordance with the intake air amount / engine speed (A / N), the output ratio K0 will almost correspond to the engine output torque. Become. That is, when the intake air amount / engine speed (A / N) is large, the engine output torque is large, so the output ratio is reduced to significantly reduce the engine output torque, and the intake air amount / engine speed (A / N) If / N) is small, the output rate is increased to reduce the engine output reduction amount. And
By changing the output ratio K0 so that it is inversely proportional to the intake air amount / engine speed (A / N), the output is reduced by the output ratio K0, regardless of the magnitude of the engine output before control. Will be obtained.
Then, the process proceeds to step S4, and the output reduction control of the engine based on the output rate K0 is executed (A command in FIG. 3). This output reduction control of the engine is continued until time t4 in FIG. 3, and its determination is based on the processing in step S5. That is,
In step S5, the differential value D <0 and the deviation DV <γ
It is determined whether (= 5). That is, the wheel speed VW peaks at time t3 due to the reduction of the engine output torque due to the A command started at time t2, and thereafter, the wheel speed VW decreases toward the vehicle speed VB. Then, at time t4, the condition of step S5 is satisfied, and the A command is ended.

By determining the slip convergence by the differential value D being negative in this way, the judgment value of the deviation DV can be set to a relatively large value, and the slip convergence can be predicted before the slip amount completely falls. However, overcontrol due to the A command can be prevented.

Then, after the A instruction is completed, the process proceeds to the processing of the B instruction after step S6. First, the time counting operation is started (step S6). Then, the deceleration of the driving wheel under control is calculated by the above K0 (step S
7). Then, the intake air amount / engine speed (A / N) is input from the engine ECU 18 to the traction control ECU 17 (step S8). Next, K1 (0) = KI
It is calculated as / a (A / N + b) (step S9). Then, output control based on K1 (0) is performed (step S1).
0). Then, K1 (t) = K1 (0) + PT is calculated (step S11). When "K1 (t)>1","K1 (t) = 1" is set (steps S12, 13), and K1
Output control is performed based on (t) (step S14).
The control by the output rate K1 is performed as a command B as shown in FIG. Here, the output rate K1 is the output rate K0
Is set larger than. Then, the engine output reduction control based on the B command is performed until the deviation DV becomes equal to or less than the vehicle body speed VB (step S12). On the other hand, when the deviation DV is larger than the vehicle body speed VB, in step S13,
The B command is repeated until it is determined to be "YES".

Since the deceleration during the B command is a negative value, the calculated output rate K1 is larger than the output rate K0. Further, during the B command, the output rate K1 is a function of time and gradually increases with the lapse of time, so the output torque is gradually recovered as shown in FIG.

Now, the relationship between the road surface torque (= μWR) and the road surface μ during the A command and the B command will be described. Road torque during A command and B command follows the change of μ (W,
Since R is constant, the road surface torque corresponds to the μ-slip ratio curve shown in FIG. That is, when the vehicle is accelerated, the torque transmitted to the road surface by the increase of the driving torque, that is, the road surface torque also increases, but “4” in FIG. 6), but the maximum torque that can be transmitted to the road surface is increased by the driving torque. When it exceeds, the slip of the driving wheels becomes excessive and the road surface torque does not increase (between “1” and “2” in FIG. 6). In the A command, the driving torque is reduced from the excessive slip condition to shift the condition from the vicinity of "2" in FIG. 6 to the "1" side condition, and by the B command, the "A" condition in FIG. The control is performed so that the value of "1", that is, the value of the torque transmitted to the road surface becomes the highest value. Here, the output rate K1 calculated in step S9 is calculated. Generally, the relationship between the driving torque Tl and the road surface torque Tr which is the torque actually transmitted from the driving wheels to the road surface is Tl = Tr + I ·. Is the angular acceleration of the drive wheels.

As is clear from this equation, when a certain drive torque T1 is applied to the drive wheels, if the maximum torque that can be transmitted to the road surface is smaller than the drive torque, the remaining torque is spent on the rotation of the drive wheels, It will spin idle.

Therefore, when the wheel angular velocity ω changes as shown in FIG. 4, the road surface torque Tr after the output is reduced at the output rate K0 is as follows.

Tr = Tl-I ・ = K0 ・ T0-I ・ ・ ・ ・ (1) Therefore, it can be transmitted to the road surface by the torque (K0 ・ T0) and the angular acceleration () of the driving wheel when the control is performed by the A command. Maximum torque can be calculated.

Here, the driving torque T0 when the traction control is not performed is T0 = ρ · Te = a · (A / N + b) (a and b are constants) (2) and the equations (1) and (2) Therefore, the road surface torque Tr becomes Tr = K0 · a · (A / N + b) −I ·.

Therefore, the output rate K1 for actually obtaining the road surface torque Tr, which is the maximum torque that can be transmitted to the road surface, is K1 = Tr / T0 = K0−I · / {a · (A / N + b)}. By setting the output rate K1 in this way, the torque obtained by this output rate K1 is restored to a value corresponding to the maximum torque that can be transmitted to the road surface (road surface torque Tr), and the vehicle will not slip excessively. It is possible to actually obtain a drive torque suitable for accelerating.

Then, by recovering the torque reduced by the A command to the maximum torque that can be transmitted to the road surface by the B command, it is possible to prevent the recurrence of the slip that occurs when the output is simply returned to the value before the control when the slip converges. You can

Next, a second embodiment of the present invention will be described with reference to FIGS. In the embodiment of FIG. 8, the traction control ECU 17 of FIG. 1 to the engine ECU
The output to 18 is the same as in the configuration diagram of FIG. 1 except that the command value Q is output. The same parts as those in FIG. 1 are denoted by the same reference numerals and detailed description thereof will be omitted. First, in the traction control ECU 17, the processing shown in the flowchart of FIG. 9 is performed. First, "0" is set to the command value Q (step S21). Next, it is judged whether the deviation DV> 0 and its differential value D> 0 (step S2).
2). That is, the difference between the wheel speed VW and the vehicle body speed VB starts to open from time t1 in FIG. This is because the drive wheels start to slip due to sudden acceleration. And time t2
After that, the wheel speed VW exceeds the reference speed Vth,
The deviation DV> 0. Furthermore, the differential value D> 0 at time t2
Therefore, it is determined to be “YES” in step S1, and the process of reducing the output of the engine and preventing the occurrence of slip is started as described later. First, as shown in FIG. 10, it is determined whether D> 2g (step S23). Here, if “D> 2g”, the command value Q is set to “15” (step S24), and if “DV ≦ 2g”, the command value Q = 8 + (5/7) DV (Step S2)
Five). Then, the command value Q set in steps S25 and S26 is sent to the engine ECU, and the process of reducing the output of the engine is executed (step S26). Then, the maximum wheel speed Vb shown in FIG. 10 while the command value Q is being output.
And the time b at that time are stored (step S27). This engine output reduction control is continued until time t4 in FIG. 10, and the determination is based on the process of step S28. That is, in step S28, the differential value D <0 and the deviation DV
It is determined whether or not <γ (= 5). That is, the wheel speed VW peaks at time t3 due to the reduction of the engine output torque due to the A command started at time t2, and thereafter, the wheel speed VW decreases toward the vehicle speed VB. Then, at time t4, the condition of step S28 is satisfied, and the A command is ended.

By the way, at time t4 in FIG.
When the determination of 8 is satisfied, the process proceeds to step S29, where α · t is set as the command value Q, and t = vb−vt / (t−b) is set (step S29). 10th based on this command value Q
Engine output reduction processing is executed according to the B command shown in the figure (step S30). Then, the engine output reduction control by the B command is performed until the deviation DV becomes smaller than "0" (step S31). On the other hand, if the deviation DV is equal to or greater than "0", the process is repeated until "NO" is determined in step S31. On the other hand, the above step S3
When it is determined to be "NO" in 1, the time t when "DV = 0" is stored as the time d, and the command value Q at that time is stored.
Is stored as Qd (step S32). Next, the command value Q
Is set to "Qd-β / t-d" (step S33), and the engine output reduction process is executed based on this command value Q (step S34). This output reduction processing is continued until the deviation DV reaches the vehicle body speed VB. That is, when it is determined to be “YES” in step S35, the process returns to step S21, and the process ends. On the other hand, the above step S3
When it is determined to be “NO” in 5, that is, when the deviation DV is larger than the vehicle body speed VB, “DV> 0” and “DV> 0”
> 0 ”(step S36), the above step S
The process after 33 is repeated.

On the other hand, if "YES" is determined in the above step S36, vd, b, d, vd are cleared and the process is ended.

[Effects of the Invention] As described in detail above, according to the present invention, the control signal A for immediately stopping the slip of the driving wheels and the control signal B for making an appropriate output according to the road surface μ after the control signal A are provided. Since the control is performed, it is possible to provide an acceleration slip prevention method capable of preventing the occurrence of the slip quickly when the slip is started and by controlling according to the road surface μ (particularly low μ road). You can

[Brief description of drawings]

FIG. 1 is a block diagram showing an acceleration slip prevention method according to an embodiment of the present invention, FIG. 2 is a flowchart showing the operation of the same embodiment, and FIG. 3 is a time-dependent change of wheel speed, output rate, and output torque. Fig. 4 is a diagram showing changes in wheel speed over time, and Fig. 5 is a diagram showing a relationship between engine torque Te-engine speed Ne and intake air amount / engine speed (A / N). Fig. 6 shows the relationship between slip ratio and road surface μ, and Fig. 7 shows the intake air amount / engine speed (A / N) and output ratio K0.
FIG. 8 is a block diagram showing an acceleration slip prevention method according to another embodiment of the present invention, FIG. 9 is a flowchart showing the operation of another embodiment of the present invention, and FIG. Diagram showing changes over time in wheel speed, output rate, and output torque,
Fig. 11 shows intake air amount / engine speed (A / N) and command value Q
It is a figure which shows the relationship between and an output coefficient. 11,12 …… Drive wheel wheel speed sensor, 13,14 …… Driven wheel wheel speed, 15,16 …… Average circuit, 17 …… Traction control ECU, 18 …… Engine ECU.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Ikeda 5-3-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (56) Reference JP 62-237047 (JP, A) JP 62-203939 (JP, A) JP-A-63-38625 (JP, A)

Claims (4)

(57) [Claims] 1. An acceleration slip prevention method for preventing an acceleration slip of a vehicle by detecting an acceleration slip state of a drive wheel and reducing an engine output in accordance with the degree of the slip state to increase a drive wheel speed. Shows a fast trend,
When it is detected that the vehicle speed exceeds the reference speed that is calculated based on the vehicle speed and the driving wheel speed shows a deceleration tendency and becomes lower than the predetermined speed based on the reference speed, the predetermined means is used. A first step of executing a reduction of the engine output based on the determined first output rate, and a driving force larger than the first output rate and driving until it is determined that the slip has stopped after the completion of the first step. The second output rate required to obtain a drive torque equal to the torque that can be transmitted from the wheels to the road surface is set based on the drive wheel rotation deceleration at the time of deceleration of the drive wheels during the execution of the first step. Acceleration slip is prevented by the second step of executing the recovery of the engine output reduced in the first step based on the second output ratio, and the acceleration slip. Stop method. 2. The second output rate K1 of the second step is an initial value of K1 based on the output rate K0 of the first step, the intake air amount A / N at the start of the second step, and the deceleration. Is defined as K1 = K0-I · / {a · (A / N + b)}, and then K1 is set so as to increase and correct the initial value in accordance with the passage of time. The acceleration slip prevention method according to claim 1. 3. The acceleration slip prevention method according to claim 1, wherein the output ratio K0 in the first step is set in correspondence with the intake air amount A / N. 4. The first and second output rates are determined in each step based on a command value determined respectively and a map preset by the intake air amount A / N detected at each time. An acceleration slip prevention method characterized by the following.