JPH0466735A - Traction control method of vehicle - Google Patents

Abstract

PURPOSE:To surely prevent generation of engine stall at the time of traction control by setting a driving torque and the like to a specified limit value when engine speed and the like drops to a specified value or less, and determining the limit value as a function of vehicle speed and the like. CONSTITUTION:Signals of respective speed sensors 23 provided on rear wheels 22R, 22L which are driving wheels and front wheels 21R, 21L which are driven wheels, an accelerator opening sensor 31, an air flow meter 32, a throttle opening sensor 33, a rotational sensor 36, a vehicle inclination sensor 37 and the like, are inputted to the sensor input circuit 13 of a control circuit 1. An output signal is given from a driving circuit 16 to a stepping motor 34 which drives a throttle valve 35 in its opening/closing state in response to a processed result by a CPU 11. In this case, when at least one of an engine speed, an intake pipe pressure and an intake quantity is at a specified value or less a driving torque or a control torque is set to the specified minimum or maximum value. The above respective values are determined as functions of at least one of the vehicle speed, frictional coefficient of road surface and inclination of the road surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a traction control method for a vehicle, and more particularly to a traction control method for a vehicle that can effectively prevent engine stall during traction control in a manual transmission vehicle.

[Prior Art] Traction control is performed on so-called low μ roads such as snowy roads to prevent lateral vibration due to wheel slip during sudden start. For example, as shown in Fig. 7, after the throttle valve is opened and the vehicle starts moving, if the drive wheel speed becomes excessive compared to the vehicle body speed, that is, the slip ratio becomes excessive, the throttle opening is reduced (as shown in the figure). Point A), the drive wheel speed is reduced to a target speed that indicates a predetermined slip ratio.

[Problem to be Solved by the Invention] By the way, when the driving wheel speed decreases to the target speed (point B in the figure), an attempt is made to open the throttle valve again to maintain the driving wheel speed at the target speed, but the surge tank, etc. Due to the intake side capacity, the engine output does not increase immediately, and the driving wheel speed decreases to the vehicle speed. If this vehicle speed is low, an engine stall may occur (point 0 in the diagram).

In addition, when the vehicle is in a low gear, the torque reduction rate is reduced (Japanese Unexamined Patent Publication No. 62-186021), or when the vehicle speed is low, the slip tolerance is increased (Japanese Patent Application Laid-Open No. 63-1155).
No. 48), there is something to prevent the occurrence of engine stalling, or engine stalling is unavoidable when the load is large, such as when starting on a slope.

In addition, Japanese Patent Application Laid-open No. 63-31862 proposes setting a lower limit to the throttle opening during traction control, but as is clear from Figure 18 of the publication, the lower limit is set when the vehicle speed is zero, that is, when the vehicle starts. If the engine speed also becomes zero, there is a possibility that the engine will stall.

The present invention has been made in view of this background, and an object of the present invention is to provide a traction control method for a vehicle that can reliably prevent the occurrence of engine stalling during traction control.

[Means for Solving the Problems] The present invention will be described in detail. In a vehicle traction control method for controlling driving torque or braking torque in order to suppress the wheel slip rate to a certain limit, engine speed, intake pipe pressure and When at least one of the intake air amounts is below a predetermined value, the driving torque or braking torque is set to a predetermined lower limit value or upper limit value, and the lower limit value or upper limit value is set to the vehicle speed, the friction coefficient of the road surface, and the road surface. It is characterized in that it is determined as a function of at least one of the gradients.

[Operation] According to the control method of the present invention, the risk of engine stall is detected when at least one of the engine speed, intake pipe pressure, and intake air amount falls below a predetermined value, and the driving torque or braking torque is adjusted to a predetermined value. Set to the lower limit or upper limit of . Since this lower limit value or upper limit value is determined as a function of at least one of vehicle speed, road surface friction coefficient, and road surface slope, an appropriate lower limit value or upper limit value is determined depending on the presence or absence of a slope and the magnitude of the road surface friction coefficient. A value is applied to the driving torque or braking torque to prevent engine stalling.

[Embodiment] FIG. 1 shows the overall configuration of a control system that implements the control method of the present invention. In the figure, the control circuit 1 is composed of a sensor input circuit 13, a ROM 14, a RAM 15, and a drive circuit 16, which are connected to CFULL by a bus bar 12. Wheel 22R122L and driven wheel front wheel 21R121
Each speed sensor 23 and accelerator opening sensor 31 provided in L
, an air flow meter 32, a throttle opening sensor 33 that detects the opening of the throttle valve 35, a rotational speed sensor 36 that detects the engine rotational speed, a vehicle inclination sensor 37, and the like.

The drive circuit B16 operates according to the processing result by the CPU, which will be described later.
Stepping motor 3 that opens and closes throttle valve 35
4 gives an output signal.

The processing procedure of the CPU will be explained below with reference to FIG.

In FIG. 2, in step 100, the accelerator opening degree AA
, engine rotation speed Ne, vehicle inclination angle (road surface slope) θ, left and right rear wheel speed VWL = VWR1 left and right front wheel speed VL,
VR is input, and in step 101 the slip rate S is calculated using the following formula.

S= (VW-V)/VW Here, VW is the value of the greater of the left and right rear wheel speeds,
■ is the vehicle speed, which is the average value of the left and right front wheel speeds.

Next, in step 10B, it is determined whether the slip rate S exceeds a limit slip rate (for example, 20%) Ss, and if not, normal throttle control is performed in step 110. That is, the target throttle opening TAo is obtained from the accelerator opening AA and the engine speed Ne using a two-dimensional map prepared in advance.

In step 103 above, whether the slip rate S or the limit slip rate S
If it exceeds s, shift to traction control,
In step 104, the slip rate S is set to the target slip rate S.
Throttle opening TAt such that a (for example, 10%)
rC is calculated by the PI control of the following formula.

TAtrC=K 1 ·ΔV+2 fΔVdt Here, ΔV=(1+Sa) ·V −VWKl, K2 is a constant.

In step 105, a throttle opening lower limit value TAmin is set according to the road surface slope θ, the road surface friction coefficient μ, and the vehicle speed V. This lower limit value TAmin is calculated by the following formula.

TAmln=μm TAmlrlO+TAθ Here, TAminO is set as shown in FIG. 3 according to the vehicle speed V at the start of traction control, and becomes zero in a region where the vehicle speed is high (for example, ICHtm/h or higher). The reason for this is
This is because the engine speed does not fall below a value corresponding to the vehicle speed, so even if the throttle opening is reduced, the engine will not stall.

The correction value TAθ is set as shown in FIG. 4 with respect to the road surface gradient detected by the vehicle inclination sensor. This is because when the vehicle is uphill and the slope is θ, a load of Mg5 in θ is applied, assuming the vehicle weight is Mg. Downhill is the opposite.

The correction coefficient μ is set as shown in FIG. 5 with respect to the friction coefficient μ of the road surface. That is, on a low μ road such as on ice, excessive torque will be applied to the rear wheels unless the lower limit value is made smaller than on compacted snow.

In this case, μ can be determined by detecting the torque at the beginning of slippage at the start of traction control using a torque sensor, or by calculating the rear wheel acceleration at the start of slippage from the rear wheel speeds VWR and VWL.

In step 106, the throttle opening TAtrc is compared with the lower limit value TAmin, and if TAtrC is larger, this is set as the target throttle opening TAo (step 109).
).

If TAtrC is small in step 106, the engine speed Ne is set to a predetermined value Neo(
For example, if Ne≧Neo, step 109 is executed. If Ne<Neo, the lower limit is set as the target throttle opening TAo in step 108.
shall be.

Therefore, in step 111, the actual throttle valve 3
5 (Fig. 1) is set as the target throttle opening TA.
The throttle valve 35 is driven to open and close via the stepping motor 34 so as to match the angle o.

The effect of the above control is shown in FIG. In the figure, when the driving wheel speed exceeds the vehicle speed and the slip ratio exceeds the limit slip ratio (point A in Figure 3), traction control is started and the throttle opening is reduced to approximately zero. The engine speed starts to drop and when it drops below 11000 rpm (
8 points in Figure (3)) The throttle opening degree is set to the lower limit value instead of the control-calculated value, and as a result, the throttle valve opens.

As a result, the throttle valve is opened before the drive wheel speed decreases to the target speed, and the drive wheel speed is prevented from significantly overshooting downward beyond the target speed due to a delay in the engine intake system, resulting in the occurrence of an engine stall. is effectively prevented.

In the embodiments described above, the intake pipe pressure, intake air amount, etc. using the throttle opening can be used as indicators of the driving torque.

As in the above embodiment, the lower limit value of the throttle opening is determined by the vehicle speed,
It is not necessary to determine it as a function of both the road surface friction coefficient and the road surface gradient, but it can be determined as a function of at least one of them. Further, the timing at which the control value is switched to the lower limit value is not limited to the engine speed as in the above embodiment, but may be based on the time when the intake pipe pressure or the intake air amount reaches a predetermined value.

In the above traction control, when controlling braking torque instead of driving torque, an upper limit value is set instead of a lower limit value.

"Effects of the Invention" As described above, according to the traction control device of the present invention,
Good traction control at the time of starting can always be performed on low μ roads with various road surface friction coefficients and gradients.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an apparatus that implements the method of the present invention, Fig. 2 is a processing flowchart of C and PU, Figs. 3 to 5 are graphs of change characteristics of various variable values, and Fig. 6 is a diagram of various signals. FIG. 7 is a time chart of various signals in conventional traction control. 1... Control circuit 11... CPU 21R121L... Front wheel 22R122L... Rear wheel (drive wheel) 23... Speed sensor 33... Throttle opening sensor 34... Stepping motor 35... Throttle valve 36...Engine speed sensor 37...Vehicle inclination sensor Fig. 1 Fig. 4 Road surface arrangement Fig. 5 Fig. 6 (rl)m)

Claims (1)

[Claims] In a vehicle traction control method that controls driving torque or braking torque in order to suppress the wheel slip rate to a certain limit, when at least one of the engine speed, intake pipe pressure, and intake air amount falls below a predetermined value, the above-mentioned drive A vehicle characterized in that torque or braking torque is set to a predetermined lower limit value or upper limit value, and the lower limit value or upper limit value is determined as a function of at least one of vehicle speed, road surface friction coefficient, and road surface slope. Traction control method.