JPH07115606B2 - Vehicle driving force control system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle driving force control system for controlling a driving force of a vehicle.

Conventional technology Originally, in the drive system of a vehicle, the throttle valve opens according to the amount of depression of the accelerator, and the driving force increases. However, when the vehicle starts or accelerates on a road surface with low frictional resistance, for example, on a snowy road or ice, the tires slip and cause an excessive spin, and the driving force of the vehicle does not sufficiently contribute to the operation of the vehicle.
A driving force control device (traction control device that suppresses the driving force by automatically detecting the amount of spin and automatically throttles the throttle valve to detect the amount of spin in order to speedily operate the vehicle while eliminating such loss of driving force. (Also called) (Japanese Patent Publication No. 58-20051 and Japanese Patent Laid-Open No. 60-240531).

For example, when an excessive spin of the drive wheels occurs due to the driver's excessive depression of the accelerator pedal, traction control is performed to suppress the excessive spin. This control compares the threshold value with a control variable that uses the spin speed or its acceleration.When the control variable exceeds the threshold value, the throttle valve is closed, while the control variable is below the threshold value. Then, control the throttle valve to open.

However, the conventional driving force control system has the following problems (1) and (2) because the opening / closing speed of the throttle valve is kept substantially constant during the traction control.

Problems to be Solved by the Invention (1) On a road surface having a small friction coefficient, for example, an icy road or a snow-covered road, the driving wheel receives a small force from the road surface. Therefore, if the throttle valve is controlled to open and close at a predetermined speed, the opening and closing speed of the throttle valve will be too fast and the throttle valve will be opened and closed more than necessary, and excessive spin will occur periodically. However, there is a problem in that the pitching vibration of the vehicle body is generated and the engine noise is periodically increased, which gives the driver a strange feeling.

On the other hand, if excessive spin occurs on a road surface with a normal friction coefficient, such as asphalt road surface,
If the opening / closing speed of the valve is controlled at a predetermined speed, the opening / closing speed of the throttle valve will not be sufficient and it will take time for the throttle valve to open up to the throttle valve opening determined by the driver's accelerator depression. There is a drawback that it becomes worse and you cannot drive as you wish.

(2) Due to the characteristics of the engine, excessive spin is likely to occur when the vehicle speed is low and the engine rotation has a margin. This relationship can be understood from the graph of FIG. As shown in the graph, the spin speed (driving wheel speed-vehicle body speed) is 0 to
When changing in the range of 10 km / h, when the vehicle speed is 0 km / h,
The change value of the spin rate is 0 to 1. At 10 km / h, the spin rate variation range is 0 to 0.5.

The spin rate of 0.5 means that the vehicle speed is Vkm / h, while the drive wheel speed is 2Vkm / h.

Then, as the vehicle body speed increases, the change rate of the spin rate becomes narrower, and becomes 0-0.2 at 40 km / h. In general, the friction coefficient μ between the road surfaces of tires has a peak value with respect to the spin rate as shown in FIG. 6, and the friction coefficient decreases as the peak is crossed to the right, so that spin is more likely to occur. That is, as the vehicle body speed becomes slower, the variation range of the spin rate becomes larger with respect to a constant spin rate variation, so that spin is likely to occur.

Therefore, if excessive spin occurs like in the conventional system, if traction control is always performed at the same throttle valve opening / closing speed, excessive spin may occur periodically at low speed. On the other hand, when excessive spin occurs at high speed, there is a drawback that the acceleration of the vehicle deteriorates.

The same problems as described above can be applied to a vehicle equipped with a constant speed traveling device (auto drive device). That is, the constant speed traveling device is a device that automatically controls the opening of the throttle valve so as to maintain the target speed set by the driver. In this device, if the throttle valve opening speed is controlled to be constant, the acceleration / deceleration is controlled to be large when the target speed is low, while the acceleration / deceleration is controlled to be bad when the target speed is high. There is a drawback that

Means for Solving Problems When a vehicle driving force control system according to the present invention is used in a vehicle equipped with a constant speed traveling device for controlling throttle valve opening so as to maintain a vehicle speed at a target speed. Is a means for detecting a vehicle speed, a means for calculating a control change in relation to the difference between the vehicle speed and a target speed, and a throttle valve opening speed and a closing speed in relation to the vehicle speed. Means and means for judging whether or not the control variable is larger than the predetermined threshold value are provided, and if it is judged to be larger, the throttle valve is controlled at the calculated closing speed of the throttle valve. If it is judged to be small, the throttle valve is controlled at the calculated opening speed of the throttle valve to run at a constant speed.

Further, when the driving force control system for a vehicle according to the present invention is used in a vehicle equipped with a traction control device that controls the throttle valve opening so as to suppress the excessive spin, the excessive spin is detected, and the excessive spin is detected. Means for calculating a control variable in relation to the spin, means for detecting the vehicle body speed, means for detecting the vehicle body acceleration, and the vehicle body speed and the opening and closing speeds of the throttle valve in relation to the vehicle body speed. A means for calculating and a means for judging whether or not the control variable is larger than a predetermined threshold value are provided, and when it is judged to be larger, the throttle valve is controlled at the calculated closing speed of the throttle valve. On the other hand, if it is determined to be small, the traction control is performed by controlling the throttle valve at the calculated opening speed of the throttle valve.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First Embodiment FIG. 1 shows a first embodiment of a driving force control system for a vehicle according to the present invention, and shows a case where the driving force control system is applied to a vehicle equipped with a traction control device. The left drive wheel speed detector Vd1 detects the rotational speed of the left drive wheel, and the right drive wheel speed detector Vd2 is
The rotation speed of the right drive wheel is detected. The left non-driving wheel speed detector Vn1 detects the rotational speed of the left non-driving wheel, and the right non-driving wheel speed detector Vn2 detects the rotational speed of the right non-driving wheel.

The signals from the left and right non-driving wheel speed detectors Vn1 and Vn2 are sent to the vehicle body speed detector V and the vehicle body acceleration detector A, respectively.
Is calculated. Both calculation results are sent to the driving force control unit 2.

Further, receiving the signals from the detectors Vd1 and Vn1, the left spin detector S1 calculates the speed difference between the left and right front wheels, that is, the spin amount of the left driving wheel. Similarly, receiving signals from the detectors Vd2 and Vn2, the right spin detector S2 calculates the speed difference between the right and left front wheels, that is, the spin amount of the right driving wheel. The spin amounts S1 and S2 are both sent to the driving force control unit 2 and the driving force control variable Fe that represents the spin behavior of the driving wheel due to the spin. To calculate. The driving force control variable Fe is not limited to the above equation,
Other expressions, for example Etc. can also be used. Also, the spin amount S1, S2
May be calculated in the driving force control unit 2. Further, the input information of the vehicle body acceleration detector A is not limited to the above-mentioned information, and the longitudinal acceleration sensor of the vehicle body may be directly attached to the vehicle body, and its output value may be input through the A / D converter. There is something. Incidentally, in the figure, the dotted line portion can be housed in one unit.

The driving force control unit 2 controls the throttle
An open signal, a close signal or a hold signal for opening and closing the valve at a calculated speed is sent to a dynamic power actuator 4 composed of a stepping motor to open and close a throttle valve (not shown). As a result, the driving force of the engine 6 is controlled. A DC motor, hydraulic or negative pressure solenoid
It is also possible to use a valve or the like. Driving force control unit 2
Is further connected to the accelerator 8 and the accelerator opening signal Ac
Receive.

Next, the operation of the driving force control system according to the present invention will be described with reference to the flow chart of FIG.

In step # 1, the driving force control variable Fe is calculated. In step # 2, a scale factor Ka Ka = Ca × A + C ₁ (Ca and C ₁ are constants) that depends on the vehicle body acceleration A is calculated, and in step # 3, a scale factor Kv Kv = Cv × V + C that depends on the vehicle body speed V. Calculate ₂ (Cv and C ₂ are constants). The multiplication factor Ka is 0.25 when the vehicle body acceleration is zero as shown in FIG. 3A, increases as the acceleration increases, and becomes 1 when the acceleration increases to 0.3G. The magnification Ka is kept at 1 when the vehicle body acceleration is 0.3 G or more. As shown in FIG. 3B, the multiplication factor Kv is 0.5 when the vehicle speed is zero, increases as the vehicle speed increases, and becomes 1 when the vehicle speed increases to 40 km / h. The magnification Kv is kept at 1 when the vehicle speed is 40 km / h or higher.

In step # 4, the speed at which the throttle valve is closed by traction control Ec Ec = Ka × Kv × Ecm is calculated. Here, Ecm is the maximum closing speed of the throttle valve in traction control. Further, in step # 5, the speed at which the throttle valve is opened by traction control Eo E ₀ = Ka × Kv × Eom is calculated. Here, Eom is the maximum opening speed of the throttle valve in traction control.

The open / close direction of the opening / closing speed signal of the throttle valve may be distinguished by using the signs (+) and (−). In the following, when comparing the magnitudes of the opening / closing speed signals, the absolute values are compared without considering (+) and (-).

As is clear from the above formula, the speed Ec at which the throttle valve is closed and the speed Eo at which the throttle valve is opened are proportional to the magnification factors Ka and Kv, and therefore increase as the vehicle body acceleration increases and the vehicle body speed increases. The velocities Ec and Eo do not increase with the maximum velocities Ecm and Eom, respectively.

In step # 6, the driving force control variable Fe is compared with a predetermined threshold value Ft. If the driving force control variable Fe is equal to or exceeds the threshold value Ft, the process proceeds to step # 7 to open / close the throttle valve. While selecting Ec as the speed signal E,
If not, go to Step # 9 and throttle
Eo is selected as the valve opening / closing speed signal E.

In step # 8, the timer is reset and then the process proceeds to step # 12. In step # 10, it is determined whether the timer is counting up to the maximum value. If the timer has counted up to the maximum value, it proceeds to step # 12, and if it has not counted up to the maximum value, it proceeds to step # 11 to count up the timer, and then proceeds to step # 12.

In step # 12, the count value Te of the timer is the threshold value Tt.
(Threshold value Tt is smaller than the maximum count value of the timer) It is judged whether or not it exceeds, and if it exceeds or equal, the process proceeds to step # 14, and the throttle valve opening / closing speed signal E is opened / closed in the normal mode. Speed signal Eg,
That is, the throttle valve opening (or closing) speed signal is selected so that the throttle valve opening quickly follows the accelerator opening. The normal opening / closing speed signal Eg
Changes depending on the difference between the accelerator depression amount and the throttle valve opening, and its maximum value is larger than the maximum opening (or closing) speed signal Eom (Ecm) during traction control. After that, the routine proceeds to step # 15, the opening / closing speed signal E of the throttle valve is output in the normal mode, and then the routine returns.

On the other hand, when the count value Te of the timer does not exceed the threshold value Tt, the process proceeds to step # 13 and traction control is executed. In this case, the throttle valve opening / closing speed signal E uses either the calculated signal Ec or Eo. Then proceed to step # 16 and return.

Now, consider the operation when starting on a relatively slippery road surface. As shown in FIG. 4 (A), at start t ₀
At −t _1, only the driving wheels start to rotate vigorously, and the non-driving wheels
It barely turns, and if it is left as it is, it will not start as the driver desires. During this period, the driving force control unit 2
The driving force control variable Fe is calculated (step # 1), and the calculation result is shown in FIG. 4 (B). Steps # 2, # 3, #
In 4 and # 5, the throttle valve opening speed Eo and closing speed Ec for traction control are calculated. At start t ₀ −t ₁ ,
Since the driving force control variable Fe is smaller than the threshold value Ft, the process proceeds from step # 6 to step # 9, and the signal Eo is selected as the opening / closing speed signal E of the throttle valve. Next step # 10
Then, it is determined whether or not the timer provided in the control unit 2 is in the state of counting up to the maximum value. Initially, the maximum value is set, so the process proceeds to step # 12, and then to step # 14. In step # 14, the opening / closing speed signal E of the throttle valve is replaced with the signal Eg, and the throttle valve is controlled in the normal mode, that is, the opening degree that follows the accelerator opening degree (step # 15). In the control in the normal mode, the solid line showing the accelerator opening Ac and the dotted line showing the throttle valve opening Th overlap with each other as shown by time t ₀ -t ₁ in FIG. 4 (D). Can also understand.

Since the driving force control variable Fe exceeds the threshold value Ft until time t ₂ after time t ₁ , step # 7 is entered after step # 1 to # 6 and the opening / closing speed signal E of the throttle valve is set. After selecting the signal Ec as, the timer is reset to zero in step # 8. Here, since the count value Te of the timer is smaller than the threshold value Tt, steps # 12 to #
Proceeding to 13, traction control is started. That is, the throttle valve opening is suppressed to a small value by the signal Ec for closing the throttle valve, and the going spin is suppressed.

At time t ₀ -t ₁ , both the vehicle body acceleration A and the vehicle body speed V are small, so the speed signal for closing the throttle valve is
Ec is small. This can be understood from the fact that the negative slope of the dotted line Th is small. Also, in the figure, the dotted line Th is shown as a straight broken line, but in reality, the speed signal Ec may change from moment to moment, so the dotted line Th is rather a curve.

Until time t ₃ after time t ₂ , the driving force control variable Fe becomes smaller than the threshold value Ft, so that steps # 1, # 2, # 3, # 4,
Proceeding to # 5, # 6 and # 9, the signal Eo is set as the opening / closing speed signal E of the throttle valve. After that, the process proceeds to steps # 10 and # 11 to start counting up the timer. While the count value Te is smaller than the threshold value Tt, the process proceeds to steps # 12 and # 13, and the throttle valve opening degree is gradually increased by the signal Eo for opening the throttle valve.

Now, at time t ₃ , before the count value Te of the timer reaches the threshold value Tt, the spin increases again and the driving force control variable Fe becomes larger than the threshold value Ft. In this case, steps # 1, # 2, # 3, # 4, # 5, # 6, #
7, the timer is reset after setting E = Ec, and the process proceeds to steps # 12 and # 13. As a result, the throttle valve is closed again by the signal Ec for closing the throttle valve again.

Such control is repeated several times, and at time t ₄ ,
It is assumed that the driving force control variable Fe becomes smaller than the threshold value Ft again. This causes the timer to start counting from zero again.
Up, steps # 1, # 2, # 3, # 4, # 5,
# 6, # 9, # 10, # 11, # 12, # 13 and # 16 are repeatedly executed, and the throttle valve is opened. Since the vehicle speed is also high at this point, the opening speed of the throttle valve is also higher than the opening speed at the start (t ₀ −t ₁ ).

At time t ₅ , when the count value of the timer exceeds the threshold value Tt, the traction control ends, and thereafter, steps # 1, # 2, # 3, # 4, # 5, # 6, # 9, # 10. ,
# 11, # 12, # 14, # 15, # 16 are repeatedly executed, and the throttle valve opening Th is set to follow the accelerator opening Ac.
Is controlled. The throttle valve opening Th matches the accelerator opening Ac before the time t ₅ , but the control is performed in # 13 so that Th ≦ Ac even during the control.

Next, a second embodiment of the driving force control system according to the present invention will be described.

The second embodiment is an embodiment in which the driving force control system is used in a vehicle equipped with a constant speed traveling device. Compared with the configuration of the first embodiment, the constant speed traveling device 10 (shown by a chain line in FIG. 1) is used. ), And sends a signal Vt corresponding to the target vehicle speed set by the driver to the driving force control unit 2. When the constant speed traveling device 10 is activated, the flowchart shown in FIG. 5 is executed. The operation of the second embodiment will be described below with reference to this flowchart.

In step # 21, the driving force control variable Fe To calculate. In the case of constant speed traveling, it is not necessary to consider the vehicle body acceleration A or the spin amounts S1 and S2, and therefore the driving force control variable Fe is calculated using the vehicle body speed V and the target speed Vt. Second
The control variable Fe in the embodiment is, for example, Also good.

In step # 22, the magnification Kv depending on the vehicle body speed V is calculated in the same manner as described above, and in steps # 23 and # 24, the throttle valve opening speeds Eo for constant speed running control, Eo = Kv × Eom closed. The velocity Ec Ec = Kv x Ecm is calculated.

Here, the reason why the magnification Ka that depends on the vehicle body acceleration A is not used is that the acceleration is almost equal to zero when the vehicle is traveling at a constant speed.

In step # 25, the control variable Fe and the threshold Ft are compared, and if the control variable Fe is equal to or larger than the threshold Ft,
Proceeding to step # 26, the signal Ec is selected as the opening / closing speed signal E of the throttle valve. On the other hand, the control variable Fe is the threshold
If it is smaller than Ft, the routine proceeds to step # 27, where the signal Eo is selected as the throttle valve opening / closing speed signal E.

Then, in step # 28, it is determined whether or not the constant speed traveling has been canceled. This determination is made by detecting an action that hinders constant-speed running, such as depression of a clutch, depression of a brake, depression of an accelerator, or the like.

If it is determined that the constant speed running has been canceled, the process proceeds to step # 29, and the throttle valve opening / closing speed signal E
Select the opening / closing speed Eg in the normal mode as.

In step # 30, the opening / closing speed of the throttle valve is controlled by the selected opening / closing speed signal, and the process returns.

In the second embodiment, the opening / closing speed of the throttle valve for achieving constant speed running is changed according to the vehicle body speed V. Therefore, when the constant speed running is set to a low speed, the throttle valve is relatively open. Even if the opening / closing speed of the is slow, the constant speed can be maintained quickly, but if the constant speed running is set to high speed, the opening / closing speed of the throttle valve should be faster than the low speed and the speed should be set quickly. Achieve speed maintenance.

In both the first and second embodiments, the second threshold value Ft '(Ft'<Ft) of the control variable Fe is set, and when the control variable Fe exceeds the threshold value Ft, the throttle valve When the control variable Fe falls below the threshold value Ft ′, the throttle valve is opened and the control variable Fe is closed.
If is between the thresholds Ft and Ft ′, the opening of the throttle valve may be maintained or controlled to be opened at a value much smaller than Eo.

Further, in both the first and second embodiments, if the mechanism for opening and closing the throttle valve by the stepping motor, the change in the opening / closing speed of the throttle valve depends on the pulse rate of the pulse applied to the stepping motor. It is also possible to change the pulse rate or keep the pulse rate constant while adding pulse groups intermittently. Also, if the DC motor is used to open and close the throttle valve,
You may use the PWM control system which changes the duty ratio of the pulse added to a DC motor. In addition, if the solenoid valve is used to open and close the throttle valve, various methods such as using the above-mentioned PWM control method or varying the continuous execution time of the open or close signal and outputting at a certain fixed period are possible. To be

As described above in detail, when the vehicle driving force control system according to the present invention is applied to the traction control device, the opening / closing speed of the throttle valve is controlled in relation to the vehicle body speed and the vehicle body acceleration. In other words, in other words, when opening and closing the throttle valve at high speed or low speed,
Alternatively, the throttle valve is controlled slowly at low speed or when traction control is performed on a road surface with a small friction coefficient because it is executed at a speed suitable for a road surface with a large friction coefficient or a road surface with a small friction coefficient. ,
While suppressing excessive spin rapidly without periodically generating excessive spin, when traction control is performed at high speed or on a road surface with a large friction coefficient, the throttle valve is controlled promptly and acceleration performance is impaired. It becomes possible to drive as the driver desires without the need.

Further, when the vehicle driving force control system according to the present invention is applied to a constant speed traveling device, the opening / closing speed of the throttle valve is controlled in relation to the vehicle body speed.
In other words, since the opening / closing speed of the throttle valve is executed at a speed suitable for low speed or high speed, when the constant speed traveling control is performed at low speed, the throttle valve is controlled slowly. When the constant speed running control is performed at high speed, the throttle valve is quickly controlled, the constant speed running can be maintained more quickly, and the deviation of the vehicle speed from any target vehicle speed can be kept to the minimum. .

As is apparent from the above, in the driving force control system according to the present invention, the driving force is controlled as smoothly as possible, and the vehicle acceleration and the cornering force are reduced due to the unnecessary change of the spin of the driving wheels. It is effective when used in a traction control system that controls the driving force of the vehicle or a constant-speed running system that keeps the vehicle speed constant, because it prevents deterioration of vehicle body stability and discomfort given to the driver due to changes in engine sound. Target.

[Brief description of drawings]

FIG. 1 is a block diagram of a vehicle driving force control system according to the present invention, FIG. 2 is a flowchart of the first embodiment, and 3A.
Figures and 3B are graphs showing magnification Ka and Kv, respectively.
FIG. 5 is an operation explanatory view of the first embodiment, FIG. 5 is a flow chart of the second embodiment, and FIG. 6 is a graph showing the relationship between the friction coefficient and the spin rate. 2 ... Driving force control unit 4 ... Driving force actuator 6 ... Engine, 8 ... Accelerator 10 ... Constant speed traveling device

Claims (2)

[Claims] 1. A vehicle equipped with a constant speed traveling device for controlling a throttle valve opening so as to maintain a vehicle speed at a target speed (Vt), and a means for detecting the vehicle speed (V), Means for calculating the control variable (Fe) in relation to the difference between the vehicle speed (V) and the target speed (Vt), and the opening speed (Eo) of the throttle valve in relation to the vehicle speed (V) Means for calculating the closing speed (Ec) of the throttle valve in relation to the vehicle speed (V), and whether the control variable (Fe) is greater than the predetermined threshold value (Ft). When it is judged to be large, the throttle valve is controlled by the calculated closing speed (Ec) of the throttle valve, while when it is judged to be small, the calculated throttle valve The throttle valve is controlled by the opening speed (Eo) to run at a constant speed. Driving force control system for a vehicle according to claim Rukoto. 2. A vehicle provided with a traction control device for controlling throttle valve opening so as to suppress excessive spin of a vehicle drive wheel, wherein the excessive spin is detected and a control variable is associated with the excessive spin. Means for calculating (Fe), means for detecting the vehicle body speed (V), means for detecting the vehicle body speed (A), and throttle for the vehicle body speed (V) and the vehicle body acceleration (A). A means for calculating the closing speed (Ec) of the valve, a means for calculating the opening speed (Eo) of the throttle valve in relation to the vehicle body speed (V) and the vehicle body acceleration (A), and the control variable (Fe ) Is larger than a predetermined threshold value (Ft), and if it is larger, the throttle valve is controlled by the calculated closing speed (Ec) of the throttle valve. On the other hand, if it is judged to be small, The opening speed of the issued throttle valve (Eo)
A driving force control system for a vehicle, characterized in that a throttle valve is used to control traction.