JPH01125529A - Drive force controller for vehicle - Google Patents

Abstract

PURPOSE:To restrain drive wheels from slip while trying to obtain an optimum slip rate irrespective of road surface conditions by calculating desired engine torque generating the optimum slip according to a road surface condition to permit a deduced value of engine torque to coincide with a desired value. CONSTITUTION:The slip rate of drive wheels is calculated by a means (h) on the basis of drive wheel speed and driven wheel speed detected respectively by means (a), (b). Also, deduced engine torque is calculated by a means (g) on the basis of engine rotational frequency and engine boost pressure detected respectively by means (d), (e). Further, wheel acceleration is calculated by a means (c) on the basis of the drive wheel speed. Desired engine torque giving an optimum slip rate is calculated by a means (i) on the basis of the gear position, wheel acceleration and deduced engine torque detected by a means (f). Then, when the drive wheel slip rate exceeds a set slip rate, a drive force is controlled by a means (j) so that the deduced engine torque coincides with the desired engine torque.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a driving force control device for a vehicle that prevents drive wheel slippage when traveling on a road with a low friction coefficient, when starting, when accelerating, and the like.

(Prior Art) Conventionally, as a driving force control device for a vehicle, for example,
As shown in Publication No. 8-38347, 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 drive wheel slip, the fuel is cut. A device is known that prevents drive wheel slippage by (stopping fuel supply).

Furthermore, as shown in Japanese Patent Application Laid-open No. 58-202142, a device is known that prevents slippage by applying the brake when a drive wheel slip occurs. As described above, a device is known that prevents drive wheel slip by controlling a throttle valve in the closing direction when slip occurs.

(Problem to be Solved by the Invention) However, in such conventional devices, uniform control is performed when slip occurs, regardless of the road surface condition or engine condition at the time of occurrence of drive wheel slip. Because of this configuration, it was not possible to control the driving force according to road conditions and engine conditions, and the amount of control became excessive.
Otherwise, there is a problem that the control becomes too small, and furthermore, the control tends to be prone to hunting.

For example, in the device disclosed in Japanese Patent Application Laid-Open No. 58-38347, when slip occurs, a fuel cut is performed to rapidly reduce the engine output regardless of the driving wheel slip occurrence condition, and when the slip subsides, fuel recovery (fuel supply restart) and rapidly increase engine output. As a result, if slipping occurs again, the slip is prevented by cutting the fuel again. Therefore, when driving on a road with a low friction coefficient such as an icy road, slipping occurs and is prevented repeatedly during this control. Not only is it not possible to achieve reliable slip prevention, but also during this period, the engine output torque repeatedly increases and decreases, causing the vehicle to be violently shaken back and forth, significantly impairing ride comfort.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems. As shown, there is a driving wheel speed detecting means a for detecting the wheel speeds of the driving wheel and the driven wheel, and a driven wheel speed detecting means for detecting the wheel speeds of the driving wheel and the driven wheel. Calculation means C
, an engine rotation speed detection means d for detecting the engine rotation speed, a boost pressure detection means e for detecting the engine boost pressure, a gear position detection means f for detecting the gear position,
estimated engine torque calculating means g for estimating engine torque based on the engine rotation speed and engine boost pressure; wheel acceleration calculating means g for calculating wheel acceleration based on the wheel speed of the driving wheels; and the gear position, wheel acceleration, a target engine torque calculation means i that calculates a target engine torque from which an optimum slip ratio can be obtained from the estimated engine torque; and a driving force control means j for controlling the driving force so as to match the driving force.

(Function) When the vehicle is running, the slip rate is calculated by the slip rate calculation means C based on the driving wheel speed determined by the driving wheel speed detection means a and the driven wheel speed determined by the driven wheel speed detection means A, and the slip rate calculates the driving wheel slip. The occurrence of slip in the drive wheels is monitored to see if the slip rate exceeds a predetermined set slip rate.

When a slip occurs, the estimated engine torque is calculated by the estimated engine torque calculating means g based on the engine speed and engine boost pressure from the engine speed detecting means d and the boost pressure detecting means e.
The target engine torque is a target engine torque that allows an optimum slip ratio to be obtained based on the gear position from the gear position detection means f, the wheel acceleration from the wheel acceleration calculation means C, and the estimated engine torque from the estimated engine torque calculation means g. The engine torque is calculated by the engine torque calculation means i, and the driving force is controlled by the driving force control means j so that the estimated engine torque matches the target engine torque.

Therefore, the target engine torque that generates the optimal slip can be obtained according to various road surface conditions, and by matching the estimated engine torque to the target engine torque, the drive wheels can slip while converging to the optimal slip rate regardless of the road surface condition. can be suppressed.

(Example) Embodiments of the present invention will be described below based on the drawings.

First, the configuration will be explained.

Figure 2 is a block diagram of the entire system, where l is a wheel speed sensor that generates a frequency proportional to the wheel speed of the driven wheel, the output of which is input to the frequency-voltage converter 3, and a voltage Vc proportional to the wheel speed is input. becomes. A wheel speed sensor 2 generates a frequency proportional to the wheel speed of the driving wheels, and its output is input to a frequency-voltage converter 4, and becomes a voltage Vω proportional to the wheel speed.

The blue voltages Vc and Vω are input to a slip ratio calculation circuit 5, and the calculation result is output as a slip ratio signal S.

On the other hand, the voltage Vω is input to the differentiation circuit 6 and becomes the wheel acceleration Vω. Further, the slip ratio signal S is input to a comparator 7.8 whose output becomes "l" when it is 2% or less and 10% or more, respectively.

The output of comparator 7 is the reset input of flip-flop 9, and the output of comparator 8 is the reset input of flip-flop 9.
is input to the set input of

The output of flip-flop 9 drives relay element IO.

Boost pressure sensor 1 that detects engine boost pressure
1 is input to the amplifier 14, and the amplifier 14 (7) output E
B is input to the engine torque calculation circuit 17. Further, the engine rotation sensor 12 outputs a frequency proportional to the engine rotation speed, which is input to the frequency-voltage converter 15, becomes a voltage ER proportional to the engine rotation speed, and is input to the engine torque calculation circuit 17. The output ET of this engine torque calculation circuit 17 is input to a road surface reaction force calculation circuit 19. The output ETO of the road surface reaction force calculation circuit 19 is input to the optimum throttle opening calculation circuit 20.
Signal A is output from 0.

The accelerator opening sensor 13 outputs a voltage proportional to the accelerator opening, which is input to an amplifier 16, which outputs a signal B.

On the other hand, the engine rotation signal ER is input to the optimum engine rotation storage circuit 18. The output of the comparator 8 is input to this circuit 18, and the storage timing is determined by the output of the comparator 8.

The output of the optimal engine rotation storage circuit 18 is input to the optimal throttle calculation circuit 20.

Signal A from the optimal throttle opening calculation circuit 20 and signal B from the amplifier 16 are input to the relay element 10, and the output of the relay element IO for selecting signal A or signal B is input to the throttle actuator 21. , controls the opening degree of the throttle valve 22.

The gear position sensor 23 detects the gear position, and its sensor output is input to the gear ratio signal generation circuit 24 and the inertia calculation circuit 25, and the outputs from both circuits 24 and 25 are input to the road reaction force calculation circuit 19. Ru.

Next, the effect will be explained.

First, as shown in Figure 3, the wheels have inertia.
Torque IeM(I; inertia moment, i;
The motion is determined by the driving torque TE, the road reaction force Drukr@W (p; friction coefficient tr between road surface and tires; turning radius; W; wheel load); however, the engine torque When it is smaller than the road reaction force, the wheel speed Vω of the driving wheels is slightly larger than the wheel speed Vc of the driven wheels, and the wheels rotate in an optimum slip ratio region with a small slip ratio.

For example, if the accelerator opening is constant, the torque generated by the engine is constant, so the driving torque of the drive wheels by the engine is balanced with the reaction torque from the road surface, and the vehicle runs at a constant speed. In other words, this state is shown from time to to 1+ in FIG.

Next, when the driver depresses the accelerator pedal, the engine torque becomes large, exceeding the reaction torque from the road surface, and the drive wheels begin to slip significantly.

Here, if we look at the relationship between the slip ratio S, the friction coefficient in the longitudinal direction of the wheel, and the lateral force CF, we can see that as the slip ratio S increases, the friction coefficient decreases and the lateral force CF increases. It can be seen that there is a significant decrease. This means that the vehicle is unstable in the lateral direction and is likely to spin.In order to prevent this situation, the slip ratio S must be reduced to a small value, as is done in conventional systems. All you have to do is maintain this condition, and all you have to do is control the engine torque to achieve this.

Therefore, an overview of the driving force control in this embodiment will be described.

By detecting the condition of the engine, the engine torque is detected when the slip becomes large, and by detecting the behavior of the wheels, the friction condition between the road surface and the tires is detected, and both of these will optimize the slip. The throttle opening is controlled so as to generate the target engine torque.

More specifically, control is performed as follows.

First, the slip rate S of the driving wheel is calculated by the slip rate calculation circuit 5 based on the wheel speeds of the driven wheel and the driving wheel.

Further, the engine torque calculation circuit 17 estimates and detects the engine torque ET from the engine boost pressure and the engine rotational speed, and the differentiation circuit 6 calculates the wheel acceleration ω based on the wheel speed Vω of the driving wheels.

In this way, the engine torque R when slip occurs
This means that T and the wheel acceleration ma ω can be found.

When the wheels are moving with slippage, they are balanced by the following equation as shown in Figure 3.

I @ tL= go r e W-T
E・−・■In other words, if you know TE, you can know φr・W. Further, the slip rate varies greatly depending on the road surface, but reaches its maximum value at a slip rate of 10% to 20% on any road surface. Furthermore, the number of tiles increases monotonically with respect to the slip rate until this maximum value is reached.

Therefore, if we find the engine torque, wheel acceleration, and gear position when the wheel slip approaches the maximum value (for example, when the slip rate is 10%), we can find that the friction coefficient L becomes the maximum, stable slip occurs, and This means that it is possible to predict the engine generated torque TENG at which the wheel lateral force CF results in a large slip ratio (for example, about 5%).

That is, when S=0.1, the snake is mu0.1, TEITE
If O,1,g is JLO,1, then the road reaction torque is po,1 er IIW= I ・(+)0.1
+TE0.1...Can be calculated with ■. Also, if the value of Le when the slip rate is 5% is po, 05, and this is set to 2.0.1, then the road reaction torque at JLo, 05 is #L0.05* r *W= * JLo, 1 *
It can be expressed as r eW 1 hat strange. As a result, if ω is set to a specified value (for example, 0), the value of TH at this time is: TE=Ke Bo, 1 e reW-I 6M
...It can be calculated as ■. In other words, the slip rate S is 0.1
Based on the engine torque and wheel acceleration when , the slip ratio is set to 0.05. Driving torque T where wheel acceleration is M
E can be calculated.

In addition, the driving torque TE is TE=N・TENG...■(N; gear ratio, TENG, engine generated torque), and the inertia moment I is I=N・IENG+IW...■(IEN
G: Engineer inertia moment, IW: Wheel inertia moment).

Therefore, it is sufficient to control the throttle opening so as to generate this driving torque TE.

Hereinafter, the effects will be explained in the following order: before the slip occurs, when the slip occurs, and when the slip decreases.

(a) Before the occurrence of slip The slip rate calculating circuit 5 always calculates the slip rate S based on the wheel speed Vc detected from the driven wheels and the wheel speed Vω detected from the driving wheels. Since there is little slip from time to to tl in FIG. 5, comparator 7 outputs "1",
Flip-flop 9 is outputting °'0'.

Further, based on this output, the relay element selects the signal B, and the throttle actuator 21 opens and closes the throttle valve 22 in accordance with the B signal.

That is, since the signal B is a signal that detects the accelerator opening degree, the throttle valve 22 is ultimately moving in response to the accelerator pedal.

(b) When a slip occurs When the operator depresses the accelerator pedal greatly at time t1 in Fig. 5, the throttle opening opens widely accordingly.
Engine torque increases (Figure 7). This engine torque then increases the slip between the wheels and the road surface.

Now, as shown in FIG. 6, the torque generated by the engine is determined by the engine speed and the boost pressure of the engine. Further, the engine boost pressure has good responsiveness to the engine generated torque.

Therefore, a signal EB proportional to the boost pressure obtained by the boost pressure sensor 11 and the amplifier 14, and a signal EB proportional to the engine rotation speed obtained by the engine rotation sensor 12 and frequency-voltage converter 15, which generate a frequency proportional to the engine rotation speed. Based on the signal ER, the engine torque can be estimated using the engine torque estimating circuit 17 having an internal data map. Note that the engine torque estimating circuit 17 outputs a signal ET proportional to the estimated engine torque.

On the other hand, the gear position sensor 23 sends a signal (
For example, the gear ratio signal generating circuit 24 generates an output N proportional to the gear ratio. Further, the inertia calculation circuit 25 calculates the sum I of the engine inertia and the wheel inertia according to the gear ratio at that time. Further, the differentiation circuit 6 calculates the wheel acceleration Vω. And said N, I,? Based on ω and ET, the engine torque calculation circuit 19 calculates the above equations ① and ②.

According to (2), calculate the engine torque ETO that generates the optimum slip.

Now, when the slip rate S exceeds 10% at time t2 in FIG. Set the output of 9, “l”
output. As a result, the relay element 10 switches its contacts, selects the signal A instead of the signal B, and drives the throttle actuator 21.

On the other hand, the output of the comparator 8 is input to an optimum engine rotation storage circuit 18, which stores a value obtained by multiplying the engine rotation speed when the output of the comparator 8 becomes lp by a constant. L is calculated as follows.

The output of comparator 8 occurs when the slip ratio is 0.1.
Assuming that the vehicle speed does not change, the slip rate is 0.
．． Let the engine speed at 05 be the optimum engine speed. This engine rotational speed signal is input to the throttle opening calculation circuit 20 together with the above-mentioned ETO, and becomes the A signal. The throttle opening calculation circuit 20 has a stator table showing the relationship between engine rotation speed, throttle opening, and engine torque as shown in FIG. 7, and calculates the throttle opening according to the input of engine torque and engine rotation speed. .

(c) When the slip decreases At time t2 in FIG. 5, the relay element 10 selects signal B, so the throttle opening is controlled to the value calculated by the throttle opening calculation circuit 20, and the throttle valve 22 is closed. , and the engine torque decreases. As a result, the slip decreases and approaches a slip rate close to the optimum slip rate.

On the other hand, since the vehicle speed increases with these masses, the slip ratio becomes 2% or less at time t3, the comparator 7 outputs "1", the flip-flop 9 is reset, and the relay is activated again. Element 10 selects signal B so that throttle opening is controlled in response to the operator's accelerator pedal input.

Although the embodiment has been described above based on the drawings, the specific configuration is not limited to this embodiment, and even if there is a design change within the scope of the gist of the present invention, it is included in the present invention. .

For example, in the embodiment, an example was shown in which the driving force is controlled by controlling the throttle opening, but it can also be applied to control the driving force by controlling the fuel injection amount to the engine, fuel cut, or wheel braking.

(Effects of the Invention) As described above, the vehicle driving force control device of the present invention includes a driving wheel speed detection means and a driven wheel speed detection means for detecting the wheel speeds of the driving wheel and the driven wheel; slip ratio calculating means for calculating a driving wheel slip ratio based on the driving wheel speed and driven wheel speed; engine rotation speed detection means for detecting engine rotation speed; boost pressure detection means for detecting engine boost pressure; gear position detection means for detecting the position; estimated engine torque calculation means for estimating engine torque based on the engine rotation speed and engine boost pressure; and wheel acceleration calculation means for calculating wheel acceleration based on the wheel speed of the driving wheels. , target engine torque calculation means for calculating a target engine torque that provides an optimal slip ratio from the gear position, wheel acceleration, and estimated engine torque; and driving force control means for controlling the driving force so that the engine torque matches the target engine torque, so that the target engine torque that generates the optimum slip can be adjusted under various road surface conditions. By matching the estimated engine torque to the target engine torque, it is possible to suppress drive wheel slip while converging to an optimal slip ratio regardless of road surface conditions.

[Brief explanation of the drawing]

Fig. 1 is a claim correspondence diagram showing the vehicle driving force control device of the present invention, Fig. 2 is an overall system block diagram of the vehicle driving force control device of the embodiment, and Fig. 3 shows the relationship of forces at the drive wheels. FIG. 4 is a characteristic diagram showing the relationship between the friction coefficient and vehicle lateral force with respect to slip ratio, FIG. 5 is a time chart diagram of the vehicle driving force control device of the embodiment, and FIG. FIG. 7 is a diagram showing the relationship between engine boost pressure and engine speed. FIG. 7 is a diagram showing the relationship between engine torque, throttle opening, and engine speed. a... Drive wheel speed detection means b... Driven wheel speed detection means C... Slip ratio calculation means d... Engine rotation speed detection means e... Boost pressure detection means f... Gear position detection Means g: Estimated engine torque calculation means h: Wheel acceleration calculation means: Target engine torque calculation means j: Driving force control means

Claims (1)

[Claims] 1) Drive wheel speed detection means and driven wheel speed detection means for detecting the wheel speeds of the drive wheels and the driven wheels, and a drive wheel slip rate calculated based on the drive wheel speeds and the driven wheel speeds. A slip ratio calculation means, an engine rotation speed detection means for detecting the engine rotation speed, a boost pressure detection means for detecting the engine boost pressure, a gear position detection means for detecting the gear position, and the engine rotation speed and the engine boost pressure. estimated engine torque calculation means for estimating engine torque based on the wheel speed of the drive wheels; wheel acceleration calculation means for calculating wheel acceleration based on the wheel speed of the driving wheels; and an optimum slip ratio obtained from the gear position, wheel acceleration, and estimated engine torque. a target engine torque calculation means for calculating a target engine torque to be calculated; and a drive for controlling driving force so that the estimated engine torque matches the target engine torque when the drive wheel slip ratio exceeds a predetermined set slip ratio. A vehicle driving force control device comprising: a force control means;