JPH05294225A - Traction control device - Google Patents

Abstract

PURPOSE:To prevent heavy load from being applied to the differential gear of lateral driving wheels on the basis of the traction control by inhibiting the action of a brake at need. CONSTITUTION:The rotating speed difference DELTAN between lateral driving wheels is obtained (S13), and torque Tin to be inputted into a differential gear from the driving wheels in the case of putting a brake in action is estimated (S16). Whether there is the possibility of applying heavy load to the differential gear is judged from DELTAN and Tin (S17), and in the case of this possibility existing, the action (pressure boosting) of the brake in traction control is inhibited (S19). The heavy load is not therefore applied to the differential gear, and the control of driving torque is secured even if inhibiting the action of the brake, so that the function of traction control is not lowered much.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traction control device for preventing drive wheels from idling when a vehicle is driven by using both drive torque control and brake control. The present invention relates to a technique for reducing a load applied to a wheel differential device.

[0002]

2. Description of the Related Art A traction control device for preventing a drive wheel from idling due to an excessive drive torque is already known. This is generally disclosed in the applicant's JP 62-137.
As described in Japanese Patent Publication No. 255-255, the drive torque of each drive wheel is reduced and the brake of each drive wheel is applied so that each drive wheel does not idle when the vehicle is driven.

By the way, the applicant has studied the influence of the action of the brakes of the left and right drive wheels on the differential device, and as a result, has found the following fact. That is, the stronger the braking action is, the larger the torque is input to the differential device from the left and right driving wheels. The burden is on the differential amount of the differential (eg,
They found that the larger the difference in the rotational speeds of the left and right drive wheels, the rotational speed ratio, etc., the heavier it is. Therefore, in order to reduce the load on the differential device, it is important not to generate a large differential device input torque or a large differential amount when the vehicle is driven. The relationship between the differential device input torque, the differential amount, and the load on the differential device will be specifically described in the embodiments.

[0004]

However, the above-mentioned conventional traction control device performs the traction control regardless of the load applied to the differential device, so that the input torque of the differential device may be reduced in some cases. In some cases, it becomes large, and the differential amount becomes large. For example, a vehicle is operated by suddenly accelerating a large acceleration operation member such as an accelerator pedal on a split road where the friction coefficient is greatly different between the left and right (for example, one of the left and right is an icy road and the other is an asphalt road). Traction control is performed because the vehicle has started, and the traction is caused when the brakes act strongly on both the left and right drive wheels under a large differential amount, or when the acceleration operation member is suddenly and greatly accelerated while turning the vehicle. Control takes place,
When the brake is strongly applied to both the left and right drive wheels under a large differential amount, the differential device input torque and the differential amount may increase.

In view of such circumstances, the present invention provides a traction control without impairing the original function of the traction control which maintains the directional stability without deteriorating the acceleration of the vehicle at the time of starting or accelerating the vehicle. The object of the present invention is to reduce the load applied to the differential device as much as possible.

[0006]

In order to solve this problem, the gist of the present invention is to provide a drive system including an engine, a power transmission device and a differential device to which left and right drive wheels are connected. A device that is provided in a vehicle in which brakes are provided on the left and right drive wheels and that performs traction control that reduces the drive torque of each drive wheel so that each drive wheel does not idle when the vehicle is driven and that applies a brake on each drive wheel 1, as shown in FIG. 1, (a) differential device load estimating means 1 for estimating the load applied to the differential device when the brakes of the respective drive wheels are applied, and (b) the estimated load The brake action permitting / inhibiting means 2 is provided for permitting the action of the brake for traction control when it is light and for inhibiting it when it is heavy.

The "differential device load estimating means 1" in the present invention may have various modes. For example, as described above, the differential amount of the differential device, the input torque of the differential device, and the differential torque. This is a mode utilizing the fact that there is a certain relationship between the load on the device and the differential amount acquisition means for acquiring the differential amount of the differential device, and the braking of each drive wheel is applied. In this case, the differential device input torque acquisition means for acquiring the differential device input torque expected to be input from each drive wheel to the differential device, and the acquired differential amount and differential device input torque are scheduled. If the condition is satisfied, the load on the differential device is light, and if not, it is determined to be heavy. It should be noted that, for the "differential amount" in the differential amount acquisition means, for example, a rotational speed difference or a rotational speed ratio between the left and right drive wheels can be selected.

The "differential device load estimating means 1" in the present invention also includes one of the differential amount acquiring means and the differential device input torque acquiring means, and the acquired differential amount and differential device input torque. It is also possible to include a load magnitude determining means for determining that the load on the differential device is light when one of the two does not exceed the predetermined threshold value and is heavy when the one is more than the threshold value.

In implementing the present invention, various methods can be used to control the drive torque of each drive wheel. For example, a method of controlling the throttle valve of the engine or a fuel injection amount of the engine can be used. It is possible to adopt a method of controlling the ignition timing or the like, or a method of using them together. Further, in implementing the present invention, the brake control may be a system for controlling left and right independently or a system for controlling left and right simultaneously.

[0010]

In the traction control device according to the present invention, the differential device load estimating means 1 estimates the load applied to the differential device when the brakes of the respective drive wheels are applied, and the brake action permitting / inhibiting means. According to 2, when the estimated load is light, the action of the brake for traction control is permitted, and when it is heavy, it is prohibited. Therefore, when it is estimated that a heavy load is applied to the differential gear when the brake is applied, the brake is not applied and the heavy load is not actually applied to the differential gear.

Further, in the traction control device according to the present invention, since the control of the drive torque is executed regardless of whether the action of the brake is permitted or prohibited in this way, when the action of the brake is inhibited. However, the idling of each drive wheel is suppressed by the reduction of the drive torque.

[0012]

As is apparent from the above description, according to the present invention, the load applied to the differential device based on the traction control is reduced, and the reliability of the differential device can be easily improved. Is obtained. Further, according to the present invention, since the control of the drive torque is ensured even if the action of the brake is prohibited because the heavy load may be applied to the differential device, the traction control is performed even if the action of the brake is prohibited. There is also an effect that the function of does not have to be reduced so much.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A traction control device according to an embodiment of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 2, the traction control device is provided in a four-wheeled vehicle having left and right front wheels 10 and left and right rear wheels 12. The left and right front wheels 10 are idle wheels and are deflected by a steering wheel (not shown), while the left and right rear wheels 12 are drive wheels, and the output torque from the engine 22 is an automatic transmission (hereinafter, T / M) 24, a propeller shaft (not shown), and a final reduction gear 28 to transmit and drive. The final speed reducer 28 includes a speed reducer 29 and a differential device 30.

That is, in this embodiment, the drive system is configured to include the engine 22, the T / M 24 and the propeller shaft as the power transmission device, and the final reduction gear device 28.

Inside the intake manifold 32 of the engine 22, a main throttle valve 34 and a sub throttle valve 36 are arranged in series. The main throttle valve 34 is mechanically linked with an accelerator pedal 38 which is depressed by a driver, and the opening degree θ _M thereof is detected by a main throttle position sensor 42. On the other hand, the sub-throttle valve 36 is electrically driven by the sub-throttle actuator 44, and the opening degree θ _S thereof is detected by the sub-throttle position sensor 48.

The detected opening degrees θ _M and θ _S are input to an engine & T / M control computer (hereinafter, simply referred to as a control computer) 52 together with the rotation speed N _e of the engine 22 and the like. Based on the input signal, the control computer 52 outputs an engine control signal including a fuel injection control signal, an ignition timing control signal, etc. to the engine 22, and a gear change control signal and a lock to the T / M 24. A T / M control signal including an up control signal is output.

A brake 60 is provided on each of the front left and right wheels 10 and the rear left and right wheels 12. The brake 60 suppresses the rotation of the wheels 10 and 12 by pressing a brake pad (not shown) against the rotor 62 that rotates with the wheels 10 and 12 by the brake pressure. The brake pressure of each of the brakes 60 can be electrically controlled by an ABS & TRC computer 68 via a brake pressure control device 70. Brake pressure controller 7
0 is provided with an electromagnetic pressure control valve for each brake 60, and the brake pressure of each brake 60 can be controlled independently of each other.

The ABS & TRC computer 68 monitors the wheel speeds of the four wheels 10, 12 via the wheel speed sensors 74, and at the time of vehicle braking, the wheels 10, 1
The anti-lock control for controlling each brake 60 so that the vehicle 2 does not fall into the locked state, and the brake 60 for each rear wheel 12 so that each rear wheel 12 (each driving wheel) does not idle when the vehicle is driven.
It is designed to perform traction control and control. Antilock control is well known, and
The description is omitted because it is not essential for understanding the present invention. On the other hand, in the traction control of the present embodiment, the brake control for suppressing the idling of the rear wheel 12 by the control of the brake 60, the control of the sub-throttle valve 36 and the control of the ignition timing of the engine 22 are performed in cooperation with each other. The ABS & TRC computer 68 executes the former brake control. Therefore, ABS & T
The RC computer 68 stores the program represented by the flowchart in FIG. 3, the contents of which will be described later.

The TRC computer 80 controls the latter engine. This TRC computer 80
It is connected to the ABS & TRC computer 68 and the control computer 52, four wheel speeds are inputted via the ABS & TRC computer 68, and the main throttle opening θ _M and the sub throttle opening θ _S are inputted via the control computer 52. Is entered. T
The RC computer 80 is also connected to the sub-throttle actuator 44, and controls the opening degree θ _S of the sub-throttle valve 36 based on the input signal so that the rear wheels 12 do not idle. TRC computer 80
Further, it is possible to communicate with the control computer 52, and outputs a signal to the control computer 52 to retard the ignition timing of the engine 22 more than usual during traction control.

The brake pressure control routine (for traction control) shown in FIG. 3 is the CP of the ABS & TRC computer 68.
Performed regularly by U. It should be noted that this routine is prepared for each of the left rear wheel 12 and the right rear wheel 12, and the CPU executes these routines alternately and periodically so that the brake pressure P of each rear wheel 12 alternates. It is designed to be controlled independently of each other. However, in the following description, only one of the left and right rear wheels 12 will be representatively described, and description of the other will be omitted.

In each execution of this routine, first, in step S1 (hereinafter, simply referred to as S1; the same applies to other steps), an idle signal from the main throttle position sensor 42 (accelerator pedal 38).
Is a non-operation state and a signal indicating whether the engine 22 is in an idling state), it is determined whether or not the accelerator pedal 38 is depressed by the driver. If this is not the case this time, the determination is no, and in S2, the control flag XC (also for each rear wheel 12
(Provided for each) is reset, and in S3, a signal is issued to the brake pressure control device 70 to restore it to the original state. The routine is executed once as described above.

The original purpose of S3 is to terminate the traction control being executed and return the brake pressure control device 70 to the original state. However, the traction control is not yet executed in this execution of this routine. It was conducted in an undisclosed state and has no substantial meaning.

Thereafter, if the accelerator pedal 38 is depressed, the determination at S1 becomes YES, and at S4, it is determined whether or not the control flag XC is set. Since it has been reset this time, the determination is NO and S5
Move to. In this step, the vehicle speed V _V estimated from the wheel speeds V _FL and V _FR of the left and right front wheels 10, which are idle wheels, is read from the RAM. The vehicle speed V _V is estimated in another routine, and the result is stored in the RAM.

Subsequently, in S6, the current control start speed of the traction control is set based on the vehicle speed V _V , and in S7, one wheel speed of the left and right rear wheels 12 (hereinafter, simply wheel speed of the rear wheel 12 is set. V _RL , V _RR ) has exceeded the set control start speed.
Assuming that it has not exceeded this time, the judgment is NO,
One execution of this routine is completed through the steps from S2 onward.

On the other hand, the wheel speed V _RL of the rear wheel 12,
If V _RR exceeds the control start speed, the determination in S7 is Y.
After ES, and the control flag XC is set in S8, the main throttle valve 34 is set in S9.
The opening degree θ _M and the engine speed N _e are read via the control computer 52, respectively, and based on them, the current engine torque T _{E / G} currently output from the engine 22 is estimated. The relationship between the opening degree θ _M , the engine speed N _e, and the current engine torque T _{E / G} is stored in the ROM in advance, and the current engine torque T is calculated using the relationship.
_{E / G} is estimated.

Then, in step S10, the current speed ratio γ _{T / M of the T / M} 24 is read from the control computer 52, the current speed ratio γ _{T / M} , the current engine torque T _{E / G,} and the final speed ratio. Based on the speed reduction ratio γ _FINAL of the speed reducer 28, the current drive torques DT _RL and DT _RR actually transmitted from the drive system to the rear wheels 12 are calculated.

Subsequently, in S11, the friction coefficients μ _RL and μ _RR between one of the left and right rear wheels 12 and the road surface are estimated based on the rotational motion equation of the rear wheel 12. Specifically, the friction coefficient μ _RL on the left rear wheel 12 side is μ _RL = (DT _RL −I · (dV _RL / dt) / R) / (W ·
R), the friction coefficient μ _RR on the right rear wheel 12 side is μ _RR = (DT _RR −I · (dV _RR / dt) / R) / (W ·
R) is estimated using the following formula. However, DT _RL , DT _RR : Current drive torque (calculated value) of each rear wheel 12 I: Moment of inertia that integrates the inertia of each rear wheel 12, the drive system and the engine (known for both left and right rear wheels 12) Value) V _RL , V _RR : Wheel speed of each rear wheel 12 (detection value) R: Dynamic load radius of each rear wheel 12 (known value common to the left and right rear wheels 12) W: Ground load of each rear wheel 12 (Known value common to the left and right rear wheels 12) The estimated friction coefficients μ _RL and μ _RR are stored in a predetermined position of the RAM.

Then, in S12, the left and right rear wheels 12 are
The wheel speeds V _RL and V _RR of the vehicle are read. The wheel speeds V _RL and V _RR are calculated in another routine (not shown) based on the output signals from the wheel speed sensors 74, and the results are stored in the RAM.

Subsequently, in S13, the rotational speed difference ΔN between the left and right rear wheels 12 is calculated from the wheel speeds V _RL and V _RR and stored in a predetermined position of the RAM. Subsequently, in S14, the current pressure control (meaning the pressure control performed by one execution of this routine. The pressure control at each time is performed at substantially the same timing for the left and right rear wheels 12). If the above is performed as scheduled, future brake pressures P _RL and P _RR that are expected to reach the brake pressures P _RL and P _{RR of the} rear wheels 12 at the end of this execution are respectively estimated. Specifically, the future brake pressure P of the left rear wheel 12
_RL , when the pressure control mode this time is pressure increase,
It is currently calculated as the sum of the product of the brake pressure P _RL , the pressure increase gradient K and the pressure increase time Δt.
It is calculated by subtracting the product of the depressurization gradient K and the depressurization time Δt from the current brake pressure P _{RL. In the} pressure-holding mode (also in the non-control mode), the current brake pressure P _RL is directly used as the future brake pressure P _RL . To be done. The same applies to the future brake pressure P _RR of the right rear wheel 12.

The pressure increase / decompression gradient K is variable according to the current values of the brake pressures P _RL and P _RR , and the relationship between the pressure increase / decompression gradient K and the brake pressure P is stored in advance in the ROM.
The current pressure increase / pressure decrease gradient K is estimated in accordance with the current values of the brake pressures P _RL and P _RR . Further, whether the current pressure control mode is pressure increase, pressure decrease, or pressure retention is determined based on the correlation between the wheel speeds V _RL , V _{RR of the} rear wheels 12 and the estimated vehicle speed V _V. It Further, the estimated future brake pressures P _RL and P _RR are stored in a predetermined position in the RAM.

Thereafter, in S15, future braking torques BT _RL and BT _RR that are expected to act on the rear wheels 12 at the end of the current execution if the current pressure control is performed as planned are estimated. Specifically, the future braking torque BT _RL of the left rear wheel 12 is estimated using the formula BT _RL = 2 · μ ′ · r · S · P _RL , while the future braking torque BT of the right rear wheel 12 is estimated. _RR is estimated using the formula BT _RR = 2 · μ ′ · r · S · P _RR . Where μ ': coefficient of friction between rotor 62 and brake pad in each brake 60 (known value common to left and right rear wheels 12) r: effective radius of each rotor 62 (known common to left and right rear wheels 12) Value) S: Effective wheel cylinder pressure receiving area of each brake 60 (known value common to the left and right rear wheels 12) P _RL , P _RR : Future brake pressure of each rear wheel 12 (calculated value) Estimated future braking torque BT _RL and BT _RR are stored in a predetermined location of RAM.

Next, at S16, if the current pressure control is performed as planned, the future differential input torque T expected to be input from the two rear wheels 12 to the final reduction gear 28 at the end of the current execution. _in is estimated. Specifically, the future differential input torque T _in is the sum of the future braking torque BT _RL and the rolling resistance torque (= μ _RL · WR) and the future braking torque BT _RR and the rolling resistance torque (= μ _RR / W
-The smaller of the sum of R) and R is calculated as twice. Calculated future differential input torque T _in is RAM
Is stored in a predetermined position of. The future differential input torque T
Strictly speaking, _in should be calculated in consideration of not only the static factor but also the dynamic factor, but it is estimated that the static factor has a larger influence on the final reduction gear 28 than the dynamic factor. For,
In this embodiment, the differential input torque T _in is calculated _{in the} future by ignoring the dynamic factor and considering only the static factor.

After that, in S17, if the current pressure control is performed as planned, it is determined whether or not a heavy load may be applied to the final reduction gear 28 from the left and right rear wheels 12. The applicant's research has revealed that there is a relationship between the differential input torque T _in , the rotational speed difference ΔN, and the load applied to the final reduction gear 28 _{in the} future, as shown in the graph of FIG. Based on this fact, in this step,
If an intersection of the current values of the differential input torque T _in and the rotational speed difference ΔN exists in the heavy load region on the graph _{in the} future, a heavy load may be applied from the left and right rear wheels 12 to the final reduction gear 28. It is determined that there is. If the intersection exists in the light load area instead of the heavy load area, the final reduction gear 2
It is determined that there is no possibility that a heavy load will be applied to No. 8, and the determination is NO. In S18, it is increased to prohibit the pressure increase in the set state and to allow the pressure increase in the reset state. The pressure prohibition flag XP is reset. On the other hand, if the intersection exists in the heavy burden area, S17
Is YES, and the pressure increase prohibition flag XP is set in S19.

Subsequently, in S20, one-time pressure control is performed via the brake pressure control device 70. This step is executed many times while this routine is executed many times, thereby performing one brake control (a group of a plurality of pressure controls). The one-time brake control means that when each rear wheel 12 is about to idle, the brake pressure of the rear wheel 12 is increased to prevent the rear wheel 12 from idling, and then the wheel speed V of the rear wheel 12 is set as a control target. Until the speed is sufficiently close, that is, until the determination in S21 is YES,
The rear wheel 12 is estimated while estimating the slip state of the rear wheel 12 from the correlation between the wheel speeds V _RL , V _{RR of the} rear wheel 12 and the estimated vehicle speed V _V.
To increase or decrease the brake pressure. However, in this one-time brake control, while the pressure increase prohibition flag XP is set, pressure holding is performed instead of the pressure increase that should be originally performed, while while it is reset, the pressure increase is performed as planned. Is to be done.

If the determination in S21 is YES, that is, if it is determined that the current traction control may be terminated, the current execution of this routine is terminated through the steps from S2 onward. This completes one traction control.

After the control flag XC is set once, in each execution of this routine, S5 to S1
The execution of 1 is omitted.

Therefore, in this embodiment, when a heavy load may be applied to the final reduction gear device 28,
The action of the brake 60 for traction control is prohibited (in this embodiment, only the increase of the brake pressure P is prohibited), the increase of the actual value of the differential input torque T _in is prevented, and the final speed reducer 28 is prevented. Heavy burden will be avoided.

However, even if the increase of the brake pressure P is prohibited, the engine control by the TRC computer 80 is ensured, so that the traction control function does not deteriorate so much.

As is clear from the above description, in this embodiment, the ABS & TR among the components shown in FIG.
The C computer 68, the TRC computer 80, the brake pressure control device 70, the sub-throttle valve 36, the sub-throttle position sensor 48, the sub-throttle actuator 44, etc. constitute a traction control device, and here, each of the left and right rear wheels 12 is arranged. The wheel speed sensor 74 and the part of the ABS & TRC computer 68 that executes S12 and S13 of FIG. 3 cooperate with each other to form a rotation speed difference acquisition means that is one aspect of the differential amount acquisition means. Of the computer 68, the part that executes S9 to S11 and S14 to S16 in the figure constitutes one mode of the differential device input torque acquisition means, and the part that executes S17 to S19 in the figure is the present invention. It constitutes one mode of the "brake action permission / prohibition means 2". . Further, the rotational speed difference acquisition means and the one aspect of the differential gear input torque acquisition means cooperate with each other to configure one aspect of the "differential gear load estimation means 1" of the present invention.

In addition, in addition, in the present embodiment, the rotational speed difference ΔN is constantly monitored, but this fact can be utilized for various purposes. For example, it can be used for a failure determination of the brake pressure control device 70, and specifically, the brake control for the traction control is performed while the increase of the brake pressure P is permitted. If the tendency that the rotational speed difference ΔN decreases does not appear, it can be determined that the brake pressure control device 70 may be out of order.

While one embodiment of the present invention has been described in detail with reference to the drawings, various modifications and improvements can be made based on the knowledge of those skilled in the art without departing from the scope of the claims. The present invention can be carried out in the manner in which it is applied.

[Brief description of drawings]

FIG. 1 is a block diagram conceptually showing the structure of the present invention.

FIG. 2 is a flowchart showing a brake pressure control routine used by a traction control device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a vehicle traveling state control system including the traction control device.

FIG. 4 is a graph showing a relationship used by the traction control device to determine whether or not a heavy load may be applied to the final reduction gear device.

[Explanation of symbols]

 10 front wheel 12 rear wheel 22 engine 24 transmission 28 final reduction gear device 30 differential device 36 sub-throttle valve 52 engine & T / M control computer 60 brake 68 ABS & TRC computer 70 brake pressure control device 80 TRC computer

Claims (1)

[Claims] 1. A vehicle equipped with a drive system including an engine, a power transmission device and a differential device, wherein left and right drive wheels are connected in the differential device, and brakes are provided on the left and right drive wheels, respectively. In a device for performing traction control that reduces the drive torque of each drive wheel so as to prevent each drive wheel from idling when driving, and applies the brake of each drive wheel, the differential when the brake of each drive wheel is applied. A differential device load estimating means for estimating a load applied to the device, and a brake action permitting / inhibiting means for permitting the action of the brake for the traction control when the estimated load is light, and for prohibiting the action when the estimated load is heavy. And a traction control device characterized by being provided.