JP2006335229A - Vehicle with suppressed driving slip of wheel on split road surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle capable of suppressing large slip of wheels on a side with low friction coefficient on a split road surface, which is caused by increase in ground contact load on a side with high friction coefficient, whereas the total of the product of grounding load and friction coefficient is increased thereby, but the radius of friction circle is further minimized on the side with low friction coefficient due to the low friction coefficient and the reduced ground contact load. <P>SOLUTION: Based on friction coefficients of the road surface to left wheels and right wheels, the ground contact load is distributed between the left wheels and the right wheels by a ground contact load distribution means, and a driving force is distributed between the left wheels and the right wheels by a driving force distribution means, whereby a steering means is steered in a direction of canceling a moment caused in the vehicle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle traveling on a general road surface with four or more wheels such as an automobile.

  The force in the direction along the road surface that can be transmitted between the road surface and the wheel is limited by the force that pushes the wheel against the road surface (ground load) multiplied by the coefficient of friction between the road surface and the wheel. An almost circular contour shape drawn around the contact point between the road surface and the wheel is called a “friction circle”, and the size of the radius is the transmission between the road surface and the wheel obtained in the direction along the radius. Indicates the maximum force.

  By the way, four or more wheels such as automobiles are arranged separately on the left and right, and in a vehicle such as an automobile traveling on a general road surface, the friction of the road surface against the left wheel and the right wheel according to the road surface condition. It happens that the coefficients are different. Such a road surface exhibiting a different friction coefficient with respect to the left wheel and the right wheel is called a split road surface. If the friction coefficient of the road surface with respect to the wheels decreases, the radius of the friction circle decreases even under the same ground load, and the maximum value of the driving force of the wheels decreases.

The ground contact load of the left and right wheels corresponds to the weight of the vehicle body, and if the ground contact load of the wheel on one side is increased, the ground load of the wheel on the other side is reduced accordingly. If you look at the product of the contact load and the friction coefficient on the left and right wheels, the sum of the product of the contact load and the friction coefficient on the left and right wheels will increase when the contact load on the side with the higher friction coefficient is increased. Patent Document 1 below describes that an active suspension is operated on a road surface to increase a ground contact load on a road surface having a higher coefficient of friction. Further, the following Patent Document 2 has a control means for changing the grounding load of each of the front, rear, left and right wheels, and each grounding load of one of the diagonal wheels and each grounding of the other pair of diagonal wheels. Friction of the road surface where the left and right wheels are grounded during braking in a vehicle in which the load can be changed in the opposite direction of increase and decrease and the ground contact load on each diagonal wheel can be changed in the same increase and decrease direction It is described that the coefficient is estimated, the ground load on the high friction coefficient side front wheel and the low friction coefficient side rear wheel is increased, and the ground load on the low friction coefficient side front wheel and the high friction coefficient side rear wheel is decreased.
JP-A-3-109115 JP2004-66996A

  As described above, on the split road surface, increasing the contact load on the side with the higher friction coefficient increases the sum of the product of the contact load and the friction coefficient on the left and right wheels, but at this time, on the side with the lower friction coefficient on the road surface, A combination of the low friction coefficient and the reduction of the ground contact load may further reduce the radius of the friction circle, which may cause a large slip on the wheel on the low friction coefficient side.

  This invention pays attention to said situation, and makes it a subject to provide the vehicle which improves the drive capability on the split road surfaces of vehicles, such as a motor vehicle, suppressing the slip of a wheel.

  In order to solve the above problems, the present invention includes a friction coefficient detection unit that individually detects a friction coefficient of a road surface with respect to the left wheel and the right wheel, and a ground load distribution unit that distributes a ground load between the left wheel and the right wheel. Driving force distribution means for distributing drive force between the left wheel and the right wheel, and steering means, and the contact load distribution based on the friction coefficient of the road surface with respect to the left wheel and the right wheel detected by the friction coefficient detection means The steering means is steered in such a direction that the grounding load is distributed between the left wheel and the right wheel by the means, and the driving force is distributed between the left wheel and the right wheel by the driving force distribution means, thereby canceling the moment generated in the vehicle. The present invention proposes a vehicle that is characterized by the above.

  The ground load distribution means may include at least one of an active suspension or an active stabilizer.

  The driving force distribution means may include differential means acting between the left wheel and the right wheel, and differential limiting means for restricting the differential action of the differential means.

  The distribution of the ground load between the left wheel and the right wheel by the ground load distribution means based on the friction coefficient of the road surface with respect to the left wheel and the right wheel and the distribution of the driving force between the left wheel and the right wheel by the driving force distribution means are wheels. May be performed until the wheel driving force does not exceed the product of the ground load and the friction coefficient on the side where the friction coefficient of the road surface is low.

  The vehicle has a friction coefficient detecting means for individually detecting a friction coefficient of the road surface with respect to the left wheel and the right wheel, a ground load distributing means for distributing a ground load between the left wheel and the right wheel, and a driving force between the left wheel and the right wheel. A driving force distribution means for distributing the power and a steering means, and the grounding load distribution means makes contact between the left wheel and the right wheel based on the friction coefficient of the road surface with respect to the left wheel and the right wheel detected by the friction coefficient detection means. If the steering means is steered in such a direction that the load is distributed and the driving force is distributed between the left wheel and the right wheel by the driving force distributing means and the moment generated in the vehicle is thereby canceled, the split road surface By allocating more contact load to the wheel with the higher friction coefficient, the friction circle radius on the higher friction coefficient side and the friction circle radius on the lower friction coefficient side big Even if the friction circle occurs, the wheel driving force can be differentiated so that the driving force is larger on the side where the friction circle is larger than on the side where the friction circle is smaller. Thus, even if a moment is generated in the vehicle, this can be canceled by the steering of the steering means.

  If the ground load distribution means includes at least one of an active suspension or an active stabilizer, the distribution of the ground load between the left and right wheels can be quickly changed, and the vehicle enters the split road surface and the split road surface. The distribution of the ground load between the left and right wheels can be controlled by following the escape from the vehicle and the change in the friction coefficient along the split road surface without delay.

  If the driving force distribution means includes differential means acting between the left wheel and the right wheel and differential limiting means for restricting the differential action of the differential means, the ground load distribution means between the left and right wheels The driving force distribution between the left and right wheels can be accurately performed according to the distribution of the ground load.

  The distribution of the contact load between the left wheel and the right wheel by the contact load distribution means based on the friction coefficient of the road surface with respect to the left wheel and the right wheel and the distribution of the driving force between the left wheel and the right wheel by the drive force distribution means By performing until the wheel driving force does not exceed the product of the ground load and the friction coefficient on the low friction coefficient side, it is possible to accurately determine the stop timing of the split road surface control as described above.

  FIG. 1 attached herewith is a schematic diagram schematically illustrating a functional configuration according to the present invention of a vehicle according to the present invention. In the figure, 10FL, 10FR, 10RL, and 10RR are the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel of the four-wheeled vehicle, and the active suspensions 12FL, 12FR, and 12RL are respectively shown from the vehicle body not shown in the figure. , 12RR. A front wheel side active stabilizer 14F is provided between the left front wheel 10FL and the right front wheel 10FR, and a rear wheel side active stabilizer 14R is provided between the left rear wheel 10RL and the right rear wheel 10RR. The left front wheel 10FL and the right front wheel 10FR are steered by a steering device 26 including left and right king pins 16L and 16R, left and right knuckle arms 18L and 18R, a steering tie rod 20, a steering gear 22, a steering wheel 24, and the like. Yes.

  The illustrated vehicle is a four-wheel drive vehicle, front wheels 10FL and 10FR are passed through a front wheel differential gear device 28, and rear wheels 10RL and 10RR are passed through a rear wheel differential gear device 30 and are shown in the figure. It is driven by a non-internal combustion engine through a transmission not shown in the figure.

  Reference numeral 32 denotes an electric control device (ECU) for a vehicle incorporating a microcomputer. The figure shows an arithmetic means and a control means according to the present invention functionally provided by the electric control device. Yes.

  One of the target yaw rate calculation means 34 is a signal indicating a steering angle from a steering sensor 36, a signal indicating a vehicle speed from a vehicle speed sensor not shown in the figure, and a vehicle from a lateral acceleration sensor not shown in the figure. The target yaw rate calculation means 34 calculates a target yaw rate γt based on these signals. The calculated target yaw rate γt is compared with the actual yaw rate γ detected by a yaw rate sensor not shown in the figure, and the difference between the target yaw rate γt and the actual yaw rate γ is used as the yaw rate deviation to determine the friction coefficient μ of the road surface with respect to the left and right wheels. The left and right μ estimation means 38 to be calculated is supplied.

  In addition, the left and right μ estimating means 38 are supplied with a signal indicating the vehicle speed, a signal indicating the lateral acceleration, a signal indicating the actual yaw rate, and a signal indicating the acceleration of the left and right front wheels and the rear wheels. When the vehicle is a two-wheel drive of the rear wheel or the front wheel, detection of acceleration for the front wheel or the rear wheel that is not driven may be omitted. The left and right μ estimation means 38 estimates and calculates the road surface friction coefficient μl for the left wheel and the road surface friction coefficient μr for the right wheel based on these signals. The calculated friction coefficients μl and μr of the road surface with respect to the left wheel and the right wheel are supplied to the side slip angle estimating means 40, and also active suspension control means 42, active stabilizer control means 44, steering device control means 46, and differential device control means 48. Supplied to.

  In addition, the side slip angle estimating means 40 is supplied with a signal indicating the steering angle, a signal indicating the vehicle speed, a signal indicating the lateral acceleration, a signal indicating the yaw rate deviation, a signal indicating the actual yaw rate, and a signal indicating the acceleration of each wheel. Yes. The side slip angle estimating means 40 estimates and calculates the side slip angle based on these signals, and the signals indicating the calculated side slip angle are the active suspension control means 42, the active stabilizer control means 44, the steering device control means 46, and the differential device control. Supplied to means 48.

  The active suspension control means 42, the active stabilizer control means 44, the steering device control means 46, and the differential control means 48 are respectively supplied with the friction coefficient μl and μr of the road surface for the left wheel and the right wheel, signals indicating the sideslip angle, The active suspensions 12FL, 12FR, 12RL, and 12RR, the front wheel side active stabilizer 14F and the rear wheel side active stabilizer 14R, the steering device 26, and the differential devices 28 and 30 are controlled based on a signal indicating the acceleration of the wheel.

  FIG. 2 is a flowchart showing one embodiment of the wheel drive slip suppression control performed in the vehicle of the present invention for the split road surface traveling of the vehicle. This flowchart is shown as control for a pair of front wheels or rear wheels as drive wheels. In the case of four-wheel drive in which both the front wheels and the rear wheels are driven, a series of controls as shown in the figure may be performed alternately on the pair of front wheels and the pair of rear wheels. Control along such a flowchart may be repeated in a cycle of several tens to several hundreds of milliseconds.

  When the control is started, in step 10, the friction coefficients μl and μr of the road surface with respect to the left wheel and the right wheel are estimated and calculated by means such as the left and right μ estimating means 38 in FIG. Control then proceeds to step 20 where it is determined whether the friction coefficient μl for the left wheel is greater than a suitable deviation Δμ over the friction coefficient μr for the right wheel. If the answer is yes (Y), it indicates that the road surface is a split road surface that is equal to or greater than the control target according to the present invention, and the friction coefficient of the road surface with respect to the right wheel is lower than that with respect to the left wheel. At this time, the control proceeds to step 30, and whether or not the driving force Fdr of the right driving wheel is larger than the product of the friction coefficient μr for the right wheel and the ground load Wr of the right driving wheel, that is, the driving force Fdr of the right driving wheel is It is determined whether the friction circle for the drive wheel is exceeded. If the answer is no (N), no slip occurs due to wheel driving even on the right wheel side where the friction coefficient of the road surface is low, so this control is finished.

  If the answer to step 30 is yes, control proceeds to step 40. In step 40, the ground load variation ΔW per cycle for shifting the wheel ground load from the right wheel side to the left wheel side is, for example, the difference between the friction coefficient μl and μr of the road surface for the left and right wheels. Calculated as a function fw (μl−μr), based on this, the ground load target value Wl for the left wheel is increased by ΔW, and the ground load target value Wr for the right wheel is decreased by ΔW. The function ΔW = fw (μl−μr) may be stored in the microcomputer of the electric controller 32 in the form of an appropriate map showing the relationship between μl−μr and ΔW.

  Next, the control proceeds to step 50, where the wheel driving force variation ΔFd per cycle for shifting the wheel driving force distribution from the right wheel side to the left wheel side is, for example, the difference between the ground load Wl and Wr of the left and right wheels. The left wheel driving force target value Fdl is increased by ΔFd, and the right wheel driving force target value Fdr is decreased by ΔFd based on the calculated function fd (Wl−Wr). The function ΔFd = fd (W1−Wr) may also be stored in the microcomputer of the electric controller 32 in the form of an appropriate map showing the relationship between W1−Wr and ΔFd.

  Next, the control proceeds to step 60, where the change in the steering angle of the steering control for canceling the moment (mainly the yaw moment) acting on the vehicle due to the shift of the wheel driving force distribution from the right wheel to the left wheel is changed per cycle. For example, the minute Δα is calculated as a function fs (Fdl−Fdr) of the difference between the wheel driving forces Fdl and Fdr for the left and right wheels. The function Δα = fs (Fdl−Fdr) may also be stored in the microcomputer of the electric controller 32 in the form of an appropriate map showing the relationship between Fdl−Fdr and Δα.

  Following the above calculation of the control target value, at step 70, the left wheel active suspension is used to achieve the amount to be achieved by the left wheel active suspension out of the left wheel ground load Wl based on the above calculated Wl and ΔW. The left wheel active suspension is controlled by the active suspension control means 42, and the amount to be achieved by the right wheel active suspension out of the right wheel ground load Wr is determined based on Wr and ΔW calculated above in step 80. The active suspension control means 42 controls the active suspension of the right wheel so that it can be achieved by the active suspension of the right wheel.

  Furthermore, in step 90, based on Wl, Wr, and ΔW calculated above, the amount to be achieved by the active stabilizer among the ground load Wl of the left wheel and the ground load Wr of the right wheel is achieved by the active stabilizer. The active stabilizer is controlled by the active stabilizer control means 44.

  Next, in step 100, the differential device 28 or 30 is controlled by the differential device control means 48 so that the wheel driving forces of the left and right wheels are set to Fdl and Fdr, respectively, based on Fdl, Fdr and ΔFd calculated above. Is done. This is achieved by actuating a differential limiting device not shown in the figure provided in the differential device 28 or 30 to appropriately limit the differential action of the differential device. In the illustrated embodiment, the distribution or transfer of the wheel driving force between the left and right wheels is performed by a differential device provided between the left and right wheels and a differential limiting device for limiting the differential. However, the distribution or transfer of the wheel driving force between the left and right wheels may be performed using a traction control device, and each wheel is directly driven individually by each motor. In a motor-type vehicle, it may be performed by output control of an electric motor for each wheel.

  Further, in step 110, the steering device 36 is steered by the steering angle variation Δα per one flow cycle by the steering device control means 46 based on Δα calculated above.

  By the split road surface correspondence control in steps 40 to 110 as described above, the transfer of the wheel contact load and the transfer of the wheel driving force to the higher side than the lower friction coefficient of the road surface are repeatedly performed for each minute control amount at a minute cycle time. At this time, if the latter transfer ratio is appropriately increased compared to the former transfer ratio, the answer to step 30 will eventually turn from yes to no, so that the wheel ground load transfer corresponding to the split road surface and the wheel It suffices if the transfer of driving force is stopped. Thereafter, if the vehicle goes out of the split road surface as the vehicle travels, the answer to step 20 is no and the control proceeds to step 120. In step 120, it is determined whether or not the friction coefficient μr for the right wheel is greater than a certain appropriate deviation Δμ than the friction coefficient μl for the left wheel. When the vehicle goes out of the split road surface, the answer to step 120 is no. At this time, the control proceeds to step 130, the split correspondence control is canceled, the left wheel active suspension, the right wheel active suspension, the active stabilizer, the difference. The operating state of the moving device and the steering device is reset to the original state before the start of the split correspondence control. Even if the answer to step 20 and the answer to step 120 are no from the beginning, the control proceeds to step 130, and each device remains in a reset state as far as the split correspondence control is concerned.

  If the vehicle approaches a split road surface where the coefficient of friction of the road surface with respect to the left wheel is lower than that with respect to the right wheel, the answer is yes when the control reaches step 120. At this time, the left wheel and the right wheel are reversed, and control similar to the control described above for steps 30 to 110 is performed as steps 140 to 220. Since the control mode seems to be clear from the above description for steps 30-110, the same detailed description for steps 140-220 is omitted to avoid redundancy of the specification.

  While the present invention has been described in detail with respect to one embodiment thereof, it will be apparent to those skilled in the art that various modifications can be made within the scope of the present invention.

1 is a schematic diagram illustrating a functional configuration according to the present invention of a vehicle according to the present invention. The flowchart which shows the driving slip suppression control of the wheel performed in the vehicle of this invention with respect to the split road surface driving | running | working of the vehicle about the one embodiment.

Explanation of symbols

  10FL, 10FR, 10RL, 10RR ... Left front wheel, Right front wheel, Left rear wheel, Right rear wheel, 12FL, 12FR, 12RL, 12RR ... Active suspension, 14F, 14R ... Active stabilizer, 16L, 16R ... King pin, 18L, 18R ... Knuckle arm, 20 ... Steering tie rod, 22 ... Steering gear, 24 ... Steering wheel, 26 ... Steering device, 28 ... Front wheel differential gear device, 30 ... Rear wheel operating gear device, 32 ... Electric control device (ECU) 34... Target yaw rate calculating means 36. Steering sensor 38... Right and left .mu. Estimating means 40 .. side slip angle estimating means 42... Active suspension control means 44... Active stabilizer control means 46. ... Differential device control means

Claims (4)

  Friction coefficient detection means for individually detecting the friction coefficient of the road surface with respect to the left wheel and the right wheel, contact load distribution means for distributing the wheel contact load between the left wheel and the right wheel, and driving force between the left wheel and the right wheel A driving force distribution means for distributing, and a steering means, and a ground load between the left wheel and the right wheel by the ground load distribution means based on a friction coefficient of a road surface with respect to the left wheel and the right wheel detected by the friction coefficient detection means. And the steering means is steered in such a direction that the driving force is distributed between the left wheel and the right wheel by the driving force distribution means and thereby cancels out the moment generated in the vehicle. Vehicle.   The vehicle according to claim 1, wherein the ground load distribution means includes at least one of an active suspension or an active stabilizer.   3. The driving force distribution means includes differential means acting between a left wheel and a right wheel, and differential limiting means for restricting the differential action of the differential means. The listed vehicle. The distribution of the ground load between the left wheel and the right wheel by the ground load distribution means based on the friction coefficient of the road surface with respect to the left wheel and the right wheel, and the distribution of the driving force between the left wheel and the right wheel by the driving force distribution means are: The vehicle according to any one of claims 1 to 3, wherein the vehicle is driven until the wheel driving force does not exceed the product of the ground load and the friction coefficient on the side where the friction coefficient of the road surface is low.

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