JPH0485118A - Tire air pressure control device - Google Patents

Abstract

PURPOSE:To obtain optimum turning force by constructing a vehicular tire air pressure control device for changing a suspension characteristic according to the travel state, in such a way as to compute the load moving quantity generated in association with turning at the time of starting turning motion and to control tire air pressure predictively according to the computed result so as to obtain the maximum turning force. CONSTITUTION:A control unit 20 performs specified control on the basis of information detected by a vehicle speed sensor 23, a road surface sensor 24, an outside air temperature sensor 25 and a steering angle sensor 26. When the vehicle speed is judged to be more than the specific value from the information of the vehicle speed sensor 23 and steering angle sensor 26, lateral acceleration is predictively computed from the vehicle speed and steering speed. The load moving quantity of the vehicle is then computed from the predicted result, and the correction air quantity is obtained from the specified correction air quantity vs. lateral acceleration characteristic line. The air pressure of a left and a right front wheels is then corrected according to the turning direction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a tire air pressure control device, and more particularly, to a tire air pressure control device that changes tire air pressure in order to change suspension characteristics depending on the driving condition of a vehicle. This invention relates to a pneumatic control device.

(Prior Art) It is known that the air pressure of tires in a vehicle not only affects the ride comfort of the vehicle but also affects the suspension characteristics, thereby affecting driving performance such as cornering performance and steering characteristics. . Therefore, by variably controlling this tire air pressure according to the load on each tire (hereinafter referred to as wheel load) and driving conditions, good running performance is always achieved regardless of the number of passengers or the amount of luggage loaded. Attempts are being made to make it possible.

As such a tire pressure control device, Japanese Patent Application Laid-open No. 58
There is a device described in Japanese Patent No. 8411, and the device described in this publication is provided with an air supply/discharge means for supplying and discharging air to each tire, and a means for detecting the air pressure of each tire. The control means includes a means for detecting the wheel load of each tire, a means for detecting the running state of other vehicles, and a control means for controlling the air pressure of each tire based on these. In order for each tire to obtain cornering power and cornering force that will give a positive value for the static margin that indicates physical stability, in other words, so that the steering characteristics tend to understeer, or when the level of vibration transmitted from the road surface to the vehicle body is high. The air pressure of each tire is feedback-controlled to lower the air pressure, and to increase the air pressure when driving at high speeds.

(Problem to be Solved by the Invention) By the way, when the tire air pressure is made variable according to the driving conditions as described above, the air pressure supply/discharge means may be a compressed air pump, an air tank or an accumulator, an air pressure supply/discharge valve, etc. In this case, the internal pressure of the tires is quite high from the beginning, and each tire carries the weight of the vehicle, so in order to supply more air into the tires, a large amount of pressure is required. A large-capacity pump that can obtain pressure is required, and it takes a long time to supply air to the target air pressure, resulting in a delay in the response of air pressure control depending on the driving state. Moreover, since this control is performed by feedback control as described above, the above-mentioned response delay is particularly noticeable during actual turning, and there is a problem that good cornering power and even cornering force cannot be obtained during turning. Ta.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a tire air pressure control device that can obtain cornering power and cornering force suitable for turning a vehicle while the vehicle is turning.

(Means for Solving the Problems) The present invention provides a tire air pressure control device that changes the tire air pressure in order to change the suspension characteristics according to the running condition of the vehicle. The present invention is characterized in that the tire air pressure is predictively controlled in advance so as to obtain the maximum cornering force according to the predicted amount of load movement.

Note that the predictive control of the tire air pressure is preferably performed by discharging air from the inner wheel during turning. Further, it is desirable that the larger the predicted load movement amount is, the larger the amount of the predicted control of the tire is. It is preferable that the predicted load movement amount is calculated by predicting the lateral acceleration during the turn.

(Operations and Effects of the Invention) The tire air pressure control device of the present invention predicts and calculates the amount of load movement when the vehicle turns, and thereby controls the tire air pressure so that the maximum cornering force (i.e., cornering power) is obtained. As a result, the cornering limit is improved, and it is possible to achieve both stability of the vehicle body posture and steering stability when turning.

(Embodiments) Hereinafter, a tire air pressure control device according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a tire air pressure control device according to an embodiment of the present invention. As shown in FIG. The air supply system lO to the tires 1 to 4 is provided. This air supply system 10 includes a compressed air pump 11,
an air supply passage 14 that supplies compressed air to each tire 1 to 4 from a pressure accumulator 13 into which compressed air discharged from the pump 11 is introduced via a check valve 12 and maintained at a predetermined pressure; Branch parts 141 to 144 of each tire 1 to 4 of
Three-way switching valves 15, 15. It is made up of. And each of the three-way switching valves 15. ~1
Reference numerals 54 indicate a closed position where the air inside the tires 1 to 4 is confined, an open position where the insides of the tires 1 to 4 are communicated with the pressure accumulator 13 side, and an atmospheric position where the insides of the tires 1 to 4 are opened to the atmosphere. It can be switched to the open position.

In addition, the three-way switching valve 15. - 154 are connected to a control unit 20 composed of a microcomputer or the like, and this control unit 20 controls the three-way switching valves 15 . 154 to control the air pressure in each tire 1 to 4.

This control unit 20 includes three-way switching valves 15 at each branch section 141 to 144 of the air supply passage 14.
．． ~15. Output signals from the air pressure sensors 21, 214, which detect the downstream pressure of the tires 1 to 4, that is, the internal pressure of each tire 1 to 4, and output signals from the wheel load sensors 22, 224, which detect the load applied to each tire 1 to 4, respectively. An output signal, an output signal from a vehicle speed sensor 23 that detects the vehicle speed of the vehicle, and 1
, an output signal from a road surface sensor 24 that detects the road surface resistance of the running road, and an output signal from an outside temperature sensor 25 that detects the outside temperature are input. The control unit 20 then operates each of the three-way switching valves 151 to 15 . in response to these input signals. Switch and operate each tire 1 to 4.
By supplying and discharging air to and from, the air pressure is controlled.

Here, the specific configuration of the air supply/discharge system for each tire 1 to 4 will be explained with reference to FIG. is provided in the first air passage 31a, and the branch portion 14. of the air supply passage 14 shown in FIG. 1 is provided in the first air passage 31a.
(14a to 144) are connected to the axle 32, which is rotatably supported by the axle support member 31.
A circumferential groove 32a communicating with the first air passage 31a and a second air passage 32b communicating with the circumferential groove 32a and opening at the tip of the axle 32 are provided. One end of the vibe 33 is connected to the tip of the second air passage 32b, and the other end of the vibe 33 is connected to the wheel 34 of the tire 1 (2 to 4).
As a result, the branch portion 14 of the empty supply passage 14. (14
2 to 144) are constantly communicated within the tire 1 (2 to 4).

Next, each tire 1 is controlled by the control unit 20.
The specific operations of the air pressure control in steps 4 to 4 will be explained according to the flowchart in FIG.

First, in step S1, the control unit 20
It is determined whether the ignition switch of the engine is ON or not, and when it is ON, that is, while the engine is operating, in step S2, each air pressure sensor 2 shown in FIG.
1. ~211, each wheel load sensor 22. 224 and the output sensor from the vehicle speed sensor 23, each tire 1 to 4
The air pressures p, -P4, wheel loads W1 to W4, and vehicle speed V are detected. Then, in step S3, it is determined whether the acceleration A obtained from the vehicle speed V is smaller than a negative predetermined value -α, that is, whether it is during sudden braking where the deceleration is larger than the predetermined value. If it is not the time of sudden braking, it is determined in step S4 whether the vehicle speed V is 0, that is, whether the vehicle is stopped.

Then, during normal driving when the vehicle is not stopped and is not under sudden braking, the vehicle speed V is set to 40 Km/h in step S5.
It is determined whether or not the above conditions are met, and when the speed is medium to high speed of ≧40 km/h or more, the air pressure of each tire 1 to 4 is set in steps 56 to S10.

That is, first in step S6, based on the characteristic diagram of cornering power against air pressure for each wheel weight value shown in FIG.
Pneumatic pressure PHAχ1 to pneumatic pressure P xAx+ at which the value of cornering power at 4 (hereinafter referred to as CP value) is maximum
4 and calculate the static margin at that time.

This static margin indicates the steering characteristics of the vehicle and is calculated according to the following formula, and its value (hereinafter referred to as
When the SM value (referred to as SM value) is positive, it indicates that the steering characteristic is understeer, and when it is negative, it indicates that the steering characteristic is oversteer.

S M = CP F / (CP F + CP a
)-a/ (a + b) Here, CPF is the total value of the CP values of the tires 12 on the front wheel side, CPll is the total value of the CP values of the tires 3.4 on the rear wheel side,
a indicates the distance from the center of gravity of the vehicle to the center of the front wheels, and b indicates the distance from the center of gravity to the center of the rear wheels.

Soshite, control unit 20! ;! , step S
In step S7, it is determined whether the SM value obtained as described above is larger than a positive predetermined value β, and when SM>β, that is, when the steering characteristic is understeer, in step S8,
The maximum CP air pressure P MAXI l ~ P MAI of each tire 1 to 4 obtained from the above FIG.
4 target air pressure P1°~P,. Set to .

Also, when SM≦β, that is, when the steering characteristic is oversteer (or neutral steer), the air pressure on the rear wheel side 3.4 is set to the maximum CP air pressure P 1ll
By changing the air pressure of the front tire 1.2 while fixing Af + s and P MAXI 4,
Within the range where SM>β holds true, the CP of the tires 1 and 2
The air pressure P that has the largest value.

Calculate P2°. In other words, the air pressure of the front tire 1.2 is the maximum CP air pressure P MAXI , P MA
If the cornering power is gradually reduced by lowering the cornering power to
or neutral steer) to understeer.

Then, in step 310, each air pressure P1° p, ", P MAl, s, P obtained as described above is
MA friend + 4 to target air pressure P+o-P for each tire 1-4
4o, and the air pressures P1 to P of the tires 1 to 4 are the target air pressures P1 to P set in step 510. Alternatively, the control unit 20 controls each of the three-way switching valves 151 to 15. Outputs a switching control signal to.

As a result, when the vehicle speed V is medium to high speed of 40 km/h or higher, the air pressures P1 to P of each tire 1 to 4 are set to the pressure that provides the maximum cornering power while maintaining the steering characteristics at understeer (SM/β). Therefore,
This results in high cornering limits and excellent handling stability.

On the other hand, at low speeds such as V<40 krn/h, the control unit 20 performs the steps from step S5 to step S12.
is executed, the friction coefficient μ of the road surface is detected based on the output signal from the road surface sensor 24, and in step S13,
It is determined whether the friction coefficient μ is larger than a predetermined value μ0. And μ〉μ. In other words, when the vehicle is traveling on a normal dry road, the air pressures of the tires 1 to 4 are set in steps 314 to S18.

That is, in this case, first, in step S14, the lowest tire pressure P, 1 to Pmtx, 4 (for example, 1.3 kg/ca) that guarantees safe driving as shown in FIG.
The SM value is calculated based on the CP value of each tire 1 to 4 in step S15, and it is determined in step S15 whether or not this SM value is smaller than a negative predetermined value -β.
When <-β, that is, when the steering characteristic is oversteer, the above minimum air pressure P1llIN+I~PMIN+4 is set to each tire 1~PMIN+4 in step S16.
4 target air pressure P r o-P set to 4°.

Further, when SM≧−β, that is, when the steering characteristic is understeer or neutral steer), in step S17, the air pressure of the rear tire 3.4 is set to the minimum air pressure P MIN, S , P M 18.4. By changing the air pressure of the front tire 1.2 in a fixed state, the air pressures P1° and P2° are set such that the CP value of the tire 1.2 is the smallest within the range where SM<-β holds.
Calculate. In other words, in this case, the front tire is 1.2
The air pressure is the minimum air pressure P MINI l , P M
When the cornering power is gradually increased by increasing INI a, the air pressure at which the steering characteristic changes from understeer (neutral steer) to oversteer is found.

Then, in step 318, each of the air pressures P l', P2', P MENl, PMI obtained as described above is
N+4 is set to the target air pressure P1° to P4° of each tire 1 to 4, respectively, and the air pressure P, -P of each tire 1 to 4 is set to the target air pressure P1° to Pao set in this step 318 or the above. In step Sll, a switching control signal is output to each of the three-way switching valves 15. to 154 so that the target air pressure PIO to P4 (1) set in step S16 is reached.

As a result, when the vehicle speed V is 40 km/h or less and the vehicle is traveling on a normal dry road, the air pressures p, - of each tire 1 to 4 are determined.
P4 changes the steering characteristics to oversteer (SM<-β
) while maintaining the pressure at the lowest level within the range that guarantees safety, resulting in a soft ride and excellent turning performance.

Further, when the vehicle speed is low (below 4Q km/h), the road surface friction coefficient μ is the predetermined value μ. When traveling on the following low μ road, the control unit 20 performs the step S
13, execute steps S19 and S20,
The outside air temperature T is detected based on a signal from the outside air temperature sensor 25, and it is determined whether the outside air temperature T is lower than a predetermined value To.

When the outside temperature T is lower than the predetermined value T0 when traveling on a low μ road, in other words, when traveling on a snowy or frozen road, the control unit 20, in step S21,
Similar to step S14 above, the minimum air pressure P MINT
The SM value is calculated based on the CP value at l to P MINT 4, and it is determined in step S22 whether or not this SM value is larger than a positive predetermined value β. And SM＞
At the time of understeer of β, the step 316 described above is performed.
The minimum air pressure PHINl l -P MINT 4 is set to the target air pressure P10=P40 for each tire 1 to 4.

Further, during oversteer (or neutral steer) where SM≦β, in step S23, the air pressure of the front tire 1.2 is set to the minimum air pressure PmrN, +,
With the P work □8.2 fixed, the rear tire 3.4
By changing the air pressure, the air pressures P3° and P4 at which the CP value of each tire 3.4 becomes the largest are calculated within the range where SM>β holds true. In other words, in this case, the air pressure of the rear tire 3.4 is the minimum air pressure P MINT
8. Find the air pressure at which the steering characteristics change from oversteer (neutral steer) to understeer when the cornering power is gradually increased by increasing P MZNl.

Then, in step S24, each of the air pressures P□Nl l , P MINll 2 , P
aP4' is the target air pressure Pro for each tire 1 to 4.
~P. and each tire 1 to 4.
The air pressures P1 to P4 are the target air pressure PIO=P40 set in this step S24 or the above step 316.
In step Sll, a switching control signal is output to each of the three-way switching valves 15° to 154 so that the target air pressure P r o -P 4° set in is achieved.

As a result, when driving at low speeds on snowy or frozen roads,
The air pressure of each tire 1 to 4 is made as low as possible while maintaining the steering characteristics to understeer (SM>β), and therefore good followability and driving stability of each tire 1 to 4 to the road surface are obtained. , it becomes possible to drive well on these road surfaces without slipping.

On the other hand, even when driving on a low μ road, the outside temperature T is at the predetermined value To.
In the following cases, in other words, when the road surface is wet due to rain, the control unit 20 executes steps S20 to SIO to step SIO,
Similarly to the above-mentioned medium to high speed, the air pressure of each tire 1 to 4 is
Set the air pressure to obtain the greatest cornering power while maintaining steering characteristics with understeer.

That is, in this case, by increasing the air pressure and increasing the installation surface pressure of the tire, rainwater is drained from between the road surface and the tire, and the tire can be installed reliably.

This prevents the tires from slipping on wet road surfaces and provides good driving performance in rainy conditions.

Furthermore, the control unit 20 performs the above step S.
When it is determined in step 4 that the vehicle speed V is 0, that is, when the vehicle is stopped, steps S8 to 311 are executed to determine the maximum CP air pressure PMAK of each tire 1 to 4 from FIG.

Set to 1 to P MAIII 4.

This means that when the vehicle is stopped, the air pressure is higher than when the vehicle is moving.
By reducing the ground contact area of each tire 1 to 4, it is possible to reduce the steering wheel operation in a stopped state, which is generally called stationary steering, and to increase the cornering power or grip on the road surface of each tire 1 to 4 when the next time the vehicle starts moving. This is to maximize the acceleration and obtain good starting acceleration. In this case, the change in the air pressure of each tire 1 to 4 due to the load shift during start acceleration is anticipated in advance, and the maximum CP air pressure PklAK+l~PMA' is determined by this change.
The air pressure while the vehicle is stopped may be set so that t + 4 is obtained.

Furthermore, when the acceleration A is smaller than the negative predetermined value -α, that is, during sudden braking, the control unit 20 executes steps S3 to S5 and does not make the determination as to whether or not the vehicle is stopped in step S4. This is because if the tires lock during sudden braking, the vehicle is determined to be stopped even though it is moving (skid-like), and in this case, the control to increase the air pressure in step S8 above is performed. This is because the skid condition becomes even more severe.

Further, when the ignition switch is OFF, that is, while the vehicle is parked, the control unit 20 executes steps S1 to S25 to control each three-way switching valve 15. ~15. are in the open state, that is, these three-way switching valves 15. The pneumatic pressure of each tire 1 to 4 is not controlled by the switching operation of 1 to 154, and each tire 1 to 4 and the pressure accumulator 13 are completely communicated with each other. As a result, each tire 1~
4, the high-pressure air in the pressure accumulator 13 is introduced as is, making the air pressure even higher than when the tire is stopped. This is to prevent vibrations caused by flat spots when the vehicle is running.

As described above, the control unit 20 sets the target air pressure P r o -P 4° of each tire 1 to 4 according to the driving condition, and also sets the actual air pressure P.

~P, becomes its target air pressure P ro-P 40, the three-way switching valve 15. - 154 are switched and controlled to ensure that a good running condition is always obtained.

In the above control, the tire air pressure when the vehicle turns is controlled, and the lateral acceleration changes due to the turning, and the resulting changes, that is, the wheel loads W1 to W after the load transfer, are detected, and this detected Tire air pressure is controlled to obtain the maximum cornering power and cornering force (slip angle multiplied by cornering power) based on the wheel load W I-W 4, and this control is performed using feedback control. As a result, a control delay occurs and a predetermined tire pressure and cornering power cannot be obtained at an appropriate time during a turn. Therefore, the present invention predicts and calculates the load movement during the corner, that is, the change in the wheel loads W, -W, and controls the tire air pressure based on this to maximize the cornering power. This is what I did.

Next, with reference to the flowchart of FIG. 5, an example of predictive control of the air pressures PI-P4 of the tires 1 to 4 will be described so that the cornering power is maximized during the above-mentioned turning. In addition, in this example, since the front tire 1.2 generally greatly controls turning, the rear tire 3.4 maintains the air pressure as it is, and the air pressure of the front tire L2 is changed. The cornering power is controlled by controlling the cornering power. Furthermore, if particularly responsiveness is required, the tire pressure on only the inner tire side may be lowered to cope with the problem.

The control shown in FIG. 5 is executed as a subroutine that interrupts the main routine shown in FIG. vJ3 as appropriate. Further, for this control, a steering angle sensor 26 is connected to the control unit 20, which detects the steering angle of the steering wheel of the vehicle and outputs a signal indicating the steering angle eB.

In this control, first, in step S40, the steering angle e and the vehicle: sv are read, and then in step S40, the steering angle e and the vehicle: sv are read.
In step 41, a steering speed of 00 days is calculated from this steering angle of 0 days. After this, in step 342, the current vehicle speed V is set to 4.
It is determined whether the vehicle is at a medium-high speed of Qkm/h or more. This is because at low speeds, there is no need to consider cornering limits. If this determination is YES, step S43
Then, it is determined whether the absolute value of the steering speed αe is larger than a predetermined value αeHo. This is because if the steering is done slowly, there is no need to take cornering limits into consideration in this case as well. Note that when the determinations in steps S42 and 343 are No, the process returns to the main flow.

When the determination in step S43 is YES, in step S44, the lateral acceleration of the vehicle that will occur during the turn is predicted from the vehicle speed V and the steering speed αeB. By calculating this lateral acceleration, the amount of weight movement of the vehicle that will occur is indirectly calculated. After the calculation of the lateral acceleration is completed, in step 345, the calculated lateral acceleration is compared with the corrected air amount P0-lateral acceleration characteristic line l shown in FIG. 6 to calculate the corrected air amount P0.

As can be seen from this characteristic line 1, the corrected air amount P0 is set so that when the lateral acceleration exceeds a predetermined value, the lateral acceleration increases proportionally.

After that, in step S46, it is determined whether the steering angle eII is larger than 0, and it is determined whether the turning is to the right or to the left. When the steering angle ell is larger than 0, it is a right turn, and when it is smaller, it is a left turn. When this determination is YES, that is, when turning to the right, in step S47, the outer wheel side of the front wheel is
In other words, the target air pressure PIO for the left front wheel is the air pressure P MA
The value obtained by adding the above corrected air amount Pa to l, on the other hand,
The target air pressure P20 for the inner wheel side of the front wheels, that is, the right front wheel, is
The value is obtained by subtracting the corrected air amount P0 from the air pressure PMAI,2.

Further, when the above determination is NO, that is, when turning to the left, in step 548, the target air pressure P of the outer wheel side of the front wheels, that is, the right front wheel. is the value obtained by subtracting the corrected air amount P0 from the air pressure P 111412, and the target air pressure PIO of the inner wheel side of the front wheels, that is, the left front wheel, is the air pressure P 1
The value is obtained by subtracting the above corrected air amount P0 from mAl+1. The air pressure, especially the air pressure of the front wheels, is set to this corrected value by open control, thereby making it possible to obtain the cornering power necessary for the relevant turn.

As described above, the tire air pressure during turning is corrected.

As described above, according to the present invention, when the vehicle turns, the amount of load movement is predicted and calculated, and the tire air pressure is controlled so as to obtain the maximum cornering force (that is, cornering power). In addition, it is possible to achieve both stability of the vehicle body posture and steering stability when turning.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a tire air pressure control device according to an embodiment of the present invention, FIG. 2 is a sectional view showing a specific configuration of an air supply and discharge passage for a tire, and FIG. 3 is a control operation of air pressure control. FIG. 4 is a characteristic diagram of cornering power with respect to tire air used in this control. FIG. 5 is a flowchart diagram showing tire air pressure control when the vehicle turns. FIG. 6 is a correction diagram. FIG. 3 is a graph diagram showing an air amount-lateral acceleration characteristic line.

Claims (4)

[Claims] (1) In order to change the suspension characteristics according to the driving condition of the vehicle, a tire air pressure control device that changes the tire air pressure calculates the predicted amount of load movement associated with the turn when entering a turn, and calculates the predicted load movement. 1. A tire air pressure control device, characterized in that tire air pressure is predictively controlled in advance so that the maximum cornering force can be obtained according to the amount of cornering force. (2) The tire air pressure control device according to claim 1, wherein the tire air pressure is controlled by discharging air from an inner wheel during turning. (3) The tire air pressure control device according to claim 2, wherein the larger the predicted load movement amount, the larger the amount of the predictive control of the tire. (4) A tire air pressure control device characterized in that the predicted load movement amount is calculated by predicting and calculating the lateral acceleration at the time of the turn.