JPH10297239A - Ground load controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To temporarily increase the ground load of a tire by the reaction force, by generating the inertia force in a vertical direction on a car body, by the expansion acceleration of an actuator mounted between the car body and an axle, when it is judged that the desired acceleration can not be achieved without changing the present condition, on the basis of the opening of a throttle, a speed or the like at the acceleration. SOLUTION: The tires 1 are supported in such manner that they are vertically movable to a car body 3, by the upper and lower suspension arms 2, 3, and a linear actuator 5 is mounted between the lower suspension arm 3 and the car body 4. The ground load is a sum of the sprung inertia force and the unsprung inertia force, so that the ground load can be changed by changing one of the inertia force of the sprung mass and that of the unsprung mass by controlling the expansion acceleration of the linear actuator 5. Accordingly the ground load can be temporarily increased every tire by controlling the expansion acceleration of the actuator 5, whereby the grip force, that is, the accelerating performance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact load control device capable of instantaneously increasing a contact load by generating acceleration in at least one of a sprung mass and an unsprung mass, and more particularly to an acceleration performance. Field of the Invention The present invention relates to a ground load control device that can contribute to the improvement of the load.

[0002]

2. Description of the Related Art Conventionally, at the time of sudden acceleration such as when starting a vehicle, a driving force generated by a tire is controlled so as to be near a peak value determined by a slip ratio between the tire and a road surface so that the tire does not slip. A so-called traction control system is known in which the vehicle is accelerated stably and efficiently.

On the other hand, a linear sliding actuator capable of actively changing the stroke is provided between the vehicle body and the axle, and the distribution of the grounding load of each tire according to the motion state of the vehicle at that time is set to a predetermined target. An active suspension system in which the stroke of the actuator is feedback-controlled so as to obtain a value has already been put to practical use.

[0004] For example, a conventional active suspension system as proposed in Japanese Patent Publication No. Sho 60-500662 basically basically uses a thrust (stroke) of a hydraulic actuator so as to suppress a change in posture of a vehicle body during traveling. The load is transferred between the front and rear axles so that the tire follows the unevenness of the road surface so as to suppress the change in the center of gravity of the sprung mass during straight traveling, and to suppress pitching during braking and acceleration. It is common to control the amount and control the amount of load movement between the tires so as to suppress rolling during turning.

[0005]

The grip force F of a tire is given by the product (F = μW) of the coefficient of friction μ between the tire and the road surface and the vertical load W applied to the contact surface of the tire. That is, it can be said that the grip force of the tire, which greatly affects the mobility of the vehicle, is proportional to the ground contact load if the friction coefficient between the tire and the road surface is constant.

However, in the traction control system as described above, since the ground contact load is constant, the distribution of the driving force of each wheel according to the vehicle behavior at that time is within the range of the friction coefficient determined by the road surface and the tire. It was only possible to optimize, and it was not possible to further increase the margin of the grip force of the tire beyond this.

Similarly, even in the active suspension system as described above, the load distribution of each wheel according to the vehicle behavior at that time can be optimized within the range of the vehicle weight, and the load distribution beyond the range of the vehicle weight can be optimized. It was not possible to further increase the margin of tire grip.

The present invention has been devised to solve such problems imposed on the prior art, and its main purpose is to temporarily and selectively reduce the ground contact load of each wheel. An object of the present invention is to provide a vehicle control device capable of further increasing the generation limit of the grip force of each tire by increasing the value, and in particular, stably obtaining a high acceleration performance at the time of acceleration such as starting.

[0009]

According to the present invention, in order to achieve the above object, it is determined that a desired acceleration cannot be obtained as it is from acceleration, throttle opening vehicle speed, wheel speed, acceleration and the like. A vertical inertial force is generated in the vehicle body by the expansion acceleration of an actuator provided between the vehicle body and the axle, and the reaction force thereof temporarily increases the contact load of the tire. According to this, a load exceeding the vehicle weight can be temporarily applied to the contact surface of the tire, so that the generation limit of the grip force of the tire can be raised as desired, and temporary acceleration at the time of starting or the like can be achieved. Performance is improved. Also, depending on the road surface condition, by increasing the ground contact load when the road surface friction coefficient is lower than when it is high,
More detailed control according to the situation becomes possible.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 schematically shows a schematic configuration of a main part of an active suspension device to which the present invention is applied. Tire 1
The upper and lower suspension arms 2 and 3
It is supported so that it can move up and down. A linear actuator 5 driven by hydraulic pressure is provided between the lower suspension arm 3 and the vehicle body 4.

The linear actuator 5 is of a cylinder / piston type, and uses a servo valve 10 to supply hydraulic oil supplied from a variable displacement hydraulic pump 9 to oil chambers 7 and 8 above and below a piston 6 inserted into the cylinder. To generate a vertical thrust on the piston rod 11,
As a result, the relative distance between the center (axle) of the tire 1 and the vehicle body 4 can be freely changed.

The oil discharged from the pump 9 is stored in an accumulator 12 for removing the pump pulsation and ensuring the oil amount in a transient state. Are supplied via servo valves 10 provided individually.

An unload valve 13, an oil filter 14, a check valve 15, a pressure regulating valve 16, an oil cooler 17, and the like are connected to the hydraulic circuit, as in a known active suspension system.

The servo valve 10 provides a control signal issued from an electronic control unit (ECU) 18 to a solenoid 10a via a servo valve driver 19, so that the hydraulic pressure and the direction applied to the hydraulic actuator 5 are continuously adjusted. The vehicle body 4 and the piston rod 1 are controlled.
1, a load sensor 20 provided between the vehicle body 4 and the lower suspension arm 3, a sprung acceleration sensor 22 for detecting a vertical acceleration on the vehicle body, and a vertical sensor on the tire side. Control is performed based on a signal obtained by processing a signal of the unsprung acceleration sensor 23 for detecting acceleration by the ECU 18.

The ECU 18 includes a driving wheel idling prediction unit 27
, A target load calculator 24, a stabilization calculator 25, and a displacement limit comparison calculator 26. A slip prediction signal (drive wheel) generated by the drive wheel slip prediction unit 27 based on signals from the vehicle speed sensor 29, the longitudinal acceleration sensor 30, the throttle opening sensor 31, and the road surface condition setting switch 32 provided on the driven wheels. With reference to the signal from the sprung acceleration sensor 22 and the signal from the unsprung acceleration sensor 23, a target load calculating unit 24 obtains a tentative target load with reference to the value of the target load. Load sensor 2
After the difference from the signal of 0 is processed by the stabilization calculation unit 25, the servo valve is controlled by the displacement limit comparison calculation unit 26 with reference to the signal of the stroke sensor 21 so that the control within the stroke range of the actuator 5 is performed. The command value given to the driver 19 is adjusted. And by this adjusted command signal,
The servo valve 10 is driven so that the target load becomes equal to the actual load, a stroke is generated in the actuator 5, and the vertical acceleration in a direction to increase the tire contact load is increased by at least one of the sprung mass and the unsprung mass. Generate on one side.

Next, the principle of temporarily increasing the contact load will be described. In the model shown in FIG. 2, M2: sprung mass M1: unsprung mass Z2: sprung coordinates Z1: unsprung coordinates Kt: tire spring constant Fz: actuator thrust The equations of motion of the unsprung mass M1 are given by the following equations, respectively. However, the ^* mark in the equation represents the first derivative, and the ^** mark represents the second derivative. M2 · Z2 ^** =-Fz M1 · Z1 ^** + Kt · Z1 = Fz

Accordingly, the tire contact load W is given by the following equation. W = −Kt · Z1 = −Fz + M1 · Z1 ^** = M2 · Z2 ^** + M1 · Z1 ^**

That is, since the ground contact load W is the sum of the sprung inertia force and the unsprung inertia force, the expansion / contraction acceleration of the actuator 5 is controlled to at least one of the sprung mass and the unsprung mass. Is changed, the contact load W can be changed. Therefore, by controlling the extension acceleration of the actuator 5, it is possible to temporarily increase the contact load W for each tire. When a 1-ton thrust is generated in the actuator 5 with a suspension stroke of 200 mm, about 0.2
Can be activated for seconds.

For example, when the front wheel drive vehicle suddenly starts and accelerates, the load on the front wheels is slightly larger than the load on the rear wheels even under normal conditions (FIG. 3A). And then temporarily increase (Fig. 3
(B)) The grip force of the front wheels is improved, and the acceleration performance is improved. Similarly, when the rear wheel drive vehicle suddenly starts and accelerates, as shown in FIG. In the case of a driving vehicle, as shown in FIG. 4 (b), by temporarily increasing the contact loads of all the front and rear wheels as compared with the normal case, the grip force of the driving wheels is improved, and the acceleration performance is improved. improves.

FIGS. 3 and 4 conceptually show the distribution of the contact load (= grip force) of the tire. The contact load in the range of the static load is represented by a solid circle and increased by the stroke control of the actuator 5. The obtained ground contact load is represented by a two-dot chain line circle.

In general, a suspension spring for supporting the vehicle weight and a damper for generating a damping force are used together in order to save energy consumption of the actuator (see FIG. 5). In this case, Ks: Spring constant C: damping coefficient of damper Assuming that, the equations of motion of the sprung mass M2 and the unsprung mass M1 are given by the following equations, respectively. M2 · Z2 ^** + C · (Z2 ^* −Z1 ^* ) + Ks · (Z2-Z1)
= −Fz M1 · Z1 ^** + C · (Z1 ^* −Z2 ^* ) + Ks · (Z1−Z2)
+ Kt.Z1 = Fz

Accordingly, the tire contact load W is given by the following equation. W = −Kt · Z1 = −Fz + M1 · Z1 ^** + C · (Z1 ^* −Z2 ^* ) + Ks · (Z1−Z2) = M2 · Z2 ^** + M1 · Z1 ^**

That is, it can be seen that the ground load W can be changed by controlling the expansion and contraction acceleration of the actuator in the same manner as described above.

The actual inertial force of the vehicle is generated not only by the vertical motion but also by the rolling motion and the pitching motion. Here, the rotational movement around each axis passing through the center of gravity of the sprung mass is defined as roll rate: φ pitch rate: θ yaw rate: γ, and the center line in the front-rear direction and the center line in the left-right direction with respect to the center of gravity position The distance to the grounding center is Lf,
Lr, Tf / 2, and Tr / 2 (see FIG. 6), and the thrust of the actuator of each wheel is represented by Fz1 (front left), Fz2 (front right), Fz
Assuming that z3 (rear right) and Fz4 (rear left) and the direction of the force, moment, and coordinate system are as shown in FIG. 7, the rolling moment is: Mx = Tf / 2. (-Fz1 + Fz2) -Tf / 2・ (−Fz3
+ Fz4), and the pitching moment is as follows: My = Lf · (−Fz1−Fz2) −Lr · (−Fz3−Fz4)

If the rolling moment of inertia: Ix and the pitching moment of inertia: Iy, the rolling moment of inertia is And the pitching inertial force is Iyθ ^* = My = Lf · (−Fz1−Fz2) −Lr · (−Fz3−Fz4).

Further, the inertial force of the vertical motion is M2 · Z2 ^** = − Fz1−Fz2−Fz3−Fz4. By controlling at least one of these inertial forces, the rolling motion and the pitching motion are included. The stability at the time of rapid acceleration is further improved by controlling the contact load individually for each tire. In the conventional vehicle, since the load is distributed to the four wheels, the rolling inertia force, the pitching inertia force, and the inertia force of the vertical movement are not generated, and these values become zero.

Next, the slip prediction process by the drive wheel slip predicting section 27 and the subsequent contact load increasing process will be specifically described with reference to the flowcharts of FIGS. First, in steps 1 and 2, the throttle opening .theta.th is read from the throttle opening sensor 31 and the longitudinal acceleration Gacc is read from the longitudinal acceleration sensor 30, and these are read in step 3 as the reference throttle opening .theta.
By comparing th0 with the reference longitudinal acceleration Gacc0, it is determined whether rapid acceleration is required. If rapid acceleration has not been requested, the process returns to step 1; if rapid acceleration has been requested, the process proceeds to step 4 to read the vehicle speed Vc.
It is predicted from the h and the vehicle speed Vc whether or not the drive wheels idle.
Then, if it is not predicted in the step that the driving wheel is running idle, the process returns to the step 1, and if it is predicted that the wheel runs idle, the process proceeds to a step 6, where the target acceleration Gacct is calculated from the throttle opening θth and the vehicle speed Vc. Next, the contact load to be increased, that is, the urging contact load Wadd is calculated in a procedure described later (step 7), and the contact load is actually increased by the above-described method (step 8).

The procedure for calculating the biasing contact load Wadd in step 7 will be described with reference to FIG. First, at step 71, the set value S by the road surface state setting switch 32 is set.
w, the current driving force TRa is obtained from the road surface condition set value Sw, the vehicle speed Vc, and the throttle opening degree θth in step 72, and in step 73, the required driving force TRn for the target acceleration Gacct is determined in consideration of the aerodynamic effect. Calculate. And
Proceeding to step 74, the urging driving force, that is, the necessary driving force TRn
And the current driving force TRa, and the road surface friction coefficient μ based on the road surface state setting value Sw, to calculate the biased ground load Wadd. That is, when Sw3 is selected in a situation where the road surface μ is small, the urging contact load Wadd becomes larger than when Sw1 is selected.

Here, in the present configuration, the road surface condition setting means is used as the road surface state setting switch 32 to obtain the road surface friction coefficient μ from the set value Sw, and this is used. However, the road surface condition setting means is automatically determined from the vehicle speed, steering reaction force and the like. It is also possible to detect, and in that case, it is possible to obtain a finer biasing contact load Wadd.

In the above-described embodiment, an actuator using a hydraulically driven cylinder device as the actuator has been described. This can be achieved by using other electric thrust generating means such as a linear motor or a voice coil, or by using a cam. The same effect can be obtained even if the acceleration is generated using a mechanism or a spring means.

Further, the sensor used can be simplified without departing from the gist of the present invention. For example, sprung,
Since the position detection signal can also be obtained by integrating the output difference of the unsprung acceleration sensors into the second order, the stroke sensor can be eliminated, and the actual measured values of the sprung and unsprung weights and the sprung and sprung weights can be obtained. Since the force generated by the actuator can be obtained by calculating the output values of the lower acceleration sensors, the load sensor can be omitted.
Furthermore, a state estimator can be configured based on signals from the load sensor and the displacement sensor, and both sprung and unsprung accelerations can be obtained indirectly. Furthermore, it goes without saying that the ECU can be realized by any of digital, analog, and hybrid.

[0033]

As described above, according to the present invention, one or both of the sprung mass and the unsprung mass can be directly controlled by the thrust generated by the actuator to control one or both of the sprung mass and the unsprung mass. By generating the inertial force and applying the reaction force to the contact surface, the contact load of the tire at the time of rapid acceleration can be temporarily increased. Therefore, the generation limit of the grip force of the tire at the time of sudden acceleration at the time of starting or the like can be increased, and it is possible to accelerate stably and efficiently.

[Brief description of the drawings]

FIG. 1 is a schematic system configuration diagram of an active suspension device to which the present invention is applied.

FIG. 2 is a model diagram for explaining the principle of the present invention.

FIG. 3 (a) is a conceptual ground load distribution diagram when a conventional front wheel drive vehicle suddenly starts, and FIG. 3 (b) is a conceptual ground load distribution when a front wheel drive vehicle to which the present invention is applied suddenly starts. FIG.

FIG. 4A is a conceptual ground load distribution diagram at the time of sudden start of a rear wheel drive vehicle to which the present invention is applied, and FIG. 4B is a diagram at the time of sudden start of a four wheel drive vehicle to which the present invention is applied; Conceptual grounding load distribution diagram.

FIG. 5 is a model diagram of a general active suspension device.

FIG. 6 is an explanatory diagram showing a relationship between a vehicle center of gravity position and a contact position.

FIG. 7 is an explanatory diagram showing a relationship between a force, a moment, and a direction of a coordinate system.

FIG. 8 is a flowchart showing a slip prediction procedure by a drive wheel slip prediction unit 27;

FIG. 9 is a flowchart showing a procedure for calculating a contact load.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tire 2 Upper suspension arm 3 Lower suspension arm 4 Body 5 Actuator 6 Piston 7.8 Oil chamber 9 Hydraulic pump 10 Servo valve 11 Piston rod 12 Accumulator 13 Unload valve 14 Oil filter 15 Check valve 16 Pressure adjustment valve 17 Oil cooler Reference Signs List 18 electronic control unit (ECU) 19 servo valve driver 20 load sensor 21 stroke sensor 22 sprung acceleration sensor 23 unsprung acceleration sensor 24 target load calculation unit 25 stabilization calculation unit 26 displacement limit comparison calculation unit 27 drive wheel idling prediction unit 29 Vehicle speed sensor 30 longitudinal acceleration sensor 31 throttle opening sensor

Claims (2)

[Claims] An actuator for actively changing a vertical relative distance between a vehicle body and an axle is given a thrust to generate acceleration in at least one of a sprung mass and an unsprung mass, and the acceleration is generated. Ground load control means for applying a reaction force of inertia force of at least one of a sprung mass and an unsprung mass to a ground load acting between a tire and a road surface, and predicting idle of a drive wheel during acceleration of a vehicle A contact load control device for increasing a contact load of a drive wheel in accordance with a result of detection by the drive wheel idling prediction means. 2. The apparatus according to claim 1, further comprising a road surface condition setting means for judging a road surface condition, wherein the lower the road surface friction coefficient set by the road surface condition setting device, the larger the contact load is set. Ground load control device.