JPH1148736A - Grounding load control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten stable motion condition at turn time. SOLUTION: This grounding load control device is provided with an actuator 5 for actively changing a vertical direction relative distance between a car body 4 and a tire 1, yaw rate sensor 31 detecting a yaw rate of a vehicle, a steering angle sensor 33, a car speed sensor 34, and a reference yaw rate arithmetic part 35 calculating a reference yaw rate based on a detection value of each sensor. When a difference between an actual yaw rate and the reference yaw rate is increased, a spin and plow out tendency generated during a turn of the vehicle can be judged and the actuator of a wheel objective for resetting from these behavior conditions is controlled in a direction increasing the vertical direction relative distance. The rear wheel in the case of the spin, the front wheel in the case of the plow out, can be restored from the unstable behavior of the vehicle by respectively increasing a grounding load.

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.

[0002]

2. Description of the Related Art Conventionally, there has been a device for automatically controlling the damping force of a vehicle suspension, such as that disclosed in Japanese Patent Application Laid-Open No. 3-114914. In this device, a fluid cylinder is disposed between both the sprung and unsprung portions, and a so-called active suspension in which the suspension characteristics of the vehicle are varied by controlling the flow rate supplied to each fluid cylinder is used. Means for detecting the pressure of the fluid, and means for detecting the weight balance of the vehicle based on this means, and from this weight balance, the load movement amount at the front of the vehicle body becomes larger than the load movement amount at the rear part of the vehicle body when turning the vehicle. The control gain is changed as described above, and the control is performed so as to obtain an appropriate understeer characteristic.

[0003]

However, in the above-mentioned prior art, the distribution of the roll stiffness before and after is dynamically controlled, so that the ratio of the load to the tire having a sufficient load among the four-wheel grounding load is reduced. The balance of the front and rear wheels is optimized without changing the magnitude of the total load of the four wheels. Therefore, when the vehicle shifts from the optimal balance state of the four wheels to a more severe turning state during turning, there is a problem that the vehicle shifts to a motion state such as spin-plowout.

The present invention has been devised in order to solve such a problem imposed on the prior art, and a main object of the present invention is to further enhance a stable motion state during turning. An object of the present invention is to provide a ground load control device.

[0005]

According to the present invention, there is provided a vehicle and an axle for controlling at least one of a sprung mass and an unsprung mass. Actuator for increasing / decreasing the ground contact load of the wheels by actively changing the vertical relative distance between the vehicle, yaw rate detecting means for detecting the actual yaw rate of the vehicle, and steering angle detecting means for detecting the steering angle of the vehicle And a vehicle speed detecting means for detecting a vehicle speed of the vehicle, calculating a reference yaw rate of the vehicle based on the steering angle and the vehicle speed, wherein a difference of not less than a predetermined value between both the reference yaw rate and the actual yaw rate is obtained. If the actual yaw rate is lower than the reference yaw rate, the ground load on the front wheel side of the vehicle is increased, and the actual yaw rate is higher than the reference yaw rate. It is in the case high was used to control the actuator so as to increase the vertical load rear wheel side of the vehicle.

By doing so, it is possible to judge that the wheel may exceed the lateral limit characteristic and shift to the spin-plowout behavior during the turn, and that the wheel is in the course of the shift, and to determine the yaw rate, the steering angle, and the like. Judging from the vehicle speed, it is possible to judge any of the behaviors, and the rear wheel is increased in the case of spin tendency, the front wheel is increased in the case of plow out, and the contact load of each target wheel is increased. It is possible to control the actuator that performs the turning operation, and to ensure the turning behavior desired by the driver during the turning of the vehicle up to a high turning G.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to specific examples shown in the accompanying drawings.

FIG. 1 schematically shows a schematic configuration of a main part of an active suspension system to which the present invention is applied. The tire 1, which is integral with the axle, consists of upper and lower suspension arms 2.3
, So as to be vertically movable with respect to the vehicle body 4.
And between the lower suspension arm 3 and the vehicle body 4,
A hydraulically driven linear actuator 5 is provided.

The linear actuator 5 is of a cylinder / piston type, and uses a servo valve 10 to supply hydraulic pressure 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.

In the ECU 18, signals from the sprung acceleration sensor 22 and the unsprung acceleration sensor 23 are input to a target load calculating section 24, and the yaw rate sensor 3
1. Lateral G sensor 32, steering angle sensor 33, vehicle speed sensor 34
Are input to the reference yaw rate calculation unit 35, and the output signal from the reference yaw rate calculation unit 35 is input to the target load calculation unit 24. In the target load calculating unit 24, a tentative target load is obtained by referring to each of the signals,
After the difference between this value and the signal of the load sensor 20 is processed by the stabilization calculation unit 25, the displacement limit comparison calculation unit 26 refers to the signal of the stroke sensor 21 and performs control within the stroke limit of the actuator 5. The command value given to the servo valve driver 19 is adjusted so as to be adjusted.

The adjusted command signal drives the servo valve 10 so that the target load becomes equal to the actual load, generates a stroke in the actuator 5, and increases the vertical acceleration in the direction to increase the tire contact load. It is generated in at least one of the sprung mass and the unsprung mass.

Next, the principle of the present invention will be described. FIG.
M2: sprung mass M1: unsprung mass Z2: sprung coordinates Z1: unsprung coordinate Kt: tire spring constant Fz: actuator thrust, and if the downward direction is the positive direction, the sprung mass M2 and the unsprung mass The equations of motion of the 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 expansion and contraction 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.

In general, a suspension spring for supporting the weight of the vehicle and a damper for generating damping force are used together in order to save energy consumption of the actuator (see FIG. 3). In this case, Ks: suspension spring Where C is the damping coefficient of the damper, and the equations of motion for 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 · (Z
1−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, Tr / 2 (see FIG. 4), 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 force, moment, and direction of the coordinate system are as shown in FIG. 5, 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)

Assuming that the rolling moment of inertia is Ix and the pitching moment of inertia is Iy, the rolling moment of inertia is Ixφ ^* = Mx = Tf / 2 · (−Fz1 + Fz2) −Tf / 2 · (−Fz3 + F
z4), 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. It can be seen that the contact load can also be controlled 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.

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

Next, control for returning from an unstable state of the vehicle, such as spin, plow-out, and four-wheel drift, for example, when turning the vehicle by using the actuator 5 will be described with reference to the flowchart of FIG. Shown in From the first step ST1 to the third step ST3, the yaw rate sensor 31, the steering angle sensor 33, and the vehicle speed sensor 34 read the respective signals of the yaw rate, the steering angle, and the vehicle speed.

In a fourth step ST4, a reference yaw rate calculation section 35 calculates a reference yaw rate γs from each signal of the steering angle and the vehicle speed, and in a next fifth step ST5, the actual yaw rate γ read in the first step ST1 is calculated. It is determined whether or not a difference equal to or more than a predetermined value α has occurred between the reference yaw rate γs and the reference yaw rate γs. Note that the calculation of the reference yaw rate γs
May be used together, but this is not essential.

If the difference is smaller than the predetermined value α in the fifth step ST5, it can be determined that the vehicle is turning substantially along the reference yaw rate γs, and in that case, the contact load control is not performed. If it is larger, it is determined that the vehicle may or may not be transitioning to the spin or plow-out state, that is, it is determined that the vehicle has not achieved the behavior desired by the driver, and the process proceeds to the sixth step ST6.

The determination of each behavior state can be made based on the difference between the reference yaw rate γs and the actual yaw rate γ,
This determination is made in the sixth step ST6. In making this decision,
If there is no brake operation and the steering angle is constant or increased, it is understood that a higher turn is required.
When γ> γs, there is a spin tendency, and γ <γs
In the case of, it can be determined that there is a tendency to plow out. γ>
If γs, the process proceeds to the seventh step ST7, in which control is performed to increase the contact load of the rear wheel. If γ <γs, the process proceeds to the eighth step ST8, where control to increase the contact load of the front wheel is performed.

When the process proceeds to the seventh step ST7, it is determined that the vehicle has a tendency to spin. The load for returning from the spin state is calculated, and the acceleration of the sprung acceleration sensor 22 and the unsprung acceleration sensor 23 is calculated. Referring to each signal,
The provisional target load signal obtained internally is input to the stabilization calculation unit 25 by feeding back the signal of the load sensor 20. By comparing the output signal of the stabilization calculation unit 25 and the signal of the stroke sensor 21 with the displacement limit comparison calculation unit 26, the adjustment is performed so that the control is performed within the limit of the suspension displacement. Then, the displacement limit comparison operation unit 26
By controlling the servo valve 10 via the servo valve driver 19 in response to the signal output of the above, the actuator 5 is driven to increase the ground contact load of a desired wheel, thereby returning from the spin state.

The spin state is a behavior that occurs when the moment around the center of gravity due to the total lateral force of the front wheels exceeds the moment due to the lateral forces of the total rear wheels during turning of the vehicle. Therefore, in order to return from that behavior, it is sufficient to reduce the tire contact load on the front wheel or increase the tire contact load on the rear wheel to make the front-rear balance of the moment even. The load is increasing.
For example, as shown in FIG. 7, which conceptually shows the distribution of the grounding load (= grip force) of each tire of the turning vehicle, the tire grounding load of the rear wheels is indicated by the imaginary line in the figure from the state shown by the solid line in the figure. It is good to increase to the state that is.

Further, at the time of plow-out, it is possible to return from the plow-out by increasing the contact load of the front wheel or increasing the contact load of the rear wheel outer wheel. In the illustrated example, as shown in the eighth step ST8, the contact load of the front wheels is increased.

It should be noted that, without departing from the spirit of the present application,
The sensors used can be simplified. For example, although the sensor is redundantly configured in the present embodiment, the stroke sensor 21 is eliminated, and the values obtained by multiplying the unsprung acceleration sensor 23, the sprung acceleration sensor 22, the unsprung mass, and the sprung mass are subtracted. And load sensor 2
It is also possible to abolish 0. Also, the load sensor 20
It is also possible to configure a state estimator from the stroke sensor 21 and obtain the unsprung acceleration and the sprung acceleration. As described above, the system configuration can be appropriately changed as needed. Further, the ECU of FIG. 1 can be realized by any of digital, analog and hybrid.

Further, according to the present invention, in a vehicle (for example, an RV vehicle that can be ridden by a large number of people) having a large change in vehicle weight between a driver-only state and a fixed-load state, the behavior of the vehicle is changed by the change in vehicle weight. Can be prevented by controlling the grounding load. For example, if the load capacity increases and the front wheel axle weight becomes smaller than the rear wheel axle weight with respect to the optimal ratio of the front and rear wheel axle weights, the ground contact load of the front wheels is increased. , The cornering force generated by the front and rear wheels can be properly balanced, and stable running can be achieved. These controls can be performed by the control during the turning without providing a separate control structure.

[0038]

As described above, according to the present invention, when the vehicle exceeds the lateral limit characteristics of the tire while turning, there is a possibility that the tire will behave as a spin or a plow-out. Or that it is in the middle of the transition, it can be determined by comparing the standard yaw rate calculated from the vehicle speed and the steering angle with the actual yaw rate detected by the yaw rate sensor. By directly controlling at least one of the unsprung acceleration and arbitrarily controlling the unsprung ground contact load, the above behavior can be restored.

[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 is a model diagram of a general active suspension device.

FIG. 4 is an explanatory diagram showing a relationship between a vehicle center of gravity position and a contact position.

FIG. 5 is a diagram illustrating a relationship between a force, a moment, and a direction of a coordinate system.

FIG. 6 is a flowchart showing control based on the present invention.

FIG. 7 is a diagram showing a state of a ground contact load of each tire during turning.

[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 control 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 31 yaw rate sensor 32 lateral G sensor 33 steering angle sensor 34 vehicle speed sensor 35 norm yaw rate calculation unit

Claims (1)

[Claims] 1. A ground contact load of a wheel is increased or decreased by actively changing a vertical relative distance between a vehicle body and an axle to control a movement speed of at least one of a sprung mass and an unsprung mass. Actuator, a yaw rate detection unit that detects an actual yaw rate of the vehicle, a steering angle detection unit that detects a steering angle of the vehicle, and a vehicle speed detection unit that detects a vehicle speed of the vehicle. The reference yaw rate of the vehicle is calculated based on the vehicle speed, and when a difference equal to or more than a predetermined value occurs between the reference yaw rate and the actual yaw rate, and the actual yaw rate is lower than the reference yaw rate. Increases the ground contact load on the front wheel side of the vehicle, and increases the ground contact load on the rear wheel side of the vehicle when the actual yaw rate is higher than the reference yaw rate. Ground contact load control device and controls the actuator.