JP3132190B2 - Vehicle control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle control device for controlling a motion state of a vehicle.

[0002]

2. Description of the Related Art Generally, a vehicle control device has means for changing a wheel state quantity, which is at least one of a longitudinal force, a lateral force, and a vertical force generated between a wheel and a road surface. It is configured to control the motion state of the vehicle.
One prior art example of this device is a driving force longitudinal distribution control device described in Japanese Patent Application Laid-Open No. 61-229616, which distributes driving force to front and rear wheels so that the actual yaw rate of the vehicle body always follows the target yaw rate. By controlling the ratio, the relationship between the front wheel lateral force and the rear wheel lateral force (specifically, the yawing moment) is controlled.

[0003]

In controlling the wheel state quantity, the present applicant considers the degree of the load actually applied to the wheels, that is, the magnitude of the margin to the limit, in the vehicle. It is important to control the motion state of the vehicle as scheduled, and as a parameter indicating the degree of the load, the combined force of the longitudinal force and the lateral force actually generated between the wheel and the road surface Use of the wheel friction force as the ratio of the actual friction force to the maximum friction force, which is the product of the actual friction coefficient between the wheel and the road surface and the vertical force actually generated between the wheel and the road surface I also noticed that rates are useful.

[0004] However, the driving force front-rear distribution control device described in the above publication does not consider the actual load applied to each wheel, and considers the actual behavior of the vehicle body (specifically, the actual yaw rate and the target yaw rate). The lateral force of the wheel is controlled as a wheel state quantity by controlling the front-rear distribution ratio taking only the relationship between the front and rear wheels into consideration. Therefore, in this device, only some of the wheels have an excessively large load and approach the limit, and the behavior of the vehicle body may not be controlled as scheduled.

In short, the conventional vehicle control device is designed to control the wheel state quantity in consideration of the load on each wheel, as typified by the driving force front-rear distribution control device described in the publication. Therefore, there is a problem that the load on some of the wheels may become excessively large and the motion state of the vehicle may not be controlled as planned, and the present invention has been made to solve this problem. Things.

[0006]

In order to solve this problem, according to the first aspect of the present invention, there is provided a vehicle control device for controlling a motion state of a vehicle having a plurality of wheels , as shown in FIG.
(a) of the actual frictional force which is actually the resultant force of the longitudinal force and the lateral force is generated between each and the road surface of all the wheels of the vehicle, all
The actual friction coefficient and the ratio of the maximum frictional force is the product of the vertical force actually generated is the wheel frictional force utilization between each wheel and the road surface between each and the road surface of the wheels Each car
A wheel friction utilization rate obtaining means 1 obtains for each wheel, and (b) the longitudinal force, the wheel state quantity changing means 2 for changing the wheel state quantity is at least one of the lateral force and the vertical force, (c )
All vehicles acquired by the wheel frictional force utilization rate acquisition means 1
For each wheel, based on the actual wheel friction force utilization rate of each wheel
Of the target wheel frictional force, and the actual wheel frictional force utilization of each wheel is calculated by the wheel state changing means 2.
And a wheel frictional force utilization rate control means 3 for approaching the target frictional force utilization rate determined for each wheel. Also,
The invention according to claim 2 further comprises a wheel friction force utilization rate control means.
3, the target wheel frictional force utilization rate of each of all the wheels is approximately
It is characterized by including means for determining the same value.

The "wheel frictional force utilization rate acquiring means 1" here is, for example, a method of directly detecting the longitudinal force and the lateral force of the wheel by a sensor and acquiring the actual frictional force of the wheel as a resultant force thereof. can do. Further, for example, a two-wheel vehicle model is assumed for a four-wheel vehicle, and vehicle motion state quantities (for example, yaw rate and acceleration of the vehicle body) other than the front-rear force and the lateral force of the wheels are directly detected by a sensor, and the vehicle motions are detected. Based on the state quantities, a method of indirectly acquiring the forces generated in the x-axis direction and the y-axis direction of the vehicle fixed coordinates between the wheel and the road surface by calculation and acquiring the actual friction force of the wheel as their resultant force. It can also be.

The "wheel state quantity changing means 2" here may be, for example, a system for controlling the longitudinal force of the wheel by controlling the driving / braking torque applied to the wheel, the slip angle of the wheel or the slip ratio in the longitudinal direction. To control the lateral force of the wheel, to control the suspension force of the wheel to control the vertical force of the wheel, or to use two or more of them simultaneously. be able to. The method of controlling the front-rear force of the wheels includes, for example, the anti-lock control, the traction control, the braking force front-rear distribution idealization control (this will be described in detail in the embodiment), the braking force left-right distribution control, and the like. The method of controlling the lateral force of the wheel is employed, for example, when the present invention is implemented together with the rear wheel steering control, the drive / braking force front-rear distribution control, and the like, and the method of controlling the vertical force of the wheel. For example, the control method is generally adopted when the present invention is implemented together with suspension control or the like.

The "wheel friction force utilization rate control means 3" here is, for example, a system for controlling the wheel state quantity change means 2 so that the wheel friction force utilization rates of all the wheels of the vehicle coincide with each other. Can be. Further, a certain magnitude relationship is established between all wheels (for example, for a four-wheel vehicle,
The wheel state is such that the wheel friction force utilization rate increases in the order of the turning inner wheel of the left and right front wheels, the turning inner wheel of the left and right rear wheels, the turning outer wheel of the left and right front wheels, and the turning outer wheel of the left and right rear wheels. A method of controlling the amount changing means 2 may be employed.

As in these two systems, it is sufficient to consider only the relative relationship between the wheel friction force utilization rates between the wheels, and it is not necessary to consider the absolute size of each wheel. In this case, by assuming that the actual coefficient of friction between each wheel and the road surface is the same for all wheels, the ratio of the actual friction force to the actual vertical force of each wheel is determined by the wheel friction force of each wheel. It is possible to substitute for the utilization rate. In other words, in practicing the present invention, it is not always necessary for the “wheel frictional force utilization rate acquiring means 1” to always acquire the actual friction coefficient to acquire the wheel frictional force utilization rate.

[0011]

In the vehicle control device according to the first aspect of the present invention, the wheel frictional force utilization rate obtaining means 1 obtains all of the vehicles.
The longitudinal force F actually generated between each of the wheels and the road surface
actual frictional force which is the resultant force of the _x and the lateral force ^{_{F y (= (F x 2}} + F
_y ^{2) 1/2)} of the vertical force F that is actually generated between the actual friction coefficient μ and the wheel and the road surface between each wheel and the road surface
maximum friction force is the product of _z (= _μ · F _z) is a ratio of the wheel frictional force utilization is obtained for each wheel, these
To the wheel friction force utilization obtained for each wheel
The target wheel frictional force utilization rate for each wheel is determined based on each wheel.
Then, the actual wheel friction of each wheel is controlled by the wheel friction force utilization rate control means 3 via the wheel state quantity changing means 2.
Control so that the force utilization rate approaches the target wheel friction force utilization rate.
It is. That is, in the device of the present invention, the wheel friction force utilization rate representing the degree of the load on the wheel is obtained in consideration of not only the forward and backward motion state of the wheel but also the lateral motion state, and the load is individually applied to each wheel. The motion state of the vehicle is controlled while taking the degree of the vehicle into consideration. Claims
In the vehicle control device according to the second aspect of the present invention,
Target wheel friction force utilization rate for each wheel
Approximately based on wheel friction force utilization obtained for
Determined by the value. For example, obtained for each wheel
The average value of the wheel friction utilization rate is calculated as the target wheel friction force of each wheel.
Utilization rate.

[0012]

As described above, according to the first aspect of the present invention,
Since the degree of wheel load is acquired in consideration of not only the forward and backward motion state of the wheel but also the lateral motion state, the degree of wheel load is accurately acquired not only in the straight traveling state of the vehicle but also in the turning state of the vehicle. The effect is obtained.

[0013] Furthermore, the motion state of the vehicle is controlled while individually considering the degree of load for all wheels.
The effect of avoiding the situation where only some of the wheels approach the limit can be avoided. According to the invention of claim 2
If the target wheel friction force utilization rate of each wheel is
About the same based on the wheel friction force utilization rate obtained for
It is more effective because it is determined to be the same value.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention;

As shown in FIG. 2, the electrically controlled brake system includes a master cylinder 10 and an electrically controlled hydraulic pressure source 12 connected to four wheels FR,
Each of the brakes FL, RR and RL is connected to the wheel cylinder 20 of the brake. The two-position valve 14 makes it possible to select either the master cylinder 10 or the electric control hydraulic pressure source 12 as the hydraulic pressure source for the wheel cylinder 20.

The master cylinder 10 is a tandem type arranged in series with each other are two pressure chambers, mechanically generating the height of the fluid pressure corresponding to the brake pressing force F _p of the brake pedal 24 to their pressure chambers Let it. One of the pressurizing chambers is connected to the wheel cylinders 20 of the left and right front wheels FL and FR, and the other pressurizing chamber is connected to the wheel cylinders 20 of the left and right rear wheels RL and RR.
It is connected to the.

The electric control hydraulic pressure source 12 includes the accumulator 3
0, a pump 34 for pumping hydraulic fluid from the reservoir 32 and storing it in the accumulator 30, and a linear hydraulic pressure control valve 40 for controlling the hydraulic pressure to a height proportional to the exciting current. The obtained high hydraulic pressure is reduced to an appropriate level by the linear hydraulic pressure control valve 40 and output. The linear hydraulic pressure control valve 40 changes the height of the hydraulic pressure linearly with respect to the magnetic force by balancing the magnetic force and the hydraulic pressure acting on the spool in opposite directions by the spool itself. The linear hydraulic pressure control valve 40 is provided individually for each wheel cylinder 20.

The two-position valve 14 is also used for each wheel cylinder 2
0 is provided individually. In the non-energized state, the two-position valve 14 is in a position where the master cylinder 10 is communicated with the wheel cylinder 20 and the linear hydraulic pressure control valve 40 is shut off from the wheel cylinder 20. 40 is the wheel cylinder 20
And a direction switching valve that can be switched to a position where the master cylinder 10 is disconnected from the wheel cylinder 20.

The linear hydraulic pressure control valve 40 and the two-position valve 14 are connected to the output side of a controller 50 mainly composed of a computer, and various sensors are connected to the input side of the controller 50. As shown in FIG. 3, a brake depression force sensor 52, the longitudinal force sensor 54 for detecting a longitudinal force F _x which occur between the same road surface is provided at each wheel for detecting a brake depression force F _p, each wheel lateral force sensor 56, the vertical force sensor 58 provided at each wheel to detect it in the vertical force F _z, of the wheel cylinders 20 brakes for detecting a lateral force F _y generated between the same road surface provided The pressure sensor 60 for detecting the pressure P and the like are connected. The longitudinal force sensor 54, the lateral force sensor 56, and the vertical force sensor 58 are described in, for example,
It can be configured as a 6-component force meter as described in JP-A-9-223569.

Various programs are stored in the ROM of the computer of the controller 50, and the CPU 50 executes various programs to execute scheduled control. Specifically, it is sequentially determined whether or not the electric control hydraulic pressure source 12 is normal. If the electric control hydraulic pressure source 12 is normal, the two-position valve 14 is energized and the electric control hydraulic pressure source 12 is enabled. electrically controlled based on the brake pressure P of the cylinder 20 to the brake pedal force F _p, and the like. This electric brake pressure control will be described later in detail. On the contrary,
If the electric control hydraulic pressure source 12 is not normal, the controller 50 activates the master cylinder 10 by turning off the two-position valve 14, and the brake pressure of each wheel cylinder 20 is mechanically controlled by the master cylinder 10. State.

When the electric control hydraulic pressure source 12 is enabled, the discharge of the hydraulic fluid from the master cylinder 10, that is, the displacement of the brake pedal 24 is prevented by the two-position valve 14, so that the brake operation feeling is reduced. Becomes quite hard. Therefore, even when the electric control hydraulic pressure source 12 is enabled, the same brake operation feeling as when the master cylinder 10 is enabled is obtained.
As shown in FIG. 2, the pressurizing chamber of the master cylinder 10 has a stroke through a two-position valve 70 (also connected to the output side of the controller 50), which is a normally closed solenoid on-off valve. Simulator 72 is connected. While the electric control hydraulic pressure source 12 is enabled, 2
When the position valve 70 is energized and is kept open,
The hydraulic fluid discharged from the master cylinder 10 is accumulated under pressure, whereby the displacement of the brake pedal 24 is realized in a pseudo manner.

The above-described electric brake pressure control is realized by the CPU executing the program shown in the flowchart of FIG. 4, and the outline thereof will be described first.

[0023] In this electrical braking pressure control is first in response to the brake pressing force F _p, overall braking force F _bt to be generated is determined by the brake all four wheels. Is the total braking force F _bt appropriately sized to generate vehicle deceleration of a magnitude consistent with the brake pressing force F _p is determined. Then, the total braking force F _bt within each wheel, as distributed according planned ideal longitudinal ratio, reference braking force F _BW0 to be generated by each wheel brake is determined. Subsequently, the actual wheel load factor A (this is one aspect of the “wheel frictional force utilization factor” in the present invention) A is calculated from the longitudinal force _Fx , the lateral force _Fy, and the vertical force _Fz of each wheel. Then, the average value of the actual wheel load factors A of all the wheels is set as the target wheel load factor A ^{* of} each wheel. Then, the linear hydraulic pressure control valve 40 of each wheel is controlled so that the target wheel load factor A ^* is realized in each wheel. In short, the longitudinal force F _x for each wheel by the actual braking force F _bw of each wheel is controlled, longitudinal force F _x of the lateral force F _y and the vertical force F _z is controlled, thereby fruit of each wheel The wheel load factors A are controlled so as to match each other, and as a result, the load on the wheels is made uniform among all the wheels.

[0024] Here, the term "longitudinal force F _x" means a component force generated in the direction parallel to the wheel center plane in each wheel, "lateral force F
" _y " means the component force generated in each wheel in a direction perpendicular to the wheel center plane. Further, since the “actual wheel load factor A” is one mode of the “wheel frictional force utilization factor”, the actual frictional force F _w , which is originally the sum of the longitudinal force F _x and the lateral force F _y , is originally used.
With the actual friction coefficient μ between each wheel and the road surface and the vertical force F _z
Should be acquired by dividing the maximum friction force F _MAX is the product of the. However, in the present embodiment, since it is sufficient to control the actual frictional force utilization rates of the respective wheels to match each other, the actual friction coefficient μ between each wheel and the road surface is equal to Assuming that
Actual wheel load factor A ignoring friction coefficient μ, that is, F _w
/ F _MAX is used.

Next, this electric brake pressure control will be described in detail with reference to FIG.

First, in step S1 (hereinafter simply referred to as S1; the same applies to other steps), initial setting is performed. Then, in step S2, the brake depression force is determined based on the output signal from the brake depression force sensor 52. F _p
Is detected. Then, in S3, the longitudinal force sensor 5
4, a longitudinal force _Fx , a lateral force _Fy, and a vertical force _Fz are detected for each wheel based on output signals from the lateral force sensor 56 and the vertical force sensor 58, respectively. These detection results are stored in the RAM of the computer.

[0027] Subsequently, in S4, overall braking force F _bt is determined according to the detected brake pedal force F _p. Specifically, the relationship between the total braking force F _bt the brake pedal force F _p (an example of which is graphically represented in FIG. 5) have been be stored in advance in the computer ROM, comprehensive using the relationship The braking force _Fbt is determined. Then, S
In 5, the overall braking force F _bt within each wheel, by the vertical force F _z of each wheel are distributed according to the percentage of total weight vehicle, reference braking force F _BW0 of each wheel is calculated. That is, the reference braking force F _{bw0 of} each wheel is calculated using the formula F _bw0 = (F _z / ΣF _z ) · F _bt . However, in this equation, “ΔF _z ” means the total weight of the vehicle, and is obtained as the sum of the vertical forces F _z common to each wheel.

[0028] Then, in S6, for each wheel, the actual wheel load factor A by dividing the resultant force of the longitudinal force F _x and the lateral force F _y in the vertical force F _z is calculated. That is, the ^{_{A = (F x 2 + F}} y 2) actual wheel load factor A using ^1/2 / F _z becomes equation is calculated.
After that, in S7, the average value of the actual wheel load ratio A between all the wheels is calculated, and this is set as the target wheel load ratio A ^{* of} each wheel. That is, the target wheel load factor A ^* common to each wheel is calculated using the equation A ^* = ΣA / 4. However, in this equation, “ΣA” means the total value of the actual wheel load factors A between all the wheels, and is obtained as the sum of the actual wheel load factors A of the respective wheels. Then, S8
, The wheel load factor deviation ΔA of each wheel is calculated by subtracting the target wheel load factor A ^* from the actual wheel load factor A.

Thereafter, in S9, for each wheel, a control amount ΔF _{bw of} each wheel braking force F _bw according to the wheel load factor deviation ΔA.
Is calculated. The wheel load factor deviation ΔA and the control amount ΔF
The relationship with _bw (an example of which is shown in the graph of FIG. 6) is stored in the ROM in advance, and the current value of the control amount ΔF _bw is calculated using the relationship. further,
In S9, the control amount ΔP of the brake pressure P corresponding to the control amount ΔF _bw is calculated for each wheel. The relationship between the control amount ΔF and the control amount ΔP is stored in the ROM in advance, and the current value of the control amount ΔP is calculated using the relationship. Thereafter, in S10, while the brake pressure of each wheel cylinder 20 is monitored by the pressure sensor 60, the linear hydraulic pressure control valve 4 of each wheel is controlled according to the control amount ΔP.
0 is controlled. Subsequently, the process returns to S2.

Therefore, in this embodiment, when the vehicle is braked, the distribution of the braking force is maintained as close to the ideal state as possible while the load on each wheel is evenly distributed. Even when the performance (specifically, the relationship between the brake pressure and the braking torque) varies, control in which only some of the wheels approach the limit is avoided, and the effect that the braking limit of the vehicle is improved is obtained. .

As is clear from the above description, in the present embodiment, the portion of the controller 50 that executes S3 and S6 in FIG.
In combination with the vertical force sensor 58, one aspect of the “wheel frictional force utilization rate obtaining means 1” of the present invention is configured, and the linear hydraulic pressure control valve 40 is configured as one of the “wheel state quantity changing means 2” of the present invention. A part of the controller 50 that executes S2, 4, 5, 7 to 10 in FIG. 4 of the controller 50 constitutes one aspect of the "wheel frictional force utilization rate control means 3" in the present invention.

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

[Brief description of the drawings]

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

FIG. 2 is a system showing an electrically controlled brake system including a vehicle control device according to one embodiment of the present invention.

FIG. 3 is a block diagram showing an electrical configuration of the electrically controlled brake system.

FIG. 4 is a flowchart showing a program for electric brake pressure control used by a controller in FIG. 3;

5 is a graph showing an example of the relationship of Figure 4 program and the brake pedal force F _p using a comprehensive braking force F _bt.

6 is a graph showing an example of a relationship between a load factor deviation ΔA and a control amount ΔF _bw used by the program of FIG. 4;

[Explanation of symbols]

 Reference Signs List 20 wheel cylinder 40 linear hydraulic pressure control valve 50 controller 52 brake depression force sensor 54 longitudinal force sensor 56 lateral force sensor 58 vertical force sensor

Continuation of the front page (56) References JP-A-2-182521 (JP, A) JP-A-3-220056 (JP, A) JP-A-4-185560 (JP, A) JP-A-4-193633 (JP) JP-A-4-146819 (JP, A) JP-A-2-182520 (JP, A) JP-A-5-162629 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B60T 8/58 B60T 8/24 B60G 17/015

Claims (2)

(57) [Claims] 1. A vehicle control device for controlling a motion state of a vehicle having a plurality of wheels , wherein a longitudinal force and a lateral force actually generated between each of all wheels of the vehicle and a road surface. is the resultant force of the actual friction force, it
A wheel which is a ratio to a maximum frictional force which is a product of an actual coefficient of friction between each of all the wheels and a road surface and a vertical force actually generated between each wheel and the road surface. Wheel friction force utilization rate acquisition means for acquiring the friction force utilization rate for each of the wheels , and wheel state quantity change means for changing a wheel state quantity which is at least one of the longitudinal force, the lateral force, and the vertical force. And the total obtained by the wheel frictional force utilization rate obtaining means.
Based on the actual wheel friction force utilization of each wheel
The target wheel frictional force utilization rate for each wheel is obtained, and the actual wheel friction of each of the wheels is determined via the wheel state changing means.
To the target frictional force utilization rate determined for each wheel.
A vehicle frictional force utilization rate control means for approaching the vehicle. 2. The method according to claim 1, wherein the wheel frictional force utilization rate control means includes:
Determine the target wheel frictional force utilization rate of all wheels to almost the same value
The vehicle control device according to claim 1, further comprising: