JP3085060B2 - Vehicle characteristic control device for four-wheel steering vehicle - 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 characteristic control device for a four-wheel steering vehicle capable of assisting at least the rear wheels in accordance with a steering angle or the like to improve ride comfort and steering stability. is there.

[0002]

2. Description of the Related Art A conventional vehicle characteristic control device for a four-wheel steering vehicle is disclosed in, for example, Japanese Patent Application Laid-Open No.
There is one described in No. 5969. This conventional example includes a suspension capable of switching and controlling suspension characteristics such as a spring constant, a damping force, and a roll rigidity, an auxiliary steering device for auxiliary steering of at least one of a front wheel and a rear wheel, and an auxiliary steering device for adjusting a steering angle and the like. In a four-wheel steering vehicle provided with a steering control means for controlling the suspension characteristic change, the suspension characteristic change detection means for detecting a change in the suspension characteristic, and the steering control means according to a characteristic detection value of the suspension characteristic change detection means. By providing an auxiliary steering amount correcting means for correcting the auxiliary steering amount, the steering characteristics of the four-wheel steering vehicle are maintained in an appropriate state regardless of the change in the suspension characteristics.

[0003]

However, in the above-mentioned conventional vehicle characteristic control apparatus for a four-wheel steering vehicle, for example, the damping force of a variable damping force shock absorber is simply determined based on a steering angle detection value and a vehicle speed detection value. Calculate the expected roll amount,
When the predicted roll amount is small, the damping force of the variable damping force shock absorbers of all four wheels is controlled to a low damping force to improve ride comfort. When the predicted roll amount is large, the damping force of the variable damping force variable shock absorbers of all four wheels is reduced. Although the steering stability is improved by controlling the force to a high damping force, since the control mode at the time of turning is determined as either emphasis on ride comfort or emphasis on steering stability, the turning outer wheel and the turning inner wheel are determined. There is an unsolved problem that fine damping force control cannot be performed.

Accordingly, the present invention has been made in view of the above-mentioned unsolved problems of the prior art, and provides a vehicle characteristic control device for a four-wheel steering vehicle capable of finely controlling damping force during turning. It is intended to be.

[0005]

In order to achieve the above object, a vehicle characteristic control apparatus for a four-wheel steering vehicle according to the first aspect of the present invention includes a suspension having a variable damping force shock absorber and an auxiliary steering of at least a rear wheel. An auxiliary steering device; damping force control means for controlling the damping force of the variable damping force shock absorber in accordance with vertical movement of the vehicle body; and steering control means for controlling the auxiliary steering device in accordance with a steering angle or the like. In a vehicle characteristic control device for a four-wheel steering vehicle, a turning state detecting means for detecting a turning state of the vehicle, and a damping coefficient of a damping force variable shock absorber on at least a turning outer wheel according to the turning state detected by the turning state detecting means. And a damping coefficient changing means for changing

According to a second aspect of the present invention, in the vehicle characteristic control device for a four-wheel steering vehicle, the turning state detecting means includes a yaw rate sensor for detecting a target yaw rate during turning.
The damping coefficient changing means is configured to change a control width of the damping coefficient according to the magnitude of the target yaw rate.

[0007]

In the vehicle characteristic control device for a four-wheel steering vehicle according to the first aspect, the turning state of the vehicle is detected, and the damping coefficient of the damping force variable shock absorber on the turning outer wheel side and the turning inner wheel side according to the turning state. Can be individually controlled, and optimal damping force control according to the turning state is performed.

Further, in the vehicle characteristic control device for a four-wheel steering vehicle according to the second aspect, when the target yaw rate of the turning outer wheel is small, the control range of the damping coefficient is widened,
Emphasis is placed on ride comfort, and when the target yaw rate is medium, the control width of the damping coefficient is slightly narrowed toward the high damping coefficient side to emphasize steering stability, and when the target yaw rate is further increased, the control width of the damping coefficient is increased. The control is made narrower on the high damping coefficient side to place more emphasis on steering stability.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing one embodiment in which the present invention is applied to a four-wheel steering vehicle.
The variable damping force shock absorbers 3FL to 3RR constituting a suspension device are disposed between the vehicle body 2 and the vehicle body 2, respectively. Is controlled by a control signal from

The front wheels 1FL, 1RR are connected to a knuckle (not shown) at one end of tie rods 73L, 73R, and the other ends of the tie rods 73L, 73R are connected to a rack shaft 74a of a rack and pinion type steering device 74.
A steering shaft 75 of the rack and pinion type steering device 74 is connected to a steering wheel 76, and by steering the steering wheel 76, the front wheels 1FL, 1RR are steered in the same direction as the steering direction.

On the other hand, the rear wheels 1RL, 1RR are connected to a knuckle (not shown) through tie rods 78L, 78R, and a piston rod 79a of a rear wheel auxiliary steering cylinder 79. The rear wheels 1RL and 1RR are connected to the output side of a differential device 81 via axles 80L and 80R, and the input side of the differential device 81 is connected to a transmission 84 to which the rotational force of an engine 83 is input via a propeller shaft 82. And is rotationally driven.

Further, the rear wheel assist steering cylinder 79 has pressure chambers 89L, 89R defined by a piston 79b.
Are connected to a protruding side of a hydraulic pump 88 which is rotationally driven by an engine 83 via an unload valve 87, and drain ports are connected to each other and connected to an oil tank 89 via an unload valve 87. I have. Reference numeral 90 denotes an accumulator for accumulating the line pressure. Here, a rear wheel steering device is constituted by the rear wheel assist steering cylinder 79, the servo valve 85, the unload valve 87, the hydraulic pump 88, the oil tank 89, and the accumulator 90.

Variable damping force shock absorber 3FL-3RR
Is a twin-tube gas-filled strut type having a cylinder tube 7 composed of an outer cylinder 5 and an inner cylinder 6 as shown in FIGS. 8 define upper and lower pressure chambers 9U and 9L. 4 to 7, the piston 8 has a cylindrical lower half 11 having a sealing member 9 molded on the outer peripheral surface thereof in sliding contact with the inner cylinder 6 and having a center opening 10 on the inner peripheral surface. The lower half 11 has an upper half 12 fitted therein.

The lower half body 11 has an extension oil passage 13 penetrating vertically and a sealing member 9 extending downward from the upper surface side.
The hole 14 a having a diameter larger than that of the extension-side oil flow path 13 and extending from the outer peripheral surface of the cylindrical body 11 to the hole 14.
a, a pressure-side oil flow path 14 formed of a hole 14b drilled in communication with the bottom of the hole a, annular grooves 15U, 15L formed at the upper and lower open ends of the central hole 10, and formed on the upper surface side. A long groove 16 communicating with the annular groove 15U and the expansion-side oil flow path 13 and a long groove 17 formed on the lower surface side and communicating with the annular groove 15L are formed. The long groove 17 is closed by the extension-side disk valve 18, and the upper end side of the compression-side oil flow path 14 is closed by the compression-side disk valve 19.

The upper half 12 has a small-diameter shaft portion 21 inserted into the center opening 10 of the lower half body 11 and the shaft portion 2.
The lower end face of the small-diameter shaft portion 21 is formed at the center of the small-diameter shaft portion 21 and the large-diameter shaft portion 22. 23a extending from the side to the middle of the large-diameter shaft portion 22, and a hole 23b communicating with the upper end of the hole 23a and having a smaller diameter than the hole 23a.
And a hole 23c having a larger diameter than the hole 23c communicating with the upper end side of the hole 23b. The through hole 23 is formed at a position facing the annular grooves 15U and 15L of the small diameter shaft 21 respectively. Pair of through holes 24 penetrating the inner peripheral surface side in the direction
a, 24b and 25a, 25b are drilled, and the upper end side of the hole 23a of the large-diameter shaft portion 22 is connected to the arc-shaped groove 2 communicating therewith.
6 is formed, and an L-shaped pressure-side oil flow path 27 communicating with the arc-shaped groove 26 and the lower end face is formed.
Is blocked by

The lower half 11 and the upper half 12 are positioned below the lower half 11 of the small-diameter shaft 21 with the small-diameter shaft 21 inserted into the central opening 10 of the lower half 11. The nut 29 is screwed into the lower end protruding from the nut, and the nut 29 is tightened to be integrally connected. Further, a cylindrical valve body 31 whose upper end is closed in a hole 23a of the upper half body 12 and constitutes a variable throttle is rotatably disposed. As shown in FIG. 4, the upper half 1
2, a through-hole 32 is formed at a position facing the arc-shaped groove 26 of the large-diameter shaft portion 22 so as to reach the inner peripheral surface in the radial direction, and the small-diameter shaft of the upper half body 12 as shown in FIGS. A communication groove 33 is formed in the outer peripheral surface corresponding to the space between the through holes 24a and 25a of the portion 21, and further, as shown in FIG. 6, the through hole 24b of the small diameter shaft portion 21 of the upper half body 12 is formed.
An elongated hole 34 extending in the axial direction is formed in the outer peripheral surface corresponding to the area between the inner peripheral surface and the inner peripheral surface side.
Then, the positional relationship between the through hole 32, the communication groove 33, and the long hole 34 is selected so as to obtain the damping force characteristic with respect to the rotation angle of the valve body 31 shown in FIG. 8, that is, the step angles of the step motors 41FL to 41RR described later. ing.

That is, for example, at the position A in FIG. 8 which is the maximum rotation angle position in the clockwise direction, as shown in FIG. 4, only the through hole 32 communicates with the arc-shaped groove 26, so that the piston 8 descends. For pressure side movement, lower pressure chamber 9L
A pressure-side flow path C1 (shown by a dashed line) passing through the orifice formed by the open end of the pressure-side oil flow path 14 and the pressure-side disc valve 19 toward the upper pressure chamber 9U, and a lower pressure chamber 9L.
Through the inner peripheral surface of the valve body 31, through hole 32, arc-shaped groove 2
6. A pressure-side flow path C2, shown by a broken line, which passes through the pressure-side oil flow path 27, passes through an orifice formed by the opening end thereof and the pressure-side disc valve 28, and goes to the upper pressure chamber 9U, and the piston 8 rises. For the extension side movement, the upper pressure chamber 9U passes through the long groove 16 and the extension side flow path 13 and passes through the orifice formed by the opening end and the extension side disc valve 18 to the broken line toward the lower pressure chamber 9L. Only the expansion side flow path T1 shown in the figure is formed, and a high damping force is generated on the expansion side, which rapidly increases in accordance with an increase in the piston speed, and a low damping force on the compression side is slightly increased in accordance with the increase in the piston speed. Generates damping force.

By rotating the valve body 31 in the counterclockwise direction from the position A, the communication groove 33 of the valve body 31 and the through holes 24a, 25a of the small diameter shaft portion 21 communicate with each other as shown in FIG. The opening area between the communication groove 33 and the through holes 24a and 25a gradually increases as the rotation angle increases. For this reason, as shown in FIG. 5 (a), when the piston 8 moves on the extension side, the long groove 16 and the annular groove 15 are arranged in parallel with the flow path T1.
U, the through-hole 24a, the communication groove 33, the through-hole 25a, the annular groove 15L, the long groove 17, and the lower pressure chamber 9 through the orifice formed by the long groove 17 and the pressure-side disc valve 18.
A flow path T2 toward L is formed, and the maximum value of the damping force gradually increases as the opening area between the communication groove 33 and the through holes 24a and 25a of the small diameter shaft portion 21 increases as shown in FIG. As shown in FIG. 5B, for the movement on the extension side, the state where the flow paths C1 and C2 are formed is maintained, so that the minimum damping force state is maintained.

Further, when the valve element 31 is rotated counterclockwise to a position near the position B, as shown in FIG. 6, a state is established in which the through hole 24b, 25b of the valve element 31 is communicated by the elongated hole 34. Become. For this reason, as shown in FIG. 6A, the elongated groove 16, the annular groove 15U, the through hole 24a, the elongated hole 3 are arranged in parallel with the flow paths T1 and T2 with respect to the extension side movement of the piston 8.
4. Flow path T3 passing through hole 23a toward lower pressure chamber 9L
Is formed, the extension-side damping force becomes the minimum damping force state, and the piston 23 moves against the compression side in addition to the flow passages C1 and C2 as well as the hole 23a, the long hole 34, and the through hole 2
4b, the flow path C reaching the long groove 16 through the annular groove 15U
3, a flow path C4 is formed that reaches the long groove 16 through the hole 23a, the long hole 34, the through hole 25b, the annular groove 15L, the through hole 25a, the communication groove 33, the through hole 24a, and the annular groove 15U. As shown in FIG. 8, the minimum damping force state is maintained.

Further, when the valve element 31 is rotated in the counterclockwise direction, the opening area between the elongated hole 34 and the through holes 24b and 25b is reduced, and the elongated hole 34 and the through hole 24 are rotated at the rotation angle θ _B2.
7, the opening area between the through hole 32 and the arc-shaped groove 26 gradually decreases from the rotation angle θ _B2 . For this reason, between the rotation angle θ _B2 and the maximum rotation angle θ _{C in the} counterclockwise direction, the flow path T1 and T2 coexist for the movement of the piston 8 on the extension side, so that the minimum damping force state is set. On the contrary, when the piston 8 is moved on the pressure side, the opening area between the through hole 32 and the arc-shaped groove 26 is gradually reduced, so that the maximum damping force is gradually increased, and the valve body 31 is moved to the position. As shown in FIG. 7, when the piston reaches pressure C, the space between the through-hole 32 and the arc-shaped groove 26 is cut off.
The flow path from L to the upper pressure chamber 9U is only the flow path C1, and the pressure side is in a high damping force state.

On the other hand, a cylindrical piston rod 35 is fitted into the hole 23c of the upper half body 12, and the upper end of the piston rod 35 projects upward from the cylinder tube 7, as shown in FIG. The upper end side is the vehicle body side member 36.
Is fixed by a nut 39 via rubber bushes 38U and 38L to a bracket 37 attached to the piston rod 35, and the step motors 41FL to 41RR are mounted on the upper end of the piston rod 35 via a bracket 40 by the rotation shaft 41a.
The rotating shaft 41a and the above-described valve element 31 are connected by a connecting rod 42 loosely inserted into the piston rod 35. 43 is a bumper rubber. The lower end of the cylinder tube 7 is connected to a wheel-side member (not shown).

The controller 4 has, on its input side,
As shown in the figure, according to the vertical acceleration provided on the vehicle body side corresponding to each wheel position, the vertical acceleration detection values X _2FL ″ to X composed of analog voltages that are upwardly positive and downwardly negative are provided.
Vertical acceleration sensors 51FL to 51RR as vertical acceleration detecting means for outputting _2RR ", and an inductance which is built in, for example, the cover of each of the damping force variable shock absorbers 3FL to 3RR and which corresponds to the relative displacement between the vehicle body side member and the wheel side member. Relative displacement detection value X consisting of analog voltage due to change
_DFL (= X _2FL −X _1FL ) to X _DRR (= X _2RR −
X _1RR ), stroke sensors 52FL to 52RR as relative displacement detecting means, a vehicle speed sensor 53 for detecting a vehicle speed, a steering angle sensor 54S for detecting a steering angle of the steering wheel 76, and a rear wheel assist steering cylinder 79. A rear wheel steering angle sensor 54R for detecting a rear wheel steering angle by detecting a moving amount of the vehicle and a yaw rate sensor 55 for detecting a yaw rate generated by the vehicle body are connected, and each of the damping force variable shock absorbers 3FL to 3RR is provided on the output side. The step motors 41FL to 41RR for controlling the damping force of the motor and the servo valve 85 are connected.

The controller 4 includes a microcomputer 56 having at least an input interface circuit 56a, an output interface circuit 56b, an arithmetic processing device 56c, and a storage device 56d;
The vertical displacement detection values X _2FL ″ to X _2RR ″ of the _FL to _51RR are converted into digital values and supplied to the input interface circuit 56a, and the relative displacement detection values X of the A / D converters 57FL to 57RR and the stroke sensors 52FL to 52RR. input interface circuit 56a converts the _DFL to X _DRR to a digital value
A / D converters 58FL to 58RR supplied to the A / D converter 6 and an A / D converter 6 which converts the detected steering angle θ _S of the steering angle sensor 54 into a digital value and supplies the digital value to the input interface circuit 56a.
0R and the rear wheel steering angle detection value δ _rd of the rear wheel steering angle sensor 54R are converted into digital values and input interface circuit 56a
A / D converter 60R that supplies the yaw rate sensor 5
5 of the yaw rate detection value Y _D converted to a digital value input interface circuit 56a to supply the A / D converter 6
0Y, a step control signal for each of the step motors 41FL to 41RR output from the output interface circuit 56b is input, and the motor drive circuits 59FL to 59RR for converting this into step pulses to drive each of the step motors 41FL to 41RR. Drive circuits 61a and 61 for driving the servo valve 85 of the rear wheel steering device with the drive control signals CS _ra and CS _rb output from the output interface circuit 56b.
1b.

Here, the arithmetic processing unit 56c of the microcomputer 56 executes the processing of FIGS.
A vehicle body vertical velocity X _2FL '~X _2RR' obtained by integrating the vehicle body vertical acceleration detection value X _2FL "~X _2RR" input from the vertical acceleration sensor 51FL～51RR, stroke sensor 52FL
To 52RR, the relative displacement detection values X _DFL (= X _2FL -X _1FL ) to X _DRR (= X _2RR -X)
_1RR ), the damping force coefficient C for performing the skyhook control is determined based on the relative speeds X _DFL ′ to X _DRR ′, and the step motor 4 corresponding to the determined damping coefficient C is determined.
Calculates a target step angle theta _T of 1FL～41RR, this calculates the difference value between the target step angle theta _T and the current step angle theta _P, the motor driving circuit a step control amount corresponding to 5
And outputs the 9FL～59RR, calculates a front wheel steering angle [delta] _f based on the steering angle detected value theta _S of the steering angle sensor 54S, then the steering angle ratio k of the front and rear wheels based on the vehicle speed detection value V of the vehicle speed sensor 53 Is calculated based on the steering angle ratio k.
calculating a _r, and outputs a switching control signal CS _ra and CS _rb as difference value between the rear wheel steering angle [delta] _r and the rear wheel steering angle detected value [delta] _rd becomes zero, further steering angle detection value theta _S and The target yaw rate Y _O is calculated based on the vehicle speed detection value V, the yaw rate feedback control gain k _P in the steering control is changed according to the magnitude of the target yaw rate Y _O , and the damping force variable shock absorber on the turning outer wheel side is changed. Change the damping coefficient.

The storage device 56d stores the arithmetic processing device 5
A program necessary for the arithmetic processing of FIG. 6c is stored in advance, necessary values in the arithmetic processing process and arithmetic results are sequentially stored, and a target yaw rate map for calculating a target yaw rate is stored in advance. Here, as shown in FIG. 13, the target yaw rate map has a steering angle detection value θ _S of the steering angle sensor 54S on the X axis and a vehicle speed sensor 53 on the Y axis.
And a target yaw rate Y _O on the Z-axis, respectively, and a three-dimensional map that peaks when the steering angle detection value θ _S is 90 degrees and the vehicle speed detection value V is 60 km / h, for example. I have. Incidentally, the target yaw rate map is determined by only the tire characteristics, for example in high grip tires, etc., would span to a large extent a peak point steering angle detection value theta _s is different from the FIG. 13, it If it passes too long, the characteristic will decrease sharply.

Next, the operation of the above embodiment will be described with reference to a micro computer.
Of the damping force control processing of the arithmetic processing unit 56c of the computer 56
FIG. 10 showing an example, FIG. 11 showing an example of a steering control process, and
A description will be given with reference to FIG. 12 showing an example of the attenuation coefficient setting process.
You. That is, the damping force control processing of FIG.
(For example, every 20 msec)
First, in step S1, the vehicle speed detection value V and the steering angle detection value θ
_SAnd each vertical acceleration detection value X_2i″ (I = FL, FR, RL, R
R), and then proceeds to step S2, where each phase is read.
Displacement detection value X_DiAnd then proceed to step S3
Then, the vertical acceleration detection value X read in step S1_2i″
Is integrated by, for example, low-pass filtering.
Body vertical speed X_2i′ Are calculated and these are stored in the storage device 56 d
Is temporarily stored in a predetermined storage area, and then the process proceeds to step S4.
And the relative displacement detection value X read in step S2._DiThe example
For example, by performing high-pass filter processing,
Speed X_Di′ Are calculated, and these are stored in a predetermined
After the temporary storage in the storage area, the process proceeds to step S5.

In step S5, step S3
And the vehicle vertical speed X calculated in S4 _2i'And relative velocity X
_Di'And control gain C_SCalculation of the following equation (1) based on
To calculate the damping coefficient C for performing the skyhook control.
Then, the process proceeds to step S6. C = C_S・ X_2i'/ X_Di'(1) In step S6, a control gain setting process of FIG.
Resets both the damping force control flags FM and FH to “0”.
It is determined whether or not the damping force control flag F has been set.
If it has been reset to "0", then step S
The process proceeds to 16 and one of the control flags FM and FH is
If it is set to "1", the process moves to step S7.
Run.

In step S7, the control flag FM is set
It is determined whether or not it is set to “1”, and the control flag
If FM is set to "1", step S8
To the damping force variable system on the turning outer wheel side of the front wheels.
Damping coefficient C for shock absorber_FOSet in advance
Medium damping coefficient C_MIt is determined whether it is the above or not, _FO
≧ C_MIf it is, the process directly proceeds to step S10, and C
_FO<C_M, The process proceeds to step S9 and the front wheels
Damping coefficient C on the turning outer wheel side_FOIs the medium damping coefficient C_MSet to
Then, the process proceeds to step S10.

[0029] In step S10, the damping coefficient C _RO for damping force control shock absorber as a turning outer wheel side of the rear wheel is equal to or in the in the attenuation coefficient C _M or more, when it is C _RO ≧ C _M is , proceeds directly to step S16, C _RO <C damping coefficient of the turning outer wheel side of the rear wheel moves to step S11 when it is _M C _RO coefficient middle attenuating C
_After setting to _M , the process proceeds to step S16.

On the other hand, the result of the determination in step S7 is
When the lag FM is reset to "0"
Have the control flag FH set to "1"
The process proceeds to step S12, and
For variable damping force shock absorber on the turning outer wheel side
Damping coefficient C_FOIs a preset medium attenuation coefficient C_MAnd maximum reduction
Decay coefficient C_MAXHigh damping coefficient C in between_HOr not
Is determined, C_FO≧ C _HIf step S
Go to 14 and C_FO<C_H, The step S
13 and the damping coefficient C on the turning outer wheel side of the front wheels._FODecrease
Decay coefficient C_HThen, the process proceeds to step S14.

[0031] In step S14, the damping coefficient C _RO to the plate in the damping force variable shock absorber which is a turning outer side of the rear wheel is equal to or in the high damping coefficient C _H above, C _RO ≧ C _H In some cases, the process directly proceeds to step S16, and when C _RO <C _H , the process proceeds to step S15, where the damping coefficient C _RO on the turning outer wheel side of the rear wheel is set to the high damping coefficient C _RO.
After setting to _H , the process proceeds to step S16.

In step S16, in step S6 or
Indicates that the damping coefficient C calculated in S7 is a predetermined damping force.
Minimum damping force C at the variable shock absorber 3i_MINBelow
It is determined whether or not there is, and C> C_MINIf the
To step S17 to shift the vehicle body vertical speed X_2i′ Is positive
Judge whether or not X_2iIf '> 0, step S
18, the process proceeds to steps S5, S9, S11, S
13 or the damping coefficient C calculated in S15 is set on the extension side.
Thus, in the control map corresponding to FIG._A~ Θ _B1Area of
And the target step angle θ_TStep after calculating
Move to S19.

In this step S19, the storage device 56d
Current step angle θ stored in _PAnd target step angle
θ_TIs calculated as a step control amount S.
While updating and storing in a predetermined storage area of the storage device 56d,
The target step angle θ_TIs the current step angle θ_PUpdate as
The new storage is performed, and then the process proceeds to step S20, where the storage device
Step control stored in a predetermined storage area of the storage 56d
Outputs the amount S to the motor drive circuit 59i and then interrupts the timer
The process ends and returns to the predetermined main program.

The result of the determination in step S17 is X _2i ′.
If <0, the process proceeds to step S21, and step S5, S9, S11, S13 or S1 is performed.
8 so that the damping coefficient C calculated in step 5 is set on the pressure side.
With reference to the region of theta _B2 through? _C of the corresponding control map shifts after calculating the target step angle theta _T in the step S19 to.

Further, the determination result of step S16 is C
When ≦ C _MIN , the process proceeds to step S22,
Wherein after calculating a target step angle theta _T with reference to the region of the theta _B1 through? _B2 of the corresponding control map in FIG. 8 step S1
Move to 9. The processing in FIG. 10 corresponds to the damping force control means, and the processing in steps S7 to S15 and the later-described damping coefficient setting processing in FIG. 12 correspond to the damping coefficient changing means.

The steering control process of FIG. 11 is executed as a timer interrupt process every predetermined time (for example, 20 msec), similarly to the above-described damping force control process. First, in step S31, the vehicle speed detection value V of the vehicle speed sensor 53, the steering The steering angle detection value θ _{S of} the angle sensor 54S, the yaw rate detection value Y _D of the yaw rate sensor 55 and the rear wheel steering angle detection value δ _rd of the rear wheel steering angle sensor 54R are read, and then the process proceeds to step S32 to detect the steering angle. The value θ _S is divided by the steering gear ratio N to obtain the front wheel steering angle δ.
Calculate _F (= θ _S / N).

Next, the routine proceeds to step S33, where the following equation (2) is calculated based on the detected vehicle speed V to calculate the steering angle ratio k between the front and rear wheels. k = {bL−mV ² (a / C _r )} / {aL−mV ² (a / C _f )} (2) Then, the process proceeds to step S34, where the vehicle speed detection value V and the steering angle detection value θ are obtained. Based on _S , the target yaw rate Y _O is calculated with reference to the target yaw rate map of FIG. 13, and then the process proceeds to step S35, where the deviation between the target yaw rate Y _O and the yaw rate detection value Y _D read in step S31. ε (=
Y _O −Y _D ), and then proceeds to step S36 to differentiate the yaw rate deviation ε by, for example, high-pass filter processing to calculate a yaw rate deviation differential value ε ′, and then proceeds to step S37 to obtain the following (3) ) is calculated rear wheel steering angle [delta] _r by performing the calculation of the equation.

Δ _r = k · δ _f + k _P · ε + k _D · ε ′ (3) Here, k _P is a yaw rate feedback control gain, and is a storage device in a control gain setting process of FIG. The value updated and stored in the predetermined storage area of 56d is read and used, and k _D is a preset fixed value control gain. Then, the process proceeds to step S38, the rear wheel steering angle [delta] _r
Deviation between the rear wheel steering angle detected value [delta] _rd and _{Δδ r (= δ r -δ rd} )
Calculates, when the difference value .DELTA..delta _r is zero, the servo valve 8
It is both a logic value "0" to the control signal CS _ra and CS _rb for 5, when a difference value .DELTA..delta _r is positive (Δδ _r> 0), the control signal CS _ra to the logical value "1", the control signal CS _rb
To logic value "0", when the difference value .DELTA..delta _r is negative (Δδ _r <0), the control signal CS _ra to the logical value "0", respectively set the control signal CS _rb to the logical value "1" Drive circuit 61
a, 61b, then terminates the timer interrupt process and returns to the predetermined main program.

The processing in FIG. 11 corresponds to the steering control means. Further, the control gain setting process of FIG. 12 is executed as a timer interrupt process every predetermined time (for example, 20 msec), similarly to the above-described damping force control process and steering control process. First, in step S41, the vehicle speed detection value V and the steering The angle detection value θ _S is read, and then the process proceeds to step S42, and based on the vehicle speed detection value V and the steering angle detection value θ _S , FIG.
The target yaw rate Y _O is calculated with reference to the target yaw rate map shown in FIG.

[0040] Then, the process proceeds to step S43, calculates the target yaw rate Y _O were it is determined whether a relatively small first set value Y _OS1 than a preset, Y _O <Y
_If it is _OS1 , the process _proceeds to step S44 to reset both the middle damping force control flag FM and the high damping force control flag FH in the damping force control process to “0” and to set the yaw rate feedback control gain k _P in the steering control process. Set the low control gain k _PL and store it in the storage device 5
After the update is stored in the predetermined storage area 6d, the timer interrupt processing is terminated and the process returns to the predetermined main program.

Also, if the determination result of step S43 is Y _O ≧
When a Y _OS1, the process proceeds to step S45, and determines whether the target yaw rate Y _O is first set value Y _OS1 greater than the second set value Y _OS2 or more set in advance, Y _O < If Y _OS2 , the process _proceeds to step S46 to set the middle damping force control flag FM to “1” and set the yaw rate feedback control gain k _P to a standard control gain k _PN higher than the low control gain k _PL. Then, this is updated and stored in a predetermined storage area of the storage device 56d, and then the timer interrupt processing is terminated to return to the predetermined main program.

Further, the determination result of step S45 is Y _O
If ≧ Y _OS2 , the process _proceeds to step S47,
While setting the high damping force control flag FH to “1”,
The yaw rate feedback control gain k _P is set to a high control gain k _PH higher than the standard control gain k _PN , and this is updated and stored in a predetermined storage area of the storage device 56d. Return to.

Therefore, assuming that the vehicle is traveling straight ahead on a flat good road at a constant speed, there is almost no vertical movement of the vehicle body in this state.
Vertical acceleration detection value X _2FL ″ output from 1RR
X _2RR ″ is substantially zero, and the detected steering angle θ _S is also zero.
As a result, when the damping coefficient setting process of FIG. 12 is executed, the target yaw rate Y _O calculated in step S42 also becomes substantially zero. Therefore, the process proceeds to step S44 via step S43, where the middle damping force control flag FM and the high damping force control flag FH are both reset to “0”, and
The yaw rate feedback control gain k _P in the steering control is set to the low control gain k _PL .

Therefore, when the damping force control process of FIG. 10 is executed, the vehicle body vertical speeds X _2FL ′ to X _2RR ′ calculated in step S3 become substantially zero, and the middle and high damping force control flags FM and Since both FH are reset to “0”, the damping coefficients C _{FL to} C _RR for the respective damping force variable shock absorbers 3 _FL to 3 _RR also become substantially zero in step S 5, so that step S 16 passes from step S 16 to step S 22. Then, the step angles within the range of the step angles θ _{B1 to} θ _B2 at which the extension-side and _compression- side minimum damping coefficients C _nMIN and _CaMIN are set as the target step angle θ _T , and the step angles of the step motors 41FL to 41RR are set. Is the target step angle θ
Driven to match _T. For this reason, the valve elements 31 of the variable damping force shock absorbers 3FL to 3RR are set at the position B shown in FIG. 6, whereby the extension side and _compression side damping coefficients C of the piston 8 are _{reduced to the} minimum damping coefficients _CnMIN and Cn, respectively.
Set to _aMIN . Therefore, in this state, even if vibrations due to fine unevenness of the road surface are input to the wheels, the vibrations are absorbed by the variable damping force shock absorbers 3FL to 3RR and are not transmitted to the vehicle body, so that a good ride comfort can be secured. Thus, it is possible to perform damping force control with emphasis on ride comfort.

On the other hand, when the steering control processing of FIG. 11 is executed, the vehicle is in a straight running state, and therefore, the detected steering angle θ
_{Since S} is zero and the target yaw rate Y _O calculated in step S35 is also zero, the rear wheel steering angle δ _r calculated in step S37 is also zero, so that the control signals CS _ra and CS
_rb both assume the logical value “0” and maintain the straight traveling state.

In this good road running state, for example,
When passing through a temporary step such as a difference,
When the vehicle does not move up and down due to
_2FL'~ X_2RR′ Remain zero, so that the minimum damping coefficient C
_aMINAnd C_nMINWheels ride on steps to maintain condition
Although it can absorb the pushing force when raised,
Riding on a relatively large step, absorbing the thrust
Otherwise, the vehicle will be displaced upward.
Therefore, the vehicle vertical speed X_2FL'~ X_2RR′ Is positive
Will increase. Thus, the vehicle vertical speed X
_2FL'~ X_2RR′ Increases in the positive direction, step S1
7 to step S18, the step angle θ in FIG.
_A~ Θ_B1Target step angle θ according to the damping coefficient C in the region of
_TIs calculated, so that the damping force variable shock absorber 3
The switching of the valve element 31 of FL to 3RR is controlled as shown in FIG.
You. As a result, the relative speed X_DFL′
~ X_DRRIs negative, ie, the displacement speed X on the vehicle body side._2iCar
Wheel side displacement speed X_1i'Is fast and piston 8 moves to the compression side
The minimum damping coefficient C on the pressure side_aMINMaintain
Therefore, vibration input to the wheel side can be absorbed,
The climb speed on the wheel side by overcoming the step from the state of
When the degree becomes lower than the ascent speed on the vehicle side, the relative speed
X _DFL'~ X_DRR′ Becomes positive and the piston 8 moves to the extension side.
Will move. At this time, the attenuation coefficient C is large.
Value, so it has a damping effect that suppresses the rise of the body
Then, when the vehicle body stops rising, the vehicle body vertical speed X
_2FL'~ X_2RR′ Becomes zero,
Then, the step motors 41FL to 41RR are turned counterclockwise.
To return to position B, whereby both the compression side and the extension side
The minimum damping coefficient C _aMINAnd C_nMINControlled by the car
When the body starts descending, the vehicle vertical speed X
_2FL'~ X_2RR′ Increases in the negative direction,
The process proceeds from step S17 to step S21, and the control shown in FIG.
Step angle θ with reference to the map_B2~ Θ _CAttenuator in the range
Target step angle θ according to number C_TBy calculating
As a result, the valve element 31 is further rotated counterclockwise, as shown in FIG.
It is turned to the turning position shown. For this reason, the body descends,
And relative speed X_DFL'~ X_DRR'Becomes negative and piston
In the state where 8 moves to the compression side, the damping force increases.
As a result, a great damping effect is exhibited.

Conversely, when the wheels pass through the step of descending forward, the relative speeds X _DFL 'to X _DRR ' increase in the forward direction by first rebounding the wheels. At this time, however, the vehicle body does not move up and down. Body vertical speed X _2FL '~ X
_{Since 2RR} 'is zero, the damping coefficients of the damping force variable shock absorbers 3FL to 3RR are the minimum damping coefficients C _aMIN and C _{nM IN}
Maintaining, allowing the lowering of the wheels, then the vehicle starts to descend, the vehicle body vertical velocity X _2FL '~X _2RR' is increased in the negative direction, is the attenuation coefficient C is a large value, the step angle θ will _{be B2} through? _C target step angle theta _T ranging is calculated, since the valve body 31 is rotated to the position shown in FIG. 7, a large damping force against movement of the compression side of the piston 8 As a result, the valve body 31 is rotated clockwise as the vehicle vertical speeds X _2FL ′ to X _2RR ′ become smaller and the damping coefficient C becomes smaller. Return to the B side, and the vehicle vertical speed _X2FL '~
When X _2RR ′ becomes zero, the valve element 31 is at the position B, and has the minimum damping coefficients C _aMIN and C _nMIN . Thereafter, when the vehicle body starts rising by _swinging back, the vehicle body vertical speeds X _2FL ′ to X _2RR ′ increase in the positive direction, and the relative speeds X _DFL ′ to X _DRR ′ become the positive direction. is the target step angle theta _T as a step angle theta _a side with an increase in the calculation, by the valve body 31 is a position shown in FIG. 5 is rotated in the clockwise direction, the movement of the extension side of the piston 8 , A large damping force can be given to exert a vibration damping effect.

As described above, when the vehicle travels on a temporary step while traveling on a good road, a good vibration damping effect can be exerted by the skyhook control, and the vehicle travels on a bad road. also, by the target step angle theta _T positive vehicle body vertical velocity X _2FL '~X _2RR' (or negative) by the step angle theta _a side (or step angle theta _C side) is calculated, the vehicle body is raised When the relative speeds X _DFL 'to X _DRR ' are negative and the vehicle body descends and the relative speeds X _DFL 'to X _DRR ' are positive, the damping coefficient C is set to the minimum damping coefficient C.
_aMIN and _CnMIN , the vehicle body rises and the relative speeds X _DFL 'to X _DRR ' become positive, and the vehicle body descends and the relative speed X
_DFL 'to X _DRR' vertical velocity of the damping coefficient C when it is damping direction as the negative X _2FL 'to X _2RR' and relative velocity X
_By controlling to the optimal damping coefficient according to _DFL 'to _XDRR ',
Good ride comfort can be ensured.

Also, even when the vehicle is traveling on a rough road, the vehicle body rises and the relative speeds X _DFL 'to X
_DRR 'is negative and the body descends and the relative speed X _DFL ' ~ X
_{When DRR} 'is in the excitation direction where it is positive, the damping coefficient C is controlled to the minimum damping coefficients C _aMIN and C _nMIN , and conversely, the vehicle body rises and the relative speeds X _DFL ' to X _DRR 'become positive and the vehicle body becomes When the relative velocity X _DFL 'to X _DRR ' is lowered and the relative velocity X _DFL 'to X _DRR ' is negative, the damping coefficient C is _{adjusted according} to the vertical velocity X _2FL 'to X _2RR ' and the relative velocity X _DFL 'to X _DRR '. By controlling to an optimal damping coefficient, a good ride comfort can be secured.

Therefore, when the vehicle is traveling straight, the control range of the damping force of each of the variable damping force shock absorbers 3FL to 3RR becomes wide as shown by the solid line in FIG. Can be. In addition, the steering wheel 76 is shifted from a straight running state on a good road.
Turn right (or left) and shift to the right turning state.
As a result, the left wheel side, which is the turning outer wheel, sinks into the vehicle body,
When viewed from the rear wheel side, where the right wheel side, which is the turning inner wheel side, floats, a roll that falls to the left is generated. As described above, when the vehicle turns right, when the process of FIG. 12 is executed, the target yaw rate Y _O calculated based on the detected vehicle speed V and the detected steering angle θ _S at that time is set to the first value. Is smaller than the set value Y _OS1, that is, when the lateral force for rolling the vehicle is small, the process proceeds from step S43 to step S44, so that the damping force variable shock absorbers 3FL to 3FL continue.
The RR skyhook control state is continued and the control state focusing on ride comfort is continued, and the damping force on the turning outer wheel side is increased to suppress the roll of the vehicle body, and conversely, the damping force on the turning inner wheel side is reduced. The rigidity of the right and left rolls increases.

However, if the vehicle makes a sharp turn to some extent or performs relatively large steering at high speed, the roll of the vehicle body increases accordingly, and when the processing of FIG. 12 is executed, the roll is calculated in step S42. The target yaw rate Y _O exceeds the first set value Y _OS , and step S43
When the target yaw rate Y _O is less than the second set value Y _OS2 , the process _proceeds to step S45.
The process moves to, while being set in the middle damping force control flag FM "1", the yaw rate feedback control gain k _P in the steering control is set to a standard control gain k _PN.

Therefore, when the damping force control process of FIG. 10 is executed, the process proceeds from step S6 to step S8 via step S7, and the front left wheel side (or the front right wheel side) which is the front outer turning wheel side. ) Variable damping force shock absorber 3FL
(Or 3FR) to determine whether a damping coefficient C _FL (or C _FR) is a medium damping force C _M or higher for, C _FL (or C _FR)
≧ C when it is _M, the attenuation coefficient is set as it is, when it is C _FL (or C _FR) <C _M is before the front turning outer wheel and proceeds to step S9 left wheel side (or the front right wheel side damping coefficient C _FL (or C _FR) coefficient middle attenuation C _M) of
Is restricted to, the damping coefficient C _RL (or C _RR) also turning outer rear wheel in the same manner is set to medium or higher damping coefficient C _M.
For this reason, the skyhook control is continued on the turning inner wheel side, but the damping coefficient C is limited to the middle damping coefficient _CM or more for the turning outer wheel, so that as shown by the broken line in FIG. Of the turning outer wheel is improved, and the riding comfort is somewhat deteriorated, but the steering stability can be ensured.

On the other hand, in the steering control process of FIG.
Feedback control gain k_PIs the standard control gain k_PN
, The target yaw rate is set in step S37.
Y _OAnd yaw rate detection value Y_DFeed based on deviation of
The amount of back control becomes larger than that during slow steering.
This also improves steering stability.
You.

Further, when the vehicle turns sharply, the roll of the vehicle body further increases accordingly, and when the processing of FIG. 12 is executed, the target yaw rate Y _O calculated in step S42 becomes the second set value. Y _OS2 will be exceeded,
Proceeding from step S45 to step S47, the high damping force control flag FH is set to “1”, and the yaw rate feedback control gain k _P in the steering control is set.
Is set to the high control gain k _PH .

For this reason, the damping force control processing of FIG. 10 is executed.
When the process is completed, the process proceeds from step S6 to step S7.
Proceeding to step S12, the front left side on the turning outer wheel side of the front wheel
Wheel side (or front right wheel side) damping force variable shock absorber 3
Attenuation coefficient C for FL (or 3FR)_FL(Or C_FR) Is high
Damping force C_HIt is determined whether it is the above or not,_FL(Or
C _FR) ≧ C_H, The attenuation coefficient remains unchanged
Set, C_FL(Or C_FR) <C_HIf
The process proceeds to step S9, and the front left wheel side becomes the turning outer wheel of the front wheel.
(Or front right wheel side) damping coefficient C_FL(Or C_FR) Is high attenuation
Coefficient C_HThe same applies to the rear turning outer wheel.
Damping coefficient C_RL(Or C_RR) Is the high damping coefficient C_HSet above
Is done. As a result, the inner
Ifook control is continued, but the turning outer wheel is damped.
Coefficient C is high damping coefficient C_HBecause of the above restrictions, FIG.
As shown in the dashed line, the damping force at the turning outer wheel is highly damped.
Power, and the grounding of the turning outer wheel is improved.
Therefore, handling stability will be emphasized.

On the other hand, since the yaw rate feedback control gain k _P is set to the high control gain k _PH in the steering control processing of FIG. 11, the feedback based on the deviation between the target yaw rate Y _O and the yaw rate detection value Y _D in step S37. Since the control amount becomes a value larger than that at the time of the relatively sharp steering, the steering stability can be further improved.

In the above embodiment, the case where the steering state of the vehicle is detected based on the detected steering angle θ _S and the detected vehicle speed V has been described. However, the present invention is not limited to this. The lateral acceleration may be detected by a lateral acceleration sensor, and the turning state of the vehicle may be detected based on the detected value of the lateral acceleration. Further, in the above-described embodiment, the case where the valve element 31 for controlling the damping force is configured as a rotary type is described. However, the present invention is not limited to this. Different flow paths may be formed. In this case, a pinion is connected to the rotating shaft 41a of the step motors 41FL to 41RR, and a rack meshing with the pinion is attached to the connecting rod 42 or an electromagnetic solenoid is applied. Thus, the sliding position of the valve element 31 may be controlled, and instead of changing the damping force continuously, a damping force variable shock absorber capable of switching the damping force in a plurality of stages may be applied.

Further, in the above embodiment, the rear wheel assist steering cylinder 79 is connected to the closed sensor type servo valve 8.
5, the feedback control has been described. However, the present invention is not limited to this. An open center type servo valve is applied, and the piston rod 79a of the four-wheel drive 79 is returned to the neutral position accordingly. The control may be performed with a return spring interposed.

Further, in the above-described embodiment, the case where the yaw rate feedback control of the above-described formula (3) is performed in the rear wheel steering control is described. However, the present invention is not limited to this. may be performed only feedforward control based on the [delta] _f, in this case may be changed in accordance with the control gain of the feed-forward term in the turning state.

Further, in the above embodiment, the case where the control is performed by using the microcomputer 56 has been described. However, the present invention is not limited to this. The comparator, an integrator for integrating the output of the vertical acceleration sensor 51i, An electronic circuit such as a differentiating circuit for differentiating the output of the stroke sensor 52i or a function generator may be combined. Further, in the above embodiment, the case where the potentiometer is applied as the stroke sensor has been described.However, the present invention is not limited to this, and an ultrasonic distance sensor and a detection coil for detecting a relative distance between the vehicle body and the road surface are used. Any relative displacement detection means such as a displacement sensor that detects displacement by impedance change or inductance change can be applied.

Further, in the above-described embodiment, the vertical acceleration sensors 51FL to 51FL
Although the case in which the 51RR is provided has been described, any one of the vertical acceleration sensors may be omitted, and the vertical acceleration at the omitted position may be estimated from the values of the other vertical acceleration sensors. In the above embodiment, the case where the step motors 41FL to 41RR are subjected to open loop control has been described. However, the present invention is not limited to this. You may do so.

[0062]

As described above, according to the suspension control system of the first aspect, the turning state of the vehicle is detected by the turning state detecting means, and at least the turning outer wheel is detected by the damping coefficient changing means in accordance with the turning state. Since the damping coefficient of the variable damping force shock absorber on the side is changed,
The damping force variable shock absorber of the turning outer wheel and the turning inner wheel can be individually controlled according to the turning state,
The effect is obtained that the ride comfort and steering stability can be finely controlled.

According to the second aspect of the present invention, when the target yaw rate of the turning outer wheel is small, the control range of the damping coefficient is widened so that ride comfort is emphasized, and when the target yaw rate is medium, The control width of the damping coefficient is slightly narrowed toward the high damping coefficient side to emphasize steering stability, and when the target yaw rate increases, the control width of the damping coefficient is narrowed to the high damping coefficient side to emphasize steering stability. Since the control width of the damping force is changed, there is an effect that a margin can be provided even in the limit running state.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a basic configuration of the present invention.

FIG. 2 is a schematic configuration diagram showing one embodiment of the present invention.

FIG. 3 is a partially sectional front view showing an example of a variable damping force shock absorber.

FIG. 4 is an enlarged sectional view showing a damping force adjusting mechanism in a maximum damping force state when the vehicle body is lifted.

FIGS. 5A and 5B are enlarged cross-sectional views showing a damping force adjusting mechanism in an intermediate damping force state when the vehicle body is lifted, wherein FIG. 5A shows a hydraulic oil path on the extension side and FIG.

FIGS. 6A and 6B are enlarged cross-sectional views showing a damping force adjustment mechanism when the vehicle body does not fluctuate, wherein FIG. 6A shows a hydraulic oil path on the extension side and FIG.

FIGS. 7A and 7B are enlarged cross-sectional views showing a damping force adjusting mechanism in a state of maximum damping force when the vehicle body descends, wherein FIG. 7A shows a hydraulic oil path on the extension side and FIG.

FIG. 8 is an explanatory diagram showing a damping force characteristic with respect to a step angle of a variable damping force shock absorber.

FIG. 9 is a block diagram illustrating an example of a controller.

FIG. 10 is a flowchart illustrating an example of a damping force control processing procedure of a controller.

FIG. 11 is a flowchart illustrating an example of a steering control processing procedure of a controller.

FIG. 12 is a flowchart illustrating an example of a control gain setting processing procedure of the controller.

FIG. 13 is a characteristic diagram showing a target yaw rate map showing a relationship between a detected steering angle, a detected vehicle speed, and a target yaw rate.

FIG. 14 is a characteristic diagram illustrating a relationship between a piston speed and a damping force.

[Explanation of symbols]

 1FL to 1RR Wheel 2 Body 3FL to 3RR Damping force variable shock absorber 4 Controller T1 to T3 Expansion side flow path C1 to C4 Pressure side flow path 41FL to 41RR Step motor 51FL to 51RR Vertical acceleration sensor 52FL to 52RR Stroke sensor 53 Vehicle speed sensor 54S Steering Angle sensor 54R Rear wheel steering angle sensor 55 Yaw rate sensor 56 Microcomputer 59FL-59RR Motor drive circuit 76 Steering wheel 79 Rear wheel auxiliary steering cylinder 85 Servo valve

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B60G 17/015

Claims (2)

(57) [Claims] 1. A suspension having a variable damping force shock absorber, an auxiliary steering device for auxiliary steering of at least a rear wheel, and damping force control means for controlling a damping force of the variable damping force shock absorber in accordance with a vertical movement of a vehicle body. When,
In a vehicle characteristic control device for a four-wheel steering vehicle, comprising: a steering control unit configured to control the auxiliary steering device according to a steering angle or the like; a turning state detection unit that detects a turning state of the vehicle; A vehicle characteristic control apparatus for a four-wheel steering vehicle, comprising: damping coefficient changing means for changing at least a damping coefficient of a variable damping force shock absorber of a turning outer wheel according to a detected turning state. 2. The turning state detecting means comprises a yaw rate sensor for detecting a target yaw rate at the time of turning, and the damping coefficient changing means changes a control width of the damping coefficient according to a magnitude of the target yaw rate. The vehicle characteristic control device for a four-wheel steering vehicle according to claim 1, wherein: