JP3963195B2 - Vehicle suspension system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle suspension system that optimally controls a damping force characteristic of a shock absorber, and more particularly to a technique for ensuring steering stability during braking and turning.
[0002]
[Prior art]
Conventionally, as a vehicle suspension device that controls the damping force characteristics of a shock absorber in order to ensure steering stability during braking and turning, for example, a vehicle suspension described in JP-A-6-64429 Control devices are known.
The conventional suspension control device for a vehicle includes a steering state detection unit that detects a steering state of the vehicle and a braking state detection unit that detects a braking state of the vehicle, and a traveling state detection unit that detects a traveling state of the vehicle. The control means for switching and controlling the control characteristics of the suspension device in at least three stages or more based on the detection signal of the running state detection means, and the turning and braking that the detection signals of the steering state detection means and the braking state detection means exceed a predetermined level. The structure includes a determination unit that determines whether or not the vehicle is in a state, and a blocking unit that prevents switching to a higher stage where the determination result of the determination unit is equal to or higher than the first set value.
In other words, during turning of the vehicle, the change in the posture of the vehicle body is allowed by preventing the control characteristic of the suspension device from switching to a high stage that is equal to or higher than the first set value set in advance. The load sharing amount on the side and the load sharing amount on the turning inner ring side can be reduced to reduce the shared load difference between the inner and outer rings, and the steering stability is improved by suppressing the decrease in total cornering power. It will be able to be.
[0003]
[Problems to be solved by the invention]
However, as described above, the conventional suspension control device for a vehicle reduces the suspension control characteristics as a whole. As a result, the wheel load fluctuation increases and the braking performance decreases due to the overall lack of damping. There was a problem that there was a case.
[0004]
The present invention has been made paying attention to the above-mentioned conventional problems, and provides a vehicle suspension device that can improve the turning performance of the vehicle without reducing the braking performance during braking and turning. It is the purpose.
[0005]
[Means for Solving the Problems]
  In order to achieve the above object, in the vehicle suspension system according to claim 1 of the present invention, the shock is provided with damping force characteristic changing means a that is interposed between the vehicle body side and the wheel side and can change the damping force characteristic. Absorber b, vehicle vertical behavior detecting means c for detecting the vertical behavior of the vehicle, and damping force of the shock absorber during normal traveling of the vehicle based on the vertical behavior of the vehicle detected by the vehicle vertical behavior detecting means c Damping force characteristic control means e having a normal-time control unit d for optimally controlling the characteristics, braking state detection means f for detecting the braking state of the vehicle, turning state detection means g for detecting the turning state of the vehicle, and the braking When the braking state and turning state of the vehicle are detected by the state detection means f and the turning state detection means g, the damping force characteristic of at least the extension stroke side of the left and right rear wheel side shock absorbers b is obtained. By controlling at least the extension stroke side of the inner wheel side shock absorber b of the front wheel to soft characteristics and controlling at least the pressure stroke side of the outer ring side shock absorber b of the front wheel to hard characteristics, A braking / turning correction control unit that controls the roll rigidity on the front wheel side to be lower than the roll rigidity of,in frontWhen the braking state and turning state of the vehicle are detected by the braking state detection means f and the turning state detection means g, the damping force characteristic during the extension stroke of the left and right rear wheel side shock absorbers b is controlled to a hard characteristic. It is configured to control the damping force characteristic during the extension stroke of the inner wheel side shock absorber b of the front wheel to a soft characteristic and to control the damping force characteristic during the compression stroke of the outer wheel side shock absorber b of the front wheel to a hard characteristic.,in frontThe shock absorber b has a soft area where the damping force characteristic is soft on both the expansion side and the compression side, and an expansion side hard area where the expansion side damping force characteristic can be changed in multiple stages and the compression side damping force characteristic is soft. The compression-side damping force characteristics can be changed in multiple stages, and the expansion-side damping force characteristics are soft and the compression-side hard region has a characteristic.The
[0006]
[Action]
  Claims of the present invention1The above-described vehicle suspension device is configured as described above, and therefore, during normal driving of the vehicle (when the braking state and the turning state are not detected), the normal time control unit d of the damping force characteristic control means e Optimal control of the damping force characteristic of the shock absorber b is performed based on the vertical behavior of the vehicle detected by the vertical behavior detecting means c, and thereby damping force characteristic control is performed with emphasis on the riding comfort of the vehicle. When the braking state and turning state of the vehicle are detected by the braking state detection means f and the turning state detection means g, the braking / turning correction control unit h determines the ratio of the roll rigidity before and after the vehicle on the front wheel side. Thus, the steering characteristic is prevented from becoming an understeer state, and the vehicle turning performance can be improved without reducing the braking performance during braking and turning. Specifically, when the braking state and turning state of the vehicle are detected by the braking state detection means f and the turning state detection means g, the left and right rear wheel side shock absorbers are controlled in the braking / turning correction control unit h. By performing the correction control for controlling the damping force characteristic of at least the extension stroke side or the extension stroke of b to a hard characteristic and controlling at least the extension stroke side or the extension stroke of the front wheel inner shock absorber b to a soft characteristic. The ratio of the roll rigidity before and after the vehicle is changed in the direction of lowering the front wheel side, thereby preventing the steering characteristics from being understeered and improving the vehicle turning performance during braking and turning. Also, during braking and turning, braking performance is controlled by controlling the dive of the vehicle during braking and turning by controlling at least the pressure stroke side or pressure stroke side of the front wheel outer side shock absorber b to hard characteristics. While improving the turning performance of the vehicle.The
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
FIG. 2 is a configuration explanatory view showing the vehicle suspension device of the embodiment of the present invention, which is interposed between the vehicle body and the four wheels and has four shock absorbers SA._FL, SA_FR, SA_RL, SA_RR(In the description of the shock absorber, when these four are collectively referred to and when the common configuration thereof is described, it is simply indicated as SA. The lower right sign indicates the wheel position._FLIs the front wheel left,_FRIs the front wheel right,_RLIs the rear left wheel,_RRIndicates the right rear wheel. ) Is provided. Each wheel position has a vertical acceleration G (G_FL, G_FR, G_RL, G_RR) Detecting a sprung vertical acceleration sensor (hereinafter referred to as a vertical G sensor) 1 (1_FL, 1_FR, 1_RL, 1_RRThe steering wheel ST is provided with a steering sensor 2 for detecting the turning state of the vehicle from the steering angle θ. Further, although not shown in the figure, the steering operation state (braking state) is not shown. A brake lamp switch 5 for detection is provided, and each vertical G sensor 1 (1_FL, 1_FR, 1_RL, 1_RR), Signals from the steering sensor 2 and the brake lamp switch 5 are input, and each shock absorber SA is input._FL, SA_FR, SA_RL, SA_RRA control unit 4 for outputting a drive control signal to the pulse motor 3 is provided.
The system block diagram of FIG. 3 shows the above configuration, and the control unit 4 includes an interface circuit 4a, a CPU 4b, and a drive circuit 4c. The interface circuit 4a includes the upper and lower G sensors 1 (1_FL, 1_FR, 1_RL, 1_RR) The sprung vertical acceleration G (G_FL, G_FR, G_RL, G_RR) Signal, the steering angle θ signal from the steering sensor 2, and the switch signal (ON, OFF) from the brake lamp switch 2 are input, and the control unit 4 receives each shock absorber SA (SA) based on these input signals._FL, SA_FR, SA_RL, SA_RR) Damping force characteristic control is performed.
[0008]
Further, the control unit 4 includes the upper and lower G sensors 1 (1_FL, 1_FR, 1_RL, 1_RR) The sprung vertical acceleration G (G_FL, G_FR, G_RL, G_RR) The bounce speed component, the pitch speed component, and the roll speed component at each wheel position are obtained based on the signals, and the control signal V (V (V) at each wheel position is obtained from these speed components._FL, V_FR, V_RL, V_RR) Is provided. Details of the signal processing circuit will be described later.
[0009]
Next, FIG. 4 is a sectional view showing the configuration of the shock absorber SA. The shock absorber SA includes a cylinder 30, a piston 31 that defines the cylinder 30 as an upper chamber A and a lower chamber B, and a cylinder. An outer cylinder 33 having a reservoir chamber 32 formed on the outer periphery thereof, a base 34 defining the lower chamber B and the reservoir chamber 32, and a guide member 35 for guiding the sliding of the piston rod 7 connected to the piston 31; A suspension spring 36 interposed between the outer cylinder 33 and the vehicle body and a bumper bar 37 are provided.
[0010]
Next, FIG. 5 is an enlarged cross-sectional view showing a portion of the piston 31. As shown in this figure, the piston 31 has through holes 31a and 31b and the through holes 31a and 31b. A compression-side damping valve 20 and an extension-side damping valve 12 are provided for opening and closing each. A stud 38 that penetrates the piston 31 is screwed and fixed to the bound stopper 41 that is screwed to the tip of the piston rod 7, and the stud 38 bypasses the through holes 31 a and 31 b. Communication for forming a channel (an extension side second channel E, an extension side third channel F, a bypass channel G, and a pressure side second channel J, which will be described later) communicating the upper chamber A and the lower chamber B. A hole 39 is formed, and an adjuster 40 for changing the cross-sectional area of the flow path is rotatably provided in the communication hole 39. Further, on the outer peripheral portion of the stud 38, there are provided an extension side check valve 17 and a pressure side check valve 22 that allow or block the flow on the flow path side formed by the communication hole 39 according to the direction of fluid flow. Yes. The adjuster 40 is rotated by the pulse motor 3 via the control rod 70 (see FIG. 4). In addition, the first port 21, the second port 13, the third port 18, the fourth port 14, and the fifth port 16 are formed in the stud 38 in order from the top.
[0011]
On the other hand, the adjuster 40 is formed with a hollow portion 19, a first lateral hole 24 and a second lateral hole 25 communicating between the inside and the outside, and a longitudinal groove 23 formed on the outer peripheral portion.
[0012]
Therefore, between the upper chamber A and the lower chamber B, as a flow path through which fluid can flow in the extension stroke, the inside of the extension side damping valve 12 is opened through the through hole 31b and reaches the lower chamber B. The extension-side second flow path that reaches the lower chamber B by opening the outer peripheral side of the extension-side damping valve 12 via the extension-side first flow path D, the second port 13, the longitudinal groove 23, and the fourth port 14. E, through the second port 13, the longitudinal groove 23, and the fifth port 16, the extension side check valve 17 is opened to reach the lower chamber B, and the third port 18, the third port 18, There are four flow paths, bypass flow path G, which reaches the lower chamber B via the two horizontal holes 25 and the hollow portion 19. Further, as a flow path through which a fluid can flow in the pressure stroke, a pressure side first flow path H that opens the pressure side damping valve 20 through the through hole 31a, a hollow portion 19, a first lateral hole 24, and a first port 21 are provided. The pressure side check valve 22 is opened via the pressure side second flow path J reaching the upper chamber A, and the bypass flow path reaching the upper chamber A via the hollow portion 19, the second horizontal hole 25, and the third port 18. There are three channels with G.
[0013]
That is, the shock absorber SA is configured so that the damping force characteristic can be changed in multiple stages with the characteristics shown in FIG. 6 on both the expansion side and the pressure side by rotating the adjuster 40. That is, as shown in FIG. 7, when the adjuster 40 is rotated counterclockwise from a state where both the expansion side and the compression side are soft (hereinafter, referred to as a soft region SS), the damping force characteristic is multi-stage only on the expansion side. The pressure side becomes a region fixed to the low damping force characteristic (hereinafter referred to as the extension side hard region HS). Conversely, when the adjuster 40 is rotated clockwise, the damping force characteristic is multistaged only on the pressure side. The structure can be changed and the extension side becomes a region fixed to the low damping force characteristic (hereinafter referred to as a compression side hard region SH).
[0014]
Incidentally, in FIG. 7, when the adjuster 40 is disposed at positions (1), (2), (3), the KK cross section, the LL cross section, the MM cross section, and the NN cross section in FIG. The cross sections are shown in FIGS. 8, 9, and 10, and the damping force characteristics at each position are shown in FIGS.
[0015]
Next, in the control operation of the control unit 4, each vertical G sensor 1 (1_FL, 1_FR, 1_RL, 1_RR) The sprung vertical acceleration G (G_FL, G_FR, G_RL, G_RR) The bounce speed component, the pitch speed component, and the roll speed component at each wheel position are obtained based on the signals, and the control signal V (V (V) at each wheel position is obtained from these speed components._FL, V_FR, V_RL, V_RR) Will be described based on the block diagram of FIG.
[0016]
First, in B1, each vertical G sensor 1 (1_FL, 1_FR, 1_RL, 1_RR) The sprung vertical acceleration G (G_FL, G_FR, G_RL, G_RR) Signal, the front wheel bounce acceleration component G based on the following equations (1), (2), (3), (4)_BF, Rear wheel side bounce acceleration component signal G_BR, Pitch acceleration component signal G_P , Roll acceleration signal G_R For each.
[0017]
G_BF= (G_FL+ G_FR) / 2 ... (1)
G_BR= (G_RL+ G_RR) / 2 (2)
G_P = (G_FL+ G_FR-G_RL-G_RR) / 2 (3)
G_R = (G_FR-G_FL+ G_RR-G_RL) / 2 (4)
In subsequent B2, a phase lag compensation formula is used, and each front wheel side bounce acceleration component G is used._BF, Rear wheel side bounce acceleration component signal G_BR, Pitch acceleration component signal G_P , Roll acceleration signal G_R The front wheel bounce speed component V at each tower position_BF, Rear wheel bounce speed component signal V_BR, Pitch velocity component signal V_P , Roll speed signal V_R Convert to
[0018]
The general formula for phase lag compensation can be expressed by the following transfer function equation (5).
G_(S) = (AS + 1) / (BS + 1) (5) (A <B)
It has the same phase and gain characteristics as the integration (1 / S) in the frequency band (0.5 Hz to 3 Hz) required for damping force characteristic control, and gain on the low frequency (up to 0.05 Hz) side. The following transfer function equation (6) is used as a phase lag compensation equation for lowering.
G_(S) = ((0.001 S + 1) / (10S + 1)) × r (6)
Note that r is a gain for matching a gain characteristic with a signal when speed conversion is performed by integration (1 / S), and is set to r = 10 in the embodiment of the present invention. As a result, as shown in the solid line gain characteristics in (a) of FIG. 15 and the solid line phase characteristics in (b) of FIG. 15, in the frequency band (0.5 Hz to 3 Hz) necessary for damping force characteristic control. Only the gain on the low frequency side is lowered without deteriorating the phase characteristics. Note that the dotted lines (a) and (b) in FIG. 15 indicate the gain characteristic and phase characteristic of the sprung vertical speed signal that has been speed-converted by integration (1 / S).
[0019]
In subsequent B3, a band-pass filter process for blocking components other than the target frequency band to be controlled is performed. That is, this band pass filter BPF is composed of a secondary high pass filter HPF (0.8 Hz) and a secondary low pass filter LPF (1.2 Hz), and the front wheel bounce speed targeting the sprung resonance frequency band of the vehicle. Component signal V_BF, Rear wheel bounce speed component signal V_BR, Pitch velocity component signal V_P , Roll speed signal V_R Ask for.
[0020]
In subsequent B4, the control signal V (V (V) at each wheel position is calculated based on the following equations (7), (8), (9), (10)._FL, V_FR, V_RL, V_RR)
V_FL= K_BF・ V_BF+ K_PF・ V_P -K_RF・ V_R  ... (7)
V_FR= K_BF・ V_BF+ K_PF・ V_P + K_RF・ V_R  ... (8)
V_RL= K_BR・ V_BR-K_PR・ V_P -K_RR・ V_R  ... (9)
V_RR= K_BR・ V_BR-K_PR・ V_P + K_RR・ V_R  ················(Ten)
K_BFIs the front wheel bounce gain, K_BRIs the rear wheel bounce gain, K_PFIs the front wheel side pitch gain, K_PRIs the rear wheel pitch gain, K_RFIs the front wheel roll gain, K_RRIs the rear wheel roll gain.
[0021]
Next, of the damping force characteristic control operation of the shock absorber SA in the control unit 4, the contents of the normal control by the normal control unit performed when the vehicle is not braked will be described based on the flowchart of FIG. This normal control is performed for each shock absorber SA._FL, SA_FR, SA_RL, SA_RREvery time.
[0022]
In step 101, it is determined whether or not the control signal V is a positive value. If YES, the process proceeds to step 102 and each shock absorber SA is controlled to the expansion side hard region HS. If NO, the process proceeds to step 103. move on.
[0023]
In step 103, it is determined whether or not the control signal V is a negative value. If YES, the process proceeds to step 104 to control each shock absorber SA to the compression side hard region SH. If NO, the process proceeds to step 105. .
[0024]
Step 105 is a processing step when it is determined NO in Step 101 and Step 103, that is, when the value of the control signal V is 0. At this time, each shock absorber SA is controlled to the soft region SS. To do.
[0025]
Next, the operation of the damping force characteristic control will be described with reference to the time chart of FIG.
When the control signal V changes as shown in this figure, as shown in the figure, when the value of the control signal V is 0, the shock absorber SA is controlled to the soft region SS.
[0026]
Further, when the value of the control signal V becomes a positive value, the compression side damping force characteristic is fixed to the soft characteristic by controlling to the extension side hard region HS, while the extension side damping force characteristic (target damping force characteristic position P)._T ) Is changed in proportion to the control signal V based on the following equation (11).
P_T = (V / V_HT  ) × P_T-max  ... (11)
V_HTIs the expansion side proportional range, P_T-max Is the extension side maximum damping force characteristic position. That is, the target damping force characteristic position P on the extension side in proportion to the value of the control signal V_T Is variably controlled on the hardware characteristic side.
[0027]
When the value of the control signal V becomes a negative value, the compression side hard region SH is controlled to fix the extension side damping force characteristic to the soft characteristic, while the compression side damping force characteristic (target damping force characteristic position P)._C ) Is changed in proportion to the control signal V based on the following equation (12).
P_C = (V / V_HC  ) × P_C-max  ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (12)
V_HCIs the pressure-side proportional range, P_C-max Is the compression side maximum damping force characteristic position. That is, the target damping force characteristic position P on the compression side is proportional to the control signal V value._C Is variably controlled on the hardware characteristic side.
[0028]
Next, of the damping force characteristic control operation of the control unit 4, the switching operation state of the control region of the shock absorber SA will be mainly described based on the time chart of FIG.
[0029]
In the time chart of FIG. 17, area a is a state in which the control signal V based on the sprung vertical speed is reversed from a negative value (downward) to a positive value (upward). At this time, the relative speed is still negative. Since the region is a value (the stroke of the shock absorber SA is the pressure stroke side), at this time, the shock absorber SA is controlled to the extension side hard region HS based on the direction of the control signal V. In this region, the pressure stroke side which is the stroke of the shock absorber SA at that time has soft characteristics.
[0030]
The region b is a region where the control signal V remains a positive value (upward) and the relative speed is switched from a negative value to a positive value (the stroke of the shock absorber SA is on the extension stroke side). At this time, the shock absorber SA is controlled to the extension-side hard region HS based on the direction of the control signal V, and the stroke of the shock absorber is also the extension stroke. Therefore, in this region, the shock absorber SA at that time The stroke side, which is the stroke, has a hard characteristic proportional to the value of the control signal V.
[0031]
In the region c, the control signal V is reversed from a positive value (upward) to a negative value (downward). At this time, the relative speed is still a positive value (the stroke of the shock absorber SA is the extension stroke). At this time, the shock absorber SA is controlled to the compression side hard region SH based on the direction of the control signal V. Therefore, in this region, the stroke of the shock absorber SA at that time A certain stretch side has soft characteristics.
[0032]
In addition, the region d is a region where the control signal V remains a negative value (downward) and the relative speed is changed from a positive value to a negative value (the stroke of the shock absorber SA is on the extension stroke side). The shock absorber SA is controlled to the compression side hard region SH based on the direction of the control signal V, and the stroke of the shock absorber is also the pressure stroke. Therefore, in this region, the stroke of the shock absorber SA at that time is The pressure stroke side has a hard characteristic proportional to the value of the control signal V.
[0033]
As described above, in the embodiment of the present invention, when the control signal V based on the sprung vertical velocity and the relative velocity have the same sign (region b, region d), the stroke side of the shock absorber SA at that time is hard. When the sign is different (region a, region c), the same control as the damping force characteristic control based on the Skyhook theory is performed, in which the stroke side of the shock absorber SA at that time is controlled to a soft characteristic. Will be. Further, in the embodiment of the present invention, when the stroke of the shock absorber SA is switched, that is, when the region a is changed to the region b and the region c is changed to the region d (from the soft characteristic to the hard characteristic). Since the damping force characteristic position on the process side to be changed has already been switched to the hard characteristic side in the previous areas a and c, switching from the soft characteristic to the hard characteristic is performed without time delay.
[0034]
Next, of the damping force characteristic control operation in the control unit 4, normal control by the normal control unit and correction control by the correction control unit (braking initial stage control, steady braking control and turning braking control) The contents of the switching control and the contents of each correction control will be described based on the flowcharts of FIGS. 18 and 19 and the time chart of FIG.
[0035]
First, in the flowchart of FIG. 18, in step 201, it is determined whether or not the vehicle is being braked by determining whether or not the switch signal from the brake lamp switch 5 is in the ON state. When the signal is OFF (non-braking state), the routine proceeds to step 203, where the normal control unit switches to the normal control (skyhook control), and then one control flow is completed. In this normal time control, as described above, the damping force characteristic control of the shock absorber SA is performed with an emphasis on the riding comfort of the vehicle.
[0036]
On the other hand, when the determination in step 201 is YES (switch signal ON = during braking), the routine proceeds to step 202, where it is determined whether or not it is in the initial stage of braking (the control content of this step 202). Details will be described later). When the determination at step 202 is YES (braking initial stage), the routine proceeds to step 204, where switching to the braking initial stage control is performed, and then one control flow is completed.
[0037]
Further, when the determination in step 202 is NO (during steady braking), the routine proceeds to step 205. In step 205, the steering angle θ signal is a predetermined threshold value θ._T To determine whether or not the vehicle is turning. If YES (during steady braking and turning), the routine proceeds to step 206, where the control for turning braking control is performed. After switching, this completes one control flow.
[0038]
On the other hand, when it is determined NO in step 205 (during non-turning steady braking), the routine proceeds to step 207, where switching to steady braking control is performed, and then one control flow is completed.
Thereafter, the above flow is repeated.
[0039]
Next, the control content of step 202 for determining whether or not it is the initial stage of braking in the flowchart of FIG. 18 will be described based on the flowchart of FIG.
[0040]
In step 301 of the flowchart of FIG. 19, after the switch signal from the brake lamp switch 5 is turned on, a predetermined time T_B By determining whether or not the time has elapsed, it is determined whether or not the vehicle is in the initial stage of braking._B When the following is true, the routine proceeds to step 303 where the braking initial stage determination (YES determination at step 202) is performed.
[0041]
Also, YES (predetermined seconds T_B If it is (elapsed), the process proceeds to step 302, where the actual vehicle pitch rate (pitch speed component signal V_P ) Is a predetermined threshold VP_T To determine whether or not braking initial stage control is necessary, and YES (V_P > VP_T ), The routine proceeds to step 303, where an initial braking stage determination (YES determination at step 202) is made, and NO (V_P ≦ VP_T ), The routine proceeds to step 304, where the judgment at the time of steady braking is made (NO judgment at step 202).
[0042]
Next, of the damping force characteristic control operation in the control unit 4, normal control by the normal control unit and correction control by the correction control unit (braking initial stage control, steady braking control and turning braking control) The contents of the switching control and the contents of each correction control will be described based on the time chart of FIG.
[0043]
(B) Non-braking (normal control)
During normal driving of the vehicle (when the braking state is not detected), normal control (skyhook control) by the above-described normal control unit is performed as damping force characteristic control of each shock absorber SA. The ride comfort of the vehicle during traveling can be ensured.
[0044]
(B) Early stage of braking (correction control)
While the vehicle's pitch rate exceeds the predetermined value at the initial stage of braking, the left and right front wheel side shock absorbers SA_FL, SA_FRThe damping force characteristics of the left and right rear wheel side shock absorbers SA are fixed at the compression side hard area SH side while the pressure stroke is fixed to the hard characteristics (the extension stroke side is the soft characteristic)._RL, SA_RRThe braking initial stage control is performed to fix the damping force characteristic of the extension side hard region HS to the hard characteristic (the pressure stroke side is the soft characteristic) on the extension side hard region HS side. In addition, the braking performance can be improved by suppressing the wheel load fluctuation.
[0045]
(C) During steady braking (correction control)
At the time of steady braking in which the vehicle pitch rate drops below a predetermined value after the initial stage of braking, steady braking that increases the control gain of damping force characteristic control in each shock absorber SA than the normal control by the normal control unit. Time control is performed, and thereby, it is possible to improve the braking performance by suppressing the wheel load fluctuation at the time of steady braking without deteriorating the ride comfort of the vehicle more than necessary.
[0046]
(D) During braking and turning (compensation control)
When the vehicle is in steady braking when the vehicle's pitch rate drops below a predetermined value after the initial braking stage and the vehicle is turning by steering, the left and right rear wheel side shock absorbers SA_RL, SA_RRThe damping force characteristic of the left and right front wheels shock absorber SA is fixed to the hard characteristic (soft characteristic on the compression stroke side) on the expansion side hard region HS side._FL, SA_FRAmong them, the damping force characteristic of the turning inner wheel side shock absorber SA is controlled to the compression side hard area SH side where the stroke side is fixed to the soft characteristic, while the damping force characteristic of the turning outer ring side shock absorber SA is controlled to the pressure side hard area SH side. Control during turning braking is performed in which the stroke side is fixed to a hard characteristic (the extension stroke side is a soft characteristic).
[0047]
That is, by controlling the damping force characteristics of the shock absorbers SA of the rear wheel side left and right and front wheel side turning inner wheels as described above, the ratio of the roll rigidity in the front and rear of the vehicle is changed in the direction of lowering the front wheel side. The steering characteristic can be prevented from becoming an understeer state, and the pressure stroke side of the outer wheel side shock absorber SA of the front wheel, which is most heavily loaded at the time of turning, is controlled to be a hard characteristic, so that it can be applied during braking and turning. It is possible to improve the turning performance of the vehicle while suppressing the dive of the vehicle and improving the braking performance.
[0048]
As described above, according to the vehicle suspension device of the embodiment of the present invention, the vehicle dive at the initial stage of braking is suppressed during vehicle braking while ensuring the riding comfort of the vehicle during normal traveling. While suppressing the wheel load fluctuation and improving the braking performance, it is possible to improve the braking performance by suppressing the wheel load fluctuation without deteriorating the ride comfort of the vehicle during the subsequent steady braking more than necessary, During braking and turning, there is an effect that the turning performance of the vehicle can be improved without reducing the braking performance.
[0049]
Although the embodiments of the invention have been described above, the specific configuration is not limited to the embodiments of the invention, and any design changes or the like without departing from the gist of the invention are included in the invention. It is.
[0050]
For example, in the embodiment of the invention, when the damping force characteristic of one stroke side is controlled to the heart characteristic side in the extension stroke or the compression stroke, the damping force characteristic of the other stroke side is fixed to the soft characteristic. Although the example using the shock absorber having the structure described above is shown, the present invention can also be applied to a system using a shock absorber having a structure in which the damping force characteristics of the extension stroke and the pressure stroke change in the same direction.
[0051]
In the embodiment of the invention, the left and right rear wheel side shock absorbers SA are used as correction control during braking and turning._RL, SA_RRThe damping force characteristic of the left and right front wheels shock absorber SA is fixed to the hard characteristic (soft characteristic on the compression stroke side) on the expansion side hard region HS side._FL, SA_FRAmong them, the damping force characteristic of the turning inner wheel side shock absorber SA is controlled to the compression side hard area SH side where the stroke side is fixed to the soft characteristic, while the damping force characteristic of the turning outer ring side shock absorber SA is controlled to the pressure side hard area SH side. Although the stroke side is fixed to the hard characteristic (the extension stroke side is the soft characteristic), the damping force characteristic correction control may be performed by changing the control gain of the normal control by the normal control unit. .
[0052]
In the embodiment of the invention, the brake lamp switch is used as the braking state detection means. However, the braking state can be detected from the brake fluid pressure and the longitudinal acceleration signal, and also from the output signal of the anti-skid control device. Can be detected. In the embodiment of the invention, the determination of the initial stage of braking is performed by determining the threshold value of the vehicle pitch rate. However, the determination may be performed by determining the change rate of the longitudinal acceleration of the vehicle. .
[0053]
In the embodiment of the present invention, the steering angle signal is determined as a threshold value as the vehicle turning state detection means. However, the vehicle roll rate or the lateral acceleration signal is determined as a threshold value. You may do it.
[0054]
【The invention's effect】
  As described above, the present invention claims1In the above-described vehicle suspension device, as described above, when the braking state and turning state of the vehicle are detected by the braking state detection unit and the turning state detection unit, the roll rigidity on the front wheel side is higher than the roll rigidity on the rear wheel side. By adopting a configuration that includes a braking / turning correction control unit that controls in a lower direction, the turning performance of the vehicle can be improved without reducing the braking performance during braking and turning. An effect is obtained. Specifically, when the braking state and turning state of the vehicle are detected by the braking state detection means and the turning state detection means, the damping force characteristics at least on the extension stroke side or at the extension stroke of the left and right rear wheel side shock absorbers are obtained. Control to hard characteristics, control at least the extension stroke side or extension stroke of the inner wheel side shock absorber of the front wheel to soft characteristics, and control at least the pressure stroke side or pressure stroke of the front wheel outer ring side shock absorber to the hard characteristics. Therefore, the braking / turning correction control unit that controls the roll rigidity on the front wheel side to be lower than the roll rigidity on the rear wheel side improves the braking performance at the time of braking and turning. The effect that the turning performance of the vehicle can be improved is obtained.The
[Brief description of the drawings]
FIG. 1 is a view corresponding to a claim showing a vehicle suspension system of the present invention.
FIG. 2 is a configuration explanatory view showing a vehicle suspension device according to an embodiment of the present invention.
FIG. 3 is a system block diagram showing the vehicle suspension device according to the embodiment of the present invention.
FIG. 4 is a cross-sectional view showing a shock absorber applied to the vehicle suspension system of the embodiment of the present invention.
FIG. 5 is an enlarged sectional view showing a main part of the shock absorber.
FIG. 6 is a damping force characteristic diagram corresponding to the piston speed of the shock absorber.
FIG. 7 is a damping force characteristic diagram corresponding to the step position of the pulse motor of the shock absorber.
8 is a cross-sectional view taken along the line KK of FIG. 5, showing the main part of the shock absorber.
9 is a cross-sectional view taken along the line LL and the line MM in FIG. 5 showing the main part of the shock absorber.
10 is a cross-sectional view taken along the line NN in FIG. 5, showing the main part of the shock absorber.
FIG. 11 is a characteristic diagram of a damping force when the shock absorber is hard on the extension side.
FIG. 12 is a damping force characteristic diagram of the shock absorber in the extended side / compressed side soft state.
FIG. 13 is a damping force characteristic diagram of the shock absorber in the compression side hard state.
FIG. 14 is a block diagram showing a signal processing circuit for obtaining a control signal from sprung vertical acceleration in the vehicle suspension system of the embodiment of the present invention.
FIG. 15 is a diagram showing gain characteristics (A) and phase characteristics (B) of a sprung vertical velocity signal converted using a phase lag compensation equation;
FIG. 16 is a flowchart showing a normal-time control operation of the damping force characteristic of the control unit in the vehicle suspension system according to the embodiment of the present invention.
FIG. 17 is a time chart showing a normal time control operation of the damping force characteristic of the control unit in the vehicle suspension system of the embodiment of the present invention.
FIG. 18 is a flowchart showing the contents of switching control between normal control by the normal control unit and correction control by the correction control unit in the vehicle suspension system of the embodiment of the present invention.
FIG. 19 is a flowchart showing the control content of step 202 for determining whether or not it is in the initial stage of braking in the flowchart of FIG.
FIG. 20 is a time chart showing the contents of switching control between normal control by the normal control unit and correction control by the correction control unit in the vehicle suspension system of the embodiment of the present invention.
[Explanation of symbols]
a Damping force characteristic changing means
b Shock absorber
c Vehicle vertical behavior detection means
d Control unit during normal operation
e Damping force characteristic control means
f Braking state detection means
g Turning state detection means
h Braking / turning correction controller

Claims (1)

A shock absorber having damping force characteristic changing means interposed between the vehicle body side and the wheel side and capable of changing the damping force characteristic;
Vehicle vertical behavior detecting means for detecting vertical behavior of the vehicle;
Damping force characteristic control means having a normal time control unit for optimally controlling the damping force characteristic of the shock absorber during normal driving of the vehicle based on the vertical movement behavior of the vehicle detected by the vehicle vertical behavior detection means;
Braking state detection means for detecting the braking state of the vehicle;
A turning state detecting means for detecting a turning state of the vehicle;
When the braking state and turning state of the vehicle are detected by the braking state detection means and the turning state detection means, the damping force characteristic of at least the extension stroke side of the left and right rear wheel side shock absorbers is controlled to a hard characteristic, and the front wheel By controlling at least the extension stroke side of the inner ring side shock absorber of the front wheel with soft characteristics and controlling at least the pressure stroke side of the outer ring side shock absorber of the front wheel with hard characteristics, the roll rigidity on the front wheel side rather than the roll rigidity on the rear wheel side A braking / turning correction control unit that controls in a direction in which
The braking / turning correction control unit
When the braking state and turning state of the vehicle are detected by the braking state detection means and the turning state detection means, the damping force characteristic during the extension stroke of the left and right rear wheel side shock absorbers is controlled to a hard characteristic, and the front wheel It is configured to control the damping force characteristics during the extension stroke of the inner ring side shock absorber to soft characteristics, and to control the damping force characteristics during the compression stroke of the outer ring side shock absorber of the front wheels to hard characteristics.
The shock absorber is
A soft region where the damping force characteristics are soft on both the extension side and the compression side,
The extension side hard region where the extension side damping force characteristic can be changed in multiple stages and the compression side damping force characteristic is soft,
The compression side hard region where the compression side damping force characteristic can be changed in multiple stages and the expansion side damping force characteristic is soft
Vehicle suspension system, characterized in that it has a characteristic comprised of.

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