JPH08230436A - Vehicle suspension device - Google Patents

Abstract

PURPOSE: To dispense with a sensor detecting rear wheel side vehicle behavior and to simplify a system by finding vehicle behavior in each of left and right rear wheel side tower positions on the basis of a vehicle vertical behavior constituent and the like found by multiplying an inverted vertical behavior signal by a gain complying with an acceleration/deceleration of a vehicle. CONSTITUTION: A vehicle suspension device is provided with a longitudinal acceleration/ deceleration detecting means (c) detecting a longitudinal acceleration/deceleration in a vehicle and a left and right front wheel side vehicle behavior detecting means (d) detecting vehicle vertical behavior in the left and right front wheel positions. On the basis of these detection signals, respective vehicle vertical behavior constituents employing a road face input as a transmission path and a vehicle body as a transmission path are found by means of a left and right rear wheel side vehicle behavior detecting means (e), and then, a vehicle vertical behavior constituent, which is found by multiplying an inverted vertical behavior signal by a gain complying with the acceleration/deceleration of the vehicle, is added to the respective vehicle vertical behavior constituents, and as a result, vehicle behavior in each of the left and the right rear wheel side tower positions is found. Subsequently, by means of a control signal forming means (f), respective left and right front wheel side control signals and left and right rear wheel side control signals are found from respective vehicle behavior signals so as to be outputted to a damping force characteristic controlling means (g).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension system for optimally controlling the damping force characteristic of a shock absorber.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension system for controlling a damping force characteristic of a shock absorber, for example, Japanese Unexamined Patent Publication No. Heisei 4-
The one described in Japanese Patent No. 339010 is known.

This conventional vehicle suspension system is mounted on a vehicle body portion ahead of a front wheel of the vehicle by a foreseeing distance, and is equipped with a displacement gauge for measuring a relative displacement between the vehicle body and a traveling road surface, and a vehicle body mounted near the displacement gauge. An acceleration circuit for measuring the vertical acceleration of the vehicle, an integration circuit for second-order integrating the acceleration to obtain the vertical displacement of the vehicle body part on which the displacement gauge is mounted, and a road surface by calculating the vehicle displacement from the relative displacement. It includes a subtraction circuit that calculates the displacement and a control circuit that sets the suspension stroke that is suitable for the road surface displacement after the vehicle has traveled the foreseeable distance based on the vehicle speed of the vehicle. It was something that was controlled.

[0004]

However, since the conventional apparatus is constructed as described above,
There were problems as described below.

That is, with this conventional device, it is not possible to predict the vertical movement of the vehicle body due to the pitching of the vehicle body that occurs when the vehicle accelerates or decelerates, so that optimal control may not be performed in some cases. There was a problem.

The present invention has been made by paying attention to the above-mentioned conventional problems. The omission of the sensor for detecting the behavior of the vehicle on the rear wheel side simplifies the system configuration to improve the vehicle mountability and reduce the system cost. (EN) Provided is a vehicle suspension device capable of reducing the amount of the vehicle suspension and capable of accurately estimating the vehicle vertical movement especially on the rear wheel side even with respect to the vehicle pitching and generating an optimum control force. It is intended.

[0007]

In order to achieve the above-mentioned object, the vehicle suspension system according to claim 1 of the present invention is arranged between the vehicle body side and each wheel side as shown in the claim correspondence diagram of FIG. Shock absorbers b ₁ and b ₂ interposed and capable of changing damping force characteristics by damping force characteristic changing means a; front and rear acceleration / deceleration detecting means c for detecting forward / backward acceleration / deceleration of the vehicle;
Left and right front wheel side vehicle behavior detection means d for detecting vehicle vertical behavior at the left and right front wheel positions, and left and right front wheel side vehicle behavior detection means d
From the vehicle up-and-down behavior signals of the left and right front wheel positions detected by
The vehicle vertical movement component transmitted to each of the left and right rear wheels using the road surface input as the transmission path, the vehicle vertical movement component transmitted to each of the left and right rear wheels using the vehicle body as the transmission path, and the vehicle vertical movement signal at each of the left and right front wheel positions. The vehicle vertical behavior component obtained by multiplying the inverted vertical behavior signal obtained by vertically inverting the direction determination code by the gain according to the acceleration / deceleration of the vehicle detected by the front / rear acceleration / deceleration detection means c is added to each of the left and right rear wheel side tower positions. Left and right rear wheel side vehicle behavior detection means e for obtaining the vehicle behavior of the left and right front wheel side vehicle behavior signals and control for obtaining left and right front wheel side control signals and left and right rear wheel side control signals from the left and right rear wheel side vehicle behavior signals The left and right front wheel side shock absorbers b are based on the signal generating means f, the left and right front wheel side control signals, and the left and right rear wheel side control signals.
₁ and damping force characteristic control means g for controlling the damping force characteristics of the left and right rear wheel side shock absorbers b ₂ .

Further, in the vehicle suspension system according to claim 2,
The left and right front wheel side vehicle behavior detecting means d is constituted by a left and right front wheel side acceleration sensor for detecting a sprung vertical acceleration on each of the left and right front wheels.

Further, in the vehicle suspension system according to claim 3,
The left and right front wheel side vehicle behavior detecting means d is composed of a left and right front wheel side displacement sensor for detecting the sprung vertical displacement of each of the left and right front wheels. Further, in the vehicle suspension system according to claim 4, the left and right front wheel side vehicle behavior detecting means d is provided at a place other than the left and right front wheel side tower positions, and the left and right front wheel side control signal generating means f for obtaining the left and right front wheel side control signals. Includes position correction means h for obtaining the vehicle behavior at the left and right front wheel side tower positions based on a predetermined transfer function from the left and right front wheel side vehicle behavior detected by the left and right front wheel side vehicle behavior detection means d.

Further, in the vehicle suspension system according to claim 5,
The left and right front wheel side vehicle behavior detecting means d are provided at the left and right front wheel side tower positions. Further, in the vehicle suspension system according to claim 6, a sprung vertical velocity detecting means i for detecting the sprung vertical velocity at each wheel position is provided, and the shock absorber b ₁ ,
The damping force characteristic changing means a of b ₂ is a soft region (S where the damping force characteristics on the extension stroke side and the compression stroke side are both soft characteristics).
S), the compression stroke side is held to the soft characteristic, and only the damping force characteristic on the extension stroke side can be variably controlled to the hard characteristic side. The stretch side hard area (HS) is set to the soft characteristic on the extension stroke side. A damping-side hard region (SH) capable of variably controlling only the damping force characteristic on the pressure stroke side to the hardware characteristic side while being held, and the damping force characteristic control means g is detected by the sprung vertical velocity detection means i. When the direction discrimination code of the sprung vertical velocity signal is near 0, the shock absorber b is controlled in the soft region (SS), and when it is positive in the upward direction, the extension side hard region (HS) side is set to the extension side. Damping force characteristics, and pressure side hard area (SH) when downward negative
The damping force characteristic on the pressure stroke side is variably controlled based on the front wheel side or rear wheel side control signal created by the control signal creating means f.

Further, in the vehicle suspension system according to claim 7,
The front / rear acceleration / deceleration detecting means C is composed of a vehicle speed sensor or a wheel speed sensor for detecting a vehicle speed, and an arithmetic circuit for obtaining a longitudinal acceleration / deceleration of the vehicle from a vehicle speed signal detected by the vehicle speed sensor or the wheel speed sensor.

[0012]

Since the vehicle suspension system according to claim 1 of the present invention is configured as described above, when the vehicle behavior on the left and right front wheels is detected by the vehicle behavior detecting means d on the left and right front wheels, the left and right rear wheel sides are detected. In the vehicle behavior detecting means e, the vehicle vertical behavior component and the vehicle body behavior which are transmitted from the vehicle behavior of the left and right front wheels detected by the vehicle behavior detecting means d of the left and right front wheels to the left and right rear wheels using the road surface input as a transmission path. The vertical acceleration / deceleration detecting means c outputs the vertical component of the vehicle vertical behavior transmitted to the left and right rear wheels as a transmission path and the inverted vertical behavior signal obtained by vertically inverting the direction determination code of the vehicle vertical behavior signal at the front and rear wheel positions. The vehicle behavior at each of the left and right rear wheel tower positions is obtained by adding the vehicle vertical behavior components multiplied by the gain according to the detected acceleration / deceleration of the vehicle.

That is, it is possible to omit the installation of the sensor for detecting the vehicle behavior at the left and right rear wheel side tower positions, thereby improving the vehicle mountability and reducing the system cost by simplifying the system configuration. Can be promoted.

In addition to the vehicle vertical movement component transmitted from the front wheel side to the rear wheel using the road surface input as a transmission path and the vehicle vertical movement component transmitted to the rear wheel using the vehicle body as a transmission path,
A vehicle vertical movement component obtained by multiplying an inverted vertical movement signal obtained by vertically inverting the direction discrimination code of the vehicle vertical movement signal at each of the left and right front wheel positions by a gain according to the vehicle acceleration / deceleration detected by the front / rear acceleration / deceleration detecting means c. By adding the values, the vehicle vertical behavior on the rear wheel side can be accurately estimated even with respect to the vehicle pitching that occurs when the vehicle accelerates or decelerates, and thus an optimal control force can be generated.

Further, according to claim 4, the position correcting means h included in the control signal creating means f for obtaining the front wheel side control signal determines a predetermined value from the front wheel side vehicle behavior detected by the left and right front wheel side vehicle behavior detecting means d. The vehicle behavior at each of the left and right front wheel side tower positions is obtained based on the transfer function.
Since the front wheel side vehicle behavior detecting means d can be provided at any place other than the left and right front wheel side tower positions, the vehicle mountability is improved.

In the sixth aspect, when the damping force characteristic control means g indicates that the direction identification code of the sprung vertical velocity signal detected by the sprung vertical velocity detecting means i is upward, the shock absorbers b ₁ , b ₂ are detected. When the extension stroke side damping force characteristic is downward, the compression stroke side damping force characteristic is variably controlled based on the control signal, while the reverse stroke side is fixedly controlled to the low damping force characteristic. Therefore, in the damping range where the direction discrimination codes of the sprung vertical velocity and the sprung unsprung relative velocity match, the stroke side of the shock absorbers b ₁ and b ₂ at that time is high. The damping force of the vehicle is variably controlled to increase the damping force of the vehicle, and in the vibration range where the direction identification codes of the two do not match, the damping force of the shock absorbers b ₁ and b ₂ at that time is reduced. Characteristics In weakening the vibration force of the vehicle, such as would be switching control of the basic damping force characteristic based on skyhook theory it is performed.

[0017]

Embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a structural explanatory view showing a vehicle suspension device of an embodiment of the present invention, in which four shock absorbers SA _FL , SA _FR , SA _RL , and SA _RR are inserted between a vehicle body and four wheels. , 4 in explaining shock absorbers
When referring collectively to one, and when describing these common configurations, they are simply denoted as SA. Also, the lower right code indicates the wheel position, _FL is the front wheel left, _FR is the front wheel right,
_RL indicates the left rear wheel, and _RR indicates the right rear wheel. ) Is provided. Further, vertical acceleration sensors (hereinafter referred to as vertical G sensors) 1 _FL and 1 _FR for detecting acceleration G in the vertical direction are provided on the vehicle body at positions (tower positions) near the shock absorbers SA _FL and SA _{FR on} the left and right front wheels. Is provided,
A front-rear direction acceleration / deceleration sensor (hereinafter referred to as front-rear G sensor) 2 for detecting the front-rear direction acceleration / deceleration Ge of the vehicle body is provided in the vehicle body at the center position on the front wheel side. A control unit 4 is provided which inputs signals from the up and down G sensors 1 (1 _FL , 1 _FR ,) and the front and rear G sensors 2 and outputs a drive control signal to the pulse motor 3 of each shock absorber SA. The sprung vertical acceleration G signal from each vertical G sensor 1 (1 _FL , 1 _FR ,) is obtained as a positive value when the acceleration direction is upward and a negative value when the acceleration direction is downward. The longitudinal acceleration / deceleration Ge from the longitudinal G sensor 2 is obtained with a positive value in the vehicle acceleration direction and a negative value in the vehicle deceleration direction.

The above configuration is shown in the system block diagram of FIG. 3, in which the control unit 4 comprises an interface circuit 4a, a CPU 4b and a drive circuit 4c, and the interface circuit 4a is provided with the left and right upper and lower G sensors 1. The sprung vertical accelerations G _FL and G _FR signals from _FL and 1 _FR ,
The front / rear acceleration / deceleration Ge signal from the front / rear G sensor 2 is input. Then, as shown in FIGS. 14 and 16, the interface circuit 4a uses the sprung vertical accelerations G _FL and G _FR signals and vehicle speed signals at the front and rear wheel positions to determine the springs at the rear and left wheel positions. Up-down acceleration G _RL , G
_{From the} signal processing circuit for _{obtaining the RR} signal and the sprung vertical accelerations G _FL , G _FR , G _RL and G _RR signals at the wheel positions, the sprung vertical velocities Δx _FL , Δx _FR , Δx _RL and Δx at the wheel positions are obtained.
A signal processing circuit for determining _RR is provided. The details of this signal processing circuit will be described later.

Next, FIG. 4 is a sectional view showing the structure of the shock absorber SA.
A is a cylinder 30, a piston 31 defining the cylinder 30 into an upper chamber A and a lower chamber B, an outer cylinder 33 having a reservoir chamber 32 formed on the outer periphery of the cylinder 30, a lower chamber B and a reservoir chamber 32. Defining the base 34 and the piston 31
A guide member 35 that guides the sliding of the piston rod 7 that is connected to the vehicle, a suspension spring 36 that is interposed between the outer cylinder 33 and the vehicle body, and a bumper bar 37.

Next, FIG. 5 is an enlarged sectional view showing a portion of the piston 31, and as shown in this figure, the piston 31 is formed with through holes 31a and 31b, and each through hole is formed. A compression side damping valve 20 and an expansion side damping valve 12 that open and close 31a and 31b respectively are provided. Further, a stud 38 penetrating the piston 31 is screwed and fixed to the bound stopper 41 screwed to the tip of the piston rod 7, and the stud 38 bypasses the through holes 31a and 31b. Communication for forming a flow path (an expansion-side second flow path E, an expansion-side third flow path F, a bypass flow path G, and a compression-side second flow path J described later) that connects the upper chamber A and the lower chamber B with each other. A hole 39 is formed and this communication hole 3
An adjuster 40 for changing the flow passage cross-sectional area of the flow passage is rotatably provided inside the passage 9. Also, the stud 38
The communication hole 3 is formed on the outer peripheral portion of the communication hole 3 depending on the direction of fluid flow.
An expansion-side check valve 17 and a pressure-side check valve 22 that allow and block the flow passage formed by 9 are provided. It should be noted that this adjuster 40 corresponds to the pulse motor 3
Is rotated via the control rod 70 (see FIG. 4). Also, the stud 38 has
A first port 21, a second port 13, a third port 18, a fourth port 14, and a fifth port 16 are formed in this order from the top. On the other hand, in the adjuster 40, the hollow portion 19 is formed, and the first lateral hole 24 and the second lateral hole 25 that communicate the inside and the outside communicate with each other.
And a vertical groove 23 is formed in the outer peripheral portion.

Therefore, a through hole 31 is provided between the upper chamber A and the lower chamber B as a flow passage through which a fluid can flow in the extension stroke.
The inside of the extension side damping valve 12 is opened through b and the lower chamber B
To the extension side first flow path D, the second port 13, the vertical groove 23,
Via the expansion side second flow path E, which opens the outer peripheral side of the expansion side damping valve 12 to the lower chamber B via the fourth port 14, the second port 13, the vertical groove 23, and the fifth port 16. Then, the extension side check valve 17 is opened to reach the lower chamber B by way of the third side flow passage F extending to the lower chamber B and the third port 18, the second lateral hole 25, and the hollow portion 19. There are four channels, channel G. Further, as a flow path through which the fluid can flow in the pressure stroke, the pressure side first valve that opens the pressure side damping valve 20 through the through hole 31a is used.
Flow path H, hollow portion 19, first lateral hole 24, first port 21
Via the pressure side check valve 22 to the upper chamber A, and the bypass flow to the upper chamber A via the hollow portion 19, the second lateral hole 25, and the third port 18. Road G
There are three channels.

That is, the shock absorber SA is constructed so that the damping force characteristics can be changed in multiple stages on both the extension side and the compression side with the characteristics shown in FIG. 6 by rotating the adjuster 40. That is, as shown in FIG.
Both the pressure side are soft (hereinafter soft area SS
When the adjuster 40 is rotated counterclockwise from
Only the extension side can change the damping force characteristic in multiple stages, and the compression 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 can be changed in multiple steps only on the compression side, and the extension side is a region fixed to the low damping force characteristic (hereinafter, referred to as compression side hard region SH).

By the way, in FIG. 7, the KK cross section, the LL cross section and the MM cross section, and the NN cross section in FIG. 8, FIG. 9, and FIG. 10, and the damping force characteristics at each position are shown in FIGS.

Next, in the control operation of the control unit 4, the sprung vertical acceleration G at each wheel position.
The configuration of the signal processing circuit for _obtaining (G _FL , G _FR , G _RL , G _RR ) will be described based on the block diagram of FIG. 14 and the time chart of FIG.

First, at A1, from the sprung vertical accelerations G _FL and G _FR signals at the left and right front wheel positions detected by the left and right front wheel side vertical G sensors 1 _FL and 1 _FR , the road surface input shown in the following equation (1) is obtained. Transfer function G from front wheel position to rear wheel position
Based on _{R (S)} , the sprung vertical acceleration component Gr transmitted to the rear wheel tower position of the vehicle using the road surface input as the transmission path is obtained.

G _{R (S)} = G _{1 (S)}・ G _{2 (S)}・ G _{3 (S)} (1) In addition, G _{1 (S)} is a front wheel side spring Transfer function from top to road surface,
G _{2 (S)} is the transfer function from the rear wheel side road surface to the rear wheel side sprung,
G _{3 (S)} is a delay transfer function of the input time difference between the front and rear of the vehicle body. The delay transfer function G _{3 (S)} is
As shown in (2), the vehicle wheel base W _B and vehicle speed S
Determined by _V.

G3 _(S) = e- ^{s (WB / Sv)} ... (2) Next, in A2, the left and right front wheel side vertical G sensors 1 _FL , 1 _FR
The vertical sprung acceleration G _{FL at} each front wheel position detected by
The sprung vertical acceleration transmitted from the G _FR signal to the rear wheel tower position of the vehicle through the body spring on the basis of the transfer function G _{P (S)} in the front-and-back direction on the body spring. Find the component Gb.

Next, in A3, as shown in the following equation (3),
Inverted vertical acceleration signal obtained by inverting the sign of the direction of the sprung vertical acceleration G (G _FL , G _FR ) signal at the front and rear left and right wheel positions detected by the vertical G sensors 1 _FL and 1 _FR (× (-1)) Then, in A4, when the vehicle pitching occurs due to acceleration or deceleration of the vehicle by multiplying the gain k according to the vehicle longitudinal acceleration / deceleration Ge detected by the longitudinal G sensor 2, The vertical acceleration component G-p of the vehicle body position on the left and right rear wheels is obtained.

G−p = G · (−1) · k ···· (3) That is, when the vehicle front-rear acceleration / deceleration Ge occurs due to deceleration due to acceleration or braking of the vehicle. Since pitching of the vehicle occurs and the rear wheel side of the vehicle body moves upside down with respect to the front wheel side, the vertical movement component of the rear wheel side due to pitching is obtained, and as shown in the time chart of FIG. By using the absolute value of the value in which the vehicle front-rear acceleration / deceleration Ge exceeds a predetermined dead zone as the gain k, the sprung vertical acceleration G (G _FL , G _FR ) signals at the left and right front wheel positions are used to pitch the left and right rear wheels. The vertical acceleration component G-p of the side vehicle body position can be obtained.

In subsequent A5, the sprung vertical acceleration components Gr, Gb, G on the left and right rear wheels obtained in A1 to A4.
The sprung vertical accelerations G _RL and G _RR signals at the left and right rear wheel positions are obtained by adding -p.

As described above, in this signal processing circuit, the sprung vertical acceleration G (G _FL , G _FL , G _FL , at the left and right front wheel positions) is generated even when the vehicle pitches during acceleration or deceleration of the vehicle.
The accurate sprung vertical accelerations G _RL and G _RR signals at the left and right rear wheel positions can be estimated from the G _FR ) signals.

Next, in the control operation of the control unit 4, the sprung vertical acceleration G at each wheel position.
The configuration of the signal processing circuit for obtaining the sprung vertical velocity Δx at each wheel position from (G _FL , G _FR , G _RL , G _RR ) will be described based on the block diagram of FIG. 16.

First, in B1, the phase delay compensation formula is used,
The sprung vertical acceleration G (G _FL , G _FR , G _RL , G _RR ) at each wheel position obtained by the signal processing circuit of FIG.
It is converted to a sprung vertical velocity signal at each wheel position. The general equation for phase delay compensation can be expressed by the following transfer function equation (4).

G _(S) = (AS + 1) / (BS + 1) (4) (A <B) Then, the frequency band (0.5 Hz to 3) necessary for damping force characteristic control is obtained.
Has the same phase and gain characteristics as the case of integrating (1 / S) at (Hz), and the following transfer function formula (5) is used as a phase lag compensation formula for lowering the gain on the low frequency side (up to 0.05 Hz). ) Is used.

G _(S) = (0.001 S + 1) / (10 S + 1) × γ (5) Note that γ is a signal and gain characteristic in the case of speed conversion by integration (1 / S). Is a gain for matching, and is set to γ = 10 in this embodiment. As a result,
The gain characteristic of the solid line in (a) of 7 and the gain characteristic of FIG.
As shown by the solid line phase characteristics in (b), only the gain on the low frequency side is reduced without deteriorating the phase characteristics in the frequency band (0.5 Hz to 3 Hz) required for damping force characteristic control. . In addition, the dotted lines of (a) and (b) in FIG.
The gain characteristic and the phase characteristic of the sprung vertical velocity signal whose velocity is converted by integration (1 / S) are shown.

At B2, a bandpass filter process for cutting off components other than the target frequency band to be controlled is performed. That is, this bandpass filter BPF is composed of a secondary high-pass filter HPF (0.3 Hz) and a secondary low-pass filter LPF (4 Hz), and has a sprung vertical velocity targeting the sprung resonance frequency band of the vehicle. Δx (Δx _FL ,
Δx _FR , Δx _RL , Δx _RR ) signals are obtained.

As described above, the signal processing circuits shown in FIGS. 14 and 16 constitute the rear wheel side vehicle behavior detecting means and the sprung vertical speed detecting means in the claims.

Next, of the control operations of the control unit 4, the details of the damping force characteristic control operation of each shock absorber AS will be described with reference to the flowchart of FIG. This control is performed by each shock absorber S
This is performed for each of A _FL , SA _FR , SA _RL , and SA _RR .

In step 101, the sprung vertical velocity Δx
Is a positive value. If YES, the process proceeds to step 102 to control each shock absorber SA to the extension side hard region HS, and if NO, the process proceeds to step 103.

In step 103, the sprung vertical velocity Δx
Is a negative value, and if YES, the routine proceeds to step 104, where each shock absorber SA is controlled to the pressure side hard region SH, and if NO, the routine proceeds to step 105.

Step 105 is a processing step when it is judged NO in steps 101 and 103, that is, when the value of the sprung vertical velocity Δx is 0,
At this time, set each shock absorber SA to the soft area SS.
To control.

Next, the operation of damping force characteristic control will be described with reference to the time chart of FIG. The sprung vertical velocity Δx is
When changing as shown in this figure, as shown in the figure, when the value of the sprung vertical velocity Δx is 0, the shock absorber SA is controlled to the soft region SS.

Further, when the value of the sprung vertical velocity Δx becomes a positive value, the expansion side hard region HS is controlled to fix the damping force characteristic on the compression side to the soft characteristic, while the extension side forming the control signal is controlled. The target damping force characteristic position P _T is obtained based on the following equation (6). P _T = α _T · Δx (6) Note that α _T is a proportional constant on the extension side.

Further, when the value of the sprung vertical velocity Δx 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 pressure side target damping which constitutes the control signal is set. The force characteristic position P _C is obtained based on the following equation (7). P _C = α _C · Δx (7) Note that α _C is a proportional constant on the pressure stroke side.

As described above, the control signal forming means in the claims is constituted by the arithmetic circuit for obtaining the target damping force characteristic positions P _T , P _C based on the equations (6), (7).

Next, of the damping force characteristic control operation of the control unit 4, mainly the switching operation state of the control area of the shock absorber SA will be described with reference to the time chart of FIG.

In the time chart of FIG. 19, area a
Indicates that the sprung vertical velocity Δx is reversed from a negative value (downward) to a positive value (upward). At this time, the relative velocity (Δx−Δx ₀ ) is still negative (shock absorber SA).
Since the stroke is on the pressure stroke side), at this time, the shock absorber SA is controlled to the extension side hard area HS based on the direction of the sprung vertical velocity Δx.
Therefore, in this area, the shock absorber SA at that time
The pressure stroke side, which is the stroke of, has soft characteristics.

In the region b, the sprung vertical velocity Δx remains a positive value (upward), and the relative velocity (Δx−Δx ₀ ) is a negative value to a positive value (the stroke of the shock absorber SA is the extension stroke). Side), the shock absorber SA is controlled to the extension side hard area HS based on the direction of the sprung vertical velocity Δx at this time, and the stroke of the shock absorber is also the extension stroke. Therefore, in this region, therefore, the extension side, which is the stroke of the shock absorber SA at that time, has a hard characteristic proportional to the value of the sprung vertical velocity Δx.

In the region c, the sprung vertical velocity Δx is reversed from a positive value (upward) to a negative value (downward), but at this time, the relative velocity (Δx-Δx ₀ ) is still positive. Since this is the region where the value of is (the stroke of the shock absorber SA is the extension side), at this time, the sprung vertical velocity Δx
The shock absorber SA is controlled in the compression side hard region SH based on the direction of the above, and therefore, in this region, the extension side, which is the stroke of the shock absorber SA at that time, has a soft characteristic.

In the region d, the sprung vertical velocity Δx remains a negative value (downward), and the relative velocity (Δx-Δx ₀ ) is a positive value to a negative value (the stroke of the shock absorber SA is the extension stroke). Side), the shock absorber SA is controlled to the compression side hard region SH based on the direction of the sprung vertical velocity Δx at this time, and the stroke of the shock absorber is also the pressure stroke. Therefore, in this region, the pressure stroke side, which is the stroke of the shock absorber SA at that time, has a hard characteristic proportional to the value of the sprung vertical velocity Δx.

As described above, in this embodiment, when the sprung vertical velocity Δx and the relative velocity (Δx-Δx ₀ ) have the same sign (region b, region d), the shock absorber S at that time is determined.
Damping force characteristic control based on the skyhook theory, in which the stroke side of A is controlled to have a hard characteristic, and when the signs are different (area a, area c), the stroke side of the shock absorber SA at that time is controlled to have a soft characteristic. The same control as above will be performed. Further, in this embodiment, when the stroke of the shock absorber SA is changed, that is, when the area a is changed to the area b and the area c is changed to the area d (soft characteristic to hard characteristic), the stroke side is changed. Since the damping force characteristic position of has been already switched to the hard characteristic side in the previous regions a and c, the switching from the soft characteristic to the hard characteristic can be performed without time delay.

Next, the function of preventing signal drift due to an extra low frequency input will be described. When the vehicle is being braked, the front wheel side sinks and the rear wheel side floats up, so that the vehicle body leans due to the so-called dive phenomenon of the vehicle body. The G sensor 1 detects as a downward (negative) sprung vertical acceleration component, and this continuously input low frequency downward sprung acceleration component causes a signal to drift.

It should be noted that the above is true when the vehicle is suddenly accelerated to cause the scut phenomenon or when the vehicle is traveling on a long uphill (in this case, the upward sprung vertical acceleration component is detected). , Or even when accelerating on a long downhill, and further when a low-frequency DC component is input to the signal of each vertical G sensor 1.

However, in this embodiment, as the speed converting means for converting each sprung vertical acceleration G detected by each vertical G sensor 1 into a sprung vertical speed signal at each wheel position,
By using the phase delay compensation formula, the sprung vertical velocity signal with only the low frequency gain reduced can be obtained without deteriorating the phase characteristic in the frequency band (0.5 Hz to 3 Hz) required for damping force characteristic control. To be

Therefore, even in a situation in which an extra low frequency component is added to the signal of the upper and lower G sensors 1, such as during braking, the lowering of the low frequency gain affects the damping force characteristic control. It can be lost.

As described above, the vehicle suspension system of this embodiment has the following effects. Even when the vehicle pitches during acceleration or deceleration, the sprung vertical acceleration G at the left and right front wheel positions
Accurate sprung vertical accelerations G _RL and G _RR signals at the left and right rear wheel positions can be estimated from the (G _FL , G _FR ) signals, and thus an optimum control force can be generated. Become.

The sprung vertical velocity Δx at each wheel position can be obtained from the signals obtained from the two vertical G sensors 1 _RL and 1 _FR provided on the front wheel side, which reduces the number of sensors. This makes it possible to simplify the system and reduce the cost.

As a means for converting the sprung vertical acceleration G into the sprung vertical velocity Δx, by using the phase delay compensation formula, a signal drift due to an extra low frequency signal input, such as during braking, is eliminated. Prevent and by this
It becomes possible to prevent the controllability of the damping force characteristic of the shock absorber SA from deteriorating and ensure the riding comfort of the vehicle.

In the damping force characteristic control based on the skyhook theory, switching from the soft characteristic to the hard characteristic is performed without a time delay, which makes it possible to obtain high control response and to change from the hard characteristic to the soft characteristic. Switching is performed without driving the actuator, which makes it possible to improve the durability of the pulse motor 3 and save power consumption.

Although the embodiment has been described above, the specific structure is not limited to this embodiment, and the present invention includes a design change and the like without departing from the scope of the invention.

For example, in the embodiment, in A3 of FIG. 14, the case where the vertical acceleration component G-p of the vehicle body position on the left and right rear wheels due to the pitching of the vehicle is obtained based on the equation (3) is shown. Is based on a transfer function representing the relationship between the front-rear acceleration / deceleration Ge detected by the front-rear G sensor 2 and the vertical acceleration component G-p of the left-right rear-wheel body position due to the front-rear acceleration / deceleration Ge. Vertical acceleration component of position Gp
May be estimated.

Further, in the embodiment, when the damping force characteristic on one stroke side is variably controlled on the hard characteristic side, the shock absorber having the damping force characteristic changing means for making the reverse stroke side a soft characteristic is used. The present invention can be applied to a system using a shock absorber in which both pressure strokes can be changed at the same time.

Further, in the embodiment, the case where the above equations (1) to (3) and the like are used as the transfer function for obtaining the rear wheel sprung vertical acceleration signal from the front wheel sprung vertical acceleration is shown.
When the transfer function is a high-order function, the discretized equation becomes complicated and the program capacity becomes large. Therefore, a low-order transfer function or a normal bandpass filter BPF, highpass filter HPF, or the like is required for damping force characteristic control. It is also possible to use an approximation function or an approximation filter that does not significantly change the gain and phase characteristics of the frequency band.

Further, the proportional constants of the equations (6) and (7) for obtaining the target damping force characteristic position as the control signal may be changed according to the vehicle speed.

Further, in the embodiment, the sprung vertical acceleration sensor is used as the vehicle behavior detecting means for the left and right front wheels, but a left and right front wheel side displacement sensor for detecting the vertical displacement on the spring may be used.

Further, in the embodiment, the case where the left and right front wheel side vehicle behavior detecting means is provided at each of the left and right front wheel side tower positions is shown, but the left and right front wheel side vehicle behavior detecting means is provided at a place other than each of the left and right front wheel side tower positions. At the same time, position correction means may be provided to obtain the vehicle behavior at each of the left and right front wheel side tower positions based on a predetermined transfer function from the left and right front wheel side vehicle behavior signals detected by the left and right front wheel side vehicle behavior detection means.

In the embodiment, the longitudinal acceleration / deceleration of the vehicle is detected by the front / rear G sensor, but it may also be detected by differentiating the vehicle speed signal detected by the vehicle speed sensor or the wheel speed sensor. You can

In the embodiment, the soft area SS is controlled only when the sprung vertical velocity signal is 0.
Control hunting can be prevented by providing a predetermined dead zone centered on the center of the range and maintaining the damping force characteristic in the soft region SS while the sprung vertical velocity is changing within the dead zone.

[0069]

As described above, the present invention claims 1.
In the vehicle suspension system described above, as described above, the front-rear acceleration / deceleration detecting means for detecting the front-rear direction acceleration / deceleration of the vehicle, the left / right front wheel side vehicle behavior detecting means for detecting the vehicle up / down behavior of each of the left and right front wheel positions, and the left / right From the vehicle vertical behavior signals at the left and right front wheel positions detected by the front wheel side vehicle behavior detection means, the vehicle vertical behavior component transmitted to the left and right rear wheel sides using the road surface input as the transmission path and the vehicle body left and right rear wheels as the transmission path. The vehicle vertical movement component transmitted to the side and the inverted vertical movement signal obtained by vertically inverting the direction discrimination code of the vehicle vertical movement signal at each of the left and right front wheel positions are determined by the acceleration / deceleration of the vehicle detected by the front / rear acceleration / deceleration detecting means. By adding the vehicle vertical behavior component multiplied by the gain to obtain the vehicle behavior at the left and right rear wheel side tower positions, the configuration is provided with the left and right rear wheel side vehicle behavior detection means, so that when the vehicle accelerates or decelerates. Jill vehicle vertical behavior of the rear wheel side can accurately estimate the relative pitching of the vehicle, thereby, the effect is obtained that it is possible to generate an optimum control force.

Further, since it is possible to omit the installation of sensors for detecting the vehicle behavior at the left and right rear wheel side tower positions, it is possible to improve the vehicle mountability and reduce the system cost by simplifying the system configuration. Will be able to.

Further, in the vehicle suspension system according to claim 4,
Since the front wheel side vehicle behavior detecting means is provided with the position correcting means for obtaining the vehicle behavior at the front wheel side tower position based on the predetermined transfer function from the front wheel side vehicle behavior detected by the front wheel side vehicle behavior detecting means. It can be provided at any place other than the position, and as a result, vehicle mountability can be improved.

Further, in the vehicle suspension system according to claim 6,
The damping force characteristic changing means of the shock absorber is centered on the soft region (SS) where both the damping force characteristics on the extension stroke side and the damping stroke side are soft characteristics, and the extension stroke is carried out while the soft characteristics are maintained on the compression stroke side. The extension side hard area (HS) in which only the damping force characteristic on the side can be variably controlled to the hard characteristic side,
The extension stroke side is provided with a pressure side hard region (SH) capable of variably controlling only the damping force characteristic on the pressure stroke side to the hard characteristic side while being held at the soft characteristic, and the damping force characteristic control means,
When the direction discrimination code of the sprung vertical velocity signal detected by the sprung vertical velocity detecting means is near 0, the shock absorber b is controlled to the soft region (SS), and when it is upward positive, the extension side hard region. The damping force characteristic on the extension stroke side on the (HS) side, and the damping force characteristic on the compression stroke side on the compression side hard area (SH) side when the pressure is downward negative, the front wheel side generated by the control signal generating means or Since the variable control is performed based on the rear wheel side control signal, the damping force characteristic control based on the skyhook theory can be performed.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a claim showing a vehicle suspension device of the present invention.

FIG. 2 is a structural explanatory view showing a vehicle suspension device of an embodiment of the present invention.

FIG. 3 is a system block diagram showing a vehicle suspension system of the embodiment.

FIG. 4 is a cross-sectional view showing a shock absorber applied to the apparatus of the embodiment.

FIG. 5 is an enlarged cross-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.

FIG. 8 is a K of FIG. 5 showing a main part of the shock absorber.
FIG.

FIG. 9 is an L of FIG. 5 showing a main part of the shock absorber.
It is a -L cross section and a MM cross section.

FIG. 10 is a sectional view taken along line NN of FIG. 5, showing a main part of the shock absorber.

FIG. 11 is a damping force characteristic diagram of the shock absorber when the extension side is hard.

FIG. 12 is a damping force characteristic diagram of the shock absorber in a soft state on the extension side and the compression side.

FIG. 13 is a damping force characteristic diagram of the shock absorber in a compression side hard state.

FIG. 14 is a block diagram showing a signal processing circuit for obtaining left and right rear-spring-side sprung vertical accelerations in the embodiment apparatus.

FIG. 15 is a time chart showing a variable gain control state in the apparatus of the embodiment.

FIG. 16 is a block diagram showing a signal processing circuit for obtaining a sprung vertical velocity at each wheel position in the embodiment apparatus.

FIG. 17 is a gain characteristic (a) and a phase characteristic of the sprung vertical velocity signal obtained by the signal processing circuit in the embodiment apparatus.
It is a figure which shows (b).

FIG. 18 is a flowchart showing a damping force characteristic control operation of the control unit in the embodiment apparatus.

FIG. 19 is a time chart showing the damping force characteristic control operation of the control unit in the embodiment apparatus.

[Explanation of symbols]

a damping force characteristic changing means b ₁ front wheel side shock absorber b ₂ rear wheel side shock absorber c front and rear acceleration / deceleration detecting means d left and right front wheel side vehicle behavior detecting means e left and right rear wheel side vehicle behavior detecting means f control signal generating means g damping force Characteristic control means h Position correction means i Sprung vertical speed detection means

Claims (7)

[Claims] 1. A shock absorber interposed between a vehicle body side and each wheel side and capable of changing a damping force characteristic by a damping force characteristic changing means; and a front / rear acceleration / deceleration detecting means for detecting a front / rear direction acceleration / deceleration of a vehicle. The road surface input is used as a transmission path from the left and right front wheel side vehicle behavior detection means for detecting the vehicle up and down behavior at each of the left and right front wheel positions, and the vehicle up and down behavior signal at each of the left and right front wheel positions detected by the left and right front wheel side vehicle behavior detection means. The vehicle vertical behavior component transmitted to the left and right rear wheels and the vehicle vertical behavior component transmitted to the left and right rear wheels using the vehicle body as a transmission path, and the direction discrimination code of the vehicle vertical behavior signal at the left and right front wheel positions are inverted upside down. The vehicle behavior at each of the left and right rear wheel tower positions is obtained by adding the vehicle up-and-down behavior component obtained by multiplying the inverted up-and-down behavior signal obtained by the above-described gain according to the vehicle acceleration / deceleration detected by the front / rear acceleration / deceleration detection means. Left and right rear wheel side vehicle behavior detection means, and control signal creation means for obtaining left and right front wheel side control signals and left and right rear wheel side control signals from the left and right front wheel side vehicle behavior signals and the left and right rear wheel side vehicle behavior signals, And a damping force characteristic control means for controlling damping force characteristics of the left and right front wheel side shock absorbers and the left and right rear wheel side shock absorbers based on the left and right front wheel side control signals and the left and right rear wheel side control signals. A characteristic vehicle suspension system. 2. The vehicle suspension device according to claim 1, wherein the left and right front wheel side vehicle behavior detecting means is composed of a left and right front wheel side acceleration sensor for detecting a sprung vertical acceleration of each of the left and right front wheels. . 3. The vehicle suspension system according to claim 1, wherein the left and right front wheel side vehicle behavior detecting means is composed of a left and right front wheel side displacement sensor for detecting a sprung vertical displacement of each of the left and right front wheels. . 4. The left and right front wheel side vehicle behavior detecting means is provided at a place other than the left and right front wheel side tower positions, and the left and right front wheel side vehicle behavior detecting means is provided in the control signal generating means for obtaining the left and right front wheel side control signals. The vehicle suspension according to any one of claims 1 to 4, further comprising position correction means for determining a vehicle behavior at each of the left and right front wheel side tower positions based on a predetermined transfer function from the detected left and right front wheel side vehicle behaviors. apparatus. 5. The vehicle suspension system according to claim 1, wherein the left and right front wheel side vehicle behavior detecting means are provided at left and right front wheel side tower positions. 6. A sprung vertical velocity detecting means for detecting a sprung vertical velocity at each wheel position, wherein the damping force characteristic changing means of the shock absorber has soft damping force characteristics on both the extension stroke side and the compression stroke side. With a soft area (SS) being the characteristic, the extension side hard area (HS) in which only the damping force characteristics on the extension stroke side can be variably controlled to the hard characteristics side while maintaining the soft characteristics on the compression stroke side,
The extension stroke side is provided with a pressure side hard region (SH) capable of variably controlling only the damping force characteristic on the pressure stroke side to the hard characteristic side while being held at the soft characteristic, and the damping force characteristic control means,
When the direction discrimination code of the sprung vertical velocity signal detected by the sprung vertical velocity detecting means is near 0, the shock absorber b is controlled to the soft region (SS), and when it is upward positive, the extension side hard region. The damping force characteristic on the extension stroke side on the (HS) side, and the damping force characteristic on the compression stroke side on the compression side hard area (SH) side when the pressure is downward negative, the front wheel side generated by the control signal generating means or The vehicle suspension system according to any one of claims 1 to 5, wherein the vehicle suspension system is configured to be variably controlled based on a rear wheel side control signal. 7. The front / rear acceleration / deceleration detecting means comprises: a vehicle speed sensor or a wheel speed sensor for detecting a vehicle speed; and an arithmetic circuit for obtaining a longitudinal acceleration / deceleration of the vehicle from a vehicle speed sensor or a vehicle speed signal detected by the wheel speed sensor. The vehicle suspension system according to any one of claims 1 to 6, wherein