JP3396117B2 - Vehicle suspension system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension system, and more particularly, to a technique for detecting abnormality in tire air pressure while the vehicle is traveling and a technique for processing the abnormality.

[0002]

2. Description of the Related Art Conventionally, for example, a "tire pressure detecting device" disclosed in Japanese Unexamined Patent Publication No. 5-330322 is known as a device for detecting an abnormality in tire pressure during running of a vehicle.

This conventional "tire pressure detecting device" is
Based on the wheel speed signal from the wheel speed sensor provided on each wheel, the resonance frequency in the vertical direction and the front-back direction under the spring of the vehicle is calculated, and the tire pressure state is detected based on this resonance frequency. Met. This utilizes a phenomenon in which the spring constant of the tire rubber portion changes when the tire air pressure changes, so that the resonance frequencies in the up-down direction and the front-rear direction under the spring of the vehicle also change.

In the conventional example, when an abnormality is detected, an occupant is notified of the occurrence of the abnormality by displaying a warning on a display section provided in the vehicle compartment.

[0005]

However, in the conventional device, as described above, when the tire pressure is abnormal (decreased) due to a puncture or the like, the occupant is warned by the display unit provided in the passenger compartment. You can know the occurrence of the abnormality from the display, but if you continue to drive as it is, there is a risk of damaging the tires and wheels of the wheels where the abnormality has occurred due to the load on the tires, so it is necessary to stop the running of the vehicle immediately. There was a problem.

The present invention has been made in view of the above-mentioned conventional problems, and provides a vehicle suspension device capable of preventing damage to a tire and a wheel of a wheel whose tire air pressure is lowered by a flat tire or the like. The purpose is.

[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. A shock absorber b interposed and capable of changing the damping force characteristic by the damping force characteristic changing means a, and a sprung vertical state quantity detecting means c for detecting the sprung vertical state quantity of the vehicle.
And a damping force characteristic control means e having a basic control section d for variably controlling the damping force characteristic of each of the shock absorbers b based on the sprung vertical state quantity detected by the sprung vertical state quantity detecting means c. , and a tire air pressure reduction detecting means f for detecting a decrease <br/> tire pressure of each wheel, before
The damping force characteristic changing means a of the shock absorber b is
The damping force characteristics on the stroke side and the pressure stroke side are both soft and
Centered on the soft area (SS), the pressure stroke side is soft
Only the damping force characteristics on the extension side are retained while the characteristics are maintained.
Expansion side hard area (HS) that can be variably controlled on the card characteristics side
And, the extension stroke side is kept at the soft characteristic and the pressure stroke side
Pressure side that can variably control only the damping force characteristics of the
A damping region characteristic control means including a hard region (SH)
The basic controller d of e detects the sprung vertical speed detecting means h.
The direction discrimination code of the sprung vertical velocity signal is around 0.
The shock absorber b to the soft area (SS) when
However, when it is positive upward, it is on the extension side hard area (HS) side.
The damping force characteristics on the extension side and the downward negative
The pressure side hard area (SH) side, the pressure stroke side is reduced.
The damping force is adjusted according to the sprung vertical velocity at that time.
Is configured to variably control the over de characteristics, said have been provided in the damping force characteristic control means e, when the decrease in tire air pressure is detected by the tire air pressure reduction <br/> detecting means f is the reduction Shock absorber at the wheel position where the
The damping force characteristic of b is set to the compression side soft expansion side hard area (HS).
The damping force characteristics of the shock absorber at other wheel positions are fixed to the pressure side hard area (S
When the tire air pressure reduction to fix the correction control unit g is a means that is example Bei <br/> to H).

[0008]

Further, in the vehicle suspension system according to claim 2 ,
Each of the tire air pressure drop detecting means f is provided with an unsprung resonance frequency band component extracting means for extracting an unsprung resonance frequency band component from the sprung up and down state quantity detected by the sprung up and down state quantity detecting means c. The unsprung resonance frequency band component extraction means is configured to detect a decrease in tire air pressure based on the level of the unsprung resonance frequency band component of the sprung vertical state quantity.

Further, in the vehicle suspension system according to claim 3 ,
Each of the tire air pressure drop detecting means f determines the level of the unsprung resonance frequency band component of the sprung up / down state amount detected by the unsprung resonance frequency band component extracting means when the tire air pressure is normal. The means configured to detect the decrease in tire air pressure by comparing with the level of the resonance frequency band component is used.

Further, in the vehicle suspension system according to claim 4 ,
The unsprung resonance frequency band component extraction means includes unsprung vertical state quantity estimation means for estimating the unsprung up and down state quantity based on a predetermined transfer function from the sprung up and down state quantity. The unsprung resonance frequency band component is extracted from the unsprung vertical state quantity estimated by the state quantity estimating means.

Further, in the vehicle suspension system according to claim 5 ,
The sprung vertical state amount detected by the sprung vertical state amount detecting means c is defined as the sprung vertical acceleration.

[0013]

[Action] In the vehicle suspension system of the present invention according to claim 1, wherein, as described above, when a decrease in tire air pressure is detected by the tire air pressure reduction detecting means f is the tire pressure decrease time correction control unit g, decrease The damping force characteristic of the shock absorber b at the detected wheel position is set to the compression side soft with the expansion side hard
The damping force characteristics of the shock absorber at other wheel positions are fixed to the area (HS), and the damping force characteristics of the compression side hardware are compared.
The process of fixing the tire in the dead region (SH) is performed, which can prevent damage to the tire and the wheel of the wheel whose tire air pressure has decreased due to puncture or the like.

Further, since the tire air pressure can be detected based on the sprung vertical state quantity signal obtained by the sprung vertical state quantity detecting means provided on the sprung side, the electronic control unit also provided on the sprung side. The wiring up to is simplified and simplified, which improves the vehicle mountability and enables sharing of the damping force characteristic control signal of each shock absorber, thereby reducing the system cost.

[0015] In addition, at the time of normal tire air pressure,
In the basic control unit d of the damping force characteristic control means e, when the direction discrimination code of the sprung vertical velocity signal of each wheel position detected by the sprung vertical velocity detecting means h is near 0, the shock absorber b is soft. The damping force characteristic on the extension stroke side is controlled by the region (SS) when it is positive in the upward direction, and the damping force characteristic on the compression stroke side when it is negative in the downward direction, depending on the sprung vertical velocity at that time. While the variability is controlled to the hardware characteristic, the damping force characteristic on the reverse stroke side is fixedly controlled to the soft characteristic, and therefore, the sprung vertical velocity and the sprung-unsprung relative velocity are controlled. In the damping range in which the direction discrimination codes of No. 1 and No. 2 coincide with each other, the damping force characteristics of the shock absorber b at that time are variably controlled on the hardware characteristic side to enhance the damping force of the vehicle, Disagreement In the vibration area, the basic damping force characteristic switching control based on the skyhook control theory, in which the vibration force of the vehicle is weakened by softening the damping force characteristic on the stroke side of the shock absorber b at that time Will be performed.

Further, when a decrease in tire air pressure occurs, the damping force characteristic of the shock absorber at the wheel position where the decrease is detected shows the expansion side hard region (H) where the compression side becomes soft.
In which the compression side damping force characteristics of the shock absorber b wheel other positions is fixed to the S) is fixed to the compression side hard region (SH) as a hard, thereby, wheel tire pressure has dropped by Pas link etc. It is possible to prevent damage to the tires and wheels.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 2 is a structural explanatory view showing a vehicle suspension system according to a first embodiment of the present invention, in which four shock absorbers S are interposed between a vehicle body and four wheels.
A _FL , SA _FR , SA _RL , SA _RR (When describing shock absorbers, when referring to these four collectively and when describing their common configuration, simply display SA. Also, right The lower symbols indicate the wheel positions. _FL is the front wheel left, _FR is the front wheel right, _RL is the rear wheel left, and _RR is the rear wheel right.) Then, each shock absorber SA _FL , SA _FR , SA _RL , S
Position near the A _RR (hereinafter, referred to as the wheel position) to the vehicle body, sprung mass vertical acceleration sensor for detecting a vertical acceleration G sprung (hereinafter, vertical referred G sensor) 1 (1 _FL, 1 _FR,
1 _RL , 1 _RR ) is provided, and the pulse of each shock absorber SA is provided in the vicinity of the driver's seat based on the signal from each vertical G sensor 1 (1 _FL , 1 _FR , 1 _RL , 1 _RR ). A control unit 4 that outputs a drive control signal to the motor 3 is provided.

The above-mentioned 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 each of the vertical G sensors 1 _FL. , 1 _FR , 1 _RL , 1 _RR sprung vertical acceleration G _FL ,
The G _FR , G _RL , and G _RR signals are input.

In the interface circuit 4a, as shown in FIG. 14, the sprung vertical accelerations G _FL , G _FR , G _RL , and G _{RR at} the wheel positions are used to determine the sprung vertical speed Δx _{FL at the} wheel positions. , Δx _FR , Δx _RL , Δx _RR, and relative sprung-unsprung velocity (Δx-Δx ₀ ) _FL , (Δx-Δx ₀ ).
A signal processing circuit for determining _FR , (Δx−Δx ₀ ) _RL , (Δx−Δx ₀ ) _RR, and an unsprung low-frequency processed signal Gj-p as a tire air pressure determination signal at each wheel is provided. ing. The details of these signal processing circuits 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. As shown in FIG. 5, 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, a hollow portion 19 is formed, a first lateral hole 24 and a second lateral hole 25 which communicate the inside and the outside are formed, and a vertical groove 23 is formed in the outer peripheral portion. There is.

Therefore, the through hole 31 is provided between the upper chamber A and the lower chamber B as a flow passage through which the 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 characteristic can be changed in multiple stages on both the extension side and the compression side with the characteristic 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.
From (G _FL , G _FR , G _RL , G _RR ), the sprung vertical velocity Δx at each wheel position and the sprung-unsprung relative velocity (Δ
x-Δx ₀ ) and the unsprung low-frequency processed signal Gj-p as the tire pressure determination signal for each wheel will be described with reference to the block diagram of FIG.

First, in B1, the phase delay compensation formula is used,
The sprung vertical acceleration G (G _FL , G _FL , 1 _FL , 1 _FR , 1 _RL , 1 _RR ) at each wheel position detected by the vertical G sensor 1 (1 _FL , 1 _FR , 1 _RL , 1 _RR )
G _FR , G _RL , G _RR ) is converted into 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 (1). G _(S) = (AS + 1) / (BS + 1) ... (1) (A <B) And the frequency band (0.5 Hz to 3) required for damping force characteristic control.
Has the same phase and gain characteristics as the case of integrating (1 / S) at (Hz), and the following transfer function formula (2) is used as a phase delay 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 (2) Note that γ is a signal and a gain characteristic when speed conversion is performed by integration (1 / S). Is a gain for matching, and in this embodiment, γ = 10 is set. as a result,
The gain characteristic of the solid line in (a) of FIG. 15 and FIG.
As shown in the solid line phase characteristic in (b) of 5, the state where only the low frequency side gain is reduced without deteriorating the phase characteristic in the frequency band (0.5 Hz to 3 Hz) required for damping force characteristic control. Becomes The dotted lines (a) and (b) in FIG. 15 indicate the gain characteristic and phase characteristic of the sprung vertical velocity signal whose velocity is converted by integration (1 / S).

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 highpass filter HPF (0.3 Hz) and a secondary lowpass filter LPF (3 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.

On the other hand, at B3, as shown in the following equation (3),
The vertical acceleration G (G _FL , G _FR , G _RL , G _{RR )} detected by each vertical G sensor 1 using the transfer function Gu _(S) from each sprung vertical acceleration to the relative speed between the sprung and unsprung _portions. ) Signal, the relative speed (Δx-
Δx ₀ ) [(Δx−Δx ₀ ) _FL , (Δx−Δx ₀ ) _FR ,
(Δx−Δx ₀ ) _RL , (Δx−Δx ₀ ) _RR ] signals are obtained. Gu _(S) = -ms / (cs + k) (3) where m is the sprung mass, c is the damping coefficient of the suspension, k is the spring constant of the suspension, and s is the Laplace operator. is there.

On the other hand, at B4, the sprung vertical acceleration G
From the (G _FL , G _FR , G _RL , G _RR ) signals, as shown in the time chart of FIG. 20, band pass filter processing for obtaining a high-frequency unsprung resonance frequency band component Gj is performed.
That is, a second-order bandpass filter BPF (11 Hz) is used as this bandpass filter.

In the subsequent B5, the unsprung resonance frequency band component G
The unsprung low-frequency processed signal Gj-p is created by calculating the absolute value of the peak value of j and holding the absolute value of the peak value until the absolute value of the next peak value is detected (FIG. 2).
0).

Next, of the damping force characteristic control operation of the shock absorber SA in the control unit 4, the contents of the basic control when the tire pressure is normal will be described with reference to the flowchart of FIG. This basic control is performed with each shock absorber SA _FL , SA _FR , SA
_It is performed for each _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, of the damping force characteristic control operation of the shock absorber SA in the control unit 4, the contents of the basic control when the tire pressure is normal will be described.
This will be described with reference to the time chart of FIG.

When the sprung vertical speed Δx changes as shown in this figure, the sprung vertical speed Δx is changed as shown in the figure.
When the value of is 0, the shock absorber SA is controlled in 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 of the control signal is controlled. Damping force characteristic (Target damping force characteristic position P _T )
Is changed in proportion to the sprung vertical velocity Δx based on the following equation (4). P _T = α · Δx · Ku (4) where α is a constant on the extension side, and Ku is the relative speed between the sprung part and the unsprung part (Δx). The gain is variably set according to −Δx ₀ ).

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 compression side damping force forming the control signal is controlled. Characteristic (target damping force characteristic position P _C )
It is changed in proportion to the sprung vertical velocity Δx based on the following equation (5). P _C = β · Δx · Ku (5) Note that β is a constant on the pressure side.

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

In the time chart of FIG. 17, 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 sprung-unsprung relative velocity (Δx-Δx ₀ ) changes from a negative value to a positive value (shock absorber). Since the stroke of SA is the area switched to the extension 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, and the shock absorber SA is also controlled. Is also an extension stroke, and therefore, in this region, 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 sprung-unsprung relative velocity (Δx) is still.
-Δx ₀ ) is a positive value area (the stroke of the shock absorber SA is the extension stroke side), and at this time, the shock absorber SA is in the compression side hard area SH based on the direction of the sprung vertical velocity Δx. Is controlled by
In this region, the extension side, which is the stroke of the shock absorber SA at that time, has soft characteristics.

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

As described above, in this embodiment, the sprung vertical velocity Δx and the sprung-unsprung relative velocity (Δx-Δ
x ₀ ) has the same sign (area b, area d), the stroke side of the shock absorber SA at that time is controlled to a hardware characteristic, and when it has a different sign (area a, area c), it is the shock absorber at that time. The same control as the damping force characteristic control based on the skyhook control theory of controlling the stroke side of SA to the soft characteristic is performed based on only the sprung vertical velocity Δx signal. 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 is changed. The damping force characteristic position on the side is the previous area a,
Since the switching to the hardware characteristic side has already been performed in c, the switching from the soft characteristic to the hardware characteristic can be performed without a time delay, and thus high control response can be obtained and the hardware characteristic to the soft characteristic can be obtained. Switching to the pulse motor 3 is performed without driving the pulse motor 3, which improves the durability of the pulse motor 3 and
Power consumption will be saved.

Among the control operations of the control unit 4, the contents of the tire air pressure detection operation and the switching control between the basic control when the tire air pressure is normal and the correction control when the tire air pressure is abnormal are shown in the flowchart of FIG. 19 and FIG. This will be described based on the time chart of.

18A is a frequency characteristic diagram of the sprung vertical acceleration, and FIG. 18B is a frequency characteristic diagram of the unsprung low-frequency processed signal Gj-p. As shown, the level of the unsprung low-frequency processed signal Gj-p is lower when the tire pressure is lower than when the tire pressure is normal. Therefore, by judging this level change with a threshold value, it is possible to detect the variation state of the tire air pressure.

Therefore, in step 201 of the flowchart of FIG. 19, the unsprung low-frequency processed signal G for each wheel is
jp is compared with a predetermined threshold value Gj-v, and only the unsprung low-frequency processed signal Gj-p of one of the four wheels has a predetermined threshold value Gj.
Less than jv, unsprung low-frequency processed signal Gj-p of other rings
It is determined whether or not the predetermined threshold value Gj-v is exceeded, and Y
If it is ES, the tire pressure may be abnormal, so the routine proceeds to step 202, where the timer is started (Tt =
Time-Ton), and then proceeds to step 204. If NO, it is determined that the tire pressure is normal and the routine proceeds to step 203, where the timer count Tt is reset to 0 (Tt = 0), and then the routine proceeds to step 206, where the basic control when the tire pressure is normal is performed. Switch to.

In step 204, it is determined whether or not the timer count Tt has passed the predetermined time Δt, and YES.
If it is, it is determined that the tire air pressure is abnormal, and the routine proceeds to step 205, where switching to the tire air pressure abnormal correction control is performed. When the answer is NO, it is determined that the tire air pressure is normal, and the routine proceeds to step 206 to perform the basic control.

In the tire air pressure abnormality correction control, the damping force characteristic of the shock absorber SA at the wheel position where the abnormality is detected is set to the expansion side hard region (H of the compression side software).
S) while fixing the damping force characteristics of the shock absorber SA at the other three wheel positions to the pressure side hard region (SH) of the pressure side hard, that is, the three normal wheels. At the position, the load on the pressure stroke side is supported by the hard damping force characteristic of the shock absorber SA, while at the abnormal wheel position, the wheel load is reduced by the soft damping force characteristic of the shock absorber SA.
This is intended to prevent damage to the tire and the wheel of the wheel whose tire air pressure has dropped due to puncture or the like.
With the above, one flow is ended, and thereafter, the above flow is repeated.

In the tire pressure abnormality correction control executed in step 205, blinking of an alarm lamp provided in the passenger compartment and abnormality notification processing for an occupant by an alarm sound and a voice are also performed. In the basic control performed in step 206, the reset process of the abnormality notification process, the normality confirmation process, and the like are also performed.

Next, the function of preventing signal drift due to an extra low frequency input will be described. During braking of the vehicle, the vehicle body leans due to the so-called dive phenomenon of the vehicle body in which the front side sinks and the rear side floats, and the vehicle body speed is decelerated in this leaning state, so that the component force of the deceleration is increased or decreased by the vertical direction. The 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 at the time of sudden acceleration of the vehicle that causes the scut phenomenon, when the vehicle accelerates on a long uphill (in this case, the upward sprung vertical acceleration component is detected), or This occurs even when accelerating on a long downhill, and further when a low-frequency DC component is input to the signal of the vertical G sensor 1.

However, in this embodiment, each upper and lower G
By using the phase delay compensation formula as the speed conversion means for converting each sprung vertical acceleration G detected by the sensor 1 into a sprung vertical speed signal at each wheel position, a frequency band ( A sprung vertical velocity signal in which only the low-frequency gain is reduced can be obtained without deteriorating the phase characteristic at 0.5 Hz to 3 Hz).

Therefore, even in a situation where an extra low frequency component is added to the signal of the vertical G sensor 1, such as during braking, the lowering of the low frequency gain has an effect on the damping force characteristic control. It can be lost.

As described above, the vehicle suspension system of this embodiment has the following effects. It is possible to detect each tire air pressure based on the signals of the upper and lower G sensors 1 provided on the springs of the respective wheel positions, and it is possible to share the tire pressure with the upper and lower G sensors 1 installed for damping force characteristic control. Therefore, it is possible to reduce the cost of the system and improve the vehicle mountability.

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, and thus, a high control responsiveness is obtained and at the same time, 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.

Next, another embodiment of the present invention will be described. In the description of the other embodiments, the same components as those in the first embodiment will be designated by the same reference numerals and the description thereof will be omitted, and only different points will be described.

(Second Embodiment) In the vehicle suspension system of the second embodiment, the level fluctuations of two different frequency (10 Hz, 11 Hz) components in the unsprung resonance frequency band component are observed. Therefore, a decrease in tire air pressure is detected, which will be described in detail below.

First, in the control operation of the control unit 4, the sprung vertical acceleration G at each wheel position.
The configuration of a signal processing circuit for obtaining two tire pressure determination signals from (G _FL , G _FR , G _RL , G _RR ) is shown in FIG.
It will be described based on the block diagram of FIG. B4 and B5 of this signal processing circuit are the same as B4 and B5 of the signal processing circuit shown in FIG. 14 of the first embodiment, and the unsprung low frequency processed signal Gj-H of 11 Hz is created. Be done.

Further, in B6 of this signal processing circuit, as shown in the time chart of FIG. 24, the unsprung mass of 10 Hz is calculated from each sprung vertical acceleration G (G _FL , G _FR , G _RL , G _RR ) signal. Bandpass filtering is performed to obtain the resonance frequency component GjL. That is, a second-order bandpass filter BPF (10 Hz) is used as this bandpass filter.

In the subsequent B7, the unsprung resonance frequency band component G
The unsprung low-frequency processed signal Gj-L is created by calculating the absolute value of the peak value of jL and holding the absolute value of the peak value until the next absolute value of the peak value is detected (FIG. 2).
4).

22 (a) shows that both unsprung low-frequency processed signals Gj-H and Gj-L when the tire pressure is normal.
22 shows the frequency characteristic diagram of FIG. 22, (b) shows the low-frequency processed signals Gj-H and Gj- under both springs when the tire air pressure is reduced.
It is a frequency characteristic diagram of L. As shown in this characteristic diagram,
With the unsprung low frequency processed signal Gj-L of Hz, the signal level becomes higher when the tire pressure is lower than when the tire pressure is normal, and conversely, with the unsprung low frequency processed signal Gj-H of 11 Hz, the tire pressure is The signal level is lower when the tire pressure is lower than normal. Therefore, the fluctuation state of the tire air pressure can be detected by determining the level change at these two points by the threshold value.

Next, among the control operations of the control unit 4, the tire air pressure detection operation will be described based on the flowchart of FIG. 23 and the time chart of FIG. Incidentally, steps 302 to 3 in this embodiment
Since 06 is the same as the contents of steps 202 to 206 of the block diagram shown in FIG. 19 of the first embodiment, detailed description thereof will be omitted.

First, at step 300, the first unsprung low-frequency processed signal Gj-H for each wheel is set to a predetermined threshold value Gf.
Determine if it is less than H, YES (Gj-H <GfH)
If so, it is possible that the tire pressure is abnormal, so the routine proceeds to step 301, and NO (Gj-H ≧ Gf
If it is H), the tire pressure is normal, so the routine proceeds to step 303.

In step 301, the second unsprung low-frequency processed signal Gj-L for each wheel is set to a predetermined threshold value GfL.
It is judged whether or not it exceeds, and YES (Gj-L> GfL)
If so, the tire pressure may be abnormal, so the routine proceeds to step 302, and NO (Gj-L ≤ Gf
If it is L), the tire pressure is normal, so the routine proceeds to step 303.

As described above, also in the vehicle suspension system according to the embodiment of the present invention, as in the case of the first embodiment, the vertical G provided on each spring at each wheel position.
Each tire air pressure can be detected based on the signal of the sensor 1, and can be shared with the vertical G sensor 1 installed for damping force characteristic control, thus reducing system cost and improving vehicle mountability. It is possible to obtain such an effect.

(Third Embodiment) As shown in the block diagram of FIG. 25, the vehicle suspension system of the third embodiment has a transfer function Ga from the sprung vertical acceleration to the unsprung vertical velocity at B0 thereof. _{(S) The} unsprung vertical velocity is estimated from the sprung vertical acceleration G detected by the G sensor 1 based on (Sequence (6)), and the unsprung resonance frequency band component is calculated from the unsprung vertical velocity in the subsequent B4. It is designed to be extracted. The processing contents of B4 and B5 are the same as those of B4 and B5 of the block diagram of FIG. 14 in the first embodiment.
Since it is substantially the same as, the detailed description will be omitted.

Ga _(S) = (M ₁ · s ² + c ₁ · s + k ₁ ) / (c ₁ · s ² + k ₁ · s) ··· (6) In addition, M ₁ is a sprung mass, c ₁ is the damping coefficient of the suspension, and k ₁ is the spring constant of the suspension. Also,
This equation is obtained by Laplace transforming the equation of motion.

As described above, also in the vehicle suspension system of this embodiment, the same effect as that of the first embodiment can be obtained.

Although the embodiments of the present invention have been described above, the specific configuration is not limited to the embodiments of the present invention, and even if there are design changes and the like within the scope not departing from the gist of the present invention, Included in the invention.

For example, in the embodiment, the soft region SS is controlled only when the sprung vertical velocity signal is 0. However, a predetermined dead zone centered at 0 is provided and the sprung vertical range is within this dead zone. Control hunting can be prevented by maintaining the damping force characteristic in the soft region SS while the speed changes.

In the embodiment of the present invention, when the damping force characteristic of either the extension stroke or the pressure stroke is variably controlled on the hard side, the damping force characteristic on the reverse step side is fixed to the soft side. Although the case of using the shock absorber having the structure described above is shown, the present invention can be applied to a system using the shock absorber having the structure in which the damping force characteristics of the extension stroke and the compression stroke change at the same time.

[0075]

As described above, the present invention claims 1.
In the vehicle suspension system as claimed, as described above, the tire pressure drop detecting means for detecting a decrease in tire air pressure of each wheel, provided in the damping force characteristic control means, the tire pressure by the tire pressure drop detecting means when reduction is detected, and the extension side hard region (H of the compression side soft damping force characteristics of the shock absorber of the wheel position where the drop is detected
S) and the damping force characteristics of the shock absorber at other wheel positions are set to the pressure side hard region of the pressure side hard.
A correction control unit at the time of tire pressure drop fixed to (SH) ,
With the configuration including the above, it is possible to obtain an effect that it is possible to prevent damage to the tire and the wheel of the wheel whose tire air pressure has decreased due to puncture or the like.

Further, since the tire air pressure can be detected based on the sprung vertical state quantity signal obtained by the sprung vertical state quantity detecting means provided on the sprung side, the electronic control unit also provided on the sprung side. The wiring up to is simplified and simplified, which improves the vehicle mountability and can be shared with the damping force characteristic control signal, thereby reducing the system cost.

[0077] The front SL comprises a sprung mass vertical velocity detecting means for determining the sprung mass vertical velocity of each wheel position from the sprung vertical acceleration of the respective wheel position detected by the sprung mass vertical acceleration detecting means, said shock absorber The damping force characteristic changing means is centered on the soft region (SS) in which both the damping force characteristics on the extension stroke side and the damping stroke side are soft characteristics, and the damping force on the extension stroke side is maintained while maintaining the soft characteristics on the compression stroke side. The expansion side hard area (H
S) and a compression side hard region (SH) capable of variably controlling only the damping force characteristic on the compression stroke side to the hard characteristic side while maintaining the soft characteristic on the extension stroke side. The control unit controls the shock absorber to the soft region (SS) when the direction discrimination code of the sprung vertical velocity signal detected by the sprung vertical velocity detecting means is near 0, and extends when the upward positive is positive. The damping force characteristics on the extension stroke side on the side hard area (HS) side, and the damping force characteristics on the compression stroke side on the compression side hard area (SH) side depending on the sprung vertical speed at that time. By adopting the means configured to variably control the hard characteristic, it becomes possible to perform the damping force characteristic control based on the skyhook control theory when the tire pressure is normal.

Further, when a decrease in tire air pressure occurs, the damping force characteristic of the shock absorber at the wheel position where the decrease is detected shows the expansion side hard region (H
By the so compression side damping force characteristics of the shock absorber b wheel other positions is fixed to the S) is fixed to the compression side hard region (SH) as a hard, wheel tire pressure has dropped by Pas link etc. It is possible to prevent damage to the tires and wheels.

[Brief description of drawings]

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

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

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

FIG. 4 is a cross-sectional view showing a shock absorber applied to the first 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 a sprung vertical velocity, a sprung-unsprung relative velocity, and an unsprung resonance frequency band component in the first embodiment.

FIG. 15 is a diagram showing a gain characteristic (a) and a phase characteristic (b) of a sprung vertical velocity signal obtained by the signal processing circuit according to the first embodiment.

FIG. 16 is a flowchart showing the contents of basic control when the tire pressure is normal, of the damping force characteristic control operation of the control unit in the first embodiment.

FIG. 17 is a time chart showing the contents of basic control when the tire pressure is normal in the damping force characteristic control operation of the control unit in the first embodiment.

FIG. 18 is a sprung vertical acceleration in the first embodiment.
FIG. 6B is a frequency characteristic diagram of (a) and the unsprung low-frequency processed signal (b).

FIG. 19 is a flowchart for explaining the contents of the tire air pressure detection operation and the switching control between the basic control when the tire air pressure is normal and the correction control when the tire air pressure is abnormal in the first embodiment.

FIG. 20 is a time chart for explaining the contents of the tire air pressure detection operation and the switching control between the basic control when the tire air pressure is normal and the correction control when the tire air pressure is abnormal in the first embodiment.

FIG. 21 is a block diagram showing a configuration of a signal processing circuit for obtaining an unsprung low-frequency processed signal in the vehicle suspension system of the second embodiment.

FIG. 22 is a frequency characteristic diagram of both unsprung low frequency processed signals when the tire pressure is normal in the second embodiment (a) and a frequency characteristic diagram of both unsprung low frequency processed signals when the tire pressure is abnormal (b). is there.

FIG. 23 is a flowchart showing a tire pressure detection operation of the control operations of the control unit according to the second embodiment.

FIG. 24 is a time chart for explaining a tire pressure abnormality determination operation based on an unsprung resonance frequency band component and an unsprung low-frequency processed signal in the second embodiment.

FIG. 25 is a block diagram showing a configuration of a signal processing circuit for obtaining an unsprung low-frequency processed signal according to the third embodiment. a damping force characteristic changing means b shock absorber c sprung vertical state amount detecting means d basic control section e damping force characteristic control means f tire air pressure abnormality detecting means g tire air pressure abnormal correction control section h sprung vertical velocity detecting means i Unsprung resonance frequency band component extracting means j Unsprung vertical direction state quantity estimating means

Claims (5)

(57) [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 sprung vertical direction for detecting a sprung vertical direction state amount of a vehicle. State quantity detection means, damping force characteristic control means having a basic control unit for variably controlling the damping force characteristic of each shock absorber based on the sprung vertical direction state quantity detected by the sprung vertical state quantity detection means, Low tire pressure to detect a decrease in tire pressure on each wheel
It includes a lower detecting unit, the damping force characteristic changing means of said shock absorber
However, the damping force characteristics on the extension stroke side and the compression stroke side are both soft
Centering on the characteristic soft area (SS), on the pressure stroke side
It is the damping force characteristic on the extension side while being held in the soft characteristic.
The extension side hard area (H
S) and the stroke side are compressed while being held in soft characteristics
It is possible to variably control only the damping force characteristic on the side to the hardware side.
And a compression side hard area (SH), and the basic control unit of the damping force characteristic control means controls the sprung vertical speed.
The direction of the sprung vertical velocity signal detected by the degree detection means
If the code is near 0, set the shock absorber to the soft range.
Control in the range (SS), when the upward positive, the extension side hard
In the region (HS) side, the damping force characteristics on the extension side,
When it is negative downward, it is on the compression side hard area (SH) side.
The damping force characteristics on the compression stroke side,
It is configured to variably control the hardware characteristics according to the speed.
Is the provided in the damping force characteristic control means, when a decrease in tire air pressure is detected by the tire pressure drop detecting means, the compression side soft damping force characteristics of the shock absorber of the wheel position where the drop is detected Stretch side hard area (H
S) and the damping force characteristics of the shock absorber at other wheel positions are set to the pressure side hard region of the pressure side hard.
Vehicle suspension system when a tire pressure drop compensation control unit is characterized by being e Bei <br/> secured to (SH). 2. The tire pressure drop detecting means for each tire is
Sprung sprung up and down detected by state quantity detection means
If the unsprung resonance frequency band component is extracted from the downward state quantity,
The unsprung resonance frequency band component extraction means is provided,
The sprung vertical state quantity detected by the wave number component extraction means
Tire pressure from the level of the unsprung resonance frequency band component of
The vehicle suspension system according to claim 1, wherein the vehicle suspension system is configured to detect a drop . 3. The sprung mass detected by the unsprung resonance frequency band component extracting means by each of the tire air pressure drop detecting means.
The level of the unsprung resonance frequency band component of the vertical state quantity is
Unsprung resonance frequency band formation when tire pressure is normal
Low tire pressure by comparing with the minute level
The vehicle suspension system according to claim 2 , wherein the vehicle suspension system is configured to detect the lower side . 4. The unsprung resonance frequency band component extraction means
Is based on the predetermined transfer function from the sprung vertical state quantity
Vertical unsprung state for estimating vertical unsprung state quantity
The unsprung vertical state quantity estimating means.
From the estimated unsprung vertical state quantity, the unsprung resonance frequency
Vehicle suspension according to claim 2 or 3 , characterized in that it is arranged to extract band components . 5. The sprung vertical state quantity detecting means detects the sprung vertical state quantity.
The sprung vertical state quantity that is output is the sprung vertical acceleration.
Vehicle suspension system according to any one of claims 1 to 4, characterized in that there.