JPH04274917A - Active type suspension - Google Patents

Abstract

PURPOSE:To equip a sky hook damper and a passive damper and maintain excellently the damping performance of the total and at the same time co-work the damping forces of both dampers according to a travel condition and reduce a consumption flow quantity. CONSTITUTION:A stroke sensor 34 and a pump rotation number sensor 36 between vehicle wheels and a vehicle body are connected to a controller 38. The controller 38 contains an adding machine 68 and a function generater 70 besides an operating machine 62 that conducts the input of a stroke signal X and the estimation operation of a consumption flow quantity Q1, a function generater 66 that estimates a discharge quantity Q2 that is according to a pump rotation number N. The machine 68 operates a difference portion signal Q2-Q1, and the generater 70 outputs to a sky hook damper SF a regulation signal KS that increases according to the increase of the difference signal Q2-Q1, and also outputs to a variable throttle 24 that acts as a passive damper, a regulation signal KP that decreases according to the increase of the difference portion signal Q2-Q1.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an active suspension for a vehicle, and in particular, it has a fluid pressure cylinder such as a hydraulic cylinder between the vehicle body and the wheels, and the operating pressure of the fluid pressure cylinder is applied to the vertical direction of the vehicle body. Equipped with both a skyhook damper that actively generates damping force by controlling it according to absolute speed, and a passive damper that generates damping force according to the relative speed between the vehicle body and wheels, reducing energy consumption. Regarding active suspension.

0002

2. Description of the Related Art Conventionally, as an active suspension equipped with a mechanism for obtaining an active damping force and a passive damping force, the one shown in FIG. 10 is known (for example, the one shown in FIG. Kaihei 1-116813,
Utility Model Publication No. 2-33109, and Japanese Patent Application Publication No. 1-275217
(see issue).

In the configuration shown in FIG. 10, reference numeral 1 denotes a hydraulic source, a pressure control valve 2 is connected to the hydraulic source 1, and an output port of the pressure control valve 2 is connected to the vehicle body and between the wheels via a pipe 3. It is connected to a hydraulic cylinder 4 interposed therein. A vertical acceleration sensor 5 is installed at a position corresponding to a wheel on the vehicle body, and a detection signal GZ of this sensor 5 is supplied to a controller 6. The controller 6 calculates the vertical speed by integrating the vertical acceleration signal GZ, calculates a pressure command value for bounce control by multiplying this vertical speed by a gain constant KS, and calculates a command current i corresponding to the pressure command value. is supplied to the proportional solenoid of the pressure control valve 2. Further, a coil spring 7 is inserted between the sprung portion and the unsprung portion to indicate the static load of the vehicle body. The above configuration is
It is expressed equivalently to the skyhook damper shown in FIG.

Therefore, the operating pressure of the hydraulic cylinder 4 can be controlled in proportion to the command current i, thereby actively generating a damping force that damps the bounce of the vehicle body. Further, the output port of the pressure control valve 2 is provided with a throttle A, and the cylinder chamber of the hydraulic cylinder 4 is connected to an accumulator 9 via a pipe 8, with a throttle B inserted in the middle of the pipe 8. Then, aperture B attenuates relatively high-frequency road surface input (vibration) corresponding to the unsprung resonance region, and aperture A attenuates low-frequency road surface input corresponding to the sprung mass resonance region, thereby obtaining a passive vibration damping effect. Can be done.

[0005]

However, in the conventional active suspension shown in FIG. 10, the gain constant KS that determines the damping constant of the skyhook damper is
, and the fluid passage resistance (including the throttle A) seen from the cylinder side of the pressure control valve 2, which determines the characteristics as a passive damper for sprung mass damping, is constant depending on the vehicle running condition, and both It was an individual control configuration with no correlation between damping forces. For this reason, for example, if the detected vertical acceleration value GZ increases due to driving on a large undulating road, and the flow consumption of the skyhook damper for performing active damping increases, even though there is surplus capacity in the passive damping constant. , there is no cooperative relationship between the active damping by the skyhook damper and the passive damping by the passive damper, and in terms of flow consumption, the increase in the skyhook damper directly leads to an increase in the vehicle's energy consumption. There was a need for reconsideration from this perspective.

[0006] The present invention was made in view of the above situation, and provides good overall damping performance in an active suspension equipped with a skyhook damper and a passive damper, and also provides both active and passive damping. It is an object of the present invention to provide an active suspension that can variably adjust the damping force while coordinating each other, thereby reducing the flow rate consumed by the load and saving energy.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the invention according to claim 1 has a fluid pressure cylinder inserted between a vehicle body and a wheel. a skyhook damper that generates a damping force according to an absolute speed and a changeable damping constant; a fluid pressure source that uses a vehicle engine as a rotation source and has a fluid pressure pump that supplies working fluid to the skyhook damper; A passive damper is provided that generates a damping force according to the relative speed between the vehicle body and the wheels and a changeable damping constant, and
a stroke detection means for detecting the relative stroke amount between the vehicle body and the wheels; a consumption flow calculation means for calculating the consumption flow rate of the fluid pressure cylinder based on the detected value of the stroke detection means; A pump rotation detecting means for detecting, a discharge amount estimating means for estimating the discharge amount of the fluid pressure pump based on the detection information of the pump rotation detecting means, and a calculation of the consumption flow rate calculating means based on the estimated value of the discharge amount estimating means. A damping constant adjusting means is provided for lowering the damping constant of the skyhook damper and increasing the damping constant of the passive damper as the values approach.

[0008] Furthermore, the invention according to claim 2 has a fluid pressure cylinder inserted between the vehicle body and the wheels, and the fluid pressure cylinder is provided with a damping constant according to the vertical absolute velocity of the vehicle body and a changeable damping constant. a skyhook damper that generates a damping force; a fluid pressure source that uses a vehicle engine as a rotation source and has a fluid pressure pump that supplies working fluid to the skyhook damper; and a relative speed between the vehicle body and the wheels that can be changed. a passive damper that generates a damping force according to a damping constant; a vehicle speed detecting means for detecting vehicle speed; and as the detected value of the vehicle speed detecting means decreases, the damping constant of the skyhook damper is lowered; A damping constant adjusting means for increasing the damping constant of the passive damper is provided.

[0009]

[Operation] In the invention as claimed in claim 1, when the vehicle travels on a large undulating road, for example, the stroke detection means detects a large and relatively low frequency relative displacement between the wheels and the vehicle body. Based on this, the consumption flow calculation means estimates and calculates a large consumption flow value. Further, the discharge amount estimating means estimates the discharge flow rate of the pump based on information such as engine rotation speed, which indicates the rotation status of the fluid pressure pump from the pump rotation detection means. Therefore, as the estimated value of the cylinder consumption flow increases due to driving on an undulating road, etc., and the estimated value of the consumption flow approaches the estimated value of the pump discharge amount, the damping constant adjusting means lowers the damping constant of the skyhook damper, and the passive Increase damper damping constant. As a result, when the skyhook damper is in a driving state where the flow consumption is large, the active damping force by the skyhook damper is lowered, and the decrease is compensated for by the increase in the damping force by the passive damper, and the total damping force is reduced by the active damper. Compared to before lowering the damping force, it is maintained almost the same and good bounce control is achieved. At this time,
The consumption amount of the skyhook damper decreases due to the reduction in the damping force borne by the skyhook damper, and the amount of working fluid passing through the passive damper decreases, so that the total consumption flow rate decreases.

The invention according to claim 2 is based on the fact that the vehicle speed is generally low when traveling on a undulating road or the like where the flow rate consumed by the load is large. Therefore, the damping constant adjusting means lowers the damping constant of the skyhook damper and increases the damping constant of the passive damper as the detected vehicle speed value becomes smaller. As a result, in the case of traveling on a undulating road, the degree of active damping control is reduced and the reduced amount is covered by the passive damping force, so that the same effect as the invention described in claim 1 can be obtained.

[0011]

[Embodiment] The first embodiment of the present invention will be described below with reference to FIG. 1 of the accompanying drawings.
This will be explained based on FIGS. This embodiment corresponds to the invention set forth in claim 1.

In FIG. 1, 10 denotes an arbitrary wheel, 12
indicates the vehicle body. 14 is the actuator part of wheel 1
1 shows an active suspension of a vehicle interposed between 0 and a vehicle body 12.

The active suspension 14 includes a hydraulic cylinder 18 as a fluid pressure cylinder interposed between the wheels 10 and the vehicle body 12, and a pressure that controls the operating pressure of the hydraulic cylinder 18 based on a command current iC (command value). control valve 20
and a hydraulic source 22 as a fluid pressure source for the suspension system, a variable throttle 24 as a sprung passive damper inserted between the pressure control valve 20 and the hydraulic cylinder 18, and a hydraulic pressure source 22 as a fluid pressure source for the suspension system. Cylinder chamber R
Fixed aperture 2 as an unsprung passive damper connected to
6 and an accumulator 28 connected to this fixed aperture 26.
It is equipped with

Furthermore, the active suspension 14 includes, as its electrical system, a vertical acceleration sensor 30 that detects acceleration acting in the vertical direction of the vehicle body;
A vibration damping controller 32 inputs a detection signal GZ of 0 and a gain constant KS to be described later and supplies a command current iC to the pressure control valve 20 as necessary. sensor 3
4, a pump rotation speed sensor 36 for estimating the operating status of the hydraulic power source 22, and a damping constant controller 38 that inputs the detection signals DX and PN of both sensors 34 and 36 and changes the damping constant as necessary. It has and.

A coil spring 40 is provided between the wheels 10 and the vehicle body 12 to support the static load of the vehicle body. The hydraulic cylinder 18 is a single-acting cylinder, and the lower end of the cylinder tube 18a is attached to the wheel 10 side, the upper end of the piston rod 18b is attached to the vehicle body 12 side, and the cylinder chamber in the cylinder tube 18a is attached to the vehicle body 12 side. R is connected to the output port of the pressure control valve 20 via an output pipe 42. The variable throttle 24 is interposed in this output pipe 42 .

The variable throttle 24 has at least a proportional electromagnetic solenoid, a poppet valve, and a throttle, and the plunger of the solenoid moves in proportion to the magnitude of the control current iP supplied to the proportional electromagnetic solenoid. It has a well-known structure in which the valve is pushed in the axial direction to change the flow path diameter of the throttle. In other words, the damping constant CP of the variable diaphragm 24 changes in proportion to the control current iP as shown in FIG. It is set to attenuate.

The cylinder chamber R of the hydraulic cylinder 18 is connected to the accumulator 28 by a sub-piping 44, and the fixed throttle 2 having a predetermined damping constant is installed in the middle of the sub-piping 44.
6 is interposed. This fixed diaphragm 26 is tuned to absorb high frequency pressure changes corresponding to the unsprung resonance region.

On the other hand, the pressure control valve 20 is, for example,
This is a conventionally well-known three-port proportional electromagnetic pressure reducing valve described in Japanese Patent No. 179,524, the supply port of which is connected to the hydraulic pump 52 of the hydraulic power source 22 via the supply pipe 50, and the return port connected to the hydraulic pump 52 of the hydraulic power source 22 via the return pipe 54. It is connected to the reservoir tank 56 of the hydraulic power source 22, and the output pipe 42 is connected to the output port. The proportional solenoid of the pressure control valve 20 receives an excitation command current i from the vibration damping controller 32.
Since the pressure control valve 20 is supplied with the command current iC
As shown in FIG. 3, a proportional control pressure PC can be outputted from the output port.

The hydraulic power source 22 has a structure including the above-described hydraulic pump 52 and a reservoir tank 56, and the rotating shaft of the hydraulic pump 52 is connected to the shaft of the vehicle engine. As shown in FIG. 4, the flow rate characteristics of the hydraulic pump 52 are such that as the pump rotation speed N increases, the discharge flow rate Q2 gradually increases, and when the pump rotation speed N becomes larger than a predetermined value,
A constant discharge flow rate Q2 is output. In this embodiment, the characteristics shown in FIG. 4 are converted into the discharge amount per wheel.

The vertical acceleration sensor 30 is installed at a position corresponding to the wheel of the vehicle body 12, and this vertical acceleration sensor 30 senses the acceleration generated in the vertical direction of the vehicle body, and generates a voltage value corresponding to the vertical acceleration. Vertical acceleration signal GZ
is output to the vibration damping controller 32. The stroke sensor 34 is, for example, a cylinder tube 18.
a and the vehicle body 12, and supplies a voltage signal DX corresponding to the stroke amount to the damping constant controller 38 as a stroke signal. Further, the pump rotation speed sensor 36 also serves as an engine rotation speed sensor, and outputs a pulse signal PN corresponding to the rotation speed of the hydraulic pump 52 to the damping constant controller 38.

As shown in FIG. 5, the damping constant controller 38 includes a low-pass filter (LPF) 60 to which the stroke signal DX is input, a flow estimation calculator 62 on the output side of this filter 60, and a pump rotation speed signal. P.N.
The output side of this calculation circuit 64 includes a function generator 66 for estimating the discharge amount Q2, and an adder 68 and another function generator are provided on the output side of both circuits 62 and 66. 70 and a drive circuit 72.

Among them, a low pass filter (LPF) 60
outputs only the low-frequency side component X of the stroke signal DX to the flow rate estimation calculator 62, and its cutoff frequency is set so as to cut off the high-frequency stroke change component on the unsprung resonance side. There is. In addition, if you want to cut even the extremely small stroke change when adjusting the vehicle height,
A bandpass filter with a lower cutoff frequency set in this manner may also be used.

The flow rate estimation calculator 62 which receives the output signal X of the low-pass filter (LPF) 60 calculates Q1 = (A/
T)∫0 T |X'|dt... Based on the formula (1), the integral value of the stroke change (differential value) X',
That is, the amount of movement Q1 into and out of the cylinder corresponding to "(1/T)∫0 T | This estimated signal Q1 is supplied to the minus terminal of adder 68. In equation (1), A is a calculation gain based on the pressure receiving area of the hydraulic cylinder 18, and further assumes that the state in which the cylinder discharges hydraulic oil is a non-consumption state, and the gain A is a calculation gain based on the pressure-receiving area of the hydraulic cylinder 18. In order to exclude the state, the integral value “(1
/T)∫0 T |X'|dt" is set to a value that reduces it by half.

The rotation speed calculation circuit 64 inputs the pump rotation speed signal PN which is a pulse signal, counts the number of pulses per unit time, and outputs the rotation speed signal N having a voltage value proportional to the count value to the subsequent stage. It is designed to output to a function generator 66. The function generator 66 stores the function characteristics corresponding to FIG. 4 in advance, estimates the discharge flow rate Q2 corresponding to the rotation speed signal N, and generates the signal Q2 corresponding to the estimated value.
is supplied to the plus terminal of adder 68. Therefore, the adder 68 selects "Q2" from both the input signals Q1 and Q2.
-Q1'' and outputs a signal corresponding to the result of the calculation to the function generator 70. In other words, as the consumption flow rate estimation signal Q1 increases and approaches the pump discharge flow rate estimation signal Q2, the calculation signal "Q2 - Q1" supplied from the adder 68 to the function generator 70 approaches zero. ing.

The function generator 70 stores characteristics corresponding to FIG. 6 in advance, and has a two-output structure that outputs attenuation constant adjustment signals KP and KS in accordance with increases and decreases in the input signal "Q2 - Q1". are doing. Of these damping constant adjustment signals KP and KS, the former KP adjusts the passive damping force, and the latter KS adjusts the active damping force. In FIG. 6, the input signal “Q2 −
When “Q1”=Qa (positive value), that is, the consumption flow rate Q2
exceeds the discharge flow rate Q1 by a predetermined value Qa, the adjustment signals KP and KS are both equal to the predetermined value K1.
Take (=KP =KS). Then, as the difference "Q2 - Q1" increases from this state, the adjustment signal K
While S gradually increases and the adjustment signal KP gradually decreases, almost symmetrically, "Q2 - Q
It is set so that as the difference "Q2 - Q1" decreases from the state of "1"=Qa, the adjustment signal KS gradually decreases and the adjustment signal KP gradually increases.

Of the damping constant adjustment signals KP and KS, one signal KP is directly supplied to the damping controller 36, and the other signal KS is supplied to the drive circuit 72. The drive circuit 72 converts the input voltage signal KP into a corresponding current signal iP and outputs it to the variable aperture 24.

On the other hand, in this embodiment, the vibration damping controller 36 is configured to include an A/D converter, a microcomputer, a drive circuit, etc., and the microcomputer receives the vertical acceleration signal GZ and the damping constant adjustment signal related to active damping. KS is input and the process shown in FIG. 7, which will be described later, is performed. As a result of the processing, the vibration damping controller 36 can supply the command current iC to the pressure control valve 20 in accordance with the rocking motion on the spring.

The vibration damping controller 36 is configured not only mainly by a microcomputer as described above, but also by, for example, an integrator that integrates the vertical acceleration signal GZ, and an integrator that is proportional to the magnitude of the damping constant adjustment signal KS. a gain adjuster that calculates a command value by multiplying the gain by the integral value;
The configuration may include a drive circuit that converts the output signal of the gain adjuster into a command current iC.

In the above configuration, the stroke sensor 3
4 forms a stroke detection means, and the pump rotation speed sensor 36 forms a pump rotation detection means. Further, the low-pass filter 60 and the flow rate estimation calculator 62 of the damping constant controller 38 form a consumption flow estimation means, the rotation speed calculation circuit 64 and the function generator 66 of the controller 38 form a discharge amount estimation means, and further, The adder 68, function generator 70, and drive circuit 72 of the controller 38 form a damping constant adjusting means. On the other hand, the vertical acceleration sensor 30, the vibration damping controller 36, the pressure control valve 20, and the hydraulic cylinder 18 constitute the skyhook damper SF of this embodiment (the imaginary line portion in FIG. 5). Further, the variable aperture 24 serves as a passive damper for the sprung mass.

In this embodiment, the configuration for estimating consumption flow rate and damping vibration is illustrated for only one arbitrary wheel, but the configuration is similar for other wheels as well. Next, the operation of this embodiment will be explained.

First, the active vibration damping process on the spring that is executed by the CPU of the microcomputer installed in the vibration damping controller 32 as a timer interrupt every minute time Δt will be explained with reference to FIG. In step 101 of FIG.
The PU reads the vertical acceleration detection signal GZ of the vehicle body for a certain period of time via an A/D converter, stores these values as the vertical acceleration, and then performs the process of step 102. At step 102, the CPU similarly reads the damping constant adjustment signal KS, stores the value, and then performs the processing from step 103 onwards.

In step 103, the vertical acceleration GZ is integrated, and thereby the absolute velocity VZ with respect to the vertical displacement of the vehicle body is calculated. In step 104, the pressure command value DV is calculated using the formula DV=VZ·KS+DVN. Here, KS is the signal value read in step 102, that is, the control gain, and DVN is the operating neutral pressure for maintaining the vehicle height.

Furthermore, in step 105, the CPU outputs the calculated pressure command value DV to the drive circuit within the controller 32. As a result, a command current iC corresponding to the pressure command value DV is supplied from the drive circuit, that is, the vibration damping controller 32 to the pressure control valve.

Next, the overall operation of the first embodiment will be explained. First, assume that a vehicle is traveling straight at a constant speed on a good road with no unevenness or undulations. In this case, since no vertical acceleration acts on the vehicle body 12, the vertical acceleration GZ≒0, and the detection signal DX of the stroke sensor 34≒a constant value. Further, the pump rotation speed sensor 36 outputs a signal PN corresponding to the engine rotation speed that is responsible for the constant vehicle speed V at that time. As a result, the flow rate estimation calculator 62 of the damping constant controller 38 estimates a state in which the consumption flow rate Q1 is also almost zero, since the change in the stroke amount X is X'≈0. On the other hand, the function generator 66 of the controller 38 generates a discharge flow rate Q2 (
≠0). Therefore, the output of adder 68 (Q2
-Q1 )>0, for example, the output Q2 -Q
1 =Qb, the function generator 70 generates damping constant adjustment signals KS =K2, KP =K3 (
<K2).

Therefore, a small control current iP corresponding to the damping constant adjustment signal KP=K3 is supplied from the damping constant controller 38 to the variable diaphragm 24, and a larger damping constant adjusting signal KS=K2 is supplied to the vibration damping controller 32.
supplied to

In parallel with this, the vibration damping controller 32 repeats the process shown in FIG.
Larger attenuation constant adjustment signal KS =
K2 is imported (step 102 in FIG. 7). However, since there is no vertical vibration input to the vehicle body in the straight-ahead state, the vertical acceleration GZ = 0, and the CP of the vibration damping controller 32
The pressure command value DV calculated by U is equal to DVN, and there is only a component that supports the vehicle height.

For this reason, since the command current iC corresponding to the command value DVN is supplied from the controller 32 to the pressure control valve 20, the pressure control valve 20 adjusts the pressure PC in the cylinder chamber R to a value proportional to the command current iC. Control. Therefore, the stroke amount X of the vehicle body 12 and the wheels 10 becomes a value corresponding to the neutral pressure command value DVN, and the vehicle body 12 assumes a flat posture parallel to the road surface. In other words, the skyhook damper SF does not actively generate bounce damping force in the current straight-ahead state.

On the other hand, the variable diaphragm 24 exhibits a small damping constant CP proportional to the small commanded current value iP. However, in the current running condition, there is no excitation input from the road surface, so there is no pressure fluctuation in the cylinder chamber R, and the hydraulic oil does not pass through the variable throttle 24. Therefore, the variable throttle 2
4 also does not generate any damping force.

Assuming that the vehicle passes through a series of small irregularities on the road surface while traveling straight, the pressure in the cylinder chamber R will oscillate at a small frequency corresponding to the irregularities, and along with this pressure vibration, the hydraulic fluid will be pumped into the actuator. Goes back and forth between 28 and 28. As a result, a passive damping force having a predetermined damping constant is generated in the fixed diaphragm 26, and the vibration of the unsprung side is damped against the vibration input from the road surface. At this time, since the damping constant CP related to the variable aperture 24 is adjusted to be low, the excitation force from the road surface is difficult to be transmitted to the vehicle body 12 side, resulting in a good ride comfort.

Furthermore, suppose that while the vehicle is traveling straight, the vehicle now travels on a undulating road while maintaining the same vehicle speed. When the vehicle travels on this undulating road, the stroke sensor 34 detects a stroke signal DX that changes greatly and at low frequency as the vehicle travels on the undulating road. Therefore, the flow rate estimation calculator 62 adjusts the consumption flow rate Q1 (>0) according to the change in the stroke amount X.
is estimated, the output signal of the adder 68 is ``Q2 −Q1
” is smaller than in the case of the above-mentioned good road. Assuming that this output signal is, for example, Q2 - Q1 = QC, as shown in FIG. =K5 (<K4) is set. Therefore, when traveling on a undulating road, the damping constant of the skyhook damper SF (ie, the adjustment signal KS) is lowered, and the damping constant CP of the variable aperture 24 is raised, contrary to the case of the above-mentioned good road.

Then, with the start of traveling on this undulating road, a vertical force is applied to the vehicle body 12, and the pressure in the cylinder chamber R changes with a relatively large amplitude although the frequency is small, and the hydraulic fluid flows into the hydraulic cylinder 18 and the hydraulic pressure. It begins to travel to and from the source 56. As a result, the hydraulic oil passes through the variable throttle 24, so
At that point, the variable throttle 24 has a large damping constant CP set as described above (i.e., the flow path diameter becomes small,
According to the degree of aperture (increasing degree of aperture), a larger damping force than when driving on a good road is passively generated, thereby suppressing vertical rocking of the vehicle body 12.

On the other hand, when traveling on an undulating road, a vertical excitation force is applied to the vehicle body 12 and the vehicle body attempts to move up and down, and the vertical acceleration GZ at that time is detected by the vertical acceleration sensor 30. Therefore, the vibration damping controller 3
CPU 2 calculates the vertical absolute velocity VZ of the vehicle body based on the detected value GZ, and multiplies the calculated value by the damping constant adjustment signal KS lowered as described above to obtain the pressure command value DV.
Calculate. As a result, Skyhook Damper SF is
The cylinder pressure of the hydraulic cylinder 18 is controlled in proportion to the pressure command value DV, and a force proportional to the vertical absolute velocity VZ, that is, a damping force, is actively generated in the cylinder 18, thereby suppressing vertical movement on the spring. The active damping force at this time has a smaller value than when driving on a good road.

When driving on a undulating road in this way, the passive damping force is increased and the active damping force is lowered instead, so that the total damping force is kept almost constant regardless of the road surface condition, and the vehicle body 12 It is possible to accurately suppress the vertical movement of. Moreover, when it is estimated that the flow rate consumed by the Skyhook damper SF is likely to increase, such as on an undulating road, the damping force sharing ratio of the Skyhook damper SF is lowered, and the variable throttle 24 is also narrowed. The amount of hydraulic oil flowing back and forth through the throttle 24 is reduced. the result,
While maintaining substantially the same damping force, the increase in actual flow consumption can be suppressed or reduced compared to the prior art, and energy savings can be achieved accordingly.

Next, a second embodiment will be explained using FIGS. 8 and 9. This second embodiment corresponds to the invention set forth in claim 2. Note that the same reference numerals are used for the same components as in the first embodiment.

This second embodiment is intended to more easily determine the state in which the consumed flow rate is large. In other words, attention is paid to the fact that the vehicle speed is generally low when driving on a undulating road where the flow rate consumed by the skyhook damper SF is large.

Therefore, as shown in FIG. 8, the active suspension 14 of the second embodiment includes a vehicle speed sensor 80 as a vehicle speed detecting means, and a damping constant adjusting means for inputting the detection signal DV of the vehicle speed sensor 80. A constant controller 82 is provided.

The vehicle speed sensor 80 detects, for example, the rotational speed of the output shaft of a transmission in the form of a pulse signal DV. As shown in FIG. 9, the damping constant controller 82 receives the vehicle speed pulse signal DV.
A vehicle speed calculation circuit 84 that inputs
A two-output function generator 86 provided on the output side of the function generator 86, and a drive circuit 8 that receives one of the two outputs of the function generator 86.
8.

The vehicle speed calculation circuit 84 is, for example, an F/V converter that converts the vehicle speed pulse signal DV into F/V, and the input signal D
A vehicle speed signal V having a voltage value corresponding to V is output to the function generator 86. The function generator 86 has a structure in which the characteristics shown in FIG. 9 are stored in advance, and outputs attenuation constant adjustment signals KP and KS in accordance with an increase or decrease in the input signal V. Of these damping constant adjustment signals KP and KS, the former KP adjusts the passive damping force, and the latter KS adjusts the active damping force. In FIG. 9, when the input signal V=Va, both the adjustment signals KP and KS take the same predetermined value K1 (=KP=KS). Then, as the vehicle speed V increases from this state, the adjustment signal KS gradually increases and the adjustment signal KP gradually decreases, and almost symmetrically, V=Va
As the vehicle speed decreases from the state of
is set so that the adjustment signal KP gradually decreases and the adjustment signal KP gradually increases.

Of the damping constant adjustment signals KP and KS, one signal KS is directly supplied to the damping controller 32, and the other signal KP is supplied to the drive circuit 88. The drive circuit 88 converts the input voltage signal KP into a corresponding current signal iP and outputs it to the variable aperture 24.

The rest of the structure is the same as that of the first embodiment. Therefore, when driving at high speed, one of the damping constant adjustment signals KS is set high, and the control gain related to active damping is also adjusted high, so the degree of control of the skyhook damper SF becomes high. At the same time, the other attenuation constant adjustment signal KP is set to a lower value, and the attenuation constant CP of the variable aperture 24 related to passive damping is also adjusted to a lower value. As a result, when driving at high speed, it is estimated that the vehicle is not normally traveling on rough roads such as undulating roads, and the flow consumption of the Skyhook damper SF is small, so the active damping force of the total damping force of the vehicle is estimated to be low. By increasing the ratio of , an accurate vibration damping effect on the spring and good riding comfort are ensured.

[0051] When the state reaches a low speed running state from this state,
There is a high probability that the vehicle is traveling on a rough road such as a undulating road, and if the control ratio of the skyhook damper SF is increased while traveling on such a rough road, it is recognized that the flow consumption will be large. Therefore, in a low speed state, the attenuation constant adjustment signal KS for active damping is lowered, and instead, the attenuation constant adjustment signal KP for passive damping is increased. As a result, instead of reducing active damping force, passive damping force increases, and the total damping force remains almost the same as at high speeds, so even when driving at low speeds on rough roads, the sprung mass increases. Vibration is definitely suppressed. At the same time, the degree of control of the skyhook damper SF is reduced, and the flow rate consumption can be reduced by the amount of hydraulic oil passing through the variable throttle 24.
As a result, the pump load can be reduced and an increase in vehicle fuel efficiency can be suppressed.

Furthermore, in the second embodiment, by checking the magnitude of the vehicle speed, it is possible to easily estimate whether the vehicle is traveling on a winding road or the like, that is, whether or not the consumption flow is large. , the apparatus is simplified compared to the first embodiment.

[0053] The variable aperture as a passive damper of the present invention is not limited to one having a structure in which the damping constant can be continuously changed as described above, but, for example, one or two fixed apertures and their The structure may include an on-off valve inserted in a pipe that bypasses the throttle, and the damping constant can be switched in two or three stages.

Further, the curve of the damping constant adjusted by the damping constant adjusting means of the present invention smoothly increases and decreases according to changes in the difference signal "Q2 - Q1" or the vehicle speed signal V, as shown in FIGS. 6 and 9 described above. For example, it may be changed stepwise.

Furthermore, the calculation circuit of the consumption flow calculation means in the present invention is not necessarily limited to the above-described configuration, but may, for example, calculate the detected values of both the front left wheel and front right wheel stroke sensors using the above equation (1). It is also possible to calculate the consumption flow rate of the four wheels individually by calculating the flow rate of the four wheels (however, by adjusting the gain A to a value based on the pressure receiving area) and adding up the two calculated values. In other words, since the calculated value of equation (1) is the integrated value of the inflow and discharge of hydraulic oil to one wheel, the calculated value for the front two wheels almost matches the consumption amount (inflow amount) of hydraulic oil for the four wheels. In this case, the estimated value of the discharge amount estimation means estimates the total discharge amount of the pump.

Furthermore, the attenuation constant controller in each of the embodiments described above may be configured to include a microcomputer.

[0057]

As described above, the invention according to claim 1 estimates and calculates the consumption flow rate of the fluid pressure cylinder of the skyhook damper based on the detected stroke value between the vehicle body and the wheels, and at the same time calculates the flow rate consumption of the fluid pressure cylinder of the skyhook damper. The discharge amount of the fluid pressure pump is estimated based on the detected information, and as the estimated flow rate consumption approaches the estimated discharge amount, the damping constant of the skyhook damper is lowered and the damping constant of the passive damper is increased. For example, when driving on a rough road such as a undulating road, the estimated flow consumption value increases, the damping constant of the skyhook damper decreases, and the damping constant of the passive damper increases, weakening the degree of control of the skyhook damper. This is supplemented by the damping force generated by the passive damper. In this way, by adjusting the damping force of both dampers depending on whether the vehicle is traveling on good or bad roads and making them work together, the total damping force is kept almost constant and a good damping effect on the spring can be obtained. On the other hand, the actual flow consumption is suppressed when driving on rough roads where the flow consumption is likely to be high, and the pump load is reduced, making it possible to achieve significant energy savings compared to conventional devices and improve vehicle fuel efficiency. Contribute.

Furthermore, in the second aspect of the invention, the vehicle speed is detected, and as the detected vehicle speed value decreases, the damping constant of the skyhook damper is lowered and the damping constant of the passive damper is increased. This invention focuses on the fact that it is possible to determine with good probability whether or not the driving condition is on a rough road such as a undulating road that consumes a large amount of water depending on the magnitude of the vehicle speed detection value. Assuming that the skyhook damper is in a running state where the flow consumption is large, the degree of control of the skyhook damper is lowered, and the amount of control is compensated for by increasing the damping force of the passive damper. The same effect can be obtained. In addition, since the magnitude of the consumed flow rate is estimated simply by checking the vehicle speed, the estimation mechanism is simplified and the device can be made more compact.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing attenuation constant characteristics of a variable aperture.

FIG. 3 is a control pressure characteristic diagram of a pressure control valve.

FIG. 4 is a discharge flow rate characteristic diagram of a hydraulic pump.

FIG. 5 is a block diagram showing a control system of the first embodiment.

FIG. 6 is a graph showing changes in the damping constant adjustment signal with respect to the flow rate difference in the first embodiment.

FIG. 7 is a flowchart illustrating an example of processing related to active damping control of the vibration damping controller.

FIG. 8 is a block diagram showing the overall configuration of a second embodiment of the present invention.

FIG. 9 is a block diagram showing a control system of a second embodiment.

FIG. 10 is a block diagram showing the configuration of a conventional example.

FIG. 11 is an explanatory diagram illustrating a skyhook damper model and its vibration characteristics.

[Explanation of symbols]

10 Wheels 12 Vehicle body 14 Active suspension 18 Hydraulic cylinder 20 Pressure control valve 22 Hydraulic source 24 Variable throttle (passive damper) 30
Vertical acceleration sensor 32 Vibration damping controller 34 Stroke sensor 36 Pump rotation speed sensor 38 Damping constant controller 80 Vehicle speed sensor 82 Damping constant controller SF Skyhook damper

Claims (2)

[Claims] [Claim 1] A skyhook that has a fluid pressure cylinder inserted between a vehicle body and wheels, and generates a damping force in the fluid pressure cylinder according to the vertical absolute speed of the vehicle body and a changeable damping constant. a damper, a fluid pressure source having a fluid pressure pump that uses a vehicle engine as a rotation source and supplies working fluid to the skyhook damper, and damping that is responsive to the relative speed between the vehicle body and wheels and a changeable damping constant. A passive damper that generates a force is provided, a stroke detection means that detects the relative stroke amount between the vehicle body and the wheels, and a consumption flow calculation that calculates the consumption flow of the fluid pressure cylinder based on the detected value of the stroke detection means. means, pump rotation detection means for detecting the rotation status of the fluid pressure pump, discharge amount estimating means for estimating the discharge amount of the fluid pressure pump based on the detection information of the pump rotation detection means, and the discharge amount estimating means. and a damping constant adjusting means for lowering the damping constant of the skyhook damper and increasing the damping constant of the passive damper as the calculated value of the consumption flow calculating means approaches the estimated value of . type suspension. 2. A skyhook that has a fluid pressure cylinder inserted between a vehicle body and wheels, and generates a damping force in the fluid pressure cylinder according to the vertical absolute speed of the vehicle body and a changeable damping constant. a damper, a fluid pressure source having a fluid pressure pump that uses a vehicle engine as a rotation source and supplies working fluid to the skyhook damper, and damping that is responsive to the relative speed between the vehicle body and wheels and a changeable damping constant. A passive damper that generates a force is provided, and a vehicle speed detection means that detects the vehicle speed, and as the detected value of the vehicle speed detection means decreases, the damping constant of the skyhook damper is lowered, and the damping constant of the passive damper is lowered. An active type suspension characterized by being provided with a damping constant adjusting means for increasing the damping constant.