JPH02151513A - Active suspension for vehicle - Google Patents

Abstract

PURPOSE:To enhance physical riding comfortableness by outputting a roll control signal for controlling a car body to the reverse roll side only in a region where a detected lateral G is relatively small, and operating each control valve independently in response to the output signal to control each actuator for adjusting the car height. CONSTITUTION:Each oil passage 4F, 4R on the front wheel side and the rear wheel side of a feed passage 4 connected to the delivery side of an oil pump 1 is connected to each suspension unit 12 (12FL, 12FR, 12RL, 12RR) provided for each wheel. Each suspension unit 12 consists of a suspension spring 13 and a single acting hydraulic actuator 14, and controls the supply of oil pressure to a hydraulic oil chamber of the hydraulic actuator 14 by means of a control valve 18 to adjust the car height. In this instance, a lateral G sensor 27 is provided to permit a controller 30 to output a roll control signal for controlling the car body to the reverse roll side only in a region where a detected lateral G is relatively small, and operate each control valve 16 independently in response to the output signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in active suspensions for vehicles.

(Prior Art) Conventionally, as a suspension that actively controls roll occurring in a vehicle body, there is one disclosed in, for example, Japanese Patent Laid-Open No. 181713/1983.

In this conventional example, the roll occurring in the vehicle body is reduced by controlling the hydraulic pressure acting on the actuator provided for each wheel in accordance with the lateral force acting on the vehicle body.

(Problems to be Solved by the Invention) However, since the above-mentioned conventional device is simply intended to reduce the roll that occurs on the vehicle body, the 1G that acts on the vehicle body while the vehicle is turning directly acts on the occupant. There is a problem in that the lateral G that the occupant receives actually increases. Even in a normal vehicle, if the lateral G acting on the vehicle body is large, the occupants will experience a large lateral G. However, with the above conventional device, the lateral G in the lateral G region where the occupants rarely experience the lateral G in a normal vehicle. However, there is a problem in that the passenger j is more likely to experience <lateral G, resulting in poor ride comfort, especially for passengers in the front passenger seat and rear seats.

(Means for Solving the Problems) The present invention was devised to solve the above problems, and operates in response to a fluid pressure source and fluid pressure supplied from the fluid pressure source to adjust the vehicle height. An actuator is provided between each wheel and the vehicle body for adjustment, and an actuator is provided between each actuator and the fluid pressure source to supply and discharge fluid pressure to the actuator. A control valve provided, a lateral G detection means provided to detect lateral G acting on the vehicle body, and a controller that independently controls the operation of each of the control valves according to a detected value of the lateral G detection means. In the active suspension for a vehicle, the controller outputs a roll control output that controls the vehicle body in a reverse roll direction only in a region where the detected lateral G is relatively small, and performs each of the above controls according to this roll control output. The active suspension for a vehicle is characterized in that it is configured to control supply and discharge of fluid pressure to each of the actuators by independently operating valves.

(Function) According to the present invention, the controller that independently controls the operation of each control valve outputs a roll control output that controls the vehicle body to the reverse roll side only in a region where the detected lateral G is relatively small,
Since each of the control valves is operated independently according to this roll control output to control the supply and discharge of fluid pressure to each of the actuators, the vehicle body will not roll in a reverse direction in a region where the lateral G is relatively small. A part of the lateral G that acts on the occupant is felt by the occupant in the vertical direction, and the lateral G sensitivity of the occupant is reduced, improving the perceived riding comfort.

In addition, by performing a reverse roll, the feeling when the vehicle turns is improved, and the steering characteristic also shows a tendency to oversteer, making it easier to drive the vehicle when turning. In addition, since reverse roll control is performed only in areas where the detected lateral G is relatively small, the vehicle does not roll in reverse during sudden steering or cornering when the lateral G acting on the vehicle is large, and the vehicle remains stable. without compromising safety and security.

(Example) Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a system configuration diagram of this embodiment. In FIG. 1, an oil pump 1 is provided to suck oil stored in a reserve tank 3 through an oil passage 2 and discharge the oil to a supply oil passage 4. As shown in FIG. An accumulator 5 that absorbs the pulsation of the oil pressure supplied by the oil pump 1 is connected to the supply oil path 4 near the oil pump l, and an oil cooler 21 is interposed downstream of the accumulator 5 and communicates with the reserve tank 3. discharge oil passage 6 and supply oil passage 4
An IJ-IJ-7 oil passage 7 is provided which communicates with the IJ and IJ-7.

A relief valve 8 is installed in this relief oil passage 7, and when the upstream oil pressure of the relief valve 8 exceeds a predetermined value, the oil discharged from the oil pump 1 is discharged to the reserve tank 3 side. ing. The supply oil passage 4 is provided with an oil filter 9 and a check valve 10 on the downstream side from the connection part with the IJ-IJ oil passage 7.
The check valve 10 prohibits oil from flowing from the downstream side to the upstream side. The supply oil path 4 branches into a front wheel oil path 4F and a rear wheel oil path 4R downstream of the check valve IO, and accumulators 11F and 11R for maintaining line pressure are connected to each oil path 4F and 4R, respectively. has been done. Each oil passage 4F, 4R is connected to an accumulator 11F, 11, respectively.
Oil passages 4FL, 4FR, and 4RL for each wheel on the downstream side of R
and 4RR, each oil line 4FL, 4FR,
4RL.

4RR has suspension units 12FL, 12FR, 12RL, and 12RR provided for each wheel.
are connected to each suspension unit, and a discharge oil passage 6 is also connected to each suspension unit.

Since each suspension unit has the same structure, the suspension unit (12FL) for the left front wheel will be explained in detail. Between the vehicle body and the wheel, there is a suspension spring 13 and a single-acting hydraulic actuator 14.
The hydraulic pressure is supplied to the hydraulic chamber of the hydraulic actuator 14 by a control valve 16 interposed between the oil passage 15 communicating with the hydraulic chamber of the hydraulic actuator 14, the supply oil passage 4FL, and the discharge oil passage 6. Emissions are controlled.

As the control valve 16, a proportional solenoid valve is used. That is, this control valve 16 introduces the hydraulic pressure acting from the supply oil path 4FL side through the pilot oil path 17 as pilot pressure, and the oil pressure flows out from the pilot pressure chamber through the oil path 18 to the discharge oil path 6 side. The valve opening degree is controlled by controlling the pilot pressure by controlling the oil flow rate using a duty-controlled solenoid valve.

Therefore, this control valve 16 is capable of controlling the pressure within the hydraulic actuator 14 in proportion to the commanded duty rate. Further, an accumulator 20 is connected to the oil passage 15 communicating with the hydraulic chamber of the hydraulic actuator 14 via a throttle 19, and the throttle 19 exerts a vibration damping effect, and the accumulator 20 is filled with gas. It is designed to exert a gas spring action.

The operation of each control valve 16 is controlled by a controller 30 comprised of a microcomputer. This controller 30 includes vehicle height sensors 22 to 25 that are provided for each wheel and detect the stroke amount of the wheel.
, the detection output of the steering sensor 26 that detects the steering angular velocity of the steering wheel, the detection output of the G sensor 27 that detects the longitudinal and lateral acceleration acting on the vehicle body, and the detection output of the vehicle speed sensor 28 that detects the running speed of the vehicle. The detection outputs are inputted, and the controller 30 controls the hydraulic pressure to each hydraulic actuator 14 by controlling the operating state of each control valve 16 for each wheel based on the detection outputs of these sensors. Figure 2 shows the supply and discharge of controller 3.
2 shows control operations performed for each wheel within 0.

In FIG. 2, control is started with an on signal of the ignition key, and in step S1, the vehicle speed sensor 28
After the vehicle speed V detected from is read, step S2
In step S3, the suspension stroke X is read from the output of the vehicle height sensor, and the stroke X in step S3 is read as a deviation from the reference vehicle height. After that, in step S3, the vehicle speed V is 3 km/
h It is determined whether or not it is under JJ, and the speed is 3 km/h.
If it is less than or equal to
These FFS and FFU will be described later.

Then, in step S5, the suspension stroke X is integrated to calculate the average vehicle height (average deviation from the reference vehicle height)
After calculating +, in step S6, the vehicle height adjustment force command value F
・xl is calculated in FH=. Here step S
The integration process in step S6 has a relatively large time constant in order to prevent the output of the vehicle height control from repeating fluctuations, and FFH in step S6 uses the hydraulic actuator 14 to maintain the vehicle height at the reference vehicle height. This corresponds to the correction amount of the internal oil pressure, and when the average vehicle height xt is 0 (if the standard vehicle height is already maintained), FFH = 0, and the average vehicle height x1
The command is a pressure increase command or a pressure decrease command depending on the sign of the . In addition, here, is the suspension unit 12
This is a constant that equivalently incorporates the spring constant and damping force characteristics of . In particular, the process in step S6 is for keeping the vehicle height constant against changes in the loading conditions of the vehicle due to changes in occupants and cargo.

Thereafter, in step S7, the vehicle weight correction coefficient kINT corresponding to FFH calculated in step S6 based on the map shown in FIG. 3 is read and stored. This vehicle weight correction coefficient killa is a correction coefficient for roll control and is used to keep the steering characteristics constant even if the load distribution between the front and rear wheels changes. In addition, since the shared load is different between the front wheels and the rear wheels, it is a correction factor! Different maps are used for the front wheels and rear wheels when calculating 7, but it may be calculated by correcting the values read using the same map with coefficients specific to the front wheels and rear wheels. In step S8, the fluid pressure command value CF = F F H+ k I N□ ・F
FS + FFU is calculated, but when stopped, FFS and FFU are calculated.
Since both FU are 0, the hydraulic pressure command value CF becomes the vehicle height adjustment force command value FFH, and the control valve 16 operates at the drive density corresponding to the hydraulic pressure command value CF, so that each suspension unit reaches the reference vehicle height. It is maintained.

In addition, in the operation control of the control valve 16, the hydraulic pressure command value CF
When is 0, a drive duty of 50% is output, and the drive duty to be output is increased or decreased depending on the positive or negative magnitude of CF.

On the other hand, in step S3, the vehicle speed V is 3 km/h.
If it is determined that it is not below, the process proceeds to step S9, where the lateral G detected from the G sensor is read, and the control gain for roll control corresponding to tJ G detected based on the map shown in FIG. Ask for GG. In this embodiment, as is clear from FIG. 4, a roll in the forward direction is first set above the dead band in the extremely low G region, and as the detected lateral G increases, the roll in the forward direction decreases and then reverses. The roll in the opposite direction is reversed and the roll in the opposite direction increases, but the lateral G
A control map is used in which the roll in the opposite direction decreases, reverses to the roll in the forward direction again, and the roll in the forward direction increases after the value reaches a predetermined value.

In other words, in an area where lateral G is relatively low, a reverse roll is generated to improve the turning feeling of the vehicle, and in an area where lateral G is high, a positive roll is generated to make it easier for the driver to feel the cornering limit. It is set. The roll control gain CG is naturally reversed in polarity depending on the wheels on the inner side of the turn and the wheels on the outer side of the turn. After that, in step SIO, the steering sensor 26
The steering angular velocity θ of the steering wheel is read from the detected value, and the process proceeds to step S1'1, where θ is determined as the steering angular velocity correction coefficient corresponding to the steering angular velocity θ□ based on the map shown in FIG. This correction coefficient θ is used to correct the roll control gain GG obtained in step S9, and when the steering angular velocity θ□ is high, the roll control gain GG is reduced to correct the amount of roll generated in the positive direction. It has become a thing. Further, in step 512, a vehicle speed correction coefficient kv corresponding to the vehicle speed V is determined based on the map shown in FIG. This correction coefficient kv is
This is to correct the gain GG for roll control found in step 9, and when the vehicle speed V is high, the gain GG for roll control is reduced to correct the amount of roll generated in the positive direction. Then, in step S13, each step S9. S
11. Based on GG and θ+kV determined in 11.512, the attitude control force command value FF5=GG- for roll control is determined as θ·kv. This attitude control force command value FFS is a control value of the force that opposes the attitude change input acting on the spring needle thread, and corresponds to the correction amount of the hydraulic pressure in the hydraulic actuator 14 for roll control. Roll control is commanded in accordance with the acting lateral G, '44 steering angular velocity θ□, and vehicle speed V.

After that, in step S14, a stroke change speed X is calculated based on the suspension stroke X detected by the vehicle height sensor, and in step S15, a ride comfort control force command value FFU is calculated based on the suspension stroke x and the stroke change speed arrow. "kn 'X+kl
lln'X is calculated. Here, ka and kiln
is a constant, kIl+ is a gain slightly less than the spring constant of the suspension unit 12, and ko+ is a gain slightly less than the damping rate and resistance of the suspension unit 12. This ride comfort control force command value FFU is a control value for the force that absorbs vibrations input to the spring bobbin thread, that is, correction of the oil pressure in the hydraulic actuator 14 to suppress stroke changes in the wheel caused by road surface input. This corresponds to the amount of vibration and is used to prevent vehicle body vibration.

When the process of step S15 is completed, the processes of steps 85 to 7 described above are performed, but these processes that are performed while the vehicle is running are caused by lift force generated by air resistance acting on the vehicle body when the vehicle is running or by running on a slope. It calculates the vehicle height adjustment force command value FFH to keep the vehicle height constant against changes in the shared load, and the k IHT corresponding to FFH. The same values as FFH and k I, IT are obtained.

Then, when the process proceeds to step S8 while the vehicle is running, the fluid pressure command value CF = FF H+ k s lI is determined as described above.
A ・FFS+FFU is calculated, but in this case, FF
Since S and FFU are not 0, the hydraulic pressure command value CF that commands the drive duty of the control valve that adjusts the internal pressure of the hydraulic actuator is the command value FFH for maintaining the reference vehicle height.
, the command value k INT for executing roll control is
The hydraulic pressure command value is the sum of the FFS and the command value FFU, which suppresses wheel stroke changes caused by road surface input to suppress vehicle body vibration, and the operation of each suspension unit 12 is determined for each wheel. By controlling each independently based on the CF, the roll attitude of the vehicle body can be actively controlled while ensuring good riding comfort. In particular, the command value for executing roll control is □,・
FFS uses IHT to correct the correction coefficient corresponding to the change in the shared load of each wheel with respect to the attitude control force command value FFS, so stable roll control can be achieved regardless of changes in the shared load of each wheel. Therefore, constant steering characteristics can be obtained with respect to the roll control command value.

Note that after step S8, step S1 is performed.According to the above embodiment, the ride comfort control command value is added to the roll control command value FFS according to the lateral acceleration, the steering angular velocity, and the vehicle speed, and the ride comfort control command value according to the suspension stroke and stroke change speed. F
Since the hydraulic pressure in the hydraulic actuator 14 is controlled by taking FU into consideration, active roll control can be performed while ensuring good ride comfort, and posture control and ride comfort control are balanced at a high level. This enables control to be achieved, and ride comfort is significantly improved, especially during posture control while driving on rough roads.

Further, the command value FFS for roll control is determined with reference to the map in FIG. 4 corresponding to lateral acceleration, the map in FIG. 5 corresponding to steering angular velocity, and the map in FIG. 6 corresponding to vehicle speed. Therefore, when the vehicle is in a relatively low lateral G region, the vehicle speed is in the medium-low speed range, and it is close to steady turning (normal curve driving), reverse roll control is executed, improving turning performance. . In other words, by performing a reverse roll, a portion of the lateral G acting on the occupant is felt vertically by the occupant, which improves the perceived riding comfort (feeling) and improves the steering characteristics. It now exhibits oversteer characteristics (in general independent suspensions, due to its camber change characteristics, if reverse roll occurs, the wheels will fall inward in the turn, resulting in a tendency to oversteer), making it easier to drive the vehicle when turning. This improves maneuverability. Moreover, since this reverse roll only occurs in a relatively small area, the vehicle body does not reverse roll during limit cornering, resulting in excellent vehicle stability and safety.

Furthermore, even in the lateral G region where the control gain to the reverse roll side is output, the control gain to the reverse roll side decreases when the steering angular velocity is high (during sudden steering) and when driving at high speed (
The roll that occurs in the vehicle body is corrected in the positive roll direction), and the steering characteristic is corrected in the understeer side (due to the above-mentioned camber change characteristic), thereby ensuring safety and stability.

Furthermore, in areas where the detected lateral G is high, the control gain for the reverse roll side is reduced to generate a positive roll, ensuring vehicle stability and giving the driver a sense of the cornering limits. In this respect, it is also excellent in safety.

In particular, when the steering angular speed is high, the control gain toward the reverse roll side decreases (reducing the roll control force that counters the lateral G input), so roll control during slalom running (generally when the steering angular speed is high) is reduced. There is no fear that the vibration will diverge (the vehicle body will be vibrated due to a delay in control action), and waste of control energy can be prevented, and there are advantages in that control stability is excellent and control energy can be used efficiently.

In addition, the command value FFS for roll control is corrected by a correction coefficient k1IIT that changes in accordance with the vehicle height adjustment force command value FFH (corresponding to changes in the shared load). Steering characteristics during roll control (US10
It has the advantage of being able to keep the S characteristics constant and providing excellent maneuverability.

In addition, unlike the conventional example, each wheel is not provided with a load sensor, and each wheel is not provided with a vertical G sensor, so the system has the advantage of being simple and inexpensive. be.

Note that the present invention is not limited to the above-mentioned embodiment in any way, and it is also possible to provide a vertical G sensor for each wheel and directly detect the stroke change speed (vehicle height change speed) of the suspension using the vertical G sensor. However, the control gain map shown in FIG. 7 or FIG. 8 may be used as the control gain map for lateral G. Furthermore, the stroke (vehicle height) of each wheel may be detected as an absolute value and compared with the reference vehicle height. Alternatively, a sensor may be provided to detect the steering angle and the steering angular velocity may be calculated from the detected steering angle. Also good. It goes without saying that various other modifications can be made without departing from the gist of the present invention.

(Effects of the Invention) As specifically explained above in conjunction with the embodiments, according to the present invention, the ride comfort and maneuverability during normal turns are improved while ensuring the stability and safety of the vehicle during limit running. This has the effect of providing an improved active suspension for a vehicle.

[Brief explanation of the drawing]

Fig. 1 is a system configuration diagram showing one embodiment of the present invention;
3 is a flowchart showing the control operation in the controller 30, FIG. 3 is a map of the vehicle weight correction coefficient k fllT with respect to the vehicle height adjustment force command value FFH, and FIG. 4 is a map of the control coefficient GG with respect to lateral acceleration. FIG. 5 is a map of the steering angular velocity correction coefficient θ with respect to the steering angular velocity θ□, FIG. 6 is a map of the vehicle speed correction coefficient kv with respect to the vehicle speed V, and FIG. 7 is a diagram corresponding to FIG. 4 showing other embodiments. FIG. 8 is a diagram corresponding to FIG. 4 showing still another embodiment. 1... Oil pump, 14... Actuator. 16...Control valve, 22-25...Vehicle height sensor. 27...G sensor, 30...Controller Fig. FH Fig. fL ← Product q -YayuG Shin figure left) - #q → Right G

Claims (1)

[Claims] A fluid pressure source, an actuator provided between each wheel and the vehicle body so as to operate in response to fluid pressure supplied from the fluid pressure source and adjust the vehicle height, and each actuator and the fluid pressure source a control valve provided for each actuator to supply and discharge fluid pressure to the actuator, and lateral G detection means provided to detect lateral G acting on the vehicle body; In a vehicle active suspension comprising a controller that independently controls the operation of each of the control valves according to the detected value of the lateral G detecting means, the controller controls the vehicle body only in a region where the detected lateral G is relatively small. It is configured to output a roll control output to control the reverse roll side, and to independently operate each of the control valves according to this roll control output to control supply and discharge of fluid pressure to each of the actuators. Features of active suspension for vehicles