JPH04169312A - Active suspension for vehicle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an active suspension for a vehicle, and particularly to control for improving vibration damping characteristics.

(Prior Art) Conventionally, as a control for improving vibration damping performance in an active suspension, for example, Japanese Patent Laid-Open No. 63-4121
There is known a device that controls the operation of an actuator based on the relative displacement speed between a sprung member and an unsprung member, as shown in Japanese Patent No. 7.

In other words, it attempts to dampen the vibrations generated in the vehicle body by applying a control force to the actuator that corresponds to the rate of change in the vertical stroke of the wheel, and has the same function as the shock absorber used in general suspensions. This is a technology that allows active suspension to perform its functions.

(Problems to be Solved by the Invention) By the way, when performing the above-mentioned control, it is necessary to achieve both ride comfort and steering stability of the vehicle. For this reason, in the conventional example described above, the effective control gain for the rate of change in a region where the vibration frequency of the human force applied to the suspension is lower than the vicinity of the sprung mass resonance point is set to be different from that in other regions. However, in the conventional example described above, the control gain is only changed based on the input vibration frequency, so it is not possible to efficiently achieve both stability against disturbances such as crosswinds and ride comfort under normal conditions. In particular, when attempting to improve stability against disturbances such as crosswinds, there is a problem in that normal ride comfort is forced to be sacrificed.

(Means for Solving the Problems) The present invention has been devised to solve the above problems, and is provided between the wheels of a vehicle and the vehicle body to provide a force for supporting the vehicle body to the wheels. an actuator that can be increased or decreased; displacement speed detection means for detecting a change rate of relative displacement in the vertical direction between the wheel and the vehicle body; and disturbance detection means for detecting the presence or absence of a predetermined disturbance input to the vehicle; control means for controlling the operation of the actuator in a direction to suppress a change in the amount of displacement based on the speed of change detected by the displacement speed detection means, and the control means controls the predetermined movement by the disturbance detection means. The active suspension for a vehicle is characterized in that it is configured to increase a control gain corresponding to the rate of change when it is detected that a disturbance input is acting, compared to a normal time.

(Function) According to the present invention, the control gain of the control for operating the actuator to suppress the change in the vertical displacement amount between the wheel and the vehicle body in response to the change speed of the vertical displacement amount is When the detection means detects that a predetermined disturbance input is acting, the control means is configured to increase the amount of disturbance input compared to normal conditions. During operation, stability can be improved by efficiently increasing vibration damping performance and suppressing disturbances in the vehicle's posture.

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

FIG. 2 is a configuration diagram of the hydraulic system of this embodiment. Second
In the figure, 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. Accumulators 5 and 6 are connected in series in the supply oil path 4 near the oil pump 1 to absorb pulsations in the discharge oil pressure from the oil pump 1, and each accumulator 5 and 6 has a different set frequency. It has become. Further, an oil filter 7.8 is connected to the downstream side of the accumulator 6, and a pilot relief oil passage 9 and a relief oil passage 10 are connected to the downstream side of the oil filter 8.

The pilot relief oil passage 9 is connected to a solenoid valve 11, and the solenoid valve 11 connects a discharge oil passage 12 communicating with the reserve tank 3 to a control valve return oil passage 13 or a pilot) IJ relief oil passage, which will be described later. It is designed to be selectively communicated. An operating check valve 14 is installed in the return oil passage 13 on the upstream side of the solenoid valve 11, and operates by receiving the pressure of the pilot relief oil passage 9 as pilot pressure.
J IJ-When the oil passage 9 and the discharge oil passage 12 are in communication, they are blocked and the vehicle height is maintained by prohibiting oil discharge, while the return oil passage 13 and the discharge oil passage 12 are in communication. When the valve is open, it is opened to allow oil to drain and enable suspension control as described below.

Further, the relief oil passage 10 is connected to the discharge oil passage 12 on the downstream side of the solenoid valve 11, and a relief valve 15 is interposed in the middle of the IJ-IJ oil passage 10. When the upstream oil pressure of the relief valve 15 becomes equal to or higher than a predetermined pressure, the oil discharged from the oil pump 1 is discharged to the reserve tank 3 side. Furthermore, this relief valve 15 is connected to the pilot relief oil passage 9.
Pilot pressure is received from the pilot relief oil passage 9.
The above-mentioned set pressure changes depending on the state of the solenoid valve 11 that changes the pressure, and the set pressure decreases when the vehicle height is maintained as described above when the pilot relief oil passage 9 and the discharge oil passage 12 are communicated. This reduces the load on the pump 1.

Note that an oil cooler 16 and an oil filter 17 are installed in series in the discharge oil passage 12, and the oil filter 1
A relief valve 18 is provided in parallel with the oil filter 17 for compensation when the oil filter 7 becomes clogged.

Further, the supply oil path 4 branches into a front wheel side oil path 4F and a rear wheel side oil path 4R on the downstream side from the branching point with the relief oil path 1o, and each oil path 4F and 4R has a line. Accumulators 19F and 19R for maintaining pressure and check valves 20F and 2OR are interposed, and each check valve prohibits oil from flowing from the downstream side to the upstream side.

Note that an oil filter 21 is interposed in the rear wheel side oil passage 4R on the upstream side of the accumulator 19R. Each oil passage 4
F and 4R are branched into oil passages for each wheel on the downstream side of the check valves 20F and 2OR, respectively, and each oil passage is connected to a suspension unit 2 provided for each wheel.
2FL, 22PR, 22RL, and 22RR are connected. In addition, each suspension unit 22FL, 22F
R.

22RL and 22RR are check valves 23FL that prohibit the flow of oil from the downstream side to the upstream side.

It is connected to the return oilway work 3 via 23FR, 23RL, and 23RR, but the check valve 23F on the front wheel side
The upstream sides of L and 23FR are communicated via the throttle 24F,
Check valves 23RL and 23RR on the rear wheel side have aperture 2.
4RL and 24RR are provided in parallel. These throttles 24F, 24RL, and 24RR are provided to average the internal pressures of the actuators of each wheel during the vehicle height maintenance described above.

Note that an accumulator 25 is provided in the return oil passage 13R on the rear wheel side to prevent pulsation in the return oil passage, and the return oil passage 4R on the rear wheel side and the supply oil passage 1 on the rear wheel side
3R, there is an IJ valve 26 and a cock 2 for maintenance to prevent the return oil path from becoming high pressure.
7 are provided in parallel.

Each suspension unit has the same structure.To explain the left front wheel suspension 22PL, a single-acting hydraulic actuator 3o is installed between the vehicle body and the wheel in parallel with a suspension spring (not shown). are provided, and an oil passage 31, a supply oil passage 4F, and a discharge oil passage 13 communicating with the hydraulic chamber of the hydraulic actuator 30.
．． The supply and discharge of hydraulic pressure to the hydraulic chamber of the hydraulic actuator 14 is controlled by a control valve 32 interposed between the hydraulic actuator 14 and the hydraulic chamber F. As the control valve 32, a proportional solenoid valve is used, and by controlling the valve opening according to the supplied current, the pressure within the hydraulic actuator 14 can be controlled in proportion to the supplied current. . Note that the hydraulic actuator 30 has an oil passage 32.
is also connected, and the oil leaking from the hydraulic chamber is sent to the discharge oil path 12.

Further, an accumulator 34 is connected to the oil passage 31 communicating with the hydraulic chamber of the hydraulic actuator 30 via a throttle 33, and the throttle 33 exerts a vibration damping effect, and the gas sealed in the accumulator 34 It has a gas spring effect. Furthermore, a damping force control valve 35 is provided in parallel with the throttle 33,
By driving the damping force control valve 35 to the open position, the damping force can be set softly. Further, a pressure sensor 36 for detecting the internal pressure of the hydraulic actuator 30 is provided in the oil passage 31.

Each control valve 32. The operation of each damping force control valve 35 and solenoid valve 11 is controlled by a controller 40 constituted by a microcomputer, and the solenoid valve 11 is activated when it is necessary to control the operating state of the hydraulic actuator 3o. 2
The state shown in the figure is switched to the state where the return oil path 13 and the discharge oil path 12 are connected, allowing oil to be discharged from the hydraulic actuator 3o, and when there is no need to control the operating state of the hydraulic actuator 30, such as when parking. The state is switched to the state shown in FIG. 2, and the discharge of oil from the hydraulic actuator 30 is prohibited to maintain the vehicle height.

As shown in FIG. 3, the controller 40 includes, in addition to the detection output from the pressure sensor 36 described above, a detection output from a lateral G sensor 41 that detects lateral acceleration acting on the vehicle body, and a steering angle that detects the steering angle of the steering wheel. The detection output of the sensor 42, the detection output of the vehicle speed sensor 43 that detects the running speed of the vehicle, the detection output of the longitudinal G sensor 44 that detects the longitudinal acceleration acting on the vehicle body, and the detection output of the brake switch 45 that detects the operation of the brake pedal. Detection output, detection output of a throttle sensor 46 that detects the throttle opening of the engine, detection output of a stroke sensor 47 that is provided for each wheel and that detects the vertical stroke state of each wheel, and a detection output that is provided for each wheel and acts on the vehicle body. Vertical G sensor 4 that detects vertical acceleration
8 and the detection output of a preview sensor 49 that detects the condition of the road surface in front of the vehicle are respectively input, and the controller 40 controls the control valve 32 and damping based on the detection outputs of these sensors. The operating state of the force switching valve 35 is controlled for each wheel.

A schematic configuration inside the controller 40 is represented by a control block diagram shown in FIG.

In FIG. 3, the roll control unit 50 includes a lateral G sensor 4.
1. Steering angle sensor 42. The detection output of the vehicle speed sensor 43 is manually inputted, and a control amount for supporting the amount of load movement during steering and suppressing changes in the attitude of the vehicle body is output.

The US10S control unit 51 also includes a steering angle sensor 4.
2 and the detection output of the vehicle speed sensor 43 are input, and control for controlling the vehicle body steering characteristics by increasing/decreasing the roll stiffness ratio between the front and rear wheels based on the steering angular velocity and vehicle speed calculated from the output of the steering angle sensor 42. The amount is output.

In the pitch control unit 52, the vehicle speed sensor 43 degrees
Sensor 44. Brake switch 45. and the detection output of the throttle sensor 46 are input, and based on the output of the longitudinal G sensor 44, a control amount for supporting the load movement amount during acceleration and deceleration and suppressing changes in the posture of the vehicle body is output, especially during braking and acceleration. At times, the gain for the output of the longitudinal G sensor 44 is increased.

Furthermore, in the skyhook damper control section 53, the steering angle sensor 42. Vehicle speed sensor 43. Lateral G sensor 44. Brake switch 45. Throttle sensor 46. and upper and lower G
The detection output of the sensor 48 is manually input, and control is performed to reduce the sprung absolute speed calculated from the detection output of the vertical G sensor 48 to suppress the bouncy feeling of the vehicle body, especially during sudden steering.
During high-speed running, braking, and acceleration, the gain with respect to the vertical absolute speed increases.

The stroke damper control section 54 includes a lateral G sensor 41, a steering angle sensor 42. Vehicle speed sensor 431 Front and rear G sensor 44.
Brake switch 45. Throttle sensor 46. and the detection output of the stroke sensor 47 are input, and control is performed to reduce the stroke speed calculated from the detection output of the stroke sensor 47 to damp vehicle body vibration. Especially during sudden steering, braking, and acceleration, the stroke speed is reduced. The gain increases. Note that details of the stroke damper control section will be described later.

Furthermore, the detection outputs of the vehicle speed sensor 43 and the stroke sensor 47 are input to the vehicle height control 855, and the control amount for obtaining the target vehicle height corresponding to the vehicle speed is determined by integral control based on the detection output of the stroke sensor 47. Output.

The ride comfort control section 56 includes a vehicle speed sensor 43. The detection outputs of the stroke sensor 47 and the vertical G sensor 48 are manually input,
A control amount is output based on mass increase control that suppresses the sprung rudder speed and reduces the vibration transmission force, and reverse spring control that reduces the vibration transmission force by decreasing the spring constant at the time of a minute stroke.

Each control amount output from each of the control units 50 to 56 described above is input to an adder 57 for each wheel, and the total control amount added by the adder 57 is input to a drive circuit 58. Then, the drive circuit 58 outputs a current corresponding to the input control amount to the control valve 32 to actively control the operation of the hydraulic actuator 30, thereby realizing control that provides good riding comfort with little change in posture. Ru. Further, the detection output of the pressure sensor 36 is manually input to the drive circuit 58, and constant pressure control is performed in which feedback control is performed so that the internal pressure of the hydraulic actuator 30 becomes the target control pressure (output of the adder 57).

In addition, in the preview control unit 59, the vehicle speed sensor 4
3 and the detection outputs of the preview sensor 49 are input manually, and when it is detected from the output of the preview sensor 49 that there is a protrusion or step in front of the vehicle, the time point at which the wheel passes the protrusion or step is calculated based on the relationship on the vehicle speed, By outputting a control signal to the drive circuit 60 to open the damping force switching valve 35 when passing over a protrusion or step, vibration transmission when the vehicle passes over the protrusion is reduced.

FIG. 1 shows a schematic configuration of the stroke damper control section 54 mentioned above. In FIG. 1, a stroke signal X detected from a stroke sensor 47 is input to a differentiator 61, and a stroke speed magnitude is calculated. Differentiator 61
The stroke speed signal sentence output from the stroke speed gain setter 62 is multiplied by a control gain Kx corresponding to the stroke speed X based on the map shown in FIG. The gain set in the stroke speed gain setter 62 is 0 in a dead zone region where the stroke speed is smaller than a predetermined value, increases as the number of sentences increases when the stroke speed exceeds a predetermined value, and then becomes a constant value. It has become a thing. With this setting, a control amount that effectively suppresses an increase in the loaf speed is outputted.

The output of the stroke speed gain setter 62 is input to a vehicle speed gain setter 63 and multiplied by Kv.

The control gain Kv in the vehicle speed gain setter 63 is variably set by the vehicle speed signal V detected from the vehicle speed sensor 43 as shown in FIG. That is, the control gain Kv is constant until the vehicle speed V reaches a predetermined value, but once the predetermined value is exceeded, the control gain Kv increases as the vehicle speed V increases, and after that, when the vehicle speed V exceeds a certain value, the control gain Kv becomes constant again. The settings are as follows. As a result, as the vehicle speed increases, the gain for suppressing the increase in stroke speed increases, thereby improving stability during high-speed running.

Furthermore, the output of the vehicle speed gain setter 63 is manually input to the stroke gain setter 64 and multiplied by Kx.

The control gain Kx in the stroke gain setter 64 is variably set by the stroke signal X detected from the stroke sensor 47 as shown in FIG. That is, the control gain KX is set to be constant until the stroke X in the bump and rebound directions reaches a predetermined value, but once it exceeds the predetermined value, the control gain Kx increases as the stroke X increases. This ensures ride comfort when the suspension stroke is small, while increasing the control gain to suppress the increase in stroke speed when the stroke is large, effectively preventing excessive suspension stroke. .

The output section of the stroke gain setter 64 described above is connected to the brake switch 65. It is connected in parallel to a sudden acceleration switch 66 and a crosswind switch 67.

The brake switch 65 is normally in the OFF position and cuts off human power from the stroke gain setting device 64, but when it detects that the brake pedal has been operated by the detection signal from the brake switch 45, it becomes the ON position and the stroke gain setting device 64 is turned off. The input from the setting device 64 is transferred to the front and rear G gain setting device 68.
It is intended to be communicated to Front and rear G gain setting device 68
is to multiply the output of the stroke gain setter 64 transmitted via the brake switch 65 by Knc, and the control gain Kac in the longitudinal G gain setter 68 is the longitudinal acceleration signal detected from the longitudinal G sensor 44. It is variably set as shown in FIG. 7 depending on the GX. In other words, the control gain KBG is constant until the longitudinal acceleration G reaches a predetermined value, but once it exceeds the predetermined value, the control gain KBG increases as the longitudinal acceleration Gx increases, and after that, when the longitudinal acceleration G When it exceeds the threshold, the control gain Ki+c is set to become constant again. With this setting, during braking, the gain for suppressing the increase in the stroke speed increases as well as the increase in longitudinal acceleration GX, and nose dive during braking is effectively suppressed.

Further, the sudden acceleration switch 66 is normally in the off position, cutting off human power from the stroke gain setting device 64. The switching of the sudden acceleration switch 66 is controlled by the output of the sudden start sudden acceleration determining section 69, and the sudden starting sudden acceleration determining section 69 determines when the throttle opening speed calculated from the detection signal of the throttle sensor 46 is equal to or higher than a predetermined value. A signal for switching the sudden acceleration switch 66 to the on position is output. Rapid acceleration switch 6
6 is in the on position, the output of the stroke gain setter 64 is transmitted to the rapid acceleration gain setter 70 and multiplied by KA. The control gain KA of the sudden acceleration gain setting device 70 is a constant value, and the control amount that suppresses the large increase in stroke speed output from the sudden acceleration gain setting device 70 suppresses the swat phenomenon at the time of sudden start and sudden acceleration. Ru.

On the other hand, the crosswind switch 67 is normally in the normal position NOR.
The human power from the stroke gain setting device 64 is transmitted to the steering angular velocity gain setting device 71.

The control gain θ in the steering angular velocity gain setter 71 is determined by a differentiator 72 that differentiates the output signal θ of the steering angle sensor 42.
As shown in FIG. 8, the steering angular velocity signal θ obtained from the steering angular velocity signal θ is variably set. Then, in the steering angular velocity gain setting device 71,
The output of the stroke gain setter 64, which is input manually via the crosswind switch 67, is multiplied by six. That is, until the steering angular velocity 6 reaches a predetermined value, the control gain 4 is a constant value K.
. However, when the predetermined value is exceeded, the control gain is set to rapidly increase by 6 as the steering angular velocity θ increases.

As a result, while ensuring ride comfort when the steering speed is low, the control gain for suppressing a large increase in stroke speed during sudden steering increases, thereby improving stability when the vehicle turns.

By the way, the switching of the crosswind switch 67 is performed by the crosswind determination section 73.
is controlled by the output of The crosswind determination section 73 executes control as shown in the flowchart shown in FIG. 9 based on the outputs of the lateral G sensor 41 and the steering angle sensor 42. That is, when the lateral acceleration G output from the lateral G sensor 41 is 0.15 g or more and the steering angle θ of the steering wheel output from the steering angle sensor 42 is 10 degrees or less, the vehicle is not substantially being steered. However, since lateral G is occurring despite this, it is determined that the vehicle is being affected by a crosswind or road surface disturbance, and the crosswind switch 67 is switched to the stability position STB, but in other cases, it is switched to the normal position NOR described above. Can be switched.

When the crosswind switch 67 is switched to the STB position, the output of the stroke gain setter 64 is transmitted to the crosswind gain setter 74 and multiplied by Ksw. The control gain Ksw of the crosswind gain setter 74 is the control gain K when the aforementioned steering angular velocity is small.

It is a constant value that is larger (for example, twice), and when traveling straight and is affected by crosswinds or road surface disturbances, the control gain that suppresses the increase in stroke speed increases, Improves vehicle stability against impacts.

The aforementioned front and rear G gain setter 68. Rapid acceleration gain setting device 7
0. Steering angular velocity gain setter 71. and each output of the crosswind gain setting device 74 is manually added to an adder 75,
An overall control amount for each wheel is calculated to suppress a large increase in stroke speed. The output of this adder 75 is then output to the adder 57 described above.

According to the above embodiment, the control gain for suppressing the increase in stroke speed Since the control gain is efficiently increased, it is possible to appropriately control the vibration damping properties of the vehicle and achieve both ride comfort and stability.

In particular, in the above embodiment, when the steering angular velocity θ is below a predetermined value, the control gain K is constant regardless of the steering angular velocity θ.
. The control gain is set to increase as the steering angular velocity θ increases when the steering angular velocity θ exceeds a predetermined value. It is set low when driving straight and increases efficiently when making sudden turns. Therefore, while ensuring good ride comfort during gentle steering or straight-ahead driving, the vibration damping performance can be effectively increased during sudden steering, and the vehicle body posture can be efficiently stabilized.

Furthermore, when traveling substantially straight and being affected by crosswinds or road surface disturbances, the normal control gain K is applied. By using a larger control gain K sw, stability can be improved by effectively suppressing disturbances in vehicle body posture due to the effects of crosswinds or road surface disturbances, without sacrificing ride comfort during normal driving. It has the advantage of being able to

It should be noted that the present invention is not limited to the above-mentioned embodiment in any way, and the control gain may be similarly changed in the skyhook damper control section 53 in conjunction with the change in control gain accompanying switching of the crosswind switch 67. good. In addition, the crosswind determination section 7
The control gain may be simply switched based on the output of No. 3, or a wind pressure sensor may be attached to the vehicle body in place of the crosswind determining section to detect the presence or absence of a crosswind. Furthermore, a sensor that detects only road surface disturbance may be used.

In any case, it goes without saying that various modifications can be made without departing from the spirit of the invention.

(Effects of the Invention) As described above in detail with the embodiments, according to the present invention, without sacrificing ride comfort during normal driving,
The present invention provides an active suspension for a vehicle that effectively suppresses disturbances in vehicle body posture due to disturbances such as crosswinds or road surface disturbances, thereby improving stability.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a stroke damper control section 5β in an embodiment of the present invention, FIG. 2 is a system configuration diagram of the above embodiment, FIG. 3 is a schematic configuration diagram of a controller 40, and FIG.
8 are control gain map diagrams used for stroke change speed, and FIG. 9 is a flowchart regarding crosswind determination processing. DESCRIPTION OF SYMBOLS 1... Oil pump, 30... Hydraulic actuator 32... Control valve, 40... Controller 41... Lateral G sensor, 42... Steering angle sensor 43
... Vehicle speed sensor 54 ... Stroke damper control section 67 ... Crosswind switch 71 ... Steering angular velocity gain setter 74 ... Crosswind gain setter Vehicle speed V Fig. 5 Fig. 6 Longitudinal acceleration GX jI7 Fig. Steering Angular velocity θ Fig. 8 Fig. 9

Claims (1)

[Claims] An actuator is interposed between a vehicle wheel and a vehicle body and is capable of increasing or decreasing a force supporting the vehicle body relative to the wheel, and detects a rate of change in relative displacement in the vertical direction between the wheel and the vehicle body. a displacement speed detection means, a disturbance detection means for detecting the presence or absence of a predetermined disturbance input to the vehicle, and a disturbance detection means for detecting the presence or absence of a predetermined disturbance input to the vehicle; and control means for controlling the operation, and when the disturbance detection means detects that the predetermined disturbance input is acting, the control means increases a control gain corresponding to the rate of change compared to normal times. An active suspension for a vehicle characterized by being configured as follows.