JPH03224815A - Suspension controller - Google Patents

Abstract

PURPOSE:To control damping force, and to suppress the vibration of a car body with good response by controlling the damping force to a smaller level at the time of excitation, while to a larger level at the time of damping, based on the direction of a damping force calculated from a rate of damping force change as well as of spring upper acceleration. CONSTITUTION:The generation pattern of the damping force at a shock absorber SA provided between a wheel WH and a car body US is controlled, and the vibration of a car is suppressed. A rate of damping force change at the shock absorber SA is detected by a damping force rate of change detection means M1. The detected damping force rate of change is integrated, so as to estimate the damping force that works on the shock absorber SA by a damping force estimation means M2. Vertical acceleration of the car body is detected by a spring upper acceleration detection means M3. When the direction of the estimated damping force and that of the detected acceleration are identical, the damping force of the shock absorber SA is controlled to be lower level, while higher level on the contrary occasion, by a damping force controller M4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a suspension control device, and more particularly to a suspension control device equipped with a shock absorber that can vary the generation pattern of damping force.

[Prior art] Conventionally, this type of suspension control device incorporates an actuator whose drive source is a piezoelectric element with excellent responsiveness into a shock absorber, and uses a signal of the rate of change in damping force from a load sensor using a piezoelectric element. It is known to switch the damping force characteristics of a shock absorber based on
For example, Japanese Patent Application Laid-Open No. 64-67407).

[Problems to be Solved by the Invention] Such a suspension control device can change the setting of the damping force characteristics based on the road surface condition, and is excellent in improving ride comfort. However, the damping force change rate is Signals cannot deal with the vertical vibration of the vehicle body, that is, the absolute acceleration of the sprung mass, so the setting of the damping force generation pattern may not be optimal. The system detects the relative displacement speed of the unsprung portion and the absolute vertical displacement speed of the sprung portion, and determines whether the suspension is in an excitation state or a vibration suppression state based on the sign of both displacement speeds. Devices that switch the damping force setting have been proposed (for example, Utility Model Application No. 61-1
Publication No. 27007). In this technique, the relative displacement speed between the sprung mass and the unsprung mass and the absolute vertical displacement velocity of the sprung mass are detected as the displacement between the sprung mass and the unsprung mass, and the detected displacement is obtained by differentiating the detected displacement. For this reason, if the sampling time is increased in an attempt to improve the response speed (controllability), the detected displacement amount becomes smaller, making it difficult to distinguish it from noise. Therefore, with this configuration, there is a limit to the improvement in response speed.

The suspension control device of the present invention solves the above problems,
The purpose is to accurately capture the movement between the sprung mass and the unsprung mass, and to control the damping force of a shock absorber with good response.

The structure of the present invention that achieves the above object will be described below.

[Means for Solving the Problems] As illustrated in FIG. 1, the suspension control device of the present invention sets the damping force generation pattern of the shock absorber SA provided between the wheel WH and the vehicle body US. A suspension control device for controlling vibrations of a vehicle, comprising a damping force change rate detecting means M1 for detecting a damping force change rate of the shock absorber SA, and a damping force change rate detecting means M1 for integrating the detected damping force change rate. , damping force estimating means M2 that estimates the damping force acting on the shock absorber SA; sprung front speed detecting means M3 that detects the vertical acceleration of the vehicle body US; and the estimated damping force and the detected damping force. If the direction of the acceleration 4 is the same, the shock absorber S
The main feature is that the damping force control means M4 controls the setting of the damping force of A to the lower side, and controls the setting of the damping force to the higher side when the two directions are opposite.

[Function] The suspension control device of the present invention having the above configuration has the following features:
The setting of the generation pattern of the damping force of the shock absorber SA provided between the wheel Wl-1 and the vehicle body US is determined by the damping force acting on the shock absorber SA (the damping force change rate detected by the damping force change rate detection means M1). is integrated and estimated by the damping force estimating means M2) and the acceleration in the vertical direction of the vehicle body US (detected by the sprung front speed detecting means M3), and the vibration of the vehicle is controlled as follows. That is, when the estimated damping force direction and the detected acceleration direction are the same, the damping force control means M4 controls the setting of the damping force of the shock absorber SA to the lower side, and the two directions are reversed. In this case, the damping force setting is controlled to be high.

Here, since the damping force is estimated as a force acting on the shock absorber SA, the direction of the damping force and the direction of relative movement of the unsprung part with respect to the sprung part coincide. That is, the direction in which the shock absorber SA is moving can be determined from the direction of the estimated damping force, and in an excitation state where this is the same direction as the movement on the spring, the damping force of the shock absorber SA is set to the low side. In a damping state where the movement of the shock absorber SA and the movement of the spring are in opposite directions, the damping force is not set to a large side, and as a result, the vibration of the vehicle is suppressed. Moreover, the movement of the shock absorber SA can be determined from the aspects of road surface conditions and acceleration/deceleration that result in vehicle body vibration (i.e.,
(from the rate of change in damping force), enabling highly responsive and highly accurate control.

[Examples] In order to further clarify the configuration and operation of the present invention described above, preferred embodiments of the suspension control device of the present invention will be described below.

FIG. 2 is a schematic configuration diagram showing the overall configuration of this suspension control device 1, FIG. 3(A) is a partially cutaway sectional view of the shock absorber, and FIG. 3(B) is a main part of the shock absorber. FIG.

As shown in FIG. 2, the suspension control device 1 of the present embodiment includes shock absorbers 2FL, 2FR, 2RL, and 2RR that can change the damping force in two stages, and is connected to each of these shock absorbers to control the damping force. It is composed of an electronic control unit 4 that performs the following operations.

Each shock absorber 2FL, 2FR, 2RL,
2RR has left and right front and rear wheels 5FL, 5FR, 5 respectively.
RL, 5RR suspension lower arm 6FL
, between 6FR, 6RL, 6RR and the vehicle body 7,
Coil springs 8FL, 8FR.

It is located alongside 8RL and 8RR.

Shock absorber 2FL, 2FR, 2RL,
2RR is a shock absorber 2FL as described later.
, 2FR.

A piezo load sensor that detects the force acting on 2RL and 2RR, and shock absorbers 2FL, 2FR, and 2
R.L.

Each of the 2RRs has 7 sets of piezo actuators for switching the setting of the damping force generation pattern in the 2RR.

Next, each of the above shock absorbers 2FL and 2FR.

The structure of 2RL and 2RR will be explained, but each of the above shock absorbers 2FL, 2FR, 2RL, 2RR
Since all of the structures are the same, the shock absorber 2FL on the left front wheel 5FL side will be explained here as an example. In addition, in the following description, the reference numerals of each member provided on each wheel include front left wheel 5 FL and front right wheel 5 FR, as necessary.

Subscript FL corresponding to left rear wheel 5RL, right rear wheel 5RR,
F.R.

RL and RR shall be added, and if there is no difference regarding each wheel, the subscripts shall be omitted.

The shock absorber 2, as shown in FIG. 3(A),
The lower end of the cylinder 11 is fixed to the suspension lower arm 6 via the axle side member 1a, while the bearing 7 is fixed at the upper end of the rod 13 inserted through the cylinder 1.
It is fixed together with a coil spring 8 to the vehicle body 7 via a vibration-proof rubber 7b.

Inside the cylinder 11 is an internal cylinder connected to the lower end of the rod 13]5. Connecting members 16 and 8 - A cylindrical member 17 and a main piston 8 that is slidable along the inner peripheral surface of the cylinder 11 are provided. Shock absorber 2 rod] Internal cylinder 1 connected to 3
5 houses a piezo load sensor 25 and a piezo actuator 27.

The main piston 18 is fitted onto the outside of the cylindrical member [7], and a sill material 19 is interposed on the outer periphery that fits into the cylinder [1]. Therefore, the inside of the cylinder 11 is divided into a first liquid chamber 21 and a second liquid chamber 23 by the main piston 18. A backup member 28 is screwed onto the tip of the cylindrical member 17, and between the cylindrical member 17 and the main piston 18, a spacer 29 and a leaf valve 30 are placed on the cylindrical member 17 side. and color 3
2 are pressed and fixed to the backup member 28 side. Further, a main valve 34 and a spring 35 are interposed between the leaf valve 31 and the backup member 28, and urge the leaf valve 31 in the direction of the main piston 18.

These leaf valves 30, 31 are connected to the main piston 18.
When the main piston is stopped, the extension side and the contraction narrow passage 18a provided in the main piston]8.

18b are each closed on one side, and the main piston 1
8 opens to one side as it moves in the direction of arrow A or B. Therefore, as the main piston 18 moves, the hydraulic oil filled in both the liquid chambers 21 and 23 flows through both passages 18a and 23.
18b, and moves between the two liquid chambers 21 and 23. In this state, where the movement of hydraulic oil between the two liquid chambers 21 and 23 is limited to both passages 18a and 18b, the damping force generated against the movement of the rod 13 is large, and the suspension characteristics are hard. Become.

A piezo load sensor 2 is housed inside the internal cylinder 15.
5 and the piezo actuator 27 are shown in FIG. 3(A),
As shown in (B), this is an electrostrictive element laminate in which thin plates of piezoelectric ceramics are stacked with electrodes in between. Each electrostrictive element of the piezo load sensor 25 is polarized by the force acting on the shock absorber 2, that is, the damping force. Therefore, by extracting the output of the piezo load sensor 20-5 as a voltage signal through a circuit with a predetermined impedance, the rate of change in damping force can be detected.

The piezo actuator 27 is made by stacking electrostrictive elements that expand and contract with good response when a high voltage is applied to increase the amount of expansion and contraction, and directly drives the piston 36 .

When the piston 36 is moved in the direction of arrow B in FIG. 3(B), the plunger 37 and H
The spool 41, which has a letter-shaped cross section, is also moved in the same direction. When the spool 41 in the position shown in FIG. 3(B) (origin position) moves in the direction B in the figure, the first liquid chamber 2
The sub-flow path 16c connected to the liquid chamber 1 and the sub-flow path 39b of the bushing 39 connected to the second liquid chamber 23 are communicated with each other. This sub-flow path 39b is further connected to the flow path 17a in the cylindrical member 17 via an oil hole 45a provided in the plate valve 45.
As a result, when the spool 41 moves in the direction of arrow B, the seventh liquid chamber 21 and the second liquid chamber 2
The flow rate of the hydraulic oil flowing between 3 and 3 increases. In other words, when the piezo actuator 27 expands due to the application of a high voltage, the shock absorber 2 switches its damping force characteristic from a high damping force (hard) state to a low damping force (soft) state, and when the electric charge is discharged and the shock absorber 2 contracts. Change the damping force characteristics to large damping force (
hard) state.

The amount of movement of the leaf valve 31 provided on the lower surface of the main piston 18 is controlled by a spring 35.
It is regulated compared to Further, the plate valve 45 is provided with an oil hole 45b having a larger diameter than the oil hole 45a on the outside of the oil hole 45a.
When it moves in the direction of the bush 39 against the urging force of 6, the hydraulic oil becomes movable through the oil hole 45b. Therefore,
Regardless of the position of the spool 4], the main piston 1
8 moves in the direction of arrow B, the flow rate of hydraulic oil becomes larger than when the main piston 18 moves in the direction of arrow A. That is, the damping force is changed depending on the moving direction of the main piston 18, thereby improving the characteristics as a shock absorber. Further, a hydraulic oil supply path 38 is provided between the oil-tight chamber 33 and the first liquid chamber 21, together with a check valve 38a, to keep the flow rate of the hydraulic oil in the oil-tight chamber 33 constant.

Next, the electronic control device 4 that switches and controls the generation pattern of the damping force of the shock absorber 2 described above will be explained using FIG. 4.

This electronic control unit a4 includes a piezo load sensor 25 for each shock absorber 2 as a sensor for detecting the running state of the vehicle, a steering sensor 50 for detecting the steering angle of a steering wheel (not shown), and a steering sensor 50 for detecting the steering angle of the steering wheel (not shown), and a steering sensor 50 for detecting the steering angle of the steering wheel (not shown). A shift position sensor 52 detects the shift position of a transmission (not shown), a stop lamp switch 53 detects the operation of a brake pedal (not shown), and an acceleration sensor 51 detects the vertical acceleration α of the vehicle body. A sensor 54 etc. are connected.

The electronic control device 4 that outputs control signals to the piezo actuator 27 described above based on these detection signals etc. is a well-known CPLI61. ROM62. It is configured as an arithmetic and logic operation circuit centered around the RAM 64, and input/output with the outside is performed through an input section 67 and an output section 68 which are connected to these circuits via a common bus 65.

In addition, the electronic control device 4 includes a damping force change rate detection circuit 70 to which the piezo load sensor 25 is connected, a waveform shaping circuit 73 to which the steering sensor 50 and vehicle speed sensor 51 are connected, and a high voltage sensor connected to each piezo actuator 27. A voltage application circuit 75 receives power from a battery 77 via an ignition switch 76, and a so-called switching regulator-type high voltage power supply circuit 79 outputs a drive voltage for driving a piezo actuator. A constant voltage power supply circuit 80 and the like that generate an operating voltage (5V) for the control device 4 are provided. Each piezo load sensor 25. Shift position sensor 52. Stop lamp switch 53. Acceleration sensor 54. Damping force change rate detection circuit 70. The waveform shaping circuit 73 has an input section 671;
High voltage application circuit 75. The high voltage power supply circuit 79 is the output section 68
are connected to each.

The damping force change rate detection circuit 70 is connected to each piezo load sensor 25.
It consists of four detection circuits provided corresponding to FL, FR, RL, and RR, and each detection circuit receives an output from a circuit including the piezo load sensor 25 according to the acting force that the shock absorber 2 receives from the road surface. The voltage signal V that
CPU61 as damping force change rate of shock absorber 2
It is configured to output to . In addition, the waveform shaping circuit 7
3 (Friend) This is a circuit that shapes and outputs the detection signals from the steering sensor 50 and the vehicle speed sensor 51 into signals suitable for processing in the CPU 61. Therefore, the CPU 61
are the damping force change rate detection circuit 70 and the waveform shaping circuit 73.
and the output signal from the stop lamp switch 53.
The driving state of the vehicle can be determined based on signals from etc. Based on this processing, the CPU 61 outputs a control signal to the high voltage application circuit 75 provided corresponding to each wheel.

This high voltage application circuit 75 is a circuit that applies a voltage of +500 volts or 1]O15-0 volts output from the high voltage power supply circuit 79 to the piezo actuator 27 in response to a control signal from the CPU 61. Therefore, in response to this damping force switching signal, the piezo actuator 27 expands (when +500 volts is applied) or contracts (when -100 volts is applied), and the hydraulic oil flow rate is switched to change the damping force characteristics of the shock absorber 2 from soft to hard. can be switched to 4. The damping force characteristic of each shock absorber 2 is such that when a high voltage is applied to extend the piezo actuator 27, the damping force characteristic of the shock absorber 2 is As the flow rate of the hydraulic oil flowing between the first liquid chamber 21 and the second liquid chamber 23 increases, the damping force becomes small, and when the piezo actuator 27 is contracted by discharging the electric charge with a negative voltage, Since the hydraulic oil flow rate decreases, the damping force becomes large. Note that once the charge accumulated in the piezo actuator 27 is discharged, the piezo actuator 27 will remain in a contracted state even if the negative voltage is removed, and the shock absorber 2 will remain in a state with a large damping force. maintain.

Next, the damping force control performed by the suspension control device 1 of this embodiment having the above-described configuration will be explained based on the flowchart of FIG. 5. Note that this process is executed independently for the shock absorbers 2 FL, FR, RL, and RR of each wheel 5 FL, FR, RL, and RR, but the process for each wheel 5 remains the same. , will be explained without making any particular distinction.

When the damping force switching control routine shown in Fig. 5 is started,
First, a process is performed to detect the rate of change V of the damping force acting on the shock absorber 2 from the damping force change rate detection circuit 70 via the input section 67 (step 100), and based on this damping force change rate V, the damping force Perform processing to calculate U (
Step 110). In this embodiment, a piezo load sensor 25 made of piezoelectric ceramics is used to detect the force acting on the shock absorber 2, and by detecting the output of the piezo load sensor 25 with a circuit of a predetermined impedance, It is possible to obtain a signal of the damping force change rate V that detects the road surface condition with extremely good responsiveness. Therefore,
After this damping force change rate V is processed by a low-pass filter of a predetermined frequency configured by software, such as weighted average processing, the damping force U can be calculated by integrating. In this embodiment, the damping force U was calculated by software, but it may be calculated by a discrete integrating circuit or the like.

Next, a process is performed to read the vehicle body vibration trajectory, that is, the acceleration α on the spring from the acceleration sensor 54 via the input unit 67 (Step 20), and the direction of this acceleration α is determined (Step 30). Furthermore, the direction of the damping force U calculated in step 110 is also determined (steps 140 and 14).
5). As a result, as shown in FIG. 6, the following four states of the suspension are distinguished, and the characteristics of the shock absorber 2 are controlled accordingly.

The acceleration α on the spring is upward and the shock absorber 2
When the direction of the damping force acting on is the contraction side, or when the acceleration α is downward and the direction of the damping force U is the expansion side (that is, when the directions of the acceleration α and the damping force U are the same) Assuming that the suspension is in an excitation state, a high voltage of +500 volts is applied from the high voltage application circuit 75 to the piezo actuator 27 to control the damping force setting of the shock absorber 2 to a small state (soft)] 50), exit to rNEXTJ and temporarily end this routine.

On the other hand, if the acceleration α on the spring is upward and the direction of the damping force acting on the shock absorber 2 is the extension side, or if the acceleration α is downward and the direction of the damping force U is the contraction side (that is, the acceleration α (When the directions of damping force U are opposite)
In step 160), the damping force setting of the shock absorber 2 is controlled to a large state (hard).
Exit to XTJ and end this routine once. The reason for hard control of the shock absorber 2 is to apply 1100 volts from the high voltage application circuit 75 using the control signal from the output section 68 immediately after the damping force setting of the shock absorber 2 is switched from soft to hard. This is done by applying a voltage to the piezo actuator 27 and contracting it by 9-, and if the piezo actuator 27 is already in a contracted state, it is held as it is.

In the suspension control device of this embodiment having the above configuration, when the suspension is in an excited state, that is, the movement of the sprung mass and the movement of the shock absorber 2 (relative movement between the sprung mass and the unsprung mass) are in the same direction. In this case, the damping force of the shock absorber 2 is set to a small value, and when the vibration is suppressed, that is, the movement of the spring and the movement of the shock absorber 2 are in opposite directions, the damping force of the shock absorber 2 is set to a large value. . As a result, the most essential control of damping force is performed, and vibrations of the vehicle body when traveling on rough roads can be quickly suppressed. Moreover, it is possible to realize optimal damping force control of the shock absorber 2 even when riding over a step, etc., thereby improving riding comfort. Moreover, since the relative movement between the sprung mass and the unsprung mass is judged from the direction of the damping force U, which is the integral of the signal of the damping force change rate V, there is no delay in response, and there is no risk of misjudgment due to external disturbances, etc. Nor. According to the suspension control device of this embodiment,
The damping force characteristics of the shock absorber 2 can be controlled with high precision and responsiveness, and ride comfort can be significantly improved.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way. For example, the damping force is not controlled independently for each wheel, but is controlled as a combination of left and right wheels or front and rear wheels. It goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention, such as a configuration in which:

Effects of the Invention As detailed above, according to the suspension control device of the present invention, the damping force of the shock absorber is adjusted in the excitation state based on the direction of the damping force calculated from the damping force change rate and the acceleration on the spring. Since the setting is controlled to the small side, and the setting is controlled to the large side in the damping state, the damping force can be optimally controlled with good responsiveness, which is an extremely excellent effect. Therefore, vibrations of the vehicle body, such as when driving on rough roads, can be quickly suppressed, and ride comfort is significantly improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the basic configuration of the present invention, FIG. 2 is a schematic configuration diagram showing the overall configuration of a suspension control device as an embodiment of the present invention, and FIG. 3 (A) is a shock absorber 2 Fig. 3 (B) is a partial cross-sectional view showing the structure of
) is an enlarged cross-sectional view of the main part of the shock absorber 2. FIG. 4 is a block diagram showing the configuration of the electronic control device 4 of this embodiment. FIG. 5 is a flowchart showing the damping force switching control routine.
FIG. 6 is an explanatory diagram showing a combination of the directions of the sprung front speed α and the damping force U. 1...Suspension control device 2 FL, FR, RL, RR...Shock absorber 4...Electronic control device 25 FL, FR, RL, RR-...Piezo load sensor 27 FL, FR, RL, RR・... Piezo actuator 50 ... Steering sensor 51 ...
・Vehicle speed sensor 70... damping force change rate detection circuit

Claims (1)

[Scope of Claims] 1. A suspension control device that suppresses vehicle vibration by controlling the setting of a damping force generation pattern of a shock absorber provided between a wheel and a vehicle body, comprising: damping force change rate detection means for detecting a force change rate; damping force estimating means for integrating the detected damping force change rate to estimate a damping force acting on the shock absorber; and vertical acceleration of the vehicle body. When the direction of the estimated damping force and the detected sprung mass acceleration is the same, the damping force of the shock absorber is controlled to a lower side, and the damping force of the shock absorber is controlled to be lower. A suspension control device comprising a damping force control means for controlling the setting of the damping force to a higher side when the direction is reversed.