JP5162283B2 - Control device and control method for damping force variable damper - Google Patents

Description

  The present invention relates to a control device for a damping force variable damper, and more particularly to a technique for improving riding comfort when traveling on rough roads.

2. Description of the Related Art In recent years, various types of cylindrical dampers used in automobile suspensions have been developed that can control the damping force stepwise or steplessly in order to improve ride comfort and handling stability. For vehicles equipped with a variable damping force damper (hereinafter simply referred to as a damper), it is possible to improve steering stability and ride comfort by variably controlling the damping force of the damper according to the running state of the vehicle. Become. For example, when the vehicle is turning, the vehicle body rolls in the left-right direction due to inertial force (lateral acceleration) that accompanies lateral movement, but the vehicle body becomes excessively large by increasing the target damping force of the damper according to the differential value of the lateral acceleration. Rolls can be suppressed. Moreover, the unsprung control current is set based on the product of the damper displacement and the stroke speed, and this is added to the target current of the skyhook control, thereby effectively suppressing the unsprung vibration in the unsprung resonance region. (See Patent Document 1).
JP 2006-321259 A

  However, when the unsprung control current is set so that the unsprung vibration is reliably controlled, there is a problem that the riding comfort deteriorates depending on the traveling state of the vehicle. For example, if a vehicle climbs over a large step while driving straight ahead at a constant speed (that is, in a state where no pitching or rolling occurs), the unsprung portion vibrates greatly in a short cycle, but the unsprung resonance frequency (10 to 12 Hz) ) And the sprung (vehicle body) resonance frequency (1 to 3 Hz), the vehicle body does not always vibrate greatly at this time. However, if the unsprung control current value is set to a large value due to unsprung vibration, the damping force of the damper increases (damper rigidity increases), so the input from the road surface is directly transmitted to the vehicle body. In other words, the ride comfort is deteriorated when traveling on rough roads.

  The present invention has been made in view of such a background, and provides a control device and a control method for a damping force variable damper that realizes an improvement in riding comfort when traveling on rough roads.

1st invention is mounted in the vehicle by which the damping force variable damper of the current control type which the damping force of both an expansion side and a contraction side increases so that control current becomes large , respectively was interposed between a vehicle body and each wheel , A control device used for controlling the damping force variable damper, wherein a posture change amount detecting means for detecting a posture change amount of the vehicle body, and a relative for detecting a vertical relative displacement amount of the vehicle body and the wheel. Displacement amount detection means; first control current setting means for setting a first control current for restraining a posture change supplied to the damping force variable damper based on a detection result of the posture change amount detection means; and the relative displacement amount. A second control current setting means for setting a second control current for unsprung vibration to be supplied to the variable damping force damper based on a detection result of the detection means; and a first control current and a second control current. Out of which And a target current selection means for selecting as a target current of the variable damping force damper, the second control current is characterized in that its upper limit is lower than the upper limit value of the first control current.

The second invention is a method for controlling a variable damping damper of a current control type that is provided for suspension of a vehicle and that increases both the expansion side and the contraction side damping force as the control current increases. A process for detecting an attitude change amount of the vehicle, a process for detecting a relative displacement amount in the vertical direction between the vehicle body and the wheel, and a process for suppressing an attitude change to be supplied to the damping force variable damper based on the attitude change amount. A process of setting one control current, a process of setting a second control current for unsprung vibration to be supplied to the damping force variable damper based on the relative displacement amount, the first control current and the second control And a process of selecting the larger one of the currents as the target current of the damping force variable damper, wherein the upper limit value of the second control current is lower than the upper limit value of the first control current. And

  According to the first and second inventions, since the upper limit value of the second control current is low, for example, when the vehicle travels straight ahead at a constant speed, the second control current is set as the target control current. However, the damping force of the damper does not become excessive, and the deterioration of the riding comfort due to the input from the road surface being transmitted to the vehicle body is suppressed.

  Hereinafter, embodiments in which the present invention is applied to a four-wheeled vehicle will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a four-wheeled vehicle according to an embodiment, FIG. 2 is a longitudinal sectional view of a damper according to the embodiment, and FIG. 3 is a block diagram illustrating a schematic configuration of a damping force control device according to the embodiment. It is.

<< Configuration of Embodiment >>
<Schematic configuration of automobile>
First, a schematic configuration of an automobile according to an embodiment will be described with reference to FIG. In the description, for the four wheels and members arranged for them, that is, tires, suspensions, and the like, suffixes indicating front, rear, left, and right are attached to the reference numerals, for example, wheel 3fl (front left), wheel 3fr (front right), wheel 3rl (rear left), wheel 3rr (rear right) and collectively referred to as wheel 3, for example.

  As shown in FIG. 1, an automobile (vehicle) V includes four wheels 3 on which tires 2 are mounted. Each wheel 3 includes a suspension arm, a spring, an MRF damping force variable damper (hereinafter simply referred to as a damper). It is suspended on the vehicle body 1 by a suspension 5 consisting of 4 etc. The vehicle V is provided with an ECU (Electronic Control Unit) 7 and an EPS (Electric Power Steering) 8 which are the control body of the suspension system. Further, the vehicle V includes a vehicle speed sensor 9 for detecting the vehicle speed, a lateral G sensor 10 for detecting lateral acceleration, a longitudinal G sensor 11 for detecting longitudinal acceleration, a yaw rate sensor 12 for detecting yaw rate, and the like installed at appropriate positions on the vehicle body 1. In addition, a stroke sensor 13 for detecting the displacement of the damper 4 and a vertical G sensor (vertical momentum detecting means) 14 for detecting vertical acceleration in the vicinity of the wheel house in the vehicle body 1 are installed for each wheel 3.

  The ECU 7 includes a microcomputer, ROM, RAM, peripheral circuit, input / output interface, various drivers, and the like, and the damper 4 of each wheel 3 via a communication line (CAN (Controller Area Network in this embodiment)). And each sensor 9-14.

<Damper structure>
As shown in FIG. 2, the damper 4 of the present embodiment is a monotube type (de carvone type), and a cylindrical cylinder tube 21 filled with MRF and an axial direction with respect to the cylinder tube 21. A piston rod 22 that slides, a piston 26 that is attached to the tip of the piston rod 22 and divides the inside of the cylinder tube 21 into an upper oil chamber 24 and a lower oil chamber 25, and a high-pressure gas chamber 27 under the cylinder tube 21. The main components are a defined free piston 28, a cover 29 for preventing dust from adhering to the piston rod 22 and the like, and a bump stop 30 for buffering at the time of full bound.

  The cylinder tube 21 is connected to the upper surface of the trailing arm 35 that is a wheel side member via a bolt 31 that is fitted into the eyepiece 21a at the lower end. The piston rod 22 has a pair of upper and lower bushes 36 and a nut 37, and a stud 22a at the upper end thereof is connected to a damper base (upper part of the wheel house) 38 which is a vehicle body side member.

  The piston 26 is provided with an annular communication passage 39 that allows the upper oil chamber 24 and the lower oil chamber 25 to communicate with each other, and an MLV coil 40 that is disposed inside the annular communication passage 39. When an electric current is supplied from the ECU 7 to the MLV coil 40, a magnetic field is applied to the MRF flowing through the annular communication path 39, and the ferromagnetic fine particles form a chain cluster, and the appearance of the MRF passing through the annular communication path 39. The upper viscosity increases.

<Damping force control device>
The ECU 7 includes a damping force control device 50 whose schematic configuration is shown in FIG. The damping force control device 50 is a posture change suppression that sets a damping force for posture change suppression based on the input interface 51 to which the above-described sensors 9 to 14 and the like are connected and the detection signals input from the sensors 9 to 12 and 14. Unit 52, a first control current setting unit 53 that sets a first control current of each damper 4 based on a setting result of posture change suppression unit 52 and a detection signal (stroke signal) input from stroke sensor 13, and a vehicle speed sensor 9 and the detection signal input from the stroke sensor 13, the unsprung damping part 56 for setting the damping force for unsprung damping of each damper 4, and the setting result of the unsprung damping part 56 and the stroke signal. a second control current setting unit 57 for setting a second control current of each damper 4, the target current selection to select the larger value out of the first control current and a second control current as a target current And parts 54, a target current target current selection unit 54 selects / sets and an output interface 55 for outputting to each damper 4 (MLV coil 40). The posture change suppression unit 52 accommodates a skyhook control unit 61 used for skyhook control, a roll control unit 62 used for roll control, and a pitch control unit 63 used for pitch control. Has been.

<< Operation of Embodiment >>
When the vehicle V starts traveling, the damping force control device 50 executes damping force control whose procedure is shown in the flowchart of FIG. 4 at a predetermined processing interval (for example, 2 ms). When the damping force control is started, the damping force control device 50 detects each acceleration of the vehicle body 1 obtained from the lateral G sensor 10, the longitudinal G sensor 11, and the vertical G sensor 14 in step S1 of FIG. The motion state of the vehicle V is determined based on the vehicle speed input from the vehicle, the steering speed input from the steering angle sensor (not shown), and the like. Next, the damping force control device 50 calculates the skyhook control target value Dsh of each damper 4 in step S2 based on the motion state of the vehicle V, and calculates the roll control target value Dr of each damper 4 in step S3. In step S4, the pitch control target value Dp of each damper 4 is calculated. Further, the damping force control device 50 calculates the unsprung control target value Dw of each damper 4 as the second target damping force Dtgt2 based on the stroke position Ps of each damper 4 and the vehicle speed v.

  Next, the damping force control device 50 determines whether or not the stroke speed Ss of each damper 4 is a positive value in step S6, and if this determination is Yes (ie, the damper 4 is on the extension side). In the case of operation), the largest control value among the three control target values Dsh, Dr, Dp is set as the first target damping force Dtgt1 in step S7. In addition, when the determination in step S5 is No (that is, when the damper 4 is operating on the contraction side), the damping force control device 50 includes the three control target values Dsh, Dr, and Dp in step S8. The smallest value is set as the first target damping force Dtgt1.

  When the first target damping force Dtgt1 is set in step S7 or step S8, the damping force control device 50 calculates the first control current Itb1 corresponding to the first target damping force Dtgt1 from the first control current map of FIG. 5 in step S9. Search / set, and search / set the second control current Itb2 corresponding to the second target damping force Dtgt2 from the second control current map of FIG. 6 in step S10. As shown in FIGS. 5 and 6, the upper limit value of the first control current Itb2 is 5A, but the upper limit value of the second control current Itb2 is limited to 4A.

  When the first and second control currents Itb1 and Dtgt2 are set in steps S9 and S10, the damping force control device 50 selects / sets the larger absolute value of these as the target current Itgt in step S11, and then step S12. Then, a drive current corresponding to the target current Itgt is output to the MLV coil 40 of each damper 4.

  In this embodiment, by adopting such a configuration, excessive unsprung vibration damping without reducing damping force (roll damping force, pitch damping force, skyhook damping force) for posture change control. Deterioration of ride comfort due to force is effectively suppressed. FIG. 7 is a graph showing the temporal change of the sprung acceleration when the automobile V goes over a large step while driving straight ahead at a constant speed. As can be seen from FIG. 7, this embodiment (solid line in the figure). In this case, the upper limit value of the second control current Itb2 for unsprung vibration suppression is limited to 4A, so that the maximum value of the sprung acceleration is higher than when the upper limit value is 5A (indicated by a broken line in the figure). A value can be made small and riding comfort can be improved.

  Although description of specific embodiment is finished above, the aspect of the present invention is not limited to the above embodiment. For example, although the above-described embodiment applies the present invention to roll control, it can also be applied to pitch control, bounce control, safety control, and the like. In the above embodiment, the vertical G sensor that detects the vertical acceleration of the wheel is used as the vertical momentum detection means. However, the vertical speed sensor that detects the vertical speed of the wheel is used, or the detection signal of the vertical speed sensor is differentiated. Thus, the vertical acceleration may be obtained. In addition, the specific configuration of the automobile and the control device, the specific control procedure, and the like can be changed as appropriate without departing from the spirit of the present invention.

1 is a schematic configuration diagram of a four-wheeled vehicle according to an embodiment. It is a longitudinal cross-sectional view of the damper which concerns on embodiment. It is a block diagram which shows schematic structure of the damping-force control apparatus which concerns on embodiment. It is a block diagram which shows schematic structure of the roll control part which concerns on embodiment. It is a 1st control current map concerning an embodiment. It is a 2nd control current map concerning an embodiment. It is a graph which shows the time change of the sprung acceleration which concerns on embodiment.

Explanation of symbols

1 Body 3 Wheel 4 Damper 7 ECU
9 sensor 9 vehicle speed sensor 10 lateral G sensor (attitude change amount detecting means)
11 Front / rear G sensor (Attitude change detection means)
12 Yaw rate sensor (Attitude change detection means)
13 Stroke sensor (relative displacement detection means)
14 Vertical G sensor (Attitude change detection means)
DESCRIPTION OF SYMBOLS 50 Damping force control apparatus 52 Posture change suppression part 53 1st control current setting part (1st control current setting means)
54 target current selection unit (target current selection means)
57 second control current setting section (second control current setting means)
V car

Claims (2)

A damping force variable damper of current control type in which both the damping force on the expansion side and the contraction side increases as the control current increases is mounted on a vehicle interposed between the vehicle body and each wheel, and the damping force variable damper A control device used for control,
Posture change amount detecting means for detecting the posture change amount of the vehicle body;
A relative displacement amount detecting means for detecting a relative displacement amount between the vehicle body and the wheel in the vertical direction;
First control current setting means for setting a first control current for suppressing a posture change supplied to the variable damping force damper based on a detection result of the posture change amount detecting means;
Second control current setting means for setting a second control current for unsprung vibration supplied to the damping force variable damper based on a detection result of the relative displacement amount detection means;
A target current selecting means for selecting a larger one of the first control current and the second control current as a target current of the damping force variable damper;
The damping force variable damper control device, wherein the upper limit value of the second control current is lower than the upper limit value of the first control current. A method of controlling a variable damping damper of a current control type that is used for suspension of a vehicle and increases both the expansion side and the contraction side damping force as the control current increases .
Processing for detecting the amount of change in posture of the vehicle body;
A process for detecting a relative displacement in the vertical direction between the vehicle body and the wheel;
A process for setting a first control current for suppressing a posture change to be supplied to the damping force variable damper based on the posture change amount;
A process of setting a second control current for unsprung vibration to be supplied to the damping force variable damper based on the relative displacement amount;
A process of selecting a larger one of the first control current and the second control current as a target current of the damping force variable damper,
The method for controlling a damping force variable damper, wherein an upper limit value of the second control current is lower than an upper limit value of the first control current.

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