JP5144289B2 - Control device 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 realizing improvement in steering stability during turning.

  In a car with a rear-wheel drive layout such as FR (front engine / rear drive), if the driver depresses the accelerator pedal and increases the driving force during turning, the lateral force and driving force of the tire When the resultant force deviates from the friction circle, the rear wheels begin to slip, and a yaw rate is generated in the vehicle body toward the inside of the turn. At this time, in order to suppress the oversteer state of the vehicle body, the driver often steers outward (that is, performs a countersteer operation). As a result, a yaw rate toward the outside of the turn is generated in the vehicle body, and the above-described yaw rate toward the inside of the turn is canceled to prevent the vehicle body from spinning. In addition, on rainy roads and icy and snowy roads (hereinafter referred to as low μ roads) with a low friction coefficient, the tire friction circle is smaller than on dry paved roads, etc. When done, it easily falls into an oversteer state. To solve this problem, the throttle opening is reduced by TBW (Throttle By Wire), or the wheel outside the turn is braked by VSA (Vehicle Stability Assist: Vehicle Behavior Stabilization Control System). Methods are known.

On the other hand, various types of damping dampers that can variably control the damping force stepwise or steplessly have been developed as cylindrical dampers used in automobile suspensions in order to improve ride comfort and steering 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. Also, when traveling on rough roads with continuous small irregularities, the wheels move up and down in a short cycle, but by lowering the target damping force of the damper according to the stroke speed of the damper, the wheel moves up and down. Transmission to the vehicle body can be suppressed (see Patent Document 1).
JP 2006-69527 A

  In conventional automobiles, even when the driver performs a countersteer operation, the oversteer state during turning may not be effectively suppressed. That is, even if the countersteer operation is performed, if the rigidity of the suspension (spring and damper) is low, the vehicle body rolls, and the yaw rate toward the outside of the turn is less likely to occur. As a method for solving such problems, it is conceivable to increase the steering ratio (steering gain) so that the countersteer operation can be easily performed. It becomes difficult. In addition, it is conceivable to use a suspension spring having a high spring rate or to increase the damping force of the damper. However, these are difficult to adopt because they cause a deterioration in ride comfort.

  Further, when the driver depresses the accelerator pedal during high-speed turning, a large yaw rate is generated toward the inside of the turn, and an oversteer state is likely to occur. When the damping force of the damper is lowered to suppress such an oversteer state, it becomes difficult to perform posture control by depressing the accelerator pedal during medium / low speed turning. On the other hand, in the above-described method of suppressing the oversteer state when turning on a low μ road by TBW or VSA, the vehicle is decelerated against the driver's intention to accelerate. There was a problem.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a control device for a damping force variable damper that realizes improvement in steering stability during turning.

A first invention is a control device that is mounted on a rear wheel drive type vehicle in which a damping force variable damper is interposed between a vehicle body and a wheel, and is used for damping force control of the damping force variable damper. A base value setting means for setting a target damping force base value based on a motion state of the vehicle body, a turning determination means for determining whether or not the vehicle is in a turning traveling state, and the turning determination means to When it is determined that the vehicle is in a turning state, a damping force correction value is set according to at least one of the driving operation state, the driving state, and the driving environment of the vehicle, and the damping force correction value is set as the target damping force base value. The target damping force setting means for setting the target damping force on the drive wheel side by adding, the depression state amount detection means for detecting the depression state amount of the accelerator pedal by the driver, and the vehicle speed detection for detecting the vehicle speed of the vehicle Means and running And a friction coefficient estimation means for estimating the friction coefficient of the road surface, the target damping force setting means is damped such that the value becomes large when depression speed of the accelerator pedal detected by the depression state quantity detecting means is high While the force correction base value is set, when the vehicle speed detected by the vehicle speed detection means is higher than a predetermined value, the damping force correction base value is multiplied by a vehicle speed gain that becomes smaller as the vehicle speed increases. When the friction coefficient detected by the friction coefficient estimating means is lower than a predetermined value, the damping force correction value is calculated by multiplying the damping force correction base value by a μ gain that decreases as the friction coefficient decreases. characterized in that it.

According to the present invention, for example, when an oversteer condition is likely to occur during turning, the target damping force setting means increases or decreases the target damping force depending on the situation, so that a yaw rate toward the outside of the turn is likely to occur. Or an oversteer state is suppressed by making it difficult to generate a yaw rate toward the inside of the turn. Also, when the driver depresses the accelerator pedal during turning, the target damping force is set by increasing the target damping force base value according to the accelerator pedal depression amount and stepping speed. It is likely to occur due to the countersteer operation (that is, the yaw rate sensitivity is increased), and the oversteer state is less likely to occur. During high-speed turning, the target damping force is set by decreasing the target damping force base value in accordance with the vehicle speed, so even if the driver depresses the accelerator pedal and increases the driving force, The yaw rate that goes to is less likely to occur (that is, the yaw rate sensitivity is lowered), and the oversteer condition is less likely to occur. Also, when turning on low μ roads, the target damping force is set by reducing the target damping force base value according to the friction coefficient of the road surface, so the driver depresses the accelerator pedal to increase the driving force. Even if it is increased, yaw rate toward the inside of the turn is less likely to occur, and an oversteer state is less likely to occur.

  Hereinafter, an embodiment in which the present invention is applied to a four-wheeled vehicle having an FR layout 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. FIG. 4 is a block diagram showing a schematic configuration of the rear wheel damping force correction unit according to the embodiment.

<< 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 corresponding members (tires, suspensions, etc.), suffixes indicating front, rear, left and right are attached to the reference numerals (numbers), respectively, so that the wheels 3fl (front left) and wheels 3fr (front right) ), Wheel 3rl (rear left), wheel 3rr (rear right), and the like, and when referring generically, it is denoted as wheel 3 or the like using a symbol without a suffix.

  As shown in FIG. 1, a vehicle body 1 of an automobile (vehicle) V has wheels 3 with tires 2 mounted on the front, rear, left and right, and each wheel 3 has a suspension arm 4, spring 5, variable damping force type. Each suspension is suspended from the vehicle body 1 by a suspension 7 including a damper (hereinafter simply referred to as a damper) 6 and the like. In the vehicle V, an ECU (Electronic Control Unit) 8 used for various controls, a vehicle speed sensor (vehicle speed detection means) 9, a lateral G sensor 10, a front / rear G sensor 11, a yaw rate sensor 12, etc. Is installed. In the vehicle V, a vertical G sensor 13 for detecting the vertical acceleration of the vehicle body 1 and a stroke sensor 14 for detecting the stroke position of the damper 6 are installed for each of the wheels 3fl to 3rr.

  The main component of the automobile V is a steering gear 21 including a rack and a pinion (not shown), a steering shaft 23 with a steering wheel 22 attached to the rear end, and an EPS motor 24 that applies a steering assist force to the steering shaft 23. An EPS (Electric Power Steering) 25 is mounted, and a steering angle sensor (steering angle detecting means) 26 for detecting the steering angle of the steering wheel 22 is attached in the vicinity of the steering shaft 23. Further, an accelerator sensor 28 (depression state amount detection means) for detecting the depression amount (accelerator position) of the accelerator pedal 27 is installed in the lower part of the driver's seat of the automobile V.

  The ECU 8 includes a microcomputer, a ROM, a RAM, a peripheral circuit, an input / output interface, various drivers, and the like, and a damper for each wheel 3 via a communication line (CAN (Controller Area Network in this embodiment)). 6 and each sensor 9-14, 26, 28.

<Damper>
As shown in FIG. 2, the damper 6 of this embodiment is a monotube type (de carvone type), and a cylindrical cylinder 32 filled with MRF (Magneto-Rheological Fluid), A piston rod 33 that slides in the axial direction with respect to the cylinder 32, a piston 36 that is attached to the tip of the piston rod 33 and divides the inside of the cylinder 32 into an upper oil chamber 34 and a lower oil chamber 35, and a lower portion of the cylinder 32 The main components are a free piston 38 that defines a high-pressure gas chamber 37, a cover 39 that prevents dust from adhering to the piston rod 33 and the like, and a bump stop 40 that performs buffering during full bouncing.

  The cylinder 32 is connected to the upper surface of the suspension arm 4 that is a wheel side member via a bolt 41 that is fitted into the lower eyepiece 32a. Also, the piston rod 33 is connected to a damper base (upper part of the wheel house) 44 as a vehicle body side member through a pair of upper and lower rubber bushes 42 and a nut 43.

  The piston 36 is provided with a communication passage 45 that allows the upper oil chamber 34 and the lower oil chamber 35 to communicate with each other, and an MLV coil 46 that is positioned inside the communication passage 45. When a current is supplied from the ECU 8 to the MLV coil 46, a magnetic field is applied to the MRF flowing through the communication path 45, and the ferromagnetic fine particles form a chain cluster. As a result, the apparent viscosity of the MRF passing through the communication path 45 (hereinafter simply referred to as viscosity) increases, and the damping force of the damper 6 increases.

<Schematic configuration of damping force control device>
As shown in FIG. 3, the ECU 8 includes a damping force control device 50 that controls the damper 6. The damping force control device 50 includes the input interface 51 to which the above-described sensors 9 to 14, 26, and 28 are connected, and the roll moment, pitch moment, and sprung obtained from the detection signals of the sensors 9 to 14, 26, and 28. A damping force setting unit 52 that sets the target damping force of each damper 6 based on the speed, etc., and each damper 6 (in accordance with the target damping force input from the damping force setting unit 52 and the stroke speed Ss input from the stroke sensor 14. The drive current generator 53 generates a drive current to the MLV coil 46), and an output interface 54 outputs the drive current generated by the drive current generator 53 to each damper 6.

  The damping force setting unit 52 includes a skyhook base value calculation unit 55 that calculates a skyhook control base value Dbsh, a roll base value calculation unit 56 that calculates a roll control base value Dbr, and a pitch that calculates a pitch control base value Dbp. After the base value calculation unit 57, the turning determination unit 58 that determines whether or not the vehicle V is in a turning traveling state, the target damping force base value Dbtgt on the rear wheel side is corrected and the target damping force Dtgt is set during turning traveling. A wheel damping force correction unit 59 (target damping force setting means) is accommodated. The roll base value calculation unit 56 sets the roll control base value Dbr based on the differential value of the lateral acceleration Gy input from the lateral G sensor 10 and the second-order differential value of the yaw rate γ input from the yaw rate sensor 12. . In addition, the turning determination unit 58 determines whether or not the vehicle V is turning, based on the lateral acceleration Gy and the yaw rate γ.

<Rear wheel damping force correction unit>
As shown in FIG. 4, the rear wheel damping force correction unit 59 includes a damping force correction unit 61, a phase compensation unit 62, a correction base value calculation unit 63, a correction value setting unit 64, and a road surface μ estimation unit 65 ( Friction coefficient estimating means), a μ gain setting unit 66, and a vehicle speed gain setting unit 67.

  The phase compensation unit 62 compensates for the time phase of the accelerator position Pa input from the accelerator sensor 28 (time delay from when the accelerator pedal 27 is depressed until the rear wheel driving force is generated). Further, the correction base value calculation unit 63 obtains the depression speed Sa of the accelerator pedal 27 by second-order differentiation of the phase compensated accelerator position Pa, and then multiplies this by a predetermined coefficient, etc. The value DCb is calculated. The road surface μ estimation unit 65 estimates the friction coefficient μ of the traveling road surface based on the yaw rate γ, the steering angle δ, the vehicle speed v, and the like. Further, the μ gain setting unit 66 sets the μ gain Gμ according to the friction coefficient μ, and the vehicle speed gain setting unit 67 sets the vehicle speed gain Gv according to the vehicle speed v.

  On the other hand, the correction value setting unit 64 sets the damping force correction value DC by multiplying the damping force correction base value DCb by the μ gain Gμ and the vehicle speed gain Gv. The damping force correction unit 61 sets the target damping force Dtgt by adding the damping force correction value DC to the target damping force base value Dbtgt.

<< Operation of Embodiment >>
<Damping force control>
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. 5 at a predetermined processing interval (for example, 10 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 front and rear G sensor 11, and the vertical G sensor 13 in step S1 of FIG. The motion state of the vehicle V is determined based on the vehicle speed input from the steering angle sensor 26 and the steering angle δ input from the steering angle sensor 26. Next, the damping force control device 50 calculates the skyhook control base value Dbsh of each damper 6 in step S2 based on the motion state of the vehicle V, and calculates the roll control base value Dbr of each damper 6 in step S3. In step S4, the pitch control base value Dbp of each damper 6 is calculated.

  Next, the damping force control device 50 determines whether or not the stroke speed Ss of each damper 6 is a positive value in step S5, and if this determination is Yes (that is, the damper 6 is on the extension side). In the case of operation), the largest damping value among the three damping force control base values Dbsh, Dbr, Dbp is set as the target damping force Dtgt in step S6. Further, the damping force control device 50 determines that the three damping force base values Dbsh, Dbr, and Dbp are determined in step S7 when the determination in step S5 is No (that is, when the damper 6 is operating on the contraction side). The smallest value is set as the target damping force base value Dbtgt.

  When the target damping force base value Dbtgt is set in step S6 or step S7, the damping force control device 50 determines whether or not the vehicle V is turning based on the lateral acceleration Gy and yaw rate γ in step S8. If the determination in step S8 is No, the damping force control device 50 sets the target damping force base value Dbtgt as it is as the target damping force Dtgt in step S9, and if Yes, the rear wheel damping force described later in step S10. Correction processing is performed to set the target damping force Dtgt. When the target damping force Dtgt is set in step S9 or step S10, the damping force control device 50 searches / sets the target current Itgt corresponding to the target damping force Dtgt and the stroke speed Ss from the target current map of FIG. 6 in step S11. Thereafter, a drive current is output to the MLV coil 46 of each damper 6 in step S12.

<Rear wheel damping force correction processing>
When the vehicle V shifts to turn and the determination in step S8 in the damping force control becomes Yes, the rear wheel damping force correction unit 59 in the damping force control device 50 shows the procedure shown in the flowchart of FIG. A damping force correction process is performed. When the rear wheel damping force correction process is started, the rear wheel damping force correction unit 59 calculates the depression speed Sa of the accelerator pedal 27 based on the accelerator position Pa input from the accelerator sensor 28 in step S21 of FIG. In step S22, a damping force correction base value DCb is calculated based on the stepping speed Sa.

  Next, in step S23, the rear wheel damping force correction unit 59 is based on the yaw rate γ input from the yaw rate sensor 12, the steering angle δ input from the steering angle sensor 26, and the vehicle speed v input from the vehicle speed sensor 9. After estimating the friction coefficient μ of the traveling road surface using a vehicle model or the like, in step S24, a μ gain Gμ (a value smaller than 1) corresponding to the friction coefficient μ is retrieved from the friction coefficient-μ gain map shown in FIG. Set. Next, in step S25, the rear wheel damping force correction unit 59 is based on the vehicle speed v input from the vehicle speed sensor 9, and the vehicle speed gain Gv (value smaller than 1) corresponding to the vehicle speed v from the vehicle speed-vehicle speed gain map shown in FIG. ) Is set.

  Next, the rear wheel damping force correction unit 59 calculates a damping force correction value DC by multiplying the damping force correction base value DCb by the μ gain Gμ and the vehicle speed gain Gv in step S26. Thereafter, in step S27, the rear wheel damping force correction unit 59 sets and outputs the target damping force Dtgt by adding the damping force correction value DC to the target damping force base value Dbtgt to perform rear wheel damping force correction processing. Exit.

  In this embodiment, by adopting such a configuration, when the driver suddenly depresses the accelerator pedal 27, the target damping force Dtgt of the damper 6 increases, and the counter steer operation moves toward the outside of the turn. An effective suppression of the oversteer condition is realized by immediately generating the yaw rate. In addition, the target damping force Dtgt of the damper 6 becomes low during high-speed turning, and even if the driver depresses the accelerator pedal to increase the driving force, yaw rate toward the inside of the turn is less likely to occur, and an oversteer state is less likely to occur. Further, when turning on a low μ road, the target damping force Dtgt of the damper 6 becomes low, and even if the driver depresses the accelerator pedal to increase the driving force, it is difficult for yaw rate toward the inside of the turn to occur, and an oversteer state also occurs. It becomes difficult.

  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 is an application of the present invention to a vehicle with an FR layout, it is naturally applicable to a vehicle with an FF layout or a 4WD (4-wheel drive). In the above embodiment, the target damping force is increased according to the depression speed of the accelerator pedal. However, the target damping force may be increased according to the depression amount. In addition, as long as it does not deviate from the gist of the present invention, the specific configuration of the automobile and the control device, the specific procedure of control, and the like can be appropriately changed.

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 rear-wheel damping force correction | amendment part which concerns on embodiment. It is a flowchart which shows the procedure of damping force control which concerns on embodiment. It is a target current map concerning an embodiment. It is a flowchart which shows the procedure of the rear-wheel damping force correction process which concerns on embodiment. It is a friction coefficient-micro gain map concerning an embodiment. It is a vehicle speed-vehicle speed gain map concerning an embodiment.

Explanation of symbols

1 Body 3 Wheel 6 Damper 8 ECU
9 Vehicle speed sensor (vehicle speed detection means)
10 lateral G sensor 12 yaw rate sensor 26 steering angle sensor 28 accelerator sensor (depression state quantity detection means)
50 Damping force control device 56 Roll base value calculation unit (base value setting means)
58 Turning determination unit (turning determination means)
59 Rear wheel damping force correction unit (target damping force setting means)
61 Damping force correction unit 63 Correction base value calculation unit 64 Correction value setting unit 65 Road surface μ estimation unit (friction coefficient estimation means)
66 μ gain setting part 67 Vehicle speed gain setting part V Automobile

Claims (1)

A control device mounted on a rear wheel drive type vehicle in which a damping force variable damper is interposed between a vehicle body and a wheel, and used for damping force control of the damping force variable damper,
Base value setting means for setting a target damping force base value based on the motion state of the vehicle body;
Turning determination means for determining whether or not the vehicle is in a turning traveling state;
When the turning determination means determines that the vehicle is in a turning state, a damping force correction value is set according to at least one of the driving operation state, the traveling state, and the traveling environment of the vehicle, and the target damping force Target damping force setting means for setting the target damping force on the drive wheel side by adding the damping force correction value to the base value;
Depression state amount detection means for detecting the depression state amount of the accelerator pedal by the driver;
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
Friction coefficient estimating means for estimating the friction coefficient of the road surface,
The target damping force setting means sets a damping force correction base value so that the value is increased when the accelerator pedal depression speed detected by the depression state quantity detection means is high, while the vehicle speed detection means detects When the measured vehicle speed is higher than a predetermined value, the damping force correction base value is multiplied by a vehicle speed gain that decreases as the vehicle speed increases, and the friction coefficient detected by the friction coefficient estimating means is lower than the predetermined value. In this case, the damping force correction value is calculated by multiplying the damping force correction base value by a μ gain that becomes smaller as the friction coefficient becomes lower .

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