JP4972440B2 - 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 achieving both ride comfort and steering stability when traveling on a road where there is a large and small vertical displacement.

  2. Description of the Related Art In recent years, various types of cylinder dampers used in automobile suspensions have been developed in which a damping force variable damper capable of variable damping force control is installed in order to improve ride comfort and handling stability. In vehicles equipped with variable damping force dampers, the direction of the vertical speed of the vehicle and the vertical speed of the wheels relative to the vehicle coincided based on the Skyhook theory in order to suppress the vertical movement of the vehicle when traveling on rough roads. In such a case, a control method is known in which the damping force is reduced and the damping force is increased when the directions of the two vertical speeds conflict (see Patent Document 1).

In an automobile adopting such a control method, when overcoming a relatively small bump, as shown in FIG. 11, when the wheel 3 rides on the bump b, the damping force of the damping force variable damper 4 becomes small. The rise of the vehicle body 1 due to thrusting is suppressed (a), and when the wheel 3 approaches the apex of the bump b, the damping force is increased to suppress the increase of the vehicle body 1 due to inertia (b). When descending from the bump b, the damping force is reduced, so that the lowering of the vehicle body 1 following the wheel 3 is suppressed (c), and when the wheel 3 is completely lowered from the bump b onto the flat road, the damping force is increased. This suppresses the lowering of the vehicle body 1 due to inertia (d). As a result, compared to the case where a damper having a constant damping force is used, the vertical movement of the vehicle body 1 is significantly reduced, so that the riding comfort is improved.
JP-A-4-334614

  However, when the control method of Patent Document 1 is adopted, for example, when overcoming a large bump, a state in which the damping force becomes small continues for a relatively long time, so that the distance between the vehicle body and the wheel becomes small while ascending the bump. In some cases, the distance between the vehicle body and the wheel becomes too large while going down the bump. In this case, there is a problem that the suspension alignment greatly changes from the state when running on a flat road, and the steering stability deteriorates depending on the suspension type. In addition, when the damping force variable damper makes a full stroke on the bounce side or the rebound side, there is a possibility that a margin for absorbing small unevenness on the road surface is lost and riding comfort and the like may be reduced.

  The present invention has been made in view of such a background, and provides a damping force variable damper control device that achieves both steering stability and riding comfort when traveling on a road with large and small vertical displacements. With the goal.

The invention according to claim 1 is a control device for a damping force variable damper that is used for damping relative vibration between a vehicle body and a wheel, wherein a value related to a moving speed of the wheel in a vertical direction with respect to a road surface is determined as a road surface vertical speed. Road surface vertical speed detecting means for detecting the road surface vertical speed, and a target damping force setting means for setting a load catch control target value of the damping force variable damper by multiplying the road surface vertical speed by a predetermined load catch control gain. Features.

According to a second aspect of the present invention, in the damping force variable damper control device according to the first aspect, the stroke speed detecting means for detecting the stroke speed of the variable damping force damper, and the absolute value of the stroke speed is large. The load catch control target value correcting means for correcting the load catch control target value by increasing the load catch control gain is further included.

According to a third aspect of the present invention, in the damping force variable damper control device according to the first or second aspect, the vehicle body vertical speed detecting means for detecting the vehicle vertical speed as the vehicle vertical speed, and the damping force Stroke speed detecting means for detecting the stroke speed of the variable damper, and the target damping force setting means sets a skyhook control target value by multiplying the vehicle body vertical speed and the stroke speed by a predetermined gain. One of the load catch control target value and the skyhook control target value having a larger value is set as the target damping force.
According to a fourth aspect of the present invention, in the damping force variable damper control device according to the third aspect, the vibration of the damping force variable damper caused by the unevenness of the traveling road surface based on the detection result of the stroke speed detecting means. Damper vibration frequency detecting means for detecting a frequency as a damper vibration frequency, and the target damping force setting means sets a skyhook control target value as a target damping force when the damper vibration frequency exceeds the resonance frequency of the vehicle body. It is characterized by doing.

  According to the first aspect of the present invention, for example, even when an automobile gets over a relatively large bump, the damping force is not reduced easily, and a large change in suspension alignment is suppressed. According to the second and third aspects of the present invention, when the damper vibrates at a vibration frequency exceeding the resonance frequency of the vehicle body when traveling on an irregular road, the damping force is reduced, and the vertical movement of the wheel is reduced. It is difficult for the vehicle to be transmitted to the vehicle, and the decrease in ride comfort 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 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, in the vehicle V, a lateral G sensor 10 that detects lateral acceleration, a longitudinal G sensor 11 that detects longitudinal acceleration, and the like are installed at appropriate positions of the vehicle body 1, and a stroke sensor 12 that detects the displacement of the damper 4; A vertical G sensor 13 for detecting vertical acceleration in the vicinity of the wheel house is 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 10-13.

<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.

  As shown in FIG. 3, the piston 26 is provided with an annular communication passage 39 that communicates the upper oil chamber 24 and the lower oil chamber 25, and an MLV coil 40 that is disposed inside the annular communication passage 39. Yes. 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.

<Schematic configuration of damper control device>
The ECU 7 includes a damper control device 50 whose schematic configuration is shown in FIG. The damper control device 50 includes an input interface 51 to which the above-described sensors 10 to 13 and the like are connected, and a damping force setting unit that sets a target damping force of each damper 4 based on detection signals input from the sensors 10, 11, and 13. 52, a target damping force selection unit 53 that selects one of the target damping forces input from the damping force setting unit 52 based on the detection result of the stroke sensor 12, and a target damping selected by the target damping force selection unit 53 The drive current generator 54 generates a drive current to each damper 4 (MLV coil 40) according to the force and the detection result of the stroke sensor 12, and outputs the drive current generated by the drive current generator 54 to each damper 4. Output interface 55.

  The damping force setting unit 52 accommodates a skyhook control unit 56 that is used for skyhook control and a load catch control unit (target damping force setting means) 57 that is used for load catch control. The damping force setting unit 52 also accommodates a roll control unit and a pitch control unit used for roll control and pitch control, and performs damping force control based on the roll control target value and the pitch control target value. Since the explanation becomes complicated, these are not mentioned in the present embodiment.

<< Operation of Embodiment >>
When the automobile starts running, the damper control device 50 executes damping force control whose procedure is shown in the flowchart of FIG. 4 at a predetermined processing interval (for example, 10 ms). When the damping force control is started, the damper control device 50 detects the acceleration of the vehicle body 1 obtained from the lateral G sensor 10, the longitudinal G sensor 11, and the vertical G sensor 13 in step S1 of FIG. 1), the motion state of the automobile V is determined based on the vehicle speed input from the steering angle sensor (not shown), the steering speed input from the steering angle sensor, and the like.

  Next, the damper control device 50 sets the skyhook control target value Dsh of each damper 4 based on the motion state of the automobile V in step S2. The skyhook control target value Dsh is the vertical speed of the vehicle body 1 (vehicle vertical speed) calculated from the detection results of the stroke sensor 12 and the vertical G sensor 13, and the stroke speed of the damper 4 calculated from the detection results of the stroke sensor 12. It is set by multiplying Ss by a predetermined gain, and becomes smaller when the direction of the vertical speed of the vehicle body and the direction of the vertical speed of the wheel 3 with respect to the vehicle body 1 coincide (low damping force). Increased when conflicting (high damping force). When the damping force is high, the damping force is made proportional to the vertical speed of the vehicle body to reduce the switching sound and the uncomfortable feeling.

  Next, the damper control device 50 calculates the load catch control target value Drc of each damper 4 in step S3. The load catch control target value Drc is obtained by calculating the vertical speed of the vehicle body 1 calculated from the detection results of the stroke sensor 12 and the vertical G sensor 13 and the vertical speed of the wheel 3 relative to the vehicle body 1 calculated from the detection results of the stroke sensor 12. It is set by multiplying the vertical speed (road surface vertical speed) of the wheel 3 obtained by summing by a predetermined load catch control gain. The load catch control gain is retrieved from the damper contraction gain map shown in FIG. 5 when the road surface vertical speed is positive (when the damper 4 is in the contraction direction), and when the road surface vertical speed is negative (the damper 4 is extended). If it is in the direction), it is retrieved from the gain map at the time of extension of the damper shown in FIG. As shown in FIGS. 5 and 6, the load catch gain is 0 in the region where the stroke position and the stroke speed Ss of the damper 4 are small. This is because the stroke of the damper 4 is near the center position, or This is because it is not necessary to perform load catch control when the stroke position is moving near the center even if it is away from the vicinity.

  When the calculation of the skyhook control target value Dsh and the load catch control target value Drc is finished in steps S2 and S3, the damper control device 50 has a damper with a vibration frequency equal to or higher than the sprung resonance frequency (eg, 1.3 Hz) in step S4. It is determined whether or not 4 is vibrating (that is, whether or not the automobile V is traveling on a road with small unevenness). In the case of the present embodiment, the vibration frequency of the damper 4 is a point in time when the stroke speed Ss of the damper 4 exceeds either one of positive and negative threshold values (shown by a broken line in FIG. 7) as shown in FIG. Is calculated as the reciprocal of a value obtained by doubling this elapsed time t1. When the stroke speed Ss of the damper 4 does not exceed the threshold value even after the half period t2 of the sprung resonance frequency has elapsed since the stroke speed Ss finally exceeded the threshold value, the damper control device 50 It is determined that the vibration at the upper resonance frequency or more has subsided (the small unevenness on the road surface has been eliminated).

  If the determination in step S4 is Yes, the damper control device 50 selects the skyhook control target value Dsh as the target damping force Dtgt in step S5. This is because when the load catch control is performed when traveling on an irregular road, the damping force of the damper 4 is increased, so that the vertical movement of the wheel 3 is transmitted to the vehicle body 1 and the riding comfort is deteriorated. On the other hand, when the determination in step S4 is No, the damper control device 50 selects the larger one of the two control target values Dsh and Drc as the target damping force Dtgt in step S6. When the selection of the target damping force is completed in step S5 or step S6, the damper control device 50 determines the target driving current from the driving current map of FIG. 8 based on the target damping force Dtgt and the stroke speed Ss of the damper 4 in step S7. In step S8, a drive current is output to the MLV coil 40 of each damper 4.

  FIG. 9 is an explanatory diagram illustrating the behavior of the vehicle body when the load catch control is performed. As shown in the figure, by performing the load catch control, when the wheel 3 rides on the bump b, the damping force of the damper 4 increases, thereby improving the followability of the wheel 3 to the road surface (a ) When the wheel 3 approaches the apex of the bump b, the damping force is reduced, so that the lifting of the wheel 3 due to the rise of the vehicle body 1 is suppressed (b), and when the wheel 3 descends from the bump b When the damping force is increased, the followability of the wheel 3 to the road surface is improved (c), and when the wheel 3 has descended from the bump b to the flat road, the damping force is reduced to reduce the wheel 3 to the road surface. (D). As a result, the grounding property of the wheel 3 with respect to the road surface is improved as compared with the case where a damper having a constant damping force is used.

  On the other hand, FIG. 10 is a one-wheel model diagram showing the behavior of the automobile V according to the embodiment when overcoming bumps. When the vehicle V gets over a relatively small bump b (left side in FIG. 8), the load catch gain is zero in the region where the absolute value of the stroke position and the stroke speed Ss of the damper 4 is small as described above. The target value Dsh is selected as the target damping force Dtgt. Therefore, the damping force of the damper 4 changes in the same flow as in the conventional device described above, and the vertical movement of the vehicle body 1 is extremely effectively suppressed.

  Further, when the automobile V gets over a relatively large bump B (right side in FIG. 8), the absolute value of the stroke position and the stroke speed Ss of the damper 4 is increased, so that the load catch gain is set to a high value (that is, the load). The catch control target value Drc is increased), and the load catch control target value Drc is selected as the target damping force Dtgt. As a result, the damping force of the damper 4 increases both in the upward and downward gradients of the bump B, so that the expansion and contraction of the damper 4 is greater than in the case of only skyhook control (indicated by a two-dot chain line in FIG. 7). Almost never occurs. As a result, a large change in suspension alignment, which has been a problem with conventional devices, is suppressed, making it difficult for steering stability and ride quality to deteriorate.

  Although description of specific embodiment is finished above, the aspect of the present invention is not limited to the above embodiment. For example, in the above embodiment, the vertical speed of the wheel is used as the vertical speed of the road surface, but a differential value (acceleration) thereof may be used, or an integrated value of the vertical acceleration of the wheel may be used. In the above embodiment, the larger one of the skyhook control target value and the load catch control target value is selected (high selected). However, each of the skyhook control target value and the load catch control target value is selected. A method such as multiplication by a predetermined gain and addition may be adopted. In the above embodiment, the control is performed based on the stroke speed of the damper. However, the vertical acceleration of the vehicle body may be used instead of the stroke speed. In the above embodiment, the skyhook control is performed when the damper vibrates with a vibration frequency equal to or higher than the sprung resonance frequency. However, the load catch control target value is multiplied by a predetermined reduction gain before loading. You may make it perform catch control. In that case, the load catch control target value may be reduced for each wheel, or if at least two wheels vibrate the damper, the load catch control target value for all the wheels. May be reduced. In addition, the specific configuration of the control device, the specific procedure of the control, 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 flowchart which shows the procedure of damping force control which concerns on embodiment. It is a gain map at the time of damper contraction concerning an embodiment. It is a gain map at the time of damper extension concerning an embodiment. It is a graph which shows the change of the stroke speed at the time of driving concerning an embodiment. It is a drive current map concerning an embodiment. It is explanatory drawing which shows a vehicle body behavior when load catch control is performed. It is a 1-wheel model figure which shows the behavior at the time of bump over of the motor vehicle based on embodiment. It is explanatory drawing which shows a vehicle body behavior when skyhook control is performed.

Explanation of symbols

1 Car body 3 Wheel 4 Damping force variable damper 5 Suspension 7 ECU
12 Stroke Sensor 13 Vertical G Sensor 50 Damper Control Device 52 Damping Force Setting Unit 53 Target Damping Force Selection Unit (Selection Unit)
56 Skyhook control unit (first base value setting means)
57 Load catch control section (second base value setting means)
B Bump b Bump V Car

Claims (4)

A control device for a damping force variable damper used for damping relative vibration between a vehicle body and a wheel,
A road surface vertical speed detecting means for detecting a value related to a moving speed in the vertical direction with respect to the road surface of the wheel as a road surface vertical speed;
A damping force variable damper control device comprising target damping force setting means for setting a load catch control target value of the damping force variable damper by multiplying the road surface vertical speed by a predetermined load catch control gain. . Stroke speed detection means for detecting the stroke speed of the damping force variable damper;
The load catch control target value correcting means for correcting the load catch control target value by increasing the load catch control gain as the absolute value of the stroke speed increases , further comprising: The control device for the described damping force variable damper. Vehicle body vertical speed detection means for detecting the vehicle vertical speed as the vehicle vertical speed;
Stroke speed detecting means for detecting the stroke speed of the damping force variable damper;
Further comprising
The target damping force setting means sets a skyhook control target value by multiplying the vehicle body vertical speed and the stroke speed by a predetermined gain, and among the load catch control target value and the skyhook control target value, The control device for a variable damping force damper according to claim 1 or 2, wherein a value having a large value is set as a target damping force. Based on the detection result of the stroke speed detection means, further comprising a damper vibration frequency detection means for detecting a vibration frequency of the damping force variable damper caused by unevenness of the running road surface as a damper vibration frequency,
The variable damping force according to claim 3, wherein the target damping force setting means sets a skyhook control target value as a target damping force when the damper vibration frequency exceeds a resonance frequency of the vehicle body. Damper control device.

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