JP2006076319A - Variable attenuating force damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the unpleasant trembling of a vehicle body due to a nose-dive phenomenon, when a vehicle reduces speed and stops while controlling attenuating force of a damper. <P>SOLUTION: If vehicular speed becomes not more than a predetermined value immediately before reducing speed and stopping, target attenuating force of the damper 14 sky-hook controlled is corrected in a decreasing direction. Therefore, even if the target attenuating force of the damper 14 is increased so as to suppress nose-dive when the vehicle stops, by decreasing the attenuating force of the damper 14 at the moment of stopping of the vehicle, fore-and-aft vibrations of the vehicle body can be suppressed immediately after stopping of the vehicle, and incompatible feeling of an occupant can be solved. Immediately after the vehicle stops while nose-diving, the target attenuating force of the damper 14 sky-hook controlled is corrected in an increasing direction, so that trembling when the vehicle body recovers from nose-dive to a horizontal position can be promptly settled, and the incompatible feeling of the occupant can be solved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a variable damping force damper that variably controls a damping force of a damper provided in a suspension device of a vehicle according to a motion state of the vehicle by a control means.

As the viscous fluid of the variable damping force damper for the suspension device, a magnetic viscous fluid (MRF: Magneto-Rheological Fluids) whose viscosity is changed by the action of a magnetic field is adopted. Patent Document 1 below discloses a coil provided with a coil for applying a magnetic field to a magnetorheological fluid in a passage. According to this variable damping force damper, the damping force of the damper can be arbitrarily controlled by changing the viscosity of the magnetorheological fluid in the fluid passage by a magnetic field generated by energizing the coil.
JP-A-60-113711

  By the way, when the vehicle decelerates and stops, the wheels try to stop by braking, but the vehicle body keeps moving forward due to inertia, so the posture of the vehicle body is lowered and the rear of the vehicle body is raised (nose dive) Will occur. At this time, if the nose dive is suppressed by increasing the damping force of the variable damping force damper, the vertical movement of the vehicle body is suppressed. May give. In addition, when a vehicle that has stopped with a nose dive returns to a horizontal position, if the damping force of the variable damping force damper is insufficient, the pitch fluctuation of the vehicle body (nose dive swaying) will not stay indefinitely. The passenger may feel uncomfortable.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress unpleasant shaking of the vehicle body caused by a nose dive phenomenon when the vehicle decelerates and stops while controlling the damping force of the damper. .

  In order to achieve the above object, according to the first aspect of the present invention, a variable damping force that variably controls the damping force of a damper provided in the suspension device of the vehicle according to the motion state of the vehicle by the control means. In the damper, when the vehicle speed becomes a predetermined value or less immediately before the vehicle decelerates and stops, the control means corrects the target damping force of the damper determined in accordance with the motion state of the vehicle in a decreasing direction. A variable damping force damper is proposed.

  According to the second aspect of the present invention, in the variable damping force damper that variably controls the damping force of the damper provided in the vehicle suspension device in accordance with the motion state of the vehicle, the vehicle decelerates. Immediately after stopping, a variable damping force damper is proposed in which the control means corrects the target damping force of the damper determined according to the motion state of the vehicle in the increasing direction.

  The electronic control unit U of the embodiment corresponds to the control means of the present invention.

  According to the configuration of claim 1, when the vehicle speed becomes equal to or less than a predetermined value immediately before the vehicle decelerates and stops, the target damping force of the damper determined according to the motion state of the vehicle is corrected in the decreasing direction. Even if the damper's target damping force increases to suppress nose dive when the vehicle stops, reducing the damper's damping force at the moment when the vehicle stops will cause longitudinal vibration of the vehicle body immediately after the vehicle stops Can be suppressed and the sense of incongruity of the occupant can be resolved.

  According to the configuration of the second aspect, immediately after the vehicle stops while nose diving, the target damping force of the damper determined according to the motion state of the vehicle is corrected in the increasing direction. The sway when returning to the vehicle can be quickly converged to eliminate the passenger's uncomfortable feeling.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  1 to 4 show an embodiment of the present invention, FIG. 1 is a front view of a vehicle suspension device, FIG. 2 is an enlarged sectional view of a variable damping force damper, and FIG. 3 is a view showing a model of a suspension. FIG. 4 is an explanatory diagram of skyhook control.

  As shown in FIG. 1, a suspension device S that suspends a wheel W of a four-wheeled vehicle has a suspension arm 13 that supports a knuckle 12 in a vertically movable manner on a vehicle body 11, and a variable damping that connects the suspension arm 13 and the vehicle body 11. A force damper 14 and a coil spring 15 connecting the suspension arm 13 and the vehicle body 11 are provided. The electronic control unit U that controls the damping force of the damper 14 includes a signal from the sprung acceleration sensor Sb that detects the sprung acceleration, a signal from the damper displacement sensor Sc that detects the displacement (stroke) of the damper 14, and A signal from the lateral acceleration sensor Sd that detects the lateral acceleration of the vehicle and a signal from the longitudinal acceleration sensor Se that detects the longitudinal acceleration of the vehicle are input.

  As shown in FIG. 2, the damper 14 includes a cylinder 21 whose lower end is connected to the suspension arm 13, a piston 22 that is slidably fitted into the cylinder 21, and an upper wall of the cylinder 21 that extends upward from the piston 22. And a free piston 24 that is slidably fitted to the lower part of the cylinder, and is partitioned by the piston 22 inside the cylinder 21. An upper first fluid chamber 25 and a lower second fluid chamber 26 are partitioned, and a gas chamber 27 in which a compressed gas is sealed in a lower portion of the free piston 24 is partitioned.

  A plurality of fluid passages 22a are formed in the piston 22 so that the upper and lower surfaces thereof communicate with each other, and the first and second fluid chambers 25 and 26 communicate with each other through these fluid passages 22a. The magnetorheological fluid sealed in the first and second fluid chambers 25 and 26 and the fluid passages 22a is a dispersion of magnetic fine particles such as iron powder in a viscous fluid such as oil. By aligning the magnetic fine particles along the magnetic field lines, it is difficult for the viscous fluid to flow, and the apparent viscosity increases. A coil 28 is provided inside the piston 22, and energization of the coil 28 is controlled by the electronic control unit U. When the coil 28 is energized, a magnetic flux is generated as indicated by an arrow, and the viscosity of the magnetorheological fluid changes due to the magnetic flux passing through the fluid passages 22a.

  When the damper 14 contracts and the piston 22 moves downward with respect to the cylinder 21, the volume of the first fluid chamber 25 increases and the volume of the second fluid chamber 26 decreases. Passes through the fluid passage 22a of the piston 22 and flows into the first fluid chamber 25. Conversely, when the damper 14 extends and the piston 22 moves upward relative to the cylinder 21, the volume of the second fluid chamber 26 increases. Since the volume of the first fluid chamber 25 decreases, the magnetorheological fluid in the first fluid chamber 25 passes through the fluid passage 22a ... of the piston 22 and flows into the second fluid chamber 26, and at that time, the fluid passage 22a The damper 14 generates a damping force due to the viscous resistance of the magnetorheological fluid passing through.

  At this time, if the coil 28 is energized to generate a magnetic field, the apparent viscosity of the magnetorheological fluid existing in the fluid passage 22a of the piston 22 increases and it becomes difficult to pass through the fluid passage 22a. Damping force increases. The amount of increase in the damping force can be arbitrarily controlled by the magnitude of the current supplied to the coil 28.

  When a shocking compressive load is applied to the damper 14 to reduce the volume of the second fluid chamber 26, the free piston 24 descends while the gas chamber 27 is contracted to absorb the impact. Further, when a shocking tensile load is applied to the damper 14 to increase the volume of the second fluid chamber 26, the impact is absorbed by the free piston 24 rising while the gas chamber 27 is expanded. Further, when the piston 22 descends and the volume of the piston rod 23 accommodated in the cylinder 21 increases, the free piston 24 descends so as to absorb the increase in the volume.

  Thus, the electronic control unit U detects the sprung acceleration detected by the sprung acceleration sensor Sb, the damper displacement detected by the damper displacement sensor Sc, the lateral acceleration detected by the lateral acceleration sensor Sd, and the longitudinal acceleration detected by the longitudinal acceleration sensor Se. Based on the above, the damping force of each of the four dampers 14 of each wheel W is individually controlled, so that the vehicle can be prevented from being shaken when overcoming road irregularities, thereby improving the ride comfort, or when the vehicle is turning The rolling performance of the vehicle can be suppressed to improve the steering performance, and the steering performance can be improved by suppressing the pitching during sudden acceleration or deceleration of the vehicle.

  Next, based on FIG. 3 and FIG. 4, the skyhook control for suppressing the vehicle shake and enhancing the ride comfort will be described.

  As apparent from the suspension device model shown in FIG. 3, an unsprung mass 18 is connected to the road surface via a virtual spring 17 of the tire, and the unsprung mass 18 is coupled to the unsprung mass 18 via the damper 14 and the coil spring 15. 19 is connected. The damping force of the damper 14 is variable by energizing the coil 28. The rate of change dX2 / dt of the displacement X2 of the sprung mass 19 corresponds to the sprung speed obtained by integrating the sprung acceleration output detected by the sprung acceleration sensor Sb. The rate of change d (X2−X1) / dt of the difference between the displacement X2 of the sprung mass 19 and the displacement X1 of the unsprung mass 18 corresponds to a damper speed obtained by differentiating the output of the damper displacement sensor Sc.

dX2 / dt × d (X2−X1) / dt> 0
In other words, when the sprung speed and the damper speed are in the same direction (same sign), the damper 14 is controlled to increase the damping force. on the other hand,
dX2 / dt × d (X2−X1) / dt ≦ 0
In this case, that is, when the sprung speed and the damper speed are in opposite directions (reverse signs), the damper 14 is controlled in a direction to decrease the damping force.

  Therefore, considering the case where the wheel W passes over the protrusion on the road surface as shown in FIG. 4, the vehicle body 11 moves upward while the wheel W ascends along the first half of the protrusion as shown in (1). The sprung speed (dX2 / dt) becomes a positive value, the damper 14 is compressed, and the damper speed d (X2-X1) / dt becomes a negative value. Controlled to reduce damping force.

  Also, as shown in (2), immediately after the wheel W passes over the top of the protrusion, the vehicle body 11 still moves upward due to inertia, and the sprung speed (dX2 / dt) becomes a positive value. Since the damper 14 is extended and the damper speed d (X2-X1) / dt becomes a positive value, the damper 14 is controlled to have the same sign and increase the damping force in the extension direction.

  Further, as shown in (3), while the wheel W descends along the latter half of the protrusion, the vehicle body 11 moves downward and the sprung speed (dX2 / dt) becomes a negative value. Since the damper 14 is extended faster and the damper speed d (X2-X1) / dt becomes a positive value, both are reversed in sign and the damper 14 is controlled to reduce the damping force in the extension direction. Is done.

  Further, as shown in (4), immediately after the wheel W completely gets over the protrusion, the vehicle body 11 still moves downward due to inertia, the sprung speed (dX2 / dt) becomes a negative value, and the wheel W decreases. By stopping, the damper 14 is compressed and the damper speed d (X2−X1) / dt becomes a negative value. Therefore, the damper 14 is controlled to have the same sign and increase the damping force in the compression direction. .

  When the traveling vehicle decelerates and stops, the wheel W is braked and tries to stop, but the vehicle body 11 keeps moving forward due to inertia, so the front part of the vehicle body 11 is lowered and the rear part of the vehicle body 11 is A so-called nose dive is generated. At this time, the front part of the vehicle body descends and the sprung speed (dX2 / dt) becomes a negative value, and the damper 14 of the front wheel is compressed and the damper speed d (X2-X1) / dt becomes a negative value. The damping force of the damper 14 is increased by skyhook control in the same manner as in the state shown in 4 (4). On the other hand, the rear part of the vehicle body rises and the sprung speed (dX2 / dt) becomes a positive value, and the damper 14 of the rear wheel is extended and the damper speed d (X2-X1) / dt becomes a positive value. The damping force of the damper 14 is increased by the skyhook control as in the state shown in (2). That is, when the traveling vehicle decelerates and stops, the nose dive of the vehicle body 11 is suppressed by increasing all the damping forces of the four-wheel dampers 14 to improve the riding comfort.

  In this way, when the vehicle decelerates and stops, if all the damping forces of the four-wheel dampers 14 are increased to suppress the nose dive of the vehicle body 11, the dampers 14 become stiff and the vehicle body 11 is moved in the vertical direction. Since movement is suppressed, vibration in the front-rear direction may occur at the moment when the vehicle stops, giving a sense of discomfort to the passenger. Therefore, in the present embodiment, when the vehicle speed becomes equal to or less than a predetermined value immediately before the vehicle decelerates and stops, a command value of the damping force of the dampers 14 for skyhook control (coil 28) is given by a command from the electronic control unit U. Is reduced in the decreasing direction, and the damping force of the dampers 14 at the moment when the vehicle stops is reduced. Thereby, the vibration in the front-rear direction of the vehicle body 11 at the moment when the vehicle stops can be prevented, and the discomfort of the occupant can be eliminated. Since the above-described reduction control of the damping force of the dampers 14 is performed immediately before the vehicle stops, it hardly affects the suppression of the nose dive by the skyhook control.

  Even if the skyhook control is performed, it is difficult to completely suppress the nose dive when the vehicle is stopped, and the nose dive vehicle body 11 is shaken in the pitch direction to return to the horizontal posture. At this time, if the damping force of the dampers 14 is kept reduced, the swaying of the vehicle body 11 will not converge indefinitely, giving the passenger a sense of incongruity. Therefore, in this embodiment, when the vehicle stops, the command value of the damping force (target current of the coil 28) of the dampers 14 for skyhook control is corrected in the increasing direction by the command from the electronic control unit U. The damping force of the dampers 14 after the vehicle stops is increased. Thereby, the shake of the vehicle body 11 due to the nose dive turning back can be quickly converged, and the discomfort of the occupant can be eliminated.

  Although the embodiments of the present invention have been described above, various design changes can be made without departing from the scope of the present invention.

  For example, in the embodiment, the damping force decrease control of the dampers 14 immediately before the vehicle stops and the damping force increase control of the dampers 14 after the vehicle stops are performed, but only one of them is performed. You can go.

  In the embodiment, the dampers 14 are subjected to the skyhook control, but the control is not limited to the skyhook control as long as the control is performed to suppress the vehicle shake and increase the ride comfort.

  In the embodiment, the damping force of the dampers 14 is variably controlled using a magnetorheological fluid, but any method for variably controlling the damping force is arbitrary.

Front view of vehicle suspension system Expanded sectional view of variable damping force damper Diagram showing suspension model Illustration of skyhook control

Explanation of symbols

14 Damper S Suspension device U Electronic control unit (control means)

Claims (2)

In the variable damping force damper that variably controls the damping force of the damper (14) provided in the suspension device (S) of the vehicle according to the motion state of the vehicle by the control means (U),
When the vehicle speed becomes equal to or less than a predetermined value immediately before the vehicle decelerates and stops, the control means (U) corrects the target damping force of the damper (14) determined in accordance with the motion state of the vehicle in a decreasing direction. Characteristic variable damping force damper. In the variable damping force damper that variably controls the damping force of the damper (14) provided in the suspension device (S) of the vehicle according to the motion state of the vehicle by the control means (U),
Immediately after the vehicle decelerates and stops, the control means (U) corrects the target damping force of the damper (14) determined according to the motion state of the vehicle in the increasing direction, and the variable damping force damper is characterized in that .

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