JP4690759B2 - Control device for variable damping force damper - Google Patents

Description

  The present invention relates to a control device for a variable damping force damper that variably controls a damping force of a damper provided in a vehicle suspension device in accordance with a motion state of a vehicle.

  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.

Also, set the damping force of the damper higher when the sprung speed and damper speed of the suspension device are the same direction, and set the damping force of the damper lower when the sprung speed and the damper speed are opposite directions. When the absolute value of the sprung speed is less than the threshold, the damper's damping force is set to a medium level and the ride performance and steering stability performance are improved. It is known from Patent Document 2 below to achieve both of the above.
JP-A-60-113711 Japanese Utility Model Publication No. 5-54010

  By the way, as described in the above-mentioned Patent Document 2, when the absolute value of the sprung speed is less than the threshold value and the skyhook control is not performed, the damping force of the damper is set to a constant value. Both performance and ride performance could not always be satisfied.

  Therefore, when the absolute value of the sprung speed is less than the threshold value and the skyhook control is not performed, the damping force of the damper is not set to a constant value, but is increased according to the increase of the steering angular speed, thereby It is conceivable to achieve both stable performance and ride comfort performance. However, if the damping force of the damper is increased in accordance with the increase of the steering angular velocity, the damping damping force rises slowly at the beginning of the turn, and rolling cannot be effectively suppressed, and the steering stability performance is degraded. There is a concern that it will.

  The present invention has been made in view of the above circumstances, and an object thereof is to satisfy both steering stability performance and riding comfort performance by accurately and variably controlling the damping force of the damper of the suspension device.

In order to achieve the above object, according to the first aspect of the present invention, the damping force of the damper provided in the vehicle suspension device is determined according to the steering angular speed when the absolute value of the sprung speed is less than the threshold value. variable control, and also when the absolute value of the sprung speed is above the threshold comprises a control means for performing skyhook control, wherein, when the absolute value of the sprung speed is less than the threshold value, the steering angular velocity is defined The damping force of the damper is set to 0 until reaching the value, and when the steering angular velocity becomes a specified value or more, the damping force of the damper is increased so that it increases linearly as the steering angular velocity increases. a control device for a variable damping force damper for setting the damping force value determined in accordance with the steering angular velocity, said control means, an absolute value of the sprung speed in the case of less than the threshold value, the steering angle Degree is a predetermined time from the time when it becomes less than the prescribed value, proposes a damping force of the damper, the control device of the variable damping force damper, characterized in that said set larger than the damping force value determined in accordance with the steering angular velocity Is done.

  According to the invention described in claim 2, in addition to the configuration of claim 1, the control means sets the damping force of the damper according to the steering angular speed when performing the skyhook control. A control device for a variable damping force damper is proposed.

  The electronic control unit U of the embodiment corresponds to the control means of the present invention, and the minimum specified value of the embodiment corresponds to the specified value of the present invention.

According to the configuration of the first aspect, in the region where the absolute value of the sprung speed is less than the threshold value and the influence on the riding comfort is small, the damping force of the damper is variably controlled according to the steering angular speed, and the steering angular speed is specified. The damping force of the damper is set to 0 until the value reaches the value, and when the steering angular velocity exceeds a specified value, the damping force of the damper is increased linearly as the steering angular velocity increases. Since the damping force value determined according to the steering angular velocity is set larger than the damping force value determined according to the steering angular velocity for a predetermined time after the steering angular velocity becomes equal to or higher than the specified value, The handling stability of the vehicle can be improved. In addition, in a region where the absolute value of the sprung speed is equal to or greater than the threshold value and the influence on the ride comfort is great, the ride comfort can be ensured by performing the skyhook control.

  Also, if the damping force of the damper slowly increases with the increase of the steering angular velocity immediately after the steering angular velocity exceeds the specified value, the damping force of the damper will be insufficient and the rolling of the vehicle immediately after the start of turning will be sufficiently suppressed. However, the rolling force of the vehicle immediately after the start of the turn is effectively suppressed by setting the damping force of the damper larger than the value determined according to the steering angular speed for a predetermined time after the steering angular speed becomes equal to or higher than the specified value. As a result, the steering stability performance can be ensured.

  According to the second aspect of the present invention, the damping force of the damper is set according to the steering angular velocity when the steering angular velocity is equal to or higher than the predetermined value and the skyhook control is performed. The stability control and the skyhook control can be basically made common, and the occupant's uncomfortable feeling when switching between the two controls can be eliminated.

  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 8 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, FIG. 5 is an explanatory diagram of separation of skyhook control and steering stability control, FIG. 6 is a graph showing changes in steering angle and steering angular velocity at the time of lane change, and FIG. FIG. 8 is a graph showing changes in the damping force output ratio with respect to time.

  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 Sa that detects the sprung acceleration, a signal from the damper displacement sensor Sb that detects the displacement (stroke) of the damper 14, and A signal from the steering angle sensor Sc that detects the steering angle of the vehicle and a signal from the lateral acceleration sensor Sd that detects the lateral 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 increase amount of 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.

  Therefore, the electronic control unit U detects the sprung acceleration detected by the sprung acceleration sensor Sa, the damper displacement detected by the damper displacement sensor Sb, the steering angle detected by the steering angle sensor Sc, and the lateral acceleration detected by the lateral acceleration sensor Sd. Based on the above, by controlling the damping force of each of the four dampers 14 of each wheel W individually, such as skyhook control that increases the ride comfort by suppressing the vehicle swaying when overcoming the road surface unevenness Ride comfort control and steering stability control that suppresses rolling during turning of the vehicle and pitching during sudden acceleration and deceleration of the vehicle are selectively executed according to the driving state 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 Sa. 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 Sb.

dX2 / dt × d (X2−X1) / dt> 0
In this case, that is, 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 reduce 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.

  Also, as shown in (4), immediately after the wheel W has completely passed over the protrusion, the vehicle body 11 still moves downward due to inertia, and the sprung speed (dX2 / dt) becomes negative, and the wheel W is lowered. 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. .

  The horizontal axis and the vertical axis in FIG. 5 are the damper speed and the sprung speed, respectively, and the damping force of the damper 14 increases in the first quadrant and the third quadrant by the above-described skyhook control, and the second quadrant and the fourth quadrant. Thus, the damping force of the damper 14 decreases. However, skyhook control to improve ride comfort performance is performed when the absolute value of the sprung speed is greater than or equal to the threshold value, that is, when the vehicle moves greatly up and down over the road surface unevenness. When the value is less than the threshold value (refer to the shaded area), steering stability control that suppresses rolling and pitching of the vehicle is performed instead of the above-described skyhook control.

  When the vehicle performs a lane change, the steering wheel is operated in one direction in the first half and the steering wheel is operated in the other direction in the second half. Therefore, as shown in FIG. 6, the steering angle θ detected by the steering angle sensor Sc is It changes to a sine curve. The electronic control unit U calculates a steering angular velocity θ ′ obtained by time-differentiating the steering angle θ. FIG. 6 shows the minimum prescribed value and the maximum prescribed value of the steering angular velocity θ ′ set according to the vehicle speed. In FIG. 4, when the absolute value of the sprung speed is less than the threshold value, that is, when the skyhook control is not performed, the steering stability control is performed when the steering angular velocity θ ′ exceeds the minimum prescribed value at point a in FIG. Is started.

As shown in FIG. 7, the damping force output ratio ( ratio of the damping force output value to the maximum output value) is set to 0 until the steering angular velocity θ ′ reaches the minimum specified value, and the steering angular velocity θ ′ is set to the maximum specified value. When the value is exceeded, the damping force output ratio is set to 1, and while the steering angular velocity θ ′ increases from the minimum side specified value toward the maximum side specified value, the damping force output ratio increases linearly from 0 to 1. When the damping force output ratio is 1, the damper 14 generates the maximum damping force. Therefore, when the steering angular velocity θ ′ increases from the minimum side specified value toward the maximum side specified value, the damping force of the damper 14 set to 0 until the steering angular velocity θ ′ reaches the specified value becomes the damping force output ratio. The value increases from 0 to the maximum value in accordance with the increase of.

  In FIG. 6, when the steering angular velocity θ ′ reaches the minimum specified value at the point a at the initial stage of operating the steering wheel to change the lane, the steering stability control is started from that moment, and the damping force of the damper 14 rises. When the steering angular velocity θ ′ reaches the maximum steering angular velocity θ′max (see point b), which is the first peak value, the damping force output ratio α at that time (see FIG. 7) regardless of the subsequent change in the steering angular velocity θ ′. ) Is continuously output to suppress rolling and pitching of the vehicle.

  FIG. 8 shows the change of the damping force with respect to the time axis. When the steering angular velocity θ ′ reaches the minimum side specified value at time T1, the damping force output ratio of the damper 14 instantaneously rises to the maximum value 1 at that moment, and the maximum value 1 is maintained for a predetermined time (40 msec in the embodiment). Is done. When the predetermined time elapses at time T2, the damping force output ratio once decreases and then gradually increases with a value proportional to the steering angular velocity θ ′. When the steering angular velocity θ ′ reaches the maximum steering angular velocity at time T3, the damping at that time A damping force corresponding to the force output ratio is continuously output.

  When the skyhook control is performed when the absolute value of the sprung speed is equal to or greater than the threshold value in the first quadrant and the third quadrant of FIG. 5, the damping force of the damper 14 is controlled in the increasing direction. In the first quadrant and the third quadrant, when the absolute value of the sprung speed increases or decreases across the threshold, the skyhook control and the steering stability control are switched. In the first quadrant and the third quadrant of FIG. In both stable controls, the damping force of the damper 14 is controlled in the increasing direction. In this embodiment, when the skyhook control is performed when the absolute value of the sprung speed is greater than or equal to the threshold value, the damping force is set to be proportional to the steering angular velocity θ ′. In this way, by making the magnitude of the damping force of the damper 14 common to both the skyhook control and the steering stability control, that is, by setting both the damping forces to be proportional to the steering angular velocity θ ′, An occupant's uncomfortable feeling when switching between control and steering stability control can be eliminated.

  As described above, when the absolute value of the sprung speed is less than the threshold value and the steering stability control is performed, the damping force of the damper 14 is set according to the steering angular velocity θ ′ without maintaining a constant value. By generating a small damping force when the steering angular velocity θ ′ is small and generating a large damping force when the steering angular velocity θ ′ is large, not only the steering stability performance but also the riding comfort performance can be ensured.

  Further, in both skyhook control and steering stability control, the magnitude of the damping force of the damper 14 is determined based on the steering angular velocity θ ′. Steering stability control can be performed in a region where the absolute value of is less than the threshold value, and the control law can be simplified.

  Immediately after the steering angular velocity θ ′ becomes equal to or greater than the minimum prescribed value, the damping force output ratio of the damper 14 is set to a maximum value (damping force output ratio = 1) larger than the value determined according to the steering angular velocity θ ′. Therefore, immediately after the start of turning, the damping force of the damper 14 can be quickly increased, and the rolling of the vehicle can be effectively suppressed to ensure the steering stability performance. In addition, the predetermined time during which the damping force output ratio of the damper 14 is set to the maximum value is set to a necessary minimum length, and after the predetermined time has elapsed, the damping force of the damper 14 is increased according to an increase in the steering angular velocity θ ′. By increasing it, ride comfort performance can be secured.

  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 predetermined time during which the damping force output ratio of the damper 14 is maintained at the maximum value 1 after the steering angular velocity θ ′ reaches the minimum specified value is set to 40 msec. Can be set as appropriate.

  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 Illustration of separation of skyhook control and steering stability control Graph showing changes in steering angle and steering angular velocity during lane change Graph showing change in damping force output ratio with respect to steering angular velocity Graph showing the change in damping force output ratio over time

14 Damper S Suspension device U Electronic control unit (control means)
θ ′ Steering angular velocity

Claims (2)

The damping force of the suspension apparatus of a vehicle damper provided in (S) (14), when the absolute value of the sprung speed is less than the threshold value variably controlled according to the steering angular velocity (θ '), also the absolute sprung speed Control means (U) for performing skyhook control when the value is greater than or equal to the threshold is provided , and the control means (U) defines the steering angular velocity (θ ′) when the absolute value of the sprung speed is less than the threshold. Until the value reaches the value, the damping force of the damper (14) is set to 0, and when the steering angular velocity (θ ′) exceeds a specified value, the damping force of the damper (14) becomes the steering angular velocity (θ A control device for a variable damping force damper that is set to a damping force value determined in accordance with the steering angular velocity (θ ′) so as to increase linearly in accordance with an increase in ′),
When the absolute value of the sprung speed is less than the threshold value, the control means (U) reduces the damping force of the damper (14) for a predetermined time after the steering angular speed (θ ′) becomes equal to or greater than a specified value. , the steering angular velocity (theta ') variable damping force control apparatus of the damper, characterized in that said set larger than the damping force value determined in accordance with. The control means (U)
The variable damping force damper control device according to claim 1, wherein when performing the skyhook control, the damping force of the damper (14) is set according to the steering angular velocity (θ ').

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