JP2006321259A - Adjustable damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adjustable damper capable of securing damping performance on a spring and while effectively damping under the spring when riding over a stage difference in a road face. <P>SOLUTION: In the case wherein the product of damper displacement and damper speed of a damper of a suspension device for a vehicle exceeds the predetermined threshold value, since damping force of the damper is controlled on the basis of the product of the damper displacement and the damper speed, damping performance on the spring can be secured and while vibration under the spring caused when riding over a large stage difference can be effectively restricted by accurately grasping vibrating condition under the spring. Even in the case of combining with other control, interference with other control can be prevented by controlling in the only case wherein both the damper displacement and damper speed increase together like a case of riding over a stage difference and wherein it is necessary to damp under the spring. Since the damper displacement detected by a damper displacement detecting means is differentiated to detect damper speed, the number of detecting means can be reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

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, and the fluid is applied to the piston that is slidably fitted into the cylinder. 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.

The sprung speed obtained by integrating the sprung acceleration detected by the sprung acceleration sensor is compared with the damper speed obtained by differentiating the damper displacement detected by the damper displacement sensor, and the damping force of the damper is controlled according to the magnitude relationship. Thus, it is known from Patent Document 2 below to improve the riding comfort performance and the steering stability performance by suppressing the unsprung vibration while suppressing the primary resonance on the spring.
JP-A-60-113711 JP-A-9-39534

  By the way, in the conventional skyhook control for the purpose of vibration suppression of the sprung behavior, the damping force of the damper is controlled based on the sprung acceleration, so input from the unsprung state is made, and the level difference of the road surface is reduced. It was not possible to generate a large damping force that converges vibrations input from under the spring when getting over.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to enable effective vibration suppression under a spring when overcoming a step on a road surface while ensuring vibration suppression performance on the spring. .

  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. The damper includes a damper displacement detecting means for detecting a damper displacement and a damper speed detecting means for detecting a damper speed, and the control means controls a damping force of the damper based on a product of the damper displacement and the damper speed. A variable damping force damper is proposed.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect, the control means is configured to provide a damper based on the product when the product of the damper displacement and the damper speed exceeds a predetermined threshold value. A variable damping force damper characterized by controlling the damping force is proposed.

  According to a third aspect of the present invention, in addition to the configuration of the first aspect, the damper speed detecting means performs differential processing on the damper displacement detected by the damper displacement detecting means to detect the damper speed. A characteristic variable damping force damper is proposed.

  The electronic control unit U of the embodiment corresponds to the control means of the present invention, the differentiator 16 of the embodiment corresponds to the damper speed detection means of the present invention, and the damper displacement sensor Sb of the embodiment corresponds to the damper displacement of the present invention. Corresponds to the detection means.

  According to the configuration of the first aspect, the damping force of the damper provided in the vehicle suspension device is controlled based on the product of the damper displacement detected by the damper displacement detecting means and the damper speed detected by the damper speed detecting means. Therefore, while ensuring the vibration suppression performance on the spring, it is possible to accurately grasp the vibration state under the spring and to effectively suppress the unsprung vibration that occurs when overcoming a large step.

  According to the configuration of claim 2, when the product of the damper displacement and the damper speed exceeds a predetermined threshold value, the damping force of the damper is controlled based on the product. By performing this control only when the damper displacement and the damper speed, such as overcoming the vehicle, are both increased and the unsprung vibration control is required, interference with other controls can be prevented.

  According to the third aspect of the present invention, the damper speed detecting means differentiates the damper displacement detected by the damper displacement detecting means to detect the damper speed, so that both the damper displacement and the damper speed are detected from the output of the damper displacement detecting means. It can be obtained and the number of detection means can be reduced.

  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 7 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 the skyhook control, FIG. 5 is a graph showing the vibration transmissibility in the skyhook control, FIG. 6 is a diagram showing an area for performing unsprung vibration suppression control, and FIG. 7 is a damper for the culvert road and the choppy road. It is a graph which shows the actual value of speed x damper displacement.

  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, 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. The The electronic control unit U includes a differentiator 16 that differentiates the damper displacement detected by the damper displacement sensor Sb to detect the damper speed. Thus, the damper displacement detected by the damper displacement sensor Sb is differentiated by the differentiator 16 to detect the damper speed, so that both the damper displacement and the damper speed can be obtained from the output of the damper displacement sensor Sb. The number of detection means can be reduced.

  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.

  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. Further, based on the longitudinal acceleration detected by the longitudinal acceleration sensor Se, the damping force of a total of four dampers 14 of each wheel W is individually controlled, so that the vehicle can be prevented from shaking when getting over the road surface unevenness. Select ride comfort control, such as skyhook control that enhances ride comfort, and steering stability control that suppresses rolling during turning of the vehicle and pitching during sudden acceleration or deceleration of the vehicle according to the driving state of the vehicle. To run.

  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 the damper speed obtained by differentiating the output of the damper displacement sensor Sb by the differentiator 16.

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. .

  Incidentally, as shown in FIG. 5, in the above-described skyhook control, even if the control gain is changed, the vibration transmissibility in the vicinity of 1 Hz which is the sprung resonance frequency only changes, and the vicinity of 10 Hz which is the unsprung resonance frequency. There is a problem that the vibration transmissibility of the motor cannot be controlled.

  Therefore, paying attention to the product of the damper speed and the damper displacement as an index to grasp and control the vibration in the unsprung resonance region, especially when the damper speed and the damper displacement are large, (proportional constant) x (damper speed) x ( The unsprung control current calculated by the damper displacement) is added to the target current of the skyhook control to obtain the final target current of the damper 14. As a result, it is possible to suppress vibration in the unsprung resonance region in the vicinity of 10 Hz, independently of the skyhook control.

Control of the damping force of the damper 14 based on the product of the damper speed and the damper displacement sets a predetermined threshold A,
Damper speed x Damper displacement ≥ A
6 is performed, that is, in the region outside the four hyperbolas in the graph of FIG. 6, and normal skyhook control is performed in the region inside. The areas outside the four hyperbolas include culvert roads that require unsprung resonance control, capital high-speed step roads, part of EC roads, etc., and the areas inside the four hyperbolas do not require unsprung resonance control Choppy roads (when the vehicle speed is high) and bounce roads (when the damper displacement is high).

  FIG. 7 is a graph in which the damper speed × damper displacement is measured for the culvert road (solid line) and the choppy road (broken line), and it is possible to reliably identify the ride over the seam on the road surface of the culvert road using the damper speed × damper displacement as an index. I understand.

  As described above, when the product of the damper displacement and the damper speed exceeds the predetermined threshold A, the damping force of the damper 14 is controlled based on the product of the damper displacement and the damper speed. It is possible not only to effectively suppress unsprung vibration that occurs when overcoming a large level difference, but also to suppress unsprung vibration even when combined with other controls such as skyhook control. Interference with other controls can be prevented by performing this control only when necessary.

  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, although the damper speed is detected by differentiating the damper displacement detected by the damper displacement sensor Sb in the embodiment, a sensor for directly detecting the damper speed may be provided.

Front view of vehicle suspension system Expanded sectional view of variable damping force damper Diagram showing suspension model Illustration of skyhook control Graph showing vibration transmissibility in skyhook control The figure which shows the field which performs unsprung damping control Graph showing measured values of damper speed x damper displacement for culvert road and choppy road

Explanation of symbols

14 Damper 16 Differentiator (Damper speed detection means)
S suspension device Sb damper displacement sensor (damper displacement detection means)
U Electronic control unit (control means)

Claims (3)

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),
Damper displacement detecting means (Sb) for detecting the damper displacement, and damper speed detecting means (16) for detecting the damper speed,
The variable damping force damper, wherein the control means (U) controls a damping force of the damper (14) based on a product of a damper displacement and a damper speed.   The control means (U) controls the damping force of the damper (14) based on the product when the product of the damper displacement and the damper speed exceeds a predetermined threshold value. The variable damping force damper described. The variable damping force damper according to claim 1, wherein the damper speed detecting means (16) detects the damper speed by differentiating the damper displacement detected by the damper displacement detecting means (Sb).

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