JP2006077787A - Variable damping force damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compensate for a change in damping force of a variable damping force damper caused by variable viscosity of a viscous fluid due to a temperature change. <P>SOLUTION: In a damper 14 of a suspension device of an automobile, a fluid passage 22a is provided in a piston 22 slidably fitted to a cylinder 21 filled with a magnetic viscous fluid, and the fluid passage 22a is provided with a coil 28 for generating a magnetic field, whereby the apparent viscosity of the magnetic viscous fluid is varied by applying an electric current to the coil 28 to arbitrarily control the damping force. At a low temperature causing increase in viscosity of the magnetic viscous fluid, an electric current is applied to the coil 28 to generate heat, and the magnetic viscous fluid is heated to return to an ordinary viscosity, thereby compensating for a change in viscosity of the viscous fluid due to temperature so that the damping force of the damper 14 can be precisely controlled. The current application to the coil 28 to heat the magnetic viscous fluid is performed at the time of stopping not to worsen the ride quality of the vehicle. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, a cylinder filled with a viscous fluid is partitioned into a first fluid chamber and a second fluid chamber by a piston, and the first fluid chamber and the second fluid chamber are formed by a fluid passage formed so as to penetrate the piston. The present invention relates to a variable damping force damper communicated with each other.

In such a variable damping force damper, a magnetorheological fluid (MRF: Magneto-Rheological Fluids) whose viscosity is changed by the action of a magnetic field is adopted, and the magnetorheological fluid in the fluid passage is fitted to a piston slidably fitted in the cylinder. A variable damping force damper for a suspension device provided with a coil for causing a magnetic field to act on is known from Patent Document 1 below. 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

  However, since the viscosity of the conventional fluid increases when the temperature of the viscous fluid decreases at low temperatures, the viscous fluid becomes difficult to pass through the fluid passage of the piston, and the damping force of the damper becomes higher than the target value. is there. In particular, since this tendency is strong in the magnetorheological fluid, the damping force of the damper becomes excessive at low temperatures, which may impair the riding comfort of the vehicle.

  The present invention has been made in view of the above circumstances, and an object thereof is to compensate for a change in the damping force of a variable damping force damper due to a change in viscosity of a viscous fluid due to a temperature change.

  To achieve the above object, according to the first aspect of the present invention, the interior of the cylinder filled with the viscous fluid is partitioned by the piston into the first fluid chamber and the second fluid chamber so as to penetrate the piston. In the variable damping force damper in which the first fluid chamber and the second fluid chamber communicate with each other through the formed fluid passage, temperature detecting means for detecting the temperature of the viscous fluid, and temperature variable means for changing the temperature of the viscous fluid There is proposed a variable damping force damper comprising control means for controlling the temperature variable means based on the temperature detected by the temperature detection means.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect, the viscous fluid is a magnetorheological fluid whose viscosity is changed by the action of a magnetic field, and the temperature varying means is a magnetic fluid in the fluid passage. A variable damping force damper is proposed, which is a coil that applies a magnetic field to a viscous fluid.

  According to a third aspect of the invention, in addition to the configuration of the second aspect, the variable damping force damper is for a vehicle suspension device, and controls the temperature variable means based on the temperature detected by the temperature detection means. A variable damping force damper is proposed, which is performed while the vehicle is stopped.

  The magnetorheological fluid of the embodiment corresponds to the viscous fluid of the present invention, the temperature sensor Sa of the embodiment corresponds to the temperature detecting means of the present invention, and the electronic control unit U of the embodiment corresponds to the control means of the present invention. The coil 28 of the embodiment corresponds to the temperature variable means of the present invention.

  According to the configuration of the first aspect, the piston having the fluid passage is slidably fitted to the cylinder, and the first and second fluid chambers defined on both sides of the piston are communicated with each other through the fluid passage of the piston, thereby reducing the damping force. When the fluid is generated, the control means controls the temperature variable means to change the temperature of the viscous fluid based on the temperature of the viscous fluid detected by the temperature detection means, so that the change in the viscosity of the viscous fluid due to the temperature is compensated. Thus, the damping force of the variable damping force damper can be accurately controlled.

  According to the configuration of the second aspect, since the magnetorheological fluid whose viscosity is changed by the action of the magnetic field is adopted as the viscous fluid, the viscosity of the magnetorheological fluid in the fluid passage of the piston is generated by energizing the coil to generate the magnetic field. The damping force can be arbitrarily controlled by changing. Focusing on the fact that heat is generated when the coil is energized, and using this coil as a temperature variable means makes it possible to eliminate the need for special heat generating means such as a heater and reduce the number of components and installation space.

  According to the configuration of claim 3, in the variable damping force damper used for the suspension device of the vehicle, the coil is energized while the vehicle is stopped based on the temperature of the magnetorheological fluid detected by the temperature detecting means. It is possible to avoid energizing the coil for heat generation while the vehicle is running and thereby increasing the damping force of the damper unnecessarily, thereby preventing the ride comfort of the vehicle from being lowered.

  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 and 2 show an embodiment of the present invention. FIG. 1 is a front view of a vehicle suspension device, and FIG. 2 is an enlarged sectional view of a variable damping force damper.

  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 temperature sensor Sa that detects the temperature of the magnetorheological fluid sealed in the damper 14 and a sprung acceleration sensor Sb that detects the sprung acceleration. A signal, a signal from a damper displacement sensor Sc that detects the displacement (stroke) of the damper 14, a signal from a lateral acceleration sensor Sd that detects the lateral acceleration of the vehicle, and a 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.

  By the way, at low temperatures, the viscosity of the magnetorheological fluid decreases and the viscosity increases, so that it becomes difficult to pass through the fluid passages 22a of the piston 22, and the damping force of the damper 14 becomes larger than the target value, so Stability performance may be reduced. In such a case, the control gain of the damping force control of the damper 14 by the electronic control unit U is corrected in a decreasing direction according to the temperature of the magnetorheological fluid detected by the temperature sensor Sa, and the damping force of the damper 14 is excessive. Correct so that it does not become.

  In parallel with this, the magnetorheological fluid is positively heated to raise its temperature, whereby the viscosity is raised to an allowable value and normal damping force is generated in the damper 14. A coil 28 provided on the piston 22 is used as a heat source at this time. That is, when the temperature of the magnetorheological fluid detected by the temperature sensor Sa is less than a predetermined value, the coil 28 is energized by the command from the electronic control unit U to generate heat, and the heat is used to heat the magnetorheological fluid to the temperature. Raise. In this case, if the coil 28 is energized while the vehicle is running, the damping force of the damper 14 is further increased, which may adversely affect the riding comfort performance and the steering performance of the vehicle. Energization of the coil 28 is performed only when the vehicle is stopped.

  When the vehicle travels on a rough road, the frequency of energization of the coil 28 of the damper 14 increases, so that the magnetorheological fluid rises relatively quickly due to its heat generation. However, when the vehicle travels continuously on a flat straight road, the coil 28 of the damper 14 is less frequently energized, so it takes a long time for the magnetorheological fluid to rise in temperature. The present embodiment is particularly effective in such a case. For example, if the coil 28 is energized to increase the temperature of the magnetorheological fluid between the time when the ignition switch is turned on and the time when the vehicle starts, immediately after starting. Therefore, it is possible to generate an appropriate damping force on the damper 14 to ensure the ride performance and the steering performance of the vehicle.

  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 damper 14 for the automobile suspension apparatus S has been described. However, the variable damping force damper according to the invention described in claim 1 can be applied to any application other than the automobile suspension apparatus, and It is not limited to the one using a magnetorheological fluid. When using a general viscous fluid that is not a magnetorheological fluid, the damping force can be arbitrarily controlled by changing the opening degree of the fluid passage provided in the piston with a control valve. Furthermore, in the invention described in claim 1, instead of energizing the coil 28, the temperature of the magnetorheological fluid can be increased by energizing a heater or the like.

  In the embodiment, the temperature of the magnetorheological fluid is directly detected by the temperature sensor Sa, but the temperature of the magnetorheological fluid may be estimated from the output of the outside air temperature sensor or the output of the engine water temperature sensor.

Front view of vehicle suspension system Expanded sectional view of variable damping force damper

Explanation of symbols

21 Cylinder 22 Piston 22a Fluid passage 25 First fluid chamber 26 Second fluid chamber 28 Coil (Temperature variable means)
S suspension device Sa temperature sensor (temperature detection means)
U Electronic control unit (control means)

Claims (3)

The fluid passage formed so that the inside of the cylinder (21) filled with the viscous fluid is partitioned by the piston (22) into the first fluid chamber (25) and the second fluid chamber (26), and penetrates the piston (22). 22a), in the variable damping force damper in which the first fluid chamber (25) and the second fluid chamber (26) communicate with each other.
A temperature detecting means (Sa) for detecting the temperature of the viscous fluid, a temperature variable means (28) for changing the temperature of the viscous fluid, and a temperature variable means (28) based on the temperature detected by the temperature detecting means (Sa). A variable damping force damper comprising control means (U) for controlling.   The viscous fluid is a magnetorheological fluid whose viscosity is changed by the action of a magnetic field, and the temperature variable means (28) is a coil for applying a magnetic field to the magnetorheological fluid in the fluid passage (22a), The variable damping force damper according to claim 1. The variable damping force damper is for a suspension device (S) of a vehicle, and control of the temperature variable means (28) based on the temperature detected by the temperature detection means (Sa) is performed while the vehicle is stopped. The variable damping force damper according to claim 2.

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