JP2009168057A - Adjustable damping force damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lower a strength of an adjustable damping force damper while securing maneuvering stability and comfort of a vehicle. <P>SOLUTION: As adjustable damping force of the adjustable damping force damper has its maximum valve within a low piston speed area in which the piston speed is not less than 0.1 m/s and less than 0.3 m/s, the maneuvering stability is secured by enhancing the total damping force of basic damping force and the adjustable damping force in the low piston speed area and suppressing change in a rolling attitude and change in a pitch attitude of the vehicle. Not only securing the comfort of the vehicle but also preventing excessive load from being applied on the damper are provided by preventing the total damping force from being excessive in a high piston speed area, which lowers the strength of the damper to perform simplification of the structure, reduction in weight, downsizing, and cost reduction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention includes a damping force control mechanism that can variably control a damping force generated by a piston that moves in a cylinder as the wheel moves up and down, and the damping force control mechanism increases as the piston speed increases. The present invention relates to a variable damping force damper that controls the magnitude of a variable damping force added to a basic damping force.

  In general, to improve the ride comfort of the vehicle, it is preferable to set the damping force generated in the damper low. To suppress the change in the posture of the vehicle and improve steering stability, set the damping force generated in the damper high. It is known to be preferred.

  Also, a variable damping force damper that makes the magnitude of the damping force variable by adsorbing a magnetized attracting member with an electromagnetic coil and changing the diameter of the orifice is known from Patent Document 1 below.

In the variable damping force damper that attenuates the vibration of the suspension of the vehicle, the damping force is set to increase linearly in the region where the piston speed is 0 m / s to 2 m / s, and in the region where the piston speed is 2 m / s or more. It is known from Patent Document 2 below that the damping force is set to increase nonlinearly.
JP-A-10-184755 Special table 2007-508501 gazette

  By the way, what is described in Patent Document 1 described above is that the damping force increases rapidly from 0 in the low piston speed region as the piston speed increases, and attenuates in the high piston speed region as the piston speed increases. The force is controlled to increase slowly. Therefore, if setting is made so that a high damping force is generated in the low piston speed region, the damping force becomes excessively high in the high piston speed region. Therefore, it is necessary to design the variable damping force damper with a high strength so that it can withstand a high damping force, and there is a problem in that the weight, size, and cost increase.

  Moreover, although what was described in the said patent document 2 differs in the magnitude | size of damping force in the area | region where the piston speed is less than 2 m / s, and the area | region more than 2 m / s, this inventor etc. An experiment was conducted to measure the piston speed of a damper that changes according to the condition of the road surface. As a result, it was found that the normal use range of the piston speed is about 1 m / s, and it rarely reaches 2 m / s. did. Therefore, even if the damping force is set to increase nonlinearly in the region where the piston speed is 2 m / s or more, such a high piston speed rarely actually occurs, and the characteristics of the damping force are effective. It is thought that it cannot be used for this.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to reduce the strength of a variable damping force damper while ensuring steering stability and riding comfort of a vehicle.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a damping force control mechanism capable of variably controlling the damping force generated by the piston that moves in the cylinder as the wheel moves up and down. The damping force control mechanism is a variable damping force damper that controls the magnitude of the variable damping force that is added to the basic damping force that increases as the piston speed increases. The damping force control mechanism has a piston speed of 0. A variable damping force damper is proposed in which the variable damping force is controlled so as to have a maximum value in a region of 1 m / s or more and less than 0.3 m / s.

  According to the invention described in claim 2, in addition to the configuration of claim 1, the damping force control mechanism is configured such that the piston speed is 0.3 m / s or more in response to an increase in piston speed. A variable damping force damper characterized by gradually reducing the variable damping force to zero is proposed.

  According to the invention described in claim 3, in addition to the configuration of claim 2, the damping force control mechanism reduces the variable damping force to 0 in a region exceeding the piston speed at which the variable damping force becomes 0. A variable damping force damper is proposed, which is characterized by maintaining the above.

  According to the configuration of claim 1, the variable damping force of the variable damping force damper has the maximum value in the low piston speed region where the piston speed is 0.1 m / s or more and less than 0.3 m / s. Steering stability can be ensured by increasing the total damping force of the basic damping force and the variable damping force in the region to suppress changes in the vehicle roll posture and pitch posture. Moreover, by preventing the total damping force from becoming excessive in the region of high piston speed, not only can the ride comfort of the vehicle be secured, but also the damper can be prevented from being overloaded. By reducing the strength, the structure can be simplified, the weight can be reduced, the dimensions can be reduced, and the cost can be reduced.

  According to the second aspect of the present invention, the variable damping force gradually decreases to 0 as the piston speed increases in the region of a high piston speed of 0.3 m / s or higher, so that the piston speed is 0.3 m / s or higher. It is possible to prevent the total damping force from increasing in the middle piston speed range from when the variable damping force becomes zero, and to ensure the riding comfort of the vehicle.

  According to the third aspect of the present invention, the variable damping force is maintained at 0 in the region exceeding the piston speed at which the variable damping force becomes zero. Therefore, in the region of the high piston speed after the variable damping force becomes zero. The damping force can be made equal to the basic damping force, and an excessive load can be prevented from being applied to the damper.

  Embodiments of the present invention will be described below based on the embodiments of the present invention shown in the accompanying drawings.

  1 to 7 show a first 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. FIG. 4 is a sectional view taken along line 3-3 in FIG. 4, FIG. 4 is a sectional view taken along line 4-4 in FIG. 3, FIG. 5 is an explanatory diagram of the action corresponding to FIG. FIG. 7 is a graph showing the relationship between the piston speed and the damping force of the damper.

  First, the structure of the variable damping force damper will be described with reference to FIGS.

  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. A signal from a damper displacement sensor Sa that detects the displacement (stroke) of the damper 14 is input to the electronic control unit U that controls the damping force of the damper 14. The electronic control unit U controls the magnitude of the damping force generated in the damper 14 based on the piston speed obtained by time-differentiating the displacement of the damper 14.

  As shown in FIG. 2, the damper 14 slides on the cylinder 22 having a lower end connected to the suspension arm 13, an upper end plate 23 and a lower end plate 24 that respectively close the upper end and the lower end of the cylinder 22, and the cylinder 22. A piston 25 that fits freely, a piston rod 27 that extends upward from the piston 25 and penetrates the seal member 26 provided on the upper end plate 23 in a liquid-tight manner, and has an upper end connected to the vehicle body 11, and a lower portion of the cylinder 22 And a free piston 28 that is slidably fitted to the housing.

  An upper first fluid chamber 29 and a lower second fluid chamber 30 partitioned by a piston 25 are defined inside the cylinder 22, and the first and second fluid chambers 29 and 30 are oil-like. Filled with a viscous fluid. A gas chamber 32 filled with high-pressure gas is defined at the lower portion of the free piston 28.

  As shown in FIGS. 3 and 4, the piston 25 including the damping force variable mechanism 31 includes a piston body 36 fixed to the piston rod 27 with a nut 35 via a pair of upper and lower washers 33 and 34. A central portion of a first valve plate 37 in which a magnetic shape memory alloy is formed in a disc shape is fixed between the upper surface of the piston body 36 and the washer 33, and between the lower surface of the piston body 36 and the washer 34. A central portion of the second valve plate 38 in which the magnetic shape memory alloy is formed in a disc shape is fixed. Four fluid passages 39, 39; 40, 40 pass through the outer periphery of the piston main body 36 at intervals of 90 °, and the two first fluid passages 39, 39 are arranged at both ends in the diametrical direction, and the other two fluid passages 39, 39; The two second fluid passages 40, 40 are disposed at both ends in the diametrical direction shifted by 90 °.

  The second valve plate 38 has through holes 38a and 38a facing the lower ends of the first fluid passages 39 and 39, and the first valve plate 37 has through holes 37a and 37a facing the upper ends of the second fluid passages 40 and 40. Is formed. Further, four stopper pins 41 for restricting the closed positions of the first valve plate 37 and the second valve plate 38 are arranged on the outer peripheral portion of the piston main body 36.

  An annular coil 44 is embedded in the piston main body 36 radially inward of the first and second fluid passages 39, 39; 40, 40 so as to surround the piston rod 27, and the coil 44 is connected to the electronic control unit U. The power supply is controlled by being connected to. The magnetic shape memory alloy is deformed by a magnetic field. When the coil 44 is demagnetized, the first valve plate 37 and the second valve plate 38 are flat, and when the coil 44 is excited, the first valve plate 37 is excited. The second valve plate 38 tends to be deformed so as to bend toward the piston body 36. However, since the first valve plate 37 and the second valve plate 38 abut against the stopper pins 41 cannot be bent toward the piston body 36, the first valve plate 37 and the second valve plate 38 are closed in the valve closing direction. A set load that urges the load is generated.

  Next, the operation of the first embodiment having the above configuration will be described.

  As shown in FIG. 3, when the damper 14 contracts and the piston 25 moves downward relative to the cylinder 22 when the coil 44 is not excited, the volume of the first fluid chamber 29 increases and the second fluid chamber 30 increases. Therefore, the viscous fluid in the second fluid chamber 30 passes through the through holes 38a and 38a of the second valve plate 38 and flows into the first fluid passages 39 and 39. Then, as shown in FIG. 5, the viscous fluid that has flowed into the first fluid passages 39 and 39 pushes up the lower surface of the first valve plate 37 to open the valve, so that the viscous fluid flows from the second fluid chamber 30 to the first fluid passage. The damper 14 moves to the first fluid chamber 29 through 39, 39, and the damper 14 generates a damping force by the flow resistance of the viscous fluid at that time.

  Thus, the damping force of the damper 14 generated when the coil 44 is not excited is called a basic damping force, and the magnitude of the damping force is indicated by the broken line in FIG. Increases in a quadratic function as the number increases.

  As shown in FIG. 6, when the coil 44 is energized by a command from the electronic control unit U, a set load in the valve closing direction is generated as the first valve plate 37 is deformed downward by the magnetic field generated by the coil 44. Even if the damper 14 contracts and the piston 25 moves downward relative to the cylinder 22, the first valve plate 37 is difficult to open, and the damping force of the damper 14 increases accordingly.

  In FIG. 7, the damping force indicated by the solid line is the total damping force generated by the damper 14, and the difference between the damping force indicated by the solid line and the damping force indicated by the broken line (basic damping force) The variable damping force increases. In the present embodiment, the variable damping force is controlled so as to change according to the piston speed.

  When a shocking compressive load is applied to the damper 14 to reduce the volume of the second fluid chamber 30, the free piston 28 descends while the gas chamber 32 is contracted to absorb the impact. When a shocking tensile load is applied to the damper 14 to increase the volume of the second fluid chamber 30, the impact is absorbed by the free piston 28 rising while the gas chamber 32 is expanded. Furthermore, when the piston 25 descends and the volume of the piston rod 27 accommodated in the inner cylinder 22 increases, the free piston 28 descends so as to absorb the increased volume.

  The case where the piston 25 is moved downward has been described above. However, when the piston 25 is moved upward, the roles of the first valve plate 37 and the second valve plate 38 are interchanged, and the piston 25 is moved downward. Similarly to the case, the flow of the viscous fluid passing through the second fluid passages 40 and 40 can be adjusted, and the damping force of the damper 14 can be arbitrarily controlled.

  In FIG. 7, the magnitude of the variable damping force suddenly rises from 0 as the piston speed increases, reaches a maximum value near the piston speed = 0.2 m / s, and then the piston speed = 1.3 m / s. It gradually decreases until it becomes 0 in the vicinity of s, and is maintained at 0 as it is. The total damping force obtained by adding the basic damping force and the variable damping force also gradually decreases from the vicinity of the piston speed = 0.2 m / s to the vicinity of the piston speed = 1.3 m / s. In the present invention, the piston speed at which the variable damping force is maximized is set so that the variable damping force has a maximum value in a low piston speed region of 0.1 m / s or more and less than 0.3 m / s.

  As described above, the variable damping force of the damper 14 has the maximum value in the low piston speed region where the piston speed is 0.1 m / s or more and less than 0.3 m / s, that is, in the normal traveling state where the frequency of occurrence is the highest. In this region, the total damping force of the basic damping force and the variable damping force can be increased to suppress changes in the vehicle roll posture and pitch posture, thereby ensuring the steering stability of the vehicle.

  Also, in the region where the variable damping force exceeds 0, the total damping force is equivalent to the basic damping force, so that an excessive load is prevented from being applied to the damper 14 and the strength of the damper 14 is reduced. Simplification of the structure, weight reduction, size reduction, and cost reduction can be achieved.

  Next, a second embodiment of the present invention will be described with reference to FIG.

  In the first embodiment shown in FIG. 7, after the total damping force of the damper 14 reaches the maximum value, the total damping force gradually decreases in the middle piston speed region until the variable damping force becomes zero. However, in the second embodiment shown in FIG. 8, the total damping force is kept constant in the region of the medium piston speed.

  Next, a third embodiment of the present invention will be described with reference to FIG.

  In the first embodiment shown in FIG. 7, the variable damping force of the damper 14 is finally zero, but in the third embodiment shown in FIG. 9, the variable damping force of the damper 14 is zero. After becoming close to a small value, the small value is maintained.

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

  For example, the structure of the damping force variable mechanism 31 that variably controls the damping force of the damper 14 is not limited to the embodiment, and an arbitrary structure can be selected.

1 is a front view of a vehicle suspension device according to a first embodiment. Expanded sectional view of variable damping force damper FIG. 3 is an enlarged view of part 3 of FIG. 2 and is a cross-sectional view taken along line 3-3 of FIG. Sectional view taken along line 4-4 in FIG. Action diagram corresponding to FIG. 3 (when not excited) Action diagram corresponding to FIG. 3 (when excited) Graph showing the relationship between piston speed and damper damping force Graph corresponding to FIG. 7 according to the second embodiment Graph corresponding to FIG. 7 according to the third embodiment

Explanation of symbols

22 Cylinder 25 Piston 31 Damping force control mechanism W Wheel

Claims (3)

A damping force control mechanism (31) capable of variably controlling the damping force generated by the piston (25) moving inside the cylinder (22) as the wheel (W) moves up and down is provided, and the damping force control mechanism (31 ) Is a variable damping force damper that controls the magnitude of the variable damping force added to the basic damping force that increases as the piston speed increases.
The damping force control mechanism (31) controls the variable damping force so that the variable damping force has a maximum value in a region where the piston speed is 0.1 m / s or more and less than 0.3 m / s. .   2. The damping force control mechanism (31) according to claim 1, wherein the variable damping force is gradually reduced to 0 as the piston speed increases in a region where the piston speed is 0.3 m / s or more. Variable damping force damper.   The variable damping force damper according to claim 2, wherein the damping force control mechanism (31) maintains the variable damping force at 0 in a region exceeding a piston speed at which the variable damping force becomes 0. .

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