JP2018069949A - Dynamic damper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamic damper capable of easily obtaining a sufficient vibration damping effect even at the time of minute amplitude vibration of an unsprung member. A dynamic damper (1) provides resistance to a weight (2), a spring element (3) interposed between an unsprung member (L) of the vehicle (V) and the weight (2), and a flow of working fluid contained therein, thereby reducing the weight of the weight (2). And a damping element 4 that exhibits a damping force for suppressing vibration. The damping element 4 is set such that when the stroke speed is less than the predetermined speed, hysteresis due to the elasticity of the hydraulic fluid is larger than when the stroke speed is higher than the predetermined speed. [Selection] Figure 1

Description

  The present invention relates to a dynamic damper.

  Conventionally, it is known that when a dynamic damper is used to suppress vibration of an unsprung member in a vehicle (unsprung vibration), the ride comfort of the vehicle can be improved (for example, Patent Document 1). This is because the dynamic damper includes a weight that vibrates in synchronization with the unsprung member and suppresses the vibration of the unsprung member by applying the inertial force of the weight as a reaction force. This is because it is possible to make the structure not transmitted to the upper member.

JP 2003-014037 A

  The dynamic damper includes a weight and a spring element that elastically supports the weight, and adds the mass of the weight to the unsprung member that is the object of vibration suppression via the spring element. . In the dynamic damper, the mass of the weight, the spring constant of the spring element, etc. are designed so that the natural frequency can obtain the optimum vibration damping effect according to the natural frequency of the unsprung member to be controlled. ing.

  The unsprung member that is the object of vibration suppression includes a wheel and an arm that positions the wheel while supporting the wheel so as to move up and down. Generally, a rubber bush is provided on the mounting portion of the arm so that the arm can move to some extent other than the swinging direction (up and down).

  However, the movement of the arm may deteriorate due to the influence of the rubber bush or the like. In such a case, the unsprung member behaves as if the natural frequency has increased when the stroke amount of the unsprung member is very small. In this way, when the natural frequency of the unsprung member becomes apparently higher and the substantial natural frequency exceeds the assumed frequency, a deviation occurs between the vibration frequency of the unsprung member and the vibration frequency of the dynamic damper. In this case, it is impossible to obtain a sufficient damping effect by the dynamic damper.

  Note that the natural frequency of the unsprung member returns as expected during normal vibration when the amount of movement of the arm (stroke amount of the unsprung member) increases to some extent. For this reason, the vibration frequency of the unsprung member deviates from the vibration frequency of the dynamic damper due to the influence of the rubber bush or the like, which is a temporary phenomenon that is limited to the case of small amplitude vibration. However, in order to obtain a consistently excellent unsprung vibration damping effect, it is preferable to change the natural frequency of the dynamic damper according to the amplitude of the unsprung member. Specifically, the natural frequency of the dynamic damper may be set so as to increase only when the unsprung member vibrates slightly.

  The natural frequency of the dynamic damper is mainly determined by the spring constant of the spring element and the mass of the weight. For this reason, the spring constant of the spring element of the dynamic damper may be given an amplitude dependency. However, when the spring element is constituted by a spring such as a coil spring, a disc spring, a leaf spring, etc., the spring constant of the spring is unsprung. It is difficult to increase only when the member vibrates slightly. This is because the stroke amount of the dynamic damper at the time of minute amplitude vibration affected by a rubber bush or the like is extremely small.

  Therefore, an object of the present invention is to provide a dynamic damper that can easily obtain a sufficient vibration damping effect even when the unsprung member vibrates with a small amplitude.

  The dynamic damper that solves the above problem includes a damping element that exerts a damping force that suppresses vibration of the weight by applying resistance to the flow of the working fluid contained therein. The damping element is set such that when the stroke speed is less than the predetermined speed, hysteresis due to the elasticity of the hydraulic fluid is larger than when the stroke speed is higher than the predetermined speed. Since the hysteresis acts as a spring component in the hydraulic damping element, according to the above configuration, the natural frequency of the dynamic damper can be easily increased when the stroke speed is less than the predetermined speed. Therefore, it is possible to suppress the deviation of the vibration frequency of the unsprung member and the vibration frequency of the dynamic damper during the minute amplitude vibration of the unsprung member.

  In the dynamic damper, when the stroke speed is less than the predetermined speed, the damping coefficient of the damping element is set to be large, and the hysteresis may be increased by increasing the damping coefficient. According to this configuration, it is possible to easily increase the hysteresis when the stroke speed is less than the predetermined speed.

  According to the dynamic damper of the present invention, a sufficient vibration damping effect can be easily obtained even when the unsprung member vibrates with a small amplitude.

It is the front view which showed a part of vehicles provided with the dynamic damper concerning one embodiment of the present invention simply. It is a conceptual diagram which shows the vibration model of the suspension which provided the dynamic damper which concerns on one embodiment of this invention. It is the longitudinal cross-sectional view which expanded and showed a part of damping element of the dynamic damper which concerns on one embodiment of this invention. It is the figure which showed the characteristic of the damping force of the damping element of the dynamic damper which concerns on one embodiment of this invention. It is the figure which showed the relationship between the damping coefficient of the damping element of the dynamic damper which concerns on one embodiment of this invention, and hysteresis.

  Embodiments of the present invention will be described below with reference to the drawings. The same reference numerals given throughout the several drawings indicate the same or corresponding parts.

  As shown in FIG. 1, a dynamic damper 1 according to an embodiment of the present invention is mounted on a vehicle V such as a four-wheeled vehicle, and suppresses vibration of an unsprung member L (unsprung vibration). It is used.

  Although detailed illustration of the vehicle V is omitted, the vehicle V includes a vehicle body B, wheels W disposed on the front, rear, left and right of the vehicle body B, one end rotatably connected to the vehicle body B, and the like. An arm A whose end is connected to the wheel W and supports the wheel W so as to move up and down is provided, and a suspension spring S and an actuator D interposed between the arm A and the vehicle body B. The dynamic damper 1 according to the present embodiment is attached to the arm A.

  The actuator D is an electric cylinder device, and includes an outer shell d1 and a rod d2 that goes in and out of the outer shell d1, and is driven to extend and contract by a control device (not shown) mounted on the vehicle V.

  The suspension spring S is a coil spring, is disposed on the outer periphery of the actuator D, and is interposed between the outer shell d1 and the rod d2. The suspension spring S exhibits an elastic force corresponding to the amount of compression, and the elastic force acts in the direction of pushing up the vehicle body B. For this reason, the vehicle body B can be elastically supported by the suspension spring S. In the vehicle V, the member including the vehicle body B and the like supported by the suspension spring S is the sprung member U, and the member including the wheel W and the arm A hanging from the suspension spring S is the unsprung member L.

  Further, when the actuator D exerts a thrust in the extending direction, the thrust acts in a direction in which the sprung member U and the unsprung member L are separated. On the other hand, when the actuator D exerts a thrust in the contraction direction, the thrust acts in a direction in which the sprung member U and the unsprung member L approach each other. For example, when a sensor for detecting the vertical speed of the sprung member U is provided, and the thrust of the actuator D is controlled by the control device based on the Skyhook theory based on the information detected by the sensor, the actuator D is The vibration of the sprung member U can be effectively suppressed by functioning like a hook damper.

  It goes without saying that a control law other than the skyhook control law may be used to suppress the vibration of the sprung member U. Moreover, the structure of the suspension spring S and the actuator D can also be changed suitably. For example, the suspension spring S is a coil spring, but may be an air spring. The actuator D is a direct acting cylinder device, but may be a motor. In this case, the actuator is provided on the rotating shaft portion of the arm or the like. Furthermore, the actuator D may be replaced with a damper. In this case, the damper may be a hydraulic damper that exerts a resistance against the flow of fluid such as hydraulic oil and exhibits a damping force, or an electromagnetic damper that uses an electromagnetic force to exert a damping force, and other dampers. But you can.

  Subsequently, the dynamic damper 1 includes a weight 2 and a spring element 3 and a damping element 4 interposed between the weight 2 and the arm A. The weight 2 is supported by the arm A through the spring element 3 so as to be movable up and down, and the mass of the weight 2 can be added to the unsprung member L through the spring element 3. The spring element 3 is a spring such as a coil spring and has elasticity and exhibits an elastic force commensurate with the amount of compression. The damping element 4 is a hydraulic damper (hydraulic damper), and exhibits a damping force that suppresses the vertical movement of the weight 2 relative to the unsprung member L.

  A vibration model of the suspension including the dynamic damper 1 is as shown in FIG. In FIG. 2, Mb represents the sprung mass that is the mass of the sprung member U, and Mw represents the unsprung mass that is the mass of the unsprung member L. ACT and Ks provided between the sprung mass Mb and the unsprung mass Mw indicate the actuator D and the suspension spring S having a spring constant of Ks, respectively. Further, Kt provided between the unsprung mass Mw and the road surface indicates a tire having a spring constant of Kt. Md represents an additional mass that is the mass of the weight 2 of the dynamic damper 1, and Kd and Cd provided between the additional mass Md and the unsprung mass Mw have a spring constant of the dynamic damper 1 that is Kd. The spring element 3 and the damping element 4 having a damping coefficient Cd are shown.

  In the dynamic damper 1, the additional mass Md, the spring constant Kd, and the damping coefficient are set so that the natural frequency can obtain an optimum vibration damping effect in accordance with the natural frequency of the unsprung member L that is a vibration suppression target. Cd is designed.

  An example of a specific configuration of the damping element 4 is shown in FIG. The damping element 4 includes a cylinder 5, a piston 6 that is slidably inserted into the cylinder 5, and a rod 7 having one end connected to the piston 6 and the other end protruding outside the cylinder 5. The cylinder 5 is connected to the arm A (FIG. 1), and the rod 7 is connected to the weight 2 (FIG. 1) provided on the upper side of the arm A.

  For this reason, when the weight 2 moves upward with respect to the unsprung member L, the rod 7 moves out of the cylinder 5 and the damping element 4 extends. On the contrary, when the weight 2 moves downward relative to the unsprung member L, the rod 7 enters the cylinder 5 and the damping element 4 contracts.

  Although detailed illustration is omitted, the cylinder 5 is formed in a bottomed cylindrical shape, and an annular rod guide is attached to the opening end of the cylindrical portion of the cylinder 5. The rod 7 is inserted through the insertion hole formed at the center of the rod guide. The rod 7 is supported by a rod guide so as to be slidable in the axial direction of the cylinder 5. The rod guide is provided with an annular seal that is in sliding contact with the outer periphery of the rod 7, and the cylinder 5 is liquid-tightly closed by the seal.

  Inside the cylinder 5 is formed a liquid chamber R filled with hydraulic fluid such as oil, water, and aqueous solution. The liquid chamber R is divided into two chambers by the piston 6. Hereinafter, of the two rooms, a room that is reduced when the damping element 4 is expanded is referred to as an expansion side chamber R1, and a room that is reduced when the attenuation element 4 is contracted is referred to as a compression side chamber R2.

  Although not shown, a reservoir or accumulator is connected to at least one of the extension side chamber R1 and the compression side chamber R2. And by the said structure, the volume change in a cylinder for the rod volume which goes in and out of the cylinder 5 can be compensated, or the volume change of the hydraulic fluid by a temperature change can be compensated. The damping element may be a double rod type, and the rod may protrude from both sides of the piston to the outside of the cylinder. In this case, the volume of the accumulator or the like can be reduced.

  An extension side passage 6a and a pressure side passage 6b are formed in the piston 6 that partitions the extension side chamber R1 and the pressure side chamber R2. In FIG. 3, one extension side passage 6a and one pressure side passage 6b are shown, but the number of each passage can be changed as appropriate.

  Further, an extension side valve 60 is laminated on the lower side of the piston 6 in FIG. The extension side valve 60 closes the outlet of the extension side passage 6a surrounded by the extension side valve seat 6c so as to be openable and closable. On the other hand, a pressure side valve 61 is laminated on the upper side of the piston 6 in FIG. The pressure side valve 61 closes and opens the outlet of the pressure side passage 6b surrounded by the pressure side valve seat 6d.

  The expansion side valve 60 is configured to include a plurality of annular leaf valves that are stacked, and has an outer diameter that reaches the expansion side valve seat 6c. The expansion side valve 60 is fixed to the outer periphery of the rod 7 together with the piston 6 by a nut 70 with the inner peripheral portion being allowed to bend on the outer peripheral side.

  The inlet of the extension side passage 6a leads to the outside of the compression side valve seat 6d, and the pressure in the extension side chamber R1 pushes the outer peripheral portion of the extension side valve 60 downward in FIG. 3 through the extension side passage 6a. Acts on. On the contrary, the pressure in the compression side chamber R2 acts in a direction in which the outer peripheral portion of the expansion side valve 60 is pressed against the expansion side valve seat 6c. When the pressure in the expansion side chamber R1 exceeds the pressure in the compression side chamber R2, and when these differential pressures reach the valve opening pressure of the expansion side valve 60, the outer peripheral portion of the expansion side valve 60 moves away from the expansion side valve seat 6c. The side valve 60 opens the extension side passage 6a.

  In addition, the pressure side valve 61 includes an annular leaf valve in which a plurality of sheets are stacked and has an outer diameter that reaches the pressure side valve seat 6d. The compression side valve 61 is fixed to the outer periphery of the rod 7 together with the piston 6 and the expansion side valve 60 with a nut 70 while allowing the outer side deflection to be permitted.

  The inlet of the pressure side passage 6b leads to the outside of the expansion side valve seat 6c, and the pressure in the pressure side chamber R2 acts in the direction of pushing the outer periphery of the pressure side valve 61 upward through the pressure side passage 6b in FIG. . On the contrary, the pressure in the extension side chamber R1 acts in a direction in which the outer peripheral portion of the pressure side valve 61 is pressed against the pressure side valve seat 6d. When the pressure in the pressure side chamber R2 exceeds the pressure in the expansion side chamber R1, and the differential pressure reaches the valve opening pressure of the pressure side valve 61, the outer peripheral portion of the pressure side valve 61 moves away from the pressure side valve seat 6d, and the pressure side valve 61 The pressure side passage 6b is opened.

  The extension side valve seat 6c and the pressure side valve seat 6d are each provided with a notch K, and a known orifice is formed by the notch K. For this reason, even when the expansion side valve 60 and the pressure side valve 61 are closed, the expansion side chamber R1 and the pressure side chamber R2 are communicated with each other through the notch K.

  In the present embodiment, the orifice is formed by a notch formed in the valve seat. However, the method of forming the orifice can be changed as appropriate. For example, a notch may be provided on the valve body side such as the expansion side valve 60 and the pressure side valve 61, and an orifice may be formed by the notch.

  According to the above configuration, when the damping element 4 with which the rod 7 is retracted from the cylinder 5 is extended, the expansion side chamber R1 is contracted, and the hydraulic fluid in the expansion side chamber R1 that is contracting is moved to the pressure side chamber R2 in which the expansion fluid is expanded. Resistance is given by the orifice or the extension side valve 60 to the flow of the working fluid from the extension side chamber R1 toward the compression side chamber R2. Therefore, when the damping element 4 exhibits the extension operation, the pressure in the extension side chamber R1 increases and the pressure in the compression side chamber R2 decreases to generate a differential pressure. The differential pressure acts on the piston 6 to prevent the extension operation. Side damping force is generated.

  When the damping element 4 is extended, if the stroke speed of the damping element 4 is low, the differential pressure between the extension side chamber R1 and the compression side chamber R2 does not increase. As described above, when the stroke speed of the damping element 4 is low and the speed range in which the differential pressure is less than the valve opening pressure of the expansion side valve 60 is a low speed range, the stroke is reduced when the expansion side stroke speed is in the low speed range. The working fluid in the extension side chamber R1 moves to the compression side chamber R2 through the notch K (orifice). In this case, the damping characteristic of the damping element 4 (a characteristic of the damping force with respect to the stroke speed) is an orifice characteristic and a characteristic having a large damping coefficient (solid line X in FIG. 4).

  Further, when the stroke speed of the damping element 4 increases when the damping element 4 is extended, the differential pressure between the stretching side chamber R1 and the compression side chamber R2 increases. When the differential pressure reaches the valve opening pressure of the expansion side valve 60, the expansion side valve 60 opens the expansion side passage 6a. As described above, when the speed region equal to or higher than the stroke speed at which the expansion side valve 60 is opened is a high speed region, when the expansion side stroke speed is in the high speed region, the hydraulic fluid in the expansion side chamber R1 to be reduced is reduced. And moves to the compression side chamber R2 through a gap formed between the extension side valve seat 6c. In this case, the attenuation characteristic of the attenuation element 4 is a valve characteristic and a characteristic having a small attenuation coefficient (solid line Y in FIG. 4).

  On the contrary, when the damping element 4 that the rod 7 enters into the cylinder 5 contracts, the compression side chamber R2 contracts and moves to the expansion side chamber R1 in which the hydraulic fluid in the contracting compression side chamber R2 expands. A resistance is given by the orifice or the pressure side valve 61 to the flow of the working fluid from the pressure side chamber R2 toward the extension side chamber R1. Therefore, when the damping element 4 exhibits the contraction operation, the pressure in the compression side chamber R2 increases and the pressure in the expansion side chamber R1 decreases to generate a differential pressure. The differential pressure acts on the piston 6 to prevent the contraction operation. Damping force is generated.

  When the damping element 4 contracts, if the stroke speed of the damping element 4 is low, the differential pressure between the expansion side chamber R1 and the compression side chamber R2 does not increase. Thus, when the stroke speed of the damping element 4 is low and the speed range in which the differential pressure is less than the valve opening pressure of the compression side valve 61 is a low speed range, the compression side chamber is reduced when the compression side stroke speed is in the low speed range. The hydraulic fluid in R2 moves to the extension side chamber R1 through the notch K (orifice). In this case, the attenuation characteristic of the attenuation element 4 is an orifice characteristic and a characteristic having a large attenuation coefficient.

  Further, when the stroke speed of the damping element 4 increases during the contraction of the damping element 4, the differential pressure between the extension side chamber R1 and the compression side chamber R2 increases. When the differential pressure reaches the valve opening pressure of the pressure side valve 61, the pressure side valve 61 opens the pressure side passage 6b. As described above, when the speed region equal to or higher than the stroke speed at which the pressure side valve 61 is opened is a high speed region, when the pressure side stroke speed is in the high speed region, the hydraulic fluid in the pressure side chamber R2 to be reduced is reduced to the pressure side valve 61 and the pressure side valve. It moves to the extension side chamber R1 through a gap formed between the seat 6d. In this case, the attenuation characteristic of the attenuation element 4 is a valve characteristic and a characteristic having a small attenuation coefficient.

  That is, when the damping element 4 exhibits an expansion / contraction operation and the stroke speed is in the low speed range, the damping coefficient of the damping element 4 becomes high. On the other hand, when the stroke speed of the damping element 4 is in the high speed range, the damping coefficient of the damping element 4 is lower than the damping coefficient in the low speed range.

  In the case of a hydraulic damper such as the damping element 4, the hydraulic fluid behaves as a liquid having a slight elasticity due to the influence of the gas dissolved in the hydraulic fluid. Due to the influence of the elasticity of the hydraulic fluid, hysteresis occurs in the damping characteristic of the damping element 4 (broken line in FIG. 5). The hysteresis of the hydraulic damper tends to be large in a region with a high attenuation coefficient and small in a region with a low attenuation coefficient. FIG. 5 is an explanatory diagram showing the relationship between the damping coefficient and the hysteresis. The solid line shows the characteristic of the damping force that is a reference not considering hysteresis, and the broken line shows the characteristic of the damping force considering hysteresis.

  In the low speed range where the hysteresis is large, the hysteresis acts like a spring component. Assuming that the spring constant of the spring component due to the hysteresis is Kh, in the region where the hysteresis is large, as shown by the broken line in FIG. The spring element is added, and the natural frequency of the dynamic damper 1 increases. On the other hand, since the spring constant Kh is close to zero in the region where the hysteresis is small, the natural frequency of the dynamic damper 1 is small.

  Hereinafter, the operation of the dynamic damper 1 according to the present embodiment will be described.

  When the vehicle V travels on an uneven road surface, the wheel W moves up and down, and the arm A swings up and down. Then, the weight 2 of the dynamic damper 1 vibrates up and down in synchronism, and the inertial force of the weight 2 is applied as a reaction force, and the up and down vibration of the unsprung member L is suppressed.

  When the unsprung member L vibrates and the unsprung member L has a small amplitude vibration, the stroke amount of the unsprung member L is very small, and the speed of the weight 2 (the stroke speed of the dynamic damper 1) is low. The speed of the weight 2 is equal to the stroke speed of the damping element 4, and when the stroke speed is in the low speed range, the expansion side valve 60 and the compression side valve 61 are maintained closed.

  For this reason, the hydraulic fluid moves between the extension side chamber R1 and the compression side chamber R2 through the notch K, and the damping element 4 exhibits a damping force due to the resistance of the orifice. Thus, when the damping element 4 exhibits the damping force of the orifice characteristic, the damping coefficient is increased and the hysteresis is increased. Then, due to the hysteresis, the spring constant Kh (FIG. 2) increases, so that the natural frequency of the dynamic damper 1 increases.

  Therefore, even when the natural frequency of the unsprung member L is apparently increased due to the influence of a rubber bush or the like provided at the mounting portion of the arm A during the minute amplitude vibration of the unsprung member L, As a result, the natural frequency of the dynamic damper 1 increases. For this reason, a deviation between the vibration frequency of the unsprung member L and the vibration frequency of the dynamic damper 1 during the minute amplitude vibration is suppressed, and a sufficient unsprung vibration suppression effect by the dynamic damper 1 can be obtained even during the minute amplitude vibration. .

  Further, when the unsprung member L vibrates and the stroke amount of the unsprung member L increases, the speed of the weight 2 and the stroke speed of the damping element 4 increase. When the stroke speed of the damping element 4 reaches a high speed region, the expansion side valve 60 or the compression side valve 61 opens, and the attenuation element 4 exhibits a damping force due to the resistance of the expansion side valve 60 or the compression side valve 61. In this way, when the damping element 4 exhibits the damping force of the valve characteristic, the damping coefficient is reduced and the hysteresis is reduced. Then, since the spring constant Kh (FIG. 2) resulting from the said hysteresis becomes small, the natural frequency of the dynamic damper 1 becomes small.

  Therefore, when the substantial natural frequency of the unsprung member L returns to the assumed frequency during normal vibration of the unsprung member L, the natural frequency of the dynamic damper 1 also decreases. That is, even if the natural frequency of the dynamic damper 1 during the small amplitude vibration is increased, the natural frequency is decreased during the normal vibration, so that a good unsprung vibration suppression effect by the dynamic damper 1 during the normal vibration is impaired. There is nothing.

  Hereinafter, the effect of the dynamic damper 1 according to the present embodiment will be described.

  In the present embodiment, the damping element 4 has a larger damping coefficient than when the stroke speed is in the low speed range (when the stroke speed is less than the predetermined speed) and when the stroke speed is in the high speed range (when the speed is greater than the predetermined speed). Is set to The hysteresis is increased by increasing the attenuation coefficient. In the damping element 4, since it is easy to switch the damping coefficient according to the stroke speed, the hysteresis can be easily increased according to the stroke speed.

  In the present embodiment, the damping element 4 has an orifice, an expansion side valve 60, and a compression side valve 61. When the stroke speed is in a low speed range, the damping element 4 exhibits a damping force of the orifice characteristic, and the stroke speed is high. Demonstrate the damping characteristics of the valve characteristics when in the range. For this reason, it is easy to increase the attenuation coefficient in the low speed region and reduce the attenuation coefficient in the high speed region.

  In the present embodiment, the expansion side valve 60 and the pressure side valve 61 are configured to have leaf valves. Since the leaf valve is a thin annular plate, the use of the leaf valve can suppress the damping element 4 from being bulky in the axial direction. Further, since the damping element 4 includes the expansion side valve 60 and the compression side valve 61, the stroke speed at which the hysteresis increases can be set in accordance with the operating direction (extension / compression) of the attenuation element 4.

  The configuration of the attenuation element 4 is not limited to the above, and can be changed as appropriate. For example, the expansion side valve 60 and the pressure side valve 61 may be replaced with valves other than the leaf valve. In the damping element 4, the damping coefficient is changed by switching from the damping force of the orifice characteristic to the damping force of the valve characteristic, but other methods may be adopted to change the damping coefficient. The damping element 4 increases the hysteresis when the stroke speed is less than the predetermined speed by increasing the damping coefficient when the stroke speed is less than the predetermined speed, but other methods are employed. May be.

  Further, the dynamic damper 1 according to the present embodiment gives resistance to the weight 2, the spring element 3 interposed between the unsprung member L of the vehicle V and the weight 2, and the flow of the working fluid contained therein. And a damping element 4 that exhibits a damping force that suppresses vibration of the weight 2. The damping element 4 has hysteresis due to the elasticity of the hydraulic fluid as compared with the case where the stroke speed is in the low speed range (when the predetermined speed is not reached) and the case where the stroke speed is in the high speed range (when the predetermined speed or higher). It is set to be large.

  During the small amplitude vibration of the unsprung member L, the stroke speed of the damping element 4 is low, and in the region where the stroke speed is low (low speed region), the spring constant Kh (FIG. 2) increases and the natural frequency of the dynamic damper 1 is increased. Becomes larger. Therefore, even if the natural frequency of the unsprung member L during the slight amplitude vibration is apparently increased due to the influence of the rubber bush or the like, the natural frequency of the dynamic damper 1 increases accordingly. For this reason, even when the unsprung member L has a small amplitude vibration, a deviation between the vibration frequency of the unsprung member L and the vibration frequency of the dynamic damper 1 is suppressed, and a sufficient damping effect by the dynamic damper 1 can be obtained.

  The hysteresis in the damping element 4 can be changed by, for example, the damping coefficient, and the damping coefficient can be changed by switching the damping characteristic from the orifice characteristic to the valve characteristic, for example. For this reason, even when the natural frequency of the dynamic damper 1 has the amplitude dependency as described above and the spring element 3 is a spring such as a coil spring, a leaf spring, or a disc spring, There is no need to add a special device for changing the spring constant of the spring. Therefore, the configuration of the spring element is not limited, and the structure of the dynamic damper 1 is not complicated. Therefore, it is easy to make the natural frequency of the dynamic damper 1 have an amplitude dependency.

  In the present embodiment, the damping element 4 uses an orifice, an expansion side valve 60, and a pressure side valve 61 as a throttle member for imparting resistance to the flow of hydraulic fluid contained therein. However, the configuration of the diaphragm member can be changed as appropriate.

  Further, in the present embodiment, the dynamic damper 1 is attached so that the weight 2 is disposed above the arm A, the cylinder 5 of the damping element 4 is connected to the arm A, and the rod 7 is connected to the weight 2. Has been. Therefore, with the dynamic damper 1 attached, the extension side chamber R1 is disposed on the upper side, and the compression side chamber R2 is disposed on the lower side. When the weight 2 moves upward with respect to the unsprung member L, the damping element 4 expands and the extension side chamber R1 shrinks. On the contrary, when the weight 2 moves downward with respect to the unsprung member L, the damping is reduced. The element 4 contracts and the compression side chamber R2 contracts.

  However, the method of attaching the dynamic damper 1 can be changed as appropriate. For example, the cylinder of the damping element may be connected to a weight, the rod may be connected to an unsprung member such as an arm, and the extension side chamber may be disposed on the lower side and the compression side chamber may be disposed on the upper side. When the dynamic damper is attached, the weight is provided on the lower side of the arm. When the weight moves downward with respect to the unsprung member, the damping element extends, and the weight moves upward with respect to the unsprung member. In this case, the damping element may be contracted.

  In the present embodiment, the dynamic damper 1 is attached to the arm A. However, the dynamic damper may be attached to other than the arm as long as the vibration of the unsprung member can be suppressed by the dynamic damper.

  These changes can be appropriately changed regardless of the configuration of the attenuation element.

  The preferred embodiments of the present invention have been described above in detail, but modifications, changes and modifications can be made without departing from the scope of the claims.

L: Unsprung member, V ... Vehicle, 1 ... Dynamic damper, 2 ... Weight, 3 ... Spring element, 4 ... Damping element

Claims (2)

A weight,
A spring element interposed between the unsprung member of the vehicle and the weight;
A damping element that exerts a damping force that suppresses vibration of the weight by providing resistance to the flow of the working fluid contained therein,
The damping element is set such that when the stroke speed is less than a predetermined speed, hysteresis due to the elasticity of the hydraulic fluid is larger than that when the stroke speed is higher than the predetermined speed. Dynamic damper. The damping element is set so that the damping coefficient is larger when the stroke speed is less than the predetermined speed, compared to the case where the stroke speed is equal to or higher than the predetermined speed.
The dynamic damper according to claim 1, wherein the hysteresis is increased by increasing the damping coefficient.

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