JP2012082850A - Suspension device - Google Patents

Abstract

The present invention provides a suspension device that can sufficiently exhibit a damping force reduction effect in response to a frequency and can improve riding comfort in a motorcycle without causing a shortage of stroke.
In a suspension device including a pair of front forks F1 and F2 interposed between a vehicle body and a front wheel axle in a motorcycle, a shock absorber D that suppresses vibration of the vehicle body is incorporated in only one front fork F1. The shock absorbers are provided in the cylinder 1, the piston 2, and communicate with the extension side chamber R1 and the pressure side chamber R2 and form the damping passages 4 and 5 that give resistance to the flow of the passing liquid, and the pressure chamber C. A housing 6, a free piston 9 that is slidably inserted into the pressure chamber 6 and divides the pressure chamber C into an extension side pressure chamber 7 and a compression side pressure chamber 8, and an extension side chamber R 1 and an extension side pressure chamber 7. The expansion side passage 10 that communicates, the pressure side passage 11 that communicates the pressure side chamber R2 and the pressure side pressure chamber 8, and the spring element 12 that exerts an urging force that suppresses the displacement of the free piston 9 relative to the housing 6 are provided.
[Selection] Figure 1

Description

  The present invention relates to an improvement of a suspension device.

  Conventionally, in a suspension device interposed between the vehicle body of this type of motorcycle and the front wheel axle, generally, an outer tube, an inner tube slidably inserted into the outer tube, It is comprised by a pair of front fork provided with the shock absorber interposed between an outer tube and an inner tube.

  By incorporating a shock absorber in the pair of left and right front forks in this way, each front fork exerts a damping force to suppress the vibration of the vehicle body, and also suppresses the front wheel from fluttering. Is good.

  By the way, considering the structure of a motorcycle, since the vehicle body is supported by a tire that acts as a spring and a suspension spring, if the vibration frequency input to the motorcycle is near the natural frequency (resonance frequency) of the vehicle body, Vibration will be excited.

  For this reason, if the shock absorber in the front fork exerts a large damping force against vibration having a frequency around the resonance frequency of the vehicle body, vibration of the vehicle body can be suppressed. However, if the shock absorber exerts an excessive damping force against vibrations other than the vicinity of the resonance frequency, the vibration insulation effect on the vehicle body by the suspension spring may be disturbed, and on the contrary, the riding comfort in the motorcycle may be impaired. .

  Therefore, if the damping force is changed depending on the frequency of vibration input to the front fork, the ride comfort of the vehicle can be improved, and so-called frequency-sensitive shock absorbers have been developed. Has been done.

  As this frequency-sensitive shock absorber, for example, a cylinder, a piston that is slidably inserted into the cylinder, and divides the inside of the cylinder into an upper chamber and a lower chamber, and an upper chamber and a lower chamber provided in the piston communicate with each other. A damping passage that provides resistance to the flow of liquid passing therethrough, a housing that is provided at the tip of the piston rod to form a pressure chamber, and is slidably inserted into the housing to communicate the pressure chamber with the upper chamber. A free piston that is divided into an upper chamber and a lower chamber that communicates with the lower chamber, and a coil spring that urges the free piston, and as shown in FIG. 4, has a relatively low frequency band. A large damping force is exhibited with respect to vibration, and a small damping force is exhibited with respect to vibration in a high frequency band by exhibiting a damping force reducing effect (for example, see Patent Documents 1 and 2). .

JP 2006-336816 A JP 2007-78004 A

  By the way, when the shock absorber is used by being incorporated in a front fork interposed between a motorcycle body and a front axle, the weight of the motorcycle is very light relative to that of a four-wheeled vehicle. Since the light vehicle body is supported by the two front forks, the differential pressure between the upper chamber and the lower chamber at the time of expansion and contraction of each shock absorber built in each front fork is significantly smaller than that for automobiles.

  Therefore, even if a conventional shock absorber is built in the front fork of the suspension device for a motorcycle, the damping force reduction effect cannot be sufficiently obtained, and the riding comfort in the motorcycle may not be sufficiently improved. .

  In addition, in a two-wheeled vehicle, in order to improve the riding comfort by reducing the damping force, it is required to set the frequency at which the damping force reduction effect appears lower than that of the four-wheeled vehicle. In order to satisfy this requirement, it is only necessary to reduce the spring multiplier of the coil spring, but since the motorcycle body is lightweight, the spring multiplier of the coil spring must be set very small. As a result, the amount of displacement of the free piston increases remarkably, and the free piston interferes with the housing in the middle of the stroke of the front fork, so that the damping force reduction effect is lost and the damping force may increase rapidly. In order to avoid this, it is necessary to lengthen the housing and increase the allowable stroke length of the free piston, and in this case, a long housing is accommodated in the cylinder and the stroke length of the shock absorber is shortened. As a result, the front fork may run out of stroke.

  Therefore, the present invention was devised in order to improve the above-described problems, and the object of the present invention is to sufficiently exhibit the damping force reduction effect in response to the frequency and not cause a shortage of stroke. An object of the present invention is to provide a suspension device that can improve the riding comfort of a motorcycle.

  In order to solve the above-mentioned object, the problem solving means in the present invention includes an outer tube and an inner tube that is slidably inserted into the outer tube, and is interposed between a vehicle body and a front wheel axle in a two-wheeled vehicle. In the suspension device including a pair of front forks, a shock absorber that suppresses vibration of the vehicle body is incorporated in only one of the front forks, and the shock absorber is attached to one of the outer tube and the inner tube. A cylinder to be connected, a piston that is slidably inserted into the cylinder and divides the cylinder into an extension side chamber and a pressure side chamber, one end is connected to the piston, and the other end is connected to the other of the outer tube and the inner tube. The piston rod is connected to the extension side chamber and the compression side chamber, and the damping passage provides resistance to the flow of the liquid passing therethrough. And a housing that forms a pressure chamber, a free piston that is slidably inserted into the pressure chamber and divides the pressure chamber into an expansion side pressure chamber and a pressure side pressure chamber, and the expansion side chamber and the expansion side pressure chamber communicate with each other It is characterized by comprising an extension side passage, a pressure side passage communicating the pressure side chamber and the pressure side pressure chamber, and a spring element that exerts an urging force that suppresses displacement of the free piston relative to the housing.

  According to the suspension device of the present invention, since the shock absorber that exhibits the damping force sensitive to the frequency is incorporated in only one of the front forks, when supporting the body of a lightweight motorcycle. Even if it exists, the damping force reduction effect can be sufficiently obtained, and the riding comfort in the two-wheeled vehicle can be improved.

  Further, as described above, even when supporting the body of a lightweight two-wheeled vehicle, the pressure difference between the expansion side chamber and the compression side chamber in the shock absorber can be increased when the front fork is expanded and contracted. Even if the constant is set to be larger than when two shock absorbers are used, it is possible to obtain a damping characteristic that is sensitive to the frequency suitable for two-wheeled vehicles. There is no invitation.

It is a longitudinal cross-sectional view of the suspension apparatus in one embodiment. It is a partial expanded longitudinal cross-sectional view of the shock absorber in the suspension apparatus in one embodiment. It is a figure which shows the characteristic (damping characteristic) of the damping force with respect to the input frequency in the suspension apparatus of this invention. It is a figure which shows the characteristic (damping characteristic) of the damping force with respect to the input frequency in the conventional suspension apparatus.

  Hereinafter, the present invention will be described with reference to the drawings. As shown in FIG. 1, the suspension device of the present invention includes a pair of front forks F1 and F2 interposed between a vehicle body (not shown) and a front wheel axle (not shown) in a motorcycle. A shock absorber D is built in one front fork F1, and a suspension spring S2 is built in the other front fork F2. A suspension spring S1 is also built in one front fork F1, and in this suspension apparatus, a vehicle body (not shown) is elastically supported by suspension springs S1 and S2 formed of coil springs provided on the front forks F1 and F2. ing.

  Each of the front forks F1 and F2 includes outer tubes O1 and O2 and inner tubes I1 and I2 that are slidably inserted into the outer tubes O1 and O2, respectively. , O2 is closed, the lower ends of the inner tubes I1, I2 are closed, and a closed space is formed between the outer tubes O1, O2 and the inner tubes I1, I2.

  And the shock absorber D and suspension spring S1 are accommodated in the said closed space formed of the outer tube O1 and the inner tube I1 in one front fork F1. That is, the shock absorber D is built in one front fork F1. A suspension spring S2 is accommodated in the closed space formed by the outer tube O2 and the inner tube I2 in the other front fork F2. The other front fork F2 does not include a shock absorber D.

  The other front fork F2 includes a cylindrical member 54 connected to the bottom of the inner tube I2, a rod 55 connected to the upper end of the inner tube I2 and inserted into the cylindrical member 54, and a diagram of the cylindrical member 54. 1 An annular rod guide 56 that is provided at the upper end in the middle and supports the rod 55, a spring receiver 50 provided on the outer periphery of the rod guide 56, and a suspension interposed between the spring receiver 50 and the bottom of the outer tube O2. The spring S2 is accommodated. Therefore, the suspension spring S2 urges the outer tube O2 and the inner tube I2 to be separated from each other. When the front fork F2 is interposed between the vehicle body and the front wheel axle, the suspension spring S2 is compressed. Thus, the vehicle body is elastically supported.

  A cylindrical bearing 51 that is in sliding contact with the outer periphery of the inner tube I2 is provided on the inner periphery of the outer end of the outer tube O2, and a cylindrical bearing that is in sliding contact with the inner periphery of the outer tube O2 is provided on the outer periphery of the inner end of the outer tube O2. A bearing 52 is provided. In order to lubricate the bearings 51, 52, a perforation 53 is formed in a side portion of the inner tube I 2, and lubricating oil stored in the inner tube I 2 is passed through the perforation 53. It can supply between outer tube O2 and inner tube I2. Further, since the other front fork F2 does not exhibit a damping force, it is not necessary to incorporate a mechanism necessary for generating the damping force, and it is not necessary to fill the inside with hydraulic oil for generating the damping force. Lubricating oil does not need to be filled below the stroke range of the rod 55 of the member 54, and a partition wall 58 is provided and an air chamber is provided in the cylindrical member 54 and below the partition wall 58. Therefore, this front fork F2 is very light compared to a front fork equipped with a shock absorber.

  In the other front fork F2, the maximum extension length can be regulated by the stopper 57 provided at the tip of the rod 55 and the rod guide 56 provided in the cylindrical member 54, and the suspension spring S2 Although there is an advantage that the standard for adjusting the initial load is clear, it is not particularly necessary to regulate the maximum extension length, or when the regulation is performed on the outer tube O2 and inner tube I2 side, the inner tube A spring receiver that closes the inner tube I2 and closes the inner tube I2 as an air chamber may be provided in I2, and a suspension spring S2 may be interposed between the spring receiver and the outer tube O2. In this case, the front fork F2 can be further reduced in weight.

  When both the bearings 51 and 52 are fixed to the outer tube O2 or to the inner tube I2, the lubricating oil is between the outer tube O2 and the inner tube I2 and the bearings 51 and 52. It is also possible to fill only the gap surrounded by, and it is not necessary to form a storage chamber for storing lubricating oil in the inner tube I2.

  Further, although the outer tube O2 is disposed upward and the inner tube I2 is disposed downward in the drawing, it can be interposed between the vehicle body and the front wheel axle as an upside down.

  Next, one front fork F1 will be described. As described above, the front fork F1 includes the outer tube O1 and the inner tube I1 that is slidably inserted into the outer tube O1, and is interposed between the outer tube O1 and the inner tube I1. A shock absorber D and a suspension spring S1 are provided.

  Further, similarly to the other front fork F2, even in the front fork F1, a cylindrical bearing 41 slidably contacting the outer periphery of the inner tube I1 is provided on the inner periphery of the outer end of the outer tube O1. A cylindrical bearing 42 that is in sliding contact with the inner periphery of the outer tube O1 is provided on the outer periphery of the opening end of I1. Furthermore, in this case, the suspension spring S1 is interposed between the spring receiver 43 provided at the upper end in FIG. 1 of the cylinder 1 of the shock absorber D and the bottom of the outer tube O1, and the outer tube O1 and the inner tube of the front fork F1. The tube I1 is urged away from the tube I1, and when the front fork F1 is interposed between the vehicle body and the front wheel axle, it is compressed by the vehicle weight to elastically support the vehicle body.

  On the other hand, as shown in FIGS. 1 and 2, the shock absorber D includes a cylinder 1 connected to the bottom of the inner tube I1, and two working chambers that are slidably inserted into the cylinder 1. The piston 2 partitioned into the extension side chamber R1 and the pressure side chamber R2, the piston rod 3 having one end connected to the piston 2 and the other end connected to the outer tube O1, and the extension side chamber R1 and the pressure side chamber R2 are communicated with each other. Damping passages 4 and 5, a housing 6 forming a pressure chamber C, and a free piston which is slidably inserted into the housing 6 and divides the pressure chamber C into an expansion side pressure chamber 7 and a pressure side pressure chamber 8. 9, the expansion side passage 10 that communicates the expansion side chamber R1 and the expansion side pressure chamber 7, the pressure side passage 11 that communicates the compression side chamber R2 and the pressure side pressure chamber 8, and the displacement of the free piston 9 with respect to the housing 6 are suppressed. Attachment It is constituted by a spring element 12 to exert a force.

  Also, a partition wall 31 is provided below the cylinder 1 and a valve disk 32 is provided on the piston side of the partition wall. An air chamber 33 is formed below the partition wall 31 of the cylinder 1 in FIG. A gap 34 is formed between the valve disk 32 and the pressure side chamber R 2 and the air chamber 33. The valve disk 32 is provided with a suction passage 36 provided with a check valve 35 that allows only a flow from the gap 34 to the pressure side chamber R2 in the middle, and allows only a flow from the pressure side chamber R2 to the gap 34 in the middle A discharge passage 38 having a base valve 37 that provides resistance to the flow of liquid passing therethrough is formed. Further, the gap 34 is communicated with an annular gap between the cylinder 1 and the inner tube I1 by a through hole 39 formed in the cylinder 1. The extension side chamber R1, the pressure side chamber R2, and further the pressure chamber C are filled with a liquid such as hydraulic oil, and the front fork F1 has a closed space between the outer tube O1 and the inner tube I1. The reservoir R is used, and the reservoir R is filled with hydraulic oil and gas. As the liquid filled in the extension side chamber R1, the pressure side chamber R2, the pressure chamber C and the reservoir R, for example, a liquid such as water or an aqueous solution can be used in addition to the hydraulic oil.

  When the front fork F1 extends, basically, the expansion side chamber R1 of the shock absorber D is compressed by the piston 2 to increase the pressure, and the hydraulic oil in the expansion side chamber R1 is compressed through the damping passage 4 to the compression side. When moving to the chamber R2, the damping passage 4 provides resistance to the flow of the hydraulic oil, thereby causing a differential pressure between the pressures in the extension side chamber R1 and the pressure side chamber R2. As a result, the shock absorber D exhibits a damping force, and apparently bypasses the damping passage 4 according to the frequency of vibration input to the shock absorber D, and draws hydraulic oil through the pressure chamber C to the expansion side chamber R1. In order to move to the compression side chamber R2, a damping force sensitive to the frequency is exhibited. When the front fork F1 is extended, the piston rod 3 retracts from the cylinder 1, so that the hydraulic oil corresponding to the retracted volume of the piston rod 3 that is insufficient in the cylinder 1 passes through the suction passage 36 and the reservoir R. Supplied from within.

  On the other hand, when the front fork F1 contracts, the piston 2 compresses the compression side chamber R2, so that the pressure in the compression side chamber R2 rises, and the hydraulic oil in the compression side chamber R2 is attenuated to the expansion side chamber R1 that expands. Since the piston rod 3 enters the cylinder 1 and the volume of hydraulic oil entering the piston rod 3 is excessive in the cylinder 1, the hydraulic oil enters the base 1 from the cylinder 1. It is also discharged to the reservoir R through the valve 37.

  Since the base valve 37 provides resistance to the flow of hydraulic oil and the damping passage 5 also provides resistance to the flow of hydraulic oil, a pressure difference occurs between the pressure side chamber R2 and the extension side chamber R1, and the front fork F1 According to the frequency of vibration input to the shock absorber D, the hydraulic fluid is apparently bypassed the damping passage 5 and moved from the pressure side chamber R2 to the extension side chamber R1 via the pressure chamber C. It is designed to exhibit a damping force that is sensitive to frequency.

  The front fork F1 uses the closed space as the reservoir R, but the shock absorber D itself has a reservoir or an air chamber that compensates the volume in the cylinder 1 during the expansion and contraction. Therefore, the closed space does not have to function as the reservoir R. As described above, when the shock absorber D itself is an independent shock absorber provided with the reservoir R and the air chamber, there is an advantage that it can be easily incorporated into the front fork F1, but the closed space functions as the reservoir R. Thus, the hydraulic oil stored inside can be used as the lubricating oil for the bearings 41 and 42. When the shock absorber D itself is provided with the reservoir R and the air chamber and is an independent shock absorber, the outer In addition to the seal member that seals between the tube O1 and the inner tube I1, a seal member that tightly seals the inside of the cylinder 1 between the cylinder 1 and the piston rod 3 of the shock absorber D is required, and the front fork F1 Since the frictional resistance at the time of expansion and contraction tends to increase, there is also an advantage obtained by causing the closed space to function as the reservoir R of the shock absorber D.

  Further, the partition wall 31 described above forms an air chamber in the cylinder 1 to keep the amount of hydraulic oil filled in the front fork F1 and the shock absorber D to the minimum necessary, thereby reducing the weight and cost of the front fork F1. Since it is sufficient to be able to achieve the object and form an air chamber in the cylinder 1, it may be in the shape of a container that forms an air chamber inside.

  Next, each part of the shock absorber D will be described in detail. The piston 2 is connected to one end 3 a of a piston rod 3 that is movably inserted into the cylinder 1, and the other end 3 b of the piston rod 3 is inside an annular rod guide 15 fixed to the upper end of the cylinder 1 in the figure. It protrudes out of the cylinder 1 through the circumference and is connected to the bottom of the outer tube O1. In the illustrated example, the piston rod 3 is configured such that one end 3a to which the piston 2 is assembled and the other end 3b are divided in the middle and integrated by screw fastening. Good. In the present embodiment, the cylinder 1 is connected to the inner tube I1 and the piston rod 3 is connected to the outer tube O1. Conversely, the cylinder 1 is connected to the outer tube O1, and the piston is connected. The other end 3b of the rod 3 may be connected to the inner tube I1. In this embodiment, no seal member is provided between the rod guide 15 and the piston rod 3 to tightly seal them, and the upper end of the cylinder 1 in FIG. Regardless of the state, the hydraulic oil filled in the reservoir R is maintained in an oil-immersed state.

  The piston 2 includes damping passages 4 and 5 that communicate the expansion side chamber R1 and the pressure side chamber R2, and the lower end of the damping passage 4 in FIG. 1 is opened and closed by a leaf valve 17, and the upper end of the damping passage 5 in FIG. 1 is opened and closed by a leaf valve 18 as a damping valve stacked above the piston 2 in FIG. Yes. The leaf valve 17 is annular and is attached to one end 3a of the piston rod 3 together with the piston 2, so that the liquid extends through the damping passage 4 during the extension stroke of the shock absorber D in which the piston 2 moves upward in FIG. When the fluid flows from the side chamber R1 toward the pressure side chamber R2, it bends to open the attenuation passage 4 and provide resistance to the flow of the liquid, and closes the attenuation passage 4 against a reverse flow. The damping passage 4 is set as a one-way passage that allows only the flow from the extension side chamber R1 to the compression side chamber R2. On the other hand, the leaf valve 18 is annular and is attached to one end 3a of the piston rod 3 together with the piston 2, so that the liquid passes through the damping passage 5 during the contraction stroke of the shock absorber D in which the piston 2 moves downward in FIG. When the fluid flows from the chamber R2 toward the extension chamber R1, it bends to open the attenuation passage 5 and provides resistance to the flow of the liquid, and closes the attenuation passage 5 against the reverse flow. The damping passage 5 is set as a one-way passage that allows only the flow from the compression side chamber R2 to the extension side chamber R1. That is, the leaf valve 17 functions as an expansion-side damping valve that provides resistance to the flow of liquid flowing through the attenuation passage 4 during the extension stroke, and the leaf valve 18 provides resistance to the flow of liquid flowing through the attenuation passage 5 during the contraction stroke. Functions as a compression side damping valve. As described above, when a plurality of attenuation passages 4 and 5 are provided, the attenuation passage may be set to be one-way so that the liquid flows only during the extension stroke or during the contraction stroke. In addition to the leaf valve described above, the damping valve may serve as a damping passage that provides resistance to the flow of liquid passing through the damping passage. Various damping valves such as poppet valves, orifices, and chokes can be used. The damping passages 4 and 5 can be provided in addition to the piston 2.

  Subsequently, in the case of this embodiment, the pressure chamber C is formed by a hollow housing 6 that is screwed into a screw portion 3c provided at the outermost outer periphery of the one end 3a of the piston rod 3. The piston 2 and the leaf valves 17 and 18 also function as a piston nut that fixes the piston rod 3 to one end 3a.

  The pressure chamber C formed in the housing 6 is a free piston 9 that is slidably inserted into the pressure chamber C. The expansion side pressure chamber 7 in the upper part in FIG. 2 and the pressure side pressure chamber in the lower part in FIG. 2, the free piston 9 can be displaced in the vertical direction in FIG. 2 with respect to the housing 6 in the pressure chamber C.

  Specifically, the housing 6 covers a nut portion 20 that is screwed into a screw portion 3 c formed at one end 3 a of the piston rod 3, a cylindrical portion 22 that is suspended from the outer periphery of the nut portion 20, and an opening of the cylindrical portion 22. A bottomed cylindrical housing cylinder 21 having a bottom 23 is provided, and a step 22 a is formed on the inner periphery of the cylindrical part 22 by reducing the diameter of the lower side of the cylindrical part 22 in the housing cylinder 21. The pressure chamber C is defined in the pressure side chamber R2.

  Moreover, the nut part 20 is provided with the screw part 20a and the flange 20b which screw together with the screw part 3c of the piston rod 3 in the inner periphery. The housing cylinder 21 has a bottomed cylindrical shape as described above, and is integrated with the nut portion 20 by crimping the upper end opening in FIG. 2 toward the outer periphery of the flange 20b of the nut portion 20. . In addition, integration of the nut part 20 and the housing cylinder 21 can employ | adopt other process directions, such as welding and screwing, besides a caulking process. Furthermore, a step portion 22a is provided on the inner periphery of the cylindrical portion 22 of the housing cylinder 21 so as to face the expansion side pressure chamber 7 side, which is the upper side in FIG.

  It should be noted that the outer peripheral cross-sectional shape of at least a part of the cylindrical portion 22 of the housing cylinder 21 is a shape other than a circle so as to be gripped by a tool (not shown) and matches the tool, for example, a part is cut away The outer periphery of the cylindrical portion 22 is gripped by a tool, the housing 6 is rotated in the circumferential direction, and a predetermined tightening torque is applied to the nut portion 20 to the screw portion 3c. It can be screwed. Further, a port 22b is provided on the side portion of the cylindrical portion 22, the pressure chamber C and the pressure side chamber R2 communicate with each other at the port 22b, and the port 23a is also provided at the bottom portion 23. The pressure chamber C and the pressure side chamber R2 communicate with each other at 23a.

  The expansion side pressure chamber 7 communicates with the expansion side chamber R1 by an expansion side passage 10 that leads from the side of the piston rod 3 facing the expansion side chamber R1 to the end of the one end 3a. The extension side passage 10 is constituted by a horizontal hole 10a that opens from the side facing the extension side chamber R1 of the piston rod 3, and a vertical hole 10b that opens from the end of one end 3a and leads to the horizontal hole 10a.

  The free piston 9 inserted into the pressure chamber C includes a sliding contact cylinder 24 that is in sliding contact with the cylindrical portion 22 of the housing cylinder 21 and a mirror portion 25 that closes the inner periphery of the sliding contact cylinder 24. The interior is divided into an extension side pressure chamber 7 communicated with the extension side chamber R1 and a pressure side pressure chamber 8 communicated with the compression side chamber R2. The free piston 9 includes an annular groove 26 provided over the entire outer circumference of the sliding contact cylinder 24 and a communication hole 27 that communicates the annular groove 26 with the pressure side pressure chamber 8. 6, the pressure side chamber R2 communicates with the pressure side pressure chamber 8, and the annular groove 26 does not face the port 22b, and the sliding contact cylinder 24 closes the port 22b. In this case, the communication between the pressure side chamber R2 and the pressure side pressure chamber 8 via the port 22b is cut off. The port 22b provides resistance to the flow of liquid passing therethrough to cause a predetermined pressure loss, and generates a differential pressure between the pressure side chamber R2 and the pressure side pressure chamber 8. Further, the port 23a provided at the bottom 23 of the housing cylinder 21 also functions as a throttle passage, which gives resistance to the flow of liquid passing therethrough and causes a predetermined pressure loss. A differential pressure is generated between the pressure chamber 8 and the pressure chamber 8. This port 23a is not closed by the free piston 9 and is always open. That is, the pressure side pressure chamber 8 communicates with the pressure side chamber R2 through the ports 22b and 23a when the port 22b is in communication, and the pressure side only through the port 23a when the port 22b is in the shut off state. The pressure side passage 11 is formed by the ports 22 b and 23 a, the annular groove 26 and the communication hole 27.

  Further, in order to apply an urging force that suppresses the displacement of the free piston 9 relative to the housing 6, it is within the extension side pressure chamber 7 between the nut portion 20 and the mirror portion 25 of the free piston 9, and In the compression-side pressure chamber 8, coil springs 28 and 29 are both interposed in a compressed state as the spring element 12 between the bottom 23 and the mirror portion 25 of the free piston 9. As described above, the free piston 9 is sandwiched from above and below by the spring elements 12 of the coil springs 28 and 29, and is positioned at a predetermined neutral position in the pressure chamber C. When the free piston 9 is displaced from the neutral position, 29 exerts an urging force to return the free piston 9 to the neutral position. The neutral position does not indicate the axial center of the pressure chamber C, but a position where the free piston 9 is positioned by the spring element 12.

  As the spring element 12, it is only necessary to position the free piston 9 at the neutral position and to exert an urging force. Therefore, elements other than the coil springs 28 and 29 may be employed, for example, an elastic body such as a disc spring. May be used to elastically support the free piston 9. When a single spring element whose one end is connected to the free piston 9 is used, the other end may be fixed to the nut portion 20 or the bottom portion 23.

  The coil spring 28 is loosely fitted to the inner periphery of the sliding contact cylinder 24 of the free piston 9 and is positioned at an approximate position in the radial direction. The upper end of the coil spring 29 in FIG. 1 is the mirror portion 25 of the free piston 9. Is loosely fitted to a protrusion 25a formed at the lower end of the member and positioned at an approximate position in the radial direction. As described above, the coil springs 28 and 29 are centered together by the free piston 9 as described above, and are prevented from being displaced with respect to the free piston 9, so that the urging force is stably applied to the free piston 9. It is possible to make it.

  As described above, the free piston 9 is elastically supported by the coil springs 28 and 29 as the spring element 12 in the housing 6, and is in a neutral position in the housing 6 when no force other than the urging force by the spring element 12 is applied. When in the neutral position, the annular groove 26 always faces the port 22b so that the pressure side pressure chamber 8 and the pressure side chamber R2 communicate with each other. On the other hand, when the free piston 9 is displaced from the neutral position to some extent, the outer periphery of the sliding contact cylinder 24 of the free piston 9 completely overlaps the port 22b to close it. The amount of displacement from the neutral position at which the free piston 9 begins to close the port 22b can be arbitrarily set, and the side of the expansion side pressure chamber 7 that is the upper side in FIG. 1 of the free piston 9 that starts to close the port 22b. The displacement amount from the neutral position to the neutral position may be set differently from the displacement amount of the free piston 9 starting to close the port 22b from the neutral position toward the pressure side pressure chamber 8 which is the lower side in FIG. In this embodiment, two ports 22b are provided, but the number thereof is arbitrary. An annular groove communicating with the pressure side chamber R2 is provided on the inner periphery of the cylindrical portion 21, and the outer side of the free piston 9 is provided. A port for communicating with the pressure side pressure chamber 8 may be provided in the free piston 9.

  The suspension device is configured as described above. Next, the operation of the suspension device will be described. As described above, the other front fork F2 exerts an urging force commensurate with the compression state of the suspension spring S2 during expansion and contraction, and the one front fork F1 urges an urging force commensurate with the compression state of the suspension spring S1 during expansion and contraction As well as the damping force of the shock absorber D. The suspension springs S1, S2 exhibit an urging force proportional to the displacement of the front forks F1, F2.

  On the other hand, since the shock absorber D exhibits a damping force corresponding to the frequency of vibration input to the front fork F1, the detailed operation of the shock absorber D will be described below.

  First, the operation in the shock absorber D when the displacement amount from the neutral position in the free piston 9 is within a range where the port 22b does not begin to be closed will be described. In this case, the free piston 9 can be displaced while maintaining the communication state of the port 22b.

  When the input frequency to the shock absorber D is low and high, the input amplitude is increased and the amplitude of the free piston 9 is increased when the input frequency is low. When the amplitude of the free piston 9 increases within a range in which the port 22b does not begin to close, the free piston 9 is displaced, so that an urging force is exerted to return the free piston 9 to the neutral position by the coil springs 28 and 29. In accordance with the urging force of 28 and 29, a difference occurs between the pressure of the expansion side pressure chamber 7 and the pressure side pressure chamber 8 between the chamber in which the volume is expanded and the chamber in which the volume is decreased. The pressure is higher than the chamber.

  Then, the differential pressure between the expansion side pressure chamber 7 and the expansion side chamber R1 and the differential pressure between the compression side pressure chamber 8 and the compression side chamber R2 become small, and the flow rate passing through the expansion side passage 10 and the compression side passage 11 decreases. . As the flow rate passing through the extension side passage 10 and the pressure side passage 11 decreases, the flow rate of the damping passages 4 and 5 increases, and the generated damping force of the shock absorber D increases.

  On the other hand, since the input amplitude is small at the time of high frequency input, the flow rate in one cycle moving from the compression side chamber R1 to the expansion side chamber R2 or from the compression side chamber R2 to the expansion side chamber R1 is small, and the displacement of the free piston 9 is also small. . Then, the biasing force of the coil springs 28 and 29 received by the free piston 9 is also reduced. Accordingly, the difference between the pressure in the expansion side pressure chamber 7 and the pressure in the compression side pressure chamber 8 becomes smaller, the differential pressure between the expansion side pressure chamber 7 and the expansion side chamber R1, and the differential pressure between the compression side pressure chamber 8 and the compression side chamber R2. Therefore, the flow rate passing through the expansion side passage 10 and the pressure side passage 11 becomes larger than that at the low frequency, and the flow rate of the attenuation passages 4 and 5 is reduced accordingly, and the damping force generated by the shock absorber D is also increased. Will be reduced.

  Thus, as shown by the solid line in FIG. 3, the shock absorber D generates a large damping force for vibrations in the low frequency range and exhibits a damping force reducing effect for vibrations in the high frequency range. Thus, the damping force can be reduced, and a damping force depending on the input vibration frequency can be generated. In the case where a variable valve capable of changing the flow path area is provided in the middle of the extension side passage 10 or the pressure side passage 11, the flow path area is changed by the variable damping valve, and the solid line in FIG. It is also possible to adjust the damping force reduction range in the damping characteristics shown. When the flow path area is reduced, the damping force reduction effect is weakened, and on the contrary, the damping force reduction effect can be strengthened. In the case of this embodiment, since the extension side passage 10 is provided in the piston rod 3, a variable valve is provided in the piston rod 3, and the variable valve passes through the piston rod 3 in the axial direction and is accessed from the outside. It is recommended to adopt a structure that adjusts with a possible control rod.

  On the other hand, the operation of the shock absorber D when the free piston 9 is displaced from the neutral position to the point where it begins to close the port 22b will be described. When the amplitude of vibration input to the shock absorber D increases, the amount of displacement of the free piston 9 from the neutral position also increases, and the free piston 9 begins to close the port 22b, and finally the port 22b is completely closed. It becomes a state.

  That is, after the free piston 9 starts to close the port 22b, the flow path resistance of the pressure side passage 11 gradually increases according to the amount of displacement, and when the free piston 9 closes the port 22b, the flow path resistance in the pressure side passage 11 is increased. Maximum.

  As described above, when the free piston 9 is displaced beyond the position where it begins to close the port 22b, the flow path resistance of the pressure side passage 11 gradually increases. The moving speed to the stroke end side is reduced, and the apparent amount of liquid movement between the extension side chamber R1 and the pressure side chamber R2 via the pressure chamber C is reduced, and the liquid passing through the attenuation passages 4 and 5 correspondingly. As a result, the damping force generated by the shock absorber D gradually increases regardless of the vibration frequency.

  When the free piston 9 is stroked until the port 22b is completely closed, the apparent movement of the liquid between the expansion side chamber R1 and the pressure side chamber R2 is eliminated via the pressure chamber C, and the expansion and contraction direction of the shock absorber D is eliminated. The liquid passes only through the damping passages 4 and 5 until it turns, and the shock absorber D generates a damping force with the maximum damping coefficient regardless of the vibration frequency.

  For the vibration in the frequency range where the shock absorber D produces a damping force reducing effect, the shock absorber D has a relatively low damping until the free piston 9 is displaced from the neutral position to a position where the port 22b starts to close. When the free piston 9 begins to close the port 22b, the damping force gradually increases. When the free piston 9 is further displaced toward the stroke end side and completely closes the port 22e, the maximum is generated. A damping force is generated with a damping coefficient of. In other words, the shock absorber D is exhibiting a damping force reduction effect, and even when a large amplitude vibration is input, the shock absorber D does not suddenly change the magnitude of the damping force. The damping force change to a high damping force can be made gentle. Therefore, in this shock absorber D, even if vibration with a large amplitude is input, the generated damping force changes gently, and it is not necessary for the passenger to perceive a shock due to the change in the damping force. In particular, when the vibration frequency is high, since a low damping force is generated, a sudden change in the generated damping force can be effectively mitigated.

  Thus, the shock absorber D exhibits a large damping force for vibrations in the low frequency range and a small damping force for vibrations in the high frequency range in response to the input vibration frequency. However, in the suspension device of the present invention, the shock absorber D is built in only one front fork F1 of the pair of front forks F1, F2.

  Thus, when the shock absorber D is built in only one front fork F1, one shock absorber D expands and contracts and exhibits a damping force that suppresses vibration of the vehicle body supported by both front forks F1 and F2. Thus, the difference in pressure between the expansion side chamber R1 and the compression side chamber R2 in the cylinder 1 during expansion and contraction is greater than when the shock absorber D is built in each of the front forks F1, F2.

  When the pressure difference between the extension side chamber R1 and the compression side chamber R2 increases, the amount of displacement of the free piston 9 increases, and accordingly, the extension side chamber apparently bypasses the damping passages 4 and 5 via the pressure chamber C. Since the amount of hydraulic fluid that exchanges R1 and the pressure side chamber R2 increases, the damping force reduction effect with respect to the input of high-frequency vibration is greater than when the shock absorber D is built in each of both front forks F1, F2. This is because the suspension device of the present invention in which the shock absorber D is incorporated only in one front fork F1 appears more remarkably. That is, as shown in FIG. 3, in the suspension device unit, in the suspension device of the present invention indicated by the solid line, the damping characteristic when the shock absorber D is built in both the front forks F1 and F2 indicated by the broken line. Since the damping force reduction range in the damping characteristic is increased, the damping force reduction range can be ensured even when the weight of a lightweight two-wheeled vehicle is supported.

  Therefore, according to the suspension device of the present invention, since the shock absorber D exhibiting the damping force sensitive to the frequency is incorporated only in one of the front forks F1, F2, the lightweight two-wheeled vehicle. Even when the vehicle body is supported, the damping force can be sufficiently reduced, and the riding comfort of the motorcycle can be improved.

  Further, as described above, even when supporting the body of a lightweight two-wheeled vehicle, the pressure difference between the expansion side chamber R1 and the compression side chamber R2 in the shock absorber D can be increased when the front fork F1 is expanded and contracted. Even if the spring constant of the spring element is set to be larger than that in the case of using two shock absorbers D, a damping characteristic sensitive to a frequency suitable for a two-wheeled vehicle can be obtained, so that the housing 6 is not lengthened. There is no shortage of stroke of the front fork F1.

  Furthermore, if the pressure difference between the extension side chamber R1 and the pressure side chamber R2 in the shock absorber D is not sufficiently large, there is a possibility that the free piston 9 cannot be operated (displaced) due to friction generated between the free piston 9 and the housing 6. However, in the suspension device of the present invention, the pressure difference between the expansion side chamber R1 and the compression side chamber R2 in the shock absorber D can be increased when the front fork F1 expands and contracts, so that the free piston 9 does not malfunction and reliably occurs. In addition, the damping force reduction effect can be obtained, and the damping characteristic sensitive to the frequency can be realized without impairing the riding comfort of the two-wheeled vehicle.

  Further, since the shock absorber D is provided only on one front fork F1, and the suspension spring S2 is provided on the other front fork F2, the shock absorber D is compared with the one built in both front forks F1, F2. Thus, the suspension device becomes lighter, and fuel consumption in the motorcycle can be reduced.

  The housing 6 is provided in the cylinder 1 in the above-described embodiment. However, the housing 6 can be provided outside the cylinder 1, and a configuration in which the housing 6 is provided in the extension side chamber R1 is adopted. You can also. Further, the above-described damping force reducing effect of the shock absorber D can be enjoyed regardless of the presence or absence of the port 22b and the annular groove 26, and these can be eliminated. Further, the suspension spring S1 or the suspension spring S2 can be aggregated in either one and the other can be discarded, and the cylinder 1 of the shock absorber D is connected to the vehicle body side through the outer tube O1 or the inner tube I1. It is also possible to set an inverted buffer.

  This is the end of the description of the embodiment of the present invention, but the scope of the present invention is of course not limited to the details shown or described.

  The suspension device of the present invention can be used for vibration control applications of motorcycles.

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3 Piston rod 3a One end 3b of a piston rod The other end 3c of a piston rod Screw part 4, 5 of a piston rod Damping passage 6 Housing 7 Extension side pressure chamber 8 Pressure side pressure chamber 9 Free piston 10 Extension side passage 10a Side hole 10b Vertical hole 11 Pressure side passage 12 Spring element 15 Rod guide 17, 18 Leaf valve 20 Nut portion 20a Screw portion 20b Fitting recess 21 Housing tube 22 Tube portion 22a Step portion 22b Port 23 Bottom portion 23a Port 21a Port 23 Valve seat member 23a Annular valve seat 24 Sliding tube 25 Mirror part 26 Annular groove 27 Communication holes 28 and 29 As a spring element, coil spring 31 Partition 32 Valve disk 33 Air chamber 34 Air gap 35 Check valve 36 Suction passage 37 Base valve 38 Discharge passage 39 Through holes 41, 42 , 51, 52 Bearing 43, 50 Spring holder 53 Drilling 54 tubular member 55 rod 56 rod guide 57 stopper 58 partition wall C pressure chamber D buffer F1, F2 front fork I1, I2 inner tube O1, O2 outer tube R reservoir R1 expansion side chamber R2 compression side chamber S1, S2 suspension springs

Claims (2)

In the suspension device having an outer tube and a pair of front forks interposed between a vehicle body and a front wheel axle in a two-wheeled vehicle having an inner tube slidably inserted into the outer tube, each of the front forks A shock absorber that suppresses vibration of the vehicle body is incorporated only in one of the cylinders, and the shock absorber is slidably inserted into the cylinder and connected to one of the outer tube and the inner tube. A piston that divides the extension side chamber and the pressure side chamber, a piston rod having one end connected to the piston and the other end connected to the other of the outer tube and the inner tube, and a fluid passing through the extension side chamber and the pressure side chamber. Attenuating passage that provides resistance to flow, housing forming pressure chamber, and slidably inserted into pressure chamber A free piston that divides the pressure chamber into an extension side pressure chamber and a pressure side pressure chamber, an extension side passage that connects the extension side chamber and the extension side pressure chamber, and a pressure side passage that connects the pressure side chamber and the pressure side pressure chamber. And a spring element that exerts an urging force that suppresses displacement of the free piston with respect to the housing. The suspension device according to claim 1 or 2, wherein the front fork without the shock absorber includes a suspension spring that is interposed between the inner tube and the outer tube and elastically supports the vehicle body.

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