WO2018105683A1

WO2018105683A1 - Front forks

Info

Publication number: WO2018105683A1
Application number: PCT/JP2017/043940
Authority: WO
Inventors: 慶彦宮内
Original assignee: Ｋｙｂモーターサイクルサスペンション株式会社
Priority date: 2016-12-09
Filing date: 2017-12-07
Publication date: 2018-06-14
Also published as: JP2018096412A

Abstract

Front forks (F) comprising: a pair of legs (L1), (L2) that support a wheel; and a suspension spring (2) that elastically supports a vehicle body. The suspension spring (2) has: a first coil spring (20) housed in one leg (L1) and exerting elastic force over the entire stroke range; and a second coil spring (21) housed in the other leg (L2) and exerting elastic force from mid-stroke to the compression-side stroke.

Description

Front fork

The present invention relates to a front fork.

Generally, a suspension device used for a vehicle includes a spring called a suspension spring, and the body can be elastically supported by the spring. In some suspension devices, for example, as disclosed in JP2003-97615A, a suspension spring is a multi-stage coil spring, and the spring constant of the suspension spring can be switched during the stroke.

Also, a suspension device for suspending a front wheel of a saddle-ride type vehicle called a front fork includes a pair of legs that support the front wheel from both sides. When such a suspension spring having the stroke dependency described above is used for such a front fork, a common multi-stage coil spring is accommodated in each of the pair of legs, and the suspension spring is usually constituted by the pair of multi-stage coil springs. It is.

The multi-stage coil spring has, for example, a coarsely wound portion with a large pitch connected in series and a densely wound portion with a small pitch, and has a structure in which two types of coil springs are connected in series. And when the stroke amount to the contraction side of the front fork is increased and the compression amount of the multistage coil spring is increased, one coil spring (for example, the closely wound portion) is in close contact length, and the spring constant of the suspension spring is switched.

However, in the case of a structure in which a plurality of coil springs exert force in series as in the above-described multistage coil spring, the combined spring constant of the plurality of coil springs is smaller than the spring constant of the coil spring alone. For this reason, in order to obtain a desired elastic force as the suspension spring, the number of turns of the multi-stage coil spring must be increased, which increases the weight of the suspension spring as a whole and increases the cost.

Therefore, the present invention aims to provide a front fork that can eliminate such problems and reduce the weight of the suspension spring and reduce the cost even if the spring constant of the suspension spring is changed according to the stroke amount. .

Therefore, the front fork includes a suspension spring that includes a first coil spring and a second coil spring, and the first coil spring is accommodated in one of the pair of legs that support the wheel. The second coil spring is accommodated in the other leg, the first coil spring exerts elastic force over the entire stroke, and the second coil spring exerts elastic force in the stroke region on the contraction side from the middle of the stroke. It is characterized by exhibiting.

FIG. 1 is a front view showing a front fork according to an embodiment of the present invention. FIG. 2 is an enlarged longitudinal sectional view of a front fork according to an embodiment of the present invention. FIG. 3 is a partially enlarged sectional view showing a part of FIG. FIG. 4 is an enlarged perspective view showing a front fork spacer according to an embodiment of the present invention. FIG. 5 is a diagram showing the characteristic of the elastic force of the suspension spring with respect to the stroke amount of the front fork according to the embodiment of the present invention.

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.

1 and 2 is a suspension device for suspending front wheels in a straddle-type vehicle such as a two-wheeled vehicle or a three-wheeled vehicle. Hereinafter, for convenience of explanation, the upper and lower sides of the front fork F attached to the vehicle are simply referred to as “upper” and “lower” unless otherwise specified.

As shown in FIG. 1, the front fork F includes a pair of leg portions L1 and L2 that stand on both sides of the front wheel W, a vehicle body side bracket BU that connects upper ends of the leg portions L1 and L2, and each leg portion L1. , And an axle bracket BL for connecting the lower end of L2 to the axle of the front wheel W, respectively. A steering shaft S is attached to the vehicle body side bracket BU.

Although not shown, the steering shaft S is rotatably inserted into the head pipe of the vehicle body frame that is the skeleton of the vehicle body, and rotates by the operation of the handle. When the steering shaft S is rotated, the front fork F rotates about the steering shaft S while supporting the front wheel W, so that the direction of the front wheel can be changed by a steering operation.

Also, the pair of leg portions L1 and L2 play different roles. One leg L1 shown on the right side in FIG. 2 is a spring leg and does not have a damping force generation function. On the other hand, the other leg portion L2 shown on the left side in FIG. 2 is a damper leg and has a damping force generating function. Hereinafter, in order to distinguish these leg portions L1 and L2, one leg portion that is a spring leg is referred to as a first leg portion L1, and the other leg portion that is a damper leg is referred to as a second leg portion L2.

First, a common configuration in the first leg L1 and the second leg L2 will be described. Both the first leg portion L1 and the second leg portion L2 include a telescopic tube member 1 configured to include an outer tube 10 and an inner tube 11 that enters and exits the outer tube 10.

The tube member 1 is set upside down, and the outer tube 10 is a vehicle body side tube and the inner tube 11 is a wheel side tube. The outer tube 10 is fixed to the vehicle body side bracket BU by welding, and the inner tube 11 is fixed to the axle bracket BL by screwing. More specifically, the axle bracket BL has a bottomed cylindrical socket portion bs, and the lower end portion of the inner tube 11 is screwed to the inner periphery of the cylindrical portion b1 of the socket portion bs.

For this reason, when the front wheel W (FIG. 1) vibrates up and down, for example, when the vehicle travels on an uneven road surface, the inner tube 11 enters and exits the outer tube 10, and the first leg portion L1 and the second leg portion L2 move. The front fork F expands and contracts.

A cap 12 is attached to the inner periphery of the upper end of each outer tube 10, and the upper end opening (vehicle body side opening) of each tube member 1 is closed by the cap 12. On the other hand, the lower end opening (wheel side opening) of each tube member 1 is closed by the axle bracket BL. That is, in the present embodiment, the axle bracket BL also functions as a cap member (bottom cap) that closes the wheel side opening of the tube member 1.

Further, on the inner periphery of the lower end portion of each outer tube 10, a bush 13, a oil seal 14, and a dust seal 15 that are in sliding contact with the outer periphery of the inner tube 11 are mounted in this order from the upper side. For this reason, the inside of the outer tube 10 can be smoothly slid in a state where the inner tube 11 is supported by the bush 13. Further, the oil seal 14 and the dust seal 15 can prevent the liquid and gas from leaking out from between the overlapping portions of the outer tube 10 and the inner tube 11.

In the present embodiment, a liquid injection hole b3 that is closed by the plug member 16 is formed in the bottom b2 of the socket bs of the axle bracket BL. The plug member 16 is detachable. When the plug member 16 is removed, the liquid can be supplied into the tube member 1 from the liquid injection hole b3.

Further, in the present embodiment, the outer tube 10 is provided with a support portion 10 a that has an inner diameter substantially equal to the inner diameter of the bush 13 and is in sliding contact with the outer periphery of the inner tube 11. That is, in the present embodiment, the inner periphery of the support portion 10 a of the outer tube 10 and the outer periphery of the inner tube 11 are in direct sliding contact, and the inner tube 11 can be slidably supported by the support portion 10 a and the bush 13.

The configuration for supporting the inner tube 11 so as to be slidable is not limited to the above. Specifically, another bush may be provided on the upper side of the bush 13, and the outer tube 10 may support the inner tube 11 slidably through the pair of upper and lower bushes. In this case, the upper bush to be added may be attached to the outer periphery of the inner tube 11 and slidably contacted to the inner periphery of the outer tube 10, or may be attached to the inner periphery of the outer tube 10 and slidably contacted to the outer periphery of the inner tube 11. It may be allowed.

Next, different configurations of the first leg L1 and the second leg L2 will be described. The first leg portion L1 and the second leg portion L2 accommodate coil springs having different lengths that function as the suspension spring 2 in cooperation with each other. Among these coil springs, the long spring accommodated in the first leg L1 is the first coil spring 20, and the short spring accommodated in the second leg L2 is the second coil spring 21.

The first coil spring 20 and the second coil spring 21 exert an elastic force when compressed. The elastic force increases as the amount of compression increases, and acts to extend the front fork F and push up the vehicle body. Therefore, the vehicle body can be elastically supported by the suspension spring 2.

Further, the first leg portion L1 which is a spring leg has an upper end fixed to the cap 12 and a lower side inserted into the inner tube 11 and a lower end of the rod 3 attached to the inner tube 11. A movable spring receiver 30 that moves in the axial direction, an annular fixed spring receiver 40 that is fixed to the upper end of the inner tube 11 and through which the rod 3 passes, and a movable spring receiver 30 and a fixed spring receiver 40. And an extension spring 4 interposed therebetween. The first coil spring 20 is interposed between the bottom b2 of the axle bracket BL and the movable spring receiver 30.

The upper and lower ends of the rod 3 are respectively formed with screw grooves, and the cap 12 and the movable spring receiver 30 are connected to the upper and lower outer circumferences of the rod 3 by screwing. The rod 3 is connected to the outer tube 10 via a cap 12, and when the front fork F expands and contracts, the rod 3 enters and exits the inner tube 11, and the movable spring receiver 30 moves up and down in the inner tube 11. Moving.

The movable spring receiver 30 has a bottomed cylindrical connecting portion 30a that is screwed onto the outer periphery of the rod 3, and an annular flange portion 30b that protrudes radially outward from the lower end portion of the connecting portion 30a. And the lower end of the extending spring 4 contacts the upper surface of the flange portion 30b, and the upper end of the first coil spring 20 contacts the lower surface of the flange portion 30b.

The extension spring 4 is a coil spring, and the upper end of the extension spring 4 is separated from the fixed spring receiver 40 in a normal stroke range. However, when the stroke amount to the extension side of the front fork F becomes larger than a predetermined amount, the upper end of the extension spring 4 abuts against the fixed spring receiver 40. Then, the extending spring 4 is compressed between the fixed spring receiver 40 and the movable spring receiver 30 to exert an elastic force. The elastic force of the extending spring 4 acts in the direction in which the movable fork receiver 30 is pushed down and the front fork F is contracted.

On the other hand, the upper end of the first coil spring 20 is supported by the movable spring receiver 30, and the lower end is supported by the bottom b2 of the axle bracket BL. The elastic force of the first coil spring 20 acts to push up the movable spring receiver 30 and extend the front fork F. The upper end and the lower end of the first coil spring 20 are always in contact with the movable spring receiver 30 and the axle bracket BL. For this reason, the first coil spring 20 exerts an elastic force over the entire stroke of the front fork F, and biases the front fork F in the extending direction.

Further, the outer diameter of the movable spring receiver 30 is formed smaller than the inner diameter of the inner tube 11, and the inner diameter of the fixed spring receiver 40 is formed larger than the outer diameter of the rod 3. For this reason, the liquid and gas accommodated in the tube member 1 move through a gap formed between the movable spring receiver 30 and the inner tube 11 and a gap formed between the fixed spring receiver 40 and the rod 3. it can.

Therefore, the liquid stored in the tube member 1 can lubricate the sliding surfaces such as the outer periphery of the inner tube 11, the inner periphery of the support portion 10 a of the outer tube 10, and the inner periphery of the bush 13. In addition, the movable spring receiver 30 or the fixed spring receiver 40 may be provided with a through hole or a notch to allow movement of liquid and gas.

Subsequently, the second leg portion L2 that is a damper leg includes a cylinder 5 disposed inside the inner tube 11, a piston 60 that is slidably inserted into the cylinder 5, and a lower end connected to the piston 60. And a rod 6 whose upper end protrudes outside the cylinder 5 and an annular rod guide 50 which is attached to the upper end opening of the cylinder 5 and supports the rod 6 slidably. The spacer 7 is provided inside the cylinder 5 and below the piston 60, and the second coil spring 21 is provided below the spacer 7.

The cylinder 5 is disposed along the axial direction inside the inner tube 11. In the present embodiment, when the lower end of the cylinder 5 is abutted against the bottom b2 of the axle bracket BL and the upper end of the inner tube 11 is crimped inward with the rod guide 50 fitted to the upper end of the cylinder 5, The cylinder 5 and the rod guide 50 are fixed to the inner tube 11.

The inside of the cylinder 5 is divided into two chambers by a piston 60. Of these two rooms, assuming that one of the chambers that contracts when the front fork F extends is the expansion side chamber R1, and the other chamber that contracts when the front fork F contracts is the compression side chamber R2, in this embodiment, the expansion side chamber R1. Is arranged on the upper side, and the pressure side chamber R2 is arranged on the lower side. The extension side chamber R1 and the compression side chamber R2 are filled with liquid such as hydraulic oil.

On the other hand, a liquid storage chamber R3 is formed on the outer periphery of the cylinder 5, and the liquid is stored and gas is sealed above the liquid surface to form an air chamber G.

Further, the cylinder 5 is formed with an extension side communication hole 5a and a pressure side communication hole 5b communicating with the inside and outside of the cylinder 5. The extension side communication hole 5a and the pressure side communication hole 5b function as a throttle and provide resistance to the flow of the liquid. The extension side communication hole 5a is formed at an upper portion of the cylinder 5 and at a position always lower than the liquid level of the liquid reservoir chamber R3. The pressure side communication hole 5b is formed at a position lower than the extension side communication hole 5a. In the normal stroke range, the piston 60 moves between the expansion side communication hole 5a and the pressure side communication hole 5b.

The piston 60 is formed in an annular shape and is fixed to the outer periphery of the lower end of the rod 6. A screw groove is formed in the upper end portion of the rod 6, and the cap 12 is connected to the outer periphery of the upper end portion of the rod 6 by screwing. The rod 6 is connected to the outer tube 10 via the cap 12, and when the front fork F expands and contracts, the rod 6 enters and exits the cylinder 5 and the piston 60 moves up and down in the cylinder 5.

The piston 60 is provided with a communication passage 60a that connects the extension side chamber R1 and the pressure side chamber R2, and a pressure side valve 61 that opens and closes the communication passage 60a. As shown in FIG. 3, in the present embodiment, the pressure side valve 61 is an annular plate-like leaf valve. The outer peripheral side is allowed to bend. The outer peripheral portion of the pressure side valve 61 can be attached to and detached from a valve seat 60b that surrounds the upper end opening of the communication passage 60a.

The pressure in the extension side chamber R1 acts in a direction to close the pressure side valve 61 by pressing the outer periphery of the pressure side valve 61 against the valve seat 60b. On the other hand, the pressure in the pressure side chamber R2 acts on the pressure side valve 61 through the communication passage 60a, and acts in a direction to open the pressure side valve 61 by separating the outer periphery of the pressure side valve 61 from the valve seat 60b.

Further, in the present embodiment, the pressure side valve 61 is a check valve, and when the pressure in the pressure side chamber R2 exceeds the pressure in the expansion side chamber R1, the outer periphery of the pressure side valve 61 moves away from the valve seat 60b and quickly passes through the communication passage 60a. Open.

A notch is formed in the valve seat 60b on which the pressure side valve 61 is seated. The orifice 62 is formed by the notch. Therefore, even when the pressure side valve 61 is closed and the outer peripheral portion of the pressure side valve 61 is seated on the valve seat 60b, the expansion side chamber R1 and the pressure side chamber R2 are communicated with each other through the orifice 62.

The configuration of the pressure side valve 61 can be changed as appropriate. For example, the pressure side valve 61 may be a valve other than a leaf valve such as a poppet valve. The method for forming the orifice 62 is not limited to the above, and can be changed as appropriate. For example, a notch may be formed in the outer peripheral portion of the leaf valve, and an orifice may be formed by the notch.

Subsequently, the rod guide 50 is connected to the inner periphery of the upper end portion of the cylinder 5 and the outer side of the fitting portion 50a. And an annular large outer diameter portion 50b larger than the outer diameter. An annular step 50c is formed on the outer periphery of the rod guide 50 at the boundary between the fitting portion 50a and the large outer diameter portion 50b, and the upper end of the cylinder 5 is abutted against the step 50c.

Further, a through hole 50d is formed in the large outer diameter portion 50b. By this through hole 50d, a space formed between the inner tube 11 and the cylinder 5 on the outer periphery of the cylinder 5 and a space formed between the rod 6 protruding outside the cylinder 5 and the outer tube 10 are communicated, Liquid and gas can freely move between these. That is, the liquid reservoir chamber R3 is prevented from being partitioned by the rod guide 50 by the through hole 50d.

Therefore, the position of the liquid level in the liquid reservoir R3 can be lowered to the outer periphery of the cylinder 5 to secure the volume of the air chamber G, and the pressure in the air chamber G can be prevented from becoming excessive when the front fork F contracts. The load on the seal can be reduced.

Furthermore, even if the position of the liquid level of the liquid reservoir R3 is lowered to the outer periphery of the cylinder 5, the outer periphery of the inner tube 11, the inner periphery of the support portion 10a of the outer tube 10 with the liquid accommodated inside the tube member 1, The sliding surface such as the inner periphery of the bush 13 can be lubricated. Note that a cutout may be provided on the outer periphery of the large outer diameter portion 50b, and the movement of the liquid and gas may be allowed by the cutout.

According to the above configuration, when the front fork F extends, the rod 6 moves out of the cylinder 5 and the piston 60 moves upward in the cylinder 5. Then, the liquid in the expansion side chamber R1 to be reduced moves to the pressure side chamber R2 that expands through the orifice 62 (FIG. 3), and also moves to the liquid reservoir chamber L3 through the expansion side communication hole 5a.

The flow of liquid from the expansion side chamber R1 to the pressure side chamber R2 or the liquid reservoir L3 is resisted by the orifice 62 or the expansion side communication hole 5a, so that the pressure in the expansion side chamber R1 rises and the front fork F The extension side damping force that prevents the extension operation is generated. Further, when the front fork F extends, the rod volume of liquid that retreats from the cylinder 5 is insufficient in the cylinder 5, but the insufficient liquid is supplied from the liquid reservoir chamber R <b> 3 through the pressure side communication hole 5 b. To R2.

Further, when the stroke amount to the extension side of the front fork F increases beyond the normal stroke range, the piston 60 moves upward beyond the extension side communication hole 5a. Then, the liquid in the extension side chamber R1 cannot move to the liquid storage chamber R3 through the extension side communication hole 5a, so that the liquid in the extension side chamber R1 flows out of the extension side chamber R1 only through the orifice 62 (FIG. 3). become.

That is, when the stroke amount to the extension side of the front fork F increases, the flow passage area of the flow passage that allows the flow of the liquid flowing out of the extension side chamber R1 decreases, so that the damper leg (second leg portion L2) The extension side damping force is increased.

On the contrary, when the front fork F contracts, the rod 6 enters the cylinder 5 and the piston 60 moves downward in the cylinder 5. Then, the liquid in the pressure side chamber R2 to be reduced opens the pressure side valve 61 and moves to the extension side chamber R1 through the communication path 60a. As described above, since the pressure side valve 61 is a check valve, when the front fork F is contracted, the pressures in the extension side chamber R1 and the pressure side chamber R2 are substantially equal.

Further, when the front fork F is contracted, the liquid for the volume of the rod that enters the cylinder 5 becomes surplus in the cylinder 5, so that the surplus liquid passes through the pressure side communication hole 5b and passes from the pressure side chamber R2 to the liquid reservoir chamber. Move to R3. Then, since resistance is given to the flow of the liquid by the pressure side communication hole 5b, the pressure in the cylinder 5 rises, and a pressure side damping force that prevents the contraction operation of the front fork F is generated.

Subsequently, the spacer 7 and the second coil spring 21 provided on the lower side of the piston 60 are disposed in the compression side chamber R2. As shown in FIG. 4, the spacer 7 includes a columnar main body portion 7 a and a convex portion 7 b that protrudes downward from the lower end of the main body portion 7 a and into which the second coil spring 21 is fitted.

The cross section of the main body portion 7a is substantially constant in the axial direction and has a substantially cross shape. In other words, the main body portion 7a has a shape in which four protrusions 7d extend radially outward from the center portion 7c in the radial direction. Assuming that the recesses formed between the

adjacent protrusions

7d and 7d are cutouts 7e, the cutouts 7e are continuously formed from one end to the other end in the axial direction of the main body portion 7a.

Further, if the diameter of the circle connecting the tips of all the protrusions 7d is the outer diameter of the main body portion 7a, the outer diameter of the main body portion 7a is smaller than the inner diameter of the cylinder 5 and larger than the outer diameter of the convex portion 7b. . For this reason, the spacer 7 can move up and down in the cylinder 5 while being stacked on the second coil spring 21. Furthermore, the liquid in the pressure side chamber R2 can freely move in the gap formed between the protrusion 7d and the cylinder 5 and the gap formed between the spacer 7 and the cylinder 5 by the notch 7e. Therefore, the pressure side chamber R2 is not partitioned by the spacer 7 and the pressure side communication hole 5b is not blocked by the spacer 7. Even if the pressure side chamber R2 has the spacer 7, the second leg L2 functions as a damper. Can exert damping force.

Next, as shown in FIG. 2, the second coil spring 21 provided on the lower side of the spacer 7 has its upper end abutted against the lower surface of the main body portion 7a with its upper end fitted to the convex portion 7b. The lower end is supported by the bottom b2 of the axle bracket BL. In the stroke region where the contraction amount of the front fork F is small, the upper end of the spacer 7 is separated from the lower end of the rod 6, and the elastic force of the second coil spring 21 is not transmitted to the rod 6.

However, when the contraction amount of the front fork F becomes larger than a predetermined value and the lower end of the rod 6 hits the spacer 7, the second coil spring 21 is compressed between the rod 6 and the axle bracket BL, and the amount of compression depends on the compression amount. Demonstrate the elastic force. The elastic force of the second coil spring 21 acts in the direction of pushing up the rod 6 via the spacer 7.

Therefore, the second coil spring 21 functions only in a partial stroke region on the contraction side from the middle of the stroke, and urges the front fork F in the extending direction. In the present embodiment, the lower end of the rod 6 projects downward from the piston 60, and the spacer 7 strikes the portion. However, the spacer 7 may be abutted against the lower surface of the piston 60.

Hereinafter, the operation of the front fork F according to the present embodiment will be described.

When the front wheel W moves up and down as the vehicle travels on an uneven road surface, the inner tube 11 of the first leg L1 and the second leg L2 enters and exits the outer tube 10 and the front fork F expands and contracts. Then, the second leg portion L2 which is a damper leg functions as a damper and exhibits a damping force, and the suspension spring 2 configured to include the first coil spring 20 and the second coil spring 21 is compressed. Delivers the corresponding elastic force.

More specifically, if the stroke position at which the second coil spring 21 starts compression is P (FIG. 5), the second coil spring 21 does not function in the stroke region X on the extension side of the stroke position P, and the stroke It functions in the stroke area Y on the contraction side with respect to the position P. Accordingly, in the stroke region X where the second coil spring 21 does not function, only the first coil spring 20 substantially functions as the suspension spring 2. For this reason, the spring constant of the suspension spring 2 in the stroke region X is equal to the spring constant of the first coil spring 20.

On the other hand, in the stroke region Y where the second coil spring 21 functions, both the first coil spring 20 and the second coil spring 21 function as the suspension spring 2. For this reason, the spring constant of the suspension spring 2 in the stroke region Y is a combined spring constant of the spring constant of the first coil spring 20 and the spring constant of the second coil spring 21. Then, the spring constant of the suspension spring 2 in the stroke region Y becomes larger than the spring constant of the suspension spring 2 in the stroke region X.

Therefore, as shown in FIG. 5, the spring constant of the suspension spring 2 is increased in the stroke region Y where the stroke amount toward the contraction side is larger than the predetermined (stroke position P), and the elastic force of the suspension spring 2 with respect to the stroke amount. Becomes larger.

In other words, in the front fork F, the suspension spring 2 has a stroke dependency that switches to a large spring constant when the contraction amount becomes larger than a predetermined amount. The elastic force of the suspension spring 2 is reduced in the stroke region X where the contraction amount of the front fork F is small, and the elastic force of the suspension spring 2 is increased in the stroke region Y where the contraction amount is large.

For this reason, for example, when the passenger is only the driver, the elastic force of the suspension spring 2 when the loaded load is small can be reduced to improve the riding comfort of the vehicle. Further, the elastic force of the suspension spring 2 when the loaded load becomes large due to the influence of passengers, cargo, etc. can be increased, and the frequency with which the front fork F is bottomed (becomes the most compressed state) can be reduced. That is, in the front fork F, the spring constant of the suspension spring 2 can be switched according to the stroke amount so as to be a spring constant according to the load, so that the riding comfort of the vehicle can be improved.

Further, when the front fork F extends beyond the normal stroke range, the front fork F has an elastic force of the extending spring 4 of the first leg L1 and a large extension side damping force of the second leg L2. The extension speed can be reduced. Therefore, the impact when the front fork F is fully extended can be alleviated, and the riding comfort of the vehicle can be further improved.

In the present embodiment, the second coil spring 21 is compressed via the spacer 7. For this reason, for example, if the spacer 7 is changed to a spacer having a different length, the stroke position P for switching the spring constant of the suspension spring 2 can be changed. That is, since the stroke position P can be changed without changing the second coil spring 21, the stroke position P can be easily adjusted.

Furthermore, the spacer 7 is disposed between the piston 60 and the second coil spring 21. For this reason, the spacer 7 can be used as a spring receiver, and there is no need to provide a spring receiver on the piston 60 or the rod 6. The spacer 7 is provided so as to be separable from the piston 60 and the rod 6. For this reason, replacement of the spacer 7 is easy.

The spacer 7 has a columnar main body 7a and a convex portion 7b that is connected to the lower end (one end in the axial direction) of the main body 7a and has an outer diameter smaller than the outer diameter of the main body 7a. And the 2nd coil spring 21 fits to the outer periphery of the convex part 7b. For this reason, it can prevent that the spacer 7 and the 2nd coil spring 21 shift | deviate laterally by the said convex part 7b, and can suppress that the load concerning the 2nd coil spring 21 is biased.

Further, the outer diameter of the main body portion 7a is smaller than the inner diameter of the cylinder 5, and a notch 7e is formed on the outer periphery of the main body portion 7a so as to continue from one end to the other end in the axial direction. For this reason, even if the spacer 7 is provided in the pressure side chamber R2, the pressure side chamber R2 is not partitioned by the spacer 7. In addition, the spacer 7 does not hinder the flow of the liquid flowing back and forth between the expansion side chamber R1 and the pressure side chamber R2, and the flow of the liquid flowing back and forth between the pressure side chamber R2 and the liquid storage chamber R3, and generates a damping force. Will not hinder.

Further, when the spacer 7 is formed of a synthetic resin, the spacer can be reduced in weight and the design freedom of the shape is high. Therefore, as described above, it is easy to provide the convex portion 7b or the notch 7e.

The configuration of the spacer 7 is not limited to the above, and the shape, material, and arrangement can be changed as appropriate. For example, the spacer may be connected to the piston 60 or the rod 6 to integrate them, or may be provided below the second coil spring 21. Further, if the stroke position P can be set arbitrarily, the spacer may be eliminated.

Further, in the present embodiment, the second leg (the other leg) L2 is a damper leg that functions as a damper, and exerts a damping force by imparting resistance to the flow of liquid contained therein. The monopod (one leg) L1 does not have such a function. Of the first coil spring 20 and the second coil spring 21 constituting the suspension spring 2, the longer first coil spring 20 is accommodated in the first leg L1, and the shorter second coil spring 21 is the first coil spring 21. Housed in the bipod L2.

That is, according to the above configuration, the long first coil spring 20 is accommodated in the first leg L1 that does not accommodate components (cylinder 5, rod 6, piston 60, etc.) necessary for generating the damping force. For this reason, even if the length of the 1st coil spring 20 is long, it can suppress that the 1st leg part L1 is bulky in an axial direction.

Further, since the length of the second coil spring 21 accommodated in the second leg portion L2 is shorter than that of the first coil spring 20, the second leg portion L2 that accommodates the parts necessary for generating the damping force is second. Even if the two-coil spring 21 is accommodated, the second leg L2 can be prevented from being bulky in the axial direction.

Therefore, according to the above configuration, the storage length of the front fork F can be shortened to improve the mountability. For example, in a front fork in which the steering shaft projects greatly upward from the upper end of the leg portion as shown in FIG. 1, the length of the leg portion cannot often be increased. For this reason, it is effective to employ the above configuration particularly in such a form of front fork.

The second leg portion (the other leg portion) L2 which is a damper leg includes a telescopic tube member 1 having an outer tube (vehicle body side tube) 10 and an inner tube (wheel side tube) 11, and an inner tube 11. Are connected to the outer tube 10, are connected to the cylinder 5, are slidably inserted into the cylinder 5, are slidably inserted into the cylinder 5, and are divided into an extension side chamber R 1 and a pressure side chamber R 2. And a rod 6 whose tip (one end) is connected to the piston 60. A liquid is stored between the tube member 1 and the cylinder 5 to form a liquid storage chamber R3. The cylinder 5 resists the flow of liquid from the pressure side chamber R2 to the liquid storage chamber R3. A pressure side communication hole 5b is formed.

According to the above configuration, when the front fork F contracts, the rod volume of liquid that enters the cylinder 5 becomes surplus in the cylinder 5, and the liquid passes through the pressure side communication hole 5b from the pressure side chamber R2 to the liquid reservoir chamber R3. Move to. Therefore, resistance is given to the flow of the liquid by the pressure side communication hole 5b to obtain the pressure side damping force.

That is, in the present embodiment, the compression side communication hole 5b is a compression side damping force generation element, so the configuration of the compression side damping force generation element is very simple and the manufacture of the front fork F can be facilitated. Moreover, since the pressure side communication hole 5b is formed in the side part of the cylinder 5, when the 2nd coil spring 21 is arrange | positioned in the pressure side chamber R2, it can suppress that the 2nd leg part L2 is bulky in an axial direction.

More specifically, the pressure-side damping force generating element is a valve such as a leaf valve, and when the valve gives resistance to the flow of liquid from the pressure-side chamber R2 to the liquid reservoir chamber R3, it is fixed to the lower end portion of the cylinder 5. Generally, the valve is attached to the partition member, and resistance is given to the flow of the liquid passing through the passage formed in the partition member by the valve.

However, in this case, the number of parts of the damper leg is increased and the structure becomes complicated, and the second coil spring 21 must be disposed on the upper side by providing the partition member. Therefore, when the second coil spring 21 is provided in the pressure side chamber of such a damper leg, the damper leg becomes longer in the axial direction, and the front fork may not fit in a predetermined space.

On the other hand, according to the above configuration, the configuration of the second leg L2 which is the damper leg can be simplified. Furthermore, since the lower end of the second coil spring 21 can be directly supported by the axle bracket BL, the support mechanism of the second coil spring 21 can be extremely simplified. Therefore, the structure of the front fork F can be simplified and the cost can be reduced. In addition, since the position of the second coil spring 21 can be lowered, it is possible to prevent the second leg portion L2 from being bulky in the axial direction.

In addition, the structure of the 1st leg part L1 and the 2nd leg part L2 is not restricted above, and can be changed suitably. For example, the compression-side damping force generating element in the second leg L2 may be changed to a valve such as a leaf valve.

Further, in the second leg portion L2 of the present embodiment, the orifice 62 and the extension side communication hole 5a are elements for generating a damping force on the extension side. For this reason, the structure of the damping force generating element on the extension side is very simple, and the manufacture of the front fork F can be facilitated. However, the extension side damping force generation element may be only one of the orifice 62 and the extension side communication hole 5a. Further, the extension side damping force generating element may be a valve such as a leaf valve. In this way, the configuration of the damping force generating elements on the extension side and the compression side in the damper leg can be appropriately changed.

Further, in the second leg portion L2 of the present embodiment, the inside of the cylinder 5 is communicated with the liquid reservoir chamber L3 via the pressure side communication hole 5b, and the cylinder volume change due to the rod protruding and retracting volume and the cylinder due to the temperature change The volume change of the liquid in 5 can be compensated by the liquid reservoir R3. That is, the liquid reservoir L3 functions as a reservoir liquid reservoir, and the tube member 1 constitutes a reservoir housing. However, an air chamber that can be expanded and contracted in the cylinder 5 may be defined by a movable partition wall such as a free piston or a bladder, and volume compensation may be performed in the air chamber. Thus, when providing a volume compensation air chamber in the second leg, the cylinder 5 is eliminated, the piston 60 is slidably contacted with the inner periphery of the inner tube 11, and the inner tube 11 functions as a cylinder. Also good.

Moreover, in the 1st leg part L1 and 2nd leg part L2 of this Embodiment, each tube member 1 is set to the inverted type, the outer tube 10 becomes a vehicle body side tube, and the inner tube 11 becomes a wheel side tube. ing. For this reason, since an axle bracket can be reduced in size compared with the case where an upright tube member in which an outer tube and an axle bracket are integrated is used, a front fork can be formed at a low cost. However, the tube member 1 may be an upright type. Thus, the structure of the tube member of each leg can be changed as appropriate.

And such a change of the 1st leg part L1 and the 2nd leg part L2 is possible irrespective of the structure of a spacer, and the presence or absence. Further, the first leg portion L1 may be a damper leg that functions as a damper, and the second leg portion L2 may be a spring leg that does not function as a damper.

In the present embodiment, the front fork F includes a first leg L1 and a second leg L2 (a pair of legs) that support the front wheel (wheel) W, and a suspension spring 2 that elastically supports the vehicle body. Prepare. The suspension spring 2 includes a first coil spring 20 that is accommodated in the first leg portion (one leg portion) L1 and exhibits an elastic force over the entire stroke of the front fork F, and a second leg portion (the other leg portion). Part) The second coil spring 21 that is housed in L2 and that exerts an elastic force in the stroke region Y on the contraction side from the middle of the stroke.

According to the above configuration, the stroke region X in which only the first coil spring 20 functions and the stroke region Y in which both the first coil spring 20 and the second coil spring 21 function are formed. It can be changed according to the stroke amount.

Moreover, according to the said structure, since the 1st coil spring 20 and the 2nd coil spring 21 exhibit force in parallel, two types of coil springs, the 1st coil spring 20 and the 2nd coil spring 21, are used as the suspension spring 2. Even if it is used, the combined spring constant of the two coil springs is larger than the spring constant of the coil spring alone. For this reason, the number of turns of the coil spring as a whole suspension spring can be reduced as compared with a conventional front fork using a multistage coil spring in which two types of coil springs exert a force in series. Therefore, the weight of the suspension spring is reduced, and the cost can be reduced.

Furthermore, according to the above configuration, since the first coil spring 20 and the second coil spring 21 are individually accommodated in the pair of leg portions, it is possible to prevent the diameter of each leg portion from increasing. Therefore, the front fork F can be reduced in size, and the front fork can be reduced in weight and further reduced in cost.

In the present embodiment, the spring constant of the suspension spring 2 is switched approximately at the center of the entire stroke area of the front fork F. However, the stroke position P at which the spring constant of the suspension spring 2 is switched can be appropriately changed according to the desired spring characteristic of the suspension spring 2. The change can be made regardless of the configuration and presence of the spacer and the configuration of the pair of legs.

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.

This application claims priority based on Japanese Patent Application No. 2016-239681 filed with the Japan Patent Office on December 9, 2016, the entire contents of which are hereby incorporated by reference.

Claims

A front fork,
A pair of legs that support the wheels;
A suspension spring that elastically supports the vehicle body,
The suspension spring is accommodated in one leg of the pair of legs, and is accommodated in the other leg of the pair of legs, and a first coil spring that exerts elasticity over the entire stroke. And a second fork configured to have a second coil spring that exhibits elasticity in the stroke region on the contraction side from the middle of the stroke.
The front fork according to claim 1,
A front fork that functions as a damper that exerts a damping force by applying resistance to the flow of liquid contained in the other leg only.
The front fork according to claim 2,
The other leg portion is a telescopic tube member having a vehicle body side tube and a wheel side tube, a cylinder connected to the wheel side tube and disposed inside thereof, and slidably inserted into the cylinder. A piston that divides the cylinder into an extension side chamber and a pressure side chamber, and a rod that is connected to the vehicle body side tube and has one end connected to the piston,
Between the tube member and the cylinder, a liquid is stored to form a liquid storage chamber,
The cylinder is formed with a pressure side communication hole that gives resistance to a flow of liquid from the pressure side chamber toward the liquid reservoir.
The second coil spring is disposed in the pressure side chamber.
The front fork according to claim 1,
The second coil spring is a front fork that is compressed through a spacer.
The front fork according to claim 3,
A spacer interposed between the second coil spring and the piston;
The spacer includes a column-shaped main body portion and a convex portion which is connected to one end portion in the axial direction of the main body portion and whose outer diameter is smaller than the outer diameter of the main body portion and one end of the second coil spring is fitted to the outer periphery. And
The outer diameter of the main body is smaller than the inner diameter of the cylinder,
A front fork in which a notch continuous from one end to the other end in the axial direction is formed on the outer periphery of the main body.