CN110520648B

CN110520648B - Front fork

Info

Publication number: CN110520648B
Application number: CN201880025849.0A
Authority: CN
Inventors: 大岳和己; 河田繁和
Original assignee: KYB Motorcycle Suspension Co Ltd
Current assignee: KYB Motorcycle Suspension Co Ltd
Priority date: 2017-04-25
Filing date: 2018-03-14
Publication date: 2021-03-23
Anticipated expiration: 2038-03-14
Also published as: CN110520648A; WO2018198560A1; TWI728242B; JP2018184977A; TW201842280A; JP6826487B2

Abstract

A front fork, comprising: a damper (D) which has a cylinder (5) and a piston rod (6) inserted into the cylinder (5) so as to be movable in the axial direction, and which is interposed between the outer tube (1) and the inner tube (2); a suspension spring (S) formed by winding a wire material, wherein the suspension spring (S) forms a cylindrical partition wall (7) by being in close contact with the wire material at one end in the axial direction before the amount of stroke toward the contraction side becomes maximum; and a cushion rubber (8) capable of entering into the partition wall (7), a restriction passage (70) being formed between the partition wall (7) and the cushion rubber (8) when the cushion rubber (8) enters into the partition wall (7), the restriction passage (70) applying resistance to the flow of the fluid moving to the outside from inside the partition wall (7), the cushion rubber (8) being compressed when the cushion rubber (8) further enters into the partition wall (7).

Description

Front fork

Technical Field

The present invention relates to an improvement of a front fork.

Background

Conventionally, as disclosed in, for example, JPH08-303518A, a front fork for a straddle-type vehicle includes: an outer tube; an inner tube movably inserted into the outer tube; a shock absorber and a suspension spring which are interposed between the outer tube and the inner tube; an oil lock box provided in a state of being immersed in oil; and an oil lock member that enters the oil lock case when a stroke amount of the front fork toward a contraction side becomes large.

In such a front fork, the vehicle body is elastically supported by a suspension spring. When vibration is input from the road surface to the front wheels during vehicle running, the suspension springs expand and contract, and the transmission of vibration to the vehicle body is suppressed. Further, when the suspension spring expands and contracts, the vehicle body vibrates by exerting an elastic force, but the shock absorber exerts a damping force to rapidly converge the vibration.

In the front fork, when the stroke amount of the front fork toward the contraction side increases, the oil lock member enters the oil lock box. Then, the oil in the oil lock case is pressurized by the oil lock member to increase the pressure in the oil lock case, thereby generating a large damping force (hereinafter, referred to as "damping force of the oil lock mechanism") that interferes with the contraction operation of the front fork. Therefore, the stroke speed of the front fork toward the contraction side can be reduced, and the impact at the time of full contraction can be alleviated.

Disclosure of Invention

The damping force of the oil lock mechanism has a characteristic dependent on the stroke speed, and increases when the stroke speed increases, and conversely decreases when the stroke speed decreases.

Therefore, when the front fork contracts and the oil lock member enters the oil lock case at a certain speed, the damping force of the oil lock mechanism temporarily increases. However, when the front fork continues to contract further, the stroke speed decreases, and therefore the damping force of the oil lock mechanism decreases. Fig. 5 shows this situation. Fig. 5 is a graph showing the characteristics of the damping force of the oil lock mechanism, in which the horizontal axis represents the elapsed time during which the front fork continues to contract, and the vertical axis represents the damping force of the oil lock mechanism as a load.

In the conventional front fork including the oil lock mechanism having such damping force characteristics, the damping force of the oil lock mechanism is reduced when the front fork is nearly completely contracted, and there is a possibility that the passenger feels uncomfortable such as a load kick when the front fork is completely contracted. In this way, in the oil lock mechanism having the speed-dependent damping force characteristic, it is difficult to increase the damping force in the low speed region.

Further, in the front fork disclosed in JPH08-303518A, the oil lock box is provided in the piston rod guide that pivotally supports the piston rod, and the structure of the piston rod guide becomes complicated and the price increases. Further, the oil lock member is generally formed of aluminum or the like, and is expensive. Therefore, the cost is high in the conventional front fork.

The present invention has been made to solve such problems, and an object of the present invention is to provide a front fork that can prevent a passenger from feeling uncomfortable with a load kick when the front fork is completely retracted, and can reduce the cost.

The front fork for solving the problems comprises: a suspension spring formed by winding a wire material, wherein a cylindrical partition wall is formed by closely contacting the wire material at one end portion in an axial direction until a stroke amount of a front fork toward a contraction side becomes maximum; and a cushion rubber capable of entering into the partition wall. Further, when the cushion rubber enters into the partition wall, a restriction passage that applies resistance to the flow of the fluid moving from inside to outside of the partition wall is formed between the partition wall and the cushion rubber, and when the cushion rubber further enters into the partition wall after the restriction passage is formed, the cushion rubber is compressed.

Drawings

Fig. 1 is a longitudinal sectional view schematically showing a front fork according to an embodiment of the present invention.

Fig. 2 is an enlarged vertical cross-sectional view showing a part of the front fork of fig. 1 in detail and showing a state when the cushion rubber starts to enter into the partition wall.

Fig. 3 is an enlarged vertical cross-sectional view showing a part of the front fork of fig. 1 in detail and showing a state when the cushion rubber is compressed.

Fig. 4 (a) is a diagram showing the characteristics of the damping force of the restricting passage with respect to the contraction time of the front fork, and fig. 4 (b) is a diagram showing the characteristics of the elastic force of the rubber pad with respect to the stroke amount of the front fork.

Fig. 5 is a diagram showing characteristics of the damping force of the oil lock mechanism with respect to the contraction time of the conventional front fork.

Detailed Description

Hereinafter, a front fork according to an embodiment of the present invention will be described with reference to the drawings. Like reference symbols in the various drawings indicate like elements. Note that, unless otherwise specified, "up" and "down" of the front fork in a state where the front fork is mounted on the vehicle are referred to as "up" and "down" of the front fork.

A front fork F according to an embodiment of the present invention shown in fig. 1 is a suspension device for suspending and mounting a front wheel in a straddle-type vehicle such as a motorcycle or a tricycle. The front fork F has: a telescopic pipe member T configured to have an outer pipe 1 and an inner pipe 2; and a shock absorber D and a suspension spring S which are housed in the tube member T.

In the present embodiment, the pipe member T is an inverted type. That is, the outer tube 1 is a vehicle-body-side tube and is disposed above the inner tube 2, and the inner tube 2 is an axle-side tube and is disposed below the outer tube 1.

The outer tube 1 is coupled to the vehicle body via a bracket on the vehicle side (not shown), and the inner tube 2 is coupled to the axle of the front wheel via a bracket 3 on the axle side.

Bearings

10 and 20 are provided between the overlapping portions of the outer tube 1 and the inner tube 2, and the inner tube 2 can slide smoothly in the outer tube 1. When the front wheel vibrates up and down due to the vehicle running on a road surface with irregularities, the inner tube 2 moves in and out of the outer tube 1 and the front fork F expands and contracts.

A steering shaft (not shown) is fixed to the bracket on the vehicle side. The steering shaft is inserted into a steering column of a vehicle body frame as a vehicle body frame so as to be rotatable by operation of a steering wheel. When the steering shaft is rotated, the front fork F supports the front wheel and rotates about the steering shaft, and therefore the orientation of the front wheel can be changed by operating the steering wheel.

The upper end opening of the outer tube 1 is closed by a cap 4. Further, the lower end opening of the inner tube 2 is closed by an axle-side bracket 3. The overlapping portion between the outer tube 1 and the inner tube 2 is sealed by a sealing member 11 such as an oil seal or a dust seal. In this way, in the front fork F according to the present embodiment, the liquid and the gas are sealed in the tube member T by dividing the inside and the outside of the tube member T, and the liquid and the gas are prevented from leaking to the outside of the tube member T.

Next, the damper D provided in the tube member T is a hydraulic damper, and the damper D includes: a cylinder 5; a piston rod 6 inserted into the cylinder 5 so as to be movable in the axial direction, and having one end protruding outward of the cylinder 5; a piston rod guide 50 provided at one end of the cylinder 5 and axially supporting the piston rod 6 to be movable in the axial direction; and a damping force generating element (not shown) that is provided in the cylinder 5 and applies resistance to the flow of liquid generated when the cylinder 5 and the piston rod 6 move relatively in the axial direction.

In the present embodiment, the shock absorber D is of a vertical type, and is disposed such that the piston rod 6 faces the vehicle body side (upper side) and the cylinder 5 faces the axle side (lower side). An upper end portion of a piston rod 6 projecting upward from the cylinder 5 is coupled to the outer tube 1 via a cap 4. On the other hand, the cylinder 5 is provided inside the inner tube 2, and is coupled to the inner tube 2 via the axle-side bracket 3.

Thus, the damper D is interposed between the outer tube 1 and the inner tube 2, and when the front fork F expands and contracts, the piston rod 6 enters and exits the cylinder 5 to expand and contract the damper D. When the shock absorber D extends or contracts, the damping force that hinders the extending or contracting operation of the front fork F is exerted by the resistance of the damping force generating element.

A reservoir R is formed outside the damper D and inside the tube member T. A liquid such as operating oil is stored in the reservoir R, and a gas is sealed above the liquid surface of the liquid to form a gas chamber G. In the present embodiment, the reservoir R communicates with the inside of the cylinder 5, and the liquid having a volume corresponding to the piston rod 6, which enters and exits the cylinder 5 when the shock absorber D extends and contracts, moves between the inside of the cylinder 5 and the reservoir R. This makes it possible to compensate for a change in the volume of the liquid in the reservoir R due to a change in the volume of the liquid caused by a change in the temperature and a change in the volume of the cylinder corresponding to the amount of the piston rod that advances.

However, the structure of the damper D can be modified as appropriate. For example, an air chamber capable of expansion and contraction may be provided in the cylinder, and a change in the volume of the liquid due to a change in temperature and a change in the volume of the cylinder corresponding to the amount of advance and retraction of the piston rod may be compensated for in the air chamber. Further, in the present embodiment, the shock absorber D is of a single-rod type and the piston rod 6 extends to one side of the piston (not shown), but the shock absorber may be of a double-rod type and the piston rod extends to both sides of the piston.

Next, the suspension spring S provided in the pipe member T together with the damper D is a compression coil spring formed by winding a wire material, and exerts an elastic force according to the amount of compression. The suspension spring S is provided on the outer periphery of the piston rod 6 projecting upward from the cylinder 5, and the upper end of the suspension spring S is supported by the outer tube 1 on the vehicle body side via the cap 4, and the lower end of the suspension spring S is supported by the cylinder 5 via the piston rod guide 50. Thus, the suspension spring S is interposed between the pipe member T and the cylinder 5.

When the front fork F contracts and the cylinder 5 enters the outer tube 1, the compression amount of the suspension spring S increases, and the elastic force of the suspension spring S increases. The elastic force of the suspension spring S separates the outer tube 1 from the inner tube 2 and acts in a direction to extend the front fork F. In the front fork F, the vehicle body is elastically supported by a suspension spring.

In the present embodiment, the suspension spring S includes a large-pitch portion and a small-pitch portion, and is provided at one end in the axial direction of the suspension spring S even if the small-pitch portion is small. Hereinafter, the portion with a small pitch provided at one end in the axial direction of the suspension spring S is referred to as the small pitch portion S1, and the other portion is referred to as the suspension spring main body S2.

When the front fork F contracts, the wire of the small space s1 is set to closely contact with each other until the stroke amount toward the contraction side of the front fork F becomes maximum and the front fork F is in the fully contracted state (fig. 2). The stroke amount toward the contraction side of the front fork F is a distance between the positions A, B when moving from the reference position (position a) to an arbitrary position (position B) in the direction in which the front fork F contracts, and is maximum in the fully contracted state. For example, when the position of the piston rod 6 relative to the cylinder 5 when the front fork F is in the most extended state is set as the reference position, the stroke amount of the front fork F toward the contraction side is equal to the movement amount (distance) of the piston rod 6 from the reference position.

As shown in fig. 2, in a state where the wires of the small space s1 are in close contact with each other, the small space s1 serves as a cylindrical partition wall 7, and prevents liquid from moving between the wires of the small space s 1. On the other hand, the pitch of at least a part of the suspension spring main bodies s2 is set to be larger than the pitch of the small pitch portions s1, and the wire materials are set so as not to come into close contact even when the front fork F is in the fully contracted state.

In the present embodiment, the small space portion S1 is provided at the side end of the cylinder 5 of the suspension spring S and is disposed in a state of being immersed in the liquid in the pipe member T. When the stroke amount of the front fork F toward the contraction side is larger than a predetermined value, as shown in fig. 2, the cushion rubber 8 attached to the outer periphery of the piston rod 6 starts to enter the partition wall 7.

The cushion rubber 8 is a cylindrical member formed of rubber (elastic body), and is fixed to the outer periphery of the piston rod 6 by press fitting. A contact portion 80 is fixed to the outer periphery of the piston rod 6 directly above the cushion rubber 8, and the upper end of the cushion rubber 8 contacts the contact portion 80. The contact portion 80 prevents the cushion rubber 8 from being displaced upward with respect to the piston rod 6.

The outer diameter of the cushion rubber 8 is smaller than the inner diameter of the partition wall 7 formed by the small pitch portion s 1. As described above, when the stroke amount of the front fork F toward the contraction side is larger than the predetermined value, the cushion rubber 8 enters the partition wall 7. Then, a restricting passage 70 is formed between the outer periphery of the cushion rubber 8 and the partition wall 7, and resistance is applied to the flow of the liquid from the inside toward the outside of the partition wall 7 by the restricting passage 70.

Therefore, when the front fork F contracts, the cushion rubber 8 increases the pressure in the partition wall 7 in the stroke region where it advances to the back side (downward) in the partition wall 7, and generates a damping force that interferes with the contraction operation of the front fork F. That is, in this stroke region, the main damping force exerted by the shock absorber D adds to the damping force of the restricting passage 70, and therefore the force against compression of the entire front fork F increases. Therefore, the stroke speed (contraction speed) of the front fork F toward the contraction side can be reduced, and the impact at the time of full contraction can be alleviated.

The damping force of the restricting passage 70 has a stroke speed-dependent characteristic, and the damping force of the oil lock mechanism increases when the stroke speed increases, and conversely decreases when the stroke speed decreases. Therefore, when the cushion rubber 8 enters the partition wall 7 at a certain speed, the damping force of the limiting passage 70 increases, and the partition wall 7 is formed by the contraction of the front fork F. However, when the front fork F further continues to contract to decrease the stroke speed, the damping force of the restricting passage 70 decreases. Fig. 4 (a) shows this situation. Fig. 4 (a) is a graph showing the characteristics of the damping force of the limiting path 70, in which the horizontal axis represents the elapsed time during which the front fork F continues to contract, and the vertical axis represents the damping force of the limiting path 70 as the load.

Further, when the front fork F further contracts after the cushion rubber 8 enters the partition wall 7, as shown in fig. 3, the lower end of the cushion rubber 8 abuts against the piston rod guide 50, and the cushion rubber 8 is compressed by the piston rod guide 50 and the abutting portion 80. Then, the cushion rubber 8 exerts an elastic force in accordance with the amount of compression. The elastic force of the cushion rubber 8 withdraws the piston rod 6 from the cylinder 5 and acts in a direction to extend the front fork F.

The elastic force of the cushion rubber 8 has a characteristic that depends on the stroke position (the position of the piston rod 6 in the axial direction with respect to the cylinder 5), and the elastic force of the cushion rubber 8 becomes maximum when the front fork F is in the maximum compression state as the stroke amount toward the compression side of the front fork F becomes larger and the elastic force of the cushion rubber 8 becomes maximum. Fig. 4 (b) shows this situation. Fig. 4 (b) is a graph showing the characteristics of the elastic force of the cushion rubber 8 with respect to the stroke amount, where the horizontal axis represents the stroke amount of the front fork F and the vertical axis represents the elastic force of the cushion rubber 8 as the load.

Thus, the cushion rubber 8 can exert the elastic force without depending on the stroke speed. Therefore, even if the stroke speed is decreased and the damping force of the restricting passage 70 is reduced when the front fork F is nearly completely contracted, the contraction operation of the front fork F can be inhibited by the elastic force of the cushion rubber 8. That is, even if the front fork F is close to the fully contracted state and the contraction speed is reduced, the load against the contraction is increased by the cushion rubber 8 to obtain a rigid feeling. Therefore, the front fork F prevents the passenger from being given a feeling of discomfort such as load kick when the front fork F is completely retracted, and the riding comfort of the vehicle can be improved.

Further, when the hardness or the shape of the cushion rubber 8 is changed, the feeling when the front fork F is completely contracted is changed. Therefore, the adjustment can be made by changing the cushion rubber 8 to a cushion rubber having a different hardness or shape. Further, since the cushion rubber 8 can be easily changed, adjustment is also easy, and the ride quality of the vehicle can be further improved.

The operation and effect of the front fork F according to one embodiment of the present invention will be described below.

The front fork F of the present embodiment includes: a telescopic pipe member T having an outer pipe (vehicle body side pipe) 1 and an inner pipe (axle side pipe) 2; a damper D having a cylinder 5 and a piston rod 6 inserted into the cylinder 5 so as to be movable in the axial direction, and interposed between the outer tube 1 and the inner tube 2; a suspension spring S formed by winding a wire material, interposed between the pipe member T and the cylinder 5, and forming a cylindrical partition wall 7 by being in close contact with the wire material at one end portion in the axial direction until the stroke amount of the front fork F toward the contraction side becomes maximum; and a cushion rubber 8 attached to the piston rod 6 and capable of entering the partition wall 7. When the cushion rubber 8 enters the partition wall 7, a restricting passage 70 is formed between the partition wall 7 and the cushion rubber 8, and the restricting passage 70 applies resistance to the flow of the fluid moving from the inside of the partition wall 7 to the outside. Further, when the cushion rubber 8 further enters into the partition wall 7 after the formation of the restricting passage 70, the cushion rubber 8 is compressed.

According to this configuration, when the cushion rubber 8 starts to enter the partition 7, the damping force exerted by the damper D adds to the damping force of the restricting passage 70, so that the force against compression of the entire front fork F becomes large, and the contraction speed of the front fork F can be reduced to alleviate the impact at the time of complete contraction.

Further, according to the above configuration, even if the stroke speed of the front fork F is decreased and the damping force of the restricting passage 70 is reduced, when the front fork F further contracts after the cushion rubber 8 enters the partition 7, the cushion rubber 8 functions to bias the front fork F in the extending direction. Therefore, since a rigid feeling can be obtained when the front fork F is completely contracted, and a feeling of discomfort such as load kick can be prevented from being given to the passenger, the riding feeling of the vehicle can be improved.

In addition, according to the above configuration, even if the partition wall 7 is formed instead of the conventional oil lock case, the cushion rubber 8 can be formed at a lower price than the conventional oil lock member without complicating and increasing the number of parts, so that the cost of the front fork F can be reduced.

In the present embodiment, the cushion rubber 8 is formed of one rubber sheet. Therefore, the number of parts of the front fork F can be reduced, and the cost can be reduced. However, the cushion rubber may be configured to have two or more rubber pieces having different hardness, shape, or the like. In this way, when two or more rubber sheets different in hardness, shape, or the like are used in combination, more fine adjustment can be performed, and therefore the ride quality of the vehicle can be further improved.

In the present embodiment, the shock absorber D is of a vertical type, and the piston rod 6 is coupled to the outer tube (vehicle body side tube) 1, and the cylinder 5 is coupled to the inner tube (axle side tube) 2. The cylinder 5 is provided in the inner tube (axle-side tube) 2, and a cushion rubber 8 is attached to the outer periphery of the piston rod 6 protruding outward from the cylinder 5. The suspension spring S has a small pitch portion (one end portion) S1 facing the cylinder 5 and interposed between the cylinder 5 and the outer tube (vehicle body side tube) 1.

According to the above configuration, the cushion rubber 8 can be easily attached as compared with the case where the cushion rubber 8 is attached to the cylinder 5, and the structure of the front fork F can be simplified. However, the damper may be inverted, the piston rod may be connected to the axle-side tube, and the cylinder may be connected to the vehicle-body side tube. In such a case, it is preferable to mount the cushion rubber to the cylinder via a rod guide or the like by directing the small pitch portion S1 of the suspension spring S to the opposite side of the cylinder after disposing the partition wall 7 in the liquid in the pipe member T, but this may be naturally done. Such a modification can be made regardless of the structure of the cushion rubber 8.

In the present embodiment, the pipe member T is an inverted type, the outer pipe 1 is a vehicle body side pipe, and the inner pipe 2 is an axle side pipe. However, the pipe member may be of a vertical type, the outer pipe may be an axle-side pipe, and the inner pipe may be a vehicle-side pipe. Such changes of the pipe member can be made regardless of the structure of the cushion rubber 8, the style of the shock absorber D, and the orientation of the suspension spring S.

In the present embodiment, a small space S1 is provided at one end of the suspension spring S, and the partition wall 7 is formed by the small space S1. However, the one end portion of the suspension spring S that can form the partition 7 may be set so that the wire material of the portion comes into close contact with the partition 7 when the cushion rubber 8 enters, or may not necessarily be a portion with a small pitch.

The partition 7 may be formed before the cushion rubber 8 is compressed, and the timing of forming the partition 7 may be appropriately changed. For example, the partition wall 7 may be formed in a 1G state in which a load of a vehicle weight is applied to the front fork F, or the partition wall 7 may be formed in a 1G state in which a load of one passenger is applied to the vehicle 1G. Alternatively, one end portion of the suspension spring may be densely wound in advance, and the partition wall 7 may be formed by the densely wound portion. In these cases, the cushion rubber 8 enters after the partition wall 7 is formed, and therefore, the degree of stroke at which the damping force of the restricting passage 70 can be obtained can be extended. Further, the suspension spring S can be designed to be simple as long as the spring characteristics of the suspension spring main body S2 can be set to the desired spring characteristics of the suspension spring S.

However, the partition wall 7 may be formed after the cushion rubber 8 is inserted into one end portion of the suspension spring S, and then the cushion rubber 8 may be compressed. The stroke amount of the front fork F required for the cushion rubber 8 to enter the partition 7 can be set arbitrarily according to the axial length of the partition 7, the position of the cushion rubber 8, and the like. The configuration of the suspension spring body S2 can be appropriately changed in accordance with the desired spring characteristics of the suspension spring S, and it goes without saying that the suspension spring body S2 may be provided with a small pitch portion and a large pitch portion.

While the preferred embodiments of the present invention have been illustrated and described in detail, modifications, variations and changes may be made without departing from the scope of the claims.

The present invention claims priority from Japanese patent application 2017-085815, filed on the patent office on 25.4.2017, the entire contents of which are incorporated herein by reference.

Claims

1. A front fork, comprising:

a telescopic pipe member having a vehicle body side pipe and an axle side pipe;

a shock absorber having a cylinder and a piston rod inserted into the cylinder so as to be movable in an axial direction, and interposed between the vehicle body side tube and the axle side tube:

a suspension spring formed by winding a wire material, the suspension spring being interposed between the pipe member and the cylinder, the wire material at one end portion in an axial direction being in close contact with each other to form a cylindrical partition wall until a stroke amount toward a contraction side becomes maximum; and

a cushion rubber attached to the cylinder or the piston rod and capable of entering the partition wall,

when the cushion rubber enters into the partition wall, a restriction passage that applies resistance to the flow of the fluid moving from inside to outside of the partition wall is formed between the partition wall and the cushion rubber,

when the cushion rubber further enters into the partition wall after the limiting passage is formed, the cushion rubber is compressed.

2. The front fork of claim 1,

the cushion rubber is configured to have two or more rubber pieces having different hardness or shape.

3. The front fork of claim 1,

the cylinder is disposed in the axle side tube,

the suspension spring is interposed between the cylinder and the vehicle body side pipe with the one end portion directed toward the cylinder side,

the buffer rubber is mounted on the periphery of the piston rod.