JPH08270709A - Different diameter structure of cylinder - Google Patents

Abstract

PURPOSE: To provide preferable riding comfortableness by suppressing the increment of the weight of a spring lower side without leading an accelerator bracket to increase its diameter as well as to employ a base valve part which is a size smaller than a cylindrical diameter, while the cylindrical diameter is increased so that performance of pressure side damping force in the middle speed area of a piston speed is improved. CONSTITUTION: The diameter of the lower end part of a cylinder 1 is shrunk, which is comprised by slidably housing a piston part successively arranged to a piston rod, and also arranging a base valve part 4 on the inner circumference side of the lower end part of the piston part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder having a different diameter structure suitable for use as a cylinder constituting a hydraulic shock absorber such as a front fork mounted on a motorcycle.

[0002]

2. Description of the Related Art In a hydraulic shock absorber, for example, a front fork mounted on a motorcycle, it is said that the compression side damping force in the medium speed range of the piston speed greatly affects the riding comfort of the motorcycle. There is.

Further, in order to improve the performance of the compression side damping force by the back valve in the piston portion sliding in the cylinder, the diameter of the cylinder is increased to increase the amount of oil passing through the back valve to set the degree of freedom of the back valve. Is taken, that is, the plate thickness of the valve is made flexible.

Therefore, the above measure, that is, by increasing the diameter of the cylinder, the piston portion having a larger diameter and the lower base valve portion have the desired pressure side in the medium speed range of the piston speed. The damping force can be obtained, and the riding comfort of the motorcycle can be improved.

However, when the cylinder is set to have a large diameter, it is conventionally said that the cylinder is formed as a straight cylinder, so that even in the base valve portion arranged on the inner peripheral side of the lower end portion of the cylinder. The diameter of the valve body forming the base valve portion is also increased so that the valve body is set to match the inner diameter of the cylinder.

Therefore, increasing the diameter of the cylinder causes not only the diameter of the piston portion but also the diameter of the base valve portion, and as a result, the lower end portion of the cylinder having the base valve portion, that is, the outer tube. However, the diameter of the axle bracket that holds the lower end of the cylinder so as to wrap it is also necessarily increased.

[0007] And, to increase the diameter of the axle bracket,
As a matter of course, there is a risk that the front fork will deteriorate the mountability of the motorcycle, but as is well known, the base valve part is equivalent to the intruder volume of the piston rod when the piston part enters the cylinder. It is set to generate a damping force of a predetermined magnitude when the amount of oil that passes through is passed.

Therefore, even if the diameter of the cylinder is increased, it is not always necessary to increase the diameter of the base valve portion, that is, the valve body forming the base valve portion. When the diameter of the base valve portion is excessively increased, the diameter of the axle bracket is eventually increased as described above, and the weight of the lower end side of the front fork, that is, the motorcycle is extended. In this case, the weight on the lower side of the spring is increased to rather deteriorate the riding comfort.

The present invention was made in view of the above circumstances, and an object thereof is to increase the cylinder diameter to improve the performance of the compression side damping force in the medium speed range of the piston speed. On the other hand, it is possible to adopt a so-called slightly smaller base valve portion as compared with the cylinder diameter, and it is preferable to suppress an increase in the weight of the unsprung side without increasing the diameter of the axle bracket. (EN) It is possible to provide a different diameter structure of a cylinder that makes it possible to obtain a comfortable ride and is optimal for use in a hydraulic shock absorber such as a front fork mounted on a motorcycle.

[0010]

In order to achieve the above-mentioned object, the structure of the present invention is basically arranged such that a piston portion connected to a piston rod is slidably accommodated and the lower end portion thereof is accommodated. In the cylinder in which the base valve portion is provided on the inner peripheral side of the cylinder, the lower end portion of the cylinder has a reduced diameter.

More specifically, the outer diameter of the lower end portion of the cylinder is reduced to such an extent that the outer diameter of the lower end portion of the cylinder substantially matches the inner diameter of the piston sliding portion, which is the upper end side of the cylinder, and the diameter reduction is performed. The tapered portion is formed in the vicinity of the lower end that is the connecting portion of the piston and the sliding portion of the piston, or the inner circumference of the lower end of the cylinder is approximately the same as the inner diameter of the piston sliding portion that is the upper end of the cylinder. It is assumed that auxiliary pipes having a diameter are connected in series, and a base valve portion is arranged on the inner peripheral side of the auxiliary pipes.

[0012]

Therefore, the lower end of the diameter-reduced cylinder enables the base valve portion, which has been arranged before setting the cylinder diameter to be large, on the inner peripheral side thereof.

By reducing the diameter of the lower end of the cylinder, the diameter of the axle bracket that encloses the lower end of the outer tube together with the lower end of the outer tube is not increased.

Further, since the diameter of the axle bracket is not increased, for example, the weight of the lower end side of the front fork, that is, the weight of the lower spring side of the motorcycle is not increased.

When the lower end of the cylinder is forcibly reduced in diameter by using a roller or the like, the thickness of the lower end becomes thicker than the thickness of the upper end of the cylinder, and a communication hole is opened to the lower end. Facilitates perforation and formation of inner thread.

Further, when the diameter of the lower end of the cylinder is reduced, when the vicinity of the lower end is tapered, the stress concentration phenomenon does not occur in the so-called reduced diameter portion.

When reducing the diameter of the lower end of the cylinder, when the outer diameter of the cylinder is reduced to such an extent that it substantially matches the inner diameter of the upper end of the cylinder, the diameter reduction process using rollers is facilitated.

Further, when an auxiliary pipe having a diameter smaller than the cylinder diameter is continuously provided on the inner circumference of the lower end of the cylinder to form the lower end of the cylinder, the diameter of the auxiliary pipe is freely set regardless of the expansion ratio of the cylinder. Can be set to.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the illustrated embodiments. A cylinder having a different diameter structure according to an embodiment of the present invention has a front fork F as a hydraulic shock absorber as shown in FIG. It is embodied in the cylinder 1 that constitutes the.

The front fork F is connected to the cylinder 1
The axle side tube 2 disposed on the outer peripheral side of the axle bracket 3, the axle bracket 3 having the upper end side screwed therein so as to include the lower end portion of the axle side tube 2, and the cylinder bracket 1 from the bottom portion of the axle bracket 3. A base valve unit 4 inserted toward the lower end of the cylinder 1, and by screwing the base valve unit 4 to the inner circumference of the lower end portion of the cylinder 1, the cylinder 1, the axle side tube 2, and the axle The bracket 3 and the base valve unit 4 are integrated.

A reservoir chamber B is formed between the cylinder 1 and the axle side tube 2 to connect the piston side oil chamber A in the cylinder 1 via the base valve portion 4a of the base valve unit 4. There is.

A communication hole 1a is formed at the lower end of the cylinder 1 to allow communication between the base valve portion 4a side on the inner peripheral side and the reservoir chamber B on the outer peripheral side. Although not shown, a piston portion connected to a piston rod is slidably accommodated therein, and the piston side oil chamber A is defined inside the lower end side of the cylinder 1.

In the front fork F formed as described above, the cylinder 1 in this embodiment has a reduced diameter from the lower end portion below the piston sliding portion 1b to the lower end portion. The diameter reduction is realized by using a roller or the like, for example.

It is assumed that the diameter reduction is performed so that the outer diameter of the lower end portion is substantially equal to the inner diameter of the piston sliding portion 1b. In the case of the diameter, it is possible to easily realize a predetermined diameter reduction without so-called irrational force.

Further, the diameter reduction in this embodiment is such that the outer diameter is reduced to such an extent that it is substantially equal to the inner diameter of the piston sliding portion 1b, and the diameter reduction portion 1c and the piston slide. It is realized so that the tapered portion 1d is formed in the vicinity of the upper end portion which is a connecting portion with the portion 1b.

By thus reducing the diameter of the lower end of the cylinder 1 to form the reduced diameter portion 1c, the reduced diameter portion 1c, that is,
The thickness of the lower end portion becomes thicker than the thickness of the upper piston sliding portion 1b, and as a result, when the communication hole 1a is opened therein and the thread 1e is formed on the inner periphery thereof, the lower end portion You will not have to worry about the strength being reduced.

Further, by setting the vicinity of the lower end of the cylinder 1 to be the tapered portion 1d, it becomes possible to avoid the concentration of stress on the so-called reduced diameter portion.

The base valve unit 4 is screwed onto the thread 1e.

Therefore, in the different diameter structure of the cylinder according to this embodiment formed as described above, the diameter of the cylinder 1 is increased as a whole and the rear surface of the piston portion sliding in the cylinder 1 Even if the compression side damping force of the valve is increased, the diameter of the lower end portion of the cylinder 1 is not increased.

Therefore, the base valve unit 4 disposed on the lower end of the cylinder 1, that is, on the inner peripheral side of the reduced diameter portion 1c,
That is, there is no need to increase the diameter of the base valve unit 4a, and particularly when the diameter of the piston rod that connects the piston units is not changed, it is not necessary to increase the size of the base valve unit 4a. 4 will not be required to increase the diameter.

Since the lower end of the cylinder 1 is not enlarged, that is, it can be set so small that it is smaller than the piston sliding portion 1b of the cylinder 1, the base valve unit 4 used up to that point can be continued. It is possible to use it.

Further, since the diameter of the lower end of the cylinder 1 is reduced, it is not necessary to increase the diameter of the axle bracket 3 which encloses the lower end of the cylinder 1 together with the lower end of the axle side tube 2, thus eliminating the need for an axle bracket. 3 does not cause deterioration of the mounting property of the front fork F due to the increase in diameter.

Further, since the diameter of the axle bracket 3 is not increased, the weight of the lower end side of the front fork F, that is, the weight of the unsprung side of the motorcycle is not increased due to the increased diameter, and the riding comfort is improved. Eliminate the fear of worsening.

FIG. 2 shows a different diameter structure of a cylinder according to another embodiment of the present invention. In this embodiment,
It is characterized in that the diameter of the lower end of the cylinder 1 is reduced while the lower end of the cylinder 1 is formed by connecting a separately prepared auxiliary pipe 10 having a smaller diameter to the inner circumference of the lower end of the cylinder 1.

Therefore, in the following, parts having the same constructions as those of the above-mentioned embodiment will be designated by the same reference numerals in the drawings unless necessary, and detailed description thereof will be omitted. To do.

Explaining a little, the auxiliary pipe 10 is made of a straight cylindrical body having an outer diameter substantially corresponding to the inner diameter of the cylinder 1 in which the auxiliary pipe 10 is continuously provided, and is formed on the outer circumference of the upper end portion and the inner circumference of the lower end portion of the cylinder 1. Has a thread 10a to be screwed into the thread 1e, and has a thread 10b to which the base valve unit 4 is screwed at the inner periphery of the lower end thereof. Further, the base valve unit 4a side of the base valve unit 4 side. It has a communication hole 10c for communicating with the reservoir chamber B.

The auxiliary pipe 10 is continuously connected to the lower end of the cylinder 1 with the seal member 11 provided on the outer periphery of the upper end above the thread 10a.

Therefore, this embodiment is disadvantageous in that the number of members is increased because the auxiliary pipe 10 is indispensable as compared with the above-mentioned embodiment, but the labor of reducing the diameter of the lower end of the cylinder 1 is required. Is advantageous in that it can be omitted.

Further, in this embodiment, as compared with the above-mentioned embodiments, the diameter of the auxiliary pipe 10 can be freely set to the diameter expansion ratio of the cylinder 1 regardless of how the wall thickness of the auxiliary pipe 10 is set. .

Therefore, in this embodiment, the auxiliary pipe 1
On the inner peripheral side of 0, the base valve portion 4a having a smaller diameter, that is,
It is also possible to distribute the base valve unit 4 having a smaller diameter, which is advantageous in that the base valve unit 4 whose diameter changes finely can be used as compared with the above-described embodiment.

The above description has been made by taking the case where the different diameter structure of the cylinder according to the present invention is embodied as the cylinder 1 constituting the front fork F, but from the intent of the present invention, this cylinder Needless to say, the different-diameter structure may be embodied in the cylinder 1 constituting another hydraulic shock absorber such as a shock absorber mounted on a four-wheel vehicle. As a matter of course, the same effect as that of the case can be expected.

[0042]

As described above, according to the present invention, since the lower end of the cylinder is reduced in diameter, the cylinder diameter is set to a large value to increase the amount of oil passing through the rear valve in the piston portion, thereby damping the compression side. Even if the degree of freedom in setting the force valve is improved, it is not necessary to structurally increase the diameter of the base valve portion arranged on the inner peripheral side of the lower end portion of the cylinder.

Therefore, in particular, when the diameter of the piston rod connecting the piston portions is not changed, it is not necessary to change the base valve portion to a large diameter structurally, and the base valve portion is used before the diameter expansion of the cylinder. The base valve part that had been used can be used as it is.

Since the diameter of the lower end of the cylinder is reduced, it is not necessary to increase the diameter of the axle bracket that encloses the lower end of the cylinder together with the lower end of the axle side tube. It will not cause deterioration of the front fork mounting property.

Further, since the diameter of the axle bracket is not increased, the weight of the lower end side of the front fork, that is, the weight of the unsprung side of the motorcycle is not increased due to the increased diameter, and the riding comfort is deteriorated. There is no fear of causing it.

Further, when the lower end portion of the cylinder is forcibly reduced in diameter, the wall thickness of the lower end portion becomes thicker, and when a communication hole is formed in the lower end portion and a thread is formed on the inner periphery thereof, Therefore, there is no need to worry that the strength of the lower end portion will be reduced.

Further, according to the present invention, when the diameter of the lower end of the cylinder is reduced, when the vicinity of the upper end and the lower end which is a connecting portion with the upper end of the cylinder is tapered, a so-called reduction is made. It is possible to avoid stress concentration on the diameter portion.

According to the present invention, when reducing the diameter of the lower end of the cylinder, when an auxiliary pipe having a diameter smaller than the cylinder diameter is connected to the inner circumference of the lower end of the cylinder,
Not only the work of reducing the diameter of the lower end of the cylinder can be omitted, but the inner diameter of the auxiliary pipe can be freely set regardless of what is called the diameter expansion ratio of the cylinder. Will also be available.

As a result, according to the present invention, the cylinder diameter is increased to improve the degree of freedom in valve setting of the compression side damping force in the medium speed range of the piston speed, while the base is so-called slightly smaller than the cylinder diameter. In addition to enabling the use of a valve portion, it is possible to suppress the increase in the weight of the unsprung side without increasing the diameter of the axle bracket, and it is mounted on a motorcycle for the purpose of improving riding comfort. There is an advantage that it is most suitable for use in a hydraulic shock absorber such as a front fork.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional front view showing a front fork having a cylinder according to an embodiment of a different diameter structure of a cylinder of the present invention in a broken manner.

FIG. 2 is a partial cross-sectional view showing a front fork having a cylinder according to another embodiment of the different diameter structure of the cylinder of the present invention in a cutaway manner.

[Explanation of symbols]

 1 Cylinder 1a, 10c Communication hole 1b Piston sliding part that is the upper end of the cylinder 1c Reduced diameter part that is the lower end of the cylinder 1d Tapered part that is near the lower end of the cylinder 1e, 10a, 10b Thread 2 Axle side tube 3 Axle bracket 4 Base valve unit 4a Base valve part 10 Auxiliary pipe 11 Seal member A Piston side oil chamber B Reservoir chamber F Front fork

Claims (3)

[Claims] 1. A cylinder in which a piston portion connected to a piston rod is slidably accommodated and a base valve portion is arranged on the inner peripheral side of the lower end portion of the cylinder, wherein the lower end portion of the cylinder has a reduced diameter. Different diameter structure of cylinder 2. A reduced diameter portion reduced in diameter such that an outer diameter of a lower end portion of the cylinder substantially matches an inner diameter of a piston sliding portion which is an upper end side of the cylinder, and the reduced diameter portion and the piston sliding portion. The different diameter structure of the cylinder according to claim 1, wherein the vicinity of a lower end portion which is a connecting portion with is a tapered portion. 3. An auxiliary pipe having an outer diameter substantially corresponding to an inner diameter of a piston sliding portion, which is an upper end side of the cylinder, is connected to an inner circumference of a lower end portion of the cylinder, and a base is provided on an inner peripheral side of the auxiliary pipe. The different diameter structure of the cylinder according to claim 1, characterized in that the valve portion is distributed.