JPH0227704Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to an improvement of a front fork for a two-wheeled vehicle.

(Prior art and its problems) In general, front forks for two-wheeled vehicles generate damping force in accordance with the contraction speed.
In order to improve the ground contact of the front wheels when the vehicle body sinks during cornering, or to prevent the piston from bottoming out by effectively absorbing and mitigating the impact when the front wheels receive a large impact, It is desirable that the damping force of the front fork be changed depending on the stroke.

An example of this type of front fork is Utility Application No. 171195/1985, which was previously proposed by the applicant, which adjusts the opening pressure of the relief valve according to the displacement of the suspension spring. It is designed to generate a strong damping force in the latter half of the stroke to prevent the piston from bottoming out.

However, when the relief valve opens, it tries to push back the suspension spring, etc.
When the movable mass becomes large and the contraction speed of the front fork is not very high, sufficient operational response cannot be ensured, making it difficult to obtain desired damping force characteristics over a wide stroke range.

The purpose of this study is to solve the above problems.

(Means for Solving the Problems) The present invention consists of slidably inserting an inner tube into an outer tube, installing a sheet pipe inside the outer tube, and providing an oil reservoir inside the sheet pipe. In a front fork for two-wheeled vehicles that has a suspension spring interposed between the seat pipe and the outer tube, a relief valve is installed inside the seat pipe to open against excess hydraulic oil flowing into the oil reservoir chamber. A retainer that receives one end of the relief spring that biases the valve is provided so as to be slidable in the axial direction, and a damping port is formed in the seat pipe to allow excess hydraulic fluid to flow in, bypassing the relief valve. A detection spring is interposed at the lower end, a detection seat is sandwiched between the two springs, and a transmission rod is connected at one end to the detection seat to drive the retainer. A valve is connected that slides on the inner circumferential surface and adjusts the opening area of the damping port.

(Function) As a result, the relief valve and the damping port each generate a damping force characteristic depending on the stroke of the front fork via the detection seat and the transmission rod based on the amount of contraction of the suspension spring.

By setting the damping port so that it is narrowed from the first half of the stroke, the damping port generates a compression-side damping force that is secondarily proportional to the flow speed of the hydraulic oil, depending on the stroke, even when the front fork contraction speed is small. On the other hand, under conditions where the contraction speed is large to a certain extent, the relief valve 15 opens and generates a damping force that is linearly proportional to the flow velocity depending on the stroke, so the desired damping force can be set over a wide range of the stroke. It can be done.

(Example) Hereinafter, an example of the present invention will be described based on the accompanying drawings.

As shown in FIG. 1, the front fork 1 is
An inner tube 3 connected to the vehicle body side is slidably housed in an outer tube 2 connecting an axle, and a seat pipe 4 is provided inside the inner tube 3 and erected on the outer tube 2.

An inner tube 3 is attached to the upper end of the seat pipe 4.
A piston portion 4 inscribed in the inner tube 3 is provided, while an oil reservoir chamber C partially filled with gas is provided in the upper interior of the inner tube 3.

A suspension spring 5 is interposed between the seat pipe 4 and the inner tube 3 to elastically support the weight of the vehicle. A detection spring 7 is interposed between the lower end of the suspension spring 5 and the upper end of the seat pipe 4.

The detection spring 7 is formed so that the winding portions at both ends thereof are in close contact with each other even in a free state, and the length in the axial direction is longer than the width in the radial direction when the spring is fully compressed.

A detection sheet 8 is held between the suspension spring 5 and the detection spring 7, and the upper end of the transmission rod 10 is fixed to the center of the detection sheet 8 via a nut 11.

At the lower end of the transmission rod 10 there is a valve 22 and a collar 2.
Fix 4 by caulking.

The valve 22 is slidably inscribed in the seat pipe 4, and a damping port 13 is formed in the seat pipe 4, and the opening area of the damping port 13 increases or decreases based on the displacement of the valve 22. Resistance is applied to the hydraulic fluid passing through the damping port 13, which is quadratically proportional to the flow velocity.

Further, an orifice 27 is formed directly above the valve 22 of the seat pipe 4.

A port 23 is formed below the damping port 13 of the seat pipe 4, and a relief valve 15 is provided inside the seat pipe 4. A valve seat 17 on which the relief valve 15 is seated is fixed to a guide 18, while one end of a relief spring 16 that biases the relief valve 15 is slidably supported by a rod 19 via a retainer 21.

As a result, the relief valve 15 is connected to the port 23.
This provides a resistance that is primarily proportional to the flow velocity to excess hydraulic oil flowing from the lower oil chamber A to the oil reservoir chamber C through the lower oil chamber A.

The collar 24 projects from the transmission rod 10;
The detection sheet 8 is formed so that its annular end surface comes into contact with the retainer 21 when the detection sheet 8 is displaced to a certain extent. As a result, in the latter half of the stroke, the transmission rod 10 and the collar 24 are moved based on the displacement of the detection sheet 8.
The retainer 21 is lowered through the holder 21 to increase the initial load of the relief spring 16.

The guide 18 is screwed into the rod 19, and the rod 19
The guide 18 to which the valve seat 17 is attached is rotated relative to the end cap 20 by inserting a tool such as a screwdriver from the outside.
by displacing the relief spring 16 in the axial direction.
The initial load can be adjusted.

A check valve 25 is disposed on the valve seat 17 and is seated opposite the relief valve 15.
This check valve 25 is connected from oil reservoir chamber C to port 2.
The valve opens with almost no resistance to the hydraulic oil returning to the lower oil chamber A through 3.

This is the structure, and its operation will be explained next.

During the pressure side stroke of the front fork 1, excess hydraulic oil corresponding to the intrusion volume of the inner tube 3 flows from the lower oil chamber A to the damping port 13 and the orifice 2.
7 into the oil reservoir chamber C, and when the pressure in the lower oil chamber A rises beyond the set value, the relief valve 1
5 is opened, and excess hydraulic oil also flows in from port 23. On the other hand, when the front fork 1 operates on the extension side, the hydraulic oil in the oil reservoir chamber C opens the check valve 25 and flows out into the lower oil chamber A with almost no resistance.

As the suspension spring 5 contracts, the detection spring 7 also contracts, and the detection seat 8 descends in accordance with the stroke. The transmission rod 10 transmits the displacement of the detection seat 8 to the valve 22.
reduces the opening area of the damping port 13 according to the stroke, and in the latter half of the stroke, the displacement of the detection sheet 8 is reduced by the collar 24 and the retainer 21.
The pressure is transmitted to the relief spring 16 via the stroke, and the opening pressure of the relief valve 15 is increased in accordance with the stroke.

Therefore, under conditions where the contraction speed of the front fork 1 is low to a certain extent, the compression side damping force which is quadratically proportional to the flow speed increases depending on the stroke due to the damping port 13, while under conditions where the contraction speed is high to a certain extent, the relief valve 15 When the valve opens, the damping force, which is linearly proportional to the flow velocity, increases depending on the stroke.In actual driving, a soft ride is ensured in the first half of the stroke, and the vehicle body is stabilized during cornering. This provides ideal damping force characteristics that improve the ground contact of the front wheels in the event of sinking, and generate strong damping force in the latter half of the stroke to prevent bottoming out.

Furthermore, since the transmission rod 10 connects the detection seat 8 and the valve 22 and does not come into contact with the inner circumferential surface of the seat pipe 4 along the way, there is little sliding friction or biting of foreign objects, and the displacement of the detection seat 8 is reduced. The information can be reliably transmitted to the valve 22.

Since the valve 22 has a plurality of through holes 29 and has a shape that hardly receives the dynamic pressure of the hydraulic oil, the valve 22 is held at a constant position where the spring loads of the detection spring 7 and the suspension spring 5 are balanced according to the stroke.

In addition, since the length of the detection spring 7 in the axial direction is larger than the width in the radial direction even when the detection spring 7 is at the maximum compression, it is prevented from tilting greatly within the inner tube 3, and the friction with the inner circumferential surface of the inner tube 3 is prevented. can be reduced and good operability can be ensured.

Next, in another embodiment shown in FIG. 2, the valve 31 for adjusting the opening area of the damping port 13 is formed into a cylindrical shape with a bottom.

This valve 31 has a disc-shaped upper surface 32 with the tip of the transmission rod 10 fixed to the center thereof by caulking, and a plurality of ports 33 are formed on this upper surface 32. The cylindrical body portion 34 is formed so as to be in sliding contact with the inner circumferential surface of the seat pipe 4, so that the opening area of the damping port 13 can be adjusted. Torso 34
The end face is formed to abut against the retainer 21 to adjust the opening pressure of the relief valve 15. Note that a plurality of through holes 35 are also formed in the retainer 21.

(Effects of the invention) As described above, the present invention has the advantage of controlling the opening pressure of the relief valve that opens against the relief spring and the damping port parallel to the relief valve against excess hydraulic oil in a double-tube float fork. Since both the opening area and the opening area are adjusted according to the amount of contraction of the suspension spring, it is possible to set a desired stroke-dependent damping force over a wide stroke range.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention. FIG. 2 is a sectional view showing another embodiment. 1...Front fork, 2...Outer tube, 3...Inner tube 3, 4...Seat pipe 4, 5...Suspension spring, 7...Detection spring, 8...Detection seat, 10...Transmission rod, 13... Damping port, 15... Relief valve, 16... Relief spring, 21... Retainer, 22... Valve, A... Lower oil chamber, C...
Oil sump room.

Claims (1)

[Scope of utility model registration request] The inner tube is slidably inserted into the outer tube, a seat pipe is installed inside the outer tube, an oil reservoir is provided inside the seat pipe, and a suspension spring is interposed between the seat pipe and the inner tube. In the front fork for two-wheeled vehicles, a relief valve that opens against excess hydraulic oil flowing into the oil reservoir is installed inside the seat pipe, and a retainer that receives one end of the relief spring that biases the relief valve is installed in the axial direction. At the same time, a damping port is formed in the seat pipe to allow surplus hydraulic oil to bypass this relief valve, and a detection spring is interposed at the lower end of the suspension spring, which is held between the two springs. and a transmission rod connected at one end to the detection sheet to drive the retainer, and the transmission rod is in sliding contact with the inner peripheral surface of the sheet pipe to adjust the opening area of the damping port. A front fork for two-wheeled vehicles that features connected valves.