JPS6357273B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a front fork of a motorcycle, and in particular, it is possible to freely adjust the characteristic of preventing the front fork from sinking during braking.

(Prior Art) Compressive force acts on the front fork of a motorcycle due to the movement of the center of gravity and inertia force that occurs during braking, and especially during sudden braking, the front fork sinks significantly and stability is impaired. In addition, when the effective stroke of the shock absorber is reduced due to sinking, if a shock is received from the road surface, the shock cannot be absorbed or alleviated, and the shock is directly transmitted to the steering wheel, significantly reducing steering stability. inhibit.

In order to prevent this phenomenon, brake torque or brake operation during braking is detected and a passage for hydraulic oil to escape from the oil chamber, which shrinks when the shock absorber is compressed, is opened and closed, and this hydraulic oil escapes during braking. For example, a device that suppresses the sinking of the front fork by a small amount is disclosed in Japanese Patent Application Laid-Open No. 50-97042,
51-23921, 52-16748 or Jitsukai 52-19850
etc. have been proposed.

However, in all of these systems, the hydraulic oil passage is opened and closed on and off (fully closed during braking), so when a shock is received from the road surface during braking, the shock can be absorbed to some extent due to hydraulic oil leakage, but most of the time it is not locked. In such a situation, the impact tends to propagate to the handlebar side, and it is not always possible to exhibit sufficient cushioning characteristics, thereby reducing steering stability during braking.

As a countermeasure, the compression damping force to prevent sinking during braking is controlled to increase or decrease in accordance with the braking force, and when a shock is received during braking, a predetermined buffering characteristic is provided according to the shock. Such a buffer has been proposed by the applicant.

This will be explained based on FIG.

The upper part of the device, which is the same as usual in telescopic front forks, is not shown.

In the figure, 1 is an outer tube connected to the axle side, and 2 is a hollow pipe installed vertically at the bottom of the outer tube.

An inner tube (not shown) connected to the vehicle body side is slidably inserted into the outer tube 1, and an annular piston fixed to the tip thereof is oil-tight between the inner circumferential surface of the outer tube 1 and the outer circumferential surface of the hollow pipe 2. The oil chambers are defined on the upper and lower surfaces of the piston. A in the figure shows the oil chamber on the pressure side.

The hollow pipe 2 is connected to the bottom wall 1a of the outer tube 1.
A tightening rod 6 with a threaded portion 5 inserted through the
It is screwed together and fixed to the outer tube 1.

A valve case 7 is attached adjacent to the bottom wall 1a of the outer tube 1, and a relief valve 8 housed in the valve case 7 has a passage 9a communicating with the oil chamber A, and an internal oil reservoir chamber B of the hollow pipe 2. It is interposed so as to open and close the connection with the communicating passage 9b.

In the relief valve 8, a cylindrical valve body 11 that can freely slide in a valve hole 10 is pressed against the valve seat 3 via a set spring 12, and when the oil chamber A is compressed, the pressure force of the spring 12 acts counter to the pressure. The valve body 11 moves depending on the balance with the hydraulic pressure.

In order to increase or decrease the pressing force of this spring 12 in accordance with the braking force, a push rod 13 is provided that can freely slide, one end of which presses against the spring 12, and the other end of this push rod 13 is used to guide the brake pressure. The load on the spring 12 is increased in response to the brake pressure of the hydraulic brake generated during braking.

Reference numeral 15 denotes a conduit through which a portion of pressure oil from the master cylinder of the brake device is guided, and transmits brake pressure to a pressure chamber 16 partitioned off by bellows 14.
Then, as the brake pressure increases, the bellows 1
4 and push the push rod 13 downward.

The push rod 13 and the bellows 14 are housed in an adjustment sleeve 17 that is screwed to the valve case 7, and a connecting tube 18 for connecting the pipe line 15 is screwed to the sleeve 17.

The passage 9b is connected to the oil reservoir chamber B via a communication passage 19 formed in the center of the tightening rod 6,
A through hole 20 is formed in the middle of the communication path 19, and a check valve 22 formed of a thin cylindrical elastic body opens and closes to communicate with the through hole 21 provided in the hollow pipe 2. During the extension stroke), the check valve 22 opens to suck in oil from the oil reservoir chamber B.

In such a configuration, when the shock absorber operates in the compression direction in response to an impact load from the road surface, a portion of the hydraulic oil in the oil chamber A, which is compressed by the entry of the inner tube (not shown), is transferred between the piston and the inner tube. At the same time, the excess oil corresponding to the volume of entry into the inner tube is sucked into the piston part of the expanding oil chamber formed by the inner tube through the check valve, and pushes up the relief valve 8 and flows into the passage 9a,
It escapes to oil sump chamber B via 9b.

In this case, a buffer spring (not shown) is compressed as the inner tube enters and absorbs the impact, and the compression-side damping force characteristic is set according to the opening degree of the relief valve 8.

For example, if the opening degree of the relief valve 8 is small, the amount of hydraulic oil escaping from the oil chamber A will be small, so the oil pressure in the oil chamber A will increase, the damping force will become large, and the approach speed of the inner tube will be reduced. Conversely, when the opening degree of the relief valve 8 increases, the hydraulic oil escapes smoothly and the damping force becomes smaller.

The opening degree of the relief valve 8 is based on the balance between the pressure in the oil chamber A acting on the valve body 11 and the pressing force of the spring 12. Therefore, spring 1
By increasing the load 2 to strengthen the valve closing force, the pressure in the oil chamber A during the compression stroke can be increased.

When a shock is received from the road surface during normal driving, the shock absorber operates as described above to absorb and alleviate the shock, but when the brakes are applied, the front fork contracts as the center of gravity of the vehicle moves forward, as described above. Impairs steering stability.

This sinking of the front fork occurs in response to braking force. Therefore, the set load of the relief valve 8 is increased based on the brake pressure which is proportional to the braking force to effectively suppress the sinking.

The set load of the spring 12 of the relief valve 8 is the bellows 1 that presses the push rod 13.
Since the brake pressure is transmitted to the internal pressure chamber 16 of the bellows 14, the load on the spring 12 eventually increases in proportion to the brake pressure.

For this reason, when the front forks try to sink during braking, the brake pressure is detected and the set load on the relief valve 8 increases, so the oil pressure in the oil chamber A that balances this increases in response to the braking force. .

Therefore, prevention of sinking is always performed in accordance with the braking force, and functions effectively even during sudden braking.

As a result, if the internal pressure of the oil chamber A further increases due to reasons other than braking factors, the balance between the load of the spring 12 and the relief valve 8 will be lost, and the relief valve 8 will open in response to this increase in internal pressure.

In other words, if you receive an impact from the road surface when braking,
The opening degree of the relief valve 8 increases immediately, and the impact is alleviated.

Since the relief set load corresponds to the brake pressure, this action always takes place instantaneously when an external force other than the braking factor acts on the front fork, regardless of the magnitude of the braking force. The handling stability of the vehicle is significantly improved.

In this case, if a relief valve is simply provided and the relief valve is opened by increasing internal pressure, the relief valve will operate based on the magnitude of the impact load from the road surface because the relief set load is constant. Depending on the load, there will be a region where it is impossible to absorb the impact force, but if the relief set load is set in accordance with the brake pressure as described above, if an impact is received during braking, the magnitude of the load will be reduced. Relief valve 8 must be installed regardless of
can be opened and absorbed.

Of course, the degree of opening of the relief valve 8 at this time is determined according to the magnitude of the impact input, and it is possible to obtain a shock absorbing characteristic that is almost the same as the shock absorbing characteristic other than during braking. This characteristic is an override characteristic based on the function of the relief valve that gradually increases the damping force as the compression piston speed of the front fork increases and the amount of deflection of the spring 12 increases accordingly. It can exhibit excellent shock absorption properties.

In this way, by making the set load of the relief valve proportional to the brake pressure, the front fork is prevented from sinking. and,
If the frictional force of the brake butt changes over time due to long-term use, the relationship between braking characteristics and brake pressure will change from its initial state, and it may not always be possible to effectively suppress sinking. ,
In addition, from the viewpoint of driving feeling, it is desirable to be able to freely adjust the anti-sinking characteristic according to the driver's preference. A guide tube 31 having a bottomed cylindrical shape with a flange portion 30 is provided, and a retaining spring 32 that carries brake pressure is interposed between the guide tube 31 and the adjustment sleeve 17 in series with the bellows 14. At the same time, the push rod 13 is brought into contact with the end 31a of the guide cylinder 31.

When brake pressure is supplied to the internal pressure chamber 16 of the bellows 14 and it expands, eventually overcoming the elastic force of the retaining spring 32, the guide tube 3
1 separates from the seat surface 34 of the connecting cylinder 18 and presses the push rod 13 downward to increase the setting pressure of the relief valve 8. The retaining spring 32 is adjusted so that the initial load of the retaining spring 32 can be adjusted freely. The connecting cylinder 18 and the adjusting sleeve 17, which are in pressure contact with each other at both ends thereof, are configured so that their mutual spacing can be varied by means of a threaded portion 35. Furthermore, so that the interval adjustment at this time does not change the initial load of the set spring 12 of the relief valve 8 via the push rod 13, the sleeve 1 is
The threaded portion 36 that connects the valve case 7 and the valve case 7 is
It is formed at the same pitch as the threaded portion 35.

Therefore, when adjusting the initial load of the spring 32, by rotating the adjusting sleeve 17 in either direction while keeping the positional relationship between the connecting tube 18 and the valve case 7 the same, the adjusting sleeve 17 and the connecting tube 18 can be adjusted. The positional relationship with the sleeve 17 is displaced in the axial direction, and the initial load of the retaining spring 32 changes.

Note that even if the sleeve 17 is displaced with respect to the connecting cylinder 18, the absolute positional relationship of the connecting cylinder 18 (that is, the guide cylinder 31) with respect to the valve case 7 remains unchanged.
It is possible to prevent the initial loads of the set springs 12 of the relief valve 8 from changing at the same time.

By changing the initial value of the retaining spring 32 in this way, it is possible to change the braking pressure setting value of the internal pressure chamber 16 of the bellows 14 from which the push rod 13 starts to be pushed out, thereby adjusting the anti-sinking property as required. Can be adjusted.

(Problem to be Solved by the Invention) By the way, in this device, the pressure chamber 16 that guides the brake pressure is defined by the bellows 14, so it has high pressure resistance against high hydraulic pressure during braking that is frequently applied, and durability for long-term use. In addition, when brake pressure is applied, the bellows 14 and the retaining spring 32 are in a series relationship, and the spring constant of the bellows 14 is involved in the setting force of the retaining spring 32. It is difficult to balance the above-mentioned pressure resistance strength with the spring rigidity of the holding spring 32, which limits the degree of freedom in design, and furthermore, improvements have been desired in terms of production costs.

In order to solve this problem, the present invention includes a plunger that responds to brake pressure in place of the bellows, which improves durability and reliability, and also provides the same pressure resistance and spring constant as when using bellows in setting the load of the retaining spring. It is an object of the present invention to provide a device that has a structure that does not require consideration of the above factors, increases the degree of freedom in designing and changing settings, and is also inexpensive in terms of cost.

(Means for Solving the Problems) The present invention, which achieves the above object, has an inner tube and an outer tube that slide on each other in the axial direction, and when the oil chamber contracts when the pressure side is operated, the excess operation of the oil chamber is carried out. The front fork is equipped with a relief valve in the passage for relief, and the spring set load of the relief valve is increased or decreased according to the handlebar brake pressure. One end of the hollow adjusting sleeve located at the back is screwed together, and a connecting cylinder provided with a pressure chamber into which brake pressure is introduced is screwed into the other end of the adjusting sleeve at the same pitch as one end of the adjusting sleeve. A push rod, which is connected to the pressure chamber and has one end in contact with the rear of the relief valve via its set spring, is slidably fitted into the adjusting sleeve, and the plunger is positioned between the other end of the push rod and the pressure chamber. The push rod or plunger is slidably mounted on the connecting cylinder and biased in a direction opposing the brake pressure via a retaining spring interposed between a flange provided around the push rod or the plunger and an adjusting sleeve.

(Function) In the above configuration, when brake pressure acts on the pressure chamber during braking, the plunger descends to a position where this is balanced with the tension of the holding spring, pushing down the push rod by the same amount and increasing the load on the set spring of the relief valve. . This suppresses the sinking phenomenon of the front fork during braking.

Additionally, if the adjustment sleeve is rotated in either direction while maintaining the same positional relationship between the connecting tube and the valve case, the positional relationship between the connecting tube and the adjusting sleeve will shift in the axial direction, causing the holding The initial load of the spring changes.

By varying the initial load of the retaining spring in this manner, the brake pressure setting at which the push rod begins to be pushed out can be varied. Therefore, the above sinking prevention characteristics can be adjusted as desired.

The proportionality between the brake pressure and the displacement of the plunger and push rod can be set arbitrarily by selecting the diameter of the plunger, so it can be set in advance to the optimum state according to the usage conditions. .

(Example) The present invention will be described below based on the example shown in the drawings.

In FIG. 2, reference numeral 17 denotes a hollow adjusting sleeve whose one end is screwed to the valve case 7 attached to the outer tube 1 so as to be located behind the relief valve 8, similar to the conventional one shown in FIG. be. A sealing material such as an O-ring is interposed between the adjustment sleeve 17 and the valve case 7.
Reference numeral 18 denotes a connecting cylinder screwed to the other end of the adjustment sleeve 17. One end of the plunger 40 freely slides toward a pressure chamber 16 formed in a part of the connecting cylinder 18 into which brake pressure is introduced.

A push rod 13 is attached to the end face of the plunger 40.
A retaining spring 32 for setting a load is interposed between a spring receiver 42 forming a flange fitted in the middle of the push rod 13 and the adjusting sleeve 17, and the plunger 40 is connected to the pressure chamber 16.
The hydraulic pressure of the pump is counter-energized. If the friction force of the brake butt changes over time due to long-term use, the relationship between braking characteristics and brake pressure will change from the initial state, and this retention spring 32 may not necessarily be able to effectively prevent sinking. Furthermore, from the viewpoint of driving feeling, it is desirable to be able to freely adjust the sinking prevention characteristic according to the driver's preference, so this measure is provided.

A sealing material 4 made of, for example, an O-ring is provided on the sliding surfaces of the plunger 40 and the push rod 13 with respect to the connecting tube 18 and the adjustment sleeve 17, respectively.
3 and 44 are interposed.

The plunger 40 has a stepped portion 45 with a small diameter tip.
A snap spring 46 is fitted to the plunger 4.
0 rises, this snap spring 46 comes into contact with the stepped portion 47 of the connecting cylinder 18, restricting the retreat position of the plunger 40 and push rod 13 when the brake pressure is low (when not braking), and reducing the load of the spring 12 of the relief valve 8. is set to apply a predetermined compression damping force during normal operation.

Further, 48 is an annular stopper fitted to the inner surface of the connecting cylinder 18, which contacts the snap spring 46 when the plunger 40 is lowered to limit the lowering of the plunger 40 and regulate the maximum relief pressure during braking.

When the brake pressure introduced into the pressure chamber 16 eventually overcomes the elastic force of the holding spring 32, the plunger 40 presses the push rod 13 downward to increase the set pressure of the relief valve 8. In order to make the initial load of the spring 32 freely adjustable, the mutual spacing is variable by the adjustment sleeve 17 to which one end of the holding spring 32 is pressed, the connection cylinder 18 to which the snap ring 46 fitted to the plunger 40 is pressed, and the threaded portion 35. It is configured so that In order to prevent the interval adjustment at this time from changing the initial load of the set spring 12 of the relief valve 8 via the plunger 40 and the push rod 13, the threaded portion 36 connecting the adjustment sleeve 17 and the valve case 7 is , are formed at the same pitch as the threaded portion 35.

Therefore, when adjusting the initial load of the holding spring 32, the adjustment sleeve 17 is
When rotated in either direction, connecting tube 1
8 and the adjustment sleeve 17 are displaced in the axial direction, and the initial load of the holding spring 32 changes.

Note that even if the adjusting sleeve 17 is displaced with respect to the connecting cylinder 18, the connecting cylinder 18 with respect to the valve case 7
(i.e. plunger 40 and push rod 13)
Since the absolute positional relationship of the relief valve 8 remains unchanged,
It is possible to prevent the initial loads of the set springs 12 from changing at the same time.

By changing the initial value of the holding spring 32 in this way, the brake pressure setting value of the pressure chamber 16 that starts pushing out the push rod 13 can be changed, and thereby the anti-sinking characteristic can be adjusted as desired. .

In addition, in this embodiment, the check valve 22 as in the example shown in FIG. Since a movable oil lock piece 23 is provided which fits vertically into the oil chamber A, when there is a possibility that the oil chamber A may exhibit negative pressure during the extension side operation, the oil chamber B, the hollow pipe 2, and the through hole 21 are connected to each other.
- the movable oil lock piece internal passage 24 - the lower end cavity 25 - the oil lock piece 23 to the oil chamber A;
Since the hydraulic oil is flowed by the lift, there is no practical problem.

In the above configuration, when brake pressure acts on the pressure chamber 16 during braking, this and the holding spring 3
The plunger 40 is displaced (descended) to a position where it is in balance with the valve 2, and the push rod 13 is pushed down by the same amount to increase the set load of the spring 12 of the relief valve 8.

As in the case described above, this effectively prevents the front fork from sinking during braking.

In this case, brake pressure and plunger 4
0 (push rod 13), the proportionality constant can be arbitrarily set by selecting the diameter of the plunger 40, so it can be set in advance to the optimum state according to the intended usage conditions or purpose of the two-wheeled vehicle. It is possible to keep it.

Furthermore, in this embodiment, since the orifice 50 is formed in the cylindrical valve body 11 of the relief valve 8, the compression side damping force in the low speed region of the piston is dominated by the throttling effect of this orifice 50, and thereafter The relief valve 8 will begin to open.

Next, a second embodiment of the present invention shown in FIG. 3 will be described. In this embodiment, the spring receiver 42
a is formed into a cylinder having a flange portion 51, and is fitted into the small diameter portion 52 of the plunger 40.

Therefore, the push rod 13 comes into contact with the bottom surface 53 of this spring receiver 42a, and moreover, this bottom surface 53
The diameter of the push rod 13 is larger than that of the push rod 13, and comes into contact with the sleeve 17 when the plunger 40 is lowered to its maximum, thereby regulating the maximum relief pressure.

FIG. 4 shows a third embodiment of the present invention, in which a push rod 13' and a plunger 40' are integrally formed, and a flange portion 54 and an adjusting sleeve 17 are formed integrally with each other. A retaining spring 32 is interposed between them.

A spring receiver 55 is fitted to the tip of the push rod 13' to support one end of the spring 12 of the relief valve 8.

In the second and third embodiments described above, other points are the same as those in the first embodiment, so the same parts in the drawings are denoted by the same reference numerals and the explanation thereof will be omitted.

(Effects of the Invention) As described above, according to the present invention, the pressure chamber on which brake pressure acts is separated by a plunger, so the pressure resistance is increased compared to the case where a bellows is used, and the stability is maintained over a long period of time. This has the effect that it is possible to obtain a stable operation and to reduce production costs.

In addition, by preselecting the effective diameter of the plunger based on the proportional characteristics of the brake pressure and the displacement of the push rod, it is possible to set the optimum relief load corresponding to the usage conditions.

Furthermore, according to the present invention, the spring set load of the relief valve is variably controlled according to the brake pressure, so the main damping force characteristics during braking change and the piston speed (compression speed of the front fork) increases. As a result, an override characteristic occurs in which the damping force increases, and therefore, not only the effect of suppressing sinking but also excellent shock absorption against thrust input during the braking process can be obtained.

In the present invention, the characteristic configuration is as follows:
Since a plunger is provided in place of the bellows, flexibility in design is increased, such as being able to select and adjust the retaining spring without considering the spring constant of the bellows.Also, by providing an adjustment sleeve, the retaining spring can be set as described above. An excellent practical effect is obtained in that changes and adjustments can be made freely and easily without being constrained by, for example, brake hydraulic piping.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a prior art example by the applicant;
FIG. 2 is a sectional view showing the main parts of the first embodiment of the present invention, and FIGS. 3 and 4 are enlarged sectional views of the main parts of the second and third embodiments, respectively. 1...outer tube, 2...hollow pipe,
8... Relief valve, 9a, 9b... Passage, 1
1... Cylindrical valve body, 12... Set spring,
13...Push rod, 16...Pressure chamber, 17
... Adjustment sleeve, 18 ... Connection tube, 40 ... Plunger, 42 ... Spring holder, 43, 44 ... Seal material, 46 ... Snap spring, 48 ... Stopper, A ... Oil chamber, B ... Oil Reservoir.

Claims (1)

[Claims] 1 It has an inner tube and an outer tube that slide on each other in the axial direction, and a relief valve is interposed in the passage that releases excess operation of the oil chamber that contracts during pressure side operation to the oil reservoir chamber, and a spring set for this relief valve is installed. A front fork whose load is increased or decreased in accordance with handlebar brake pressure, wherein one end of a hollow adjustment sleeve located behind the relief valve is screwed to a valve case housing the relief valve; A connecting tube with a pressure chamber into which brake pressure is introduced is screwed to the other end of the adjustment sleeve at the same pitch as one end of the adjustment sleeve, and a push rod is connected at one end behind the relief valve via its set spring. is slidably fitted into the adjustment sleeve, a plunger is slidably provided in the connecting cylinder so as to be located between the other end of the push rod and the pressure chamber, and the push rod or plunger is fitted around the adjusting sleeve. A front fork for two-wheeled vehicles that is biased in a direction that opposes brake pressure via a retaining spring that is interposed between a flange and an adjustment sleeve.