WO2019054169A1

WO2019054169A1 - Damper

Info

Publication number: WO2019054169A1
Application number: PCT/JP2018/031703
Authority: WO
Inventors: 栗田　典彦
Original assignee: Ｋｙｂ株式会社
Priority date: 2017-09-14
Filing date: 2018-08-28
Publication date: 2019-03-21
Also published as: JP2019052672A

Abstract

In a damper which provides damping force by applying resistance to the flow of liquid occurring during the extension and contraction of the damper, when the amount of gas dissolved in the liquid is large, the gas dissolved in the liquid forms bubbles to cause a phenomenon known as cavitation, delaying the build-up of damping force at the time of the start of extension and contraction of the damper. A damper (D) provided as a means for solving such a problem has a gas chamber G formed in the damper (D) and filled with helium, the damper (D) providing damping force by applying resistance to the flow of liquid occurring during the extension and contraction of the damper (D).

Description

Shock absorber

The present invention relates to improvements in shock absorbers.

Conventionally, in a shock absorber, as disclosed in, for example, JP2011-174502, a liquid and a gas are enclosed inside, and the flow of the liquid generated at the time of expansion and contraction is provided to exert a damping force. There is. In such shock absorbers, it is most common to use air as the gas filled with the liquid inside, and sometimes nitrogen is also used.

In a shock absorber, if there is a large amount of dissolved gas in the liquid, a phenomenon called cavitation occurs in which the dissolved gas in the liquid forms bubbles, and the rise of damping force is delayed at the beginning of expansion and contraction of the shock absorber. Have problems

Therefore, the present invention is devised to improve the above-mentioned problems, and an object of the present invention is to provide a shock absorber capable of suppressing the occurrence of cavitation and making a damping force generation response excellent.

The means for solving the above problems is to form a helium filled air chamber in a shock absorber that exerts a damping force by resisting the flow of the liquid generated during expansion and contraction. Helium has a low molecular weight and low solubility in the liquid, and according to this configuration, the occurrence of cavitation can be suppressed and the generation response of the damping force can be improved because the dissolved gas in the liquid is reduced.

FIG. 1 is a longitudinal sectional view schematically showing a shock absorber according to one embodiment of the present invention. FIG. 2 is a diagram showing the relationship between gas solubility in water and temperature. FIG. 3 is a longitudinal sectional view showing a first modified example of the shock absorber according to one embodiment of the present invention and simplifying the shock absorber according to the modified example. FIG. 4 is a longitudinal sectional view showing a second modified example of the shock absorber according to one embodiment of the present invention and simplifying the shock absorber according to the modified example. FIG. 5 is a longitudinal sectional view showing a third modified example of the shock absorber according to one embodiment of the present invention and simplifying the shock absorber according to the modified example.

Hereinafter, a shock absorber according to an embodiment of the present invention will be described with reference to the drawings. The same reference numerals as in the several figures indicate the same or corresponding parts.

As shown in FIG. 1, a shock absorber D according to an embodiment of the present invention is used for a front fork, and is interposed between a vehicle body of a straddle-type vehicle and an axle of a front wheel. The shock absorber D includes a telescopic tube member 1 and a single rod shock absorber body 2 housed in the tube member 1.

The tube member 1 is configured to have an outer tube 3 and an inner tube 4 slidably inserted into the outer tube 3 via a pair of

bushes

30 and 40. In the present embodiment, the tube member 1 is an inverted type, and the outer tube 3 is disposed on the upper side (vehicle body side) and the inner tube 4 is disposed on the lower side (axle side). That is, in the present embodiment, the outer tube 3 is a vehicle body side tube, and the inner tube 4 is an axle side tube.

Then, the outer tube 3 is connected to the vehicle body of the saddle-ride type vehicle via the vehicle body side bracket (not shown), and the inner tube 4 is connected to the axle of the front wheel of the saddle-ride type vehicle via the axle side bracket 10 There is. As described above, the shock absorber D is interposed between the vehicle body and the axle, and when the front wheel vibrates up and down due to the straddle type vehicle traveling on the uneven road surface, the inner tube 4 becomes the outer tube. The shock absorber D expands and contracts in and out of 3.

The tube member 1 may be an upright type, and the outer tube 3 may be an axle tube and the inner tube 4 may be a vehicle tube. Further, the application of the shock absorber D is not limited to the front fork, and may be used for a rear cushion unit that suspends the rear wheel of a straddle-type vehicle, a suspension of an automobile, or the like.

Subsequently, the upper side of the outer tube 3 in FIG. 1 is closed with a cap 11. Further, the lower side in FIG. 1 of the inner tube 4 is closed by the axle side bracket 10. Furthermore, the sealing member 12 is closed between the overlapping portion of the outer tube 3 and the inner tube 4. Thus, the tube member 1 is sealed, and the shock absorber main body 2 is accommodated inside thereof.

The shock absorber main body 2 includes a cylinder 5, a piston 6 axially slidably inserted in the cylinder 5, and a piston rod 60 having one end connected to the piston 6 and the other end protruding out of the cylinder 5; It has an annular rod guide 50 fixed to one end of the cylinder 5 and slidably supporting the piston rod 60, and a valve case 7 fixed to the lower end of the cylinder 5.

Further, the shock absorber main body 2 is an upright type, and the piston rod 60 is disposed on the upper side (vehicle body side) and the cylinder 5 is directed to the lower side (axle side). The piston rod 60 is connected to the outer tube 3 via the cap 11, and the cylinder 5 is connected to the inner tube 4 via the axle side bracket 10. Thus, the shock absorber main body 2 is interposed between the outer tube 3 and the inner tube 4, and when the shock absorber D expands and contracts, the piston rod 60 moves in and out of the cylinder 5 and the shock absorber main body 2 expands and contracts. The piston 6 moves up and down in the cylinder 5.

The upper side of the cylinder 5 in FIG. 1 is closed by a rod guide 50. On the other hand, the lower side of the cylinder 5 is closed by a valve case 7. Assuming that the cylinder 5 is inward and the space between the rod guide 50 and the valve case 7 is in the cylinder 5, the inside of the cylinder 5 is divided by the piston 6 into an expansion side chamber L 1 and a pressure side chamber L 2. The hydraulic oil is filled in the expansion side chamber L1 and the pressure side chamber L2, respectively. The piston 6 is formed with a damping passage 6a that communicates the expansion side chamber L1 with the pressure side chamber L2. The damping passage 6a is provided with a damping element 6b that resists the flow of hydraulic fluid moving between the expansion side chamber L1 and the pressure side chamber L2 through the damping path 6a.

Subsequently, a reservoir R is formed outside the cylinder 5 with the tube member 1. The reservoir R stores hydraulic oil and is filled with a gas above the liquid surface. In the reservoir R, a portion where hydraulic oil is stored is referred to as a liquid reservoir L3, and a portion filled with a gas is referred to as an air chamber G.

In the valve case 7, a suction passage 7a and a discharge passage 7b are formed, which communicate the pressure side chamber L2 and the liquid storage chamber L3. The suction passage 7a is provided with a check valve 7c that allows the flow of hydraulic oil from the liquid storage chamber L3 to the pressure side chamber L2 and blocks the flow in the opposite direction. On the other hand, the discharge passage 7b is provided with a damping element 7d that resists the flow of hydraulic fluid moving between the pressure side chamber L2 and the liquid storage chamber L3 through the discharge passage 7b.

According to the above configuration, when the shock absorber D extends, the piston rod 60 withdraws from the cylinder 5 and the shock absorber main body 2 extends, and the piston 6 moves upward in the cylinder 5 in FIG. 1 to compress the expansion chamber L1. Then, the hydraulic oil in the expansion side chamber L1 moves to the pressure side chamber L2 through the damping passage 6a. Since the damping element 6b applies resistance to the flow of the hydraulic fluid, the pressure of the expansion chamber L1 increases when the shock absorber D is extended, and the shock absorber body 2 exerts a damping force that suppresses the extension operation. Do.

Conversely, when the shock absorber D contracts, the piston rod 60 enters the cylinder 5 and the shock absorber main body 2 contracts, and the piston 6 moves downward in the cylinder 5 in FIG. 1 to compress the pressure chamber L2. The hydraulic oil in the pressure side chamber L2 moves to the expansion side chamber L1 and the liquid reservoir chamber L3 through the damping passage 6a and the discharge passage 7b. Since the resistances of the hydraulic fluid are given by the

damping elements

6b and 7d, respectively, the pressure of the pressure side chamber L2 rises when the shock absorber D contracts, and the shock absorber main body 2 suppresses the contraction operation. Demonstrate damping force.

Thus, in the shock absorber D, the hydraulic fluid flows in the cylinder 5 or between the cylinder 5 and the reservoir R along with the extension operation, and the flow of the hydraulic fluid is damped by giving resistance to the flow of the hydraulic fluid by the

damping elements

6b and 7d. Force is supposed to be generated. In addition, while being able to change suitably the structure of the flow path through which hydraulic fluid flows at the time of expansion-contraction of the buffer D, the structure of

damping element

6b, 7d can also be changed suitably. For example, an orifice, a choke, a valve or the like can be used as the

damping elements

6b and 7d.

Further, when the shock absorber D is extended, the check valve 7c is opened, and the hydraulic oil for the piston rod volume which has been withdrawn from the cylinder 5 is supplied from the reservoir R to the pressure side chamber L2 through the suction passage 7a. On the contrary, at the time of contraction of the shock absorber D, the working oil of the piston rod volume entering the cylinder 5 is discharged from the pressure side chamber L2 to the reservoir R through the discharge passage 7b. Thus, in the shock absorber D, the reservoir R compensates for the volume of the piston rod 60 that moves into and out of the cylinder 5 as the expansion and contraction operation is performed.

Subsequently, the gas filled in the air chamber G of the reservoir R is helium. A gas spring A is formed with the air chamber G, and the gas spring A functions as a suspension spring for urging the shock absorber D in the extension direction to elastically support the vehicle body.

Then, when the shock absorber D is extended and the inner tube 4 is withdrawn from the outer tube 3, the volume of the air chamber G is expanded and the pressure is decreased, so that the elastic force of the gas spring A is decreased. Conversely, when the shock absorber D contracts and the inner tube 4 enters the outer tube 3, the volume of the air chamber G decreases and the pressure rises, so the elastic force of the gas spring A increases.

FIG. 2 is a diagram showing the relationship between the solubility of oxygen (O ₂ ), nitrogen (N ₂ ) and helium (He) in water and the temperature. As can be seen from the figure, the solubility of helium is small and the change in solubility with temperature is small compared to oxygen and nitrogen. Also, the solubilities of nitrogen and oxygen decrease with increasing temperature, but the solubilities of helium increase slightly at higher temperatures. Although the solubility of gas in oil is greater than the solubility of gas in water, it is known that the temperature dependence of solubility by gas type has a similar tendency.

That is, helium is less soluble in hydraulic oil than oxygen and nitrogen, and the change in solubility due to temperature change is also small. Also, the solubility of oxygen and nitrogen in hydraulic fluid decreases with increasing temperature, while the solubility of helium in hydraulic fluid increases slightly with increasing temperature.

Conventionally, air is most commonly used as a gas with which the shock absorber is filled with the hydraulic oil, and nitrogen may also be used. The composition of air is about 80% nitrogen and about 20% oxygen. As mentioned above, helium is less soluble in hydraulic oil compared to oxygen and nitrogen. Therefore, in the case of the shock absorber D filled with helium as in the present embodiment, the dissolved gas in the hydraulic oil is reduced as compared with the conventional shock absorber filled with air or nitrogen.

Therefore, according to the shock absorber D of the present embodiment, the occurrence of cavitation can be suppressed and the occurrence response of the damping force can be made better as compared with the conventional shock absorber. Further, helium is relatively inexpensive and easily available, and therefore, according to the above configuration, the occurrence of cavitation can be suppressed and the improvement of damping force generation responsiveness can be realized inexpensively and easily.

In addition, when the hydraulic oil is agitated by vibration during traveling of the vehicle, the gas dissolved in the hydraulic oil is separated and generated as air bubbles, so the internal pressure of the shock absorber D rises. Furthermore, since the temperature rises when the shock absorber D operates due to the vibration when the vehicle travels, the internal pressure of the shock absorber D also rises. For this reason, when the saddle-ride type vehicle starts traveling, the internal pressure of the shock absorber D is increased, and the elastic force of the gas spring A tends to be increased.

In addition, since the solubility of nitrogen and oxygen decreases as the temperature rises, in the case of a conventional shock absorber filled with air or nitrogen, the internal pressure rises when the temperature of the shock absorber rises as the straddle-type vehicle starts to travel. Is promoted. For this reason, in the conventional shock absorber, the elastic force of the gas spring increases when the vehicle travels, and the riding comfort changes.

On the other hand, since the solubility of helium is small due to the temperature rise and slightly increases with the temperature rise, the shock absorber D according to the present embodiment filled with helium starts traveling Even if the temperature of the shock absorber D rises, the rise in internal pressure can be suppressed. Therefore, in the shock absorber D, it is possible to suppress the change in the elastic force of the gas spring A when the vehicle is traveling, and to suppress the change in the ride comfort of the vehicle.

In particular, when the gas spring A functions as a suspension spring that elastically supports the vehicle body as in the shock absorber D of the present embodiment, compared to a shock absorber having a suspension spring consisting of a coil spring, The change in the elastic force has a large effect on the ride quality of the vehicle.

Furthermore, in motocross, since a traveling vehicle called motocrosser travels on an unpaved circuit course, a strong vibration is added to the shock absorber when the vehicle is traveling. For this reason, when a shock absorber using a conventional air spring or a gas spring configured to have an air chamber filled with nitrogen as a suspension spring is used as a motocross, the ride quality of the vehicle is degraded several laps after the start of traveling . In this case, it is necessary to return to the pit and adjust the pressure of the air chamber again, and it takes time and effort because it can not cope during traveling.

On the other hand, in the shock absorber D having the gas spring A configured to have the air chamber G filled with helium as a suspension spring, as described above, the change in the elastic force of the gas spring A can be suppressed. , Can maintain a good ride. That is, in the case where the gas spring A functions as a suspension spring that elastically supports the vehicle body, it is particularly effective to fill with helium when the shock absorber D is used for motocross.

Furthermore, when the gas spring A is used as a suspension spring, the pressure in the air chamber G may rise to about 15 atm (atm), depending on the setting. Under such a high pressure environment, the hydraulic oil and oxygen may combine to generate carbon dioxide. Since the solubility of carbon dioxide is higher than the solubility of oxygen, there is a risk that dissolved gas may be further increased. Therefore, if the buffer D is filled with helium as in the present embodiment, such a problem does not occur.

Further, in the shock absorber D filled with helium, if the air in the working oil is replaced with helium in advance by the helium purge and then the shock absorber D is filled, the dissolved gas in the working oil can be further reduced. For this reason, it is advantageous in suppressing the occurrence of cavitation and improving the damping force response.

However, helium has the property of permeating rubber. Furthermore, helium molecules are so small that they can also penetrate metals in some cases. In addition, an oil film is formed by the seal member 12 on the outer peripheral surface of the inner tube 4 which is withdrawn from the outer tube 3 when the shock absorber D is extended. Therefore, helium in the oil film exposed to the outside air is released to the atmosphere, and nitrogen, oxygen and the like in the atmosphere are dissolved in the oil film. Then, the oil film returns into the outer tube 3 when the shock absorber D contracts. Under these circumstances, even if the shock absorber D is filled with helium, helium leaks with the passage of time and operation, and helium and air are replaced.

Furthermore, in the shock absorber D of the present embodiment in which the gas spring A is used as a suspension spring, the pressure in the air chamber G is set higher compared to a shock absorber provided with a suspension spring consisting of a coil spring. Since the amount of gas that is soluble in a certain amount of solvent is proportional to the pressure, a large amount of helium dissolves in the working oil in the high-pressure buffer D. Then, when the hydraulic oil containing a large amount of helium is carried out of the shock absorber D as an oil film at the time of extension of the shock absorber D, helium which can not be dissolved due to the pressure drop is released to the atmosphere.

For this reason, it is a shock absorber D filled with helium, and in particular, when the gas spring A configured to have a gas chamber G filled with helium is used as a suspension spring, the helium is periodically replenished. While it is necessary to use. Therefore, such a shock absorber is suitable for use in a competition vehicle whose maintenance is frequently performed, or a vehicle provided with a spring force adjustment device or the like that automatically adjusts the pressure in the air chamber. This is because in these vehicles, helium can be supplied to the air chamber G at the time of maintenance or adjustment of the air chamber pressure.

In addition, the shock absorber D itself may be provided with a replenishment device for replenishing helium to the air chamber G. In this case, application of the shock absorber D to a general vehicle is easy. The filling device may have any configuration, for example, a tank filled with helium, a passage connecting the tank and the air chamber G, and a pressure from the tank to the air chamber according to the pressure in the air chamber G It may be configured to have a valve or the like for supplying helium to G.

Further, as in the present embodiment, the shock absorber D is connected to the cylinder 5, the piston 6 slidably inserted in the cylinder 5, and one end is connected to the piston 6 and the other end protrudes out of the cylinder 5 When the gas is in contact with the oil surface of the hydraulic fluid in the reservoir R, it is particularly effective to use helium as the gas, provided with the piston rod 60 and the reservoir R communicated in the cylinder 5.

Because, according to the above configuration, the dissolved air in the hydraulic oil can be replaced with helium in the reservoir R, and the hydraulic oil moves between the reservoir R and the cylinder 5 when the shock absorber D expands and contracts. If helium is contained, the dissolved gas in the hydraulic oil in the cylinder 5 can be reduced, and the effect of preventing the occurrence of cavitation and improving the response of generation of damping force can be obtained.

Such an effect can also be obtained when the air chamber G filled with helium is not used as a suspension spring. For example, a suspension spring consisting of a coil spring may be provided between the rod guide 50 and the cap 11, and the pressure of the air chamber G at the time of the maximum extension may be approximately atmospheric pressure.

Further, as in the shock absorber D1 according to the first modification shown in FIG. 3, the reservoir R is formed between the outer cylinder 51 provided on the outer periphery of the cylinder 5 and the cylinder 5, and A chamber 8 forming a second air chamber G1 may be provided, and a gas spring A1 having a second air chamber G1 and functioning as a suspension spring may be configured.

According to the configuration, if the air chamber G in the reservoir R is filled with helium, the air in the hydraulic oil can be replaced with helium in the reservoir R. Therefore, the gas filling the air chamber G1 in the chamber 8 may be other than helium, and the chamber 8 may be eliminated and a suspension spring made of a coil spring may be provided.

Note that when the air chamber G1 in the chamber 8 is filled with helium, the air in the working oil and the helium in the chamber 8 via the oil film formed on the outer periphery of the piston rod 60 which is withdrawn from the cylinder 5 when the shock absorber D1 extends. Is replaced. That is, by filling the air chamber formed on the outer periphery of the piston rod 60 entering and exiting the cylinder 5 with helium, the air in the working oil can be replaced with helium even if the working oil is not in contact with the helium in the reservoir R Dissolved gas in hydraulic oil can be reduced.

Therefore, for example, as in a shock absorber D2 according to a second modified example shown in FIG. 4, the liquid storage chamber L3 of the reservoir R and the air chamber G may be partitioned by the free piston 52. Further, as in the shock absorber D3 according to the third modification shown in FIG. 5, the piston rod is removed from the reservoir R and enters and exits the cylinder 5 in the expandable air chamber G2 partitioned by the free piston 53 in the cylinder 5. 60 volume compensation may be performed.

Furthermore, as mentioned above, helium is easy to permeate. For this reason, even if the air chamber filled with helium and the oil chamber filled with the working oil are partitioned by a movable piston such as a free piston, a bladder or a bellows, the helium in the air chamber can move to the oil chamber side. That is, even in the case where the air chamber partitioned from the oil chamber by the movable partition is filled with helium, the air in the working oil can be gradually replaced with helium, and the dissolved gas in the working oil can be reduced.

Therefore, for example, the communication hole 5a provided in the cylinder 5 of the shock absorber D2 according to the second modification shown in FIG. 4 is eliminated to divide the air chamber G into the inside and outside of the cylinder 5, and to the air chamber Ga in the cylinder 5. Helium may be filled, and the air chamber Gb outside the cylinder 5 may be filled with a gas other than helium.

Further, helium is filled in the air chamber G2 of the shock absorber D3 according to the third modification shown in FIG. 5, and the chamber 8 is filled with a gas other than helium, or the chamber 8 is discarded, and the gas spring A1 is replaced A suspension spring consisting of a coil spring may be provided.

As described above, when helium is filled in the air chambers Ga and G2 partitioned from the oil chamber by the movable partitions such as the

free pistons

52 and 53, the movement of the helium to the oil chamber side is promoted. The pressure in the chambers Ga and G2 may be increased.

Further, in the shock absorbers D, D1, D2 and D3 shown in FIGS. 1 and 3, the piston rod 60 extends to one side of the piston 6 and is of a single rod type. However, the piston rod 60 may be extended to both sides of the piston 6 to be a double rod type. Furthermore, in the shock absorbers D, D1, D2 and D3, although hydraulic oil is used as a liquid for generating damping force, water may be used, and the temperature dependence characteristics of the solubility of oxygen, nitrogen and helium are similar to FIG. As long as the liquid is a characteristic, a liquid other than hydraulic oil and water may be used.

While the preferred embodiments of the present invention have been described above in detail, modifications, variations and changes are possible without departing from the scope of the claims.

The present application claims priority based on Japanese Patent Application No. 2017-176331 filed on September 14, 2017, to the Japanese Patent Office, and the entire contents of this application are incorporated herein by reference.

Claims

A shock absorber,
A shock absorber that resists the flow of liquid generated during expansion and contraction and exerts a damping force,
An air chamber filled with helium is formed inside.
The shock absorber according to claim 1, wherein
With the cylinder,
A piston slidably inserted in the cylinder;
A piston rod having one end connected to the piston and the other end projecting out of the cylinder;
And a reservoir in communication with the cylinder.
The air chamber is formed in the reservoir,
The helium is in contact with the liquid level in the reservoir.
The shock absorber according to claim 1, wherein
It is interposed between the car body and the axle in the vehicle,
A gas spring is configured to have the air chamber,
The gas spring functions as a suspension spring that elastically supports the vehicle body.
The shock absorber according to claim 1, wherein
A buffer comprising a replenishment device for replenishing helium into the air chamber.
The shock absorber according to claim 1, wherein
Shock absorbers used in racing vehicles.