JP2006194283A - Axial force generating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an axial force generating device having excellent low friction characteristics. <P>SOLUTION: In this axial force generating device for generating axial direction damping force provided with a cylinder 2, a piston 3 slidably stored in the cylinder 2, a piston seal member 4 arranged on a slide part of the piston 3 and the cylinder 2, working fluid L filled in the cylinder 2, a piston rod 5 connected to the piston 3, a guide member 6 slidably supporting the piston rod 5, a rod seal member 7 arranged in the cylinder 2 and sealing a slide part with the piston rod 5, at least one of slide surfaces of the cylinder 2, the piston 3, the piston seal member 4, the piston rod 5, the guide member 6 and the rod seal member 7 is coated by hard carbon thin film containing 20 atom% or less hydrogen, and oxygen containing grease containing ester oil and/or ether oil as base oil is contained in working fluid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an axial force generator such as a shock absorber that generates an axial damping force.

  Conventionally, as the above-described axial force generating device, for example, a cylinder, a piston slidably accommodated in the cylinder, hydraulic oil filled in the cylinder, a piston rod connected to the piston, and the cylinder There is a shock absorber provided with a guide member that is slidably supported in the piston rod and a rod seal member that is arranged in the cylinder and seals a sliding portion with the piston rod. In the shock absorber, an axial damping force is generated by a pressure difference when hydraulic oil in the cylinder passes through a communication hole provided in the piston by sliding of the piston.

  In the shock absorber, the outer peripheral surface of the piston slides with respect to the cylinder, and the piston rod slides with respect to the guide member and the rod seal member. The lubrication of these sliding portions is performed by the hydraulic oil. Yes.

Here, if the friction of the sliding part is large,
A) During the suspension stroke when traveling on rough terrain, the frictional force in the translational direction hinders the smooth stroke of the suspension, and the function is not performed effectively. In addition to not having a high level of handling stability is not easy,
B) When the suspension is a strut suspension, it is difficult to say that the frictional force in the rotational direction with the cylinder and piston rod as an axis is increased, and the steering feeling can be sufficiently enhanced.
C) The use of metal materials for the outer peripheral surface of the piston and the guide member is avoided from the viewpoint of wear, and the rigidity in the direction orthogonal to the axis of the cylinder and piston rod cannot be said to be sufficient. It is not easy to obtain high-level steering stability as above, due to a decrease in rigidity and lateral rigidity.
Therefore, it is extremely important to reduce the friction of the sliding portion.

  In recent years, various hard thin film materials have been applied to the sliding portion in order to reduce the friction of the sliding portion. Even if the DLC (diamond-like carbon) material of the hard carbon thin film material is separated, It is expected as a low friction sliding material because its friction coefficient in air and in the absence of lubricating oil is lower than that of wear-resistant hard thin film materials such as titanium oxide (TiN) and chromium nitride (CrN). Yes.

The above-described shock absorber is described in, for example, Patent Document 1, while the friction characteristics of the DLC material are reported in, for example, Non-Patent Document 1.
Japanese Patent No. 2517808 Kano et al., Proceedings of Japan Society of Tribology, May 1999, p. 11-12

  However, Non-Patent Document 1 reports that a general DLC material having excellent low friction properties in air does not necessarily have a large friction reducing effect in the presence of lubricating oil. In other words, it has been found that even if the DLC material is applied to reduce the friction of the sliding portion in the above-described shock absorber, the friction reducing effect may not be sufficiently exhibited in the presence of hydraulic oil.

  The present invention has been made in view of such problems of the prior art, has an excellent low friction characteristic, and realizes an improvement in operating efficiency, a long life of a sliding member, and an improvement in quietness. For example, in the case of a shock absorber, an axial force generator that can obtain better riding comfort and higher steering stability and can also sufficiently enhance the steering feeling. It is intended to provide.

  As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by using a hard carbon material such as DLC in combination with a specific grease, and the present invention has been completed. It was.

  That is, the axial force generator of the present invention includes a cylinder, a piston slidably accommodated in the cylinder, a piston seal member disposed in a sliding portion of the piston with the cylinder, and a filling in the cylinder. A working fluid, a piston rod coupled to the piston, a guide member disposed in the cylinder and slidably supporting the piston rod, and a sliding portion disposed in the cylinder and sealing the piston rod. In an axial force generating device that includes a rod seal member, has a communication hole in the piston, and generates a damping force in an axial direction due to a pressure difference when the working fluid in the cylinder passes through the communication hole by sliding of the piston. Cylinder sliding surface with piston, piston sliding surface with cylinder, piston sealing member sliding surface with cylinder, piston rod guide At least one sliding surface of the sliding surface with the member, the sliding surface with the piston rod of the guide member, and the sliding surface with the piston rod of the rod seal member is coated with a hard carbon thin film, and the hard carbon thin film In this axial force generating device, the hydrogen content of the oil is set to 20 atomic% or less, and the working fluid contains grease based on ester oil and / or ether oil as a base oil. The configuration is a means for solving the above-described conventional problems.

  In the preferred embodiment of the axial force generator of the present invention, the grease is configured to use a metal soap or a urea compound containing calcium or lithium as a thickener.

  According to the axial force generator of the present invention, since the hard carbon material such as DLC and the specific grease are used in combination, the present invention exhibits excellent low friction characteristics, which improves the operating efficiency and length of the sliding member. For example, in the case of a shock absorber, the ride comfort can be further improved and the driving stability can be greatly improved. As a result, it is possible to achieve an excellent effect that it is possible to improve the steering feeling.

  Hereinafter, the axial force generator of the present invention will be described in detail. In the present specification, “%” represents mass percentage unless otherwise specified.

  As shown in FIG. 1, a shock absorber 1 as an axial force generator of the present invention includes a cylinder 2, a piston 3 slidably accommodated in the cylinder 2, and a sliding of the piston 3 with the cylinder 2. The piston seal member 4 disposed in the portion, the working fluid L filled in the cylinder 2, the piston rod 5 connected to the piston 3, and the guide member disposed in the cylinder 2 for slidably supporting the piston rod 5 6 and a rod seal member 7 which is disposed in the cylinder 2 and seals the sliding portion with the piston rod 5, and is provided with a communication hole 8 in the piston 3. An axial damping force is generated by the pressure difference when the fluid L passes through the communication hole 8.

  In this case, the sliding surface of the cylinder 2 with the piston 3, the sliding surface of the piston 3 with the cylinder 2, the sliding surface of the piston seal member 4 with the cylinder 2, and the sliding surface of the piston rod 5 with the guide member 6 , At least one sliding surface of the sliding surface of the guide member 6 with the piston rod 5 and the sliding surface of the rod seal member 7 with the piston rod 5 is covered with a hard carbon thin film. The working fluid L contains grease based on ester oil and / or ether oil as a base oil.

  The shock absorber 1 may be configured such that at least one of the piston seal member 4 and the rod seal member 7 is impregnated with a lubricant containing grease. In this case, the piston seal member 4 and the rod seal member The lubrication in 7 is surely performed.

  Further, in the shock absorber 1, a configuration in which both the cylinder 2 and the piston 3 are made of a metal material can be adopted. If this configuration is adopted, the rigidity in the direction orthogonal to the axes of the cylinder 2 and the piston 3 can be adopted. As a result, camber rigidity and lateral rigidity are improved, and as a result, high-level steering stability can be obtained.

  Further, in the shock absorber 1, a configuration in which both the piston rod 5 and the guide member 6 are formed of a metal material can be adopted. In this case as well, in the direction orthogonal to the axes of the cylinder 2 and the piston 3 The rigidity is increased and the camber rigidity and the lateral rigidity are improved. As a result, a high level of steering stability can be obtained.

  Furthermore, in the shock absorber 1, a configuration in which at least one of the cylinder 2 and the piston seal member 4 is formed of a resin material can be adopted. As a result, the friction is reduced and the quietness is improved.

  Furthermore, the shock absorber 1 may be configured such that at least one of the piston rod 5 and the guide member 6 is formed of a resin material. In this case as well, low friction and improved quietness can be achieved. Will be illustrated.

Here, examples of the hard carbon thin film include a crystalline or amorphous thin film containing carbon, particularly a diamond thin film and a DLC thin film. This DLC thin film is composed of a so-called DLC material, and this DLC material is an amorphous material mainly composed of carbon atoms, and the bonding form between the carbon atoms is a diamond structure (SP ³ bonding). ) And graphite bonds (SP ² bonds).

  Specifically, aC (amorphous carbon) consisting only of carbon atoms, aC: H (hydrogen amorphous carbon) containing hydrogen, and some metal atoms such as titanium (Ti) and molybdenum (Mo). In the present invention, the lower the hydrogen content, the more preferable. The hydrogen content is 20 atomic% or less, preferably 10 atomic% or less, particularly 0.5 atomic% or less, An aC-based (amorphous carbon-based) material that does not contain hydrogen can be preferably used.

  The film thickness of the hard carbon thin film is determined in consideration of the required specifications of the target sliding part, the type of material (base material) constituting the sliding member, the surface roughness of the sliding surface, etc. However, in the case of a DLC thin film, it is typically about 0.3 to 2.0 μm.

  The surface roughness of the DLC thin film is also determined in consideration of the required specifications of the target sliding portion, the type of material (base material) constituting the sliding member, the surface roughness of the sliding surface, and the like. However, Ra is typically 0.1 μm or less.

  The hard carbon thin film normally covers the entire sliding surface of the sliding member, but may cover only a part of the sliding surface.

  Next, the material (base material) constituting the sliding member is not particularly limited, and metal materials represented by iron-based alloys such as steel and non-ferrous metal alloys such as aluminum alloys, various rubbers and plastics Examples thereof include resin materials and ceramic materials represented by the above.

  Therefore, the sliding subject to the present invention is the sliding in the state where the hard carbon thin film and the predetermined grease are interposed between the above-mentioned same or different materials, or both the sliding members are the hard carbon thin film. The sliding is performed in a state where the predetermined grease is interposed between the hard thin films, which is a case of coating.

  The surface roughness of the base material of the sliding member, that is, the surface roughness of the sliding member before coating with the hard carbon thin film is affected by the required specifications of the target sliding portion, but the base material is steel. In the case of rubber and plastic, Ra is preferably 0.1 μm or less, and in the case where the substrate is an aluminum alloy, 0.02 μm or less is preferable.

Here, as described above, the grease used is based on ester oil and / or ether oil, but this base oil is not limited to those containing only ester oil or ether oil. However, other natural oils and synthetic oils may be included.
Examples of other base oil components include mineral oil, silicone oil, fluorocarbon oil, and the like.

  The ester oil is not particularly limited as long as it can be used as a component of a lubricant. Examples include decyl adipate, dioctyl sebacate, trimethylolpropane caprylate, trimethylolpropane pelargonate, trimethylolpropane isostearinate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, and the like. Rate is preferred.

  The ether oil may be a natural oil or a synthetic oil as long as it can be used as a component of a lubricant. Specific examples include polyoxyalkylene glycol, dialkyl diphenyl ether, and polyphenyl ether. Dialkyl diphenyl ether is preferable.

The base oil containing the above components typically has a base oil viscosity at 100 ° C. of about ^{2 to} 100 mm ² / S, preferably about ² to 40 mm ² / S, and more preferably about 10 to 20 mm ² / S. It becomes.

In addition, when kinematic viscosity is less than 2 mm < ² > / S, since sufficient abrasion resistance is not obtained and an evaporation characteristic may be inferior, it is unpreferable. On the other hand, when the kinematic viscosity exceeds 100 mm ² / S, it is difficult to exhibit low friction performance, and low temperature performance may be deteriorated, which is not preferable.

  The viscosity index of such base oil is typically 100 or more, preferably 120 or more, and more preferably 140 or more. By selecting a base oil having a high viscosity index, it is possible to obtain a composition that not only has excellent low-temperature viscosity characteristics, but also has low oil consumption and excellent low-temperature viscosity characteristics, fuel saving performance, and friction reduction effects.

On the other hand, examples of the thickener contained in the grease include various metal soap-based materials and non-metal soap-based materials.
Examples of the metal soap material include sodium, calcium, aluminum, lithium, barium, copper and lead salts of higher fatty acids, and complex salts of higher fatty acids with lower fatty acids or dibasic acids.
As these metal soap materials, calcium stearate, lithium hydroxystearate, lithium stearate, sodium stearate and aluminum stearate are suitable.

Non-metallic soap materials include inorganic materials (organic thickeners) such as silica gel and bentonite, and organic materials (inorganic thickeners) such as copper phthalocyanine, allylurea, imide derivatives and indanthrene blue. be able to.
As these non-metallic soap thickeners, urea compounds such as diurea, sodium terephthalate and PTFE are suitable.

  In the above-described grease, an antioxidant, a detergent, an antiwear agent, and the like can be added to the base oil and the thickener.

  The antioxidant is not particularly limited, and examples thereof include those conventionally used in greases. Examples thereof include amine compounds, phenols, sulfur compounds, and carbamates.

  Further, the detergent is not particularly limited, and examples thereof include those conventionally used in greases, and examples thereof include sulfonates, phenates, salicylates, and amine compounds.

  The antiwear agent is not particularly limited, and examples thereof include those conventionally used in grease. Examples thereof include phosphate esters, zinc dialkyldithiophosphates, sulfur compounds, and chlorides.

  The properties of the above grease itself are affected by the purpose and operating conditions of the sliding mechanism used, but typically the consistency is about 265 to 295 and the dropping point is about 100 to 300 ° C. Is preferred.

  In the above-described embodiment, the axial force generating device of the present invention is provided with the communication hole 8 in the piston 2, and the pressure difference when the working fluid L in the cylinder 2 passes through the communication hole by sliding of the piston 2. Although the case of a shock absorber that generates a damping force in the axial direction has been shown, the present invention is not limited to this.

  As another embodiment of the axial force generator of the present invention, for example, a cylinder, a piston slidably accommodated in the cylinder, and a piston seal member disposed at a sliding portion of the piston with the cylinder, A working fluid filled in the cylinder; a piston rod coupled to the piston; a guide member disposed in the cylinder for slidably supporting the piston rod; and a sliding member disposed in the cylinder and coupled to the piston rod. A rod seal member for sealing the moving part is provided, and a flow path along the axial direction is provided in the piston rod, and the working fluid is taken into and out of the cylinder through the flow path, whereby the shaft is interposed between the cylinder and the piston rod. In the axial force generator that produces relative displacement in the direction, the sliding surface of the cylinder with the piston, the sliding surface of the piston with the cylinder, At least one of a sliding surface of the seal member with the cylinder, a sliding surface of the piston rod with the guide member, a sliding surface of the guide member with the piston rod, and a sliding surface of the rod seal member with the piston rod. The moving surface is coated with a hard carbon thin film, the hydrogen content of the hard carbon thin film is set to 20 atomic% or less, and the working fluid contains grease based on ester oil and / or ether oil. Can be adopted.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

(Examples 1-4)
In order to measure the coefficient of friction using a cylinder-on-disk single-piece reciprocating friction tester shown in FIG. 2, a cylinder-shaped test piece 10 and a disk-shaped test piece were made of SUJ2 steel.
Next, the surface of the upper sliding surface of the disk-shaped test piece is measured by PVD arc ion ion plating method with a hydrogen atom amount of 0.5 atomic% or less, Knoop hardness Hk = 2170 kg / mm ² , and surface roughness Ry = 0.03 μm. Then, a DLC thin film having a thickness of 0.5 μm is formed to produce a disk-shaped test piece 20, and the sliding mechanism of this example is manufactured using the cylindrical test piece 10 and the disk-shaped test piece 20 as sliding members. did.

Next, about 0.3 g of the grease shown in Table 1 was applied between the cylindrical test piece 10 and the disk-shaped test piece 20, and a friction test was performed under the following conditions to measure the friction coefficient.
Table 1 shows the test piece material and grease component display. Further, the coefficient of friction of the sliding mechanism of each example after 10 minutes from the test was graphed and shown in FIG.

[Friction test conditions]
・ Test equipment: Cylinder-on-disk reciprocating friction tester ・ Sliding side test piece; φ15 × 22 mm cylindrical test piece ・ Math side test piece; φ24 × 7.9 mm disk-like test piece ・ Load; 100 N (sliding side test (Pressing load of one piece)
・ Amplitude: 1.5mm
・ Frequency: 50Hz
Test temperature: 80 ° C
・ Measurement time: 10 min

(Comparative Examples 1-6)
Except that no DLC thin film was formed on the disk-shaped test piece, the same operation as in Examples 1 to 4 was repeated, and the friction coefficient was measured. The obtained results are also shown in FIG.

It is a section explanatory view of a shock absorber showing one embodiment of the axial force generator of the present invention. It is a perspective view explanatory drawing showing roughly a cylinder on disk simple substance reciprocating friction tester. It is a graph which shows together the friction coefficient of Examples 1-4 obtained by the friction test, and the friction coefficient of Comparative Examples 1-6.

Explanation of symbols

1 Shock absorber (Axial force generator)
2 Cylinder 3 Piston 4 Piston seal member 5 Piston rod 6 Guide member 7 Rod seal member 8 Communication hole 10 Cylinder-shaped test piece 20 Disc-shaped test piece

Claims (11)

  A cylinder, a piston slidably accommodated in the cylinder, a piston seal member disposed at a sliding portion of the piston with the cylinder, a working fluid filled in the cylinder, and a piston coupled to the piston A rod, a guide member disposed in the cylinder and slidably supporting the piston rod, and a rod seal member disposed in the cylinder and sealing a sliding portion with the piston rod, the communication hole in the piston In an axial force generator that generates a damping force in the axial direction by the pressure difference when the working fluid in the cylinder passes through the communication hole by sliding the piston, the sliding surface of the cylinder with the piston, The sliding surface with the cylinder, the sliding surface with the cylinder of the piston seal member, the sliding surface with the guide member of the piston rod, At least one sliding surface of the sliding surface with the stone rod and the sliding surface with the piston rod of the rod seal member is covered with a hard carbon thin film, and the hydrogen content of the hard carbon thin film is 20 atomic% or less. In addition, an axial force generator characterized in that the working fluid contains grease based on ester oil and / or ether oil as a base oil.   A cylinder, a piston slidably accommodated in the cylinder, a piston seal member disposed at a sliding portion of the piston with the cylinder, a working fluid filled in the cylinder, and a piston coupled to the piston A rod, a guide member disposed in the cylinder and slidably supporting the piston rod, and a rod seal member disposed in the cylinder and sealing a sliding portion with the piston rod. In an axial force generator that creates a relative displacement in the axial direction between a cylinder and a piston rod by providing a flow path along the direction and taking in and out the working fluid into the cylinder through the flow path, the piston of the cylinder Sliding surface with piston, sliding surface with piston cylinder, sliding surface with piston seal member cylinder, piston rod The hard carbon thin film is used to cover at least one of the sliding surface with the id member, the sliding surface with the piston rod of the guide member, and the sliding surface with the piston rod of the rod seal member. An axial force generator characterized in that the hydrogen content of the thin film is 20 atomic% or less, and the working fluid contains grease based on ester oil and / or ether oil.   The axial force generator according to claim 1 or 2, wherein at least one of the piston seal member and the rod seal member is impregnated with a lubricant containing grease.   The axial force generator according to any one of claims 1 to 3, wherein both the cylinder and the piston are made of a metal material.   The axial force generator according to any one of claims 1 to 4, wherein both the piston rod and the guide member are formed of a metal material.   The axial force generator according to any one of claims 1 to 5, wherein at least one of the cylinder and the piston seal member is formed of a resin material.   The axial force generator according to any one of claims 1 to 6, wherein at least one of the piston rod and the guide member is formed of a resin material.   The axial force generator according to any one of claims 1 to 7, wherein the hydrogen content of the hard carbon thin film is 10 atomic% or less.   The axial force generator according to any one of claims 1 to 7, wherein the hydrogen content of the hard carbon thin film is 0.5 atomic% or less.   The axial force generator according to any one of claims 1 to 9, wherein a surface roughness of the sliding surface before coating with the hard carbon thin film is set to 0.1 μm or less in terms of Ra.   The axial force generator according to any one of claims 1 to 10, wherein the grease contains a metal soap containing calcium or lithium, or a urea compound as a thickener.

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