Patent Publication Number: US-2017350509-A1

Title: Sealing member and fluid pressure device provided therewith

Description:
TECHNICAL FIELD 
     The present invention relates to a sealing member and a fluid, pressure device provided with the sealing member. 
     BACKGROUND ART 
     Patent Document 1 discloses a conventional sealing device. The sealing device is retained in an opening of an outer tube into which an inner tube reciprocated in a projected state is inserted. The sealing device includes a dust seal and a scraper. The dust seal is made of nitrile rubber and has a dust seal body and a seal lip continuously provided on an inner periphery at the distal end side of the dust seal body. A garter spring is fit onto an outer periphery of the distal end of the seal lip. The garter spring presses an inner peripheral end of the seal lip against the inner tube. The scraper is disposed at the inner side of the dust seal. The scraper is made of fluorine resin and has a scraper body and a lip continuously provided on an inner periphery of the scraper body. The lip is formed so that an inner circumference thereof has a diameter smaller than an outer diameter of the inner tube. Furthermore, the lip has a hardness set to be higher than that of the seal lip. In this sealing device, the lip of the scraper can scrape off a foreign substance which is adhered to the outer periphery of the inner tube and which has not completely been scraped off by the seal lip. 
     PRIOR ART DOCUMENT 
     Patent Documents 
     Patent Document 1: Japanese Patent Application Publication NO. JP 2013-96495 
     SUMMARY OF THE INVENTION 
     Problem to be Overcome by the Invention 
     However, the dust seal provided in the sealing device of patent document 1 is elastically deformable since it is made of nitrile rubber. Accordingly, there is a possibility that a foreign substance such as mud firmly adherent to the outer periphery of the inner tube cannot be scraped off by the seal lip. Furthermore, there is a possibility that the scraper would be damaged by the foreign substance which cannot be scraped off by the seal lip. In this case, the foreign substance might enter the outer tube and the inner tube thereby to result in occurrence of failure. 
     The present invention was made in view of the foregoing prior art circumstances and an object thereof is to provide a sealing member which can successfully scrape off foreign substances and prevent failure caused by incorporation of foreign substances. 
     Means for Overcoming the Problem 
     A sealing member in accordance with the present invention includes a seal body and a lip member. The seal body has a predetermined elasticity and is retained in an opening of a body into which a moving body reciprocated in a projected state. The lip member is attached to a distal end of the seal body and having a distal end which is brought into sliding contact with a side surface of the moving body. The lip member is harder than the seal body. 
     In the sealing member in accordance with the invention, at least one of the distal end of the lip member and the moving body may be covered with a film harder than the lip member. 
     Furthermore, a fluid pressure device may include the sealing member in accordance with the invention. An operating fluid is encapsulated in the body. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross section of a major part of a front fork provided with a dust seal which is the sealing member of a first embodiment; 
         FIG. 2  is a cross section of the dust seal of the first embodiment; 
         FIG. 3  is a cross section of the dust seal where the distal end of the lip member has a semicircular cross section; 
         FIG. 4  is a cross section of the dust seal where a distal end of the lip member, in a sectional configuration, is pointed at the inner peripheral surface side; 
         FIG. 5  is a cross section of the dust seal where a distal end of the lip member, in a sectional configuration, is pointed at the outer peripheral surface side; and 
         FIG. 6  is a cross section of the dust seal where a distal end of the lip member is brought into face-to-face contact with an outer peripheral surface of the inner tube. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     A first embodiment of a fluid pressure device provided with the sealing member in accordance with the invention will be described with reference to the drawings. 
     First Embodiment 
     The fluid pressure device of the first embodiment is an inverted front fork  10  functioning as a damper which suspends a front wheel of a two-wheel vehicle and damps road vibration input to the front wheel. The front fork  10  has a suspension body  20 , a damper (not illustrated), and a sealing device  30  as shown in  FIG. 1 . The suspension body  20  includes an outer tube  21  and an inner tube  23 . The damper is housed in the suspension body  20  to suppress expansion/contraction motion. 
     The outer tube  21  is cylindrical in shape and has a lower end formed with an opening  25 . The lower end of the outer tube  21  has an outer peripheral surface formed with a thread groove  27  into which a seal case  31  is screwed as will be described later. Furthermore, the lower end of the outer tube  21  has an inner peripheral surface formed with a stepped part  29  into which a slide bearing  33  is fitted as will be described later. 
     The inner tube  23  is inserted into the opening  25  of the outer tube  21  and reciprocated in a projected state. Thus, the front fork  10  having the outer tube  21  and the inner tube  23  is expandable/contractible. 
     The front fork  10  has a reservoir (not illustrated) formed between the suspension body  20  and the damper. The reservoir stores an operating fluid and a gas to provide the damper with temperature compensation and volume compensation. The operating fluid is water, glycol solution, oil, or the like. The gas is an inert gas such as nitrogen. 
     The suspension body  20  has a cylindrical gap  22  defined between overlapping parts of the outer tube  21  and the inner tube  23 . The sealing device  30  closes the gap  22 . As a result, the operating fluid in the reservoir is prevented from leaking out of the suspension body  20  in the front fork  10 . 
     The sealing device  30  has a seal case  31 , a slide bearing  33 , a holder  35 , an oil seal  37 , and a dust seal  39  serving as a sealing member. The slide bearing  33  is cylindrical in shape and is fitted in the stepped part  29  provided in the inner peripheral surface of the lower end of the outer tube  21 . The slide bearing  33  has an inner peripheral surface which is brought into sliding contact with the outer peripheral surface of the inner tube  23 , whereby the inner tube  23  is allowed to reciprocate smoothly. 
     The holder  35  is annular in shape and is retained on the seal case  31 . The holder  35  abuts against a lower end surface of the slide bearing  33  while the seal case  31  is screwed into the thread groove  27  formed in the outer peripheral surface of the lower end of the outer tube  21 , thereby preventing displacement of the slide bearing  33 . 
     The oil seal  37  is disposed below the holder  35  and is retained on the seal case  31  by a snap ring  32  fitted with the inner periphery of the seal case  31 , so as not to drop out of a predetermined position. The oil seal  37  is annular in shape. The oil seal  37  is made of nitrile rubber and has elasticity. Furthermore, the oil seal  37  has an outer periphery  37 A and a lip part  37 B. A substantially cylindrical member  34 A made of stainless steel is inserted into the outer periphery  37 A. The outer periphery  37 A has a lower end which is bent to the inner peripheral side thereof and from which the lip part  37 B extends in the up-down direction. In this oil seal  37 , two garter springs  34 B are fitted on outer peripheries of an upper end and a lower end of the lip part  37 B respectively, so that inner peripheral surfaces of the upper end and the lower end of the lip part  37 B are in sliding contact with the outer peripheral surface of the inner tube  23 . Thus, the oil seal  37  prevents the operating fluid in the reservoir from leaking outside from the suspension body  20 . 
     The dust seal  39  includes a dust seal body  36  and a lip member  38  as illustrated in  FIGS. 1 and 2 . The dust seal body  36  is annular in shape. Furthermore, the dust seal body  36  is made of nitrile rubber and is accordingly elastic. The dust seal body  36  has a base  36 A, a first lip part  36 B, and a second lip part  36 C. A substantially cylindrical member  36 D made of stainless steel is inserted into the base  36 A thereby to be retained on the inner peripheral surface of the lower end of the seal case  31 . The first lip part  36 B extends aslant inwardly downward from a middle part of the inner peripheral surface of the base  36 A and has a distal end in sliding contact with the outer peripheral surface of the inner tube  23 . The second lip part  36 C extends aslant inwardly downward from the lower end of the inner peripheral surface of the base  36 A. Thus, the dust seal body  36  is retained via the seal case  31  in the opening  25  of the outer tube  21 . 
     The lip member  38  is substantially cylindrical in shape and has a diameter which is gradually reduced downward. Furthermore, the lip member  38  is made of stainless steel and is accordingly harder than the dust seal body  36 . The lip member  38  is attached integrally to the second lip part  36 C of the dust seal body  36  by insert molding. The lip member  38  has a proximal end  38 C at an upper end thereof formed so as to be curved to spread outward. As a result, the lip member  38  is less likely to drop out of the dust seal body  36 . The lip member  38  has a distal end at a lower end thereof with a distal end surface formed to be orthogonal to outer and inner peripheries thereof. Diamond-like carbon (DLC) coating  38 A is applied to the distal end of the lip member  38  as illustrated in  FIG. 2 . In other words, the distal end at the lower end of the lip member  38  is covered with a film harder than the lip member  38 . The distal end at the lower end of the lip member  38  has an inner corner  38 B formed to have an inner peripheral diameter that is substantially equal to an outer diameter of the inner tube  23 . As a result, the inner corner  38 B of the distal end at the lower end of the lip member  38  is brought into sliding contact with an outer peripheral surface of the inner tube  23 . 
     Thus, the dust seal  39  provided on the front fork  10  includes the dust seal body  36  and the lip member  38 . The dust seal body  36  is elastic and is retained via the seal case  31  in the opening  25  of the outer tube  21  into which the inner tube  23  is inserted, which inner tube is reciprocated in the projected state. The lip member  38  is made of stainless steel and is attached to the distal end of the seal body  36 . The inner corner  38 B of the distal end of the lip member  38  is brought into sliding contact with the outer peripheral surface of the inner tube  23 . 
     The lip member  38  is harder than the dust seal body  36 . Accordingly, the dust seal  39  is less likely to be deformed (or to open) even when the distal end thereof is slid on the side surface of the inner tube  23 , with the result that the dust seal  39  can successfully scrape off a foreign substance, such as mud, adhered to the outer peripheral surface of the inner tube  23 . Furthermore, the dust seal  39  has the stainless lip member  38  attached to the distal end of the elastic dust seal body  36 . Accordingly, the dust seal  39  can be slid without any gap between inner corner  38 B of the distal end of the lip member  38  and the outer peripheral surface of the inner tube  23  while following displacement of the inner tube  23  during reciprocation of the inner tube  23 , and furthermore, the dust seal  39  is less likely to damage the outer peripheral surface of the inner tube  23 . Thus, the dust seal  39  can successfully scrape off even foreign substance, such as mud, firmly fixed to the outer peripheral surface of the inner tube  23 . 
     Accordingly, the dust seal  39  and the front fork  10  provided with the dust seal  39  in the first embodiment can successfully scrape off the foreign substance such as mud and can prevent failure caused by incorporation of a foreign substance such as mud into the operating fluid or leakage of the operating fluid. 
     Furthermore, the DLC coating  38 A is applied to the distal end of the lip member  38 . As a result, the dust seal  39  has high slidability, high wear and abrasion resistance, and low aggressivity. In other words, the distal end of the lip member  38  is smoothly slid on the outer peripheral surface of the inner tube  23  with the result that the distal end of the lip member  38  is less likely to be worn and to damage the side surface of the inner tube  23 . 
     The present invention should not be limited to the first embodiment described above with reference to the drawings, but the technical scope of the invention encompasses the following embodiments, for example.
     (1) Various shapes of the distal end of the lip member can be considered as illustrated in  FIGS. 3 to 6 . In other words, a lip member  138  ( FIG. 3 ) may have a distal end with a semicircular cross section, a lip member  238  ( FIG. 4 ) may have a distal end the cross sectional shape of which is inclined from a distal end of the inner peripheral surface at the inner tube  23  side toward the outer peripheral surface thereby to be pointed (the inner peripheral surface side is pointed), a lip member  338  ( FIG. 5 ) may have a distal end the cross sectional shape of which is inclined from a distal end of the outer peripheral surface toward the inner peripheral surface at the inner tube  23  side thereby to be pointed (the outer peripheral surface side is pointed), or a lip member  438  ( FIG. 6 ) may have a shape such that the corner of the inner peripheral surface at the inner tube  23  side is cut out so that the distal end is brought into face-to-face contact with the outer peripheral surface of the inner tube  23 . In  FIGS. 3 to 6 , identical or similar constructions are labelled by the same reference symbols as those in the first embodiment.   (2) Although the DLC coating is applied to the distal end of the lip member in the first embodiment, another surface treatment (for example, chromium nitride (CrN) coating, or titanium nitride (TiN) coating) may be applied. On the contrary, the surface treatment such as the DLC coating may not be applied.   (3) Although the DLC coating is applied to only the distal end of the lip member in the first embodiment, surface treatment such as the DLC coating may be applied to the outer peripheral surface of the inner tube as well as the distal end of the lip member.   (4) Although the DLC coating is applied to the distal end of the lip member in the first embodiment, surface treatment such as the DLC coating may not be applied to the distal end of the lip member but applied to only the outer peripheral surface of the inner tube.   (5) Although the dust seal which is a sealing member is applied to the front fork in the first embodiment, the sealing member may be applied to the damper, the cylinder device, or another fluid pressure device. When the sealing member is applied to the damper or the cylinder device, a piston rod serves as the moving body, and a cylinder serves as the body.   (6) Although the lip member is made of stainless steel in the first embodiment, the lip member may be made of any resin having a higher hardness than the sealing body.   

     EXPLANATION OF REFERENCE SYMBOLS 
       10  . . . front fork (a fluid pressure device),  21  . . . outer tube (a body),  23  . . . inner tube (a moving body),  25  . . . opening,  36  . . . dust seal body (seal body),  38  . . . lip member,  38 A . . . diamond-like carbon (DLC) coating (rigid film),  39  . . . dust seal (sealing member).