Relative combination of apex seal and rotor housing in rotary piston internal combustion engine
United States Patent 1191 Sasame et a1.  
 [451 Apr. 15, 1975 1 RELATIVE COMBINATION OF APEX SEAL AND ROTOR HOUSING IN ROTARY PISTON INTERNAL COMBUSTION ENGINE [75] Inventors: Takao Sasame, Hiroshima; Kentaro Takahashi, Omiya, both of Japan [73] Assignee: Nippon Piston Ring Co., Ltd.,  
 Tokyo, Japan [22] Filed: Sept. 10, 1973 [21] Appl. No.: 395,874  
 .[30] Foreign Application Priority Data Sept. 12, 1972 Japan 47-90912 [52] US. Cl. 418/178; 29/195 M; 117/931 PF; 277/235 A [51] Int. Cl. F016 21/00 [58] Field of Search ..418/178,179;  
 117/931 PF, 93.1 R, 105, 105.1, 105.2;  
 [56] References Cited UNITED STATES PATENTS 2,311,240 2/1943 Marien et a1. 277/235 A 3,033,180 5/1962 Bentele 418/179 3,061,525 10/1962 Grazen 29/195M 3,289,649 12/1966 Lamm 418/179 3,513,084 5/1970 Breton et a1. 418/179 3,731,941 5/1973 Mori et a1. 418/179 FOREIGN PATENTS OR APPLICATIONS 1,003,118 9/1965 United Kingdom 117/931 PF Primary Examiner-C. .1. Husar Assistant Examiner-O. T. Sessions Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn &amp; Macpeak [5 7 ABSTRACT In the relative combination of an apex seal and a rotor housing in a rotary piston internal combustion engine, the apex seal made of a ferrous or nonferrous metal is provided with a sparyed layer of FE-O compound,  
 which contains oxygen in the range from 15.0 to 30.05  
  wt,%, having the thickness of more than 0.1 mm at least on the sliding surface thereof and the rotor housing is provided with a cast-iron member of which graphite is precipitated on the surface thereof in the range from 1 to 15%, by area, based on the surface area of the cast-iron member at least on the sliding surface on which the apex is&#39;slided, &#39;whereby the wear and scuffing resistances of both sliding surfaces of the apex seal and the rotor housing are improved.  
 1 Claim, 2 Drawing Figures RELATIVE COMBINATION OF APEX SEAL AND ROTOR HOUSING IN ROTARY PISTON INTERNAL COMBUSTION ENGINE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the relative combination of an apex seal and a rotor housing in a rotary piston internal combustion engine, more particularly to the improvements of both sliding surfaces of the apex seal and the rotor housing, which contact slidingly with each other, so that wear and scuffing resistances of both sliding surfaces are improved.  
 2. Description of the Prior Art Heretofore. in view of the wear resistance, a rotor housing, which is made ofa light alloy, such as Al, as its base metal, in a rotary piston internal combustion engine is provided with a nickel plated layer having a hardened part of hard chrome, silicon carbide, etc.. on the sliding surface thereof on which an apex seal is slided, however, manufacturing processes for applying the plating treatment to the sliding surface of the rotor housing and machining process after applying the plating treatment are considerably complex because the shape of the sliding surface of the rotor housing is very complex. As a result of this, the cost ofthe article becomes dear. In addition, a problem on the relative combination between the conventional apex seal and rotor housing, that is to say, chatter mark&#34; which is considered to be resulted mainly from a discontinuity of the lubrication between the apex seal and the rotor housing has not been solved completely.  
 SUMMARY OF THE INVENTION A primary object of this invention is to provided the relative combination of an apex seal and a rotor housing in a rotary piston internal combustion engine which exhibit high wear and scuffing resistances on both sliding surfaces of the apex seal and the rotor housing so that the durability of the engine may increase.  
  Another object of this invention is to provide the relative combination of an apex seal and a rotor housing in a rotary piston internal combustion engine which overcomes the problem of chatter mark&#34; which is considered to be resulted mainly from a discontinuity of the lubrication between the apex seal and the rotor housing.  
  Further object of this invention is to provide an apex seal and a rotor housing which have high wear and scuffing resistances and which are produced very economically.  
  According to this invention, an apex seal which is made of a ferrous or nonferrous metal as its base metal and which is provided with a sprayed layer of Fe-O compound, which contains oxygen in the range from 15.0 to 30.05 wt.%, having the thickness of more than 0.l mm is used in a rotary piston internal combustion engine in the relative combination with a rotor housing which is provided with a cast-iron member of which graphite is precipitated on the surface thereof in the range from I to bv area, based on the surface area of the cast-iron member.  
  The amount of oxygen in the FeO compound sprayed at least on the sliding surface of the apex seal is closely relative to the self-lubrication of the apex seal, and accordingly restricted to the above described range, namely from 15.0 to 30.05 wt.%.  
  The thickness of the sprayed layer of the Fe-O&#39;compound must be at least 0.1 mm. Because, if the thickness is not more than 0.1 mm. the desired durability of the apex seal will not be expected. And the upper limit of the thickness is determined from the results of many experiments and from the economical reason, and is preferably 5 mm or less.  
  On the other hand, the cast-iron member is formed at least on the sliding surface of the rotor housing by casting a body of the rotor housing with a cast-iron or, in view of lightening the weight of the rotor housing body and of the radiation of heat on the rotor housing, by fixing the cast-iron member at least to the sliding surface of the rotor housing made of a light alloy, such as Al or the like, as its base metal by a metallurgic method, such as included casting, etc., or a mechanical method, such as the press-fitting, etc.  
  The shape of graphite precipitated on the surface of the cast-iron member, which functions as the sliding surface of the rotor housing, in the range from 1 to 15 71, by area, based on the sliding surface of the rotor housing may be effectually selected from flakes globales and spherical.  
  If the precipitating amount of graphite is less than 1.0 the scuffing resistance of the sliding surface of the rotor housing becomes worse since the oil-humidity and the self-lubricating property peculiar to graphite become worse, on the contrary, if the amount is over 15%, the wear resistance of the sliding surface of the rotor housing becomes worse. Therefore, the precipitating amount of graphite on the sliding surface of the rotor housing is determined in the range from I to 15 by area, based on the sliding surface of the rotor housing.  
  As for the hardness of the cast-iron member, the castiron member having the hardness in the range of 150 to 300 HB may be used preferably. But, at least one element selected from the group consisting of Cr, B, Mo, etc., which form a carbide is effectually contained in the cast-iron member or a proper heat treatment is subjected to the cast-iron member since the cast-iron member must be possessed of the durability and a high hardness in response to the type of the engine. In the case of this, the hardness of the cast-iron member becomes in the range from 300 to 700 HB.  
 BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 showing an enlarged photograph which shows a microstructure (magnitude of a sprayed layer of Fe-O compound formed on the sliding surface of an apex seal according to this invention, a white part indicates the sprayed layer of FeO compound containing oxygen therein in the range from 15.0 to 30.05 wt.% and black parts indicate void spaces formed into the sprayed layer during the spraying treatment.  
  Such structure of the sprayed layer exhibits the excellent wear resistance and scuffing resistance due to the self-lubricating property of the Fe-O compound. Besides, the void spaces in the sprayed layer cause the porous and oil-impregnating structure. As the Fe-O compound is readily converted into drops during the spraying treatment due to the relatively low melting point (about l;500C), the sprayed particles are mutually entangled to increase the strength of the sprayed layer itself. Accordingly, the acceleration of the abrasion of the apex seal and the rotor housing by the peeled off particles is never coused.  
  As for the rotor housing, by forming the cast-iron member of which graphite is precipitated on the surface thereof in the range from i to by area, based on the surface area of the member at least on the sliding surface of the rotor housing, the sliding surface of the rotor housing exhibits the wear and&#39;scuffing resist- .v ances due to mutual effect of the oil -humidity and the self-lubricating property which are peculiar &#39;t&#39;ograph&#39;i&#39;te, at the sameotime, .graphitefunc&#39;tions&#39;to absorb loadof the apex seal to the rotor housing caused by the mechanical vibration of the engine, thereby resulting in the stable operation of the apex seal.  
  As described above, the combination of the apex seal and the rotor housing according to this invention brings out unexpectedly high wear resistance therebetween, and reduces the forming of the scuffing due to mutual effect of the self-lubricating property and the oil- Elemen Total c Si Mn P 5 Fe Content (Wtzfi) 3.25 L82 0.55 0.20 0.07 balance Matrix structure: pearlite Shape of graphite: The precipitating amount of graphite: Hardness: 215 (HB) flakes of graphite 9.8 71 (by area) The apex seal and the rotor housing thus treated wear combined with each other, and the combination was subjected to the wear resistance test in the actual engine.  
 Specification of the engine used:  
 water cooled 2 rotor type Rotary Piston Internal Combustion Engine Type:  
 2. total exhaust volume; 982 cc 3. maximum output; I00 PS/7U00 rpm. 4. maximum tork; l3.5 Kg m/SSOO r.p.m.  
  test conditions: i l. rotating number; 2680 r.p.m. 2. boosting pressure; -350 mm.Hg. 3. running time; 50 hr.  
 EXAMPLE 2 rotor hausing made of Al as its base metal of which a.  
 Cr plating layer (having the thickness of 0.15 mm and the hardness of 950 Hv) is provided on the sliding surimpregna ing pr p y of h li ing surface of the p 30 face thereof under the following plating conditions and plating conditions of the Cr plating layer;  
 current density; liquid temp. in the plating bath; 60C composition of the liquid;  
 (iOA/diameter chromic acid anhydride ZSOg/l sulfuric acid 2.5 g/l seal, and the self-lubrication property, the oil-humidity and the vibration absorbing property of graphite formed on the sliding surface of the rotor housing even if the discontinuity of the lubrication exists between the apex seal and the rotor housing, thus resulting in the prevention of the occurrence of chatter mark.  
  Now, some examples of this invention will be described hereinafter with reference to the drawings.  
 EXAMPLE I A Fe0 compound containing 27.6 wt.% of oxygen was plasma-sprayed on the sliding surface of cast-iron apex seal made of the castiron (.llS FC-) as its base metal to form the layer of 1 mm thickness. The Hv() hardness of the resultant sprayed layer was 700.  
 The spraying conditions were as follows:  
 Meteco 3M type plasma spraying gun spraying gun.  
 N gas pressure; lb/in N gas flow rate; 150 ftVhr. H gas pressure; 50 lb/in? H gas flow rate; 10 ft &#39;lhr. electric current applied: 500A spraying distance: 4 inch On the other hand, a rotor housing is formed by casting with the following cast-iron.  
 .COmpositiom&#39; rotor housing No. 2 is only about one-fifth of that of rotor housing No. 1 accordingly this invention has the excellent durability.  
  The chatter mark is not observed in the combination according to&#39;this invention.  
 EXAMPLE 3 The scuffing resistance test was carried out with using the rotary type wear resistance tester.  
  Aspecimen having the sprayed surface layer was thrusted on a turn table which was rotated supplying the lubricating oil between the surface layer of the specimen and the upper surface of the turn table. The  
 load to thrust the specimen on the turn table wasgradually increased at every one hour to detect the limit load to cause the scuffing.  
  testing conditions: 1. testing specimen;  
 6. running time;  
  obtained by plasma-spraying Fe-O compound containing oxygen 27.6 on the surface of a cast-iron (J 18 FC-25) to have the thickness of 0.1 mm and the Hv (30) hardness of 700. 2. turn table;  
 composition;  
 composition;  
 element total C Si Mn P 5 Fe content (wt. 71) 3.32 2.05 0.61 0.18 0.09 balance the matrix structure: pearlite the shape of graphite: flakes of graphite the precipitating amount of graphite: 10.9 7! (by area) the hardness: 223 HR 3. temperature of the lubricating oil;  
 4. rate of feeding the lubricating oil;  
 5. lubricating oil;  
 0.6 l/hr.  
 Daphni oil No. 65 50% and lamp oil 50% every 1 hr. for the load 50kglcm&#39;.  
 lOO kg/cm lSO kg/cm and 200 kglcm As a result of the above, &#39;the&#39;specimen was observed to cause the scuffing by the load of 300 kglcm lt will be, therefor, understood from this test result that the combination of the apex seal and the rotor housing according to this invention exhibits the high resistance to the scuffing under the high compression.  
  The base metal of the apex seal is not restricted to the castiron, but may be Al, Cu or the like nonferrous metals.  
  While the invention has been described with reference to particular embodiments thereof, it will be understood that the numerous modifications may be compound. which contains oxygen in the range from 15.0 to 30.05 wt.7r, having the thickness ofmore than 0.1 mm and saidtrotor housing is provided with a castiron member of which graphite is precipitated on the surface thereofin the range from 1 to l5 by area, based on the surfacearea of said cast-iron member, at least on the apex seal sliding surface of said rotor housing.