Rotary piston engine sealing mechanisms

An apex seal of a rotary piston engine comprising a sealing groove formed in each apex portion of the rotor, a sealing piece and a support piece disposed in the sealing groove with a superposed relationship. A corner seal at each end of the apex seal including a corner seal member formed with a longitudinally extending slit for receiving an adjacent end of the apex seal pieces. The slit in the corner seal member is generally wider than the sealing groove of the apex seal but has a minimum width portion that is narrower than the sealing groove. The minimum width slit portion is disposed against only one of the sealing and support pieces of the apex seal so that the sideward movement of the other piece is not disturbed by the corner seal member.

The present invention relates to apex seals for rotary piston engines and 
more particularly to apex seals of a two-piece construction comprising an 
elongated sealing piece and an elongated support piece which are in a 
superposed relationship substantially throughout their lengths. 
In the U.S. patent application which has been filed on Nov. 13, 1979 by 
Shimizu et al. and given with an unofficial serial number of Ser. No. 
93,435, there is proposed an apex seal construction of the aforementioned 
type. The proposed type of apex seal is considered as being advantageous 
in that the sealing piece possesses a flexibility in radial direction of 
the rotor so that it can be engaged with the inner wall surface of the 
rotor housing with a substantially uniform pressure throughout its length 
even when the inner wall of the rotor housing is radially outwardly 
deformed due to a thermal expansion to provide a concave configuration as 
often experienced in a rotary piston engine. Further, it is noted that the 
support piece functions to suppress vibrations of the sealing piece. A 
further advantage of the above type of apex seal is that the arrangement 
provides an increased length of gas leakage path through the gap between 
the apex seal and the apex seal groove to thereby decrease gas leakage 
through the gap. 
Such type of apex seal may be associated with a side piece at one or each 
end thereof as in conventional apex seals. Further, at each end of the 
apex seal, there may be provided a corner seal which generally comprises a 
cylindrical sealing member adapted to be fitted to a cylindrical bore 
formed in each corner portion of the side surface of the rotor. The 
sealing member of the corner seal has a longitudinally extending slit for 
receiving an end of the apex seal and resiliently forced into sliding 
engagement with the inner surface of the side housing. 
Conventionally, such sealing member of the corner seal has been formed with 
the longitudinal slit for receiving an end of the apex seal larger in 
width than the apex seal groove and there has been noticeable amount of 
gas leakage through the gap between the apex seal and the slit of the 
corner seal member. In order to avoid such problem, the width of the slit 
in the corner seal member may be decreased so that it becomes narrower 
than the apex seal groove. However, such type of corner seal is not 
recommendable where the apex seal is of the aforementioned two-piece 
construction. In the apex seal of the two-piece construction, it is 
intended to force the sealing piece sidewardly in one direction into 
contact with one of the side walls of the apex seal groove and the support 
piece in the opposite direction into contact with the other of the side 
walls of the apex seal groove to thereby suppress the gas leakage through 
the gap between the apex seal and the seal groove. Such sideward forces 
may be applied to the apex seal pieces making use of the combustion gas 
pressure but the effects can further be enhanced by providing sidewardly 
slanted mating surfaces between the sealing and support pieces and forcing 
the support piece toward the inner wall surface of the rotor housing to 
produce sideward wedge forces. Where the corner seal member is of the type 
having a narrow longitudinal slit, the sideward movements of the sealing 
and support pieces of the apex seal may be disturbed by the wall of the 
slit so that the desired sealing function cannot be obtained. 
It is therefore an object of the present invention to provide a novel 
combination of an apex seal of two-piece construction and a corner seal. 
Another object of the present invention is to provide a corner seal for use 
with an apex seal of a two-piece construction. 
Still further object of the present invention is to provide a combination 
of an apex seal of a two-piece construction and a corner seal which is so 
formed that it does not disturb the sideward movements of the apex seal 
pieces. 
According to the present invention, the above and other objects can be 
accomplished by a rotary piston engine including a casing which comprises 
a rotor housing having an inner wall of trochoidal configuration and a 
pair of side housings having inner walls and secured to the opposite sides 
of the rotor housing to define a rotor cavity in the casing, a rotor of 
substantially polygonal configuration having opposite side surfaces and 
disposed in said rotor cavity for rotation with apex portions in sliding 
engagement with the inner wall of the rotor housing, apex seal means 
provided in each apex portion of the rotor and comprising a sealing groove 
formed in the rotor at the apex portion to extend in axial direction of 
the rotor, an elongated sealing piece and an elongated support piece 
disposed in said sealing groove in a superposed relationship substantially 
throughout their lengths with said sealing piece faced to the inner wall 
of the rotor housing, spring means disposed between the support piece and 
the sealing groove to bias the sealing and support pieces toward the inner 
wall of the rotor housing, corner seal means provided in each side surface 
of the rotor at each apex portion, said corner seal means comprising a 
corner seal recess formed in the side surface at each apex portion, a 
corner seal member fitted to the corner seal recess and having an axially 
extending slit for receiving an end portion of the apex seal means and 
spring means for biasing the corner seal member toward the inner wall of 
the side housing, at least a portion of said slit of the corner seal 
member being of a minimum width which is smaller than width of the sealing 
groove of the apex seal means, said portion of the minimum width of slit 
of the corner seal member being disposed against only one of the sealing 
and support pieces of the apex seal means. Where the corner seal member is 
of a relatively thin ring-shaped cross-sectional configuration, the 
longitudinal slit may be of a uniform width and may be placed only against 
the sealing piece. Where the corner seal member has a relatively large 
thickness at the slit, the slit may have a narrow portion of the minimum 
width and a wide portion which is larger in width than the sealing groove 
of the apex seal means. In this instance, the narrow portion may be placed 
against either the sealing piece or the support piece. 
The minimum width portion of the longitudinal slit in the corner seal 
member may be defined by a pair of opposed parallel flat surfaces. One of 
the flat surfaces may then be located during a certain period of operation 
coplanar with one of the side walls of the sealing groove in the apex seal 
means and the other flat surface may be projected beyond the plane of the 
other side wall of the sealing groove. The corner seal member should 
preferably have resiliency in radial direction and fitted to the corner 
seal recess with a radially compressed condition so that it has a radially 
outwardly directed resiliency to thereby closely fit to the wall of the 
corner seal recess. 
In practice, the apex seal means may be associated with a side piece at one 
or each end portion thereof as in conventional apex seals. Further, in 
order to produce sideward wedge forces, the sealing and support pieces may 
be superposed through sidewardly inclined interfaces.

Referring now to the drawings, particularly to FIG. 1, the rotary piston 
engine shown therein includes a casing C comprised of a rotor housing 9 
having an inner wall 9a of trochoidal configuration and a pair of side 
housings 10 having inner surfaces 10a and secured to the opposite sides of 
the rotor housing 9. In the casing C, there is disposed a rotor 1 of 
substantially triangular configuration which is carried by an eccentric 
shaft S for rotation with apex portions 1a in sliding contact with the 
inner wall 9a of the rotor housing 9 to define working chambers 11, 12 and 
12a. 
Referring now to FIG. 2, in each apex portion 1a, the rotor 1 is formed 
with an axially extending sealing groove 2 for receiving an apex seal 5 
therein. The apex seal 5 comprises an elongated sealing piece 6 and an 
elongated support piece 7. The sealing and support pieces 6 and 7 are 
disposed along the sealing groove 2 with a superposed relationship. A leaf 
spring 3 is provided in the groove 2 with its opposite ends in engagement 
with the support piece 7. Thus, the pieces 6 and 7 are resiliently forced 
toward the inner wall 9a of the rotor housing 9. 
At the opposite ends of the sealing groove 2, the rotor 1 is formed with 
corner seal recesses 14 for receiving corner seals 15. Referring also to 
FIG. 3, it will be noted that the corner seal 15 includes a cylindrical 
corner seal member 20 adapted to be fitted to the recess 14. The member 20 
has a longitudinally extending slit 22 and a circular opening 21 which is 
eccentric with respect to the cylindrical outer surface of the member 20 
so as to provide a thin resilient portion 20a at a position diametrically 
opposite to the slit 22. Thus, the member 20 has a radial resiliency and 
fitted to the recess 14 with a radially compressed condition so that it 
has a tendency of expanding radially outwardly. This provides a close 
contact between the outer surface of the corner seal member 20 and the 
recess 14 to establish a reliable seal. A leaf spring 18 is provided in 
the recess 14 for urging the corner seal member 20 toward the inner wall 
10a of the side housing 10. The sealing and support pieces 6 and 7 of the 
apex seal 5 are received at each end by the slit 22 of the corner seal 
member 15. In the illustrated embodiment, the sealing and support pieces 6 
and 7 respectively have sidewardly inclined surfaces 6a and 7a which are 
engaged with each other so that, when they are forced toward the inner 
wall surface 9a of the rotor housing 9 under the action of the spring 3, a 
sideward force is produced to urge the sealing piece 6 in one side and the 
support piece in the other side. 
As shown in FIG. 3, the apex seal groove 2 has a pair of opposed parallel 
surfaces 2a and 2b and the sealing and support pieces 6 and 7 are 
respectively forced against the side walls 2a and 2b of the groove 2. The 
slit 22 is generally defined by a pair of parallel flat walls 22a and 22b 
which are spaced apart by a distance greater than the width of the groove 
2 and receives end portions of the sealing and support pieces 6 and 7. 
At the radially outward end of the slit 22, the side walls 22a and 22b are 
respectively formed with projections 23 and 24 which have opposing 
parallel flat surfaces 23a and 24a, respectively, to define a minimum 
width slit portion. The surfaces 23a and 24a are substantially parallel 
with the side walls 2a and 2b. The distance between the surfaces 23a and 
24a is smaller than that between the side walls 2a and 2b. In the 
illustrated positions of the parts, the surface 23a is coplanar with the 
side wall 2a of the apex seal groove 2 and the surface 24a is projected 
beyond the plane of the side wall 2b so as to be placed against the 
sealing piece 6 with a slight clearance. It will thus be understood that 
the sealing piece 6 is sidewardly forced under the wedge action as 
provided by the slanted surfaces 6a and 7a into contact with the side wall 
2a of the groove 2 and the surface 23a of the projection 23. Further, 
since the minimum width slit portion as defined by the surfaces 23a and 
23b are located only against the sealing piece 6, the support piece 7 can 
also be forced into contact with the side wall 2b of the apex seal groove 
2 without being disturbed by the projections in the corner seal member 20. 
It should further be noted that the minimum width slit portion is 
effective to restrict gas leakage through the gap between the apex seal 
and the slit in the corner seal member. 
Referring now to FIG. 4, the embodiment shown therein is similar in 
arrangements to the previous embodiment so that corresponding parts are 
designated by the same reference numerals as in the previous embodiments. 
In the embodiment, in lieu of the projections 23 and 24 formed at the 
radial outward end of the slit 22 in the previous embodiment, the side 
walls 22a and 22b of the slit 22 are formed at the radially inward 
portions thereof with projections 25 and 26, respectively, which have 
opposed flat parallel surfaces 25a and 26a to define a minimum width slit 
portion. As in the previous embodiment, the slit 22 of this embodiment has 
a width which is generally greater than the width of the apex seal groove 
2 but the minimum width slit portion is narrower than the groove 2. In the 
illustrated position of the parts, the surface 26a is coplanar with the 
side wall 2b of the groove 2 so that the support piece 7 is maintained in 
contact with the side wall 2b of the groove 2 and the surface 26a of the 
projection 26. The surface 25a of the projection 25 is located against the 
support piece 7 with a slight gap. Since the minimum width slit portion is 
located only against the support piece 7, the sideward movement of the 
sealing piece 6 is not disturbed. 
Referring to FIG. 5, the embodiment shown therein is different from the 
embodiment in FIG. 3 in that the minimum width slit portion is defined by 
a single projection 27 formed on the side wall 22b of the slit 22 at a 
radially outward end portion thereof. In the illustrated position of the 
parts, the side wall 22a of the slit 22 is coplanar with the side wall 2a 
of the apex seal groove 2 and the sealing piece 6 is maintained in contact 
with the side walls 2a and 22a. The projection 27 has a flat surface 27a 
which is located against the sealing piece 6 with a slight gap. 
In FIG. 6, the embodiment shown therein includes a corner seal having a 
corner seal member 120 of a ring-shaped cross-sectional configuration 
having a relatively thin wall of substantially uniform thickness. A 
longitudinally extending slit 122 is formed to receive an end portion of 
the sealing piece 6. The slit 122 is defined by a pair of opposed flat 
surfaces 122a and 122b which are parallel with the side walls 2a and 2b 
and has a width which is smaller than the width of the apex seal groove 2. 
In the illustrated position, the surface 122a is coplanar with the side 
wall 2a of the groove 2 and the sealing piece 6 is in contact with the 
side wall 2a and the surface 122a. The surface 122b projects beyond the 
plane of the side wall 2b of the groove 2 and located against the sealing 
piece 6 with a slight gap. The support piece 7 is located out of the slit 
122 so that its sideward movement is not restricted by the slit 122. 
The invention has thus been shown and described with reference to specific 
embodiments, however, it should be noted that the invention is in no way 
limited to the details of the illustrated structures but changes and 
modifications may be made without departing from the scope of the appended 
claims. For example, the invention has been described with reference to 
such apex seal having no side pieces. However, the invention can also be 
applied to apex seals having side pieces. Further, the interface between 
the sealing and support pieces of the apex seal may not necessarily be 
sidewardly inclined.