US 2679210 A
Description (OCR text may contain errors)
y 1954 T. MULLER 2,679,210
' EXPANSIBLE CHAMBER TYPE RADIAL PISTON ENGINE Filed Sept. 14; 1948 i 2 Sheets-Sheet 1 IN V EN TOR.
May 25, 1954 T. MULLER EXBANSIBLE CHAMBER TYPE RADIAL PISTON ENGINE Filed Sept. 14, 1948 I 2 Sheets-Sheet 2 Patented May 25, 1954 ATENT OFFICE SIBEE CHAMBER TYPE RADIAL PISTON ENGINE Tlieodora Miiller, Wifiterthiug- Switzerland, as- Signor 'to" Schweizerische Lokomotivund Maschinenfabrik; .Winterthur, Switzerland Application'septemb'er 14, 1948;-SerialNo.'49,140 J Claimsipriority, application Switzerland. September 18, 1947 -My present inventionrela'testo improvements:
in "exp'ansible-chamber type engines: of the: type including a'radiating cylindenfreciprocating"pis tons-and annutside abutment and-in particular theconstruction of "the relief chambers provided 1 5 on' the *piston "end+faces-. The construction of the piston "heads :and of the extended" cylinder wallsi'inengines'of "such type; forms the subject: matter "of my tcopending application" .Ser. N 0;
It is known in'the art'to definitelyispacethe sliding surfaces of fmachine iparts sliding upon each other," and 'thus'to subtantiallyreduce the friction;- in; that a "pressure'cham-ber is recessed '1 fromf one of the'saidsurfaceaiwhich" chamber is supplied through? a throttling aperture with: a pressure fluid:
It also ;is known'in' the ;artto' use; in. engines of :the type described; pressure "chambers :sup
plied :from'the.cylinderispacer Insuchrconnection;: however,- ,certain" 'diflic'ulti'es "arise," iri'that forces-additional" to. the fluid pressure may arise ontherpistons in their axial""dir.ectio'ns, such as accelerating or centrifugal forces whichmay'be.
counteracted, during the pressure stroke, but not during the suction stroke byjmeansof'the. pressure" chamber recessed from the piston-head slidingsface, that during the;suction:stroke the pressure-fluid supply;to"the "pressure cham-. bers from the side of; the cylinder ceases; It" is? true Tthat'the, "pressure 'chamber'could :be kept under pressure also. during the suction stroke, by"- means of a special pump; which continuously pro duces' pressure fluid,'. Whicharrangement; how-' ever, results in a complicated structure'and Rd ditio'nal manufacturing costs: But :also' when thepiston engine runsidle orunder -a slight "load,"- sufliciently high pressure also no-longer isavailable the "working space of the" engine'- cylin der'during'thepressurestrokeyso that the slide- 4:
sure chambersnf decreasing the friction: Such" provision afiords-notonly a lower weight of the entire pistons; but also the advantage that during thepressure period the high oii-pressure is communicatedf practically instantaneously, at
least'to theentire'lubricating film'on the-support .55
5Claims: (Cl. 103 -161) 2 ingfaces disposed within the pressure chambers, so that'the lubricating film during the suction period is displaced more slowlyfrom the said- When the .piston' engine is so "operated. that "also the suction space is under a certain slight pressure, e. g: 2-5 atm.,' there results the faces."
advantage that thefacesat idlingalso still .are
lubricated by pressure :oils, which is possible only at aless .efficient. degree when the'supporting faces are arranged outside the pressure-chambers; .Furthenthe danger of pitting of the slide faces when the throttling aperture is. clogged.
also is diminished.
Various forms of mypresent invention are '11- lustrated in the accompanying drawings, in which:
Fig. 1 shows asection'. through a three-cylin? der radial. piston; engine,
Fig. 2 is. a longitudinal axial section'through'a three'cylinder radial :piston'engine having pistons of modified design. with respect .to those shownin Fig. 1,
Fig. 3 shows in'a larger scale; a piston accord: ingto Figil partlyin longitudinal section,"
Fig. 4 is -a;view"of.'the.piston .head of'Fig. 3; v
in direction'of thearrowA in Fig. 3,
Fig; '5 isa longitudinal section .through a. piston'ofi'the type shown in. Fig; 2."
Fig. 6 is a'view'of the piston head of Fig. 5 in; direction .of the arrow B. in'Fig; 5.
Fig.7.? isa fragmentary sectional view of a modified piston along the line. VII-1VII of Fig. 8..
Fig. '8 is anplanview of the piston'endas seen in the direction of the arrow. B in Fig. '7.
In Figs. land 2; the cylinder block 3 of the engine, which mayoperateias pump or motor, is mounted rotatably on the control stud 2 which is rigidlysecuredto the. .cas-ing I which block comprises .threeradially disposed. cylinders. In the casing I ,r further, theabutment-5 is rotata bly mounted at-6 and andeccentrically-to the axis 2a of stud z. The abutment 5 is so coupled .7 to the cylindervblock- 3 through. a follower 9, in-
form of a cross-loopcoupling or universahcou- 4D pling, that the block 3 and the abutment 5 always rotate at the Lsamemumber of revolutions. On the inside wall of the abutment 5, which may be driven throughr-the "stub shaft 5 EL: when the engineshall operate-as pump, three plane'faces l l 'are' provided for; against each of which the head of one piston l2 abuts by :means of atslidee shoe "or piston head I5..
In': the rigid control 'stud2; two bores 1 are provided for supplying and delivering the working fiuid; e.-- g. in the-sense of the=-arrows shown in Fig. 2. The cylinders situated above the horizontal median plane of stud 2, communicate with the upper one, and the cylinders below the said plane with the lower one of the said two bores 4. The web 8 separates the engine suction space from the pressure space.
The structure of piston I2, in which the piston and the head I5 are integral, is shown in a larger scale in Figs. 3, 4. A shallow chamber I6 is recessed from the end face of the head I5 abutting against the face I I, and is supplied with pressure fluid from the cylinder interior Iii through the bore and the throttling aperture ZI of the piston. The chamber is confined by the narrow annular face 23. In the chamber I6, additional supporting faces in form of six ring sectors 24 are provided, which faces fill up the pressure chamber I6 with the exception of the six radial grooves 25, the central recess 25 and the circular groove 29. Outside the pressure chamber, the additional annular supporting face I4 is provided, which is separated from the chamber I6 through the annular groove II.
Pressure fluid flows from the pressure chamber I6 or, respectively, the groove 29 through the narrow gap between the annular face 23 and the flattened face II into the annular groove II from which it may flow outwardly through the grooves I8 into the interior of abutment '5 and through an opening 31, back into the casing I. The chamber pressure thus cannot propagate into the gap between the additional pressure face It and the flat face II.
The piston is subject, in the direction from the cylinder space, to a fluid pressure, acting onto the piston face 22, of the magnitude Fk, as well as to an additional force C, e. g., as radially acting centrifugal force of the piston in the engine construction according to Fig. l. The lubricating layer between piston head I5 and plate I I should have a thickness, e. g., of approximately 0.01 mm. so as to ensure fluid friction and thus to keep the friction as small as possible. To such end, the sum of the fluid forces tending to push away the piston head I5 from the fiat face IIat a fluid pressure in in the chamber Iii-has to equal the sum of the forces tending to press the piston head I5 against the face I I. Fluid then will flow from the chamber It through the gap between the faces I I and 23, so that the pressure 121 therein, due to the throttling of the supply at 2 I, becomes less than the pressure p in the cylinder I9. Denoting the full circular area of the chamber I6 within the annular face 23 by F1, and that of the annular face 23 by F2, the requirement is:
The area F2 is multiplied by only half the chamber pressure, since the pressure onto the face 23 drops, from the inside to the outside, approximately linearly from 101 to zero. When 101:1), the oil flow in the lubricating layer ceases, and a semi-fluid friction occurs. The above equation, when dividing by p, then reads:
In order to attain fluid friction in the case of full-load working-pressure, the sum of the chamber area and half the marginal area, therefore,
must exceed the sum of the piston area and the quotient from the centrifugal force and full-load pressure. Advantageously measures are taken for attaining such ratio at the maximum additional force C occurring within the most common work- (iii ing range of the engine even at a pressure less than the full-load pressure.
During the pressure stroke, the piston pressure at the said dimensioning of the relief chamber area is slightly withdrawn from the face I I, ample oil flowing between the slide faces II and 23, 24 and, to a lesser extent, onto the face I4. During the suction stroke, the relief in chamber I6 is no longer effective, and the said faces 23, 24 and I l intercept the non-compensated additional forces C. Oil then is squeezed from between the supporting faces 23, 24 and I4, and the oil layer becomes thinner until the pressure rise associated with the succeeding pressure stroke arrives in the chamber I6. In this manner, provision is made for sufliciently lubricating the faces of the piston head during the entire working period of the piston.
In order to ensure a sufiicient lubrication of the piston-head faces also when the engine is slightly loaded and the pressure of the working fluid is low, the suction side of the piston engine advantageously also is held under a slight pressure of, e. g., from 2 to 5 atm. by means of a special pump. In this case, of course, a greater friction on the piston head than when the engine is more highly loaded has to be taken into account nevertheless. When the maximum additional force C occurs only at rare intervals in operation, the faces F1 and F2 also can be made smaller than according to the rule set forth above.
Ledges 21 provided on the abutment 5 prevent too great a rise of the piston heads I5 from the fiat faces I I, in that these ledges engage the said heads from the rear. The groove Il may be omitted, in which case the outside diameter of the head I5 and perhaps also that of the chamber It may be reduced somewhat, since then the annular face I4 also aids the action of the pressure chamber I6. In such case, however, when the chamber pressure is falling out, the outside supporting face M in particular is lubricated less efilciently through the oil bath which is always present in the rotor abutment space outside the pistons.
The structure of the piston I3 is more fully shown in Figs. 5 and 5. Such piston structure differs from the one described above, besides the adjustable spherical segment 28 inserted between piston and slide face II, in that the enlarged piston head isguided on the cylinder, and in that additional supporting faces no longer. are provided outside the annular face 23. The segment 28 permits balancing small deviations of the piston axis from the direction normal to the face II. Its spherical seat on the piston may be relieved, at least partially, by means of a pressure chamber 3|. The segment 28 is traversed by a bore 39 through which the pressure chamber I6 communicates with the oil supply bore 2t2I from the cylinder space IS.
The enlarged piston head 32 is guided, over the entire piston stroke, by means of the guide 3-3 rigidly secured to or integral with the cylinder block 3. In the inner dead-center position of the piston, the end face 35 of said guide is situated quite close to the slide face II, as indicated in Fig. 5 by the dash line.
In order to energize the pressure chamber It, the annular groove 2%, which is supplied with pressure oil from inside through the radial grooves 25, should extend at least over of the circumference. Under certain conditions it is of advantage to subdivide the sector-like supporting faces 24 by means of further smaller grooves in order to facilitate a penetration of the pressure liquid between the said faces 24 and the faces H.
In order to improve the bearing capacity of the lubricating layer of the pressure-chamber center, the radial grooves '25 may be extended only for a certain distance toward the center, as shown in Figs. 7 and 8. The said grooves 25 are supplied through a plurality of bores 36 from the chamber 3!. The bores 36 may be interconnected through an annular groove (not shown).
With a given fluid pressure Fk and, if such is the case, a given additional force C, a gap of definite depth is established between the abutment face H and the annular piston end faces ill and 23, which gap has to be only slightly deeper than the irregularities of the said faces in order to reduce the sliding friction practically to zero. The depth of said gap tends to be constant from the following reason. When, on one hand, the gap should increase in depth, the fluid flow through and from the chamber I6 is increased, and thus the pressure in the latter drops due to the throttle 2 I, whereby the forces acting on the piston depress the latter down to the original depth of gap. When, on the other hand, the gap is decreased and the pressure in chamber [6 increased over that acting on the piston through the cylinder, i. e. the original depth of gap again is re-established.
The use of pistons shown in Figs. 5 to 8 permits the adoption of the smallest diameter for the piston head abutting against the slide face i H, of all the forms of invention described.
The width of the marginal portion 23 may be held rather small, as has been proved by tests, and may preferably be made less than of the chamber radius.
The guide ledges 21 provided on the abutment 5 are engaged in a recess 34, of the thickened piston and portion 32. The recess 34 may be provided in form of a circular turned-out groove, as shown in Fig. 5, or only in form of lateral milled grooves 38 as shown in Fig. '7. r
The pistons suitably are made of light metal with a view of diminishing the inertia forces.
If the piston head 15 in Fig. 3 is made as long as in Fig. 5, it also may be better guided by means of guide lugs 33 disposed intermediate of the ledges 21.
In place of a liquid, one also may use a gas as working and pressure agent.
What I claim as new and desire to secure by Letters Patent is:
1. An expansible chamber typ radial piston engine comprising a housing, a rotor movable in said housing, a cylinderblock having radial cylinders eccentrically mounted in said rotor, reciprocating pistons in said cylinders, each piston having a longitudinal bore therein and being provided with a head at the outer end remote from the cylinder space, flat abutment faces on said rotor providing each for sliding engagement with one piston head, each piston head being recessed to form a pressure chamber between the head end face and the piston abutment face, said pressure chamber being supplied with pressure fl from the cylinder space through said bore in the piston, a fluid throttling means in said bore near the end thereof at the piston head face, said pressure chamber being arranged in the form of a circular groove having a diameter ap proximately equal to the piston diameter, and a plurality of ducts establishing communication between said circular groove and the throttling point of said pressure fluid supply bore, said ducts extending partially in the form of open radial grooves along the end face of the piston head whereby the areas of the piston head end face intermediate the annular groove and said radial grooves form piston head supporting faces acting as abutment pressure relief faces.
2. A fluid pump or motor as claimed in claim 1, wherein said pressure chamber is confined within an annular supporting face provided on said head end face, the radial width of said annular supporting face does not exceed 15 of the radius of said pressure chamber.
3. A fluid pump or motor as claimed in claim 1, wherein said pressure chamber is confined within an annular supporting face provided on said head end face, the sum of the area of the pressure chamber and one half the area of said annular supporting face are greater than the sum of the inner piston end area and the ratio between the centrifugal force acting on the piston during normal operation and a cylinder pressure which is smaller than the cylinder pressure at full load operation of the pump or motor.
4. A fluid pump or motor comprising a cylinder block having radial cylinders, a piston operating in each cylinder, each piston including a body portion and a separate end portion at the end thereof remote of the cylinder space, said end portion being in the form of a spherical segment having a spherical surface fitting a spherical recess in the piston body portion and a flat end face, a thrust member surrounding said cylinder block, said thrust member being provided with flat abutment faces each being in sliding engagement with the flat end face of a spherical segment of a piston end, each piston having a longitudinal bor therein extending through the piston body portion and said spherical segment, the end face of the spherical segment of each piston being recessed to form a pressure chamber between said end face and said abutment face on the thrust member, said pressure chamber being supplied with pressure fluid from the cylinder space through said bore in the piston, a fluid throttling means in said bore near the end thereof at the piston head face, said pressure chamber being arranged in the form of a circular groove having a diameter approximately equal to the piston diameter, and a plurality of ducts establishing communication between said circular groove and the throttling point of said pressure fluid supply bore, said ducts extending partially in the form of open radial grooves along the end face of the piston head whereby the areas of the piston head end face intermediate the annular groove and said radial grooves form piston head supporting faces acting as abutment pressure relief faces.
5. A fluid pump or motor as defined in claim 4, wherein a second fluid pressure chamber is provided between the spherical surface of said spherical segment and the surface of the spherical recess in the body portion of each piston.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 388,522 .Beauchemin Aug. 28, 1888 580,838 Almond Apr. 20, 1897 1,398,788 Mayer Nov. 29, 1921 2,299,234 Snader et al. Oct. 20, 1942 2,421,846 Neuland June 10, 1947 2,483,856 Temple Oct. 4, 1949