US 3568574 A
Description (OCR text may contain errors)
United States Patent  Inventor Peter John Dupen Hutton, Essex, England  Appl. No. 809,152
 Filed Mar. 21, 1969  Patented Mar. 9, 1971  Assignee Hydrostatic Transmissions Limited Brentwood, Essex, England  Priority Mar. 22, 1968 [3 3] Great Britain  PUMPS OR MOTORS WITH CIRCULARLY DISPOSED CYLINDERS 11 Claims, 6 Drawing Figs.
 0.8. CI. 91/499  Int. Cl. F04b 1/02  Field of Search 103/ 162 (Complete); 230/177  References Cited UNIT ED STATES PATENTS Re26,519 1/1969 DAmato 103/162 1,817,063 8/1931 Carrie et a1 103/162 2,356,101 8/1944 Temple 103/162 2,430,753 11/1947 Ziska 103/162 2,847,984 8/1958 Gallant 103/162 3,188,969 6/1965 Brundage 103/162(X) 2,956,506 10/1960 Brundage 103/162 3,208,395 9/1965 Budzich 103/162 Primary Examiner-Wil1iam L. Freeh AttorneyShapiro and Shapiro ABSTRACT: The described invention relates to fluid pressure machines in the nature of pumps or motors in which the working fluid pressure causes radial loads on the bearings of a rotary part. The invention resides in the provision of balancing pressure space to which the working pressure is communicated and of which the effective pressure-exposed areas substantially balance the radial loads otherwise imposed: it is particularly directed to the pressure balancing of a rotary valve.
Patented March 9, 1971 4 Sheets-Sheet 1 KW Q - Patented March 9,1971 3,568,574
Patented March 9, 1971 3,568,574
4 Sheets-Shani. 5
Patented March 9, 1971 4 Sheets-Sheet 4 mm M M mQ MUMPS R MOTORS Wl'llll-ll CHRCULARLY DESPGSED QTMNDEIRS The invention relates to fluid pressure machines such as pumps or motors which have cylinders and pistons disposed in a circular array around an axis, for brevity to be referred to as machines. Typical of such a machine, of the kind to which the invention is to be applied, is a fixed-swashplate pump having a rotating cylinder block with a circular array of substantially xially arranged cylinders, the block rotating in a fixed body. The invention may also be applied to a motor of similar arrangement; or to a pump or motor having a radially arranged array of cylinders, and pistons which are moved by an eccentric, cam track, or crank. i
The primary object of the invention is to balance radial loads imposed by the fluid pressure on such parts of the machine as are exposed thereto; by the invention such loads are balanced by fluid pressure.
The element to which balancing is most desirably applied is the valve element which controls flow through the machine. In a preferred example of application, such element is basically a hollow cylinder which rotates with the cylinder block with which it is coaxial. In some forms it can be arranged that such valve element is rigid or integral with the cylinder block so that balancing of side loads on the element also relieves the block of side loads; then the valve element and the block can be supported laterally by the fluid pressure which arises in the machine.
When reference is made herein to the rotation of parts it is to be taken that relative rotation is meant. Thus, a machine may have a stationary cylinder block and valve element, the surrounding casing being rotary. MOreover there are machines (to which the invention is applicable) which are in the nature of pumps, and which form part of a hydraulic coupling (either clutch or torque converter) in which for example, complete stoppage of the fluid flow locks a rotor and stator together, whilst complete freedom of l flow corresponds to transmission freedom. To such devices the invention is applicable, even though the whole device is rotatable.
The invention resides primarily in a machine of the kind stated in which a valve element rotates with the cylinder block relatively to the casing and has passages which intermittently and cyclically communicate each one of the circular array of cylinders to a pressure fluid connection of the casing, which connection extends circumferentially subtending an angle centered on the rotation axis, the valve element having an interface of coaxial circular section with part of the casing, the interface being interrupted to form a pressure chamber which subtends substantially the same angle and which has pressure communication with said connection and which is so dimensioned that the effective radial force on the valve element due to pressure in the connection is substantially balanced by that due to pressure in the chamber.
The invention is preferably applied to machines in which there is one piston stroke per revolution as in a swashplatetype machine; in such case there are provided an inlet and an outlet connection and corresponding pressure chambers; moreover and especially if the fluid be a practically incompressible liquid, the inlet and outlet chambers are constituted by lobelike chambers formed in the casing each subtending an angle centered on the, rotation axis of the valve and of such magnitude as to include a number of valve passages corresponding to half the total number of cylinders in the array minus one (if the cylinders are of uneven number) or two. This results in all the cylinders which are substantially under compression being simultaneously connected to one connection and all of those which are substantially at no pressure or only some nominal pressure being simultaneously connected to the other connection. The pistons in the cylinders which are transitionally passing from one stroke to the other may be considered to be virtually at dead center.
The invention further includes features of construction, which features will be found in the following descriptions and are defined by the claims.
The actual arrangement for achieving the sought-for balance may be considerably varied; moreover if the valve element be made rigid or integral with the cylinder block the balancing chambers may be directly connected with the pressure spaces of the cylinders, and in such a case moreover, the valve element beingin effect hydrostatically borne, it may be arranged that side loads in the block-for example a vector of the swashplate angle-are also balanced by fluid pressure.
The invention is illustrated in three examples, with reference to the accompanying drawings. In these:
FIG. 1 is a section elevation in the axis of a seven-cylinder swashplate pump and 1A is a section on line A-A thereof.
FIGS. 2, 2A and 3, 3A are corresponding views of variants.
in FIGS. 3., 1A, the pump has a driving shaft 1 to which is secured a cylinder block 2 having axially directed cylinders 3 in a circular array. In the cylinders 3 pistons 4 moved by a swashplate 5 which is fixed in (or adjustably tiltable in) the pump casing 6. The shaft ll runs in bearings and seals at 7, ll, in the casing 6. Towards one end the casing 6 has an internally cylindrical bore at 9 which has formed between its ends two more or less crescentic-o'r lobelike pressure spaces, it), ill, which are respectively inlet and outlet valve chests, connected in the pump circuit by leads indicated by 10A, HA.
In the casing 6 is fixed an endplate 112 which has an inwardly extending cylindrical journal skirt l3 surrounding the shaft l. There is consequently formed a hollow cylindrical chamber, between the bore 9 and skirt l3, and on this, as journal fit, rotates a sleevelike valve element M. This element M is made with axial bores MA corresponding to and permanently registering with the cylinders 3. The outer end of the element 14 bears axially sealedly against an annular sealing plate 15, each bore MA having an individual seal ring l6. Also, sealing ferrules or cuffs l7 (which act as couplings) are provided between the cylinders 3 and each valve bore MA. The valve element 114 is therefore sealed to, and rotates with, the cylinder block 2, though it is not necessarily confined to absolute alignment therewith. Radially in the element M and traversing each bore MA is a valve port 14B, of such diameter as to be wholly closed when in transition between the chests 110, ll, (see uppermost port in FIG. 1A), but in other positions to open a cylinder 3 either to the entry or outlet, (10A or 11A). The cuffs 17 may afford some flexibility, the better to act as couplings.
The exterior wall of the skirt i3 is fashioned with two balancing member chambers, 10B and 1113, with which the inner ends of the ports MB communicate cyclically. The effective area (from the point of view of the radial load exerted by the fluid pressure) of the chambers 10B, 11B, is equal to or approximate to, theeffective area of the external surface of the valve element 14 which is exposed to fluid pressure in (respectively) it) or 11. It follows that forces otherwise imposed on the valve element in a diametrical direction by fluid pressure are balanced or nearly balanced.
In the example of FIGS. 2 and 2A, the general arrangement of the pump is quite similar, and where applicable the same references are used.
In this case the valve element 20 is integral with the cylinder block 2. it surrounds, and runs in journal fit on a journal stub shaft 21 extending inwards from the end cap 12. The element 20 has axial bores 23 which are in permanent communication with the respective cylinders 3. The radial ports 24, which are openings from the bores 23, communicate cyclically with the chests ll), ll as before. The balance chambers ME, R13, are formed in the stub shaft 21. This arrangement may be preferred for smaller machines; it is shorter and in other respects more compact than that of FIG. i.
it may here be mentioned that, as a matter of proper drawing, the sections of the H68. on the AA lines ought not to afford the showing of 10, H in FIGS. 1, 2 or 3, of the valve elements in broken line; but such are shown for convenience; in
reality it must be realized that the broken-line showing would be at 90 from the section shown.
Referring now to FIGS. 3-3A, again the general arrangement is very much like that of FIG. and again corresponding references apply. In the example, the valve element 14 is connected for rotation with the cylinder block 2 by studs or dowels 30, sealing between the cylinders 3 and bores 14A being provided by O-n'ng 17A, or like means (FIG. 3). The balance chambers B, 11B, are in this case connected permanently to the valve chests 10, 11, by a series of bores forming ducts 31, in which at some convenient location there are, preferably, flow restrictors 32. Thus, the chests 10, 11, are kept at a pressure which (save for rapid fluctuations) is equal to that in the chambers 10B, 118. Moreover, the virtually continuous fluid pressure will keep the journal and end bearing surfaces flooded, whereby good bearing will result.
t can be seen that each of the valve chests, which constitute inlet and outlet connections, subtends an angle centered on the rotation axis which angle is also approximately subtended by the respective pressure chamber. Moreover, such angle includes a plurality of the cylinder and their respective valve passages, each chest corresponding to half the total minus one, of the number of cylinders arrayed in the ordinary case in which there is an uneven number of cylinders. If, for any reason, the number of cylinders is selected to be an even number then each chest corresponds to half the total number, minus two.
In a variant of the invention which may be particularly suitable in a variable-delivery pump (i.e. one with variable swashplate angle) the rotor body is preferably borne on a fixed coaxial stub shaft which extends through the valve element and through most of the axial length of the cylinder block; the balance chambers are formed in the surface of the stub shaft and further chambers or ports are provided also at the interface of the stub shaft and cylinder block so as to balance radial loads set up by the offset of the reaction between the pistons and the swashplate.
l. A machine of the kind stated comprising:
a hollow casing having an axially extending internal wall of generally circular cross section, said wall defining at least one circumferentially extending stationary passage open in the radially inward sense and having a fluid pressure connection to the exterior;
a rotary assembly borne for rotation in the casing and comprising a cylinder block having a circular array of cylinders formed therein with swashplate-actuated pistons working in the cylinders and a valve element formed as a solid of revolution rotating closely within said wall, the valve element having an axially directed bore corresponding to each cylinder, each bore having a radial fluid connection to the external surface of the element to establish cyclic connection to said stationary passage;
an annular stationary surface within said casing against which bears axially an end surface of the rotary assembly remote from the swashplate through which end surface are formed openings in communication with each cylinder so that said stationary surface is exposed to the fluid pressures in the cylinders; and
a stub shaft extending axially inwardly from that end of the casing at which is the said stationary surface and fonning a journal rotatably supporting said valve element, the valve element and stub shaft defining between them at least one fluid pressure balancing chamber operative in the radial sense and so connected as cyclically to receive pressure from cylinders of the machine in correspondence with the pressure in said stationary passage and over the same circumferential angle, the effective area of said pressure balancing chamber and its location being such as to balance the valve element radially against the pressure in said passage acting upon it.
2. Machine according to claim 1 in which the valve element is inte al with the cylinder block.
3. achine according to claim 1 m which the valve element boxes are sealed by a rubbing seal axially against the annular surface in the casing.
4. Machine according to claim 1 in which ducting is provided through the casing from the casing passage to the balancing chamber.
5. Machine according to claim 4 in which said ducting includes a flow restrictive orifice.
6. Machine according to claim 1 in which the casing defines an inlet and an outlet connection and corresponding passages.
7. Machine according to claim 6, in which the cylinders are substantially axial and the cylinder block is supported by bearing means in the casing, and in which said valve element is mounted at one of said block for rotation therewith and said bores are in open communication with each respective cylinder and cyclically open through said radial fluid connections to the said inlet and outlet connections.
8. Machine according to claim 1, in which said valve element bores are axial and correspond in position and number to the cylinders, and further comprising a flexible hollow coupling element interconnecting the end of each cylinder to its corresponding bore for fluid passage.
9. Machine according to claim 8, in which the said couplings collectively also constitute a mechanical rotational coupling between the cylinder block and the valve element.
10. Machine according to claim 1 in which inlet and outlet connections are constituted as casing was walls defining lobelike passages each subtending an angle centered on the rotation axis of the valve element and of such magnitude as to include a number of adjacent valve element connections corresponding to half the total number of cylinders minus two.
11. Machine according to claim 10 in which the valve element bores correspond in number to the cylinders and each radial connection leads outwardly to the casing wall and inwardly to the pressure balancing chamber so that the pressure therein is equalized.