US2791185A - Hydraulic rotary transmission device - Google Patents

Description

*May 7, 1957 A. F. BoHNHoFF ET AL 2,791,185

HYDRAULIC ROTARY TRANSMISSION DEVICE 2 Sheets-Sheet 1 Filed July 19, 1954 May `7, 1957 A, F. BoHNHor-'F x-:T AL

HYDRAULIC ROTARY TRANSMISSION DEVICE 2 Sheets-Sheet 2 Filed July 19, 1954 HYDAULIC ROTARY TR AN 'SlVISSllI DEVICE rthnr' F. Bolinhoft and D'iinitar Toscliliolf, Saginaw, Mc'h'., a's'signrs to'f General Motors; Corporation, Dc-

tr'ot, Micha; a corporation of' Delaware- Application Jul-y 1'9', 1954, S'erialb'. 444,042 zr Clarins. (armar-136)@ This invention relates to hydraulic rotary transmission devices and more particularly pertains to rotary pumpsand-motorsof the .type comprising a circulan rotor adapted to turn within a ring engaged by the outer endsof-a plurality of radially movable vanesU carried., by the rotor, the

surface of the ringy in which the rotorl turns a condition-i, which in time is` boundtobe reflected in; the operating efficiency. of the pump.

T'he. present invention iSv-based on the-disfcovery thatlthel wearing qualities of the pump ring aredeterxninedfby the internalcontouring thereof'. Moref specifically, we have found` that the pump `ring-.wear inthe-case of thefpreviousy designs owes to .the fact that the vanes do not contact the ring inthe essentially evenV anduniform manner supposed. Rathenthecontact- (especially at high speeds) is marked in certain areas byhigh frequency impingement ori tle'vane'slag-ains-tthe ring surfaces and in other areas variationsin the load applied: against: the ring surfaces bythe vaines: f v

@onside'riigtheforegoing, itshould? bel clearfthat ring wear isa f'ri'ctionof shock and that* the 'degree' of' shock relates to the radial acceleration characteristics of the vanes as set by the ring contour. Obviously the shock will be greater the greater the value of (F) in the formula (F) =Ma, where M equals the mass of the vane and a its radial acceleration.

The principal object of our invention is implicit from the foregoing, i. e., our main purpose is to reduce ring wear, thereby to lengthen the life of the pump or other device and render it maximally eflicient over a longer period. A further and more specific object is to provide a ring for rotary vane hydraulic transmission devices in which the inner contouring is such as to avoid high frequency impingement of the vanes and to substantially lessen variations in the load imposed thereby. A corollary object is the provi-sion of a ring contour whereby (a) Centrifugal force alone will be nearly suticient to maintain vane contac-t at the speeds contemplated.

(b) Vane acceleration is zero lat the beginning and at the end of rise.

(c) Though retaining features (a) and (b), displacement in the intake areas is greater than in the case of conventional devices of similar design.

Still another object of the invention is to provide such a contour which is easily land accurately reproduced and which is based on a curve capable of definition by an algebraic equation to the end that for any given applica- Patent/ed May 7, 1,957

tion the radial velocity and acceleration of.v thevanes and" the physical dimensions and properties of' the contour can be readily determined, regardless ofV the amount of rise and the travel used to achieve it. l

In the accompanying drawings which will be referred tofin thev further description: Y

Fig. l is a side View of a pump conforming to the invention, the pump-cover being removed to showithe principal. parts; Y

Figs. 2 and 2A show the development of? the equation'v denitive ofV the cycloidal curve on which tlie infernal contour of the pump -ring is basedyand y Figs. 3-5 are graphs affording@ comparison of' the performance of the pumpf with that of a prior' art pump heretofore used for the particular prposenamelfy, power. steering. 'Phe velocity and' acceleration curves (Figs. 4`

and 5) are for nf=1000 R. P. M; v

Referring. rst to Figi 1it willbe seen. that the illus trated pump is ofthe general'type disclosed for instance, in U. S. Patent 2,544,987 to Gardiner etal. Thus, the principalparts are-the ring 10,', the rotor 1`2 and the vanes 14, the outer ends of which are maintained against the inner surfaces of the ring` by centrifugal forcel plus a hydraulic force developed atrk 16, thesecharnbersy 1'6, with the'pump iny operation, being filled withI tluidI under rlisy charge pressure. As well understood: on turningY ofthe rotor 12 counterclocloiviseI (clockwise rotationmay be provided for by means of the expedient of'an interchangeable cover piece altering. the porting. as'required) the inner vane chambers become-lledwith oil inthe vicinity ofthe inletports 1S and discharge oil in the vicinity of the outletports 20, the vanes 1'4A mov-ingin or out as determined by the lring contour 22.- y

It shouldbe, evident that the construction shown is adapted for use as ahydraulic' motor. as'well.v as a pinp. WhenV so appliedt1he pressure fluid,.supplied from. apump,

accumulator, or other source,. may v enterthe system;

through. either the ports, 1S or ZO The rotary motionof the rotor shaft' induced by the impact'ofA the lluidagainstl the vanesimay be translated by knowny means iiito'an'y othervv type of motion which may be` dsi`re'd. l

We' have broughtl out' in therforepart hereof the' ini# portance: of the inner contoin`` 22' of thering' 102 In acl cordancewith our invention; we bas' this" co' 1"itoir"on'v a' ey'e'lo'idally'l formed crve StichI4 a curve as illustrated by' of a point on the straight line (or spiral) OA minus the displacement (-H sine 2 21r 7F00 of a point on the circumference of the generating circle of radius whose center moves along the line (or spiral) OA while it rotates through the angle senting an algebraic summation of an Archimedes spiral and a sine curve having its generating radius equal to thctotal risc divided by 21r.

The advantage of the cycloidal curve as a basis for the inner contour of the` ring 10 is demonstrated graphically by Figures 3-5 wherein the symbol P refers to the old contour, and the symbolC to the contour 22. Figure 3 shows the displacement, i. e., the linear distance, expressed in inches, between the contour 22 and the base circle for each'degree. of rotation of the latter through the arc indicated by the arrow (Fig. 1). that the C contour provides for the displacement of substantially more uid in the filling area than the P contour (note thev spread .between the `curves through the distance 42"--72), a substantial advantage in many ap plications.

ly sufficient to maintain contact between the vanes and ring in the instance of curve C, an infinite acceleration is demanded in the case of curve P to effect the contact at the beginningA of the rise. As a consequence, using curve P, there is no contact on initiation of the rise and when contact does occur it is so abrupt as to cause dcformation of the ring surfaces. Similar contact with similar eects, occurs (curve P) at the end of the rise, on the abrupt reversal in the direction of radial movement of the vanes without a dwell. In other words, this sharp reversal results in momentary loss of contact, followed by a quick, hard rebound of the vanes against the ring, spelling obvious adverse effects on the ring surfaces involved. Continuing with reference to curve P, it should be clear that the stepping of this curve between the rise and fall retiects changes in acceleration which are also adverse from a wear standpoint, even though vane contact may be maintained through the area. In practical effect the symmetry of curve C means that such wearing The figure demonstrates i of theiring surfaces as may occur is substantially uniform,

4without pitting orl indentation.- VSignificantly the vanes have zero acceleration both at the beginning and at the end of the rise.

Having thus described and illustrated our invention what we claim is:

1. A hydraulic transmission device of the type includ ing a rotor mounting radially movable vane means and a ring member surrounding and contacting the vane means so as to determine the radial positioning of the latter for each increment of rotation of the rotor, the inner contour of said ring member comprising two rise portions and two fall portions connected by dwell portions of predetermined length, the contour of said rise and fall portions being substantially set by application of the following equation:

`0o=total angular distance from start to end of contour H :total rise (or fall) of contour in angular distance 0o, the units of linear measurement as to S and H being the same, the units of angular measurement as to 0 and 0o likewise being the same.

2. A hydraulic transmission device of the type including a rotor mounting radially movable vane and a ring member surrounding and contacting the vane means so as to determine the radial positioning of the latter for each increment of rotation of the rotor, the inner con tour of said ring member comprising two rise portions and two fall portions connected by dwell portions of predetermined length, said inner contour being based on a curve representing an algebraic summation of an i Archimedes spiral and a sine curve having its generating radius equal to the total rise divided by 21r.

References Cited in the tile of this patent UNITED STATES PATENTS 2,165,963 Curtis July 11, 1939 2,272,635 Davis Feb. 10, 1942 2,321,190 Ellinwood June 8, 1943 2,470,987 Johnson May 24, 1949 2,588,430 Svenson Mar. 1l, 1952

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