US2633104A

US2633104A - Motor port construction

Info

Publication number: US2633104A
Application number: US105016A
Authority: US
Inventors: John A Lauck; Fred C Haberland
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1949-07-15
Filing date: 1949-07-15
Publication date: 1953-03-31
Anticipated expiration: 1970-03-31

Description

March 31, 1953 J. A. LAUCK ETAL 2,633,104

MOTOR PORT CONSTRUCTION Filed July 15, 1949 2 SHEETSSHEET 1 March 1953 J. A.'LAUCK ETAL 2,633,104

MOTOR PORT CONSTRUCTION I Filed July 15, 1949 2 SP-IEET S-SHEET 2 fnveriors: \J-OIZLTL Q. .L auck and 2| so that the total area of areas 22a exceeds that of 22b by a slight margin in accordance with established pressure loading practice. A pair of radially spaced, annular grooves 220 formed in the left end surface of block 2| and disposed coaxially of shaft |4 define the inner and outer periphery of areas 22?) and communicate with the sump of the transmission through radially outwardly extending grooves 2201, as shown in Fig. 1.

Cylinder block 2| is supported on and splined to shaft l4, and a piston 23 is slidably journalled in each of the cylinders 20. Each piston 23 has associated therewith a piston rod 24 whereby connection is made between the piston and a swash or wobble plate assembly designated generally at 25. To provide a suitable connection, at each end of each connecting rod 24 a ball 26 is mounted, the ball at the left end being received in a suitable spherical recess 21 formed in the associated piston, while the ball at the right end of the connecting rod is received in a socket cup 30 mounted in the swash plate 25. These spherical terminations permit angular displacement of the connecting rods 24 with respect to the axis of reciprocation of the pistons 23 as the position or inclination of the swash plate 25 is changed.

More specifically, the swash plate assembly 25 comprises an inner, annular, dish-shaped socket housing 32 which is pivotably supported on a-constant velocity universal joint 3| and an outer, generally annular, supporting carrier or bed 33, the angular position of which may be varied with respect to shaft l4 about an axis lying transverse to the axis of shaft M. A constant velocity universal joint is essential in order that uniformity of transmission of motion be provided. In a constant velocity universal joint of the type illustrated, the point of contact, or of motion transfer, is always at equal radial distances from the axes of the two elements, that is the point of contact always lies in the plane bisecting the angle between the connected elements. Constant velocity universal joint 3| is of generally conventional design and is splined on shaft l4 adjacent the right end of a motor block 2|. An annular bearing assembly 34 is interposed between the outer member 33 of the swash plate and the socket housing 32 so that the socket housing 32 may rotate with respect to the outer member 33 in a plane determined by the angular position of the outer member. The socket cups 30 are disposed in annular array about the left face of housing 32, being received in suitable apertures 35 formed in the housing and secured to the housing as by welding or swaging.

Outer member or carrier 33 is supported on a pair of oppositely disposed, radially extending

stub shafts

36 and 31, as shown in Fig. 1, journalled in suitable, axially aligned trunnion bearings indicated generally at 38, which bearings are mounted between the housing sections I and I2. Stub shaft 31 is keyed to the angularly adjustable carrier 33 of the swash plate 25 by a pin 39 which extends transversely through the shaft and into the carrier. Thus, by rotating shaft 31, the angular adjustment or inclination of the swash plate assembly 25 may be controlled.

It will be evident that with this arrangement, torque is applied to the shaft M from the socket ring which is, in effect, splined to the shaft, through supporting universal joint 3|. The swash plate assembly is thus pivotable about the axis of

stub shafts

36 and 31, and the socket housing 32, while rotatable relatively to the supporting carrier 33 as the hydraulic motor block and shaft M are rotated, is not rotatable with respect to shaft l4. By rotating stub shaft 31 and thereby pivoting carrier 33, the relative inclination of swash plate assembly 25 may be changed, and the effective displacement of the hydraulic motor may thus be varied from a minimum when the plate is at right angles to shaft M to a maximum as the inclination toward the shaft I4 is reduced in either direction.

In order to control the application of pressure to the hydraulic motor, the pressure control assembly housing It) mounted at the left end of motor housing section H, has formed therein a pressure chamber 40 and a suction chamber 4|. Both chambers are suitably connected through ducts, not shown, to a pressure generator, such as a gear pump, the chamber 4|] being connected to the outlet side of the pump and the chamber 4| being connected to the inlet side thereof. A suitable arrangement is shown and described in the co-pending application of Minshall et al., Serial No. 104,924 filed July 15, 1949.

The right end wall of housing section I0 has a wide recess 42 of generally cylindrical configuration formed therein to receive the manifold porting plate 43, and plate 43 is rigidly secured to housing l0 by bolts 44. It will be noted that a slot 45 is formed in the upper edge of the porting plate, as viewed in Fig. 1, and a locating pin 46 mounted in the right end wall of the housing section l0 extends into the slot 45. This pin and the cooperating slot facilitate proper location of the manifold porting plate during assembly of the transmission. Manifold porting plate 43 has formed therein on the left side thereof, as viewed in Fig. 1, two sets of cylindrical porting recesses 41 and 48, respectively, which communicate at their right ends with two generally

arcuate kidney ports

50 and 5|, respectively, formed by recessing the right surface of plate 43. Kidney port 50 constitutes the pressure port of this transmission in normal operation and registers at the left side thereof, as viewed in Fig. 1, through porting recesses 41 with the right end of a passage 52, the left end of passage 52 connecting with pressure chamber 4|). Similarly, the left side of kidney port 5| registers through porting recesses 48 with the right end of a passage 53 formed in housing section II), and the left grlid of passage 53 connects with suction chamber Ports 22 formed at the left ends of cylinders 20 of the hydraulic motor are arranged so that as the motor block 2| rotates on the shaft M, the ports 22- will sequentially register with the

kidney ports

50 and 5| in the manifold porting plate, thus alternately applying pressure and then suction to the cylinders. When the motor is operating the pressure in the cylinders, by virtue of the selection of pressure areas 22a and 22b, is sufficient to provide a tight seal between the left end surfaces of the motor block and the right end surfaces of the manifold plate 43, both of which surfaces are ground flat and smooth. In order to maintain these surfaces in suitable contact when no load is transmitted, however, a helically coiled spring 54 is disposed on a sleeve portion 55 of the universal joint 3|, the sleeve 55 being mounted on and keyed to shaft i4 and extending into a deep cylindrical recess 56 formed at the center of the motor cylinder block. The left end of spring 54 bears against the inner end wall of recess 56, while the right portion of spring 52 bears against a re- 5 taining ring 51, which is held in position on sleeve 55 by-a shoulder 58 formed about the periphery of the sleeve '55 adjacent its right end.

Heretofore, it has been the general practice to form the

arcuate kidney ports

50 and 51 in a coring operation whereby the ends of the ports were slightly tapered but on the whole of generally semicylindrical configuration. In accordance with the present invention, however, it has been discovered that the configuration of the kidney ports, and particularly the terminations thereof, must be critically designed in order to obtain smooth and eific'ient operation of the transmission and to avoid the objectionably noisy operatien, heretofore often considered an inherent characteristic of this type of transmission.

In Fig. 3, a curve 60 is presented illustrating the travel of a hydraulic motor piston from top dead center to bottom dead center position, Fig. 3 thus illustrating half of a piston cycle, both halves of the cycle being identical. From this graph itwill be noted that the initial movement of the piston, starting from the rest position, which coincides with vertical line I), is one of increasing "acceleration. By the time the piston has reached a position designated at 61 and approximately coinciding with vertical line 4, a substantially constant "velocity is reached. The velocity remains constant then during the major portion of piston travel and until a position designated at 62 is reached, coinciding approximately with vertical line 3, after which the piston begins toslow down preparatory to stopping and reversing direction of movement. .At position 63, representing bottom dead reenter, the piston is again at rest. This curve is typical of normal operation and may be regarded as characteristic of piston travel in this type of motor.

Referring now to Fig. 4, wherein a curve 64 is presented representing the pressure within .a

cylinder plotted against piston travel during the power stroke using a conventional cor-d porting arrangement, as described, it will be evident that as the cylinder port 22 begins to register with the end ofa conventional kidney port theresis an initial momentary, gradual application of pressure,but when the port "22 has moved only a very short distance, full registry is obtained and maximum pressure is abruptly applied.

This maximum pressure is thus applied prior to the time that piston travel has reached or can reach maximum velocity, that is, the .zone of constant velocity, and consequently the piston is undesirably loaded. After the piston has delivered its useful work during the power stroke portion of its cycle of operation and has begun to slow down, that is to say is operating on the portion of curve '60 lying between

points

62 and 63 "in'Fig. 3,1naximum pressure is still applied since itis desirable that the piston deliver full power to the end of its power stroke. Actually, there may be an actual sharp chamber pressure increaseimmediately preceding the pressure exhaust phase due to the'failure 'ofprior portingarrangements to provide a graduated reduction in inlet flow proportioned to the deceleration of the piston as it reaches the end of its power stroke. Thereafter,

upon registration of the motor port with the exhaust passage inthe porting plate there is an equally abrupt release of pressureirom the piston chamber. From the foregoing it will be evident that considerable pressure wasted since during a substantial portion of piston travel in each cycle, the piston actually reacts against application of pressure rather than responds thereto. In

6 addition to this loss of power with resulting reduction in the possible .efliciency of the transmission, the abrupt admission and release of pressure causes the transmission to be undesirably noisy.

In accordance with the present invention, the terminations of each of the kidney ports 501and ii are tapered in such a manner that the rate of flow or the fiu'identering the cylinders is made to be in direct proportion to the pistonveloc'ity at any instant from top dead center position to bottom dead center position. Stated otherwise, thekidney ports are so constructed and their ends are tapered so that the volume of fluid flow into the piston chamber at any instant is proportioned or selected to provide a piston energizing pressure commensurate with the capacity or the piston to reactor move at that instant. Thus, instead of abruptly applying maximum fluid pressure to the "piston during the initial phase of movement when the piston is moving relatively slowly and can only move relatively slowly, the pressure in accordance with this invention is also applied relatively slowly and at a rate selected to take maximum advantage of the travel charac teristic of this type of piston without wasting fluid pressure. This not only results in -ma terially increased operating eiiiciency but a tion and later withdrawal of pressure is provided paralleling insofar as possible the power stroke and exhaust stroke phases of piston travel, as shown in Fig. 3.

To some extent, the degree or taper of the fish tails 59a and em may be calculated in advance,

since the degree of taper is directly related to the portion of the curve Gillying between top dead center position and position 6i and also the portion of the curve lying betweenpoint E2 and bottom dead center position designated 63 in Fig. 3. For any particular transmission, however, it has been found that the final design must be worked out experimentally. Curve '65 of Fig. 4 represents a desirable pressure value characteristic applied to the piston, that is, the displacement chamber within the motorcylinder plotted against piston travel from the start position, .or bottom dead center, of the power stroke through the end of the power stroke and to approximately the beginning of the constant velocity portion of the exhaust stroke. From this curve it will be evident that pressure is applied at a graduallyincreasing rate starting from bottom dead center position and over substantially the entire accelerating portion of travel of the piston. Thus, for example, considering the direction as being clockwise as to Fig. 2, a motor port registers at its right edge with the upper the piston, thus tending to provide a constant value maximum chamber pressure during this period of maximum piston velocity. Thereafter, as the motor port begins to register with the start of the tapered termination at the lower end of kidney port i), the rate of flow of fluid into the piston chamber is gradually reduced paralleling the reduction in piston velocity but maintaining a constant chamber pressure value. If the rate of flow of fluid were not reduced concurrently with the reduction in velocity of the piston, and at a rate paralleling the reduction in piston .velocity, there would be an undesirable rise in chamber pressure during the last part of the pressure stroke.

After the end of the piston power stroke, the associated motor port for an instant is in registry neither with the inlet kidney port nor the outlet kidney port and maximum pressure is maintained in the piston chamber. However, continued rotation of the motor block in a clockwise direction then brings the leading edge of the motor port in registry with the lower, tapered termination Sl-a of the exhaust port 5|. The

. operation here is the reverse of that during the .power stroke, pressure in the piston chamber being released at a gradually increasing rate during the accelerating phase of piston travel on the exhaust stroke up to a maximum rate coinciding with the maximum velocity phase of the exhaust stroke. The rate of exhaust is thereafter reduced to parallel the piston velocity characteristic during the decelerating phase of the piston exhaust stroke as the motor port registers with the upper tapered termination 5l-a of the exhaust port. It will be apparent that the present arrangement lends itself equally well to rotation of the motor block in either direction.

When the transmission is in a neutral position, that is to say, the vehicle with which it may be associated is not moving, if a cylinder port 22 is located at the dead center position, that is located exactly between manifold plate porting openings, considerable difiiculty may be encountered in attempting to shift the inclination of the swash plate assembly. This is due to the seal provided between the manifold porting plate and left end of the cylinder block whereby fluid ;is substantially prevented from either entering or leaving a cylinder when a cylinder port does not register at least in part with either an inlet or outlet manifold port. In accordance with this invention, in order to permit shifting of the swash plate so that the torque multiplication ratio of the transmission may be changed, means are provided for admitting fluid to or exhausting fluid from a cylinder even though the cylinder port is not in registry with a manifold port.

Referring to Fig. 1, it will be noted that a small aperture 66 is formed through the left end wall of cylinder block 2| radially outside of port 22, the aperture 66 extending at a slight downward angle, as viewed in this figure, from area 2211 to below groove 220. A short, radial slot 61 is formed in the adjacent surface of manifold plate 43 and is adapted to register at its radially inner end with the left end of aperture 66 when the associated port 22 is located between the two manifold plate ports 56 and 5|. The other end of slot 61 communicates with the sump portion of the transmission. Thus, when an aperture 66 and slot 61 are in registry, oil may be readily exhausted from or taken into the associated cylinder, thereby facilitating shifting of the swash plate.

Where herein the various parts of this invenright or a left or an upper or lower position, it will be understood that this is done solely for the purpose of facilitating description and that such references relate only to the relative positions of the parts as shown in the accompanying drawings.

While but one embodiment of this invention has been shown and described, it will be understood that many changes and modifications may be made therein without departing from the spirit or scope of the invention.

What is claimed is:

1. In a hydraulic displacement device adapted to operate as either a hydraulic pump or motor, a piston associated with said device, and a manifold porting plate for controlling application of pressure to and release of pressure from said piston, said manifold porting plate having an exhaust port and a pressure port formed therein and said ports having uniformly tapered terminations, the cross sectional area of said tapered terminations at the point of junction with said port being equal to the cross sectional area of the port end portion, the remaining cross sectional area of said tapered terminations varying according to the characteristic rate of change of volumetric size of said power piston chamber accomplished by movement of said piston whereby the pressure of the fluid on said piston at any instant is in substantially direct proportion to the piston velocity at that instant.

2. In a hydraulic transmission including a hydraulic motor of the type having reciprocable pistons journalled in cylinders formed in a cylinder block, a shaft supporting said motor cylinder block and rotatable therewith, each of said cylinders having a port formed therein, a manifold plate for controlling application of pressure to said cylinders and having ports formed therein, said cylinder ports being adapted to register with said manifold plate ports, means for holding said manifold plate stationary with respect to said rotatable cylinder block, and each of said manifold plate ports having uniformly tapered terminations at either end thereof, the cross sectional area of each of said tapered terminations at the point of junction with said port being equal to the cross sectional area of the port end portion, the cross sectional area of the remaining portion of each of said tapered terminations varying according to the characteristic rate of change of volumetric size of said power piston chamber accomplished by movement of said piston so that the rate of flow of the fluid entering and leaving the cylinders through the ports at any instant is in substantially direct proportion to the piston velocity at that instant.

3. A hydraulic displacement device comprising means defining a piston chamber, a reciprocable piston in said chamber, said chamber having a port formed therein for admitting fluid to and releasing fluid from said chamber, a manifold plate associated with said piston chamber defining means, and having a pressure port and an exhaust port formed therein, said manifold plate ports and said chamber port being adapted to move into registry, and each of said manifold plate ports having uniformly tapered terminations at either end thereof, the cross sectional area of each of said tapered terminations at the point of junction with said port being equal to the cross sectional area of the port end portion, the remaining cross sectional area of each of said tapered terminations varying according to the characteristic rate of change of volumetric size of said power piston chamber accomplished by movement of said piston whereby the rate of flow of the fiuid passing through said chamber port at any instant is proportioned to the velocity of the piston at that instant.

4. A hydraulic motor including a cylinder block having a piston chamber formed therein, a piston reciprocable in said chamber, means defining a port associated with said chamber for controlling the admission of fiuid pressure to and the release of fiuid pressure from said chamber, said port having an elongated configuration with tapered terminations at either end and an intermediate portion joining said termination of uniform width and being arranged so that the effective size of said port at any instant is varied in accordance with the velocity at that instant of said piston, said effective size of said tapered terminations being accomplished by providing said tapered terminations with a cross sectional area equal to the cross sectional area of the port end portion and varying the cross sectional area of the remainder of said tapered terminations according to the characteristic rate of change of volumetric size of said power piston chamber accomplished by movement of said piston, one of said tapered terminations being arranged to provide a uniformly increasing application of hydraulic pressure to said piston chamber during the accelerating phase of the power stroke of said piston, the intermediate portion of said port providing a substantially constant pressure in said piston chamber during the substantially constant velocity phase of the power stroke, and the other of said terminations providing a substantially constant chamber pressure during the decelerating phase of the power stroke.

5. A hydraulic motor including a cylinder block having a plurality of piston chambers formed therein and disposed in annular array, a shaft supporting said cylinder block, a piston reciprocable in each of said chambers, each of said chambers having a port formed therein, a manifold plate having an exhaust port formed therein and a pressure port formed therein, said piston chamber ports being adapted to register successively with said pressure and said exhaust ports, each of said manifold plate ports having uniformly tapered terminations at either end thereof joined by an intermediate portion of uniform width, each of said tapered terminations having a cross sectional area equal to the cross sectional area of the port end portion, the cross sectional area of the remainder of each of said tapered terminations varying according to the characteristic rate of change of volumetric size of said power piston chamber accomplished by movement of said piston, whereby each of said piston chamber ports in progressively registering with said pressure port first permits application of a uniformly increasing hydraulic pressure to the associated piston during the accelerating phase of the power stroke of the piston, then registering with the uniform diameter portion of the pressure port in the manifold plate permits application of a uniform rate of pressure fiow to said piston, and finally registering with the tapered termination of the pressure port maintains a substantially uniform pressure in said piston chamber during the decelerating phase of the power stroke, and whereby said piston chamber port thereafter is progressively placed in communication with one tapered termination of the exhaust port so that during the acclerating phase of the exhaust stroke a uniformly increasing release of pressure from the piston chamber is permitted, then is progressively placed in communication with the uniform diameter portion of the exhaust port so that during the constant velocity phase of the exhaust stroke a constant rate of pressure release flow is permitted and finally is progressively placed in communication with the other tapered termination of the exhaust port so that during the decelerating phase of the exhaust stroke a uniformly decreasing release of pressure is permitted.

JOHN A. LAUCK. FRED C. HABERLAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 924,787 Janney June 15, 1909 1,081,810 Carey Dec. 16, 1913 1,867,308 Durner July 12, 1932 2,297,518 Wegerdt Sept. 29, 1942 FOREIGN PATENTS Number Country Date 442,450 Great Britain Feb. 10, 1936