Gerotor device with lubricant system

A rotary fluid pressure device of the type including agerotor gear set having an externally-toothed rotor orbiting and rotating within an internally-toothed stator. An intermediate shaft has one end in splined engagement with the rotor and the other end defining a large set of internal splines. The device includes an output shaft assembly, also defining a large set of internal splines. A large dogbone shaft having external splines at each end transmits torque between the intermediate shaft and the output shaft assembly. The intermediate shaft has an axial bore which communicates pressurized lubricant to the one end of the dogbone shaft, a portion of the pressurized lubricant flowing radially outward over the end of the dogbone and through the spline connection between the dogbone and the intermediate shaft. Another portion of the pressurized lubricant flows through an axial lubricant passage in the dogbone to the opposite end of the dogbone, from where it flows radially over that end of the dogbone and through the spline connection between the dogbone and the output shaft assembly. These portions of lubricant then recombine and enter a return lubricant path.

BACKGROUND OF THE DISCLOSURE 
The present invention relates to rotary fluid pressure devices, and more 
particularly, to an improved lubricant system for use therein. 
The present invention is particularly applicable to rotary fluid pressure 
devices of the gerotor type, and will be described in connection 
therewith. However, it should be appreciated that the invention may have 
broader application and may be utilized in any rotary fluid pressure 
device wherein torque is transmitted from one internally splined member to 
another such as by means of an externally splined dogbone shaft where it 
is desirable to maintain a constant flow of lubricant through both spline 
connections. 
The invention is especially suited for use with hydraulic gerotor motors, a 
typical example of which is shown in U.S. Pat. No. 3,572,983, assigned to 
the assignee of the present invention. Because of the relatively low 
torques being transmitted from the rotor to the output shaft by the main 
drive shaft in such motors, lubrication of the spline connections at 
either end of the main drive shaft usually did not present a serious 
problem. However, proper lubrication of these spline connections became 
more important as the size and torque capability of gerotor motors 
increased. More recently, the torque output capability of gerotor motors 
was greatly increased by the development illustrated in U.S. Pat. No. 
3,782,866, also assigned to the assignee of the present invention. The 
basis for this development was the realization that the primary factor 
limiting the torque output capability of the motor was the strength of the 
spline connection between the rotor and the main shaft and between the 
main shaft and the output shaft. Thus, it is now well-known in the art to 
provide a high torque gerotor motor utilizing an intermediate shaft, one 
end of which is connected to the rotor of the gerotor by a set of straight 
splines and the other end of which defines the relatively large set of 
internal splines. At the same time, the output shaft also defines a 
relatively large set of internal splines and a large dogbone shaft, having 
external splines at either end thereof, provides the main drive connection 
between the intermediate shaft and the output shaft. With the increased 
size and strength of these spline connections, the greater amount of 
torque being transmitted resulted in the generation of more frictional 
heat, as well as the creation of more wear particles. Initially, 
lubrication of the spline connections in hgh torque motors such as those 
illustrated in the referenced patent was accomplished merely by providing 
a lubricant sump that the external splines on the main shaft would pass 
through as the shaft orbited and rotated. However, this means of 
lubrication has not proven consistently satisfactory. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a rotary fluid pressure 
device having an improved lubricant system for large spline connections in 
high torque gerotor motors. 
It is a more specific object of the present invention to provide such a 
lubricant system which utilizes a constant flow of lubricant to transfer 
frictional heat more effectively and to transport wear particles away from 
the spline connections. 
It is another object of the present invention to provide a lubricant system 
for a rotary fluid pressure device which accomplishes the above-stated 
objects and which divides the lubricant flow into two separate portions, 
each of the portions lubricating one of the spline connections. 
The above and other objects of the present invention are accomplished by 
the provision of an improved rotary fluid pressure device and lubrication 
system therefor, which includes a casing, a gerotor gear set, and an 
orbiting means associated with the gerotor gear set. The orbiting means 
defines first internal splines having both orbital and rotational 
movement. An output shaft assembly is rotatably associated with the casing 
and defines second internal splines, and a connecting shaft member 
includes first external splines in engagement with said first internal 
splines and second external splines in engagement with said second 
internal splines to transmit torque between the orbiting means and the 
output shaft assembly. The connecting shaft member has first and second 
ends and defines an axially-oriented lubricant passage having first and 
second end portions disposed adjacent the first and second external 
splines, respectively. The fluid pressure device includes means defining a 
lubricant path disposed to communicate pressurized lubricant to one of the 
first and second ends of the connecting shaft member. One portion of the 
pressurized lubricant flows over the one end and into the adjacent 
external splines, while another portion of the pressurized lubricant flows 
through the lubricant passage and over the other end of the connecting 
shaft member and into the adjacent external splines. Preferably, the fluid 
pressure device includes means defining a return lubricant path and the 
two portions of pressurized lubricant flow from the first and second 
external splines into the return lubricant path.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, which are not intended to limit the present 
invention, FIG. 1 illustrates an hydraulic motor including an output 
section, generally designated 11, a gerotor section, generally designated 
13, and a valve section, generally designated 15. The valve section 15 may 
be of the type well-known in the art, such as is illustrated in U.S. Pat. 
No. 3,572,983, which is incorporated herein by reference. The referenced 
patent also describes and illustrates the operative association of the 
valve section 15 with the gerotor section 13. The configuration of the 
output section 11, as well as its operative association with the gerotor 
section 13, is described and illustrated in U.S. Pat. No. 3,782,866, which 
is also incorporated herein by reference. Thus, the details and operation 
of sections 11, 13 and 15, will be described only briefly. 
The valve section 15 includes a body portion 17 and a port plate 19. The 
body portion 17 defines an inlet port 21 and an outlet port 23 (see flow 
arrows), and a disc valve member 25 is rotatably disposed within the body 
portion 17. A valve drive shaft 27 transmits an orbital and rotational 
movement of the gerotor section 13 to the disc valve member 25, and a 
valve balancing ring 29 is seated within the body portion 17 and against 
the disc valve member 25. 
In the subject embodiment, the hydraulic motor is a high torque output 
motor and thus, the gerotor section 13 comprises a pair of substantially 
identical gerotor gear sets 31 and 33, each of which, as may best be seen 
in FIG. 2, includes a stator member 35 having a plurality of generally 
semi-cylindrical pockets receiving rollers 37, serving as the internal 
teeth of the stator 35. Each gerotor gear set also includes a rotor 39 
having a plurality of external teeth 41, the number of teeth 41 being one 
less than the number of rollers 37, such that the external teeth 41 and 
rollers 37 interengage to define a plurality of expanding and contracting 
volume chambers 43 as is well-known in the art. The stator member 35 
defines a bore 45 extending axially therethrough, the function of which 
will be described subsequently. 
An intermediate shaft assembly 47 includes a shaft portion 49 in splined 
engagement with each of the rotors 39, such that the gerotor gear sets 31 
and 33 will, at any instant, have all of their component parts in the same 
relative position. The shaft portion 49 defines a generally axial bore 51, 
the function of which will also be described subsequently. 
The output section member includes a casing 53 within which an annular 
output member 55 is mounted for rotation, such as by means of a pair of 
tapered roller bearing sets 57 and 59. The intermediate shaft assembly 47 
includes a flange portion 61 to which is attached by any suitable means a 
sleeve member 11 (see FIG. 3). Disposed within the sleeve member 63 is an 
internally-splined member 65, with relative rotation between the sleeve 
member 63 and internally splined member 65 being prevented by means of a 
plurality of torque pins 67. Relative axial movement between the sleeve 
member 63, spline member 65, and torque pins 67 is prevented by a retainer 
plate 69, attached at the forward end of the intermediate shaft assembly 
47. Disposed within the output member 55, and at the forward end thereof, 
is an internally splined member 71, which may be similar, or even 
identical to the internally splined member 65. The splined member 71 may 
be positioned non-rotatably relative to the output member 55 by means of a 
plurality of torque pins 73, with axial retention of the spline members 71 
and pins 73 being achieved by means of a cover 75, bolted to the output 
member 55. 
Disposed within the output member 55 is a dogbone shaft 81, having a set of 
external splines 83 in splined engagement with the internally-splined 
member 65 and set of external splines 85 in splined engagement with the 
internally splined member 71, to transmit the orbital and rotational 
movement of the intermediate shaft assembly 47 into pure rotational 
movement of the output member 55. The dogbone shaft 81 further defines an 
axial passage 87, the function of which will be described subsequently. 
It should be appreciated that although the present invention is being 
described in connection with a high torque motor, it may be utilized with 
various other types of fluid pressure devices, such as a pump, in which 
case the output section 11 would actually be the input. Therefore, it 
should be understood that, as used herein, such terms as "output shaft" 
are not intended to limit the present invention, and the use of such terms 
is intended to mean and include input shafts, as in the case of a pump, as 
well as elements such as output member 55 which are not actually in the 
form of a conventional shaft. 
Referring now to the valve section 15 of FIG. 1, the disc valve member 25 
defines an angled passageway 91, such that a thin film of the pressurized 
fluid entering the motor through inlet port 21 is able to pass between the 
valve balancing ring 29 and the face of the disc valve member 25 and enter 
the passageway 91 as is well-known in the art. Typically, the fluid 
pressure at the inlet port 21 and in the expanding volume chambers of the 
gerotor section 13 may be about 3,000 psi, while the fluid pressure in the 
contracting volume chambers (assuming use as a motor) and the outlet port 
23 may be about 100 psi. With such fluid pressures present, the fluid 
pressure in the passageway 91 and in the remainder of the lubrication 
circuit to be described is generally about 5 or 10 psi above return fluid 
pressure (i.e., about 105 to 110 psi). 
From the passageway 91, the lubrication fluid flows over the spline 
connection between the valve drive shaft 27 and the disc valve member 25, 
then flows axially to the left in FIG. 1 where it lubricates the spline 
connection between the valve drive shaft 27 and the rotor 39 of gerotor 
gear set 33. 
The lubricant next enters the axial bore 51 and continues flowing to the 
left in FIG. 1 until it passes from the bore 51 and becomes available to 
lubricate the dogbone shaft 81. At this point, the total lubricant flow 
divides into two portions which, preferably, each comprise about one-half 
of the total lubricant flow reaching this point. One portion of the 
lubricant flows radially outward over the right-hand end surface of the 
dogbone shaft 81. This portion of the lubricant then flows through the 
connection between the external splines 83 and the internally splined 
member 65, with the flow of lubricant being more effective than a sump for 
purposes of dissipating frictional heat and carrying away metal wear 
particles breaking loose at the spline connection. 
The other portion of the lubricant flow enters the axial passage 87 and 
flows to the left until it leaves the passage 87 and flows radially 
outward over the left-hand end surface of the dogbone shaft 81. This 
lubricant then flows toward the right in FIG. 1 through the connection 
between the external splines 85 and the internally splined members 71. As 
the two portions of the lubricant flow out of their respective spline 
connections, they re-combine as shown by the flow arrows and enter what 
may be considered a return lubricant path defined by the inner surface of 
the output member 55 and the outer surface of the intermediate shaft 
assembly 47. The return lubricant then enters an axial bore 93 in the 
casing 55, the bore 93 being in alignment with each of the bores 45 in the 
gerotor gear sets 31 and 33, then flows into an aligned bore 95 in the 
port plate 19 and finally, through a bore 97 in the body portion 17. The 
return lubricant in bore 97 unseats a ball check valve 99, enters an 
angled passage 101, and flows into annular chamber 103 defined by the disc 
valve member 25 and the body portion 17. Annular chamber 103 also contains 
the return flow from the contracting volume chambers, and from annular 
chamber 103, the return fluid flows through outlet port 23 to the 
reservoir. 
Thus, it will be apparent that the lubricant system of the present 
invention provides an improved arrangement for lubricating large, 
high-torque spline connections at opposite ends of a dogbone shaft by 
dividing the lubricant flow into two separate portions, with one portion 
flowing through one of the spline connections and the other passing 
axially through the dogbone shaft and then through the opposite spline 
connection. Although the invention has been described in connection with a 
preferred embodiment, it will be apparent to those skilled in the art that 
various modifications and alterations may be made within the scope of the 
present invention, and it is my intention to include all such 
modifications and alterations insofar as they come within the scope of the 
appended claims.