Casing and cover for fluid energy converter

A fluid energy converter having a cover to support a cylinder barrel positioned and mounted on the casing main body. At the opening end of the casing main body, a helical taper plane at an angle not more than 45.degree. with respect to the axial centerline of the body open end is formed, helically of the casing body. The taper plane faces the open end of the casing main body and a taper plane at the same angle is formed on the cover. The cover is fitted to the casing main body by threading together the taper planes so that the cover is correctly positioned by the taper guide action. Because the angle of taper plane is not more than 45.degree., the cover and casing main body are not dislocated if a force is applied in a radial direction.

In general radial piston type liquid pressure pump/motor, or, as stated 
below, special liquid pressure pump/motor, a rear cover is fitted to the 
opening end of the casing, and a cylinder barrel disposed within the 
casing is supported on the rear cover by way of an eccentric pintle. In 
such arrangement, due to the effects of working fluid at high pressure, a 
large misaligning force in the radial direction may occur between the 
casing main body and rear cover. What is more important, smooth operation 
is spoiled unless the casing and the rear cover are coupled in a correctly 
positioned state. 
Conventionally, therefore, a spigot has been provided between the casing 
main body and the rear cover, and a flange coupling part has been disposed 
at its outer side with the two parts accurately coupled together by a bolt 
or other fixing means in the flange coupling part. 
However, in order to keep a high positioning precision at the spigot, 
machining of high precision is required. When the precision is too high, 
it is hard to fit the two parts to each other. Besides, since the flange 
coupling part must be provided at the outer side of the spigot, the casing 
outside dimension increases, and is hard to design compactly. In 
particular, when two sets of such fluid energy transducer are placed side 
by side, and one is used as the pump and the other as a motor, that is, 
when composing a unitized HST or HMT system transmission by two fluid 
energy converters, the entire structure becomes very large due to the 
bulkiness in the direction of diameter of the both parts. 
This invention is therefore intended to solve these problems securely and 
easily. 
BRIEF SUMMARY OF THE INVENTION 
This invention, in order to achieve said object, is characterized by the 
thread-fitting structure and the helical taper plane provided in the 
coupling part of the casing main body and cover. 
That is, the fluid energy transducer of this invention is composed by 
helically forming a taper plane at an angle of 45.degree. or less with 
respect to the axial center on the inner circumference or outer 
circumference of the opening end part of the casing main body, forming a 
helical taper plane at a same angle as said taper plane on the cover and a 
stopping plane to stop the opening end of the casing main body, and 
threading the taper plane forming part of the casing main body up to the 
position where the opening end is stopped on the stopping plane. 
In such construction, by threading the cover having a helical taper plane 
having a same angle into the outer circumference or inner circumference of 
the opening end of the casing main body helically forming a taper plane, 
and tightening until the opening end of the casing main body abuts against 
the stopping plane, the taper plane of the casing main body rides on the 
taper plane of the cover in tight contact. As a result, the taper guide 
action is exhibited, and the cover and casing main body are positioned in 
specified state. Thus, in this state, the gap between the casing main body 
and cover in the radial direction is completely eliminated. 
Moreover, since these taper planes are slightly inclined at 45.degree. or 
less with respect to the axial center, the taper plane of the cover will 
hardly slide along the taper plane of the casing main body if a load is 
applied in the radial direction. Accordingly, due to the effects of the 
fluid pressure, if a misaligning force should occur in the radial 
direction between the casing main body and cover, the two parts will never 
be dislocated. 
Besides, since the taper planes are formed helically the casing main body 
and cover may be coupled by a simple threading operation. Still more, by 
fitting the opening end of the casing main body on the stopping plane of 
the cover, the positioning of the two parts in the axial direction may be 
accurately achieved. 
Therefore, in such construction, without using spigot and flange coupling 
part, the casing main body and cover can be securely and accurately joined 
together.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIG. 1 to FIG. 5 and FIG. 7 to FIG. 10, preferable 
embodiments of this invention are described in details below. 
The fluid energy converter shown in FIG. 1 to FIG. 3 has a structure as 
disclosed in the Japanese Laid-open Patent No. 58-77179. That is, this 
energy converter is composed of casing 1, a torque ring 4 having inner 
flat planes 3 respectively at the inside of the positions corresponding to 
plural first static pressure bearings 2 rotatably fitted relatively 
through static pressure bearings 2 provided on the inner circumference 1a 
of casing 1, plural pistons 6 being disposed inside of this torque ring 4 
with their ends fitted to the inner flat planes 3 through second static 
pressure bearings 5, a cylinder barrel 8 holding pistons 6 in a slidable 
manner and forming a free space 7 for entry and discharge of fluid in 
pistons 6, a pintle 9 for rotatably supporting cylinder barrel 8 being 
disposed reciprocatably in the direction orthogonal to the axial center m 
of casing 1 and torque ring 4, and fluid passages 11, 12 forming a pair to 
communicate with the space 7 of which volume is increased and with the 
space 7 of which volume is decreased when the casing 1 and torque ring 4 
are relatively rotated with the axial center n of pintle 9 deviated from 
the axial center m of the casing. In this setup, the fluid to fill up the 
spaces 7 is led into corresponding first and second static pressure 
bearings by way of the fluid passages 13, 14, and it is designed to 
develop a couple in the torque ring 4 around the rotation axial center m 
by the static pressure of the fluid let into the first static pressure 
bearing 2 and the static pressure of the fluid let into the second static 
pressure bearing 5. 
In this construction, thus, with the axial center n of pintle 9 deviated 
from the rotation axial center m, when a high pressure fluid is supplied 
into the space 7 existing in the right region A in FIG. 3, through, for 
example, the first fluid passage 11, couple to rotate the torque ring 4 in 
the direction of the arrow S occurs in torque ring 4, and the function as 
a motor is exhibited. Or, when torque ring 4 is rotated in the direction 
of, for example, arrow R by an external force, the high pressure fluid is 
discharged from the first fluid passage (see arrow Q), so that the 
function as a pump is fulfilled. 
The casing 1 of the fluid energy converter of FIGS. 1 to 3 is composed of a 
casing main body 21, and a rear cover 22 fitted to the opening end of this 
casing main body. The casing main body 21 is shaped like a cup to 
accommodate torque ring 4, piston 6, and cylinder barrel 8, and its rear 
end is opened. A taper plane 23, FIG. 4, is formed in the inner 
circumference of the opening end 21a of this casing main body 1. This 
taper plane has an angle .alpha. of 45.degree. or less with respect to the 
axial center m of casing main body 1, with a specified width, and is 
formed helically. That is, this taper plane 23 has a helical taper 
surface. A steep slope 24 of a specified width is formed between the top 
edge and bottom edge of the taper plane 23. 
On the other hand, the rear cover 22 is shaped like a disc to support the 
cylinder barrel 8 by way of the pintle 9, and it has a trapezoidal groove 
22a in which the base end part 9a of the pintle 9 is fitted slidably. The 
rear cover 22 has an annular stopping plane 25 for stopping the opening 
end 21b of the casing main body 21, and a circular bulging part 26 formed 
inside this stopping plane 25. On the outside of this circular bulging 
part 26, there is a spiral taper plane 27 having the same angle as said 
taper plane 23. This taper plane 27 has the same angle .alpha. width 
respect to the axial center m of the casing main body 21, with a specified 
width, and is formed helically in the same pitch as that of said taper 
plane 23. 
In the taper plane 27 forming area of this rear cover 22, the taper plane 
23 forming area of the casing 21 is tightened by threading to the position 
where the opening end 21 is fixed on the stopping plane 25. 
In this construction, due to the reaction force the casing main body 21 
receives from the stopping plane 25 of the rear cover 22, the helical 
taper plane 23 provided inside the casing main body 21 rides over the 
taper plane 27 of the rear cover 22 to contact tightly. As a result, the 
taper guide action is exhibited, and the casing main body 21 and rear 
cover are coupled in an accurately positioned state. 
In this state, the gap in the radial direction between the casing main body 
21 and rear cover 22 is completely eliminated. Still more, since these 
taper planes 23, 27 are slightly inclined at an angle of 45.degree. or 
less with respect to the axial center, if a considerably large load in the 
radial direction is applied on the casing main body 21, the taper plane 23 
of the casing main body 21 will hardly slide along the taper plane 27 of 
the rear cover 22. Accordingly, if a relative misaligning force in the 
radial direction should be applied between the casing main body 21 and 
rear cover 22, the both parts will not be dislocated from each other. That 
is, if having a steep helical plane at 45.degree. or more with respect to 
the axial center, as in an ordinary thread, slipping of the parts along 
the helical plane may occur when a radial load is applied to cause 
dislocation easily, but when the taper planes 23, 27 are used, as in this 
invention, as far as the range of load is normal, using ordinary members, 
the relative positions of the casing main body 21 and rear cover 22 will 
be accurately maintained. 
In the practice of the instant invention, as best shown in FIG. 7, both 
taper planes 23 and 24 may have the same angle of 45.degree. and the 
relative positions of the casing main body 21 and rear cover 22 will be 
accurately maintained. 
Therefore, it is not necessary to form a spigot between the casing main 
body and rear cover to set the relative tolerance strictly as required in 
the prior art, and the machining may be facilitated and the difficulty of 
assembling will be solved spontaneously. 
In addition, since the casing main body 21 can be positioned by abutting 
its opening end 21b against the stopping plane 25 of the rear cover 22, 
the repeatability of positioning in the axial direction will be also 
excellent. 
In this composition, furthermore, when the both taper planes 23, 27 are 
tightened, the wedge actions are induced between the taper planes 23, 27 
not only in the rotating direction but also in the axial direction, so 
that the coupling is hardly loosened. This construction, still more, since 
the flange coupling part is not needed, the maximum outside diameter of 
the casing 1 may be reduced, so that the entire equipment may be designed 
compactly. FIG. 5 and FIG. 6 are explanatory drawings showing the 
compactness afforded by the invention. That is, in FIG. 5, beside the 
fluid energy converter Il explained hereabove, another fluid energy 
converter I2 of the same constitution is disposed, and the rear covers 22, 
22 of these two fluid energy converters 11, 12 are coupled together into 
one body. Moreover, the first and second fluid passages 11, 12 of one 
fluid energy converter Il, and the first and second fluid passages (not 
shown) of the other fluid energy converter I2 are connected with each 
other by way of first and second communicating routes 28, 29 formed at 
both sides of the rear cover 22, thereby composing a liquid pressure 
transmission of so-called HST type. Thus, in such mode of use, when the 
junction of the casing main bodies 21 and rear covers 22 of the fluid 
energy converters 11, 12 are achieved by threading of the helical taper 
planes 23, 27, the spacing distance La between the casing main bodies 21 
of the fluid energy converters Il, I2 may be defined to an extremely small 
length. On the other hand, in the case of the prior art shown in FIG. 6, 
the casing main bodies a and rear covers b of the fluid energy converters 
II1, II2 are positioned by the spigots c, and by placing bolts e into the 
flange connection parts d provided outside, the casing main bodies a and 
rear covers b are joined, which means it is difficult to reduce the 
spacing distance Lb between the two casing main bodies a. In this 
invention, therefore, as compared with the conventional equipment, the 
outside diameter can be notably reduced, and the entire equipment may be 
reduced in size and weight. 
In the embodiment of FIGS. 1-3 described herein, the taper plane is formed 
inside the opening end of the casing main body, which is not, however, 
limitative. For example, a spiral taper plane may be formed outside the 
casing main body, and a taper plane fitting with this taper plane may be 
formed inside the dent part provided in the rear cover. Such an embodiment 
of the invention is illustrated in FIGS. 8-10. 
The fluid energy converter in the embodiment shown in FIGS. 8 and 9 is of 
the same structure as described with respect to FIGS. 1-3, above, and like 
reference numerals are used with respect thereto. Where the embodiments 
differ is that, in the embodiment of FIGS. 8 and 9, the taper plane is 
formed outside the opening end of the casing main body 1'. Thus, the taper 
plane 23', FIG. 10, is formed on the outer circumference of the opening 
end 21a' of main casing body 1' and is received in the inside circular 
recess 22a' of rear cover 22' and spiral taper plane 27' thereof having 
the same angle .alpha. with respect to the axial center m of the casing 
main body 21'. Thus, as in the embodiment of FIGS. 1-3, the angle .alpha. 
is 45.degree. or less. 
In the taper plane 27' forming area of rear cover 22', in the embodiment of 
FIGS. 8-10, the taper plane 23' forming area of the casing 21' is 
tightened of threading to the position where the opening end is fixed on 
the stopping plane 25', FIG. 10. 
The internal structure of the fluid energy transducer is not limited to the 
above constructions, and may be also, for example, applied to an ordinary 
radial piston type pump/motor. 
This invention, having such organization, is intended to position and joint 
the casing main body and cover accurately, without requirement of high 
precision in machining or difficulty in assembling work, and if a large 
misaligning force in the radial direction is applied between the casing 
main body and cover, its positioning will not be spoiled, so that it is 
possible to present an excellent fluid energy converter reduced in both 
size and weight by spontaneously reducing the maximum outside diameter of 
the entire assembly.