U.S. patent application number 12/231783 was filed with the patent office on 2009-01-08 for axial plunger pump or motor.
Invention is credited to Raphael Zhu.
Application Number | 20090007773 12/231783 |
Document ID | / |
Family ID | 38509056 |
Filed Date | 2009-01-08 |
United States Patent
Application |
20090007773 |
Kind Code |
A1 |
Zhu; Raphael |
January 8, 2009 |
Axial plunger pump or motor
Abstract
An axial plunger pump or motor comprises a casing (1), a main
shaft (2), a rotor cylinder (14), a rotary swash plate (9) and a
plurality of plunger assemblies (10), wherein a constant velocity
universal coupling (11) transmits torque between the rotary swash
plate and the main shaft, such that the main shaft (14) and the
rotary swash plate (9) rotate about the main shaft axis (41) and
the swash plate axis (91) forming an angle therebetween,
respectively, so as to realize transition between hydraulic energy
and rotary mechanical energy.
Inventors: |
Zhu; Raphael; (Beijing,
CN) |
Correspondence
Address: |
LAW OFFICES OF CLEMENT CHENG
17220 NEWHOPE STREET #127
FOUNTAIN VALLEY
CA
92708
US
|
Family ID: |
38509056 |
Appl. No.: |
12/231783 |
Filed: |
September 5, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/CN2007/000807 |
Sep 20, 2007 |
|
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12231783 |
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Current U.S.
Class: |
91/505 ;
417/222.1; 417/269 |
Current CPC
Class: |
F04B 1/128 20130101;
F04B 1/2078 20130101; F04B 1/146 20130101 |
Class at
Publication: |
91/505 ; 417/269;
417/222.1 |
International
Class: |
F01B 13/04 20060101
F01B013/04; F04B 1/20 20060101 F04B001/20; F04B 1/30 20060101
F04B001/30 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2006 |
CN |
200620007920.7 |
Claims
1. A axial plunger pump or motor, comprising: a casing; a main
shaft rotatably supported on the casing; a rotor cylinder with a
plurality of plunger holes, which is coupled to the main shaft and
is driven to rotate about a main shaft axis by the main shaft and
which has an oil-distributing end surface; an oil-distributing disk
in cooperation with an oil-distributing end surface of the rotor
cylinder; a rotary swash plate whose end surface is disposed in a
manner axially opposing the plurality of plunger holes of the rotor
cylinder and which can rotate about a swash plate axis forming an
angle with respect to the main shaft axis; a plurality of plunger
assemblies, an end of each being articulated to an end surface of
the rotary swash plate and another end of each being slidably
disposed in the plunger holes of the rotor cylinder; a constant
velocity universal coupling which is provided between the rotary
swash plate and the main shaft and transmits torque therebetween,
so that the main shaft and the rotary swash plate rotate about the
main shaft axis and the swash plate axis forming an angle
therebetween, respectively.
2. The axial plunger pump or motor according to claim 1,
characterized in that, said constant velocity universal coupling is
a Rzeppa constant velocity universal coupling, a half angular
Rzeppa constant velocity universal coupling, a ball joint constant
velocity universal coupling or a Weiss constant velocity university
coupling.
3. The axial plunger pump or motor according to claim 2,
characterized in that, said Rzeppa constant velocity universal
coupling comprises an inner race ring with an outer raceway, a
plurality of steel balls, a holder and an outer race ring with an
inner raceway, wherein said steel balls are arranged on the holder
and are located in the inner raceway and the outer raceway, said
inner race ring is coupled to the main shaft, said outer race ring
is coupled to the rotary swash plate, such that the main shaft and
the rotary swash plate are respectively rotated about the main
shaft axis and the swash plate axis via the Rzeppa constant
velocity universal coupling, the cross point of the said two axis
locate at the center point of the said Rzeppa constant velocity
universal coupling.
4. The axial plunger pump or motor according to claim 1,
characterized in that, said rotary swash plate is supported on the
casing via a swash plate bearing, so as to form a constant-capacity
axial plunger pump or motor, or said rotary swash plate is
supported on a pendulous disk via a swash plate bearing, the
pendulous disk is supported on said casing via a pendulous disk
bearing, said swash plate bearing is a combination bearing of a
needle bearing and a cylinder or taper roller thrust bearing, said
pendulous disk bearing is a needle bearing or sliding bearing in a
crescent form, and the rotation axis of the pendulous disk is
perpendicular to the main shaft axis and passes through the center
of the constant velocity universal coupling, said pendulous disk is
connected with a variable displacement adjustment mechanism for
adjusting the deflection angle of the pendulous disk, such that an
angle between the swash plate axis of the rotary swash plate
supported thereon and the main shaft is adjusted through changing
the deflection angle of the pendulous disk, so as to form a
variable-capacity axial plunger pump or motor.
5. The axial plunger pump or motor according to claim 4,
characterized in that, said variable displacement adjustment
mechanism is a variable displacement oil cylinder, the piston of
which is connected to the pendulous disk so as to drive the
pendulous disk to deflect through extending and retracting of the
piston.
6. The axial plunger pump or motor according to claim 4,
characterized in that, the variable displacement adjustment
mechanism is a variable displacement adjustment mechanism of a
trunnion type, which includes a trunnion connected to the pendulous
disk and a driving mechanism for driving the trunnion to rotate, a
rotation axis of the trunnion is coincident with the rotation axis
of the pendulous disk so as to drive the pendulous disk to deflect
through rotation of the trunnion.
7. The axial plunger pump or motor according to claim 1,
characterized in that, said rotor cylinder is in a taper shape, a
diameter thereof at the end closer to the rotary swash plate is
larger than that at the other end; the plurality of plunger holes
on said rotor cylinder are fairly distributed in a taper form
accordingly.
8. The axial plunger pump or motor according to claim 1,
characterized in that, said plunger assembly is a plunger assembly
of a ball joint type, which comprises a plunger and a ball-headed
rod with a ball head at each of both ends thereof, said rotary
swash plate is provided with a socket, a ball head at an end of the
ball-headed rod is located in the socket to form a ball-joint
connection with the rotary swash plate, and a ball head at the
other end is located in the plunger to form a ball-joint connection
with the plunger, and the plunger is slidably provided in the
plunger hole.
9. The axial plunger pump or motor according to claim 8,
characterized in that, in the middle portion of the ball-headed rod
and the plunger there is provided with a oil hole in communication
with the plunger holes to introduce pressurized oil to lubricate
the ball head at the both ends.
10. The axial plunger pump or motor according to claim 1,
characterized in that, articulation centers of said plurality of
plunger assemblies on the rotary swash plate are located in a same
plane, and an intersection point of the plane with the main shaft
axis is coincident with the center of the constant velocity
universal coupling.
11. The axial plunger pump or motor according to claim 1,
characterized in that, the rotor cylinder is axially positioned
along the main shaft through a pressure spring and a pressure
spring stop collar, an end of the main shaft is provided with an
oil hole and a radial oil path, such that the pressure between the
rotor cylinder and the oil-distribution disk is adjusted through
introducing pressurized oil into the radial oil path.
12. The axial plunger pump or motor according to claim 1,
characterized in that, the oil-distribution end surface of said
rotor cylinder is a spheric surface, said oil-distribution disk
forms a spherical surface fit with the oil-distribution end
surface.
Description
[0001] This application claims priority from and is a continuation
of and hereby expressly incorporates by reference in its entirety,
PCT application PCT/CN/2007/000807 having publication number WO
2007/104257 for AN AXIAL PLUNGER PUMP OR MOTOR which was published
Sep. 20, 2007 which in turn claims priority from Chinese
application for the same AN AXIAL PLUNGER PUMP OR MOTOR application
filed Mar. 14, 2006 having Chinese application number
200620007920.7 both by same inventor ZHU, Raphael, the disclosure
of which is incorporated herein by reference in its entirety.
FIELD
[0002] The present invention relates to a hydraulic pump or motor
device in hydraulic mechanisms, particularly to an axial plunger
pump or motor.
BACKGROUND
[0003] In hydraulic mechanisms, a hydraulic pump or motor is the
heart of the hydraulic device. Theoretically, a hydraulic pump and
a motor are switchable, except for some partial differences.
Therefore, the description of the invention will only focus on the
design of the pump, and the structure of a motor will be omitted in
that it is similar to that of the pump. Plunger pumps or so named
piston pump have been increasingly widely employed in engineering
mechanisms due to their high efficiency, adaptation to high
pressure and aptness to carry out variable displacement
adjustment.
[0004] The plunger pump can be classified into two categories
according to the stroke direction of the plunger, that is, an axial
plunger pump and a radial plunger pump. In the axial plunger pump,
according to the mechanism of motion transition, it may be
classified into a swash plate plunger pump and a bent axis plunger
pump, the structural characteristics of which are referred to FIGS.
1 through 3, respectively.
[0005] An axial plunger pump of a swash plate type is a variable
displacement pump of high pressure, high speed, high impact
resistance and high integration degree. As shown in FIGS. 1 and 2,
a rotor is driven to rotate by the main shaft through involute
splines. A plurality of plungers, which are uniformly distributed
in the rotor, press the sliding shoes of the plunger assemblies
against the plane of the frictional plate of the swash plate
through a ball joint and a return press plate. Since there is an
angle between the swash plate plane and the rotation axis, the
plunger body not only rotates with the rotor, but also reciprocates
along the plunger hole of the rotor. In this way, the plunger pump
carries out oil intaking and oil outleting. The stroke of the
plunger can be changed through adjusting the inclination angle of
the swash plate plane, so as to perform variable displacement
adjustments. Changing the inclination direction of the swash plate
leads to variations of the flow direction of the pressurized oil,
or the rotation direction of the rotor in case of serving as a
hydraulic motor.
[0006] In such an axial plunger pump of a swash plate type, it is
easy to perform variable displacement adjustments, and convenient
to change the direction of the pressurized oil and the rotation
direction of the rotor and to switch between the pump state and the
motor state. It has a low cost, with relatively simple structure
and small volume. However, an axial plunger pump of a swash plate
type has three main friction pairs, i.e., a pair between rotor and
oil-distributing disk, a pair between plunger and plunger hole, and
a pair between the sliding shoe of the plunger and swash plate. In
the friction pair between plunger and plunger hole, the plunger is
not only subject to an axis force, but also to a tangential force
and a moment due to a normal force acted upon the sliding shoe of
the plunger by the swash plate. The force and moment are balanced
by the pressure applied on the plunger by the plunger hole of the
rotor. The sliding friction caused by such force and moment leads
to a reduced mechanical efficiency and component wearing.
Therefore, the rotor needs to be balanced through a center axis
supporting or an additional bearing since it is also acted upon by
a rollover moment. Thus, such a pump has three disadvantages: (i)
the overall efficiency is relatively low, wherein the volume
efficiency of the oil pump is between 0.92 and 0.98 and the
mechanical efficiency is between 0.90 and 0.95, and the overall
efficiency is not higher than 0.95; (ii) it is susceptible to
staining from oil, thus resulting in a short pump service life;
(iii) the allowable rotation speed is not high.
[0007] As shown in FIG. 3, the working principle of a bent axis
plunger pump is fairly similar to that of a swash plate pump.
However, they have large differences in structure, and they also
have different force profiles. In a bent axis plunger pump, the
method of articulating the ball head of the plunger is substituted
for the approach of employing the sliding shoes and the swash plate
in the swash plate pump, such that the structural strength and the
impact resistance are improved. When the pump is operating, since
the angle between the axis of the linking rod and the axis of the
plunger is not large, the lateral pressure between the plunger and
the cylinder wall is much smaller than that in the case of a swash
plate pump. Therefore, wearing during operation is small, and the
inclination angle .beta. may also be increased to 25 through 30
degrees (less than 20 degrees in case of a swash plate pump), such
that the variation range of flow flux is enlarged. Furthermore, the
drive shaft of a bent axis plunger pump is small in dimension, or
it does not penetrate through the oil-distributing disk, such that
the rotor diameter of the cylinder is correspondingly reduced.
Thus, leakage and friction loss are decreased, resulting in a
higher overall efficiency than that of the swash plate pump, e.g.,
higher by 2-3% under the same technical level. The pump performance
in oil-intaking is thus improved since the circumferential speed of
the oil cylinder is decreased, and the rotation speed limit of the
pump can therefore be increased. Furthermore, the requirement on
the accuracy of oil-filtering in a bent axial pump is low, e.g.,
generally 25 m, in comparison with 10 to 15 m in a swash plate
pump.
[0008] Due to above advantages, such bent axis plunger pumps have
been increasingly employed in the hydraulic mechanisms. However,
such a pump carries out variable displacement through cylinder
swinging, and the profile dimension is large. The inclination
between the rotor and the power shaft makes the profile form a
corner shape, which is not desirable in situations of narrow space
or in case where coaxial assembly is required. In addition,
structure and technical requirements are relatively complicated,
thus leading to a high cost.
SUMMARY
[0009] The object of the invention is to provide an axial plunger
pump or motor, which enables to increase the efficiency of the
plunger pump or motor, has a simplified structure, a decreased
volume, a lower cost, and a wider application range, and
particularly is applicable to situations where special installation
requirements should be meet, such as in transmissions of motor
vehicles.
[0010] The above mentioned object of the invention may be achieved
by the following technical solutions, i.e., an axial plunger pump
or motor, comprising:
[0011] a casing;
[0012] a main shaft rotatably supported on the casing;
[0013] a rotor cylinder with a plurality of plunger holes, which is
coupled to the main shaft and is driven to rotate about a main
shaft axis by the main shaft and which has an oil-distributing end
surface;
[0014] an oil-distributing disk in cooperation with the
oil-distributing end surface of the rotor cylinder;
[0015] a rotary swash plate, whose end surface is disposed in a
manner axially opposing the plurality of plunger holes of the rotor
cylinder and which can rotate about a swash plate axis forming an
angle with respect to the main shaft axis;
[0016] a plurality of plunger assemblies, an end of each being
articulated to the end surface of the rotary swash plate and
another end of each being slidably disposed in the plunger holes of
the rotor cylinder;
[0017] a constant velocity universal coupling, which is provided
between the rotary swash plate and the main shaft and transmits
torque therebetween, so that the main shaft and the rotary swash
plate rotate about the main shaft axis and the rotary swash plate
axis with an angle therebetween, respectively.
[0018] In the invention, said constant velocity universal coupling
may be a Rzeppa constant velocity universal coupling, a half
angular Rzeppa constant velocity universal coupling, a ball joint
constant velocity universal coupling or a Weiss constant velocity
university coupling and etc.
[0019] The Rzeppa constant velocity universal coupling in the
invention comprises an inner race ring with an outer raceway, an
even number of steel balls, a holder and an outer race ring with an
inner raceway, wherein said steel balls are arranged on the holder
and are located in the inner raceway and the outer raceway, said
inner race ring is coupled to the main shaft, said outer race ring
is coupled to the rotary swash plate, such that the main shaft and
the rotary swash plate are respectively rotated about the main
shaft axis and the swash plate axis via the Rzeppa constant
velocity universal coupling.
[0020] In the invention, as a particular example, said outer race
ring may be integrally formed on the rotary swash plate.
[0021] In the invention, as an alternative example, said rotary
swash plate may be supported on the casing via a swash plate
bearing.
[0022] In the invention, as another alternative example, said
rotary swash plate is supported on a pendulous disk via a swash
plate bearing, the pendulous disk is supported on said casing via a
pendulous disk bearing, and a rotation axis of the pendulous disk
bearing is perpendicular to the main shaft axis and passes through
the center of the constant velocity universal coupling.
[0023] In the above example, said pendulous disk may be connected
with a variable displacement adjustment mechanism for adjusting the
deflection angle of the pendulous disk, such that an angle between
the swash plate axis of the rotary swash plate supported thereon
and the main shaft axis is adjusted through changing the deflection
angle of the pendulous disk, and therefore the strokes of the
plunger assemblies are changed so as to carry out variable
displacement adjustment.
[0024] As an alternative example, said variable displacement
adjustment mechanism in the invention is a variable displacement
oil cylinder, the piston of which is connected to the pendulous
disk so as to drive the pendulous disk to deflect through extending
and retracting of the piston.
[0025] As another alternative example, the variable displacement
adjustment mechanism is a variable displacement adjustment
mechanism of a trunnion type, which includes a trunnion connected
to the pendulous disk and a driving mechanism for driving the
trunnion to rotate, a rotation axis of the trunnion is coincident
with the rotation axis of the pendulous disk so as to drive the
pendulous disk to deflect through rotation of the trunnion.
[0026] In the invention, said rotor cylinder is in a taper shape, a
diameter thereof at the end closer to the rotary swash plate is
larger than that at the other end.
[0027] In the above-mentioned example, the plurality of plunger
holes on said rotor cylinder are also distributed in a taper form,
wherein the diameter of the circle in which the plunger hole center
is located at the end in corporation with the plunger assemblies is
larger than that at the other end.
[0028] In the invention, said plunger assembly may particularly be
a plunger assembly of a ball joint type, which comprises a plunger
and a ball-headed rod with a ball head at each of both ends
thereof, in an end surface of said rotary swash plate there is
provided with a socket, a ball head at an end of the ball-headed
rod is located in the socket to form a ball-joint connection with
the rotary swash plate, and a ball head at the other end thereof is
located in the plunger to form a ball-joint connection with the
plunger, and the plunger is slidably provided in the plunger hole.
In the middle portion of the ball-headed rod and the plunger there
is provided with an oil hole in communication with the plunger
holes so as to introduce pressurized oil to lubricate the ball head
at the both ends.
[0029] In the invention, articulation centers of said plurality of
plunger assemblies on the rotary swash plate are located in a same
plane, and an intersection point of the plane with the main shaft
axis is coincident with the center of the constant velocity
universal coupling.
[0030] In the invention, said rotor cylinder is provided with an
oil-distribution disk at the rear end thereof, the rotor cylinder
is axially positioned along the main shaft through a pressure
spring and a pressure spring stop collar, at an end of the main
shaft there is provided with an oil hole and a radial oil path,
such that the pressure between the rotor cylinder and the
oil-distribution disk is adjusted through introducing pressurized
oil into the radial oil path.
[0031] In the invention, as an alternative embodiment, the
oil-distribution end surface of said rotor cylinder may be a
spherical surface, said oil-distribution disk forms a spherical
surface fit with the oil-distribution end surface.
[0032] In the invention, said swash plate bearing may be a
combination bearing of a needle bearing and a cylindrical or taper
roller thrust bearing. The pendulous disk bearing in the invention
is a needle bearing in a crescent form.
[0033] By employing the above-mentioned structure of the invention,
while the main shaft is driving the rotary cylinder to rotate, the
axial plunger pump or motor according to the invention may drive,
via the constant velocity universal coupling, the rotary swash
plate to rotate about the swash plate axis forming an angle with
respect to the main shaft axis. In this way, the plunger assemblies
reciprocate in the plunger holes of the rotor cylinder, causing
volume variations in the cylinder, and communicate with the inlet
port and the outlet port sequentially via the cooperation with the
oil-distributing disk at the rear end of the rotor cylinder. In
this way, oil-intaking and oil-extruding are carried out, or in
other words, transition between rotation mechanical energy and
hydraulic energy is achieved. Wherein, since the constant velocity
universal coupling transfers the rotating motion and the moment of
the main shaft to the rotary swash plate which is rotating relative
to the main shaft about a inclined axis, the inclination angle of
the rotary swash plate may be changed through driving the pendulous
disk to swing by the variable displacement mechanism, so as to
conveniently perform variable displacement adjustments.
[0034] As compared to a prior art axial plunger pump or motor of a
swash plate type or a prior art axial plunger pump or motor of a
inclined axial type, the axial plunger pump or motor according to
the present invention has the following effects:
[0035] (A) When compared with a variable displacement swash plate
pump, the method of articulating the plunger assembly and the
rotary swash plate is substituted for the sliding shoe and the
swash plate in a swash plate pump, therefore structures
corresponding to the three main friction pairs of the swash plate
pump are changed to a large extent: (i) Sliding friction between
the sliding shoe of the plunger and the swash plate is changed to
rolling friction, thus friction and leakage are decreased, and the
surface area of the ball head which forms a ball joint is larger
than the discal area of a sliding shoe of the same diameter,
thereby the radial dimension of the swash plate is decreased; (ii)
As for the friction pair between the plunger and the rotor
cylinder, the friction force is accordingly decreased since the
lateral pressure is much less than in the case of the swash plate
pump, the requirement on the accuracy of oil-filtering is largely
relaxed, and the wearing is suppressed. (iii) As for the friction
pair between the rotor cylinder and the oil-distribution disk,
since the main shaft is free of the bending moment and only serves
to support at the rotor end, the dimension of the friction pair can
be reduced, thereby the diameter of the oil-distributing port of
the rotor cylinder may decreased, such that the circumference of
the oil port and the linear velocity of the relative motion is
decreased and the power loss due to friction and leakage is
suppressed. In addition, since the inclination angle .beta. of the
rotary swash plate of the pump may be increased to 25 through 30
degrees (not larger than 20 degrees in case of a swash plate pump),
the variation range of flow flux is enlarged, the dimension of the
pump is decreased and the pump performance in oil-intaking is thus
improved since the circumferential speed of the oil cylinder is
decreased; at the same time, the hydraulic thrusting acted upon the
plunger is directly transferred to the casing through the ball
head, the rotary swash plate, the bearing and the pendulous disk
support, such that movement components, such as the main shaft and
the rotor cylinder, etc., are free of other additional forces and
moments. In this way, the force profile of the movement components
is improved, and friction and leakage are suppressed. The above
factors have the following effects:
[0036] (1) a higher overall efficiency than that of a swash plate
pump, (2) an increased structural strength, a higher impact
resistance, an increased resistance to staining from oil, a
decreased wearing and an extended service life, (3) an increased
rotation speed limit of such a pump or motor, (4) a further
decreased dimension of such a pump or motor.
[0037] (B) When compared with a variable displacement bent axis
axial plunger pump, although in structural point of view, a
synchronous constant velocity universal coupling is added, leading
to a certain power loss (generally, 1-3%), four benefits can be
obtained, that is:
[0038] (1) a decreased volume and a decreased weight. The means of
deflecting and adjusting the pendulous disk is substituted for
swinging the rotor body, so the radial dimension required by the
same deflection angle is decreased. Because of the change of the
force profile, the power shaft is subject to a large bending moment
while being acted upon by a torque, thus a certain axial length is
necessary for the purpose of balancing, leading to a longer power
shaft; in addition, the oil-distributing disk, the pendulous disk
and the variable displacement adjustment mechanism located at the
afterbody may occupy large space. With the same parameters, the
axial length and the radial dimension of the inventive variable
displacement plunger pump is decreased by more than 1/3 as compared
to the conventional bent axis axial plunger pump.
[0039] (2) coaxial transmission or transmission by a common shaft
is achieved. It is suitable for applications of limited
installation space which needs coaxial transmission or transmission
by a common shaft, such as the case in which a plurality of pumps
are required to be connected in serials. This may simplify or
optimize the mechanical systems in some application.
[0040] (3) an easy adjustment and switch. The output flow flux may
be adjusted only by varying the inclination angle of the pendulous
disk, and the flow direction and the switch between pump and motor
may be changed simply by changing the direction of inclination
angle. However, in prior art inclined axial plunger pump, a large
stroke space and drive power are necessary to perform the same
implementation.
[0041] (4) a further increased efficiency. Although the additional
constant velocity universal coupling leads to a somewhat decrease
in the efficiency, the prior art structure, which needs three
heavy-duty bearings to bear the radial force, the axial force and
the bending moment of the main shaft, is significantly simplified,
i.e., only one heavy-duty bearing is needed. Thus the power loss
due to friction is lowered, this is because the power shaft is free
of bending moment and the end surface bearing functions to
positioning only. The inventive structure dispenses with a sliding
fit surface between the oil-distributing disk and the velocity
adjusting disk as compared with the prior art mechanism which
carries out velocity adjustment through swinging the rotor, thus
corresponding leakage is suppressed and the volume efficiency is
increased. In this way, the overall efficiency is higher than a
conventional variable displacement bent axis axial plunger
pump.
DRAWINGS
[0042] FIG. 1 is a schematic view of the structure of a prior art
swash plate pump;
[0043] FIG. 2 is a sectional view taken along line A-A in FIG.
1;
[0044] FIG. 3 is a schematic view of the structure of a prior art
bent axis axial plunger pump;
[0045] FIG. 4 is a view showing the principles of the structure of
the invention;
[0046] FIG. 5 is a schematic view showing the structure of the
embodiment 1 of the invention in a front view;
[0047] FIG. 6 is a sectional view taken along line A-A in FIG.
5;
[0048] FIG. 7 is a sectional view taken along line B-B in FIG.
6;
[0049] FIG. 8 is a schematic view showing the structure of the
embodiment 2 of the invention in a front view;
[0050] FIG. 9 is a schematic view showing the assembly structure of
a Rzeppa constant velocity universal coupling; and
[0051] FIG. 10 is a perspective view showing the exploded structure
of the Rzeppa constant velocity universal coupling.
DESCRIPTION OF REFERENCE NUMBERS
[0052] 1--casing, 2--pendulous disk bearing, 3--
DETAILED DESCRIPTION OF EMBODIMENTS
[0053] As shown in FIG. 4, an axial plunger pump or a motor
according to the invention mainly includes a casing 1, a main shaft
4 rotatably supported on the casing 1, a rotor cylinder 14 with a
plurality of plunger holes which is coupled to the main shaft 4 and
is driven to rotate about the main shaft axis 41 by the main shaft
4 and which has an oil-distributing end surface, an
oil-distributing disk 15 in cooperation with the oil-distributing
end surface of the rotor cylinder 14, a rotary swash plate 9 whose
end surface is disposed in a manner axially opposing the plurality
of plunger holes of the rotor cylinder 14 and which may rotate
about the swash plate axis 91 forming an angle with respect to the
main shaft axis 41, a plurality of plunger assemblies 10, an end of
each articulated to an end surface of the rotary swash plate 9 and
another end of each slidably disposed in the plunger holes of the
rotor cylinder 14, a constant velocity universal coupling 11 which
is provided between the rotary swash plate 9 and the main shaft 4
and transmits torque therebetween, and which rotates the main shaft
4 and the rotary swash plate 9 about the main shaft axis 41 and the
swash plate axis 91 forming an angle therebetween, respectively. In
this way, when the invention is employed as an axial plunger pump,
the main shaft 4 is driven to rotate about the main shaft axis 41,
and the rotary swash plate 9 is driven, by constant velocity
universal coupling 11, to rotate about the swash plate axis 91
forming an angle with respect to the main shaft axis 41. Thus the
plunger assemblies 10 axially reciprocate in the plunger holes of
the rotor cylinder 14, causing volume variations in the rotor
cylinder 14 to carry out oil-intaking and oil-extruding, or in
other words, transition between rotation mechanical energy and
hydraulic energy is achieved. When the invention is employed as an
axial plunger motor, the rotary swash plate 9 rotates about the
swash plate axis 91 by the hydraulic oil in the plunger holes so as
to drive the main shaft 4 to rotate about the main shaft axis 41
via the constant velocity universal coupling 11 and to drive the
rotor cylinder 14 coupled with the main shaft 4 to rotate
simultaneously. In this way, the plunger assemblies 10 reciprocate
in the plunger holes, such that hydraulic energy is transited to
rotary mechanical energy of the main shaft. In view of similarity
in basic structures whether the inventive axial plunger pump or
motor is employed as a pump or as a hydraulic motor, the present
invention will mainly describe in detail the situation where the
inventive axial plunger pump or motor is employed as a pump.
[0054] In the present invention, as one particular example, the
casing 1 and a rear end cap 18 are connected to each other via
screws so as to form a closed box, and the main shaft 9 is
supported in the box via a front bearing 6 and a rear bearing 16,
as shown in FIGS. 4 to 7. An inlet slot and an outlet slot in the
oil-distributing disk 15 are communicated with an inlet port 13 and
an outlet port 20, respectively. The main shaft 9 penetrates
through the oil-distributing disk 15, the rotor cylinder 14, a
pressure spring 19, the constant velocity universal coupling 11 and
the rotary swash plate 9 in order, and projects through an end seal
cap 5 from an end of the box. The rotor cylinder 14 is
circumferentially fixed to the main shaft 4 via a spline, and is
pressed against the oil-distributing disk 15 by the pressure spring
19 surrounding the main shaft 4 so as to achieve an initial seal
between the rotor cylinder 14 and the oil-distributing disk 15. The
rotating main shaft 4 drives rotary swash plate 9 to rotate about
the swash plate axis 91 via the constant velocity universal
coupling 11, while driving the rotor cylinder 14 to rotate via the
spline. In this way, the plunger assemblies 10 are driven to
reciprocate in the plunger holes in the rotor cylinder 14, causing
volume variations in the plunger holes. These plunger holes
communicates with the inlet port 13 and the outlet port 20
sequentially via the cooperation with the oil-distributing disk 15.
In this way, oil-intaking and oil-extruding are conducted, i.e.,
transition between rotation mechanical energy and hydraulic energy
is achieved.
[0055] In the invention, the constant velocity universal coupling
11 may be a Rzeppa constant velocity universal coupling, a half
angular Rzeppa constant velocity universal coupling, a ball joint
constant velocity universal coupling or a Weiss constant velocity
university coupling, etc. The invention mainly takes a Rzeppa
constant velocity universal coupling as an example and gives a
detailed explanation thereof. Other types of constant velocity
universal coupling, such as a half angular Rzeppa constant velocity
universal coupling, a ball joint constant velocity universal
coupling, a Weiss constant velocity university coupling, and the
like, are also applicable if it is permitted by space dimension,
even though their structures are relatively complicated as compared
with the structure of a Rzeppa constant velocity universal
coupling. Therefore detailed explanations thereof are omitted. As
shown in FIGS. 5 through 10, in an example where the constant
velocity universal coupling 11 is a Rzeppa constant velocity
universal coupling, it comprises an inner race ring 111 with an
outer raceway, an even number of steel balls 112, a holder 113 and
an outer race ring 114 with an inner raceway, wherein the outer
race ring 114 is coupled to the rotary swash plate 9 and the inner
race ring 111 is coupled to the main shaft 4, such that the main
shaft 4 can drive the rotary swash plate 9 which is coupled to the
outer race ring 114 to rotate about the swash plate axis 91 forming
an angle with respect to the main shaft axis 41 (i.e., the rotation
axis about which the outer race ring 114 rotates) while driving the
inner race ring 111 to rotate about the main shaft axis 41. As a
particular example, the inner holes of the outer race ring and the
rotary swash plate 9 may be combined so as to integrate the outer
race ring 114 with the rotary swash plate 9, thus space
effectiveness in the radial direction is ensured. Even though the
inner race ring 111 and the main shaft 4 may also be combined such
that the inner race ring 111 is integrated with the main shaft 4,
in this embodiment, they are provided separately in consideration
of manufacture process and installation feasibility, the inner race
ring 111 is circumferentially fixedly coupled to the main shaft 4
via a spline and is restrained in the axial direction by a stop
collar 21 on the shaft. As shown in FIG. 9, according the
principles of a Rzeppa constant velocity universal coupling, the
sphere centers of both the inner race ring and the outer race ring
should be arranged on the main shaft axis 41 and be located on each
side of the center point of the constant velocity universal
coupling 11 with equal distances thereto. The holder 113 confines
the even number of steel balls 112 in a same plane which also
passes through the center point of the coupling.
[0056] As an alternative example, the plurality of plunger
assemblies 10 in the invention may be plunger assembles of a ball
joint type, which comprises a plunger and a ball-headed rod with a
ball head at both ends thereof and which is provided with an oil
hole for introducing pressurized oil to lubricate the ball head at
the both ends. The structure of the plunger assemblies 10 is the
same as the structure of the plunger assemblies of the bent axis
axial plunger pump. Uniformly distributed on the right end of the
rotary swash plate 9 are a plurality of sockets with their center
points located in a same plane. The ends of ball heads of the
plunger assemblies 10 are imbedded into the sockets of the rotary
swash plate 9 and restrained therein by a retainer plate 23, and
the plunger ends of the plunger assemblies 10 projects into the
plunger holes of the rotor cylinder 14. The number of the plunger
assemblies 10 is equal to the number of the sockets in the rotary
swash plate 9 and the number of plunger holes in the rotor. The
center point of the constant velocity universal coupling 11 is
coincident with the intersection point of the central plane of the
plurality of sockets in the rotary swash plate 9 with the main
shaft axis.
[0057] In the invention, as shown in FIG. 4 through 8, the middle
case of casing 1 and the front end cap may be an integral structure
cast from cast iron or die-cast from aluminum alloy, while the rear
end cap 18 is connected to the middle case via screws. Certainly,
other structural forms may be employed, e.g., the middle case and
the front end cap are separated and they are coupled with each
other via screws. The integral structure has a higher strength, but
it is more difficult to process, contrary to the latter case.
[0058] As shown in FIGS. 4 through 7, as an alternative example of
the invention, in embodiment 1, the axial plunger pump or motor
according to the invention may carry out variable displacement
adjustment. The rotary swash plate 9 may be embedded into a
pendulous disk 7 via a swash plate bearing 8 which can resist a
radial force, an axial force and a bending moment at the same time.
The pendulous disk 7 is supported to the casing 1 via a pendulous
disk bearing 2. The rotation axis of this pendulous disk bearing 2
is perpendicular to the main shaft axis 41 and passes through the
center of the constant velocity universal coupling 11. In other
words, the pendulous disk 7 can only swing about the center of the
constant velocity universal coupling 11 in a plane parallel to the
main shaft axis 41. In this way, the inclination angle of the
rotary swash plate 9 (i.e., the inclination angle of the swash
plate axis 91 with respect to the main shaft axis 41) may be
adjusted through deflecting the pendulous disk 7 so as to carry out
variable displacement adjustment. In embodiment 1, as shown in
FIGS. 4 through 7, the pendulous disk 7 may be connected with a
variable displacement adjustment mechanism for adjusting the
deflection angle of the pendulous disk 7. The constant velocity
universal coupling 11 transfers the rotation motion of the main
shaft 4 and thus the moment to the rotary swash plate 9 rotating
about the swash plate axis 91, therefore it is very convenient to
carry out variable displacement adjustment of a pump or motor
through driving, via the variable displacement adjustment
mechanism, the pendulous disk 7 to swing so as to change the
inclination angle of the rotary swash plate 9.
[0059] As shown in FIG. 4 through 6, in the embodiment 1, the
pendulous disk 7 comprises an upper partial cylinder and a lower
partial cylinder, and is supported to the casing 1 via the
pendulous disk bearing 2, with its right end provided with an inner
cylinder surface of a stepped shape for the swash plate bearing 8
to be embedded. As shown in FIG. 6 and FIG. 7, as one example of a
variable displacement adjustment mechanism, the variable
displacement adjustment mechanism may be an variable displacement
adjustment mechanism of a trunnion type which conducts adjustment
from outside. It includes a trunnion 24 connected to the pendulous
disk 7 and a driving mechanism for driving the trunnion 24 to
rotate. The rotation axis of the variable displacement trunnion 24
is coincident with the swing axis of the pendulous disk 7. In this
way, the variable displacement adjustment is achieved through the
peripherally provided driving mechanism driving the trunnion 24 to
rotate. In this example, at one side of the pendulous disk 7 there
may be provided with a seat 26 for the variable displacement
trunnion via a threaded member 27. The variable displacement
trunnion 24 is circumferentially fixedly connected to the trunnion
seat 26 via a spline or a flat key so as to install the variable
displacement trunnion 24 to the pendulous disk 7. Thus, the
structure is simple and straightforward in that the pendulous disk
7 can be driven to swing only through rotating the trunnion 24. As
another example of a variable displacement adjustment mechanism,
the variable displacement adjustment mechanism may also be a
variable displacement oil cylinder 28, the piston of which is
connected to the pendulous disk 7 so as to drive the pendulous disk
7 to deflect through extending and retracting the piston, thereby
carry out variable displacement adjustment. The variable
displacement adjustment mechanism may certainly assume other forms,
for example, they may take use of variable displacement mechanism
of various swash plate pumps, only if the deflection angle of the
pendulous disk 7 can be changed by means of the variable
displacement adjustment mechanisms. Herein explanations thereof are
omitted.
[0060] As shown in FIG. 5 and FIG. 6, the swash plate bearing 2 in
the embodiment 1 may be two needle bearings in a crescent form
which are up and down symmetric. The rotation axis of the bearing 2
is perpendicular to the axis of the main shaft 4 and passes through
the center of the constant velocity universal coupling 11. The
outer race ring of the bearing is fixed to the bearing seat of the
casing 1, and the inner race ring thereof is fixed to the
cylindrical surface of the pendulous disk 7 on the left side or is
integral with the cylindrical surface. The function of the bearing
is to transfer the thrust force acted upon the pendulous disk 7 to
the casing 1 and to suppress the swinging resistance to the
pendulous disk 7. The bearing may be other types of bearing, such
as a sliding bearing.
[0061] In the embodiment 1, the rotary swash plate 9 may be
provided with a flare-shaped inner hole at its left end through
which the main shaft 4 passes, and does not interfere with the main
shaft 4 when swinging with the pendulous disk 7. The rotary swash
plate 9 is also provided with an outer cylinder surface at its left
end so as to install the swash plate bearing 8. The rotary swash
plate 9 has a plurality of sockets on its right end surface, the
center points of which sockets are located in a same plane.
Generally, the number of the sockets is odd, such as 5 to 11. At
the central portion of its right end, the rotary swash plate 9 is
provided with a spherical hole, and there is engraved an inner
raceway along the direction of the main shaft 4, serving as the out
race ring of the Rzeppa constant velocity universal coupling
11.
[0062] As shown in FIG. 8, in the embodiment 2 which is another
embodiment of the invention, the axial plunger pump or motor of the
invention may be applicable to a constant displacement pump. Since
no variable displacement adjustment is needed, the pendulous disk
7, the pendulous disk bearing 2 and the variable displacement
mechanism in embodiment 1 can be dispensed with and the rotary
swash plate 7 can be directly supported at the oblique surface of
the casing 1 by the swash plate bearing 8, such that the whole
structure is very simple and compact.
[0063] The important friction surface in the invention may be
subject to plating or coating, for example, molybdenum disulfide
plating so as to decrease friction loss and improve efficiency and
service life.
[0064] The swash plate bearing 8 of the invention need resist an
axial force, a radial force and a rollover moment from the swash
plate. Therefore, the combination of a needle/cylinder (tape)
roller thrust bearing may be employed, and other types of bearings
or combination bearings are also applicable if only they can
perform the same functions.
[0065] In the present invention, as shown in FIGS. 4 through 6 and
FIG. 8, the main shaft 4 is provided with a spline or a flat key at
its front end so as to be connected to other motive machines or
working machines. On the middle of main shaft 4 there is provided
with splines to be circumferentially fixedly connected to the
constant velocity universal coupling 11 and rotor cylinder 14,
respectively, so as to drive the rotary swash plate 9 and the rotor
cylinder 14 to rotate and to transfer torque. At the middle of the
main shaft 4 there is supported a disk pressure spring 19 with a
pressure spring stop collar 21 and a pressure spring seat. The
pressure spring 19 may also be a cylinder-shaped coil spring.
Generally, a residual pressure method is employed to calculate the
pre-compression force of the spring, with the principle being to
ensure reliable seal between the rotor cylinder 14 and the
oil-distributing disk 15. The right end of the main shaft 4 is
provided with an oil hole and a radial oil path, such that the
pressurized oil introduced from the outside of the pump acts upon
the right end surface of the rotor cylinder 14. Thus, the pressure
between the rotor cylinder 14 and the oil-distributing disk 15 may
be adjusted through adjusting the pressure of the pressurized oil
from outside. In this way, the pressure between the rotor cylinder
14 and the oil-distributing disk 15 can be conveniently adjusted to
ensure a higher overall efficiency of the pump under various
working conditions.
[0066] As shown in FIGS. 4 through 6 and FIG. 8, the rotor cylinder
14 in the invention may be a cylinder with a plurality of plunger
holes arranged uniformly in the circumferential direction. These
plunger holes are in a close movable fit with the plungers of the
plunger assemblies 10. As shown in FIG. 5 and FIG. 8, the
oil-distribution end surface of the rotor cylinder 14 is a spheric
surface, which is in a close fit with the spheric oil-distributing
disk 15, thus generating a spheric surface fit therebetween and
presenting a good self-centering characteristics. The rotor
cylinder 14 may be made of such materials as copper, spheroidal
graphite cast iron, cast steel, forged steel, etc. The inner
surface of the plunger holes and the spheric oil-distribution
surface are subject to the treatment (such as embedding and
plating) to decrease friction and enhance wear resistance. Since
the constant velocity universal coupling 11 should be installed at
the center of the rotary swash plate 9, the radial dimension
thereof will consequentially be increased in case of the pump of
small displacement. In this case, the rotor cylinder 14 may be
formed in a taper shape, that is, its diameter on the left end is
larger than its diameter on the right end. The plurality of plunger
holes are shaped in a taper form, wherein, the diameter of the
circle in which the plunger hole center is located at the end (in
the left end of the drawing) in corporation with the plunger
assemblies 10 is larger than that at the other end (in the right of
end the drawing). In this way, it is not necessary to increase the
diameter of the rotor cylinder 14 on the whole, and it is possible
to decrease the diameter of the oil-distribution hole. As shown in
FIG. 4, the oil-distribution end surface of the rotor cylinder 14
may be in a planar form, such that the process is easy.
[0067] Next, the characteristics of the structure dimensions of the
invention will be set forth in combination with calculation of
particular parameters of the variable displacement pump as
described in the embodiment 1 according to the invention, which has
a displacement of 16 l/r and a rating pressure of 35 Mpa.
[0068] Assuming the number of the plungers of this pump is 7, thus
each plunger has an effective volume of 2.3 ml. The maximal stroke
of the piston is 1.8 cm to 2.0 cm, and the diameter of the plunger
is 12 mm to 13 mm. The diameter of the circle in which the plunger
center is located is dependent on the swinging angle of the
pendulous disk 7. The swinging angle is chosen to be 20 degrees
according to experience, such that the diameter of said circle
should be 56 mm. The outer diameter of the rotor cylinder 14 is 75
mm.times.40 mm. The rating output torque of the pump is 89 Nm,
therefore, the diameter of the power shaft (main shaft 4) which
employs simple steel is only between 15 mm and 20 mm. In
consideration of the constrains on strength, dimension and angle of
the constant velocity universal coupling 11 itself, and the
strength and stiffness of the power shaft, the rotor cylinder 14 is
formed in a taper shape, the rotor diameter at the larger end being
82 mm and that at the smaller end being 72 mm. The rotary swash
plate 9 has a diameter of 85 mm, and the pendulous disk 7 has a
diameter of 100 mm. Thus the dimension of the whole pump is 120
mm.times.150 mm (the extension length of the shaft end not
included). Obviously, the dimension and the weight of the pump are
smaller than those of the swash plate pump with the same
displacement, and are even much smaller than those of the bent axis
axial plunger pump.
* * * * *