U.S. patent application number 11/162240 was filed with the patent office on 2007-03-08 for improved design of integrated electro-hydraulic power unit.
This patent application is currently assigned to SAUER-DANFOSS INC.. Invention is credited to Michael D. Gandrud, Jeff L. Herrin, Douglas B. Ruffner.
Application Number | 20070053780 11/162240 |
Document ID | / |
Family ID | 37817124 |
Filed Date | 2007-03-08 |
United States Patent
Application |
20070053780 |
Kind Code |
A1 |
Ruffner; Douglas B. ; et
al. |
March 8, 2007 |
IMPROVED DESIGN OF INTEGRATED ELECTRO-HYDRAULIC POWER UNIT
Abstract
An electro-hydraulic power unit with an improved hydraulic fluid
flow through the unit. The unit accomplishes the improved fluid
flow by having an inlet port in a housing that is fluidly connected
to an electric motor that has a rotor with vanes cast thereon and
at least one opening within the rotor. A hydraulic pump inlet is
fluidly connected to the electric motor such that the vanes of the
electric motor will supply hydraulic fluid to the hydraulic pump
inlet.
Inventors: |
Ruffner; Douglas B.; (Ames,
IA) ; Gandrud; Michael D.; (Ames, IA) ;
Herrin; Jeff L.; (Ankeny, IA) |
Correspondence
Address: |
ZARLEY LAW FIRM P.L.C.
CAPITAL SQUARE
400 LOCUST, SUITE 200
DES MOINES
IA
50309-2350
US
|
Assignee: |
SAUER-DANFOSS INC.
2800 East 13th Street
Ames
IA
|
Family ID: |
37817124 |
Appl. No.: |
11/162240 |
Filed: |
September 2, 2005 |
Current U.S.
Class: |
417/410.1 |
Current CPC
Class: |
F04B 17/03 20130101;
F04B 1/128 20130101; F04B 1/14 20130101 |
Class at
Publication: |
417/410.1 |
International
Class: |
F04B 35/04 20060101
F04B035/04 |
Claims
1. An electro-hydraulic power unit comprising: a housing; an inlet
port within the housing; an electric motor within the housing that
is fluidly connected to the inlet port and the motor having at
least one opening therein; vanes operatively connected to the
electric motor; and a hydraulic pump fluidly connected to the
electric motor.
2. The electro-hydraulic power unit of claim 1 wherein the electric
motor is an integrated AC electrical motor.
3. The electro-hydraulic power unit of claim 1 wherein the
hydraulic pump is a checkball hydraulic pump.
4. The electro-hydraulic power unit of claim 1 wherein hydraulic
pump is a rotary cam hydraulic power unit.
5. The electro-hydraulic power unit of claim 1 wherein the opening
within the rotor is semi-circular.
6. The electro-hydraulic power unit of claim 1 wherein the rotor of
the electric motor is fluidly connected to the hydraulic pump at a
hydraulic pump inlet.
7. The electro-hydraulic power unit of claim 1 wherein the
hydraulic pump that increases fluid pressure through centrifugal
rotation.
8. The electro-hydraulic power unit of claim 1 wherein the
hydraulic pump has a wobble plate.
9. The electro-hydraulic power unit of claim 8 wherein the opening
within the rotor balances the rotor and the wobble plate.
10. An electro-hydraulic power unit comprising: a housing; an inlet
port within the housing; an electric motor within the housing and
fluidly connected to the inlet port; said electric motor having a
rotor with at least one opening therein; and a hydraulic pump
having an inlet port fluidly connected to the electric motor.
11. The electro-hydraulic power unit of claim 10 wherein the rotor
supplies oil to the inlet port of the hydraulic pump.
12. The electro-hydraulic power unit of claim 10 wherein the
electric motor is an integrated AC electrical motor.
13. The electro-hydraulic power unit of claim 10 wherein the
hydraulic pump is a checkball hydraulic pump.
14. The electro-hydraulic power unit of claim 10 wherein hydraulic
pump is a rotary cam hydraulic power unit.
15. The electro-hydraulic power unit of claim 10 wherein the
opening within the rotor is in a non-symmetric pattern.
16. The electro-hydraulic power unit of claim 10 wherein the
hydraulic pump is a piston pump
17. The electro-hydraulic power unit of claim 10 wherein the
hydraulic pump has a wobble plate.
18. The electro-hydraulic power unit of claim 17 wherein the
openings within the rotor balance, the rotor, and the wobble
plate.
19. The electro-hydraulic power unit of claim 10 wherein a
centrifugal pump is provided to increase fluid pressure through
centrifugal rotation.
20. The electro-hydraulic power unit of claim 18 wherein the
electric motor is an internal permanent magnet motor.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an electrical hydraulic
fluid power converter. More specifically, the present invention
relates to a device that includes an electrical machine coupled to
a hydraulic machine.
[0002] In material handling and other related fields, lift trucks
are often used for transporting heavy materials. Such trucks often
use a large lead acid storage battery or a similar device as a
source of electrical power. Lift trucks also typically use a system
of hydraulic cylinders for the purpose of raising, lowering,
tilting, reaching, shifting, and other load manipulation functions.
With conventional trucks, it is common to use a battery powered
electric motor to turn a hydraulic pump. With this system,
hydraulic pressure and flow are produced by the pump and are
modulated through a system of valves that are fluidly connected to
a series of hydraulic cylinders for moving the payload.
[0003] In the prior art, the use of various direct current electric
motors is well known. Recent developments in the art of solid state
power electronics have enabled the use of alternating current (AC)
motors to perform various functions within industrial trucks. Such
AC motors and their solid state controls provide several advantages
in industrial trucks which are well known in the art.
[0004] Additionally, the use of an electric motor coupled with a
hydraulic pump is well known in the art. An example of a prior art
electro-hydraulic power converter is disclosed by U.S. Pat. No.
5,591,013 to Kawafune et al. The Kawafune et al. patent, as well as
the prior art cited therein discloses a swashplate type axial
piston pump disposed within the center of the rotor of an electric
motor. Advantages and disadvantages of this design are apparent to
persons skilled in the art.
[0005] The present invention improves on Kawafune by teaching a
device which places a rotary cam type hydraulic machine, such as a
hydraulic piston unit or more specifically, a pump, adjacent to and
within the same housing as the electric machine. The best known
forms of rotary cam type hydraulic power machines are the wobble
plate pump and the radial piston pump. Other variations of the
rotary cam hydraulic power units could optionally be used in the
present invention.
[0006] Hydraulic pumps need adequate oil supply to prevent
cavitations and to perform properly. They typically require a
flooded inlet and minimal negative suction head (positive section
head is optimal). In the integrated pump drive, oil is used to cool
the electric motor. This is done by drawing oil across the electric
motor components. Oil enters the unit at one end and is pulled
across the electric motor components where it is available to the
pistons at the opposite end. The flow path across the motor is a
small air gap between the rotor and stator, which is restrictive
and severely limits performance of the pump. Thus, a problem exists
in the art in the method of getting oil from one end of the unit to
the other with minimal resistance. Thus, the present invention
seeks to build upon recent developments in the field of electric
motors and related components for battery powered industrial
trucks.
[0007] The present invention enhances the art of electric fork lift
trucks and similar battery powered industrial vehicles. More
specifically, the present invention pertains to an improved method
of constructing an electro-hydraulic power unit with a rotary cam
hydraulic power unit (pump). In particular, the present invention
teaches an improved method of communicating hydraulic fluid from
the inlet of the assembly to the inlet of the pump contained
therein in a manner that it enhances the suction performance of a
pump and enhances cooling performance of an electric motor. It is
also the intention of the present invention to (1) reduce the cost
of the assembly; (2) improve the dynamic characteristics of the
electric motor; and (3) improve the method to dynamically balance
the mechanical elements in the assembly as a system and not
component by component.
[0008] It is therefore a primary object of the present invention to
provide an electro-hydraulic power converter including a rotary cam
hydraulic power unit that has improved efficiency, reduced costs,
decrease size, simplified installation, improved suction
performance and improved reliability.
[0009] Yet another object of the present invention is to provide
such a unit where the housing provides for a pathway for oil to get
from one end of the unit to another with minimal resistance and
with boosted pressure.
[0010] Another object of the present invention is to provide
openings within the rotor of an electric motor to properly balance
with a wobble plate assembly to minimize inertia on the rotor.
[0011] Yet another object of the present invention is to use rotor
vanes in order to super charge hydraulic pump inlet supply.
[0012] Still another object of the present invention is to provide
an electro-hydraulic power unit that is capable of operating at
increased speed and increased flow rates.
[0013] These and other objects, features, or advantages of the
present invention will become apparent from the specification and
claims.
BRIEF SUMMARY OF THE INVENTION
[0014] An electro-hydraulic power unit having a housing that has an
inlet port within. Additionally within the housing is an electric
motor that is fluidly connected to the inlet port and that has a
specially designed rotor having at least one opening therein. Also,
the rotor has a shorting ring or similar disk with vanes cast onto
the shorting ring that may be used to super charge the hydraulic
pump inlet supply. Additionally, the power unit has a hydraulic
pump that has an inlet fluidly connected to the electric motor. The
power unit is designed so that oil flows into the inlet port of the
housing and into the electric motor where the openings within the
rotor help cause the oil to move to the inlet of the hydraulic
pump.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a perspective view of a shaft rotor, and wobble
plate assembly as used in an electro-hydraulic power unit;
[0016] FIG. 2 is a sectional view of an electro-hydraulic power
unit;
[0017] FIG. 3 is a sectional view of an electro-hydraulic power
unit; and
[0018] FIG. 4 is a sectional view of a stator of an
electro-hydraulic power unit.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0019] With reference to FIGS. 1 and 2, and electric hydraulic
power converter 10 is disclosed with a rotary cam hydraulic power
unit 12. This unit 12 includes a housing 14, and an electric
machine or motor 16, and a supercharged hydraulic machine or pump
18.
[0020] The electric machine, preferably is an alternating current
(AC) induction motor, but may be any conventional electric machine,
including an alternating current (AC) machine; a direct current
(DC) machine; an induction machine; a single phase machine; a three
phase machine; a poly phase machine; a switched reluctance machine;
a written pole machine; a permanent magnet alternating current
(PMAC) machine; a permanent magnet direct current (PMDC) machine; a
shunt wound machine; a series wound machine; a compound wound
machine; a synchronous machine; a separately excited machine; a
brushless machine; a brushed machine; a brushless direct current
machine; and a transversal flux machine.
[0021] The electric machine 16 is controlled and optionally caused
to turn at a desired speed and direction by an electronic
controller (not shown). This electronic controller is preferably a
three phase alternating current inverter. For simplicity, this
inverter may be designed as a variable voltage/variable frequency
inverter. For improved accuracy of control, the inverter is
preferably a vector type or field oriented control type inverter.
The inverter (not shown) preferably contains solid state power
switches which are preassembled into a power module. The inverter
is preferably integrated with the electro-hydraulic unit described
herein. Alternatively, the inverter may optionally be remotely
mounted from the device.
[0022] FIG. 2 shows one embodiment of an electro-hydraulic power
converter wherein the motor of the electric machine is known in the
art as a squirrel cage motor. One skilled in the art will
understand that other electric motors such as an Internal Permanent
Magnet motor may be used. Thus, in FIG. 2 the electric motor 16
includes a stator 20, a stator winding 22 composed of a series of
conductive wires, and a rotating assembly 23 having a rotating
portion known as a rotor 24 comprising a so called "squirrel cage"
assembly 26, and a shaft 28. The stator 20 preferably is pressed
fit into the housing 14. The rotating assembly 23 also includes a
wobble plate 30 which has an inclined surface. As the rotor 24
rotates, the wobble plate 30 will "wobble" with respect to the
hydraulic machine 18. The wobbling motion of the wobble plate will
sequentially press each piston 32 into the respective cylinder bore
34, and gives axial piston pump 18 its name of a wobble plate
pump.
[0023] Additionally, the housing has an inlet port 36 that receives
fluid. The rotor 24 has a plurality of axially lined holes, or
openings, or porting 38 therein to help push the fluid within the
unit directly towards the hydraulic pump inlet 39. Furthermore, in
this embodiment, the rotor 24 has centrifugal pumping fins, or
vanes 40, that are integrally cast onto the rotor 24 shorting ring
42.
[0024] Alternatively, as shown in FIG. 3, an internal permanent
magnet (or IPM) motor design is present. In this embodiment a
plurality of permanent magnets 44 are disposed within the rotor 24.
The stator 20 has a plurality of slots 46 (see FIG. 4) wherein
wires 22 are extended therethrough. When the internal permanent
magnet motor is used, the centrifugal pump fins 40 are formed
integrally with a rotor magnet retainer disk.
[0025] In yet another embodiment, the centrifugal pump fins 40 are
formed on a separate disk that is attached to the wobble plate 30
or the rotor 24. Thus in these embodiments centrifugal pumps are
present. In another embodiment a centrifugal pump is used in
conjunction with a hydraulic piston pump to supercharge fluid. In
all embodiments the centrifugal pump fins are used to supercharge
fluid within the system and cause each embodiment to have a
supercharged hydraulic pump 18.
[0026] In operation, the electro-hydraulic power unit 10 allows for
hydraulic fluid to be drawn into the inlet port 36 and flows along
the fluid line shown by numeral 44. The hydraulic fluid is drawn
from the inlet port 36 past various components of the motor 16,
through the holes or openings 38 within the rotor 24 and is
eventually expelled from the rotor 24 on the pump side. The
centrifugal pumping fins or vanes 40 throw fluid away from the fins
causing the pumping action. Therefore, the centrifugal pumping fins
or vanes 40 provide a "boost" in oil pressure prior to the oil
entering the reciprocating piston pump thus supercharging the
fluid. As the rotor turns, especially at high speed, the vane 40
accelerates the hydraulic fluid radially thus providing a pumping
action. Consequently, the fluid is sucked through the rotor 24 and
pumped into the piston pump.
[0027] Thus, this invention applies to an integrated AC electrical
motor and checkball hydraulic pump. The unit is also used in any
application requiring integration of a pump and electric prime
mover. Additionally, this unit is specifically designed for the
fork lift industry. Furthermore, the unit applies to any
combination of at least one electrical machine, such as, for
example, the integration of a hydraulic motor and an electrical
generator. The unit also could be a single electric motor and a
plurality of hydraulic units.
[0028] Furthermore, by having holes or openings through the motor
rotor 24 minimizes the restriction through the unit of hydraulic
fluid and thus improves filling of the pistons. Additionally, these
openings, or oil ports 38, in one embodiment are to be drilled in a
non-symmetrical pattern, such as semi-circular pattern to
counteract the inherent mechanical imbalance of the wobble plate
30. Thus, the openings, or porting configuration, will be designed
to balance the rotor/wobble plate assembly and minimize inertia
(weight) of the rotor 24. Wobble plate 30 may optionally be
provided with counter-balancing features thus making the wobble
plate internally balanced and removing the need to provide a
counter balanced rotor openings pattern. Therefore, the present
invention creates a simplified balancing of the mechanical
assembly.
[0029] One skilled in the art will also appreciate that the vanes
40, or fins, at the end of the rotor 24 nearest the piston group,
act as an impeller and tend to super charge the piston inlets with
supply fluid. Additionally, this invention provides for improved
filling of the hydraulic pump through pre-charging the oil through
centrifugal pumping action at the face of the rotor 24. Thus, this
causes a cost reduction/simplification of the wobble plate design
and an improved dynamic response of the electric motor through
reduced weight of the rotor 24. Furthermore, by centrifugally
supercharging the piston pump, the piston pump may be operated at
increased speeds therefore increasing the flow rates of hydraulic
fluid. Therefore, at the very least, all of the stated objectives
have been met.
[0030] It will be appreciated by those skilled in the art that
other various modifications could be made to the device without the
parting from the spirit in scope of this invention. All such
modifications and changes fall within the scope of the claims and
are intended to be covered thereby.
* * * * *