US20130115108A1

US20130115108A1 - Hydraulic power system

Info

Publication number: US20130115108A1
Application number: US13/808,290
Authority: US
Inventors: Jacob Segal; Ilan Meiri; Rahamin Nakash
Original assignee: SAN HITEC Ltd
Current assignee: SAN HITEC Ltd
Priority date: 2010-07-06
Filing date: 2011-07-05
Publication date: 2013-05-09
Also published as: WO2012004788A1; IL206839A0; IL206839A

Abstract

A hydraulic power system comprises a hydraulic pump coupled to a brushless motor. The brushless motor may comprise stators having a plurality of windings and at least one outrunning rotor having a plurality of magnetic poles and optionally coupled to a drive shaft via flexible couplings which may be coaxial with the drive shaft and rotor.

Description

FIELD OF THE INVENTION

This invention relates to motorized pumps, in particular hydraulic pumps driven by brushless electric motors.

BACKGROUND OF THE INVENTION

Hydraulic machinery is commonly used to provide compact portable tools which have powerful actions. Such tools may be particularly useful where access is limited, for example in emergency and rescue situations and the like.
Hydraulic tools are driven by pressurized hydraulic fluid at pressures of up to 720 bar or so. The pressurized fluid is typically generated by a hydraulic pump connected to the tool via piping. Various hydraulic pumps may be considered for use with hydraulic tools. For example manually operated pumps or foot pumps may be used where no power supply is available. However, motorized hydraulic pumps are a more convenient and typically more popular option. Currently, the most commonly used power unit for the hydraulic motor is a combustion engine. Alternatively, for lighter-duty use, electric pumps may be used. Where appropriate, these may be integrated into the tool itself.
It is noted that electric pumps may provide more compact power provision for hydraulic tools as they avoid the necessity for a separate power unit and associated lengths of piping. However, the lifetime of an electric motor may be limited by degradation of brushes typically used in mechanical commutators. Commutator brushes become worn during normal use of the motor. Consequently, brushless direct current (DC) motors are often preferred over brushed motors as these obviate the need for a mechanical commutator thereby reducing wear-and-tear and Improving the reliability and longevity of the motor.
A number of publications describe pumps powered by electric meters. For example, WO 2009142284 to JTEKT CORP. and KAGAWA HIROKI [JP] describes an electric pump device for supply of hydraulic pressure to hydraulically actuated equipment that is also of reduced size. The electric pump device is provided with a brushless motor.
Similarly, WO/2009/127471 to CONTINENTAL TEVES AG & CO. OHG [DE] depicts a motor pump aggregate having an electronic activation circuit for the regulated activation of an electrical pump motor which drives the pump, wherein the motor is a brushless electric motor. The pump drive is used in electronic brake control devices in motor vehicles.
Further, WO/2009/102692 to CATERPILLAR INC. [US] describes a dual pump strategy for a hybrid electric automatic transmission necessitating one infernal mechanically driven pump linked to the engine output shaft and an external fixed displacement pump powered by a brushless permanent magnet motor.
Another patent application, WO/2008/117724 to HITACHI, LTD. [JP] describes an electric brake device that has a brushless motor for driving a pump for raising the pressure in a wheel cylinder that is installed on a wheel and generates braking force.
A further application, WO/2008/029624 to DAI KIN INDUSTRIES, LTD. [JP] explains how to improve the structure of the brushless DC motor, especially the structure of the rotor. This reduces the pressure pulsation in a hydraulic pump system.
Similarly, WO/2008/022726 to BUSCH PRODUCTIONS GMBH [DE] describes a system of a rotating-slide vacuum pump or compressor having a brushless disc-rotor synchronous motor fitted in the axial direction to a rotor shaft.
Still another application, WO/2008/017212 to Liu, Jun et at. [CN] is directed to a braking controller of a three-phase permanent magnetic brushless DC motor for directly driving a screw pump.
Finally, WO/2008/016898 to FEDERAL-MOGUL CORPORATION [US] describes a system and method for manufacturing a brushless direct current (BLDC) motor fluid pump.
All the brushless electric motors described in these prior art documents are inrunner brushless motors, in an inrunner motor, windings are provided upon a stator which forms a sleeve around a magnetic rotor. Electric current flowing through the stator windings produces magnetic force driving the magnetic rotor and providing torque.
Commutation of the brushless motors is provided by semiconductor switches which are configured to turn the stator windings on and off at the appropriate times during the revolution of the rotor. Sensors, such as Hall switches for example, may be provided on the stator to detect sensor magnets situated on the rotor, such that the stator windings are switched on only when permanent magnetic poles on the rotor pass thereby.
An alternative configuration for the brushless DC motor is an outrunner motor in which the rotor forms a revolving sleeve about a stationary stator. Outrunners spin much slower than their inrunner counterparts and can produce more torque. However, because the stator is entirely enclosed within the rotor, heat is not easily dissipated from the stator windings leading to possible overheating of the motors. As a result, outrunner motors have not gained ground in mainstream applications such as hydraulic pump systems.
Although inrunner motors used in the prior art hydraulic systems produce less torque and may be heavier than equivalent outrunner motors, if is noted that none of the above cited publications nor other commercially available hydraulic systems include outrunner brushless motors
The need remains therefore for a controllable, powerful, lightweight and compact motorized hydraulic pump system. The system may be used in rescue equipment such as rams or the like used to break down doors for forced entry. Embodiments described herein address this unmet need.

SUMMARY OF THE INVENTION

A hydraulic power system is herein disclosed comprising at least one hydraulic pump coupled to at least one brushless motor. The brushless motor may comprise at least one stator having a plurality of windings and at least one outrunning rotor having a plurality of magnetic poles. The rotor may be configured to rotate around the stator thereby transmitting torque to the hydraulic pump via a drive shaft. Optionally, the rotor may be coupled to the drive shaft via at least one flexible coupling. The flexible coupling may be coaxial with the drive shaft and the rotor.
The system disclosed herein may further comprise a fluid reservoir. A protective sleeve may be configured to encompass the fluid reservoir.
Optionally, the system may comprise a pump housing. The system may further comprise a motor housing. Where appropriate, the pump housing may be contiguous with the motor housing.
In some systems the rotor comprises m magnetic poles. Accordingly, the stator may comprise n windings and m magnetic sensors configured to sense the magnetic poles. Optionally, m and n equal eighteen.
The hydraulic pump may be variously selected from a group consisting of: gear pumps, gerotor pumps, rotary vane pumps, screw pumps, tent axis pumps, axial piston pumps swashplate principle, radial piston pumps, peristaltic pumps and the like.
The hydraulic pump may comprise an inlet and outlet. The outlet may be configured to couple with at least one item of hydraulic machinery. For example, the hydraulic machinery may he selected from a group consisting of: cutters, jacks, rams, spreaders, spreader-cutters and the like.
The system may further comprise a motor controller configured to control operation of the motor. The motor controller may be configured to stop operation of the motor after a predetermined time delay. Optionally, the further comprises at least one temperature sensor configured to monitor temperature of components of the system. Accordingly, the motor controller may be configured to stop or redoes operation of the motor if the temperature exceeds or approaches a threshold value. Optionally, a remote control module may foe provided in communication with the motor controller, the remote control module configured to enable the motor to be controlled remotely.
A further system is disclosed comprising: an outrunner, a hydraulic reservoir, at least one hydraulic cylinder, a coupling, and a hydraulic pump. The pump may comprise an inlet, at least one outlet and a shaft, the outrunner may comprise an outrunner housing, a rotor and a stator, the hydraulic pump may comprise a shaft and a pump housing. Accordingly, the coupling may be coaxial with, positioned between and coupled to both the shaft and the rotor, the pump housing and the outrunner housings may be contiguous to each other and enclose at least the rotor, stator, coupling and shaft, the reservoir may be coupled to the inlet of the pump and the cylinders coupled to each outlet of the pump. Upon rotation of the rotor the shaft may rotate and the cylinders advance.
Where required, the system may be portable.

BRIEF DESCRIPTION OF THE FIGURES

For a better understanding of the invention and to show how it may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings.

With specific reference now to the drawing in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention; the description taken with the drawing making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the accompanying drawings:

FIG. 1 a is an isometric projection of an exemplary embodiment of a hydraulic power system;

FIG. 1 b is a side view of the exemplary embodiment of a hydraulic power system;

FIG. 2 is a cross sectional view of the exemplary embodiment of the hydraulic power system;

FIGS. 3 a and 3 b are isometric views of respectively the stator and the rotor of a brushless outrunning electric motor; and

FIG. 4 is a block diagram representing the main components in a block control system for embodiments of the hydraulic power system.

DETAILED DESCRIPTION OF THE INVENTION

Reference is now made to FIGS. 1 a and 1 b showing an isometric projection and a side view respectively of an exemplary embodiment of a hydraulic power system 100. The system 100 Includes a hydraulic pump unit 120, a motor unit 140 and a fluid reservoir unit 160.
The hydraulic power system 100 is configured to provide power to hydraulic machinery. Accordingly, a fluid outlet 122 is provided via which the pump 120 may be coupled to an external power tool unit (not shown) typically via piping. It is noted that such a power system 100 may be lightweight and compact such that it is readily transported to the required point of use. It will be appreciated that this feature is particularly useful in situations where access is limited, such as in emergency rescue environments or the like. The exemplary embodiment of the hydraulic power system 100 may allow hydraulic machinery, such as jacks, rams, spreaders, spreader-cutters and the like, to be operated in environments inaccessible to larger or heavier power systems.
In order to protect the hydraulic power system, the pump unit 120 and electric motor unit 140 may he housed within protective casings 128, 146. Where appropriate, the motor housing 146 may he contiguous with the pump housing 126. The hydraulic fluid reservoir unit 160 which includes a fluid canister 162 containing hydraulic fluid is typically protected by a protective jacket 164. The protective jacket 164 is configured to sheathe the fluid canister 162 preventing damage being caused thereto for example by being knocked or hanged during use.
It is noted that a solid protective jacket may provide good protection to the canister 162. Nevertheless the protective jacket 164 of the exemplary embodiment has a plurality of holes 165 within its surface; such an arrangement may reduce the weight of the overall system 100. If will be appreciated that protective casings and covers may be constructed from a variety of materials such as metal, hard plastic, or the like as suit requirements.
Reference is now made to the orthogonal cross-sectional views of the exemplary embodiment shown in FIGS. 2 a and 2 b. As noted, the hydraulic power system 100 is provided to power hydraulic equipment typically coupled thereto via piping connected to the external fluid outlet 122 of the pump unit 120. An internal inlet 124 is situated in the interior of the hydraulic power system 100 and is typically in liquid communication with the hydraulic fluid of the reservoir 160. The pump 120 is configured to pump hydraulic fluid from the Internal inlet (not shown) to the outlet 122 (FIG. 1 a) thereby generating high fluid pressure at the external outlet 122. The high pressure hydraulic fluid may then be used to transmit force to the hydraulic power tool coupled thereto.
Various pumps are known in the art which may he used as the hydraulic pump 120 in embodiments of the system 100. For example, pumps such as a gear pumps, gerotor pumps, rotary vane pumps, screw pumps, bent axis pumps, axial piston pumps swashplate principle, radial piston pumps, peristaltic pumps and the like or combinations thereof may be used.
It is a particular feature of the hydraulic power system 100 of the exemplary embodiment that the hydraulic pump 120 is driven by a brushless outrunner electric motor unit 140. The brushless outrunner electric motor 140 includes a stator 142 and a rotor 144.
Reference is now made to FIG. 3 a, showing a side view of the staler 142 includes multiple windings 141 about mountings 143 held stationary relative to the casing 146 (FIG. 2 a). With reference now to FIG. 3 b, showing a out through side view of the rotor 144, the rotor 144 comprises a plurality of magnetic elements 145. An axle shaft 147 is provided which is configured to fit into the mounting 143 of the stator 142 along a central axis. The mounting 143 of the stator is typically nested within the rotor 144 such that the magnetic elements 145 encompass the windings 141 of the stator 142 and rotate freely thereabout. In operation, torque is generated by the magnetic elements 145 exerting force upon the windings 141 as they pass. Other arrangements of the motor may occur to those skilled in the art for example the stator may comprise a multi-poled permanent magnet or the like.
Referring back to FIGS. 2 a and 2 b, the outrunning rotor 142 is coupled to the hydraulic pump 120 via a drive shaft 130. Accordingly, because outrunners produce greater torque than inrunner motors, the outrunning rotor 144 of the exemplary embodiment imparts greater torque upon the drive shaft 130 than would an inrunning rotor in a similarly sized motor. Consequently, it is noted that although the outrunner motor 140 may be lightweight and compact it is able to impart a large torque upon the hydraulic pump 120.
As noted above, outrunner systems are generally considered liable to overheating. As a result, outrunners have traditionally been used for travelling motors, such as those used in model vehicles, such as model aircraft and the like. By the nature of their application, such travelling motors are protected from overheating of the motor by heat dissipation aided by the fast movement of the vehicle. Outrunner systems have not previously been considered practical for applications where the motor is not travelling.
Surprisingly, though, it has been found that outrunner systems may not appreciably overheat in applications requiring intermittent use. Furthermore, it was previously not appreciated that because outrunners generate greater torque, a hydraulic power system driven by an outrunner motor may he able to complete a given task in a much shorter time. Consequently the outrunner motor of such a hydraulic power system is typically operational for short periods resulting in less heating.
For example, in one embodiment an outrunner is used to drive a hydraulic power system coupled to a forced-entry hydraulic power tool. Whereas commercial hydraulic forced entry systems may be capable of breaking down a door in about 60 seconds, the outrunner drivers embodiment has been shown to achieve the same task in only 10 seconds. It is further noted that for a given weight of 2 kg, an outrunner may be able to produce a power of 2800 W whereas an inrunner may produce only 600 W.
Thus, despite the hydraulic system's lack of movement during operation, overheating may be prevented due to the task being completed in a very short period of time. The space between the rotor 144 and the motor housing 146 may also help to prevent overheating of the motor 140.
Typically, the outrunning rotor 144 of the electric motor 140 is coaxial with the drive shaft 130. Furthermore, the rotor 144 of the exemplary embodiment is coupled to the drive shaft 130 via a flexible coupling 132. The flexible coupling 132 is configured to provide some freedom of lateral movement during revolutions, thus reducing wear during revolutions and thereby increasing longevity of the system 100.
Although the number of magnetic poles of the rotor 144 may be selected to suit requirements, according to a specific embodiment an eighteen poled magnetic rotor may be used in combination with a stator having eighteen sets of windings so as to provide torque in the system.
Referring to the block diagram of FIG. 4, in some embodiments it may be preferable to incorporate a hydraulic block control 180 and a motor drive control 110 to provide sophisticated control of the pressure, output flow rate and power output of the system 100 and thus optimize the use of the system.
Hydraulic block control 180 may be used to provide graduated power operation to a hydraulic cylinder 200, for example In law enforcement applications, where personnel may use a forced entry system In two stages. First low power may be applied to slowly and slightly pry open a locked door sufficient to inspect the interior, for example in order to decide bow to proceed. Where appropriate, higher power may then foe applied to quickly and suddenly force the door open. Accordingly, the inhabitants may be surprised preventing their escape or otherwise aiding the law enforcement agents.
As required, the motor controller may be further configured to stop operation of said motor after a predetermined time delay in order to prevent overheating. In still other embodiments, temperature sensors, such as thermometers, thermistors, thermocouples or the like may be provided so as to monitor temperature of the components of the system. Accordingly, the controller may be configured to shut the motor down or reduce its power if the temperature exceeds or approaches a threshold value.
Other embodiments incorporating the hydraulic system may include for example embodiments requiring quiet operation that may be finely controlled, for example slow and gentle raising and lowering of a hospital bed.
As opposed to most commercially available hydraulic forced entry systems, that are equipped with brushed motors that produce sparks and thereby noise, the disclosed system is typically spark-less and may be very quiet.
The system may be configured to additionally include a remote control module in communication with the motor drive control 110 and/or hydraulic control 180, which allows personnel to safely control the hydraulic system from a distance.
In some embodiments the hydraulic system such as in FIG. 2 may weigh as little as eight kilograms only; and thus is fully portable, yet be capable of an operating pressure of up to 500 bar or so.
In other embodiments, high-power batteries may be used in the system to power the motor, for example Ni—Cd or the like further boosting the power of the system in comparison to most currently available systems while reducing the weight of the system.
A person holding ordinary skill in the art would readily recognize that this invention is not limited in its application to the details of construction and the arrangement of components set hereinabove in the mentioned description. It should be appreciated that various modifications can be made without materially changing the scope or spirit of the current invention. It should be noted that practicing the invention is not limited to the applications hereinabove mentioned and many other applications and alterations may be made without departing from the intended scope of the present invention. Also, it is to be understood that the lexicography employed herein is for the purpose of description and should not be taken as limiting.
It should be clear that the description of the embodiments and attached Figures set forth in this specification serves only for a better understanding of the invention, without limiting its scope as covered by the following claims.
It should also he clear that a person skilled in the art, after reading the present specification, can make adjustments or amendments to the attached Figures and above described embodiments that would still be covered by the following claims.

Claims

1. A hydraulic power system comprising at least one hydraulic pump coupled to at least one brushless motor, wherein said brushless motor comprises:

at least one stator having a plurality of windings; and

at least one outrunning rotor having a plurality of magnetic pole;

said rotor being configured to rotate around said stator thereby transmitting torque to said hydraulic pump via a drive shaft.

2. The system of claim 1, wherein said rotor is coupled to said drive shaft via at least one flexible coupling.

3. The system of claim 2, wherein said flexible coupling is coaxial with said drive shaft and said rotor.

4. The system of claim 1 further comprising a fluid reservoir.

5. The system of claim 3 further comprising a protective sleeve configured to encompass said fluid reservoir.

6. The system of claim 1 further comprising a pump housing.

7. The system of claim 1 further comprising a motor housing.

8. The system of claim 6, further comprising a motor housing, wherein said pump housing is contiguous with the motor housing.

9. The system of claim 1, wherein said rotor comprises m magnetic poles, said stator comprises n windings and m magnetic sensors configured to sense said magnetic poles, and m and n equal eighteen.

10. (canceled)

11. (canceled)

12. The system of claim 1, wherein said hydraulic pump is selected from a group consisting of: gear pumps, gerotor pumps, rotary vane pumps, screw pumps, bent axis pumps, axial piston pumps swashplate principle, radial piston pumps, and peristaltic pumps.

13. The system of claim 1, wherein said hydraulic pump comprises an inlet and outlet.

14. The system of claim 13, wherein said outlet is configured to couple with at least one item of hydraulic machinery.

15. The system of claim 14, wherein said hydraulic machinery is selected from a group consisting of: cutters, jacks, rams, spreaders, and spreader-cutters.

16. The system of claim 1 further comprising a motor controller configured to control operation of said motor.

17. The system of claim 16, wherein said motor controller is configured to stop operation of said motor after a predetermined time delay.

18. The system of claim 15 further comprising at least one temperature sensor configured to monitor temperature of components of said system.

19. The system of claim 18, further comprising a motor controller configured to control operation of said motor, wherein said motor controller is configured to stop or reduce operation of said motor if the temperature exceeds or approaches a threshold value.

20. The system of claim 16 further comprising a remote control module in communication with said motor controller, said remote control module being configured to enable said motor to be controlled remotely.

21. A hydraulic power system comprising:

an outrunner comprising an outrunner housing, a rotor, and a stator;

a hydraulic reservoir;

at least one hydraulic cylinder;

a coupling, and

a hydraulic pump comprising an inlet, at least one outlet, a shaft, and a pump housing,

wherein the coupling is coaxial with positioned between and coupled to both the shaft and the rotor,

wherein the pump housing and the outrunner housings are contiguous to each other and enclosing at least the rotor, stator, coupling and shaft.

wherein the reservoir is coupled to the inlet of the pump and the cylinder are coupled to each outlet of the pump, and

whereby upon rotation of the rotor the shaft rotates and the cylinder advance.

22. The system of claim 1, wherein the system is portable.