US20200217314A1

US20200217314A1 - Oscillating piston pump for fluids

Info

Publication number: US20200217314A1
Application number: US16/639,159
Authority: US
Inventors: Conrad Nickel; Franz Pawellek
Original assignee: Nidec GPM GmbH
Current assignee: Nidec GPM GmbH
Priority date: 2017-09-28
Filing date: 2018-07-16
Publication date: 2020-07-09
Also published as: DE102017122611B3; BR112020004076A2; WO2019063159A1; CN111164311B; EP3688309A1; CN111164311A

Abstract

The invention relates to an oscillating piston pump for liquid and gaseous fluids, comprising: a pump housing having at least two sector-shaped working chambers, which are diametrically opposed relative to a pivot axis arranged in-between; an oscillating piston, having at least two displacement portions which extend diametrically relative to the pivot axis and are each received pivotably in one of the working chambers; an electric drive, which moves the oscillating piston alternately on a pivot movement between two turning points delimited within the working chambers; a group of outlet valves, which ensure the discharge of a volume displaced from the working chambers to a pump outlet; and a group of inlet valves, which ensure the entry of a volume flowing into the working chambers from a pump inlet. The group of outlet valves or inlet valves is arranged on both sides of each working chamber and communicates through the pump housing with the pump outlet or the pump inlet. The other group of inlet valves or outlet valves is arranged in the oscillating piston and communicates via a cavity in the oscillating piston with the pump inlet or the pump outlet.

Description

The present invention relates to an electric swivel piston pump for liquid and gaseous fluids, which may be applied universally for different applications, e. g., as an oil pump or as a compressor.
For this purpose, primarily revolving displacement pumps, for example, vane pumps or rotary vane pumps, are known in the related art, which are widely used for liquid as well as gaseous fluids. During production, a great number of components, such as vanes, springs and seals, must be installed at such vane pumps due to their configuration. Furthermore, in order to ensure a long durability, numerous fits relevant for sliding or sealing must be manufactured with great dimensional accuracy at vanes, sliding slit pockets and the like, because occasional tolerance deviations limit the functionality.
In addition, non-revolving displacement pumps with oscillating pump components, such as swivel piston pumps or pendulum piston pump, are known from other applications, e.g. oil-free vacuum pumps, which are able to operate with gasses without a lubrication supply, the pistons of the pendulum running up against an air cushion at a stationary chamber wall. The pump assembly of such swivel piston pump may include relatively few components, i.e., a piston capable of swinging or a pendulum, and a pump chamber with valves, to be more precise.
The patent application DE 10 2016 119 985.0 of the same applicant, which was not yet published on the date of filing of the present patent application, describes a pendulum piston pump in an exemplary application as an oil-free vacuum pump at a break booster of a vehicle.
This pendulum piston pump includes a pendulum, a pump housing, a plurality of check valves, intake ports and an eccentric driving mechanism. The pendulum is pivotable around a pivot point and has two pistons. The pump housing has two sector-shaped pump chamber segments and lateral run-up surfaces that respectively limit outer-most positions of the pivoting motion of the pendulum at each piston. Check valves unblock a connection to the outside when receiving pressure from the pump chamber segments. Intake ports of the inlet are closed against the pump chamber segments during the pivoting motion of the pendulum due to an overlap with the respective piston. They are unblocked in a turning area when passing through the outermost position of the piston. An eccentric driving mechanism is provided between the pendulum and an electric motor.
Such pendulum piston pumps or swivel piston pumps are relatively compact and powerful and have a simple assembly with few individual pump components. However, they are limited to the supply of gasses, i.e., compressible mediums.
The object of the present invention is to provide another compact pump with an economic assembly that is also suitable for supplying fluids or liquid mediums.
This object is achieved according to the present invention with a swivel piston pump having the features of claim 1 for liquid and gaseous fluids.
The electrically driven swivel piston pump comprising, among other elements, a swivel piston having displacement sections which extend diametrically and which are received in sector-shaped working chambers of a pump housing, as well as a set of inlet valves or outlet valves arranged on both sides of the working chambers, is particularly characterized by the fact that the other set of the inlet valves or outlet valves is disposed in the swivel piston and communicates with the pump inlet or the pump outlet via a cavity in the swivel piston.
The invention thus provides, for the first time, a swivel piston pump of which the inlet guide or outlet guide opens into the working chamber through the pump housing on the one hand and through the swivel piston on the other hand.
In conventional assemblies, in which the inlet guide as well as the outlet guide open into the working chamber through the pump housing, an orifice, usually the one of the inlet guide, is covered by the piston and only temporarily unblocked. A charge exchange with the working chamber may thus only take place during a part of the piston stroke. In order to configure a volumetrically efficient operating path of the piston effectively in favor of the displacement volume for each piston stroke, a corresponding ability for charge exchange only extends to the turning area of the piston. Due to the short available time frame for filling or taking in a pumping medium in an emptied working chamber, such swivel piston pumps or pendulum piston pumps are only suitable for an efficient operation with compressible, gaseous mediums.
By means of the assembly according to the present invention, the orifice of the inlet guide and the orifice of the outlet guide guarantee a continual charge exchange across the entire piston stroke, which enables a volumetrically efficient operation to be realized with incompressible, liquid mediums or a fluid with any arbitrary ratio of gas phase to liquid phase, in addition to compressible, gaseous mediums.
Compared with revolving displacement pumps, such as vane pumps, which are suitable for supplying liquid mediums, the swivel piston pump according to the present invention achieves an improved performance-dimension ratio.
In addition, the assembly of the swivel piston pump according to the present invention includes fewer components compared to vane pumps and fewer sliding contact surfaces, such that it may be produced more economically with respect to assembly work and choice of materials.
Advantageous further embodiments of the swivel piston pump according to the present invention are the object of the dependent claims.
According to an aspect of the invention, the cavity of the swivel piston is opened towards an axial side relative to the pivot axis, and an orifice of the pump inlet or pump outlet facing the swivel piston may be formed in the pump housing so as to overlap an opening cross-section of the cavity.
Due to a corresponding end-face intersection of the inlet guide or the outlet guide between the housing wall and the moved piston, a flow connection may be realized by means of a gap seal or the like without interfering with the piston motion. Compared to a flexible passage or the like, a non-fatiguing flow connection is thus provided.
According to an aspect of the invention, the opening cross-section of the cavity may extend annularly around the pivot axis, and the orifice of the pump inlet or the pump outlet may be disposed centrally with respect to the pivot axis.
This configuration achieves a regular flow cross-section at the intersection between the pump housing and the swivel piston across the entire pivoting motion.
According to an aspect of the invention, the cavity takes the form of a hollow space matching the outer contour of the swivel piston.
Due to this configuration, the flow cross-section is maximized in the swivel piston. At the same time, the oscillating mass of the swivel piston and the necessary material usage is minimized, which lowers a drive power and material costs.
According to an aspect of the invention, the swivel piston may be produced as a moulded plastic part having an overmoulded steel shaft as a pivot axis.
This choice of materials further favors the goals of a low, oscillating mass as well as an economic implementation of the swivel piston as a molding piece.
According to an aspect of the invention, the outlet valves may be formed by flexible lock vanes that release an outlet side of a valve opening.
Due to this configuration, the valves of the pump are provided as economic bent sheet-metal parts or other flexible materials as a single part, which are, for example, punched out in the shape of a brace or the like, formed, and inserted into a receptacle of the pump housing.
According to an aspect of the invention, the inlet valves are each formed by an arrangement of prisms of triangular cross-section which are flexibly movable with respect to each other, said prisms being disposed facing a flow direction with an apex edge of the cross-section and being disposed perpendicularly facing a shut-off direction with a lateral side of the cross-section.
Due to this configuration, the valves of the pump are manufactured by selecting a material of suitable elasticity as a molded piece or even integrally with the molded piece of the swivel piston. The flow-effective shape and alignment of such flexible, prismatic valve elements causes the same to automatically spread or press together as a function of the flow-through direction. In the shown application as inlet valves at a swivel piston, the functionality of closing and opening is additionally, simultaneously supported by the mass inertia of the flexible valve elements in the oscillating acceleration progression of the piston.
According to an aspect of the invention, the electric drive may be configured as a rotary solenoid drive, the armature of which may be pivoted electromagnetically around the pivot axis between two working points, and is fixed non-rotatably with the swivel piston.
The drive concept of a rotary solenoid drive is ideal for the operating mode of an oscillating displacement piston, because the generated and the required torque progression are not constant but increase equally towards the working points of the rotary solenoid or towards the turning points of the swivel piston.
In addition, a direct drive connection may be configured by means of a shaft without eccentric kinematics or the like. In addition, more economic control electronics may be implemented as an ECU common in the related art for a brushless dc motor.
According to an aspect of the invention, the electric drive may be configured as an electrically rotating motor that is coupled to the swivel piston via an eccentric actuator mechanism.
In the case of this alternative, an available variety of economic standard drives may be used at least with respect to the electric motor.

The invention is described below in detail based on one exemplary embodiment with reference to the drawings. They show:

FIG. 1 a cross-section through the swivel piston pump according to the present invention with a plan view of the swivel piston, the working chambers and the valves;

FIG. 2 a perspective view of the swivel piston pump according to the present invention with a central intake port and a pressure socket;

FIG. 3 a longitudinal section through the swivel piston pump according to the present invention with a rotary solenoid drive.

First, the structure of an exemplary embodiment of the swivel piston pump according to the present invention designed to be used as an oil pump in a low-pressure lubricant system, e.g., for supplying lubrication oil to gears in a transmission will be described with reference to FIG. 1.
In FIG. 1, at the top left and lower right of a pivot axis 12, two sector-shaped working chambers 10 opposing each other diametrically are illustrated that extend inside the pump housing 1 on one plane with the pivoting motion of the swivel piston 2. The flanks of the working chamber 10 form run-up surfaces for the swivel piston 2.
Illustrated at the top right and lower left of the pivot axis 12, two areas of a pump outlet 14 connected via a bow-shaped channel in the pump housing 1 are arranged between the working chambers 10. Between the working chambers 10 and the pump outlet 14, valve openings are formed in the run-up surfaces of the working chambers 10. The valve openings, together with clasp-like, flexible lock vanes 40 that respectively cover a side lying on the outside with respect to the working chamber 10, of the valve opening, form outlet valves 4 of the swivel piston pump.
The swivel piston 2 is fixed on the pivot axis 12 which is simultaneously a drive shaft of the electric drive 3. The swivel piston 2 includes two displacement sections 20 which are alternately pivoted in the working chambers 10 over a rotational angle of approximately 90°, as shown by the double arrow. Between the displacement sections 20, the swivel piston 2 has a circular outer contour. The inside of the swivel piston 2 is a hollow part and opened to the side of the viewer of the illustration, which results in a cavity 25. The cavity 25 surrounds an accommodation of the pivot axis 12 and extends into the displacement sections 20.
Inlet valves 5 of the swivel piston pump are provided in the flanks of the displacement sections 20 that are pivoted towards the run-up surfaces of the working chambers 10. The inlet valves 5 are formed by prismatic sections 50 and openings in the area of the wall of the swivel piston 2 lying therein between. The prismatic sections 50 have a triangular cross-section and are formed integrally with the swivel piston 2 at one end. Due to the fact that in the exemplary embodiment it is inlet valves 5 which allow a sucked-in delivery flow to pass through from the cavity 25 into a working chamber 10 and which are supposed to block in the reverse direction, all triangular cross-sections are arranged in a flow-efficient manner such that they point towards the cavity 25 with an apex and point towards the pump chamber 10 with a surface or hypotenuse of the triangle.
The prismatic sections 50 have a free end towards the open side of the cavity 25, such that they may incline at the free end like cantilevers clamped in on one side when a material with sufficient elasticity is chosen, particularly a plastic material. When the pump medium flows through, the prismatic sections 50 are thus flexibly inclined, either spreading apart at the free end or pressing together depending on the flow direction due to the different flow resistance of the triangular cross-section. A passage function and a blocking function thus result in opposing flow directions.
In the exemplary embodiment of the swivel piston pump, which is configured for use as a lubrication oil pump, that is, for pumping mediums of higher viscosity, a sufficient valve function may already be achieved by means of the illustrated arrangement of three prismatic sections 50 with a central, larger cross-section, and two smaller cross-sections offset thereto, the blocking function being improved by selecting different cross-section sizes.
In FIG. 2, an outer side of a pump cover 11 of the swivel piston pump is illustrated at which an intake port of the pump inlet 15 and a pressure socket of the pump outlet 14 are apparent. The intake port of the pump inlet 15 is arranged centrally with respect to the pivot axis 12 in the pump cover 11, such that it opens directly into the cavity 25 within the circular outer contour of the swivel piston 2, independently of its position. As is apparent from FIGS. 1 and 2, the pressure socket of the pump outlet 14 opens into the area of the pump outlet 14 illustrated at the lower left of the pivot axis 12.
As shown in FIG. 3, the pump housing 1 furthermore includes a flange section, in which an electric drive 3 is accommodated, directed in the direction of the working chamber 10. At a side of the pump housing 1 shown on the right, another flange section closed by a cover 13 is provided in which a control circuit 34 of the electric drive 3 is accommodated. Lead terminals leading towards solenoids 30 of the electric drive 3 exit from the pump housing 1 through a socket illustrated as being directed upwards.
In the shown embodiment, the electric drive 3 is provided by what is called a bistable rotary solenoid including two solenoids 30 and an armature 32. The solenoids 30 are axially separated from one another and are in contact with two pole rings 31, which are also axially separated, and with a coaxial ferrite core 33. The armature 32 is pivotable on the pivot axis 12 and has two armature bodies which each have a diametrically longer extension of the circumference and, offset by 90° thereto, a diametrically shorter extension of the circumference, i.e., for example, a circular area with two ring segments recessed at the inside opposite of one another. The armature bodies are each accommodated and mounted in a central recess of a pole ring 31. Each recess of the pole rings 31 has two opposing pole shoes.
When one of the solenoids 30 is supplied with current, the armature 32 pivots into a position by means of a reluctance force, in which the corresponding armature body aligns itself with its longer diametric extension between the pole shoes of the recess of the corresponding pole ring 31 in order to decrease the air gap and thus the magnetic resistance in a magnetic circuit passing through the solenoid 30, the ferrite core 33, the pole ring 31 and the armature body.
The pole shoes of the two pole rings 31 or the two armature bodies of the armature body 32 are off-set to one another by 90°. Thus an alternating pivoting motion of the pivot axis 12 by 90° is generated when the two solenoids 30 are alternately supplied with current by the control circuit 34.
In the following, the functionality of the swivel piston pump will be explained.
When the swivel piston 2 moves from the initial position shown in FIG. 1 in a counterclockwise direction, a volume of the pumping medium is displaced in front of the swivel piston 2 or discharged from the working chambers 10. The flexible lock vanes 40 of the outlet valves 4 are thereby pushed in an outward direction at the pressure side of the swivel piston 2 in the pump housing 1 and unblock the valve openings. The prismatic sections 50 of the inlet valves 5 at the front pressure side of the swivel piston 2 are press against one another at the free ends and block a passage to the cavity 25.
At the same time, negative pressure is generated in a section of the working chamber 10 at the rear side of the swivel piston 2 such that a volume of the pumping medium sucked in through the pump inlet 15 follows and flows into the working chamber 10. Prismatic sections 50 of the inlet valves 5 at the rear intake side of the swivel piston 2 are thereby spread apart the the free ends by the delivery flow taken in and open for a flow from the cavity 25 into the working chamber 10. The flexible lock vanes 40 of the outlet valves 4 are pulled against the valve openings in the pump housing 1 at the intake side of the swivel piston 2 and block the outlet valves 4.
The same functionality is provided in a reverse pivoting motion back to the initial position of the swivel piston 2 in FIG. 1. The swivel piston pump is thus a double-stroke pump.

Claims

1. A swivel piston pump for liquid and gaseous fluids, comprising:

a pump housing having at least two sector-shaped working chambers opposing each other diametrically with respect to a pivot axis positioned therebetween;

a swivel piston having at least two displacement sections which extend diametrically with respect to the pivot axis and which are each received in a swiveling manner in one of the working chambers;

an electrical drive which moves the swivel piston alternately between two turning points on a pivoting motion contained within the working chamber;

a set of outlet valves which allow a volume displaced from the working chambers to exit toward a pump outlet; and a set of inlet valves which allow a volume flowing into the working chambers to enter from a pump inlet; wherein

at least one of the set of outlet valves and set of inlet valves) is arranged on both sides of each working chamber and communicates with one of the pump outlet or and pump inlet through the pump housing; and

configured such that the other set of the inlet valves or set of the outlet valves is disposed in the swivel piston and communicates with the pump inlet or pump outlet via a cavity in the swivel piston.

2. The swivel piston pump according to claim 1, wherein the cavity of the swivel piston is opened towards an axial side relative to the pivot axis, and an orifice of the pump inlet or pump outlet facing the swivel piston is formed in the pump housing so as to overlap an opened cross-section of the cavity).

3. The swivel piston pump according to claim 1, wherein the opened cross-section of the cavity extends annularly around the pivot axis, and the orifice of the pump inlet or pump outlet is disposed centrally with respect to the pivot axis.

4. The swivel piston pump according to claim 1, wherein the cavity takes the form of a hollow space matching the outer contour of the swivel piston.

5. The swivel piston pump according to claim 1, wherein the swivel piston is produced as a molded plastic part having an overmolded steel shaft as the pivot axis.

6. The swivel piston pump according to claim 1, wherein the outlet valves are formed by flexible lock vanes which release an outlet side of a valve opening.

7. The swivel piston pump according to claim 1, wherein the inlet valves are each formed by an arrangement of prisms of triangular cross-section which are flexibly movable with respect to each other, said prisms being disposed with an apex edge of the cross-section facing a flow direction and being disposed perpendicularly facing a shut-off direction with a lateral side of the cross-section.

8. The swivel piston pump according to claim 1, wherein the electrical drive is configured as a rotary solenoid drive having an armature which can be pivoted electromagnetically around a pivot axis between two working points, and is fixed non-rotatably with the swivel piston.

9. The swivel piston pump according to claim 1 7, wherein the electrical drive is configured as an electrically rotating motor that is coupled to the swivel piston via an eccentric actuator mechanism.

10. A method of using a swivel piston pump according to claim 1 for pumping liquid and/or gaseous fluids.

11. A method of using a swivel piston pump according to claim 1 as a lubricating oil pump for a transmission.