Patent Application
20160377082
The present invention relates to an electric motor driven liquid pump. In particular, the invention relates to a liquid pump such as used on a large scale in modern motor vehicles for the forced lubrication of manual transmissions.
A manual transmission, which is arranged in the motor vehicle in a drive train between an internal combustion engine and vehicle wheels to be driven, has a lubricant system for lubrication by a lubricant such as transmission oil, which lubricant system serves the purpose of fetching the lubricant from a lubricant sump in the transmission housing to areas to be lubricated. Included in the latter are, in particular, meshing gearwheels and bearings for rotating parts, particularly shafts and gearwheels.
In conventional lubricant systems in manual transmissions distinction is basically made between splash lubrication, in which the gearwheels ‘splash’ in the lubricant sump and during further rotation distribute the lubricant to the gearwheels and bearings, and forced lubrication by one or more pumps, which convey the lubricant from the lubricant sump by way of a duct system to the places to be lubricated. If forced lubrication alone is provided, i.e. none of the gearwheels intentionally dips into the lubricant sump, this is termed ‘dry sump lubrication’, which by comparison with splash lubrication or combined lubrication has the advantage that there is no induction of air into the lubricant by the gearwheels and thus no formation of oil foam, which can lead to disruptions in the transmission lubrication. In addition, in manual transmissions with dry sump lubrication so-called ‘splash losses’ impairing transmission efficiency are avoided.
Electric motor driven lubricant pumps are already used in the prior art for the lubricant system of manual transmissions with dry sump lubrication (see, for example, document DE-A-10 2005 005 154). Distinction has to be made here between lubricant systems in which the lubricant is conveyed by the pump—usually a gear pump—under pressure to nozzles, by way of which the lubricant is sprayed on the places to be lubricated, and lubricant systems with a pump—for example a centrifugal pump—by which the lubricant is merely conveyed to a distributor with a reservoir, from where the lubricant substantially free of pressure rains down or drips onto mesh zones and bearing locations. The last-mentioned, low-pressure lubricant system represents the field of pump use preferred here, in particular because it offers cost advantages by comparison with the solution involving pressure. Thus, a filter arrangement for avoidance of nozzle blockage is redundant, susceptibility to contamination is less overall, lower motor power can be provided for the electric motor, etc.
Constructional details of an electric motor driven centrifugal pump for lubricant supply of a transmission are evident from, for example, document DE-A-10 2007 018 504 (FIG. 7). In this instance an electric motor and a pump driven by it form a motor/pump unit, which is arranged directly in the lubricant (‘operating medium’ in the terminology of this document) below a liquid level. The electric motor and the pump in this prior art lie in succession and the motor/pump unit is additionally surrounded by a duct system serving the purpose of conducting the intake flow along the surface of the electric motor, which heats up due to operation, to a suction port of the pump. Heat transfer is to be improved and the lubricant heated by thermal contact between the electric motor and the lubricant conducted therealong, so that the viscosity of the lubricant is reduced and thus also the intake resistance. As a result, the conveying rate of the pump is to be increased and thus the quantity of lubricant supplied to the lubricating points; in addition, a downward extension of the temperature range at which the pump can still reliably convey lubricant is intended. A disadvantage of this prior art, however, is that the motor/pump unit together with the duct system therearound demands a relatively large amount of space not only in radial direction, but also in axial direction. However, the available installation space at the bottom of the transmission housing is usually very tightly dimensioned.
In addition, an electric motor driven oil booster pump arranged within an oil pan of an automatic transmission is known from document DE-A-10 2006 012 838 (FIG. 3c). In this prior art, as well, the pump and the electric motor lie in succession, the latter being located outside the oil pan. In that case, drive of the pump takes place mechanically by way of a shaft which passes through the wall of the oil pan and is sealed relative to this wall. This arrangement of pump and electric motor in succession also demands a relatively large amount of space. Moreover, use is preferably made of a brush motor, which, as such, necessarily has to be arranged outside the oil chamber and in addition is susceptible to wear.
Moreover, documents DE-A-199 34 382 and DE-A-199 56 380 disclose liquid pumps usable as cooling water pumps for the cooling circuit/heating circuit of a motor vehicle. These liquid pumps have an integrated electric motor with a stator and a rotor, the stator being a claw pole stator and the rotor forming an impeller of the pump. In this prior art (DE-A-199 34 382: column 3, lines 47 to 51; DE-A-199 45 380: column 4, lines 17 to 22) a magnetic field sensor (not illustrated) can be provided, particularly for commutation of the electric motor, at a location (not specified in more detail) where it is exposed to the variable magnetic field of the rotating rotor.
Similarly, an electric motor driven water pump is known from DE-A-10 2009 049 904 (FIG. 1), in which a partition sealingly arranged between a stator and a rotor unit is constructed in a simpler and more economic manner from a corrosion-resistant material capable of being deep drawn. In that case, a substantially hollow conical retaining element is integrally formed at a central location of the partition, which element is provided on its side facing the rotor unit with a spherical bearing surface for a spherical slide body for mounting the rotor unit and on its side remote from the rotor unit bounds a cavity in which a temperature and/or magnetic field sensor (not illustrated) can be received (see claims 9 and 10 as well as the Abstract [0027] of the description), so that the bearing points for the rotor unit and the sensor are necessarily arranged axially in succession with respect to the axis of rotation of the pump.
Finally, further electric motor driven pumps which are, however, of relatively lengthy construction as seen along the pump rotational axis and which are used as, in particular, water pumps in heating circuits are evident from documents DE-A-100 45 597 (FIGS. 7 and 8) and DE-A-100 52 797 (FIG. 1).
The invention has the object of providing, particularly for forced lubrication of a manual transmission for motor vehicles, an electric motor driven liquid pump which avoids the above disadvantages and in particular has by comparison with the outlined prior art, in a more economic design, a lower constructional height.
This object is fulfilled by the features indicated in claim 1. Advantageous or expedient developments of the invention are the subject matter of claims 2 to 15.
An electric motor driven liquid pump according to the invention, which is usable particularly for forced lubrication of a manual transmission for motor vehicles, comprises a housing, which has a liquid inlet and a liquid outlet, and an electronically commutated electric motor, which is received therein and which comprises a substantially cup-shaped magnetic rotor, which is rotatable about an axis of rotation, with means for conveying liquid, an annular stator, which has a motor winding and which as seen along the axis of rotation at least partly surrounds the rotor in coaxial arrangement with respect to the axis of rotation, and a magnetic field sensor for positional recognition of the rotor, wherein the housing has a stator housing section which carries the stator, separates this from a liquid chamber in which the rotor is arranged and as seen along the axis of rotation extends into the rotor by a housing offset constructed for reception of the magnetic field sensor.
Due to the fact that from the start the drive of the liquid pump according to the invention is formed by an electronically commutated electric motor as distinct from a brush motor, the susceptibility to wear and disturbance as discussed above with respect to the prior art is absent; the liquid pump can also be freely positioned, for example in or directly at an oil chamber of a manual transmission.
In that regard, a particularly compact constructional form is favored at the outset if the rotor is both a pump component (means for liquid conveying) and a motor component (magnetic). Any form of (co-)rotating connection between the drive side and the pump side is thus redundant. Moreover, with respect to low constructional height of a liquid pump according to the invention, the design of the stator housing section, which also separates media in the pump housing, has a special role: on the one hand, the stator housing section carries the annular stator in such a way that this covers the cup-shaped rotor at least partly as seen in axial direction. On the other hand, the stator housing section has the housing offset which protrudes into the cup-shaped rotor and at which the magnetic field sensor for the electronic commutation is received. Through this quasi ‘nested’ arrangement of the components relevant to drive substantially in the rotor plane with utilization as well of the rotor internal area, the liquid pump has a very flat construction. In other words, by contrast to the prior art outlined further above a pure arrangement of the individual components in succession is not present, but rather an arrangement thereof ‘one in the other’.
In an advantageous development of the liquid pump the housing can be flange-mounted on a liquid container by way of a flange surface external to the pump and can have in multi-part construction, apart from the stator housing section, a pump housing section, which has the liquid inlet and liquid outlet and which together with the stator housing section bounds the liquid chamber, and a motor housing section, which together with the stator housing section bounds an electronics chamber in which at least the stator is disposed. In this embodiment the pump housing comprises, in a simpler and more assembly-friendly manner, only a minimum of housing components to separate ‘wet’ regions of the pump from ‘dry’ regions of the pump and to bound the latter overall relative to the liquid or environment/atmosphere, namely (a) the pump housing section as a boundary, which is permeable in defined manner by way of the liquid inlet and outlet, for the liquid, (b) the stator housing section as a media-separating boundary between the ‘wet’ liquid chamber and the ‘dry’ electronics chamber in the pump and (c) the motor housing section as a boundary relative to the rest of the environment/atmosphere.
In principle, the housing components of the liquid pump can consist of a light metal such as, for example, an aluminum alloy. However, with regard to low production costs it is preferred if the housing components are executed as plastics material parts, which can be produced by injection technology, i.e. by plastics material injection molding. A screw connection, rivet connection or snap connection, for example, is conceivable for fastening the housing components to one another. However, for a particularly economic housing design it is preferred if the pump-housing and motor-housing sections produced as plastics material parts are welded together.
Moreover, the stator housing section can have, with respect to a simple and axially as well as radially positionally precise fastening in the housing of the liquid pump, a stator housing flange which is clamped in place between the pump housing section and the motor housing section and which (additionally) centers the stator housing section at the motor housing section with respect to the axis of rotation of the rotor.
In a particularly preferred embodiment of the liquid pump a sealing element can be provided, which—in multi-functional manner—at the same time (firstly) seals relative to the liquid container at the flange surface of the housing external to the pump (‘pump external’ separation between liquid and environment/atmosphere), (secondly) separates the liquid chamber from the electronics chamber (‘pump internal’ media separation) and (thirdly) seals the electronics chamber relative to the environment (sealing against penetration of moisture or contamination of the pump).
By contrast to the current prior art, a multiplicity of seal inserts is not required and does not have to be handled and the disadvantages connected therewith (assembly cost, risk of ‘migration’ of individual seals, etc.) are avoided without alternative measures such as, for example, sealed welding of housing components having to be provided at the housing. Since, in addition, the pump already carries the means for sealing ‘external to pump’, the assembly/flange-mounting of the pump at the liquid container is simple in form. As a result, an inexpensive pump sealing which has process security and thus also reliability can be achieved.
In that regard, the flange surface, which is external to the pump, of the housing can be provided with an encircling groove for receiving a first sealing section of the sealing element, which protrudes by at least one sealing lip, but preferably two sealing lips, beyond the flange surface external to the pump so as to seal relative to the liquid container. A double sealing of that kind seals in a manner which is particularly insensitive to contamination and reliable. Scratches or the like at the flange surface of the liquid container can be ‘bridged over’; consequently, there are no special demands on cleanliness or smoothness of the flange surface.
Moreover, the arrangement can be such that the pump housing section has a pump housing flange at which the flange surface external to the pump and a flange surface internal to the pump are formed at opposite sides, which flange surface internal to the pump is provided with an encircling groove for receiving a second sealing section of the sealing element and which second sealing section protrudes by two sealing lips beyond the flange surface internal to the pump, wherein—in a clearer and unique functional assignment of the sealing lips—one sealing lip co-operates with the stator housing section in order to separate the liquid chamber from the electronics chamber, whilst the other sealing lip co-operates with the motor housing section in order to seal the electronics chamber relative to the environment. In that case, the sealing lips can advantageously compensate for different housing thicknesses—which may differ only due to tolerances—in the flange regions of the stator housing section and the motor housing section.
In addition, the sealing element, consisting of an elastomeric material, can be attached to the pump housing section so that the sealing element is, in a more assembly-friendly manner, a captive component of the liquid pump. In principle, the sealing element can in that case be incorporated in or plugged onto the pump housing section. However, with respect to simple capability of production and process reliability (avoidance of assembly errors) it is preferred if the sealing element is injection-molded at the pump housing section to be interlocking.
For a reliable mechanically positive fixing of the sealing element to the pump housing section there can be provided between the encircling groove at the flange surface external to the pump and the encircling groove at the flange surface internal to the pump a plurality of openings which are spaced apart in circumferential direction and through which the elastomeric material of the sealing element is injection-molded in order to connect the first sealing section and the second sealing section of the sealing element together. The sealing element can thus advantageously be injection-molded on the pump housing section in one working step. In the case of an overlapping or a congruent arrangement of the grooves on the two sides of the pump housing flange the sealing arrangement is also a very compact construction in radial direction. Beyond that, such an arrangement, in which sealing with respect to two sides takes place quasi on one diameter, has the advantage that even in the case of relative ‘soft’ or flexible housing components the risk of leakages due to housing deformation is minimized.
In an advantageous development of the liquid pump, pole sheets of the stator can be embedded in the stator housing section, which consists of a plastics material, by plastics material injection-molding encapsulation. As a result, an optimum heat dissipation from the motor winding and pole sheets to the liquid chamber is made possible. At the same time, the motor winding is electrically insulated by the injection-molded encapsulating plastics material.
In further pursuance of the concept of the invention a temperature sensor can be integrated, preferably near the liquid outlet, in the housing of the liquid pump, in particular received in a receiving recess in the stator housing section, as a result of which an external temperature sensor and the (assembly) cost connected therewith are eliminated in all cases. Through detection of the temperature of the conveyed liquid, a conclusion can be made about its viscosity—which in the case of oil is important for the lubricating effect thereof—together with the need for cooling and the rotational speed of the electric motor can be suitably controlled, in which regard, for example, a tendency to higher temperatures signals a greater need for cooling and thus a requirement for higher pump rotational speeds. Positioning of the temperature sensor near the liquid outlet additionally has the advantage that the temperature detected thereat makes a statement of greatest validity with respect to the characteristics of the liquid delivered by the pump; moreover, there is no risk of erroneous detection due to heat build-up at the liquid outlet as a consequence of the liquid flow taking place thereat when conveying takes place.
Further, an electronic circuit board can be integrated in the housing, which circuit board carries at least the electronic components necessary for electronic commutation of the electric motor as well as optionally the sensor elements and with which contact by the electrical parts of the liquid pump is made by way of press-fit connections. By comparison with welded or soldered connections, which are equally conceivable, press-fit connections can be produced at lower cost.
In a preferred and similarly particularly compact embodiment of the liquid pump the liquid outlet of the housing can in addition be oriented transversely to the axis of rotation of the rotor. Such a radial feed for the liquid to be conveyed functions without problem and without inducting air even in the case of a very low liquid level.
Moreover, it can be provided that the rotor has a permanently magnetic outer cylinder selection, which co-operates with the motor winding, as well as, on the side remote from the housing offset of the stator housing section, a base section which is formed as an impeller and which is injection-molded from a magnetic material, which is incorporated in plastic, directly onto a rotor shaft rotatably mounted in the housing. On the one hand, such a rotor can be produced particularly economically. On the other hand, such a shaft solution has advantages—by comparison with an axle solution which is equally conceivable in principle and in which the rotor rotates on an axis fixed relative to a housing—of such a kind that a bearing shank or the like at the rotor for provision of a sufficient supporting length is redundant, which in turn is conducive to a short constructional length, and the rotational mounting of the rotor shaft in the housing leads to bearing points which are further apart, this being beneficial for good rotation of the rotor.
In principle, the bearing points can in that case ultimately be formed by bearing bushes or the like let into the housing. However, with respect to low costs it is preferred if the rotor shaft is mounted on either side of the base section at least radially directly in the housing, in particular on the one hand in the housing offset of the stator housing section and on the other hand in a bearing extension of the pump housing section.
The invention is explained in more detail in the following by way of preferred embodiments with reference to the accompanying—in part schematic—drawings, in which for simplification of the illustration elastomeric or elastic parts are illustrated in undeformed state and in which:
In the figures the reference numeral 10 designates in general an electric motor driven liquid pump for forced lubrication of a manual transmission for motor vehicles, of which in
An electronically commutated electric motor 26 is received in the housing 16 (see
In a particularly compact embodiment the stator housing section 40 extends, as seen along the axis A of rotation, into the rotor 28 by a housing offset 48, which is constructed for reception of the magnetic field sensor 36. In addition, as will be similarly described in more detail in the following, a sealing element 50 is provided at the housing 16, which sealing element in a triple function simultaneously seals at the flange surface 14, which is external to the pump, of the housing 16 relative to the transmission housing 12, separates the liquid chamber 42 from the electronics chamber 46 and seals the electronics chamber 46 with respect to the environment.
Further details with respect to the pump housing section 38, which is constructed as a plastics material part from a laser-transparent, glass-fiber-reinforced polyphthalamide (PPA 35 GF), can be inferred from, in particular
The pump housing section 38 is formed with a dome-like elevation radially within the pump housing flange 52 and bounds, in part together with the rotor 28 and the stator housing section 40, in the region of the liquid chamber 42 a pump channel 56 which can be substantially divided into four regions, namely—as seen in direction from radially inwardly to radially outwardly—(1st) a central, i.e. centered with respect to the axis A of rotation, substantially funnel-shaped inlet region 58 (see, in particular,
According to
The motor housing section 44, which is similarly injection-molded as a plastics material part from a glass-fiber reinforced polyphthalamide (PPA 50 GF), is laser-welded to the pump housing section 38—suitably aligned indirectly by way of the stator housing section 40—and in particular with its collar 72 encircling in the groove 70 of the pump housing flange 52 (indicated in
In the illustrated embodiment the motor housing section 44 has, radially outwardly, four fastening eyes 80 which are each lined by a metallic sleeve 82 encapsulated in interlocking manner by injection-molding. As illustrated in
The motor housing section 44 is provided between the fastening eyes 80 on the left in
The stator housing section 40 is also injection-molded as a plastics material part from a glass-fiber-reinforced polyphthalamide (PPA 50 GF). In that regard, not only the said electrical conductors 90, but also the pole sheets 102 of the stator 34 are embedded by injection-molding encapsulation by the plastics material of the stator housing section 40. Only after the injection-molding process is the motor winding 32 mounted, which is economically constructed as an orthogonal layer winding. The stator 34 is completed by a slotted (not shown) metallic ground ring 104, which is drawn with friction fit onto radially outwardly protruding edges of the pole sheets 102 and in addition connected by crimping with the edges of the pole sheets 102 (not visible in the figures).
The region, which carries the stator 34, of the stator housing section 40 surrounds the central housing offset 48 of the stator housing section 40 in coaxial positional relationship with respect to the axis A of rotation while leaving an annular space 106 into which the rotor 28 enters. According to
According to
Finally, the stator housing section 40 has, radially outwardly, a stator housing flange 116 which is clamped in place in sandwich-like manner between the pump housing section 38 and the motor housing section 44 and which radially centers the stator housing section 40 in an associated step 118 at the motor housing section 44 with respect to the axis A of rotation.
Further details with respect to the encircling sealing element 50, which for simplification of the illustration is shown undeformed, are evident from, in particular,
In the illustrated embodiment the sealing element 50 is injection-molded at the pump housing flange 52 of the pump housing section 38 to be interlocking. For that purpose, formed in the pump housing flange 52 between the encircling groove 120 at the flange surface 14 external to the pump and the encircling groove 128 at the flange surface 54 internal to the pump is a plurality of openings 138, which are preferably uniformly spaced apart in the circumferential direction, i.e. as seen along the grooves 120, 128, and which connect the grooves and are penetrated by the elastomeric material of the sealing element 50 by injection molding so as to interconnect the first sealing section 122 and the second sealing section 130 of the sealing element 50 by way of a material bond.
Finally, further details with respect to the rotor 28 and the mounting thereof in the housing 16 are shown by, in particular,
In the following, the liquid pump 10 according to the second embodiment shall be described with reference to
The significant differences here consist of the construction of the stator housing section 40 in the region of the rotor 28 and the mounting—which is at the bottom in
The bearing section 152 is open towards the rotor 28 and provided at the axial height of the sensor section 154 with the cylindrical recess 146 for direct radial mounting of the rotor shaft 144. However, here the rotor shaft 144 does not extend as far as the bottom or base of the cylindrical recess 146 in the bearing section 152, but ends beforehand at an axial spacing therefrom. For that purpose the bearing section 152 is constructed to be longer than the bearing projection 110 in the first embodiment and ends, as seen in the direction of the axis A of rotation, only shortly in front of the base section 142 of the rotor 28. A second thrust washer 158, which surrounds the rotor shaft 144 and by way of which the rotor 28 can be axially supported on the bearing section 152, is inserted between an annular end surface 156 of the bearing section 152 and the base section 142 of the rotor 28.
On the other hand, the sensor section 154 is provided with the recess 108, which is open towards the electronics chamber 46 or the electronic circuit board 92, for receiving the magnetic field sensor 36 and extends to only half the height of the cylinder section 140 of the rotor 28. As a result, also in this embodiment the magnetic field sensor 36 and the radial bearing point for the rotor shaft 144 are arranged in very compact constructional form in the rotor 28 on the side of the stator housing section 40 in one plane which extends transversely or perpendicularly to the axis A of rotation.
An electric motor driven liquid pump usable for forced lubrication of a manual transmission for motor vehicles comprises a housing, which has a liquid inlet and a liquid outlet, and an electronically commutated electric motor received therein. The latter comprises a substantially cup-shaped magnetic rotor, which is rotatable about an axis of rotation, with means for conveying liquid, an annular stator, which has a motor winding and which as seen along the axis rotation at least partly surrounds the rotor in coaxial arrangement with respect to the axis of rotation, and a magnetic field sensor for positional recognition of the rotor. The housing has in that connection a stator housing section which carries the stator, separates this from the liquid chamber in which the rotor is arranged, and as seen along the axis of rotation extends into the rotor by a housing offset which is constructed for reception of the magnetic field sensor so that the liquid pump overall has only a low constructional height.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 017 975.0 | Nov 2013 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/002563 | 9/22/2014 | WO | 00 |
