Patent Application
20150030476
The invention relates to a pump unit that can be driven by electric motor, for the generation of negative pressure for a pneumatic brake force booster, comprising a pump housing that can be closed off by a working chamber cover and comprising at least one elastic displacement element, wherein a working chamber is delimited between the displacement element and the working chamber cover, and said working chamber is assigned in each case inlet and outlet valves and inlet and outlet ducts assigned to the valves.
To boost the braking force in hydraulic brake systems, use is made of brake force boosters, wherein a pneumatic or vacuum-type brake force booster is a very widely used, reliable and inexpensive solution.
To generate a vacuum for a pneumatic brake force booster, the interior of which is divided into at least one vacuum chamber and one working chamber, negative pressure is required. In many cases, the required negative pressure can be ensured by means of a connection of the vacuum chamber to an intake pipe of a naturally aspirated internal combustion engine. In the case of diesel, turbocharged or electric drives, and in the presence of an increased braking force demand for example owing to higher vehicle weights, the supply of negative pressure cannot be adequately provided, or cannot be provided at all, by the vehicle drive. To reliably ensure an adequate supply of negative pressure, dedicated vacuum pumps are used which draw residual air out of the vacuum chamber of the brake force booster and discharge said air into the atmosphere.
Numerous vacuum pump concepts exist; for example, DE102009054499A1, which is incorporated by reference, discloses a dry-running pump unit that can be driven autonomously by electric motor.
In the automotive industry, very high demands are set with regard to safety, durability, costs and noise emissions even under extreme driving conditions. Dry-running units in particular are however relatively noisy and necessitate high outlay for sound deadening by way of internal vibration damping and decoupling from the vehicle body. Owing to structural space requirements, pump units that can be driven autonomously may be positioned in a vehicle for example at an installation location where they are at risk of being struck by water, and require protection against contamination in order to protect internal components against corrosion or premature wear as a result of contamination with foreign media.
Because such units in some cases incorporate sound deadening measures into the interior thereof, air outlet units of complex construction are required, and these are considered to have room for improvement with regard to measures for preventing an ingress of water. Furthermore, diaphragm-type pump units, for example, have a relatively complex construction and there is a demand for optimization with regard to producibility and for a reduction in costs and assembly outlay.
The invention is therefore based on the problem of providing an inexpensive pump unit which exhibits improved noise emissions, is optimized with regard to production and assembly outlay, and exhibits increased reliability.
The problem is solved by virtue of the fact that means are provided for reducing an area of contact between the working chamber cover and the pump housing. The means may preferably be in the form of at least three molded protuberances distributed over the circumference of a housing flange.
It is likewise possible, in a further advantageous embodiment, for the means to be provided on the lower bottom cover flange of a working chamber cover and to be in the form of at least three molded protuberances distributed over the circumference of the lower bottom cover flange, such that spatially stable support, preferably three-point support, can be realized between the working chamber cover and the pump housing.
The means may likewise be provided for reducing a mutual area of contact between a top cover and a bottom cover of a working chamber cover, and may preferably be in the form of at least three molded protuberances distributed over the circumference of a top cover flange or of an upper bottom cover flange, or simultaneously over both flanges, such that spatially stable support, preferably three-point support, can be realized between the top cover and the bottom cover.
It is thus possible to realize spatially stable, geometrically determinate three-point support between the working chamber cover and the pump housing and also within a working chamber cover. This gives rise to a contact pattern that is expedient with regard to vibrations, and sound generation and sound emissions are reduced. Contact pressure is distributed more uniformly in the seal region between the working chamber cover and the pump housing and also within the working chamber cover, whereby the number of fastening points required between the working cover and the pump housing, and thus also production costs and assembly outlay, can be reduced.
In one advantageous refinement of the invention, the working chamber cover may be separated from the pump housing, and/or the top cover may be separated from the bottom cover, by means of at least one elastic decoupling element for the purpose of reducing a transmission of vibrations. In addition to a regular seal element, it is possible, for example, for a thin elastomer or polymer foil to be arranged in a contact region of the molded protuberances and of the counterpart component. In this way, the transmission of sound in the contact regions is reduced yet further, acoustic decoupling is improved, and the sound emission characteristics are attenuated and lessened. It is likewise conceivable for multiple individual sub-elements to be provided in order to isolate individual regions on the respectively corresponding flanges against direct contact with a molded protuberance.
In a further advantageous refinement of the invention, the described decoupling element may be connected to at least one or more seal elements to form a single gasket, thus promoting a simple assembly process and eliminating assembly errors.
In a further advantageous embodiment of the invention, it is possible, within a working chamber cover, for at least one insert part that can be loaded in the valve opening direction by a valve plate to be arranged, so as to be secured against rotation, in an inlet duct or an outlet duct or in both ducts. In this way, it is for example possible for the bottom cover to be produced in a particularly simple manner by punching or deformation, which can considerably reduce unit costs owing to cheaper tools and starting materials and higher cycle times. The insert part can be injection-molded from plastic in a simple and inexpensive manner and, in the assembled pump unit, can serve for the support of a valve disk or valve plate. A particularly expedient design of impact surfaces for the abutment of the valve plate during the valve opening process is made possible in an inexpensive manner.
It is accordingly possible, in a particularly advantageous embodiment, for the insert part to have at least one impact surface, which is rounded in a valve opening direction, for the abutment of the valve plate during the valve opening process. In this way, noise generation at the valves during the operation of the pump unit can be reduced considerably.
In one advantageous refinement of the invention, the insert part may be equipped with means for locking the insert part, which means engage into locking openings provided for the purpose. It is preferably possible for locking openings of said type to be provided in the bottom cover, which does not increase the complexity of the manufacture of the bottom cover and nevertheless permits simple and effective locking of the insert part.
In a further advantageous embodiment, a valve support surface for the support of a valve plate in a closed valve state may have at least one recess for reducing an area of contact between the valve plate and the valve support surface. Here, it is possible for the above-described recess to be arranged both on the bottom cover and on the top cover. As a result of a reduction in the area of contact between the respective valve plate and the valve support surface, and the associated back-ventilation of the valve plate, the impact noise of the valve plate against the valve support surface can be reduced considerably. A tendency of the valve plate to adhere to the valve support surface is counteracted in an effective manner. As a result, the valve operates altogether more smoothly and more quietly.
In a particularly advantageous embodiment of the working chamber cover according to the invention, the top cover may be shaped such that a length of its outer contour directed toward the bottom cover is significantly smaller than a length of an outer contour of the corresponding bottom cover. In this way, the top cover can be reduced substantially to just an encasement of the inlet and outlet ducts and valves. This yields great savings in terms of material, weight and structural space. Furthermore, the manufacture and assembly both of the top cover and also of the bottom cover can be simplified, and the number of fastening points can be drastically reduced. Furthermore, the inlet ducts and outlet ducts can be configured so as to be of particularly streamlined form.
In another advantageous embodiment, the pump unit can be fastened in elastically vibration-decoupled fashion in a base holder, wherein the elastic decoupling can be realized by means of damping elements, and wherein the base holder has supporting elements for receiving damping elements, and wherein at least one supporting element is manufactured by deformation of the base holder. The integrated support elements, generated by the deformation process, on the base holder make it possible for damping elements to be received and positioned directly, without the need for further intermediate elements, for example screws or bolts. It is thus possible to dispense with separate supporting elements, whereby both the number of parts and also the number of assembly operations required can be reduced. Furthermore, the base holder is additionally stiffened, and thus improved in terms of its acoustic sound emission characteristics.
In a further advantageous embodiment, a damping element may have an inner shell with a conical inner contour and an outer shell, wherein the inner shell may be connected to the outer shell by an encircling collar, which is directed obliquely with respect to the axis of rotation of the damping element, and by the radial webs that are arranged at least on one side of the collar.
By means of the described form, it is possible to provide a damping element that has a particularly pronounced progressive spring characteristic. The damping element generates a particularly low resistance force in the presence of low loads or deformations, whereas it generates a particularly high resistance force in the presence of intense deformations. In this way, the damping element can provide effective damping over a broad load and vibration spectrum, and can thus realize effective decoupling of the pump unit with relatively little outlay.
In a further advantageous embodiment, an intermediate base, which is provided with passage openings, of an air outlet unit provided for the discharge of the air into the surroundings of the pump unit may be equipped with means that are suitable for closing the passage openings in the manner of a check valve, and preferably in water-tight fashion.
In one advantageous refinement, said means may be in the form of an elastically resilient tab that is integrally formed on the intermediate base. In this way, effective protection against an ingress of water into the housing interior of the pump unit can be realized in a particularly simple and inexpensive manner without additional assembly steps. The above-mentioned tab can, in an effective manner, prevent water that has ingressed into the air outlet unit from the outside through the passage openings from passing onward into the housing interior of the pump unit through the passage openings and causing a malfunction or damage.
In a further advantageous embodiment, the elastic valve disk of a check valve arranged within the air outlet unit can be loaded counter to the valve opening direction by means of an elastic element, wherein the elastic element may preferably be in the form of a spiral spring. In this way, an undesired opening of the check valve, for example owing to chattering of the valve disk or owing to unpredictable pressure difference fluctuations, can be counteracted in an effective manner. Furthermore, the protection afforded by the check valve against an ingress of water into the housing interior from the surroundings of the pump unit is improved considerably.
In one advantageous refinement of the invention, it is furthermore possible for a disk element to be arranged between the elastic element and the valve disk; this promotes a particularly uniform distribution of the pressure force of the valve disk on the valve seat, and thus uniform quiet opening and closing of the check valve.
In a further advantageous embodiment of the invention, it is possible for at least two elastic intermediate elements to be interposed, so as to act in parallel, between the pump housing and the drive unit that drives the pump unit, wherein an inner intermediate element is provided for pneumatic and hydraulic sealing with respect to the surroundings of the pump unit, and an outer intermediate element contributes primarily to the vibration decoupling of the drive unit from the pump housing.
In an advantageous refinement, the intermediate elements may be connected to one another by at least two, and preferably four, elastic connecting webs.
In this way, a transmission of vibrations between the drive unit and the pump housing can be reduced in an effective manner without impairment of the seal function, and an assembly operation can be simplified.
In a particularly advantageous embodiment of the invention, the displacement element may comprise a connecting rod element and a diaphragm element, the latter being non-detachably connected to the connecting rod element by means of an insert molding process. Here, the connecting rod element may be produced in one piece in a particularly simple and inexpensive manner from a plastics material preferably in an injection molding process, and may have a connecting rod ring part integrated therein. In this way, the displacement element can not only be produced in an inexpensive and effective manner in only a small number of process steps, but can also exhibit a particularly low weight. In this way, the vibration characteristics of the crank drive can be improved, noise emissions can be reduced overall, and the mass of the pump unit can be reduced.
Further details, features, advantages and possible uses of the invention will emerge from the subclaims together with the description and with reference to the drawings. Corresponding components and structural elements are denoted, where possible, by the same reference signs. In the drawings:
a and 3b show an embodiment according to the invention of a bottom cover.
a-6e show an embodiment according to the invention of a pump housing, and sectional detail illustrations of the assembled state.
a and 7b show a further embodiment according to the invention of a working chamber cover.
a and 12b show an embodiment according to the invention of a damping element in a three-dimensional view and in a sectional view.
a and 14b show an embodiment according to the invention of a displacement element, and a detail illustration of a connecting rod element.
Because basic functional principles of generic pump units and of pneumatic brake force boosters that can be connected to such pump units are well known, a precise explanation of these will not be given below unless considered essential to the description of the invention.
The outlet duct 9 is pneumatically connected to a housing interior 53 of the pump unit. From the housing interior 53, the air is discharged into the surroundings via an air outlet unit 34. The air outlet unit 34 is divided by an intermediate base 35 with passage openings 36, and comprises further structural elements such as a check valve 38, which is arranged between an air outlet unit base 66 and the intermediate base 36 and which prevents an ingress of air into the housing interior 53.
The displacement elements 4 are moved in opposite directions by means of a crank drive 52 such that, as a result, a volume of the working chamber 5 is periodically varied and thus, in interaction with the inlet and outlet valves, a transfer of air is effected from a connected brake force booster into the surroundings of the pump unit via the working chamber 5.
The crank drive 52 is set in motion by means of an electronically controllable drive unit 42.
To illustrate the valve function,
By means of a lower bottom cover flange 11, the working cover 2 presses the diaphragm element 46 shown in
For the support of a valve disk during the opening process of a generic valve as per
In the closed valve state, the valve plate 19 bears against the valve support surface 22. Said valve support surface 22 has an encircling recess 23. In this way, the area of contact between the valve support surface 22 and the valve plate 19 is reduced, and a tendency of the elastic material of the valve plate 19 to adhere or stick to the valve support surface 22 is thereby reduced in an effective manner. Furthermore, the air flowing out of the working chamber 5 through the air ducts 24 is split up in the recess 23 and acts on the valve plate 19 more uniformly and over a greater effective area. During the closing process, the impact noise of the valve plate 19 against the valve support surface 22 is likewise reduced owing to back-ventilation and a reduction in the area of contact. In this way, the valve operates altogether more smoothly and more quietly. It is self-evident that, within the scope of the invention, the recess 23 may also assume shapes other than the encircling trapezoidal profile that is shown.
By contrast to the embodiments described in the introduction, the top cover 12 is of elongate shape and, in terms of form, is substantially reduced to a tunnel-like encasement of the inlet duct 8 and of the outlet duct 9 and has an impact surface 58′, of integrated form, for the outlet valve 7 and a valve support surface 22′ for the inlet valve 6. By contrast to the embodiments described in the introduction, the length of the outer contour 25 of the top cover 12 is in this case considerably shorter than the length of the outer contour (26) of the bottom cover 13. It is thus possible for the working cover 2 to be made altogether considerably simpler and more lightweight and for the air ducts to be optimized in terms of flow. In the embodiment shown, the combination seal 55 is of very simple and space-saving form and has the valve plates 19 and 19′ integrated therein.
The bottom cover 13 receives the combination seal and is equipped with positioning studs 60 which serve primarily for the positioning of the top cover 12 on the bottom cover 13 and which may additionally be provided for absorbing longitudinal and transverse forces between said two cover parts by virtue of said positioning studs engaging into the corresponding stud guides 61 integrally formed on the top cover 12. It is likewise possible for the positioning studs 60 to be used, by virtue of their being deformed after the mounting of the top cover 12, for permanently fixing the top cover 12 to the bottom cover 13. For sealing of the studs, the combination seal 55 has integrated O-rings 62 which engage around the positioning studs 60 in the assembled state. The O-rings 62 can sometimes stiffen the combination seal 55 overall and stabilize it against deformations and thus contribute, overall, to a reliable and simple assembly operation.
During operation of the pump unit 1, noises or sound waves are generated both in the working chamber cover 2 and also in the pump housing 3, said noises or sound waves then being radiated through all of the existing surfaces. Noises at and in the working chamber cover 2 are generated primarily owing to air turbulence at the valves 6, 7 and in the air ducts 8, 9, and are normally of a higher frequency than noises at and in the pump housing 3, which originate primarily from the drive unit 42 and from the mechanical crank drive 52. At all of the areas of contact between the working chamber cover 2 and the pump housing 3, the sound waves are transmitted and repeatedly superposed on one another, which can give rise, for example, to undesired resonance.
Owing to the high contact pressure in the areas of contact between the molded protuberances 16 and the working chamber cover 2 and the elimination of further sound-transmitting areas of contact, sound transmission effects between the working chamber cover 2 and the pump housing 3 are reduced, and resonance is prevented. Sound emissions both from the working chamber cover 2 and also from the pump housing 3 are likewise reduced considerably. To further intensify this expedient effect, a thin elastic decoupling element 17 is provided which is arranged between the working chamber cover 2 and the pump housing 3 and which both reduces a direct transmission of sound from one to the other counterpart at the 3 above-mentioned areas of contact and also permits extensive sound decoupling. In the exemplary embodiment shown, the decoupling element 17 is in the form of an elastomer foil and is connected to two seal elements 18 so as to form a single gasket. The two seal elements 18 serve for the sealing of the inlet duct and of the outlet duct at their parting point between the working chamber cover 2 and the pump housing 3.
In a further embodiment according to the invention, it is however also possible to dispense with a decoupling element of said type.
It is known that, in a three-dimensional space, three-point support constitutes a spatially stable and mathematically determinate mounting configuration of a body, because a center of mass of the body is situated within a virtual triangle, the ends of which are the support points. Because, in a three-dimensional space, it is furthermore the case that more than three vectors are always linearly dependent, it would, in the presence of more than three support points, be more cumbersome from a production aspect to ensure simultaneous and uniform contact at all of the support points. Within the scope of the invention, it is nevertheless also possible to provide more than three molded protuberances in order, for example, to limit material loads as a result of high contact pressure in the contact regions, and nevertheless reduce sound transmission and sound emission effects.
The pump housing 3 shown in
b illustrates that the molded protuberances 16 are arranged, so as to be substantially uniformly spaced from one another, on an outer edge of the housing flange 10 and provide an area of contact, which is very small in relation to the total area of the housing flange 10, for the support of the working chamber cover. From the view c, it can be seen that the molded protuberances 16 project only slightly beyond the surface of the housing flange 10.
d shows a detail of a side view of an assembled pump unit 1. The decoupling element 17 is arranged between the working chamber cover 2 and the pump housing 3, said decoupling element being compressed in the region of the molded protuberance 16. From
After a certain amount of air has escaped through the passage openings 36, the pressure difference decreases, and the tab 36 springs back elastically, thus closing the passage openings 36 and preventing the ingress of air, dirt and moisture into the housing interior 53. The sound emissions from the housing interior 53 are also reduced as a result of the closure of the passage openings 36. In the event of an ingress of relatively large amounts of water into the air outlet unit 34, the water surge that has ingressed causes the tab 37 to be pressed with even greater intensity against the passage openings 36, with said tab thus preventing a further advancement of moisture in an effective manner.
Further structural designs of the tab are also conceivable within the scope of the invention:
In the embodiment shown, the tab 37 is in the form of a single, foldable integrally molded portion on the intermediate base, though it is likewise possible for more than one tab to be provided which is assigned to the individual passage openings 36 or groups of passage openings 36.
It is likewise possible, for example, for the tabs 37 to be provided not so as to be integrally formed on the intermediate base 35 but so as to be rotatably mounted thereon and pressed against the surface of the intermediate base by means of an elastic element.
An undesired opening of the check valve 37, for example owing to chattering of the valve disk 39 or unpredictable pressure difference fluctuations owing to interactions with the tab 37 described above, is thus counteracted.
The described additional elastic support of the valve disk 39 between the valve seat 65 and the intermediate base 35 furthermore considerably improves the protection afforded by the check valve against an ingress of water into the housing interior 53 from the surroundings of the pump unit 1.
To receive damping elements 27, the base holder 28 has supporting elements 29, 29′. The supporting elements 29′ of the known embodiment are formed as separate components which, in a separate joining process, are inserted into the openings provided for them in the base holder. By contrast, the embodiment according to the invention as per
If required, support elements 29 formed in this way may for example be provided with a rolled or cut internal thread, for example in order to serve as a fixing point for plug connectors, cable holders or other peripheral elements or units.
Further exemplary embodiments of integrated support elements generated by deformation processes—for example by means of punching and bending, or upsetting—are likewise conceivable within the scope of the invention.
The inner shell 30 is connected to the outer shell 31 via an encircling collar 32 that is arranged obliquely with respect to the axis of rotation R. Furthermore, the inner shell 30 is connected to the outer shell 31 via multiple webs 33 which are arranged on one side of the collar and which run radially from the inner shell 30 to the outer shell 31. Assisted by the conically running inner contour of the inner shell 30 together with the collar 32 and the webs 33, the damping element 27, under load, deforms both transversely and along or obliquely with respect to the axis of rotation R and generates a resistance force counter to the load, which resistance force is dependent on the degree of deformation and is initially weak (soft), increases progressively (hard) with increasing deformation, and is particularly high after a collapse of the free intermediate spaces between the inner shell 30 and the outer shell 31. In this way, small vibrations of the pump unit are intercepted in an effective manner by the “soft” part of the spring characteristic curve and are not transmitted to the body, and a relatively large movement of the pump unit is damped by the hard part of the spring characteristic curve, with effective decoupling thus being realized over a broad range.
The connecting point between the drive unit 42 and the pump housing 3 must be of both sealed and also vibration-decoupled design. In the embodiment according to the invention shown in
The cross section of the outer intermediate element 44 and of the connecting webs 45 is preferably cuboidal, and in this case configured such that the outer intermediate element 44 and optionally also the connecting webs 45 are compressed between the pump housing 3 and the drive unit 42 when the pump unit 1 is in an assembled state. Here, a defined air gap remains between the pump housing 3 and the drive unit 42 at least in the region around the outer intermediate element 44. In this way, a transmission of vibrations between the drive unit 42 and the pump housing 3 is reduced by way of a conversion of the kinetic energy into heat, without the seal function being impaired.
The connecting rod element 47 is of unipartite form and is composed substantially of a shank part 48 and of a connecting rod ring part 49 integrally formed on the shank part 48. The connecting rod element may preferably be produced from a plastics material in an injection molding process, although other production methods, for example punching or sintering, and metal materials are likewise possible.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2012 201 407.1 | Feb 2012 | DE | national |
This application is the U.S. National Phase Application of PCT/EP2013/052088, filed Feb. 1, 2013, which claims priority to German Patent Application No. 10 2012 201 407.1, filed Feb. 1, 2012, the contents of such applications being incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2013/052088 | 2/1/2013 | WO | 00 |
